Development of a Surface Acoustic Wave Planar Motor under Closed Loop Control
نویسنده
چکیده
This paper describes the development of a Surface Acoustic Wave (SAW) planar motor under closed loop control, which can be applied as an ultra precision multi-axis manipulator. In papers presented so far on this topic, a SAW motor is driven in open loop. The slider is manipulated by inducing a repetitive small number of wave periods. In this way a slow slider motion can be generated, which however, is not constant during the cycle time. Although very small steps have been reported for SAW actuators operating in open loop (in the order of 2 nm), the reproducibility of such open loop steering is low in an environment with disturbances. Therefore, one of our focus points is closed loop control of the SAW actuator. To investigate the openand closed-loop behaviour, two linear SAW motor demonstrators have been developed. Measurements have shown that for conventional actuation a dead band appears in the response of the input signal to the speed of the motor. To overcome this phenomenon, a different way of continuous actuation is presented in this paper, on which a patent has been filed. As a result of the investigations of the linear demonstrators, a closed loop controlled planar SAW motor has been designed, which is under construction and is scheduled to be operational in the spring of 2002. This planar motor concept features a simple and compact construction with low moving mass, since the driveand guiding-systems are combined, without the need for external bearings, transmissions or guiding systems. Compared to stacked linear systems, a high stiffness and good dynamic behaviour can be achieved. Further experiments are planned to establish the potential benefits of a planar SAW motor in applications of precision engineering and nanotechnology.
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