Task space control of a robot through dynamics

Hello everyone

I am trying to drive my robot using torque. I am using Robotic system toolbox mainly in simulink.

My model consists of:

1. Trajectory Velocity Profile block that has a square trajectory defined in task space. It has 3 outputs, all 3x1 vectors: q,qd,qdd.

2. I supply q output to Coordinate Transformation Conversion and than to Inverse Kinematics. It gives me the needed joint configuration for my task space trajectory. Its a 2x1 vector since my robot is a 2dof robot.

3. I added Inverse Dynamics block in order to control my robot through torque. Its inputs are:

Config: I supply that from Inverse Kinematics

JointVel: I got joint velocities by using Get Jacobian block and supplying config output of Inverse Kiematics to in, than getting the last 3 rows of it since those are the linear velocities, doing a pseudo inverse, and mulitplying that with qd from Trajectory using Matrix multiply.

JointAccel: No idea how to get that, would appreciate help.

4. I than supply torque output of Inverse Dynamics to my robot.

Here is an image of how it looks:

I tried multiple ways of building that system.

My goal is to basically control robot using toruq in task space. Robot has to do a square with its en effector. Becouse model includes dynamics square wont be perfect as it would be if i just included kinematics. Than I will build a control system to improve trajectory following.

But how do i make the robot at least try to do my desired trajectory?

How do i compute join acceclerations for Inverse Dynamics block?

Is there an example/tutorial of how to control a robot in task space with dynamics(preferably using Robotic System toolbox in simulink)? All i could find were joint space videos/posts.

I will appreciate all the help.

Best regards,

Szymon

Answer 1

[Szymon Blazejewicz]

Maybe to ilustrate my problem better this image will help:

I can controll my robot using JUST inverse kinematics fine, it follows the trajectory. But i want to use torque and to include dynamics in the simulation.

However i cant seem to move the robot using dynamics. My model can be found in the attachement

Answer 2

[Sam Chak]

Hi @Szymon Blazejewicz

This Simulink example shows you how to generate the trajectories for the end effector of the robot manipulator to trace the shape of MATLAB® membrane logo in the robot workspace.

https://www.mathworks.com/help/robotics/ug/manipulator-shape-tracing.html

[Szymon Blazejewicz]

Hello Sam

What you linked is a simple inverse kinematics example and not at all what I am looking for. I am able to trace my trajectory using inverse kinematics with ease. What i want is to use dynamics and control the robot using torque while tracing a trajectory.