Parasitic inertia type piezoelectric actuator implementing backlash elimination

Abstract

The present application provides an innovative stick-slip parasitic inertia driver, aiming at effectively eliminating the back-off phenomenon in the movement process and realizing high-precision positioning. The driver adopts a double piezoelectric stack structure, and the two driving feet are driven by the alternating extension and contraction movement. Under the control of the unified input signal, the two piezoelectric stacks are synchronized to elongate at a specific time, the first driving foot pushes the guide rail forward, and the second driving foot is separated from the guide rail at the same time; when the stack is contracted, the second driving foot is inhibited from back-off through the clamping mechanism. The present application combines the organic combination of double-foot cooperative driving and clamping effect, completely solves the back-off problem caused by stick-slip effect, and significantly improves the positioning accuracy, movement stability and load capacity of the driver. The driver has the advantages of compact structure, simple control and easy integration, and can be widely applied to high-precision fields such as precision machinery, automation equipment, micro-nano operation platform, etc., and has important engineering application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of precision driving and micro-operation, in particular to a piezoelectric driver, and more particularly to a parasitic inertia type piezoelectric driver based on double piezoelectric stack cooperative driving and capable of effectively eliminating the back-off phenomenon in the movement process. BACKGROUND

[0002] The piezoelectric driver is widely used in high-end technical fields such as precision optics, semiconductor manufacturing, biomedical engineering and micro-nano operation due to its high resolution, fast response speed, no electromagnetic interference and large output force. The stick-slip type piezoelectric driver, as an important branch of the piezoelectric driver, has attracted widespread attention due to its simple structure, low cost and large stroke.

[0003] The parasitic inertia type piezoelectric driver is an application of the stick-slip driving principle. Its working principle usually consists of two steps: in the slow "stick" phase, the piezoelectric stack is slowly elongated, and the slider (mover) is pushed to move together with the driving foot through the static friction force between the driving foot and the guide rail; in the fast "slip" phase, the piezoelectric stack is quickly contracted, and due to the inertia effect, the slider cannot follow the driving foot to quickly return, thereby generating a net displacement.

[0004] However, this driving method has a significant defect - the back-off phenomenon. That is, in the "slip" phase, the rapid contraction of the driving foot may exert a reverse friction force on the slider, causing the slider to produce a small displacement (back-off) opposite to the forward direction, which seriously restricts the positioning accuracy and movement stability of the driver.

[0005] In the prior art, in order to suppress the back-off phenomenon, complex waveform driving signals (such as trapezoidal wave, triangular wave with phase) or additional pre-tightening control mechanisms are usually used. These methods can alleviate the back-off to some extent, but result in complex control systems, increased cost and reduced reliability. Therefore, there is an urgent need for a new driver scheme that can fundamentally eliminate the back-off without complex control strategies from the mechanical structure itself. SUMMARY

[0006] The present application aims to overcome the shortcomings of the prior art and provide a parasitic inertia type piezoelectric driver with novel structure, simple control and effective elimination of the back-off phenomenon.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] A kind of parasitic inertia type piezoelectric driver of realizing back elimination, comprising first drive unit, it includes first piezoelectric stack and the first drive foot driven by the first piezoelectric stack;Second drive unit, it includes second piezoelectric stack and the second drive foot driven by the second piezoelectric stack;And a drive circuit configured to simultaneously apply the same non-phase difference triangular wave voltage signal to first piezoelectric stack and second piezoelectric stack;Wherein, first drive unit and second drive unit are arranged as follows: in the rising edge phase of triangular wave voltage signal, the first drive foot acts on the mover to push it forward, while the second drive foot is disengaged from the mover;In the falling edge phase of triangular wave voltage signal, the first drive foot resets, while the second drive foot acts on the mover to clamp it, so as to eliminate the back movement of the mover.

[0009] Further, the first drive unit includes a first flexible hinge mechanism, and the first drive foot is part of the first flexible hinge mechanism.

[0010] Further, the first drive foot is a right triangle plate structure.

[0011] Further, the height of the right triangle drive foot is 10-30 mm.

[0012] Further, the second drive unit includes a second flexible hinge mechanism, which is an integrated bending structure and includes a flexible hinge for displacement amplification and reset.

[0013] Further, the second drive foot is a convex arc surface structure, and the included angle between the convex arc surface and the horizontal direction is 5°-15°.

[0014] Further, the first flexible hinge mechanism and the second flexible hinge mechanism are provided with a clamping groove, and a gasket is arranged in the clamping groove for connecting the piezoelectric stack;Two piezoelectric stacks are mechanically coupled with the first flexible hinge mechanism and the second flexible hinge mechanism respectively;The two piezoelectric stacks are arranged perpendicular to each other.

[0015] The present application has the following advantages:

[0016] 1. Eliminate back completely: through the cooperative work of the two drive feet with asymmetric design, one push and one clamp, the reverse movement in the "slip" phase is fundamentally eliminated from the mechanical structure principle, and high-precision linear displacement output is realized.

[0017] 2. High load and high stiffness: the triangular drive foot of the first flexible hinge mechanism effectively disperses and transmits load stress by using its stable geometric characteristics, significantly improving the carrying capacity and overall stiffness of the driver.

[0018] 3. High energy efficiency: The design of the second flexible hinge mechanism can store and release elastic potential energy during driving, improving the utilization efficiency of energy and ensuring the rapid reset of driving.

[0019] 4. Simple and reliable control: The single, non-phase difference triangular wave signal is used to synchronously drive two piezoelectric stacks, eliminating the need for complex multi-channel phase control circuit, and the system structure is simple, control is convenient, and reliability is high.

[0020] 5. Compact structure: Both flexible hinge mechanisms are integrally processed and formed, compact structure, easy to assemble and integrate into various precision systems. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the overall structure of the driver described in the application. The schematic diagram is shown.

[0022] Figure 2 is the front view of the driver described in the application.

[0023] Figure 3 is the left view of the driver described in the application.

[0024] Figure 4 is the schematic diagram of the movement process of the driver described in the application.

[0025] Figure 5 is the physical assembly diagram of the driver described in the application.

[0026] Figure 6 is the time-displacement diagram of the movement of the driver described in the application.

[0027] Figure 7 is the optimization result diagram of the first driving foot triangle height (L) described in the application.

[0028] Figure 8 is the optimization diagram of the angle (θ) between the second driving foot and the horizontal direction described in the application.

[0029] Figure 9 is the load performance diagram of the driver described in the application.

[0030] BRIEF DESCRIPTION OF DRAWINGS:

[0031] 1: base; 11: positioning hole; 2: single degree of freedom displacement platform I; 6: single degree of freedom displacement platform II; 21: pre-tightening knob I; 61: pre-tightening knob II; 3: first flexible hinge mechanism; 5: second flexible hinge mechanism; 33: first piezoelectric stack;

[0032] 34: composite lever amplification mechanism; 35: first driving foot; 4: moving guide rail; 41: fixed guide rail;

[0033] 52: second piezoelectric stack; 54a: first flexible hinge unit; 54b: second flexible hinge unit; 54c: third flexible hinge unit; 55: second driving foot. DETAILED DESCRIPTION

[0034] The present application will be described in detail below with reference to the accompanying drawings and specific examples, so that those skilled in the art can better understand the technical solutions of the present application, but the scope of protection of the present application is not limited thereto.

[0035] The present application provides a parasitic inertia piezoelectric driver with back-lash elimination, which mainly consists of a mover mechanism, a stator mechanism, a base, a displacement platform, a pre-tightening knob, a fixing screw, a pre-tightening mechanism and a piezoelectric stack. The mover mechanism includes a movable guide rail that can be driven by the driver. The stator mechanism is installed on the base. The pre-tightening mechanism is used to adjust the pre-tightening force between the driving foot and the mover mechanism. Each component is clearly corresponding through the reference signs.

[0036] 1. Overall structure and installation base

[0037] Referring to Figures 1-3 , the base 1 serves as the installation base and support platform of the entire driver, and is provided with a positioning hole 11 for ensuring the accurate alignment and installation between components. The fixed guide rail 41 is firmly installed on the base 1 by screws to constitute a static reference. The movable guide rail 4, as the core component of the mover mechanism, is slidably assembled on the fixed guide rail 41 and is responsible for outputting precise linear displacement.

[0038] To provide accurate position and pre-tightening force adjustment, a single degree of freedom displacement platform I 2 and a single degree of freedom displacement platform II 6 are installed on the base 1. The core of the stator mechanism, the first flexible hinge mechanism 3 and the second flexible hinge mechanism 5, are fixed on these two displacement platforms, respectively.

[0039] 2. Stator mechanism: core driving and motion conversion

[0040] The stator mechanism includes the asymmetrically arranged first flexible hinge mechanism 3 and the second flexible hinge mechanism 5, which is the core of the driving and back-lash elimination function.

[0041] The first flexible hinge mechanism 3 is a flexible amplification mechanism for amplifying the output displacement of the piezoelectric stack, which is composed of a first driving foot 35 and a compound lever amplification mechanism 34 and is integrally formed. The first driving foot 35 is in the form of a right-angled triangular plate, and the compound lever amplification mechanism 34 is in the form of a pentagon, with the upper and lower edges parallel to the horizontal direction, the edge close to the first driving foot 35 parallel to the vertical direction, and the edge far from the driving foot in the form of a bend, so that the compound lever amplification mechanism is closed, and is used to generate a force to pull the driving foot back to the original state when the piezoelectric stack is contracted. The first driving foot 35 is designed in the form of a right-angled triangular plate with a height of 10-30 mm. This innovative structure has the dual advantages of displacement amplification and high load support: first, it can efficiently amplify the longitudinal displacement of the piezoelectric stack into horizontal propulsion displacement through the inclined surface effect; second, its stable triangular configuration can excellently disperse and transmit the load stress, as shown in the experimental verification Figure 9 Figure 9 The single-step displacement and vertical load relationship under the condition of a frequency of 1 Hz and a voltage of 120 V is shown. As the vertical load increases, the single-step displacement gradually decreases. When the vertical load is greater than 14 kg, the output tends to zero and the prototype machine cannot operate stably. Therefore, under the condition of a frequency of 1 Hz and a voltage of 120 V, the vertical load capacity of the driver can reach 14 kg.

[0042] The second flexible hinge mechanism 5 is in the form of a "C" curved structure, which is composed of a second driving foot 55 and a curved beam structure and is integrally formed. The second driving foot 55 is in the form of a convex arc surface structure, and the curved beam structure has a free end without fixed constraints, and the second driving foot 55 is located at the free end of the curved beam structure. The other end of the curved beam structure includes three flexible hinge units, all of which are in the form of circular arcs. Among them, the first flexible hinge unit 54a deforms when the piezoelectric stack deforms, causing the curved beam with the second driving foot 55 to deflect; the second flexible hinge unit 54b is used to improve the displacement amplification ratio, and the third flexible hinge unit 54c is used to form a closed loop around the second piezoelectric stack, so that the deflected beam is reset when the second piezoelectric stack is contracted. Through the coordinated design of multiple straight and circular flexible hinges inside the mechanism, the deflection of the driving foot and the displacement amplification when the piezoelectric stack is elongated are realized, and the elastic restoring force of the flexible unit is used to quickly reset the driving foot when it is contracted.

[0043] ​When the piezoelectric stack is elongated, the flexible hinge of the first flexible hinge unit 54a deforms, causing the curved beam with the driving foot to deflect downward to the right, at this time, the curved beam temporarily stores part of the mechanical energy as elastic potential energy, this storage of elastic potential energy is similar to the process of a spring being compressed, the included angle between the convex arc surface of the second driving foot 55 and the horizontal direction is 5°-15°, preferably 10°, when the included angle between the convex arc surface of the second driving foot 55 and the horizontal direction is 10°, the compression amount of the second driving foot 55 downward is the largest compared with other degrees; when the piezoelectric stack is contracted, the flexible hinge of the third flexible hinge unit 54c will pull the curved beam back to its original state, at this time, the flexible hinge of the first flexible hinge unit 54a will cause the curved beam with the second driving foot to deflect upward to the left, the second driving foot 55 will contact the guide rail and generate friction. Therefore, when the piezoelectric stack is contracted, the elastic potential energy accumulated by the curved beam when the piezoelectric stack is elongated will be released, which is used to eliminate the guide rail rollback, reducing the loss and waste of energy, and improving the energy utilization rate of the whole driving process.

[0044] The first flexible hinge mechanism 3 and the second flexible hinge mechanism 5 are provided with clamping grooves on the side away from the mover, and spacers are arranged in the clamping grooves for connecting the piezoelectric stacks; two piezoelectric stacks are mechanically coupled with the first flexible hinge mechanism 3 and the second flexible hinge mechanism 5 respectively; the two piezoelectric stacks are arranged perpendicular to each other.

[0045] 3. Pre-tightening mechanism and cooperative control

[0046] The pre-tightening mechanism includes pre-tightening knobs I 21 and pre-tightening knobs II 61, which are used to fine-tune the initial contact pre-tightening force between the entire stator mechanism and the moving guide rail 4.

[0047] The control strategy of the present driver is extremely simple: applying the same non-phase-difference triangular wave voltage signal to the first piezoelectric stack 33 and the second piezoelectric stack 52 can realize the cooperative movement of the two driving feet.

[0048] 4. Working process and rollback elimination principle

[0049] The driver works according to the following steps to realize non-backlash linear motion, see Figure 4 :

[0050] Step 1 (t=t0, initial state): the voltage is 0V, the two piezoelectric stacks are not elongated or contracted, and the entire driver remains stationary.

[0051] Step 2 (t0-t1, phase 1: slow elongation): the voltage slowly rises, and the two piezoelectric stacks are synchronously elongated. The first driving foot 35 generates deformation upward to the left, pushing the moving guide rail 4 to slowly advance to the maximum displacement through static friction; at the same time, the second driving foot 55 deforms downward to the right, disengaging from the guide rail and not interfering with the movement.

[0052] Step 3 (t=t1, phase 2: fast contraction): the voltage is rapidly decreased, and the two piezoelectric stacks are synchronously contracted. The first driving foot 35 is rapidly retreated to the initial position, and in this process, the friction force 1 driving the moving guide rail 4 to retreat is generated, and the moving guide rail 4 generates a slight retreat trend; at this moment, the second driving foot 55 generates a movement to the upper left, and in this process, the friction force 2 driving the moving guide rail 4 to continue to advance is generated, which can offset the friction force 1 in the opposite direction, and the moving guide rail 4 is timely clamped to keep still, effectively eliminating the retreat movement.

[0053] Step 4 (cycle): steps 2 and 3 are repeated, that is, the continuous, stable and non-retreat precise linear motion is realized.

[0054] Figure 5 The figure shows the physical assembly diagram of the driver. The tested driver is tested under the condition that the working frequency is 10 Hz, and the output displacement of the driver is tested under the condition that the working voltage is 70V-120V, and the output displacement of the driver is obtained Figure 6 The time-displacement diagram of the driver motion is shown, and from the diagram, it can be known that the driver does not produce the phenomenon of displacement retreat, which further verifies that the design of the driver can realize the elimination of the retreat movement.

[0055] Figure 7 The figure is the optimization result diagram of the first driving foot triangular height (L) of the application. The first driving foot triangular height (L) has a significant influence on the displacement amplification ratio and the structural stress. The blue line in the figure represents the relationship between the amplification ratio and the first driving foot triangular height (L), and the red line represents the relationship between the equivalent stress and the first driving foot triangular height (L). As can be seen from the figure, the amplification ratio increases with the increase of the first driving foot triangular height (L), but when the first driving foot triangular height (L) is greater than 15mm, the equivalent stress will increase significantly, for example, when the first driving foot triangular height (L) increases from 15mm to 17mm, the amplification ratio only increases by 0.05, but the equivalent stress increases by 21MPa, which has the risk of material fatigue or failure. Therefore, in order to balance the comprehensive performance and reliability, in a preferred embodiment, the first driving foot triangular height (L) is selected to be 15mm. Of course, those skilled in the art can understand that, under the premise of meeting the performance requirements, the first driving foot triangular height (L) is adjusted within the range of 10-30mm, which falls within the protection idea of the application.

[0056] Figure 8is an optimization diagram of the angle (θ) between the second driving foot and the horizontal direction according to the present application. The angle (θ) between the second driving foot and the horizontal direction directly affects the deformation and the energy storage efficiency. In the diagram, the green line represents the influence of the change of the angle (θ) between the second driving foot and the horizontal direction on the horizontal direction (X direction) deformation, the blue line represents the influence of the change of the angle (θ) between the second driving foot and the horizontal direction on the vertical direction (Y direction) deformation, and the red line represents the influence of the change of the angle (θ) between the second driving foot and the horizontal direction on the equivalent stress. As can be seen from the diagram, the smaller the θ, the greater the deformation in the X and Y directions. When θ = 10°, the driver can obtain a larger deformation while the equivalent stress is smaller, thereby achieving the highest energy utilization rate. Therefore, in a most preferred embodiment, the angle θ is set to 10°. Generally, the range of 5°-15° can achieve the beneficial effects of the present application.

Claims

1. A parasitic inertia type piezoelectric actuator which realizes backlash elimination, characterized by The application relates to a piezoelectric actuator, comprising: a first driving unit comprising a first piezoelectric stack and a first driving foot driven by the first piezoelectric stack; a second driving unit comprising a second piezoelectric stack and a second driving foot driven by the second piezoelectric stack; and a driving circuit configured to simultaneously apply a same non-phase-difference triangular wave voltage signal to the first piezoelectric stack and the second piezoelectric stack; wherein the first driving unit and the second driving unit are arranged such that, in a rising edge phase of the triangular wave voltage signal, the first driving foot acts on a mover to push it forward, while the second driving foot is disengaged from the mover; and in a falling edge phase of the triangular wave voltage signal, the first driving foot is reset, while the second driving foot acts on the mover to clamp it, thereby eliminating the back movement of the mover. The first driving unit comprises a first flexible hinge mechanism, and the first driving foot is part of the first flexible hinge mechanism.

2. The parasitic inertia type piezoelectric driver implementing back- off cancellation according to claim 1, wherein, The first driving foot is a right-angled triangular plate structure.

3. The parasitic inertia type piezoelectric driver implementing back- off cancellation according to claim 1, wherein, The height of the right-angled triangular driving foot is 10-30 mm.

4. The parasitic inertia type piezoelectric driver implementing back- off cancellation according to claim 3, wherein, The second driving unit comprises a second flexible hinge mechanism which is an integrated bending structure and contains a flexible hinge for displacement amplification and reset.

5. The parasitic-inertial piezoelectric actuator implementing back- elimination according to any one of claims 1-4, characterized in that, The second driving foot is a convex arc surface structure, and the included angle between the convex arc surface and the horizontal direction is 5-15 degrees.

6. The parasitic inertia type piezoelectric driver implementing back- off cancellation according to claim 1, wherein, The first flexible hinge mechanism and the second flexible hinge mechanism are provided with clamping grooves, and spacers are arranged in the clamping grooves for connecting the piezoelectric stacks; two piezoelectric stacks are mechanically coupled with the first flexible hinge mechanism and the second flexible hinge mechanism respectively; and the two piezoelectric stacks are arranged perpendicularly to each other.

7. The parasitic inertia type piezoelectric driver implementing back- off cancellation of claim 1, wherein: ​

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