Hardware-in-the-loop Simulation and Real-time Control

In the previous chapters, Simulink was used to model complicated systems. Single variable and multivariable systems, linear and nonlinear systems, continuous, discrete and hybrid systems, time invariant and time varying systems, engineering and non-engineering systems can all be simulated by Simulink. With the use of S-function and Stateflow techniques, complicated systems, as well as discrete event systems can also be modeled and simulated. So far, numerical simulation approaches in Simulink have been studied. However, the interaction with the real world has yet to be considered. For many practical processes, accurate mathematical models cannot be obtained, so exact Simulink models cannot be constructed. Sometimes due to the complexity of actual systems, the Simulink models established may not be accurate. The actual system should somehow be embedded in the simulation loop to get more accurate simulation results. This kind of simulation is usually referred to as a hardware-in-the-loop simulation. Since this kind of simulation is often performed in real-time, it is sometimes referred to as real-time simulation. Real-Time Workshop provided by MathWorks can translate the Simulink models into C code, and the standalone executable files can also be generated using this tool, so that real-time control can be performed. Also, third-party software and hardware also provide interfaces to Simulink. Good examples of these products are dSPACE, with its Control Desk and Quanser plus WinCon (which can be used to implement hardware-in-the-loop simulation and real-time control experiments). MATLAB and Simulink support many products from well-known hardware manufacturers such as Motorola, Texas Instruments etc, and can directly generate executable code for them from Simulink models. A low-cost NIAT tool can also be used to implement hardware-in-the-loop simulation and experiments. Moreover, a much lower cost platform using Arduino is introduced. In this chapter, these tools will be demonstrated with applications in real-time control.