Vibration Control of Flexible Joint Robots Using a Discrete-Time Two-Stage Controller Based On Time-varying Input Shaping and Delay Compensation

2021 ◽  
Author(s):  
Minh-Nha Pham ◽  
Bruce Hazel ◽  
Philippe Hamelin ◽  
Zhaoheng Liu
Keyword(s):  
Disturbance Rejection ◽  
Robot Manipulator ◽  
Rigid Body Dynamics ◽  
Smith Predictor ◽  
Input Shaping ◽  
Delay Compensation ◽  
Two Stage ◽  
Flexible Joint ◽  
Flexible Joint Robots ◽  
Flexible Mode

Abstract Most industrial serial robots use decentralized joint controllers assuming rigid body dynamics. To prevent exciting the flexible mode, gains are kept low, resulting in poor control bandwidth and disturbance rejection. In this paper, a two-stage flexible joint discrete controller is presented, in which the decentralized approach is extended with a stiffness to take into account the dominant coupling mode. In the first-stage, an input shaping feedforward shapes the rigid closed-loop dynamics into desired dynamics that does not produce link vibrations. Robotic dynamic computation based on a recursive Newton-Euler Algorithm is conducted to update the feedforward link inertia parameter during robot motion. A second-stage is added to increase disturbance rejection. A generalized Smith predictor is developed to compensate for delay and feedback sensor filtering. An effective methodology is presented to optimize the control loop gains. Numerical simulations and experiments on a six-joint robot manipulator confirm that the proposed controller improves control performances in terms of bandwidth, vibration attenuation, and disturbance rejection.

Delay Compensation for Teleoperation Systems Based on Communication Disturbance Observers

2016 ◽  
Vol 20 (7) ◽  
pp. 1044-1050
Author(s):  
Wen-An Zhang ◽  
◽  
Junkai Jin ◽  
Xiang Qiu ◽  
Li Yu
Keyword(s):  
Control Problem ◽  
Disturbance Rejection ◽  
Disturbance Observer ◽  
Controller Design ◽  
Design Method ◽  
Smith Predictor ◽  
Time Varying ◽  
Communication Delays ◽  
Delay Compensation ◽  
Teleoperation Systems

This paper investigates the control problem for a class of teleoperation systems with communication delays. The network-induced delays are usually inevitable in teleoperation systems, and may be time varying and unpredictable. Since the conventional Smith predictor is only useful for fixed delays, a novel delay compensation and controller design method is proposed in this paper. The proposed method combines a disturbance rejection controller and a communication disturbance observer (CDOB). Simulations are provided to show the effectiveness and superiority of the proposed delay compensation and controller design method.

scholarly journals Global adaptive partial state feedback tracking control of rigid-link flexible-joint robots

Robotica ◽  
2000 ◽  
Vol 18 (3) ◽  
pp. 325-336 ◽  
Author(s):  
W.E. Dixon ◽  
E. Zergeroglu ◽  
D.M. Dawson ◽  
M.W. Hannan
Keyword(s):  
State Feedback ◽  
Robot Manipulator ◽  
Parametric Uncertainty ◽  
State Feedback Control ◽  
Velocity Measurements ◽  
Linear Filters ◽  
Flexible Joint ◽  
Rigid Link ◽  
Flexible Joint Robots ◽  
Partial State

This paper presents a solution to the global adaptive partial state feedback control problem for rigid-link, flexible-joint (RLFJ) robots. The proposed tracking controller adapts for parametric uncertainty throughout the entire mechanical system while only requiring link and actuator position measurements. A nonlinear filter is employed to eliminate the need for link velocity measurements while a set of linear filters is utilized to eliminate the need for actuator velocity measurements. A backstepping control strategy is utilized to illustrate global asymptotic link position tracking. An output feedback controller that adapts for parametric uncertainty in the link dynamics of the robot manipulator is presented as an extension. Experimental results are provided as verification of the proposed controller.

SELF-TUNING PID CONTROLLER DESIGN USING FUZZY LOGIC FOR A SINGLE-LINK FLEXIBLE JOINT ROBOT MANIPULATOR

2016 ◽  
Vol 78 (6-13) ◽  
Author(s):  
Ali Dehghani ◽  
Hamed Khodadadi
Keyword(s):  
Fuzzy Logic ◽  
Pid Controller ◽  
Controller Design ◽  
Robot Manipulator ◽  
Flexible Joint ◽  
Flexible Joint Robots ◽  
Pid Controller Design ◽  
Self Tuning ◽  
Intelligent Methods ◽  
Parameter Values

Although flexible joint robots are widely used in the industry, they are not without problems. It is especially so in their joints, links and complex dynamic where the interaction between loops, non-linearity, and flexibility in the joints can be difficult. The purpose of the present paper is to improve the tracking performance of flexible joint robots. Therefore the physical relations of the system dynamics need to be used to determine a non-linear model for the flexible joint robot. This paper attempts to achieve the desired performance flexible joint robot based on Fuzzy Logic Self-Tuning PID controller. Generally, the classic PID controller is different from the newly introduced form of PID. In classic PID, the parameter values are calculated based on various methods such as Ziegler-Nichols, while in fuzzy logic self-tuning PID, they are obtained by intelligent methods such as fuzzy logic. After deriving the system model, this logic self-tuning PID controller is designed in two cases: using error and its derivative and employing error and its integral for the inputs. The simulation results indicate that the proposed controllers can improve the overall efficiency of the system.

Quantitative Feedback Input Shaping for Flexible-Joint Robot Manipulator

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Withit Chatlatanagulchai ◽  
Dumrongsak Kijdech ◽  
Takat Benjalersyarnon ◽  
Supparat Damyot
Keyword(s):  
Reference Model ◽  
Robot Manipulator ◽  
Simple Zero ◽  
Input Shaping ◽  
Residual Vibration ◽  
Flexible Joint ◽  
Input Shaper ◽  
Time Varying Systems ◽  
Shaping System ◽  
Point To Point

Input shaping technique has been applied to flexible-joint robot to suppress its residual vibration from fast point-to-point movement. Input shaping performance deteriorates when the knowledge of the mode parameters of the robot is not accurate. Several robust input shapers were proposed at the expense of longer move time. A novel input shaping system, consisting of a quantitative feedback controller, a feed-forward reference model, and a simple zero-vibration (ZV) input shaper, is proposed in this paper. Advantages over the existing robust input shapers include toleration of substantially larger amount of uncertainty in the mode parameters, shorter move time that does not increase with insensitivity, application to nonlinear and time-varying systems, and suppression of vibration induced by disturbance and noise.

Model-based control of rigid-link flexible-joint robots: an experimental evaluation

Robotica ◽  
1998 ◽  
Vol 16 (1) ◽  
pp. 11-21 ◽  
Author(s):  
M. S. de Queiroz ◽  
S. Donepudi ◽  
T. Burg ◽  
D. M. Dawson
Keyword(s):  
Experimental Evaluation ◽  
Robot Manipulator ◽  
Position Tracking ◽  
Direct Drive ◽  
Order Model ◽  
Flexible Joint ◽  
Rigid Link ◽  
Model Based ◽  
Flexible Joint Robots ◽  
Position Tracking Control

In this paper, we present an experimental evaluation of several link position tracking control algorithms for rigid-link flexible-joint robot manipulators. To study the performance of the controllers, an IMI 2-link direct-drive planar robot manipulator was modified to approximate linear torsional spring couplings from the actuators to the links. Preliminary experimental results seem to indicate that reduced-order, model-based controllers with an actuator feedback loop provide relatively good link position tracking while a full-order, model-based controller offers some further improvement in link position tracking at the expense of increased computation.

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