The Research Of A Langevin Type Piezoelectric Tracked Travelling System

Lunar rover is the essential tools and necessary means for the realization of scientific objectives in second and third Chinese lunar exploration projects. There are three basic forms of lunar rover driving systems include wheeled, legged and tracked types, and the tracked driving systems are paid widespread attention with the characteristics of strongly obstacle capability, low vehicle sinkage and highly drawbar pull, but the complexity of drive train mechanism and large weight hinders the applications of the tracked driving system in the lunar rovers. Aimed at simplified structure, enhanced the ability to resist pollution and reduced weight and energy consumption, the essays utilized the principle of piezoelectric excitation and friction driving to explore the new method of tracked lunar rover drive system. Based on the research of the bonded type piezoelectric tracked travelling system, a novel tracked travelling system driven by a Langevin piezoelectric transducer is proposed, and then the structure optimization of the piezoelectric vibrator, kinematics and dynamics behavior of the surface particles and the interaction between the contact boundary conditions and the structural dynamic behavior were investigated.1. The driving principle of the bonded type piezoelectric tracked travelling s ystem was simply analyzed, and then the driving principle and method of the Langevin type piezoelectric tracked travelling system were proposed to solve the problem of low power. A pair of electric signals with ?/2 phase shift are applied to four sets of piezoelectric elements located in the beam, which lead to rotating travelling waves in the annular parts placed at the ends of the beam, and then the microscopic elliptical motions of the outer surfaces particles of the annular parts will be generated to drive the track to move by friction force.2. In order to reduce the frequency difference of operating modes and to increase the frequency difference of the interference modes, the optimization software ISIGHT with the multi-objective optimization toolbox was used to optimize the structure of the piezoelectric vibrator by calling the finite element program for conducting the iterative calculation. The frequency difference of the operating modes is reduced to 8Hz from 605 Hz, the front interference mode frequency difference is increased from 169 Hz to 1098 Hz, and the later interference mode frequency difference is added from 400 Hz to 1323 Hz.3. The motion characteristics of the prototype were investigated by experiments: the optimal driving frequency is 35.1kHz. Its sarting time and stopping time are 120 ms and 25 ms, respectively, and the transient velocity changed periodically. The average velocity of the prototype was 72mm/s under the voltage of 500 V_pp. When applying a pair of sinusoidal voltages of 300 V_pp, the maximum load weight reached to 1.44 kg with the prototype weight of 0.4kg, and the traction force was 0.48 N under the driving voltage of 320 V_pp.The structure design and working principle of the Langevin type piezoelect ric tracked travelling system are analyzed, and then the feasibility of the design scheme is verified by experiments. However, in the theoretical model, the components of assembly process, design and experimental aspects need to be further improved, includ ing the scientific explanation on the relationships between the surface roughness, contact stiffness, pressure and velocity and the research on the environmental adaptability.