A method and system for controlling the pressure of a polishing head of a polishing machine associated with a trajectory
By generating a target pressure associated with the trajectory, interpolation and PID control are performed to solve the problem of inaccurate pressure control in polishing machines, achieving low-cost continuous variation and stable control, which is suitable for polishing machines with CNC systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN HUAZHONG NUMERICAL CONTROL
- Filing Date
- 2023-08-18
- Publication Date
- 2026-07-10
AI Technical Summary
Existing technologies lack continuous pressure control in polishing machines that takes into account polishing stages and changes in workpiece position, resulting in inaccurate control and high costs.
By generating a target pressure associated with the trajectory, interpolation and PID control are performed. Combined with the pressure sensor and the filter and interpolator built into the CNC system, continuous changes in pressure and trajectory are achieved, and low-cost closed-loop control is adopted.
It achieves precise and stable control of the polishing machine's pressure and trajectory, reduces system complexity and cost, is easy to debug, and has a wide range of applications.
Smart Images
Figure CN117130323B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of CNC technology, specifically relating to a method and system for controlling the pressure of a polishing machine grinding head associated with a trajectory. Background Technology
[0002] Currently, CNC technology is developing towards high-speed and high-precision trajectory control. In polishing machine applications, the main factors affecting processing effect and efficiency include the grinding head material, pressure control between the grinding head and the workpiece, grinding time, and feed speed. The polishing process is typically divided into rough polishing, semi-finish polishing, finish polishing, and final polishing. The pressure requirements for different polishing stages and different workpiece positions often vary. When the grinding head pressure is too high, friction is intense, heat generation increases, and a high gloss ring is easily produced, resulting in unsatisfactory results. When the grinding head pressure is too low, although the frictional movement is relatively smooth, it is difficult to achieve the desired effect. Therefore, pressure control related to the trajectory is a crucial factor in determining whether a machine is a high-end polishing machine.
[0003] Existing technologies employ a dual-closed-loop vector torque control mode (current and pressure) for polishing machine head pressure control, combined with a fuzzy PID algorithm to apply pressure to the polishing machine's stepper motor; alternatively, they utilize a pressure closed-loop control system composed of a pneumatic control system and an electrical control system, with pressure regulation achieved using a modified particle swarm optimization-based fuzzy PID control. While these methods can achieve pressure control of the polishing machine head, they significantly increase operating costs and system complexity, and fail to consider the continuous pressure variations that occur with different polishing stages and workpiece positions. Therefore, currently, there is no precise, stable, and reliable control method that considers the correlation between polishing machine pressure and trajectory. Summary of the Invention
[0004] The purpose of this invention is to overcome the defects of the prior art. This invention provides a method and system for controlling the pressure of a polishing machine grinding head in relation to a trajectory. This invention can achieve pressure control of the polishing machine grinding head and has low operating costs. At the same time, considering the continuous change of pressure with different polishing stages and different workpiece positions, it can achieve precise control of polishing machine pressure in relation to the trajectory. It is also easy to implement and simple to operate.
[0005] To achieve the desired effect, the present invention adopts the following technical solution:
[0006] This invention discloses a method for controlling the pressure of a polishing machine grinding head associated with a trajectory, comprising:
[0007] Generate target pressure associated with the trajectory;
[0008] Interpolation control is applied to the target pressure.
[0009] Based on the target pressure after interpolation control, the measured pressure is subjected to PID control.
[0010] Furthermore, the method also includes filtering control of the measured pressure before performing PID control on the measured pressure.
[0011] Furthermore, the filtering control of the measured pressure specifically includes: acquiring the original measured pressure value through a pressure sensor, filtering the data through a high-speed acquisition IO board with a variable sampling frequency, and then performing analog-to-digital conversion to align with the PID control cycle of the CNC system, thereby achieving filtering control of the measured pressure and obtaining periodic measured pressure.
[0012] Furthermore, the step of performing PID control on the measured pressure based on the target pressure after interpolation control specifically includes: using the difference between the periodic measured pressure and the periodic target pressure as the input of PID control, the output of PID control being the corrected pressure value, and based on the corrected pressure value, converting the pressure into shaft movement through a force-displacement conversion module for pressure adjustment.
[0013] Furthermore, the periodic measured pressure is obtained through a pressure sensor, analog-to-digital conversion, and data filtering.
[0014] Furthermore, the generation of the target pressure associated with the trajectory specifically includes: performing overall pressure planning based on the polishing trajectory and pressure values of key points formed by the G-code running inside the control system of the polishing machine, and appending pressure values after each line of G-code to generate the target pressure associated with the trajectory.
[0015] Furthermore, the step of performing overall pressure planning based on the polishing trajectory and key point pressure values formed by the G-code running inside the polishing machine's control system, and appending pressure values to the end of each line of G-code to generate a target pressure associated with the trajectory, specifically includes: creating a cubic Bezier pressure curve that satisfies the continuous change of the target pressure throughout the entire trajectory based on the beginning and end points of the trajectory curve and its unit tangent; and appending each line of pressure values generated on the cubic Bezier pressure curve to the end of that line of G-code to obtain trajectory G-code with target pressure values.
[0016] Furthermore, the interpolation control of the target pressure specifically includes: obtaining the target pressure for each PID control cycle by linearly interpolating the target pressure of two adjacent lines of G code, and aligning the target pressure with the PID control cycle to achieve interpolation control of the target pressure.
[0017] Furthermore, the step of obtaining the target pressure for each PID control cycle by linearly interpolating the target pressure of two adjacent lines of G code, and aligning the target pressure with the PID control cycle to achieve interpolation control of the target pressure specifically includes:
[0018] Assume the target pressure of this line of G code is P. target The composition process of this line of G code is L. total The target pressure value at the end of the previous line of code G is P. last The stroke that needs to be completed at the end of the current PID control cycle is L. will The target pressure for the current PID control cycle is:
[0019]
[0020] This invention also discloses a trajectory-correlated polishing machine grinding head pressure control system, comprising:
[0021] Pressure sensor, used to collect pressure values from the polishing machine's grinding head;
[0022] The control system generates a target pressure associated with the trajectory; based on the interpolated target pressure, it performs PID control on the measured pressure.
[0023] An interpolator is used for interpolation control of the target pressure.
[0024] Compared with existing technologies, the advantages of this invention are: This invention provides a method and system for controlling the pressure of a polishing machine grinding head in relation to a machining trajectory. This invention does not significantly increase the software load of the CNC system and does not require other expensive equipment. It automatically plans the correlation between pressure and trajectory within the CNC system based on the machining trajectory G-code and the pressure values at key points. Then, a closed-loop pressure PID control is formed through a pressure sensor, achieving continuous, accurate, stable, and reliable pressure-trajectory correlation. It is also convenient for debugging and optimization. This invention has advantages such as wide application range, low cost, and simple debugging. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.
[0026] Figure 1 A flowchart illustrating a method for controlling the pressure of a polishing machine grinding head associated with a trajectory, provided as an embodiment of the present invention;
[0027] Figure 2 This is a schematic diagram of the mobile phone frame grinding trajectory provided in an embodiment of the present invention;
[0028] Figure 3This is a partially enlarged schematic diagram of the mobile phone frame trajectory in a polishing machine grinding example provided by an embodiment of the present invention;
[0029] Figure 4 This is a schematic diagram of pressure curve fitting between two adjacent key points of a polishing machine provided in an embodiment of the present invention;
[0030] Figure 5 This invention provides a schematic diagram of periodic interpolation of the current segment pressure of a CNC system interpolator.
[0031] Figure 6 This is a schematic diagram of a measured pressure filtering control for a polishing machine provided in an embodiment of the present invention;
[0032] Figure 7 This is a schematic diagram of PID control for pressure in a polishing machine, provided as an embodiment of the present invention. Detailed Implementation
[0033] 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.
[0034] See Figures 1 to 7 This invention discloses a method for controlling the pressure of a polishing machine grinding head associated with a trajectory, comprising:
[0035] Generate target pressure associated with the trajectory;
[0036] Interpolation control is applied to the target pressure.
[0037] Based on the target pressure after interpolation control, the measured pressure is subjected to PID control.
[0038] This invention does not significantly increase the software load of the CNC system and does not require other expensive equipment. It automatically plans the correlation between pressure and trajectory within the CNC system based on the machining trajectory G-code and key point pressure values. Then, a closed-loop pressure PID control is formed through a pressure sensor, achieving continuous, accurate, stable, and reliable pressure-trajectory correlation. It is also convenient for debugging and optimization. This invention has advantages such as wide application range, low cost, and simple debugging.
[0039] Preferably, the method further includes: filtering the measured pressure before performing PID control on the measured pressure.
[0040] Furthermore, the filtering control of the measured pressure specifically includes: acquiring the original measured pressure value through a pressure sensor, filtering the data through a high-speed acquisition IO board with a variable sampling frequency, and then performing analog-to-digital conversion to align with the PID control cycle of the CNC system, thereby achieving filtering control of the measured pressure and obtaining periodic measured pressure.
[0041] Specifically, since pressure sensor sampling frequencies include 800Hz (1.25ms), 1200Hz (0.83ms), and 2400Hz (0.42ms), this invention uses a high-speed acquisition I / O board with a variable sampling frequency to filter the data, then performs analog-to-digital conversion to align it with the PID control cycle of the CNC system (i.e., the CNC system interpolation cycle), thereby achieving closed-loop control, that is, achieving filtered control of the measured pressure and obtaining periodic measured pressure. Figure 6 As shown.
[0042] In one embodiment, the step of performing PID control on the measured pressure based on the target pressure after interpolation control specifically includes: using the difference between the periodic measured pressure and the periodic target pressure as the input of the PID control, the output of the PID control being a corrected pressure value, and based on the corrected pressure value, converting the pressure into shaft movement through a force-to-displacement conversion module for pressure adjustment. Figure 7 As shown.
[0043] Furthermore, the periodic measured pressure is obtained through a pressure sensor, analog-to-digital conversion, and data filtering.
[0044] In another embodiment, generating the target pressure associated with the trajectory specifically includes: performing overall pressure planning based on the polishing trajectory and pressure values of key points formed by the G-code running inside the control system of the polishing machine, and appending pressure values after each line of G-code to generate the target pressure associated with the trajectory.
[0045] For example, in the polishing of the bezels of devices such as mobile phones and laptops, the polishing trajectory is formed by the G-code control axis movement within the polishing machine's control system (i.e., the CNC system). Therefore, by calculating the pressure values at key points based on the G-code trajectory and performing overall pressure planning, by appending a pressure value P after each line of G-code, the goal of associating pressure with the trajectory can be achieved. Figure 2 and 3 As shown, the processing and polishing of the mobile phone frame typically consists of multiple lines of G-code. Due to factors such as different material infeed amounts at different locations, different target pressure values need to be specified at key points pos at different locations. Furthermore, multiple lines of G-code may exist between two adjacent key points pos.
[0046] Furthermore, the step of performing overall pressure planning based on the polishing trajectory and key point pressure values generated by the G-code running within the polishing machine's control system, and appending pressure values to each line of G-code to generate a target pressure associated with the trajectory, specifically includes: creating a cubic Bezier pressure curve that satisfies the continuous change of the target pressure throughout the entire trajectory based on the beginning and end points of the trajectory curve and its unit tangent; and appending each line of pressure values generated on the cubic Bezier pressure curve to the end of that line of G-code to obtain trajectory G-code with the target pressure value. This step can satisfy the continuous change of the target pressure throughout the entire trajectory and perform corresponding control to improve the polishing effect.
[0047] For example, such as Figure 4 As shown in the pressure curve, given two adjacent keypoints (e.g., the beginning and end points of the polishing trajectory curve) O0 and O3, their unit tangents T0 and T3, the total stroke between the beginning and end points (total_len), and the sub-len of the total stroke for each row between the keypoints, we create a cubic Bezier pressure curve B that satisfies the continuous change of target pressure throughout the entire trajectory, based on the beginning and end points of the polishing trajectory curve and their unit tangents. t as follows:
[0048] B(t)=(1-t) 3 O0+3(1-t) 2 tO1+3(1-t)t 2 O2+t 3 O3,
[0049] in, t=0 represents the first endpoint, and t=1 represents the last endpoint;
[0050] The polishing trajectory curve should have the same speed at its starting point, ending point, and midpoint, i.e., satisfy the following:
[0051]
[0052] Then, from the derivatives at the beginning and end points of the cubic Bezier curve, we can obtain the following equation:
[0053]
[0054] Applying the De Casteljau algorithm at t = 1 / 2 yields:
[0055]
[0056]
[0057] By combining the equations, we can obtain:
[0058]
[0059] After sorting, we get:
[0060] aβ 2 +bβ+c=0;
[0061] in:
[0062]
[0063] but:
[0064]
[0065] Will Substitution We can obtain control points O1 and O2. Substituting O1 and O2 into B(t) = (1-t) 3 O0+3(1-t) 2 tO1+3(1-t)t 2 O2+t 3 O3 can obtain a cubic Bezier pressure curve that satisfies the continuous change of the target pressure throughout the entire trajectory. The pressure value generated on the cubic Bezier pressure curve is appended to the end of the line of G code to obtain the trajectory G code with the target pressure value.
[0066] In a preferred embodiment, the interpolation control of the target pressure specifically includes: obtaining the target pressure for each PID control cycle (interpolation cycle) by linearly interpolating the target pressure of two adjacent lines of G code, and aligning the target pressure with the PID control cycle to achieve interpolation control of the target pressure.
[0067] Furthermore, the step of obtaining the target pressure for each PID control cycle by linearly interpolating the target pressure of two adjacent lines of G code, and aligning the target pressure with the PID control cycle to achieve interpolation control of the target pressure specifically includes:
[0068] Assume the target pressure of this line of G code is P. target The composition process of this line of G code is L. total The target pressure value at the end of the previous line of code G is P. last The stroke that needs to be completed at the end of the current PID control cycle is L. will The target pressure for the current PID control cycle is:
[0069]
[0070] Specifically, the PID control cycle of the pressure sensor is set to the same parameter as the interpolation cycle of the CNC system. The interpolation cycle of the CNC system is typically 0.25ms, 0.5ms, 1ms, 2ms, 4ms, etc., and each line of G-code is usually completed over multiple interpolation cycles. Therefore, when executing the interpolation of each line of G-code, the target pressure of adjacent lines of G-code is linearly interpolated to obtain the target pressure for each interpolation cycle. The target pressure is then aligned with the PID control cycle, thereby achieving the technical effect of interpolation control of the target pressure.
[0071] This invention also discloses a trajectory-correlated polishing machine grinding head pressure control system, comprising:
[0072] Pressure sensor, used to collect pressure values from the polishing machine's grinding head;
[0073] The control system generates a target pressure associated with the trajectory; based on the interpolated target pressure, it performs PID control on the measured pressure.
[0074] An interpolator is used for interpolation control of the target pressure.
[0075] The embodiments of the system correspond one-to-one with the aforementioned method embodiments, and will not be repeated here.
[0076] Based on the same inventive concept, this invention also discloses an electronic device, which may include: a processor, a communication interface, a memory, and a communication bus, wherein the processor, communication interface, and memory communicate with each other via the communication bus. The processor can call logical instructions from the memory to execute a polishing head pressure control method associated with a trajectory, including:
[0077] Generate target pressure associated with the trajectory;
[0078] Interpolation control is applied to the target pressure.
[0079] Based on the target pressure after interpolation control, the measured pressure is subjected to PID control.
[0080] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and sold or used as independent products, and can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.
[0081] On the other hand, embodiments of the present invention also provide a computer program product, the computer program product including a computer program stored on a non-transitory computer-readable storage medium, the computer program including program instructions, and when the program instructions are executed by a computer, the computer is able to execute a trajectory-associated polishing machine grinding head pressure control method provided in the above-described method embodiments, including:
[0082] Generate target pressure associated with the trajectory;
[0083] Interpolation control is applied to the target pressure.
[0084] Based on the target pressure after interpolation control, the measured pressure is subjected to PID control.
[0085] In another aspect, embodiments of the present invention also provide a non-transitory computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements a trajectory-associated polishing machine grinding head pressure control method provided in the above embodiments, comprising:
[0086] Generate target pressure associated with the trajectory;
[0087] Interpolation control is applied to the target pressure.
[0088] Based on the target pressure after interpolation control, the measured pressure is subjected to PID control.
[0089] It should be understood that although the steps in the flowcharts of the accompanying figures are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the accompanying figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.
[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for controlling the pressure of a polishing machine grinding head associated with a trajectory, characterized in that, include: Generate target pressure associated with the trajectory; Interpolation control is applied to the target pressure. Based on the target pressure after interpolation control, the measured pressure is subjected to PID control; The generation of target pressure associated with the trajectory specifically includes: performing overall pressure planning based on the polishing trajectory and pressure values of key points formed by the G-code running inside the control system of the polishing machine, and appending pressure values after each line of G-code to generate target pressure associated with the trajectory. The process of planning overall pressure based on the polishing trajectory and pressure values at key points generated by the G-code running within the control system of the polishing machine, and appending pressure values to the end of each line of G-code to generate a target pressure associated with the trajectory, specifically includes: creating a cubic Bezier pressure curve that satisfies the continuous change of the target pressure along the entire trajectory based on the beginning and end points of the trajectory curve and its unit tangent; and appending each line of pressure values generated on the cubic Bezier pressure curve to the end of that line of G-code to obtain trajectory G-code with target pressure values.
2. The method for controlling the pressure of a polishing machine grinding head associated with a trajectory as described in claim 1, characterized in that, The method also includes filtering the measured pressure before applying PID control to it.
3. The method for controlling the pressure of a polishing machine grinding head associated with a trajectory as described in claim 2, characterized in that, The filtering control of the measured pressure specifically includes: acquiring the original measured pressure value through a pressure sensor, filtering the data through a high-speed acquisition IO board with a variable sampling frequency, and then performing analog-to-digital conversion to align with the PID control cycle of the CNC system, thereby achieving filtering control of the measured pressure and obtaining the periodic measured pressure.
4. The method for controlling the pressure of a polishing machine grinding head associated with a trajectory as described in claim 3, characterized in that, The step of performing PID control on the measured pressure based on the target pressure after interpolation control specifically includes: using the difference between the periodic measured pressure and the periodic target pressure as the input of PID control, the output of PID control as the corrected pressure value, and based on the corrected pressure value, converting the pressure into shaft movement through a force-displacement conversion module for pressure adjustment.
5. The method for controlling the pressure of a polishing machine grinding head associated with a trajectory as described in claim 4, characterized in that, The periodic measured pressure is obtained through a pressure sensor, analog-to-digital conversion, and data filtering.
6. The method for controlling the pressure of a polishing machine grinding head associated with a trajectory as described in claim 1, characterized in that, The interpolation control of the target pressure specifically includes: linearly interpolating the target pressure of two adjacent lines of G code to obtain the target pressure of each PID control cycle, and aligning the target pressure with the PID control cycle to achieve interpolation control of the target pressure.
7. The method for controlling the pressure of a polishing machine grinding head associated with a trajectory as described in claim 6, characterized in that, The step of obtaining the target pressure for each PID control cycle by linearly interpolating the target pressure of two adjacent lines of G-code, and aligning the target pressure with the PID control cycle to achieve interpolation control of the target pressure specifically includes: Assume the target pressure of this line of G code is The synthesis process of this line of G code is as follows: The target pressure value at the end of the previous line of G code is The stroke that needs to be completed at the end of the current PID control cycle is The target pressure for the current PID control cycle is: .
8. A polishing machine grinding head pressure control system associated with a trajectory, characterized in that, include: Pressure sensor, used to collect pressure values from the polishing machine's grinding head; A control system used to generate target pressure associated with the trajectory; Based on the target pressure after interpolation control, the measured pressure is subjected to PID control; An interpolator is used for interpolation control of the target pressure. The generation of target pressure associated with the trajectory specifically includes: performing overall pressure planning based on the polishing trajectory and pressure values of key points formed by the G-code running inside the control system of the polishing machine, and appending pressure values after each line of G-code to generate target pressure associated with the trajectory. The process of planning overall pressure based on the polishing trajectory and pressure values at key points generated by the G-code running within the control system of the polishing machine, and appending pressure values to the end of each line of G-code to generate a target pressure associated with the trajectory, specifically includes: creating a cubic Bezier pressure curve that satisfies the continuous change of the target pressure along the entire trajectory based on the beginning and end points of the trajectory curve and its unit tangent; and appending each line of pressure values generated on the cubic Bezier pressure curve to the end of that line of G-code to obtain trajectory G-code with target pressure values.