A Novel Robust Control Method for Motion Control of Uncertain Single-Link Flexible-Joint Manipulator

2019 ◽  
pp. 1-8 ◽  
Author(s):  
Ze Yan ◽  
Xuzhi Lai ◽  
Qingxin Meng ◽  
Min Wu
Keyword(s):  
Robust Control ◽  
Motion Control ◽  
Control Method ◽  
Flexible Joint ◽  
Single Link ◽  
Flexible Joint Manipulator

Observer-based robust control for flexible-joint robot manipulators: A state-dependent Riccati equation-based approach

2020 ◽  
Vol 42 (16) ◽  
pp. 3135-3155
Author(s):  
Neda Nasiri ◽  
Ahmad Fakharian ◽  
Mohammad Bagher Menhaj
Keyword(s):  
Robust Control ◽  
Control Problem ◽  
Riccati Equation ◽  
Power Transmission ◽  
Control Method ◽  
Main Idea ◽  
Robotic Systems ◽  
Flexible Joint ◽  
State Dependent ◽  
Highly Nonlinear

In this paper, the robust control problem is tackled by employing the state-dependent Riccati equation (SDRE) for uncertain systems with unmeasurable states subject to mismatched time-varying disturbances. The proposed observer-based robust (OBR) controller is applied to two highly nonlinear, coupled and large robotic systems: namely a manipulator presenting joint flexibility due to deformation of the power transmission elements between the actuator and the robot known as flexible-joint robot (FJR) and also an FJR incorporating geared permanent magnet DC motor dynamics in its dynamic model called electrical flexible-joint robot (EFJR). A novel state-dependent coefficient (SDC) form is introduced for uncertain EFJRs. Rather than coping with the OBR control problem for such complex uncertain robotic systems, the main idea is to solve an equivalent nonlinear optimal control problem where the uncertainty and disturbance bounds are incorporated in the performance index. The stability proof is presented. Solving the complicated robust control problem for FJRs and EFJRs subject to uncertainty and disturbances via a simple and flexible nonlinear optimal approach and no need of state measurement are the main advantages of the proposed control method. Finally, simulation results are included to verify the efficiency and superiority of the control scheme.

A model-based PID-like motion control method for flexible-joint manipulator with harmonic drives

2021 ◽  
pp. 095440622110369
Author(s):  
Guocai Yang ◽  
Yechao Liu ◽  
Junhong Ji ◽  
Minghe Jin ◽  
Songhao Piao
Keyword(s):  
Position Control ◽  
Control Method ◽  
Joint Torque ◽  
Dynamics Model ◽  
Motion Error ◽  
Flexible Joint ◽  
Speed Range ◽  
Position Controller ◽  
Flexible Joint Manipulator ◽  
Better Than

A novel control method is proposed to achieve high trajectory tracking precision, for flexible-joint manipulators. The method consists of three major parts: joint torque generator, joint torque tracker and motor position controller. The expected torque is generated by a PID controller based on the manipulator’s rigid dynamics model. In the torque tracker, motor position is corrected in both feedback and feedforward ways. Finally, the motor position controller is responsible to track the corrected motor trajectory to achieve the torque and position control. To suppress nonlinear friction, a disturbance observer is also implemented. The method is verified with a seven-DOFs manipulator. Simulation and experimental results show that, the proposed method is efficient and practical to suppress vibration caused by flexible transmission and disturbance due to friction. As result, high positioning accuracy is achieved in a certain wide working speed range. The no-load motion accuracy is better than 0.6 mm with a manipulator whose length is 1.8 meter, and the motion error is less than 3 mm with loading of four kilograms.

Special Issue on Control Systems in Mechatronics

1996 ◽  
Vol 8 (3) ◽  
pp. 217-217
Author(s):  
Kiyoshi Ohishi ◽  
Keyword(s):  
Control System ◽  
Robust Control ◽  
Control Theory ◽  
Control Systems ◽  
Motion Control ◽  
Force Control ◽  
Disturbance Observer ◽  
Control Method ◽  
Mechanical Systems ◽  
Robust Control System

The special issue on Control Systems in Mechatronics is a significant and timely issue since many robotics and mechatronics engineers now pay attention to the research field of motion control and control theory. In Japan, advanced motion control technology is a key technics to improving the performance of robot systems and/or mechanical automation equipment. The definition of motion control in this issue is the control of mechanical systems driven by electrical actuators such as a do servo motor or an ac servo motor. The means or strategy of motion control has so far been of interest only to electrical engineers and mechanical engineers; it has not been as familiar to robotics engineers. Recently, a control system has been developed with industry applications. Advanced motor control technology in Japan is based on the robust control system, such as the disturbance observer, the H00 control system, the two-degrees-of-freedom control system and so on. The disturbance observer has a simple structure, and it is quite valid for disturbance torque rejection. The robust control system based on the disturbance observer is now widely used in robot and mechanical systems in Japan. The disturbance observer is the original Japanese technology designed by two electrical engineers, Prof. Ohnishi and myself, from the viewpoint of the electrical actuator but control theory. Ho control is linear control technics popular around the world. It can make the desired loop shaping of frequency characteristics for a plant system such as the actuator of a mechanical system. The robust control system based on the mixed sensitivity problem of H00 control theory has good frequency characteristics. Moreover, the availability of large amounts of computational power has enabled us to use complex control theory, and actuators for robotics applications are now mainly electrical ones because of the remarkable progress in power electronics. This change in the control of mechanical systems is a new and attractive one. Motion control is becoming a field of interest to control, electrical, and mechanical engineers who work in robotics. In this issue, the eight papers and the two news reports have been selected to show the current topics concerned with control systems in mechatronics. The first paper is a review paper titled ""robust motion control by the disturbance observer"". Prof. Ohnishi describes the physical meaning of motion control and the purpose of robust control. This review paper also shows the effectiveness of motion control based on the disturbance observer. Four papers in this issue deal with robot motion control systems using the disturbance observer. Mr. Oda explains the decoupling force control method of redundant robot manipulation by workspace disturbance observer which is not a joint space disturbance observer such as an ordinary disturbance observer. Dr. Komada explains the hybrid position/force control method based on second derivatives of position and force, which uses the force-based disturbance observer. Dr. Shimada explains the servo system considering a robot of low stiffness, which is based on the disturbance and velocity observer. This observer is mounted with each joint. Prof. Kuroe explains the decoupling control method of robot manipulation using a variable structure disturbance observer which is not an ordinary linear disturbance observer. The other three papers in this issue deal with robot motion control using the other advanced control system. Prof. Ohishi, myself explains the hybrid position/force control method without a force sensor, which is based on H00 acceleration controller and torque observer. This torque observer is the same observer as the ordinary disturbance observer. Mr. Fujimoto explains the three dimensional digital simulation of legged robots for advanced motion control. Mr. Kang explains the state estimation for mobile robots using a partially observable Markov decision process. This method can estimate the mobile robot state precisely and robustly. The two news reports in this issue deal with control and robot laboratory news from Japanese universities such as news generated by Prof. Hori of the University of Tokyo and Prof. Hori of Mie University. Both Prof. Horis are famous and active researchers in advanced motion control. This issue scans only one aspect of control systems, not the whole. Adaptive control, learning control, and other advanced control methods such as the LMI method are not mentioned. The subject of control systems in mechatronics is now expanding and developing. I greatly appreciate the efforts of the reviewers and authors in producing this issue, and I thank the Chief-Editor, Prof. Toshio Fukuda, for encouraging us to prepare it.

A new control method of flexible-joint manipulator with harmonic drive

2020 ◽  
Vol 234 (9) ◽  
pp. 1868-1883
Author(s):  
Guocai Yang ◽  
Yechao Liu ◽  
Minghe Jin
Keyword(s):  
Control Method ◽  
Controller Design ◽  
Joint Stiffness ◽  
Adaptive Controller ◽  
Harmonic Drive ◽  
Flexible Joint ◽  
Assignment Method ◽  
Uncertain Dynamics ◽  
Tracking Controller ◽  
Flexible Joint Manipulator

Considerable elasticity and nonlinear friction caused by harmonic transmission challenge the performance of flexible-joint manipulators. The uncertain dynamics of manipulator and the inadequate measurable states also limit the controller design. A new control method is proposed to address these problems, achieving the precise motion control of the flexible-joint manipulator. The method consists of three cascaded controllers: an adaptive controller, a torque-tracking controller, and a motor controller. The adaptive controller was adopted to generate the desired torque ensuring the robustness for uncertain dynamics. The torque-tracking controller derived the position compensation for motor control according to the torque error. As the elastic torque is under control, the vibration caused by harmonic drive can be eliminated. The motor was controlled based on poles-assignment method and friction compensation. The Kalman observer based on the Brownian motion model observed both velocity and the high-order derivatives of torque sensing. The stability of the control method was strictly proved. Calibration was performed on each joint to obtain the required joint stiffness and motor friction parameters. The control method was verified on a single joint and the frequency response of the system was obtained. The results show that the controller has good performance. The controller was realized on the self-developed seven-degree-of-freedom manipulator. The results reveal that the controller has high-precision tracking performance.

Vibration Control of Redundant Flexible-Joint Manipulators

1997 ◽  
Vol 119 (1) ◽  
pp. 119-125
Author(s):  
Fengfeng Xi
Keyword(s):  
Numerical Simulations ◽  
Vibration Control ◽  
Control Method ◽  
Optimization Technique ◽  
Main Idea ◽  
The Other ◽  
Control Law ◽  
Flexible Joint ◽  
Flexible Joint Manipulator

Presented in this paper is a method for controlling vibrations of a redundant flexible-joint manipulator. The main idea behind this method is to utilize joint redundancy to minimize the change in the manipulator inertia, so that a simple gain-fixed control law can be used to control joint vibrations. For this purpose, two optimal joint trajectory generators are proposed; one is based on the extended Jacobian method and the other is based on an optimization technique. Numerical simulations are provided to demonstrate the effectiveness of the proposed control method.

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