Real-time Implementation of Multi-rate Sampling Systems in RT-Linux environment

For real-time implementation of multi-rate sampling system, the position control of servo unit with real-time PID control algorithm-using RT-Linux thread program is considered. In the RT-Linux environment, effect of varying time-delays on performance and stability in the single-channel multi-rate hybrid system consisting of a continuous-time plant and a discrete-time controller is presented in this paper. The best sampling rate is chosen for the sampled-data system, which is the slowest rate meets all performance requirements. The multi-rate controller is composed by a slow sampler (operating at a low frequency) and a fast hold (operating at a high frequency). Each of the slow samples is converted into a group of N fast samples (Hold) and thus only one of each group of N samples can be used as information feedback to the controller since sensor operates at low frequency. The main result of our experiment shows that the multi-rate control technique in RT-Linux can solve the stability problems caused by the random access delays and asynchronization with required performance.