Analysis of Factors Influencing Peak Torques and Peak Losses of Rotary Voice Coil Actuators Used in Aerospace

Abstract

Rotary voice coil actuators (RVCAs) are commonly used for precision servo drive systems working within limited angle range in some fields including aerospace. In this paper, expressions of RVCAs' peak torque and peak loss are derived based on a simple magnetic circuit model, and influences of wire diameter and equivalent area on peak torque and peak loss are analyzed. Especially, two unique influences of installing dimension and environment temperature for this type of motor are researched as well. Armature reaction and its restraining for this type of actuator are also studied. Finally, several effective measures of improving RVCAs' torques are summarized, which are of important value in practical engineering applications.INDEX TERMS armature reaction, peak torque, peak loss, rotary voice coil actuator, structure parameters. I. INTRODUCTIONVoice coil actuators (VCAs) are special electrical machines which operate only within a range of stroke lengths or angles. Compared with traditional electrical machines, VCAs have many outstanding advantages, such as small volume, direct driving without gears, high precision and low inertia[1]-[5], and so used for driving light weight and low inertia loads. VCAs can be classified into single magnetic circuit VCAs and dual magnetic circuit VCAs from aspect of magnetic circuit structure; or classified into linear VCAs (LVCAs) and rotary VCAs (RVCAs) from aspect of motion type[6], [7]. In this paper, dual magnetic circuit RVCAs are mainly studied, whose typical applications include scanning mirror drive in space cameras, mirror positioning in laser technique and swing type valve brake, etc [8].Generally, the main performance of a RVCA includes peak torque, peak loss, angular stroke, electrical time constant, torque sensitivity, thermal resistance of coil, etc., among which peak torque of the actuator is most important [9]-[11]. The factors influencing peak torque in this type of motors need to be further studied, because there is a significant difference between the structures of RVCAs and general motors.

Calculation, simulation and fast estimation of thermal resistance of rotary voice coil actuators

“…The peak torque (or torque sensitivity) and effective volume of the coil frame are the two special factors which have close relations with the thermal resistance of the RVCA, even though there are many other relative parameters. To a manufactured RVCA, its peak torque, torque sensitivity and stroke are determined by its installation radius to the rotating centre corresponding to the same coil current [16]. Corresponding to the same RVCA, its peak torque will increase and stroke will decrease when its installation radius increases, as shown in Figure 17.…”