Vibration suppression in flexible structures via the sliding-mode control approach

Sliding mode control became very popular recently because it makes the closed loop system highly insensitive to external disturbances and parameter variations. Sliding algorithms for flexible structures have been used previously, but these were based on finite-dimensional models. An extension of this approach for differential-difference systems is obtained. That makes if possible to apply sliding-mode control algorithms to the variety of nondispersive flexible structures which can be described as differential-difference systems. The main idea of using this technique for dispersive structures is to reduce the order of the controlled part of the system by applying an integral transformation. We can say that transformation 'absorbs' the dispersive properties of the flexible structure as the controlled part becomes dispersive

A unified parameter identification method for nonlinear time-delay systems

This paper deals with the problem of identifying unknown time-delays and model parameters in a general nonlinear time-delay system. We propose a unified computational approach that involves solving a dynamic optimization problem, whose cost function measures the discrepancy between predicted and observed system output, to determine optimal values for the unknown quantities. Our main contribution is to show that the partial derivatives of this cost function can be computed by solving a set of auxiliary time-delay systems. On this basis, the parameter identification problem can be solved using existing gradient-based optimization techniques. We conclude the paper with two numerical simulations

Variable Structure Control in Automotive Control Systems

This work presents a control design for an automotive antilock braking systems. Our approach is based on the sliding mode control concept. We formulate the problem of achieving minimum stopping distance as that of extremum searching in a highly uncertain situation when the optimized function is not known analytically but its output values can be observed on-line. For the braking problem the magnitude of the tire/road friction force is a maximized variable. It is considered to be an output of a nonlinear dynamic system which includes the model of mechanical motion and equations of the hydraulic circuit. This setting is complicated by the optimized variable (friction force) not being directly measurable. To overcome this difficulty a sliding mode observer was designed