Motor Using Mechanical Vibration of Multiple Bimorph Beams

Abstract

The present paper proposes a non-magnetic motor with a rotor rotated by the mechanical resonance energy of four bimorph cantilever beams excited by an electrostatic force. The use of a flexible material such as silicon rubber enables conversion of translational vibration to rotary movement in one direction. The rotational speed of the proposed motor increases in proportion to the input voltage when two bimorph beams are used, and the maximum rotational speed was found to be 6,804 rpm when the input voltage was set to 24.6 V. Next, the basic characteristics of a prototype motor with four bimorph cantilever beams, including rotational speed, output torque, and efficiency, were determined experimentally. The experimental results revealed that a maximum rotational speed of 6,370 rpm was obtained when the output torque was 19.6 μNm. The proposed motor was also observed to produce an output torque of 63.7 μNm when the rotational speed was 1,491 rpm. The maximum efficiency was 6.2% when the input power was 0.3 W. For the proposed motor, the volume and weight were reduced by approximately 35%, as compared with a motor from a previous study.Keywords: motor, frictional force, flexible material, bimorph cantilever beam, resonance, second vibration mode IntroducationThe electromagnetic motor is used widely in medical, welfare and industry. However, an output torque is quite small when the size of the motor becomes small. Therefore, a micro-gear is necessary to increase torque of the motor. In turn, this would require a reducer manufactured with very high precision. On the other hand, non-magnetic motors do not use electromagnets or permanent magnets, and so do not produce electromagnetic waves. More specifically, non-magnetic motors perform stably in high-magnetic-field environments. The demand has increased for non-magnetic motors for generating high torque in strong magnetic fields generated through superconductivity, as well as in medical applications such as magnetic resonance imaging (MRI) and magnetoencephalography. Non-magnetic motors have been discussed for long time. As such, many studies have investigated the mechanisms of motors using non-magnetic devices, such as electrostatic elements (Jian et al., 2006;Xiaolong et al., 2014;Peled et al., 2016;Aoyagi et al., 2016;Yu et al., 2016;Yamamoto et al., 2005; Kurosawa, 1997;Niino et al., 1997), electrorheological fluid (Yokota et al., 2004), shape memory alloys (Sharma et al., 2008), magnetostrictive elements (Pack et al., 2013;Ueno, 2009), the electrostatic optical motor by using PLZT element (Morikawa et al., 2003), and the combination of a frictional force and an electromagnetic force (Maruno et al., 2000;Yaguchi et al., 2014). An ultrasonic motor is being developed as a typical example of a non-magnetic motor, and the design and production techniques of this ultrasonic motor are almost established. However, ultrasonic motors are very expensive, although the cycle of use is short. By another means a stick-type non-magnetic motor manufactured using two bimorp...