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Exercise 5.3 - UR effort control using Robotic System Toolbox

In this exercise you will control a Universal Robots manipulator using Simulink.

Start the Simulation

urmodel = 'ur3e'
StartTutorialApplication('Simulation','Controller', 'Effort', 'Model',urmodel, 'Docker', false);
StartTutorialApplication('Trajectory', 'Docker', false);
StartTutorialApplication('Safety_nodes','docker',false, 'model','threelink'); %sends a 0 torque when no other command has been sent

Remember that you can slow down the simulation as:

SetSimulationSpeed( SpeedFactor, 'docker', false)

Load the Robot

import your Universal robot of choice using urdf files and set gravity in -z direction.

Parameters

Setup your parameters as in Exercise 4.2.

Set:

  • Kp (can be scale during simulation)
  • Kd (can be scale during simulation)
  • taulim according to your robot

Configurations

Try different configurations

store them as:

  • q_desired_1
  • q_desired_2
  • q_desired_3
  • qd_desired

Visualization

compute the transform of the desired configurations and visualize it in rviz.

Dashboard

In the Simulink file you will find the dashboard section that allows you to switch between the configurations, see the current torque output and scale the Kp and Kd matrix during simulation.

Configuration Selector

Check one of these boxes to select the desired configuration.

image_0.png

this selection block is linked to:

image_1.png

Scale Kd and Kp

By using the sliders you can alter the gain value of their corresponding K_scale blocks:

image_2.png

View Torque Trajectory

The Dashboard scope allows you to see the current torques live during simulation (like a scope).

image_3.png

Task 1

Open the file Exercise_5_3_1.slx and complete the control scheme the missing blocks from the Robotic System toolbox.

Use the following blocks:

image_4.png

specify:

  • 'robot' as Rigid body tree

Task 2

Open the file Exercise_5_3_2.slx and complete the control scheme using the following block:

image_5.png

specify:

  • 'robot' as Rigid body tree

The inputs are identical to those explained in Tutorial 4 for the function "inverseDynamics()".