Fast tool servo device and control method based on variable stiffness stress electromagnetic drive

Abstract

The present invention relates to the technical field of ultra-precision machining equipment, and provides a fast tool servo device and a control method driven by variable stiffness normal stress electromagnetism. The device includes a housing fixing component, a compliant component, two normal stress electromagnetic drivers, and two variable stiffness electromagnetic springs. The compliant component includes a straight portion and a zigzag portion. The zigzag portion has a U-shaped structure, and both ends of the zigzag portion are provided with single straight circular flexible hinges connected to the straight portion. The two normal stress electromagnetic drivers are symmetrically arranged on the left and right sides of the straight portion and are located inside the zigzag portion. The two variable stiffness electromagnetic springs are symmetrically arranged on the upper left and lower sides of the straight portion. The compliant component, the normal stress electromagnetic drivers, and the variable stiffness electromagnetic springs are all connected to the housing fixing component. The present invention solves the technical bottleneck of the mutual restriction between the motion stroke and the natural frequency in the traditional fast tool servo device, and improves the adaptability of the ultra-precision machining system to different process parameters.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-precision machining equipment, and specifically to a fast tool servo device and control method driven by variable stiffness method stress electromagnetic force. Background Technique

[0002] As a key technology in the field of ultra-precision machining, the diamond turning process based on fast tool servo shows significant advantages in the manufacturing of optical free-form surfaces and the machining of micro-nano functional surfaces. At present, the main problem in the development of this technology is the contradiction between the motion stroke and frequency bandwidth of traditional fast tool servo devices due to fixed stiffness, which restricts their application scope. In particular, fast tool servo devices with high stiffness can achieve high natural frequencies, but the motion stroke becomes shorter; while large-stroke devices have insufficient natural frequencies due to stiffness attenuation, making it difficult to meet the machining requirements of cross-scale structures. Summary of the Invention

[0003] The purpose of the present invention is to provide a fast tool servo device and control method driven by variable stiffness method stress electromagnetic force, which solves the technical bottleneck of the mutual restriction between the motion stroke and natural frequency in traditional fast tool servo devices, and improves the adaptability of ultra-precision machining systems to different process parameters.

[0004] To achieve the above purpose, the present invention provides the following technical solutions: In the first technical solution, a fast tool servo device driven by variable stiffness method stress electromagnetic force includes: a housing fixing component; a compliant component disposed at the inner center of the housing fixing component, the compliant component includes a straight portion, one end of the straight portion extends to the outside of the housing fixing component, both the left and right sides of the straight portion are provided with zigzag portions, the zigzag portions are in a U-shaped structure, and both ends of the zigzag portions are provided with single straight circular flexible hinges connected to the straight portion; two method stress electromagnetic drivers symmetrically disposed on the left and right sides of the straight portion and located inside the zigzag portions; two variable stiffness electromagnetic springs symmetrically disposed on the upper and lower left sides of the straight portion, and the compliant component, the method stress electromagnetic drivers and the variable stiffness electromagnetic springs are all connected to the housing fixing component.

[0005] In the first technical solution, preferably, the method stress electromagnetic driver includes: a first magnetic yoke, a first magnetic arm is provided on the first magnetic yoke, the first magnetic arm is disposed at the end far from the straight portion, and the first magnetic arm is an E-shaped magnetic arm; a first excitation coil wound around the first magnetic arm; a first armature disposed at the end of the first magnetic yoke close to the straight portion and connected to the middle of the straight portion; a permanent magnet disposed on the side of the first armature far from the straight portion and magnetically attracted to the first magnetic yoke.

[0006] In the first technical solution, preferably, a first air gap is provided between the first magnetic yoke and the compliant component, and the width of the first air gap is h1, 0.4mm≤h1≤0.6mm; a second air gap is provided between the first armature and the first magnetic yoke, and the width of the second air gap is h2, 0.1mm≤h2≤0.3mm; a third air gap is provided between the permanent magnet and the first armature, and the width of the third air gap is h3, 0.6mm≤h3≤0.7mm.

[0007] In the first technical solution, preferably, the variable stiffness electromagnetic spring includes: a second magnetic yoke, the second magnetic yoke is an elastic magnetic yoke, the second magnetic yoke is provided with a second magnetic arm, the second magnetic arm is arranged at one end close to the straight portion, and the second magnetic arm is an E-shaped magnetic arm; a second excitation coil is wound on the middle arm of the second magnetic arm, and the second excitation coil is an elastic excitation coil; a second armature is arranged on the side of the second excitation coil close to the straight portion and is connected to the middle of the straight portion.

[0008] In the first technical solution, preferably, a fourth air gap is provided between the second magnetic yoke and the compliant component, and the width of the fourth air gap is h4, 0.4mm≤h4≤0.6mm; a fifth air gap is provided between the second armature and one end of the second magnetic yoke close to the straight portion, and the width of the fifth air gap is h5, 0.1mm≤h5≤0.3mm; a sixth air gap is provided between the second armature and the middle arm of the second magnetic arm, and the width of the sixth air gap is h6, 0.2mm≤h6≤0.3mm.

[0009] In the first technical solution, preferably, the shell fixing assembly includes: a base; a front fixing frame, which is arranged at one end of the top surface of the base; and a rear fixing frame, which is arranged at the other end of the top surface of the base, the bottom of the rear fixing frame is connected to the base, the positions of the front fixing frame and the rear fixing frame correspond to each other, and are detachably connected to the rear fixing frame, and an assembly opening is provided at the center of the front fixing frame and the rear fixing frame, and the assembly opening is a cross-shaped structure, and the compliance assembly, the normal stress electromagnetic driver and the variable stiffness electromagnetic spring are all arranged in the assembly opening.

[0010] In the first technical solution, preferably, the middle part of the curved portion is detachably connected to the housing fixing assembly, the first magnetic yoke is detachably connected to the housing fixing assembly, the first armature is bonded to the straight portion by epoxy resin, the second magnetic yoke is detachably connected to the housing fixing assembly, and the second armature is bonded to the straight portion by epoxy resin.

[0011] In a second technical solution, a control method for a variable-stiffness normal stress electromagnetically driven fast tool servo device is provided, using the variable-stiffness normal stress electromagnetically driven fast tool servo device as described in the first technical solution, comprising the following steps: Step 1: modularly integrating the housing fixing component, the compliant component, the normal stress electromagnetic driver, and the variable-stiffness electromagnetic spring to ensure that each component achieves millimeter-level matching accuracy and completes coordinated assembly between the components; Step 2: applying a controllable current to the first excitation coil to generate electromagnetic normal stress on the surface of the first armature, thereby causing the compliant component to elastically deform, driving the diamond tool integrated in the compliant component to achieve micro-nano-level precision motion; Step 3: synchronously regulating the current parameters of the second excitation coil to change the saturation state of the magnetic circuit, achieving continuous and stepless adjustment of the effective stiffness of the system within microseconds, causing the second armature to generate electromagnetic normal stress to assist in outputting a compensating driving force for the system; Step 4: according to processing requirements, controlling the motion stroke and frequency bandwidth of the fast tool servo device in real time within a certain range, so that micro-nano-level material removal is achieved on the workpiece surface through the high-frequency reciprocating motion of the diamond tool, meeting the processing requirements of structures such as optically complex surfaces.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] (1) This invention achieves real-time control of the system's overall effective stiffness by regulating the current parameters of the second excitation coil to change the magnetic circuit saturation state. This not only enables the creation of complex cross-scale surface features with micro- and nanoscale features, but also provides innovative processing methods for high-end fields such as defense optics and biomedical devices. This invention overcomes the technical bottleneck of the mutual constraints between motion range and natural frequency in traditional high-speed tool servo devices, improving the adaptability of ultra-precision machining systems to varying process parameters.

[0014] (2) The variable stiffness stress electromagnetically driven rapid tool servo device and control method proposed in this invention overcomes the inherent and irreconcilable contradiction between mechanical complexity and dynamic performance in traditional hierarchical drive technology. Compared to rapid tool servo devices that rely on multi-stage transmission mechanisms, this device precisely controls the current parameters of the second excitation coil to change the magnetic circuit saturation state, achieving continuous and stepless adjustment of the system's overall effective stiffness. This allows for varying the motion range and frequency bandwidth within a certain range, making it particularly suitable for creating complex cross-scale surface features with micro- and nano-scale features.

[0015] (3) The present invention proposes a variable-stiffness normal stress electromagnetic drive fast tool servo device and control method, in which the normal stress electromagnetic drive uses Maxwell electromagnetic force to achieve micro-nanoscale reciprocating motion of the diamond tool. This drive method has the advantages of fast response speed and high force density, and can achieve efficient power transmission. The variable-stiffness electromagnetic spring can dynamically adjust the overall effective stiffness of the system by precisely controlling the input current, and can also assist in outputting compensating driving force for the system, with the advantages of a wide adjustable stiffness range and high energy utilization. The device deeply integrates the normal stress electromagnetic drive and the variable-stiffness electromagnetic spring, significantly improving the drive efficiency and processing performance while maintaining a compact structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is an axonometric drawing of the present invention;

[0017] Figure 2 This is an axonometric view of the housing fixing assembly of the present invention;

[0018] Figure 3 This is an axonometric drawing of the present invention without the front fixing bracket;

[0019] Figure 4 is an axonometric view of the compliant component of the present invention;

[0020] Figure 5 This is an axonometric diagram of the compliant assembly and the normal stress electromagnetic driver of the present invention after being installed together;

[0021] Figure 6 for Figure 5 Enlarged view of point A in the middle;

[0022] Figure 7 This is an axonometric view of the compliant component and the variable stiffness electromagnetic spring of the present invention after being installed together;

[0023] Figure 8 for Figure 7 Enlarged view of point B in the middle;

[0024] Figure 9 Schematic diagram of negative stiffness generated by the variable stiffness electromagnetic spring of the present invention;

[0025] Figure 10 It is a schematic diagram of the change of the overall effective stiffness of the present invention;

[0026] Figure 11 Schematic diagram of the change of working range and resonant frequency according to the present invention.

[0027] Reference numerals include:

[0028] 1-housing fixing assembly, 11-base, 12-front fixing frame, 13-rear fixing frame, 14-assembly port, 2-compliant assembly, 21-straight portion, 22-bent portion, 23-single straight circular flexible hinge, 3-normal stress electromagnetic driver, 31-first magnetic yoke, 311-first magnetic arm, 32-first excitation coil, 33-first armature, 34-permanent magnet, 35-first air gap, 36-second air gap, 37-third air gap, 4-variable stiffness electromagnetic spring, 41-second magnetic yoke, 411-second magnetic arm, 42-second excitation coil, 43-second armature, 44-fourth air gap, 45-fifth air gap, 46-sixth air gap. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] See also Figure 1-8 The present invention provides a technical solution: a variable stiffness normal stress electromagnetic driven fast tool servo device, comprising a shell fixing component 1, a flexible component 2, two normal stress electromagnetic drivers 3 and two variable stiffness electromagnetic springs 4. The flexible component 2 comprises a straight portion 21 and a curved portion 22, and both ends of the curved portion 22 are provided with a single straight circular flexible hinge 23 connected to the straight portion 21. The two normal stress electromagnetic drivers 3 are symmetrically arranged on the left and right sides of the straight portion 21, and the two variable stiffness electromagnetic springs 4 are symmetrically arranged on the left and upper sides of the straight portion 21. The shell fixing component 1 comprises a base 11, a front fixing frame 12 and a rear fixing frame 13, and an assembly opening 14 is provided at the center of the front fixing frame 12 and the rear fixing frame 13, and the flexible component 2, the normal stress electromagnetic driver 3 and the variable stiffness electromagnetic spring 4 are all arranged in the assembly opening 14. In this embodiment, the front fixing frame 12 and the rear fixing frame 13 are fastened together by means of hexagon socket head screws, and the lower ends of the front fixing frame 12 and the rear fixing frame 13 are fastened together with the base 11 by means of hexagon socket head screws.

[0031] See also Figure 1-6The normal stress electromagnetic driver 3 includes a first magnetic yoke 31, a first excitation coil 32, a first armature 33, and a permanent magnet 34. The first magnetic yoke 31 is provided with a first magnetic arm 311. The first magnetic yoke 31 and the permanent magnet 34 are fixed by magnetic attraction. The first excitation coil 32 is precisely wound on the rear side of the E-shaped magnetic arm of the first magnetic yoke 31. The two first armatures 33 are fixed to the left and right sides of the transmission shaft of the flexible component 2 by high-strength epoxy resin adhesive. The two first magnetic yokes 31 are symmetrically arranged and embedded in the interior of the flexible component 2. The two first magnetic yokes 31 are fastened to the left and right sides of the front fixing frame 12 and the rear fixing frame 13 of the housing fixing component 1 by tightening with hexagon socket head screws. In this embodiment, a first air gap 35 is ensured to exist between the first magnetic yoke 31 and the compliant component 2, and the width h1 of the first air gap 35 is 0.5 mm. A second air gap 36 is ensured to exist between the left and right sides of the first armature 33 and the first magnetic yoke 31, and the width h2 of the second air gap 36 is 0.2 mm. A third air gap 37 is ensured to exist between one end of the permanent magnet 34 and the rear end of the first armature 33, and the width h3 of the third air gap 37 is 0.65 mm.

[0032] See also Figure 1-8 The variable-stiffness electromagnetic spring 4 includes a second magnetic yoke 41, a second excitation coil 42, and a second armature 43. The second magnetic yoke 41 is an elastic yoke with a second magnetic arm 411. The second excitation coil 42 is precision-wound around the E-shaped center arm of the second magnetic yoke 41. The second armature 43 is an elastic armature. The two second armatures 43 are fixed to the upper and lower sides of the drive shaft of the compliance component 2 using high-strength epoxy resin adhesive. The two second magnetic yokes 41 are symmetrically arranged on the outside of the compliance component 2 and fastened to the left and right sides of the front fixing bracket 12 and the rear fixing bracket 13 of the housing fixing assembly 1 using hexagon socket head cap screws. In this embodiment, a fourth air gap 44 is ensured to exist between the second magnetic yoke 41 and the compliant component 2, and the width h4 of the fourth air gap 44 is 0.5 mm. A fifth air gap 45 is ensured to exist between the left and right sides of the second armature 43 and the second magnetic yoke 41, and the width h5 of the fifth air gap 45 is 0.2 mm. A sixth air gap 46 is ensured to exist between the second armature 43 and the middle arm of the second magnetic arm 411, and the width h6 of the sixth air gap 46 is 0.25 mm.

[0033] In view of the control process of the variable stiffness electromagnetic spring 4 on the overall effective stiffness of the system, the present invention simulates and analyzes the variable stiffness electromagnetic spring 4 and the normal stress electromagnetic driver 3 in Comsol software, and combines the analytical modeling method to obtain the following Figure 9-11 The results shown. Figure 9-10Analysis shows that when the input spring current is 0A, the variable-stiffness electromagnetic spring 4 is inactive. At this point, the variable-stiffness electromagnetically driven fast tool servo device is equivalent to a high-stiffness electromagnetically driven fast tool servo device, with an overall effective stiffness of 1.141 N / μm. When the spring input current is increased to 1.5A, the variable-stiffness electromagnetic spring 4 generates a negative stiffness of 0.699 N / μm, significantly reducing the overall effective stiffness of the system to 0.442 N / μm. Simulation results show that by intelligently controlling the input current of the variable-stiffness electromagnetic spring 4, active compensation of the system stiffness can be achieved, with the maximum stiffness reduction reaching 61.3% of the original stiffness.

[0034] Figure 11 Through simulation parameter identification and analytical modeling, the dynamic regulation of the spring current on the working range (i.e., motion stroke) and resonant frequency was revealed. When the input spring current is 0A, the theoretically calculated motion stroke is 29.29μm, corresponding to a resonant frequency of 663Hz. When a spring current of 1.5A is applied, the device's motion stroke expands to 75.64μm, and the resonant frequency decreases to 412Hz. Simulation results show that by precisely controlling the drive current of the variable-stiffness electromagnetic spring 4, the working stroke of the fast tool servo device can be controlled and adjusted from 29.29 to 75.64μm, while the corresponding resonant frequency exhibits a controllable frequency shift from 663Hz to 412Hz.

[0035] The control method of the present invention includes the following steps: Step 1: Modularly integrate the housing fixing assembly 1, the compliant assembly 2, the normal stress electromagnetic driver 3, and the variable stiffness electromagnetic spring 4, ensuring millimeter-level precision in the fit of each component and achieving coordinated assembly. Step 2: Applying a controllable current to the first excitation coil 32 generates electromagnetic normal stress on the surface of the first armature 33 based on Maxwell's stress principle, thereby elastically deforming the compliant assembly 2 and driving the diamond tool integrated in the compliant assembly 2 to achieve micro- and nano-scale precision motion. Step 3: Synchronously regulating the current parameters of the second excitation coil 42 to change the magnetic circuit saturation state, achieving continuous and stepless adjustment of the system's effective stiffness within microseconds. This causes the second armature 43 to also generate corresponding electromagnetic normal stress under the action of the alternating magnetic field, providing auxiliary compensating driving force for the system. Step 4: Based on processing requirements, the motion range and frequency bandwidth of the fast tool servo device are controlled in real time within a certain range. Through the high-frequency reciprocating motion of the diamond tool, micro- and nano-scale material removal is achieved on the workpiece surface, meeting the processing requirements of structures such as complex optical surfaces.

[0036] In summary: The present invention successfully realizes the active adjustment of the dynamic characteristics of the variable stiffness fast tool servo device by real-time regulation of the input current of the variable stiffness electromagnetic spring 4. The simulation results show that under the action of current regulation, the movement stroke of the device is expanded from 29.29μm to 75.64μm, an increase of up to 158%; at the same time, the resonant frequency drops from 663Hz to 412Hz, a decrease of 37.9%. The above performance changes confirm that the in-situ stiffness change rate of the system can reach more than 2.58 times. This progress innovatively solves the technical bottleneck of the mutual constraint between the movement stroke and the natural frequency in the traditional fast tool servo device. Compared with the traditional fast tool servo device, the dynamic adjustable characteristics exhibited by this device significantly improve the adaptability of the ultra-precision machining system to different process parameters, and has important engineering application value.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0038] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A fast tool servo device driven by electromagnetic force using a variable stiffness method, characterized in that: include: Housing fixing assembly; A compliant assembly is provided at the inner center of the housing fixing assembly, the compliant assembly comprising a straight portion, one end of the straight portion extending to the outside of the housing fixing assembly, a curved portion being provided on both sides of the straight portion, the curved portion being in a U-shaped structure, and a single straight circular flexible hinge connected to the straight portion being provided at both ends of the curved portion; Two normal stress electromagnetic drivers are symmetrically arranged on the left and right sides of the straight portion and located inside the curved portion; Two variable-stiffness electromagnetic springs are symmetrically arranged on the upper and lower sides of the straight portion, and the compliance component, the normal stress electromagnetic driver and the variable-stiffness electromagnetic springs are all connected to the housing fixing component; The normal stress electromagnetic driver includes a first magnetic yoke, a first armature and a permanent magnet, a first air gap is provided between the first magnetic yoke and the compliant component, and the width of the first air gap is h1, 0.4mm≤h1≤0.6mm, a second air gap is provided between the first armature and the first magnetic yoke, and the width of the second air gap is h2, 0.1mm≤h2≤0.3mm, and a third air gap is provided between the permanent magnet and the first armature, and the width of the third air gap is h3, 0.6mm≤h3≤0.7mm; The variable-stiffness electromagnetic spring includes a second magnetic yoke and a second armature, a second magnetic arm is provided on the second magnetic yoke, a fourth air gap is provided between the second magnetic yoke and the flexible component, and the width of the fourth air gap is h4, 0.4mm≤h4≤0.6mm, a fifth air gap is provided between the second armature and one end of the second magnetic yoke close to the straight portion, and the width of the fifth air gap is h5, 0.1mm≤h5≤0.3mm, and a sixth air gap is provided between the second armature and the middle arm of the second magnetic arm, and the width of the sixth air gap is h6, 0.2mm≤h6≤0.3mm.

2. The variable stiffness method stress electromagnetic driven fast tool servo device according to claim 1, characterized in that: A first magnetic arm is provided on the first magnetic yoke, the first magnetic arm is provided at one end away from the straight portion, and the first magnetic arm is an E-shaped magnetic arm; The first armature is provided at one end of the first magnetic yoke close to the straight portion and is connected to the middle portion of the straight portion; The permanent magnet is arranged on a side of the first armature away from the straight portion and is magnetically connected to the first magnetic yoke; The normal stress electromagnetic driver further includes a first excitation coil, which is wound around the first magnetic arm.

3. The variable stiffness method stress electromagnetic driven fast tool servo device according to claim 2, characterized in that: The second magnetic yoke is an elastic magnetic yoke, the second magnetic arm is provided near one end of the straight portion, and the second magnetic arm is an E-shaped magnetic arm; The variable-stiffness electromagnetic spring further includes a second excitation coil, which is wound on the middle arm of the second magnetic arm and is an elastic excitation coil; The second armature is arranged on a side of the second excitation coil close to the straight portion and is connected to the middle portion of the straight portion.

4. The variable stiffness method stress electromagnetic driven fast tool servo device according to claim 3, characterized in that: The housing fixing assembly includes: base; A front fixing frame is provided at one end of the top surface of the base; A rear fixing frame is provided at the other end of the top surface of the base, the bottom of the rear fixing frame is connected to the base, the front fixing frame corresponds to the position of the rear fixing frame, and is detachably connected to the rear fixing frame, and an assembly opening is provided at the center of the front fixing frame and the rear fixing frame, the assembly opening is a cross-shaped structure, and the compliance component, the normal stress electromagnetic driver and the variable stiffness electromagnetic spring are all arranged in the assembly opening.

5. The variable stiffness method stress electromagnetic driven fast tool servo device according to claim 4, characterized in that: The middle part of the curved portion is detachably connected to the housing fixing assembly, the first magnetic yoke is detachably connected to the housing fixing assembly, the first armature is bonded to the straight portion via epoxy resin, the second magnetic yoke is detachably connected to the housing fixing assembly, and the second armature is bonded to the straight portion via epoxy resin.

6. A control method for a fast tool servo device driven by electromagnetic force using a variable stiffness method, using the fast tool servo device driven by electromagnetic force using a variable stiffness method as claimed in claim 3, characterized in that: The following steps are involved: Step 1: modularly integrate the housing fixing component, the compliant component, the normal stress electromagnetic driver, and the variable stiffness electromagnetic spring to ensure that each component achieves millimeter-level matching accuracy and completes the coordinated assembly of each component; Step 2: applying a controllable current to the first excitation coil to generate electromagnetic stress on the surface of the first armature, thereby causing the compliant component to elastically deform, thereby driving the diamond tool integrated in the compliant component to achieve micro-nano-level precision motion; Step 3: synchronously regulating the current parameters of the second excitation coil to change the saturation state of the magnetic circuit and achieve continuous and stepless adjustment of the effective stiffness of the system within microseconds, so that the second armature generates electromagnetic stress to assist in outputting a compensating driving force for the system; Step 4: According to the processing requirements, the motion stroke and frequency bandwidth of the fast tool servo device are adjusted in real time within a certain range. Through the high-frequency reciprocating motion of the diamond tool, micro-nano-level material removal is achieved on the workpiece surface to meet the processing requirements of optical complex curved surface structures.

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