A variable structure controller for a tentacle manipulator

The paper presents a class of tentacle arms based on the use of flexible composite materials in conjunction with active-controllable electrorheological (ER) fluids. The model consists of a finite number of segments, each segment having a specific structure and control. The dynamic behaviour of the arm is obtained using Lagrange's principle developed for infinite-dimensional systems. This model is represented by a set of integral-differential equations. An approximate model is then derived as a set of differential equations with variable coefficients. Two cases are discussed: the sliding mode with the bang-bang control; and the direct mode in which the controller is based on the use of the direct evolution of the system on the switching line by switching the fluid viscosity. The numerical simulations are presented. A nonlinear observer is introduced to estimate the inaccessible state variable distributed on the length of the arm. The conditions which assure the convergence to zero of the errors are proved.