BK21 정보기술사업단 세미나 공고
제 목 When is a linear system easy or hard to control in practice?
강 사 Shinji Hara
소 속 Department of Information Physics and Computing
The University of Tokyo
시 간 2006년 10월 17일 화요일 오전 11시-12시
장 소 301동 118호
Our focus in this talk is to characterize easily controllable plants in practical control applications rather than to design an optimal or a robust controller for a give plant. It is well known that a fundamental requirement of stabilization in feedback control systems provides intrinsic performance limitations such as Bode integral formula for the sensitivity gain.
After explaining the background and the motivation of the research topic, we first provide closed-form analytical expressions of best achievable H2 control performances in two typical optimal control problems, namely tracking and regulation problems, for both continuous-time and discrete-time systems. The results clearly show the performance limitations caused by gain characteristics as well as unstable poles, non-minimum phase zeros, time-delays of the plant. They also reveal and quantify how the lightly damped poles, the anti-resonant zeros, and the bandwidth of the plant may all affect the performance even if the plant is minimum-phase. These are confirmed by several illustrative examples. We then show how to apply those analytical expressions of control performance limitations to practical applications including control of magnetic bearing systems and networked control.
The second topic is concerned with a typical H_infinite robust control performance. We derive a quantitative result that relates the phase property of the plant and the achievable control performance in H_infinite loop shaping design. In particular, the connection between the gain at the critical phase delay of 180 [degree] and the achievable control performance is less than or equal to square root of (4 + 2 times square root of 2) is clarified. This yields guidelines of designing controlled plant under physical constraints from the control view point, which are confirmed by design examples.
문의: 김은정 (Tel: 880-7318)