Inertial rotary piezoelectric motor based on piezoelectric driving unit and control method

Abstract

The invention discloses an inertial rotary piezoelectric motor based on a piezoelectric driving unit and a control method, and belongs to the technical field of piezoelectric driving. The piezoelectric driving unit and a rotary unit are rotatably arranged on a fixed base, a friction plate is arranged at the front end of the piezoelectric driving unit, and a pre-tightening force structure is fixed on the fixed base; the two piezoelectric driving units are arranged on the two sides of the rotating unit respectively, the two sets of identical piezoelectric driving units are adopted, alternate and coordinated movement of the two sets of piezoelectric driving units is controlled by regulating and controlling excitation voltage applied to the piezoelectric driving units, and then the rotating unit is pushed to move. Due to the alternate coordinated movement of the two groups of piezoelectric driving units, the output speed and the loading capacity of the piezoelectric motor are greatly improved, and the displacement hysteresis of single-step stepping of the inertial piezoelectric motor is greatly reduced. Therefore, the output performance of the rotor is improved, the load of the rotor is greatly improved compared with that of a single-path driving motor, and the consistency of forward and reverse movement of the rotor is also improved due to the symmetrical design.

Description

Technical Field

[0001] The present invention belongs to the technical field of piezoelectric drive, and in particular relates to an inertial rotary piezoelectric motor based on a piezoelectric drive unit and a control method thereof. Background Art

[0002] At present, high-precision positioning and driving technology has been widely used in high-tech industries, such as aerospace, microelectronics, biological manipulation, robotics, and consumer electronics. Traditional electromagnetic motors work on the principle of electromagnetic induction. They have complex structures and are susceptible to electromagnetic interference. In addition, there is a contradiction between size and energy efficiency in electromagnetic motors, so they cannot achieve miniaturization, high precision, large driving force, and power-off self-locking functions.

[0003] Piezoelectric motors use the inverse piezoelectric effect of piezoelectric materials to convert electrical energy into mechanical energy, and then achieve the output of the rotor's macroscopic motion through friction coupling between the stator and the rotor. Therefore, piezoelectric motors have the characteristics of fast response speed, high power density, anti-electromagnetic interference, and power-off self-locking. Compared with other types of piezoelectric motors, inertial piezoelectric motors have the advantages of simple control, simple structure, high displacement resolution, easy integration, and large working stroke, and have received widespread attention and application.

[0004] However, the movement process of inertial piezoelectric motors is often accompanied by displacement hysteresis. Displacement hysteresis not only reduces the overall performance of inertial piezoelectric motors, but also reduces the displacement of motor steps to a certain extent, thereby reducing the speed of movement; because inertial piezoelectric motors are limited by principles during movement, their loads are generally small; and the currently known piezoelectric rotary motors used in aerospace, precision drive and other fields have low resolutions, which are difficult to meet the growing demand for motion displacement accuracy of the drive system. Summary of the invention

[0005] The object of the present invention is to provide an inertial rotary piezoelectric motor based on a piezoelectric drive unit and a control method to overcome the problems of large displacement hysteresis, small load, low precision, etc. of the existing piezoelectric motor.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] An inertial rotary piezoelectric motor based on a piezoelectric drive unit comprises a piezoelectric drive unit, a rotating unit, a preload structure and a fixed base; the bottom of the piezoelectric drive unit is fixed on the fixed base, the rotating unit is rotatably arranged on the fixed base, a friction plate capable of contacting the side of the rotating unit is arranged at the front end of the piezoelectric drive unit, the preload structure is fixed on the fixed base to provide a preload for the friction plate at the front end of the piezoelectric drive unit to contact the rotating unit, and a piezoelectric drive unit is arranged on both sides of the rotating unit.

[0008] Preferably, the two piezoelectric drive units are connected to a sawtooth wave excitation signal.

[0009] Preferably, the piezoelectric drive unit includes a mass block, a piezoelectric body and a flexible hinge unit, the mass block is fixed on a fixed base, the piezoelectric body is fixed on the mass block, and the other end of the piezoelectric body is connected to the friction plate through the flexible hinge unit.

[0010] Preferably, the piezoelectric body is made of a single piece of piezoelectric single crystal material, a single piece of piezoelectric ceramic material, a stack of multiple pieces of piezoelectric single crystal material, or a stack of multiple pieces of piezoelectric ceramic material.

[0011] Preferably, the piezoelectric body is formed by stacking a plurality of piezoelectric sheets, and the outer side surfaces of the multilayer piezoelectric sheets are short-circuited with the same internal end electrodes by means of external electrodes to form two electrodes.

[0012] Preferably, the piezoelectric body comprises a plurality of piezoelectric single crystal pieces, and the plurality of piezoelectric single crystal pieces are stacked and arranged along a thickness direction.

[0013] Preferably, the two piezoelectric drive units are symmetrically arranged along the axis of the rotating unit, or the two piezoelectric drive units are rotationally symmetrically arranged along the rotation center of the rotating unit.

[0014] A control method for the above-mentioned inertial rotary piezoelectric motor comprises the following steps:

[0015] After applying sawtooth wave excitation signals with the same duty cycle but different phase angles to the upper and lower surfaces of the two piezoelectric bodies on the two groups of piezoelectric drive units, the first-order longitudinal vibration mode of the piezoelectric body is excited through the piezoelectric working mode, and the piezoelectric body will produce a large telescopic deformation along the thickness direction; through the regulation of the two excitation signals, the friction plates on the first group of piezoelectric drive units and the friction plates on the second group of piezoelectric drive units produce telescopic movements alternately in turn.

[0016] Preferably, the sawtooth wave excitation signal applied to the upper and lower surface electrode layers of the piezoelectric body has a duty cycle greater than or equal to 90% during the extension movement; and has a duty cycle less than or equal to 10% during the contraction movement.

[0017] Preferably, the duty cycle and phase difference of the two sawtooth wave excitation signals applied to the upper and lower surface electrode layers of the piezoelectric body need to be adjusted according to different driving principles.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] The present invention provides an inertial rotary piezoelectric motor based on a piezoelectric drive unit, which adopts a piezoelectric drive unit, a rotary unit, a preload structure and a fixed base; the bottom of the piezoelectric drive unit is fixed on the fixed base, the rotary unit can be rotatably arranged on the fixed base, a friction plate capable of contacting the side of the rotary unit is arranged at the front end of the piezoelectric drive unit, the preload structure is fixed on the fixed base to provide preload for the friction plate at the front end of the piezoelectric drive unit to contact the rotary unit, a piezoelectric drive unit is arranged on both sides of the rotary unit, and the two piezoelectric drive units are connected to a sawtooth wave excitation signal. The present invention adopts two groups of identical piezoelectric drive units, and controls the alternating coordinated motion of the two groups of piezoelectric drive units by regulating the excitation voltage applied to the piezoelectric drive units, thereby promoting the rotary unit to move. Due to the alternating coordinated motion of the two groups of piezoelectric drive units, the output speed and load carrying capacity of the piezoelectric motor are greatly improved, and the displacement hysteresis of the single-step stepping of the inertial piezoelectric motor is greatly reduced. Thereby, the output performance of the rotor is improved, and the load is greatly improved compared with the single-channel drive motor, and its symmetrical design also improves the consistency of the forward and reverse motion of the rotor.

[0020] Preferably, by setting a flexible hinge unit between the piezoelectric body and the friction plate in the piezoelectric drive unit, the stress of the friction plate on the piezoelectric body along the thickness shear direction when the preload is applied is reduced, thereby protecting the piezoelectric body and increasing the displacement of the friction plate to a certain extent.

[0021] Preferably, the proposed piezoelectric rotary motor has high design flexibility, and the position of the motor's driving unit can be adjusted according to actual needs. The conversion between single-channel driving and dual-channel coordinated driving modes can also be achieved by adjusting two sets of excitation signals.

[0022] Preferably, the preload mechanism ensures that the preload force is evenly applied to the piezoelectric drive unit, thereby ensuring good contact between the friction plate of the piezoelectric drive unit and the bearing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the assembly of the inertial rotary piezoelectric motor in the embodiment of the present invention; 101 is the piezoelectric drive unit, 102 is the rotary unit, 103 is the preload structure, and 104 is the fixed base.

[0024] Figure 2 It is a schematic structural diagram of a modular piezoelectric drive unit in the inertial rotary piezoelectric motor described in an embodiment of the present invention; wherein 201 is a mass block, 202 is a piezoelectric body, 203 is a flexible hinge unit, and 204 is a friction plate.

[0025] Figure 3 Schematic diagram of the structural explosion of the inertial rotary piezoelectric motor in an embodiment of the present invention.

[0026] Figure 4 Schematic diagram of the electrical structure of the single-layer thickness polarized piezoelectric unit in an embodiment of the present invention.

[0027] Figure 5 Schematic diagram of the structure of an interdigitated electrode according to an embodiment of the present invention; arrows represent the polarization directions of different piezoelectric sheets.

[0028] Figure 6 Schematic diagram of the first-order longitudinal vibration mode in the embodiment of the present invention; wherein 601 is the unexcited state of the piezoelectric body, and 602 is the first-order longitudinal vibration mode generated by the excited piezoelectric body.

[0029] Figure 7 Schematic diagram of finite element simulation of the first-order longitudinal vibration mode of the inertial rotary piezoelectric motor in an embodiment of the present invention.

[0030] Figure 8 A schematic diagram of a driving signal of an inertial rotary piezoelectric motor according to an embodiment of the present invention; Figure 8 a in the figure is a schematic diagram of the drive signal of the motor rotating clockwise, where Signal 1 and Signal 2 have a duty cycle of 90% and a phase angle difference of Sawtooth wave excitation voltage signal; Figure 8 b is a schematic diagram of the drive signal of the motor rotating counterclockwise, where Signal1 and Signal2 have a duty cycle of 10% and a phase angle difference of The sawtooth wave excitation voltage signal.

[0031] Fig. 9 Schematic diagram of the driving principle of the inertial rotary piezoelectric motor in an embodiment of the present invention (taking clockwise rotation as an example).

[0032] Fig.10 This is a small signal impedance spectrum of the inertial rotary piezoelectric motor described in an embodiment of the present invention.

[0033] Fig.11 This is a speed test curve of the inertial rotary piezoelectric motor in an embodiment of the present invention.

[0034] Fig.12 It is the axial displacement of the center point of the piezoelectric drive unit of the inertial rotary piezoelectric motor in the embodiment of the present invention at different frequencies (10Vpp).

[0035] Fig.13 axial displacement of the center point of the piezoelectric drive unit of the inertial rotary piezoelectric motor at different voltages (30 kHz) in the embodiment of the present invention.

[0036] Fig.14FIG. 4 is a displacement resolution characteristic diagram of the inertial rotary piezoelectric motor when rotating clockwise and the inertial rotary motor in a single-channel driving mode according to an embodiment of the present invention.

[0037] Fig.15 1 is a displacement resolution characteristic diagram of the inertial rotary piezoelectric motor when rotating counterclockwise and in the single-channel driving mode of the inertial rotary motor in an embodiment of the present invention.

[0038] Fig.16 1 is a load test curve of the inertial rotary piezoelectric motor when it rotates clockwise and in the single-channel driving mode of the inertial rotary motor in an embodiment of the present invention.

[0039] Fig.17 The phase angle difference between the driving signals Signal 1 and Signal 2 when the inertial rotary piezoelectric motor rotates clockwise in the embodiment of the present invention is Displacement hysteresis diagram of single step when .

[0040] Fig.18 It is a schematic diagram of assembling the inertial rotary piezoelectric motor when the modular piezoelectric drive unit is in different positions according to the embodiment of the present invention.

[0041] Fig.19 Schematic diagram of the inertial rotary piezoelectric motor driving signal when the modular piezoelectric driving unit is in different positions in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0043] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0044] like Figure 1 As shown, the present invention provides an inertial rotary piezoelectric motor based on a piezoelectric drive unit, comprising a piezoelectric drive unit 101, a rotating unit 102, a preload structure 103 and a fixed base 104; the bottom of the piezoelectric drive unit 101 is fixed on the fixed base 104, the rotating unit 102 can be rotatably arranged on the fixed base 104, the front end of the piezoelectric drive unit 101 is provided with a friction plate 204 capable of contacting the side of the rotating unit 102, the preload structure 103 is fixed on the fixed base 104 to provide a preload force for the friction plate 204 at the front end of the piezoelectric drive unit 101 to contact the rotating unit 102, a piezoelectric drive unit 101 is respectively arranged on both sides of the rotating unit 102, and the two piezoelectric drive units 101 are connected to a sawtooth wave excitation signal. The present invention adopts two groups of identical piezoelectric drive units 101, and controls the alternating and coordinated movement of the two groups of piezoelectric drive units by regulating the excitation voltage applied to the piezoelectric drive unit 101, thereby promoting the movement of the rotating unit 102. Due to the alternating and coordinated movement of the two groups of piezoelectric drive units, the output speed and load capacity of the piezoelectric motor are greatly improved, and the displacement hysteresis of the single-step stepping of the inertial piezoelectric motor is greatly reduced.

[0045] In a specific embodiment of the present application, the piezoelectric drive unit 101 includes a mass block 201, a piezoelectric body 12 and a flexible hinge unit 13. The mass block 201 is fixed on a fixed base 104, the piezoelectric body 12 is fixed on the mass block 201, and the other end of the piezoelectric body 12 is connected to the friction plate 204 through the flexible hinge unit 13. An installation groove is set on one side of the flexible hinge unit 13, one side of the piezoelectric body 12 is fixed in the installation groove of the flexible hinge unit 13, and the other side of the flexible hinge unit 13 is fixedly connected to the friction plate 204. The rotating unit 102 is installed on the fixed base 104 through the rotating axis. The rotating unit 102 can rotate relative to the rotating axis. The preload structure 103 provides a preload perpendicular to the axial direction of the rotating unit 102 to the piezoelectric drive unit 101, so that the friction plate 204 of the piezoelectric drive unit 101 is in tangential contact with the side surface of the rotating unit 102. The entire rotating piezoelectric motor system forms a whole through the fixed base 104. In a specific embodiment of the present invention, its stator part is composed of only a piezoelectric body and a driving foot. It has a simple structure, is easy to prepare, and can be miniaturized, and is suitable for precision drive systems. In addition, due to the improved performance of the inertial piezoelectric motor, the assembly requirements of the motor are greatly reduced; by setting a flexible hinge unit between the piezoelectric body and the friction plate in the piezoelectric drive unit, the stress of the driving foot on the shear direction of the piezoelectric body when the preload is applied is reduced; the design of the two sets of piezoelectric drive unit structures of the inertial piezoelectric motor provided by the present invention has high design flexibility, and the position of the motor drive unit can be adjusted according to actual needs. Different drive modes can also be achieved by adjusting the two sets of excitation signals, and the displacement hysteresis of the single step of the inertial piezoelectric motor can be greatly reduced. The mass block 11 is made of brass material, the flexible hinge unit 13 is made of 7050 aluminum, and the friction plate 204 is made of 7050 aluminum or zirconium oxide.

[0046] In the specific implementation of the present application, the fixed base 104 is made of a solid material with relatively large rigidity and not easy to deform for easy fixation, and its material can be selected as a plastic material or a metal material. The fixed base is designed according to the driving principle of the piezoelectric motor, the shape of the bearing, and the preload structure, and is processed by 3D printing or CNC.

[0047] The piezoelectric body 12 is made of a single piece of piezoelectric single crystal material, a single piece of piezoelectric ceramic material, a stack of multiple pieces of piezoelectric single crystal material, or a stack of multiple pieces of piezoelectric ceramic material, and the piezoelectric body 12 is polarized along the thickness.

[0048] In a specific embodiment of the present application, the piezoelectric body 12 is formed by a single-layer piezoelectric sheet, a plurality of stacked piezoelectric sheets, or a plurality of co-fired piezoelectric sheets.

[0049] The piezoelectric body 12 is formed by stacking multiple piezoelectric sheets, and the outer side of the multilayer piezoelectric sheet short-circuits the internal electrodes at the same end by means of external electrodes to form two electrodes. When the piezoelectric body 12 adopts a stacked structure of multiple piezoelectric sheets, the piezoelectric body 2 includes multiple piezoelectric single crystals or ceramic sheets, and the multiple piezoelectric single crystals or ceramic sheets are stacked and arranged along the thickness direction, and the electrodes between two adjacent piezoelectric sheets are arranged in an interdigitated electrode structure; and the multiple piezoelectric layers form a mechanical series connection, and the multiple electrode layers form an electrical parallel connection structure.

[0050] Example 1

[0051] The piezoelectric body 12 is made of a single-piece piezoelectric single crystal material such as lead zinc niobate-lead titanate single crystal (PZN-PT), lead magnesium niobate-lead titanate single crystal (PMN-PT) or lead indium niobate-lead magnesium niobate-lead titanate single crystal (PIN-PMN-PT), or a single-piece piezoelectric ceramic material such as lead magnesium niobate-lead titanate ceramic (PMN-PT), lead zirconate titanate ceramic (PZT), lead indium niobate-lead magnesium niobate-lead titanate ceramic (PIN-PMN-PT) or lead zinc niobate-lead titanate ceramic (PZN-PT) containing lead piezoelectric ceramics or lead-free piezoelectric ceramics prepared from barium nitrate (BT) base, potassium sodium niobate (KNN) base, sodium bismuth titanate (BNT) base, and barium calcium zirconate titanate (BCZT) base, or a plurality of piezoelectric sheets are stacked, or a plurality of piezoelectric sheets are co-fired. The piezoelectric body 12 is polarized along the thickness or along the radial direction, and voltage is applied along the thickness direction during operation.

[0052] like Figure 4 As shown, electrode layers are provided on the upper and lower surfaces of the piezoelectric body 12. The electrode layers are prepared by thermal evaporation, magnetron sputtering, electron beam evaporation or screen printing; the electrode layers are made of conductive materials, specifically gold, silver, platinum, palladium, copper, nickel or aluminum; the electrode layers are in the shape of square, circle, triangle or rhombus.

[0053] In the specific implementation of the present application, when the piezoelectric body 12 adopts the structure of interdigital electrodes of a multilayer piezoelectric sheet, as shown in FIG. Figure 5 As shown, the piezoelectric body 12 includes multiple piezoelectric single crystals (at least two), and the multiple piezoelectric single crystals are stacked and arranged along the thickness direction, and two adjacent piezoelectric single crystals are bonded together by epoxy resin; each layer adopts a head-to-head thickness polarization method, wherein the arrow represents the polarization direction of each piezoelectric sheet, wherein 501 represents each layer of piezoelectric sheets, 502 is the internal electrode between each piezoelectric layer, and the internal same end electrode is short-circuited on the outer side of the multilayer piezoelectric sheet by an external electrode method to form two electrodes: a first external electrode 503 and a second external electrode 504. In this way, multiple piezoelectric layers form a mechanical series connection, and multiple electrode layers form an electrical parallel connection structure.

[0054] The rotating unit 102 specifically adopts a bearing structure, and the adopted bearing structure is in the shape of a sphere, a hemisphere, a cylinder or a semi-cylinder; it is made of zirconium oxide, aluminum oxide, silicon carbide ceramics, high wear-resistant metal materials or carbon fiber materials.

[0055] The friction plate 204 is in the shape of a rectangular thin plate and is made of zirconium oxide, aluminum oxide, silicon carbide ceramics, high wear-resistant metal material or carbon fiber material.

[0056] In a specific embodiment of the present application, a rectangular groove is provided on one side of the flexible hinge unit 13, and a rectangular protrusion consisting of two circular or elliptical grooves facing each other is provided on the other side of the flexible hinge unit 13. The flexible hinge unit 13 is made of 7050 aluminum with high flexibility. The flexible hinge unit 13 in the piezoelectric drive unit 101 can not only make the piezoelectric body 12 more smoothly connected to the friction plate 204, but also when a pre-tightening force perpendicular to the axial inward direction of the piezoelectric drive unit 101 is applied, the rotating unit 102 will generate a reaction force perpendicular to the axial outward direction of the piezoelectric drive unit 101 on the friction plate 204. The reaction force will cause the flexible hinge part to bend outward along the direction of the force, thereby greatly reducing the force perpendicularly applied to the piezoelectric body 12, thereby protecting the piezoelectric body 12.

[0057] In a specific embodiment of the present invention, the provided inertial rotary piezoelectric motor uses two piezoelectric drive units 101 , and the working principle of the piezoelectric body 12 in the two piezoelectric drive units 101 is a thickness expansion mode, and the polarization direction is along the thickness direction of the piezoelectric body 12 .

[0058] When the piezoelectric body 12 partially works in the thickness expansion mode, the piezoelectric body 12 is a single-layer thickness-polarized piezoelectric element. At this time, the electrodes of the piezoelectric element are arranged in a full-electrode structure on the upper surface and the lower surface. At this time, the upper surface is used to connect the positive electrode of the excitation signal, and the lower surface is used to connect the negative electrode of the excitation signal; if the piezoelectric body 12 is a multi-layer thickness-polarized piezoelectric stack (at least two pieces), then the electrodes of the piezoelectric element are arranged in a forked-finger electrode structure on the upper surface and the lower surface. At this time, the first external electrode 503 is used to connect the positive electrode of the excitation signal, and the second external electrode 504 is used to connect the negative electrode of the excitation signal.

[0059] When the electrodes of the piezoelectric body 12 are applied with an excitation signal, the first-order longitudinal vibration (L1) expansion and contraction mode of the piezoelectric body 12 along the thickness direction can be excited, and a large expansion and contraction deformation will be generated along the thickness direction. In particular, when the piezoelectric body 22 is a multi-layer piezoelectric stack, the part of the piezoelectric sheet with the same working voltage and polarization direction works in an elongated state; the part of the piezoelectric sheet with the opposite working voltage and polarization direction works in a shortened state. Therefore, the multi-layer piezoelectric stack with interdigitated electrodes can superimpose the displacements of all piezoelectric sheets to achieve the effect of displacement amplification and reduce the working voltage.

[0060] The first-order longitudinal vibration mode (L1) is as follows Figure 6 As shown, the solid line portion 601 represents the unexcited state of the piezoelectric body 12, and the dashed line portion 602 represents the first-order longitudinal vibration mode excited by applying a preset excitation voltage.

[0061] The schematic diagram of the finite element simulation of the first-order longitudinal vibration mode (L1) is as follows: Figure 7 As shown, the mass block 201 is bonded to the piezoelectric body 12 by glue, and the bottom surface of the mass block 201 is fixed and constrained.

[0062] In order to enable the piezoelectric drive unit 101 to alternately and cooperatively drive the rotating unit 102 to move, the inertial rotary piezoelectric motor drive signal provided by the present invention is as follows: Figure 8 As shown; the driving signal consists of two sawtooth waves with the same duty cycle and different phase angles. Signal 1 and Signal 2 are respectively applied to the electrodes of the piezoelectric body 12 in the two piezoelectric driving units 101. At this time, the piezoelectric body 12 can excite the first-order longitudinal vibration mode (L1), thereby generating a sawtooth wave displacement along the thickness direction with the same duty cycle and the same phase as the excitation signal.

[0063] The movement of the rotating unit 102 can be divided into clockwise rotation and counterclockwise rotation. The movement direction is controlled by the duty cycle of the excitation signal. Different phase angles of the excitation signal can control the two piezoelectric drive units 101 to produce alternating forward and backward displacements (the rotating unit 102 moves in the target direction and moves in the direction of the target). If the motor needs to rotate clockwise, its drive signal is as follows: Figure 8 As shown in a, Signal1 and Signal2 are sawtooth wave excitation voltage signals with a duty cycle of 90% and a phase angle difference of φ. If the motor is required to rotate counterclockwise, the drive signal is as follows: Figure 8 As shown in b, Signal 1 and Signal 2 are sawtooth wave excitation voltage signals with a duty cycle of 10% and a phase angle difference of φ.

[0064] The regulation of the excitation voltage described above will be described in detail in the following specific embodiments.

[0065] In one embodiment of the present application, the clockwise driving principle diagram of the inertial rotary piezoelectric motor is as follows: Fig. 9 As shown, the driving signal is Figure 8 As shown in a in FIG. The clockwise direction is defined as the positive direction. Under the coordinated action of the first piezoelectric driving unit 1 and the second piezoelectric driving unit 2, one motion cycle can be divided into four steps.

[0066] S1: At time AB, the first piezoelectric drive unit 1 slowly extends under the action of the two piezoelectric bodies, and the second piezoelectric drive unit 2 slowly extends. Due to the static friction force f between the stator and the rotor s , the bearing rotates clockwise by θ1, as Fig. 9 As shown in a in the figure, it is the first positive angular displacement;

[0067] Step 2: At time BC, the first piezoelectric drive unit 1 slowly extends, and the second piezoelectric drive unit 2 contracts rapidly. The dynamic friction force f generated by the second piezoelectric drive unit 2 is d The drive bearing rotates counterclockwise by θ2, producing Fig. 9 The first reverse angular displacement shown in b;

[0068] Step 3: At time CD, the first piezoelectric drive unit 1 continues to slowly extend, and the second piezoelectric drive unit 2 slowly extends, causing the rotor to rotate clockwise by θ3, as shown in FIG. Fig. 9 As shown in c in the figure, it is the second positive angular displacement;

[0069] Step 4: At time DE, the first piezoelectric drive unit 1 contracts rapidly, and the second piezoelectric drive unit 2 slowly extends. The dynamic friction force f generated by the first piezoelectric drive unit 1 is d The drive bearing rotates counterclockwise, producing Fig. 9 The second reverse angular displacement θ4 is shown in d in the figure. The above process completes a cycle of motion. By repeating these four steps, a large-stroke rotational motion can be achieved.

[0070] In the clockwise driving principle of the piezoelectric motor, in the first two steps of the motion cycle, θ1 is greater than θ2, because the angular displacement θ1 is generated by the first piezoelectric drive unit 1 and the second piezoelectric drive unit 2, and the backward rotation displacement θ2 is generated by the second piezoelectric drive unit 2 overcoming the friction of the first piezoelectric drive unit 1. Similarly, θ3 is greater than θ4. Therefore, the rotor's rotation angle Δθ is a positive value, which can be specifically expressed as:

[0071] Δθ=θ1-θ2+θ3-θ4

[0072] In another embodiment of the present application, if the inertial rotary piezoelectric motor is driven counterclockwise, the driving signal is as follows: Figure 8As shown in b, one movement cycle can also be divided into four steps. Different from the clockwise driving principle mentioned above, the extension and contraction movements of the first piezoelectric drive unit 1 and the second piezoelectric drive unit 2 in each step are exactly opposite. The clockwise direction is defined as the positive direction. In step 1, the first piezoelectric drive unit 1 slowly contracts under the action of the two piezoelectric bodies, the second piezoelectric drive unit 2 slowly contracts, and the bearing rotates counterclockwise by θ1, which is the first reverse angular displacement; in step 2, the first piezoelectric drive unit 1 quickly extends, the second piezoelectric drive unit 2 slowly contracts, and the bearing rotates clockwise by θ2, generating the first positive angular displacement; in step 3, the first piezoelectric drive unit 1 slowly contracts, and the second piezoelectric drive unit 2 continues to slowly contract, causing the rotor to rotate counterclockwise by θ3, which is the second reverse angular displacement; in step 4, the first piezoelectric drive unit 1 slowly contracts, the second piezoelectric drive unit 2 quickly extends, and the bearing rotates clockwise, generating the second positive angular displacement θ4. Similarly, θ1 is greater than θ2, and θ3 is greater than θ4. Therefore, the rotor angle Δθ is a negative value, which can be specifically expressed as: Δθ = -θ1 + θ2 - θ3 + θ 4。

[0073] The present invention actually prepares an inertial rotary piezoelectric motor based on the inverse piezoelectric effect, using 3D printed resin material as a fixed base, a brass block as a mass block, a directionally polarized lead zirconate titanate (PZT-5H) piezoelectric ceramic material stack as a piezoelectric body, the flexible hinge unit and the friction plate are both made of 7050 aluminum material, and the side surface material of the bearing is 304 stainless steel.

[0074] In the specific implementation of the present application, the small signal impedance spectrum of the piezoelectric drive unit of the inertial rotary piezoelectric motor is tested as follows: Fig.10 As shown in the figure, at a frequency of 45kHz, there is a resonance peak in the small signal. Fig.11 : is a no-load speed test curve of the inertial rotary piezoelectric motor proposed in the embodiment. It can be seen that the fastest rotation time of this piezoelectric motor when no-load is 12.96s, and its maximum angular velocity is 0.4848rad / s.

[0075] Angular velocity calculation formula:

[0076] At an excitation voltage of 10V pp When the inertial rotary piezoelectric motor proposed in the embodiment has the following displacement along the axial direction at different frequencies: Fig.12 It can be seen that the axial displacement of the center point of the piezoelectric drive unit of this piezoelectric motor reaches the maximum when the resonant frequency is 45kHz.

[0077] Since the proposed piezoelectric motor operates in the non-resonant ultrasonic frequency band of 20k-45kHz, the inertial rotary piezoelectric motor proposed in the embodiment selects 30kHz as the frequency of the excitation signal. Fig.13 The axial displacement of the center point of the piezoelectric drive unit of the piezoelectric motor proposed in the embodiment under different voltages. It can be seen that the axial displacement of the center point of the piezoelectric drive unit of the piezoelectric motor increases with the increase of voltage until it reaches the maximum working voltage of 10V. pp When , the displacement reaches the maximum value, and the displacement is linearly related to the voltage.

[0078] Fig.14 and Fig.15 The displacement resolution characteristic diagrams of the inertial rotary piezoelectric motor proposed in the embodiment when rotating clockwise and counterclockwise and the inertial rotary motor single-channel driving mode are shown respectively. It can be seen that the clockwise displacement step of this piezoelectric motor is 0.1020μm, the displacement resolution is 0.1672μrad, and the single-step displacement hysteresis is 19.56%; the clockwise displacement step of the inertial rotary motor single-channel driving mode is 0.0441μm, the displacement resolution is 0.0766μrad, and the single-step displacement hysteresis is 30.88%. The counterclockwise displacement step of the inertial rotary piezoelectric motor proposed in the embodiment is 0.1238μm, the displacement resolution is 0.2148μrad, and the single-step displacement hysteresis is 16.86%; the counterclockwise displacement step of the inertial rotary motor single-channel driving mode is 0.0510μm, the displacement resolution is 0.0885μrad, and the single-step displacement hysteresis is 37.11%. Compared with the single-channel drive mode of the inertial rotary motor, its single-step displacement hysteresis is greatly reduced and the performance is greatly improved.

[0079] Fig.16 The speed test curves of the inertial rotary piezoelectric motor under different loads when rotating clockwise and in the single-channel driving mode of the inertial rotary motor in the embodiment are shown in FIG. It can be seen that the maximum load when the dual-channel piezoelectric drive unit is driven in coordination is 21.313g, which is much greater than 8.878g in the single-channel driving mode.

[0080] When the inertial rotary piezoelectric motor proposed in the example rotates clockwise, the displacement hysteresis of the single stepping between the phase angles of the driving signals Signal 1 and Signal 2 which differ by 0-180° is as follows: Fig.17 It can be seen that when the phase angles of the driving signals Signal 1 and Signal 2 differ by 70°, the single-step displacement hysteresis of the piezoelectric motor is minimized to 19.56%.

[0081] When the modular piezoelectric drive unit needs to be flexibly placed in different positions, Fig.18A possible assembly diagram of an inertial rotary piezoelectric motor is given, in which two piezoelectric drive units are symmetrically distributed about the axis of the bearing shaft.

[0082] Fig.19 It is a schematic diagram of the driving signal of the inertial rotary piezoelectric motor when the modular piezoelectric driving unit is in different positions;

[0083] Fig.19 a in the figure is a schematic diagram of the drive signal of the motor rotating clockwise, where Signal1 and Signal2 have a duty cycle of 90% and 10% respectively, and a phase angle difference of Sawtooth wave excitation voltage signal;

[0084] Fig.19 b is a schematic diagram of the drive signal of the motor rotating counterclockwise, where Signal1 and Signal2 have a duty cycle of 10% and 90% respectively, and a phase angle difference of The sawtooth wave excitation voltage signal.

[0085] Finally, it should be noted that the above embodiments are only intended to illustrate the technical concept of the present invention in detail, rather than to limit it. Those skilled in the art can understand that: without departing from the spirit and scope of the present invention and the appended claims, various changes, modifications and substitutions are possible, which all belong to the protection scope of this application, and the scope of protection required by the present invention shall be subject to the scope defined in the claims.

Claims

1. An inertial rotary piezoelectric motor based on a piezoelectric drive unit, characterized in that: The invention comprises a piezoelectric drive unit (101), a rotating unit (102), a pre-tightening force structure (103) and a fixed base (104); the bottom of the piezoelectric drive unit (101) is fixed on the fixed base (104); the rotating unit (102) is rotatably arranged on the fixed base (104); a friction plate (204) capable of contacting the side of the rotating unit (102) is arranged at the front end of the piezoelectric drive unit (101); the pre-tightening force structure (103) is fixed on the fixed base (104) to provide a pre-tightening force for the friction plate (204) at the front end of the piezoelectric drive unit (101) to contact the rotating unit (102); and a piezoelectric drive unit (101) is arranged on each side of the rotating unit (102).

2. The inertial rotary piezoelectric motor based on a piezoelectric drive unit according to claim 1, characterized in that: The two piezoelectric drive units (101) are connected to sawtooth wave excitation signals.

3. The inertial rotary piezoelectric motor based on a piezoelectric drive unit according to claim 1, characterized in that: The piezoelectric drive unit (101) comprises a mass block (201), a piezoelectric body (12) and a flexible hinge unit (13); the mass block (201) is fixed on a fixed base (104); the piezoelectric body (12) is fixed on the mass block (201); and the other end of the piezoelectric body (12) is connected to a friction plate (204) via the flexible hinge unit (13).

4. The inertial rotary piezoelectric motor based on a piezoelectric drive unit according to claim 1, characterized in that: The piezoelectric body (12) is made of a single piece of piezoelectric single crystal material, a single piece of piezoelectric ceramic material, a stack of multiple pieces of piezoelectric single crystal material, or a stack of multiple pieces of piezoelectric ceramic material.

5. The inertial rotary piezoelectric motor based on a piezoelectric drive unit according to claim 4, characterized in that: The piezoelectric body (12) is formed by stacking a plurality of piezoelectric sheets, and the outer side surfaces of the multilayer piezoelectric sheets are short-circuited with the same internal end electrodes by means of external electrodes to form two electrodes.

6. The inertial rotary piezoelectric motor based on a piezoelectric drive unit according to claim 4, characterized in that: The piezoelectric body (12) comprises a plurality of piezoelectric single crystal sheets, and the plurality of piezoelectric single crystal sheets are stacked and arranged along a thickness direction.

7. The inertial rotary piezoelectric motor based on a piezoelectric drive unit according to claim 1, characterized in that: The two piezoelectric drive units (101) are symmetrically arranged along the axis of the rotating unit (102), or the two piezoelectric drive units (101) are rotationally symmetrically arranged along the rotation center of the rotating unit (102).

8. A control method for the inertial rotary piezoelectric motor according to any one of claims 1 to 7, characterized in that: The following steps are involved: After applying sawtooth wave excitation signals with the same duty cycle but different phase angles to the upper and lower surfaces of the two piezoelectric bodies on the two groups of piezoelectric drive units, the first-order longitudinal vibration mode of the piezoelectric body is excited through the piezoelectric working mode, and the piezoelectric body will produce a large telescopic deformation along the thickness direction; through the regulation of the two excitation signals, the friction plates on the first group of piezoelectric drive units and the friction plates on the second group of piezoelectric drive units produce telescopic movements alternately in turn.

9. The control method of an inertial micro-rotating piezoelectric motor according to claim 8, characterized in that: The sawtooth wave excitation signal applied to the upper and lower surface electrode layers of the piezoelectric body has a duty cycle greater than or equal to 90% during the extension movement and a duty cycle less than or equal to 10% during the contraction movement.

10. The control method of an inertial micro-rotating piezoelectric motor according to claim 8, characterized in that: The two sawtooth wave excitation signals applied to the upper and lower surface electrode layers of the piezoelectric body need to adjust the duty cycle and phase difference according to different driving principles.

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