Study On Advanced Control Technology Of Cascade Systems

In the industrial process, there is a kind of systems which are consist of multiple subsystems connection in cascade, the outputs of previous subsystem are the inputs of next subsystem, the inputs of the first subsystem are control variables of the system, the outputs of the last subsystem are output variables of the system. These systems are named cascade systems. Not only exist information and energy transmission, but also exist process and structure causal relationship between each subsystem.Starting from establishing mathematical model of cascade system, established the state-space model and controlled auto-regressive sliding integral average model of cascade system. According to the characteristics of the two kinds of model, a approximate optimal control algorithm for cascade system based on full state feedback and a multiple constrained generalized predictive control algorithm for cascade systems are proposed.The main research works and achievements are summarized as following two aspects:According to the structure information of the cascade system, extended the state feedback control theory from the conventional system to cascade system. Proceeding from the state-space expressions of each subsystem to build the state-space model of cascade system, according to the cascade connection of subsystems. Considering the tracking problem of infinite horizon and constant outputs of linear time-invariant cascade system, obtained the approximate optimal control algorithm by using the minimum principle. The cascade systems exist multiple constraints, mainly including amplitude constraints of inputs, the amplitude constraints of input increments, the amplitude constraints of internal variables, the amplitude constraints of outputs and the constraints of output errors etc. Changed all of them into the amplitude constraints of input increments, Solving control law online using the quadratic programming algorithm, a multiple constrained generalized predictive control algorithm for cascade system is presented. The simulation results show that the control algorithm is robust and works effectively for multiple constrained cascade system.