CN109129158B - Precise milling and grinding machine tool based on parallel tool system and control method thereof - Google Patents
Precise milling and grinding machine tool based on parallel tool system and control method thereof Download PDFInfo
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- CN109129158B CN109129158B CN201811281763.2A CN201811281763A CN109129158B CN 109129158 B CN109129158 B CN 109129158B CN 201811281763 A CN201811281763 A CN 201811281763A CN 109129158 B CN109129158 B CN 109129158B
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- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000003801 milling Methods 0.000 title claims abstract description 18
- 238000000227 grinding Methods 0.000 title claims abstract description 15
- 230000033001 locomotion Effects 0.000 claims abstract description 27
- 238000005498 polishing Methods 0.000 claims abstract description 27
- 230000003068 static effect Effects 0.000 claims description 42
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- 230000001360 synchronised effect Effects 0.000 claims description 12
- 230000005489 elastic deformation Effects 0.000 claims description 9
- 239000013598 vector Substances 0.000 claims description 9
- 238000006073 displacement reaction Methods 0.000 claims description 8
- 230000008859 change Effects 0.000 claims description 6
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B29/00—Machines or devices for polishing surfaces on work by means of tools made of soft or flexible material with or without the application of solid or liquid polishing agents
- B24B29/02—Machines or devices for polishing surfaces on work by means of tools made of soft or flexible material with or without the application of solid or liquid polishing agents designed for particular workpieces
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B1/00—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B47/00—Drives or gearings; Equipment therefor
- B24B47/20—Drives or gearings; Equipment therefor relating to feed movement
Abstract
The invention relates to a precise milling and grinding machine tool based on a novel parallel tool system and a control method thereof, and belongs to the field of machine manufacturing. The vertical columns are fixedly connected to four corners of the lathe bed through bolts respectively, the workbench is fixedly connected to the lathe bed through bolts, the two y guide rails are fixedly connected to the upper ends of the four vertical columns on the left side and the right side through bolts respectively, the x guide rails are fixedly connected to the sliding table of the y guide rails through bolts, the z guide rails and the self-locking device are fixedly connected to the sliding table of the x guide rails through bolts, the parallel polishing tool system is fixedly connected to the connecting plate through bolts, and the connecting plate is fixedly connected to the sliding table of the z guide rails through bolts. The tool has the advantages of novel structure, rich redundancy freedom, high structural rigidity, small tool track accumulated error and easy guarantee of precision. The macro motion and the micro motion are controlled independently, so that the problems of multi-axis interference and singular points in algorithm analysis are avoided; the accuracy is improved to a great extent.
Description
Technical Field
The invention belongs to the field of machine manufacturing, and particularly relates to a precise milling and grinding machine tool.
Background
In the high and new technical fields of national defense, military industry, automobile manufacturing, aerospace navigation and the like, the requirements for parts with complex curved surfaces are great, but the processing technology of the parts is complex, the processing difficulty is high, the precision requirement is high, and the manufacturing cost is high. How to improve the machining precision of the parts and reduce the machining difficulty are key to solving the problems. The tool head is required to have enough degrees of freedom for machining complex curved surfaces, multi-axis linkage milling and grinding machine tools are commonly adopted at present, but as the number of axes is increased, the control difficulty is increased, the axes of the machine tools are connected in series, the track accumulated error is larger, the precision is more and more difficult to control, and the cost is higher and higher. Series-parallel milling and grinding machine tools begin to appear in the field of view of people, and by separating macro-motions from micro-motions, the series-parallel milling and grinding machine tools reduce unnecessary error accumulation in motion transmission, and more students begin to add to the research, but mechanisms for realizing micro-motions must have enough redundancy degree of freedom and rigidity.
Disclosure of Invention
The invention provides a precision milling and grinding machine tool based on a parallel tool system and a control method thereof, which aim to solve the problems that the precision of the existing milling and grinding machine tool is difficult to control and the control difficulty is high.
The technical scheme includes that the polishing machine comprises an x-direction guide rail, a z-direction guide rail, a self-locking device, a y-direction guide rail, upright posts, a machine tool body, a workbench, a parallel polishing tool system and a connecting plate, wherein four upright posts are fixedly connected to four corners of the machine tool body through bolts respectively, the workbench is fixedly connected to the machine tool body through bolts, two y-direction guide rails are fixedly connected to the upper ends of the four upright posts on the left side and the right side through bolts respectively, the x-direction guide rail is fixedly connected to a sliding table of the y-direction guide rail through bolts, the z-direction guide rail and the self-locking device are fixedly connected to the sliding table of the x-direction guide rail through bolts, the parallel polishing tool system is fixedly connected to the connecting plate through bolts, and the connecting plate is fixedly connected to the sliding table of the z-direction guide rail through bolts.
The X-shaped guide rail comprises an X-shaped guide rail motor, an X-shaped guide rail base, an X-shaped guide rail synchronous belt, an X-shaped guide rail sliding table, an X-shaped guide rail tensioning wheel and an X-shaped guide rail pin shaft, wherein the X-shaped guide rail motor is fixedly connected in a motor seat of the X-shaped guide rail base through screws, the X-shaped guide rail is fixedly connected on the X-shaped guide rail base through screws, the X-shaped guide rail sliding table is in sliding connection with the X-shaped guide rail, the X-shaped guide rail tensioning wheel is fixedly arranged on the X-shaped guide rail base through the X-shaped guide rail pin shaft, the pin shaft is in threaded connection with the X-shaped guide rail base, and the X-shaped guide rail synchronous belt is wrapped on a driving wheel of the X-shaped guide rail motor and the X-shaped guide rail tensioning wheel and is fixedly connected with the X-shaped guide rail sliding table.
The Y-direction guide rail comprises a Y-direction guide rail base, a Y-direction guide rail sliding table, a Y-direction guide rail synchronous belt, a Y-direction guide rail tension wheel, a Y-direction guide rail pin shaft and a Y-direction guide rail motor, wherein the Y-direction guide rail motor is fixedly connected in the motor base of the Y-direction guide rail base through screws, the Y-direction guide rail is fixedly connected on the Y-direction guide rail base through screws, the Y-direction guide rail sliding table is in sliding connection with the Y-direction guide rail, the Y-direction guide rail tension wheel is fixedly arranged on the Y-direction guide rail base through the Y-direction guide rail pin shaft, the Y-direction guide rail pin shaft is in threaded connection with the Y-direction guide rail base, and the Y-direction guide rail synchronous belt is wrapped on the driving wheel of the Y-direction guide rail motor and the Y-direction guide rail tension wheel and is fixedly connected with the Y-direction guide rail sliding table.
The z-direction guide rail and the self-locking device comprise chain wheels, chains, a z-direction guide rail motor, weight boxes, chain connecting blocks, pneumatic push rods, couplings, a z-direction guide rail sliding table, a z-direction guide rail base, a z-direction guide rail lead screw, a z-direction guide rail lead screw mounting seat and a frame, wherein the two weight boxes are respectively connected with the left side and the right side of the back of the frame through screws, the four chain wheels are connected with four corners of the upper surface of the frame through the mounting seats, the z-direction guide rail base is fixedly connected with the front end surface of the frame through screws, the z-direction guide rail motor is fixedly connected with the upper end surface of the z-direction guide rail base through screws, two z-guide lead screw mount pad pass through screw fixed connection in z-guide rail mount pad openly, the bearing that two lead screw mount pads were passed to the z-guide lead screw passes through thrust collar fixed, the shaft coupling passes through pin connection with the main shaft of z-guide motor and z-guide lead screw, screw nut and the z-guide lead screw of z-guide slip table pass through threaded connection, the slider and the z-guide rail sliding connection of z-guide slip table, two chain connecting blocks pass through screw connection in z-guide slip table left and right sides, chain one end passes through pin connection with the chain connecting block, the balancing weight of the other end and weight box passes through pin connection, two pneumatic push rods pass through screw connection in z-guide slip table left and right sides.
The parallel polishing tool system comprises a static platform, hooke hinges, a screw rod module, connecting blocks, claw-type connecting pieces, a first connecting piece, a second connecting piece, a movable platform module and a spherical hinge, wherein the three Hooke hinges are respectively fixedly connected to the static platform through bolts, the three screw rod modules are respectively fixedly connected with the three Hooke hinges through bolts, the three connecting pieces are fixedly connected to the end faces of the screw rod module through bolts, the two claw-type connecting pieces are fixedly connected to the connecting pieces positioned on the left side and the right side of the static platform through bolts, the spherical hinge is fixedly connected to the left connecting piece and the right connecting piece of the rest through bolts, the first connecting piece is fixedly connected to the left side and the right side of the movable platform module through bolts, and the first connecting piece and the second claw-type connecting piece positioned on the left side and the right side of the static platform are hinged through pin shafts, and the second connecting piece of the rest is hinged to a cross shaft of the spherical hinge.
The screw rod module comprises a motor, a motor mounting bottom plate, a guide rail, a sliding table, a displacement sensor, a connecting bottom plate, a motor coupler, a screw rod mounting seat, a photoelectric sensor, a screw rod and a module bottom plate, wherein the motor is fixedly connected to the motor mounting bottom plate through a screw, the motor mounting bottom plate is fixedly connected to the module bottom plate through a screw, the guide rail is fixedly connected to the module bottom plate through a screw, the connecting bottom plate is connected to the module bottom plate through a screw, the screw rod mounting seat is fixedly connected to the module bottom plate through a screw, the photoelectric sensor is fixedly connected to the module bottom plate through a screw, the motor coupler is connected with a spindle of the motor and the screw rod through a pin, a screw nut of the sliding table is connected with the screw rod through a screw, a sliding block of the sliding table is connected with the guide rail in a sliding mode, and a measuring telescopic rod of the displacement sensor is fixedly connected to a connecting plate of the sliding table through a screw.
The sliding table include sensor response piece, slip table base, sensor connecting plate, screw mounting panel, screw nut, slider, wherein sensor response piece passes through screw fixed connection at the left surface of slip table base, the slider passes through screw fixed connection at the bottom surface of slip table base, sensor connecting plate passes through screw connection with the slip table base, the screw mounting panel passes through screw connection in the bottom surface recess of slip table base, screw nut passes through screw connection on the screw mounting panel.
The Hooke hinge comprises a Hooke hinge base and a short shaft, and the short shaft penetrates through a bearing of the base and is fixed by a thrust ring; the spherical hinge comprises a spherical hinge base and a cross shaft, and the cross shaft penetrates through a bearing of the spherical hinge base and is fixed by a thrust ring; the spherical hinge base and the Hooke hinge base have the same structure;
the Hooke's hinge base include bearing, go up connecting seat, end cover, lower connecting seat, go up base, lower base, short round pin, step shaft, bearing, wherein the bearing passes through the bearing mounting hole of last connecting seat and uses the end cover chucking, the end cover passes through the screw connection on last connecting seat, go up connecting seat 7 and pass through the screw fixation on lower connecting seat, go up base and lower base and pass through bolted connection, step shaft passes through two bearings and goes up base, lower base adoption both ends fixed mode is fixed, step shaft and lower connecting seat pass through short round pin connection.
The movable platform module comprises a spindle motor, a spindle motor mounting seat, a movable platform, a short taper pin and a tool head, wherein the spindle motor is connected in the spindle motor mounting seat through a screw, the spindle motor mounting seat is connected on the movable platform through a screw, and a spindle of the spindle motor is connected with the tool head through a screw thread and is fixed through the short taper pin.
A control method of a precision milling and grinding machine tool based on a parallel tool system comprises the following steps:
the method comprises the steps of (A) establishing a coordinate system XYZ by taking a geometric center of a static platform as an origin, wherein a Z axis is a straight line passing through the geometric center of the static platform in the vertical direction, an X axis is a horizontal straight line which is in a horizontal plane and is parallel to an X guide rail through the geometric center of the static platform, a Y axis is a horizontal straight line which is in a horizontal plane and is parallel to a Y guide rail through the geometric center of the static platform, and establishing a coordinate system X 'Y' Z 'by taking a geometric center of a movable platform module as the origin, wherein the Z' axis is a straight line passing through the geometric center of the movable platform module in the vertical direction, the X 'axis is a horizontal straight line which is in a horizontal plane and is parallel to the X guide rail through the geometric center of the movable platform module, and the Y' axis is a horizontal straight line which is in a horizontal plane and is parallel to the Y guide rail through the geometric center of the movable platform module; after a workpiece is clamped and fixed on a workbench through a clamp, a triaxial moving platform is utilized to send a parallel polishing tool system to the position of a point to be processed, and the positions of a static platform and the workpiece are determined;
(II) description of motion geometrical relationship of the movable platform module in the fixed platform coordinate system XYZ:
let A 1 、B 1 、C 1 The coordinate vectors in the XYZ coordinate system are:
A 1 ＝(A 1x ,A 1y ,A 1z ) T ＝(2D,0,0) T
B 1 ＝(B 1x ,B 1y ,B 1z ) T ＝(-D,H,0) T
C 1 ＝(C 1x ,C 1y ,C 1z ) T ＝(-D,-H,0) T
let A 2 、B 2 、C 2 The coordinate vectors in the X ' Y ' Z ' coordinate system are:
A 2 ＝(2d,0,0) T
B 2 ＝(-d,h,0) T
C 2 ＝(-d,-h,0) T
wherein ,A1 、B 1 、C 1 Is a hinge point of a static platform, A 2 、B 2 、C 2 Is a hinge point of the movable platform module;
the motion relation of the movable platform module relative to the continuous rotation and translation of the static platform is described by a matrix (alpha, beta, Z), wherein alpha, beta respectively represent the rotation angle of the movable platform module around X, Y axis, Z represents the movement amount of the movable platform module along the Z axis direction, and the rotation transformation matrix around the X axis, which is transformed from the movable platform module to the static platform, is R x Rotating the transformation matrix R around the Y-axis y Translation transformation matrix P along Z-axis z The specific transformation matrix is as follows:
when the movable platform module continuously rotates relative to the static platform, the gesture transformation matrix is as follows:
(A 2x ,A 2y ,A 2z ) T 、(B 2x ,B 2y ,B 2z ) T 、(C 2x ,C 2y ,C 2z ) T respectively represent A in a moving platform module coordinate system 2 、B 2 、C 2 Transforming into a coordinate vector in a static platform coordinate system;
(A 2x ,A 2y ,A 2z ) T ＝(2dcosβ,0,-2dsinβ+z) T
(C 2x ,C 2y ,C 2z ) T ＝(dcosβ-hsinαsinβ,-hcosα,dsinβ-hsinαcosβ+z) T
(III), A 1 A 2 、B 1 B 2 、C 1 C 2 Relation between length of (d) and position of movable platform module
Combining step (II), A when the movable platform module is in any posture 1 A 2 、B 1 B 2 、C 1 C 2 Length of (2)
In the posture change process, three lead screw module control motors respectively control the moving distance of the sliding table to be:
wherein lA0 、l B0 、l C0 A before the pose adjustment is respectively carried out for the movable platform module 1 A 2 、B 1 B 2 、C 1 C 2 Length of l A1 、l B1 、l C1 A is that the movable platform module carries out pose adjustment 1 A 2 、B 1 B 2 、C 1 C 2 Length Deltal of (2) A 、△l B 、△l C Representation A 1 A 2 、B 1 B 2 、C 1 C 2 The amount of change in length of (2);
in summary, any posture of the movable platform module always has a unique A 1 A 2 、B 1 B 2 、C 1 C 2 Corresponding to the length of (A) can be controlled by controlling A in the absence of external force 1 A 2 、B 1 B 2 、C 1 C 2 The length of the movable platform module can control the movable platform module to reach a theoretical correct position X, but the actual position of the movable platform module is Xa because the tool head is influenced by contact force in the processing process;
fourth, eliminate the error caused by the deformation of the tool head due to the stress
In the machining process, the tool head is contacted with the machined surface of the workpiece to generate normal contact force and tangential friction force, the tangential friction force is ignored, and in order to achieve the best machining effect, the normal contact force is controlled in a certain range and is set to be F N And analyzing the stress condition in the processing process by applying the Hertz contact theory: the tool head is regarded as a rigid material, when the tool head is contacted with a curved surface to be processed, the surface to be processed is slightly deformed at the contact point, two contacted objects are ideally processed, the workpiece is taken as a flexible body,the tool head is regarded as a rigid body, and the elastic deformation completely occurs on the workpiece;
the deformation epsilon and the contact force F are known by the Hertz theory N Satisfies the following formula:
contact force F N ：
From the known elastic deformation ε, the relative elastic modulus E * Tool head and surface R of workpiece to be processed e Are all to polishing force F N The relative elastic modulus E in one step of the process * And the relative curvature radius R of the tool head and the curved surface of the workpiece at the initial contact point e Is determined so that the normal elastic deformation epsilon and the contact force F N Directly related, normal deformation of a workpiece under expected contact force can be distributed to the motion quantity of each workbench of the machine tool according to motion track planning, and the position in a coordinate system Xb of a static platform of the tool head is set to be Xb;
fifth, impedance control contact force control model based on position
(1) Detection of tool head normal contact force
Each mechanical arm of the three-degree-of-freedom parallel structure tool system is provided with a force sensor, the force applied by the mechanical arm along the direction of the mechanical arm can be detected, and the mechanical arm A is known from the force relation 1 A 2 Component force of thrust to the movable platform along the normal direction of the movable platform:
similarly, mechanical arm B 1 B 2 Mechanical arm C 1 C 2 Component force of thrust of moving platform along normal direction of moving platform：
F 2n ＝F 2 cosγ
F 3n ＝F 3 cosδ
Tool head normal contact force:
wherein ,
is l A0 With plane A 2 B 2 C 2 Included angle of (2), gamma is l B0 With plane A 2 B 2 C 2 Delta is l C0 With plane A 2 B 2 C 2 Included angle F of (F) 1 Is along l A0 Force in the direction F 2 Is along l B0 Force in the direction F 3 Is along l C0 Force applied in the direction, G is the gravity applied to the movable platform module, and θ is the gravity and the plane A 2 B 2 C 2 Is included in the plane of the first part;
(2) Impedance model
The force sensor detects real-time contact force, and the real-time contact force is compared with the theoretical contact force required by processing, and the difference is made to obtain an error F e Will error F e Input into an outer ring impedance control model H (F), and the impedance control model generates a contact force error F according to corresponding calculation e A corresponding displacement correction amount E is input into an inner ring position control model G p The inner ring position control model outputs corresponding position correction information to a motion mathematical model G of the three-degree-of-freedom parallel polishing tool system, and the following impedance control model can be established according to a control strategy:
in order to ensure the transition stability in the tool head control process, the parameters should first satisfy the following formula:
wherein ,Md Is a target inertia matrix, B d Is a target damping matrix, K d Is a target rigidity matrix, E is a correction value of deviation between actual position and theoretical position of tool head, F e Is the difference between the detected value of the contact force and the theoretical value;
the controller can generate a position correction quantity E according to the error of the real-time polishing power value and the expected value through the control model, and the correction quantity E is added to Deltal through the kinematic inverse solution A 、△l B 、△l C The final machining position Xc is obtained.
The beneficial effects of the invention are as follows: the machine tool is designed by mainly dividing the machine tool into two parts, the movement required by polishing processing track and position is realized by a triaxial machine tool, the machine tool is a serial machine tool and is composed of X, Y and Z triaxial, triaxial movement is realized, the movement for adjusting the posture of the polishing tool head is completed by a parallel tool system, and the parallel tool system is a 3-PRS parallel mechanism with three degrees of freedom. The multi-axis linkage milling and grinding machine tool has the advantages that error accumulation caused by mutual series connection of shafts of the multi-axis linkage milling and grinding machine tool is avoided, the parallel mechanism has abundant redundancy degrees of freedom, the structural rigidity is high, the tool track accumulation error is small, and the precision is easy to guarantee. The macro motion and the micro motion are controlled independently, so that the problems of multi-axis interference and singular points in algorithm analysis are avoided; the accuracy is improved to a great extent.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a schematic view of the structure of the x-direction guide rail of the present invention;
FIG. 3 is a schematic view of the structure of the z-rail and the self-locking device of the present invention;
FIG. 4 is a schematic view of the structure of the y-direction guide rail of the present invention;
FIG. 5 is a schematic diagram of the parallel tool system of the present invention;
FIG. 6 is a schematic view of the structure of the screw module of the present invention;
FIG. 7 is a schematic diagram of a sliding table of the screw module of the present invention;
FIG. 8 is a schematic view of the hook of the present invention;
FIG. 9 is a schematic view of the structure of the spherical hinge of the present invention;
FIG. 10 is a cross-sectional view of a hook base of the present invention;
FIG. 11 is a cross-sectional view of the mobile platform module of the present invention;
FIG. 12 is a schematic diagram of a connection relationship structure of a movable platform according to the present invention;
FIG. 13 is a simplified diagram of a configuration of a parallel polishing tool system;
fig. 14 is a tool head force analysis chart.
Detailed Description
The polishing machine comprises an x-direction guide rail 1, a z-direction guide rail, a self-locking device 2, a y-direction guide rail 3, upright posts 4, a machine body 5, a workbench 6, a parallel polishing tool system 7 and a connecting plate 8, wherein the number of the upright posts 4 is four, the upright posts 4 are respectively and fixedly connected to four corners of the machine body 5 through bolts, the workbench 6 is fixedly connected to the machine body 5 through bolts, the left side and the right side of the two y-direction guide rails 3 are respectively and fixedly connected to the upper ends of the four upright posts 4 on the left side and the right side through bolts, the x-direction guide rail 1 is fixedly connected to a sliding table of the y-direction guide rail 3 through bolts, the z-direction guide rail and the self-locking device 2 are fixedly connected to a sliding table of the x-direction guide rail 1, the parallel polishing tool system 7 is fixedly connected to the connecting plate 8 through bolts, and the connecting plate 8 is fixedly connected to a sliding table of the z-direction guide rail 2 through bolts.
The X-direction guide rail 1 comprises an X-direction guide rail motor 101, an X-direction guide rail base 102, an X-direction guide rail synchronous belt 103, an X-direction guide rail 104, an X-direction guide rail sliding table 105, an X-direction guide rail tension pulley 106 and an X-direction guide rail pin shaft 107, wherein the X-direction guide rail motor 101 is fixedly connected in the motor base of the X-direction guide rail base 102 through screws, the X-direction guide rail 104 is fixedly connected on the X-direction guide rail base 102 through screws, the X-direction guide rail sliding table 105 is in sliding connection with the X-direction guide rail 104, the X-direction guide rail tension pulley 106 is fixed on the X-direction guide rail base 102 through the X-direction guide rail pin shaft 107, the pin shaft is in threaded connection with the X-direction guide rail base 102, and the X-direction guide rail synchronous belt 103 is wrapped on a driving wheel of the X-direction guide rail motor 101 and the X-direction guide rail tension pulley 106 and is fixedly connected with the X-direction guide rail sliding table 105.
The y-guide rail 3 comprises a y-guide rail base 301, a y-guide rail 302, a y-guide rail sliding table 303, a y-guide rail synchronous belt 304, a y-guide rail tension pulley 305, a y-guide rail pin shaft 306 and a y-guide rail motor 307, wherein the y-guide rail motor 307 is fixedly connected in a motor base of the y-guide rail base 301 through screws, the y-guide rail 302 is fixedly connected on the y-guide rail base 301 through screws, the y-guide rail sliding table 303 is slidably connected with the y-guide rail 302, the y-guide rail tension pulley 305 is fixedly connected on the y-guide rail base 301 through the y-guide rail pin shaft 306, the y-guide rail pin shaft 306 is in threaded connection with the y-guide rail base 301, and the y-guide rail synchronous belt 304 is wrapped on a driving wheel of the y-guide rail motor 307 and the y-guide rail tension pulley 305 and is fixedly connected with the y-guide rail sliding table 303.
The z-direction guide rail and self-locking device 2 include sprocket 201, chain 202, z-direction guide rail motor 203, weight box 204, chain connecting block 205, pneumatic push rod 206, shaft coupling 207, z-direction guide rail slip table 208, z-direction guide rail base 209, z-direction guide rail lead screw 210, z-direction guide rail 211, z-direction guide rail lead screw mount pad 212, frame 213, two weight boxes 204 respectively through the left and right sides at the frame 213 rear, four sprocket 201 pass through the mount pad and connect four angles at frame 213 upper surface, z-direction guide rail base 209 passes through screw fixed connection at the front end of frame 213, z-direction guide rail motor 203 passes through screw fixed connection at z-direction guide rail base 209 up end, two z-direction guide rail lead screw mount pads 212 pass the bearing of two lead screw mount pads 212 through the thrust collar fixed, shaft coupling 207 and the main shaft of z-direction guide rail motor 203 and z-direction guide rail lead screw 210 pass through pin connection, the lead screw nut of z-direction guide rail slip table 208 passes through screw thread connection 208, the slider 205 passes through the screw thread connection 205 and the right-direction guide rail 205, the slider passes through the screw 205 and the left and right sides 205 are connected at two both sides at two push rod 206 through the slider connecting block.
The parallel polishing tool system 7 comprises a static platform 701, a hook joint 702, a screw rod module 703, a connecting block 704, claw-shaped connecting pieces 705, a first connecting piece 706, a second connecting piece 707, a movable platform module 708 and a spherical hinge 709, wherein the three hook joints 702 are fixedly connected to the static platform 701 through bolts respectively, the three screw rod module 703 is fixedly connected with the three hook joints 702 through bolts respectively, the three connecting blocks 704 are fixedly connected to the end face of the screw rod module 703 through bolts, the two claw-shaped connecting pieces 705 are fixedly connected to the connecting blocks 704 positioned on the left side and the right side of the static platform 701 through bolts respectively, the spherical hinge 709 is fixedly connected to the left side and the right side of the movable platform module 708 through bolts respectively, the two first connecting pieces 706 and the two claw-shaped connecting pieces 705 positioned on the left side and the right side of the static platform 701 are hinged through pin shafts, and the rest of the two connecting pieces 707 are hinged to the cross shaft of the spherical hinge 709.
The screw module 703 comprises a motor 70301, a motor mounting bottom plate 70302, a guide rail 70303, a sliding table 70304, a displacement sensor 70305, a connecting bottom plate 70306, a motor coupler 70307, a screw mounting seat 70308, a photoelectric sensor 70309, a screw 70310 and a module bottom plate 70311, wherein the motor 70301 is fixedly connected to the motor mounting bottom plate 70302 through a screw, the motor mounting bottom plate 70302 is fixedly connected to the module bottom plate 70311 through a screw, the guide rail 70303 is fixedly connected to the module bottom plate 70311 through a screw, the connecting bottom plate 70306 is connected to the module bottom plate 70311 through a screw, the screw mounting seat 70308 is fixedly connected to the module bottom plate 70311 through a screw, the photoelectric sensor 70309 is fixedly connected to the module bottom plate through a screw, a main shaft of the motor coupler 70307 is connected with the screw 70310 through a pin, a screw nut of the sliding table 70304 is connected with the screw 70310 through a screw, a sliding block of the sliding table 70304 is slidably connected to the guide rail 70303, and a measuring telescopic rod of the displacement sensor 70305 is fixedly connected to a connecting plate 70304 through a screw.
The sliding table 70304 comprises a sensor sensing piece 7030401, a sliding table base 7030402, a sensor connecting plate 7030403, a nut mounting plate 7030404, a screw nut 7030405 and a sliding block 7030406, wherein the sensor sensing piece 7030401 is fixedly connected to the left side face of the sliding table base 7030402 through a screw, the sliding block 7030406 is fixedly connected to the bottom face of the sliding table base 7030402 through a screw, the sensor connecting plate 7030403 is connected with the sliding table base 7030402 through a screw, the nut mounting plate 7030404 is connected in a groove on the bottom face of the sliding table base 7030402 through a screw, and the screw nut 7030405 is connected to the nut mounting plate 7030404 through a screw.
The Hooke hinge 702 comprises a Hooke hinge base 70201 and a short shaft 70202, wherein the short shaft 70202 penetrates through a bearing of the base 70201 and is fixed by a thrust ring; the spherical hinge 709 comprises a spherical hinge base 70902 and a cross shaft 70901, wherein the cross shaft 70901 passes through a bearing of the spherical hinge base 70902 and is fixed by a thrust ring; the spherical hinge base 70902 has the same structure as the hook base 70201;
the hook hinge base 70201 includes a bearing 7020101, an upper connection seat 7020102, an end cover 7020103, a lower connection seat 7020104, an upper base 7020105, a lower base 7020106, a short round pin 7020107, a stepped shaft 7020108, and a bearing 7020109, wherein the bearing 7020101 is fastened by using the end cover 7020103 through a bearing mounting hole of the upper connection seat 7020102, the end cover 7020103 is connected to the upper connection seat 7020102 through a screw, the upper connection seat 7020102 is fixed to the lower connection seat 7020104 through a screw, the upper base 7020105 and the lower base 7020106 are connected through bolts, the stepped shaft 7020108 is fixed by two bearings 7020109, the upper base 7020105 and the lower base 7020106 through two ends, and the stepped shaft 7020108 and the lower connection seat 7020104 are connected through the short round pin 7020107.
The movable platform module 708 comprises a spindle motor 70801, a spindle motor mounting seat 70802, a movable platform 70803, a short taper pin 70804 and a tool head 70805, wherein the spindle motor 70801 is connected in the spindle motor mounting seat 70802 through screws, the spindle motor mounting seat 70802 is connected on the movable platform 70803 through screws, and a spindle of the spindle motor 70801 and the tool head 70805 are connected through threads and fixed through the short taper pin 70804.
A control method of a precision milling and grinding machine tool based on a parallel tool system comprises the following steps:
a coordinate system XYZ is established by taking the geometric center of the static platform 701 as an origin, wherein the Z axis is a straight line passing through the geometric center of the static platform 701 in the vertical direction, the X axis is a horizontal straight line which is in the horizontal plane and is parallel to the X guide rail 1 through the geometric center of the static platform 701, the Y axis is a horizontal straight line which is in the horizontal plane and is parallel to the Y guide rail 3 through the geometric center of the static platform 701, a coordinate system X 'Y' Z 'is established by taking the geometric center of the movable platform module 708 as the origin, the Z' axis is a straight line passing through the geometric center of the movable platform module 708 in the vertical direction, the X 'axis is a horizontal straight line which is in the horizontal plane and is parallel to the X guide rail 1 through the geometric center of the movable platform module 708, the Y' axis is a horizontal straight line which is in the horizontal plane and is parallel to the Y guide rail 3 through the geometric center of the movable platform module 708, and after a workpiece is clamped and fixed on a workbench through a clamp, a parallel polishing tool system is conveyed to a position of a point to be processed through a triaxial moving platform, and the position of the static platform and the workpiece is determined;
(II) description of motion geometrical relationship of the movable platform module in the fixed platform coordinate system XYZ:
let A 1 、B 1 、C 1 The coordinate vectors in the XYZ coordinate system are:
A 1 ＝(A 1x ,A 1y ,A 1z ) T ＝(2D,0,0) T
B 1 ＝(B 1x ,B 1y ,B 1z ) T ＝(-D,H,0) T
C 1 ＝(C 1x ,C 1y ,C 1z ) T ＝(-D,-H,0) T
let A 2 、B 2 、C 2 The coordinate vectors in the X ' Y ' Z ' coordinate system are:
A 2 ＝(2d,0,0) T
B 2 ＝(-d,h,0) T
C 2 ＝(-d,-h,0) T
wherein ,A1 、B 1 、C 1 Is a hinge point of a static platform, A 2 、B 2 、C 2 Is a hinge point of the movable platform module;
the motion relationship of the movable stage module 708 with respect to the continuous rotation and translation of the stationary stage 701 is described in terms of a matrix (α, β, z), where α, β respectively represents the rotation of the movable stage module 708 about the X, Y axisZ represents the amount of movement of the movable stage module 708 in the Z-axis direction, and the X-axis rotation transformation matrix of the movable stage module 708 to the stationary stage 701 is R x Rotating the transformation matrix R around the Y-axis y Translation transformation matrix P along Z-axis z The specific transformation matrix is as follows:
when the movable platform module 708 continuously rotates with respect to the stationary platform 701, the posture transformation matrix thereof is:
(A 2x ,A 2y ,A 2z ) T 、(B 2x ,B 2y ,B 2z ) T 、(C 2x ,C 2y ,C 2z ) T respectively represent A in the coordinate system of the movable platform module 708 2 、B 2 、C 2 Transformation of coordinate vectors into the coordinate system of stationary platform 701
(A 2x ,A 2y ,A 2z ) T ＝(2dcosβ,0,-2dsinβ+z) T
(C 2x ,C 2y ,C 2z ) T ＝(dcosβ-hsinαsinβ,-hcosα,dsinβ-hsinαcosβ+z) T
(III), A 1 A 2 、B 1 B 2 、C 1 C 2 Relation between length of (d) and position of movable platform module
Combining step (two), a when the movable platform module 708 is in any posture 1 A 2 、B 1 B 2 、C 1 C 2 Length of (2):
in the posture change process, three lead screw module control motors respectively control the moving distance of the sliding table to be:
wherein lA0 、l B0 、l C0 A before the movable platform module 708 adjusts the pose 1 A 2 、B 1 B 2 、C 1 C 2 Length of l A1 、l B1 、l C1 A after the movable platform module 708 is adjusted in position and posture 1 A 2 、B 1 B 2 、C 1 C 2 Length Deltal of (2) A 、△l B 、△l C Representation ofA 1 A 2 、B 1 B 2 、C 1 C 2 The amount of change in length of (2);
in summary, any posture of the motion platform module 708 always has a unique A 1 A 2 、B 1 B 2 、C 1 C 2 Corresponding to the length of (A) can be controlled by controlling A in the absence of external force 1 A 2 、B 1 B 2 、C 1 C 2 The length of the movable platform module 708 can control the movable platform module 708 to reach the theoretical correct position X, but the actual position of the movable platform module 708 is Xa because the tool head is influenced by the contact force in the processing process;
fourth, eliminate the error caused by the deformation of the tool head due to the stress
In the machining process, the tool head is contacted with the machined surface of the workpiece to generate normal contact force and tangential friction force, the tangential friction force is ignored, and in order to achieve the best machining effect, the normal contact force is controlled in a certain range and is set to be F N And analyzing the stress condition in the processing process by applying the Hertz contact theory: the tool head is regarded as a rigid material, when the tool head is contacted with a curved surface to be processed, the surface to be processed is slightly deformed at the contact point, two contacted objects are ideally processed, the workpiece is regarded as a flexible body, the tool head is regarded as a rigid body, and the elastic deformation completely occurs on the workpiece;
the deformation epsilon and the contact force F are known by the Hertz theory N Satisfies the following formula:
contact force F N ：
From the known elastic deformation ε, the relative elastic modulus E * Tool head and surface R of workpiece to be processed e Are all to polishing force F N An influence is generated. But in one step of the process, is opposed toModulus of elasticity E * And the relative curvature radius R of the tool head and the curved surface of the workpiece at the initial contact point e Is determined so that the normal elastic deformation epsilon and the contact force F N Directly related. The normal deformation of the workpiece under the expected contact force can be distributed to the motion quantity of each workbench of the machine tool according to the motion track planning, and the position in the coordinate system Xb of the static platform of the tool head is set at the moment;
fifth, impedance control contact force control model based on position
(1) Detection of tool head normal contact force
Each mechanical arm of the three-degree-of-freedom parallel structure tool system is provided with a force sensor, the force applied by the mechanical arm along the direction of the mechanical arm can be detected, and the mechanical arm A is known from the force relation 1 A 2 Component force of thrust to the movable platform along the normal direction of the movable platform:
similarly, mechanical arm B 1 B 2 Mechanical arm C 1 C 2 Component force of thrust to the movable platform along the normal direction of the movable platform:
F 2n ＝F 2 cosγ
F 3n ＝F 3 cosδ
tool head normal contact force:
wherein ,
is l A0 With plane A 2 B 2 C 2 Included angle of (2), gamma is l B0 With plane A 2 B 2 C 2 Delta is l C0 With plane A 2 B 2 C 2 Included angle F of (F) 1 Is along l A0 Force in the direction F 2 Is along l B0 Force in the direction F 3 Is along l C0 Force applied in the direction, G is the gravity applied to the movable platform module, and θ is the gravity and the plane A 2 B 2 C 2 Is included in the bearing.
(2) Impedance model
The force sensor detects real-time contact force, and the real-time contact force is compared with the theoretical contact force required by processing, and the difference is made to obtain an error F e Will error F e Input into an outer ring impedance control model H (F), and the impedance control model generates a contact force error F according to corresponding calculation e A corresponding displacement correction amount E is input into an inner ring position control model G p Is a kind of medium. The inner ring position control model outputs corresponding position correction information to a motion mathematical model G of the three-degree-of-freedom parallel polishing tool system, and the following impedance control model can be established according to a control strategy:
in order to ensure the transition stability in the tool head control process, the parameters should first satisfy the following formula:
wherein ,Md Is a target inertia matrix, B d Is a target damping matrix, K d Is a target rigidity matrix, E is a correction value of deviation between actual position and theoretical position of tool head, F e Is the difference between the detected value of the contact force and the theoretical value;
the controller can generate a position correction quantity E according to the error of the real-time polishing power value and the expected value through the control model, and the correction quantity E is added to Deltal through the kinematic inverse solution A 、△l B 、△l C The final machining position Xc is obtained.
In summary, the machine tool is generally divided into two parts: the three-axis machine tool mainly realizes the transfer of the parallel tool system to the position of a processing point, the parallel tool system mainly realizes the posture adjustment of a tool head in space and the feeding and retracting of a tool head in the Z direction, the length variation of three mechanical arms connected with a movable platform and a static platform is reversely calculated at the position of the processing point through the posture of an ideal tool system, and the purpose of controlling the position of the movable platform is achieved by controlling the lengths of the three mechanical arms.
Claims (4)
1. A control method of a precision milling and grinding machine tool based on a parallel tool system is characterized by comprising the following steps of:
the precise milling and grinding machine tool of the parallel tool system comprises an x-direction guide rail, a z-direction guide rail, a self-locking device, a y-direction guide rail, upright posts, a machine tool body, a workbench, a parallel polishing tool system and a connecting plate, wherein the number of the upright posts is four, the upright posts are respectively and fixedly connected to four corners of the machine tool body through bolts, the workbench is fixedly connected to the machine tool body through bolts, the two y-direction guide rails are respectively and fixedly connected to the upper ends of the four upright posts on the left side and the right side through bolts, the x-direction guide rails are fixedly connected to sliding tables of the y-direction guide rails through bolts, the z-direction guide rail and the self-locking device are fixedly connected to sliding tables of the x-direction guide rail through bolts, the parallel polishing tool system is fixedly connected to the connecting plate through bolts, and the connecting plate is fixedly connected to sliding tables of the z-direction guide rail through bolts;
the parallel polishing tool system comprises a static platform, a hook joint, a screw rod module, connecting blocks, claw-type connecting pieces, a first connecting piece, a second connecting piece, a movable platform module and a spherical hinge, wherein the three hook joints are fixedly connected to the static platform through bolts respectively, the three screw rod modules are fixedly connected with the three hook joints through bolts respectively, the three connecting pieces are fixedly connected to the end faces of the screw rod module through bolts, the two claw-type connecting pieces are fixedly connected to the connecting pieces positioned on the left side and the right side of the static platform through bolts, the spherical hinge is fixedly connected to the rest connecting piece through bolts, the first connecting piece is fixedly connected to the left side and the right side of the movable platform module through bolts respectively, the first connecting piece and the second claw-type connecting piece positioned on the left side and the right side of the static platform are hinged through pin shafts, and the rest connecting piece is hinged to a cross shaft of the spherical hinge;
the screw rod module comprises a motor, a motor mounting bottom plate, a guide rail, a sliding table, a displacement sensor, a connecting bottom plate, a motor coupler, a screw rod mounting seat, a photoelectric sensor, a screw rod and a module bottom plate, wherein the motor is fixedly connected to the motor mounting bottom plate through a screw;
the sliding table comprises a sensor sensing piece, a sliding table base, a sensor connecting plate, a screw mounting plate, a screw nut and a sliding block, wherein the sensor sensing piece is fixedly connected to the left side surface of the sliding table base through a screw, the sliding block is fixedly connected to the bottom surface of the sliding table base through a screw, the sensor connecting plate is connected with the sliding table base through a screw, the screw mounting plate is connected in a groove on the bottom surface of the sliding table base through a screw, and the screw nut is connected to the screw mounting plate through a screw;
the Hooke hinge comprises a Hooke hinge base and a short shaft, and the short shaft penetrates through a bearing of the base and is fixed by a thrust ring; the spherical hinge comprises a spherical hinge base and a cross shaft, and the cross shaft penetrates through a bearing of the spherical hinge base and is fixed by a thrust ring; the spherical hinge base and the Hooke hinge base have the same structure;
the Hooke hinge base comprises a bearing, an upper connecting seat, an end cover, a lower connecting seat, an upper base, a lower base, a short round pin, a stepped shaft and a bearing, wherein the bearing is clamped through a bearing mounting hole of the upper connecting seat and the end cover, the end cover is connected to the upper connecting seat through a screw, the upper connecting seat is fixed on the lower connecting seat through a screw, the upper base and the lower base are connected through bolts, the stepped shaft is fixed with the upper base and the lower base through two bearings in a mode of fixing two ends, and the stepped shaft is connected with the lower connecting seat through the short round pin;
the movable platform module comprises a spindle motor, a spindle motor mounting seat, a movable platform, a short taper pin and a tool head, wherein the spindle motor is connected in the spindle motor mounting seat through a screw, the spindle motor mounting seat is connected on the movable platform through a screw, and a spindle of the spindle motor is connected with the tool head through threads and is fixed through the short taper pin;
comprises the following steps:
the method comprises the steps of (A) establishing a coordinate system XYZ by taking a geometric center of a static platform as an origin, wherein a Z axis is a straight line passing through the geometric center of the static platform in the vertical direction, an X axis is a horizontal straight line which is in a horizontal plane and is parallel to an X guide rail through the geometric center of the static platform, a Y axis is a horizontal straight line which is in a horizontal plane and is parallel to a Y guide rail through the geometric center of the static platform, and establishing a coordinate system X 'Y' Z 'by taking a geometric center of a movable platform module as the origin, wherein the Z' axis is a straight line passing through the geometric center of the movable platform module in the vertical direction, the X 'axis is a horizontal straight line which is in a horizontal plane and is parallel to the X guide rail through the geometric center of the movable platform module, and the Y' axis is a horizontal straight line which is in a horizontal plane and is parallel to the Y guide rail through the geometric center of the movable platform module; after a workpiece is clamped and fixed on a workbench through a clamp, a triaxial moving platform is utilized to send a parallel polishing tool system to the position of a point to be processed, and the positions of a static platform and the workpiece are determined;
(II) description of motion geometrical relationship of the movable platform module in the fixed platform coordinate system XYZ:
let A 1 、B 1 、C 1 The coordinate vectors in the XYZ coordinate system are:
A 1 ＝(A 1x ,A 1y ,A 1z ) T ＝(2D,0,0) T
B 1 ＝(B 1x ,B 1y ,B 1z ) T ＝(-D,H,0) T
C 1 ＝(C 1x ,C 1y ,C 1z ) T ＝(-D,-H,0) T
let A 2 、B 2 、C 2 The coordinate vectors in the X ' Y ' Z ' coordinate system are:
A 2 ＝(2d,0,0) T
B 2 ＝(-d,h,0) T
C 2 ＝(-d,-h,0) T
wherein ,A1 、B 1 、C 1 Is a hinge point of a static platform, A 2 、B 2 、C 2 Is a hinge point of the movable platform module;
the motion relation of the movable platform module relative to the continuous rotation and translation of the static platform is described by a matrix (alpha, beta, Z), wherein alpha, beta respectively represent the rotation angle of the movable platform module around X, Y axis, Z represents the movement amount of the movable platform module along the Z axis direction, and the rotation transformation matrix around the X axis, which is transformed from the movable platform module to the static platform, is R x Rotating the transformation matrix R around the Y-axis y Translation transformation matrix P along Z-axis z The specific transformation matrix is as follows:
when the movable platform module continuously rotates relative to the static platform, the gesture transformation matrix is as follows:
(A 2x ,A 2y ,A 2z ) T 、(B 2x ,B 2y ,B 2z ) T 、(C 2x ,C 2y ,C 2z ) T respectively represent A in a moving platform module coordinate system 2 、B 2 、C 2 Transforming into a coordinate vector in a static platform coordinate system;
(A 2x ,A 2y ,A 2z ) T ＝(2dcosβ,0,-2dsinβ+z) T
(C 2x ,C 2y ,C 2z ) T ＝(dcosβ-hsinαsinβ,-hcosα,dsinβ-hsinαcosβ+z) T
(III), A 1 A 2 、B 1 B 2 、C 1 C 2 Relation between length of (d) and position of movable platform module
Combining step (II), A when the movable platform module is in any posture 1 A 2 、B 1 B 2 、C 1 C 2 Length of (2)
In the posture change process, three lead screw module control motors respectively control the moving distance of the sliding table to be:
wherein lA0 、l B0 、l C0 A before the pose adjustment is respectively carried out for the movable platform module 1 A 2 、B 1 B 2 、C 1 C 2 Length of l A1 、l B1 、l C1 A is that the movable platform module carries out pose adjustment 1 A 2 、B 1 B 2 、C 1 C 2 Length Deltal of (2) A 、△l B 、△l C Representation A 1 A 2 、B 1 B 2 、C 1 C 2 The amount of change in length of (2);
in summary, any posture of the movable platform module always has a unique A 1 A 2 、B 1 B 2 、C 1 C 2 Corresponding to the length of (A) can be controlled by controlling A in the absence of external force 1 A 2 、B 1 B 2 、C 1 C 2 The length of the movable platform module can control the movable platform module to reach a theoretical correct position X, but the actual position of the movable platform module is Xa because the tool head is influenced by contact force in the processing process;
fourth, eliminate the error caused by the deformation of the tool head due to the stress
In the machining process, the tool head is contacted with the machined surface of the workpiece to generate normal contact force and tangential friction force, the tangential friction force is ignored, and in order to achieve the best machining effect, the normal contact force is controlled in a certain range and is set to be F N And analyzing the stress condition in the processing process by applying the Hertz contact theory: the tool head is regarded as a rigid material, when the tool head is contacted with a curved surface to be processed, the surface to be processed is slightly deformed at the contact point, two contacted objects are ideally processed, the workpiece is regarded as a flexible body, the tool head is regarded as a rigid body, and the elastic deformation completely occurs on the workpiece;
the deformation epsilon and the contact force F are known by the Hertz theory N Satisfies the following formula:
contact force F N ：
From the known elastic deformation ε, the relative elastic modulus E * Tool head and surface R of workpiece to be processed e Are all to polishing force F N The relative elastic modulus E in one step of the process * And the relative curvature radius R of the tool head and the curved surface of the workpiece at the initial contact point e Is determined so that the normal elastic deformation epsilon and the contact force F N Directly related, normal deformation of a workpiece under expected contact force can be distributed to the motion quantity of each workbench of the machine tool according to motion track planning, and the position in a coordinate system Xb of a static platform of the tool head is set to be Xb;
fifth, impedance control contact force control model based on position
(1) Detection of tool head normal contact force
Each mechanical arm of the three-degree-of-freedom parallel structure tool system is provided with a force sensor, the force applied by the mechanical arm along the direction of the mechanical arm can be detected, and the mechanical arm A is known from the force relation 1 A 2 Component force of thrust to the movable platform along the normal direction of the movable platform:
similarly, mechanical arm B 1 B 2 Mechanical arm C 1 C 2 Component force of thrust to the movable platform along the normal direction of the movable platform:
F 2n ＝F 2 cosγ
F 3n ＝F 3 cosδ
tool head normal contact force:
wherein ,
is l A0 With plane A 2 B 2 C 2 Included angle of (2), gamma is l B0 With plane A 2 B 2 C 2 Delta is l C0 With plane A 2 B 2 C 2 Included angle F of (F) 1 Is along l A0 Force in the direction F 2 Is along l B0 Force in the direction F 3 Is along l C0 Force applied in the direction, G is the gravity applied to the movable platform module, and θ is the gravity and the plane A 2 B 2 C 2 Is included in the plane of the first part;
(2) Impedance model
The force sensor detects real-time contact force, and the real-time contact force is compared with the theoretical contact force required by processing, and the difference is made to obtain an error F e Will error F e Input into an outer ring impedance control model H (F), and the impedance control model generates a contact force error F according to corresponding calculation e A corresponding displacement correction amount E is input into an inner ring position control model G p The inner ring position control model outputs corresponding position correction information to a motion mathematical model G of the three-degree-of-freedom parallel polishing tool system, and the following impedance control model can be established according to a control strategy:
in order to ensure the transition stability in the tool head control process, the parameters should first satisfy the following formula:
wherein ,Md Is a target inertia matrix, B d Is a target damping matrix, K d Is a target rigidity matrix, E is a correction value of deviation between actual position and theoretical position of tool head, F e Is the difference between the detected value of the contact force and the theoretical value;
the controller can generate a position correction quantity E according to the error of the real-time polishing power value and the expected value through the control model, and the correction quantity E is added to Deltal through the kinematic inverse solution A 、△l B 、△l C The final machining position Xc is obtained.
2. The control method of the precision milling and shaping machine tool based on the parallel tool system as claimed in claim 1, wherein: the X-shaped guide rail comprises an X-shaped guide rail motor, an X-shaped guide rail base, an X-shaped guide rail synchronous belt, an X-shaped guide rail sliding table, an X-shaped guide rail tensioning wheel and an X-shaped guide rail pin shaft, wherein the X-shaped guide rail motor is fixedly connected in a motor seat of the X-shaped guide rail base through screws, the X-shaped guide rail is fixedly connected on the X-shaped guide rail base through screws, the X-shaped guide rail sliding table is in sliding connection with the X-shaped guide rail, the X-shaped guide rail tensioning wheel is fixedly arranged on the X-shaped guide rail base through the X-shaped guide rail pin shaft, the pin shaft is in threaded connection with the X-shaped guide rail base, and the X-shaped guide rail synchronous belt is wrapped on a driving wheel of the X-shaped guide rail motor and the X-shaped guide rail tensioning wheel and is fixedly connected with the X-shaped guide rail sliding table.
3. The control method of the precision milling and shaping machine tool based on the parallel tool system as claimed in claim 1, wherein: the Y-direction guide rail comprises a Y-direction guide rail base, a Y-direction guide rail sliding table, a Y-direction guide rail synchronous belt, a Y-direction guide rail tension wheel, a Y-direction guide rail pin shaft and a Y-direction guide rail motor, wherein the Y-direction guide rail motor is fixedly connected in the motor base of the Y-direction guide rail base through screws, the Y-direction guide rail is fixedly connected on the Y-direction guide rail base through screws, the Y-direction guide rail sliding table is in sliding connection with the Y-direction guide rail, the Y-direction guide rail tension wheel is fixedly arranged on the Y-direction guide rail base through the Y-direction guide rail pin shaft, the Y-direction guide rail pin shaft is in threaded connection with the Y-direction guide rail base, and the Y-direction guide rail synchronous belt is wrapped on the driving wheel of the Y-direction guide rail motor and the Y-direction guide rail tension wheel and is fixedly connected with the Y-direction guide rail sliding table.
4. The control method of the precision milling and shaping machine tool based on the parallel tool system as claimed in claim 1, wherein: the z-direction guide rail and the self-locking device comprise chain wheels, chains, a z-direction guide rail motor, weight boxes, chain connecting blocks, pneumatic push rods, couplings, a z-direction guide rail sliding table, a z-direction guide rail base, a z-direction guide rail lead screw, a z-direction guide rail lead screw mounting seat and a frame, wherein the two weight boxes are respectively connected with the left side and the right side of the back of the frame through screws, the four chain wheels are connected with four corners of the upper surface of the frame through the mounting seats, the z-direction guide rail base is fixedly connected with the front end surface of the frame through screws, the z-direction guide rail motor is fixedly connected with the upper end surface of the z-direction guide rail base through screws, two z-guide lead screw mount pad pass through screw fixed connection in z-guide rail mount pad openly, the bearing that two lead screw mount pads were passed to the z-guide lead screw passes through thrust collar fixed, the shaft coupling passes through pin connection with the main shaft of z-guide motor and z-guide lead screw, screw nut and the z-guide lead screw of z-guide slip table pass through threaded connection, the slider and the z-guide rail sliding connection of z-guide slip table, two chain connecting blocks pass through screw connection in z-guide slip table left and right sides, chain one end passes through pin connection with the chain connecting block, the balancing weight of the other end and weight box passes through pin connection, two pneumatic push rods pass through screw connection in z-guide slip table left and right sides.
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| CN110450028B (en) * | 2019-09-18 | 2020-12-22 | 浙江大学宁波理工学院 | Complex curved surface grinding and polishing device |
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