Research On L-shaped Plate Type Linear Ultrasonic Motor

Linear ultrasonic motors(LUSMs)are widely used in many fields such as aerospace,weapon equipment and precision instruments due to their simple structures,the ability to drive load directly and high precision positioning at low speed.However,many kinds of LUSMs have the characteristics of small output force or large volume,low thrust-weight ratio and complex assembly.To solve this problem,a compact LUSM with large thrust is developed in this paper.The main contents and results of the study are as follows:A novel LUSM operating in a single resonance mode is proposed,which consists of an L-shaped stator and a linear guide.The stator is composed by two rectangular plate vibrators and symmetric and anti-symmetric vibration modes are adopted to realize the bi-directional motions.The position of clamping part and piezoelectric ceramics is determined by finite element method,and the influence of slots in the head block on the amplitudes of driving foot is studied as well.Three prototypes(non-slotted,dual-slot,and single-slot)are fabricated and experimentally investigated.The single-slot prototype exhibits the best performance,whose maximum thrusts in symmetric and anti-symmetric modes are 65 N and 90 N,respectively.The mechanical model of the sandwich piezoelectric vibrator is established,and the effect of bolt clamping method on the prestress in piezoelectric ceramics is analyzed.In the view of the flat structure and large transverse dimension of the vibrator,a bolt is used on both sides of the center of cross section to fasten the vibrator to improve the value and uniformity of the prestress.Experiments shows the improved bolt clamping method can further enhance the output performance of the motor.A V-shaped cutout is designed for the head block of the stator,and the structural intensity technology is introduced into the dynamic analysis of the stator.The influence of the cutout on the vibration energy flow characteristics of the stator is studied.The design method to measure the stator driving ability based on the work done by the elliptical trajectory of driving foot is proposed,and then the structural parameters of V-shaped cutout are optimized.The test result of the prototype shows the maximum thrusts in symmetric and anti-symmetric modes are 100 N and 90 N,respectively,with a maximum thrust-weight ratio of 59.7 and a maximum output power of 13.3 W.