CN101252330A - A method and device for precise positioning using a piezoelectric stack - Google Patents

Abstract

The invention relates to a precise positioning method and device using a piezoelectric stack. The invention belongs to the technical field of sensing measurement and control, and relates to the technical field of a precise positioning method and a positioning device for a micro-actuator. First, establish the relationship curve between external force and output displacement by calibrating the precision positioning device, use the step-by-step loading method, record the results, and depict the external force and the elastic displacement of the piezoelectric ceramic stack, the external force and the piezoelectric ceramic stack two The relationship curve of the secondary inverse piezoelectric displacement, then preprocessing, then rough positioning, and finally fine positioning. The device used in the piezoelectric stack precision positioning method is composed of a base, a piezoelectric ceramic stack, an elastic sheet, an adjustment pad, an upper cover and a pre-tightening screw. The invention does not need a driving power supply, has high positioning accuracy, simple structure, low cost, small volume, and is convenient for processing and manufacturing; it can be used for precise positioning in fields such as ultra-precision processing, and sub-micron and nano-level precision compensation in microsystems.

Description

A method and device for precise positioning using a piezoelectric stack

technical field

The invention belongs to the technical field of sensing measurement and control, and relates to the technical field of a precise positioning method and a positioning device of a micro-actuator.

Background technique

Precision positioning technology is a high-tech closely related to many production practices. It has a wide range of applications in ultra-precision machining, precision machinery, semiconductor device manufacturing, electronic product assembly lines, bioengineering and micro/nano electromechanical systems. Micro-actuator technology with high precision, fast response, high displacement resolution and control precision has become an inevitable trend of its development. At present, the driving methods of micro-actuators include: electrostatic drive, electromagnetic drive, piezoelectric drive, thermal expansion drive, magnetostrictive drive, pneumatic drive, electro-hydraulic drive, and shape memory alloy diaphragm drive. Among them, the piezoelectric drive is widely used in various precision instruments and mechatronics equipment because of its high resolution, large driving force, fast response speed, low power consumption, and can work normally in harsh environments, such as ultra-low temperatures. The mechanism of piezoelectric driving is generally based on the inverse piezoelectric effect of the piezoelectric body, that is, when the piezoelectric body is subjected to the action of an electric field, it will deform and drive the micro-actuator to move. Piezoelectric ceramics, as a high-precision micro-displacement device, can produce micron or even nanometer-scale displacement or movement; and have small size, large output force, fast response speed, high positioning accuracy, no noise and no heat during use And other advantages, has been widely used in aerospace, microelectronics, precision measurement, bioengineering, robotics and precision machining and other fields. Theoretically speaking, piezoelectric actuators can obtain infinitely small displacements, but in practical applications, the resolution that piezoelectric ceramics can achieve is limited, because its output accuracy is based on the performance of the drive control power supply. To improve the output accuracy of the actuator, the performance of the drive power supply needs to be doubled, resulting in a multiple increase in cost, which restricts the further application of piezoelectric actuators. In addition, the inherent defect of piezoelectric ceramic actuators is that the hysteresis effect between the output displacement and the control voltage is obvious, and it usually needs to be supplemented by a boost and hysteresis compensation circuit. At present, most of the piezoelectric drive power supplies in China are composed of discrete devices, which not only have a complex structure, but also are prone to self-excited oscillation. The driving power supply has become a bottleneck in the development of piezoelectric actuators to higher precision fields. To solve this problem, on the one hand, researchers are working on improving the cost-effectiveness of the drive power supply. On the other hand, the exploration of new theories and technologies of functional materials is also a hot spot in the research of physical actuators.

Contents of the invention

The technical problem to be solved in the present invention is to overcome the influence of the above-mentioned drive control power supply on the performance of the piezoelectric actuator, and propose a precision positioning device different from the traditional piezoelectric drive, based on the principle of the secondary inverse piezoelectric effect of piezoelectric ceramics , without the need for a drive control power supply, it can achieve coarse and fine two-level positioning and achieve submicron or even nanometer displacement. The device has simple structure and low cost.

The technical solution adopted by the present invention is a method for precise positioning with piezoelectric stacks: firstly, the relationship curve between external force and output displacement is established by calibrating the precision positioning device, and the step-by-step loading method is adopted, starting from 10% of the full scale , step by step to the full scale, record the results, and draw the relationship curves between the external force and the elastic displacement of the piezoelectric ceramic stack 2, and the external force and the second inverse piezoelectric displacement of the piezoelectric ceramic stack 2, thereby determining the precise positioning The magnitude of the external force needs to be loaded during the process, and then the precise positioning can be achieved through the following steps: The first step, pretreatment: fix the device through the through hole c, adjust the four pre-tightening screws 6 to produce the rated pre-tightening force, to Eliminate the bonding gap between the piezoelectric wafers and the piezoelectric ceramic stack 2 and the elastic sheet 3, short-circuit the two electrodes of the piezoelectric ceramic stack 2, and neutralize the charge brought by the preload; the second step, roughly Positioning: When the circuit of the piezoelectric ceramic stack 2 is disconnected, an external force F is applied to the center line of the boss b, and the external force F acts on the piezoelectric ceramic stack 2 through the upper cover 5 to generate elastic displacement to achieve rough positioning; The third step, fine positioning: After the rough positioning is completed, the two electrodes of the piezoelectric ceramic stack 2 are short-circuited, and the induced electric field generated by the primary positive piezoelectric effect is eliminated, and the secondary reverse pressure of the piezoelectric ceramic stack 2 The piezoelectric displacement generated by the electric effect realizes precise positioning.

A device used in a precise positioning method using a piezoelectric stack is composed of a base 1, a piezoelectric ceramic stack 2, an elastic sheet 3, an adjustment pad 4, an upper cover 5 and a pre-tightening screw 6, and the base 1 consists of two cylinders The lower cylinder is composed of four through holes c evenly arranged on the lower cylinder, and the upper cylinder is hollow and provided with a groove a for centering; the piezoelectric ceramic stack 2 is placed in the groove a, and the rectangular elastic sheet 3 is glued Junction to the upper surface of the piezoelectric ceramic stack 2 coated with 704 high-resistance insulating glue, the 704 high-resistance insulating glue forms an adhesive layer 7, which will be used to adjust the preload between the upper cover 5 and the upper surface of the base 1 The adjustment pad 4 with the margin ε is placed on the elastic sheet 3, and the circular upper cover 5 is placed on the adjustment pad 4. There is a boss b for centering on the top of the adjustment pad 4, and the center of the boss b coincides with the center of the groove a. A pre-tightening screw 6 connects the upper cover 5 and the base 1.

The remarkable effect of the present invention is: the present invention is not only suitable for precision positioning in fields such as ultra-precision machining, but also suitable for flow control of nozzle baffle mechanism and control of micro- and nano-scale one-dimensional micro-motion workbench, and is also suitable for micro/nano Microgrippers for gripping and manipulating tiny objects in electromechanical systems provide a new approach for submicron and nanoscale precision compensation in microsystems. The precise positioning device has the advantages of simple structure, low cost, small volume and convenient processing and manufacturing.

Description of drawings

Figure 1 is a sectional view of A-A in Figure 2, in which: 1-base, 2-piezoelectric ceramic stack, 3-elastic sheet, 4-adjusting pad, 5-top cover, 6-preload screw, 7-adhesive layer, a-groove, b-boss, c-through hole, ε-preload allowance, F-external force.

Fig. 2 is a top view of the precision positioning device.

Figure 3 is a schematic diagram of the principle of the secondary inverse piezoelectric effect of the piezoelectric stack. In the figure: I- the piezoelectric stack is in the initial state of circuit disconnection, and II- the piezoelectric stack is subjected to an external force F to generate a positive piezoelectric effect State, III-the state of two electrodes of the piezoelectric stack short-circuited, F-external force, δ ₁ -elastic displacement, δ ₂ -secondary inverse piezoelectric displacement.

Detailed ways

The concrete implementation of the present invention is described in detail in conjunction with technical scheme and accompanying drawing, see (II) among the accompanying drawing 3 for the primary positive piezoelectric effect principle of the piezoelectric ceramic stack in the precision positioning device, namely (I) among the accompanying drawing 3 ) when the circuit of the piezoelectric stack shown in ) is disconnected and the external force F is applied, the piezoelectric ceramics will inevitably produce an elastic displacement δ ₁ under the action of the external force F, and the piezoelectric ceramics will be polarized due to the primary positive piezoelectric effect, resulting in The charges on the open-circuit piezoelectric ceramic electrode surface will not be lost, forming an electric displacement D _i ⁽¹⁾ , which is commonly referred to as the piezoelectric effect. According to the piezoelectric equation:

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; s</span>}}_{\mathrm{<span\; class="notranslate">\; \&lambda;\&mu;</span>}}^{\mathrm{<span\; class="notranslate">\; E.</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; i\&mu;</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula, T _μ - the stress acting on the piezoelectric ceramic stack, S _λ - the strain produced by the piezoelectric ceramic stack, s _λμ ^E - the elastic compliance constant, d _iμ - the piezoelectric strain constant, due to the above electric displacement D _i The existence of ⁽¹⁾ causes the relative displacement of the positive and negative charge centers inside the piezoelectric body to cause deformation, that is, the electric displacement D _i ⁽¹⁾ produces an additional piezoelectric strain S _λ ⁽²⁾ , and the piezoelectric body undergoes a secondary inverse Piezoelectric effect, available

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}^{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; i\&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; g</span>}}_{\mathrm{<span\; class="notranslate">\; i\&mu;</span>}}{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

g _iμ - piezoelectric voltage constant, it can be seen that under the action of the electric displacement D _i ⁽¹⁾ , the secondary inverse piezoelectric effect produces a piezoelectric strain S _λ ⁽²⁾ opposite to the direction of the elastic strain. The two electrodes of the electroceramic stack are equivalent to a reverse electric field acting on the piezoelectric stack, and the piezoelectric ceramic stack will produce a displacement δ ₂ in the same direction as the elastic deformation, see ( III). It can be seen from formulas (1) and (3) that both the elastic strain and the secondary inverse piezoelectric strain have a linear relationship with the external force, so the actuator designed using the principle of the secondary inverse piezoelectric effect can completely achieve coarse and fine positioning.

For example: a precision positioning device is used to adjust the distance between the baffle and the nozzle. The piezoelectric ceramic stack 2 is composed of 100 pieces of lead zirconate titanate in sequence. The maximum bearing capacity of the precision positioning device is 3000N. Rigid high-speed steel with a roughness of less than 0.02 μm. The base 1, the adjustment pad 4 and the upper cover 5 are all made of stainless steel. The adjustment pad 4 and the upper cover 5 are required to have sufficient rigidity. After the load F is applied, the piezoelectric ceramic stack 2 The generated charges of the same sex are on the same electrode, see Figure 1. When in use, adjust the pad 4 so that the preload ε between the upper cover 5 and the upper surface of the base 1 is 1mm. First, calibrate the precision positioning device, starting from 300N, increasing it step by step to 3000N, and measuring it by inductance. The instrument measures the elastic displacement under each loading and the piezoelectric displacement generated by the secondary inverse piezoelectric effect of the piezoelectric ceramic stack 2 after short circuit, records the results of 10 loadings, and calculates the external force and elastic displacement according to the results And the relationship curve between external force and secondary inverse piezoelectric displacement, which is the basis for determining the loading force in precise positioning. Then adjust the position of the baffle through the following steps. The first step is pretreatment: fix the precision positioning device through the through hole c. For a stack composed of 100 piezoelectric ceramics, it is necessary to adjust four pre-tightening screws 6 to produce about 600N preload, and then short-circuit the two electrodes of the piezoelectric ceramic stack 2 to neutralize the charge brought by the preload; the second step, coarse positioning: after pretreatment, the piezoelectric ceramic stack 2 should be in the When the circuit is disconnected, the piezoelectric ceramic stack 2 can produce multiple piezoelectric effects under the action of external force. According to the size of the rough positioning, the value of the external force F is determined through the calibration curve, and the external force F is applied to the center of the boss b. , the piezoelectric ceramic stack 2 produces elastic displacement, and drives the baffle to achieve rough positioning. The precision positioning device of 100 piezoelectric ceramic stacks applies an external force of 100N under a preload of 600N, and the baffle produces a displacement of 1.2μm; the third The first step, fine positioning: After the rough positioning of the baffle plate is 1.2 μm, the two electrodes of the piezoelectric ceramic stack 2 are short-circuited, and the secondary inverse piezoelectric effect of the 100 piezoelectric ceramic stacks produces a piezoelectric displacement of 0.08 μm, realizing Fine positioning of the baffle. Therefore, the rough positioning of 1.2 μm and the fine positioning of 0.08 μm are realized by the baffle through the above steps, and the purpose of flow control by adjusting the distance between the nozzle and the baffle is achieved.

In actual use, the number of piezoelectric ceramic stacks 2 should be determined according to specific requirements, and different positioning accuracy can be obtained by applying different external forces F. Compared with power-driven piezoelectric actuators, the driving source is easier to obtain and more efficient. It is cheap, and the precision positioning method can realize coarse and fine two-level positioning, with high positioning accuracy and simple positioning method.

Claims (2)

1. method with the piezoelectric stack precision positioning, it is characterized in that: at first by precision positioning device being demarcated the relation curve of setting up external force and output displacement, adopt Loading Method step by step, from 10% of full scale, add to full scale step by step, the record result, and depict external force respectively and piezoelectric ceramic stacks the elastic displacement of (2), external force and piezoelectric ceramic stack the relation curve of the contrary displacement bimorph of (2) secondary, need to load the size of external force in definite thus Precision Positioning, realize precision positioning by following step then:

The first step, preliminary treatment: will install fixing by through hole (c), regulating four pretension screws (6) respectively makes it produce specified pretightning force, eliminate between piezoelectric chip and piezoelectric ceramic stacks the splicing gap of (2) and flexure strip (3), the short circuit piezoelectric ceramic stacks two electrodes of (2), neutralizes the electric charge that is brought by pretension;

In second step, coarse positioning: stack at piezoelectric ceramic and apply under the circuit off-state of (2) on the center line that external force F acts on boss (b), external force F affacts piezoelectric ceramic by loam cake (5) and stacks (2) and go up and produce elastic displacement realization coarse positioning;

The 3rd step, fine positioning: after coarse positioning is finished immediately the short circuit piezoelectric ceramic stack two electrodes of (2), the induced electric field that direct piezoelectric effect produces is eliminated, and stacks the displacement bimorph that the secondary inverse piezoelectric effect of (2) produces by piezoelectric ceramic and realizes fine positioning.

2. according to the described a kind of device that adopts with the piezoelectric stack precision positioning method of claim 1, it is characterized in that: stack (2), flexure strip (3), adjusting pad (4), loam cake (5) and pretension screw (6) by base (1), piezoelectric ceramic and constitute, base (1) is made up of two cylinders, evenly arrange four through holes (c) on the following cylinder, last cylinder hollow is provided with the groove (a) that is used to feel relieved; Piezoelectric ceramic is stacked (2) and put into groove (a), the flexure strip of rectangle (3) is bonded to the upper surface that the piezoelectric ceramic that scribbles 704 high resistant insulating cements stacks (2), 704 high resistant insulating cements form adhesive layer (7), the adjusting pad (4) that will be used for regulating the pretension surplus ε between the upper surface of loam cake (5) and base (1) is put on the flexure strip (3), lay circular loam cake (5) on the adjusting pad (4), its top is useful on the boss (b) of centering, boss (b) overlaps with the center of groove (a), connects loam cake (5) and base (1) with four pretension screws (6).

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