Research On Pre-Pressure Self-adjusting Traveling Wave Ultrasonic Motor

With the deepening of research and the development of science and technology,Traveling wave type Rotary Ultrasonic Motor(TRUM)is becoming more and more mature,and the applications have been applied in engineering widely.TRUM's unique friction drive method has the advantages of low speed and large torque,fast response and self-locking without power,but it also leads to relatively low efficiency.In terms of speed control,the commonly used method of adjusting the frequency to achieve speed control has high precision and wide range.However,there is a problem of the coupling of the speed/output torque,which is not conducive to the performance of its low speed and large torque.In view of the above two problems,based on the TRUM-70 ultrasonic motor,two types of electromagnetic variable pre-pressure ultrasonic motors are designed by changing the application method and control method of the pre-pressure.The main contents and research results of this paper are summarized as follows:1)The two-dimensional friction drive model of TRUM is established.The influence of prepressure on stator vibration,friction interface contact range and constant-speed point of stator and rotor is studied.The mathematical relationship between pre-pressure,load torque and motor speed is obtained..Based on the theoretical model,the research value of two types of variable pre-pressure motors is analyzed,and the performance characteristics are predicted.2)Variable pre-pressure ultrasonic motors based on electromagnets and electromagnetic clutches are designed,which are respectively used to adjust speed by pre-pressure and improve motor efficiency.According to the working principle of the two motors,the core components are subjected to force and motion analysis,and the basic parameters of the electromagnetic mechanism are calculated according to the design requirements.Control methods for the variable pre-pressure motors are proposed,and the corresponding control circuits are designed.Using Maxwell to simulate the designed magnetic circuit,the parameters are imported into Ansys Workbench for optimization analysis,so that the electromagnetic mechanism can reduce the power and size while satisfying the requirements of use.3)The prototype is machined and assembled.The feasibility of the two motors was verified by experiments and the performance are compared to conventional ultrasonic motors.The experimental results show that the pre-pressure automatic speed can be realized by using the electromagnet-type variable pre-pressure ultrasonic motor,and the method is more advantageous under the conditions of high voltage and large load;the electromagnetic clutch type variable pre-pressure ultrasonic motor can effectively improve the output efficiency of the motor is more effective when the load changes greatly.