SWITCHING RATES TO SAVE RESOURCES IN DISTRIBUTED COMPUTER CONTROL SYSTEMS

Recent work has shown that switching on-line between controllers using different rates might be beneficial, for example to cope with scheduling or networkinduced jitter. In this paper we extend this approach to achieve a different purpose, i.e., to reduce the resource utilization of a closed-loop controller, namely CPU and network bandwidth, while maintaining its control performance. The proposed approach, named dual-rate, uses two controllers tuned for two sampling rates, a higher nominal rate determined by the usual rules and a substantially lower rate that is used whenever the system is operating close to stationarity. This approach is applied to a simulated steer-bywire automotive application based on Truetime. It is shown that the dual-rate approach allows saving substantial CPU and network bandwidth while maintaining a control performance near the one achieved with the nominal controller alone. The released resources can be used to execute other tasks, transmit other messages or simply facilitate error recovery with temporal redundancy.