This paper deals with a problem of determination of feedback gains in order to achieve required performances under linear time invariant perturbations. Based upon Lagrange multiplier method, our proposed method determines feedback gains which ensure both robust stability and robust performance for a linear uncertain system. We apply it to a nonlinear crane system control design. At first we partition the nonlinear system into some uncertain linear systems.Next we apply our proposed method to each uncertain linear systems. We can show its application is easy and consequently nonlinear crane control system can be easily designed.Finally it is shown in a numerical example that our proposed method is effective. 984T. IEE Japan, No. 8, '95

A problem of determination of feedback gains in order to achieve required performances is considered in this paper. We suggest a method that assigns any poles in a sector region which specifies the stability and damping factor by making use of coordinate transformations that is ; the imaginary axis's parallel movement and the complex plane's rotation. At first we transform the system to the augmented system by using the above transformation. Next we can show any poles can be located in the specified region very easily by designing the feedback gains which minimize the cost function in the augmented system. Finally it is shown in two numerical examples that our proposed method is effective.