Rotary piezoelectric motor based on three-phase drive and method of operation thereof

Abstract

The application discloses a rotary piezoelectric motor based on three-phase driving and a working method thereof, and the motor comprises a rotor, a first bearing, a second bearing, a shell, a base, a stator and a piezoelectric driving module; the stator comprises a fixing ring, three fixing bases, three connecting rods and three driving feet; and the piezoelectric driving module comprises three piezoelectric bimorphs. The rotor realizes bidirectional super-high-precision positioning rotary motion by controlling the time sequence and frequency of the three piezoelectric bimorphs, and can realize large torque at low speed and high-precision rotation at high speed. The application adopts macro-micro fusion design, can work in non-resonance mode and resonance mode, has high reliability, large output torque and high precision, and can be widely applied in the fields of precision optics, aerospace, mechanical manufacturing and medical instruments.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of piezoelectric precision driving, and in particular to a rotary piezoelectric motor based on three-phase driving and a working method thereof. BACKGROUND

[0002] The rotary ultrasonic motor is a kind of driver based on piezoelectric effect, ultrasonic vibration and friction coupling. It has extremely wide application in the field of mechanical manufacturing due to its fast response speed, high precision and large quality moment ratio. However, the stator structure cannot be passed through optical beams and precise mechanical arms, which greatly limits the application range of the rotary ultrasonic motor. The rotary ultrasonic motor with a hollow structure can be applied to the field of precision optics and medical instruments that require a hollow structure due to its unique hollow structure. However, the existing hollow rotary ultrasonic motor structure and driving signal are relatively complex, and the input voltage signal wave frequency band is limited, which brings challenges to the simplified design of piezoelectric driving. Therefore, how to solve the problems of complex structure and complex driving signal of the existing hollow rotary ultrasonic motor, simplify the design of the rotary ultrasonic motor structure, meet the input voltage frequency from low to high, and realize the macro-micro driving fusion under the non-resonance mode and resonance mode of the stator has become a difficult problem in the industry. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a rotary piezoelectric motor based on three-phase driving and a working method thereof to solve the defects involved in the background art.

[0004] The present application adopts the following technical solutions to solve the above technical problems:

[0005] The rotary piezoelectric motor based on three-phase driving comprises a rotor, a first bearing, a second bearing, a housing, a base, a stator and a piezoelectric driving module.

[0006] The rotor is a hollow cylinder with open ends, the first bearing is a deep groove ball bearing, and the second bearing is a thrust bearing.

[0007] The housing is fixed on the base, the outer ring of the first bearing is fixed to the housing, and the inner ring is coaxially fixed to the outer wall of the rotor, the lower ring of the second bearing is fixed to the base, and the upper ring is coaxially fixed to the lower end of the bearing, so that the rotor can freely rotate relative to the base.

[0008] The stator comprises a fixed ring, first to third fixed seats, first to third connecting rods and first to third driving feet.

[0009] The fixed ring is a hollow cylinder with open ends; the first to third fixed seats are uniformly arranged on the fixed ring in the circumferential direction and are fixedly connected to the base, so that the fixed ring is located in the rotor and coaxial with the rotor;

[0010] The first to third connecting rods are uniformly arranged between the fixed ring and the rotor in the circumferential direction, one end of each of the first to third connecting rods is fixedly connected to the outer wall of the fixed ring, and the other end is fixedly connected to the first to third driving feet, respectively; the first to third driving feet are in abutment with the inner wall of the rotor; the first to third fixed seats and the first to third connecting rods divide the fixed ring into six equal parts;

[0011] The first to third driving feet are provided with dovetail grooves on both sides of the corresponding connecting rod;

[0012] The piezoelectric driving module comprises first to third piezoelectric bimorphs;

[0013] One end of the first piezoelectric bimorph is in abutment with the dovetail groove on one side of the first driving foot, and the other end is in abutment with the dovetail groove on one side of the second driving foot; one end of the second piezoelectric bimorph is in abutment with the dovetail groove on the other side of the second driving foot, and the other end is in abutment with the dovetail groove on one side of the third driving foot; one end of the third piezoelectric bimorph is in abutment with the dovetail groove on the other side of the third driving foot, and the other end is in abutment with the dovetail groove on the other side of the first driving foot; the first to third piezoelectric bimorphs are coplanar and protrude outward simultaneously or inward simultaneously, and the plane on which the first to third piezoelectric bimorphs are located is perpendicular to the rotation axis of the rotor;

[0014] The piezoelectric ceramic sheets on both sides of the first to third piezoelectric bimorphs are polarized along the thickness direction, and the polarization is inward simultaneously or outward simultaneously.

[0015] As a further optimization scheme of the present application, the first to third driving feet are made of flexible materials.

[0016] As a further optimization scheme of the present application, the outer sides of the first to third driving feet are provided with friction layers made of ceramic materials to improve the friction performance and wear resistance.

[0017] The present application also discloses a working method of the three-phase driving based rotary piezoelectric motor, comprising the following steps:

[0018] If it is necessary to drive the rotor to rotate in the forward direction:

[0019] The voltage signal waves u1, u2, u3 of the same signal amplitude and frequency and different phases are input to the first to third piezoelectric bimorphs, and the electrical signals of u3, u2, u1 are sequentially different by 120°, so that longitudinal tensile forces with different time phase differences are generated at the two ends of the first to third piezoelectric bimorphs, and then the first to third driving feet generate reverse elliptical motion, the driving surface running track and driving direction of the first to third driving feet are completely consistent, only the phase difference in time, under the synergistic action of the first to third driving feet, the rotor obtains continuous reverse direction output torque.

[0020] B) if the rotor needs to be driven to rotate reversely:

[0021] The voltage signal waves u1, u2, u3 of the same signal amplitude and frequency and different phases are input to the first to third piezoelectric bimorphs, and the electrical signals of u3, u2, u1 are sequentially different by 120°, so that longitudinal tensile forces with different time phase differences are generated at the two ends of the first to third piezoelectric bimorphs, and then the first to third driving feet generate reverse elliptical motion, the driving surface running track and driving direction of the first to third driving feet are completely consistent, only the phase difference in time, under the synergistic action of the first to third driving feet, the rotor obtains continuous reverse direction output torque.

[0022] Compared with the prior art, the above technical scheme has the following technical effects:

[0023] 1. The hollow structure is adopted, and the first to third driving feet and the first to third piezoelectric bimorphs are combined into a simple piezoelectric driving module, so that the hollow rotary piezoelectric motor structure of the three-phase driving mode is designed to be simple, and can be applied to the fields of precision optics and medical instruments which require hollow structures.

[0024] 2. Since the piezoelectric bimorph is used as an excitation source, the first to third piezoelectric bimorphs and the first to third driving feet are non-fixedly matched and embedded in the dovetail groove of the adjacent driving feet, so that the response speed is fast, the precision is high, and the performance can be adjusted by changing the input frequency, voltage and driving mode.

[0025] 3. The three flexible driving feet are arranged to cooperate with each other, the ultrasonic motor can be converted between the resonance mode and the non-resonance mode by adjusting the amplitude and frequency of the input voltage, and macro-micro fusion driving is realized. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a top view of the present application;

[0027] Figure 2 is a sectional view of the present application;

[0028] Figure 3is a structural schematic diagram of the stator and the piezoelectric driving module cooperating in the application;

[0029] Figure 4 is a three-phase driving signal schematic diagram when the driving rotor rotates forward in the application;

[0030] Figure 5 is a three-phase driving signal schematic diagram when the driving rotor rotates reversely in the application;

[0031] Figure 6 is a deformation displacement schematic diagram of the stator when the driving rotor rotates forward in the application;

[0032] Figure 7 is a deformation displacement schematic diagram of the stator when the driving rotor rotates reversely in the application;

[0033] Figure 8 is a contrast schematic diagram of the stator working in resonance and non-resonance modes provided by the embodiment of the application.

[0034] In the figure, 1 is a shell, 2 is a base, 3 is a rotor, 4 is a stator, 5 is a first bearing, 6 is a second bearing, 7 is a fixed ring, 8 is a first fixed seat, 9 is a first connecting rod, 10 is a first driving foot, 11 is a first piezoelectric bimorph, and 12 is a second driving foot. DETAILED DESCRIPTION

[0035] To make the skilled in the art better understand the technical solutions of the application, the technical solutions of the application are further described in detail below with reference to the drawings:

[0036] The application can be implemented in many different forms, and should not be considered limited to the embodiments described herein. On the contrary, the embodiments are provided to make the disclosure thorough and complete, and to fully convey the scope of the application to those skilled in the art. In the drawings, the components are enlarged for clarity.

[0037] As Figure 1 shown, the application discloses a rotary piezoelectric motor based on three-phase driving, which comprises a rotor, a first bearing, a second bearing, a shell, a base, a stator and a piezoelectric driving module.

[0038] As Figure 2 shown, the rotor is a hollow cylinder with open ends, the first bearing adopts a deep groove ball bearing, and the second bearing adopts a thrust bearing.

[0039] The shell is fixed on the base; the outer ring of the first bearing is fixedly connected with the shell, the inner ring is coaxially fixedly connected with the outer wall of the rotor, the lower ring of the second bearing is fixedly connected with the base, and the upper ring is coaxially fixedly connected with the lower end of the bearing, so that the rotor can freely rotate relative to the base.

[0040] AsFigure 2 、 Figure 3 The stator comprises a fixed ring, first to third fixed seats, first to third connecting rods, and first to third driving feet;

[0041] The fixed ring is a hollow cylinder with open ends; the first to third fixed seats are uniformly arranged on the fixed ring in the circumferential direction and are fixedly connected to the base, so that the fixed ring is located in the rotor and coaxial with the rotor;

[0042] The first to third connecting rods are uniformly arranged between the fixed ring and the rotor, one end of each of the first to third connecting rods is fixedly connected to the outer wall of the fixed ring, and the other end is fixedly connected to the corresponding first to third driving feet; the first to third driving feet abut against the inner wall of the rotor; the first to third fixed seats and the first to third connecting rods divide the fixed ring into six equal parts;

[0043] The first to third driving feet are provided with dovetail grooves on both sides of the corresponding connecting rod;

[0044] The piezoelectric driving module comprises first to third piezoelectric bimorphs;

[0045] One end of the first piezoelectric bimorph abuts against the dovetail groove on one side of the first driving foot, and the other end abuts against the dovetail groove on one side of the second driving foot; one end of the second piezoelectric bimorph abuts against the dovetail groove on the other side of the second driving foot, and the other end abuts against the dovetail groove on one side of the third driving foot; one end of the third piezoelectric bimorph abuts against the dovetail groove on the other side of the third driving foot, and the other end abuts against the dovetail groove on the other side of the first driving foot; the first to third piezoelectric bimorphs are coplanar and protrude outward simultaneously or inward simultaneously, and the plane on which the first to third piezoelectric bimorphs are located is perpendicular to the rotation axis of the rotor;

[0046] The piezoelectric ceramic sheets on both sides of the first to third piezoelectric bimorphs are polarized along the thickness direction, and the polarization is inward simultaneously or outward simultaneously.

[0047] The first to third driving feet are made of flexible materials, and the outer sides of the first to third driving feet are provided with friction layers made of ceramic materials to improve the friction performance and wear resistance.

[0048] The application also discloses a forward driving and reverse driving working method of the rotary piezoelectric motor based on three-phase driving, which are as follows:

[0049] A) If the rotor needs to be driven to rotate forward:

[0050] As shown in Figure 4 , voltage signal waves u1, u2, and u3 with the same signal amplitude and frequency and different phases are input to the first to third piezoelectric bimorphs, and the formula expression has the following form:

[0051] ui = V i f i

[0052] The phase of the electrical signals input to the first piezoelectric bimorph, the second piezoelectric bimorph and the third piezoelectric bimorph is sequentially different by 120°, and is respectively represented as:

[0053]

[0054]

[0055]

[0056] When a forward voltage is applied to the first to third piezoelectric bimorphs, the first to third piezoelectric bimorphs can generate bending vibration, and the bending vibration causes the two ends of the first to third piezoelectric bimorphs to generate longitudinal tensile force of a certain frequency. As shown in the figure, the two ends of the first to third piezoelectric bimorphs generate longitudinal tensile force with different time phase difference, so that the first to third driving feet generate forward elliptical motion, and the elliptical motion causes the contact state of the driving surface of the first to third driving feet with the rotor to be divided into four states of disengagement, pre-contact, full contact and pre-disengagement in time sequence. Figure 6

[0057] Let the circumference of the trajectory of the driving surface of the first driving foot forming the elliptical motion be x1, and according to the friction coefficient of the contact surface and the size of the trajectory of the elliptical motion, the efficiency of driving the rotation of the rotor is μ1, and each step of the elliptical motion transmits an effective step length of μ1x1 to the friction surface of the rotor. The first driving foot performs λ1 elliptical motions after waiting for a preset time t1 seconds, and the effective step length of the forward rotation of the rotor is λ1μ1x1.

[0058] The driving surface running trajectory and driving direction of the first to third driving feet are completely consistent, only the phase difference in time, so that the rotor can obtain continuous forward direction output torque under the synergistic action of the first to third driving feet, and realize the conversion of electrical energy into mechanical energy.

[0059] B) If the rotor needs to be driven to rotate in the reverse direction:

[0060] As shown in the figure, the same signal amplitude and frequency, different phase voltage signal waves u1, u2 and u3 are input to the first to third piezoelectric bimorphs, and the formula is expressed as follows: Figure 5

[0061] u i = V i f i

[0062] The phase of the electrical signals input to the first piezoelectric bimorph, the second piezoelectric bimorph and the third piezoelectric bimorph is sequentially different by 120°, and is respectively represented as:​​

[0063]

[0064]

[0065]

[0066] The first to third piezoelectric bimorphs are applied with a forward voltage, so that the first to third piezoelectric bimorphs generate bending vibration, which causes the two ends of the first to third piezoelectric bimorphs to generate longitudinal tensile force of a certain frequency. As shown in FIG. 1, the two ends of the first to third piezoelectric bimorphs generate longitudinal tensile force with different time phase differences, so that the first to third driving feet generate reverse elliptical motion, which causes the contact state of the driving surface of the first to third driving feet with the rotor to be divided into four states of disengagement, pre-contact, full contact, and pre-disengagement in time sequence. Figure 7

[0067] The length of the trajectory of the driving surface of the first driving foot forming the elliptical motion is x2, and according to the friction coefficient of the contact surface and the size of the trajectory of the elliptical motion, the efficiency of driving the rotation of the rotor is μ2. Each step of the elliptical motion transmits an effective step length of μ2x2 to the friction surface of the rotor, and the rotor rotates in the reverse direction around the axis. After waiting for a preset time t2 seconds, the first driving foot performs λ2 elliptical motions, and the effective step length of the reverse rotation of the rotor is λ2μ2x2.

[0068] The driving surface operation trajectories and driving directions of the first to third driving feet are completely consistent, and only have a time phase difference, so that the rotor can obtain continuous reverse direction output torque under the synergistic action of the first to third driving feet, and realize the conversion of electric energy to mechanical energy.

[0069] In the two methods, by adjusting the amplitude and frequency of the voltage, the step length of the elliptical motion of each driving foot and the time required to complete one elliptical motion can be changed, so as to change the speed of the rotation of the rotor. In the two methods, the amplitude of the voltage is adjusted within the allowable range in which the first to third piezoelectric bimorphs do not break, and the voltage amplitude of the experimental embodiment is 0-500vpp; in the two methods, the adjusted voltage frequency can meet from low frequency to high frequency band, and the voltage frequency of the experimental embodiment is 0-20KHz, so as to meet the working of the motor in the non-resonance mode and the resonance mode, and realize the macro-micro hybrid driving, as shown in FIG. 2. Figure 8

[0070] ​​As used herein, and unless otherwise indicated, all terms have their ordinary meanings. It should be understood that any definitions are to be used as elucidated herein and should not be taken in any restrictive sense unless expressly defined.

[0071] The above description is further explained with reference to the specific embodiments. The specific embodiments are illustrations of a particular implementation of the present application. Numerous specific details are described in connection with the embodiments. However, in other implementations, different or similar specific details can be used. In the description herein, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one skilled in the art that the present application can be practiced without incorporating these specific details. In general, the description and examples are intended to provide an overview for understanding the application innovation and the substance desired to be protected by the patent. They are not intended to serve as limitations of the application innovation's scope as it can be found in the appended claims.

Claims

1. A rotary piezoelectric motor based on three-phase driving, characterized by, The motor comprises a rotor, a first bearing, a second bearing, a housing, a base, a stator and a piezoelectric driving module. The rotor is a hollow cylinder with open ends, the first bearing is a deep groove ball bearing, and the second bearing is a thrust bearing. The housing is fixed on the base, the outer ring of the first bearing is fixed with the housing, and the inner ring is coaxially fixed with the outer wall of the rotor, the lower ring of the second bearing is fixed with the base, and the upper ring is coaxially fixed with the lower end of the bearing, so that the rotor can freely rotate relative to the base. The stator comprises a fixed ring, first to third fixed seats, first to third connecting rods, and first to third driving feet. The fixed ring is a hollow cylinder with open ends, and the first to third fixed seats are uniformly arranged on the fixed ring and fixed with the base, so that the fixed ring is located in the rotor and coaxial with the rotor. The first to third connecting rods are uniformly arranged between the fixed ring and the rotor, one end of each connecting rod is fixed with the outer wall of the fixed ring, and the other end is fixed with the corresponding first to third driving feet, respectively. The first to third driving feet are in contact with the inner wall of the rotor. The first to third driving feet are provided with dovetail grooves on both sides of the corresponding connecting rods. The piezoelectric driving module comprises first to third piezoelectric bimorphs. One end of the first piezoelectric bimorph is in contact with the dovetail groove on one side of the first driving foot, and the other end is in contact with the dovetail groove on one side of the second driving foot.

2. The rotary piezoelectric motor based on a three-phase drive according to claim 1, characterized by One end of the second piezoelectric bimorph is in contact with the dovetail groove on the other side of the second driving foot, and the other end is in contact with the dovetail groove on one side of the third driving foot.

3. The rotary piezoelectric motor based on a three-phase drive according to claim 1, characterized by One end of the third piezoelectric bimorph is in contact with the dovetail groove on the other side of the third driving foot, and the other end is in contact with the dovetail groove on the other side of the first driving foot.

4. The method of operating a three-phase drive-based rotary piezoelectric motor according to claim 1, characterized by, The first to third piezoelectric bimorphs are coplanar and protrude outward or inward simultaneously, and the plane of the first to third piezoelectric bimorphs is perpendicular to the rotation axis of the rotor. The piezoelectric ceramic sheets on both sides of the first to third piezoelectric bimorphs are polarized along the thickness direction. The first to third driving feet are made of flexible material. The outer side of the first to third driving feet is provided with a friction layer made of ceramic material to improve the friction performance and wear resistance. The method comprises the following steps: If the rotor needs to be driven to rotate forward: Input voltage signal waves u1, u2, u3 with the same signal amplitude and frequency but different phases to the first to third piezoelectric bimorphs, and the phases of u1, u2, u3 are sequentially different by 120°, so that the first to third piezoelectric bimorphs generate longitudinal tensile forces with different time phase differences at both ends, and then the first to third driving feet generate forward elliptical motion, the driving surface track and driving direction of the first to third driving feet are completely consistent, only the phase difference in time, under the cooperation of the first to third driving feet, the rotor obtains continuous forward output torque; B) If the rotor needs to be driven to rotate reversely: The first to third piezoelectric bimorphs are inputted with voltage signal waves u1, u2, u3, u3, u2, u1 of the same signal amplitude and frequency and different phases, and the electrical signals of u3, u2, u1 are sequentially different by 120°, so that the first to third piezoelectric bimorphs generate longitudinal tensile forces with different time phase differences, and then the first to third driving feet generate reverse elliptical motions, the driving surface track and driving direction of the first to third driving feet are completely consistent, only the phase difference in time, under the synergistic action of the first to third driving feet, the rotor obtains continuous reverse direction output torque.

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