A rigid-flexible coupled electric drive grinding end effector

Abstract

The present invention discloses a rigid-flexible coupled electric drive grinding end effector, which includes a support assembly, a linear electric drive assembly, a grinding assembly, and a rigid-flexible coupling assembly; wherein, the rigid-flexible coupling assembly includes expandable honeycomb structures distributed around the end effector, and the expandable honeycomb structures can expand or contract as the end effector moves; the expandable honeycomb structures are designed based on stiffness enhancement and are formed by an array of several nested sub-cell units. Each nested sub-cell unit includes an outer sub-cell and an inner sub-cell. The inner sub-cell is nested inside the outer sub-cell and is connected to the outer sub-cell at the upper and lower ends; the outer sub-cell is integrally formed by four special-shaped units, so that the shape of the outer sub-cell in the front view of the nested sub-cell unit is butterfly-shaped; the inner sub-cell is a classic concave hexagon structure and is integrally formed by four angled plates; by changing the structural parameters of the nested sub-cell unit, the Young's modulus is changed, and thus the stiffness of the end effector is changed. This end effector is driven by a voice coil motor and has higher control accuracy and response speed compared with pneumatic drive; due to the presence of the rigid-flexible coupling assembly, it has higher stiffness and certain flexibility, and can effectively solve the problems of machining vibration caused by low stiffness and increased control difficulty caused by force overshoot.

Description

Technical Field

[0001] The present invention belongs to the technical field of automated grinding equipment, and particularly relates to a rigid-flexible coupled electric-driven grinding end effector, which has the characteristics of high precision, fast response, and rigid-flexible coupling. Background Art

[0002] Parts after various welding repairs need to be ground to ensure the integrity of the repair process. Grinding can eliminate surface defects of parts and ensure dimensional accuracy. However, traditional manual grinding has high costs, cannot guarantee accuracy, and has low safety; machine tool grinding has high accuracy, but poor adaptability and high costs. Robot grinding, with its high flexibility, has become the primary means to reduce costs and increase efficiency in grinding and polishing. Grinding and polishing can not only eliminate surface defects of parts and ensure dimensional accuracy, but also improve the surface finish of workpieces, increase surface hardness, and extend service life.

[0003] Workpieces with characteristics such as high hardness, high wear resistance, and complex shapes are difficult to perform precision grinding and polishing, and are prone to problems such as vibration, thus reducing machining accuracy. Robot grinding and polishing are achieved by installing grinding and polishing tools on the end effector, and the control of the grinding path and grinding force is realized by separately controlling the robot and the end effector. Since the robot and the end effector as a whole are in a series mechanism, the low stiffness characteristic is prone to cause machining vibration; excessive rigidity will cause force overshoot problems, increasing the difficulty of force control.

[0004] Patent applications with application numbers 202010029488.6 and 202011356093.3 respectively disclose a grinding force control end effector device and a pneumatic compliant grinding end effector. These two end effectors have similar principles, both using cylinders as driving elements and realizing force control grinding based on a servo control system, effectively reducing installation errors and path planning errors. However, the stiffness of the end effector is relatively low, prone to causing machining vibration; although the cylinder has servo control and can achieve closed-loop feedback of the grinding force, the cylinder has problems such as piston friction and unstable air supply, and the control has time lag, resulting in insufficient accuracy and affecting the grinding quality. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a rigid-flexible coupled electric-driven grinding end effector.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] A rigid-flexible coupled electric drive grinding end effector, comprising a support assembly, a linear electric drive assembly and a grinding assembly; characterized in that the end effector further comprises a rigid-flexible coupling assembly, the rigid-flexible coupling assembly comprising a stretchable honeycomb structure distributed around the end effector, and the stretchable honeycomb structure can stretch or contract with the movement of the end effector; the stretchable honeycomb structure is formed by an array of several nested sub-cell units, each nested sub-cell unit comprising an outer sub-cell and an inner sub-cell, the inner sub-cell being nested inside the outer sub-cell and connected to the outer sub-cell at the upper and lower ends; the outer sub-cell is integrally formed by four special-shaped units, so that the shape of the outer sub-cell in the front view of the nested sub-cell unit is butterfly-shaped; each special-shaped unit comprises a Z-shaped plate-like part and an L-shaped plate-like part, the side of the Z-shaped plate-like part in the front view of the nested sub-cell unit is composed of line segments IJ, JK and KA, and line segments IJ and KA are parallel; the side of the L-shaped plate-like part in the front view of the nested sub-cell unit is composed of line segments AB and BC, and line segment AB is perpendicular to line segment KA; the inner sub-cell is integrally formed by four angled plates, and the side of the angled plate in the front view of the nested sub-cell unit is composed of line segments HG and GD, line segment HG is parallel to line segments IJ and KA, and line segment GD is parallel to line segment BC.

[0008] Furthermore, by changing the structural parameters of the nested sub-cell unit, the Young's modulus is changed, and thus the stiffness of the end effector is changed; among them, the Young's modulus E1 of the outer sub-cell is:

[0009]

[0010]

[0011] The Young's modulus E2 of the inner sub-cell is:

[0012]

[0013] The Young's modulus E of the nested sub-cell unit is:

[0014] E = E1 + E2 (8)

[0015] In the formula, F1 is the load received by the outer sub-cell, l * and A * are respectively the equivalent length and equivalent area of the nested sub-cell unit, △ y1 is the displacement of the outer sub-cell in the force direction, ar1, ar2 are the lengths of line segments AB and BC, θ is the angle between line segment BC and the upper and lower center lines of the outer sub-cell, al3 / 2, al2 and al1 are the lengths of line segments IJ, JK and KA, α is the angle between line segment JK and KA, δ is the wall thickness of the inner sub-cell, E0 is the Young's modulus of the material used for the nested sub-cell unit, I2 is the moment of inertia of the inner sub-cell, and aib, ais are the lengths of line segments HG and GD.

[0016] Furthermore, according to Castigliano's second theorem, when a single heterotypic unit of the outer sub-cell is simultaneously subjected to a load and a sectional bending moment M1, the displacement △ of the outer sub-cell in the loading direction is obtained y1 as follows:

[0017]

[0018]

[0019] The sectional bending moment M1 received by the heterotypic unit is:

[0020]

[0021] In the formula, M(x) is the bending moment generated by the load acting on each part of the heterotypic unit, is the bending moment when the load acts, x is the micro-force arm length at which each part of the heterotypic unit receives the load to generate the bending moment, I1 is the moment of inertia of the outer sub-cell, F is the load received by the nested sub-cell unit, and F1 is the load received by the outer sub-cell.

[0022] Furthermore, the support assembly includes an upper support plate and a lower support plate, and the linear electric drive assembly includes a cylinder and a voice coil motor; the upper support plate is connected to the grinding robot, the cylinder barrel is connected to the upper support plate, the voice coil motor is connected to the upper support plate through a motor base, the end of the piston rod of the cylinder and the mover of the voice coil motor are connected to the lower support plate through an adapter plate, and the grinding assembly is installed on the lower support plate. The cylinder is used to compensate for the gravity of all loads on the lower support plate, and the voice coil motor provides the grinding force.

[0023] Furthermore, the linear electric drive assembly further includes a voice coil module guide rail, a voice coil module slider, an upper limit block, and a lower limit block; the voice coil module guide rail is connected to the motor base, the voice coil module slider is slidably connected to the voice coil module guide rail, and the voice coil module slider is simultaneously connected to the adapter plate; upper limit blocks and lower limit blocks are respectively provided on both sides of the voice coil module guide rail to limit the stroke of the mover of the voice coil motor.

[0024] Furthermore, the grinding assembly includes an electric spindle fixture, a micro electric spindle, and a grinding tool; the electric spindle fixture is installed on the lower support plate, the micro electric spindle is connected to the electric spindle fixture, and the grinding tool is installed at the end of the micro electric spindle.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) This actuator can effectively solve the problems of machining chatter caused by low stiffness and insufficient control accuracy caused by pneumatic drive. It is especially suitable for precision grinding of small workpieces with variable curvature, and has higher stiffness and certain flexibility, solving the problems that the motor cannot withstand impact and the force overshoot at the moment of contact. By controlling the grinding force of the actuator and combining it with the machining trajectory control of the robotic arm, high-precision and high-response-speed grinding can be achieved.

[0027] (2) The auxetic honeycomb structure has excellent buffering characteristics and can meet the compliance requirements for grinding. Aiming at the problem of generally low stiffness of the auxetic honeycomb structure, based on the stiffness strengthening calculation method, a stiffness-strengthened auxetic honeycomb structure is designed. The auxetic honeycomb structure can significantly increase the Young's modulus, that is, stiffness, based on the nested layout, and a mathematical model of the Young's modulus of a single nested sub-cell unit is established. On the premise that the materials and sizes of the auxetic honeycomb structure are the same, the stiffness of the auxetic honeycomb structure can be changed by adjusting the structural parameters of the outer sub-cell and the inner sub-cell, realizing simple and efficient customized mechanical properties, and more reasonably adapting to different working conditions, ensuring a certain degree of compliance and also improving the overall stiffness of the actuator.

[0028] (3) Compared with the cylinder, the voice coil motor has the problems of control time lag caused by unstable air supply and friction between the piston and the inner wall of the cylinder, and has the advantages of high response speed and high precision. Compared with the traditional servo motor ball screw assembly structure, which has problems such as large weight of the servo motor, complex overall transmission, large inertia caused by ball clearance, reduced mechanical efficiency, and more likely to generate vibration, the voice coil motor has the advantages of light weight, linear drive, and no cogging effect, and is more suitable as the driving element of the end effector for precision grinding. Using a cylinder to balance the load gravity can reduce the additional load on the voice coil motor and improve the motor response speed.

[0029] (4) In order to improve the response speed, a low-friction cylinder is used to compensate for the gravity of all loads on the lower platen, so that the voice coil motor does not bear additional loads. Compared with the pneumatic spindle, the electric spindle has the problem of unstable rotational speed caused by unstable air supply, and has higher control accuracy, and can achieve the constant rotational speed required during precision grinding. On the premise of maintaining a constant rotational speed, the micro electric spindle does not significantly increase the weight, reduces the inertia effect, and ensures the control accuracy. The micro electric spindle is installed in the center of the end effector, with higher stiffness, accuracy and repeatability. The voice coil motor, micro electric spindle and low-friction cylinder are installed non-coaxially, which can further improve the stiffness. To avoid the problem of tipping moment caused by non-coaxial installation, the distance between the micro electric spindle and the voice coil motor, that is, the moment arm, should be as small as possible without interference, and the problem of tipping moment caused can be basically ignored.

[0030] (5) Using an external gas path to cool the voice coil motor and the electric spindle can solve the problems that the control accuracy of the voice coil motor and the micro electric spindle decreases due to heat generation during long-term operation, and even damage the workpiece.

[0031] (6) Although the voice coil motor supports direct force control, based on the position closed-loop control of the grating scale, the output force is indirectly controlled. Since there is a linear relationship between the feed rate and the feed force, the output grinding force can be reflected by the position control of the voice coil motor. Compared with direct force control, the positioning is more accurate. The six-axis force sensor can be used to collect force signals more accurately, and the dynamic inclination sensor can compensate for the influence of the end angle on gravity. The overall force control accuracy is higher, making it more suitable for automated precision grinding. Description of the Drawings

[0032] Figure 1 is the overall three-dimensional structure schematic diagram of the present invention;

[0033] Figure 2 is the three-dimensional structure schematic diagram of the present invention after hiding two expandable honeycomb structures;

[0034] Figure 3 is the front view of the actuator of the present invention after hiding the rigid-flexible coupling component;

[0035] Figure 4 is the rear view of the actuator of the present invention after hiding the rigid-flexible coupling component;

[0036] Figure 5 is the three-dimensional structure schematic diagram of the voice coil motor module of the present invention;

[0037] Figure 6 is the three-dimensional structure schematic diagram of the expandable honeycomb structure of the present invention;

[0038] Figure 7 is the structure schematic diagram of a single nested sub-cell unit of the expandable honeycomb structure of the present invention;

[0039] Figure 8 is the force analysis diagram of a single nested sub-cell unit of the expandable honeycomb structure of the present invention;

[0040] Description of the reference numerals: 1. Connecting flange; 2. Upper support plate; 3. Upper bottom plate; 4. Expandable honeycomb structure; 5. Lower bottom plate; 6. Lower support plate; 7. Optical axis fixture; 8. Low-friction cylinder; 9. Optical axis; 10. Electric spindle fixture; 11. Dynamic inclination sensor; 12. Linear motion limit fixture; 13. Voice coil motor; 14. Voice coil motor base; 15. Six-axis force sensor; 16. Micro electric spindle; 17. Grinding tool; 18. Grating scale; 19. Flange-type linear bearing; 20. Adapter plate; 21. Voice coil module guide rail; 22. Voice coil module slider; 23. Upper limit block; 24. Adapter plate block; 25. Lower limit block. Detailed Description of the Invention

[0041] The following specific embodiments are given in conjunction with the accompanying drawings. The specific embodiments are only used to further elaborate on the technical solutions of the present invention and do not limit the protection scope of this application.

[0042] The present invention provides a rigid-flexible coupled electric drive grinding end effector (hereinafter referred to as the end effector, see Figure 1-8 ), which includes a support assembly, a linear electric drive assembly, a grinding assembly, and a rigid-flexible coupling assembly;

[0043] The support assembly includes a connecting flange 1, an upper support plate 2, a lower support plate 6, an optical axis fixture 7, an optical axis 9, a linear motion limit fixture 12, and a flange-type linear bearing 19; the connecting flange 1 is used to realize the fixed connection between the end effector and the end of the grinding robot manipulator. The upper support plate 2 is fixedly connected to the connecting flange 1. There are multiple optical axes 9 (4 in this embodiment) at the bottom of the upper support plate 2. The upper end of each optical axis 9 is tightly installed on the optical axis fixture 7, and the optical axis fixture 7 is fixedly connected to the upper support plate 2. A linear motion limit fixture 12 is provided at the lower end of the optical axis 9 to limit the movement of the lower support plate 6. The lower support plate 6 is located below the upper support plate 2 and is connected to each optical axis 9. The lower support plate 6 can perform linear reciprocating motion along the optical axis 9. A flange-type linear bearing 19 is provided at the connection between the lower support plate 6 and the optical axis 9 to limit the degrees of freedom in other directions and guide the movement of the lower support plate 6.

[0044] The linear electric drive assembly includes a low-friction cylinder 8, a voice coil motor 13, a voice coil motor base 14, a grating scale 18, an adapter plate 20, a voice coil module guide rail 21, a voice coil module slider 22, an upper limit block 23, and a lower limit block 25. Among them, the voice coil motor base 14 is fixedly connected to the upper support plate 2, the voice coil motor 13 is fixedly installed on the upper part of the voice coil motor base 14, the mover of the voice coil motor 13 is fixedly connected to the adapter plate 20, and the lower part of the adapter plate 20 is fixedly connected to the lower support plate 6. The lower support plate 6 is driven by the voice coil motor 13 to perform a linear reciprocating motion to provide a grinding force. The voice coil module guide rail 21 is fixedly installed on the lower part of the voice coil motor base 14, the voice coil module slider 22 is slidably connected to the voice coil module guide rail 21, and the voice coil module slider 22 is fixedly connected to one side of the adapter plate 20. Upper limit blocks 23 and lower limit blocks 25 are respectively arranged on both sides of the voice coil module guide rail 21, and adapter plate sections 24 are respectively arranged on both sides of the adapter plate 20. Each adapter plate section 24 is respectively located between the corresponding upper limit block 23 and lower limit block 25. The stroke of the mover of the voice coil motor 13 is limited by the upper limit block 23 and the lower limit block 25, which plays a protective role for the voice coil motor 13. A six-axis force sensor 15 is arranged between the adapter plate 20 and the lower support plate 6 for real-time detection of the grinding force. The grating scale 18 is installed on the voice coil motor base 14 through a grating scale bracket for real-time detection of the stroke of the mover of the voice coil motor 13. The cylinder barrel of the low-friction cylinder 8 is fixedly connected to the upper support plate 2, and the end of the piston rod of the low-friction cylinder 8 is fixedly connected to the lower support plate 6. The low-friction cylinder 8 is used to compensate for the gravity of all loads on the lower support plate 6, so that the voice coil motor 13 does not bear additional loads and improves the response speed of the actuator at the same time. The dynamic inclination sensor 11 is connected to the lower support plate 6 to realize real-time monitoring of the angle of the actuator.

[0045] The grinding assembly includes an electric spindle fixture 10, a micro electric spindle 16, and a grinding tool 17. The electric spindle fixture 10 is installed on the lower support plate 6, the micro electric spindle 16 is locked and installed on the electric spindle fixture 10, and the grinding tool 17 is installed at the end of the micro electric spindle 16 and locked by a spring collet. The spring collet can ensure the clamping accuracy and thus ensure the machining accuracy. The micro electric spindle 16 is maintained at a constant speed by a driver to provide the required rotational torque for the grinding tool 17.

[0046] After long-term operation, the voice coil motor 13 in the above linear electric drive assembly and the micro electric spindle 16 in the grinding assembly will cause problems such as a decrease in control accuracy and even damage to components due to heat generation. By cooperating with an external air circuit and an oil-water separator, dry low-temperature gas is used to cool the voice coil motor 13 and the micro electric spindle 16 to ensure control accuracy and the service life of components.

[0047] The rigid-flexible coupling component includes an upper bottom plate 3, an expandable honeycomb structure 4, and a lower bottom plate 5. The upper bottom plate 3 and the lower bottom plate 5 are fixedly connected to the upper support plate 2 and the lower support plate 6 respectively. A plurality of expandable honeycomb structures 4 are distributed around the upper support plate 2 and the lower support plate 6, and the upper and lower ends of each expandable honeycomb structure 4 are fixedly connected to the upper bottom plate 3 and the lower bottom plate 5 respectively. The expandable honeycomb structure 4 can expand or contract with the reciprocating linear motion of the lower support plate 6 and has a certain flexibility. Based on the nested design idea of stiffness enhancement, the stiffness of the expandable honeycomb structure is improved, realizing rigid-flexible coupling. The expandable honeycomb structure is installed on the actuator, avoiding the processing vibration caused by the low stiffness characteristics of the actuator and the end of the grinding robot manipulator as a series mechanism and the problem of excessive grinding force caused by a pure rigid actuator.

[0048] As Figure 6 shown, the expandable honeycomb structure 4 is formed by an array of several nested sub-cell units and is integrally formed by 3D printing. Each nested sub-cell unit includes an outer sub-cell and an inner sub-cell nested inside the outer sub-cell. The upper and lower ends of the inner sub-cell are respectively connected to the outer sub-cell through vertical rods. As Figure 7 , 8 shown, the outer sub-cell is a centrosymmetric structure and is integrally formed by four special-shaped units, so that the shape of the outer sub-cell in the front view of the nested sub-cell unit is butterfly-shaped. The special-shaped unit is composed of a Z-shaped plate and an L-shaped plate. The side of the Z-shaped plate in the front view of the nested sub-cell unit is composed of line segments IJ, JK, and KA, and the line segments IJ and KA are parallel. The side of the L-shaped plate in the front view of the nested sub-cell unit is composed of line segments AB and BC, and the line segment AB is perpendicular to the line segment KA. The inner sub-cell is a classic concave hexagon structure and is integrally formed by four angular plates. The side of the angular plate in the front view of the nested sub-cell unit is composed of line segments HG and GD, the line segment HG is parallel to the line segments IJ and KA, and the line segment GD is parallel to the line segment BC.

[0049] Determine the Young's moduli of the outer sub-cell and the inner sub-cell according to their structural parameters. The sum of the Young's moduli of the inner sub-cell and the outer sub-cell is the Young's modulus of the nested sub-cell unit. Since it is difficult to analyze the Young's modulus of the honeycomb structure as a whole from a mathematical perspective, and the mechanical properties of a single nested sub-cell unit can reflect the mechanical properties of the overall auxetic honeycomb structure, usually a single nested sub-cell unit is analyzed. After establishing the mathematical model of the Young's modulus of a single nested sub-cell unit, the relationship between the Young's modulus and all structural parameters has been determined. Therefore, the Young's modulus of the auxetic honeycomb structure can be changed by adjusting the structural parameters of the outer sub-cell and the inner sub-cell, and further the stiffness of the auxetic honeycomb structure can be changed. Therefore, on the premise that the materials and sizes of the auxetic honeycomb structures are the same, the stiffness of the auxetic honeycomb structure can be changed by adjusting the structural parameters of the outer sub-cell and the inner sub-cell, so that the actuator is suitable for different grinding requirements, avoiding the machining vibration caused by the low stiffness characteristics, and at the same time reducing the impact on the micro motorized spindle 16 and the voice coil motor 13, and reducing the difficulty of force control.

[0050] Denote the lengths of the line segments IJ, JK, and KA as al3 / 2, al2, and al1 respectively, and the angle between the line segments JK and KA as α; denote the lengths of the line segments AB and BC as ar1 and ar2 respectively, and the angle between them as 90° + θ / 2. The values of θ and α should ensure that there is no interference in the structures of the outer sub-cell and the inner sub-cell; denote the lengths of the line segments HG and GD as aib and ais respectively, and the angle between them as θ / 2;

[0051] In the overall honeycomb structure, due to the periodic boundary conditions between the nested cells, there are shared sides in the outer sub-cell. When taking a single nested cell as the research object, the inner and outer sub-cells need to be studied separately. For consistency, the width of the outer sub-cell is the thickness is δ; the width and thickness of the inner sub-cell are both δ;

[0052] Take a single special-shaped unit of the outer sub-cell as the analysis object. The load on the special-shaped unit is F1 is the load on the outer sub-cell; denote the cross-section of the special-shaped unit located on the left and right bisecting planes of the outer sub-cell as cross-section P. Taking the rotation angle of cross-section P as the deformation compatibility condition and applying the Mohr integral, the cross-section moment M1 of the special-shaped unit satisfies Equation (1):

[0053]

[0054] In the formula, δ 11 is the rotation angle of cross-section P when M1 is the unit moment, △ 1F is the rotation angle of cross-section P when the special-shaped unit is subjected to the load M(x) is the moment generated by the load acting on each part of the special-shaped unit, is the load The bending moment at that time, x is the length of the micro-force arm where each part of the special-shaped unit generates a bending moment under the load, E0 is the Young's modulus of the material used for the nested sub-cell unit, and I1 is the moment of inertia of the outer sub-cell; solved from Equation (1), the sectional bending moment M1 received by the special-shaped unit is:

[0055]

[0056] Based on the above solution, according to Castigliano's second theorem, when the load and the sectional bending moment M1 act simultaneously, the solution of △ y1 is:

[0057]

[0058]

[0059] Therefore, the Young's modulus E1 of the outer sub-cell is:

[0060]

[0061]

[0062] In the formula, F1 is the load received by the outer sub-cell, l * and A * are the equivalent length and equivalent area of the nested sub-cell unit respectively, △ y1 is the displacement of the outer sub-cell in the force direction, and δ is the wall thickness of the inner sub-cell;

[0063] Similarly, the Young's modulus E2 of the inner sub-cell is:

[0064]

[0065] In the formula, I2 is the moment of inertia of the inner sub-cell;

[0066] The Young's modulus E of the nested sub-cell unit is:

[0067] E = E1 + E2 (8)

[0068] The working principle and working process of the present invention are:

[0069] When a grinding task needs to be performed, the voice coil motor 13 drives the lower platen 6 to move away from the upper platen 2 to provide a grinding force, so that the grinding tool 17 acts on the workpiece; the six-axis force sensor 15 detects the grinding force in real time and feeds it back to the force feedback control system through a data acquisition card. The system issues a control command to control the output force of the voice coil motor 13 to achieve closed-loop control of the grinding force; the voice coil motor 13 indirectly reflects the output force according to the pushing stroke. Therefore, more accurate position control is achieved through the grating scale 18. Due to the existence of the grating scale, this indirect force control is more accurate than the direct force control in the current mode. Since some workpieces to be ground have problems such as large curvature changes, the actuator needs to adjust its posture to adapt to the workpiece surface. The dynamic tilt sensor 11 compensates for the influence of the end angle on gravity, making the force feedback control system more accurate.

[0070] To achieve single-degree-of-freedom force control of the actuator, the degrees of freedom in other directions need to be restricted. Therefore, the voice coil module slider 22 and the voice coil module guide rail 21 cooperate to perform a single-axis reciprocating motion, which restricts the movement of the voice coil motor 13 in other directions; the flanged linear bearing 19 cooperates with the optical axis 9 to further restrict the other degrees of freedom of the actuator and increase the overall stiffness. The evenly distributed multiple optical axes 9 avoid causing an overturning moment.

[0071] To prevent the voice coil motor 13 from being affected by additional gravity and control the response speed, a low-friction cylinder 8 is used to balance the load gravity of all components installed on the lower platen 6; to prevent the voice coil motor 13 from exceeding its stroke, an upper limit block 23 and a lower limit block 25 are installed on the voice coil motor base 14 to limit the maximum movement stroke of the adapter plate 20; a linear motion limit fixture 12 is installed at the bottom end of the optical axis 9 to limit the normal stroke, providing secondary protection for the overall components. To ensure grinding accuracy, to avoid excessive load increasing the inertia of the actuator and increasing the difficulty of force control, a micro electric spindle 16 is used as the driving element of the grinding tool 17, and the grinding tool 17 is locked by a spring collet, ensuring accurate torque transmission and good concentricity.

[0072] Matters not described in the present invention are applicable to the prior art.

Claims

1. A rigid-flexible coupled electric drive grinding end effector, comprising a support assembly, a linear electric drive assembly, and a grinding assembly; characterized in that, The actuator further includes a rigid-flexible coupling component, which includes a stretchable honeycomb structure distributed around the actuator. The stretchable honeycomb structure can stretch or contract as the actuator moves. The stretchable honeycomb structure is formed by an array of several nested sub-cell units. Each nested sub-cell unit includes an outer sub-cell and an inner sub-cell. The inner sub-cell is nested inside the outer sub-cell and is connected to the outer sub-cell at the upper and lower ends. The outer sub-cell is integrally formed by four special-shaped units, so that the shape of the outer sub-cell in the front view of the nested sub-cell unit is butterfly-shaped. Each special-shaped unit includes a Z-shaped plate and an L-shaped plate. The side of the Z-shaped plate in the front view of the nested sub-cell unit is composed of line segments IJ, JK, and KA, and line segments IJ and KA are parallel. The side of the L-shaped plate in the front view of the nested sub-cell unit is composed of line segments AB and BC, and line segment AB is perpendicular to line segment KA. The inner sub-cell is integrally formed by four angular plates. The side of the angular plate in the front view of the nested sub-cell unit is composed of line segments HG and GD, and line segment HG is parallel to line segments IJ and KA, and line segment GD is parallel to line segment BC. The support component includes an upper support plate and a lower support plate. The linear electric drive component includes a cylinder and a voice coil motor. The upper support plate is connected to the grinding robot. The cylinder barrel is connected to the upper support plate. The voice coil motor is connected to the upper support plate through a motor base. The end of the piston rod of the cylinder and the mover of the voice coil motor are connected to the lower support plate through an adapter plate. The grinding component is installed on the lower support plate. The cylinder is used to compensate for the gravity of all loads on the lower support plate, and the voice coil motor provides the grinding force. The linear electric drive component further includes a voice coil module guide rail, a voice coil module slider, an upper limit block, and a lower limit block. The voice coil module guide rail is connected to the motor base. The voice coil module slider is slidably connected to the voice coil module guide rail, and the voice coil module slider is also connected to the adapter plate. The upper limit block and the lower limit block are respectively arranged on both sides of the voice coil module guide rail to limit the stroke of the mover of the voice coil motor. The grinding component includes an electric spindle fixture, a micro electric spindle, and a grinding tool. The electric spindle fixture is installed on the lower support plate. The micro electric spindle is connected to the electric spindle fixture, and the grinding tool is installed at the end of the micro electric spindle.

2. The rigid-flexible coupled electric drive grinding end effector according to claim 1, wherein By changing the structural parameters of the nested sub-cell unit, the Young's modulus is changed, and then the stiffness of the actuator is changed. Among them, the Young's modulus E1 of the outer sub-cell is: The Young's modulus E2 of the inner sub-cell is: The Young's modulus E of the nested sub-cell unit is: E = E1 + E2 (8) where F1 is the load on the outer sub-cell, l * and A * are the equivalent length and equivalent area of the nested sub-cell unit respectively, Δ y1 is the displacement of the outer sub-cell in the direction of the force, ar1 and ar2 are the lengths of line segments AB and BC, θ is the angle between line segment BC and the upper and lower centerlines of the outer sub-cell, al3 / 2, al2 and al1 are the lengths of line segments IJ, JK and KA, α is the angle between line segment JK and KA, δ is the wall thickness of the inner sub-cell, E0 is the Young's modulus of the material used for the nested sub-cell unit, I2 is the moment of inertia of the inner sub-cell, and aib and ais are the lengths of line segments HG and GD.

3. The rigid-flexible coupled electric drive grinding end effector according to claim 2, wherein According to Castigliano's second theorem, when a single heterogeneous unit of the outer sub-cell is simultaneously subjected to a load and a sectional bending moment M1, the displacement Δ of the outer sub-cell in the loading direction is obtained y1 as follows: The sectional bending moment M1 received by the special-shaped unit is: Where, M(x) is the bending moment generated by the load acting on each part of the special-shaped unit, is the bending moment when the load is , x is the length of the micro-force arm where the bending moment is generated by the load on each part of the special-shaped unit, I1 is the moment of inertia of the outer sub-cell, and F1 is the load received by the outer sub-cell.

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