Three-degree-of-freedom large-stroke fast tool servo device and curved surface machining method thereof

Abstract

The application discloses a three-freedom-degree large-stroke fast-tool-servo device, which comprises a workbench, a voice coil motor, a Z-direction displacement transmission mechanism, a three-axis connecting mechanism, an X-direction driving platform, a Y-direction driving platform, a tool holder and a tool. The three-axis connecting mechanism comprises a three-axis connecting plate and a three-axis connecting frame, and the three-axis connecting plate is connected with the three-axis connecting frame through X-axis and Y-axis flexible hinges around the three-axis connecting plate. The flexible hinges are provided with Z-axis flexible hinge points. The double-axis flexible hinges are provided with at least one X-axis flexible hinge point and one Y-axis flexible hinge point. The Z-direction displacement transmission mechanism, the three-axis connecting mechanism and the driver connecting rod are designed in an integrated mode. The piezoelectric ceramic driver is adopted. The three-freedom-degree active cutting of the tool can be realized, the large-stroke output capacity is achieved, the machining process of a complex optical surface can be efficiently completed, the displacement errors in multiple directions can be compensated, and the cutting force disturbance problem is solved.

Description

Technical Field

[0001] This invention belongs to the field of ultra-precision machining and optical freeform surface machining technology, specifically relating to a three-degree-of-freedom large-stroke fast tool servo device and its surface machining method. Background Technology

[0002] Compared to traditional optical components, freeform optical components offer significant advantages such as improved optical performance, optimized product structure, and lightweight design. With the rapid advancements in technology, freeform optical surfaces are widely used in various fields, including core technologies such as defense, aviation, aerospace, and military, as well as medical equipment, 3D scanning, and infrared night vision. Therefore, the processing and manufacturing of optical components with freeform optical surfaces is of great significance.

[0003] Traditional optical surface machining methods, such as slow-tool servo machining, grinding, and flying cutting, can all achieve ultra-precision machining, but most are inefficient and time-consuming. Fast-tool servo devices can perform machining movements at higher frequencies, and different machining movements can be achieved depending on the structure and algorithm. With its advantages of high efficiency, high precision, low cost, and good flexibility, it is widely regarded as the most promising method for creating optical freeform surfaces.

[0004] Voice coil motor-driven fast tool servo devices are simple in structure, have a large stroke, and can achieve large-stroke displacement output. Fast tool servo systems using piezoelectric ceramics as actuators have advantages such as high frequency response, high precision, high rigidity, and large output force. By utilizing displacement amplification and transmission mechanisms, they can also achieve large-stroke output. At the same time, most fast tool servo devices can only achieve a single degree of freedom, limiting the types of optical surfaces they can machine. In contrast, multi-degree-of-freedom fast tool servo devices can achieve multi-directional active cutting and multi-directional displacement compensation, solve cutting force disturbances, achieve synchronization and coordination between the machine tool spindle and the FTS device, overcome the problems existing in single-degree-of-freedom FTS machining, and expand the field and processing capabilities of FTS diamond turning based on optical freeform surface machining. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems by providing a three-degree-of-freedom large-stroke fast tool servo device and its surface machining method.

[0006] A three-degree-of-freedom long-stroke fast tool servo device includes: a worktable 1, a voice coil motor 2, a Z-axis displacement transmission mechanism 3, a three-axis connection mechanism 4, an X-axis drive platform 5, a Y-axis drive platform 6, a tool holder 8, and a cutting tool 9.

[0007] The workbench frame 1 includes: a base plate 11, an upright plate 12, and a fixed outer frame 13. The upright plate 12 is located on one side of the base plate 11, and the voice coil motor 2 is located above the upright plate 12. The fixed outer frame 13 is located on the other side of the base plate 11.

[0008] The three-axis connection mechanism 4 includes: a three-axis connection plate 41 and a three-axis connection frame 42. The three-axis connection plate 41 is connected to the three-axis connection frame 42 around its perimeter by X-axis flexible hinges 43 and Y-axis flexible hinges 44. Each of the flexible hinges is provided with a Z-axis flexible hinge point.

[0009] The voice coil motor 2 is located above the vertical plate 12. The end of the voice coil motor mover 22 is connected to the left side of the three-axis connecting plate 41 through the biaxial flexible hinge 33 on the Z-direction displacement transmission mechanism 3. The tool holder 8 is installed on the right side of the three-axis connecting plate 41.

[0010] The biaxial flexible hinge 33 has at least one X-axis flexible hinge point and one Y-axis flexible hinge point;

[0011] The main bodies of the X-axis drive platform 5 and the Y-axis drive platform 6 are fixed on the fixed outer frame 13. The driver of the X-axis drive platform 5 is connected to the three-axis connecting frame 42 through a flexible hinge with a flexible hinge point in the Y-axis direction. The driver of the Y-axis drive platform 6 is connected to the three-axis connecting frame 42 through a flexible hinge with a flexible hinge point in the X-axis direction.

[0012] The aforementioned biaxial flexible hinges 33 are four in number, all of which are straight-round flexible hinges;

[0013] The X-axis drive platform 5 and Y-axis drive platform 6 are both two in number, using piezoelectric ceramic actuators and equipped with two-stage amplification linkage transmission;

[0014] The Z-direction displacement transmission mechanism 3, the triaxial connection mechanism 4, and the amplification connecting rod are integrated and made of 65Mn spring steel.

[0015] The servo device further includes a displacement sensor assembly, comprising: an X-axis displacement sensor 71, a Y-axis displacement sensor 72, and a Z-axis displacement sensor 73; two X-axis displacement sensors 71 and two Y-axis displacement sensors 72 are provided; all X-axis displacement sensors 71, Y-axis displacement sensors 72, and Z-axis displacement sensors 73 are inductive displacement sensors.

[0016] The servo device also includes a multi-axis controller;

[0017] The Y-axis drive platform 6 includes: an outer drive platform frame 61, an inner drive platform frame 62, a first transmission rod 63, a left first-stage amplification rod 64, a right first-stage amplification rod 65, a second-stage amplification rod 66, a Y-axis piezoelectric ceramic actuator 67, a front baffle 68, and a rear baffle 69.

[0018] The first transmission rod 63, the left first-stage amplification rod 64, the right first-stage amplification rod 65, and the second-stage amplification rod 66 are all symmetrical structures; the front baffle 68 and the rear baffle 69 are located on both sides of the drive platform outer frame 61; the drive platform inner frame 62 is located inside the drive platform outer frame 61.

[0019] The drive platform outer frame 61 has outer frame connecting rod flanges 611 on both sides; the bottom of the inner side of the drive platform outer frame 61 has a Y-direction piezoelectric ceramic mounting sleeve 612, and the bottom of the Y-direction piezoelectric ceramic driver 67 is fixed in the Y-direction piezoelectric ceramic mounting sleeve 612; the top of the Y-direction piezoelectric ceramic driver 67 is connected to the middle of the first transmission rod 63.

[0020] The first conductive rod 63 is provided with Y-shaped connecting arms 631 at both ends, and the Y-shaped connecting arms 631 at both ends are symmetrical; and the components connected to the left and right ends of the Y-shaped connecting arms 631 in sequence are also symmetrical to each other.

[0021] The Y-shaped connecting arm 631 has a first flexible hinge 632 on one side and a second flexible hinge 633 on the other side. The upper ends of one side of the Y-shaped connecting arms 631 are connected to the middle of the left first-stage amplification rod 64 through the first flexible hinge 632. The upper ends of the other side of the Y-shaped connecting arms 631 are connected to one end of the right first-stage amplification rod 65 through the second flexible hinge 633. The left end of the left first-stage amplification rod 64 has a third flexible hinge 641, and the lower left end of the left first-stage amplification rod 64 is connected to the outer frame connecting rod flange 611 through the third flexible hinge 641. The middle of the lower end of the right first-stage amplification rod 65 has a fourth flexible hinge 651, and the middle of the lower end of the right first-stage amplification rod 65 is connected to the left end of the inner frame 62 of the drive platform through the fourth flexible hinge 651.

[0022] The secondary amplification rod 66 is provided with a first connecting rod flexible hinge 661, a second connecting rod flexible hinge 662, and a third connecting rod flexible hinge 663; the lower end of the secondary amplification rod 66 near the middle is connected to the upper right side of the left primary amplification rod 64 through the first connecting rod flexible hinge 661; the lower right side of the secondary amplification rod 66 is connected to the upper right side of the right primary amplification rod 65 through the second connecting rod flexible hinge 662; the upper left side of the secondary amplification rod 66 is connected to the three-axis connecting frame 42 through the third connecting rod flexible hinge 663.

[0023] The first flexible hinge 632, the second flexible hinge 633, the third flexible hinge 641 and the fourth flexible hinge 651 are all connected by single Z-axis straight-round flexible hinges; the first link flexible hinge 661, the second link flexible hinge 662 and the third link flexible hinge 663 are all connected by double Z-axis straight-round flexible hinges.

[0024] The drive platform outer frame 61, outer frame connecting rod flange 611, drive platform inner frame 62, first transmission rod 63, Y-shaped connecting arm 631, first flexible hinge 632, second flexible hinge 633, left first-stage amplifying rod 64, third flexible hinge 641, right first-stage amplifying rod 65, fourth flexible hinge 651, second-stage amplifying rod 66, first connecting rod flexible hinge 661, second connecting rod flexible hinge 662, third connecting rod flexible hinge 663, three-axis connecting plate 41, three-axis connecting frame 42 and X-axis flexible hinge 43 are an integral structure;

[0025] The Y-axis piezoelectric ceramic mounting sleeve 612 is located inside one side of the drive platform outer frame 61; the Y-axis piezoelectric ceramic actuator 67 is sleeved in the Y-axis piezoelectric ceramic mounting sleeve 612; the Y-axis piezoelectric ceramic actuator 67 is connected to the first transmission rod 63; the left first-stage amplification rod 64, the right first-stage amplification rod 65, and the second-stage amplification rod 66 are connected by a straight-round flexible hinge. The left first-stage amplification rod 64 and the right first-stage amplification rod 65 both form a first-stage amplification lever with the fixed point of the drive platform outer frame 61 as the fulcrum; the Y-axis piezoelectric ceramic actuator 67 outputs a small displacement; the small displacement is transmitted to the right first-stage amplification rod 65 and the left first-stage amplification rod 64 through the first transmission rod 63, and after the displacement is amplified by the first stage, it is transmitted to the second-stage amplification rod 66, and then transmitted to the three-axis connection mechanism 4 by the third connecting rod flexible hinge 663. The cutting tool 9 is fixed to the cutting tool holder 8 by bolts, and the cutting tool holder 8 is fixed to the three-axis connection mechanism 4 by bolts, so that the linear movement of the cutting tool in this direction can be realized.

[0026] The X-axis drive platform 5 and the Y-axis drive platform 6 have the same structure.

[0027] A surface machining method using a three-degree-of-freedom, long-stroke fast tool servo device, comprising:

[0028] 1) The tool motion trajectory is obtained based on the surface contour of the graphic to be machined. The surface to be machined is preprocessed using relevant equipment, including the acquisition of the surface contour of the surface to be machined using LVDT, followed by tool path planning and tool radius compensation, to finally obtain the tool motion trajectory points of the graphic to be machined. After obtaining the tool trajectory points, the subsequent machining process is completed using the aforementioned device: the motion coordinates of the tool motion trajectory points are input to the multi-axis controller; the multi-axis controller controls the output displacement of the driver, which includes a voice coil motor and a piezoelectric ceramic driver; the voice coil motor is used to realize the displacement output in the Z direction, and the piezoelectric ceramic driver is used to realize the displacement output in the X and Y directions, thereby controlling the three-degree-of-freedom motion of the tool;

[0029] 2) The voice coil motor drives the reciprocating motion of the cutting tool in the Z direction alone; the reciprocating motion in the X and Y directions is achieved by two identical and symmetrically arranged X-direction piezoelectric ceramic actuators 57 and two oppositely arranged Y-direction piezoelectric ceramic actuators 67. During the cutting process, the input signals of the two symmetrically arranged X-direction piezoelectric ceramic actuators 57 and the two oppositely arranged Y-direction piezoelectric ceramic actuators 67 have opposite input rate of change, and the output displacement is amplified and transmitted to the cutting tool 9; at the same time, the characteristics of the flexible hinge are used to achieve three-degree-of-freedom decoupling; finally, the three-degree-of-freedom decoupled motion is achieved, and it also has a large stroke output capability, so as to efficiently complete the machining of complex optical surfaces;

[0030] 3) An X-axis displacement sensor 71, a Y-axis displacement sensor 72, and a Z-axis displacement sensor 73 are installed in the three directions of the three-axis connection mechanism 4. The X-axis displacement sensor 71, the Y-axis displacement sensor 72, and the Z-axis displacement sensor 73 are all inductive displacement sensors, which are simple in structure, highly sensitive, and have high resolution. They can be used to detect the actual output displacement of the cutting tool and feed the displacement back to the multi-axis controller in real time. The multi-axis controller processes the received signal and further controls the output displacement of each driver, thereby forming a closed-loop control system to achieve displacement error compensation in the X, Y, and Z directions and improve the overall machining accuracy of the fast tool servo device.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. The decoupled three-degree-of-freedom fast tool servo device disclosed in this invention employs two driving methods: a voice coil motor and a piezoelectric ceramic actuator, to realize the machining motion of the cutting tool in the X, Y, and Z directions respectively. Utilizing the transmission characteristics of flexible hinges, a straight-circular flexible hinge with mutually orthogonal opening directions is designed to decouple the cutting tool's motion in the three directions. Compared to single-degree-of-freedom fast tool servo devices, this invention can perform more complex surface machining, achieve active cutting in multiple directions and multi-directional displacement compensation, effectively solve the problem of cutting force disturbance, achieve synchronization and coordination between the machine tool spindle and the fast tool servo device, eliminate the limitations of single-degree-of-freedom fast tool servo devices in machining, and expand the diamond turning machining field and capabilities of fast tool servo devices based on surface machining.

[0033] 2. The decoupled three-degree-of-freedom fast tool servo device disclosed in this invention uses a voice coil motor to drive the Z-axis motion of the cutting tool, which has a large stroke capacity. The X and Y axes are driven by two piezoelectric ceramics respectively. The displacement is amplified by the displacement amplification mechanism and the displacement transmission mechanism, thereby meeting the large stroke machining capacity of three degrees of freedom. At the same time, the X and Y axes are driven by two piezoelectric ceramics drivers, which replaces the elastic deformation of the flexible hinge to complete the reverse motion of the cutting tool, reduces the displacement loss caused by the flexible hinge, and maximizes the performance of the piezoelectric ceramic itself.

[0034] 3. The decoupled three-degree-of-freedom fast tool servo device disclosed in this invention has a pre-tightening device designed for the piezoelectric ceramic actuator. The pre-tightening bolt pushes the pressure block to lock the piezoelectric ceramic actuator, thereby improving the overall rigidity of the device and maximizing the working performance of the piezoelectric ceramic actuator.

[0035] 4. The decoupled three-degree-of-freedom fast tool servo device disclosed in this invention adopts a highly symmetrical structure for the displacement amplification mechanism and the displacement transmission mechanism. The two are integrated into one structure, and the installation method is compact, eliminating assembly errors and parasitic displacements of flexible mechanisms, thereby improving the overall machining accuracy of the device.

[0036] 5. The decoupled three-degree-of-freedom fast tool servo device disclosed in this invention adopts an inductive displacement sensor, which has a simple structure, high sensitivity and high resolution, and can provide real-time feedback of the actual output displacement to the multi-axis processor to achieve displacement error compensation and improve the surface quality of the machined curved surface. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the overall structure of a three-degree-of-freedom large-stroke fast tool servo device according to the present invention;

[0038] Figure 2 This is a schematic diagram of the internal structure of a three-degree-of-freedom, large-stroke fast-tool servo device according to the present invention;

[0039] Figure 3 This is a schematic diagram of displacement amplification and transmission of a three-degree-of-freedom large-stroke fast tool servo device according to the present invention;

[0040] Figure 4 This is a schematic diagram of the Y-axis drive platform structure in a three-degree-of-freedom large-stroke fast tool servo device of the present invention;

[0041] Figure 5 This is a simplified kinematic diagram of the Y-displacement transmission mechanism in a three-degree-of-freedom, large-stroke fast-tool servo device of the present invention;

[0042] Figure 6 This is a schematic diagram of the Z-axis displacement transmission mechanism and the three-axis connection mechanism in a three-degree-of-freedom large-stroke fast tool servo device of the present invention;

[0043] Figure 7 This is a schematic diagram of the Y-axis piezoelectric ceramic actuator connection in a three-degree-of-freedom large-stroke fast tool servo device of the present invention;

[0044] In the diagram: 1. Workbench frame; 11. Base plate; 12. Vertical plate; 13. Fixed outer frame; 14. Reinforcing rib; 2. Voice coil motor; 21. Voice coil motor stator; 22. Voice coil motor mover; 3. Z-axis displacement transmission mechanism; 31. First connecting plate of Z-axis mechanism; 32. Second connecting plate of Z-axis mechanism; 33. Biaxial flexible hinge; 4. Three-axis connection mechanism; 41. Three-axis connecting plate; 42. Three-axis connecting frame; 43. X-axis flexible hinge; 44. Y-axis flexible hinge; 5. X-axis drive platform; 57. X-axis piezoelectric ceramic actuator; 512. X-axis piezoelectric ceramic mounting sleeve; 6. Y-axis drive platform; 61. Drive platform outer frame; 7. Outer frame connecting... Rod flange 611, drive platform inner frame 62, Y-axis piezoelectric ceramic mounting sleeve 612, first transmission rod 63, Y-shaped connecting arm 631, first flexible hinge 632, second flexible hinge 633, left first-stage amplification rod 64, third flexible hinge 641, right first-stage amplification rod 65, fourth flexible hinge 651, second-stage amplification rod 66, first connecting rod flexible hinge 661, second connecting rod flexible hinge 662, third connecting rod flexible hinge 663, Y-axis piezoelectric ceramic actuator 67, pressure block 671, front baffle 68, rear baffle 69, X-axis displacement sensor 71, Y-axis displacement sensor 72, Z-axis displacement sensor 73, sensor bracket 731, tool holder 8, tool 9. Detailed Implementation

[0045] Example 1: A three-degree-of-freedom, large-stroke fast tool servo device

[0046] See Figures 1 to 7 As shown, a three-degree-of-freedom large-stroke fast tool servo device includes: a worktable 1, a voice coil motor 2, a Z-axis displacement transmission mechanism 3, a three-axis connection mechanism 4, an X-axis drive platform 5, a Y-axis drive platform 6, a displacement sensor assembly, a tool holder 8, and a tool 9.

[0047] The workbench frame 1 includes: a base plate 11, an upright plate 12, and a fixed outer frame 13. The upright plate 12 is located on one side of the base plate 11, and a threaded hole 121 for locking the voice coil motor 2 is provided on the top of the upright plate 12. The fixed outer frame 13 is located on the other side of the base plate 11. A reinforcing rib 14 is also provided between the upright plate 12 and the base plate 11.

[0048] The voice coil motor 2 includes: a voice coil motor stator 21 and a voice coil motor mover 22, the voice coil motor mover 22 and the voice coil motor stator 21 being coaxially coupled; the voice coil motor stator 21 is fastened to the threaded hole 121 by bolts;

[0049] The voice coil motor mover 22 is bolted to the left end of the Z-direction displacement transmission mechanism 3; the right end of the Z-direction displacement transmission mechanism 3 is bolted to the three-axis connection mechanism 4; the right side of the three-axis connection mechanism 4 is bolted to the tool holder 8; that is, the voice coil motor 2 is connected to one side of the three-axis connection mechanism 4 through the Z-direction displacement transmission mechanism 3; the tool holder 8 is fixed to the other side of the three-axis connection mechanism 4.

[0050] The Z-direction displacement transmission mechanism 3 includes: a first connecting plate 31 for the Z-direction mechanism, a second connecting plate 32 for the Z-direction mechanism, and a biaxial flexible hinge 33;

[0051] The biaxial flexible hinge 33 is provided with at least one X-axis flexible hinge point and one Y-axis flexible hinge point; in this embodiment, there are 4 biaxial flexible hinges 33; the first connecting plate 31 of the Z-axis mechanism and the second connecting plate 32 of the Z-axis mechanism are connected by 4 biaxial flexible hinges 33.

[0052] The three-axis connection mechanism 4 includes: a three-axis connecting plate 41, a three-axis connecting frame 42, an X-axis flexible hinge 43, and a Y-axis flexible hinge 44; the X-axis flexible hinge 43 and the Y-axis flexible hinge 44 are both straight-round flexible hinges connected together; there are two of each of the X-axis flexible hinge 43 and the Y-axis flexible hinge 44; the left and right ends of the three-axis connecting plate 41 are respectively connected to the three-axis connecting frame 42 through the X-axis flexible hinge 43; the upper and lower ends of the three-axis connecting plate 41 are respectively connected to the three-axis connecting frame 42 through the Y-axis flexible hinge 44.

[0053] The axial displacement output of the voice coil motor mover 22 is transmitted to the three-axis connection mechanism 4 via the Z-axis displacement transmission mechanism 3; then the three-axis connection mechanism 4 drives the cutting tool 9 on the cutting tool holder 8 to achieve reciprocating motion in the Z-axis direction; wherein the voice coil motor 2 has the characteristic of large stroke in terms of displacement output, thus satisfying the large stroke displacement output in the Z-axis direction.

[0054] The four annular holes on the tool holder 8 are adjustable in the Y direction, and the cutting tool 9 is fixed to the tool holder by bolts, thereby realizing the Y-axis adjustability of the cutting tool.

[0055] The X-axis drive platform 5 and the Y-axis drive platform 6 have the same structure; there are two of each X-axis drive platform 5 and Y-axis drive platform 6; baffles are provided on both sides of the X-axis drive platform 5 and the Y-axis drive platform 6; the two X-axis drive platforms 5 are symmetrically arranged on both sides of the X-axis of the three-axis connecting mechanism 4; the two Y-axis drive platforms 6 are arranged opposite each other on both sides of the Y-axis of the three-axis connecting mechanism 4.

[0056] The X-axis drive platform 5 and the Y-axis drive platform 6 have the same structure. The specific analysis will be carried out with a single Y-axis drive platform 6, and the construction of the others is similar.

[0057] See Figure 4 As shown, the Y-axis drive platform 6 includes: an outer frame 61, an inner frame 62, a first transmission rod 63, a left first-stage amplifier rod 64, a right first-stage amplifier rod 65, a second-stage amplifier rod 66, a Y-axis piezoelectric ceramic actuator 67, a front baffle 68, and a rear baffle 69.

[0058] The first transmission rod 63, the left first-stage amplification rod 64, the right first-stage amplification rod 65, and the second-stage amplification rod 66 are all symmetrical structures; the front baffle 68 and the rear baffle 69 are located on both sides of the drive platform outer frame 61; the drive platform inner frame 62 is located inside the drive platform outer frame 61.

[0059] The drive platform outer frame 61 has outer frame connecting rod flanges 611 on both sides; the bottom of the inner side of the drive platform outer frame 61 has a Y-direction piezoelectric ceramic mounting sleeve 612, and the bottom of the Y-direction piezoelectric ceramic driver 67 is fixed in the Y-direction piezoelectric ceramic mounting sleeve 612; the top of the Y-direction piezoelectric ceramic driver 67 is connected to the middle of the first transmission rod 63.

[0060] The first conductive rod 63 is provided with Y-shaped connecting arms 631 at both ends, and the Y-shaped connecting arms 631 at both ends are symmetrical; and the components connected to the left and right ends of the Y-shaped connecting arms 631 in sequence are also symmetrical to each other.

[0061] The Y-shaped connecting arm 631 has a first flexible hinge 632 on one side and a second flexible hinge 633 on the other side. The upper ends of one side of the Y-shaped connecting arms 631 are connected to the middle of the left first-stage amplification rod 64 through the first flexible hinge 632. The upper ends of the other side of the Y-shaped connecting arms 631 are connected to one end of the right first-stage amplification rod 65 through the second flexible hinge 633. The left end of the left first-stage amplification rod 64 has a third flexible hinge 641, and the lower left end of the left first-stage amplification rod 64 is connected to the outer frame connecting rod flange 611 through the third flexible hinge 641. The middle of the lower end of the right first-stage amplification rod 65 has a fourth flexible hinge 651, and the middle of the lower end of the right first-stage amplification rod 65 is connected to the left end of the inner frame 62 of the drive platform through the fourth flexible hinge 651.

[0062] The secondary amplification rod 66 is provided with a first connecting rod flexible hinge 661, a second connecting rod flexible hinge 662, and a third connecting rod flexible hinge 663; the lower end of the secondary amplification rod 66 near the middle is connected to the upper right side of the left primary amplification rod 64 through the first connecting rod flexible hinge 661; the lower right side of the secondary amplification rod 66 is connected to the upper right side of the right primary amplification rod 65 through the second connecting rod flexible hinge 662; the upper left side of the secondary amplification rod 66 is connected to the three-axis connecting frame 42 through the third connecting rod flexible hinge 663.

[0063] The first flexible hinge 632, the second flexible hinge 633, the third flexible hinge 641 and the fourth flexible hinge 651 are all connected by single Z-axis straight-round flexible hinges; the first link flexible hinge 661, the second link flexible hinge 662 and the third link flexible hinge 663 are all connected by double Z-axis straight-round flexible hinges.

[0064] The drive platform outer frame 61, outer frame connecting rod flange 611, drive platform inner frame 62, first transmission rod 63, Y-shaped connecting arm 631, first flexible hinge 632, second flexible hinge 633, left first-stage amplifying rod 64, third flexible hinge 641, right first-stage amplifying rod 65, fourth flexible hinge 651, second-stage amplifying rod 66, first connecting rod flexible hinge 661, second connecting rod flexible hinge 662, third connecting rod flexible hinge 663, three-axis connecting plate 41, three-axis connecting frame 42 and X-axis flexible hinge 43 are an integral structure;

[0065] The Y-axis piezoelectric ceramic mounting sleeve 612 is located inside one side of the drive platform outer frame 61; the Y-axis piezoelectric ceramic actuator 67 is sleeved in the Y-axis piezoelectric ceramic mounting sleeve 612; the Y-axis piezoelectric ceramic actuator 67 is connected to the first transmission rod 63; the left first-stage amplification rod 64, the right first-stage amplification rod 65, and the second-stage amplification rod 66 are connected by a straight-round flexible hinge. The left first-stage amplification rod 64 and the right first-stage amplification rod 65 both form a first-stage amplification lever with the fixed point of the drive platform outer frame 61 as the fulcrum; the Y-axis piezoelectric ceramic actuator 67 outputs a small displacement; the small displacement is transmitted to the right first-stage amplification rod 65 and the left first-stage amplification rod 64 through the first transmission rod 63, and after the displacement is amplified by the first stage, it is transmitted to the second-stage amplification rod 66, and then transmitted to the three-axis connection mechanism 4 by the third connecting rod flexible hinge 663. The cutting tool 9 is fixed to the cutting tool holder 8 by bolts, and the cutting tool holder 8 is fixed to the three-axis connection mechanism 4 by bolts, so that the linear movement of the cutting tool in this direction can be realized.

[0066] The driving principle of the X-axis drive platform 5 is the same as that of the Y-axis drive platform. The entire X-axis and Y-axis drive platform realizes the first-level amplification, second-level amplification and transmission of displacement. At the same time, it is designed as an integrated structure with compact overall assembly, eliminating assembly errors and parasitic displacement of flexible hinges, and improving the overall machining accuracy of the fast tool servo device.

[0067] The displacement sensor assembly includes: an X-axis displacement sensor 71, a Y-axis displacement sensor 72, and a Z-axis displacement sensor 73; two X-axis displacement sensors 71 and two Y-axis displacement sensors 72 are provided; the X-axis displacement sensor 71, the Y-axis displacement sensor 72, and the Z-axis displacement sensor 73 are all inductive displacement sensors.

[0068] Two X-axis displacement sensors 71 are respectively installed on the rear baffles of the near-three-axis connecting frame 42 in the two X-axis drive platforms 5; two Y-axis displacement sensors 72 are respectively installed on the rear baffles of the near-three-axis connecting frame 42 in the two Y-axis drive platforms 6; and a Z-axis displacement sensor 73 is fixed to the base plate 11 by a sensor bracket 731.

[0069] The X-axis displacement sensor 71 serves as the X-axis displacement detection device, the Y-axis displacement sensor 72 serves as the Y-axis displacement detection device, and the Z-axis displacement sensor 73 serves as the Z-axis displacement detection device. That is, the X-axis displacement sensor 71, the Y-axis displacement sensor 72, and the Z-axis displacement sensor 73 detect the displacement output of the cutting tool 9 in the X, Y, and Z directions, and feed back the actual output displacement to the multi-axis controller in real time. The multi-axis controller is a control device independent of this device, used to process the feedback signal and perform relevant control on each driver, ultimately forming a closed-loop control system.

[0070] The Z-axis displacement transmission mechanism 3 is fixedly connected to the three-axis connection mechanism 4 by bolts; the three-axis connection mechanism 4 is locked to the tool holder 8; the Z-axis displacement is transmitted to the three-axis connection mechanism 4 through the Z-axis displacement transmission mechanism 3; the X-axis displacement and Y-axis displacement are output, amplified and transmitted through the drive platform, and finally transmitted to the three-axis connection mechanism 4 through the third link flexible hinge 663; the Z-axis displacement transmission mechanism 3 is designed with straight circular hinges with mutually orthogonal openings, and the hinge opening directions of the connecting rods connecting the inner and outer parts of the three-axis connection mechanism 4 are orthogonal to each other, thereby realizing the decoupling of the movement of the tool holder in the X, Y and Z directions, and finally realizing the three-degree-of-freedom cutting motion of the tool.

[0071] The principle of displacement amplification and transmission in the X and Y directions of this three-degree-of-freedom large-stroke fast tool servo device is explained using the Y-axis drive platform as an example. The Y-axis piezoelectric ceramic actuator 67 acts as the device driver. According to the direction of the small displacement output by the Y-axis piezoelectric ceramic actuator 67, the first transmission rod 63 transmits and amplifies the displacement, and finally outputs it to the three-axis connection mechanism 4. Based on the lever amplification principle, the large stroke output capability of the fast tool servo device in the X and Y directions is realized. The front end of the Y-axis piezoelectric ceramic actuator 67 is attached to the initial end of the displacement amplification mechanism, and the end end is attached to the pressure block 671. The end face of the pressure block 671 has a threaded hole for connection with the pre-tightening bolt. The Y-axis piezoelectric ceramic actuator 67 and the pressure block 671 are installed in the Y-axis piezoelectric ceramic mounting sleeve 612, thereby realizing the pre-tightening of the piezoelectric ceramic actuator and improving the overall rigidity of the device. The bolt pre-tightening is based on the thread self-locking principle, and the bolt can be continuously adjusted along the feed direction and the opposite direction, which is stable and reliable.

[0072] The three-degree-of-freedom, large-stroke fast tool servo device in this embodiment can be installed independently on a high-precision lathe for machining complex non-rotational optical surfaces. The voice coil motor enables large stroke output in the Z-axis, while the X and Y axes rely on piezoelectric ceramic actuators and displacement amplification mechanisms. Furthermore, a flexible hinge with three orthogonally opening directions is designed to decouple motion in the three directions, expanding the machining range and application areas. The displacement amplification mechanisms and displacement transmission rods of the X and Y drive platforms are designed as an integrated structure, eliminating parasitic displacements caused by the flexible mechanism. Inductive displacement sensors are installed in each direction to provide real-time feedback on the output displacement, improving the overall system's machining accuracy.

[0073] Example 2: A surface machining method using a three-degree-of-freedom, large-stroke fast tool servo device.

[0074] The following steps are taken for surface machining using a three-degree-of-freedom, large-stroke fast tool servo device as described in Example 1:

[0075] 1) The tool motion trajectory is obtained based on the surface contour of the graphic to be machined. The surface to be machined is preprocessed using relevant equipment, including the acquisition of the surface contour using LVDT. After tool path planning and tool radius compensation, the tool motion trajectory points of the graphic to be machined are finally obtained. After obtaining the tool trajectory points, the subsequent machining process is completed using this device: the motion coordinates of the tool motion trajectory points are input to the multi-axis controller; the multi-axis controller controls the output displacement of the driver, which includes a voice coil motor and a piezoelectric ceramic driver; the voice coil motor is used to realize the displacement output in the Z direction, and the piezoelectric ceramic driver is used to realize the displacement output in the X and Y directions, thereby controlling the three-degree-of-freedom motion of the tool.

[0076] 2) The voice coil motor drives the reciprocating motion of the cutting tool in the Z direction alone; the reciprocating motion in the X and Y directions is achieved by two identical and symmetrically arranged X-direction piezoelectric ceramic actuators 57 and two oppositely arranged Y-direction piezoelectric ceramic actuators 67. During the cutting process, the input change rate and direction of the two symmetrically arranged X-direction piezoelectric ceramic actuators 57 and the two oppositely arranged Y-direction piezoelectric ceramic actuators 67 are opposite, and the output displacement is amplified and transmitted to the cutting tool 9; at the same time, the characteristics of the flexible hinge are used to achieve three-degree-of-freedom decoupling; finally, the three-degree-of-freedom decoupled motion is achieved, and it also has a large stroke output capability, so as to efficiently complete the machining of complex optical surfaces;

[0077] 3) An X-axis displacement sensor 71, a Y-axis displacement sensor 72, and a Z-axis displacement sensor 73 are installed in the three directions of the three-axis connection mechanism 4. The X-axis displacement sensor 71, the Y-axis displacement sensor 72, and the Z-axis displacement sensor 73 are all inductive displacement sensors, which are simple in structure, highly sensitive, and have high resolution. They can be used to detect the actual output displacement of the cutting tool and feed the displacement back to the multi-axis controller in real time. The multi-axis controller processes the received signal and further controls the output displacement of each driver, thereby forming a closed-loop control system to achieve displacement error compensation in the X, Y, and Z directions and improve the overall machining accuracy of the fast tool servo device.

[0078] The surface machining method provided in this embodiment has a wide range of applications. It can achieve three-degree-of-freedom active cutting of the lathe tool while having a large stroke output capability. It can efficiently complete the machining process of complex optical surfaces and compensate for displacement errors in multiple directions. It effectively solves the problem of cutting force disturbance, realizes the synchronization and coordination between the machine tool spindle and the fast tool servo device, and expands the field and machining capability of diamond turning based on surface machining using a fast tool servo device.

Claims

1. A method for machining curved surfaces using a three-degree-of-freedom, large-stroke, fast-tool servo device, characterized in that: The three-degree-of-freedom large-stroke fast tool servo device includes: a workbench (1), a voice coil motor (2), a Z-axis displacement transmission mechanism (3), a three-axis connection mechanism (4), an X-axis drive platform (5), a Y-axis drive platform (6), a tool holder (8), a cutting tool (9), and a multi-axis controller; The workbench frame (1) includes: a base plate (11), an upright plate (12), and a fixed outer frame (13). The upright plate (12) is located on one side of the base plate (11), and the fixed outer frame (13) is located on the other side of the base plate (11). The three-axis connection mechanism (4) includes: a three-axis connection plate (41) and a three-axis connection frame (42). The three-axis connection plate (41) is connected to the three-axis connection frame (42) around its perimeter by X-axis flexible hinges (43) and Y-axis flexible hinges (44). All the flexible hinges are provided with Z-axis flexible hinge points. The voice coil motor (2) is located above the vertical plate (12). The end of the voice coil motor mover (22) is connected to the left side of the three-axis connecting plate (41) through the biaxial flexible hinge (33) on the Z-direction displacement transmission mechanism (3). The tool holder (8) is installed on the right side of the three-axis connecting plate (41). The biaxial flexible hinge (33) has at least one X-axis flexible hinge point and one Y-axis flexible hinge point; The main bodies of the X-axis drive platform (5) and the Y-axis drive platform (6) are fixed on the fixed outer frame (13). The driver of the X-axis drive platform (5) is connected to the three-axis connecting frame (42) through a flexible hinge with a flexible hinge point in the Y-axis direction. The driver of the Y-axis drive platform (6) is connected to the three-axis connecting frame (42) through a flexible hinge with a flexible hinge point in the X-axis direction. The aforementioned biaxial flexible hinge (33) consists of four types, all of which are straight-round flexible hinges; There are two X-axis drive platforms (5) and two Y-axis drive platforms (6), which use piezoelectric ceramic actuators and two-stage amplification linkage transmission. The Z-direction displacement transmission mechanism (3), the three-axis connection mechanism (4) and the amplification link are integrated and made of spring steel. The Y-axis drive platform (6) includes: drive platform outer frame (61), drive platform inner frame (62), first transmission rod (63), left first stage amplification rod (64), right first stage amplification rod (65), second stage amplification rod (66), Y-axis piezoelectric ceramic actuator (67), front baffle (68), and rear baffle (69). The first transmission rod (63), the left first-stage amplification rod (64), the right first-stage amplification rod (65) and the second-stage amplification rod (66) are all symmetrical structures; the front baffle (68) and the rear baffle (69) are located on both sides of the drive platform outer frame (61); the drive platform inner frame (62) is located inside the drive platform outer frame (61); The drive platform outer frame (61) has outer frame connecting rod flanges (611) on both sides; the drive platform outer frame (61) has a Y-direction piezoelectric ceramic mounting sleeve (612) at the bottom of the inner side, and the bottom of the Y-direction piezoelectric ceramic driver (67) is fixed in the Y-direction piezoelectric ceramic mounting sleeve (612); the top of the Y-direction piezoelectric ceramic driver (67) is connected to the middle of the first transmission rod (63); The first conductive rod (63) is provided with Y-shaped connecting arms (631) at both ends, and the Y-shaped connecting arms (631) at both ends are symmetrical in structure; and the components connected to the left and right ends of the Y-shaped connecting arms (631) are also symmetrical to each other. The Y-shaped connecting arm (631) is provided with a first flexible hinge (632) on one side and a second flexible hinge (633) on the other side. The upper end of one side of the Y-shaped connecting arm (631) at both ends is connected to the middle of the left first-stage amplifying rod (64) through the first flexible hinge (632). The upper end of the other side of the Y-shaped connecting arm (631) at both ends is connected to one end of the right first-stage amplifying rod (65) through the second flexible hinge (633). The left end of the left first-stage amplifying rod (64) is provided with a third flexible hinge (641), and the lower left end of the left first-stage amplifying rod (64) is connected to the outer frame connecting rod flange (611) through the third flexible hinge (641). The middle of the lower end of the right first-stage amplifying rod (65) is provided with a fourth flexible hinge (651), and the middle of the lower end of the right first-stage amplifying rod (65) is connected to the left end of the inner frame (62) of the drive platform through the fourth flexible hinge (651). The secondary amplification rod (66) is provided with a first connecting rod flexible hinge (661), a second connecting rod flexible hinge (662), and a third connecting rod flexible hinge (663); the lower end of the secondary amplification rod (66) near the middle is connected to the upper right side of the left primary amplification rod (64) through the first connecting rod flexible hinge (661); the lower right side of the secondary amplification rod (66) is connected to the upper right side of the right primary amplification rod (65) through the second connecting rod flexible hinge (662); the upper left side of the secondary amplification rod (66) is connected to the three-axis connecting frame (42) through the third connecting rod flexible hinge (663); The first flexible hinge (632), the second flexible hinge (633), the third flexible hinge (641) and the fourth flexible hinge (651) are all connected by single Z-axis straight-round flexible hinges; the first link flexible hinge (661), the second link flexible hinge (662) and the third link flexible hinge (663) are all connected by double Z-axis straight-round flexible hinges. The drive platform outer frame (61), outer frame connecting rod flange (611), drive platform inner frame (62), first transmission rod (63), Y-shaped connecting arm (631), first flexible hinge (632), second flexible hinge (633), left first-level amplifying rod (64), third flexible hinge (641), right first-level amplifying rod (65), fourth flexible hinge (651), second-level amplifying rod (66), first connecting rod flexible hinge (661), second connecting rod flexible hinge (662), third connecting rod flexible hinge (663), three-axis connecting plate (41), three-axis connecting frame (42) and X-axis flexible hinge (43) are an integral structure; The Y-axis piezoelectric ceramic mounting sleeve (612) is located inside one side of the drive platform frame (61); the Y-axis piezoelectric ceramic actuator (67) is sleeved in the Y-axis piezoelectric ceramic mounting sleeve (612); the Y-axis piezoelectric ceramic actuator (67) is connected to the first transmission rod (63); the left first-stage amplification rod (64), the right first-stage amplification rod (65), and the second-stage amplification rod (66) are connected by a straight-round flexible hinge, and the left first-stage amplification rod (64) and the right first-stage amplification rod (65) are both fulcrumd with the fixed point of the drive platform frame (61) as the fulcrum to form a first-stage amplification. Lever; the Y-axis piezoelectric ceramic actuator (67) outputs a small displacement; the small displacement is transmitted to the right first-stage amplification rod (65) and the left first-stage amplification rod (64) via the first transmission rod (63), and after the displacement is amplified in the first stage, it is transmitted to the second-stage amplification rod (66), and then transmitted to the three-axis connection mechanism (4) via the third link flexible hinge (663). The cutting tool (9) is fixed to the cutting tool holder (8) by bolts, and the cutting tool holder (8) is fixed to the three-axis connection mechanism (4) by bolts, thus realizing the linear motion of the cutting tool in the Y direction; The X-axis driving platform (5) and the Y-axis driving platform (6) have the same structure; The steps are as follows: 1) The tool motion trajectory is obtained based on the surface contour of the graphic to be machined. The surface to be machined is preprocessed by the equipment: this includes acquiring the surface contour of the surface to be machined using LVDT, then performing tool path planning and tool radius compensation, and finally obtaining the tool motion trajectory points of the graphic to be machined. After obtaining the tool trajectory points, the subsequent machining process is completed using the aforementioned device: the motion coordinates of the tool motion trajectory points are input to the multi-axis controller; the multi-axis controller controls the output displacement of the driver, which includes a voice coil motor and a piezoelectric ceramic driver; the voice coil motor is used to realize the displacement output in the Z direction, and the piezoelectric ceramic driver is used to realize the displacement output in the X and Y directions, thereby controlling the three-degree-of-freedom motion of the tool; 2) The voice coil motor drives the reciprocating motion of the cutting tool in the Z direction alone; the reciprocating motion in the X and Y directions is achieved by two identical X-direction piezoelectric ceramic actuators (57) and two Y-direction piezoelectric ceramic actuators (67) installed opposite to each other. During the cutting process, the two X-direction piezoelectric ceramic actuators (57) and the two Y-direction piezoelectric ceramic actuators (67) installed opposite to each other input signals with opposite rates of change, and the output displacement is amplified and transmitted to the cutting tool (9); at the same time, the three degrees of freedom are decoupled by utilizing the characteristics of the flexible hinge; finally, the three degrees of freedom decoupled motion is realized. 3) The three-axis connection mechanism (4) is equipped with X-axis displacement sensor (71), Y-axis displacement sensor (72) and Z-axis displacement sensor (73) in three directions. The X-axis displacement sensor (71), Y-axis displacement sensor (72) and Z-axis displacement sensor (73) are all inductive displacement sensors used to detect the actual output displacement of the cutting tool. At the same time, the displacement is fed back to the multi-axis controller in real time. The multi-axis controller processes the received signal and further controls the output displacement of each driver, thereby forming a closed-loop control system to realize displacement error compensation in the X, Y and Z directions.

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