Electro-Rheological Fluid Controllers

The paper proposes two new fluid controllers based on the properties ofthe ER fluids. The first controller is a modulated width pulse system in which the control variable is not the amplitude of the input, but rather the duration of the input signal with constant amplitude. An ER valve with an on/off function assures the pulse-width modulated signal. This valve operates as a hydraulic semiconductor controlled by a high-voltage signal. A processor defines the control algorithm and computes the pulse width. A special circuit assures the high-voltage pulse-width modulated signal that controls the ER valve. The dynamic equations of this system are deduced, the transfer functions of each component are obtained and the classic parameters of this controller are computed. It is shown that the proportional and integral coefficients of this controller can be easily implemented from the model parameters. The second controller is a new control system based on the viscosity control of ER fluids by an electrical field. It is shown that the motion control can be divided into two parts: a conventional control determined by the second Lyapunov method for the pressure control of the ER fluid and a non-conventional control obtained by the viscosity control. It is shown that the stability of the motion on a switching manifold is assured if some constraints determined by the non-linear elements of the system are verified. Two control methods are proposed. The first is determined by a simultaneous control of the viscosity on the overall system, a lumped control. The second method is defined by a distributed control of the viscosity associated with a decomposition of the system in a finite number of lower dimension problems. These procedures are applied to a special manipulator, a tentacle arm, and several numerical simulations are presented.