Task Space Impedance Control of the Manipulator Driven Through the Multistage Nonlinear Flexible Transmission

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Phongsaen Pitakwatchara
Keyword(s):  
Asymptotic Stability ◽  
Degrees Of Freedom ◽  
Impedance Control ◽  
Limited Information ◽  
Task Space ◽  
Flexible Joint ◽  
Motor Current ◽  
Impedance Characteristics ◽  
Control Scheme ◽  
Joint Velocity

This paper addresses the task space impedance control of a robot driven through the multistage nonlinear flexible transmission. The proposed controller uses limited information of the angle and the current of the motors to regulate the end point compliance at the specified set point. In particular, motor angle is employed to estimate the stationary robot link angle and joint velocity in real time. They are then used to constitute the stationary force on the attempt to cancel the robot gravity force and to form the task space interacting force according to the desired impedance characteristics. Motor current is used to infer the transmitted torque to the robot. This torque is fed back to mitigate the effect of the motor inertia from deteriorating the desired impedance. Asymptotic stability of this controller with the flexible joint robot is guaranteed with additional damping. Passivity of the system is also investigated. Simulation and experiments of the proposed control scheme on a two degrees-of-freedom (DOF) cable-pulley driven flexible joint robot model are examined.

Operational Space Prescribed Tracking Performance and Compliance in Flexible Joint Robots

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
Abdelrahem Atawnih ◽  
Zoe Doulgeri ◽  
George A. Rovithakis
Keyword(s):  
Degrees Of Freedom ◽  
Position Tracking ◽  
Admittance Control ◽  
Flexible Joint ◽  
Flexible Joint Robots ◽  
Operational Space ◽  
Control Scheme ◽  
Simulation Results ◽  
Flexible Joint Manipulator ◽  
Three Degrees Of Freedom

In this work, an admittance control scheme is proposed utilizing a highly robust prescribed performance position tracking controller for flexible joint robots which is designed at the operational space. The proposed control scheme achieves the desired impedance to the external contact force as well as superior position tracking in free motion without any robot model knowledge, as opposed to the torque based impedance controllers. Comparative simulation results on a three degrees-of-freedom (3DOF) flexible joint manipulator, illustrate the efficiency of the approach.

A Hierarchical Approach to Manipulator Velocity Field Control Considering Dynamic Friction Compensation

2005 ◽  
Vol 128 (3) ◽  
pp. 670-674 ◽  
Author(s):  
Javier Moreno-Valenzuela ◽  
Rafael Kelly
Keyword(s):  
Velocity Field ◽  
Degrees Of Freedom ◽  
Friction Compensation ◽  
Velocity Control ◽  
Hierarchical Approach ◽  
Direct Drive ◽  
Kinematic Control ◽  
Control Scheme ◽  
Field Control ◽  
Joint Velocity

The velocity field control of robot manipulators is addressed in this paper. The proposed algorithm has a hierarchical structure based on a velocity field kinematic control scheme for joint velocity resolution and an inner loop of joint velocity control that uses an observer for friction compensation. Experiments on a two degrees-of-freedom direct-drive arm illustrate the performance of the proposed controller.

Coping with joint velocity limits in first-order inverse kinematics algorithms: analysis and real-time implementation

Robotica ◽  
1995 ◽  
Vol 13 (5) ◽  
pp. 515-519 ◽  
Author(s):  
Pasquale Chiacchio ◽  
Stefano Chiaverini
Keyword(s):  
Real Time ◽  
Inverse Kinematics ◽  
Task Space ◽  
First Order ◽  
Slowing Down ◽  
Control Scheme ◽  
Virtual Time ◽  
Velocity Constraints ◽  
Joint Velocity

SummaryA major problem in inverse kinematics algorithms is that the generated joint velocities to be fed to the joint servos may cause violation of the speed limits of the joint actuators. In this paper, it is shown how to properly cope with joint velocity limits in first-order inverse kinematics algorithms; the proposed technique guarantees tracking of the desired end-effector path. This goal is achieved by suitably slowing down the task-space trajectory when joint velocity limits are encountered. The time law is modified through a time warp such that the introduced virtual time allows fulfillment of the velocity constraints. A case study is developed to show the effectiveness of the proposed method and a kinematic control scheme based on the presented technique is implemented to demonstrate feasibility under real-time constraints.

Adaptive path-constrained control of a robotic manipulator in a task space

Robotica ◽  
2006 ◽  
Vol 25 (1) ◽  
pp. 103-112 ◽  
Author(s):  
Mirosław Galicki
Keyword(s):  
Degrees Of Freedom ◽  
Path Following ◽  
Lyapunov Stability Theory ◽  
Robotic Manipulator ◽  
Task Space ◽  
End Effector ◽  
State Dependent ◽  
Control Scheme ◽  
Robot Task ◽  
Three Degrees Of Freedom

This study addresses the problem of adaptive controlling of both a nonredundant and a redundant robotic manipulator with state-dependent constraints. The task of the robot is to follow a prescribed geometric path given in the task space, by the end-effector. The aforementioned robot task has been solved on the basis of the Lyapunov stability theory, which is used to derive the control scheme. A new adaptive Jacobian controller is proposed in the paper for the path following of the robot, with both uncertain kinematics and dynamics. The numerical simulation results carried out for a planar redundant three-DOF (three degrees of freedom) manipulator whose end-effector follows a prescribed geometric path given in a two-dimensional (2D) task space, illustrate the trajectory performance of the proposed control scheme.

scholarly journals A model-based velocity controller for chaotization of flexible joint robot manipulators

2018 ◽  
Vol 15 (5) ◽  
pp. 172988141880252 ◽  
Author(s):  
Roger Miranda-Colorado ◽  
Luis T Aguilar ◽  
J Moreno-Valenzuela
Keyword(s):  
Vector Field ◽  
Asymptotic Stability ◽  
Chaotic Motion ◽  
Degrees Of Freedom ◽  
Robot Manipulator ◽  
Robot Manipulators ◽  
Tracking Error ◽  
Reference Vector ◽  
Flexible Joint ◽  
Model Based

This article presents a model-based velocity controller able to induce a chaotic motion on n-degrees of freedom flexible joint robot manipulators. The proposed controller allows the velocity link vector of a robot manipulator to track an arbitrary, chaotic reference vector field. A rigorous theoretical analysis based on Lyapunov’s theory is used to prove the asymptotic stability of the tracking error signals when using the proposed controller, which implies that a chaotic motion is induced to the robotic system. Experimental results are provided using a flexible joint robot manipulator of two degrees of freedom. Finally, by using Poincaré maps and Lyapunov exponents, it is shown that the behavior exhibited by the robot joint positions is chaotic.

An upper-body rehabilitation exoskeleton Harmony with an anatomical shoulder mechanism: Design, modeling, control, and performance evaluation

2017 ◽  
Vol 36 (4) ◽  
pp. 414-435 ◽  
Author(s):  
Bongsu Kim ◽  
Ashish D Deshpande
Keyword(s):  
Range Of Motion ◽  
Control Algorithm ◽  
Degrees Of Freedom ◽  
Impedance Control ◽  
Spatial Dynamics ◽  
Upper Body ◽  
Task Space ◽  
Wide Range ◽  
And Performance ◽  
Series Elastic Actuators

We present an upper-body exoskeleton for rehabilitation, called Harmony, that provides natural coordinated motions on the shoulder with a wide range of motion, and force and impedance controllability. The exoskeleton consists of an anatomical shoulder mechanism with five active degrees of freedom, and one degree of freedom elbow and wrist mechanisms powered by series elastic actuators. The dynamic model of the exoskeleton is formulated using a recursive Newton–Euler algorithm with spatial dynamics representation. A baseline control algorithm is developed to achieve dynamic transparency and scapulohumeral rhythm assistance, and the coupled stability of the robot–human system at the baseline control is investigated. Experiments were conducted to evaluate the kinematic and dynamic characteristics of the exoskeleton. The results show that the exoskeleton exhibits good kinematic compatibility to the human body with a wide range of motion and performs task-space force and impedance control behaviors reliably.

PD control with feedforward compensation for robot manipulators: analysis and experimentation

Robotica ◽  
2001 ◽  
Vol 19 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Victor Santibañez ◽  
Rafael Kelly
Keyword(s):  
Asymptotic Stability ◽  
Global Asymptotic Stability ◽  
Degrees Of Freedom ◽  
Robot Manipulators ◽  
Classical Model ◽  
Experimental Tests ◽  
Torque Control ◽  
Direct Drive ◽  
Pd Control ◽  
Control Scheme

One of the simplest and natural appealing motion control strategies for robot manipulators is the PD control with feedforward compensation. Although successful experimental tests of this control scheme have been published since the beginning of the eighties, the proof of global asymptotic stability has remained unattended until now. The contribution of this paper is to prove that global asymptotic stability can be guaranteed provided that the proportional and derivative gains are adequately selected. The performance of the PD control with feedforward compensation evaluated on a two degrees-of-freedom direct-drive arm appears as fine as the classical model-based computed torque control scheme.

scholarly journals Task-space regulation of rigid-link electrically-driven robots with uncertain kinematics using neural networks

2021 ◽  
Vol 54 (1-2) ◽  
pp. 102-115
Author(s):  
Wenhui Si ◽  
Lingyan Zhao ◽  
Jianping Wei ◽  
Zhiguang Guan
Keyword(s):  
Neural Networks ◽  
Asymptotic Stability ◽  
Control Method ◽  
Joint Space ◽  
Robot Kinematics ◽  
Rbf Neural Networks ◽  
Task Space ◽  
Actuator Dynamics ◽  
Rigid Link ◽  
On Line

Extensive research efforts have been made to address the motion control of rigid-link electrically-driven (RLED) robots in literature. However, most existing results were designed in joint space and need to be converted to task space as more and more control tasks are defined in their operational space. In this work, the direct task-space regulation of RLED robots with uncertain kinematics is studied by using neural networks (NN) technique. Radial basis function (RBF) neural networks are used to estimate complicated and calibration heavy robot kinematics and dynamics. The NN weights are updated on-line through two adaptation laws without the necessity of off-line training. Compared with most existing NN-based robot control results, the novelty of the proposed method lies in that asymptotic stability of the overall system can be achieved instead of just uniformly ultimately bounded (UUB) stability. Moreover, the proposed control method can tolerate not only the actuator dynamics uncertainty but also the uncertainty in robot kinematics by adopting an adaptive Jacobian matrix. The asymptotic stability of the overall system is proven rigorously through Lyapunov analysis. Numerical studies have been carried out to verify efficiency of the proposed method.

Development of an autonomous robotic system for beard shaving assistance of disabled people based on an adaptive force tracking impedance control

2021 ◽  
pp. 095440622098482
Author(s):  
Oladayo S Ajani ◽  
Samy FM Assal
Keyword(s):  
Impedance Control ◽  
Environmental Parameters ◽  
Robotic System ◽  
Robotic Systems ◽  
Full Potential ◽  
Robotic Assistance ◽  
Head Pose ◽  
Detection And Tracking ◽  
Control Scheme ◽  
Force Tracking

Recently, people with upper arm disabilities due to neurological disorders, stroke or old age are receiving robotic assistance to perform several activities such as shaving, eating, brushing and drinking. Although the full potential of robotic assistance lies in the use of fully autonomous robotic systems, these systems are limited in design due to the complexities and the associated risks. Hence, rather than the shared controlled or active robotic systems used for such tasks around the head, an adaptive compliance control scheme-based autonomous robotic system for beard shaving assistance is proposed. The system includes an autonomous online face detection and tracking as well as selected geometrical features-based beard region estimation using the Kinect RGB-D camera. Online trajectory planning for achieving the shaving task is enabled; with the capability of online re-planning trajectories in case of unintended head pose movement and occlusion. Based on the dynamics of the UR-10 6-DOF manipulator using ADAMS and MATLAB, an adaptive force tracking impedance controller whose parameters are tuned using Genetic Algorithm (GA) with force/torque constraints is developed. This controller can regulate the contact force under head pose changing and varying shaving region stiffness by adjusting the target stiffness of the controller. Simulation results demonstrate the system capability to achieve beard shaving autonomously with varying environmental parameters that can be extended for achieving other tasks around the head such as feeding, drinking and brushing.

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