OSEK-based multiple controllers with schedule feasibility self-testing

This paper presents a new embedded controller based on schedule feasibility self-testing, suitable for fast linear or nonlinear dynamic plants. The suggested solution provides concomitant multiple control laws working at different sampling frequencies. As protection to overloading conditions, an adaptive mechanism is introduced, meant to preserve the consistency of the control algorithms, whilst keeping the microcontroller utilization in the desired range. It performs the on-line checking of the schedule feasibility, switching temporarily to lower sampling frequencies, once the risk of violating the real time constraints occurs. This strategy permits to employ high default frequency at system start-up, with benefits on the rapid detection of disturbances. In order to provide increased safety and predictability, OSEK/VDX real time operating system was adopted. The performances of the proposed approach are experimentally illustrated on a DC motor with separate excitation, by providing both the inner current control loop and the outer speed one.