CN114928270B - A compliant control device based on a compliant mechanism and a compliant control method thereof - Google Patents
A compliant control device based on a compliant mechanism and a compliant control method thereof Download PDFInfo
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- CN114928270B CN114928270B CN202210738405.XA CN202210738405A CN114928270B CN 114928270 B CN114928270 B CN 114928270B CN 202210738405 A CN202210738405 A CN 202210738405A CN 114928270 B CN114928270 B CN 114928270B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
- H02N2/02—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing linear motion, e.g. actuators; Linear positioners ; Linear motors
- H02N2/06—Drive circuits; Control arrangements or methods
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
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- B25J13/00—Controls for manipulators
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B25—HAND TOOLS; PORTABLE POWER-DRIVEN TOOLS; MANIPULATORS
- B25J—MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES
- B25J19/00—Accessories fitted to manipulators, e.g. for monitoring, for viewing; Safety devices combined with or specially adapted for use in connection with manipulators
- B25J19/02—Sensing devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
- H02N2/02—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing linear motion, e.g. actuators; Linear positioners ; Linear motors
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Abstract
本发明提供一种基于柔顺机构的柔顺控制装置及其柔顺控制方法，柔顺机构的一端设有一体成型的柔性铰链组件，柔顺机构的中部还开设有连通柔性铰链组件的滑槽；还包括应变片、第一力传感器、第一电容传感器组件和第二电容传感器组件；还包括带有内置应变片的压电驱动器；还包括连接各检测元件和压电驱动器的控制器。本发明克服现有柔顺机构装置力控制精度及稳定性不高的不足，本发明通过力与位移的半闭环柔顺控制和全闭环柔顺控制相结合的方式，具备高精度、高带宽与稳定性，能够满足复杂的力与位移控制需求，适用更多精密控制领域。
The present invention provides a compliant control device based on a compliant mechanism and a compliant control method thereof. An end of the compliant mechanism is provided with an integrally formed flexible hinge assembly, and a slide groove connecting the flexible hinge assembly is provided in the middle of the compliant mechanism; the compliant mechanism also includes a strain gauge, a first force sensor, a first capacitance sensor assembly, and a second capacitance sensor assembly; the compliant mechanism also includes a piezoelectric driver with a built-in strain gauge; and the compliant mechanism also includes a controller connecting each detection element and the piezoelectric driver. The present invention overcomes the shortcomings of the existing compliant mechanism device in terms of low force control accuracy and stability. The present invention combines semi-closed-loop compliant control of force and displacement with full-closed-loop compliant control, and has high accuracy, high bandwidth and stability, can meet complex force and displacement control requirements, and is applicable to more precision control fields.
Description
Technical Field
The invention relates to the fields of robotics and force control, in particular to a compliant control device based on a compliant mechanism and a compliant control method thereof.
Background
In the field of mechanical engineering, research on mechanisms can be classified into rigid mechanism research and non-rigid mechanism research. Among them, the compliant mechanism occupies an important position in the study of non-rigid mechanisms. Compliant mechanism refers to a mechanism that includes one or more flexible units and that effects the transfer or conversion of force, displacement, and energy through elastic deformation of the flexible units. Compared with a rigid mechanism, the flexible mechanism has the advantages of simple design, easy processing, no assembly, no gap and easy realization of microminiaturization, can achieve the repeated positioning accuracy of submicron or nanometer level, is usually processed by adopting a whole material without assembly and lubrication, and is widely applied to the fields of micro-nano operation, ultra-precise processing and the like.
Different application requirements define the function of the compliant mechanism, thereby affecting the design of the mechanism. For example, the Chinese patent literature discloses a multi-freedom-degree flexible micro-gripper integrated with multi-variable detection, which is used in the fields of a triaxial nano positioning platform, a two-stage rigidity micro-nano clamp, a multi-diamond nested large-strain mechanism, a double-layer stacked nano positioner and the like, and the Chinese patent literature discloses a multi-freedom-degree flexible micro-gripper integrated with multi-variable detection, which is characterized in that a displacement sensor and a force sensor are arranged on a micro clamp to form a full-closed-loop servo of force and displacement, but the problems of low precision and low bandwidth exist, the Chinese patent literature discloses a piezoelectric driving cell microinjection device and a self-adaptive flexible control method thereof, the mounting mode of the sensor improves the natural frequency of the device, so that the working bandwidth is higher, but the micro sensor is arranged at the bottom of an injection needle, and the displacement sensor is integrated in the groove body to form a servo control mode of full-closed-loop and semi-closed-loop of force, so that the problem of low precision exists. The Chinese patent literature discloses a cell microinjection device and a robust impedance control method thereof, wherein a micro force sensor is arranged at the bottom of a microinjection needle, a force full-closed loop and a displacement half-closed loop servo control mode is formed by utilizing a displacement sensor integrated in a piezoelectric driver, and the adopted sensor mounting mode leads to lower working bandwidth and lower precision.
In summary, most flexible mechanical devices currently employ a single position or force signal to effect control. However, the existing force sensor mounting mode is difficult to ensure the accuracy of axial fixation, namely, the non-axial coupling amount is large, the pretightening force is uncontrollable, the first-order natural frequency of the whole device is low, quantitative design is difficult, the bandwidth is limited, the quantitative mapping relation is lacking and the improvement is difficult, a semi-closed loop servo control mode or a full-closed loop control mode of one of displacement and force is adopted, the problem of overall control accuracy and stability of force position is not high, the accuracy problem is to be solved, complex control requirements cannot be met, and the application range is limited.
Disclosure of Invention
The invention aims to overcome the defect of low force control precision and stability of the conventional compliant mechanism device and provides a compliant control device and a compliant control method based on a compliant mechanism. The invention adopts the compliant mechanism to realize compliant control, realizes the mode of combining semi-closed loop compliant control and full-closed loop compliant control of force and displacement, has high precision, high bandwidth and stability, can meet the requirements of high precision and complex control, and is suitable for more precise control fields.
In order to solve the technical problems, the invention adopts the following technical scheme:
The flexible control device based on the flexible mechanism comprises the flexible mechanism, wherein one end of the flexible mechanism is provided with an integrally formed flexible hinge assembly, the middle part of the flexible mechanism is also provided with a chute communicated with the flexible hinge assembly, the central axes of the flexible hinge assembly and the chute are positioned on the same axis of the flexible mechanism, one end of the flexible hinge assembly, which is communicated with the chute, is an input end, the other end of the flexible hinge assembly is an output end, and the middle part of the end face of the output end is provided with a load for externally acting;
The strain gauge is attached to the output end, the first force sensor is connected with the flexible hinge assembly and used for measuring the reaction force received by the output end, the first capacitance sensor assembly and the second capacitance sensor assembly are connected with the flexible mechanism and used for measuring displacement, the measuring surface of the first capacitance sensor assembly is connected with the output end, and the measuring surface of the second capacitance sensor assembly is connected with the input end;
The device also comprises a piezoelectric driver with a built-in strain gauge, one end of the piezoelectric driver is connected with the input end, the other end of the piezoelectric driver is connected with a second force sensor, and the second force sensor is positioned in the chute;
The piezoelectric sensor further comprises a controller, wherein the controller is respectively connected with the strain gauge, the first force sensor, the first capacitance sensor component, the second capacitance sensor component, the built-in strain gauge, the piezoelectric driver and the second force sensor.
The invention also provides a compliant control method of the compliant control device based on the compliant mechanism, which comprises the following steps:
The piezoelectric actuator drives the flexible hinge assembly to move and deform under the control of the controller to drive the load to apply work to the outside, the first force sensor detects the reaction force generated by the flexible hinge assembly when the load is driven to apply work to the outside, the value between the output end and the input end is transmitted, the strain gauge detects the force lost by the flexible hinge assembly, the first capacitance sensor assembly detects the actual displacement of the output end, and the controller adjusts the output voltage of the piezoelectric actuator through the first force sensor, the strain gauge and the data measured by the first capacitance sensor assembly at the output end to form the full-closed-loop compliant control with the combination of the force and the displacement;
Semi-closed loop compliant control: the built-in strain gauge detects the elongation of the piezoelectric driver, the second force sensor detects the output force value of the other end of the piezoelectric driver, the second capacitance sensor component detects the actual displacement of the input end, and the controller forms semi-closed-loop compliance control combining force and displacement by the data measured by the second force sensor and the second capacitance sensor component at the input end;
the full closed-loop compliant control and the semi-closed-loop compliant control are combined to form redundant compliant control, so that high precision and stability are realized.
The invention mainly aims to directly detect the actual displacement and force value of an output end, and the semi-closed loop compliance control mainly aims to directly measure the actual displacement and force of an input end, namely the actual value generated by a sensor, and comprehensively monitor two parameters of binding force and displacement, so that the output voltage of a piezoelectric driver is accurately regulated and controlled to realize complex processing or control requirements. When the output force is simply monitored to carry out the flexible control, the piezoelectric ceramic of the piezoelectric driver has the characteristics of hysteresis, creep and nonlinearity, so that the problem can be solved only by forming the full closed loop control, but when the displacement is simply monitored, the flexible control can not be carried out, the force and the displacement are required to be simultaneously controlled, and when the force and the displacement are combined, the complex processing or control requirements can be met.
Further, the device also comprises a pre-tightening block with two symmetrical movable clamping ends in the sliding groove, wherein a pre-tightening screw hole penetrating through the side wall of the compliant mechanism is formed in the bottom of the sliding groove, a pre-tightening screw is in threaded connection with the pre-tightening screw hole, one end of the pre-tightening screw is used for abutting the pre-tightening block, and clamping grooves for the pre-tightening block to move in the sliding groove are symmetrically formed in the inner side wall of the sliding groove.
The pre-tightening block is additionally arranged in the compliant mechanism and can move in the clamping groove under the pressure of the pre-tightening screw to transmit the pre-tightening force to the piezoelectric driver, so that the pre-tightening screw can apply the initial pre-tightening force to the piezoelectric driver, the initial pre-tightening force is controllable, the compliant control device can be conveniently applied to more application fields, and meanwhile, the pre-tightening mechanism is arranged, so that the piezoelectric driver can be pre-tightened in the mode, and meanwhile, the hidden danger of side force and endangering the piezoelectric driver is avoided.
Further, a groove is formed in one side end face of the pre-tightening block, steel balls are embedded in the groove, one end of the pre-tightening screw is movably abutted against the steel balls, a guide column is further arranged on the other side end face of the pre-tightening block, and a through hole for the guide column to pass through is formed in the second force sensor. Like this, pretension screw passes pretension screw, and one end butt in the steel ball to this transmission pretension force, the guide post that pretension piece opposite side terminal surface set up with the cooperation of passing through of second force transducer, with this provides the direction for pretension piece, can improve the stability of pretension.
Further, the flexible hinge assembly comprises a first group of flexible hinges and a second group of flexible hinges which are sequentially arranged along the direction from the output end to the input end, the axes of the first group of flexible hinges and the second group of flexible hinges are mutually overlapped, the piezoelectric driver is connected with the second group of flexible hinges, the strain gauge is attached to the first group of flexible hinges, the first force sensor is connected with the first group of flexible hinges and is located between the first group of flexible hinges and the second group of flexible hinges, the measuring surface of the first capacitance sensor assembly is connected with the first group of flexible hinges, and the measuring surface of the second capacitance sensor assembly is connected with the second group of flexible hinges. Thus, through designing two groups of flexible hinges, the flexible hinges and the flexible mechanism are integrally formed, through fixing and guiding the force sensor, the non-axial coupling can be reduced, the axial precision of the flexible hinge assembly is improved, the axial high precision of force measurement is realized, and the control precision of the flexible control process is ensured.
In addition, the initial pretightening force can be designed by taking the self rigidity of the first group of flexible hinges and the second group of flexible hinges and the interference between the two groups of flexible hinges as design parameters, and meanwhile, the natural frequency can be designed by taking the coefficient ratio of equivalent rigidity and mass of the output end as the design parameters, so that high-bandwidth servo is realized.
Further, the first capacitance sensor assembly comprises a first support which is detachably connected to the compliant mechanism, a first capacitance sensor which is arranged on the first support, a measuring surface of the first capacitance sensor is connected with a first group of flexible hinges, the second capacitance sensor assembly comprises a second support which is detachably connected to the compliant mechanism, a second capacitance sensor which is arranged on the second support, and a measuring surface of the second capacitance sensor is connected with a second group of flexible hinges.
It should be noted that, the first capacitive sensor component and the second capacitive sensor component are adaptively and respectively arranged on the side walls of the front side and the back side of the compliant mechanism according to the structural characteristics of the compliant mechanism, and the relative positions of the first capacitive sensor component and the second capacitive sensor component correspond to the first group of flexible hinges and the second group of flexible hinges respectively, so that the symmetry and the axial precision of the whole structure of the compliant mechanism are improved.
Further, the first group of flexible hinges are four groups of straight beam type flexible hinges which are symmetrically arranged, the four groups of straight beam type flexible hinges are connected through a first connecting block, the measuring surface of the first capacitance sensor is connected with the first connecting block, strain gauges are attached to the surface of each group of straight beam type flexible hinges, the second group of flexible hinges are four groups of straight round type flexible hinges which are symmetrically arranged, the four groups of straight round type flexible hinges are connected through a second connecting block, and the measuring surface of the second capacitance sensor is connected with the second connecting block. Thus, the strain gauge is attached to the surface of the straight beam type flexible hinge, contact force is generated by the contact of the load and a workpiece, the shape of the strain gauge is changed in real time along with the deformation of the surface of the straight beam type flexible hinge through the first group of flexible hinges, resistance value change is caused, resistance measurement signals are processed through a circuit and converted into voltage signals, the voltage signals react to the first group of flexible hinges to transmit lost force, and at the moment, the strain gauge can measure the actual force through measuring the lost contact force and then through the first force sensor.
Further, the device also comprises two outer reinforcing plates which are symmetrically arranged on two sides of the flexible mechanism and cover the sliding groove, and each outer reinforcing plate is provided with an observation window communicated with the bottom of the sliding groove.
Further, the device also comprises a calibration assembly for measuring the actual displacement and output force of the load, wherein the calibration assembly comprises a calibration block connected with the load, a third capacitance sensor assembly connected with the flexible mechanism and the measurement surface and connected with the calibration block, and a third force sensor connected with the measurement surface and connected with the load, and the third capacitance sensor assembly and the third force sensor are respectively connected with the controller.
Further, the third capacitance sensor assembly comprises a third support which is detachably connected to the compliant mechanism, a third capacitance sensor is arranged on the third support, and a measuring surface of the third capacitance sensor is connected with the calibration block.
It should be noted that, the calibration block is configured to calibrate the actual output force and displacement of the load, and the third capacitance sensor assembly is configured to detect the displacement of the calibration block, so as to verify whether the actual displacement of the load is the same as the displacement of the output end detected by the first capacitance sensor assembly. If not, calibrating the first capacitance sensor assembly. Because the third capacitive sensor assembly is the most direct signal source reflecting the amount of final load output displacement. Meanwhile, the calibration block is connected with the third force sensor to calibrate the actual output force of the load of the calibration block and serve as a direct measurement signal source of the force finally output by the flexible control device, so that the strain gauge and the measured value of the first force sensor are calibrated, the signal sources of the force and displacement measured by the calibration component correspond to the measured value of the strain gauge and the measured value of the first force sensor one by one, and data equivalent to the calibration component can be calculated through the measured value of the strain gauge and the measured value of the first force sensor even after the signal source of the calibration component is removed.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention realizes high-precision control of the piezoelectric driver through the unified regulation and control of the controller by designing the structure of the compliant mechanism and configuring the detection element for detecting force and displacement, and can realize complex processing or control requirements.
(2) The invention can be applied to the scientific research field of force and displacement mixed control such as micro-nano scale electro-mechanical system, nano imprinting and the like on the basis of high-precision, high-bandwidth and durable stable force and displacement mixed flexible control, and can also be applied to the industrial application sites of force interaction such as cutting, milling, grinding, punching, polishing and the like of micro-nano precision high-bandwidth servo, in particular to a tool servo workpiece table, a nano imprinting workpiece table and the like of an ultra-precision machining tool.
Drawings
FIG. 1 is an exploded view of example 1;
FIG. 2 is a schematic plan view of the compliant mechanism in embodiment 1;
FIG. 3 is a schematic diagram of parameter identification of the compliant mechanism in embodiment 1;
fig. 4 is a schematic structural view of the pre-tightening block in embodiment 1;
FIG. 5 is a schematic view of another view angle structure of the pre-tightening block in embodiment 1;
FIG. 6 is a schematic illustration of the internal connection of the compliant mechanism of embodiment 1;
FIG. 7 is a schematic diagram of the connection of the first capacitive sensor assembly of embodiment 1;
FIG. 8 is a schematic diagram of the connection of the second capacitive sensor assembly of embodiment 1;
fig. 9 is a schematic structural diagram of embodiment 3.
The graphic indicia are illustrated as follows:
The device comprises a 1-compliant mechanism, a 11-flexible hinge assembly, a 111-output end, a 112-input end, a 113-first group of flexible hinges, a 114-second group of flexible hinges, a 12-sliding chute, a 121-pre-tightening screw hole, a 2-load, a 21-calibration block, a 22-third capacitance sensor assembly, a 221-third bracket, a 222-third capacitance sensor, a 3-strain gauge, a 4-first force sensor, a 5-first capacitance sensor assembly, a 51-first bracket, a 52-first capacitance sensor, a 6-second capacitance sensor assembly, a 61-second bracket, a 62-second capacitance sensor, a 7-piezoelectric actuator, a 71-built-in strain gauge, an 8-second force sensor, a 9-pre-tightening block, a 91-groove, a 92-guide post, 93-steel balls and a 10-reinforcing plate.
Detailed Description
The invention is further described below in connection with the following detailed description. In which the drawings are for illustrative purposes only and are not intended to be construed as limiting the present patent, and in which certain elements of the drawings may be omitted, enlarged or reduced in order to better illustrate embodiments of the present invention, and not to represent actual product dimensions, it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
In the description of the present invention, it should be understood that, if there is an azimuth or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc., which are based on the azimuth or positional relationship shown in the drawings, it is merely for convenience of describing the present invention and simplifying the description, and it is not indicated or implied that the apparatus or elements referred to must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and are not to be construed as limitations of the present patent, and that the specific meanings of the terms described above should be understood by those skilled in the art according to circumstances.
Example 1
As shown in fig. 1 to 2, a compliant control device based on a compliant mechanism comprises a compliant mechanism 1, wherein one end of the compliant mechanism 1 is provided with an integrally formed flexible hinge assembly 11, the middle part of the compliant mechanism 1 is also provided with a chute 12 communicated with the flexible hinge assembly 11, the central axes of the flexible hinge assembly 11 and the chute 12 are positioned on the same axis of the compliant mechanism 1, one end of the flexible hinge assembly 11 communicated with the chute 12 is an input end 112, the other end of the flexible hinge assembly 11 is an output end 111, and the middle part of the end surface of the output end 111 is provided with a load 2 for external acting;
As shown in fig. 1 and 6, the sensor further comprises a strain gauge 3 attached to the output end 111, a first force sensor 4 connected with the flexible hinge assembly 11 and used for measuring the reaction force received by the output end 111, a first capacitance sensor assembly 5 and a second capacitance sensor assembly 6 connected with the flexible mechanism 1 and used for measuring displacement, a measuring surface of the first capacitance sensor assembly 5 is connected with the output end 111, and a measuring surface of the second capacitance sensor assembly 6 is connected with the input end 112;
as shown in fig. 6, the device further comprises a piezoelectric driver 7 with a built-in strain gauge 71, one end of the piezoelectric driver 7 is connected with an input end 112, the other end of the piezoelectric driver 7 is connected with a second force sensor 8, and the second force sensor 8 is positioned in the chute 12;
The strain gauge further comprises a controller which is respectively connected with the strain gauge 3, the first force sensor 4, the first capacitance sensor assembly 5, the second capacitance sensor assembly 6, the built-in strain gauge 71, the piezoelectric driver 7 and the second force sensor 8.
As shown in fig. 1 and 6, the device further comprises a pre-tightening block 9 with two ends symmetrically movably clamped in the sliding groove 12, a pre-tightening screw hole 121 penetrating through the side wall of the compliant mechanism 1 is formed in the bottom of the sliding groove 12, a pre-tightening screw is in threaded connection with the pre-tightening screw hole 121, one end of the pre-tightening screw is used for abutting against the pre-tightening block 9, and clamping grooves for allowing the pre-tightening block 9 to move in the sliding groove 12 are symmetrically formed in the inner side wall of the sliding groove 12.
The pre-tightening block 9 is additionally arranged in the compliant mechanism 1, the pre-tightening block 9 can move in the clamping groove under the pressure of the pre-tightening screw, and the pre-tightening force is transmitted to the piezoelectric driver 7, so that the pre-tightening screw can apply initial pre-tightening force to the piezoelectric driver 7, the initial pre-tightening force is controllable, the compliant control device can be conveniently adapted to more application fields, and meanwhile, the pre-tightening mechanism is arranged, so that the piezoelectric driver 7 can be pre-tightened in the mode, and the hidden danger of generating lateral force to endanger the piezoelectric driver 7 is avoided.
As shown in fig. 4 to 6, a groove 91 is formed in one side end surface of the pre-tightening block 9, a steel ball 93 is embedded in the groove 91, one end of the pre-tightening screw is movably abutted against the steel ball 93, a guide post 92 is further arranged on the other side end surface of the pre-tightening block 9, and a through hole for the guide post 92 to pass through is formed in the second force sensor 8. Like this, pretension screw passes pretension screw hole 121, and one end butt in steel ball 93 to this transmission pretension force, the guide post 92 that pretension piece 9 opposite side terminal surface set up with the cooperation of passing through of second force sensor 8, with this provide the direction for pretension piece 9, can improve the stability of pretension.
As shown in fig. 2, the flexible hinge assembly 11 includes a first group of flexible hinges 113 and a second group of flexible hinges 114 sequentially arranged along a direction from the output end 111 to the input end 112, axes of the first group of flexible hinges 113 and the second group of flexible hinges 114 coincide with each other, the piezoelectric actuator 7 is connected with the second group of flexible hinges 114, the strain gauge 3 is attached to the first group of flexible hinges 113, the first force sensor 4 is connected with the first group of flexible hinges 113 and is located between the first group of flexible hinges 113 and the second group of flexible hinges 114, the measuring surface of the first capacitance sensor assembly 5 is connected with the first group of flexible hinges 113, and the measuring surface of the second capacitance sensor assembly 6 is connected with the second group of flexible hinges 114. Thus, through designing two groups of flexible hinges, the two groups of flexible hinges are integrally formed with the flexible mechanism 1, through fixing and guiding the force sensor, the non-axial coupling can be reduced, the axial precision of the flexible hinge assembly 11 is improved, the axial high precision of force measurement is realized, and the control precision of the flexible control process is ensured.
As shown in fig. 7 and 8, the first capacitance sensor assembly 5 comprises a first bracket 51 detachably connected to the compliant mechanism 1, a first capacitance sensor 52 arranged on the first bracket 51, a measuring surface of the first capacitance sensor 52 is connected with a first group of flexible hinges 113, the second capacitance sensor assembly 6 comprises a second bracket 61 detachably connected to the compliant mechanism 1, a second capacitance sensor 62 arranged on the second bracket 61, and a measuring surface of the second capacitance sensor 62 is connected with a second group of flexible hinges 114.
In this embodiment, the first capacitive sensor assembly 5 and the second capacitive sensor assembly 6 are respectively disposed on the side walls of the front and back sides of the compliant mechanism 1 according to the structural features of the compliant mechanism 1, and the relative positions of the first capacitive sensor assembly and the second capacitive sensor assembly correspond to the first set of flexible hinges 113 and the second set of flexible hinges 114, so as to improve the symmetry and the axial precision of the overall structure of the compliant mechanism 1.
As shown in fig. 2 and 6, the first set of flexible hinges 113 are four sets of straight beam type flexible hinges symmetrically arranged on two side walls of the mounting groove, the four sets of straight beam type flexible hinges are connected through a first connecting block, the measuring surface of the first capacitive sensor 52 is connected with the first connecting block, strain gauges 3 are attached to the surface of each set of straight beam type flexible hinges, the second set of flexible hinges 114 are four sets of straight round type flexible hinges symmetrically arranged on two side walls of the mounting groove, the four sets of straight round type flexible hinges are connected through a second connecting block, and the measuring surface of the second capacitive sensor 62 is connected with the second connecting block. In this way, the strain gauge 3 is attached to the surface of the straight beam type flexible hinge, a contact force is generated by the contact of the load 2 and a workpiece, the shape of the strain gauge 3 changes in real time along with the deformation of the surface of the straight beam type flexible hinge through the first group of flexible hinges 113, the resistance value changes, a resistance measurement signal is processed by a circuit and converted into a voltage signal, the voltage signal is reacted to the first group of flexible hinges to transmit the lost force, and at the moment, the strain gauge 3 can measure the actual force by measuring the lost contact force and then passing through the first force sensor 1.
As shown in fig. 1 and 7, the device further comprises two outer reinforcing plates 10 symmetrically arranged at two sides of the compliant mechanism 1 and covering the sliding groove 12, and each outer reinforcing plate 10 is provided with an observation window communicated with the bottom of the sliding groove 12.
That is, given the voltage of the piezoelectric driver 7, the amount of displacement generated and the force that the load 2 can output are F 2, when the contact force generated by the contact of the load 2 with the workpiece to be processed is transmitted to the first force sensor 4 through the first set of flexible hinges 113, the first force sensor 4 displays the contact force F thereof, and the force lost through the first set of flexible hinges 113 is transmitted, which is known as F 1 through the strain gauge 3, and therefore, the corresponding relationship is F 2＝F+F1.
The initial pretightening force can be designed by taking the self rigidity of the first group of flexible hinges 113 and the second group of flexible hinges 114 and the interference between the two groups of flexible hinges as design parameters, and meanwhile, the natural frequency can be designed by taking the coefficient ratio of equivalent rigidity to mass of the output end 111 as the design parameters, so that high-bandwidth servo can be realized.
The specific design process is as follows:
As shown in FIG. 3, the design parameters of the first group of flexible hinges 113 and the second group of flexible hinges 114 of the compliant mechanism 11 define t 1、l1 and t 2、l2, r and h respectively, the input equivalent mass of the compliant mechanism is m 2, the output equivalent mass of the compliant mechanism is m 1, and the rigidity of the single flexible hinge can be calculated according to the hinge design equation in the prior reference Wherein, S=r/t 2. Wherein E is the Young's modulus of the flexible hinge material.
The integral rigidity of the two groups of flexible hinges can be respectively obtained according to the functional principle, wherein the equivalent rigidity of the first group of flexible hinges 113 isThe equivalent stiffness of the second set of flexible hinges 114 is
Assuming that the rigidity of the two groups of flexible hinges is minimum and is K 1、K2 respectively, according to the actual requirement, a value range can be set for the design parameters of the flexible hinges and is respectively expressed as K1：t1.min≤t1≤t1.max;l1.min≤l1≤l1.max;hmin≤h≤hmax;f1.min≤fK2:t2.min≤t2≤t2.max;l2.min≤l2≤l2.max;rmin≤r≤rmax;f2.min≤f, wherein h is min≤h≤hmax
Then, the parameters of the two groups of flexible hinges can be solved by using an optimization tool in MATLAB, so that the proper parameters of t, l, r, h of the flexible hinges can be found. According to the parameters, the rigidity of the two groups of flexible hinges is respectively determined, the deformation x 1、x2 of the two groups of flexible hinges is respectively deduced by the known pretightening force, the interference is x=x 1+x2, and the inherent frequency is used for the two groups of flexible hingesThe equivalent mass of the output end 111 and the input end 112 is determined, and the natural frequency is related to the equivalent mass through a natural frequency formula, so that the natural frequency can be designed, and high-bandwidth servo can be realized.
Example 2
The compliance control method of a compliance control device based on a compliance mechanism according to embodiment 1:
The piezoelectric driver 7 drives the flexible hinge assembly 11 to move and deform under the control of the controller to drive the load 2 to do work to the outside, at the moment, the first force sensor 4 detects the reaction force generated when the flexible hinge assembly 11 drives the load 2 to do work to the outside, the strain gauge 3 detects the force lost by the flexible hinge assembly 11, the first capacitance sensor assembly 5 detects the actual displacement of the output end 111, and the controller adjusts the output voltage of the piezoelectric driver 7 through the data measured by the first force sensor 4, the strain gauge 3 and the first capacitance sensor assembly 5 at the output end 111 to form the full-closed-loop compliant control with the combination of force and displacement;
Semi-closed loop compliance control, wherein a built-in strain gauge 71 detects the displacement of the piezoelectric driver 7 at the input end 112, a second force sensor 8 detects the output force value at the other end of the piezoelectric driver 7, a second capacitance sensor assembly 6 detects the actual displacement of the input end 111, and a controller forms semi-closed loop compliance control combining force and displacement by data detected by the second force sensor 8 and the second capacitance sensor assembly 6 at the input end 112;
the full closed-loop compliant control and the semi-closed-loop compliant control are combined to form redundant compliant control, so that high precision and stability are realized.
It should be noted that, in this embodiment, the full-closed-loop compliance control refers to directly detecting the actual displacement and force value of the output end 111, the semi-closed-loop compliance control refers to directly measuring the actual displacement and force of the input end 112, that is, the actual value generated by the sensor itself, and comprehensively monitoring two parameters of binding force and displacement, so as to accurately regulate and control the output voltage of the piezoelectric driver 7, and thus, complex processing or control requirements can be achieved. When the output force is simply monitored to carry out the compliance control, the piezoelectric ceramics of the piezoelectric driver 7 have the characteristics of hysteresis, creep, nonlinearity and the like, so that the problem can be solved only by forming full closed-loop control, the compliance control can not be realized by simply monitoring displacement, the force and the displacement are required to be simultaneously controlled, and the complex processing or control requirements can be met when the force and the displacement are combined.
Example 3
This embodiment is similar to embodiment 1, except that in this embodiment
As shown in fig. 9, the sensor further comprises a calibration assembly for measuring the actual displacement and output force of the load 2, the calibration assembly comprises a calibration block 21 connected with the load 2, a third capacitance sensor assembly 22 connected with the compliant mechanism 1 and the measurement surface connected with the calibration block 21, and a third force sensor connected with the measurement surface of the load 2, wherein the third capacitance sensor assembly 22 and the third force sensor are respectively connected with a controller.
As shown in fig. 9, the third capacitance sensor assembly 22 includes a third bracket 221 detachably connected to the compliant mechanism 1, a third capacitance sensor 222 disposed on the third bracket 221, and a measuring surface of the third capacitance sensor 222 is connected to the calibration block 21.
It should be noted that the calibration block 21 is configured to calibrate the actual output force and displacement of the load 2, and the third capacitance sensor assembly 22 is configured to detect the displacement of the calibration block 21, so as to verify whether the actual displacement of the load 2 is the same as the displacement of the output end 11 detected by the first capacitance sensor assembly 5. If different, the first capacitive sensor assembly 5 is calibrated. Because the third capacitive sensor assembly 22 is the most direct signal source reflecting the amount of displacement of the output of the final load 2. Meanwhile, the calibration block 21 is connected with a third force sensor, the calibration block 21 is used for calibrating the actual output force of the load 2 and is used as a direct measurement signal source of the force finally output by the flexible control device, so that the calibration is carried out on the measured value of the strain gauge 3 and the measured value of the first force sensor 4, the signal sources of the force and displacement measured by the calibration component correspond to the measured value of the strain gauge 3 and the measured value of the first force sensor 4 one by one, and therefore, even after the signal source of the calibration component is removed, the data which are equivalent to the calibration component can be calculated through the measured value of the strain gauge 3 and the measured value of the first force sensor 4.
Other structures and principles of this embodiment are the same as those of embodiment 1.
It is to be understood that the above examples of the present invention are provided by way of illustration only and not by way of limitation of the embodiments of the present invention. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the invention are desired to be protected by the following claims.
Claims (10)
1. The flexible control device based on the flexible mechanism is characterized by comprising the flexible mechanism (1), wherein one end of the flexible mechanism (1) is provided with an integrally formed flexible hinge assembly (11), the middle part of the flexible mechanism (1) is also provided with a chute (12) communicated with the flexible hinge assembly (11), the central axes of the flexible hinge assembly (11) and the chute (12) are positioned on the same axis of the flexible mechanism (1), one end of the flexible hinge assembly (11) communicated with the chute (12) is an input end (112), the other end of the flexible hinge assembly (11) is an output end (111), and the middle part of the end face of the output end (111) is provided with a load (2) for external work;
The flexible hinge assembly is characterized by further comprising a strain gauge (3) attached to the output end (111), a first force sensor (4) connected with the flexible hinge assembly (11) and used for measuring the reaction force borne by the output end (111), a first capacitance sensor assembly (5) and a second capacitance sensor assembly (6) connected with the flexible mechanism (1) and used for measuring displacement, a measuring surface of the first capacitance sensor assembly (5) is connected with the output end (111), and a measuring surface of the second capacitance sensor assembly (6) is connected with the input end (112);
The piezoelectric device further comprises a piezoelectric driver (7) with a built-in strain gauge (71), one end of the piezoelectric driver (7) is connected with the input end (112), the other end of the piezoelectric driver (7) is connected with a second force sensor (8), and the second force sensor (8) is positioned in the sliding groove (12);
The piezoelectric sensor further comprises a controller, wherein the controller is respectively connected with the strain gauge (3), the first force sensor (4), the first capacitance sensor assembly (5), the second capacitance sensor assembly (6), the built-in strain gauge (71), the piezoelectric driver (7) and the second force sensor (8).
2. The compliant control device based on the compliant mechanism according to claim 1, further comprising a pre-tightening block (9) with two symmetrical ends movably clamped in the sliding groove (12), wherein a pre-tightening screw hole (121) penetrating through the side wall of the compliant mechanism (1) and a pre-tightening screw which is in threaded connection with the pre-tightening screw hole (121) and one end of which is used for being abutted against the pre-tightening block (9) are formed in the bottom of the sliding groove (12), and clamping grooves for the pre-tightening block (9) to move in the sliding groove (12) are symmetrically formed in the inner side wall of the sliding groove (12).
3. The compliant control device based on the compliant mechanism, as set forth in claim 2, is characterized in that a groove (91) is formed in one side end surface of the pre-tightening block (9), a steel ball (93) is embedded in the groove (91), one end of the pre-tightening screw is movably abutted against the steel ball (93), a guide post (92) is further arranged on the other side end surface of the pre-tightening block (9), and a through hole for the guide post (92) to pass through is formed in the second force sensor (8).
4. The compliant control arrangement based on a compliant mechanism according to claim 1, wherein the flexible hinge assembly (11) comprises a first set of flexible hinges (113) and a second set of flexible hinges (114) arranged in sequence along the direction from the output end (111) to the input end (112), axes of the first set of flexible hinges (113) and the second set of flexible hinges (114) coincide with each other, the piezoelectric actuator (7) is connected with the second set of flexible hinges (114), the strain gauge (3) is attached to the first set of flexible hinges (113), the first force sensor (4) is connected with the first set of flexible hinges (113) and is located between the first set of flexible hinges (113) and the second set of flexible hinges (114), the measuring surface of the first capacitance sensor assembly (5) is connected with the first set of flexible hinges (113), and the measuring surface of the second capacitance sensor assembly (6) is connected with the second set of flexible hinges (114).
5. The compliant control arrangement based on a compliant mechanism as claimed in claim 4, wherein the first capacitive sensor assembly (5) comprises a first bracket (51) detachably connected to the compliant mechanism (1), a first capacitive sensor (52) provided on the first bracket (51), a measuring surface of the first capacitive sensor (52) being connected to the first set of flexible hinges (113), the second capacitive sensor assembly (6) comprises a second bracket (61) detachably connected to the compliant mechanism (1), a second capacitive sensor (62) provided on the second bracket (61), a measuring surface of the second capacitive sensor (62) being connected to the second set of flexible hinges (114).
6. The compliant control apparatus based on a compliant mechanism as claimed in claim 5, wherein the first set of flexible hinges (113) is four sets of straight beam type flexible hinges symmetrically arranged, the four sets of straight beam type flexible hinges are connected through a first connecting block, a measuring surface of the first capacitive sensor (52) is connected with the first connecting block, the strain gauge (3) is attached to a surface of each set of straight beam type flexible hinges, the second set of flexible hinges (114) is four sets of straight round type flexible hinges symmetrically arranged, the four sets of straight round type flexible hinges are connected through a second connecting block, and a measuring surface of the second capacitive sensor (62) is connected with the second connecting block.
7. The compliant control apparatus of claim 1, further comprising two outer reinforcing plates (10) symmetrically disposed on two sides of the compliant mechanism (1) and covering the sliding chute (12), wherein each outer reinforcing plate (10) is provided with an observation window communicating with the bottom of the sliding chute (12).
8. A compliance control device based on a compliance mechanism according to claim 1 or 2, further comprising a calibration assembly for measuring the actual displacement and output force of the load (2), the calibration assembly comprising a calibration block (21) connected to the load (2), a third capacitance sensor assembly (22) connected to the compliance mechanism (1) and having a measuring surface connected to the calibration block (21), and a third force sensor having a measuring surface connected to the load (2), the third capacitance sensor assembly (22) and the third force sensor being connected to the controller, respectively.
9. A compliance control device based on a compliance mechanism according to claim 8, characterized in that the third capacitive sensor assembly (22) comprises a third bracket (221) detachably connected to the compliance mechanism (1), a third capacitive sensor (222) provided on the third bracket (221), the measuring surface of the third capacitive sensor (222) being connected to the calibration block (21).
10. A compliance control method of a compliance control device based on a compliance mechanism as claimed in any one of claims 1 to 9, characterized in that:
The piezoelectric actuator (7) drives the flexible hinge assembly (11) to move and deform under the control of the controller, the load (2) is driven to do work on the outside, at the moment, the first force sensor (4) detects the reaction force generated by the flexible hinge assembly (11) when the load (2) is driven to do work outwards, the strain gauge (3) detects the force lost by the flexible hinge assembly (11), the first capacitance sensor assembly (5) detects the actual displacement of the output end (111), and the controller adjusts the output voltage of the piezoelectric actuator (7) through the data measured by the first force sensor (4), the strain gauge (3) and the first capacitance sensor assembly (5) at the output end (111) to form the full-closed-loop flexible control combining the force and the displacement;
The built-in strain gauge (71) detects the displacement of the piezoelectric driver (7) at the input end (112), the second force sensor (8) detects the output force value at the other end of the piezoelectric driver (7), the second capacitance sensor assembly (6) detects the actual displacement of the input end (111), and the controller forms the semi-closed loop compliance control combining force and displacement by the data detected by the second force sensor (8) and the second capacitance sensor assembly (6) at the input end (112);
the full closed-loop compliant control and the semi-closed-loop compliant control are combined to form redundant compliant control, so that high precision and stability are realized.
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| CN104647347A (en) * | 2014-09-26 | 2015-05-27 | 浙江大学 | Flexible hinge amplification-based piezoelectric microgripper |
| CN109713936A (en) * | 2019-03-20 | 2019-05-03 | 杨晓峰 | Elliptical vibration piezoelectric actuator and its driving method |
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| CN109613824A (en) * | 2018-12-13 | 2019-04-12 | 广东工业大学 | A rigid-flexible coupling motion platform driven by a ball screw and a control method |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104647347A (en) * | 2014-09-26 | 2015-05-27 | 浙江大学 | Flexible hinge amplification-based piezoelectric microgripper |
| CN109713936A (en) * | 2019-03-20 | 2019-05-03 | 杨晓峰 | Elliptical vibration piezoelectric actuator and its driving method |
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