Impact of Scheduling Policies on Control System Performance

It is well known that jitter has an impact on control system performance, and this is often used as an argument for static scheduling policies, e.g. a time triggered architecture. However, it is only completion jitter that seriously disturbs standard linear control algorithms in a way similar to the delay inherent in a time triggered architecture. Thus we propose that standard control algorithms are scheduled dynamically, but without preemption. Analysis of this policy is contrasted with a corresponding time triggered architecture and is shown to have better impulse response performance both in the deterministic case and under white noise disturbances. The conclusion is that under very reasonable assumptions about robustness of control algorithms,they are insensitive to relase jitter, albeit strongly sensitive to completion jitter, thus priority based scheduling without preemption is may be preferable for such systems.