Theoretical And Experimental Study On Piezoelectric Precision Step Actuator

Precision and ultra precision actuator is the important technique of modern science technology and modern industrial field. The traditional driving technique can not reach the super-precision standard of sub-micron and micro/nano level, also with the control technique. Piezoelectric precision stepper actuator can achieve ultra precision drive capability. The piezoelectric precision stepper actuator is based on the theory of the inverse piezoelectric effect phenomenon, it is named that the piezoelectric actuator can produces power and displacement under the electric field. The super-precision actuator works like the movement of the bionics. So the piezoelectric precision driving control technology is the important technology and has already become the research focus in the many college and companies in the world. The piezoelectricity actuator has the good characteristics such as linear and convenience control, high displacement resolution, good frequency respond, few heat production, heavy load driving and no-magnetism interference, no noise, etc., It is because of the piezoelectric actuator is pocket-size, light-weight, high-power density, and so on. The piezoelectric precision step actuator will make more use in the modern science and technology and modern industrial realm. With several ten years reach in piezoelectric actuator many progress is get, but many puzzle of techniques haven't solved yet, such as continuous driving ability, precision, stabilities of each step, step frequency and velocity etc. The thesis tries to study the new piezoelectric precision actuator in the new driving theory, new structure design and new control methods. Firstly,the thesis analyzed the basic theory and working principle of the piezoelectric precision step actuator. The piezoelectric pile is the vital power element of the piezoelectric precision step actuator and the working principle is the basis to make sure that the actuator can work normally. The characteristics of the piezoelectric pile include the piezoelectricity, the capacitance trait, response trait, hysteresis, dynamics trait, resolution trait, repetition trait and so on. Based on the principle of step driving mode, the new step working mode which is driving outer and inner is put forward and its working principle is labored. Besides the new step driving mode, the thesis put forward the bidirectional push working principle due to the working characteristics of the piezoelectric pile and the piezoelectric step actuator weakness that its single directional drive load is bigger but its reverse drive load is lesser, This principle of the bidirectional push working resolves the problem that the positive and the negative directional drive power are different. Based on the working principle and mode of the step actuator, linear piezoelectric precision step actuator can be divided into two groups: outer driving mode and inner driving mode. 1. Studied the piezoelectric step actuator of outer driving mode. (1).Structure design: that includes clamping structure design, driving structure design and pre-load structure design. Furthermore, the working principle and mechanical state is labored. (2).Detailed kinetics analysis. The modeling the whole structure of the outer driving piezoelectric step actuator is founded. The motion transfer function of the whole structure is elicited. The kinetics model of the clamping structure and the driving structure are founded. Furthermore, all their vibration response capabilities are analyzed and every working process is studied with finite element analysis. (3).Experiment study. From experiment, the thesis got the parameters of the outer driving piezoelectric precision step actuator: The most clamping load: 70N(voltage: 60V-100V) The clamping error: 0.016μmThe most continuum driving load: 47N (voltage: 100V) The most step: 6.0μm (voltage: 100V) The step error: 5.2%—5.6% The most system working frequency: 40Hz The resolution: 0.04μm The most step velocity: 240μm /s(40Hz, 100V) (4).The influence brought by the additive factors acting on this driver was analyses qualitative. These additive factors include design influence, outer vibration, friction damp, temperature variety and so on. The outer piezoelectric precision step actuator with new working mode can step work effectively with high resolving power, great load, high speed, high frequency and steady movement. 2. Studied the piezoelectric step actuator of inner driving mode. The clamp process and the drive process of the inner driving mode step actuator is independent. This part researched its clamp characteristic. drive characteristic, system frequency characteristic and its design principle, resolution and its driving velocity. From experiment, the thesis got the parameters of the inner driving piezoelectric precision step actuator: The most clamping load: 86N(voltage: 100V) The clamping error: 0.0036μm The most continuum driving load: 48N (voltage: 100V) The most step: 4.3μm (voltage: 100V) The step error: 3.8%—4.4% The most system working frequency: 63Hz The resolution: 0.02μm The most step velocity: 203μm /s(63Hz, 100V) From the comparison of inner driving and outer driving method of the piezoelectric precision step actuator, that the clamping force of the inner driving method is larger than the outer, the resolution, frequency and clamping error of the inner is better than the outer. But the most step of the inner driving method issmaller than the outer because of the different pre-load method. The revolving piezoelectric precision step actuator is studied. Based on the defect of the researching to electromagnetic outer clamping actuator, the new revolving piezoelectric precision step actuator with inner piezoelectric clamping model is put forward. With the analysis of the weakness of outer electromagnetic clamping precise stepper actuator, put forward the drive principle of inner clamp precise stepper actuator, and design the inner clamp precise stepper rotational actuator. The inner clamp precise stepper actuator is clamped in the stator and the rotational part is outside, distortion part and the flexible hinge structure make the stepper movement. On the theories analysis and experiment of the new model revolving step actuator, get the result that the performance of the inner clamping piezoelectric precision step rotary actuator is stable and credible. The ultra stabilization thin flexible hinge can make the stator move in high frequency and clamp tightly in the inner clamp structure. This can solve problem that the good frequency and the clamp tight can't be made at one time. The combination distortion of torsion and bending structure of the thin flexible hinge can make the step ration stability and trustiness. All this can be made a good experience for the design of the piezoelectric rotational actuator.The characteristic of the inner clamp piezoelectric precision stepper rotary actuator is: Working frequency: 40Hz Resolution: 1urad Continual torque: 50N.cm Step rotaryl speed: 325urad/s Control system of the piezoelectric precision step actuator is developed. The driving voltage sequence in this part is labored. Based on the work principle of the piezoelectric step actuator, 6 segment period wave voltage sequence is put forward. It can control the actuator step by step availability. "S"shape modified wave of echelon wave is presented on base of research actuator voltage signal wave in detail, which decreased impact and noise during work by comparing with rectangle wave, because voltage magnifying loop and push-pull magnifyingcircuit in power designed have enhanced systemic dynamic capability greatly, so high frequency discharge of piezoelectric pile can be work out effectively as output voltage achieve high stabilization and precision. Control system which developed in this thesis comprises three main qualities: multiple channels, voltage high resolution, high frequency, low signal distortion. In conclusion, the piezoelectric precision step actuator from the new principle achieved precision, high frequency, heavy load, high velocity, stability. The piezoelectric precision step actuator will be applied widly.