A compliant control device based on a compliant mechanism and a compliant control method thereof

Abstract

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

[0001] The present invention relates to the field of robot mechanism and force control, and more specifically, to a compliant control device based on a compliant mechanism and a compliant control method thereof. Background Art

[0002] In the field of mechanical engineering, the study of mechanisms can be divided into the study of rigid mechanisms and the study of non-rigid mechanisms. Among them, compliant mechanisms occupy an important position in the study of non-rigid mechanisms. A compliant mechanism refers to a mechanism that contains one or more flexible units and realizes the transmission or conversion of force, displacement and energy through the elastic deformation of the flexible units. Compared with rigid mechanisms, compliant mechanisms are simple in design, easy to process, assembly-free, gap-free and easy to miniaturize. They can achieve sub-micron or nanometer-level repeated positioning accuracy. They are usually made of a whole piece of material without assembly or lubrication, and are widely used in micro-nano operations, ultra-precision machining and other fields.

[0003] Different application requirements define the functions of compliant mechanisms, which in turn affect the design of the mechanisms. For example, they are applied to three-axis nanopositioning platforms, two-level stiffness micro-nano fixtures, multi-diamond nested large strain mechanisms, double-layer stacked nanopositioners, and other fields... Chinese patent literature discloses a patent for a multi-degree-of-freedom compliant micro-gripper with integrated multi-variable detection, which installs displacement sensors and force sensors on micro-grippers to form a full closed-loop servo of force and displacement, but has problems of low precision and low bandwidth; Chinese patent literature discloses a patent for a piezoelectric-driven cell microinjection device and its adaptive compliant control method, which installs the sensor in a way that increases the natural frequency of the device and makes its working bandwidth higher; but it installs a micro-force sensor at the bottom of the injection needle and integrates a displacement sensor inside the slot to form a servo control method of full closed-loop force and semi-closed-loop displacement, so it still has the problem of low precision. Chinese patent literature discloses a patent for a cell microinjection device and its robust impedance control method, in which a micro-force sensor is installed at the bottom of the microinjection needle, and a displacement sensor integrated inside the piezoelectric driver is used to form a servo control method with a full closed loop of force and a semi-closed loop of displacement. The sensor installation method used results in low working bandwidth and accuracy.

[0004] In summary, most flexible mechanism devices currently use a single position or force signal to achieve control. However, the existing force sensor installation method is difficult to ensure the accuracy of axial fixation, that is, the non-axial coupling is large and the preload force is uncontrollable; the first-order natural frequency of the entire device is low, which is difficult to quantitatively design, resulting in limited bandwidth, lack of quantitative mapping relationship and difficulty in improving; the use of semi-closed-loop servo control method, or full-closed-loop control method of one of displacement and force, the overall force and position control accuracy and stability are not high, the accuracy problems need to be solved, and it cannot meet complex control requirements, and the scope of application is limited. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of low force control accuracy and stability of existing compliant mechanism devices, and to provide a compliant control device based on a compliant mechanism and a compliant control method thereof. The present invention adopts a compliant mechanism to realize compliant control, and realizes a combination of semi-closed-loop compliant control of force and displacement and full-closed-loop compliant control, which has high accuracy, high bandwidth and stability, can meet high-precision and complex control requirements, and is applicable to more precision control fields.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] A compliance control device based on a compliance mechanism comprises a compliance mechanism, wherein one end of the compliance mechanism is provided with an integrally formed flexible hinge assembly, a slide groove connected to the flexible hinge assembly is further provided in the middle of the compliance mechanism, the central axis of the flexible hinge assembly and the slide groove are located on the same axis of the compliance mechanism, one end of the flexible hinge assembly connected to the slide groove is an input end, the other end of the flexible hinge assembly is an output end, and a load for external work is provided in the middle of the end surface of the output end;

[0008] It also includes a strain gauge attached to the output end, a first force sensor connected to the flexible hinge assembly and used to measure the reaction force exerted on the output end, a first capacitive sensor assembly and a second capacitive sensor assembly connected to the compliance mechanism and used to measure the displacement, the measuring surface of the first capacitive sensor assembly is connected to the output end, and the measuring surface of the second capacitive sensor assembly is connected to the input end;

[0009] Also included is a piezoelectric driver with a built-in strain gauge, one end of the piezoelectric driver is connected to the input end, the other end of the piezoelectric driver is connected to a second force sensor, and the second force sensor is located in the slide slot;

[0010] It also includes a controller, which is respectively connected to the strain gauge, the first force sensor, the first capacitive sensor assembly, the second capacitive sensor assembly, the built-in strain gauge, the piezoelectric driver and the second force sensor.

[0011] The present invention also provides a compliance control method of a compliance control device based on a compliance mechanism:

[0012] Fully closed-loop compliance control: Under the control of the controller, the piezoelectric driver drives the flexible hinge assembly to move and deform, driving the load to do work on the outside. The first force sensor detects the reaction force generated by the flexible hinge assembly when driving the load to do work on the outside, and transmits the value between the output end and the input end. The strain gauge detects the force lost by the flexible hinge assembly. The first capacitive sensor assembly detects the actual displacement of the output end. The controller adjusts the output voltage of the piezoelectric driver through the data measured by the first force sensor, the strain gauge, and the first capacitive sensor assembly at the output end, forming a fully closed-loop compliance control combining force and displacement.

[0013] Semi-closed loop compliance control: The built-in strain gauge detects the elongation of the piezoelectric driver, the second force sensor detects the output force value at the other end of the piezoelectric driver, and the second capacitive sensor assembly detects the actual displacement at the input end. The controller forms a semi-closed loop compliance control combining force and displacement through the data measured by the second force sensor and the second capacitive sensor assembly at the input end;

[0014] The full closed-loop compliance control is combined with the semi-closed-loop compliance control to form redundant compliance control, achieving high precision and stability.

[0015] It should be noted that the full-closed-loop compliance control in the present invention mainly refers to directly detecting the actual displacement and force value of the output end, and the semi-closed-loop compliance control mainly refers to directly measuring the actual displacement and force of the input end, that is, the real value generated by the sensor itself, combining the two parameters of force and displacement for comprehensive monitoring, and accurately regulating the output voltage of the piezoelectric driver in the present invention, which can achieve complex processing or control requirements; the purpose of combining the full-closed-loop compliance control with the semi-closed-loop compliance control to form a redundant compliance control is: if the piezoelectric driver is input with a fixed voltage, there will be control errors if the control is achieved by simply monitoring the output force or displacement, and the output force cannot be controlled with high precision. When the compliance control is performed by simply monitoring the output force, because the piezoelectric ceramics of the piezoelectric driver have the characteristics of hysteresis, creep, and nonlinearity, only the formation of a full-closed-loop control can solve the problem; and the compliance control cannot be performed by simply monitoring the displacement, and the force and displacement must be controlled at the same time. When the force and displacement are combined, the complex processing or control requirements can be met.

[0016] Furthermore, it also includes a pre-tightening block that is symmetrically and movably engaged in the slide groove at both ends, a pre-tightening screw hole that penetrates the side wall of the flexible mechanism is opened at the bottom of the slide groove, and a pre-tightening screw that is threadedly connected to the pre-tightening screw hole and one end is used to abut the pre-tightening block, and the inner side wall of the slide groove is symmetrically provided with a slot for the pre-tightening block to move in the slide groove.

[0017] It should be noted that a pre-tightening block is added to the compliant mechanism. The pre-tightening block can move in the slot under the pressure of the pre-tightening screw, and transmit the pre-tightening force to the piezoelectric driver. In this way, an initial pre-tightening force can be applied to the piezoelectric driver through the pre-tightening screw, and the initial pre-tightening force is controllable, which can facilitate the compliant control device of the present invention to adapt to more application fields. At the same time, a pre-tightening mechanism is provided, which can avoid the generation of lateral force and endanger the hidden danger of the piezoelectric driver while pre-tightening the piezoelectric driver in this way.

[0018] Furthermore, a groove is provided on one end face of the pre-tightening block, a steel ball is embedded in the groove, and one end of the pre-tightening screw is movably in contact with the steel ball; a guide column is also provided on the other end face of the pre-tightening block, and a through hole is provided on the second force sensor for the guide column to pass through. In this way, the pre-tightening screw passes through the pre-tightening screw hole, and one end of the pre-tightening screw abuts against the steel ball to transmit the pre-tightening force. The guide column provided on the other end face of the pre-tightening block cooperates with the second force sensor to provide guidance for the pre-tightening block, which can improve the stability of the pre-tightening.

[0019] Furthermore, the flexible hinge assembly includes a first group of flexible hinges and a second group of flexible hinges arranged in sequence 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 overlap each other, the piezoelectric driver is connected to the second group of flexible hinges, the strain gauge is attached to the first group of flexible hinges, the first force sensor is connected to 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 capacitive sensor assembly is connected to the first group of flexible hinges, and the measuring surface of the second capacitive sensor assembly is connected to the second group of flexible hinges. In this way, by designing two groups of flexible hinges, both are integrally formed with the compliance mechanism, and by fixing and guiding the force sensor, the non-axial coupling can be reduced, the axial accuracy of the flexible hinge assembly can be improved, the axial high accuracy of the force measurement can be achieved, and the control accuracy of the compliance control process can be guaranteed.

[0020] It should also be noted that the initial preload can be designed using the inherent stiffness of the first set of flexible hinges and the second set of flexible hinges, as well as the interference between the two sets of flexible hinges as design parameters; at the same time, the natural frequency can be designed using the equivalent stiffness-mass coefficient ratio at the output end as a design parameter to achieve high-bandwidth servo.

[0021] Furthermore, the first capacitive sensor assembly includes a first bracket detachably connected to the flexible mechanism, a first capacitive sensor disposed on the first bracket, and a measuring surface of the first capacitive sensor is connected to a first group of flexible hinges; the second capacitive sensor assembly includes a second bracket detachably connected to the flexible mechanism, a second capacitive sensor disposed on the second bracket, and a measuring surface of the second capacitive sensor is connected to a second group of flexible hinges.

[0022] It should be noted that the first capacitive sensor assembly and the second capacitive sensor assembly can be adaptably arranged on the front and back side walls of the compliant mechanism according to the structural characteristics of the compliant mechanism, and their relative positions correspond to the first group of flexible hinges and the second group of flexible hinges, respectively, thereby improving the overall structural symmetry and axial accuracy of the compliant mechanism.

[0023] Furthermore, the first group of flexible hinges are four groups of straight beam type flexible hinges arranged symmetrically, the four groups of straight beam type flexible hinges are connected by a first connecting block, the measuring surface of the first capacitance sensor is connected to the first connecting block, and the surface of each group of straight beam type flexible hinges is attached with a strain gauge; the second group of flexible hinges are four groups of straight round type flexible hinges arranged symmetrically, the four groups of straight round type flexible hinges are connected by a second connecting block, and the measuring surface of the second capacitance sensor is connected to the second connecting block. In this way, the strain gauge is attached to the surface of the straight beam type flexible hinge, and the contact force is generated by contacting the workpiece through the load. After passing through the first group of flexible hinges, the shape of the strain gauge changes in real time with the deformation of the surface of the straight beam type flexible hinge, causing the resistance value to change. The resistance measurement signal is processed by the circuit and converted into a voltage signal, which reflects the force lost by the first group of flexible hinges. At this time, the strain gauge can measure the lost contact force, and then pass through the first force sensor to measure the actual force.

[0024] Furthermore, it also includes two outer reinforcement plates symmetrically arranged on both sides of the flexible mechanism and covering the slide groove, and each outer reinforcement plate is provided with an observation window connected to the bottom of the slide groove.

[0025] Furthermore, it also includes a calibration component for measuring the actual displacement and output force of the load, the calibration component includes a calibration block connected to the load, a third capacitive sensor component connected to the compliance mechanism and having a measuring surface connected to the calibration block, and a third force sensor having a measuring surface connected to the load, the third capacitive sensor component and the third force sensor are respectively connected to the controller.

[0026] Furthermore, the third capacitive sensor assembly includes a third bracket detachably connected to the compliant mechanism, a third capacitive sensor disposed on the third bracket, and a measuring surface of the third capacitive sensor connected to the calibration block.

[0027] It should be noted that the calibration block is set to calibrate the actual output force and displacement of the load, and the third capacitance sensor assembly is used to detect the displacement of the calibration block, the purpose of which is to verify whether the actual displacement of the load is the same as the output end displacement detected by the first capacitance sensor assembly. If different, the first capacitance sensor assembly is calibrated. Because the third capacitance sensor assembly is the most direct signal source that reflects the final load output displacement. At the same time, the calibration block is connected to the third force sensor, and the calibration block is calibrated for the actual output force of the load, as a direct measurement signal source of the force ultimately output by the compliance control device, thereby calibrating the measured values ​​of the strain gauge and the first force sensor. The signal source of the force and displacement measured by the calibration assembly corresponds one-to-one to the measured values ​​of the strain gauge and the first force sensor. In this way, even after the signal source of the calibration assembly is removed, the measured values ​​of the strain gauge and the first force sensor can be used to calculate data equivalent to the calibration assembly.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention designs the structure of the compliant mechanism, configures detection elements for detecting force and displacement, and realizes high-precision control of the piezoelectric driver through unified regulation by a controller, which can meet complex processing or control requirements. The present invention combines full-closed-loop compliant control with semi-closed-loop compliant control, and comprehensively monitors the two parameters of force and displacement to form redundant compliant control, thereby achieving high precision and stability.

[0030] (2) Based on the flexible control of mixed force and displacement with high precision, high bandwidth, and long-lasting stability, the present invention can be applied to scientific research fields of mixed force and displacement control such as micro-nanoscale electromechanical systems and nanoimprinting. It can also be applied to industrial applications of force interaction such as cutting, milling, grinding, drilling, and polishing with micro-nanoprecision and high-bandwidth servo, such as tool servo worktables of ultra-precision machining machines and nanoimprinting worktables. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is an exploded view of Example 1;

[0032] Figure 2 Schematic diagram of the planar structure of the compliant mechanism in Example 1;

[0033] Figure 3 Schematic diagram of parameter identification of the compliant mechanism in Example 1;

[0034] Figure 4 This is a schematic diagram of the structure of the pre-tightening block in Example 1;

[0035] Figure 5 This is a schematic structural diagram of the pre-tightening block in Embodiment 1 from another perspective;

[0036] Figure 6 This is a schematic diagram of the internal connections of the compliant mechanism in Example 1;

[0037] Figure 7 This is a connection diagram of the first capacitive sensor assembly of Example 1;

[0038] Figure 8 This is a connection diagram of the second capacitive sensor assembly of Example 1;

[0039] Fig. 9 This is a schematic diagram of the structure of Example 3.

[0040] The illustrations are as follows:

[0041] 1-compliant mechanism, 11-flexible hinge assembly, 111-output end, 112-input end, 113-first group of flexible hinges, 114-second group of flexible hinges, 12-slideway, 121-pretightening screw hole, 2-load, 21-calibration block, 22-third capacitance sensor assembly, 221-third bracket, 222-third capacitance sensor, 3-strain gauge, 4-first force sensor, 5-first capacitance sensor assembly, 51-first bracket, 52-first capacitance sensor, 6-second capacitance sensor assembly, 61-second bracket, 62-second capacitance sensor, 7-piezoelectric driver, 71-built-in strain gauge, 8-second force sensor, 9-pretightening block, 91-groove, 92-guide column, 93-steel ball, 10-reinforcement plate. DETAILED DESCRIPTION

[0042] The present invention is further described below in conjunction with specific implementation methods. The accompanying drawings are only used for exemplary descriptions and are only schematic diagrams, not actual drawings, and cannot be understood as limiting this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted.

[0043] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the drawings, it is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limitations on this patent. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0044] Example 1

[0045] like Figure 1 to Figure 2 As shown, a compliance control device based on a compliance mechanism comprises a compliance mechanism 1, one end of the compliance mechanism 1 is provided with an integrally formed flexible hinge component 11, a slide groove 12 connected to the flexible hinge component 11 is further provided in the middle of the compliance mechanism 1, the central axis of the flexible hinge component 11 and the slide groove 12 are located on the same axis of the compliance mechanism 1, one end of the flexible hinge component 11 connected to the slide groove 12 is an input end 112, the other end of the flexible hinge component 11 is an output end 111, and a load 2 for external work is provided in the middle of the end surface of the output end 111;

[0046] like Figure 1 and Figure 6As shown, it also includes a strain gauge 3 attached to the output end 111, a first force sensor 4 connected to the flexible hinge assembly 11 and used to measure the reaction force exerted on the output end 111, a first capacitive sensor assembly 5 and a second capacitive sensor assembly 6 connected to the compliant mechanism 1 and used to measure the displacement, the measuring surface of the first capacitive sensor assembly 5 is connected to the output end 111, and the measuring surface of the second capacitive sensor assembly 6 is connected to the input end 112;

[0047] like Figure 6 As shown, it also includes a piezoelectric driver 7 with a built-in strain gauge 71, one end of the piezoelectric driver 7 is connected to the input end 112, and the other end of the piezoelectric driver 7 is connected to a second force sensor 8, and the second force sensor 8 is located in the slide slot 12;

[0048] It also includes a controller, which is respectively connected to the strain gauge 3, the first force sensor 4, the first capacitive sensor assembly 5, the second capacitive sensor assembly 6, the built-in strain gauge 71, the piezoelectric driver 7 and the second force sensor 8.

[0049] like Figure 1 and Figure 6 As shown, it also includes a pre-tightening block 9 with both ends symmetrically and movably engaged in the slide groove 12, a pre-tightening screw hole 121 penetrating the side wall of the compliance mechanism 1 is opened at the bottom of the slide groove 12, and a pre-tightening screw threadedly connected to the pre-tightening screw hole 121 and one end of which is used to abut the pre-tightening block 9, and the inner side wall of the slide groove 12 is symmetrically provided with a slot for the pre-tightening block 9 to move in the slide groove 12.

[0050] A pre-tightening block 9 is added to the compliance mechanism 1. The pre-tightening block 9 can move in the slot under the pressure of the pre-tightening screw to transfer the pre-tightening force to the piezoelectric driver 7. In this way, an initial pre-tightening force can be applied to the piezoelectric driver 7 through the pre-tightening screw, and the initial pre-tightening force is controllable, which can facilitate the compliance control device to adapt to more application fields. At the same time, a pre-tightening mechanism is provided, which can avoid the hidden danger of lateral force endangering the piezoelectric driver 7 while pre-tightening the piezoelectric driver 7 in this way.

[0051] like Figures 4 to 6 As shown, a groove 91 is provided on one end face of the pre-tightening block 9, a steel ball 93 is embedded in the groove 91, and one end of the pre-tightening screw is movably abutted against the steel ball 93; a guide column 92 is also provided on the other end face of the pre-tightening block 9, and a through hole is provided on the second force sensor 8 for the guide column 92 to pass through. In this way, the pre-tightening screw passes through the pre-tightening screw hole 121, and one end abuts against the steel ball 93 to transmit the pre-tightening force, and the guide column 92 provided on the other end face of the pre-tightening block 9 cooperates with the second force sensor 8 to provide guidance for the pre-tightening block 9, which can improve the stability of the pre-tightening.

[0052] like Figure 2As shown, the flexible hinge assembly 11 includes a first group of flexible hinges 113 and a second group of flexible hinges 114 arranged in sequence along the direction from the output end 111 to the input end 112, the axes of the first group of flexible hinges 113 and the second group of flexible hinges 114 coincide with each other, the piezoelectric driver 7 is connected to 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 to 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 capacitive sensor assembly 5 is connected to the first group of flexible hinges 113, and the measuring surface of the second capacitive sensor assembly 6 is connected to the second group of flexible hinges 114. In this way, by designing two groups of flexible hinges, both are integrally formed with the compliance mechanism 1, and by fixing and guiding the force sensor, the non-axial coupling can be reduced, the axial accuracy of the flexible hinge assembly 11 can be improved, the axial high accuracy of the force measurement can be achieved, and the control accuracy of the compliance control process can be guaranteed.

[0053] like Figure 7 and Figure 8 As shown, the first capacitive sensor assembly 5 includes a first bracket 51 detachably connected to the flexible mechanism 1, a first capacitive sensor 52 arranged on the first bracket 51, and a measuring surface of the first capacitive sensor 52 is connected to the first group of flexible hinges 113; the second capacitive sensor assembly 6 includes a second bracket 61 detachably connected to the flexible mechanism 1, a second capacitive sensor 62 arranged on the second bracket 61, and a measuring surface of the second capacitive sensor 62 is connected to the second group of flexible hinges 114.

[0054] In this embodiment, the first capacitive sensor assembly 5 and the second capacitive sensor assembly 6 are respectively arranged on the front and back side walls of the compliant mechanism 1 according to the structural characteristics of the compliant mechanism 1, and the relative positions correspond to the first group of flexible hinges 113 and the second group of flexible hinges 114, thereby improving the overall structural symmetry and axial accuracy of the compliant mechanism 1.

[0055] like Figure 2 and Figure 6As shown, the first group of flexible hinges 113 are four groups of straight beam type flexible hinges symmetrically arranged on the side walls of the placement groove, the four groups of straight beam type flexible hinges are connected by the first connection block, the measuring surface of the first capacitance sensor 52 is connected to the first connection block, and the surface of each group of straight beam type flexible hinges is attached with a strain gauge 3; the second group of flexible hinges 114 are four groups of straight round type flexible hinges symmetrically arranged on the side walls of the placement groove, the four groups of straight round type flexible hinges are connected by the second connection block, and the measuring surface of the second capacitance sensor 62 is connected to the second connection block. In this way, the strain gauge 3 is attached to the surface of the straight beam type flexible hinge, and the contact force is generated by contacting the workpiece through the load 2. After passing through the first group of flexible hinges 113, the shape of the strain gauge 3 changes in real time with the deformation of the surface of the straight beam type flexible hinge, causing the resistance value to change. The resistance measurement signal is processed by the circuit and converted into a voltage signal, which reflects the force lost by the first group of flexible hinges. At this time, the strain gauge 3 can measure the lost contact force, and then pass through the first force sensor 1 to measure the actual force.

[0056] like Figure 1 and Figure 7 As shown, it also includes two outer reinforcing plates 10 symmetrically arranged on both sides of the flexible mechanism 1 and covering the slide groove 12, and each outer reinforcing plate 10 is provided with an observation window connected to the bottom of the slide groove 12.

[0057] That is, the displacement generated by the voltage given by the piezoelectric driver 7 and the force that the load 2 can output is F2. When the load 2 contacts the workpiece, the contact force generated is transmitted to the first force sensor 4 through the first group of flexible hinges 113. The first force sensor 4 displays its contact force F. The force lost by the transmission through the first group of flexible hinges 113 is known to be F1 through the strain gauge 3. Therefore, the corresponding relationship is F2=F+F1.

[0058] That is, the initial preload force can be designed using the inherent stiffness of the first group of flexible hinges 113 and the second group of flexible hinges 114, as well as the interference between the two groups of flexible hinges as design parameters; at the same time, the natural frequency can be designed using the equivalent stiffness-mass coefficient ratio of the output end 111 as a design parameter to achieve high-bandwidth servo.

[0059] The specific design process is as follows:

[0060] like Figure 3 As shown, the design parameters of the first group of flexible hinges 113 of the compliant mechanism 11 are defined as t1, l1, and h, respectively, and the design parameters of the second group of flexible hinges 114 are defined as t2, l2, r, and h, respectively; the input equivalent mass of the compliant mechanism is m2, and the output equivalent mass is m1; according to the hinge design equation in the existing references, the stiffness of a single flexible hinge can be calculated respectively in, s = r / t2, where E is the Young's modulus of the flexible hinge material.

[0061] The overall stiffness of the two groups of flexible hinges can be calculated based on the functional principle: the equivalent stiffness of the first group of flexible hinges 113 is The equivalent stiffness of the second set of flexible hinges 114 is

[0062] Assume that the stiffness of the two sets of flexible hinges is the smallest, namely K1 and K2; according to actual needs, a value range can be set for the design parameters of the flexible hinges, which are expressed as K1:t 1.min ≤t1≤t 1.max ; l 1.min ≤l1≤l 1.max ;h min ≤h≤h max ; f1. min ≤fK2:t 2.min ≤t2≤t 2.max ; l 2.min ≤l2≤l 2.max ; r min ≤r≤r max ;f 2.min ≤f where: h min ≤h≤h max

[0063] Then, the optimization tool in MATLAB can be used to solve the parameters of the two sets of flexible hinges respectively, and find the appropriate parameters of t, l, r, and h of the flexible hinges. According to the parameters, the stiffness of the two sets of flexible hinges is determined respectively, and then the deformation x1 and x2 of the two sets of flexible hinges are derived respectively from the known preload, so the interference is x = x1 + x2; from the natural frequency The equivalent masses of the output terminal 111 and the input terminal 112 are determined. It can be known from the natural frequency formula that the natural frequency is related to the equivalent mass. The natural frequency can be designed to achieve high-bandwidth servo.

[0064] Example 2

[0065] A compliance control method of a compliance control device based on a compliance mechanism as described in Example 1:

[0066] Fully closed-loop compliance control: The piezoelectric driver 7 drives the flexible hinge assembly 11 to move and deform under the control of the controller, driving the load 2 to do work on the outside. At this time, the first force sensor 4 detects the reaction force generated by the flexible hinge assembly 11 when driving the load 2 to do work on the outside, the strain gauge 3 detects the force lost by the transmission of the flexible hinge assembly 11, and the first capacitive sensor assembly 5 detects the actual displacement of the output end 111. 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 capacitive sensor assembly 5 at the output end 111, forming a fully closed-loop compliance control combining force and displacement;

[0067] Semi-closed loop compliance control: 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, and the second capacitive sensor assembly 6 detects the actual displacement of the input end 111. The controller forms a semi-closed loop compliance control combining force and displacement through the data measured by the second force sensor 8 and the second capacitive sensor assembly 6 at the input end 112;

[0068] The full closed-loop compliance control is combined with the semi-closed-loop compliance control to form redundant compliance control, achieving high precision and stability.

[0069] It should be noted that the full-closed-loop compliance control in this embodiment refers to directly detecting the actual displacement and force value of the output end 111, and the semi-closed-loop compliance control mainly refers to directly measuring the actual displacement and force of the input end 112, that is, the real value generated by the sensor itself, combining the two parameters of force and displacement for comprehensive monitoring, and accurately regulating the output voltage of the piezoelectric driver 7, which can achieve complex processing or control requirements; the purpose of combining the full-closed-loop compliance control with the semi-closed-loop compliance control to form a redundant compliance control is: if the piezoelectric driver 7 is input with a fixed voltage, there will be control errors if the control is achieved by simply monitoring the output force or displacement, and the output force cannot be controlled with high precision. When the compliance control is performed by simply monitoring the output force, because the piezoelectric ceramics of the piezoelectric driver 7 have characteristics such as hysteresis, creep, and nonlinearity, only the formation of a full-closed-loop control can solve the problem; simply monitoring the displacement cannot achieve compliance control, and the force and displacement must be controlled at the same time. When the force and displacement are combined, complex processing or control requirements can be met.

[0070] Example 3

[0071] This embodiment is similar to Embodiment 1, except that

[0072] like Fig. 9As shown, it also includes a calibration component for measuring the actual displacement and output force of the load 2, the calibration component includes a calibration block 21 connected to the load 2, a third capacitive sensor component 22 connected to the compliance mechanism 1 and with the measuring surface connected to the calibration block 21, and a third force sensor with the measuring surface connected to the load 2, and the third capacitive sensor component 22 and the third force sensor are respectively connected to the controller.

[0073] like Fig. 9 As shown, the third capacitive sensor assembly 22 includes a third bracket 221 detachably connected to the compliance mechanism 1 , a third capacitive sensor 222 disposed on the third bracket 221 , and a measuring surface of the third capacitive sensor 222 connected to the calibration block 21 .

[0074] It should be noted that the calibration block 21 is set to calibrate the actual output force and displacement of the load 2, and the third capacitive sensor assembly 22 is used to detect the displacement of the calibration block 21, the purpose is 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 capacitive 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 final output displacement of the load 2. At the same time, the calibration block 21 is connected to the third force sensor, and the calibration block 21 is calibrated for the actual output force of the load 2, as a direct measurement signal source of the force finally output by the compliance control device, so as to calibrate the measured values ​​of the strain gauge 3 and the first force sensor 4. The signal source of the force and displacement measured by the calibration assembly corresponds to the measured values ​​of the strain gauge 3 and the first force sensor 4 one by one. In this way, even after the signal source of the calibration assembly is removed, the measured values ​​of the strain gauge 3 and the first force sensor 4 can be calculated to be equivalent to the data of the calibration assembly.

[0075] The other structures and principles of this embodiment are the same as those of Embodiment 1.

[0076] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A compliance control device based on a compliance mechanism, characterized in that: The compliant mechanism (1) comprises a compliant mechanism (1), one end of which is provided with an integrally formed flexible hinge assembly (11), a slide groove (12) connected to the flexible hinge assembly (11) is also provided in the middle of the compliant mechanism (1), the central axis of the flexible hinge assembly (11) and the slide groove (12) are located on the same axis of the compliant mechanism (1), one end of the flexible hinge assembly (11) connected to the slide groove (12) is an input end (112), the other end of the flexible hinge assembly (11) is an output end (111), and a load (2) for external work is provided in the middle of the end surface of the output end (111); It also includes a strain gauge (3) attached to the output end (111), a first force sensor (4) connected to the flexible hinge assembly (11) and used to measure the reaction force exerted on the output end (111), a first capacitance sensor assembly (5) and a second capacitance sensor assembly (6) connected to the compliant mechanism (1) and used to measure the displacement, wherein the measurement surface of the first capacitance sensor assembly (5) is connected to the output end (111), and the measurement surface of the second capacitance sensor assembly (6) is connected to the input end (112); It also includes a piezoelectric driver (7) with a built-in strain gauge (71), one end of the piezoelectric driver (7) is connected to the input end (112), and the other end of the piezoelectric driver (7) is connected to a second force sensor (8), and the second force sensor (8) is located in the slide groove (12); It also includes a controller, which is respectively connected to the strain gauge (3), the first force sensor (4), the first capacitive sensor assembly (5), the second capacitive sensor assembly (6), the built-in strain gauge (71), the piezoelectric driver (7) and the second force sensor (8).

2. A compliance control device based on a compliance mechanism according to claim 1, characterized in that: It also includes a pre-tightening block (9) with two ends symmetrically movably engaged in the slide groove (12); a pre-tightening screw hole (121) penetrating the side wall of the compliant mechanism (1) is provided at the bottom of the slide groove (12); and a pre-tightening screw is threadedly connected to the pre-tightening screw hole (121) and one end of the pre-tightening screw is used to abut against the pre-tightening block (9); and the inner side wall of the slide groove (12) is symmetrically provided with a slot for allowing the pre-tightening block (9) to move in the slide groove (12).

3. A compliance control device based on a compliance mechanism according to claim 2, characterized in that: A groove (91) is provided on one end surface of the pre-tightening block (9), a steel ball (93) is embedded in the groove (91), and one end of the pre-tightening screw is movably in contact with the steel ball (93); a guide column (92) is also provided on the other end surface of the pre-tightening block (9), and a through hole is provided on the second force sensor (8) for the guide column (92) to pass through.

4. A compliance control device based on a compliance mechanism according to claim 1, characterized in that: The flexible hinge assembly (11) comprises a first group of flexible hinges (113) and a second group of flexible hinges (114) which are arranged in sequence along the direction from the output end (111) to the input end (112); the axes of the first group of flexible hinges (113) and the second group of flexible hinges (114) coincide with each other; the piezoelectric driver (7) is connected to 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 to 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 capacitive sensor assembly (5) is connected to the first group of flexible hinges (113); and the measuring surface of the second capacitive sensor assembly (6) is connected to the second group of flexible hinges (114).

5. A compliance control device based on a compliance mechanism according to claim 4, characterized in that: The first capacitive sensor assembly (5) comprises a first bracket (51) detachably connected to the compliant mechanism (1), a first capacitive sensor (52) disposed on the first bracket (51), and a measuring surface of the first capacitive sensor (52) is connected to the first group 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) disposed on the second bracket (61), and a measuring surface of the second capacitive sensor (62) is connected to the second group of flexible hinges (114).

6. A compliance control device based on a compliance mechanism according to claim 5, characterized in that: The first group of flexible hinges (113) are four groups of straight beam type flexible hinges arranged symmetrically, the four groups of straight beam type flexible hinges are connected via a first connecting block, the measuring surface of the first capacitive sensor (52) is connected to the first connecting block, and the strain gauge (3) is attached to the surface of each group of straight beam type flexible hinges; the second group of flexible hinges (114) are four groups of straight circular type flexible hinges arranged symmetrically, the four groups of straight circular type flexible hinges are connected via a second connecting block, and the measuring surface of the second capacitive sensor (62) is connected to the second connecting block.

7. A compliance control device based on a compliance mechanism according to claim 1, characterized in that: It also includes two outer reinforcement plates (10) symmetrically arranged on both sides of the compliant mechanism (1) and covering the slide groove (12), and each outer reinforcement plate (10) is provided with an observation window connected to the bottom of the slide groove (12).

8. A compliance control device based on a compliance mechanism according to claim 1 or 2, characterized in that: It also includes a calibration component for measuring the actual displacement and output force of the load (2), the calibration component including a calibration block (21) connected to the load (2), a third capacitive sensor component (22) connected to the compliant 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 capacitive sensor component (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 compliant mechanism (1), a third capacitive sensor (222) disposed on the third bracket (221), and a measuring surface of the third capacitive sensor (222) connected to the calibration block (21).

10. A compliance control method of a compliance control device based on a compliance mechanism according to any one of claims 1 to 9, characterized in that: Fully closed-loop compliance control: under the control of the controller, the piezoelectric driver (7) drives the flexible hinge component (11) to move and deform, thereby driving the load (2) to perform work on the outside. At this time, the first force sensor (4) detects the reaction force generated by the flexible hinge component (11) when driving the load (2) to perform work on the outside. The strain gauge (3) detects the force lost by the transmission of the flexible hinge component (11). The first capacitive sensor component (5) detects the actual displacement of the output end (111). The controller adjusts the output voltage of the piezoelectric driver (7) based on the data measured by the first force sensor (4), the strain gauge (3) and the first capacitive sensor component (5) at the output end (111), thereby forming a fully closed-loop compliance control combining force and displacement. Semi-closed loop compliance control: 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 of the other end of the piezoelectric driver (7), the second capacitive sensor assembly (6) detects the actual displacement of the input end (111), and the controller forms a semi-closed loop compliance control combining force and displacement through the data measured by the second force sensor (8) and the second capacitive sensor assembly (6) at the input end (112); The full closed-loop compliance control is combined with the semi-closed-loop compliance control to form redundant compliance control, achieving high precision and stability.

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