Dynamic rotary cutter turning system driven by double piezoelectric ceramics

Abstract

The invention relates to the technical field of precision machining, in particular to a dynamic rotary cutter turning system driven by double piezoelectric ceramics. Comprising a machine tool shaft B and a double-piezoelectric-ceramic driving fast tool device. The device is directly fixed at the rotating end part of a shaft B and comprises a sharp knife U shaft and a sharp knife V shaft which are respectively arranged along the radial direction and the cutting depth direction of a workpiece and are driven by piezoelectric ceramics. A spiral cutter path is formed through linkage of B-axis rotation and U-axis and V-axis micro-displacement of the fast cutter and used for machining the free-form surface micro-lens array. Compared with a traditional scheme, the system has the advantages that the motion mass is concentrated on the cutter side, the structure is compact, the mass is light, the rotation center and the mass center are highly overlapped, the dynamic balance characteristic is improved, the vibration problem of a large-mass part on the workpiece side during high-speed rotation is avoided, and the machining precision and stability are improved.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology, and in particular to a dynamic rotary tool turning system driven by dual piezoelectric ceramics. Background Technology

[0002] In the field of precision optical component manufacturing, microlens arrays have attracted much attention due to their wide applications in light field manipulation, imaging sensing, and optical communication. Currently, the axis-shifting diamond cutting process is one of the mainstream methods for fabricating high-precision microlens arrays. This process typically fixes the workpiece on a rotating spindle to achieve the main rotational motion, and precisely adjusts the position of the workpiece relative to the rotation axis through a two-dimensional positioning module. Combined with the feed motion of the machine tool's X / Y / Z servo axes, independent helical tool paths are generated to complete the machining of each microlens unit. This method performs well in the machining of small-scale, regularly arranged spherical or aspherical microlens arrays, achieving high surface quality and unit consistency.

[0003] However, with the ever-increasing demands on the performance of microlens arrays in optical systems, existing technologies face significant challenges. When machining large-scale or free-form microlens arrays, especially when the workpiece diameter is large, the mass of the moving parts in the two-dimensional positioning module increases significantly, exacerbating the dynamic imbalance problem of the rotating system. Vibrations generated during high-speed rotation are directly transmitted to the machined surface, forming periodic errors that severely affect surface accuracy and surface roughness. Simultaneously, traditional machine tool servo axes, limited by motor response characteristics and mechanical transmission mechanisms, typically have a servo bandwidth below 200 Hz, making it difficult to accurately track the high-frequency trajectory changes required for complex free-form surfaces. This is particularly problematic when machining irregularly shaped microlens units with angular features, such as triangles and quadrilaterals, where trajectory tracking lag leads to edge rounding and surface distortion. Furthermore, real-time dynamic balancing of the large-mass moving parts on the workpiece side is difficult; as the rotational speed increases, the imbalance disturbance grows quadratically, further limiting machining efficiency and quality consistency. Therefore, a novel cutting system architecture is urgently needed that can significantly improve the system's dynamic response and rotational stability while maintaining high precision. Summary of the Invention

[0004] To address one of the aforementioned technical problems, the present invention adopts the following technical solution: According to one aspect of the present invention, a dual piezoelectric ceramic driven dynamic rotary tool turning system is provided, comprising: The machine tool's B-axis serves as the main rotary motion axis. The dual piezoelectric ceramic driven high-speed tool device is directly fixedly mounted on the rotating end of the B-axis of the machine tool and rotates synchronously with the B-axis. The device includes a high-speed tool U-axis and a high-speed tool V-axis. The high-speed tool U-axis is arranged radially along the workpiece, and the high-speed tool V-axis is orthogonally positioned on the actuator of the high-speed tool U-axis along the depth of cut direction. Both the U-axis and V-axis drive the actuator via piezoelectric ceramic actuators. The high-speed tool V-axis is used to mount turning tools. Among them, the rotational motion of the machine tool's B-axis is linked with the micro-displacement motion of the fast tool's U-axis and V-axis to form a real helical tool path, which is used for turning free-form surface microlens arrays.

[0005] This invention has at least one of the following beneficial effects: This invention directly fixes the dual piezoelectric ceramic driven high-speed tool device to the rotating end of the B-axis of the machine tool. Compared with the traditional solution of placing the workpiece and the two-dimensional positioning module on the rotating spindle, this fundamentally improves the dynamic balance characteristics of the system. In the prior art, when machining large-diameter workpieces, the combined mass of the workpiece and the positioning module is large. Even a slight installation eccentricity can generate significant centrifugal force during high-speed rotation, leading to vibration and affecting machining accuracy. This solution concentrates the moving mass on the tool side. The piezoelectric ceramic drive device itself is compact and lightweight, significantly reducing the total mass of the rotating parts. More importantly, as a precisely adjustable active component, the center of mass of the high-speed tool device can be pre-optimized through structural design, ensuring that the rotation center and the center of mass highly coincide, greatly reducing unbalanced torque. This "tool-side rotation" architecture avoids the dynamic disturbance problems caused by large-mass moving components on the workpiece side, enabling the system to maintain good stability under high-speed rotation conditions, providing a fundamental guarantee for high-precision microlens array machining.

[0006] Meanwhile, this invention employs a dual piezoelectric ceramic driven fast tool device, where both the fast tool's U-axis and V-axis are driven by piezoelectric ceramic actuators, significantly enhancing the system's dynamic response capability. Traditional technologies rely on machine tool servo axes (usually motor-driven) to generate complex trajectories. Limited by motor inertia and mechanical transmission chains, the system bandwidth is typically low, making it difficult to accurately track the high-frequency trajectory changes required for free-form surfaces. This is especially problematic when machining irregularly shaped microlenses with angular features, where trajectory lag and edge rounding are common. In contrast, piezoelectric ceramic actuators offer inherent advantages such as frictionless operation, zero transmission backlash, and fast response, enabling microsecond-level dynamic responses. In this solution, the U-axis and V-axis form a positively coupled two-dimensional micro-displacement platform, allowing for real-time high-frequency adjustment of the tool position during cutting. This high-bandwidth characteristic enables the system to accurately reproduce the trajectory changes required for complex free-form surfaces. Particularly for irregularly shaped microlens units with abrupt changes, such as triangles and quadrilaterals, it maintains the clarity of angular features and surface accuracy, overcoming the trajectory tracking limitations of traditional low-bandwidth systems.

[0007] Furthermore, this invention links the rotational motion of the machine tool's B-axis with the micro-displacement motions of the fast tool's U-axis and V-axis to form a true helical toolpath. This technical feature effectively solves the trajectory error problem in traditional multi-axis interpolation machining. In existing technologies, generating a helical trajectory typically requires the coordinated interpolation of multiple machine tool servo axes (such as X / Y / C axes), which is controlled by the minimum resolution and interpolation cycle of the CNC system. The actual trajectory is an approximate helix composed of many small line segments, leaving periodic tool marks on the surface. In this solution, the B-axis provides continuous main rotational motion, the U-axis controls the tool's radial position on the workpiece, and the V-axis adjusts the depth of cut in real time. The three work together to directly generate a mathematically continuous helical curve. This true helical trajectory eliminates interpolation nodes and transition marks, ensuring smooth connection between adjacent toolpaths and eliminating periodic errors on the surface. For the machining of freeform surface microlens arrays, especially applications with high optical performance requirements, this flawless surface significantly reduces light scattering and improves the imaging quality of optical components. Meanwhile, the true spiral trajectory avoids the accumulation of interpolation errors, ensuring the consistency between units of the large-scale microlens array and providing manufacturing assurance for high-performance optical systems. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is an overall structural diagram of a dynamic rotary tool turning system driven by dual piezoelectric ceramics provided in an embodiment of the present invention; Figure 2 This is an overall structural diagram of the dual piezoelectric ceramic driven fast knife device provided in an embodiment of the present invention; Figure 3 for Figure 2 A magnified view of the intermediate fast tool axis section; Figure 4 Schematic diagrams of the U-direction flexible hinge structure and the V-direction flexible hinge structure provided in the embodiments of the present invention; Figure 5 The simulation results of the structural deformation of the U-direction flexible hinge structure and the V-direction flexible hinge provided in the embodiments of the present invention under a stress state (100N); Figure 6 A comparative schematic diagram of microlens array cutting processes: (a) dynamic rotary tool cutting, (b) fast tool servo cutting, (c) dynamic rotary tool cutting driven by dual piezoelectric ceramics in this invention; Figure 7A schematic diagram of the harmonic response of the U-axis and V-axis of the fast cutter along the motion direction and the corresponding parasitic motion results provided in an embodiment of the present invention; Figure 8 A flowchart illustrating a method for controlling the motion of a fast tool axis based on dynamic imbalance, provided in an embodiment of the present invention; Figure 9 The following is a schematic diagram of the motion control of the U-axis of the fast cutter provided in the embodiment of the present invention: (a) schematic diagram of the U-axis controller of the fast cutter; (b) trajectory tracking result of the V-axis of the fast cutter. Figure 10 A schematic diagram illustrating the influence of the position and rotation speed of the microlens unit on the processing results provided in this embodiment of the invention: (a) surface roughness and (b) cross-sectional profile error of microlens units with different radial distances, and (c) surface roughness and (d) cross-sectional profile error at different rotation speeds of the machine tool B-axis (including the standard deviation obtained from 5 repeated measurements). Figure 11 A schematic diagram of the processing results of the freeform surface microlens array provided in the embodiments of the present invention: (a) the overall surface shape of the microlens array; (b) the surface shape error of the microlens unit; (c) the cross-sectional profile of the microlens unit; (d) the surface shape of the randomly distributed freeform surface microlens array and the microlens with special shapes.

[0010] Figure Labels 1. Machine tool X-axis; 2. Machine tool Y-axis; 3. Machine tool Z-axis; 4. Machine tool B-axis; 5. Machine tool C-axis; 6. Flexible tool holder; 7. Fast tool U-axis; 71. U-axis support plate; 72. U-axis piezoelectric ceramic actuator; 73. U-axis flexible hinge; 74. U-axis actuator; 8. Fast tool V-axis; 81. V-axis piezoelectric ceramic actuator; 82. V-axis flexible hinge; 83. V-axis actuator; 9. Diamond cutting tool; 10. Workpiece fixture; 11. Mass balance block. Detailed Implementation

[0011] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0012] As one possible embodiment of the present invention, such as Figure 1-3 As shown, a dual piezoelectric ceramic driven dynamic rotary tool turning system is provided, comprising: The B-axis 4 of the machine tool serves as the main rotary motion axis, used to drive the diamond tool 9 to achieve the main rotary motion.

[0013] The dual piezoelectric ceramic driven high-speed tool device is directly and fixedly mounted on the rotating end of the B-axis 4 of the machine tool, rotating synchronously with the B-axis 4. The device includes a high-speed tool U-axis 7 and a high-speed tool V-axis 8. The high-speed tool U-axis 7 is arranged radially along the workpiece, and the high-speed tool V-axis 8 is orthogonally positioned on the actuator of the high-speed tool U-axis 7 along the depth of cut direction. Both the high-speed tool U-axis 7 and the high-speed tool V-axis 8 drive the actuator via piezoelectric ceramic actuators. The high-speed tool V-axis 8 is used to mount the cutting tool.

[0014] In this process, the rotational motion of the machine tool's B-axis 4 is linked with the micro-displacement motions of the fast tool's U-axis 7 and V-axis 8 to form a realistic helical tool path for machining freeform surface microlens arrays. A dual piezoelectric ceramic driven fast tool device is integrated on the B-axis of an ultra-precision lathe to achieve dynamic rotary tool cutting. During machining, the machine tool's X-axis 1 and Z-axis 3 are controlled to precisely position the tool's rotation axis, driving the B-axis 4, fast tool's U-axis 7, and fast tool's V-axis 8 in conjunction to complete the cutting motion. Each freeform surface microlens unit is machined sequentially using an independent, realistic helical tool path, thus improving the problem of insufficient tool path continuity in traditional slow / fast tool servo turning technology, achieving efficient and highly consistent machining of large-scale freeform surface microlens arrays at higher cutting speeds.

[0015] Specifically, such as Figure 2 and 3 As shown, the V-axis 8 of the fast cutter is completely embedded inside the actuator of the U-axis 7 of the fast cutter, forming an orthogonal series nested structure.

[0016] The QuickTool U-axis 7 includes: The U-axis support plate 71 is fixed to the flexible tool holder 6 and serves as the fixed reference for the U-axis.

[0017] The U-axis piezoelectric ceramic actuator 72 has one end in contact with the U-axis support plate 71 and the other end in contact with the U-axis actuator 74. It achieves extension and contraction along the U-axis by using the inverse piezoelectric effect through the input of an electrical signal.

[0018] A U-axis flexible hinge 73 connects the U-axis support plate 71 and the U-axis actuator 74. The U-axis flexible hinge 73 consists of four identical links, each link including one leaf spring flexible hinge (LSFH) and two right circular flexible hinges (RCFH). The two ends of the leaf spring flexible hinge are respectively connected to the right circular flexible hinges, which are located between the U-axis support plate 71 and the U-axis actuator 74.

[0019] The four links are arranged in pairs, respectively within the gaps on both sides formed by the U-axis support plate 71 and the U-axis actuator 74. Two links in any pair are arranged parallel to each other along the U-axis, and the four links form a symmetrical dual-parallelogram mechanism (DPM). This mechanism converts the axial extension and retraction of the U-axis piezoelectric ceramic actuator 72 into the linear displacement of the U-axis actuator 74, while suppressing non-U-axis parasitic motion and providing elastic restoring force, so that the U-axis can maintain stable motion even under high-frequency vibration.

[0020] A U-axis displacement sensor is used to detect the displacement of the U-axis actuator 74, thereby achieving closed-loop control of the fast-moving tool's U-axis 7. A high-resolution capacitive sensor may also be used.

[0021] like Figure 2 and 3 As shown, the fast tool V-axis 8 includes: The V-axis piezoelectric ceramic actuator 81 has one end in contact with the U-axis actuator 74 and the other end in contact with the V-axis actuator. Extension and contraction along the V-axis are achieved by utilizing the inverse piezoelectric effect through an input electrical signal.

[0022] The V-axis flexible hinge 82 is fixed at one end to the surface of the U-axis actuator 74 and connected to the V-axis actuator at the other end.

[0023] The V-axis flexible hinge 82 consists of eight identical leaf springs, arranged in four groups of two parallel leaf springs per group. Each leaf spring's ends contact the U-axis actuator 74 and connect to the V-axis actuator. The four groups of leaf springs are arranged circumferentially opposite each other around the V-axis actuator, forming a crossed dual-parallelogram mechanism (CDPM). This mechanism converts the axial extension and retraction of the V-axis piezoelectric ceramic actuator 81 into linear displacement of the V-axis actuator, while simultaneously suppressing non-V-axis parasitic motion and providing elastic restoring force.

[0024] A V-axis displacement sensor is used to detect the displacement of the V-axis actuator, thereby enabling closed-loop control of the V-axis 8 of the fast cutter.

[0025] Single-objective optimization models were established for the U-axis 7 and V-axis 8 of the fast cutting tool, respectively, and the parameters corresponding to the U-axis flexible hinge 73 and V-axis flexible hinge 82 were obtained. This ensures that the U-axis 7 and V-axis 8 of the fast cutting tool meet the travel requirements and first-order resonant frequency requirements in the cutting process.

[0026] Specifically, such as Figure 4 As shown, for the U-axis 7 of the fast tool, its coordinate system O xy DPM The following is the representation of the compliance matrix: Among them, Toi C is the coordinate transformation matrix. R and C L Let be the compliance matrices of the circular flexible hinge and the leaf spring flexible hinge, respectively. Let l, h, and w be the length, thickness, and width of the leaf spring flexible hinge, respectively, and let R, t, and b be the radius, width, and thickness of the circular flexible hinge, respectively. From this, the U-axis of the fast cutter relative to the reference point o can be further calculated. D Stiffness matrix: Where Ty is a rotation matrix of π radians about the y-axis.

[0027] For the Quick Tool V-axis 8, such as Figure 4 As shown, it is in coordinate system O zx CDPM Relative to reference point O C The stiffness matrix can be expressed as: The first resonant frequency f between the U-axis 7 and V-axis 8 of the fast cutter DPM and f CDPM It can be represented as: Among them, M U and M V These are the equivalent motion masses of the fast cutter's U-axis 7 and V-axis 8, respectively.

[0028] Without considering the preload of the piezoelectric ceramic actuator, the strokes of the fast cutter U-axis 7 and fast cutter V-axis 8 can be obtained according to Newton's second law: Among them, X nom-U and X nom-V The nominal strokes of the U-axis piezoelectric ceramic actuator 72 and the V-axis piezoelectric ceramic actuator 81 are respectively, K nom-U and K nom-V These are the nominal stiffnesses of the U-axis piezoelectric ceramic actuator 72 and the V-axis piezoelectric ceramic actuator 81, respectively.

[0029] To ensure that the travel and first-order resonant frequency of the fast tool's U-axis 7 and V-axis 8 meet the cutting requirements, corresponding single-objective optimization models are established: Where w1, w2, w3, and w4 are weighting coefficients, and X is... obj-U and X obj-V The target travel distances for the U-axis 7 and V-axis 8 of the fast tool are respectively determined. The model is solved using an optimization algorithm to obtain the flexible hinge parameters that meet the performance requirements.

[0030] In this embodiment, the nominal parameter X of the piezoelectric ceramic actuator used is... nom-U X nom-V K nom-U and K nom-V The target travel X of the fast tool axis are 80μm, 16μm, 91 N / μm and 281 N / μm, respectively. obj-U and X obj-V The values ​​are 60 μm and 15 μm, respectively; the optimization results of the flexible hinge parameters are obtained by solving the model shown in equation (7) using the differential evolution algorithm, as shown in Table 1: Table 1 Based on the optimized parameters of the flexible hinge, the structural stiffness of the U-axis 7 of the fast tool was calculated using a theoretical model to be 30.04 N / μm, with a first-order resonant frequency of 2677 Hz; the structural stiffness of the V-axis 8 of the fast tool was 16.70 N / μm, with a first-order resonant frequency of 11644 Hz. For details, please refer to... Figure 5 The finite element simulation results shown in the figure are the structural deformation simulation results of each flexible hinge under a stress state (100N). The colors in the figure, from blue to red, indicate that the deformation increases. Among them, the displacement data under this stress state (e.g., 3.464×10) -3 The structural stiffness data can be calculated using μm. The calculation results show that the simulation results are basically consistent with the calculation results of the above-mentioned optimized model, indicating that the above-mentioned optimized model has high accuracy and is usable.

[0031] The dual piezoelectric ceramic driven high-speed tool device uses piezoelectric ceramic actuators as inputs for the high-speed tool's U-axis 7 and V-axis 8, enabling the diamond tool 9 to achieve high-frequency micro-displacement along the U-axis and V-axis directions. By optimizing the flexible hinge parameters, both axes exhibit high dynamic response characteristics along the feed direction, and the stroke meets machining requirements. A matching high-speed tool device was developed for the surface features of freeform microlens units, and combined with a feedforward feedback control algorithm to ensure its bandwidth and stability, significantly improving the system's response speed and forming accuracy in the machining of freeform microlens arrays.

[0032] The fast tool U-axis 7 and fast tool V-axis 8 of the dual piezoelectric ceramic driven fast tool device are arranged in orthogonal series, with a compact structure and decoupled from each other along the direction of motion. The moving parts of the fast tool device have small inertia, which can reduce the impact of the device's dynamic imbalance on machining accuracy during the rotation of the machine tool B-axis 4. The requirement for an active dynamic balancing device is small, and the system control is relatively simple.

[0033] like Figure 7As shown, a trajectory tracking experiment was conducted on the U-axis 7 and V-axis 8 of the fast-actuator. In the experiment, a simple harmonic signal was used as input to measure the output displacement of the U-axis actuator 74 and the V-axis actuator 83. The results show that the output displacement waveforms of the two axes are consistent with the input signals, and the parasitic displacement along the orthogonal directions is negligible. This indicates that the orthogonal series structure of the fast-actuator U-axis 7 and V-axis 8 can effectively achieve displacement decoupling and can be regarded as two independent single-input single-output systems.

[0034] like Figure 1 As shown, the dual piezoelectric ceramic driven dynamic rotary tool turning system also includes: A flexible tool holder 6 is located at the rotating end of the B-axis 4 of the machine tool. The dual piezoelectric ceramic driven high-speed tool device is connected to the B-axis 4 of the machine tool through the flexible tool holder 6. The flexible tool holder 6 is used to adjust the installation position of the dual piezoelectric ceramic driven high-speed tool device on the plane of the B-axis 4 of the machine tool, to perform test cuts and observe the surface processing of the workpiece, until the surface at the axis of rotation is flat and free of residual cutting marks; the flexible tool holder 6 is then locked, at which point the tip of the diamond tool 9 coincides with the axis of rotation of the B-axis 4 of the machine tool, thereby determining the position and orientation of the diamond tool 9 relative to the workpiece.

[0035] A mass balance block 11 is located at the rotating end of the B-axis 4 of the machine tool, on opposite sides of the dual piezoelectric ceramic driven high-speed tool device. It compensates for the weight of the dual piezoelectric ceramic driven high-speed tool device, achieving static balance of the cutting system. This design effectively reduces the initial imbalance of the system and decreases the initial amplitude of dynamic imbalance disturbances.

[0036] A slip ring, mounted on the B-axis 4 of the machine tool, is used to transmit electrical signals between the dual piezoelectric ceramic driven high-speed cutter device and external equipment during rotation, ensuring real-time transmission of control signals and displacement feedback signals for the high-speed cutter U-axis 7 and V-axis 8. If the slip ring is electrically connected to an external industrial control computer, the computer generates control commands based on the real-time rotation angle signal of the B-axis 4 of the machine tool, driving the high-speed cutter U-axis 7 and V-axis 8 to complete radial and depth-of-cut feed movements respectively, and reads the displacement signals of the high-speed cutter axes to achieve closed-loop control.

[0037] In addition, the dual piezoelectric ceramic driven dynamic rotary tool turning system also includes: The machine tool's X-axis 1 and Z-axis 3 are mounted on the base in a T-shape.

[0038] The Y-axis 2 of the machine tool is mounted on the slide of the X-axis 1 of the machine tool.

[0039] The C-axis 5 of the machine tool is mounted on the slide of the Y-axis 2 of the machine tool.

[0040] The workpiece fixture 10 is fixed on the C-axis 5 of the machine tool and is used to hold the workpiece to be processed so that the surface of the workpiece is perpendicular to the rotation axis of the B-axis 4 of the machine tool.

[0041] The B-axis 4 of the machine tool is mounted on the slide of the Z-axis 3 of the machine tool, and the rotation axis of the B-axis 4 is parallel to the movement direction of the Y-axis 2 of the machine tool.

[0042] Specific examples Figure 1 As shown, the structure of the dual piezoelectric ceramic driven dynamic rotary tool turning system is detailed below: The machine tool X-axis 1 and Z-axis 3 are mounted on the base in a T-shape. The machine tool Y-axis 2 is mounted on the slide of the machine tool X-axis 1, and the movement directions of the machine tool X-axis 1, Y-axis 2, and Z-axis 3 are perpendicular to each other, used to achieve reciprocating translational motion along a straight line. The machine tool B-axis 4 and C-axis 5 are respectively mounted on the slides of the machine tool Z-axis 3 and Y-axis 2. The rotation axis of the machine tool B-axis 4 is parallel to the movement direction of the machine tool Y-axis 2, used to achieve rotational motion around the axis. The fast tool U-axis 7 and fast tool V-axis 8 are orthogonally connected in series to form... The dual piezoelectric ceramic driven fast tool device has a diamond tool 9 mounted on the actuator end. The device support plate has mounting holes for fixed connection to a flexible tool holder 6. The flexible tool holder 6 is positioned within the B-axis 4 plane of the machine tool and is used to adjust the position of the dual piezoelectric ceramic driven fast tool device, ensuring the tip of the diamond tool 9 is aligned with the rotation axis of the B-axis 4. The workpiece is fixed to the C-axis 5 of the machine tool by a workpiece clamp 10, ensuring the surface to be machined is perpendicular to the rotation axis of the B-axis 4. A mass balance block 11 is installed on the B-axis 4 to compensate for the centrifugal force generated during high-speed rotation, improving the system's dynamic balance performance. The dual piezoelectric ceramic driven fast tool device is electrically connected to an external industrial control computer via a slip ring 12. It can receive control signals from the fast tool U-axis 7 and fast tool V-axis 8 in real time and feed back their displacement detection signals to achieve precise motion control of the fast tool axes.

[0043] In actual machining, the target surface is composed of multiple freeform surface microlens units. An equal-angle sampling strategy combined with a tool radius compensation algorithm is used to generate independent helical tool paths for each microlens unit. To ensure that the machine tool B-axis 4 rotates smoothly and the fast tool U-axis 7 feeds radially at a constant speed while the diamond tool 9 moves along the helical tool path, the reciprocating oscillation motion of the diamond tool 9 is concentrated in the depth of cut direction. Therefore, the tracking accuracy of the fast tool V-axis 8 directly affects the machining accuracy and efficiency of each unit. After determining the machining sequence of each microlens unit, the machine tool X-axis 1 and Z-axis 3 displacements are adjusted before cutting to align the tool rotation axis sequentially with the target center position of each microlens unit. A corresponding CNC program is generated based on the independent helical tool paths and machining sequence to control the dynamic rotary tool cutting system to complete the machining of the freeform surface microlens array.

[0044] like Figure 6As shown, the machining method of microlens arrays using a dual piezoelectric ceramic driven dynamic rotary tool in this invention is compared with the characteristics of existing dynamic rotary tool cutting and fast-tool servo cutting methods for microlens arrays. Based on the structural characteristics of the freeform surface microlens array, the method of this invention generates an independent helical toolpath for each microlens unit and sequentially completes the machining of each unit. Compared with the traditional machining method using a single helical toolpath, this method avoids toolpath differences caused by the different positions of microlens units in the array, thus ensuring consistent cutting states for each unit. Furthermore, this method overcomes the discontinuity limitation of a single helical toolpath in microlens array machining, focusing the machining target on the surface features of a single microlens unit. Through the coordinated linkage of the high-dynamic-response fast-tool axis and the machine tool rotary axis, the precise forming of complex unit structures is achieved, thereby realizing high-precision and high-consistency machining of freeform surface microlens arrays.

[0045] When the fast tool device in the above embodiment is installed at the end of the B-axis 4 of a high-speed rotating machine tool, the centrifugal force generated by the uneven mass distribution of the system increases proportionally to the square of the rotational speed. Traditional PI controllers can only provide feedback correction for existing errors and cannot actively suppress periodic disturbances. Simultaneously, the frequent displacement of the fast tool U-axis 7 during microlens array machining causes real-time changes in the center of mass, resulting in a dynamic eccentricity effect that traditional static balancing techniques cannot resolve. To meet the machining requirements of high-precision freeform surfaces, especially irregularly shaped microlenses, as another possible embodiment of the present invention, such as... Figure 8 As shown, a method for controlling the motion of a fast tool axis based on dynamic unbalance is also provided to solve the above-mentioned technical problems. This method is applied to dynamic rotary tool cutting systems (such as the dual piezoelectric ceramic driven dynamic rotary tool turning system described in the above embodiments). The method includes the following steps: S1: Real-time acquisition of reference signal features of the current machining trajectory. Reference signal features include at least: position, velocity, acceleration, and frequency characteristics of the reference trajectory. They may also include the current position of the fast tool's U-axis 7, the machine tool's B-axis 4 rotational speed, and the machine tool's B-axis 4 phase angle. Acquiring these feature parameters allows the system to comprehensively understand the current machining state, providing necessary input for predicting dynamic imbalance disturbances. Especially when U-axis displacement causes centroid shift, the current position of the fast tool's U-axis 7 serves as a key input feature, enabling the system to accurately predict the resulting dynamic imbalance disturbances.

[0046] By acquiring the reference signal characteristics of the current machining trajectory in real time, and combining them with key parameters such as the current position of the fast tool's U-axis 7, the machine tool's B-axis 4 speed and phase angle, the system can comprehensively grasp the current machining status. In particular, for the centroid shift caused by U-axis displacement, it can accurately predict the resulting dynamic imbalance disturbance, thereby achieving effective prediction and compensation for trajectory tracking errors and improving the system's trajectory tracking accuracy.

[0047] S2: Predict the corresponding tracking error using a pre-trained dynamic imbalance perturbation prediction model.

[0048] By employing a pre-trained dynamic imbalance disturbance prediction model, tracking errors under different frequency, speed, and position conditions can be predicted. This feedforward compensation mechanism enables the system to compensate for errors before they occur, actively suppressing rotation-related periodic disturbances, breaking through the bandwidth limitations of traditional feedback control, and significantly improving the system's anti-interference capability.

[0049] The dynamic imbalance disturbance prediction model is obtained through the following methods: S2.1: Under the condition that the machine tool's B-axis 4 rotates at a preset speed, a sweep frequency signal is applied to the fast tool's U-axis 7 to collect the reference trajectory of the fast tool's U-axis 7 and its corresponding actual output trajectory, thus constructing a training dataset. The frequency range of the sweep frequency signal covers the spectral characteristics required for the machining trajectory. Specifically, the actual machining speed of the machine tool's B-axis 4 is usually set to a constant value. The preset speed is consistent with the actual machining speed of the machine tool's B-axis 4, making the trained dynamic imbalance disturbance prediction model applicable to compensation control under specific speed conditions. Through this data acquisition process, the system can capture the mapping relationship between U-axis motion and tracking error at a specific speed, providing high-quality data for Gaussian process model training.

[0050] If the machine tool B-axis 4 is kept rotating at a fixed speed (e.g., 80 rpm), the fast tool U-axis 7 executes a frequency sweep signal, i.e., reciprocating linear motion, to collect position, speed, and acceleration data of the fast tool U-axis 7 at different frequencies. When collecting data, the frequency sweep signal must cover all frequencies, speeds, accelerations, and position characteristics required for the actual machining trajectory.

[0051] Based on the aforementioned dataset, the following features are constructed: Input features: position, velocity, acceleration, and frequency of the reference trajectory on the U-axis of the fast-tracking device. Output features: corresponding tracking error (the difference between the actual trajectory and the reference trajectory). Then, a Gaussian process regression (GPR) model is trained to establish a nonlinear mapping relationship between the input features and the tracking error.

[0052] S2.2: Based on the training dataset, a Gaussian process regression model is used to learn the nonlinear mapping relationship between the reference trajectory features and the tracking error, thereby obtaining a dynamic imbalance disturbance prediction model.

[0053] Specifically, the Gaussian process regression model can use automatic correlation to determine the kernel function and optimize the hyperparameters by maximizing marginal likelihood estimation. During model training, a sparse Gaussian process algorithm is employed, selecting no more than 100 induced points to reduce computational complexity while meeting real-time control requirements. This model can accurately predict tracking errors under different frequency, speed, and position conditions, providing a reliable basis for feedforward compensation.

[0054] S3: The predicted tracking error is superimposed on the original reference trajectory to generate the compensated reference trajectory signal.

[0055] S4: Use the compensated reference trajectory signal as the initial control input for the U-axis 7 of the fast tool.

[0056] By superimposing the prediction error onto the original reference trajectory, the system compensates for the error before it occurs, effectively avoiding the impact of dynamic imbalance disturbances on trajectory tracking. This feedforward compensation mechanism enables the system to actively suppress rotation-related periodic disturbances, overcoming the bandwidth limitations of traditional feedback control. The initial control input already includes prediction compensation for dynamic imbalance disturbances, making the motion trajectory of the U-axis 7 of the fast tool more accurate.

[0057] S5: Obtain the residual error between the actual output position of the U-axis 7 of the fast tool and the initial control input.

[0058] S6: A proportional-integral (PI) controller is used to adjust the residual error and generate a feedback control signal.

[0059] Regarding the radial motion characteristics of the U-axis 7 of the fast tool, such as Figure 9 As shown in (a), a feedforward feedback control method is used to improve trajectory tracking accuracy. Based on feedforward compensation, the traditional PI controller C(s) is retained as a feedback loop to handle residual errors not fully captured by the feedforward model, external disturbances, and system parameter drift. Where Y... r (t) Reference trajectory of the microlens unit to be processed, Y out (t) represents the actual output trajectory, and the controlled object G(s) represents the dynamic characteristics of the U-axis, including the electromechanical coupling behavior of the piezoelectric ceramic actuator, flexible hinge, and actuator; the predicted tracking error is e(t); the compensated input signal Y is generated. r '(t)=Y r (t)+e(t); The feedback control loop inputs Y after comparison and compensation. r '(t) and actual output Y out The deviation of (t) is adjusted in real time to ensure system stability and robustness. The feedback controller is optimized based on the characteristics of the controlled object, and dynamic compensation is achieved in the feedforward stage using a Gaussian process model. This effectively suppresses the trajectory tracking error of the fast tool U-axis 7 while maintaining system bandwidth and stability. Figure 9 As shown in (b) in the figure, the experimental results show that after feedforward compensation, the actual trajectory of the U-axis 7 of the fast tool is significantly improved in terms of its consistency with the target trajectory.

[0060] S7: The feedback control signal and the feedforward compensation signal are superimposed to jointly control the movement of the U-axis 7 of the fast cutter, forming a feedforward + feedback dual closed-loop control structure. Alternatively, existing conventional high-bandwidth control strategies can be used for the motion control of the U-axis 7 of the fast cutter.

[0061] By superimposing the feedforward compensation signal and the feedback control signal to jointly control the movement of the U-axis 7 of the fast tool, a feedforward + feedback dual closed-loop control structure is formed. This structure utilizes feedforward compensation to actively suppress predictable dynamic imbalance disturbances and feedback control to handle residual errors, ensuring that the system maintains high-precision trajectory tracking even under high-speed rotation conditions. Simultaneously, the use of a PI controller further enhances the system's stability and robustness, reducing the impact of external factors on machining quality.

[0062] This control method can be implemented simply by upgrading the control algorithm through software, without requiring additional mechanical modifications to existing equipment, thus significantly reducing implementation costs. Simultaneously, this method improves the system's adaptability to different microlens shapes, increases production flexibility, and helps enhance the company's market competitiveness.

[0063] Based on the dynamic imbalance-based fast tool axis motion control method proposed in this invention, a dual piezoelectric ceramic driven dynamic rotary tool system is controlled to perform cutting. A white light interferometer is used to measure the surface of the workpiece cut by the dual piezoelectric ceramic driven dynamic rotary tool, to evaluate the influence of the microlens unit position and the machine tool B-axis 4 rotation speed on the machined surface quality. Figure 10 As shown in (a) and (b), the radial position variation of the microlens unit has a relatively small impact on the surface roughness and contour error of the machined surface. Compared with the large surface quality differences of microlens units at different radial positions in traditional fast-tool servo cutting, the method proposed in this invention can significantly improve the consistency of microlens array machining and is beneficial for obtaining uniform surface quality. Figure 10 As shown in (c) and (d), with the increase of the B-axis speed of the machine tool, the surface roughness and contour error of the microlens unit slightly increase, but the overall surface roughness and submicron surface shape error can still be maintained at the nanometer level. This phenomenon may be due to the increase in centrifugal force caused by the increase in speed, which leads to a slight increase in the steady-state error of the system. The comprehensive analysis results show that the technical solution proposed in this invention can still maintain excellent dynamic stability and machining repeatability under high-speed machining conditions.

[0064] like Figure 11As shown in (a) and (b) of this paper, a freeform surface microlens array was machined using the dual piezoelectric ceramic driven dynamic rotary tool cutting technology proposed in this invention. The average surface roughness Sa of the 16 microlens units was measured to be 4.5 nm, with a standard deviation of 0.2 nm, indicating that this method can achieve high-quality and high-repeatability cutting of freeform surface microlens arrays. To evaluate the surface accuracy of the microlens units, as shown in (a) and (b) of this paper, a dynamic rotary tool cutting technology proposed in this invention was used to machine a freeform surface microlens array. Figure 11 As shown in (c), the cross-sectional profiles along the major axis (AA) and minor axis (BB) directions passing through the lens center were extracted and measured. The results show that the measured profiles match the design target profile well, with a profile error PV value of 126 nm along the major axis and 119 nm along the minor axis. Furthermore, as... Figure 11 As shown in (d), the randomly distributed freeform surface microlens array and the freeform surface microlens with special shapes (such as triangular and quadrangular microlens units) were further processed, and good surface quality was obtained. This shows that the method proposed in this invention can make full use of the high dynamic response characteristics of the fast tool axis to achieve the precise forming of complex microlens units, and has good process adaptability and stability.

[0065] Furthermore, although the steps of the method in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or a step may be broken down into multiple steps.

[0066] From the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein can be implemented by software or by combining software with necessary hardware. Therefore, the technical solutions according to the embodiments of this disclosure can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as a CD-ROM, USB flash drive, external hard drive, etc.) or on a network, including several instructions to cause a computing device (such as a personal computer, server, mobile terminal, or network device, etc.) to execute the methods according to the embodiments of this disclosure.

[0067] In an exemplary embodiment of this disclosure, an electronic device capable of implementing the above-described method is also provided.

[0068] Those skilled in the art will understand that various aspects of the present invention can be implemented as systems, methods, or program products. Therefore, various aspects of the present invention can be specifically implemented in the following forms: entirely in hardware, entirely in software (including firmware, microcode, etc.), or in a combination of hardware and software, collectively referred to herein as “circuit,” “module,” or “system.”

[0069] An electronic device according to this embodiment of the invention. The electronic device is merely an example and should not be construed as limiting the functionality or scope of the embodiments of the invention.

[0070] Electronic devices are manifested in the form of general-purpose computing devices. Components of an electronic device may include, but are not limited to: at least one processor, at least one memory, and buses connecting different system components (including memory and processor).

[0071] The memory stores program code that can be executed by a processor, causing the processor to perform the steps described in the "Exemplary Methods" section above, according to various exemplary embodiments of the present invention.

[0072] The storage may include readable media in the form of volatile storage, such as random access memory (RAM) and / or cache memory, and may further include read-only memory (ROM).

[0073] The storage may also include programs / utilities having a set (at least one) of program modules, including but not limited to: an operating system, one or more applications, other program modules, and program data, each or some combination of these examples may include an implementation of a network environment.

[0074] A bus can represent one or more of several bus architectures, including a memory bus or memory controller, a peripheral bus, a graphics acceleration port, a processor, or a local bus that uses any of the various bus architectures.

[0075] The electronic device can also communicate with one or more external devices (e.g., keyboards, pointing devices, Bluetooth devices, etc.), one or more devices that enable a user to interact with the electronic device, and / or any device that enables the electronic device to communicate with one or more other computing devices (e.g., routers, modems, etc.). This communication can be performed via input / output (I / O) interfaces. Furthermore, the electronic device can communicate with one or more networks (e.g., local area networks (LANs), wide area networks (WANs), and / or public networks, such as the Internet) via a network adapter. The network adapter communicates with other modules of the electronic device via a bus. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with the electronic device, including but not limited to: microcode, device drivers, redundant processors, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0076] In exemplary embodiments of this disclosure, a computer-readable storage medium is also provided, on which a program product capable of implementing the methods described above is stored. In some possible embodiments, various aspects of the present invention may also be implemented as a program product comprising program code that, when the program product is run on a terminal device, causes the terminal device to perform the steps of the various exemplary embodiments of the present invention described in the "Exemplary Methods" section above.

[0077] The program product may employ any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0078] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable signal medium may also be any readable medium other than a readable storage medium, capable of sending, propagating, or transmitting programs for use by or in conjunction with an instruction execution system, apparatus, or device.

[0079] The program code contained on the readable medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, RF, etc., or any suitable combination thereof.

[0080] Program code for performing the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute entirely on the user's computing device, partially on the user's device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0081] Furthermore, the accompanying drawings are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention and are not intended to be limiting. It is readily understood that the processes shown in the above drawings do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0082] It should be noted that although several modules or units for the device used to perform actions have been mentioned in the detailed description above, this division is not mandatory. In fact, according to embodiments of this disclosure, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided and embodied by multiple modules or units.

[0083] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A dynamic rotary tool turning system driven by dual piezoelectric ceramics, characterized in that, include: The machine tool's B-axis serves as the main rotary motion axis. A dual piezoelectric ceramic driven fast tool device is directly and fixedly mounted on the rotating end of the B-axis of the machine tool, rotating synchronously with the B-axis. The device includes a fast tool U-axis and a fast tool V-axis. The fast tool U-axis is arranged radially along the workpiece, and the fast tool V-axis is orthogonally positioned on the actuator of the fast tool U-axis along the depth of cut direction. Both the U-axis and V-axis drive the actuator via piezoelectric ceramic actuators. The fast tool V-axis is used to mount turning tools. The rotational motion of the machine tool's B-axis is linked with the micro-displacement motions of the fast tool's U-axis and V-axis to form a real helical tool path, which is used for turning free-form surface microlens arrays.

2. The dual piezoelectric ceramic driven dynamic rotary tool turning system according to claim 1, characterized in that, The fast cutter V-axis is completely embedded inside the actuator of the fast cutter U-axis, forming an orthogonal series nested structure.

3. The dual piezoelectric ceramic driven dynamic rotary tool turning system according to claim 1 or 2, characterized in that, Also includes: A flexible tool holder is disposed at the rotating end of the B-axis of the machine tool, and the dual piezoelectric ceramic driven fast tool device is connected to the B-axis of the machine tool through the flexible tool holder.

4. The dual piezoelectric ceramic driven dynamic rotary tool turning system according to claim 1 or 2, characterized in that, Also includes: A mass balance block is located at the rotating end of the B-axis of the machine tool, on opposite sides of the dual piezoelectric ceramic driven fast tool device, to compensate for the weight of the dual piezoelectric ceramic driven fast tool device and achieve static balance of the tool cutting system.

5. The dual piezoelectric ceramic driven dynamic rotary tool turning system according to claim 3, characterized in that, Also includes: A slip ring, mounted on the B-axis of the machine tool, is used to transmit electrical signals between the dual piezoelectric ceramic driven fast tool device and external equipment during rotation.

6. The dual piezoelectric ceramic driven dynamic rotary tool turning system according to claim 3, characterized in that, The fast tool U-axis includes: A U-shaped support plate is fixed to the flexible tool holder; The U-axis piezoelectric ceramic actuator has one end in contact with the U-axis support plate and the other end in contact with the U-axis actuator. A U-direction flexible hinge connects the U-direction support plate and the U-direction actuator. The U-direction flexible hinge consists of four identical links, each of which includes a leaf spring flexible hinge and two circular flexible hinges. Circular flexible hinges are connected to both ends of the leaf spring flexible hinge, and the circular flexible hinges at both ends are respectively connected between the U-direction support plate and the U-direction actuator. The four links are arranged in pairs and are respectively set in the gaps on both sides formed by the U-direction support plate and the U-direction actuator. Two links in any pair are arranged parallel to each other along the U-direction, and the four links form a symmetrical double parallelogram mechanism. This mechanism is used to convert the axial extension and retraction of the U-direction piezoelectric ceramic actuator into the linear displacement of the U-direction actuator, while suppressing non-U-direction parasitic motion and providing elastic restoring force. A U-axis displacement sensor is used to detect the displacement of the U-axis actuator.

7. The dual piezoelectric ceramic driven dynamic rotary tool turning system according to claim 6, characterized in that, The fast tool V-axis includes: The V-axis piezoelectric ceramic actuator has one end in contact with the U-axis actuator and the other end in contact with the V-axis actuator. A V-axis flexible hinge, one end of which is fixed to the surface of the U-axis actuator, and the other end of which is connected to the V-axis actuator; The V-axis flexible hinge consists of eight identical leaf springs, which are divided into four groups. Each group has two leaf springs arranged in parallel. The two ends of each leaf spring are in contact with the U-axis actuator and connected to the V-axis actuator. The four groups of leaf springs are arranged circumferentially opposite to each other around the V-axis actuator, forming a cross double parallelogram mechanism. This mechanism is used to convert the axial extension and retraction of the V-axis piezoelectric ceramic actuator into the linear displacement of the V-axis actuator, while suppressing non-V-axis parasitic motion and providing elastic restoring force. A V-direction displacement sensor is used to detect the displacement of the V-direction actuator.

8. The dual piezoelectric ceramic driven dynamic rotary tool turning system according to claim 1, characterized in that, Also includes: Base; The X-axis and Z-axis of the machine tool are mounted on the base in a T-shaped arrangement. The Y-axis of the machine tool is mounted on the slide of the X-axis of the machine tool; The C-axis of the machine tool is mounted on the slide of the Y-axis of the machine tool; A workpiece fixture, fixed on the C-axis of the machine tool, is used to hold the workpiece to be processed so that the surface of the workpiece is perpendicular to the rotation axis of the B-axis of the machine tool.

9. The dual piezoelectric ceramic driven dynamic rotary tool turning system according to claim 8, characterized in that, The B-axis of the machine tool is mounted on the slide of the Z-axis of the machine tool, and the rotation axis of the B-axis is parallel to the movement direction of the Y-axis of the machine tool.

10. A dual piezoelectric ceramic driven dynamic rotary tool turning system according to claim 7, characterized in that, Establish corresponding single-objective optimization models for the U-axis and V-axis of the fast tool respectively, and obtain the parameters corresponding to the U-axis flexible hinge and V-axis flexible hinge respectively; so that the U-axis and V-axis of the fast tool meet the stroke requirements and first-order resonant frequency requirements in the cutting process.

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