A piezoelectric actuator based on epicycloid induction principle and control method thereof

Abstract

The present invention discloses a piezoelectric driver based on the epicycloid induction principle and a control method thereof, wherein the piezoelectric driver comprises a base, an initial gap adjustment unit, a stator unit and a mover unit; the base, the initial gap adjustment unit and the stator unit are fixedly connected in sequence from bottom to top, and the position of the stator unit along the X-axis direction and the Y-axis direction is adjusted by the initial gap adjustment unit; the stator unit is fixed on the base and the stator unit and the mover unit are located in the same horizontal plane; the mover unit comprises a bearing, a guide rail and a slider, the guide rail is fixed on the base, the slider is slidably connected to the guide rail, and the bearing is fixed on the base; the bearing is in close tangential contact with the slider along the Y-axis direction, and the outer ring of the bearing generates an epicycloid motion under the drive of the stator unit, thereby driving the slider to generate a corresponding burst motion. The present invention provides a solution for studying the elimination of the retraction motion of the stick-slip piezoelectric driver.

Description

Technical Field

[0001] The present invention relates to the field of precision positioning, and in particular to a piezoelectric driver based on the epicycloid induction principle and a control method thereof. Compared with the piezoelectric drivers developed based on the existing stick-slip, inertial, parasitic and other driving principles, the piezoelectric driver based on the epicycloid induction principle and the control method thereof provided by the present invention not only suppresses the retraction motion of the stick-slip and other piezoelectric drivers from the driving principle, but also realizes significant bursting motion, greatly improves the output performance of the piezoelectric driver, and can be used in the fields of precision positioning, biomedical engineering, and precision / ultra-precision machining to achieve non-retraction, high-precision positioning. Background Art

[0002] With the increasing demand for micro / nano positioning, processing and operation in fields such as precision positioning, biomedical engineering and precision / ultra-precision machining, the demand for precision positioning platforms has become more urgent. Piezoelectric stacks based on the inverse piezoelectric effect have won the favor of many researchers due to their advantages such as high stiffness, high resolution and fast response, and have become the mainstream driving element of the actuator. Among the many types of piezoelectric actuators, stick-slip piezoelectric actuators are widely used due to their simple structure and control. However, stick-slip piezoelectric actuators generally have retraction motion during operation, which not only reduces the output performance of the actuator, but also shortens the service life of the actuator. At present, principles such as ultrasonic friction reduction effect and trajectory correction have been developed to suppress retraction motion. Although the retraction motion can be effectively suppressed, there are still problems such as incomplete suppression and small output step size.

[0003] In summary, in the field of piezoelectric actuators, how to eliminate the retraction motion and increase the output step length is a hot research issue that needs to be solved urgently. To this end, it is necessary to propose a new piezoelectric drive principle and develop corresponding devices and methods to achieve the elimination of the retraction motion and the increase of the output step length while retaining the simple structure and simple control of the existing stick-slip piezoelectric actuator. Summary of the invention

[0004] The purpose of the present invention is to provide a piezoelectric driver based on the epicycloidal induction principle and a control method thereof, which improves the output step length of the stick-slip piezoelectric driver by inducing the bursting motion of the slider using the epicycloidal motion of the bearing. The piezoelectric driver based on the epicycloidal induction principle of the present invention has a simple structure and a flexible control method. The initial gap between the driving foot, the clamping foot and the slider can be adjusted by the corresponding knob of the fine-tuning mechanism; under the appropriate initial gap, the outer raceway of the bearing can produce an epicycloidal motion by alternately pushing the bearing by the driving foot and the clamping foot, thereby driving the slider, thereby eliminating the inherent retraction motion of the stick-slip piezoelectric driver. The present invention provides a solution for studying the elimination of the retraction motion of the stick-slip piezoelectric driver, and has broad application prospects in the fields of precision positioning, biomedical engineering, and precision / ultra-precision machining.

[0005] The above-mentioned object of the present invention is achieved by the following technical solutions:

[0006] As one aspect of the present invention, a piezoelectric driver based on the epicycloid induction principle is provided, comprising a base, an initial gap adjustment unit, a stator unit and a mover unit; the base, the initial gap adjustment unit and the stator unit are fixedly connected in sequence from bottom to top, and the position of the stator unit along the X-axis and the Y-axis is adjusted by the initial gap adjustment unit; the stator unit is fixed on the base and the stator unit and the mover unit are located in the same horizontal plane; the mover unit comprises a bearing, a guide rail and a slider, the guide rail is fixed on the base, the slider is slidably connected to the guide rail, and the bearing is fixed on the base; the bearing is in close tangential contact with the slider along the Y-axis direction, and the outer ring of the bearing generates an epicycloid motion under the drive of the stator unit, thereby driving the slider to generate a corresponding burst motion.

[0007] Furthermore, the stator unit includes a bipedal flexible hinge, a clamping piezoelectric stack, a driving piezoelectric stack and an open-loop piezoelectric controller, the bipedal flexible hinge includes a fixed frame, a driving foot and a clamping foot; the driving foot and the clamping foot are respectively arranged in the fixed frame, the driving foot is in tangential contact with the outer ring of the bearing along the Y direction, the clamping foot is in tangential contact with the outer ring of the bearing along the X direction, the clamping piezoelectric stack is installed in the clamping foot, and the driving piezoelectric stack is installed in the driving foot; the open-loop piezoelectric controller is electrically connected to the clamping piezoelectric stack and the driving piezoelectric stack, respectively, the open-loop piezoelectric controller excites the clamping foot and the driving foot to extend and retract alternately, and induces the outer ring of the bearing to produce an epicycloidal motion.

[0008] Furthermore, the driving foot is arranged at the upper right of the biped flexible hinge, one end of which is connected to the fixing frame, and the other end is in tangential contact with the outer ring of the bearing along the Y direction; the clamping foot is arranged at the lower left of the biped flexible hinge, which is connected to the fixing frame and in tangential contact with the outer ring of the bearing along the X direction.

[0009] Furthermore, the open-loop piezoelectric controller model is MDT693B.

[0010] Furthermore, the induction process of the bearing epicycloidal motion is:

[0011] The diameter d of the inner and outer raceways of the bearing i d o Calculated by the following formula:

[0012]

[0013] Where, d i and d o are the diameters of the inner and outer raceways respectively; d c is the average diameter of the rolling element group; d r is the rolling element diameter; c r is the radial clearance of the bearing;

[0014] In the initial state, the outer envelope circle of the rolling element group contacts the outer raceway at point P1, and the initial deflection angle θ0 = 0;

[0015] When the outer raceway rolls without sliding along the outer envelope circle of the rolling element group, the contact point between the two is constantly changing. Point P2 represents the contact point at a certain moment. The epicycloidal motion of the outer raceway is decomposed into the following translational motion and rotational motion.

[0016] During the translational motion, the outer raceway is considered to be in translational motion along the path P1P′1. The motion equation of the translational motion is:

[0017]

[0018] Among them, x p ,y p is the component of the translational motion of the outer raceway along the X-axis and Y-axis, c r is the radial clearance of the bearing, θ0=0 is the starting deflection angle of the epicycloid motion, θ=∠P1O i P2 is the terminal deflection angle of the epicycloid motion;

[0019] In the rotational motion, the outer raceway is regarded as a point O o The rotation center rotates through an angle θ′, and the motion equation of the rotational motion is:

[0020]

[0021] Where θ′=∠P′1O o P″1 is the angle that the outer raceway rotates in the epicycloidal motion, d o is the outer raceway diameter of the bearing;

[0022] Therefore, at point O iis the origin of the coordinate system, and considering that the position of the initial contact point P1 in the coordinate system is (0,0.5d o ), combining the motion equations of translational motion and rotational motion, the epicycloidal motion equation of the outer raceway is derived as follows:

[0023]

[0024] When the bearing and the slider are in close tangential contact, the epicycloidal motion of the outer raceway will induce the slider to produce corresponding bursting motion. In the translational motion, the slider and the outer raceway keep synchronous motion. In the rotational motion, the rotation angle θ′ of the outer raceway is converted into the linear displacement l of the slider along the X direction. The linear displacement l is expressed as follows:

[0025] l=0.5dθ′

[0026] Where d is the nominal diameter of the bearing and also the rotational diameter for rotary motion;

[0027] Combine the above equations and take into account the relative position of the slider to point O. i The position of is (0,0.5d), then the induced burst motion of the slider is expressed as follows:

[0028]

[0029] Wherein, l is the linear displacement of the slider along the X direction converted by the rotation angle θ′ in the rotational motion of the outer raceway.

[0030] Furthermore, the initial gap adjustment unit includes a fine-tuning mechanism and an adapter plate, and the fine-tuning mechanism includes an X-axis fine-tuning knob, a lower slide, a middle slide, an upper slide and a Y-axis fine-tuning knob; the lower slide is fixed on the base; the middle slide is slidably connected to the lower slide, and the upper slide is slidably connected to the middle slide; the X-axis fine-tuning knob is used to adjust the relative displacement of the middle slide and the lower slide along the X-axis direction; the Y-axis fine-tuning knob is used to adjust the relative displacement of the upper slide and the middle slide along the Y-axis direction; the adapter plate is fixed on the upper surface of the upper slide; and the bipedal flexible hinge is fixed on the adapter plate.

[0031] As a second aspect of the present invention, a control method for a piezoelectric actuator based on an epicycloid induction principle is provided, comprising the following steps:

[0032] Step 1: At time t0, the stator unit is in the initial state, and the relative positions of the clamping foot, the driving foot and the bearing in the two-legged flexible hinge are adjusted by the initial gap adjustment unit. The clamping foot is in close tangential contact with the bearing, and there is a small gap between the driving foot and the bearing. Under the pre-tightening effect of the clamping foot, the starting contact point between the rolling element group and the outer raceway is P0;

[0033] Step 2: At time t1, clamp voltage Uc The clamping piezoelectric stack increases instantaneously. Based on the inverse piezoelectric effect, the clamping foot is stretched and moves in the negative Y direction until it is separated from the outer ring of the bearing. During this period, the contact point between the rolling element group and the outer raceway jumps from point P0 to point P1.

[0034] Step 3: At time t2, the driving voltage U d The force increases instantaneously, driving the piezoelectric stack to stretch instantaneously, causing the driving foot to bend and deform and gradually approach the outer ring of the bearing until it contacts the outer ring of the bearing. During this period, the contact point between the rolling element group and the outer raceway deflects from point P1 to point P2.

[0035] Step 4: At time t3, clamp voltage U c It is instantly lowered, the clamping piezoelectric stack is instantly contracted, and the clamping foot moves in the positive Y direction until it contacts the outer ring of the bearing. During this period, the contact point between the rolling element group and the outer raceway is deflected from point P2 to point P3;

[0036] Step 5: At time t4, the driving voltage U d It is instantly lowered, the driving piezoelectric stack is instantly contracted, and the driving foot gradually moves away from the outer ring of the bearing until it is separated from the outer ring of the bearing. During this period, the contact point between the rolling element group and the outer raceway is deflected from point P3 to point P4;

[0037] It can be seen from the epicycloid induction principle that in steps three to five, along with the deflection of the contact point, the outer raceway of the bearing produces an epicycloid motion, which correspondingly induces the bursting motion of the slider.

[0038] The beneficial effects of the present invention are:

[0039] Through the piezoelectric driver based on the epicycloid induction principle and the control method thereof provided by the present invention, the retreat motion occurring in stick-slip, parasitic, inertial and other types of drivers can be eliminated from the driving principle, and on this basis, the burst motion of the slider can be induced by the epicycloid motion of the outer raceway of the bearing, thereby greatly improving the output step length of the driver. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The illustrative examples of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0041] Figure 1 It is a three-dimensional structural schematic diagram of a piezoelectric actuator based on the epicycloid induction principle of the present invention;

[0042] Figure 2 is a schematic diagram of the three-dimensional structure of the substrate of the present invention;

[0043] Figure 3It is a three-dimensional structural schematic diagram of the fine adjustment mechanism of the present invention;

[0044] Figure 4 It is a schematic diagram of the three-dimensional structure of the adapter plate of the present invention;

[0045] Figure 5 It is a schematic diagram of the three-dimensional structure of the bipedal flexible hinge of the present invention;

[0046] Figure 6 The epicycloidal motion process used in the present invention; wherein (a) is a schematic diagram of the structural parameters of the bearing; (b) is a schematic diagram of the outer envelope circle and outer raceway of the rolling element group of the bearing; (c) is a schematic diagram of the translational motion after the epicycloidal motion of the outer raceway is decomposed; (d) is a schematic diagram of the rotational motion after the epicycloidal motion of the outer raceway is decomposed;

[0047] Figure 7 The epicycloid induction principle used in the present invention; wherein (a) is a schematic diagram of the initial state of the bearing; (b) is a schematic diagram of the outer raceway of the bearing inducing the slider to produce bursting motion;

[0048] Figure 8 The trajectories of the epicycloid motion and the bursting motion of the present invention; wherein (a) is a schematic diagram of the trajectory from a macroscopic perspective; (b) is a schematic diagram of the trajectory from a microscopic perspective;

[0049] Fig. 9 A timing control diagram of the electrical signal of the present invention;

[0050] FIG10 is a working principle diagram of a piezoelectric actuator based on the epicycloid induction principle of the present invention; wherein (a) is a diagram of the initial state of the stator at time t0; (b) is a diagram of the separation state of the clamping foot and the bearing at time t1; (c) is a diagram of the contact state of the driving foot and the bearing at time t2; (d) is a diagram of the contact state of the clamping foot and the bearing at time t3; (e) is a diagram of the separation state of the driving foot and the bearing at time t4;

[0051] Fig.11 In the present invention, the driving frequency is 1 Hz, and the driving electrical signal U d When the driving electric signal U is 150V, the c The experimental curve of the output displacement of the slider measured below versus time.

[0052] Fig.12 The present invention is to drive the electrical signal U c is 90V, the driving electrical signal U d The experimental curve of the output displacement of the slider over time measured at different driving frequencies when the voltage is 150V;

[0053] In the figure:

[0054] 1-base; 2-fine-tuning mechanism; 3-adapter plate; 4-biped flexible hinge; 5-clamped piezoelectric stack; 6-bearing; 7-slider; 8-guide rail; 9-driving piezoelectric stack; 201-X-axis fine-tuning knob; 202-lower slide; 203-middle slide; 204-upper slide; 205-positioning hole; 206-Y-axis fine-tuning knob; 301-biped flexible hinge mounting hole; 401-fixed frame; 402-driving foot; 403-clamping foot. DETAILED DESCRIPTION

[0055] The details of the present invention and its specific implementation methods are further described below in conjunction with the accompanying drawings.

[0056] Example 1

[0057] See also Figures 1 to 5 As shown, this embodiment is a piezoelectric actuator based on the epicycloid induction principle, including a base 1, an initial gap adjustment unit, a stator unit and a mover unit; the base 1, the initial gap adjustment unit and the stator unit are fixedly connected in sequence from bottom to top, and the position of the stator unit along the X-axis and the Y-axis is adjusted by the initial gap adjustment unit; the stator unit is fixed to the base 1 by screws and the stator unit and the mover unit are located in the same horizontal plane; the mover unit includes a bearing 6, a guide rail 8 and a slider 7, the guide rail 8 is fixed on the base 1, the slider 7 is slidably connected to the guide rail 8, and the bearing 6 is fixed on the base 1; the bearing 6 is in close tangential contact with the slider 7 along the Y-axis direction, and the outer raceway of the outer ring of the bearing 6 generates an epicycloid motion under the drive of the stator unit, thereby driving the slider 7 to generate a corresponding burst motion.

[0058] The stator unit includes a biped flexible hinge 4, a clamping piezoelectric stack 5, a driving piezoelectric stack 9 and an open-loop piezoelectric controller MDT693B. The biped flexible hinge 4 includes a fixing frame 401, a driving foot 402 and a clamping foot 403. The driving foot 402 is arranged on the upper right side of the biped flexible hinge 4, one end of which is connected to the fixing frame 401, and the other end is tangentially in contact with the outer ring of the bearing 6 along the Y direction. The clamping foot 403 is arranged on the lower left side of the biped flexible hinge 4, which is connected to the fixing frame 401 and is tangentially in contact with the outer ring of the bearing 6 along the X direction. The clamping piezoelectric stack 5 is installed on the clamping frame 401. In the foot 403, the driving piezoelectric stack 9 is installed in the driving foot 402; the clamping piezoelectric stack 5 and the driving piezoelectric stack 9 are respectively connected to the open-loop piezoelectric controller MDT693B. By inputting the square wave electrical signal generated by the signal generator into the open-loop piezoelectric controller MDT693B, the clamping foot 403 and the driving foot 402 are stimulated to extend and retract alternately, and the outer ring of the bearing 6 is induced to produce an epicycloidal motion. The clamping foot 403 contacts the bearing to generate a certain preload force, which can clamp the bearing during the rapid contraction of the driving foot 402 to prevent the bearing from rotating in the opposite direction (manifested as the retreat movement of the slider).

[0059] The initial gap adjustment unit includes a fine-tuning mechanism 2 and an adapter plate 3; the fine-tuning mechanism 2 includes an X-axis fine-tuning knob 201, a lower slide 202, a middle slide 203, an upper slide 204 and a Y-axis fine-tuning knob 206; the lower slide 202 is fixed on the base 1; the middle slide 203 is slidably connected to the lower slide 202; the upper slide 204 is slidably connected to the middle slide 203; the X-axis fine-tuning knob 201 is used to adjust the relative displacement of the middle slide 203 and the lower slide 202 along the X-axis direction; the Y-axis fine-tuning knob 206 is used to adjust the relative displacement of the upper slide 204 and the middle slide 203 along the Y-axis direction; the adapter plate 3 is fixed on the upper surface of the upper slide 204; the bipedal flexible hinge 4 is fixed to the upper surface of the adapter plate 3 by screws. The initial clearance adjustment unit adjusts the initial clearance between the driving foot 402 and the clamping foot 403 of the bipedal flexible hinge 4 in the stator unit and the bearing 6 by rotating the X-axis fine-tuning knob 201 and the Y-axis fine-tuning knob 206 respectively.

[0060] The inner ring of the bearing 6 is fixed on the base 1, and the outer ring of the bearing 6 is in tangential contact with the slider 7 along the positive Y direction; the outer ring of the bearing 6 is in tangential contact with the clamping foot 403 along the negative Y direction, and is in tangential contact with the driving foot 402 along the positive X direction. Therefore, when the outer ring of the bearing rotates, under the action of the preload force, the angular displacement of the bearing can be converted into the linear displacement of the slider, that is, relying on the epicycloidal motion generated by the outer raceway of the bearing 6, the slider 7 can generate a corresponding bursting motion (the linear displacement of the slider along the guide rail induced by the epicycloidal motion of the outer raceway of the bearing 6 is named bursting motion), which can eliminate the back-off motion and increase the output step length.

[0061] See also Figures 6 to 8 As shown, the induction process of the epicycloidal motion of the outer raceway of the outer ring of the bearing 6 is:

[0062] The structural parameters of the bearing are as follows: Figure 6 (a) shows that the inner ring is fixed. Where d is the nominal diameter of the bearing, d i and d o are the inner and outer rolling diameters, b is the width of the bearing, d is the c is the average diameter of the rolling element group, d r is the rolling element diameter, c r is the radial clearance of the bearing.

[0063] Diameter d of inner and outer raceways i ,d o It can be calculated by the following formula:

[0064]

[0065] The outer envelope circle and outer raceway of the rolling element group of the bearing are Figure 6(a) is extracted and plotted on Figure 6 (b). The small circle represents the outer envelope of the rolling element group, the large circle represents the outer raceway, and point O i , O o They are the outer envelope circle of the rolling element group and the center of the outer raceway. In the initial state, the outer envelope circle of the rolling element group contacts the outer raceway at point P1, and the initial deflection angle θ0=0.

[0066] When the outer raceway rolls without sliding along the outer envelope circle of the rolling element group, the contact point between the two is constantly changing. With point P2 representing the contact point at a certain moment, the epicycloidal motion of the outer raceway can be decomposed into Figure 6 (c) The translational motion and Figure 6 (d) The rotational motion shown.

[0067] During the translational motion, the outer raceway can be regarded as performing translational motion along the path P1P′1, and the motion equation of the translational motion is

[0068]

[0069] Among them, x p ,y p is the component of the translational motion of the external rolling along the X and Y directions, c r is the radial clearance of the bearing, θ0=0 is the starting deflection angle of the epicycloid motion, θ=∠P1O i P2 is the terminal deflection angle of the epicycloid motion.

[0070] In rotational motion, the outer raceway can be regarded as a o The rotation center rotates through an angle θ′, and the equation of motion for the rotational motion is

[0071]

[0072] Where θ′=∠P′1O o P″1 is the angle that the outer raceway rotates in the epicycloidal motion, d o is the outer raceway diameter of the bearing.

[0073] Therefore, at point O i is the origin of the coordinate system, and considering that the position of the initial contact point P1 in the coordinate system is (0,0.5d o ), combining the motion equations of translational motion and rotational motion, the epicycloidal motion equation of the outer raceway can be derived as follows:

[0074]

[0075] Furthermore, the initial state of the bearing is Figure 7As shown in (a), when the bearing and the slider are in close tangential contact, the epicycloidal motion of the outer raceway will induce the slider to produce a corresponding bursting motion, such as Figure 7 (b) In translational motion, the slider and the outer raceway keep synchronous motion, while in rotational motion, the rotation angle θ′ of the outer raceway will be converted into the linear displacement l of the slider along the X direction. The linear displacement l can be expressed as follows

[0076] l=0.5dθ′

[0077] Here, d is the nominal diameter of the bearing and also the rotational diameter for rotary motion.

[0078] Therefore, combining the above equations, taking into account the relative position of the slider to point O i The position of is (0,0.5d), then the induced burst motion of the slider can be expressed as follows:

[0079]

[0080] Wherein, l is the linear displacement of the slider along the X direction converted by the rotation angle θ′ in the rotational motion of the outer raceway.

[0081] When the radial clearance of the bearing c r When the value is 10.2 μm, the trajectories of epicycloidal motion and bursting motion under macroscopic and microscopic perspectives are as follows: Figure 8 (a) Figure 8 (b) As shown in Figure 2, it can be seen that the epicycloid induction principle is to induce the bursting motion of the slider through the epicycloid motion of the outer raceway of the bearing.

[0082] Example 2

[0083] See also Figure 9 to Figure 1 0. This embodiment provides a control method for a piezoelectric actuator based on an epicycloid induction principle, comprising the following steps:

[0084] Step 1: At time t0, the stator unit is in the initial state, and the X-axis fine-tuning knob 201 and the Y-axis fine-tuning knob 206 of the fine-tuning mechanism 2 are adjusted to make the bipedal flexible hinge 4 in a suitable initial state. Under the pre-tightening effect of the clamping foot, the starting contact point between the rolling element group of the bearing 6 and the outer raceway is P0;

[0085] Step 2: At time t1, clamp voltage U c The clamping piezoelectric stack 5 is stretched instantaneously based on the inverse piezoelectric effect, and the clamping foot 403 is stretched and moves along the negative Y direction until it is separated from the outer ring of the bearing 6. During this period, the contact point between the rolling element group of the bearing 6 and the outer raceway jumps from point P0 to point P1.

[0086] Step 3: At time t2, the driving voltage Ud The driving force increases instantaneously, driving the piezoelectric stack 9 to extend instantaneously, causing the driving foot 402 to bend and deform and gradually approach the outer ring of the bearing 6 until it contacts the outer ring of the bearing 6. During this period, the contact point between the rolling element group of the bearing 6 and the outer raceway is deflected from point P1 to point P2.

[0087] Step 4: At time t3, clamp voltage U c It is instantly lowered, the clamping piezoelectric stack 5 is instantly contracted, and the clamping foot 403 moves in the positive Y direction until it contacts the outer ring of the bearing 6. During this period, the contact point between the rolling element group of the bearing 6 and the outer raceway is deflected from point P2 to point P3;

[0088] Step 5: At time t4, the driving voltage U d It is instantly lowered, driving the piezoelectric stack 9 to shrink instantly, and the driving foot 402 gradually moves away from the outer ring of the bearing 6 until it is separated from the outer ring of the bearing 6. During this period, the contact point between the rolling element group of the bearing 6 and the outer raceway is deflected from point P3 to point P4;

[0089] It can be known from the epicycloid induction principle that in steps 3 to 5, along with the deflection of the contact point, the outer raceway of the bearing 6 generates an epicycloid motion, which correspondingly induces the bursting motion of the slider 7.

[0090] Repeating the above steps can achieve stable bursting motion, and changing the phase difference, amplitude and frequency of the square wave electrical signal can obtain different output effects.

[0091] See also Fig.11 As shown, the initial gap g of the present invention c is -20μm, initial gap g d is 10μm, the driving frequency is 1Hz, and the driving electrical signal U d When the driving electric signal U is 150V, the c The following is the experimental curve of the output displacement of the slider over time. Among them, the initial gap g c A negative value indicates that the clamping foot is in close contact with the bearing, and the initial clearance g d is a positive value, indicating that there is a small gap between the driving foot and the bearing. It can be clearly seen from the figure that the output displacement curve consists of three consecutive step displacements, showing an obvious burst characteristic. c When the voltage is less than 90V, the reverse motion occurs. c When it is greater than 90V, the retraction motion in the forward and reverse motion disappears, indicating that the retraction motion of the drive is completely eliminated.

[0092] See also Fig.12 As shown, the present invention is driven at a frequency of 1 Hz and a driving electrical signal U cWhen the driving electric signal U is 90V, the d The following is an experimental curve of the output displacement of the slider over time. It can be clearly seen from the figure that when U d When the voltage increases from 70V to 150V, the step length of the bidirectional motion increases, and no retreat motion occurs, which indicates that when the driving frequency and the driving electrical signal U are maintained, the c Under the condition of unchanged, change the driving electrical signal U d The drive's retraction motion is effectively eliminated.

[0093] The above content does not impose any formal limitation on the structure and shape of the present invention. Any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A piezoelectric actuator based on the epicycloid induction principle, characterized in that: The invention comprises a base, an initial gap adjustment unit, a stator unit and a mover unit; the base, the initial gap adjustment unit and the stator unit are fixedly connected in sequence from bottom to top, and the position of the stator unit along the X-axis direction and the Y-axis direction is adjusted by the initial gap adjustment unit; the stator unit is fixed on the base and the stator unit and the mover unit are located in the same horizontal plane; the mover unit comprises a bearing, a guide rail and a slider, the guide rail is fixed on the base, the slider is slidably connected to the guide rail, and the bearing is fixed on the base; the bearing is in close tangential contact with the slider along the Y-axis direction, and the axis The outer ring of the bearing generates an epicycloidal motion under the drive of the stator unit, thereby driving the slider to generate a corresponding bursting motion; the stator unit includes a bipedal flexible hinge, a clamping piezoelectric stack, a driving piezoelectric stack and an open-loop piezoelectric controller, and the bipedal flexible hinge includes a fixed frame, a driving foot and a clamping foot; the driving foot and the clamping foot are respectively arranged in the fixed frame, the driving foot is in tangential contact with the outer ring of the bearing along the Y direction, the clamping foot is in tangential contact with the outer ring of the bearing along the X direction, the clamping piezoelectric stack is installed in the clamping foot, and the driving piezoelectric stack is installed in the driving foot; The open-loop piezoelectric controller is electrically connected to the clamping piezoelectric stack and the driving piezoelectric stack respectively. The open-loop piezoelectric controller excites the clamping foot and the driving foot to extend and retract alternately, and induces the outer ring of the bearing to generate an epicycloidal motion.

2. A piezoelectric actuator based on the epicycloid induction principle as claimed in claim 1, characterized in that: The driving foot is arranged at the upper right of the biped flexible hinge, one end of which is connected to the fixing frame, and the other end is tangentially in contact with the outer ring of the bearing along the Y direction; the clamping foot is arranged at the lower left of the biped flexible hinge, which is connected to the fixing frame and is tangentially in contact with the outer ring of the bearing along the X direction.

3. A piezoelectric actuator based on the epicycloid induction principle as claimed in claim 1, characterized in that: The open-loop piezoelectric controller model is MDT693B.

4. A piezoelectric actuator based on the epicycloid induction principle as claimed in claim 1, characterized in that: The induction process of the bearing epicycloidal motion is: The diameter d of the inner and outer raceways of the bearing i ,d o Calculated by the following formula: Where, d i and d o are the diameters of the inner and outer raceways respectively; d c is the average diameter of the rolling element group; d r is the rolling element diameter; c r is the radial clearance of the bearing; In the initial state, the outer envelope circle of the rolling element group contacts the outer raceway at point P1, and the initial deflection angle θ0 = 0; When the outer raceway rolls without sliding along the outer envelope circle of the rolling element group, the contact point between the two is constantly changing. Point P2 represents the contact point at a certain moment. The epicycloidal motion of the outer raceway is decomposed into the following translational motion and rotational motion. During the translational motion, the outer raceway is considered to be in translational motion along the path P1P1′. The motion equation of the translational motion is: Among them, x p ,y p is the component of the translational motion of the outer raceway along the X-axis and Y-axis, c r is the radial clearance of the bearing, θ0=0 is the starting deflection angle of the epicycloid motion, θ=∠P1O i P2 is the terminal deflection angle of the epicycloid motion; In the rotational motion, the outer raceway is regarded as a point O o The rotation center rotates through an angle θ′, and the motion equation of the rotational motion is: Where θ′=∠P′1O o P″1 is the angle that the outer raceway rotates in the epicycloidal motion, d o is the outer raceway diameter of the bearing; Therefore, at point O i is the origin of the coordinate system, and considering that the position of the initial contact point P1 in the coordinate system is (0,0.5d o ), combining the motion equations of translational motion and rotational motion, the epicycloidal motion equation of the outer raceway is derived as follows: When the bearing and the slider are in close tangential contact, the epicycloidal motion of the outer raceway will induce the slider to produce corresponding bursting motion. In the translational motion, the slider and the outer raceway keep synchronous motion. In the rotational motion, the rotation angle θ′ of the outer raceway is converted into the linear displacement l of the slider along the X direction. The linear displacement l is expressed as follows: l=0.5dθ′ Where d is the nominal diameter of the bearing and also the rotational diameter for rotary motion; Combining the above equations, taking into account the relative position of the slider to point O i The position of is (0,0.5d), then the induced burst motion of the slider is expressed as follows: Wherein, l is the linear displacement of the slider along the X direction converted by the rotation angle θ′ in the rotational motion of the outer raceway.

5. A piezoelectric actuator based on the epicycloid induction principle as claimed in claim 1, characterized in that: The initial gap adjustment unit includes a fine-tuning mechanism and an adapter plate, and the fine-tuning mechanism includes an X-axis fine-tuning knob, a lower slide, a middle slide, an upper slide, and a Y-axis fine-tuning knob; the lower slide is fixed on the base; the middle slide is slidably connected to the lower slide, and the upper slide is slidably connected to the middle slide; the X-axis fine-tuning knob is used to adjust the relative displacement of the middle slide and the lower slide along the X-axis direction; the Y-axis fine-tuning knob is used to adjust the relative displacement of the upper slide and the middle slide along the Y-axis direction; The adapter plate is fixed on the upper surface of the upper slide; and the bipedal flexible hinge is fixed on the adapter plate.

6. A control method for a piezoelectric actuator based on the epicycloid induction principle as claimed in claim 1, characterized in that: The following steps are involved: Step 1: At time t0, the stator unit is in the initial state, and the relative positions of the clamping foot, the driving foot and the bearing in the two-legged flexible hinge are adjusted by the initial gap adjustment unit. The clamping foot is in close tangential contact with the bearing, and there is a small gap between the driving foot and the bearing. Under the pre-tightening effect of the clamping foot, the starting contact point between the rolling element group and the outer raceway is P0; Step 2: At time t1, clamp voltage U c The clamping piezoelectric stack increases instantaneously. Based on the inverse piezoelectric effect, the clamping foot is stretched and moves in the negative Y direction until it is separated from the outer ring of the bearing. During this period, the contact point between the rolling element group and the outer raceway jumps from point P0 to point P1. Step 3: At time t2, the driving voltage U d The force increases instantaneously, driving the piezoelectric stack to stretch instantaneously, causing the driving foot to bend and deform and gradually approach the outer ring of the bearing until it contacts the outer ring of the bearing. During this period, the contact point between the rolling element group and the outer raceway deflects from point P1 to point P2. Step 4: At time t3, clamp voltage U c It is instantly lowered, the clamping piezoelectric stack is instantly contracted, and the clamping foot moves in the positive Y direction until it contacts the outer ring of the bearing. During this period, the contact point between the rolling element group and the outer raceway is deflected from point P2 to point P3; Step 5: At time t4, the driving voltage U d It is instantly lowered, the driving piezoelectric stack is instantly contracted, and the driving foot gradually moves away from the outer ring of the bearing until it is separated from the outer ring of the bearing. During this period, the contact point between the rolling element group and the outer raceway is deflected from point P3 to point P4; It can be seen from the epicycloid induction principle that in steps three to five, along with the deflection of the contact point, the outer raceway of the bearing produces an epicycloid motion, which correspondingly induces the bursting motion of the slider.

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