Hardware-in-the-loop development and real-time testing for precision motion control under RTAI

Motion control is certainly a challenging task when faced with high speed and high precision control requirements. After the theoretical design, the motion controller should be evaluated by simulation, then refined on the real hardware, under the influence of unmodeled parameters, such as friction, update latency etc. For this purpose, we propose a hardware-in-the-loop (HIL) development and real-time testing framework based on RTAI Linux and Matlab/Simulink. The MATLAB backend of RTAI-Lab is extended to support the external mode of Simulink, such that the internal data structure of the controller running on target boards, is directly exposed to Simulink on local or distributed development workstation. Furthermore, the parameters of the controller can be changed online using the existing tools of Simulink, or through a newly developed web interface. Based on our experience, the changed workflow introduced by the HIL simulation environment is more efficient than the two phase development pattern we have used before, and the real-time testing makes the debugging of the motion control algorithms much easier.