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In this paper, an X-Y position stage simulates flexible loads completing handling or detection tasks in industrial applications are studied. The platform is driven by permanent magnet synchronous motors (PMSM) servo system, which has flexible beams with different natural vibration frequencies on the X-axis and Y-axis. The controller is designed to suppress the vibration of the flexible beams with different frequencies and reducing the contour error. The Euler-Bernoulli beam theory is adopted to obtain the mode shapes and natural frequencies of the flexible beam with clamped and endpoint mass boundary conditions. Analysis shows that the first-order vibration mode contributes the most to the displacement of the flexible beam. The trajectory motion profile based on time-shifted cosine jerk central angle interpolation (CJCI) contains prefilter to suppress low vibration frequencies in the two beams, which does not cause distortion of the actual contour. The linear phase lead iterative learning control (ILC) combined with the contour of CJCI is proposed to reduce the tracking errors of each axis, thereby reducing the overall contour error. The analysis and design process of ILC in frequency domains, which is applied to alleviate noise and disturbance effects. Comparison experiments confirm the effectiveness of the proposed method.

Flexure hinges are basic elements for constructing compliant mechanisms for micro/nano positioning. So far, few investigations have been presented on the multi-axis flexure hinges especially with revolute type notch due to the limitation of manufacturing. In this study, the revolute-notch type multi-axis flexure hinge with Circular-Elliptical-Arc-Hybrid (CEAH) notch profile is investigated. The analytical compliance equations of the CEAH flexure hinges are developed. Finite element analysis (FEA) is carried out to confirm the presented analytical model. Finally, application of the CEAH revolute-notch type flexure hinges is discussed. The presented study demonstrates that the CEAH revolute-notch type multi-axis flexure hinges have potential advantages in developing novel spatial monolithic compliant mechanisms for three dimensional micro/nano-positioning.

The short article reviews the state-of-the-art of multi-axis toolpath planning, especially for polymer extrusion. The existing approaches for geometry-based and performance-based toolpath planning are emphasized and highlighted. The future perspectives of continuous fiber-reinforced composites are addressed to overcome the research gaps as well as improve the performance of products induced by polymer extrusion.

This paper presents the design and characterization of a new multi-axis force/torque sensor based on resonant technology. This sensor is capable of simultaneously estimating the three force components as well as the three torque components. It is designed for use in collaborative robotics applications and can be integrated into handles or grippers of robotic manipulators to estimate interactions between robots and humans. Compared to the technologies currently in use and based on strain gauges, this system offers many advantages, particularly in terms of both safety and redundancy. This paper describes the design of this sensor and then compares the prototype to a state-of-the-art commercial sensor. Comparisons show that the proposed technology is at least as efficient as the industrial system, although its dimensions remain slightly larger.

The article discusses the main methods of manufacturing products by layer-by-layer polymer fusion using non-planar layers. Conclusions are drawn about the disadvantages of these approaches. A proprietary method of manufacturing products on a multi-axis FFF 3D printer is proposed.

This research developed a coupled 3-axis control VTOL autopilot using model-based design (MBD). MBD made the Autopilot compact, testable, and evolvement ready. This paper will present high-level design, key novel approaches, and MBD simulations and experimental results.

This paper proposes an multiusability reinforcement learning controller design method in low-level control of multi-axis rotor configuration unmanned aerial vehicle (UAV). In other reinforcement learning applications, the trained neural network controllers were designed to a model with specific dynamic properties and it usually cannot play a role while the system configuration changed. To fix this problem, we use a six-degree-of-freedom (6-DOF) dynamic model as the prototype of various vehicles to learn the force and moment required for stability during training, and employs a deep neural network directly mapping the states to the actuator commands. The force and moment can be adjusted according to different conditions and applied to different axis multi-rotor. Using reinforcement learning, this paper demonstrate the flight control of quadrotor and hexrotor using trained policy in simulator to present the stability on different multi-rotor structure, and compared the performance with the one previously introduced by trained quadrotor.

Aiming at the present situation of laser aiming device in our country, a new type of laser aiming axis and parallel detection system of the transmission shaft is designed with CCD device and control technology. The system uses special signal processing and algorithm to improve the accuracy of the parallel degree of digital detection. Experimental results show that the detection system is stable and reliable, with high detection accuracy, and has high practicability and popularization value.

The article considers the design and the mathematical model of multi-axis electric drive with permanent magnets. This device is aimed at use in robotics. Description of research depicts the motor construction needed for this drive, the mathematical formulas that descript the interaction between the electromagnet and the permanent magnet in the motor and two control algorithms that provide position control in three angular axes of motion. At the end of the article, the experimental results are shown.

Many manufacturing processes depend on accurate multi-axis movements. Development of drive technology has replaced the need of mechanical couplings and cams in synchronized manufacturing operations. In this paper motion synchronization of a biaxial linear tooth-belt drive is studied and, especially, the effects of the data communication's speed between the control system components on the motion synchronization successfulness is analyzed. Post-print / Final draft

The paper presents main challenges, problems, and steps involved in software implementation of robotic arm control. The arm is a multi axis robotic arm produced by 3rd party companies. It is embedded into a complex CNC cutting system with multiple motion axes and cutting heads. The control algorithm is implemented into existing complex software of real-time control system of the cutting machine. It has to be compatible with all existing and future modules of the software.

This paper proposes a controller design approach to achieve the high reproducibility of earthquake acceleration waveforms in multi-axis shaking table systems. The target shaking table system has an shaking mechanism to excite vibrations in multiple directions, where the cooperation control of each actuator is required to realize precise table motion. In order to conduct an accurate seismic test using the target multi-axis shaking table, a disturbance observer used to improve disturbance suppression capabilities is designed for the feedback control system of each actuator. In addition, an acceleration feedback compensation is added as the minor-loop, to suppress the resonant gain peak in the actuator, because the resonant vibration restricts the expansion of the observer bandwidth. The effectiveness of the designed control system is evaluated by conducting experiments using a test model.

We present a novel electromagnetically actuated Haptic fMRI Interface with five degrees-of-freedom (DOF), HFI-5. The interface uses two three DOF devices connected with a gimbal in a closed kinematic chain to achieve three-axis translation and two-axis rotation. To highlight the device's design, we develop a taxonomy of similar devices and demonstrate why HFI-5's design excels. We use a cross-correlation based novel analysis method to demonstrate that HFI-5 is transparent by showing that it does not affect unconstrained subject motions. This is due to its low friction (< 0.31 N) and lightweight design. Next, we show that HFI-5 can accurately track positions, velocities, and accelerations, in part due to a 7.5 kHz servo loop. Finally, we demonstrate that HFI-5 is fMRI-compatible and does not interfere with fMRI scans even while applying large torques with its electromagnetic motors.

This paper presents a Model Predictive Control (MPC) strategy for a triaxial piezoelectric actuators (PAs) system. PAs systems require appropriate controllers to guarantee fast and high-precision positioning performances avoiding effects of non-linearities. Typically, commercial systems provide integrated Proportional-Integral (PI) controllers guarantying to maintain system stability in the presence of uncertainty and disturbance. MPC owes its success to the ability of optimally regulate multivariable systems through the minimization of a Quadratic Programming (QP) problem subjected to prescribed constraints. Alternatively, unconstrained MPC eliminates constrains from the problem, reducing the number of operations elapsed to compute the solution. The aim of this work is to design an unconstrained MPC for a 3-DOF PA replacing PI controllers to improve control performances by a smaller increase of required computational effort. The system is described by a Multi-Input Multi-Output (MIMO) Linear Time-Invariant (LTI) model, experimentally identified by the open-loop real plant response. Effectiveness of the proposed method is validated by simulation tests and experiments on the real system, comparing MPC with PI controllers tuned to guarantee common PA stability requirements.

A laboratory study was conducted to investigate the effects of lateral and horizontal vibration on the difference threshold of vertical vibration. Twelve male subjects sat on a rigid seat and were exposed to four different vibration conditions (pure vertical vibration; combination of horizontal and vertical vibration; combination of lateral and vertical vibration; combination of horizontal, lateral and vertical vibration). Vertical vibration for four conditions was 5 Hz sinusoidal with a magnitude of 1 ms–2 r.m.s. Horizontal and lateral vibration for the last three conditions were sinusoidal with magnitude 0.5 ms–2 r.m.s. and contained ten frequencies (1 to 8 Hz in third-octave band step). The frequency-weighted acceleration of the ten frequencies was equal. Results showed that horizontal and lateral vibrations have different effects on the difference threshold of vertical vibration. The combination of vertical and horizontal vibration gave a significantly lower difference threshold of vertical vibration than the combination of vertical and lateral vibration.

Passive compliant prosthetic ankles have the advantage of energy saving, light weight, simple structure and competitive cost compared to powered devices. Despite of the variety of commercial products, these designs do not provide adequate degree-of-freedom during amputees' movement. It hampers them from walking comfortably especially on undulating and rough terrains. This paper presents a novel design of a multiaxis fully compliant prosthetic ankle. Finite element analyses are carried out to evaluate the mechanical behaviors of the design obtained by an optimization procedure. The designed prosthesis not only has a capability of bending and compression to store elastic energy and release it to assist in forward propulsion of the body but can also facilitate eversion motion when persons with disability move on rough road by integrating a circular flexure hinge. These characteristics make it more versatile and reduce the impact force on residual limbs.

Aiming at the synchronization problems of multi-axis control system of seam welder, the effect of load fluctuations on the multi-axis synchronous precision of seam welder is analyzed in this paper. The formulas for the weight of reinforcement cage are derived based on actual parameters of the cage. The control model of multi-axis control system of the seam welder is established based on virtual shaft and the results show that the ever-changing load of the reinforcement cage and moment of inertia of the plates have a significant influence on multi-axis synchronous control precision during the initial phase and the effect of the load decreases with time.

In this paper, we present a lightweight, multi-axis compliant tensegrity joint that is biologically inspired by the human elbow. This tensegrity elbow actuates by shortening and lengthening cables in a method inspired by muscular actuation in a person. Unlike many series elastic actuators, this joint is structurally compliant not just along each axis of rotation, but along other axes as well. Compliant robotic joints are indispensable in unpredictable environments, including ones where the robot must interface with a person. The joint also addresses the need for functional redundancy and flexibility, traits which are required for many applications that investigate the use of biologically accurate robotic models.

In the large and complex devices, there are a large number of multi-axis synchronization motion systems. In order to enhance the synchronization motion precision of multi-axis system, the existing synchronization control models were analyzed. A new control model based on the fuzzy PID control algorithm and the combine of master-slave model and coupling model was presented. At last, the simulation and test analysis of double-motor system, double-hydraulic system and mixed-axis system were done. The result showed that the control algorithm presented can effective decrease the motion error of multi-axis system and the influence of interference.

This paper presents a printable skin adhesive stretch sensor to estimate rotation angles of multi-axis joint for biomedical engineering applications, such as gait analysis, gesture recognition, and motion monitoring. Silicone rubber mixed with multiwall carbon nanotube composites were fabricated to make a highly stretchable (up to 120%) strain sensors. Embedding liquid state composites to the fabric leaded to enhance the adhesive force between the composites and fabric. The skin adhesive sensor system could be used to estimate rotation angles of the multi-axis joints while providing comfortable physical interfaces. To reduce misalignment to the axis of rotation, a calibration method was formulated based on geometrical relationship between the sensor axes and the joint angle. In order to validate the estimation performance of the sensor in multi-axis joint, shoulder flexion/extension and abduction/adduction angles were estimated. The results showed the system could estimate the rotation angles of the shoulder enough to identify motion intentions of the user. In the future, the proposed system can be applied to the motion monitoring system by direct attachment to skin without discomfort to the user in daily life.

The accuracy of machine tools can be improved through using the learning control algorithm which can provide a better input command toward the closed-loop system. Due to the complexity of actual contour error model, the equivalent contour error is introduced. In this study, the target of the learning control is to reduce the equivalent contour error which the actual contour error will also be reduced. The iterative learning control algorithms were verified through the experiments which were done on x-y axis system of five-axis milling machine and controlled by PC-based controller. The results from the experiments show that the actual contour error can be reduced by 80% within five times of learning.

Recent developments have enabled single-anchor long-range two-dimensional (2D) positioning using low-frequency magnetoquasistatic fields. The approach of using a single-anchor for 2D position and orientation sensing results in significantly simplified systems and setup when compared to previous multi-anchor systems. The various advantages of single-anchor systems over multi-anchor systems include accurate closed-form inverted solutions, substantially simplified system setup and calibration, no relative ground truth needs, and ability to easily perform low-latency or real-time sensing with simple systems.

This paper reports a quad-axial force sensor probe which can measure tri-axial forces and one torque around the probe. By forming piezoresistors three dimensionally on the probe supporting beams, four sensing element can detect quad-axial force/torque on the probe tip. We demonstrated that the fabricated sensor had condition number of 2.6 with force resolutions under 1.0 µN and torque resolution under 1.0 nNm.

We propose a new method for the measurement of multi-axis contact force by using vision-based fluid-type tactile sensor. The proposed sensor can also estimate the multimodal tactile information such as the slippage, the shape, the contact region and the location of the contacted object. Multi-axis contact force is transformed from the elastic membrane tensional force on the touchpad surface, and the touchpad inner pressure measured by the pressure transducer. We obtain the tensional force by solving the equilibrium equations developed in each compartmentalized segment of the membrane, based on the shape information of the touchpad. The proposed method is general and can be applied to various touchpad contact situations. The usefulness of the proposed method is demonstrated through experimental results.

The assembly process of electronic components on three-dimensional circuit carriers increases the requirements on placement machines decisively. Decreased component packages and termination sizes require a precise placement process on 3D substrates with complex geometric structures. For characterizing the quality of this three-dimensional placement process, an evaluation methodology was developed. Therefore 3D test specimens were designed. The placement equipment, that has to be investigated, places components onto these specimens. Afterwards the component positions are analyzed by an optical coordinate measurement machine (CMM) and the placement error is calculated. This paper gives an overview of Molded Interconnect Technology (MID) and introduces the functionality of the investigated placement equipment, an automated multi axis handling unit for assembling 3D-MID. Focus is the presentation of the developed method for characterizing placement equipment used for 3D assembling of MID. Thedesign of the test specimens, the procedure of component placement and of measuring the component position areexplained. The results of characterizing the automated multi axis handling unit are shown. Influences and effects on the placement quality will be discussed. The developed method provides equipment manufacturers and users with a methodology to characterize, specify, document and verify the equipment's placement accuracy.

In this article, a B-spline-decomposition (BSD)-based approach to output tracking with preview is explored to achieve high-speed, large-range nanomanipulation in experiments. When a finite (in time) preview of the future desired trajectory is available, precision output tracking of nonminimum-phase (NMP) systems can be achieved by using the preview-based stable-inversion technique. The performance of the preview-based inversion approach, however, can be sensitive to uncertainties of system dynamics. Moreover, the computation involved in the implementation can be demanding. The BSD approach has been developed recently to address these challenges. In the BSD approach, a library of desired output elements and their corresponding input elements is constructed a priori, then the previewed future desired trajectory is decomposed into a summation of finite number of output elements, and the control input is synthesized by using the corresponding input elements with chosen pre- and post-actuation times. In this work, we demonstrate and evaluate the BSD technique for precision tracking with preview in experiments, by implementing it to a nanomanipulation application using a scanning probe microscope. The experiments showed that the tracking speed can be substantially improved by using the BSD technique over using feedback control alone.

We present a technique for a crosstalk compensation of a multi-axis force and torque sensor. Multi-axis sensor generates coupled output signals inevitably because of the coupled structure or manufacturing errors. In order to minimize crosstalk in output signals, a compensation matrix which decouples the output signals is required. In this paper, the compensation matrix based on the least squares method will be derived. The LabVIEW is used in the experiment because the flexibility of LabVIEW makes the creation of user-friendly data acquisition (DAQ) programs and compensation algorithm. Finally, we will compare the performances of the multi-axis force/torque sensor before and after using compensation matrix in order to confirm the effect of this method.

Positioning and tracking devices with micrometer range and sub-micrometer resolution are becoming of special interest in recent years for an extending range of applications including metrological devices, manipulators and mechanization systems both in research and high precision industries (for example, semiconductors). The control of these systems is not an easy task because of its normally high stiffness and the coupling existing between the different degrees of freedom. The present work proposes a control strategy based on differential flatness for static positioning and dynamic trajectory tracking with a platform of three degrees of freedom. The system uses piezoelectric actuators and is specially conceived for metrological devices, which do not suffer important external loads. The proposed method permits to decouple the design of a closed loop control for each degree of freedom and calculates an open loop command directly from the trajectory definition in the three degrees of freedom. The performance of the controller has been experimentally checked both in positioning and tracking applications.

A method for the regenerative energy saving in multi-axis servo-motor-drives is presented in this paper. This energy management is achieved through a proper time-coordination between the speed commands of multi-axis drives. Moreover, the proposed approach significantly limits the peak value of the ac input current in these systems. It is mathematically proved that a time-delay can significantly increase the amount of utilized regenerative energy and consequently decreases the amount of dissipated energy. In this paper, a set of closed-form formulas is developed, where the motor losses are neglected. The findings of this investigation were experimentally verified using a two-axis permanent-magnet (PM) motor-drive system, and the results are presented in this paper. The experimental results are in remarkable agreement with the developed closed-form formulas.

This paper investigates on motion synchronization of a multiple axes system. An adaptive robust control scheme was used to synthesize the synchronization compensator with cross-coupling dynamics among axes. By using the adaptive robust strategies, the asymptotic convergence of both tracking and synchronization errors are achieved. The robust control scheme also guarantees the satisfaction of transient performance, tracking errors, and synchronization errors. Experimental results of a three-axis motion system that include system uncertainties are also illustrated to verify the effectiveness of the proposed approach. The results indicate the excellent transient and both tracking and synchronization accuracies.

In this paper, four-axis machining and five-axis machining were compared in both machining path and feed rate. And then the differences between four-axis machining and five-axis machining were analyzed. Besides, the influences of the machining path and feed rate on four-axis and five-axis machining were researched. At last, the reason why the five-axis maching had higher efficency than four-axis was found out.

The error of dynamic coupling of a multi-axis sensor is a key factor of precision affection. In this paper, a new multi-axis sensor dynamic decoupling method based on a niche genetic algorithm is proposed. The method first gets the calibration data of the multi-sensor, and then uses the system identification method and the niche genetic algorithm to calculate and optimize the decoupling network based on the analysis method of transform function matrix. In addition, it also avoids the high precision requirement of the sensor model in the traditional dynamic decoupling method. Finally, the simulation results show the method is correct and effective.

The research presented an improve algorithm in least deviation linear interpolator, which simplify the interpolation calculator. Also in the research, it designs a platform for least deviation linear interpolation with two axis linear guides, and it realizes the linear interpolator by PIC microprocessor with MPLAB C language in PIC microprocessor in the research.

The geometrical accuracy of a machined feature on a workpiece during machining processes is mainly affected by the kinematic chain errors of multi-axis CNC machines, locating precision of fixtures, and datum errors on the workpiece. It is necessary to find a way to minimize the feature errors on the workpiece. In this paper, the kinematic chain errors are transformed into the displacements of the workpiece. The relationship between the kinematic chain errors and the displacements of the position and orientation of the workpiece is developed. A mapping model between the displacements of workpieces and the datum errors, and adjustments of fixtures is established. An error elimination (EE) method of the machined feature is formulated. A case study is given to verify the EE method.

This paper describes the proposal of preview controller with time based spline approximation for multi axis manipulator. The command trajectory on the geometrical coordinates is projected into time domain trajectory function. The command of position, velocity and acceleration are calculated by time based spline approximation. Simulation result shows that the tracking error and servo lag has reduced. Experiment by the x-y table for laser cutting machine shows that the acutual tracking error has remarkably reduced. With proposed preview controller, smooth motion can be realized at the change of the velocity and acceleration.

A new method of forecast cross-coupling controller for multi-axis system is proposed in this paper. When compared with the conventional cross-coupling system, this new method has the advantages that the compensators in CCC have a simpler design process over the conventional ones and its real-time system parametric identification can improve the accuracy of the model more effectively. The proposed compensator is evaluated and compared experimentally with a traditional uncoupled controller on a dual-axis motion system. The experiment results show that the new method remarkably reduces the contour error.

In this paper we report the development of a FBG (fibre Bragg grating) interrogation system, that is capable of detecting independently the two orthogonally polarised signals reflected from a FBG fabricated in a PM (polarisation maintaining) fibre. The interrogation system imposes no limitation on the measurable strain. It is possible to detect a strain gradient by measuring independently the spectral broadening of the two polarised signals. The system has been used to fabricate and characterise FBGs in different PM fibres. As a demonstration of the feasibility of the interrogation system for multi-axis strain sensing, the transverse strain sensing characteristics of PM FBGs are presented.

The feasibility of using exoskeletons in the performance of a simple task is discussed. The exoskeleton device has a total weight of 33 lb when unsupported, and it has seven joints. A Fitts' law paradigm was used to characterize the tradeoff between speed and accuracy for the task. The results of tests with five subjects are given

In conventional three phase current hysteresis controllers, the current error along the three phasc axes arc independently controlled. This will result in random selection of switching vectors causing high inverter switching losses. In this paper, a space phasor based multi axis current hysteresis controller is proposed, in which thc current error along the orthogonal axes (jA, jB, jC ) are monitored. The current error boundary is a hexagon. The proposed control scheme can be implemented using simple look up tables. The advantages of thc proposed current hysteresis controlled PWh4 scheme, when compared to other multi level current hysteresis controllers, is that only the adjacent vectors close to the motor back emf space phasor voltage, is only used for the inverter switching, for the entire speed rangc (optimum PWM switching). In the present scheme, thc selection of the inverter voltage vectors for optimum PWM switching is achieved by, without any computation of the machine voltage space phasor, for the full speed rangc of the drive system. The proposed scheme is self adapting, as far as the motor space phasor voltage is concerned, and also maintains the controller simplicity and quick response features of a hysteresis current controller. The scheme is simulated and also experimentally verified.

Multi-axis test facilities are usually used in industry to perform vibration tests. This paper proposes a new field of application for such systems. Based on detailed model equations of a rigid body in space an identification strategy is derived, which experimentally identifies the ten rigid body inertia parameters of the loaded or unloaded test table in only one test run. >