The use of the concepts of directionality and ill-conditionedness is investigated. A lack of consistent terminology is detected, and some clarifications to the terminology are suggested. Robustness issues with respect to directionality are discussed. Control structures in the form of decoupling are discussed, and a more general formulation for dynamic decoupling is formulated. Process nonlinear...

We extend retrospective cost adaptive control (RCAC) with auxiliary nonlinearities to command following for uncertain Hammerstein systems with non-monotonic input nonlinearities. We assume that only one Markov parameter of the linear plant is known and that the non-monotonic input nonlinearity is uncertain. Auxiliary nonlinearities are used within RCAC to account for the non-monotonic input non...

piezoelectric actuators are widely used in micro manipulation applications. however hysteresis nonlinearity limits accuracy of these actuators. this paper presents a novel approach utilizing a piezoelectric nano-stage as slave manipulator of a teleoperation system. the prandtl-ishlinskii (pi) model is used to model actuator hysteresis in feedforward scheme to cancel out this nonlinearity. a pas...

this paper is concerned with the study of the existence of positive solutions for a navier boundaryvalue problem involving the p-biharmonic operator; the right hand side of problem is a nonsmoothfunctional with variable parameters. the existence of at least three positive solutions is establishedby using nonsmooth version of a three critical points theorem for discontinuous functions. our resul...

Both the forward and backward kinematics of the Gough-Stewart mechanism exhibit nonlinear behavior. It is critically important to take account of this nonlinearity in some applications such as path control in parallel kinematics machine tools. The nonlinearity of inverse kinematics is straightforward and has been first studied in this paper. However the nonlinearity of forward kinematics is mor...

The hysteresis nonlinearity of magnetically controlled shape memory alloy actuator is an obstacle in the achievement of high positioning accuracy. To eliminate the influence of hysteresis nonlinearity, a PID hybrid control method which uses the inverse Prandtl-Ishlinskii model as a feedforward controller is proposed in this paper. The PID parameters are searched by particle swarm optimization w...

This paper addresses the control design problem for a certain class of continuous-time nonlinear systems subject to actuator saturations. The system under consideration consists of a system with two nested nonlinearities of different type: saturation nonlinearity and cone-bounded nonlinearity. The control law investigated for stabilization purposes depends on both the state and the cone-bounded...