Miniaturized double-foot stick-slip type piezoelectric actuator

Abstract

The invention relates to the technical field of piezoelectricity, and discloses a miniaturized double-foot stick-slip piezoelectric actuator which comprises a stator, a rotor, a pre-tightening device and a base. The stator is in sliding connection with the base, the stator can slide on the base in the Y-axis direction, and the pre-tightening force between the stator and the rotor is adjusted through the pre-tightening device; the stator is fixedly arranged on the base, the rotor is fixedly arranged on the base, a sliding block is arranged on the rotor, and the sliding block can horizontally slide in the X-axis direction under the driving of the stator. According to the invention, the two driving feet alternately drive the mover to displace, so that the phenomenon of rollback in output displacement is effectively solved.

Description

Technical Field

[0001] The invention relates to the field of piezoelectric technology, and in particular to a miniaturized bipedal stick-slip piezoelectric driver. Background Art

[0002] In recent years, with the continuous development of science and technology, precision drive technology has become increasingly prominent in biomedical fields such as robotic cell injection, brain-computer interface, and precision control. The above biomedical fields have put forward extremely high requirements on the drive system, requiring the drive system to have high precision, large stroke, large output force, compact structure and other indicators. Traditional drives can no longer meet the above requirements. Piezoelectric drives have been widely used in the above biomedical fields due to their high precision, fast response speed, and immunity to electromagnetic interference.

[0003] The walking piezoelectric actuator is a classic bionic piezoelectric actuator that has been widely studied by a large number of scholars in recent years. It achieves movement by imitating the walking mode of animals in nature, and can achieve theoretically infinite travel by accumulating tiny single-step displacements. The basic actuation principles of existing stepping piezoelectric actuators are mostly inchworm-type and stick-slip types. The inchworm-type piezoelectric actuator is actuated by simulating the movement mode of inchworms in nature, and is usually complex in structure and slow in movement. The stick-slip piezoelectric actuator has the advantages of fast speed, large movement range and high resolution, but the common stick-slip piezoelectric actuators are mostly driven by a single driving foot, and the output displacement has a certain setback, which affects its application occasions and application effects to a certain extent. Summary of the invention

[0004] This paper designs a new type of bipedal stick-slip piezoelectric actuator, an integrated stator of a symmetrical bipedal drive, and a spring threaded stator preload device. Two piezoelectric stacks are alternately driven by two sawtooth wave signals, and the stick-slip principle is used to drive the linear motion of the guide rail mover in the vertical direction. The accumulation of single-step displacement cycles and the repetition of a single motion cycle achieve high precision and large stroke at the same time. The structure is compact and the assembly is simple, which effectively solves the problem of output displacement regression.

[0005] In order to achieve the above indicators, the technical solution adopted by the present invention is:

[0006] A miniaturized bipedal stick-slip piezoelectric actuator comprises a stator, a mover, a preload device and a base; the stator is slidably connected to the base, the stator can slide on the base along the Y-axis direction, and the preload force between the stator and the mover is adjusted by the preload device; the mover is fixedly arranged on the base, and a slider is provided on the mover, and the slider can slide horizontally in the X-axis direction under the drive of the stator.

[0007] Further, the stator includes a stator base, a first driving foot, a second driving foot, a first piezoelectric stack, a second piezoelectric stack, a first flexible hinge, and a second flexible hinge; the first driving foot and the second driving foot are respectively provided with a first flexible hinge and a second flexible hinge end, and the first driving foot and the second driving foot are respectively in contact with the mover;

[0008] The first piezoelectric stack is sleeved in the first flexible hinge, the second piezoelectric stack is sleeved in the second flexible hinge, and the first flexible hinge and the second flexible hinge are respectively arranged on the base.

[0009] Furthermore, the movement of the biped stick-slip piezoelectric actuator has bidirectional consistency, and the first flexible hinge and the second flexible hinge are both axially centrally symmetrical structures, which are used to drive the movement coupling of the foot;

[0010] Furthermore, when the driver is working, the first piezoelectric stack generates an output force in the Y direction, driving the first driving foot to extend and retract along the Y direction, and the first flexible hinge generates motion coupling to drive the first driving foot to extend and retract along the X direction; the second piezoelectric stack generates an output force in the Y direction, driving the second driving foot to extend and retract along the Y direction, and the second flexible hinge generates motion coupling to drive the second driving foot to extend and retract along the X direction.

[0011] Furthermore, the bipedal stick-slip piezoelectric actuator structure is an integrated design, and the first flexible hinge is connected to the middle of the second flexible hinge, which greatly reduces the difficulty of pre-tightening, installation and debugging.

[0012] Furthermore, the pre-tightening device is respectively arranged at two side positions between the stator and the mover, and the pre-tightening device includes a pre-tightening spring and a bolt. A threaded hole is provided on the base, and a countersunk hole is provided on the stator. The bolt passes through the countersunk hole and is connected to the threaded hole. The pre-tightening spring is sleeved on the bolt and clamped between the stator and the mover.

[0013] Furthermore, pre-tightening screws are respectively provided on the stator base at positions corresponding to the first piezoelectric stack and the second piezoelectric stack, and gaskets are respectively provided between the first piezoelectric stack and the second piezoelectric stack and the pre-tightening screws to prevent the pre-tightening force from damaging the piezoelectric stack.

[0014] Furthermore, the displacement output ends (the ends away from the gasket) of the first piezoelectric stack and the second piezoelectric stack are respectively provided with hemispherical blocks to protect the piezoelectric stacks from unnecessary shear forces.

[0015] Furthermore, a locking bolt is passed through the stator base in a vertical direction and is fixed to the base by the locking bolt.

[0016] Furthermore, the stator base is provided with a dovetail groove, which matches the dovetail guide rail on the base to limit the movement direction of the stator base.

[0017] A working process of a miniaturized bipedal stick-slip piezoelectric actuator includes the following steps:

[0018] First, the first piezoelectric stack and the second piezoelectric stack are powered off, the first piezoelectric stack and the second piezoelectric stack are preloaded, and the first driving foot and the second driving foot are in contact with the slider under the action of the preload force;

[0019] In the first step, from time 0 to t1, the first piezoelectric stack is excited by a slowly rising voltage, that is, the U1 excitation voltage rises from 0 to U 11 , pushing the first driving foot to deflect along the positive direction of the x-axis; the second piezoelectric stack is excited by a slowly decreasing voltage, that is, the U2 excitation voltage is U 21 Drop to 0, push the second driving foot to deflect along the positive direction of the x-axis, and the two driving feet drive the slider to move along the positive direction of the x-axis;

[0020] In the second step, from time t1 to t2, the first piezoelectric stack is excited by a slowly rising voltage, that is, the excitation voltage U1 is increased from U 11 Rise to U 12 , pushing the first driving foot to deflect along the positive direction of the x-axis; the second piezoelectric stack is excited by a rapidly rising voltage, that is, the U2 excitation voltage rises from 0 to the maximum value U 23 , pushing the second driving foot to deflect along the negative direction of the x-axis. At this stage, the movement directions of the two moving feet are opposite, but the extension speed of the second piezoelectric stack is faster than that of the first piezoelectric stack, resulting in the friction force of the second driving foot being smaller than that of the first driving foot, so the slider moves along the positive direction of the x-axis;

[0021] In the third step, from time t2 to t3, the first piezoelectric stack is excited by a slowly rising voltage, that is, the excitation voltage U1 is increased from U 12 Rise to U 13 , pushing the first driving foot to deflect along the positive direction of the x-axis; the second piezoelectric stack is excited by a slowly decreasing voltage, that is, the U2 excitation voltage is U 23 Descend to U 22 , pushing the second driving foot to deflect along the positive direction of the x-axis, and the two driving feet drive the slider to move along the positive direction of the x-axis;

[0022] Step 4: From time t3 to t4, the excitation voltage of the first piezoelectric stack drops rapidly from the maximum value to zero, that is, the excitation voltage U1 drops from the maximum value U 13 The voltage U2 decreases to 0, pushing the first driving foot to deflect along the negative direction of the x-axis; the second piezoelectric stack is excited by a slowly decreasing voltage, that is, the excitation voltage U2 changes from U 22 Descend to U 21, pushing the second driving foot to deflect along the positive direction of the x-axis. At this stage, the movement directions of the two moving feet are opposite, but the elongation speed of the first piezoelectric stack is faster than that of the second piezoelectric stack, resulting in the friction force of the first driving foot being smaller than that of the second driving foot, and the slider moves along the positive direction of the x-axis.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] 1) The stator structure body of the present invention adopts a symmetrical flexible hinge structure with low tensile stiffness and good fatigue resistance.

[0025] 2) The present invention uses two driving feet to alternately drive the mover to move, thereby effectively solving the problem of output displacement retreat.

[0026] 3) The present invention uses dual driving feet that are symmetrically distributed. The driving feet are designed to be a semicircular structure that fits tightly against the slider, further solving the problem of output displacement retreat.

[0027] 4) The stator flexible hinge of the present invention adopts an integrated symmetrical design, which effectively reduces the difficulty of installation and debugging.

[0028] 5) The present invention adopts a spring bolt type pre-tightening device, which is easy to install, can reduce the size of the driver, and is conducive to miniaturized design. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0030] Figure 2 This is a schematic diagram of the stator structure of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure of the pre-tightening device of the present invention;

[0032] Figure 4 This is a schematic diagram of the driving signal of the present invention;

[0033] Figure 5 This is a working principle diagram of the driver of the present invention;

[0034] 1-stator, 11-driving foot, 12-hemispherical block, 13-piezoelectric stack, 14-flexible hinge, 15-gasket, 16-preload screw, 17-countersunk hole, 18-locking bolt, 2-mover, 3-preload device, 31-preload spring, 32-bolt, 4-base, 41-threaded hole, 42-threaded mounting hole of mover. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with the accompanying drawings.

[0036] like Figure 1As shown, a miniaturized bipedal stick-slip piezoelectric actuator can be used in biomedical engineering, precision driving, micro-nano processing and other fields; it includes a stator 1, a mover 2, a pre-tightening device 3 and a base 4; the stator 1 and the mover 2 are respectively arranged on the base 4, and the pre-tightening device 3 is arranged at the gaps on both sides between the stator 1 and the mover 2.

[0037] like Figure 2 As shown, the stator 1 includes a first driving foot 11, two hemispherical blocks 12, a first piezoelectric stack 13, a first flexible hinge 14, two gaskets 15, two pre-tightening screws 16, two φ3 countersunk holes 17, two locking bolts 18 (φ3.5 countersunk holes), a second flexible hinge 19, a second piezoelectric stack 20, and a second driving foot 21.

[0038] The first flexible hinge 14 and the second flexible hinge 19 are both axially centrosymmetrical structures, and in this embodiment, are hexagonal structures;

[0039] The first piezoelectric stack 13 is sleeved in the first flexible hinge 14, the second piezoelectric stack 20 is sleeved in the second flexible hinge 19, and the gasket 15 is sandwiched between the piezoelectric stack and the pre-tightening screw 16 to prevent the pre-tightening force from damaging the piezoelectric stack. Two hemispherical blocks 12 are respectively arranged at the displacement output ends of the first piezoelectric stack 13 and the second piezoelectric stack 20 to protect the piezoelectric stack from unnecessary shear force.

[0040] The first driving foot 11 and the second driving foot 21 are in contact with the mover 2. The stator 1 is connected to the base 4 through a locking bolt 18 passing through a φ3.5 countersunk hole, and is connected to the spring bolt structure of the preload device 3 through a φ3 countersunk hole 17, so as to adjust the preload force between the stator 1 and the mover 2.

[0041] like Figure 3 As shown, the preload device is composed of a spring bolt structure, wherein a spring 31 is placed between the stator 1 and the base 4, and is sleeved on the bolt 32, and is positioned by using a threaded hole 41 on the base 4 and a countersunk hole 17 on the stator. The preload force between the stator and the mover is adjusted by the bolt clamping force and the spring force, and the fixed part of the mover is fixed to the base 4 through the threaded mounting hole 42 of the mover.

[0042] The working principle of the present invention is as follows: four steps are required to complete one stepping motion.

[0043] Preparation work: the first piezoelectric stack and the second piezoelectric stack are powered off, the first piezoelectric stack and the second piezoelectric stack are preloaded, and the first driving foot and the second driving foot are in contact with the slider under the action of the preload force.

[0044] In the first step, from time t0 to t1, the first piezoelectric stack is excited by a slowly rising voltage (U1 excitation voltage rises from 0 to U 11), pushing the first driving foot to deflect along the positive direction of the x-axis; the second piezoelectric stack is excited by a slowly decreasing voltage (the excitation voltage received in the first motion cycle is zero, and the U2 excitation voltage is U 21 The second driving foot is pushed to deflect along the positive direction of the x-axis, and the two driving feet drive the slider to move along the positive direction of the x-axis.

[0045] In the second step, from time t1 to t2, the first piezoelectric stack is excited by a slowly rising voltage (U1 excitation voltage is U 11 Rise to U 12 ), pushing the first driving foot to deflect along the positive direction of the x-axis; the second piezoelectric stack is excited by a rapidly rising voltage (the excitation voltage U2 rises from 0 to the maximum value U 23 ), pushing the second driving foot to deflect along the negative direction of the x-axis. At this stage, the movement directions of the two moving feet are opposite, but the extension speed of the second piezoelectric stack is much faster than that of the first piezoelectric stack, resulting in the friction force of the second driving foot being smaller than that of the first driving foot. Therefore, the slider moves along the positive direction of the x-axis.

[0046] In the third step, from time t2 to t3, the first piezoelectric stack is excited by a slowly rising voltage (U1 excitation voltage is U 12 Rise to U 13 ), pushing the first driving foot to deflect along the positive direction of the x-axis; the second piezoelectric stack is excited by a slowly decreasing voltage (the excitation voltage U2 is composed of U 23 Descend to U 22 ), pushing the second driving foot to deflect along the positive direction of the x-axis, and the two driving feet drive the slider to move along the positive direction of the x-axis.

[0047] Step 4: From time t3 to t4, the excitation voltage of the first piezoelectric stack drops rapidly from the maximum value to zero (U1 excitation voltage drops from the maximum value U 13 The second piezoelectric stack is excited by a slowly decreasing voltage (the excitation voltage U2 is from U 22 Descend to U 21 ), pushing the second driving foot to deflect along the positive direction of the x-axis. At this stage, the movement directions of the two moving feet are opposite, but the extension speed of the first piezoelectric stack is much faster than that of the second piezoelectric stack, resulting in the friction force of the first driving foot being smaller than that of the second driving foot, and the slider moves along the positive direction of the x-axis.

[0048] In this embodiment: t0 = 0, t1 = 0.3s, t2 = 0.4s, t3 = 0.9s, t4 = 1s; U 11 =50V, U 12 =66.7V, U 13 =150V, U 21 =50V, U 22=66.7V, U 23 =150V.

[0049] The above steps illustrate that the piezoelectric driver can drive the slider to generate displacement output in one direction within a working cycle. By repeating the above steps, a large-stroke displacement output can be obtained. Compared with the traditional single-foot stick-slip piezoelectric driver, this design uses two symmetrical driving parts to always output displacement in one direction during the movement, effectively reducing the backlash phenomenon. And because the two piezoelectric stacks are alternately energized, at least one driving foot is always kept in close contact with the slider during the movement, effectively improving the load capacity.

Claims

1. A miniaturized bipedal stick-slip piezoelectric actuator, characterized in that: The invention comprises a stator (1), a mover (2), a pre-tightening device (3) and a base (4); the stator (1) is slidably connected to the base (4); the stator (1) can slide on the base (4) along the Y direction, and the pre-tightening force between the stator and the mover can be adjusted by the pre-tightening device (3); the mover (2) is fixedly arranged on the base (4); a slider is provided on the mover (2); and the slider can slide horizontally in the X direction under the drive of the stator (1).

2. A miniaturized bipedal stick-slip piezoelectric actuator according to claim 1, characterized in that: The stator (1) comprises a stator base, a first driving foot (11), a second driving foot (21), a first piezoelectric stack (13), a second piezoelectric stack (20), a first flexible hinge (14), and a second flexible hinge (19); the first driving foot (11) and the second driving foot (21) are respectively arranged at the ends of the first flexible hinge (14) and the second flexible hinge (19), and the first driving foot (11) and the second driving foot (21) are respectively in contact with the mover (2); the first piezoelectric stack (13) is sleeved in the first flexible hinge (14), the second piezoelectric stack (20) is sleeved in the second flexible hinge (19), and the first flexible hinge (14) and the second flexible hinge (19) are respectively arranged on the base.

3. A miniaturized bipedal stick-slip piezoelectric actuator according to claim 2, characterized in that: The first flexible hinge (14) and the second flexible hinge (19) are both axially centrally symmetrical structures, and the first flexible hinge (14) is connected to the second flexible hinge (19); When in operation, the first piezoelectric stack (13) generates an output force in the Y direction, driving the first driving foot (11) to extend and retract along the Y direction, and the first flexible hinge (14) generates motion coupling, thereby driving the first driving foot (11) to extend and retract along the X direction; the second piezoelectric stack (20) generates an output force in the Y direction, driving the second driving foot (21) to extend and retract along the Y direction, and the second flexible hinge (19) generates motion coupling, thereby driving the second driving foot (21) to extend and retract along the X direction.

4. A miniaturized bipedal stick-slip piezoelectric actuator according to claim 1, characterized in that: The pre-tightening device (3) is respectively arranged at two side positions between the stator (1) and the mover (2), and the pre-tightening device (3) comprises a pre-tightening spring (31) and a bolt (32). The base (4) is provided with a threaded hole (41), and the stator is provided with a countersunk hole (17). The bolt (32) passes through the countersunk hole (17) and is connected to the threaded hole (41). The pre-tightening spring (31) is sleeved on the bolt and clamped between the stator (1) and the mover (2).

5. A miniaturized bipedal stick-slip piezoelectric actuator according to claim 2, characterized in that: Pre-tightening screws (16) are respectively provided on the stator base at positions corresponding to the first piezoelectric stack (13) and the second piezoelectric stack (20), and gaskets (15) are respectively provided between the first piezoelectric stack (13) and the second piezoelectric stack (20) and the pre-tightening screws (16) to prevent the pre-tightening force from damaging the piezoelectric stack.

6. A miniaturized bipedal stick-slip piezoelectric actuator according to claim 2, characterized in that: The displacement output ends of the first piezoelectric stack (13) and the second piezoelectric stack (20) are respectively provided with hemispherical blocks (12) to protect the piezoelectric stacks from unnecessary shear forces.

7. A miniaturized bipedal stick-slip piezoelectric actuator according to claim 2, characterized in that: A locking bolt (18) is passed through the stator base in the vertical direction and is fixed to the base (4) via the locking bolt (18).

8. A miniaturized bipedal stick-slip piezoelectric actuator according to claim 1, characterized in that: The stator base is provided with a dovetail groove which matches the dovetail guide rail on the base (4) to limit the movement direction of the stator base.

9. The working process of a miniaturized bipedal stick-slip piezoelectric actuator according to claim 1 is characterized in that: The steps include: First, the first piezoelectric stack and the second piezoelectric stack are powered off, the first piezoelectric stack and the second piezoelectric stack are preloaded, and the first driving foot and the second driving foot are in contact with the slider under the action of the preload force; In the first step, from time 0 to t1, the U1 excitation voltage rises from 0 to U 11 , the first piezoelectric stack, under the action of the U1 excitation voltage, pushes the first driving foot to deflect along the positive direction of the X axis; the U2 excitation voltage is U 21 When it drops to 0, the second piezoelectric stack pushes the second driving foot to deflect along the positive direction of the X-axis under the action of the U2 excitation voltage, and the two driving feet drive the slider to move along the positive direction of the X-axis; In the second step, from time t1 to t2, the excitation voltage of U1 is 11 Rise to U 12 , under the action of the U1 excitation voltage, the first piezoelectric stack pushes the first driving foot to deflect along the positive direction of the X-axis; the U2 excitation voltage rises from 0 to the maximum value U 23 , the second piezoelectric stack pushes the second driving foot to deflect along the negative direction of the x-axis under the action of the U2 excitation voltage. At this stage, the movement directions of the two moving feet are opposite, but the extension speed of the second piezoelectric stack is faster than that of the first piezoelectric stack, resulting in the friction force of the second driving foot being smaller than that of the first driving foot, so the slider moves along the positive direction of the x-axis; In the third step, from time t2 to t3, the excitation voltage of U1 is 12 Rise to U 13 , the first piezoelectric stack, under the action of the U1 excitation voltage, pushes the first driving foot to deflect along the positive direction of the X axis; the U2 excitation voltage is U 23 Descend to U 22 Under the action of the U2 excitation voltage, the second piezoelectric stack pushes the second driving foot to deflect along the positive direction of the X-axis, and the two driving feet drive the slider to move along the positive direction of the x-axis; Step 4: From time t3 to t4, the U1 excitation voltage of the first piezoelectric stack increases from the maximum value U 13 drops to 0, pushing the first driving foot to deflect along the negative direction of the X axis; the U2 excitation voltage is U 22 Descend to U 21 Under the action of U2 excitation voltage, the second piezoelectric stack pushes the second driving foot to deflect along the positive direction of the X-axis. At this stage, the movement directions of the two moving feet are opposite, but the elongation speed of the first piezoelectric stack is faster than that of the second piezoelectric stack, resulting in the friction force of the first driving foot being smaller than that of the second driving foot, and the slider moves along the positive direction of the X-axis.

10. The working process of a miniaturized bipedal stick-slip piezoelectric actuator according to claim 9 is characterized in that: The U 11 The value is equal to U 21 , U 12 The value is equal to U 22 , U 13 The value is equal to U 23 .

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