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Abstract This paper proposed a saturated adaptive barrier sliding mode control (SABSMC) for disturbed systems with parameter uncertainty, external disturbance, and input saturation. One distinctive feature of the proposed method is that even under the influence of input saturation, it is able to drive the system trajectory into a prespecified neighbourhood of the sliding surface, independent of the upper limit of lumped disturbance. Moreover, attributing to the designed adaptive laws, the switching gain of the proposed method can be adaptively adjusted in a wise manner. Another attractive feature of the proposed method is that it removes any presumption of constant upper limit on the lumped disturbance. Instead, SABSMC utilises a more rational state‐dependent upper limit assumption. The system dynamics of the closed‐loop system is analysed via the Lyapunov method in the presence of parameter uncertainty, external disturbance, and input saturation. The effectiveness of the proposed method is confirmed through numerical simulations.

The unmanned aerial manipulator (UAM) is a kind of aerial robot that combines a quadrotor aircraft and an onboard manipulator. This paper focuses on the problems of structure design, system modeling, and motion control of an UAM applied for water sampling. A novel, light, cable-driven UAM has been designed. The drive motors installed in the base transmit the force and motion remotely through cables, which can reduce the inertia ratio of the manipulator. The Newton–Euler method and Lagrangian method are adopted to establish the quadrotor model and manipulator model, respectively. External disturbances, model uncertainty, and joint flexibility are also accounted for in the two submodels. The quadrotor and manipulator are controlled separately to ensure the overall accurate aerial operation of the UAM. Specifically, a backstepping control method is designed with the disturbance observer (BC-DOB) technique for the position loop and attitude loop control of the quadrotor. A backstepping integral fast terminal sliding mode control based on the linear extended state observer (BIFTSMC-LESO) has been developed for the manipulator to provide precise manipulation. The DOB and LESO serve as compensators to estimate the external disturbances and model uncertainty. The Lyapunov theory is used to ensure the stability of the two controllers. Three simulation cases are conducted to test the superior performance of the proposed quadrotor controller and manipulator controller. All the results show that the proposed controllers provide better performances than other traditional controllers, which can complete the task of water quality sampling well.

Abstract Space-deployable mechanisms can be used as supporting structures for large-diameter antennas in space engineering. This study proposes a novel method for constructing the surface design of space reflector antennas based on polar scissor units. The concurrency and deployability equations of the space scissor unit with definite surface constraints are derived using the rod and vector methods. Constraint equations of the spatial transformation for space n-edge polar scissor units are summarized. A new closed-loop deployable structure, called the polar scissor deployable antenna (PSDA), is designed by combining planar polar scissor units with spatial polar scissor units. The over-constrained problem is solved by releasing the curve constraint that locates at the end-point of the planar scissor mechanism. Kinematics simulation and error analysis are performed. The results show that the PSDA can effectively fit the paraboloid of revolution. Finally, deployment experiments verify the validity and feasibility of the proposed design method, which provides a new idea for the construction of large space-reflector antennas.

This paper focuses on the tracking problem for fully-actuated mechanical systems with uncertain parameters and external disturbances. Based on the state feedback control of contraction analysis, the robust controller with extra gains is suggested to provide for the tracking of mechanical systems with uncertainties. The proposed control scheme can be redesigned with dual ideas and theoretically prove that the robust control renders uniform roundedness. Further more, the inertia matrices being uniformly bounded above are limited. The simulation is proposed to account for the effectiveness and robustness of the provided method.

The stabilization problem for a class of discrete network control system with time-delay and packet loss in both S-C side and C-A side is researched in this paper. Firstly, two independent discrete Markov chains are used to describe the network time-delay from sensor to controller and the network time-delay from controller to actuator. Two random variables obeying the Bernoulli distribution are employed to describe the packet loss between the sensor and the controller and the packet loss between the controller and the actuator. Secondly, a mathematical model for closed-loop system is established. By constructing the appropriate Lyapunov-Krasovskii functional, the sufficient conditions for the existence of the controller and observer gain matrix are obtained under the condition that the transition probabilities of S-C time-delay and C-A time-delay are both partly unknown. Finally, two examples are exploited to illustrate the effectiveness of the proposed method.

This study focuses on stabilization problem of a class of nonlinear systems. Generally, Lyapunov stability-based sliding mode technique is widely used to design controllers for nonlinear systems with uncertainties. In this paper, however, based on contraction property and sliding surfaces, the sliding mode control is suggested to provide incremental stability for nonlinear systems with uncertainties. The effectiveness of the method is illustrated by numerical simulations.

This paper focuses on improving tracking performance of totally uncoupled compliant micromanipulator based on robust control method of elliptical hysteresis model. The hysteresis model and hysteresis compensation model for proposed mechanism based on Piezoelectric transducer (PZT) are established by using elliptical model method. The values of elliptical hysteresis model parameters are identified by simulating method with different frequencies of control input. The uncertainty model is also established, the values of corresponding estimated parameters are conformed by experiment method. Based on the uncertainty model and elliptical hysteresis model, the robust tracking control method is presented and utilized to evaluate the tracking performance of proposed mechanism under inputting different tracking curves. The proposed method can accurately control the output displacement and improve tracking performance of this mechanism, which are validated and carried out by using experimental studies. Additionally, the coupling errors between two directions are kept within 0.14% and the tracking errors for different curves are within 2.5%.

The H∞ control problem for networked control system with data packet dropout in both S-C link and C-A link via observer-based controller is researched in this paper. Firstly, the networked control system with data packet dropout in both S-C link and C-A link is modeled as a discrete Markov jump linear system. Secondly, the sufficient and necessary conditions on the stochastic stability of the closed-loop system is established, the solution method of the controller and observer gain matrix are also given on condition that the transition probability matrix is completely known and partly unknown, respectively. The minimal disturbance suppression performance index is also obtained. Finally, two simulation examples illustrate the validity of the proposed method.

A microrobot with untethered control in 3D space is a good choice to be applied in the fields of biomedicine with in small and confined workspace. In this paper, an electromagnetic actuation system (EMA) which combined with Helmholtz coil and Maxwell coil for the microrobot 5 DOF locomotion in 3D space is built. The magnetic field analysis of the proposed 3D EMA system was analyzed by finite-element-method (FEM) with multi-physics COMSOL software. The proposed EMA system can produce magnetic field with different characteristics such as a controllable uniform gradient magnetic field, a rotating magnetic field and a oscillating magnetic field in a three-dimensional space by independently changing the current in each coil. In this paper the 3D motion dynamic equation model of microrobot was established. A novel control method for the gravity compensation for the wireless locomotive microrobot was proposed. The proposed method has the property that the direction of magnetic flux and the locomotion path of the microrobot are independent. Meanwhile, it can achieve the horizontal motions or nearly horizontal motions and overcome the gravity well at the same time. It has been verified by experiments in 3D liquid environment. With the proposed method, the microrobot shows good performance in horizontal motions as well as various motions in the 3D space.

The two-mode-dependent controller design problem for networked Markov system with time-delay in both S/C link and C/A link is investigated in this paper. Two independent Markov chains are used to describe the time-delay in S/C link and C/A link. A two-mode-dependent state feedback controller is proposed that depends on both the S/C time-delay and the mode of the Markov controlled plant. The sufficient conditions on the stochastic stability of the closed-loop system are established. The design method of the controller is also proposed on condition that the transition probability matrices of S/C time-delay and mode of the controlled plant are completely known and partly unknown respectively. A numerical example is exploited to illustrate the effectiveness and superiority of the proposed method.

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At present, there is a problem of visual area switching in the existing SRL (supernumerary robotic limb) operation methods. In response to this problem, the authors’ previous work proposed a new SRL operation method called relatively independent operation, and proposed a corresponding software architecture. The purpose of this paper is to solve the theoretical problems and engineering realization problems of the human-SRL skeleton algorithm module in the software architecture. Therefore, modeling, data collection, data processing, and visualization of a human-SRL system are studied in this paper. Firstly, a human-SRL skeleton visualization simulation system is developed. The condition setting, the applications, and the core algorithm of the simulation system are introduced. The core algorithm mainly contains four types of important functions, namely skeleton model building functions, human-SRL data collection functions, human-SRL data processing functions, and skeleton visualization functions. Secondly, the implementation principles of these four functions are described: (1) For the skeleton model building functions, a human-SRL skeleton model is proposed which is an integration of a human skeleton model and an SRL skeleton model. The construction methods of these three skeleton models are described. (2) For the remaining functions, how to collect and process human data, SRL data, human-SRL data, and how to visualize a human-SRL skeleton are described. Finally, the visualization effect of the developed simulation system on human-SRL skeleton movement is verified by experiments, which proves the correctness of the functions in the simulation system.

This paper proposes a multi-power reaching law-based sliding-mode control (SMC) for uncertain discrete-time systems. The proposed controller mainly consists of the multi-power function along with the perturbation estimation. Different from the existing similar works, the control gains of the controller are adaptively adjusted by the multi-power function, i.e., three power terms, according to different stages of the convergence process. Hence, the system trajectory of the controlled system can be forced toward the sliding surface with a faster convergence rate. The corresponding sliding-mode dynamics and the reaching steps to the sliding surface are theoretically analyzed. A practical example is given to examining the validity of the proposed method. The simulation results show that the proposed method reduces the reaching steps while guaranteeing better control accuracy than the single power method.

This paper focuses on improving thermal efficiency and reducing unburned carbon in fly ash by optimizing operating parameters via a novel high-efficient swarm intelligence optimization algorithm (grey wolf optimizer algorithm, GWO) for coal-fired boiler. Mathematical models for thermal efficiency and unburned carbon in fly ash of the discussed boiler are established by artificial neural network (ANN). Based on the ANN models, the grey wolf optimizer algorithm is used to obtain higher thermal efficiency and lower unburned carbon by optimizing the operating parameters. Meanwhile, the comparisons between GWO and particle swarm optimization (PSO) and genetic algorithm (GA) show that GWO has superior performance to GA and PSO regarding the boiler combustion optimization. The proposed method can accurately optimize the boiler combustion performance, and its validity and feasibility have been experimentally validated. Additionally, a run of optimization takes a less time period, which is suitable for the real-time optimization.

In recent years, cable-driven parallel robots (CDPRs) have drawn more and more attention due to the properties of large workspace, large payload capacity, and ease of reconfiguration. In this paper, we present a kinematic and dynamic modeling and workspace analysis for a novel suspended CDPR which generates Schönflies motions. Firstly, the architecture of the robot is introduced, and the inverse and forward kinematic problems of the robot are solved through a geometrical approach. Then, the dynamic equation of the robot is derived by separately considering the moving platform and the drive trains. Based on the dynamic equation, the dynamic feasible workspace of the robot is determined under different values of accelerations. Finally, experiments are performed on a prototype of the robot to demonstrate the correctness of the derived models and workspace.

With flexure-based micro-positioning stages (MPSs) being in high demand for high-precision applications, the performance and cost of flexure-based MPSs are two issues that urgently need to be addressed. In addition, the current MPSs are being developed toward complex spatial configurations, which further precludes monolithic fabrication. To address the aforementioned issues, modular MPSs using designed standardized modules are introduced in this paper. Firstly, the motivations are described, followed by the modular design. In addition, a new assembly concept analogy with composing compounds is proposed for guiding module assembly, including some proposed planar and spatial configurations. For validation, the static and dynamic performances of modular MPSs with respect to different modules and materials are presented as case studies. The proposed modular MPSs can provide better flexibility and functionality for further applications.

The Preisach model is a typical scalar mathematical model used to describe the hysteresis phenomena, and it attracts considerable attention. However, parameter identification for the Preisach model remains a challenging issue. In this paper, an improved particle swarm optimization (IPSO) method is proposed to identify Preisach model parameters. Firstly, the Preisach model is established by introducing a Gaussian−Gaussian distribution function to replace density function. Secondly, the IPSO algorithm is adopted to Fimplement the parameter identification. Finally, the model parameter identification results are compared with the hysteresis loop of the piezoelectric actuator. Compared with the traditional Particle Swarm Optimization (PSO) algorithm, the IPSO algorithm demonstrates faster convergence, less calculation time and higher calculation accuracy. This proposed method provides an efficient approach to model and identify the Preisach hysteresis of piezoelectric actuators.

Compliant mechanisms are popular to the applications of micro/nanoscale manipulations. This paper proposes a novel triaxial parallel-kinematic compliant manipulator inspired by the Tripteron mechanism. Compared to most conventional triaxial compliant mechanisms, the proposed manipulator has the merits of structure compactness and being free of assembly error due to its unique configuration and the utilize of 3D printing technology. The compliance matrix modeling method is employed to determine the input stiffness of the compliant manipulator, and it is verified by finite-element analysis (FEA). Results show that the deviations between simulation works and the derived analytical models are in an acceptable range. The simulation results also reveal that the compliant manipulator can achieve a 16 μm × 16 μm × 16 μm cubic workspace. In this motion range, the observed maximum stress is much lower than the yield strength of the material. Moreover, the dynamic characteristics of the manipulator are investigated via the simulations as well.

This article aims to present a minimum-jerk trajectory planning approach to address the smooth trajectory generation problem of 3-prismatic-universal-universal translational parallel kinematic manipulator. First, comprehensive kinematics and dynamics characteristics of this 3-prismatic-universal-universal parallel kinematic manipulator are analyzed by virtue of the accepted link Jacobian matrices and proverbial virtual work principle. To satisfy indispensable continuity and smoothness requirements, the discretized piecewise quintic polynomials are employed to interpolate the sequence of joints’ angular position knots which are transformed from these predefined via-points in Cartesian space. Furthermore, the trajectory planning problem is directly converted into a constrained nonlinear multi-variables optimization problem of which objective function is to minimize the maximum of the joints’ angular jerk throughout the whole trajectory. Finally, two typical application simulations using the reliable sequential quadratic programming algorithm demonstrate that this proposed minimum-jerk trajectory planning approach is of explicit feasibility and appreciable effectiveness.

Based on normal vector and particle swarm optimization (NVP), a point cloud registration algorithm is proposed by searching the corresponding points. It provides a new method for point cloud registration using feature point registration. First, in order to find the nearest eight neighbor nodes, the k -d tree is employed to build the relationship between points. Then, the normal vector and the distance between the point and the center gravity of eight neighbor points can be calculated. Second, the particle swarm optimization is used to search the corresponding points. There are two conditions to terminate the search in particle swarm optimization: one is that the normal vector of node in the original point cloud is the most similar to that in the target point cloud, and the other is that the distance between the point and the center gravity of eight neighbor points of node is the most similar to that in the target point cloud. Third, after obtaining the corresponding points, they are tested by random sample consensus in order to obtain the right corresponding points. Fourth, the right corresponding points are registered by the quaternion method. The experiments demonstrate that this algorithm is effective. Even in the case of point cloud data lost, it also has high registration accuracy.

Traditional rigid actuators are not applicable to robot applications involving explosive actions. Solutions suggested by previous studies have mainly focused on the concept of stiffness variation, its design and verification, and the explosive actions of variable stiffness joint actuators. This paper proposes a variable stiffness actuator that features a leaf spring as the elastic element and a pair of disks with two Archimedes spiral grooves as the stiffness adjusting mechanism, maintaining φ114 mm×130 mm overall dimensions and a full range (i.e., 127-2095 Nm/rad) of stiffness variation driven by a 7.2-W motor and, therefore, creating a competitive advantage in both compactness and energy saving capacity. The proposed actuator is intended as a dynamics model to predict the exact kicking speed under any given initial conditions of joint stiffness, kicking time, and load mass and for uses in the joints of industrial and/or service robots that frequently involve explosive actions.

Wheeled robots exhibit fast and stable motion on a flat road but lack the ability to overcome the obstacles and rough terrains. To address this shortage, a two-wheel hopping robot is proposed by combining the wheel locomotion and bounce movement. A gear train and a four-bar linkage are employed for jumping. In particular, the take-off angle is dependent on the link length of the four-bar linkage, thus providing versatile flight trajectories. Therefore, the dependency of the hopping performance on the four-bar linkage can be maximized. A four-bar linkage with the same length is used for the specific trajectory and balance control of the inverted pendulum model of the prototype. Dynamics analyses and simulations have been conducted to verify the robot design and its parameters. By jumping tests, the hopping performance is compared with other robots in a quantitative manner. The experimental results show that the wheeled hopping robot has the advantages of light mass and jumping height efficiency.