A force control tool, online force measurement system and constant force regulation method

Abstract

The application discloses a force control tool, an online force measurement system and a constant force regulation method. The force control tool comprises a machining tool, a tool adapter and a force sensor. The sensor of the force control tool detects and feeds back the contact force between the machining tool and the optical element to be machined, and the contact displacement between the machining tool and the optical element to be machined has a fixed mapping relationship with the contact force. The online force measurement system comprises the force control tool, a data transmitter, a signal conditioner, a data collector and a data processor, and is used for monitoring the contact force fluctuation, giving an early warning when the contact force exceeds the limit and outputting a displacement compensation amount to a machine tool. The constant force regulation method obtains the contact force and the corresponding micro-displacement compensation amount based on the online force measurement system, and realizes the constant control of the contact force through displacement regulation. The application can realize online monitoring, early warning and feedback control of the contact force in the machining process, prevent the workpiece or tool from being damaged due to excessive contact force, and has important significance for improving the machining safety and stability of the optical element.

Description

Technical Field

[0001] This application belongs to the field of optical component processing technology, and particularly relates to a force control tool, an online force measurement system, and a constant force control method. Background Technology

[0002] To achieve high precision and high quality in ultra-large aperture optical components, the manufacturing process needs to remain stable over a long period, and the stability of the machining tool is a crucial aspect of this stability. During efficient polishing, tool performance degradation is inevitable, affecting processing stability. Polishing force (contact force) is a vital parameter reflecting changes in process conditions. It can be used for tool condition monitoring, such as tool wear, scratches, and breakage, as well as for monitoring polishing conditions, such as vibration. Both excessively high and insufficient contact forces will result in unsatisfactory polishing results. Therefore, online detection and feedback control of the contact force between the tool and the workpiece is an important means of achieving long-term, highly stable removal.

[0003] Currently, most contact force monitoring methods for ultra-large aperture optical components are offline detection methods. These methods study the relationship between force and removal, and understand the force decay pattern, through offline force testing. Position compensation during offline programming helps suppress predictable, regular disturbances. While this offline force testing and compensation method can suppress force changes caused by predictable time-varying factors during actual grinding and polishing to a certain extent, it cannot suppress the influence of uncertainties in process conditions and the environment. Summary of the Invention

[0004] The embodiments of this application provide a force control tool, an online force measurement system, and a constant force control method, which can at least to some extent provide data support for the control of subsequent contact force and contact displacement based on the contact force detected by the force sensor, thereby improving the processing stability of optical components.

[0005] Other features and advantages of this application will become apparent from the following detailed description, or may be learned in part from practice of this application.

[0006] The first aspect of this application provides a force control tool, including: A processing tool is configured to perform contact processing on an optical element to be processed, and there is a fixed mapping relationship between the contact displacement and the contact force between the processing tool and the optical element to be processed. A tool adapter includes a tool holder and a tool disc, the tool holder including a connecting rod and a connecting base connected to each other, the side of the connecting rod away from the connecting base being configured to be connected to the spindle of a machine tool for processing the optical element to be processed, and the side of the tool disc away from the tool holder being connected to the processing tool. A force sensor is connected to the side of the connecting base away from the connecting rod and the side of the cutter head near the tool holder. The force sensor is configured to detect the contact force between the machining tool and the optical element to be processed during the machining process when the machining tool is rotated by the spindle of the machining tool.

[0007] Optionally, the processing tool is a spherical cap-shaped capsule structure; The cutter head includes: an arc-shaped cavity, which is a cavity protruding from the cutter handle toward the spherical cap-shaped capsule structure, and the outer wall of the arc-shaped cavity is connected to the spherical cap-shaped capsule structure in a conformal manner; The center of the spherical cap-shaped capsule structure, the center of the arc-shaped cavity, and the intersection of the machine tool's axis of rotation are located on the same axis.

[0008] Optionally, an annular base is provided inside the arc-shaped cavity. The interior of the annular base is hollow, and the side of the force sensor away from the handle is conformally disposed on the annular base.

[0009] Optionally, the arc-shaped cavity has an annular surface on the side near the force sensor. The annular surface has a plurality of balance adjustment holes along the circumference. Mass blocks are placed in the balance adjustment holes for balance adjustment. The imbalance of the machining tool, the tool adapter, and the force sensor at a preset rotation speed is less than or equal to a preset value. The preset rotation speed is greater than or equal to 2000 rpm, and the preset value is less than or equal to 10 μm.

[0010] Optionally, the tool adapter further includes a hollow air guide tube, which sequentially passes through the tool holder, the force sensor, and the tool disc and is inserted into the machining tool. The hollow air guide tube is configured to introduce external compressed air into the machining tool.

[0011] A second aspect of this application provides an online force measurement system, comprising: Force control tools as described in any of the first aspects; A data transmitter is fixedly connected to a machine tool via a connector. The data transmitter is spaced apart from the force sensor of the force control tool and communicates with the force sensor based on near-field remote sensing technology. The data transmitter is used to acquire the contact force signal detected by the force sensor. A data processor, communicatively connected to the data transmitter, is used to acquire the contact force signal, save, display, analyze, and provide early warnings for the contact force signal, and provide early warnings for fluctuations in the contact force and output displacement compensation amounts to the machine tool when the deviation between the contact force and the target contact force is greater than or equal to the target deviation.

[0012] Optionally, when the deviation between the contact force and the target contact force is greater than or equal to the target deviation, and when providing early warning of fluctuations in the contact force and outputting displacement compensation to the machine tool, the data processor is used to: If the deviation between the contact force signal and the preset target contact force is greater than or equal to the deviation threshold, an early warning is issued for the fluctuation of the contact force. Based on the deviation value and the mapping relationship between the contact displacement and the contact force between the processing tool and the optical element to be processed, the displacement compensation amount is determined. A micro-displacement compensation amount is sent to the machine tool sequentially so that the machine tool can compensate for the contact displacement between the optical element to be processed and the processing tool according to the micro-displacement compensation amount. After each compensation, the contact force signal is reacquired. If the deviation between the contact force signal and the target contact force is still greater than or equal to the deviation threshold, the micro-displacement compensation amount is sent to the controller again until the deviation between the contact force signal acquired in the current iteration and the target contact force is less than the deviation threshold. The micro-displacement compensation amount is less than the displacement compensation amount.

[0013] Optionally, it also includes: A signal conditioner, communicatively connected to the data transmitter, is configured to convert the contact force signal into an analog voltage signal; A data acquisition unit is communicatively connected to the signal conditioner and the data processor. The data acquisition unit is configured to acquire the analog voltage signal and convert the analog voltage signal into the contact force signal according to the signal mapping relationship between the force and voltage of the force sensor.

[0014] A third aspect of this application provides a constant force control method, including: Data acquisition and processing steps: The contact force signal is acquired by the force sensor in the force control tool as described in any of the first aspects, and the contact force signal acquired within the target time period is filtered and the mean is calculated to obtain the measured contact force; Force-position relationship calibration steps: The relative displacement between the machining tool and the optical element to be processed is controlled by the movement control of the machining tool. The magnitude and distribution of the contact force between the machining tool and the optical element to be processed are detected simultaneously by a multi-dimensional force sensor and a thin-film force sensor to establish a fixed mapping relationship between the contact displacement and the contact force. Force deviation calculation steps: Set the target contact force, compare the measured contact force with the target contact force, and determine whether the force fluctuation exceeds the tolerance. If it exceeds the tolerance, an alarm will be triggered. Displacement compensation calculation: Based on the deviation between the measured contact force and the target contact force, and the mapping relationship between the contact displacement and contact force between the processing tool and the optical element to be processed, the displacement compensation is determined. Micro-displacement compensation amount transmission and execution steps: Micro-displacement compensation amounts are sent sequentially to the machine tool so that the machine tool compensates for the contact displacement between the optical element to be processed and the processing tool based on the micro-displacement compensation amounts. After each compensation, the contact force signal is reacquired. If the deviation between the contact force signal and the target contact force is still greater than or equal to the deviation threshold, the micro-displacement compensation amount is sent to the controller again until the deviation between the currently acquired contact force signal and the target contact force is less than the deviation threshold; wherein, the micro-displacement compensation amount is less than the displacement compensation amount.

[0015] Optionally, the ratio of the micro-displacement compensation amount to the displacement compensation amount is 1 / 5 to 1 / 2.

[0016] The one or more technical solutions provided in the embodiments of the present invention achieve at least the following technical effects or advantages: (1) The present invention provides a force control tool that can both rotate and process components at high speed and detect and provide feedback on contact force in real time; at the same time, the tool adapter connects the processing tool and the rotary force sensor to ensure that the center of the tool ball coincides with the intersection point of the machine tool rotation axis, thus ensuring the accurate and controllable use of the tool ring, which is of great significance for realizing high deterministic machining of curved surfaces.

[0017] (2) This invention provides an online real-time force detection system to realize contact force monitoring and tool failure early warning, and provides a means of real-time monitoring of the processing status, providing important process guidance for operators.

[0018] (3) This invention provides a constant force control method, which adjusts the contact force by compensating for small displacements each time, thereby gradually approaching the target force and achieving constant force control. This method avoids overcompensation caused by unavoidable system delays. In addition, constant force control avoids the impact of force and removal fluctuations on processing accuracy and efficiency, which is especially important for long-term high-stability processing of ultra-large aperture optical components. On the other hand, it avoids excessive contact force that could damage the workpiece or tool, resulting in huge losses, which is of great significance for high-safety processing of thin-walled or weakly rigid components.

[0019] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings: Figure 1 A three-dimensional structural diagram of the force control tool according to an embodiment of this application is shown; Figure 2 A cross-sectional structural schematic diagram of the force control tool according to an embodiment of this application is shown; Figure 3 This invention illustrates a schematic diagram showing a preset relationship curve between the contact displacement and contact force between the processing tool and the optical element to be processed according to an embodiment of this application. Figure 4 A structural block diagram of the online force measurement system according to an embodiment of this application is shown; Figure 5 A schematic diagram illustrating the displacement compensation principle of an embodiment of this application is shown; Figure 6 A flowchart of the constant force control method according to an embodiment of this application is shown; Figure 7 This paper illustrates a schematic diagram of the compensation trajectory of the constant force control method according to an embodiment of this application. Figure 8 A comparative curve diagram of the constant force control method of this application and related technologies is shown.

[0021] 10-Force control tool; 1-Machining tool; 2-Tool adapter; 21-Tool holder; 211-Connecting rod; 212-Connecting base; 22-Tool disc; 221-Arc-shaped cavity; 222-Annular base; 223-Annular surface; 224-Balance adjustment hole; 3-Force sensor; 4-Hollow air guide tube; 41-First sealing groove; 42-Second sealing groove; 23-Third sealing groove; 20-Data transmitter; 30-Data processor; 40-Signal conditioner; 50-Data acquisition unit. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0024] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different models and / or processor devices and / or microcontroller devices.

[0025] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0026] It should also be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such uses of these terms can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described.

[0027] To achieve high precision and high quality in ultra-large aperture optical components, the manufacturing process needs to remain stable over a long period, and the stability of the machining tool is a crucial aspect of this stability. During efficient polishing, the performance of the machining tool inevitably degrades, affecting processing stability. Polishing force (contact force) is a vital parameter reflecting changes in the process state. It can be used for tool condition monitoring, such as tool wear, scratches, and breakage, as well as for monitoring the polishing state, such as vibration. Both excessively high and insufficient contact forces will result in unsatisfactory polishing results. Therefore, online detection and feedback control of the contact force between the tool and the workpiece is an important means to achieve long-term, highly stable removal.

[0028] Currently, most contact force monitoring methods for ultra-large aperture optical components are offline detection methods. These methods study the relationship between force and removal, and understand the force attenuation pattern, through offline force testing. Position compensation during offline programming helps suppress predictable, regular disturbances. While this offline force testing and compensation method can suppress force changes caused by predictable time-varying factors during actual grinding and polishing to a certain extent, it cannot suppress the influence of uncertainties in process conditions and the environment. Furthermore, the confidence level of the force and removal variation patterns established by offline force testing is poor, and its process adaptability is also limited. Changes in component configuration or process conditions may lead to significant deviations in the established patterns.

[0029] In view of this, this application provides a force control tool that connects the machining tool, force sensor, and the spindle of the machine tool through a tool adapter. During the machining process where the spindle of the machine tool drives the machining tool 1 to rotate, the force sensor can detect the contact force between the machining tool and the optical element to be processed in real time online. Since there is a preset mapping relationship between the contact displacement and the contact force, the contact force detected by the force sensor can provide data support for the subsequent control of the contact force and contact displacement, thereby improving the processing stability of the optical element.

[0030] The force control tool of the present application embodiment will be described below with reference to the accompanying drawings.

[0031] Figure 1 A three-dimensional structural diagram of the force control tool according to an embodiment of this application is shown; Figure 2 A cross-sectional structural schematic diagram of the force control tool according to an embodiment of this application is shown.

[0032] The first aspect of this application provides a force control tool 10, including: a machining tool 1, a tool adapter 2, and a force sensor 3. The machining tool 1 is configured to perform contact machining on an optical element to be machined, and a fixed mapping relationship exists between the contact displacement and contact force between the machining tool 1 and the optical element to be machined. The tool adapter 2 includes: a tool holder 21 and a cutter head 22. The tool holder 21 includes a connecting rod 211 and a connecting base 212 connected to each other. The side of the connecting rod 211 away from the connecting base 212 is configured to be connected to the spindle of a machine tool for machining the optical element to be machined. The side of the cutter head 22 away from the tool holder 21 is connected to the machining tool 1. The force sensor 3 is connected to both the side of the connecting base 212 away from the connecting rod 211 and the side of the cutter head 22 near the tool holder 21. The force sensor 3 is configured to detect the contact force between the machining tool 1 and the optical element to be machined during the machining process when the spindle of the machine tool drives the machining tool 1 to rotate.

[0033] It should be noted that configuring the processing tool 1 to perform contact processing on the optical element to be processed can mean that the processing tool 1 directly and physically contacts the surface of the optical element, and removes the material through mechanical action (such as polishing). In the embodiments of this application, a controllable contact force is generated between the processing tool 1 and the optical element to be processed, and there is a preset mapping relationship between the contact displacement and the force, thereby achieving precise and stable material removal.

[0034] It is understandable that the fixed mapping relationship between the contact displacement and contact force between the machining tool 1 and the optical element to be processed can mean that, at the contact position between the machining tool 1 and the optical element, the depth to which the tool presses into the surface of the element (i.e., the contact displacement, or the amount of pressure) and the interaction force generated between them (i.e., the contact force) follow a known fixed mapping relationship, such as a functional relationship. This mapping relationship can be non-linear or linear. Therefore, based on the contact force measured by the force sensor 3, the current contact displacement can be deduced, or the target contact force can be controlled based on the target displacement, thereby achieving closed-loop control of the machining process.

[0035] Figure 3 This paper illustrates a schematic diagram showing a preset relationship curve between the contact displacement and contact force between the processing tool 1 and the optical element to be processed according to an embodiment of this application.

[0036] For example, by setting up a calibration experimental platform, the machining tool 1 is mounted on the machine tool spindle via the tool adapter 2. A sample with the same material and surface condition as the optical element to be processed is placed below it, and the sample is placed on a high-precision force measuring platform. The machine tool spindle is controlled to move downwards at a low speed (e.g., 0.1 mm / s). For each small step Δh (e.g., 0.001 mm), the normal contact force Fn measured by the multi-dimensional force sensor 3 and the contact force distribution data measured by the thin-film force sensor 3 are recorded. The force value at the center point of the contact area is taken as the contact force corresponding to the current downward pressure. The loading-unloading cycle is repeated multiple times to obtain a series of discrete data points (h_i, Fn_i). These points are then curve-fitted, and the data conforms to the quadratic function law, yielding the functional relationship Fn = 388h² + 11h. For example, when the measured pressure h = 0.05 mm, the calculated Fn = 388 × 0.0025 + 11 × 0.05 = 0.97 + 0.55 = 1.52 N. If the force sensor 3 measures a current contact force of 1.52 N during online processing, but the surface quality is poor, and the force needs to be adjusted to 2.00 N, then solving the equation 388h² + 11h = 2.00 yields a target pressure h ≈ 0.062 mm. Therefore, an online compensation displacement of 0.012 mm is required. In this way, the preset force-displacement relationship becomes the preset basis for subsequent real-time adjustment of the tool's pressure based on force fluctuations.

[0037] For example, the connecting rod 211 of the tool holder 21 can be a slender cylinder or a stepped cylinder with an axial length greater than its diameter. One end of the connecting rod 211 can be set as a standard interface for cooperating with the machine tool spindle, and the other end of the connecting rod 211 can be integrally connected to the connecting base 212 or fastened by threads.

[0038] For example, the connecting base 212 of the tool holder 21 can be a disc or a flange, and its diameter can be larger than that of the connecting rod 211. The side of the connecting base 212 that is connected to the connecting rod 211 can be provided with a boss or a threaded hole for fixing to the connecting rod 211. The side of the connecting base 212 that is connected to the force sensor 3 can be a flat mounting surface with multiple precision threaded holes or positioning pin holes, thereby connecting to the force sensor 3.

[0039] For example, the force sensor 3 can be a rotary force sensor 3. During the detection of contact force, the force sensor 3 can rotate together with the machine tool's spindle and the machining tool 1 to detect the actual contact force between the machining tool 1 and the optical element to be processed in real time online. In some embodiments, the force sensor 3 can be a strain sensor, a piezoelectric sensor, or a capacitive-inductive sensor, etc. In other embodiments, the force sensor 3 can include a body and a conical body connected to the body. The body can be cylindrical, and the conical body can be embedded in the cutter head 22.

[0040] In some embodiments, the connection accuracy between the connecting rod 211 of the tool holder 21 and the rotating shaft of the machine tool is less than or equal to 5 μm, and the connection accuracy between the tool disc 22 and the machining tool 1 is less than or equal to 5 μm.

[0041] In some embodiments, the machining tool 1 is a spherical cap-shaped capsule structure; the cutter head 22 includes an arc-shaped cavity 221, which is a cavity protruding from the tool holder 21 toward the spherical cap-shaped capsule structure, and the outer wall of the arc-shaped cavity 221 is connected to the spherical cap-shaped capsule structure in a conformal manner; the intersection of the center of the spherical cap-shaped capsule structure, the center of the arc-shaped cavity 221, and the rotation axis of the machining tool is located on the same axis.

[0042] It should be noted that the spherical cap-shaped capsule structure is a flexible tool form used for the precision machining of optical components. "Spherical cap" refers to the outer surface of the structure resembling the top portion of a sphere truncated by a plane (similar to a hemisphere or a smaller dome shape), with a defined radius of curvature and center. "Capsule" refers to its interior being a hollow or fluid-filled, closed, soft capsule with elastic walls. When this structure is pressed against the surface of an optical component, the capsule walls undergo controllable elastic deformation, expanding the contact area from point contact to surface contact, thus uniformly distributing the contact pressure.

[0043] It is understood that in this embodiment of the application, the cutter head 22 is configured as an arc-shaped cavity 221, and the outer wall of the arc-shaped cavity 221 is conformally connected to the spherical cap-shaped capsule structure. This conformal connection means that the outer wall of the arc-shaped cavity 221 of the cutter head 22 fits snugly to the inner wall of the spherical cap-shaped capsule structure. Thus, through structural geometric constraints, the intersection of the center of the spherical cap-shaped capsule structure, the center of the arc-shaped cavity 221, and the rotation axis of the machining tool is located on the same axis. Consequently, during rotation, the center of mass of the machining tool 1 falls on the rotation axis, avoiding periodic vibrations caused by centrifugal force and protecting the signal quality of the force sensor 3. When the spherical cap contacts the workpiece, the normal force is evenly distributed on the surface of the spherical cap, without generating additional bending moment, resulting in more accurate contact force measurement. In conformal polishing, the pressure distribution in the contact area remains axially symmetrical during tool rotation, avoiding local over-polishing or edge collapse.

[0044] In some embodiments, the alignment accuracy of the intersection of the center of the spherical cap-shaped capsule structure, the center of the arc-shaped cavity 221, and the axis of rotation of the machine tool on the same axis is less than or equal to 5 μm.

[0045] In some embodiments, an annular base 222 is provided inside the arc-shaped cavity 221. The interior of the annular base 222 is hollow, and the side of the force sensor 3 away from the handle 21 is disposed on the annular base 222.

[0046] For example, the force sensor 3 is fixed to the annular base 222 by screws or clamping. The annular base 222 is located inside the arc-shaped cavity 221. It can be understood that the inner axis of the annular base 222 can coincide with the central axis of the arc-shaped cavity 221. After the force sensor 3 is installed on the annular base 222, its measurement center naturally coincides with the center of the spherical cap-shaped capsule structure and the axis of the machine tool spindle, realizing the aforementioned coaxiality.

[0047] In some embodiments, the arc-shaped cavity 221 has an annular surface 223 on the side near the force sensor 3. The annular surface 223 has a plurality of balance adjustment holes 224 along the circumference. The balance adjustment holes 224 are used to set mass blocks for balance adjustment. The imbalance of the machining tool 1, the tool adapter 2 and the force sensor 3 at a preset speed is less than or equal to a preset value. The preset speed is greater than or equal to 2000 rpm and the preset value is less than or equal to 10 μm.

[0048] Understandably, in high-speed rotary machining (e.g., speed ≥ 2000 rpm), if the center of mass of the entire rotating assembly is not on the axis of rotation, periodic centrifugal force may be generated, leading to vibration and noise, and even damage to the force sensor 3. By uniformly or non-uniformly opening multiple balance adjustment holes 224 circumferentially on the annular surface 223 of the arc-shaped cavity 221 near the force sensor 3, mass blocks can be installed. These mass blocks can be small metal pillars of known mass (such as screws, counterweights, etc.) that can be screwed into the balance adjustment holes 224. By installing different numbers or masses of mass blocks in the holes at different angles, the distribution of the center of mass of the rotating assembly can be changed. After balancing, the imbalance of the entire rotating assembly at the preset speed is small.

[0049] In some embodiments, the tool adapter 2 further includes a hollow air guide tube 4, which sequentially passes through the tool holder 21, the force sensor 3, and the tool disc 22 and is inserted into the machining tool 1. The hollow air guide tube 4 is configured to introduce external compressed air into the machining tool 1.

[0050] Understandably, the hollow air guide tube 4 is a hollow pipe that runs through the entire interior of the force control tool 10. It passes sequentially through the tool holder 21, the force sensor 3, and the tool head 22 before being inserted into the machining tool 1. For the spherical cap-shaped capsule-type machining tool 1, the introduced compressed air can cause the capsule to expand, changing its internal pressure and contact stiffness, thereby adjusting the contact force distribution and contact area between the machining tool 1 and the optical element; or, compressed air can be used to form an air film between the tool and the workpiece to achieve air-float assisted machining. To achieve penetration, the force sensor 3 can adopt a ring-shaped or hollow structure so that the air guide tube passes through its central hole. This ensures that the force sensor 3 can detect contact force without affecting the smooth flow of air.

[0051] In some embodiments, one end of the hollow air duct 4 is provided with a first sealing groove 41 and the other end is provided with a second sealing groove 42. The first sealing groove 41 and the second sealing groove 42 can be used to install a sealing ring to improve the airtightness of the hollow air duct 4.

[0052] In some embodiments, a third sealing groove 23 is provided at the connection between the cutter head 22 and the processing tool 1. The third sealing groove 23 is used to install a sealing ring to improve the airtightness of the processing tool 1.

[0053] Based on the above disclosure, the force control tool 10 of this application embodiment includes: a machining tool 1, a tool adapter 2, and a force sensor 3. The machining tool 1 is configured to perform contact machining on an optical element to be machined, and a fixed mapping relationship exists between the contact displacement and contact force between the machining tool 1 and the optical element to be machined. The tool adapter 2 includes: a tool holder 21 and a cutter head 22. The tool holder 21 includes a connecting rod 211 and a connecting base 212 connected to each other. The side of the connecting rod 211 away from the connecting base 212 is configured to be connected to the spindle of the machine tool for machining the optical element to be machined. The side of the cutter head 22 away from the tool holder 21 is connected to the machining tool 1. The force sensor 3 is connected to both the side of the connecting base 212 away from the connecting rod 211 and the side of the cutter head 22 near the tool holder 21. The force sensor 3 is configured to detect the contact force between the machining tool 1 and the optical element to be machined during the rotational machining process driven by the spindle of the machine tool. Therefore, in this embodiment, the tool adapter 2 connects the machining tool 1, the force sensor 3, and the machine tool's rotating shaft. During the machining process where the machine tool's rotating shaft drives the machining tool 1 to rotate, the force sensor 3 can detect the contact force between the machining tool 1 and the optical element to be processed in real time online. Since there is a fixed mapping relationship between contact displacement and contact force, the contact force detected by the force sensor 3 can provide data support for subsequent control of contact force and contact displacement, improving the processing stability of the optical element. The force control tool in this embodiment can both rotate the machining element at high speed and detect and feedback the contact force in real time. Simultaneously, the tool adapter connects the machining tool and the rotary force sensor, ensuring that the center of the tool sphere coincides with the intersection point of the machine tool's rotating shaft, guaranteeing accurate and controllable tool operation, which is of great significance for achieving highly deterministic machining of curved surfaces.

[0054] Figure 4 A structural block diagram of an online force measurement system according to an embodiment of this application is shown. Figure 5 A schematic diagram illustrating the displacement compensation principle of an embodiment of this application is shown.

[0055] The second aspect of this application provides an online force measurement system, comprising: a force control tool 10 as described in any of the first aspects; a data transmitter 20, fixedly connected to a machine tool via a connector, wherein the data transmitter 20 is spaced apart from the force sensor 3 of the force control tool 10 and communicates with the force sensor 3 based on near-field remote sensing technology, and the data transmitter 20 is used to acquire the contact force signal detected by the force sensor 3; and a data processor 30, communicatively connected to the data transmitter 20, wherein the data processor 30 is used to acquire the contact force signal, save, display, analyze and provide early warning of the contact force signal, and, when the deviation between the contact force and the target contact force is greater than or equal to the target deviation, provide early warning of fluctuations in the contact force and output displacement compensation to the machine tool.

[0056] like Figure 5 As shown, the contact force on the machine tool carrying the optical element to be processed is detected by the force sensor 3. The analog quantity detected by the force sensor 3 is collected and processed. The real-time force data can also be visualized. The displacement compensation quantity is output to the machine tool PLC through the measurement bus. The machine tool actuator executes the position processing program according to the displacement compensation quantity to perform displacement trajectory compensation.

[0057] For example, the data transmitter 20 can be connected via NFC, Bluetooth, Wi-Fi, or wireless inductive coupling. It is understood that, since the force sensor 3 rotates at high speed with the spindle, directly leading out the signal using ordinary wires could result in cable tangling. Near-field communication enables contactless signal transmission, facilitating data transfer between rotating and stationary components.

[0058] In some embodiments, the data processor 30 can filter and average the data collected every 0.5 seconds to obtain the currently measured contact force signal.

[0059] In some embodiments, multiple force sensors 3 (such as ring array thin film force sensors 3) can be integrated into the force control tool 10 to detect the normal component, tangential component and torque of the contact force respectively; the data transmitter 20 adopts multi-channel near-field communication to synchronously acquire data from all sensors; the data processor 30 fuses the multi-source data to calculate the center position of the contact force distribution and the direction of the total force vector, thereby calculating the displacement compensation amount more accurately.

[0060] In some embodiments, the data processor 30 can be embedded on the machine tool side as an edge computing unit, with a built-in lightweight machine learning model (such as PID parameter self-tuning or fuzzy control rules); the model optimizes the displacement compensation coefficient online based on the historical force error sequence, and adapts to different processing stages or optical elements of different materials, thereby reducing the dependence on the central controller and improving the response speed.

[0061] In some embodiments, the data transmitter 20 can also provide power to the force sensor 3 via the radio frequency energy harvesting function of near-field communication; the force sensor 3 does not require a built-in battery or slip ring power supply.

[0062] In some embodiments, when the deviation between the contact force and the target contact force is greater than or equal to the target deviation, and when providing an early warning for fluctuations in the contact force and outputting a displacement compensation amount to the machine tool, the data processor 30 is configured to: provide an early warning for fluctuations in the contact force if the deviation between the contact force signal and the preset target contact force is greater than or equal to a deviation threshold; determine a displacement compensation amount based on the deviation value and the mapping relationship between the contact displacement and contact force between the processing tool 1 and the optical element to be processed; send micro-displacement compensation amounts to the machine tool sequentially so that the machine tool compensates for the contact displacement between the optical element to be processed and the processing tool 1 based on the micro-displacement compensation amounts; reacquire the contact force signal after each compensation; if the deviation between the contact force signal and the target contact force is still greater than or equal to the deviation threshold, send the micro-displacement compensation amount to the controller again until the deviation between the contact force signal acquired this time and the target contact force is less than the deviation threshold; wherein, the micro-displacement compensation amount is less than the displacement compensation amount.

[0063] For example, assuming the preset mapping relationship between contact force and contact displacement is Fn = 388h² + 11h, the currently measured contact force Fn_actual = 2.5 N, while the target contact force Fn_target = 1.5 N, then the deviation ΔF = +1.0 N (the actual force is too large, and the downward pressure needs to be reduced). To solve for the displacement compensation Δh, the current actual downward pressure h_actual is calculated from the current force: solving the equation 388h² + 11h - 2.5 = 0, we get h_actual ≈ 0.065 mm; then, based on the target force, the target downward pressure h_target is calculated: 388h² + 11h - 1.5 = 0, we get h_target ≈ 0.052 mm. Therefore, the theoretical displacement compensation Δh = h_target - h_actual = -0.013 mm (the negative sign indicates that the tool needs to be lifted by 0.013 mm). The data processor 30 decomposes the total compensation into multiple micro-displacement values ​​(e.g., -0.002 mm each time) and sends them to the machine tool controller one by one. After each adjustment, the force value is remeasured until the contact force converges to around 1.5 N.

[0064] For example, the target contact force can be 50N, 60N, 70N, etc., and there is no limitation here.

[0065] In some embodiments, the micro-displacement compensation amount is 1 / 5 to 1 / 2 of the displacement compensation amount, such as 1 / 5, 1 / 4, 1 / 3 or 1 / 2. The specific value can be set according to actual needs and is not limited here.

[0066] Understandably, the data processor 30 acquires the contact force signal measured by the force sensor 3 and compares it with the preset target contact force to calculate the deviation value. If the deviation value is greater than or equal to the set deviation threshold, the theoretically required displacement compensation amount is calculated from the deviation value based on the aforementioned preset mapping relationship between contact force and contact displacement. However, the data processor 30 does not directly send this total displacement compensation amount, but decomposes it into multiple smaller micro-displacement compensation amounts, which are sent to the machine tool controller one by one. After each micro-displacement compensation, the controller reacquires the contact force signal and judges the deviation again: if the deviation is still greater than or equal to the threshold, the next micro-displacement compensation amount is sent, and so on iteratively until the deviation value is less than the threshold. This gradual compensation method avoids the sudden force change caused by a single large adjustment, protecting optical components and tools from impact damage; in addition, since the mapping relationship between contact force and contact displacement may be nonlinear, hysteretic, or subject to external disturbances, the gradual approximation method allows for re-evaluation of the actual force response after each small step, thereby overcoming model errors and achieving smoother and more stable constant force convergence.

[0067] Understandably, if the measured contact force is greater than the target contact force, the direction of the micro-displacement compensation is positive; if the measured contact force is less than the target contact force, the direction of the micro-displacement compensation is negative. The current displacement equals the previous displacement plus or minus the micro-displacement compensation.

[0068] In some embodiments, the device further includes: a signal conditioner 40, communicatively connected to the data transmitter 20, the signal conditioner 40 being configured to convert the contact force signal into an analog voltage signal; and a data acquisition unit 50, communicatively connected to the signal conditioner 40 and the data processor 30, the data acquisition unit 50 being configured to acquire the analog voltage signal and convert the analog voltage signal into the contact force signal according to the signal mapping relationship between the force and voltage of the force sensor 3.

[0069] Understandably, the signal conditioner 40 and data acquisition unit 50 are used to process the raw signal output by the force sensor 3. The contact force detected by the force sensor 3 is usually output as a weak change in resistance or charge, which cannot be directly recognized by the data processor 30. The signal conditioner 40 acquires this raw signal from the data transmitter 20 and amplifies, filters, and linearizes it to convert it into an analog voltage signal within a standard range. Subsequently, the data acquisition unit 50 acquires this analog voltage signal at a high sampling rate (e.g., above 1 kHz) and converts the voltage amplitude into the actual contact force value according to the pre-calibrated force-voltage mapping relationship. After this conversion, the original physical signal becomes a digitized contact force signal, which is then transmitted to the data processor 30 for deviation calculation and displacement compensation decision-making, ensuring the accuracy and real-time performance of the entire force measurement system.

[0070] Based on the above disclosure, the online force measurement system of this application realizes contact force monitoring and tool failure early warning, provides a means of real-time monitoring of the processing status, and provides important process guidance for operators.

[0071] Figure 6 A flowchart of a constant force control method according to an embodiment of this application is shown.

[0072] This application provides a constant force control method, including: Step 1. Data Acquisition and Processing Steps: The contact force signal is acquired by the force sensor in the force control tool as described in any of the first aspects. The contact force signal acquired within the target time period is filtered and the mean is calculated to obtain the measured contact force. For example, the target duration can be 0.5 seconds, 1 second, 1.5 seconds, etc., and there is no limitation here.

[0073] Step 2. Force-position relationship calibration step: The relative displacement between the machining tool and the optical element to be processed is controlled by the movement control of the machining tool. The magnitude and distribution of the contact force between the machining tool and the optical element to be processed are detected simultaneously by a multi-dimensional force sensor and a thin-film force sensor to establish a fixed mapping relationship between the contact displacement and the contact force. The process of calibrating the force-position relationship can be found in the previous text and will not be repeated here.

[0074] Step 3. Force Deviation Calculation Step: Set the target contact force, compare the measured contact force with the target contact force, and determine whether the force fluctuation exceeds the tolerance. If it exceeds the tolerance, an alarm will be triggered. Step 4. Calculation of displacement compensation: Based on the deviation between the measured contact force and the target contact force, and the mapping relationship between the contact displacement and contact force between the processing tool and the optical element to be processed, determine the displacement compensation amount; Step 5. Micro-displacement compensation sending and execution steps: Micro-displacement compensation amounts are sent sequentially to the machine tool so that the machine tool compensates for the contact displacement between the optical element to be processed and the processing tool based on the micro-displacement compensation amounts. After each compensation, the contact force signal is reacquired. If the deviation between the contact force signal and the target contact force is still greater than or equal to the deviation threshold, the micro-displacement compensation amount is sent to the controller again until the deviation between the currently acquired contact force signal and the target contact force is less than the deviation threshold; wherein, the micro-displacement compensation amount is less than the displacement compensation amount.

[0075] In some embodiments, the ratio of the micro-displacement compensation amount to the displacement compensation amount is 1 / 5; in other embodiments, the ratio of the micro-displacement compensation amount to the displacement compensation amount is 1 / 2 to 1 / 5, which is set according to actual needs and is not limited here.

[0076] Figure 7 This paper illustrates a schematic diagram of the compensation trajectory of the constant force control method according to an embodiment of this application. Figure 8 A comparative curve diagram of the constant force control method of this application and related technologies is shown.

[0077] like Figure 7 As shown, an inclined flat plate is used as the optical element to be processed. One end of the plate is raised (0.2 mm) and fixed to the worktable. The initial trajectory of the machining tool is a linear feed along the horizontal direction. By comparing the force fluctuation values ​​with and without displacement compensation function enabled, the machining tool, under the condition of not enabling compensation function, moves as follows: Figure 7 As shown, moving horizontally from right to left, the compression between the tool and workpiece continuously increases, raising the polishing normal force from 60N to 160N. With the compensation function enabled, the polishing normal force stabilizes at the set value of 60N, with fluctuations not exceeding 5N. Figure 8 As shown, S1 represents the variation curve of the polishing normal force without displacement compensation function, and S2 represents the variation curve of the polishing normal force with displacement compensation function enabled. This proves the effectiveness of the online force measurement system and the constant force control method.

[0078] Based on the above disclosure, the constant force control method of this application adjusts the contact force by compensating for minute displacements each time, thereby gradually approaching the target force and achieving constant force control. This method avoids overcompensation caused by unavoidable system delays. Furthermore, constant force control avoids the impact of force and removal fluctuations on processing accuracy and efficiency, which is particularly important for the long-term, high-stability processing of ultra-large aperture optical components. It also prevents excessive contact force from damaging the workpiece or tool, resulting in significant losses, which is crucial for the high-safety processing of thin-walled or weakly rigid components.

[0079] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A force control tool, characterized in that, include: A processing tool is configured to perform contact processing on an optical element to be processed, and there is a fixed mapping relationship between the contact displacement and the contact force between the processing tool and the optical element to be processed. A tool adapter includes a tool holder and a tool disc, the tool holder including a connecting rod and a connecting base connected to each other, the side of the connecting rod away from the connecting base being configured to be connected to the spindle of a machine tool for processing the optical element to be processed, and the side of the tool disc away from the tool holder being connected to the processing tool. A force sensor is connected to the side of the connecting base away from the connecting rod and the side of the cutter head near the tool holder. The force sensor is configured to detect the contact force between the machining tool and the optical element to be processed during the machining process when the machining tool is rotated by the spindle of the machining tool.

2. The force control tool according to claim 1, characterized in that, The processing tool has a spherical cap-shaped capsule structure; The cutter head includes: an arc-shaped cavity, which is a cavity protruding from the cutter handle toward the spherical cap-shaped capsule structure, and the outer wall of the arc-shaped cavity is connected to the spherical cap-shaped capsule structure in a conformal manner; The center of the spherical cap-shaped capsule structure, the center of the arc-shaped cavity, and the intersection of the machine tool's rotation axis are located on the same axis.

3. The force control tool according to claim 2, characterized in that, An annular base is provided inside the arc-shaped cavity. The interior of the annular base is hollow, and the side of the force sensor away from the handle is conformally disposed on the annular base.

4. The force control tool according to claim 2, characterized in that, The arc-shaped cavity has an annular surface on the side near the force sensor. The annular surface has multiple balance adjustment holes along the circumference. Mass blocks can be placed in the balance adjustment holes for balance adjustment. The imbalance of the machining tool, the tool adapter, and the force sensor at a preset speed is less than or equal to a preset value. The preset speed is greater than or equal to 2000 rpm, and the preset value is less than or equal to 10 μm.

5. The force control tool according to any one of claims 1-4, characterized in that, The tool adapter further includes a hollow air guide tube, which sequentially passes through the tool holder, the force sensor, and the tool disc and is inserted into the machining tool. The hollow air guide tube is configured to introduce external compressed air into the machining tool.

6. An online force measurement system, characterized in that, include: The force control tool as described in any one of claims 1-5; A data transmitter is fixedly connected to a machine tool via a connector. The data transmitter is spaced apart from the force sensor of the force control tool and communicates with the force sensor based on near-field remote sensing technology. The data transmitter is used to acquire the contact force signal detected by the force sensor. A data processor, communicatively connected to the data transmitter, is used to acquire the contact force signal, save, display, analyze, and provide early warnings for the contact force signal, and provide early warnings for fluctuations in the contact force and output displacement compensation amounts to the machine tool when the deviation between the contact force and the target contact force is greater than or equal to the target deviation.

7. The online force measurement system according to claim 6, characterized in that, When the deviation between the contact force and the target contact force is greater than or equal to the target deviation, and the data processor provides an early warning for fluctuations in the contact force and outputs a displacement compensation amount to the machine tool, the data processor is used to: If the deviation between the contact force signal and the preset target contact force is greater than or equal to the deviation threshold, an early warning is issued for the fluctuation of the contact force. Based on the deviation value and the mapping relationship between the contact displacement and the contact force between the processing tool and the optical element to be processed, the displacement compensation amount is determined. A micro-displacement compensation amount is sent to the machine tool sequentially so that the machine tool can compensate for the contact displacement between the optical element to be processed and the processing tool according to the micro-displacement compensation amount. After each compensation, the contact force signal is reacquired. If the deviation between the contact force signal and the target contact force is still greater than or equal to the deviation threshold, the micro-displacement compensation amount is sent to the controller again until the deviation between the contact force signal acquired in the current iteration and the target contact force is less than the deviation threshold. The micro-displacement compensation amount is less than the displacement compensation amount.

8. The online force measurement system according to claim 6, characterized in that, Also includes: A signal conditioner, communicatively connected to the data transmitter, is configured to convert the contact force signal into an analog voltage signal; A data acquisition unit is communicatively connected to the signal conditioner and the data processor. The data acquisition unit is configured to acquire the analog voltage signal and convert the analog voltage signal into the contact force signal according to the signal mapping relationship between the force and voltage of the force sensor.

9. A constant force control method, characterized in that, include: Data acquisition and processing steps: The contact force signal is acquired by the force sensor in the force control tool as described in any one of claims 1-5, and the contact force signal acquired within the target time period is filtered and the mean is calculated to obtain the measured contact force; Force-position relationship calibration steps: The relative displacement between the machining tool and the optical element to be processed is controlled by the movement control of the machining tool. The magnitude and distribution of the contact force between the machining tool and the optical element to be processed are detected simultaneously by a multi-dimensional force sensor and a thin-film force sensor to establish a fixed mapping relationship between the contact displacement and the contact force. Force deviation calculation steps: Set the target contact force, compare the measured contact force with the target contact force, and determine whether the force fluctuation exceeds the tolerance. If it exceeds the tolerance, an alarm will be triggered. Displacement compensation calculation: Based on the deviation between the measured contact force and the target contact force, and the mapping relationship between the contact displacement and contact force between the processing tool and the optical element to be processed, the displacement compensation is determined. Micro-displacement compensation amount transmission and execution steps: Micro-displacement compensation amounts are sent sequentially to the machine tool so that the machine tool compensates for the contact displacement between the optical element to be processed and the processing tool based on the micro-displacement compensation amounts. After each compensation, the contact force signal is reacquired. If the deviation between the contact force signal and the target contact force is still greater than or equal to the deviation threshold, the micro-displacement compensation amount is sent to the controller again until the deviation between the currently acquired contact force signal and the target contact force is less than the deviation threshold; wherein, the micro-displacement compensation amount is less than the displacement compensation amount.

10. The method according to claim 9, characterized in that, The ratio of the micro-displacement compensation amount to the displacement compensation amount is 1 / 5 to 1 / 2.

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