Torque Measurement of 3-DOF Haptic Master Operated by Controllable Electrorheological Fluid
Abstract This work presents a torque measurement method of 3-degree-of-freedom (3-DOF) haptic master featuring controllable electrorheological (ER) fluid. In order to reflect the sense of an organ for a surgeon, the ER haptic master which can generate the repulsive torque of an organ is utilized as a remote controller for a surgery robot. Since accurate representation of organ feeling is essential for the success of the robot-assisted surgery, it is indispensable to develop a proper torque measurement method of 3-DOF ER haptic master. After describing the structural configuration of the haptic master, the torque models of ER spherical joint are mathematically derived based on the Bingham model of ER fluid. A new type of haptic device which has pitching, rolling, and yawing motions is then designed and manufactured using a spherical joint mechanism. Subsequently, the field-dependent parameters of the Bingham model are identified and generating repulsive torque according to applied electric field is measured. In addition, in order to verify the effectiveness of the proposed torque model, a comparative work between simulated and measured torques is undertaken.
Design and Speed Control of ER Brake System Using GER Fluids
This paper presents robust control performance of a direct current(DC) motor with brake system adopting a giant electrorheological(GER) fluid, whose distinguished feature is an extremely high value of yield stress. As a first step, Bingham characteristics of the GER fluid is experimentally investigated using the Couette type electroviscometer. A cylindrical type of ER brake is then devised based on the Bingham model, and its braking torque is evaluated. Structural analysis of ER break is performed using ANSYS. After formulating the governing equation of motion for the DC motor with ER brake system, a sliding mode control algorithm, which is very robust to external disturbances and parameter uncertainties, is synthesized and experimentally realized in order to achieve desired rotational speed trajectories. The tracking responses of the control system are then evaluated and verified by presenting speed control performance.
A preliminary parametric study of electrorheological dampers
In approaching the design of an electrorheology-based, semi-active suspension, the electrorheological component (ER damper) can be built as either a flow-mode, shear-mode, or mixed-mode type of damper. The source of damping force in the flow-mode is exclusiuely from flow-inducedpressure drop across a value, while that in the shear-mode is purely from the shear stress on a sliding surface. The dynamics of the fluid flow are included in the derivation of the zero-field damping forces. The control effectiveness is found to be strongly related to the dynamic constant (which is proportional to the square root of the vibration frequency) and, for shearandflow-mode dampers, the ratio of the piston area to the cross-section of the ER control gap