Receipt date Fund project Grants from the Science Foundation. Piezoelectric ceramics have been successfully applied to various kinds of precision machinery because of its small size, large driving force and high resolution. Harmonic drive has the advantages of high motion accuracy, small backlash, large transmission ratio, light weight, small size, large carrying capacity, and can work normally in confined space and medium radiation conditions. The transmission principle was first proposed by AEMoskwijin, a joint engineer in 1947. In 1959 the American engineer CW Mussei invented a harmonic gear drive with a mechanical wave generator. Harmonic drive is widely used in aerospace, robotics, radar systems, machine tools, instrumentation, optical instruments, and medical devices. Piezoelectric harmonic motor is a new type of stepping motor driven by piezoelectric ceramics and combined with harmonic transmission technology. It combines organic piezoelectric drive and harmonic drive to achieve low-speed, high-precision drive. Precision machinery has a good application prospects. In foreign countries, in 1990, Ishida et al. first developed piezoelectric motors using the principle of harmonics, and subsequently studied and designed harmonic piezoelectric motors at TimKing, WeiXu and Oliver Barth in Germany. They only produced them. The rougher prototype has poor performance and cannot be applied to practice. Currently, it has remained at the experimental stage. In order to enable it to have excellent performance and be applied in practice, further research is required in the design principles, structural schemes, mechanical mechanisms and control system design and testing. 2 Principle of Operation of Piezoelectric Harmonic Motors Harmonic gear transmissions are usually used as a reducer to realize the function of the transmission. The high-speed motor drives the wave generator to rotate through the input shaft, which causes the flexible wheel to generate periodic elastic deformation, realize speed conversion through meshing or friction between the flexible wheel and the rigid wheel, and fixes one component in the flexible wheel or rigid wheel. A component will rotate at low speed. According to the principle of harmonic transmission, no matter whether the wave generator components are rotated or not, as long as the flexible wheel can generate periodic continuous or pulsating elastic deformation according to a certain rule, a low-speed output can be obtained. As a result, there are a variety of rotary inputs that do not pass through the wave generator, and the wave generators that drive the deformation of the flex spline are produced using periodic displacements of fixed different drive elements, such as hydraulic wave generators, pneumatic wave generators, and electromagnetic waves. Etc. In this way, the harmonic transmission plays the role of converting different energy into mechanical energy and has the nature of a prime mover. Therefore, it is called a harmonic motor. “0. Piezoelectric ceramic has an electrostrictive piezoelectric inverse effect. Therefore, A new type of harmonic wave generator can be designed by using piezoelectric ceramic as the controlled drive component. By controlling the telescopic deformation of the piezoelectric ceramic actuator, the flexible wheel can be driven to deform according to certain rules, and then the flexo or rigid wheel can be realized at a low speed. The rotation of the device thus designed is called a piezoelectric harmonic motor. 3 Design of piezoelectric harmonic motor 3.1 Piezoelectric actuator Piezoelectric actuator has two kinds of linear deformation and bending deformation. Linear type is divided into single-plate type and laminated type. When a voltage of 5 kV is applied across a PZT piezoelectric ceramic with a thickness of 1 cm, only a displacement of about 10 Lm can be obtained. Therefore, the deformation of the single plate type is too small and practicality is lacking. If 10 pieces of 1mm piezoceramics are overlapped (bonded or sintered), and a voltage of 500V is applied to each piece, the same large amount of deformation will be obtained, and it has the advantage that it is not easily destroyed under the same proportion of deformation. It is a laminated piezoelectric actuator. It is now possible to manufacture a 0.05 mm piezoelectric crystal wafer. The multilayer piezoelectric actuator has not only large deformation, but also large bearing capacity, fast response, good repeatability of displacement, high volumetric efficiency, relatively simple electric field control, etc. The WTYD080810 piezoelectric actuator manufactured by the Ministry of Electronics Industry 26 is 067N, the maximum displacement of 10Lm, zero displacement reproducibility 0.10Lm. Deformation, but its drive displacement can not meet the requirements of the flexure to drive the flex, so it must design its corresponding displacement amplification mechanism. Displacement amplifying mechanisms can generally be designed using a magnifying mechanism such as a lever mechanism, triangular geometric amplification, and buckling amplification. To avoid gaps and friction and ensure the precision of the mechanism, a relatively flexible link is often used in place of an ordinary link. With the amplification mechanism, the displacement will be amplified and the driving force will be reduced. At the same time, because of the elastic deformation of the flexible chain, the reaction force is generated and there is a displacement loss, which affects the amplification effect. Therefore, the design of the amplifying mechanism is the key to influencing the driving performance. The size of each part should be optimized to obtain the best amplification effect. 3.3 Structure type selection Harmonic transmission device according to the configuration of the wave generator relative to the flex wheel can be 2 micro-displacement amplification mechanism design 3.4 Drive type selection bookmark6 ◎ Although stacking piezoelectric § device can be relatively large ubl 呻蜱Lu friction type 1r she tsreserved.httP: divided into two types of internal and external wave transmission, so, piezoelectric harmonic motor can also be designed according to these two types. Its configuration schematic is shown as 2. Since the internal-wave harmonic motor can effectively use the inner space of the flex-turner, it is easy to miniaturize and generally has a small size. However, the size of the piezoelectric actuator is also limited, and the available effective piezoelectric actuator provides a small effective displacement. The size of the external-wave harmonic motor is larger, and a larger-sized piezoelectric actuator can be selected to obtain a more ideal drive displacement, but at the same time, the size of the motor is increased. This design is an internal wave piezoelectric harmonic motor. Capricorn type harmonic transmission, the process is relatively simple, the soft wheel and rigid wheel surface are made of wear-resistant materials, no special processing is required. There is no special requirement on the amount of deformation of the flexspline, so it is easier to drive the flexspline. However, because it mainly transmits friction by friction, the wear is more serious, and the bearing capacity, transmission efficiency, and transmission accuracy are lower. 3.4.2 Teeth-tooth-engaging tooth-tooth-type harmonic transmission drives teeth of the same modulus on the outer surface of the flexspline and the inner surface of the rigid wheel (for the outer wave form, the inner surface and the outer surface, respectively), so the process is relatively Complex, but in the work only the low-speed sliding between the flexspline and the rigid wheel teeth, so the wear is small, carrying capacity, transmission efficiency and accuracy are high. However, the requirements for the parameters such as the amount of deformation of the flexspline and the radius of the flex spline are very strict, in which the maximum deformation of the flex spline is 1/2 of the difference in the number of teeth between the flexspline and the rigid wheel (Z flex-Z rigid wheel/2) Modulus m. If you choose a two-wave two-tooth difference harmonic drive (Z-flex-Z wheel = 2) for design, when the module m = 0.3mm, the maximum deformation of the flexure wheel is wo = 0.3mm, so It is required that the maximum deformation of the piezoelectric ceramic can reach a displacement of 2 times the same value after the displacement amplification. This design uses a toothed piezoelectric harmonic motor. 3.5 Selection of Deflection Wave Number and Deformation Rule of the Flexible Wheel For the tooth-engaged double-wave transmission, the difference in the number of teeth is 2. Therefore, the number of piezoelectric actuators must be more than 4 groups and be evenly distributed along the circumferential direction, according to the number of symmetry groups. To be even array (6, 8, 10, etc.). For a three-wave transmission, the difference in the number of teeth is three, so the number of piezoelectric actuators that are uniformly distributed in the circumferential direction must be more than six, and should be a multiple of three (9, 12, 15, etc.). Although the three-wave transmission has the advantages of large depth of engagement and good self-centering, it has relatively less application due to the greater stress in the flexspline. Therefore, the flexure wave deformation wavenumber of the piezoelectric harmonic motor adopts the double wave which has the most practical application and good comprehensive performance. The deformation type adopts the standard elliptical deformation type. The elliptic polar coordinate equation is the radius of the inner cylindrical surface of the flexspline, w, w (the radial displacement of the flexspline and the maximum deformation of the radial direction, respectively). 4 The design example is a schematic structural diagram of a piezoelectric harmonic motor using a tooth meshing internal wave type dual-wave harmonic drive. The piezoelectric wave generator is composed of 8 sets of piezoelectric ceramic actuators and corresponding flexible hinge displacement amplifying mechanisms, and is evenly distributed along the circumferential direction. In order to obtain enough drive displacement, a three-level displacement amplification mechanism with a symmetrical structure and a flexible hinge is designed. The first stage adopts a triangle amplification mechanism, and the second stage size is optimized to obtain a more ideal amplification effect. In order to increase the contact area between the piezoelectric wave generator and the flexspline, buckling members are used at the last stage to help maintain the flexure wheel deformation shape and change the design of the 5 control system. The design focus of the piezoelectric harmonic motor is based on design requirements. Design the structure of the piezoelectric harmonic generator and its control circuit. Since the shape of the piezoelectric wave generator is controlled by the control circuit, the same piezoelectric wave generator can be applied to different wave generator shapes only when different wave generator shapes are applied (equivalent to selecting different wave generators. Type), it applies to the flex wheel (inner diameter does not change), rigid wheel meshing parameters (number of teeth / gear ratio, modulus, displacement coefficient, radial deformation coefficient, etc.) will be different. To drive the piezoelectric harmonic wave motor, it is only necessary to control the deformation amount of each group of piezoelectric actuators in time sequence so that the deformation of the discrete points where the displacement amplifying mechanism and the flexible wheel contact meets the deformation law of the flexspline. Make sure that the flexible wheel does not mesh with the rigid wheel tooth area. For example, because it is a dual-wave harmonic drive, the two groups of piezoelectric actuators with symmetrical diameters are completely in a state of deformation and can be controlled as a single phase, thereby dividing the eight groups of piezoelectric actuators into A, B, C, and D. Four phases. The third stage of the lever amplifying mechanism 5 is a buckling amplifying mechanism, and the control is performed by changing the direction of the machine, counting the locking torque, and the like. Net In the design of the control system, first according to the selected shape of the wave generator under the action of the flexible shape of the deformation data, the piezoelectric wave generator and the flexpin contact with each discrete point of radial displacement data stored in the microcontroller, The data sent by the SCM to the D/A conversion circuit is converted into an analog quantity, and then the groups of piezo actuators are driven by the power-amplified driving voltage (V1, V2, V3), and the phase sequence can be applied to the A, B The phases of C, D, and D are controlled, and the resulting piezo wave generator is shown in the deformed figure. Through the programming of the controller, it is easy to control the driving voltage waveform of the piezoelectric driver. The four-acting type control is adopted above. In order to ensure the smooth entry and release of the flexible wheel and the rigid wheel gear, the transmission quality is guaranteed, and the actual development is in progress. Two-force and four-force interaction control are used. 6 Conclusion Piezoelectric harmonic motor is a new type of low-speed motor based on harmonic transmission principle, with low-speed output, high power density, simple structure, small size, small moment of inertia, high positioning accuracy, high efficiency, low noise and so on. Through the control system can achieve speed control, commutation, step count, lock torque and other control functions. Due to the use of piezoelectric actuators, it can also be protected from strong magnetic and radiation influences. It has broad application prospects in precision engineering, microsystem engineering and precision positioning control systems. In order to meet the ever-increasing demands for miniaturization of the drive, if the method of reducing the size of a conventional DC drive is simply adopted instead of changing its structural principle, the produced motor must be rotated at a high speed in order to generate the required power. This type of high-speed small motor is widely used in medicine and precision engineering. However, precise positioning requires that they must be equipped with a speed reducer, which brings about disadvantages such as transmission backlash, inefficiency, large size, complicated manufacturing process, and high manufacturing cost. At present, there is no high-resolution small-size encoder. Although the piezoelectric ultrasonic motor has a small size and can output a large torque at a low speed, it uses a piezoelectric body to generate a traveling wave and relies on friction to drive, and there is a phenomenon of heat generation and inestimable slippage, so accurate positioning is required. It must also use a small encoder. In addition, as the load increases, the amplitude of the piezoelectric body becomes smaller when the same voltage is applied, which makes driving difficult. Therefore, the current electromagnetic motor can not meet the requirements of simple structure, small size, high positioning accuracy, good dynamic characteristics and positioning in the open-loop system. The piezoelectric motor technology combining a piezoelectric actuator, a displacement amplifier, a flexure wheel, and a rigid wheel can meet the above requirements. P5*P10 Transparent Led Screen,Transparent Led Glass Display,Led Glass Display,Led Display Screen Glass Shenzhen YuGuang New Material Co.,Ltd , https://www.ygsmartfilm.com