A device and method for polishing the bore of a metal piece

Abstract

The application relates to the technical field of inner hole polishing processing, in particular to a metal piece inner hole polishing device and method, which comprises the following steps: collecting amplitude data and torque feedback values at each sampling moment in the inner hole polishing process; obtaining high load intensity values of each time sequence interval at each control moment; obtaining correlation weights of each time sequence interval at each control moment; calculating polishing early stage membership degrees and polishing late stage membership degrees of each time sequence interval at each control moment; obtaining an evaluation sequence at each control moment based on the polishing early stage membership degrees and the polishing late stage membership degrees; obtaining polishing regulation strength at each control moment based on the evaluation sequence; and obtaining regulated torque feedback values based on the polishing regulation strength and the torque feedback values, so as to polish the metal piece inner hole. The application improves the smoothness and uniformity of the metal piece inner hole.

Description

Technical Field

[0001] The present application relates to the technical field of inner hole grinding processing, and in particular to a device and method for grinding the inner hole of a metal part. Background Art

[0002] Internal holes in metal parts refer to holes on the inner cylindrical surface of metal parts, typically straight or angled. They are primarily used to connect other components or transfer media. They are used in sealed containers, radiators, pipes, valves, and other devices, and have high requirements for airtightness, liquid tightness, and smoothness. Internal hole grinding, as a precision machining technology, improves the surface roughness and shape error of metal parts' internal holes, removes burrs on the inner wall, and improves the machining accuracy and service life of metal parts.

[0003] The control system of the inner hole grinding device for metal parts has a complex nonlinear relationship. The differential term in the PID control algorithm is highly sensitive, causing severe grinding oscillations. Currently, a fuzzy PI control algorithm is used to control the grinding device. The grinding force of the grinding device mainly depends on the condition of the inner hole of the metal part. The grinding force required in different inner hole grinding stages has significant variation characteristics. However, the fuzzy PI control algorithm uses a fuzzy domain with fixed values, which makes it difficult to dynamically respond to the changing characteristics of the grinding working conditions during the grinding process. It is easy to cause overshoot and oscillation in the later stages of grinding, which greatly affects the finish of the inner hole of the metal part and easily causes the inner surface of the cylindrical inner hole to be uneven. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a device and method for grinding the inner hole of a metal part. The technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides a method for grinding an inner hole of a metal part, the method comprising the following steps:

[0006] Collect amplitude data and torque feedback values ​​at each sampling moment during the inner hole grinding process of metal parts;

[0007] Obtaining each time series interval at each control moment and the amplitude sequence and torque feedback value sequence at each control moment;

[0008] Based on the magnitude of the torque feedback value, the difference between the value of the peak point in the torque feedback value sequence and the preset motor torque value, a high load intensity value of each time interval at each control moment is obtained;

[0009] Based on the correlation between the torque feedback value sequence and the amplitude sequence, the correlation weight of each time series interval at each control moment is obtained;

[0010] Based on the correlation weight, the high load intensity value and the degree of fluctuation irregularity of the torque feedback value sequence, the early polishing membership of each time interval at each control moment is obtained;

[0011] obtaining the post-polishing membership of each time interval at each control time based on the difference between the torque feedback value and the preset motor torque value and the correlation weight;

[0012] obtaining the evaluation sequence at each control time based on the early polishing membership and the post-polishing membership;

[0013] obtaining the polishing control strength at each control time based on the evaluation sequence;

[0014] obtaining the controlled torque feedback value based on the polishing control strength and the torque feedback value, and polishing the inner hole of the metal piece.

[0015] Further, the obtaining of the time interval at each control time, the amplitude sequence at each control time, and the torque feedback value sequence comprises:

[0016] taking each interval preset time length as the control time;

[0017] For each control time, obtaining the amplitude data and torque feedback value of all sampling times in the preset time period before the control time, and respectively arranging the time in ascending order to form the amplitude sequence and the torque feedback value sequence at each control time;

[0018] For each control time, the preset time period before the control time is divided into a preset number of time intervals.

[0019] Further, the method for obtaining the high load intensity value is:

[0020] For the torque feedback value sequence at each control time, obtaining the maximum value of the torque feedback value in the torque feedback value sequence, taking half of the maximum value of the torque feedback value as the load threshold, and taking the sampling time with the torque feedback value greater than the load threshold in the torque feedback value sequence as the high load time; taking the torque feedback value sequence as the input of the peak detection algorithm, and obtaining each peak point of the torque feedback value sequence;

[0021] The calculation formula of the high load intensity value is: In the formula, P is the high load intensity value of each time interval at each control time; θ is the ratio of the number of high load times in each time interval at each control time to the number of all sampling times, r v is the torque feedback value of the vth peak point in each time interval at each control time, V is the total number of peak points in the torque feedback value sequence in each time interval at each control time, and R is the preset motor torque value.

[0022] Furthermore, the calculation formula of the correlation weight is: μ=γ1+per(l1,l2); wherein μ is the correlation weight of each time interval at each control moment; l1 is the torque feedback value sequence within each time interval at each control moment, and l2 is the amplitude sequence within each time interval at each control moment; per() is the Pearson correlation coefficient, and γ1 is the preset parameter adjustment factor.

[0023] Furthermore, the method for obtaining the early polishing membership is:

[0024] The fractal dimension algorithm is used to obtain the fractal dimension of the torque feedback value sequence in each time interval at each control moment;

[0025] The calculation formula for the early grinding membership is: A=Norm[μ×(P×H)]; where A is the early grinding membership of each time interval at each control moment; H is the fractal dimension of the torque feedback value sequence in each time interval at each control moment, Norm[] is the normalization function, P is the high load intensity value of each time interval at each control moment, and μ is the correlation weight of each time interval at each control moment.

[0026] Furthermore, the method for obtaining the membership degree in the later stage of polishing is as follows:

[0027] For each timing interval of each control moment, the difference between all torque feedback values ​​in the torque feedback value sequence within the timing interval and the preset motor torque value is calculated, and the ratio of the number of torque feedback values ​​whose difference is less than the preset difference to the number of all torque feedback values ​​in the torque feedback value sequence is calculated. The normalized value of the product of the ratio and the correlation weight of each timing interval of each control moment is used as the post-polishing membership of each timing interval of each control moment.

[0028] Furthermore, the method for obtaining the evaluation sequence is:

[0029] For each time interval at each control moment, the ratio of the membership degree in the early grinding stage to the membership degree in the late grinding stage is used as the grinding intensity evaluation value of each time interval at each control moment;

[0030] The sequence of the grinding intensity evaluation values ​​arranged in ascending order of time is used as the evaluation sequence at each control moment.

[0031] Furthermore, the method for obtaining the polishing control intensity is:

[0032] The Holt exponential sliding smoothing algorithm is used to obtain the predicted value of the evaluation sequence at each control moment;

[0033] The predicted value of the evaluation sequence at each control moment is used as the input of the Tanh function, and the sum of the output value of the Tanh function and the preset constant is used as the polishing control intensity at each control moment.

[0034] Furthermore, obtaining the regulated torque feedback value includes:

[0035] Calculate the mean of the torque feedback values ​​at all sampling moments between each control moment and its previous adjacent control moment as the torque process value at each control moment; calculate the difference between the torque process value at each control moment and the preset motor torque value as the deviation of the fuzzy PI control algorithm at each control moment;

[0036] The interval formed by the product of the polishing control intensity and the upper and lower boundaries of the preset output variable fuzzy domain of the fuzzy PI control algorithm is used as the output variable fuzzy domain of the fuzzy PI control algorithm, and the updated proportional parameter and updated integral parameter at each control moment are output;

[0037] The initial proportional parameter and initial integral parameter of the PI controller at each control moment are obtained by the Ziegler-Nichols method. The sum of the updated proportional parameter and the initial proportional parameter, and the sum of the updated integral parameter and the initial integral parameter at each control moment are calculated as the proportional parameter and integral parameter at each control moment, respectively.

[0038] The deviation at each control moment is used as the input of the PI controller, which uses the proportional parameter and integral parameter at each control moment to output the regulated torque feedback value.

[0039] In a second aspect, an embodiment of the present application further provides a device for grinding inner holes of metal parts, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above-mentioned methods when executing the computer program.

[0040] This application has at least the following beneficial effects:

[0041] This application comprehensively considers the noise interference of the industrial environment of inner hole grinding of metal parts, deeply explores the correlation between torque feedback value and amplitude data, constructs the correlation weight of the time series interval during the inner hole grinding process, and improves the accuracy of the subsequent identification of the metal part grinding stage; analyzes the changing characteristics of the grinding force required for different inner hole grinding stages, obtains the grinding control force, and realizes the adaptive control of the fuzzy domain of the output variable in the fuzzy PI control algorithm, giving a higher response speed for the control of the grinding device in the early stage of grinding, and providing stronger stability for the later stage of grinding, avoiding overshoot and oscillation caused by the grinding wheel servo motor, and improving the smoothness and uniformity of the inner hole of the metal part. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0043] Figure 1 A flowchart of a method for grinding an inner hole of a metal part provided in one embodiment of the present application;

[0044] Figure 2 A schematic diagram of a metal part inner hole grinding device provided in one embodiment of the present application;

[0045] Figure 3 A schematic diagram of the undulations of the inner hole of a metal part provided in one embodiment of the present application. DETAILED DESCRIPTION

[0046] To further illustrate the technical means and effectiveness of this application to achieve the intended invention objectives, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail the specific implementation, structure, features, and effectiveness of a metal workpiece inner hole grinding device and method proposed in this application. In the following description, different references to "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0047] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0048] The following describes in detail a specific scheme of a metal part inner hole grinding device and method provided by the present application with reference to the accompanying drawings.

[0049] See also Figure 1 , which shows a flowchart of a method for grinding the inner hole of a metal part provided by an embodiment of the present application, the method comprising the following steps:

[0050] Step S1, collecting amplitude data and torque feedback values ​​at each sampling moment during the inner hole grinding process.

[0051] The internal hole grinding device for metal parts consists of a metal part, a workpiece clamp, a rotating mechanism, a grinding wheel, a grinding wheel spindle, a flexible coupling, a grinding wheel servo motor, and a control unit. The workpiece clamp is driven by a pneumatic cylinder to ensure secure clamping during the metal part's rotation. After the metal part is clamped in the fixture, the rotating mechanism is activated, and the cylindrical internal hole is ground using the grinding wheel. The metal part rotates in the opposite direction of the grinding wheel. The grinding wheel is driven by a servo motor connected to it by a flexible coupling. The control unit is connected to the grinding wheel servo motor and is controlled by the control unit.

[0052] Figure 2 Schematic diagram of a device for grinding inner holes of metal parts, where 101 is the inner hole of the metal part, 102 is the grinding wheel of the grinding device, 103 is the grinding wheel shaft of the grinding device, 104 is the flexible coupling of the grinding device, and 105 is the grinding wheel servo motor of the grinding device. The rotation direction of the grinding wheel is opposite to that of the metal part.

[0053] The grinding process of cylindrical inner holes often causes great impact on the grinding tool and is accompanied by severe vibration. This application installs a vibration sensor on the grinding wheel shaft of the metal part inner hole grinding device to collect amplitude data during the inner hole grinding process. The torque value of the grinding wheel servo motor represents the grinding force during the inner hole grinding process. This application obtains the torque feedback value of the grinding wheel servo motor during the inner hole grinding process through a control device, where the torque feedback value is described as a voltage value in volts. The amplitude data and torque feedback value are sampled synchronously and at the same frequency. The sampling frequency in this embodiment is specifically 30Hz.

[0054] Since the amplitude data and torque feedback values ​​may be affected by the accuracy of the sensor during the acquisition process, this application uses linear interpolation to fill in missing values, where the linear interpolation method is a well-known technology and will not be described in detail in this application.

[0055] At this point, the amplitude data and torque feedback values ​​at each acquisition moment are obtained.

[0056] Step S2, obtaining each time interval of each control moment and the amplitude sequence and torque feedback value sequence of each control moment; obtaining the high load intensity value of each time interval of each control moment based on the size of the torque feedback value, the value of the peak point in the torque feedback value sequence and the difference between the preset motor torque value; obtaining the correlation weight of each time interval of each control moment based on the correlation between the torque feedback value sequence and the amplitude sequence.

[0057] In order to ensure the controllability and safety of the inner hole grinding process of metal parts, the grinding wheel servo motor of the inner hole grinding device of metal parts adopts a constant speed mode, and the amount of grinding of the inner hole of the metal part is relatively small. Therefore, the preset motor torque value R of the grinding wheel servo motor in this embodiment is 0.8V.

[0058] In the early stage of grinding the inner hole of metal parts, there are complex and irregular fluctuations on the surface of the inner hole of the metal parts, and the amount of grinding is large. The inner hole grinding device of the metal parts needs to use a larger grinding force to grind away these fluctuations. The load of the grinding wheel servo motor is high, the torque feedback value is generally high, and peaks are prone to occur. Figure 3 Schematic diagram of the undulation of the inner hole of a metal part, wherein 102 is the grinding wheel of the grinding device, 201 is the undulation of the inner hole of the metal part, and 202 is the grinding amount of the undulation of the inner hole.

[0059] This application uses a preset time interval to adjust the torque of the grinding wheel servo motor to achieve grinding control that responds to the changing characteristics of the inner hole grinding process of the metal part. The acquisition time of each preset time interval is used as each control moment. In this embodiment, the preset time interval is set to 0.2s, and the implementer may select other values ​​based on actual conditions.

[0060] Furthermore, for each control moment, the amplitude data and torque feedback values ​​for all sampling moments within a preset time period prior to the control moment are obtained, and a sequence of these values, arranged in positive chronological order, is used as the amplitude sequence and torque feedback value sequence for each control moment. In this embodiment, the preset time period is set to 10 seconds; implementers may select other values ​​based on actual circumstances.

[0061] For each control moment in the torque feedback value sequence, the maximum torque feedback value in the torque feedback value sequence is obtained. Half of the maximum torque feedback value is used as a load threshold. The acquisition moment in the torque feedback value sequence when the torque feedback value exceeds the load threshold is considered a high-load moment. The torque feedback value sequence is used as input to an AMPD (Automatic Multiscale-Based Peak Detection) peak detection algorithm to obtain each peak point in the torque feedback value sequence. The AMPD (Automatic Multiscale-Based Peak Detection) peak detection algorithm is well known and will not be described in detail in this embodiment.

[0062] In order to improve the accuracy of subsequent grinding intensity evaluation, for each control moment, the preset time period before the control moment is divided into 10 time intervals.

[0063] Furthermore, according to the above analysis, based on the number of high-load moments, the difference between the peak value in the torque feedback value sequence and the preset motor torque value, the high-load intensity value P of each time interval at each control moment is obtained, and the calculation formula is: Where P is the high load intensity value of each time interval at each control moment; θ is the ratio of the number of high load moments in each time interval at each control moment to the number of all acquisition moments, r vis the torque feedback value of the vth peak point in each time interval of each control moment, V is the total number of peak points of the torque feedback value sequence in each time interval of each control moment, and R is the preset motor torque value.

[0064] It should be noted that when the high load intensity value θ is larger, it means that the high load state of the metal inner hole grinding device lasts longer. The larger the value, the more likely the grinding device is to be overloaded, and the more the grinding wheel servo motor is needed for load regulation. The greater the amount of grinding of the inner hole of the metal part, the greater the load intensity of the grinding wheel servo motor during the grinding process of the inner hole of the metal part, and the greater the high load intensity value P obtained; conversely, the smaller the high load intensity value P obtained.

[0065] Since the inner hole surface of the metal part has irregular undulations in the early stage of grinding, the torque feedback value sequence is highly complex.

[0066] Grinding the inner holes of metal parts is a typical industrial environment. There will be serious noise interference in certain time periods, which makes it easy for significant noise interference points to appear in the torque feedback value sequence. These significant noise interference points will destroy the detailed characteristics of the torque feedback value sequence and affect the analysis of the metal part grinding stage in this application. The inner hole surface of the metal part has undulating shapes due to drilling, reaming and other processing. The more protrusions on the inner hole surface that contact the grinding wheel during the grinding process, the more grinding the grinding device needs to do, and the greater the torque feedback value. At the same time, due to the irregularity of the protrusions, these irregular protrusions will cause a great impact on the grinding device and be accompanied by violent vibrations, causing strong vibrations of the grinding wheel shaft and increasing the amplitude. Therefore, the amplitude sequence and the torque feedback value sequence itself have a strong correlation.

[0067] Furthermore, according to the above analysis, based on the correlation between the torque feedback value sequence and the amplitude sequence, the correlation weight μ of each time interval at each control moment is obtained, and the calculation formula is: μ=γ1+per(l1,l2); wherein, μ is the correlation weight of each time interval at each control moment; l1 is the torque feedback value sequence in each time interval at each control moment, and l2 is the amplitude sequence in each time interval at each control moment; per() is the Pearson correlation coefficient, and γ1 is the preset parameter adjustment factor. In this embodiment, the value of γ1 is 1, which is used to make the correlation weight μ not less than 0. The implementer can select other values ​​according to actual conditions.

[0068] It should be noted that the stronger the correlation between the subsequences of the amplitude sequence and the torque feedback value sequence within the time series interval, that is, the larger pea(l1,l2), the larger the correlation weight μ, which means that the noise signal destroys the detailed information characteristics of the torque feedback value sequence less, and the smaller the interference effect on the identification of the metal part grinding stage.

[0069] The grinding force of a grinding device primarily depends on the condition of the metal part's inner hole. As the grinding device continues to operate, the condition of the metal part's inner hole changes, primarily into the early and late stages of grinding. The early stages of grinding experience high load intensity and large fluctuations. The grinding device's load changes significantly during this early stage, necessitating rapid response control of the grinding wheel servo motor.

[0070] Step S3, based on the correlation weight, the high load intensity value and the degree of fluctuation irregularity of the torque feedback value sequence, obtain the early grinding membership of each time interval at each control moment; based on the difference and the correlation weight between the torque feedback value and the preset motor torque value, obtain the late grinding membership of each time interval at each control moment; obtain the evaluation sequence of each control moment based on the early grinding membership and the late grinding membership; obtain the grinding control strength of each control moment based on the evaluation sequence.

[0071] Furthermore, the torque feedback value sequence at each control moment within each time interval is used as input to a Higuchi fractal dimension algorithm. The fractal dimension of the torque feedback value sequence at each control moment within each time interval is obtained to reflect the irregularity of the inner hole surface during the inner hole grinding process of the metal part. The Higuchi fractal dimension algorithm is a well-known technique and is not described in detail in this embodiment.

[0072] Furthermore, according to the above analysis, based on the correlation weight, the high load intensity value and the fractal dimension of the torque feedback value sequence, the grinding process corresponding to the time series interval is obtained as the membership of the early stage of grinding, that is, the early grinding membership of each time series interval at each control moment, and the calculation formula is: A=Norm[μ×(P×H)]; where A is the early grinding membership of each time series interval at each control moment; H is the fractal dimension of the torque feedback value sequence in each time series interval at each control moment, Norm[] is the normalization function, P is the high load intensity value of each time series interval at each control moment, and μ is the correlation weight of each time series interval at each control moment.

[0073] It should be noted that when the value of (P×H) is larger, it means that the load intensity of the grinding wheel servo motor in the timing interval is greater, and the undulation irregularity of the surface of the inner hole of the metal part is greater, then the timing interval is more consistent with the characteristics of the early stage of grinding. At the same time, when μ is larger, it means that the interference effect of the noise signal on the identification of the grinding stage of the metal part is smaller, and the weight of the timing interval belonging to the early stage of grinding is greater, then the grinding process corresponding to the timing interval is greater. The membership degree of the early stage of grinding is greater, and the value of the early stage of grinding membership obtained at this time is greater; conversely, the value of the obtained early stage of grinding membership is smaller.

[0074] In the later stage of grinding, the irregular protrusions on the surface of the inner hole of the metal part have been ground away, and the surface morphology is basically smooth. Under normal circumstances, the difference between the torque feedback value and the preset motor torque value is very small.

[0075] Furthermore, based on the above analysis, for each time interval at each control moment, the difference between all torque feedback values ​​in the torque feedback value sequence within the time interval and the preset motor torque value is calculated. The ratio of the number of torque feedback values ​​whose difference is less than the preset difference to the number of all torque feedback values ​​in the torque feedback value sequence is calculated. The normalized value of the product of this ratio and the correlation weight for each time interval at each control moment is used as the post-polishing membership degree B for each time interval at each control moment. In this embodiment, the preset difference value is 0.05; implementers may select other values ​​based on actual circumstances.

[0076] The early stage of grinding has a higher grinding intensity, and the grinding intensity in the early stage of grinding is relatively low. Furthermore, for each time interval of each control moment, the ratio of the early grinding membership to the late grinding membership is used as the grinding intensity evaluation value of each time interval of each control moment, which is used to evaluate the grinding intensity required for the grinding process; among them, when the late grinding membership B is 0, the value 0.01 is used as the late grinding membership B.

[0077] So far, the present application obtains the grinding intensity evaluation value of each time interval at each control moment.

[0078] Furthermore, a sequence of grinding intensity evaluation values ​​arranged in ascending order of time is used as an evaluation sequence at each control moment.

[0079] As the inner hole grinding process progresses, the required grinding intensity gradually decreases, and the evaluation sequence has a certain trend. This application uses the evaluation sequence as the input of the Holt exponential sliding smoothing algorithm, where the α value of the Holt exponential sliding smoothing algorithm is 0.8 and the β value is 0.1, and outputs the predicted value of the evaluation sequence.

[0080] It should be noted that the larger the predicted value, the greater the grinding intensity required by the subsequent grinding device for inner hole grinding. The Holt index sliding smoothing algorithm is a well-known technology and will not be described in detail in this embodiment.

[0081] In the fuzzy PI control algorithm, fuzzy reasoning is performed based on the fuzzy domain and fuzzy rule table to obtain the dynamic adjustment values ​​ΔKp and ΔKi of the PI parameters, which are added to the initial values ​​Kp and Ki respectively to realize the regulation of the grinding wheel servo motor in the metal part inner hole grinding device.

[0082] In the early stages of grinding, the inner hole of the metal part is irregular and requires a high grinding intensity. The grinding wheel servo motor should have a higher response speed to adapt to the fluctuations of the metal part's inner hole and the changes in grinding intensity. It should have higher dynamic adjustment values ​​ΔKp and ΔKi. In the later stages of grinding, the inner hole surface of the metal part is relatively flat and uniform, and the required grinding intensity is low. In order to ensure the grinding accuracy, it is necessary to pay attention to stability. The dynamic adjustment values ​​ΔKp and ΔKi should not be too large to avoid overshoot and oscillation.

[0083] According to the above analysis, the predicted value of the evaluation sequence at each control moment is used as the input of the Tanh function. The function of the Tanh function is to map the predicted value to [0,1]. The sum of the output value of the Tanh function and the preset constant is calculated as the polishing control intensity λ at each control moment. The preset constant is 0.5 in this embodiment, and the implementer can select other values ​​according to actual conditions.

[0084] It should be noted that the domain of the output variable is dynamically adjusted according to the grinding control intensity. When the grinding control intensity is greater than 1, a larger PI control parameter is provided for the early stage of grinding, giving a higher response speed. When the grinding control intensity is less than 1, stronger stability is provided for the later stage of grinding to avoid overshoot and oscillation caused by the grinding wheel servo motor control.

[0085] Step S4: obtaining a regulated torque feedback value based on the grinding regulation force and the torque feedback value, and grinding the inner hole of the metal part.

[0086] This application adopts fuzzy PI control algorithm to realize the regulation of the grinding wheel servo motor in the metal part inner hole grinding device.

[0087] Furthermore, the mean of the torque feedback values ​​at all sampling moments between each control moment and its previous adjacent control moment is calculated as the torque process value at each control moment; and the difference between the torque process value at each control moment and the preset motor torque value is calculated as the deviation of the fuzzy PI control algorithm at each control moment.

[0088] In this embodiment, the fuzzy domain of the deviation amount and the deviation change rate of the fuzzy PI control algorithm is [-1, 1], and the fuzzy domain of the preset output variable of the fuzzy PI control algorithm is ΔKp∈[-1, 1] and ΔKi∈[-0.5, 0.5].

[0089] After polishing the control intensity, the fuzzy domain of the output variable is obtained. The acquisition method is: the interval composed of the product of the polishing control intensity and the upper and lower boundaries of the preset output variable fuzzy domain of the fuzzy PI control algorithm is used as the output variable fuzzy domain of the fuzzy PI control algorithm, that is, ΔKp∈[-1λ,1λ], ΔKi∈[-0.5λ,0.5λ]. The membership function of the fuzzy PI control algorithm adopts the triangular membership function, and finally the updated proportional parameter ΔKp and the updated integral parameter ΔKi at each control moment are output.

[0090] The initial proportional parameter and initial integral parameter of the PI controller of the grinding wheel servo motor at each control moment are obtained by the Ziegler-Nichols method. The sum of the updated proportional parameter ΔKp and the initial proportional parameter Kp, and the sum of the updated integral parameter ΔKi and the initial integral parameter Ki at each control moment are calculated as the proportional parameter and integral parameter at each control moment, respectively.

[0091] The deviation at each control moment is used as the input of a PI controller. The PI controller uses the proportional and integral parameters adjusted at each control moment to regulate the torque feedback value of the grinding wheel servo motor of the metal workpiece inner hole grinding device, thereby obtaining a regulated torque feedback value. The Ziegler-Nichols method and fuzzy PI control algorithm are well-known technologies and are not described in detail in this embodiment.

[0092] At this point, a method for grinding the inner hole of a metal part is completed.

[0093] Based on the same inventive concept as the above method, an embodiment of the present application also provides a metal part inner hole grinding device, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of any one of the above-mentioned metal part inner hole grinding methods are implemented.

[0094] It should be noted that the order in which the embodiments of the present application are presented is for illustrative purposes only and does not necessarily represent the superiority or inferiority of the embodiments. Furthermore, the foregoing descriptions of specific embodiments of this specification are provided. Furthermore, the processes depicted in the accompanying drawings do not necessarily require the specific order or sequential sequence shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0095] The various embodiments in this application are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0096] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for grinding the inner hole of a metal part, characterized in that: The method comprises the following steps: Collect amplitude data and torque feedback values ​​at each sampling moment during the inner hole grinding process of metal parts; Obtaining each time series interval at each control moment and the amplitude sequence and torque feedback value sequence at each control moment; For the torque feedback value sequence at each control moment, the maximum value of the torque feedback value in the torque feedback value sequence is obtained, half of the maximum value of the torque feedback value is used as a load threshold, and the acquisition moment when the torque feedback value in the torque feedback value sequence is greater than the load threshold is used as a high-load moment; the torque feedback value sequence is used as input to a peak detection algorithm to obtain each peak point of the torque feedback value sequence; The calculation formula of the high load strength value is: Where P is the high load intensity value of each time interval at each control moment; θ is the ratio of the number of high load moments in each time interval at each control moment to the number of all acquisition moments, r v is the torque feedback value of the vth peak point in each time interval of each control moment, V is the total number of peak points of the torque feedback value sequence in each time interval of each control moment, and R is the preset motor torque value; Based on the correlation between the torque feedback value sequence and the amplitude sequence, the correlation weight of each time series interval at each control moment is obtained; Based on the correlation weight, the high load intensity value and the degree of fluctuation irregularity of the torque feedback value sequence, the early polishing membership of each time interval at each control moment is obtained; Based on the difference and correlation weight between the torque feedback value and the preset motor torque value, the post-polishing membership of each time interval at each control moment is obtained; Obtain the evaluation sequence of each control moment based on the early polishing membership and the late polishing membership; The Holt exponential sliding smoothing algorithm is used to obtain the predicted value of the evaluation sequence at each control moment; The predicted value of the evaluation sequence at each control moment is used as the input of the Tanh function, and the sum of the output value of the Tanh function and the preset constant is used as the polishing control intensity at each control moment; Calculate the mean of the torque feedback values ​​at all sampling moments between each control moment and its previous adjacent control moment as the torque process value at each control moment; calculate the difference between the torque process value at each control moment and the preset motor torque value as the deviation of the fuzzy PI control algorithm at each control moment; The interval formed by the product of the polishing control intensity and the upper and lower boundaries of the preset output variable fuzzy domain of the fuzzy PI control algorithm is used as the output variable fuzzy domain of the fuzzy PI control algorithm, and the updated proportional parameter and updated integral parameter at each control moment are output; The initial proportional parameter and initial integral parameter of the PI controller at each control moment are obtained by the Ziegler-Nichols method. The sum of the updated proportional parameter and the initial proportional parameter, and the sum of the updated integral parameter and the initial integral parameter at each control moment are calculated as the proportional parameter and integral parameter at each control moment, respectively. The deviation at each control moment is used as the input of the PI controller, which uses the proportional parameter and integral parameter at each control moment to output the regulated torque feedback value.

2. A method for grinding inner holes of metal parts according to claim 1, characterized in that: The obtaining of each time series interval at each control moment and the amplitude sequence and torque feedback value sequence at each control moment includes: The collection moments of each preset time interval are used as the control moments; For each control moment, the amplitude data and torque feedback values ​​of all sampling moments in a preset time period before the control moment are obtained, and the sequences formed in positive time order are used as the amplitude sequence and torque feedback value sequence of each control moment respectively; For each control moment, the preset time period before the control moment is divided into a preset number of time sequence intervals.

3. A method for grinding inner holes of metal parts according to claim 1, characterized in that: The calculation formula of the correlation weight is: μ=γ1+per(l1,l2); where μ is the correlation weight of each time interval at each control moment; l1 is the torque feedback value sequence within each time interval at each control moment, and l2 is the amplitude sequence within each time interval at each control moment; per() is the Pearson correlation coefficient, and γ1 is the preset parameter adjustment factor.

4. A method for grinding inner holes of metal parts according to claim 1, characterized in that: The method for obtaining the early polishing membership is: The fractal dimension algorithm is used to obtain the fractal dimension of the torque feedback value sequence in each time interval at each control moment; The calculation formula for the early grinding membership is: A=Norm[μ×(P×H)]; where A is the early grinding membership of each time interval at each control moment; H is the fractal dimension of the torque feedback value sequence in each time interval at each control moment, Norm[] is the normalization function, P is the high load intensity value of each time interval at each control moment, and μ is the correlation weight of each time interval at each control moment.

5. A method for grinding inner holes of metal parts according to claim 1, characterized in that: The method for obtaining the membership degree in the later stage of polishing is: For each timing interval of each control moment, the difference between all torque feedback values ​​in the torque feedback value sequence within the timing interval and the preset motor torque value is calculated, and the ratio of the number of torque feedback values ​​whose difference is less than the preset difference to the number of all torque feedback values ​​in the torque feedback value sequence is calculated. The normalized value of the product of the ratio and the correlation weight of each timing interval of each control moment is used as the post-polishing membership of each timing interval of each control moment.

6. A method for grinding inner holes of metal parts according to claim 1, characterized in that: The method for obtaining the evaluation sequence is: For each time interval at each control moment, the ratio of the membership degree in the early grinding stage to the membership degree in the late grinding stage is used as the grinding intensity evaluation value of each time interval at each control moment; The sequence of the grinding intensity evaluation values ​​arranged in ascending order of time is used as the evaluation sequence at each control moment.

7. A device for grinding inner holes of metal parts, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method for grinding the inner hole of a metal part as described in any one of claims 1 to 6 are implemented.

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