Research And Design Of Looper Control System In Hot Rolling Mill Based On ILQ Theory

With the rapid development of modernized industrial technology, the requisition on variety, specification, quality and yield of strip steel has become higher. Now, there are some difficulties existing in most hot-rolling production line in China, such as low control precision, so technological transformation will be intensified to change this situation. Looper control is one of the most important control items in hot strip rolling mill process, so it’s essential to do some research on control theory and method of looper system. Looper system is a typical double input-output multivariable system, the most difficult challenge in the controller design and control performance comes from the interaction between looper angle and strip tension.In this text, an in-depth research of angle and tension control is made. The structure, components and work process of looper system is detail studied; the couple relationship between tension and angle is also analyzed. This paper also investigates the strong and weak points of various control algorithms proposed in academia as well as industry.According to tension computation formula and torque balance relation of looper motor, the linear mathematical model of looper system on working point is deduced, a control resort based on“pole-place”is proposed. This paper makes a very detail research on ILQ theory (Inverse Linear Quadratic) and its asymptotical characteristic, moreover some new mathematical proof is presented. The prerequisite, normal design method of ILQ is summed up. The basic solution of weight matrix and Riccati Equation in ILQ Design is proposed.A new improved design method is proposed based on ILQ theory. This new method is applied to controller design of looper system and the“asymptotical trait”, good tuning ability, robust and disturbance attenuation of ILQ design is analyzed. The software of looper controller design is developed. Because of good human-machine interface, it’s very easy for researchers to use this software. The ILQ design method is also promoted to solve the same control problem similar with looper system, which is called“controller design of MIMO servo system”.At the end, the weak points of ILQ design and its future development is provided.