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Electricity generation in Islanded Urban Microgrids (IUMG) now relies heavily on a diverse range of Renewable Energy Sources (RES). However, the dependable utilization of these sources hinges upon efficient Electrical Energy Storage Systems (EESs). As the intermittent nature of RES output and the low inertia of IUMGs often lead to significant frequency fluctuations, the role of EESs becomes pivotal. While these storage systems effectively mitigate frequency deviations, their high costs and elevated power density requirements necessitate alternative strategies to balance power supply and demand. In recent years, substantial attention has turned towards harnessing Electric Vehicle (EV) batteries as Mobile EV Energy Storage (MEVES) units to counteract frequency variations in IUMGs. Integrating MEVES into the IUMG infrastructure introduces complexity and demands a robust control mechanism for optimal operation. Therefore, this paper introduces a robust, high-order degree of freedom cascade controller known as the 1PD-3DOF-PID (1 + Proportional + Derivative—Three Degrees Of Freedom Proportional-Integral-Derivative) controller for Load Frequency Control (LFC) in IUMGs integrated with MEVES. The controller's parameters are meticulously optimized using the Coati Optimization Algorithm (COA) which mimics coati behavior in nature, marking its debut in LFC of IUMG applications. Comparative evaluations against classical controllers and algorithms, such as 3DOF-PID, PID, Reptile Search Algorithm, and White Shark Optimizer, are conducted under diverse IUMG operating scenarios. The testbed comprises various renewable energy sources, including wind turbines, photovoltaics, Diesel Engine Generators (DEGs), Fuel Cells (FCs), and both Mobile and Fixed energy storage units. Managing power balance in this entirely renewable environment presents a formidable challenge, prompting an examination of the influence of MEVES, DEG, and FC as controllable units to mitigate active power imbalances. Metaheuristic algorithms in MATLAB-SIMULINK platforms are employed to identify the controller's gains across all case studies, ensuring the maintenance of IUMG system frequency within predefined limits. Simulation results convincingly establish the superiority of the proposed controller over other counterparts. Furthermore, the controller's robustness is rigorously tested under ± 25% variations in specific IUMG parameters, affirming its resilience. Statistical analyses reinforce the robust performance of the COA-based 1PD-3DOF-PID control method. This work highlights the potential of the COA Technique-optimized 1PD-3DOF-PID controller for IUMG control, marking its debut application in the LFC domain for IUMGs. This comprehensive study contributes valuable insights into enhancing the reliability and stability of Islanded Urban Microgrids while integrating Mobile EV Energy Storage, marking a significant advancement in the field of Load-Frequency Control. [ABSTRACT FROM AUTHOR]

This article investigates the impact of three harmonically external moments on the motion of a four-degrees-of-freedom (DOF) nonlinear dynamical system composed of a double rigid pendulum connected to a nonlinear spring with linear damping. In light of the system's generalized coordinates, the governing system (GS) of motion is derived using Lagrange's equations. With the use of the multiple-scales method (MSM), the approximate solutions (AS) of the equations of this system are obtained up to a higher order of approximation, maybe the third order. Within the framework of the absence of secular terms, the conditions of solvability are obtained. Accordingly, the different resonance cases are categorized, and three of them are investigated simultaneously. Thus, these conditions are updated in preparation for achieving the modulation equations (ME) for the examined system. The numerical solutions (NS) of the GS are achieved using the algorithms of fourth-order Runge–Kutta (4RK), which are compared with the AS, which displays their high degree of consistency and demonstrates the precision of the MSM. The motion's time history, steady-state solutions, and resonance curves are graphed to demonstrate the influence of various system physical parameters. All relevant fixed points at steady-state situations are identified and graphed in accordance with the Routh–Hurwitz criteria (RHC). Therefore, the zones of stability/instability of are checked and analyzed. Numerous real-world applications in disciplines like engineering and physics attest to the significance of the nonlinear dynamical system under study such as in shipbuilding, automotive devices, structure vibration, developing robots, and analysis of human walking. [ABSTRACT FROM AUTHOR]

The interaction force control problem for the object manipulated by the dual-arm manipulator with the unknown environment is addressed in this paper. An adaptive dual-loop impedance control scheme is designed to meet the three control targets, including the trajectory tracking control of the object, the internal force control of the object with the two arms, and the interaction force control of the object with the unknown environment. Firstly, an adaptive variable impedance control method is proposed in the outer loop to copy with the unknown stiffness and position of the environment. Secondly, an impedance control scheme based on the internal force is designed in the inner loop to plan the internal force and the modified position supplied with the outer-loop control. Thirdly, to realize the reference trajectory supplied with the inner-loop control, the virtual decomposition control (VDC) method is incorporated, which is a recursive adaptive control progress, so that the unknown dynamics of the manipulators is acceptable and the computation complexity is also very low to satisfy the real-time control requirement. The stability verifications of the inner-loop impedance control and the VDC method are given based on the Lyapunov method, and the stability analysis of the outer-loop impedance control is obtained using the Routh criterion. Finally, a plane dual-arm robotic manipulator with three degrees of freedom is used to verify the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

The discrete-like crack model (DLCM), a crack-analysis scheme incorporated with the nonlinear finite element method, is redeveloped for parallelism. The algorithm of the new DLCM based on the theory of bond redistribution is implemented through the OpenMP interface and enables analyses of a 50-story building with more than four million degrees of freedom. The analysis considers the drying shrinkage and creep during the construction and service periods, static pushover loading, and a time history of a near-fault strong ground motion. The amount of cracks is quantified as the total length that occurs on the concrete surfaces. The structural damage due to compression softening exhibits a strong correlation with the length of cracks with opening widths larger than 2 mm. The analyzed building becomes unrepairable when the total length of the >2 mm wide cracks exceeds 50 m. However, the occurrence of such serious damage induced by any seismic vibrations ever recorded is unlikely. "There's no art to find the mind's construction in the face," so King Duncan said. However, we can consider the search for structural damages on concrete surfaces a form of art. The presence of cracks proves the life of a reinforced concrete building, similar to a person's history engraved as wrinkles and scars on their face. Our novel parallel numerical scheme, namely, the discrete-like crack model (DLCM), traces not only the long history of a building starting from its construction but also resolves the issue of unexpected near-fault pulse-type earthquakes into detailed profiles. In this case study, DLCM is employed to assess structural damage using a percentage of cracks that extend up to 100 km on the entire concrete surfaces of a 50-story residential building. The profiles of cracks, stresses, and strains articulate the building's past and current status and render the possibility to improve the quality of living in the future. [ABSTRACT FROM AUTHOR]

In this work we introduce a new type of human-inspired upper-limb prostheses. The Artificial Neuromuscular Prosthesis (ANP) imitates the human neuromuscular system in the sense of its compliance, backdrivability, natural motion, proprioceptive sensing, and kinesthetics. To realize this challenging goal, we introduce a novel human-inspired and simulation-based development paradigm to design the prosthesis mechatronics in correspondence to the human body. The ANP provides body awareness, contact awareness, and human-like contact response, realized via floating base rigid-body models, disturbance observers, and joint impedance control—concepts known from established state-of-the-art robotics. The ANP mechatronics is characterized by a four degrees of freedom (dof) torque-controlled human-like kinematics, a tendon-driven 2-dof wrist, and spatial orientation sensing at a weight of 1.7 kg (without hand and battery). The paper deals with the rigorous mathematical modeling, control, design and evaluation of this device type along initially defined requirements within a single prototype only. The proposed systemic and grasping capabilities are verified under laboratory conditions by an unimpaired user. Future work will increase the technology readiness level of the next generation device, where human studies with impaired users will be done. [ABSTRACT FROM AUTHOR]

A theoretical paper based on chiral micropolar effective‐medium theory suggested the possibility of unusual roton‐like acoustical‐phonon dispersion relations in 3D elastic materials. Here, as a first novelty, the corresponding inverse problem is solved, that is, a specific 3D chiral elastic metamaterial structure is designed, the behavior of which follows this effective‐medium description. The metamaterial structure is based on a simple‐cubic lattice of cubes, each of which not only has three translational but also three rotational degrees of freedom. The additional rotational degrees of freedom are crucial within micropolar elasticity. The cubes and their degrees of freedom are coupled by a chiral network of slender rods. As a second novelty, this complex metamaterial is manufactured in polymer form by 3D laser printing and its behavior is characterized experimentally by phonon‐band‐structure measurements. The results of these measurements, microstructure finite‐element calculations, and solutions of micropolar effective‐medium theory are in good agreement. The roton‐like dispersion behavior of the lowest phonon branch results from two aspects. First, chirality splits the transverse acoustical branches as well as the transverse optical branches. Second, chirality leads to an ultrastrong coupling and hybridization of chiral acoustical and optical phonons at finite wavevectors. [ABSTRACT FROM AUTHOR]

The damping of spruce wood is analysed at different moisture content levels for the first three vibration modes of tangentially and radially vibrating samples. Two methods were used to determine the damping. The first was the vibration envelope fitting as an improved version of the well-known logarithmic decrement, and the second was the newer and recently increasingly used wavelet transform. Both methods showed that the damping of spruce wood first decreases and then increases with moisture content, with the damping in the first vibration mode being about 9% higher in the radial direction than in the tangential direction. In the second and third vibration modes, the damping in the tangential direction was higher than in the radial direction by about 10% and 8.8%, respectively. The measured damping factors from the envelope fitting had, on average, 15.9% higher values than those from the wavelet transform. It can be concluded from the results that the wavelet transform is more accurate for determining the damping factor, as it enables the decoupling of multi-degree of freedom systems if mode coupling is present. [ABSTRACT FROM AUTHOR]

Machine learning-based controllers of prostheses using electromyographic signals have become very popular in the last decade. The regression approach allows a simultaneous and proportional control of the intended movement in a more natural way than the classification approach, where the number of movements is discrete by definition. However, it is not common to find regression-based controllers working for more than two degrees of freedom at the same time. In this paper, we present the application of the adaptive linear regressor in a relatively low-dimensional feature space with only eight sensors to the problem of a simultaneous and proportional control of three degrees of freedom (left–right, up–down and open–close hand movements). We show that a key element usually overlooked in the learning process of the regressor is the training paradigm. We propose a closed-loop procedure, where the human learns how to improve the quality of the generated EMG signals, helping also to obtain a better controller. We apply it to 10 healthy and 3 limb-deficient subjects. Results show that the combination of the multidimensional targets and the open-loop training protocol significantly improve the performance, increasing the average completion rate from 53% to 65% for the most complicated case of simultaneously controlling the three degrees of freedom. [ABSTRACT FROM AUTHOR]

The pectoral fin propulsion of a bionic robotic fish always consists of two phases: propulsion and recovery. The robotic fish moves in a burst-and-coast swimming manner. This study aims to analyze a pair of bionic robotic fish with rigid pectoral fin propulsion with three degrees of freedom and optimize the elliptical propulsion curve with the minimum recovery stroke resistance using computational fluid dynamics methods. Then, the time allocated to the propulsion and recovery phases is investigated to maximize the propulsion performance of the bionic robotic fish. The numerical simulation results show that when the time ratio of the propulsion and recovery phases is 0.5:1, the resistance during the movement of the robotic fish is effectively reduced, and the drag-reducing effect is pronounced. According to a further analysis of pressure clouds and vortex structures, the pressure difference between the upstream and downstream fins of the pectoral fin varies with different stroke ratios. The increase in recovery phase time helps to prevent premature damage to the vortex ring structure generated during the propulsion process and improves propulsion efficiency. [ABSTRACT FROM AUTHOR]

The main objective of this research is to establish a new formulation and mathematical model based on graph theory to create dynamic equations and provide clarity on the fundamental formulation. We have employed graph theory as a new approach to develop a new representation and formulate the vertical dynamics of a motorcycle with four degrees of freedom, including a suspension and tire model. We have outlined the principal procedural steps required to generate the mathematical and dynamic equations. This systematic approach ensures clarity and precision in our formulation process and representation. Subsequently, we implemented the dynamics equations to examine the dynamic behavior of both the sprung and unsprung masses' vertical displacements, while considering the varying conditions of the road profile. [ABSTRACT FROM AUTHOR]

This study aims to analyze the impact of uniform and eccentric load conditions on the performance of internal feedback hydrostatic thrust and journal bearing. Two distinct models are established: a three-degrees-of-freedom uniform load model and a five-degrees-of-freedom eccentric load model. The support stiffness, overturning stiffness, and flow rate for both thrust and journal bearings are calculated. Additionally, numerical analysis is conducted to examine the influence of oil film thickness, inlet pressure, and restrictor size on the operational characteristics of the bearings, revealing the interplay between an eccentric load and journal bearing speed. The validity of the theoretical algorithm is verified through finite element simulation. The research outcomes hold significant guiding implications for the design and application of internal feedback hydrostatic bearings. [ABSTRACT FROM AUTHOR]

This paper addresses the exact controllability of vibrations in a three-dimensional Cosserat elastic solid body using mathematical techniques such as operator theory and semigroup methods. The verification of exact (shape) controllability is accomplished through the application of the Hilbert Uniqueness Method, which involves investigating the boundary observability for the dual system. In partial differential equations control theory, the concept of exact observability for the dual system is fundamental to achieving exact controllability, although it differs from the common understanding of controllability. While control theory for systems governed by ordinary differential equations (ODEs) has a relatively formal and standardized approach, systems with distributed parameters, such as the Cosserat medium under consideration, involve a multitude of technical inequalities that must be established. Notably, Cosserat media possess six degrees of freedom for microstructures, in contrast to classical media with only three degrees of freedom. Consequently, exact control is required for all six variables, encompassing three translational and three rotational degrees of freedom, while classical media only necessitate the exact control of three translational variables. The paper concludes with a series of numerical studies utilizing the fast Fourier transform (FFT) and various simulations, which serve to validate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

• A compact magnetic structure for rotary magnetic regenerators is designed. • A parametric set of simulations is performed to enhance the magnet shape. • Magnet shape strongly impacts the cooling capacity of magnetic refrigerators up to 40%. • Proposed solutions maximize the field up to 19% and minimize the magnet volume up to 44%. • Presented solutions outperform existing magnetic structures for rotary devices. A magnetic structure intended for use in a room-temperature rotary active magnetic regenerator (AMR) is presented, under construction at the University of Genoa. Given the overall size of the regenerator and the thickness of the gap, the magnet design is optimized to produce the highest possible magnetic field difference between two adjacent regions. Magnet shape optimization is obtained by introducing a geometry with four degrees of freedom corresponding to the position of the edges of each magnet, plus the remanence angle. This approach serves two main purposes: the primary is to increase the magnetic induction and, to follow, some effort is made to minimize the volume and weight of the expensive NdFeB magnets, while preserving the cooling performance. So, a balance between these two goals must be achieved. After a rough preliminary sizing, a parametric investigation is performed toward these targets and some shapes are presented. The magnetic flux density in the gap, and other consolidated and novel performance indices, are evaluated and compared to those found in the literature for similar devices. The final design achieves, in the air gap, a maximum induction value of 1.045 T, and an average flux density of 0.83 T in a volume per unit length of 0.00268 m3/m in the high induction region. This is accomplished by using 0.00606 m3/m of magnetic material (N50, NdFeB). The magnet designs presented here exhibit a well-balanced performance (in terms of greater cooling for the same magnet weight) compared to earlier designs for similar AMR devices. [ABSTRACT FROM AUTHOR]

Recent progress towards understanding the mechanism of dynamical tunneling in Hamiltonian systems with three or more degrees of freedom (DoF) is reviewed. In contrast to systems with two degrees of freedom, the three or more degrees of freedom case presents several challenges. Specifically, in higher-dimensional phase spaces, multiple mechanisms for classical transport have significant implications for the evolution of initial quantum states. In this review, the importance of features on the Arnold web, a signature of systems with three or more DoF, to the mechanism of resonance-assisted tunneling is illustrated using select examples. These examples represent relevant models for phenomena such as intramolecular vibrational energy redistribution in isolated molecules and the dynamics of Bose–Einstein condensates trapped in optical lattices. [ABSTRACT FROM AUTHOR]

In prior work [Katsanikas & Wiggins, 2021a, 2021b, 2023c, 2023d], we introduced two methodologies for constructing Periodic Orbit Dividing Surfaces (PODS) tailored for Hamiltonian systems possessing three or more degrees of freedom. The initial approach, outlined in [Katsanikas & Wiggins, 2021a, 2023c], was applied to a quadratic Hamiltonian system in normal form having three degrees of freedom. Within this context, we provided a more intricate geometric characterization of this object within the family of 4D toratopes that describe the structure of the dividing surfaces discussed in these papers. Our analysis confirmed the nature of this construction as a dividing surface with the no-recrossing property. All these findings were derived from analytical results specific to the case of the Hamiltonian system discussed in these papers. In this paper, we extend our results for quartic Hamiltonian systems with three degrees of freedom. We prove for this class of Hamiltonian systems the no-recrossing property of the PODS and we investigate the structure of these surfaces. In addition, we compute and study the PODS in a coupled case of quartic Hamiltonian systems with three degrees of freedom. [ABSTRACT FROM AUTHOR]

Not all complete set of spinors can be used as expansion coefficients of a quantum field. In fact, Steven Weinberg established the uniqueness of Dirac spinors for this purpose provided: (a) one paid due attention to the multiplicative phases for each of the spinors, and (b) one paired these to creation and annihilation operators in a specific manner. This is implicit in his implementation of the rotational symmetry for the spin half quantum field. Among the numerous complete set of spinors that are available to a physicist, Elko occupies a unique status that allows it to enter as expansion coefficients of a quantum field without violating Weinberg's no go theorem. How this paradigm changing claim arises is the primary subject of this communication. Weinberg's no go theorem is evaded by exploiting a uniquely special feature of Elko that allows us to introduce a doubling of the particle-antiparticle degrees of freedom from four to eight. Weinberg had dismissed this degeneracy on the ground that, "no examples are known of particles that furnish unconventional representations of inversions." Here we will find that this degeneracy, once envisioned by Eugene Wigner, in fact gives rise to a quantum field that has all the theoretical properties required of dark matter. [ABSTRACT FROM AUTHOR]

The AMTI VIVO™ six degree of freedom joint simulator allows reproducible preclinical testing of joint endoprostheses under specific kinematic and loading conditions. When testing total knee endoprosthesis, the articulating femoral and tibial components are each mounted on an actuator with two and four degrees of freedom, respectively. To approximate realistic physiological conditions with respect to soft tissues, the joint simulator features an integrated virtual ligament model that calculates the restoring forces of the ligament apparatus to be applied by the actuators. During joint motion, the locations of the ligament insertion points are calculated depending on both actuators' coordinates. In the present study, we demonstrate that unintended elastic deformations of the actuators due to the specifically high contact forces in the artificial knee joint have a considerable impact on the calculated ligament forces. This study aims to investigate the effect of this structural compliance on experimental results. While the built-in algorithm for calculating the ligament forces cannot be altered by the user, a reduction of the ligament force deviations due to the elastic deformations could be achieved by preloading the articulating implant components in the reference configuration. As a proof of concept, a knee flexion motion with varying ligament conditions was simulated on the VIVO simulator and compared to data derived from a musculoskeletal multibody model of a total knee endoprosthesis. [ABSTRACT FROM AUTHOR]

To research the special transmission system type of the multistage closed-loop gear system of the 3D braiding machine, a multi-degree of freedom nonlinear dynamic model was established by using the lumped mass method, taking into account parameters such as meshing stiffness, static transmission error, backlash, and meshing damping. To reduce the computational complexity, a gear system with 12 gears was selected and solved using the Runge-Kutta method. Using meshing frequency, backlash, and meshing damping ratio as control parameters, we analyzed the bifurcation and chaos of the system under different conditions through bifurcation diagrams. Simultaneously using sequence diagram, phase plane diagrams, Poincare maps, and FFT diagrams to accurately display the motion state of the system. The analysis results indicate that with the increase of meshing frequency and backlash, the system exhibits a range of motion states, such as period-one motion, multi-periodic motion, quasi-periodic motion, and chaotic motion. Meanwhile, increasing the damping ratio can effectively suppress the chaotic state of the gear system and also reduce the maximum vibration displacement of the gear system. [ABSTRACT FROM AUTHOR]

Angle measurement is an essential component of precision measurement and serves as a crucial prerequisite for high-end manufacturing. It guides the implementation of precision manufacturing and assembly. The current angle measurement methods mainly focus on multiple axes, high precision, and large measurement ranges. This article introduces the technology of angle measurement from the perspectives of single-axis and multi-axis measurement schemes. Firstly, the single-axis measurement scheme is primarily achieved through optical methods, such as encoder discs that measure energy changes and interferometric phase changes, as well as mechanical, electromagnetic, and inertial angle measurement methods, among which interferometric methods offer the highest accuracy, with high cost, and encoder discs provide the largest measurement range with an ordinary price. Secondly, in the multi-axis measurement scheme, autocollimation instruments, including plane mirrors, gratings, and self-designed targets, are the main options. Although grating encoders can achieve three degrees of freedom in angle measurement with an ordinary price, they are limited in terms of measurement range and sensitivity compared to self-designed targets. Lastly, artificial intelligence assistance precision measurement is increasingly being embraced due to significant advancements in computer performance, making it more convenient to identify the relationship between measured values and detection values. In conclusion, angle measurement plays a crucial role in precision manufacturing, and the evolving and improving technologies provide the manufacturing industry with greater choices. The purpose of this review is to help readers quickly find more suitable technical solutions according to current application requirements, such as single/multiple axes, accuracy level, measuring range, budget, etc. [ABSTRACT FROM AUTHOR]

Summary: A model predictive cascade controller is proposed in this article to resolve the actuator saturation problem of underwater human‐occupied vehicle (HOV) trajectory tracking. For the kinematic model, a grasshopper optimization‐based model predictive control (MPC) is developed to obtain control velocities with small fluctuations in allowable regions. Based on the desired velocities obtained from the improved kinematic control, the HOV dynamic model is used to generate the corresponding torques and forces using sliding mode control. With the control velocities and forces given by the cascade control strategy, the elimination of actuator saturation during the HOV trajectory tracking can be realized. The proposed controller is verified by simulations using a numerical example based on a four degrees of freedom (4‐DOFs) HOV. [ABSTRACT FROM AUTHOR]

Background: This study aimed to evaluate the accuracy of bone cuts and implant placements, simultaneously, for total knee arthroplasty (TKA) performed using a system with an active robotic arm. Methods: Two experienced orthopaedic surgeons performed TKA on ten cadaveric legs. Computed tomography scans were performed to compare the bone cuts and implant placements with the preoperative planning. The differences between the planned and actual bone cuts and implant placements were assessed using positional and angular errors in the three anatomical planes. Additionally, the cut–implant deviations were calculated. Statistical analysis was performed to detect systematic errors in the bone cuts and implant placements and to quantify the correlations between these errors. Results: The root-mean-square (RMS) errors of the bone cuts (with respect to the planning) were between 0.7–1.5 mm and 0.6–1.7°. The RMS implant placement errors (with respect to the planning) varied between 0.6–1.6 mm and 0.4–1.5°, except for the femur and tibia in the sagittal plane (2.9°). Systematic errors in the bone cuts and implant placements were observed, respectively, in three and two degrees of freedom. For cut–implant deviations, the RMS values ranged between 0.3–2.0 mm and 0.6–1.9°. The bone cut and implant placement errors were significantly correlated in eight degrees-of-freedom (ρ ≥ 0.67, p < 0.05). Conclusions: With most of the errors below 2 mm or 2°, this study supported the value of active robotic TKA in achieving accurate bone cuts and implant placements. The findings also highlighted the need for both accurate bone cuts and proper implantation technique to achieve accurate implant placements. [ABSTRACT FROM AUTHOR]

In a daily environment, several vibration energies have low amplitude and broad range of frequencies, and it is crucial to harvest them efficiently in a single triboelectric nanogenerator (TENG). Here, a multi‐degree of freedom (DOF) vibration system is coupled with TENG to make several resonant frequencies in a single device. When the number of DOF increases in the system, the number of resonant frequencies also increases. These resonant frequencies are calculated by MATLAB software using the masses and spring constant of DOF vibration system. With the masses of 20 g and the spring constant of 82.712 N m−1, it is found that 1‐DOF has one resonant frequency (20.47 Hz), 2‐DOF has two resonant frequencies (12.63 and 33.17 Hz), and 3‐DOF has three resonant frequencies (9.12, 25.55, and 36.87 Hz). At each resonant frequency, the displacement of all weight layers increases due to the constructive interference of resonance, resulting in higher output than other frequencies at the frequency sweep experiment. In addition, the magnitude and phase of output signals obtained in friction regions are evaluated through COMSOL simulation. A self‐powered wireless sensor module with 3‐DOF TENGs to detect the humidity/temperature and transmit the data every 30 min by harvesting vibration energy is demonstrated. [ABSTRACT FROM AUTHOR]

Background: Current commercially available hybrid magnetic resonance linear accelerators (MR‐Linac) use 2D+t cine MR imaging to provide intra‐fractional motion monitoring. However, given the limited temporal resolution of cine MR imaging, target intra‐frame motion deterioration effects, resulting in effective time latency and motion artifacts in the image domain, can be appreciable, especially in the case of fast breathing. Purpose: The aim of this work is to investigate intra‐frame motion deterioration effects in MR‐guided radiotherapy (MRgRT) by simulating the motion‐corrupted image acquisition, and to explore the feasibility of deep‐learning‐based compensation approaches, relying on the intra‐frame motion information which is spatially and temporally encoded in the raw data (k‐space). Methods: An intra‐frame motion model was defined to simulate motion‐corrupted MR images, with 4D anthropomorphic digital phantoms being exploited to provide ground truth 2D+t cine MR sequences. A total number of 10 digital phantoms were generated for lung cancer patients, with randomly selected eight patients for training or validation and the remaining two for testing. The simulation code served as the data generator, and a dedicated motion pattern perturbation scheme was proposed to build the intra‐frame motion database, where three degrees of freedom were designed to guarantee the diversity of intra‐frame motion trajectories, enabling a thorough exploration in the domain of the potential anatomical structure positions. U‐Nets with three types of loss functions: L1 or L2 loss defined in image or Fourier domain, referred to as NNImgLoss‐L1, NNFloss‐L1 and NNL2‐Loss were trained to extract information from the motion‐corrupted image and used to estimate the ground truth final‐position image, corresponding to the end of the acquisition. Images before and after compensation were evaluated in terms of (i) image mean‐squared error (MSE) and mean absolute error (MAE), and (ii) accuracy of gross tumor volume (GTV) contouring, based on optical‐flow image registration. Results: Image degradation caused by intra‐frame motion was observed: for a linearly and fully acquired Cartesian readout k‐space trajectory, intra‐frame motion resulted in an imaging latency of approximately 50% of the acquisition time; in comparison, the motion artifacts exhibited only a negligible contribution to the overall geometric errors. All three compensation models led to a decrease in image MSE/MAE and GTV position offset compared to the motion‐corrupted image. In the investigated testing dataset for GTV contouring, the average dice similarity coefficients (DSC) improved from 88% to 96%, and the 95th percentile Hausdorff distance (HD95) dropped from 4.8 mm to 2.1 mm. Different models showed slight performance variations across different intra‐frame motion amplitude categories: NNImgLoss‐L1 excelled for small/medium amplitudes, whereas NNFloss‐L1 demonstrated higher DSC median values at larger amplitudes. The saliency maps of the motion‐corrupted image highlighted the major contribution of the later acquired k‐space data, as well as the edges of the moving anatomical structures at their final positions, during the model inference stage. Conclusions: Our results demonstrate the deep‐learning‐based approaches have the potential to compensate for intra‐frame motion by utilizing the later acquired data to drive the convergence of the earlier acquired k‐space components. [ABSTRACT FROM AUTHOR]

The indirect approaches based on the responses of specially designed moving vehicles on bridges to extract bridge dynamic properties have received great research attention. Wavelet transform (WT) is shown to be a useful tool for the analysis of vehicle responses and bridge damage detection in the vehicle-bridge interaction system. However, past studies have demonstrated that road surface roughness poses difficulty in applying wavelet analysis to successfully detect bridge damage. In this paper, a two-step method is proposed for bridge damage detection based on WT analysis of the residual contact response of the front and rear vehicle wheels of a four degrees of freedom (4-DOF) moving vehicle to reduce the influence of road surface roughness. In the first step, the generalized Kalman filter under unknown input (GKF-UI) developed by the authors is used to identify the unknown contact forces and the state vector of the vehicle. Due to the advantages of GKF-UI, acceleration and displacement sensors can be installed conveniently on the vehicle body instead of on the wheel axles in previous studies. Then, the contact-point bridge deflection responses of the front and rear vehicle wheels are estimated from the identified contact force and vehicle state. In the second step, the residual contact-point bridge deflection response is obtained by subtracting the front contact-point bridge deflection and rear contact-point bridge deflection with a time shift to reduce the influence of road surface roughness. Then, the locations of bridge damage can be identified based on WT of the singularities of residual contact-point bridge deflection response. Numerical examples of bridge damage detection demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Aquatic organisms have evolved exceptional propulsion and even transoceanic migrating capabilities, surpassing artificial vessels significantly in maneuverability and efficiency. Understanding the hydrodynamic mechanisms of aquatic organisms is crucial for developing advanced biomimetic underwater propulsion vehicles. Underwater tetrapods such as sea turtles use fins or flippers for propulsion, which exhibit three rotational degrees of freedom, including flapping, sweeping, and pitching motions. Unlike previous studies that often simplify motion kinematics, this study employs a specially designed experimental device to mimic sea turtle fins' motion and explore the impact of pitching amplitude, asymmetric pitching kinematics, and pausing time on lift and thrust generation. Force transducers and particle image velocimetry techniques are used to examine the hydrodynamic forces and flow field, respectively. It is found that boosting the fin's pitching amplitude enhances both its lift and thrust efficiency to a certain extent, with a more pronounced effect on thrust performance. Surprisingly, the asymmetrical nature of the pitching angle's pausing time within one flapping cycle significantly influences the lift and thrust characteristics during sea turtle swimming; extending the pausing time during the forward and upward flapping process improves lift efficiency; and prolonging the pausing time during the downward flapping process enhances thrust efficiency. Furthermore, the mechanism for high lift and thrust efficiency is revealed by examining the vortices shed from the fin during different motion kinematics. This research contributes to a more comprehensive understanding of the fin's hydrodynamic characteristic, providing insights that can guide the design of more efficient biomimetic underwater propulsion systems. [ABSTRACT FROM AUTHOR]

This study demonstrates robot technology for harvesting edible bird's nests within swiftlet houses. A comprehensive manipulator's movement analysis of harvesting operation with a separating tool is provided for precisely collecting swiftlet nests. A robotic manipulator mounted on a mobile platform with a vision system is also analyzed and evaluated in this study. The actual harvesting or separating the swiftlet nests is performed with visual servo feedback. The manipulator performs the gross motions of separating tools and removing the nests under computer control with velocity and position feedback. The separating principle between the objective nest and wooden frame has been applied to a demonstration removal of nests using a four-degrees-of-freedom manipulator to perform the gross movements of tool. The actual separations using this system are accomplished as fast as the manipulator can be controlled to perform the necessary deceleration and topping at the end of separating. This is typically 2.0 s. This efficiency underscores the system's capability for swift and precise operation in harvesting an edible bird nest task. [ABSTRACT FROM AUTHOR]

Multi-degree-of-freedom piezoelectric motors have the advantages of high torque and resolution, simple structure, and direct drive, which are widely used in robot wrist joints, deep-sea mechanisms, medical equipment, and space mechanisms. To solve the problems of high force/torque coupling degree and ball low stator and rotor bonding strength of the traditional traveling wave type three-degree-of-freedom piezoelectric spherical motor, a new structure of ball-hinged piezoelectric spherical motor is proposed. Through coordinate transformation and force analysis, the driven mathematical model of the spherical motor is given. The model shows that the three degrees of freedom of the motor are coupled with each other. According to the mathematical model of the spherical motor, the mechanical properties of the motor are analyzed by the computer simulation. The results show that the stalling torque coefficient kt has a linear relationship with the friction coefficient ε and the stator preload Fc, has a nonlinear relationship with the stator radius R and the rotor radius r, and increases with the increase of R and decreases with the increase of r. The no-load speed of motor ωn is not related to the friction coefficient ε and the stator preload Fc, and increases with the increase of R and decreases with the increase of r. The anisotropic characteristics of torque and speed of a spherical motor are further analyzed, which lays a theoretical foundation for the drive control of a spherical motor. [ABSTRACT FROM AUTHOR]

With the rapid development of information and communication technology, intelligent wireless systems have a huge demand for devices with multi‐function integration and multi‐degree of freedom electromagnetic control. In this paper, a multifunctional folded transmitarray antenna (MFTA) using a reconfigurable metasurface is proposed to achieve simultaneous and independent modulation of beam and polarization. The beam scanning, arbitrary wave generator, and polarization conversion functions can be achieved only by adjusting the PIN diode bias on the reconfigurable metasurface. In order to prove the feasibility of the proposed method, a prototype is fabricated and verified by experiments. Both simulated and measured results verify the excellent performance of the MFTA. This work opens a door to multi‐functional integration and multi‐degree of freedom electromagnetic manipulate devices, which have great prospects in areas such as radar detection and wireless communication. [ABSTRACT FROM AUTHOR]

In our earlier research (see [Katsanikas & Wiggins, 2021a, 2021b, 2023a, 2023b, 2023c]), we developed two methods for creating dividing surfaces, either based on periodic orbits or two-dimensional generating surfaces. These methods were specifically designed for Hamiltonian systems with three or more degrees of freedom. Our prior work extended these dividing surfaces to more complex structures such as tori or cylinders, all within the energy surface of the Hamiltonian system. In this paper, we introduce a new method for constructing dividing surfaces. This method differs from our previous work in that it is based on 3D surfaces or geometrical objects, rather than periodic orbits or 2D generating surfaces (see [Katsanikas & Wiggins, 2023a]). To explain and showcase the new method and to present the structure of these 3D surfaces, the paper provides examples involving Hamiltonian systems with three degrees of freedom. These examples cover both uncoupled and coupled cases of a quadratic normal form Hamiltonian system. Our current paper is the first in a series of two papers on this subject. This research is likely to be of interest to scholars and researchers in the field of Hamiltonian systems and dynamical systems, as it introduces innovative approaches to constructing dividing surfaces and exploring their applications. [ABSTRACT FROM AUTHOR]

Our paper is a continuation of a previous work referenced as [Katsanikas & Wiggins, 2024b]. In this new paper, we present a second method for computing three-dimensional generating surfaces in Hamiltonian systems with three degrees of freedom. These 3D generating surfaces are distinct from the Normally Hyperbolic Invariant Manifold (NHIM) and have the unique property of producing dividing surfaces with no-recrossing characteristics, as explained in our previous work [Katsanikas & Wiggins, 2024b]. This second method for computing 3D generating surfaces is valuable, especially in cases where the first method is unable to achieve the desired results. This research aims to provide alternative techniques and solutions for addressing specific challenges in Hamiltonian systems with three degrees of freedom and improving the accuracy and reliability of generating surfaces. This research may find applications in the broader field of dynamical systems and attract the attention of researchers and scholars interested in these areas. [ABSTRACT FROM AUTHOR]

With the development of miniaturization and integration, multifunctional optical devices are necessary. However, its practical realization is a critical challenge due to the lack of simple structures with multiple functionalities. Here, a multimode metasurface is proposed by simply placing polymer nanocubes on the lithium niobate (LN) thin film. The intriguing properties of the integrated structure include high‐quality (Q) factors and different spectral characteristics, associated with quasi‐guide modes (GM) and Mie modes, respectively. The experiment demonstration reveals that Q factors of four modes are larger than 1000 and a second harmonic generation (SHG) enhancement factor of 25.4 is obtained, featuring strong light‐matter interaction. Importantly, the abundant spectral characteristics greatly boost three degrees of freedom, i.e., polarization, incident angle, and slot, to realize multifunctional designs. The results provide a sophisticated platform for developing high‐performance LN metasurfaces with the advantages of simplified fabrication processes and multifunctionality. The strategy can also be extended to other material systems, enabling the flexibility of metasurface‐inspired subwavelength engineering. [ABSTRACT FROM AUTHOR]

Optical payloads are widely used in many fields, such as aerospace, drones, autonomous vehicles, or other highly precise instrumentation. Vibration is one of the causes that greatly affect the quality of data of highly precise optical payloads. Recently, many researcher focuses on isolating the vibration for the precise equipment, those study just only mention the overcoming of vibration in one or two directions, but in reality, an object will exist vibration in six directions in space. Therefore, it is necessary to find a new mechanism that can isolate vibration in six axes in space. The parallel mechanism is considered a viable system because of its strengths in accuracy, rigidity, and stability. In this research, the author proposes a novel 6-DOF passive vibration isolator based on the Steward platform with S-shaped legs. We have developed a 6-DOF passive vibration isolator using the S-shaped non-linear stiffness and damping characteristics. In this study, the model parameters of a vibration isolator device with legs using an S-shaped will be proposed. Based on geometrical parameters and vibration sources and some loads assuming the structure's durability problem will be calculated and evaluated the efficiency of the isolator at different frequencies. With the specially designed S-shaped it can be deformity like a spring, and with the change of structural and material parameters, we can adjust the system's stiffness and damping capacity. Due to the high static stiffness and low dynamic stiffness of each leg, and thus it is designable to isolate very well vibration isolation performance in all six directions. This research is organized as firstly the kinematics and 3D model are introduced. Secondly, the stiffness matrix of the novel 6-DOF passive vibration isolators is presented. Statics analysis of the 6-DOF passive vibration isolators revealed that the S-shaped structure provides sufficient load-carrying capacity and isolation due to its very good static nonlinear stiffness. The dynamic stiffness of the isolator in this study in each direction is very low but does not reduce the load-carrying capacity of the structure. By changing the structure and material parameters (which is very simple in a purely passive manner), we can completely adjust both the dynamic and static stiffness of the mechanism. The last series of numerical simulation results on displacement and a statics response in random excitation is carried out to show the effectiveness of the proposed 6-DOF passive vibration isolator, as well as the influence of structural parameters on vibration attenuation performance. The simulation results with the different exciting are shown to demonstrate the efficiency of the 6-DOF passive vibration isolators. Considering its simulation results A proposed new 6-DOF isolator will be applied in various engineering practices with multi-degree of freedom vibration isolation such as for precise optical payloa [ABSTRACT FROM AUTHOR]

In this paper, an ultracompact combined sensor for displacement and angle-synchronous measurement is proposed based on the self-imaging effect of optical microgratings. Using a two-grating structure, linear and angular displacement can be measured by detecting the change of phase and amplitude of the optical transmission, respectively, within one single structure in the meantime. The optically transmitted properties of the two-grating structure are investigated in both theory and simulation. Simulated results indicate that optical transmission changes in a sinusoidal relationship to the input linear displacement. Meanwhile, the amplitude of the curve decreases with an input pitch angle, indicating the ability for synchronous measurement within one single compact structure. The synchronous measurement of the linear displacement and the angle is also demonstrated experimentally. The results show a resolution down to 4 nm for linear displacement measurement and a maximum sensitivity of 0.26 mV/arcsec within a range of ±1° for angle measurement. Benefiting from a simple common-path structure without using optical components, including reflectors and polarizers, the sensor shows ultra-high compactness for multiple-degrees-of-freedom measuring, indicating the great potential for this sensor in fields such as integrated mechanical positioning and semiconductor fabrication. [ABSTRACT FROM AUTHOR]

In this paper, a delayed distributed proportional control is developed for a class of multiple-input-multiple-output systems in order to reduce the effects of external disturbances and uncertain dynamics. The system under consideration is a three degrees-of-freedom planar robot, consisting of an active joint driving the first link and passive flexible joints for the second and third links. The control challenge for this system is to drive the flexible arm around the desired setpoint or trajectory by controlling the first link. Actually, by using a specific Lyapunov-Krasovskii storage functional associated with a constrained optimization problem, the robustness of the proposed proportional retarded control action is achieved. This analysis, together with the attractive ellipsoid concept allows to conclude with Ultimately-Uniformly-Bounded stability. The closed-loop control algorithm is tested in numerical simulation and a comparative study with some existing recent control schemes based on the performance error is presented. • The proposed control scheme belongs to a class of multivariable proportional time delay distributed controller. • After finite time the trajectories of a flexible manipulator stay within reduced size attractive ellipsoid. • Ultimate Uniformly Bounded Stability of the controlled system is demonstrated by using a Lyapunov-Krasovskii functional. • The proposed algorithm can also be adapted for a class of nonlinear uncertain/disturbed multivariable output systems. • A sufficient condition to guarantee the feasibility of specific Bilinear Matrix Inequality is presented. [ABSTRACT FROM AUTHOR]

High-precision positioning systems play a crucial role in various industrial applications. This study focuses on improving the performance of a high-precision multi-degrees-of-freedom (DOF) stage. In terms of the controller design, the following two key challenges must be addressed: the cross-decoupling of different DOFs and the impact of external disturbances. To address these problems, a self-tuning approach is proposed for simultaneous decoupling and disturbance suppression. Initially, the stage undergoes static decoupling using a data-based approach, facilitating feedback control for each DOF through single-input, single-output controllers. Addressing dynamic coupling and external disturbance challenges, we introduced a comprehensive evaluation index and a self-tuning multi-input, multi-output disturbance observer. This approach enabled the evaluation and optimization of the disturbance compensation for all DOFs, ensuring optimal positioning accuracy. Finally, we tested the proposed method using a high-precision multi-DOF stage with a real-time control platform. The results demonstrated a significant reduction in the standard deviations of positioning errors in the rx, ry, and z directions by 46%, 58%, and 6%, respectively. The approach used in this study opens avenues for advancements in the design and control of complex multi-DOF systems. [ABSTRACT FROM AUTHOR]

In our previous work, we developed two methods for generalizing the construction of a periodic orbit dividing surface for a Hamiltonian system with three or more degrees of freedom. Starting with a periodic orbit, we extend it to form a torus or cylinder, which then becomes a higher-dimensional object within the energy surface (see [Katsanikas & Wiggins, 2021a, 2021b, 2023a, 2023b]). In this paper, we present two methods to construct dividing surfaces not from periodic orbits but by using 2D surfaces (2D geometrical objects) in a Hamiltonian system with three degrees of freedom. To illustrate the algorithm for this construction, we provide benchmark examples of three-degree-of-freedom Hamiltonian systems. Specifically, we employ the uncoupled and coupled cases of the quadratic normal form of a Hamiltonian system with three degrees of freedom. [ABSTRACT FROM AUTHOR]

This paper reports the development and displacement self-sensing of a new four degrees-of-freedom (DOF) piezoelectric micromanipulator. In particular, each micromanipulator arm can move along the clamping and vertical directions, constructing with two degrees of freedom, and two micromanipulator arms exhibit four degrees of freedom. Thus, it improves operational flexibility. Meanwhile, the self-sensing method avoids additional external sensors when detecting output displacements. The piezoelectric micromanipulator is devised based on the transverse inverse piezoelectric effect of two sets of vertical spatial crossings. Static and dynamic characteristics are analyzed via finite element optimization of geometric parameters. Then, a displacement self-sensing method based on charge integration is proposed. This method measures the generated charge on the clamping arm surface from the piezoelectric wafer deformation under the driving voltage. A self-sensing circuit is designed to obtain the surface charge of the clamping arm. Then, several experiments are conducted to test the micromanipulator. The maximum displacements of the designed micromanipulator are about 66.29 μm and 63.09 μm along clamping and vertical directions. Moreover, output displacements, response time, and inherent frequencies obtained based on the self-sensing method agree well with those with laser sensors. In addition, an operation application for micro-shaft assembly is presented, demonstrating the grasping and docking operations of the micro-shaft in the clamping and vertical directions. • A new four-degree-of-freedom piezoelectric micromanipulator. • Self-sensing method for output displacement based on integral charge. • Various experiments and verifications. [ABSTRACT FROM AUTHOR]

This paper presents a mass-spring model to predict the normal incidence acoustic response of a metamaterial composed of a compact linear periodic array of dead-end resonators. The dead-end resonators considered are ring-shaped Helmholtz resonators. The model is based on a mass-spring analogy and considers the thermoviscous losses in the metamaterial following an effective fluid approach. A matrix equation of acoustic motion is derived for the finite case of N-periodic arrays. Under external excitation, its direct solution predicts the sound absorption coefficient and transmission loss. Under the homogeneous case, the solution of its associated eigenvalue problem predicts the acoustic eigenfrequencies and mode shapes. The dispersion relation is also solved to predict the beginning of the first stopband, and a low frequency approximation allows development of a formula to estimate the first eigenfrequency. The results show that the system with N degrees of freedom has three stopbands over the frequency range studied, with zero sound absorption and transmission. The model also helps to understand how the acoustic dissipation, at a given resonant frequency, is affected by the position of the acoustic velocity nodes (eigenmodes) in the geometry of the metamaterial. Prototypes are designed, manufactured, and tested in an impedance tube to validate the model. [ABSTRACT FROM AUTHOR]

Introduction/purpose: The study of vehicle suspension is a challenge for researchers in the field of vehicles regarding the impact of the suspension system on vehicle performances such as ride comfort, road holding, and working space. This paper presents the simulation of the Land Rover Defender 110 vehicle in the roll plane (half vehicle) in Simulink/MATLAB. The obtained results were compared with the results obtained in the ADAMS/CAR software package of the Land Rover Defender 110 simulation model previously experimentally validated. The Defender 110 vehicle has a dependent suspension system in both axles and a passive suspension type with four degrees of freedom (4 DOF). Methods: The equations of the system can be solved mathematically with a scheme in Simulink/MATLAB while half-vehicle modeling has been done in ADAMS/CAR. Results: The comparison of the vehicle characteristics obtained by the two simulation methods was done for three different scenarios, and it was noticed that there is a good correlation between them. Conclusion: It was concluded that the Defender 110 vehicle simulation model in Simulink/MATLAB is validated. The validated model can be used to perform suspension system optimization in future work [ABSTRACT FROM AUTHOR]

In the upcoming epochs, conventional energy may deplete soon. Thus, the use of conventional energy in the power industries need to be supplemented by non‐conventional energy resources. This would result in loss of synchronisms in the power grids owing to the fact that solar and wind alternate their attributes expeditiously with change in atmospheric phenomenon. To ameliorate frequency deviation within a specific range automatic generation control (AGC) implements forced allowance on system operation. A three area thermal with photovoltaic (PV), electric vehicle (EV), wind system is considered under deregulated environment to develop and to judge the efficacy of newly developed cascade fractional order hybrid controller combination of (FOTID & 3DOF‐PID). Comparing the aforementioned controller to other controllers such as the three degree of freedom proportional‐integral‐derivative (3DOF‐PID), the fractional order tilt‐integral‐derivative (FOTID) and the proportional‐integral‐derivative (PID) justifies the system's effectiveness. This assessment has been accomplished by a trendy optimization technique such as hybrid whale optimization algorithm (HWOA). However, the main intent of this write‐up is to fabricate a cascade fractional order (CC‐FO) hybrid controller that would act as the new control mechanism for the proposed system under deregulated scenario. It has been found that the suggested CC‐FO hybrid controller stabilizes the system (i.e., Under step load disruptions, frequency deviation and tie‐line power become zero) in the shortest amount of time possible. Additionally, it is seen that the recommended controller can control a wide range of nominal loading circumstances and system characteristics, demonstrating its robustness. [ABSTRACT FROM AUTHOR]

Quadrupeds are capable of dynamic movements such as fast running and long-distance jumping due to their flexible and elastic torso structures. In this paper, a compliant parallel mechanism is proposed as a bionic torso to simulate the diversified behaviors and agile locomotion of the tetrapod torso. The spring module is incorporated into the limb of the parallel mechanism to absorb external shocks, cushion, and dampen vibrations, thus improving the compliance performance of the bionic torso. For the compliant parallel mechanism, its kinematics and kinetics are analyzed, and the overall electromechanical system and control framework are devised. The multidimensional damping dynamic characteristics of the proposed mechanism are qualitatively analyzed by simplifying the limb into a spring–mass damping system. The parallel mechanism with compliant spring modules absorbs external forces to different degrees with different stiffness coefficients to avoid damage to the structure by external impacts. The parallel mechanism with different initial positions exhibits the inherent variable stiffness characteristics of the mechanism. The parallel mechanism simulates the diverse behavior of the animal torso, with independent and synthesized locomotor behavior of the six underlying motion patterns. Simulations and experiments demonstrated that the compliant parallel mechanism is effective in vibration damping and cushioning, with a rapid response and small steady-state error. The motion of the compliant parallel mechanism in one direction and the motion of the integrated multi-degree of freedom (DOF) are confirmed and exhibited in the behavioral experiment. [ABSTRACT FROM AUTHOR]

The study of formal stability of equilibrium positions of a multiparametric Hamiltonian system in a generic case is traditionally carried out using its normal form under the condition of the absence of resonances of small orders. In this paper we propose a method of symbolic computation of the condition of existence of a resonance of arbitrary order for a system with three degrees of freedom. It is shown that this condition for each resonant vector can be represented as a rational algebraic curve. By methods of computer algebra the rational parametrization of this curve for the case of an arbitrary resonance is obtained. A model example of some two-parameter system of pendulum type is considered. [ABSTRACT FROM AUTHOR]

As human–robot interaction and teleoperation technologies advance, anthropomorphic control of humanoid arms has garnered increasing attention. However, accurately translating sensor-detected arm motions to the multi-degree freedom of a humanoid robotic arm is challenging, primarily due to occlusion issues with single-sensor setups, which reduce recognition accuracy. To overcome this problem, we propose a human-like arm control strategy based on multi-sensor fusion. We defined the finger bending angle to represent finger posture and employed a depth camera to capture arm movement. Consequently, we developed an arm movement tracking system and achieved anthropomorphic control of the imitation human arm. Finally, we verified our proposed method's effectiveness through a series of experiments, evaluating the system's robustness and real-time performance. The experimental results show that this control strategy can control the motion of the humanoid arm stably, and maintain a high recognition accuracy in the face of complex situations such as occlusion. [ABSTRACT FROM AUTHOR]

Type synthesis of parallel mechanism is regarded as the theoretical basis and source for the original innovation design of mechanical devices and robots. A new method for type synthesis of the fully-decoupled two-rotational and one-translational (2R1T) parallel mechanisms with three degrees of freedom is proposed in this paper. Based on the actuation wrench screw theory, the mathematical model mapping the input and output velocity vector space of the fully-decoupled 2R1T parallel mechanism is established. The actuation wrench screws and the actuated twist screws of the corresponding branches are derived according to the mathematic model. The forms of the unactuated screws are determined in terms of the reciprocal product theory. Structural synthesis of the branch chains is realized. Then type synthesis of parallel mechanisms is completed as well and lots of novel mechanisms are obtained. Finally, a 2RUPU-PU parallel mechanism synthesized is taken as an example to analyze its mobility and kinematics. Results show that the mechanism has two-rotational and one-translational degrees of freedom and its Jacobian matrix is a diagonal matrix, i.e., it has the fully-decoupled kinematic characteristics. Therefore, the method proposed is correct and effective to synthesize the fully-decoupled 2R1T parallel mechanisms. [ABSTRACT FROM AUTHOR]

To minimize potential damage, it is crucial to carefully harvest greenhouse crops like tomatoes at the optimal time. To improve this process, the use of robotic harvesting methods has been proposed. The robotic harvester consists of important components including a mobile platform with robotics, displacement units that can move linearly or rotationally, a manipulator, a gripper, a camera, an image processingbased fruit detection unit, and a depth sensor. A robotic manipulator with three linear degrees of freedom was created in the Cartesian coordinate system. To enhance its capabilities, a gripper mechanism was incorporated, providing an additional rotational degree of freedom. The primary objective of this robot was to autonomously detect the position of ripe tomatoes. To achieve this, the displacement control of both the robot arms and gripper was executed through commands from the image processing unit. Different channel of some color space was studied. The effectiveness of this channels was assessed by conducting tests in the presence of tomato plants. The accuracy of the system in approaching the crop were thoroughly evaluated. Channels H of HSV color space, Cr of YCrCb color space, and a of Lab color space showed better result. The accuracy of detecting ripe tomatoes in channel H of HSV color space was the highest and 87%. [ABSTRACT FROM AUTHOR]