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Ball on beam

Controller design with Sysquake and Calerga VR

Virtual Experimentation

Run   reset reset viewpoint fullscreen

Observe the system to get a basic understanding of its main features: the d.c. electrical motor is on the right and drives a large wheel. Straight rails are fixed on the wheel and a ball rolls freely on them between hard stops.

Observe the movements of the wheel and ball. The controller tries to move the ball to three different rest positions.

Then interact with the system:

  • Drag a point not on the system to move the point of view around the system. You can revert to the initial view with the target icon reset viewpoint, and restart the simulation with the reset icon reset.
  • Drag the wheel to make it rotate. Note that the ball remains on the rails even for extreme accelerations: that's a limitation of the simulation we deem to be appropriate.
  • Try to bring the ball to a rest position by moving the wheel by hand.
  • Drag the ball on the rails. Keep the ball still for a while and observe the movements of the wheel. What happens?
  • You can reduce the power consumed by your computer by unselecting the “Run” checkbox to pause the simulation.

Model

For simulation and controller design, the system is represented as a state-space model. It can be split into two subsystems: the electrical drive with the d.c. motor, and the mechanical part with the wheel, rails and ball. These subsystems have a mutual influence, not an input-output connection where causality is clearly defined.

Details

Controller design

The transfer function of the two subsystems and the controller parameters can be computed with Sysquake.

Sysquake js

Questions

With the interactive Sysquake applications, you can experiment with different controller parameters, see their effect on the virtual experiment and get a better understanding, or confirm your knowledge of, automatic control.

  • Can you distinguish the effects of each parameter of the inner loop controller and the outer loop controller? Try to detune each of them in turn.
  • Is the ball position control performance the same for the central position and right or left positions? Why?
  • Can you notice differences between the models used in Sysquake and the model used in virtual reality?