Research On Hydraulic Linear Motor Driven By Piezostack

In order to meet the requirement to Micro Linear Actuator in the space of aerospace,robot,such as high output power, long trip, high output accuracy,combine piezoelectric actuator technology with hydraulic transmission technology,make a new type of structure hydraulic linear motor driven by piezostack (piezoelectric hydraulic linear motor) .As an actuter in the piezoelectric pump ,through the cycle micro-droplets of liquid the pump achieve cumulative power transmission and motion conversion ,form the macro linear movement of hydraulic cylinder.This motor integrate the superiority of piezoelectric actuter with the superiority of hydraulic motor technology,the paper includes:1,Establishe the Mechanical Model of piezoelectric stack actuator,research the relation the deformation driving force of its mechanical efficiency of the piezoelectric stack to the structural parameters of piezoelectric stack actuator. Study driving voltage and frequency effect on the deformation of piezoelectric stack. The results show that, the deformation of piezoelectric stack proportion to drive voltage and inverse proportion to the load. With increasement of work frequency, the deformation decreases,but has little relation with the waveform of voltage.it is also found that the mechanical efficiency relates with the stiffness of the load,when the piezoelectric stack works independently. when the load stiffness is equal to the rigidity of piezoelectric stack, we get the the largest mechanical efficiency-25 percent.2,Comprehensive use of the basic technology ,such as , piezoelectric, fluid dynamics, mechanical and finite element software,establish the mechanical model of piezoelectric hydraulic motor and related components.research on the effect components parameters on the mechanical efficiency and performance of the piezoelectric hydraulic Motor ,and find the design criteria and parameters method of key components. The result shows that, the mechanical efficiency relates to the type and size of load , hydraulic cylinder cavity area, pump chamber stiffness of the film.in the certain parameters,there is the best flexibility and constant load stiffness which make the largest mechanical efficiency. At the same time, change the stiffness of the pump chamber film only affect the maximum value of mechanical efficiency , but it does not change the best load value and the best flexibility value. using plunger rigid structure as the film of cavity pump , the maximum mechanical efficiency corresponding to the constant load is 50%, the maximum mechanical efficiency corresponding to the flexibility load is 25%. the stiffness of the pump chamber film is determined by the film thickness and the diameter of rigid roof block given the film thickness,we can get the stiffness through changing the diameter of rigid roof block.3,The structural parameters of film valve, the hole size and the direction of flow and the height of pump affect the performance of piezoelectric pump and piezoelectric hydraulic motors ,so,we should considere the compressibility and resistance characteristics of fluid and the rational allocation of parameters when allocate the structure parameters.Based on the theoretical analysis ,we design and make the prototype of hydraulic motorhydraulic motor. The stiffness of pump cavity film and the height of pump cavity is the adjustment target , Testing and analyzing the properties of piezoelectric pump and piezoelectric hydraulic motors,study the relevant parameters relate to the flow of piezoelectric pump, the output speed and driving force of piezoelectric hydraulic motor .The results show that: the largest driven force and speed have different frequency characteristics, in the frequency range of 0 to 400 Hz , the biggest driving force has two best frequency,but there is only one best speed ,the first best frequency of Piezoelectric hydraulic motors is less than the optimal work frequency piezoelectric pump independently.It is showed that hydraulic cylinder resistance , the fluid within the system and the load largely affect the dynamic properties of piezoelectric hydraulic motor,exist the best pump cavity height and diameter of the rigid roof blocks which make the flow of piezoelectric pump ,the speed and driving force of motor maximum.When the diameter of pump cavity is 30 mm, the film thickness is 0.2 mm, selected 0.5～0.8 mm as the height of cavity pump , the diameter of rigid roof block is 24 mm,the pump and motor has better overall performance.Test on-line the 25 mm hydraulic cylinder and piezoelectric pump , the maximum speed and driving force are 11.8 mm / s and 90 N,that prove the feasibility of research programme combined piezoelectric actuator and hydraulic drive technology as the piezoelectric linear motor.