A closed-loop inverse kinematic scheme for on-line joint-based robot control

Robotica ◽  
1990 ◽  
Vol 8 (3) ◽  
pp. 231-243 ◽  
Author(s):  
Bruno Siciliano
Keyword(s):  
Robot Control ◽  
Closed Loop ◽  
Inverse Kinematic ◽  
Kinematic Scheme ◽  
Inverse Kinematic Problem ◽  
First Order ◽  
Order Tracking ◽  
On Line ◽  
Reference Trajectories ◽  
Computed Torque

SUMMARYA computationally fast inverse kinematic scheme is derived which solves robot's end-effector (EE) trajectories in terms of joint trajectories. The inverse kinematic problem (IKP) is cast as a control problem for a simple dynamic system. The resulting closed-loop algorithms are shown to guarantee satisfactory tracking performance. Differently from previous first-order schemes which only solve for joint positions and velocities, we propose here new second order tracking schemes which allow the on-line generation of joint position + velocity + acceleration (PVA) reference trajectories for any computed torque-like controller in sensor-based robot applications. The algorithms do explicitly solve the IKP for both EE position and orientation. Simulation results for a six-degree-of-freedom PUMA-like geometry demonstrate the effectiveness of the scheme, even near singularities.

An Approach to Adaptive Control of Robot Manipulators Using the Computed Torque Technique

1989 ◽  
Vol 111 (1) ◽  
pp. 1-8 ◽  
Author(s):  
A. A. Goldenberg ◽  
J. A. Apkarian ◽  
H. W. Smith
Keyword(s):  
Closed Loop ◽  
Order Approximation ◽  
Least Square ◽  
Recursive Identification ◽  
Dynamics Model ◽  
Joint Torques ◽  
First Order ◽  
Joint Coordinates ◽  
First Order Approximation ◽  
Computed Torque

Manipulator’s control system based on computed torque techniques incorporates a model of the manipulator dynamics. The nominal torque, computed using this mathematical model, does not reflect the effects of unknown loadings and uncertainty in modelling the parameters. An approach is presented which compensates for unknown loading and parameter uncertainty. This compensation is based on the “recursive” identification of a new dynamics operator which maps a vector of generalized coordinates into the vector of generalized forces (joint torques). The identification is based on a least-square approximation. Using the identified operator, which provides the compensated nominal torque, the system is controlled in closed-loop to generate regulation of the error in joint coordinates. The regulation is obtained using a common discrete optimization feedback law which is based on a recursive identification of the first order approximation of the dynamics model. The approach is illustrated with simulation results.

scholarly journals Trajectory Planning for a 3-SPS-U Tensegrity Mechanism

2021 ◽  
Author(s):  
Swaminath Venkateswaran ◽  
Damien Chablat
Keyword(s):  
Pid Controller ◽  
Control Algorithm ◽  
Closed Loop ◽  
Test Bench ◽  
Inverse Kinematic ◽  
Universal Joint ◽  
Inverse Kinematic Problem ◽  
Inspection Robot ◽  
Dc Motors ◽  
Pass Through

Abstract This article presents the actuation strategy of a 2-DOF tensegrity type mechanism that employs three tension springs and a passive universal joint. This mechanism is proposed to be incorporated as an articulation unit for a piping inspection robot in order to overcome pipe bends and junctions. In the event of a junction, external actuations are required to allow the mechanism as well as the robot to follow a certain direction. Using DC-motors coupled with encoders, experiments are carried out on a test bench of the tensegrity mechanism. The actuation of the mobile platform is performed using cables that pass through each spring. By correlating the architecture to a 3-SPS-U parallel mechanism, the singularity-free workspace of the mechanism is analyzed to identify the tilt limits. A closed-loop PID controller is implemented using a microcomputer to perform a linear trajectory within the singularity-free workspace. The Inverse Kinematic Problem (IKP) is solved by passing input tilt angles to the controller. With the help of a force control algorithm, the experiments are carried out under no-load conditions for vertical and horizontal orientations of the mechanism. The error data of the joint positions and the motor torques are then interpreted for both orientations of the mechanism.

Control Strategies for a Highly Loaded Biological Ammonia Elimination Process

1993 ◽  
Vol 28 (11-12) ◽  
pp. 531-538 ◽  
Author(s):  
B. Teichgräber
Keyword(s):  
Closed Loop ◽  
Control Strategies ◽  
Level Control ◽  
Sludge Dewatering ◽  
Loop Control ◽  
Reject Water ◽  
Line Measurement ◽  
Control Pattern ◽  
On Line ◽  
Treatment Facilities

A nitrification/denitrification process was applied to reject water treatment from sludge dewatering at Bottrop central sludge treatment facilities of the Emschergenossenschaft. On-line monitoring of influent and effluent turbidity, closed loop control of DO and pH, and on-line monitoring of nitrogen compounds were combined to a three level control pattern. Though on-line measurement of substrate and product showed substantial response time it could be used to operate nitrification/denitrification within process boundaries.

Analysis of Reset Control Systems Consisting of a FORE and Second-Order Loop1

2001 ◽  
Vol 123 (2) ◽  
pp. 279-283 ◽  
Author(s):  
Qian Chen ◽  
Yossi Chait ◽  
C. V. Hollot
Keyword(s):  
Control Systems ◽  
Closed Loop ◽  
Second Order ◽  
Step Response ◽  
Steady State Response ◽  
First Order ◽  
State Response ◽  
Loop Transfer Function ◽  
Performance Specifications ◽  
Reset Control

Reset controllers consist of two parts—a linear compensator and a reset element. The linear compensator is designed, in the usual ways, to meet all closed-loop performance specifications while relaxing the overshoot constraint. Then, the reset element is chosen to meet this remaining step-response specification. In this paper, we consider the case when such linear compensation results in a second-order (loop) transfer function and where a first-order reset element (FORE) is employed. We analyze the closed-loop reset control system addressing performance issues such as stability, steady-state response, and transient performance.

scholarly journals Comparing the Performance of Reference Trajectory Management and Controller Reconfiguration in Attitude Fault Tolerant Control

2018 ◽  
Vol 151 ◽  
pp. 04008
Author(s):  
Rouzbeh Moradi ◽  
Alireza Alikhani ◽  
Mohsen Fathi Jegarkandi
Keyword(s):  
Control Problem ◽  
Closed Loop ◽  
Fault Tolerant ◽  
Dynamic Performance ◽  
Fault Tolerant Control ◽  
Spacecraft Attitude ◽  
Reference Trajectory ◽  
System Behavior ◽  
Closed Loop System ◽  
Reference Trajectories

Reference trajectory management is a method to modify reference trajectories for the faulty system. The modified reference trajectories define new maneuvers for the system to retain its pre-fault dynamic performance. Controller reconfiguration is another method to handle faults in the system, for instance by adjusting the controller parameters (coefficients). Both of these two methods have been considered in the literature and are proven to be capable of handling various faults. However, the comparison of these two methods has not been considered sufficiently. In this paper, a controller reconfiguration mechanism and a reference trajectory management are proposed for the spacecraft attitude fault tolerant control problem. Then, these two methods are compared under the same conditions, and it is shown that the proposed controller reconfiguration has better performance than the proposed reference trajectory management. The reason is that the controller reconfiguration has more variables to modify the closed-loop system behavior.

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