Piezoelectric driving six-degree-of-freedom compliant positioning system and control method thereof

Abstract

The application discloses a piezoelectric driving six-freedom-degree compliant positioning system, which comprises an industrial computer, the industrial computer is electrically connected with a piezoelectric ceramic controller, the piezoelectric ceramic controller is electrically connected with a plurality of piezoelectric ceramic actuators, the plurality of piezoelectric ceramic actuators are arranged at the bottom of a six-freedom-degree compliant positioning platform, four side edges of the six-freedom-degree compliant positioning platform are provided with driving branch chains, a displacement detection block is fixed at the centroid of the upper surface of the compliant positioning platform, a plurality of capacitive displacement sensors are equidistantly arranged on the surface of the displacement detection block and are parallel to a reserved gap. The compliant positioning platform adopts modularization and symmetrical design, the mechanism is simple and compact, the capacitive displacement sensors and the inclination sensors are simple and easy to use, the closed-loop control positioning is accurate, and the piezoelectric driving six-freedom-degree compliant positioning system is suitable for different application occasions.

Description

Technical Field

[0001] This invention relates to the field of workpiece compliant positioning and detection technology, specifically to a piezoelectric-driven six-degree-of-freedom compliant positioning system and its control method. Background Technology

[0002] With the rapid development of precision engineering technology and cutting-edge scientific research, the demand for nanoscale precision positioning technology is increasing daily. In fields such as synchrotron radiation sources and aerospace, the beamline spot size and sample size in high-precision experiments are at the nanometer and micrometer scale. Therefore, the positioning adjustment of precision instruments or optical devices often requires a positioning platform that meets nanometer-level precision requirements. Piezoelectric ceramics, with their advantages of small size, high displacement resolution, large output force, and fast response speed, are well-suited as actuation devices.

[0003] Single and dual-degree-of-freedom planar distributed compliant platforms have long attracted attention, while spatial integral compliant platforms can meet multi-degree-of-freedom requirements and are suitable for precision positioning, micro-manipulation, and micro-assembly, showing great potential. Currently, six-degree-of-freedom compliant positioning platforms, besides being composed of stacked combinations of low-degree-of-freedom configurations, often adopt the Stewart configuration and its evolutions proposed by Stewart in the 1970s. Stewart platforms possess six spatial degrees of freedom in a parallel configuration, also known as six-degree-of-freedom parallel platforms, and are characterized by high stiffness, strong load-bearing capacity, and non-cumulative positional errors. However, due to limitations in the mechanism's own performance, they struggle to meet the precision attitude adjustment requirements of nanometer-level rapid response.

[0004] Existing positioning platforms cannot achieve closed-loop control to eliminate the hysteresis and creep phenomena of piezoelectric ceramic actuators. They exhibit poor stability during experimental testing, hindering waveform control during scanning. Furthermore, closed-loop control compliant positioning platforms cannot achieve the linear, repeatable motion operations often required in nanoscale micro-positioning applications. Non-contact capacitive sensor probes are installed near the platform to accurately acquire precise displacement signals, but are susceptible to interference from laser interferometers. Traditional tilt sensors measure platform inclination based on gravity, resulting in complex operation and poor dynamic performance. A six-degree-of-freedom precision positioning platform based on a compliant structure (Chinese Patent No. CN103680641B) offers small platform size, high positioning accuracy, and high stability, but requires a small workspace. Another six-degree-of-freedom precision positioning platform (Chinese Patent No. CN101487989B) has a simple structure and simplifies decoupling control, but the combination of a long-range motor and piezoelectric ceramic actuator introduces cumulative errors. Summary of the Invention

[0005] The purpose of this invention is to provide a piezoelectric-driven six-degree-of-freedom compliant positioning system and its control method, so as to solve the problem that the existing six-degree-of-freedom compliant positioning systems mentioned in the background art cannot meet the six-degree-of-freedom position adjustment requirements of precision instruments or optical devices.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a piezoelectric-driven six-degree-of-freedom compliant positioning system, comprising an industrial computer, wherein the industrial computer is electrically connected to a piezoelectric ceramic controller, the piezoelectric ceramic controller is electrically connected to a plurality of piezoelectric ceramic actuators, the plurality of piezoelectric ceramic actuators are disposed at the bottom of a six-degree-of-freedom compliant positioning platform, and compliant positioning stages are disposed on the four sides of the six-degree-of-freedom compliant positioning platform;

[0007] A displacement detection block is fixed at the centroid of the upper surface of the compliant positioning platform, and several capacitive displacement sensors are equidistantly arranged on the surface of the displacement detection block with parallel pre-reserved gaps.

[0008] Inclination sensors, all of which are fixedly connected to the top of the compliant positioning stage;

[0009] A sensitive axis is provided at the bottom of the capacitive displacement sensor, and the shaft of the sensitive axis is kept parallel to the X and Y tilt axes of the six-degree-of-freedom compliant positioning platform.

[0010] To ensure stability of the drive chains and the six-degree-of-freedom compliant positioning platform during testing, in a preferred embodiment of the present invention, the top horizontal position of the six-degree-of-freedom compliant positioning platform is located on the same horizontal vertical line as the centroid of the compliant positioning stage. Several drive chains are arranged on the sides of the six-degree-of-freedom compliant positioning platform, and are symmetrically arranged in pairs in the positive and negative directions of the X and Y axes of the six-degree-of-freedom compliant positioning platform, respectively. The bottom ends of several pairs of drive chains are fixedly connected to the top of the positioning platform base.

[0011] In order to facilitate the deflection of the drive chain and the moving platform during displacement detection, as a preferred embodiment of the present invention, the top end of the drive chain is flexibly connected to the corner of the moving platform, and the side of the drive chain coincides with the edge plane of the moving platform.

[0012] In order to facilitate the connection and use of the drive branch in an inverted Y shape with a circular notch type flexible ball joint and an orthogonal Hooke joint, as a preferred embodiment of the present invention, the drive branch is in an inverted Y shape, the three branches of the drive branch are equally spaced at 120°, the top of the vertical branch is a circular notch type flexible ball joint, and the ends of the two inclined branches of the drive branch are provided with orthogonal Hooke joints.

[0013] In order to enable the positioning and installation of the six-degree-of-freedom compliant positioning platform through the positioning mounting holes, as a preferred embodiment of the present invention, the six-degree-of-freedom compliant positioning platform is provided with positioning mounting holes at its four corners.

[0014] In order to enable the microcontroller to control the electrical components on the piezoelectric-driven six-degree-of-freedom compliant positioning system, in a preferred embodiment of the present invention, a microcontroller is fixedly mounted on the top of the six-degree-of-freedom compliant positioning platform. The piezoelectric ceramic controller is electrically connected to an external power supply through the microcontroller, the piezoelectric ceramic actuator is electrically connected to an external power supply through the microcontroller, the capacitive displacement sensor is electrically connected to an external power supply through the microcontroller, and the tilt sensor is electrically connected to an external power supply through the microcontroller.

[0015] A piezoelectric-driven six-DOF compliant positioning control method, comprising a piezoelectric-driven six-DOF compliant positioning system according to any one of the above, and further comprising:

[0016] S1: Displacement detection;

[0017] S2: Environmental tracking test;

[0018] S3: Signal transmission.

[0019] To enable displacement detection, in a preferred embodiment of the present invention, the displacement detection in step S1 involves measuring the displacement at the center of the platform. A displacement detection block is installed at the centroid of the upper surface of the compliant positioning platform. A capacitive displacement sensor is arranged parallel to the three-dimensional surface of the displacement detection block without contact. A tilt sensor is fixedly connected to the top of the compliant positioning platform using screws with spring washers. Its sensitive axis is kept parallel to the X and Y tilt axes respectively without contact, which facilitates the monitoring of the platform's roll and pitch angles.

[0020] To facilitate environmental tracking testing, in a preferred embodiment of the present invention, in step S2, the piezoelectric ceramic actuator is directly nested inside the Y-shaped compliant mechanism. This allows for fast response and good dynamic performance during testing, making it suitable for dynamic tracking and applications requiring a small working stroke. In the displacement amplification branch, the piezoelectric ceramic actuator is nested in the bridge-type displacement amplification mechanism and then connected to the Y-shaped compliant mechanism. The deformation in the functional direction of the flexible hinge generates motion perpendicular to the input direction and achieves motion amplification.

[0021] To enable signal transmission, in a preferred embodiment of the present invention, in step S3, the industrial control computer inputs signals to the piezoelectric ceramic controller via host computer software. The controller then controls the piezoelectric ceramic actuator to complete six-degree-of-freedom pose adjustment. After micro-positioning adjustment, the industrial control computer receives displacement signals from the capacitive displacement sensor and deflection signals from the tilt sensor. These signals are compared with the desired values, and the control signals output by the piezoelectric ceramic controller are corrected. The coordinated action achieves closed-loop feedback control of all-space degrees of freedom.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1) Closed-loop control of the positioning platform can eliminate the hysteresis and creep of piezoelectric ceramic actuators, improve stability, and help control the waveform during scanning. The closed-loop control compliant positioning platform can realize the linear and repeatable motion operation often required in nano-micro positioning applications. The non-contact capacitive sensor probe is installed near the platform to obtain precise displacement signals, which can economically replace the laser interferometer. The tilt sensor measures the inclination of the platform based on gravity, which is simple to use and has good dynamic performance.

[0024] 2) The compliant positioning platform adopts a modular and symmetrical design, with a simple and compact structure. It uses capacitive and tilt sensors for feedback, which is easy to use. The closed-loop control provides accurate positioning and is suitable for different applications. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the piezoelectric ceramic actuator structure of the present invention;

[0027] Figure 3 This is a schematic diagram of the six-degree-of-freedom compliant positioning platform structure of the present invention;

[0028] Figure 4 This is a schematic diagram of the direct drive branch structure of the six-degree-of-freedom compliant positioning platform of the present invention;

[0029] Figure 5 This is a schematic diagram of the displacement amplification drive branch structure of the six-degree-of-freedom compliant positioning platform of the present invention;

[0030] Figure 6 This is a schematic block diagram of the six-degree-of-freedom compliant positioning system control method of the present invention.

[0031] In the diagram: 1. Industrial computer; 2. Piezoelectric ceramic controller; 3. Piezoelectric ceramic actuator; 301. First piezoelectric ceramic actuator; 302. Second piezoelectric ceramic actuator; 303. Third piezoelectric ceramic actuator; 304. Fourth piezoelectric ceramic actuator; 305. Fifth piezoelectric ceramic actuator; 306. Sixth piezoelectric ceramic actuator; 307. Seventh piezoelectric ceramic actuator; 308. Eighth piezoelectric ceramic actuator; 4. Six-degree-of-freedom compliant positioning platform; 5. Capacitive displacement sensor; 6. Tilt sensor; 7. Drive chain; 8. Circular notch type flexible ball joint; 9. Orthogonal axis type Hooke joint. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1

[0034] Please see Figure 1-5 The present invention provides a technical solution: a piezoelectric driven six-degree-of-freedom compliant positioning system, including an industrial computer 1, the industrial computer 1 being electrically connected to a piezoelectric ceramic controller 2, the piezoelectric ceramic controller 2 being electrically connected to a plurality of piezoelectric ceramic actuators 3, the plurality of piezoelectric ceramic actuators 3 being disposed at the bottom of a six-degree-of-freedom compliant positioning platform 4, and compliant positioning stages being disposed on the four sides of the six-degree-of-freedom compliant positioning platform 4;

[0035] The displacement detection block is fixed at the centroid of the upper surface of the compliant positioning platform. Several capacitive displacement sensors are equally spaced on the surface of the displacement detection block, with parallel gaps reserved.

[0036] Inclination sensor 6, all of which are fixedly connected to the top of the compliant positioning stage;

[0037] The sensitive axis is located at the bottom of the capacitive displacement sensor 5. The shaft of the sensitive axis is parallel to the X and Y tilt axes of the six-degree-of-freedom compliant positioning platform 4.

[0038] The top horizontal position of the six-degree-of-freedom compliant positioning platform 4 is on the same horizontal vertical line as the centroid of the compliant positioning stage. Several drive chains 7 are arranged on the sides of the six-degree-of-freedom compliant positioning platform 4, and are symmetrically arranged in pairs in the positive and negative directions of the X and Y axes of the six-degree-of-freedom compliant positioning platform 4. The bottom ends of several pairs of drive chains 7 are fixedly connected to the top of the six-degree-of-freedom compliant positioning platform 4. Through their control of the piezoelectric ceramic actuator 3, the six-degree-of-freedom pose adjustment is completed. After the micro-positioning adjustment, the industrial control computer receives the displacement signal from the capacitive displacement sensor 5 and the deflection signal from the tilt sensor 6, compares it with the expected value, corrects the control signal output by the piezoelectric ceramic controller 2, and achieves closed-loop feedback control of the full space degree of freedom through coordinated action.

[0039] The top of the drive chain 7 is flexibly connected to the corner of the moving platform, and the side of the drive chain 7 coincides with the edge plane of the moving platform. The flexible connection between the top of the drive chain 7 and the corner of the moving platform facilitates angular deflection when measuring displacement.

[0040] The drive chain 7 is in the shape of an inverted Y. The three branches of the drive chain 7 are distributed at 120° intervals. The top of the vertical branch 7 is a circular notch type flexible ball joint 8. The ends of the two inclined branches of the drive chain 7 are provided with axis orthogonal type Hooke joints 9. The output displacement of the piezoelectric ceramic actuator 3 is transmitted to the load moving platform by the drive chain 7.

[0041] The six-degree-of-freedom compliant positioning platform 4 has positioning mounting holes installed at its four corners. The six-degree-of-freedom compliant positioning platform 4 adopts a modular and symmetrical design. The control strategies for movement along the X-axis and rotation around the X-axis are essentially the same as the control strategies for movement along the Y-axis and rotation around the Y-axis.

[0042] A microcontroller is fixedly installed on the top of the six-degree-of-freedom compliant positioning platform 4. The piezoelectric ceramic controller 2 is electrically connected to an external power supply through the microcontroller. The piezoelectric ceramic actuator 3 is electrically connected to an external power supply through the microcontroller. The capacitive displacement sensor 5 is electrically connected to an external power supply through the microcontroller. The tilt sensor 6 is electrically connected to an external power supply through the microcontroller.

[0043] A piezoelectric-driven six-DOF compliant positioning control method, comprising a piezoelectric-driven six-DOF compliant positioning system according to any one of the above, and further comprising:

[0044] S1: Displacement detection;

[0045] S2: Environmental tracking test;

[0046] S3: Signal transmission.

[0047] In step S1, displacement detection measures the displacement at the center of the platform. A displacement detection block is installed at the centroid of the upper surface of the compliant positioning platform. A capacitive displacement sensor 5 is arranged parallel to the three-dimensional surface of the displacement detection block without contact. An inclination sensor 6 is fixedly connected to the top of the compliant positioning platform using screws with spring washers. Its sensitive axis is kept parallel to the X and Y tilt axes respectively without contact, which facilitates the monitoring of the platform's roll and pitch angles.

[0048] In step S2, during environmental tracking testing, the piezoelectric ceramic actuator 3 is directly nested inside the Y-shaped compliant mechanism, which facilitates fast response and good dynamic performance during testing. This makes it suitable for dynamic tracking and applications requiring a small working stroke. In the displacement amplification branch, the piezoelectric ceramic actuator 3 is nested in the bridge-type displacement amplification mechanism and then connected to the Y-shaped compliant mechanism. It generates motion perpendicular to the input direction by deforming in the direction of the flexible hinge and achieves motion amplification.

[0049] In step S3, the industrial control computer 1 inputs signals to the piezoelectric ceramic controller 2 through the host computer software. The controller controls the piezoelectric ceramic actuator 3 to complete the six-degree-of-freedom pose adjustment. After the micro-positioning adjustment, the industrial control computer 1 receives the displacement signal from the capacitive displacement sensor 5 and the deflection signal from the tilt sensor 6. It compares the signals with the expected values ​​and corrects the control signal output by the piezoelectric ceramic controller 2. The coordinated action realizes closed-loop feedback control of the full-space degrees of freedom.

[0050] Working principle: The output displacement of the piezoelectric ceramic actuator 3 is transmitted to the load moving platform through the drive branch 7. The actuator assembly can achieve movement along the X, Y, and Z axes and rotation around the X, Y, and Z axes. Due to the modular and symmetrical design of the six-degree-of-freedom compliant positioning platform 4, the control strategy for movement along the X axis and rotation around the X axis is essentially the same as the control strategy for movement along the Y axis and rotation around the Y axis. Figure 2 As shown, the piezoelectric ceramic actuator 3 is provided with eight piezoelectric ceramic actuators 3. When the first piezoelectric ceramic actuator 301, the second piezoelectric ceramic actuator 302, the fifth piezoelectric ceramic actuator 305, and the sixth piezoelectric ceramic actuator 306 work together, they can rotate around the X-axis. When the third piezoelectric ceramic actuator 303, the fourth piezoelectric ceramic actuator 304, the seventh piezoelectric ceramic actuator 307, and the eighth piezoelectric ceramic actuator 3 work together, they can rotate around the Y-axis. When the four piezoelectric ceramic actuators 3 are symmetrically distributed along the X and Y axes work together, they can rotate around the Z-axis. When the direction is rotated, the piezoelectric ceramic actuator 3, in coordination with the first piezoelectric ceramic actuator 301, the sixth piezoelectric ceramic actuator 306, or the second piezoelectric ceramic actuator 302 and the fifth piezoelectric ceramic actuator 3, can move along the X-axis. The third piezoelectric ceramic actuator 303, the eighth piezoelectric ceramic actuator 308, or the fourth piezoelectric ceramic actuator 304 and the seventh piezoelectric ceramic actuator 307, in coordination, can move along the Y-axis. When all the piezoelectric ceramic actuators 3 work together, they can move along the Z-axis.

[0051] The control method of the six-degree-of-freedom compliant positioning system is as follows: the industrial control computer inputs signals to the piezoelectric ceramic controller 2 through the host computer software, and through the controller, the piezoelectric ceramic actuator 3 completes the six-degree-of-freedom pose adjustment. After the micro-positioning adjustment, the industrial control computer 1 receives the displacement signal from the capacitive displacement sensor 5 and the deflection signal from the tilt sensor 6, compares them with the expected values, corrects the control signal output by the piezoelectric ceramic controller 2, and achieves closed-loop feedback control of the full-space degrees of freedom through coordinated action.

[0052] The contents not described in detail in this description are existing technologies known to those skilled in the art. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A piezoelectrically driven six degree of freedom compliant positioning system comprising a work station, characterized in that, The work computer is electrically connected with a piezoelectric ceramic controller, the piezoelectric ceramic controller is electrically connected with a plurality of piezoelectric ceramic actuators, the plurality of piezoelectric ceramic actuators are arranged at the bottom of the six-degree-of-freedom compliant positioning platform, four sides of the six-degree-of-freedom compliant positioning platform are provided with compliant positioning tables, the top horizontal position of the six-degree-of-freedom compliant positioning platform is located on the same horizontal vertical line as the center of the compliant positioning table, the side of the six-degree-of-freedom compliant positioning platform is provided with a plurality of drive branch chains, and two two symmetrically arranged drive branch chains are respectively located in the positive and negative directions of the X and Y axes of the six-degree-of-freedom compliant positioning platform, the bottom of the plurality of drive branch chains is fixedly connected with the top of the positioning platform base, the top of the drive branch chain is flexibly connected with the edge corner of the moving platform, and the side of the drive branch chain is coincident with the edge plane of the moving platform; the drive branch chain is in the shape of inverted Y, the three branch chains of the drive branch chain are equally spaced at an interval of 120 degrees, and the top end of the vertical branch chain is a circular notch type flexible spherical hinge, and the two inclined branch chains of the drive branch chain are provided with axis orthogonal type hook hinges at the ends. A displacement detection block is fixed at the center of the upper surface of the compliant positioning platform, and a plurality of capacitive displacement sensors are arranged equidistantly on the surface of the displacement detection block and are parallel to the reserved gap. An inclination sensor is fixedly connected with the top of the compliant positioning table. The bottom of the capacitive displacement sensor is provided with a sensitive shaft, and the shaft rod of the sensitive shaft is parallel to the X and Y inclined axes of the six-degree-of-freedom compliant positioning platform.

2. The piezoelectrically driven six degree of freedom compliant positioning system of claim 1, wherein: Four corner mounting holes are mounted on the six-degree-of-freedom compliant positioning platform.

3. The piezoelectrically driven six degree of freedom compliant positioning system of claim 1, wherein: A single-chip microcomputer is fixedly mounted on the top of the six-degree-of-freedom compliant positioning platform, the piezoelectric ceramic controller is electrically connected with an external power supply through the single-chip microcomputer, the piezoelectric ceramic actuator is electrically connected with the external power supply through the single-chip microcomputer, the capacitive displacement sensor is electrically connected with the external power supply through the single-chip microcomputer, and the inclination sensor is electrically connected with the external power supply through the single-chip microcomputer.

4. A piezoelectric driving six-degree-of-freedom compliant positioning control method, comprising using the piezoelectric driving six-degree-of-freedom compliant positioning system according to any one of claims 1-3, characterized in that, Further comprising: S1: displacement detection; S2: environment tracking test; S3: signal transmission.

5. The piezoelectric driving six-degree-of-freedom compliant positioning control method according to claim 4, characterized in that: In the S1 step of displacement detection, the displacement at the center of the platform is measured, the displacement detection block is installed at the center of the upper surface of the compliant positioning platform, the capacitive displacement sensor is arranged in parallel to the three-direction surface of the displacement detection block without contact, the inclination sensor is fixedly connected on the top of the compliant positioning platform by using a screw with a spring washer, the sensitive shaft thereof is parallel to the X and Y inclined axes without contact, and the platform roll and pitch angles are monitored.

6. The piezoelectric driving six-degree-of-freedom compliant positioning control method according to claim 4, characterized in that: In the S2 step of environment tracking test, the piezoelectric ceramic actuator is directly nested in the Y-shaped compliant mechanism, so that the response speed is fast, the dynamic performance is good, it is suitable for dynamic tracking and occasions requiring small working stroke, the displacement amplification type branch chain, the piezoelectric ceramic actuator is nested in the bridge type displacement amplification mechanism and then connected with the Y-shaped compliant mechanism, and the flexible hinge function direction deformation generates movement perpendicular to the input direction and realizes movement amplification.

7. The piezoelectric-driven six-degree-of-freedom compliant positioning control method according to claim 4, characterized in that: The signal transmission in the S3 step, the industrial computer inputs the signal to the piezoelectric ceramic controller through the upper computer software, controls the piezoelectric ceramic actuator through the piezoelectric ceramic controller, completes the six-degree-of-freedom pose adjustment, after the micro-positioning adjustment, the industrial computer receives the displacement signal from the capacitive displacement sensor and the deflection signal from the inclination sensor, compares with the expected value, corrects the control signal output by the piezoelectric ceramic controller, and cooperates to realize the full-space freedom closed-loop feedback control.

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