Search

Industrial robot arms experience position inaccuracies due to the output cogging torques of the DC servomotors. Therefore, in an attempt to resolve these position problems, an electro-rheological (ER) robotic system is considered as an actuator to drive the robot arm rapidly in both directions. This ER robotic system consists of two ER clutches, an ER brake, a gear train, an encoder and a robot arm. The ER clutches produce clockwise and anti-clockwise rotations. The ER brake decelerates and halts the robot arm. The main aim of this paper is to validate a controller model of the ER robotic arm. Next, a trend study is used to determine the optimum working conditions of the ER actuated-robotic arm. The robotic displacements of both the ER rotary devices and the commercial DC servomotors are compared in terms of position accuracy and speed of response. Finally, the repeatability of the robotic end positions is examined in order to determine the importance of the ER brake.

Electro-rheological (ER) fluid devices are smart actuators that possess several advantages such as controllable output dynamics and fast speed of response. Due to these output capabilities, an ER clutch is studied for the possibility of actuating the robotic arm. This is achieved by laying a few objectives. The main focus of this paper is to perform model validations of an ER velocity response of this ER clutch. Next, it is aimed to determine a method for rapid energization and de-energization of the ER output velocity for delivering fast start-stop robotic motions. The third aim is to employ the trend study on the ER output velocity response in order to define suitable input parameters for optimum ER robotic performances. The final aim is to determine the reliability of the tested ER fluids shearing in the ER clutch for long-term robotic applications.

Robot arm positioning is an important factor in the robotic process. However, the robot manipulator experiences positioning inaccuracies. This positioning error is due to the dynamic inefficiencies of its actuator: DC servomotor. In a bid to resolve this actuator problem, an electro-rheological (ER) clutch-brake mechanism is employed. This clutch-brake mechanism can actuate and halt the motion of the robot arm. This rotary mechanism consists of two similar clutches that are driven to rotate in the opposite directions and an individual ER brake that provides braking torques to halt the manipulator at the required positions. The main aim of this paper is to establish a control strategy for the ER actuated robot arm by means of model validation with the experimental results. This study is conducted to understand the ER robotic positioning control for future applications.

Positioning accuracies of the robot arms are important at fast maneuvering speeds of the manipulators. In the past, many researchers had investigated the precisions of the robotic arms. They reported that these robotic positioning errors are caused by the dynamic inefficiencies of the robotic actuators; DC servomotors. Therefore, in order to resolve this actuator's issue, a twin electro-rheological (ER) clutch mechanism that consists of two counter-rotating ER clutches is employed. This is due to its output dynamics being unaffected by the output cogging torque of the driving motors. Also, this clutch mechanism can perform rapid reversal responses in bi-directional mode. In this present paper, two kinematics models that describe the output angular velocity and displacement behaviors of this clutch mechanism undergone validations. Next, the trend studies of these angular kinematics responses are conducted in order to determine the methodology to generate the fastest reversal motions of the clutch mechanism.

This paper is concerned with an experimental investigation of the performance of an ER fluid in oscillatory squeeze-flow and a comparison of the results with those predicted by a quasi-steady theoretical model in which the rheological behaviour of the fluid is assumed to follow a bi-viscous shears stress/shear rate characteristic. The fluid is sandwiched between two parallel plane electrodes, the upper one stationary and the lower one oscillating normal to its plane. Of particular interest is the temporal variation in the force transmitted through the fluid in response to changes in the oscillation frequency and amplitude and the level of applied AC and DC voltages. The magnitude of the transmitted forces in the AC case is seen to be not only a function of the applied voltage but also of the shape of the input waveform and the electrical excitation frequency. In all cases these forces are found to be smaller than those seen in the corresponding DC case.

In previous papers a technique for comparing the performance of a particular electrorheological (ER) fluid in different situations was derived from steady, laminar, shear and flow mode experimental data and static cell tests. By plotting non-dimensional Hedström Number (He) and Friction Coefficient (Cf) against Reynolds Number (Re) via use of the Bingham plastic constitutive equation, one continuous and overlapping relationship was shown for constant field excitation over a range of operating conditions and geometries. In the present work the same treatment is extended to a different fluid, of higher solid volume fraction and different constituents, which was tested on different instruments at a different uniform temperature, so as to attest the generality of the technique. In doing this the methodology of converting low shear rate Couette viscometer data to practical flow valve performance predictions is illustrated.

This paper is concerned with an experimental and theoretical study of the characteristics of two ER fluids and their application to vibration control when used in squeeze flow. It is seen that when the fluids are sandwiched between two electrodes, the lower one oscillating and the upper one fixed, displacement control of the lower electrode can be achieved by control of the applied field. Of particular interest is the dependence of the force transmitted across the fluids on oscillation frequency and applied field. A time-dependent theoretical model is seen to satisfactorily predict the device performance when allowance is made for a non-linear dependence of the post-yield shear stress on shear rate.