Integrated predictive control and scheduling co-design for networked control systems

Abstract

A predictive control and scheduling co-design approach is proposed to deal with the controller and scheduler design for a set of networked control systems which are connected to a shared communication network. In the proposed approach, a predictive controller is applied to generate the control predictions for each system using delayed sensing data and previous control information, and a time delay compensator is designed at the actuator side to actively compensate for the network-induced delay in the forward channel when the control action is taken. Two different scheduling algorithms, the existing static rate monotonic (RM) scheduling algorithm and a new dynamic scheduling algorithm called dynamic feedback scheduling (DFS), are considered to schedule the transmissions of the control signals generated by the predictive controller, which are packed and transmitted to the actuator in one packet simultaneously. Both the scheduling algorithms are designed with the guarantee of the stability of all the systems, which is achieved by ensuring that the time delay of the systems do not exceed the upper bound under which the systems are stable. It is also pointed out that the RM algorithm is a special case of the proposed DFS algorithm, in the sense that the former can work only in a private network environment, whereas the latter extends its application to such networks where other components occupying the network. Simulations for both the RM and the DFS algorithms, illustrate the validity of the proposed approach.

Error Bounded Sensing for Packet-Based Networked Control Systems

“…This characteristic distinguishes this approach from conventional control approaches to NCSs, where, normally, a constant controller gain is used for all network conditions [6], [13].…”

“…Most of such approaches can be divided into the following two categories. One is to dynamically schedule the communication resources among different control tasks in order to make full use of the communication resources efficiently, as done in [11]- [13]. The other way is to reduce the necessary data transmissions while maintaining the system performance at an acceptable level, i.e., to find the tradeoff between the use of the communication resource and the system performance [14], [15].…”

PDV-based packet length allocation for networked control systems

“…Numerous works have been done from various perspectives in control theory, including but not limited to, time delay system theory [4], [5], switch system theory [6], [7], sampled-data system theory [8], [9], etc. Some other works consider also the controller design with the optimal utilization of the given communication resources, which enables a control strategy named "co-design" for NCSs [10].…”

“…For such a system setting, the communication resources can be measured by the data size required to encode the control signal and two extreme cases are observed in terms of the usage of the communication resources. Most conventional control algorithms use only limited data size that are able to encode one single step of the control signal while a recently reported packet-based control approach uses a much larger data size that is able to encode multiple steps (the upper bound of the round trip delay) of the control signals [10]- [12]. A further observation of the delay in NCSs reveals a fact that the packet delay variation (PDV) has roughly a piecewise constant feature.…”

Algorithm for Reducing the Effect of Network Delay of Sensor Data in Network-Based AC Motor Drives

“…However, these methods can not be applied to the system suggested in this paper, because the ac current and voltage sensor modules among the three sensor modules have the same high priority level. A predictive control to compensate for delayed sensing data and a scheduling codesign approach are proposed to deal with the controller and the scheduler design for networked control systems which are connected to a shared communication network [17]. A time delay compensator on the actuator side is designed to compensate for network induced delays, using delayed sensing data and previous information.…”