Control Systems Teaching: Virtual practicals to enhance practical perspective
“Control systems, at undergraduate level, is too often predominantly taught/learned from the pages of a textbook – however, control systems do not exist on the dead pages of a textbook. Furthermore, students struggle with abstract, mathematical concepts that are difficult to visualise – this makes them lose interest in an utterly interesting module. Laboratory sessions are then used in an attempt to overcome this barrier, but practical setups are complex and expensive – hence my endeavour to use “virtual practicals” in my undergraduate control systems course.” – Dr Karel Kruger, Mechanical and Mechatronic Engineering Lecturer, Stellenbosch University.
To give life to the control systems theory, Dr Karel Kruger introduced a Ball-on-Beam system, or BoB, to his classroom. The system can automatically balance a ball on a beam, at a specified position, by controlling the angle of the beam with a motor. The objective of BoB is to inspire interest amongst his students and to give them something tangible and fun to engage with – instead of just equations in a text book.
BoB is developed in two forms:
- a real BoB system – a physical system to be used as a class room demonstrator (Figure 1).
- a virtual BoB system – a simulation of the physical system to be used for tutorials, or “virtual practicals” (Figure 2).
Figure 1: Real BoB system.
Figure 2: Virtual BoB system.
The real BoB system is used as a classroom demonstrator – i.e. the system can be operated from the desk in front of the lecture hall. BoB can be used to demonstrate theoretical/abstract control systems concepts/phenomena immediately after being introduced in the lecture.
The virtual BoB system was constructed from a CAD model of the physical system, which was imported to the Simscape Multibody environment. The model was then interfaced to a controller, which was developed with Simulink. The virtual system takes a ball position input from the user and produces an animated system response – numerous variables are logged and can be viewed and analysed after a simulation run. The students were tasked to develop and test a state space controller in Simulink.