Mao-Hsiung Chiang

Development of a Stereo Vision Measurement System for a 3D Three-Axial Pneumatic Parallel Mechanism Robot Arm

In this paper, a stereo vision 3D position measurement system for a three-axial pneumatic parallel mechanism robot arm is presented. The stereo vision 3D position measurement system aims to measure the 3D trajectories of the end-effector of the robot arm. To track the end-effector of the robot arm, the circle detection algorithm is used to detect the desired target and the SAD algorithm is used to track the moving target and to search the corresponding target location along the conjugate epipolar line in the stereo pair. After camera calibration, both intrinsic and extrinsic parameters of the stereo rig can be obtained, so images can be rectified according to the camera parameters. Thus, through the epipolar rectification, the stereo matching process is reduced to a horizontal search along the conjugate epipolar line. Finally, 3D trajectories of the end-effector are computed by stereo triangulation. The experimental results show that the stereo vision 3D position measurement system proposed in this paper can successfully track and measure the fifth-order polynomial trajectory and sinusoidal trajectory of the end-effector of the three- axial pneumatic parallel mechanism robot arm.

Adaptive fuzzy controller with self-tuning fuzzy sliding-mode compensation for position control of an electro-hydraulic displacement-controlled system

The electro-hydraulic displacement-controlled system EHDCS performs specific non-linear and time-varying characteristics such that an exact model-based controller is complicated to be realized and the servo control is difficult to be implemented. In this study, the design method and experimental implementation of an adaptive fuzzy controller with self-tuning fuzzy sliding-mode compensation AFC-STFSMC are proposed which has on-line tuning ability for dealing with the system time-varying and non-linear uncertain behaviours for adjusting the control rule parameters. This control strategy employs the adaptive fuzzy approximation technique to design the equivalent controller of the conventional sliding-mode control SMC. Furthermore, the fuzzy sliding-mode control scheme with self-tuning ability is introduced to compensate the approximation error of the equivalent controller for improving the control performance. The proposed AFC-STFSMC scheme can design the sliding-mode controller with no requirement of the system dynamic model, be free from chattering, be stable tracking control performance, and be robust to uncertainties. Moreover, the stability proof of the proposed scheme using Lyapunov method is presented. The experimental results of the position control and the path control in EHDCS with different strokes and external disturbance forces show that the proposed AFC-STFSMC approach can achieve excellent control performance and robustness with regard to parameter variations and external disturbance.

Development of X-Y Servo Pneumatic-Piezoelectric Hybrid Actuators for Position Control with High Response, Large Stroke and Nanometer Accuracy

This study aims to develop a X-Y dual-axial intelligent servo pneumatic-piezoelectric hybrid actuator for position control with high response, large stroke (250 mm, 200 mm) and nanometer accuracy (20 nm). In each axis, the rodless pneumatic actuator serves to position in coarse stroke and the piezoelectric actuator compensates in fine stroke. Thus, the overall control systems of the single axis become a dual-input single-output (DISO) system. Although the rodless pneumatic actuator has relatively larger friction force, it has the advantage of mechanism for multi-axial development. Thus, the X-Y dual-axial positioning system is developed based on the servo pneumatic-piezoelectric hybrid actuator. In addition, the decoupling self-organizing fuzzy sliding mode control is developed as the intelligent control strategies. Finally, the proposed novel intelligent X-Y dual-axial servo pneumatic-piezoelectric hybrid actuators are implemented and verified experimentally.

Development of a 3D Parallel Mechanism Robot Arm with Three Vertical-Axial Pneumatic Actuators Combined with a Stereo Vision System

This study aimed to develop a novel 3D parallel mechanism robot driven by three vertical-axial pneumatic actuators with a stereo vision system for path tracking control. The mechanical system and the control system are the primary novel parts for developing a 3D parallel mechanism robot. In the mechanical system, a 3D parallel mechanism robot contains three serial chains, a fixed base, a movable platform and a pneumatic servo system. The parallel mechanism are designed and analyzed first for realizing a 3D motion in the X-Y-Z coordinate system of the robot’s end-effector. The inverse kinematics and the forward kinematics of the parallel mechanism robot are investigated by using the Denavit-Hartenberg notation (D-H notation) coordinate system. The pneumatic actuators in the three vertical motion axes are modeled. In the control system, the Fourier series-based adaptive sliding-mode controller with H∞ tracking performance is used to design the path tracking controllers of the three vertical servo pneumatic actuators for realizing 3D path tracking control of the end-effector. Three optical linear scales are used to measure the position of the three pneumatic actuators. The 3D position of the end-effector is then calculated from the measuring position of the three pneumatic actuators by means of the kinematics. However, the calculated 3D position of the end-effector cannot consider the manufacturing and assembly tolerance of the joints and the parallel mechanism so that errors between the actual position and the calculated 3D position of the end-effector exist. In order to improve this situation, sensor collaboration is developed in this paper. A stereo vision system is used to collaborate with the three position sensors of the pneumatic actuators. The stereo vision system combining two CCD serves to measure the actual 3D position of the end-effector and calibrate the error between the actual and the calculated 3D position of the end-effector. Furthermore, to verify the feasibility of the proposed parallel mechanism robot driven by three vertical pneumatic servo actuators, a full-scale test rig of the proposed parallel mechanism pneumatic robot is set up. Thus, simulations and experiments for different complex 3D motion profiles of the robot end-effector can be successfully achieved. The desired, the actual and the calculated 3D position of the end-effector can be compared in the complex 3D motion control.

A positioning actuator of magnetic shape memory alloys based on fuzzy sliding mode control

Magnetic shape memory alloys (MSMA) has become a potential candidate in many engineering fields. MSMA has advantage of huge strain, which is much larger than other materials. Besides, it has properties of lightness and high frequency response. All of these characteristics make MSMA as a good choice in micro engineering. However, MSMA has obvious hysteresis phenomenon of nonlinear behavior. The difficulty to use the MSMA as a positioning actuator due to the hysteresis is increased. In this paper, we present the prototype of MSMA actuator. The hysteresis phenomenon of MSMA is also discussed. We also demonstrated experiments of positioning control. Fuzzy sliding mode control (FSMC) is a method to control the system without mathematical model, and it can provide the robustness property. Controller design and experiments are discussed. Experiments show that the precise positioning of controls can be achieved.

Adaptive Fuzzy Sliding-Mode Control for Variable Displacement Hydraulic Servo System

The variable displacement hydraulic servo system performs specific characteristics on non-linearity and time-varying. An exact model-based controller is difficult to be realized. In this study, the design method and experimental implementation of an adaptive fuzzy sliding-mode controller (AFSMC) are presented, which has on-line learning ability for dealing with the system time-varying and non-linear uncertainty behaviors for adjusting the control rule parameters. The tuning algorithms are derived in the sense of the Lyapunov stability theorem; thus, the stability of the system can be guaranteed. The experimental results show that the AFSMC can perform excellent position control and path control for the variable displacement hydraulic servo system.

The Force Control of a Novel Variable Rotational Speed Hydraulic Pump-Controlled System Using Adaptive Fuzzy Controller with Self-tuning Fuzzy Sliding-mode Compensation

Abstract The conventional hydraulic valve-controlled systems have high response but low energy-efficiency. Hydraulic pump-controlled servo systems have high energy efficiency. However, the conventional pump-controlled systems, which are altered by displacement via variable displacement pumps, have lower response. This paper aims to investigate the force control performance of the high response electro-hydraulic pump-controlled systems driven by an AC servo motor with variable rotational speed. Instead of internal gear pumps, a constant displacement axial piston pump is used in this research. Thus, the new hydraulic pump-controlled system with an AC motor servo and a constant displacement axial piston pump is investigated for force control of hydraulic servo machines. For that, a novel adaptive fuzzy controller with self-tuning fuzzy sliding-mode compensation (AFC- STFSMC) is proposed for force control in the variable rotational speed pump-controlled system (VRSPCS). Thus, the developed high response variable rotational speed pump-controlled systems controlled by AFC-STFSMC are implemented and verified experimentally for force control in different force targets. The experimental results of the force control in the VRSPCS show that the proposed system and control method can achieve excellent control performance and robustness with regard to parameter variations and external disturbance.

Feedback linearization control for a wind turbine driven by a variable-speed pump-controlled hydraulic servo system

The study aims to develop a feedback linearization controller applying to a novel pitch control system for a large wind turbine driven by a variable-speed pump-controlled hydraulic servo system. The variable-speed pump-controlled hydraulic servo system is composed of an AC servo motor, a constant displacement hydraulic piston pump two differential hydraulic cylinders and hydraulic circuits. Finally, the mathematic model is verified by the experimental test rig and the tracking performance in both 5th order polynomial and sinusoidal path are implemented by the proposed feedback linearization controller.

Development of Three Dimensional Parallel Mechanism Robot with Pneumatic System

Abstract With the development of this technology, more and more robots have been used in the industries. This paper presents a three dimensional parallel mechanism robot with pneumatic systems. This article focuses on designing and implementing the mechanical parts, the pneumatic systems, and the control parts. Concerning the mechanical parts, the system is a three dimensional parallel mechanism robot which includes serial parts and parallel parts, and the end-effector of this system moves in a three dimensional motion in an X-Y-Z coordinate system. Regarding the pneumatic systems, the pneumatic actuators, the pneumatic servo valves and other pneumatic elements are used in the experiments. Concerning the control parts, a Fourier series-based adaptive sliding mode controller with Hoo tracking performance (FSB-ASMC+ H ∞ ) is proposed to control the systems. The experimental results show the end-effector performs properly. In conclusion, the three dimensional parallel mechanism robot with pneumatic systems is implemented and the controller is the most efficient way to implement the systems.

Velocity Control for a Variable Displacement Hydraulic Servo System Using Adaptive Fuzzy Sliding-Mode Control

Abstract The variable displacement hydraulic servo system performs specific characteristics on nonlinearity and time-varying. An exact model-based controller is difficult to be realized. In this study, the design method and experimental implementation of an adaptive fuzzy sliding-mode controller (AFSMC) are presented, which has on-line learning ability for dealing with the system time-varying and non-linear uncertainty behaviors for adjusting the control rule parameters. The tuning algorithms are derived in the sense of the Lyapunov stability theorem; thus, the stability of the system can be guaranteed. The experimental results show that the AFSMC can perform excellent velocity control for the variable displacement hydraulic servo system.