Suboptimal Control of Flexible Structures With Clearances in the Connecting Joints

Clearances are important sources of nonlinear behavior in connected or "built-up" structures. This paper examines the effects of clearances on the performance of a linear state-feedback and estimated state feedback control design. The control laws are designed using linear quadratic optimal contol theory and using a linear plant model. The closed-loop behavior of the linear plant is compared to that of the nonlinear plant under the action of the same control laws. It is seen that, relative to the linear plant, clearances can have detrimental or beneficial effects on the closed-loop performance depending on the nature of the clearances and depending on the system initial conditions.