CN209562434U - Isosceles trapezoidal stick-slip piezoelectric linear actuator - Google Patents

Abstract

The utility model discloses a kind of isosceles trapezoid stick-slip piezoelectric linear actuators, are made of pedestal, sliding block, isosceles trapezoid stator and pre-tightening mechanism.Sliding block and pre-tightening mechanism are installed on pedestal, are equipped with the pre-tightening mechanism of isosceles trapezoid stator for preloading isosceles trapezoid stator and sliding block.Isosceles trapezoid stator includes isosceles trapezoid compliant mechanism and four rectangular piezoelectric ceramic pieces, and isosceles trapezoid compliant mechanism is fixed on pre-tightening mechanism surface by two mounting holes.Sawtooth signal motivates piezoelectric ceramic piece, thus make isosceles trapezoid mechanism change driving foot and the x and y of shoe contact point to displacement, to change the frictional force of contact surface.Sawtooth signal rising edge, driving foot has biggish y to displacement, increase the normal pressure of slow polarizing stage, and then increase static friction driving force, sawtooth wave failing edge, driving foot have lesser y to displacement, reduce the kinetic frictional resistances in Quick-return stage, achieve the purpose that inhibit to retract, improves movenent performance.

Description

Isosceles trapezoidal stick-slip piezoelectric linear actuator

technical field

The utility model relates to a precision driving device using intelligent materials, in particular to a piezoelectric linear driver.

Background technique

Piezoelectric actuators refer to actuators made of piezoelectric materials such as lead zirconate titanate (PZT), lead zinc niobate (PZN), lead magnesium niobate (PMN), etc., which have many advantages in micro, nano or positioning applications , compared with other actuators, it has the remarkable characteristics of high resolution (sub-nanometer level), high natural frequency (greater than kilohertz) and high driving force (greater than kilonewton level), but it also has a small displacement stroke (10μm- 100μm), so it is often combined with the stick-slip motion mechanism to achieve high-resolution motion with millimeter-scale strokes.

The working principle of the piezoelectric stick-slip drive is as follows: Under the excitation of the asymmetric sawtooth voltage signal, the difference between the dynamic and static friction caused by the asymmetric vibration of the piezoelectric vibrator is used to achieve the purpose of controlling the small displacement of the driven object. For specific implementation, an asymmetrical sawtooth wave can be used to alternately excite the piezoelectric stack slowly and quickly, and the inverse piezoelectric effect can be used to excite the stator to produce slow and fast alternating motion deformation, so that the stator and the mover are in two kinds of "sticky" and "slip". In the state of motion, the mechanical motion output is realized under the action of friction.

However, due to the slow and fast deformation stages of piezoelectric stick-slip driving, the friction between the stator and the mover plays different roles, specifically, the slow deformation driving stage is represented by frictional driving force, while the fast deformation driving stage is represented by frictional resistance. . In view of this, the traditional piezoelectric stick-slip actuator has obvious back-off phenomenon and low output efficiency.

Utility model content

The utility model discloses an isosceles trapezoidal stick-slip piezoelectric linear actuator in order to realize a precision driving device combining large stroke, high precision and large load, and at the same time suppress the retreat phenomenon of the piezoelectric stick-slip drive. The isosceles trapezoidal stator of the proposed piezoelectric linear actuator can simultaneously act on the force of the piezoelectric ceramic in the two directions of the slider movement direction and the positive pressure direction of the stator, and generate lateral motion to increase the positive pressure of the slow polarization stage of the piezoelectric ceramic. , to reduce the dynamic friction force in the rapid recovery stage of piezoelectric ceramics, and achieve the purpose of inhibiting the retreat.

The technical scheme that the utility model solves its technical problem adopts is:

An isosceles trapezoidal stick-slip piezoelectric linear actuator, mainly composed of a base (1), a slider (2), an isosceles trapezoidal stator (3) and a preload mechanism (4); the slider (2) and the preload The mechanism (4) is installed on the base (1), and the pretension mechanism (4) is used for preloading the isosceles trapezoidal stator (3) and the slider (2); the isosceles trapezoidal stator (3) includes an isosceles The trapezoidal flexible mechanism (3-1) and four rectangular piezoelectric ceramic sheets (3-2), the isosceles trapezoidal flexible mechanism (3-1) is fixed to the pretension mechanism ( 4) Surface; the isosceles trapezoidal flexible mechanism (3-1) is a flexible double-rocker mechanism, wherein the horizontal axis (3-1-5) is a fixed frame, the rod where the driving foot is located is a connecting rod, and the left flexible beam (3-1-5) is a fixed frame. 1-3) and the right flexible beam (3-1-4) are pasted with left curved piezoelectric ceramics (3-2-1) and right curved piezoelectric ceramics (3-2-2) respectively as driving rockers; The four piezoelectric ceramic sheets (3-2) are excited by the same positive sawtooth wave signal, and the four piezoelectric ceramic sheets (3-2) generate the same polarization, the left flexible beam (3-1-3) and the right flexible beam (3-1-4) Under the action of the piezoelectric ceramic sheet (3-2) to produce bending deformation, the imaginary motion track of the contact point between the left driving foot (3-1-1) and the slider (2) can be decomposed into x-direction and the displacement in the y direction, when the driving foot is in close contact with the slider, the change of the imaginary motion trajectory of the contact point is shown as the left driving foot (3-1-1) and the right driving foot (3-1-2) and the slider (2) Changes in the normal positive pressure and tangential friction of the indirect contact surface; in the "sticky" stage, that is, when the left driving foot (3-1-1) is in contact with the slider (2), the imaginary trajectory of the contact point is Synthesis of positive x-direction and negative y-direction movement, a greater positive pressure will be generated between the left driving foot (3-1-1) and the slider (2), so a greater static friction force will be generated between the two to drive the slider ( 2) Movement along the positive x direction; in the "sliding" stage, that is, when the left flexible beam (3-1-3) recovers quickly due to its own elasticity, the imaginary track of the contact point is the synthesis of the negative x direction and positive y direction movement, at this time There is a small positive pressure between the left driving foot (3-1-1) and the slider (2), the dynamic friction resistance between the two will be smaller, and the retraction of the slider (2) will be smaller .

Among them, the four piezoelectric ceramic sheets (3-2) are pasted with the same polarization direction. When excited by the same positive sawtooth wave signal, the left flexible beam (3-1-3 ) and the right flexible beam (3-1-4) are slowly bent and deformed, the right driving foot (3-1-2) is separated from the slider (2), and the left driving foot (3-1-1) is separated from the slider (2) The contact point is mainly affected by static friction, and because the contact point has a negative y-direction displacement, that is, the left flexible beam (3-1-3) is closer to the slider (2), and the positive pressure of the contact point becomes larger, so the driving force of static friction is larger , has a better load capacity; in the stage of rapid decline of the sawtooth wave signal, the left flexible beam (3-1-3) returns to its original shape due to its own elasticity, and the main gap between the left driving foot (3-1-1) and the slider (2) Under the action of dynamic friction, the contact point has a positive y-direction displacement at this time, thereby reducing the positive pressure of the contact point and having a small dynamic friction resistance, so that the retraction of the slider (2) is smaller; when four pieces of piezoelectric ceramics When the sheet (3-2) is excited by the same negative sawtooth wave signal, the slide block (2) will produce negative x-direction motion under the action of the right driving foot (3-1-2).

The beneficial effect of the utility model is that the overall structure of the driver is simple, and it is convenient to adjust the output. The isosceles trapezoidal stator is used to generate lateral movement, thereby increasing the positive pressure of the piezoelectric ceramic in the slow polarization stage, and reducing the pressure of the piezoelectric ceramic in the rapid recovery stage. The dynamic friction force achieves the purpose of restraining the retreat.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the utility model is further described.

Figure 1 is a schematic diagram of an isosceles trapezoidal stick-slip piezoelectric linear actuator;

Figure 2 is a schematic diagram of an isosceles trapezoidal stator;

Fig. 3 is a schematic diagram of the direction of motion of the isosceles trapezoidal stator;

Fig. 4 is a working principle diagram of an isosceles trapezoidal stick-slip piezoelectric linear actuator;

Fig. 5 is a schematic diagram of an isosceles trapezoidal stick-slip piezoelectric linear actuator with an inclined straight plate flexible mover.

In the figure 1. Base, 2. Slider, 3. Isosceles trapezoidal stator, 4. Preload mechanism

Detailed ways

Further illustrate implementation method below in conjunction with accompanying drawing:

【Example 1】

The isosceles trapezoidal stick-slip piezoelectric linear actuator shown in Fig. 1 is mainly composed of a base (1), a slider (2), an isosceles trapezoidal stator (3) and a pretension mechanism (4). The slide block (2) and the preloading mechanism (4) are installed on the base (1), and the preloading mechanism (4) with the isosceles trapezoidal stator (3) is used for preloading the isosceles trapezoidal stator (3) and the slide block (2). In the embodiment, a cylindrical roller slider is selected, the working stroke is about 28mm, and the mass of the slider is about 23.6g; in the embodiment, the pre-tightening mechanism (4) adopts a manual displacement platform, which can be adjusted and locked to reach the position of the platform. Purpose of preloading. The isosceles trapezoidal stator (3) generates lateral motion after being energized, and the driving foot (3-1) pushes the slider (2) to move horizontally according to the principle of stick-slip motion. The isosceles trapezoidal stator (3) is the core component of the driver and is used to provide the driving force required for the movement of the slider. As shown in Figure 2, the isosceles trapezoidal stator (3) includes an isosceles trapezoidal flexible mechanism (3-1) and Four rectangular piezoelectric ceramic sheets (3-2) fix the isosceles trapezoidal flexible mechanism (3-1) on the surface of the pretension mechanism (4) through two mounting holes (3-1-6). The two piezoelectric ceramic sheets on the left are called left curved piezoelectric ceramics (3-2-1), which are bonded to the left and right sides of the left flexible beam (3-1-3) through epoxy resin, while the other two Two ceramic sheets, called right curved piezoelectric ceramics (3-2-2), are bonded to the left and right sides of the right flexible beam (3-1-4). Four piezoelectric ceramic sheets (3-2) are polarized along their thickness direction and have the same polarization direction. The moving direction of the slider is shown in Figure 3, the left driving foot (3-1-1) is used to drive the slider to move in the positive direction of x, and the right driving foot (3-1-2) is used to drive the slider to the negative direction of x move. There is an angle θ between the flexible beam and the horizontal axis, and the x- and y-direction displacement of the driving foot can be adjusted by adjusting the angle θ.

Lateral movement refers to the movement that produces movement in both x (slider movement direction) and y (positive pressure direction) directions at the same time. The isosceles trapezoidal stator of the piezoelectric linear actuator proposed in this patent can generate lateral motion to increase the positive pressure in the slow polarization stage of the piezoelectric ceramic, thereby increasing the static friction force in the driving stage and reducing the dynamic friction force in the fast recovery stage of the piezoelectric ceramic , to achieve the purpose of suppressing rollback.

The specific working principle and contact force analysis are shown in Figure 4.

In the initial state, as shown in Figure 4a, the preloading force F ₀ keeps the slider and the two driving feet in contact with each other. When time t=t ₀ , the preloading force F ₀ of the slider is equal to the positive pressure F generated by the preloading mechanism _P , the driving signal of the left and right bending piezoelectric ceramics is a sawtooth wave. Each motion cycle is divided into two steps:

Step 1: From time t ₀ to t ₁ , bend the piezoelectric ceramic left and right while slowly polarizing, so that the left driving foot of the isosceles trapezoidal flexible mechanism obtains two displacements in the x and y directions (l _x and _ly ), As shown in Figure 4b, the generated static friction force F _S pushes the slider forward ΔL along the x-axis;

Step 2: From time t ₁ to t ₂ , the left and right bent piezoelectric ceramics recover quickly at the same time, so the isosceles trapezoidal flexible mechanism returns to its initial position, and due to the action of inertial force, the slider will remain in the position shown in Figure 4c Location. By repeating steps 1 and 2, the proposed piezoelectric actuator gradually realizes a large working stroke motion along the positive x-axis.

It can be seen from Figure 4 that during the t ₀ -t ₁ stage, the static friction force F _S is the driving force for the slider to move forward, and the x-axis positive displacement l _x generated by the left driving foot is used to push the slider to move along the x-axis positive direction ; The negative displacement ly of the _y -axis is used to increase the positive pressure F _P that produces the static friction force F _S . In step 2, the kinetic friction force F _d generated by the positive pressure F _P is the resistance. The dynamic friction force F _d can be defined as F _d = μ _d F _P ; where F _d is the dynamic friction force, μ _d is the dynamic friction coefficient, F _P is the normal pressure, and the normal pressure F _P is a variable. At time t1, the positive pressure F _P reaches the maximum value, and from time t1 to t2, the positive pressure F _P rapidly decreases to F ₀ . According to the definition of dynamic friction force in the formula, it can be seen that the reduction of positive pressure F _P causes the dynamic friction force F to retreat _d decreases, thus suppressing the fallback. To realize the large-stroke movement along the negative direction of the x-axis, it is only necessary to provide a reverse sawtooth wave driving electric signal, and the right driving foot of the isosceles trapezoidal stator drives the slider to move along the negative direction of the x-axis.

[Example 2]

The structure of the isosceles trapezoidal stick-slip piezoelectric linear actuator can also be improved and optimized. As shown in Figure 5, it is an isosceles trapezoidal stick-slip piezoelectric linear actuator with an inclined straight plate type flexible mover. The flexible mover (2a) It is mainly composed of fixed guide rails and flexible sliders. The key component is the flexible slider, which is composed of sliders, slider contact ends, inclined straight beam type flexible hinges, and left and right drive foot contact ends. Among them, the slider in the fixed guide rail and the flexible slider adopts a linear guide rail slider, and the contact end of the slider, the inclined straight beam type flexible hinge and the contact ends of the left and right driving feet are processed by wire cutting. Linear sliders stick together. The driver as a whole mainly includes a base, a flexible mover, an isosceles trapezoidal stator and a preload mechanism. The flexible mover and the pre-tightening mechanism are installed on the base, the isosceles trapezoidal stator is fixed on the pre-tightening mechanism, and the locking force between the isosceles trapezoidal stator and the flexible mover is adjusted through the pre-tightening mechanism. Through the flexible mover, the preload displacement in the y direction (positive pressure direction) is also converted into the displacement in the x direction (mover movement direction) that pushes the mover to move while suppressing retreat, thereby improving the output performance of the driver.

The various technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the various technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as limiting the scope of the patent. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of this patent. Therefore, the scope of protection of this patent should be based on the appended claims.

Claims (2)

1. a kind of isosceles trapezoid stick-slip piezoelectric linear actuator, it is characterised in that: mainly by pedestal (1), sliding block (2), isosceles ladder Shape stator (3) and pre-tightening mechanism (4) composition；Sliding block (2) and pre-tightening mechanism (4) are installed on pedestal (1), and pre-tightening mechanism (4) is used In preloading isosceles trapezoid stator (3) and sliding block (2)；The pre-tightening mechanism (4) uses manual displacement platform, can pass through Position of platform is adjusted and locked, achievees the purpose that preloading；The isosceles trapezoid stator (3) includes isosceles trapezoid compliant mechanism (3-1) and four rectangular piezoelectric ceramic pieces (3-2), isosceles trapezoid compliant mechanism (3-1) are fixed by two mounting holes (3-1-6) In pre-tightening mechanism (4) surface；Isosceles trapezoid compliant mechanism (3-1) is flexible double rocker mechanism, and wherein horizontal axis (3-1-5) is to fix Rack, bar is connecting rod where driving foot, and left flexible beam (3-1-3) and right flexible beam (3-1-4) are pasted with left bending piezoelectricity respectively Ceramic (3-2-1) and right bending piezoelectric ceramics (3-2-2) are used as drive rocker；Isosceles trapezoid stator (3) generates laterally after being powered Movement drives foot that sliding block (2) is pushed to move horizontally according to stick-slip principle.

2. isosceles trapezoid stick-slip piezoelectric linear actuator according to claim 1, it is characterised in that: the piezoelectric actuator Four piezoelectric ceramic pieces (3-2) polarize along its thickness direction, and polarization direction having the same；Left driving foot (3-1-1) is used Mobile to x forward direction in driving sliding block, right driving foot (3-1-2) is for driving sliding block mobile to x negative sense；Between flexible beam and horizontal axis There is an angle, θ, drives the x and y of foot to displacement to adjust by adjusting angle, θ.