Task scheduling with feedback latency for real-time control systems

Abstract

A new task-scheduling algorithm with feedback latency is suggested for real-time control systems, which considers both point of views-control theoretic and real-time computing. Building a real-time control system has two steps in general. In the controller design stage, a control performance index is defined and a controller is designed which optimizes the given performance index while maintaining stability and rejecting disturbances. In the implementation stage, a set of controllers constitutes multiple control tasks, and scheduled to run on microprocessors, which should be schedulable with limited computing resources. The author reveals that the control performance depends not only on the control period but also on the feedback latency (latency from sensing, computation to actuation), which is revealed to have more impact. We formulate a new task-scheduling problem with a suitable control performance index including the feedback latency. An iterative search algorithm is suggested which is based on feedback latency computation method. An illustrative example demonstrated the applicability of the proposed method.