Performance assessment of cascade control systems based on LQG benchmark

Abstract

Given that the LQG benchmark is closer to the actual production, performance assessment of cascade control system based on LQG benchmark has been proposed. The joint input and output subspace identification algorithm was used to estimate the process model, noise transfer function, the inner loop controller and the outer loop controller. And three possible cases could be considered to evaluate cascade control systems. First, none of the inner and outer controllers were known and the goal was to design both controllers to get the global optimum. Second, the outer controller was considered to be fixed and one was looking for the best achievable performance by designing the inner controller. Third, the inner controller was considered to be fixed and one was looking for the best achievable performance by designing the outer controller. These three scenarios were used to evaluate the performance of the global, the inner controller performance and the outer controller. According to the simulation results, performance assessment of cascade control systems based on the LQG benchmark not only get the global performance of the system, but also show how much improvement may be achieved by designing inner and outer controllers.