Stability analysis of networked control systems.
详细信息
文摘
Feedback control systems wherein the control loops are closed through a realtime network are called networked control systems (NCSs). The defining feature of an NCS is that information (reference input, plant output, control input, etc.) is exchanged using a network among control system components (sensors, controller, actuator, etc.). The primary advantages of an NCS are reduced system wiring, ease of system diagnosis and maintenance, and increased system agility.;The insertion of the communication network in the feedback control loop makes the analysis and design of an NCS complex. Conventional control theories with many ideal assumptions, such as equal-distance sensing, synchronized control, and non delayed sensing and actuation, must be reevaluated before they can be applied to NCSs.;We first study the stability of NCSs with time-varying transmission period. Under an ideal transmission process, i.e. no transmission delay or packet dropout, we have derived sufficient conditions on the transmission period that guarantee the NCS will be stable. We also discuss methods to numerically search for such bounds on the transmission period.;Following this, we study network scheduling when a set of NCSs are connected to the network and arbitrating for network bandwidth. We first define the basic concepts of network scheduling in NCSs. Then, we apply the rate monotonic scheduling algorithm to schedule a set of NCSs. We also formulate the optimal scheduling problem under both rate-monotonic-schedulability constraints and NCS-stability constraints, and give an example of how such optimization is carried out.;Next, the assumptions of ideal transmission are relaxed. We study the stability of NCSs with network-induced delay. We first model NCSs with network-induced delay, and analyze the stability of such NCSs using the notion of stability region and a hybrid systems stability analysis technique. We also discuss a scheme to compensate for network-induced delay based on the time-domain solution of the closed-loop system. Experiments over a physical network are also carried out to validate the scheme.;Finally, we study the stability of NCSs with data packet dropout and multiple-packet transmissions. We model these scenarios as asynchronous dynamical systems (ADSs) and extend stability conditions of ADS to these setups. We also come back to the problem of network scheduling in NCSs.