Computed Torque Control of a Two-DOF Cable-Suspended Parallel Mechanism

2016 ◽  
Author(s):  
Zexiao Xie ◽  
Ben Ma ◽  
Ping Ren
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Sufficient Conditions ◽  
Torque Control ◽  
Parallel Mechanisms ◽  
Computationally Efficient ◽  
Computed Torque Control ◽  
Point Motion ◽  
Point To Point ◽  
Computed Torque

This paper presents the design of a computed torque controller for a two-degree-of-freedom (two-dof) cable-suspended parallel mechanism. Unlike fully constrained cable-driven parallel mechanisms, cable-suspended parallel mechanisms are not redundantly actuated and usually have the same number of actuated cables as the degrees of freedom. Compared with rigid-link parallel mechanisms, the control of cabled parallel mechanisms is more challenging in that the cable tensions are unidirectional. Taking the input constraints into account, the method of computed torque control is applied to the two-dof planar cable robot. The sufficient conditions and necessary & sufficient conditions of the controller’s parameters are obtained, under which the positiveness of the tensions is always maintained during the point-to-point motion within the cable robot’s static workspace. Numerical simulations show that the controller is computationally efficient and the end-effector of the robot could converge to desired final positions with exponential stability.

scholarly journals One-Step Deadbeat Control of a 5-Link Biped Using Data-Driven Nonlinear Approximation of the Step-to-Step Dynamics

Robotics ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 90
Author(s):  
Pranav A. Bhounsule ◽  
Ernesto Hernandez-Hinojosa ◽  
Adel Alaeddini
Keyword(s):  
Torque Control ◽  
Deadbeat Control ◽  
Computationally Efficient ◽  
Foot Placement ◽  
Affine Model ◽  
Computed Torque Control ◽  
Process Error ◽  
One Step ◽  
Step Dynamics ◽  
Computed Torque

For bipedal robots to walk over complex and constrained environments (e.g., narrow walkways, stepping stones), they have to meet precise control objectives of speed and foot placement at every single step. This control that achieves the objectives precisely at every step is known as one-step deadbeat control. The high dimensionality of bipedal systems and the under-actuation (number of joint exceeds the actuators) presents a formidable computational challenge to achieve real-time control. In this paper, we present a computationally efficient method for one-step deadbeat control and demonstrate it on a 5-link planar bipedal model with 1 degree of under-actuation. Our method uses computed torque control using the 4 actuated degrees of freedom to decouple and reduce the dimensionality of the stance phase dynamics to a single degree of freedom. This simplification ensures that the step-to-step dynamics are a single equation. Then using Monte Carlo sampling, we generate data for approximating the step-to-step dynamics followed by curve fitting using a control affine model and a Gaussian process error model. We use the control affine model to compute control inputs using feedback linearization and fine tune these using iterative learning control using the Gaussian process error enabling one-step deadbeat control. We demonstrate the approach in simulation in scenarios involving stabilization against perturbations, following a changing velocity reference, and precise foot placement. We conclude that computed torque control-based model reduction and sampling-based approximation of the step-to-step dynamics provides a computationally efficient approach for real-time one-step deadbeat control of complex bipedal systems.

Adaptive Computed Reference Computed Torque Control of Flexible Robots

1995 ◽  
Vol 117 (1) ◽  
pp. 31-36 ◽  
Author(s):  
I. M. M. Lammerts ◽  
F. E. Veldpaus ◽  
M. J. G. Van de Molengraft ◽  
J. J. Kok
Keyword(s):  
Degrees Of Freedom ◽  
Torque Control ◽  
Control Technique ◽  
Control Law ◽  
State Variables ◽  
Flexible Robots ◽  
Computed Torque Control ◽  
Link Flexibility ◽  
Simulation Results ◽  
Computed Torque

This paper presents a motion control technique for flexible robots and manipulators. It takes into account both joint and link flexibility and can be applied in adaptive form if robot parameters are unknown. It solves the main problems that are related to the fact that the number of degrees of freedom exceeds both the number of actuators and the number of output variables. The proposed method results in trajectory tracking while all state variables remain bounded. Global, asymptotic stability is ensured for all values of the stiffnesses of joints and links. To show the characteristics of the proposed control law, some simulation results are presented.

scholarly journals Control par calculado para seguimiento de trayectoria aplicado a la dinámica de un robot de 3gdl con propósitos didácticos

2020 ◽  
pp. 1-8
Author(s):  
Juan Carlos Hernández-Durón ◽  
José Luis Ortiz-Simón ◽  
Martha Aguilera-Hernandez ◽  
Daniel Olivares-Caballero
Keyword(s):  
Dynamic Model ◽  
Degrees Of Freedom ◽  
Torque Control ◽  
Work Place ◽  
A Value ◽  
Computed Torque Control ◽  
Christoffel Symbols ◽  
Gravitational Vector ◽  
Three Degrees Of Freedom ◽  
Computed Torque

The article shows the needed procedure to obtain the dynamic model of a robot, with the purpose of being able to follow a planned path using the control law “CTC” Computed Torque Control. The robot was designed in a simple way for didactic reasons, this robot has three degrees of freedom, four links and three joints to move around in the work place. Two out of these joints are rotatory joints meanwhile the third one is a prismatic joint. The dynamic model of the robot is obtained using the Jacobians and Christoffel symbols of the center of mas of each link. Also including the Gravitational vector and the frictions of each joint. The objective of the dynamic model is to be able to simulate the robot in “Simulink” and test different paths using the computed torque control in which the gains of the control will be manipulated until a value that satisfies the desired path is found

Servo-Constraint Based Computed Torque Control of Underactuated Mechanical Systems

2011 ◽  
Author(s):  
La´szlo´ L. Kova´cs ◽  
Jo´zsef Ko¨vecses ◽  
Ambrus Zelei ◽  
La´szlo´ Bencsik ◽  
Ga´bor Ste´pan
Keyword(s):  
Degrees Of Freedom ◽  
Control Method ◽  
Equations Of Motion ◽  
Geometric Constraints ◽  
Torque Control ◽  
Underactuated Mechanical Systems ◽  
Computed Torque Control ◽  
Distribution Matrix ◽  
Underactuated Robot ◽  
Computed Torque

This paper aims to generalize the computed torque control method for underactuated systems which are modeled by a non-minimum set of generalized coordinates subjected to geometric constraints. The control task of the underactuated robot is defined in the form of servo constraint equations that have the same number as the number of independent control inputs. A PD controller is synthesized based on projecting the equations of motion into the nullspace of the distribution matrix of the actuator forces/torques. The results are demonstrated by numerical simulation and experiments conducted on a two degrees-of-freedom device.

scholarly journals Dynamic Analysis Of Two Link Robot Manipulator For Control Design Using PID Computed Torque Control.

2016 ◽  
Vol 5 (4) ◽  
pp. 277
Author(s):  
Jolly Atit Shah ◽  
S S Rattan
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Robot Manipulator ◽  
Equation Of Motion ◽  
Torque Control ◽  
Computed Torque Control ◽  
Speed Accuracy ◽  
Accuracy And Repeatability ◽  
Computed Torque

<p>Due to their advantage of high speed, accuracy and repeatability, robot manipulators have become major component of manufacturing industries and even now a days they become part of routine life.            </p><p>Two link robot manipulator is a very basic classical and simple example of robot followed in understanding of basic fundamentals of robotic manipulator. The equation of motion for two link robot is a nonlinear differential equation. For higher degrees of freedom, as the closed form solutions are very difficult we have to use numerical solution. Here we focused mainly on control of robot manipulator to get the desired position using combination of two classical methods PID and computed torque control method after deriving the equation of motion. For the same simulation is represented using MATLAB and compared with computed torque control method.</p>

A PD Computed Torque Control Method with Online Self-gain Tuning for a 3UPS-PS Parallel Robot

Robotica ◽  
2021 ◽  
pp. 1-13
Author(s):  
Xiaogang Song ◽  
Yongjie Zhao ◽  
Chengwei Chen ◽  
Liang’an Zhang ◽  
Xinjian Lu
Keyword(s):  
Feedback Loop ◽  
Control Method ◽  
Virtual Work ◽  
Parallel Robot ◽  
Torque Control ◽  
Virtual Work Principle ◽  
Tuning Method ◽  
Computed Torque Control ◽  
Control Feedback ◽  
Computed Torque

SUMMARY In this paper, an online self-gain tuning method of a PD computed torque control (CTC) is used for a 3UPS-PS parallel robot. The CTC is applied to the 3UPS-PS parallel robot based on the robot dynamic model which is established via a virtual work principle. The control system of the robot comprises a nonlinear feed-forward loop and a PD control feedback loop. To implement real-time online self-gain tuning, an adjustment method based on the genetic algorithm (GA) is proposed. Compared with the traditional CTC, the simulation results indicate that the control algorithm proposed in this study can not only enhance the anti-interference ability of the system but also improve the trajectory tracking speed and the accuracy of the 3UPS-PS parallel robot.

Computed Torque Control Method for Two-Axis Planar Serial Robotic Arm

2021 ◽  
pp. 1-9
Author(s):  
G. Perumalsamy ◽  
Deepak Kumar ◽  
Joel Jose ◽  
S. Joseph Winston ◽  
S. Murugan
Keyword(s):  
Control Method ◽  
Torque Control ◽  
Robotic Arm ◽  
Computed Torque Control ◽  
Computed Torque
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