Pressure control method of multi-station positioning fixture for welding composite brake drum

Abstract

The invention relates to the field of workpiece welding and fixing, in particular to a pressure control method for a multi-station positioning clamp for welding a composite brake drum. The method comprises the following steps: firstly, according to the distribution of pressure data of each clamp in a preset time period before the current moment and the pressure data difference between the clamps clamping the same workpiece at the current moment, obtaining the offset possibility of each clamp at the current moment; according to the difference between the distance from the welding position to each clamp at the current moment and the distance from each clamp to the circle center of the target workpiece, the clamping deviation interference degree of each clamp at the current moment is obtained, and according to the clamping deviation interference degree difference between two clamps which clamp different workpieces and are closest to each other at the current moment, the clamping deviation interference degree of each clamp is obtained; and the clamping unbalance degree of the clamp at the current moment is obtained, and the clamping pressure of the clamp at the next moment is controlled. The clamping pressure of all the clamps can be effectively controlled, the phenomenon that the positions of the clamps deviate during welding is avoided, and the clamping effect of the clamps is improved.

Description

Technical Field

[0001] This invention relates to the field of workpiece welding and fixing, and specifically to a pressure control method for a multi-station positioning fixture used for welding composite brake drums. Background Technology

[0002] Composite brake drums are key components used in automotive braking systems, which are made by welding two or more different materials together. In the manufacturing process of composite brake drums, the welding process between different workpieces (such as friction rings and flanges) is the core process. It usually requires the use of mechanical fixtures to fix different workpieces and the use of welding torches to weld the workpieces together. During the welding process, improper control of the clamping pressure of the mechanical fixtures will reduce the welding effect. Therefore, the control of the clamping pressure of the mechanical fixtures is of great significance.

[0003] In related technologies, mechanical clamps are typically used to hold and fix different components of a composite brake drum, and then a welding torch with a fixed angle is used to weld the annular gap. The mechanical clamps are rotated and moved by a rotary positioner connected to them, so that the welding torch can continue to weld the remaining gaps between the workpieces. However, in actual practice, when welding different workpieces, a lot of vibration is generated and transmitted to the workpieces, causing the workpieces to vibrate as well. This causes some clamps with insufficient pressure to shift, reducing the clamping effect of the clamps. Summary of the Invention

[0004] To address the technical problem that vibrations generated during the welding process can cause insufficient pressure on some fixtures, leading to misalignment and reduced clamping effectiveness, this invention aims to provide a pressure control method for a multi-station positioning fixture used in welding composite brake drums. The specific technical solution adopted is as follows:

[0005] This invention proposes a pressure control method for a multi-station positioning fixture used in welding composite brake drums, the method comprising:

[0006] During the welding process of the two workpieces of the composite brake drum, the pressure data applied by each fixture of different workpieces is acquired in real time;

[0007] Using any type of workpiece of the composite brake drum as the target workpiece, and any clamp holding the target workpiece as the target clamp, the displacement probability of the target clamp at the current moment is obtained based on the distribution of pressure data of the target clamp at each moment in a preset time period before the current moment, and the difference in pressure data between the target clamp and other clamps holding the target workpiece at the current moment. Based on the difference between the distance from the welding position to the target clamp and the distance from the target clamp to the center of the target workpiece at the current moment, the clamping displacement dominance of the target clamp at the current moment is obtained. Based on the displacement probability of the target clamp at the current moment, and the clamping displacement dominance of each clamp holding the target workpiece at the current moment, the clamping displacement interference degree of the target clamp at the current moment is obtained.

[0008] Using another workpiece as a reference workpiece, and the clamping fixture that is closest to the target fixture and holds the reference workpiece as the reference fixture of the target fixture, the clamping imbalance of the target fixture at the current moment is obtained based on the difference in the clamping offset disturbance between the target fixture and the reference fixture at the current moment.

[0009] Based on the clamping imbalance, the clamping pressure of the target clamp at the next moment is controlled.

[0010] Furthermore, the probability of obtaining the target fixture's offset at the current moment includes:

[0011] The average of the absolute values ​​of the pressure differences between the target workpiece and all other clamps (excluding the target clamp) at the current moment is taken as the pressure difference characteristic value of the target clamp at the current moment.

[0012] The offset coefficient of the target fixture at the current moment is obtained based on the difference in the characteristic value of the pressure difference between the target fixture and other fixtures that hold the target workpiece.

[0013] The dispersion of pressure data of the target fixture at all times within a preset time period before the current time is analyzed to obtain the vibration disturbance degree of the target fixture at the current time.

[0014] After combining the vibration disturbance degree and the offset coefficient and performing normalization, the offset probability of the target fixture at the current moment is obtained.

[0015] Furthermore, the offset coefficient of the target fixture at the current moment includes:

[0016] The average of the absolute values ​​of the differences in the pressure difference characteristic values ​​between the target workpiece and all other clamps (excluding the target clamp) at the current moment is taken as the offset coefficient of the target clamp at the current moment.

[0017] Furthermore, the determination of the dominant clamping offset of the target clamp at the current moment includes:

[0018] If the distance from the current welding position to the target fixture is less than the distance from the target fixture to the center of the target workpiece, then the absolute value of the difference between the current welding position to the target fixture and the distance from the target fixture to the center of the target workpiece is used as the numerator, and the distance from the target fixture to the center of the target workpiece is used as the denominator. The values ​​are then compared and normalized with negative correlation to obtain the clamping offset dominance of the target fixture at the current moment.

[0019] If the distance from the current welding position to the target fixture is not less than the distance from the target fixture to the center of the target workpiece, then the absolute value of the difference between the current welding position to the target fixture and the distance from the target fixture to the center of the target workpiece is used as the numerator, and the current welding position to the target fixture is used as the denominator. The values ​​are then normalized to obtain the clamping offset dominance of the target fixture at the current moment.

[0020] Furthermore, obtaining the clamping offset disturbance degree of the target clamp at the current moment includes:

[0021] Based on the dominance of the clamping offset of each fixture holding the target workpiece at the current moment, the rotational offset fixture at the current moment is selected from all the fixtures holding the target workpiece.

[0022] The degree of rotational influence at the current moment is obtained based on the distance between each of the rotational offset fixtures and the number of rotational offset fixtures.

[0023] Based on the degree of rotational influence at the current moment, the dominance of the clamping offset of the target fixture at the current moment is adjusted, and combined with the offset probability of the target fixture at the current moment, the clamping offset interference degree of the target fixture at the current moment is obtained.

[0024] Furthermore, the step of selecting the rotational offset fixture at the current moment from all fixtures holding the target workpiece includes:

[0025] Among all the fixtures holding the target workpiece, the fixture whose clamping offset dominance is less than a preset offset threshold is selected as the rotation offset fixture at the current moment.

[0026] Furthermore, obtaining the degree of rotational influence at the current moment includes:

[0027] The average distance between any two rotation offset fixtures at the current moment is taken as the rotation influence factor at the current moment.

[0028] The degree of rotational influence at the current moment is obtained by combining and normalizing the rotational influence factor and the number of rotational offset fixtures.

[0029] Furthermore, adjusting the dominance of the clamping offset of the target clamp at the current moment based on the degree of rotational influence at the current moment, and combining the offset probability of the target clamp at the current moment to obtain the clamping offset interference degree of the target clamp at the current moment includes:

[0030] The product of the degree of rotational influence at the current moment and the dominance of the clamping offset of the target fixture at the current moment is used as the clamping offset adjustment amount of the target fixture at the current moment;

[0031] The difference between the dominant clamping offset of the target fixture at the current moment and the clamping offset adjustment amount is taken as the dominant clamping offset adjustment of the target fixture at the current moment.

[0032] The clamping offset interference degree of the target fixture at the current moment is obtained by combining and normalizing the dominant force of the clamping offset adjustment and the probability of the offset at the current moment.

[0033] Furthermore, obtaining the clamping imbalance of the target clamp at the current moment includes:

[0034] The absolute value of the difference between the clamping offset interference degree between the target fixture and the reference fixture at the current time is normalized to obtain the clamping imbalance degree of the target fixture at the current time.

[0035] Furthermore, controlling the clamping pressure of the target clamp at the next moment based on the clamping imbalance includes:

[0036] The product of the clamping imbalance of the target clamp at the current moment and the pressure data is used as the clamping pressure adjustment amount of the target clamp at the current moment.

[0037] The sum of the pressure data of the target clamp at the current moment and the clamping pressure adjustment amount is used as the clamping pressure of the target clamp at the next moment.

[0038] The present invention has the following beneficial effects:

[0039] This invention considers that vibrations generated during the welding process can cause some clamps with insufficient pressure to shift, reducing the clamping effect. Therefore, it first acquires the pressure data applied by each clamp to different workpieces in real time. Given that vibrations during welding can cause significant fluctuations in the pressure applied by the clamps, and that the pressure applied by each clamp at the same time can vary considerably, the acquired offset probability can initially reflect the likelihood of clamping offset due to welding vibration. Considering that the welding of the composite brake drum is a rotational process, the centrifugal force generated by rotation can also cause clamp position shifts, which could be mistakenly attributed to improper clamping. Therefore, the acquired clamping offset probability reflects the likelihood of clamping offset due to welding vibration. The correlation between the clamping condition and the clamping offset phenomenon is analyzed. By combining the possibility of the target fixture offset at the current moment, the clamping offset interference degree is obtained to reflect the possibility that the target fixture offsets due to improper clamping during the welding process, thereby eliminating the influence of rotational centrifugal force. At the same time, considering that different workpieces are made of different materials, their response to welding vibration varies, resulting in different offsets due to welding vibration. Therefore, by analyzing the difference in clamping offset interference degree between the target fixture and the reference fixture at the current moment, and by obtaining the clamping imbalance degree, the clamping pressure of the target fixture at the next moment is controlled, so that the fixture can clamp the workpiece more stably during welding and improve the clamping effect of the fixture. Attached Figure Description

[0040] To more clearly illustrate the technical solutions and advantages 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.

[0041] Figure 1 This is a flowchart of a pressure control method for a multi-station positioning fixture for welding composite brake drums, provided in one embodiment of the present invention. Detailed Implementation

[0042] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a multi-station positioning fixture pressure control method for welding composite brake drums according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0043] Unless otherwise defined, 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 invention pertains.

[0044] The following description, in conjunction with the accompanying drawings, details the specific scheme of the pressure control method for a multi-station positioning fixture for welding composite brake drums provided by the present invention.

[0045] Please see Figure 1 The diagram illustrates a flowchart of a pressure control method for a multi-station positioning fixture for welding composite brake drums, according to an embodiment of the present invention. The method includes:

[0046] Step S1: During the welding process of the two workpieces of the composite brake drum, the pressure data applied by each fixture of different workpieces is acquired in real time.

[0047] During the welding process of different workpieces (such as friction rings and flanges) of composite brake drums, the welding process generates significant vibration. For a particular workpiece, multiple mechanical clamps are typically used to hold it to keep it stable during the welding process and avoid large displacements caused by vibration, which would reduce the final welding effect. At the same time, since the angle of the welding torch is fixed during the welding process, it is necessary to connect the mechanical clamps to a rotary positioner and weld the workpieces held by the clamps together by rotating and welding simultaneously.

[0048] Since significant vibrations occur during welding, strict control of the clamping pressure of each clamp is necessary to ensure the stability of the workpiece and the fixture during welding. Therefore, in the welding process of two types of workpieces for the composite brake drum, one embodiment of the present invention takes the friction ring and flange as examples. First, a pressure sensor is installed between each clamp and the workpiece, and the pressure sensor is used to collect the pressure data applied by each clamp to different workpieces in real time.

[0049] Step S2: Take any type of workpiece of the composite brake drum as the target workpiece, and any clamp holding the target workpiece as the target clamp. Based on the distribution of pressure data of the target clamp at each time point in the preset time period before the current time, and the difference in pressure data between the target clamp and other clamps holding the target workpiece at the current time, obtain the offset probability of the target clamp at the current time. Based on the difference between the distance from the welding position to the target clamp and the distance from the target clamp to the center of the target workpiece at the current time, obtain the clamping offset dominance of the target clamp at the current time. Based on the offset probability of the target clamp at the current time and the clamping offset dominance of each clamp holding the target workpiece at the current time, obtain the clamping offset interference degree of the target clamp at the current time.

[0050] For multiple clamps on a workpiece, since the clamps are distributed at different positions on the workpiece, the vibrations generated during the welding process will have different degrees of impact on different clamps on each workpiece. Therefore, it is necessary to analyze each clamp individually. In this embodiment of the invention, any type of workpiece of the composite brake drum is taken as the target workpiece, and any clamp holding the target workpiece is taken as the target clamp. Since the vibration generated during the welding process will cause large fluctuations in the pressure applied by the clamps, and the pressure applied by each clamp at the same time is significantly different, the distribution of pressure data of the target clamp at each time within a preset time period before the current time, as well as the distribution of pressure data of the target clamp and other clamps holding the target workpiece, can be analyzed. The differences in pressure data between other fixtures of the component at the current moment are analyzed, and the obtained offset probability is used to initially reflect the possibility of clamping offset of the target fixture due to welding vibration. The value range of the preset time period is [10, 30]. In one embodiment of the present invention, the length of the preset time period is set to 20, that is, the preset time period includes 20 moments before the current moment. The length of the preset time period can also be set by the implementer according to the specific implementation scenario, and is not limited here. It should also be noted that when analyzing the current moment, a sufficient length of time needs to be reserved before the current moment to ensure that the preset time period before the current moment can be analyzed.

[0051] Preferably, in one embodiment of the present invention, the method for obtaining the probability of the target fixture's offset at the current moment specifically includes:

[0052] First, the average of the absolute values ​​of the pressure data differences between the target fixture and all other fixtures holding the target workpiece at the current moment is taken as the pressure difference characteristic value of the target fixture at the current moment. The larger the pressure difference characteristic value, the greater the difference in clamping pressure between the target fixture and all other fixtures holding the target workpiece at the current moment.

[0053] As an example, in one embodiment of the present invention, the expression for the characteristic value of the pressure difference of the target clamp at the current moment can be specifically as follows:

[0054]

[0055] Where ΔF represents the characteristic value of the pressure difference of the target clamp at the current moment; F represents the pressure data of the target clamp at the current moment; F i This represents the pressure data of the i-th other clamp holding the target workpiece besides the target clamp at the current moment; I represents the number of all other clamps holding the target workpiece besides the target clamp.

[0056] Using the same method described above, the pressure difference characteristic value of each clamp holding the target workpiece at the current moment can be obtained. The greater the difference in the pressure difference characteristic value between the target clamp and other clamps holding the target workpiece at the current moment, the more likely the location of the target clamp is to be the main direction of vibration propagation. Therefore, the greater the possibility that the target clamp will be affected by welding vibration and undergo positional displacement. Thus, the displacement coefficient of the target clamp at the current moment can be obtained based on the difference in the pressure difference characteristic value between the target clamp and other clamps holding the target workpiece. Subsequently, the displacement probability of the target clamp at the current moment can be accurately calculated based on the displacement coefficient.

[0057] Preferably, in one embodiment of the present invention, the method for obtaining the offset coefficient of the target fixture at the current moment specifically includes:

[0058] The average of the absolute values ​​of the pressure difference characteristic values ​​between the target workpiece and all other clamps (excluding the target clamp) at the current moment is used as the offset coefficient of the target clamp at the current moment.

[0059] As an example, in one embodiment of the present invention, the expression for the offset coefficient of the target fixture at the current moment can be specifically as follows:

[0060]

[0061] Where A represents the offset coefficient of the target clamp at the current moment; ΔF represents the pressure difference characteristic value of the target clamp at the current moment; ΔF i I represents the pressure difference characteristic value of the i-th other clamp holding the target workpiece besides the target clamp at the current moment; I represents the number of all other clamps holding the target workpiece besides the target clamp.

[0062] Then, the more obvious the fluctuation in the pressure data of the target fixture in the preset time period before the current moment is in the time series, the more likely the target fixture is to be continuously affected by vibration, and thus the greater the possibility that the target fixture is affected by welding vibration and will be displaced. Therefore, the dispersion of the pressure data of the target fixture in all moments before the current moment can be analyzed to obtain the vibration interference degree of the target fixture at the current moment.

[0063] In embodiments of the present invention, the standard deviation, variance, or range of the pressure data of the target clamp at all times within a preset time period before the current time can be used as the vibration disturbance degree of the target clamp at the current time, thereby realizing the analysis of the dispersion of the pressure data of the target clamp at all times within a preset time period before the current time. This is not limited here.

[0064] Furthermore, the vibration disturbance degree and offset coefficient are combined and normalized to limit the calculation results to the range of [0,1], thereby obtaining the offset probability of the target fixture at the current moment.

[0065] In embodiments of the present invention, the sum or product of the vibration disturbance degree and the offset coefficient of the target fixture at the current moment can be calculated to achieve the integration of the two, which is not limited here. Furthermore, the same method can be used to integrate two or more data in subsequent steps.

[0066] In embodiments of the present invention, normalization can be achieved using an activation function or a hyperbolic tangent function, which will not be elaborated upon or limited further. The same method can also be used to achieve normalization in subsequent steps.

[0067] As an example, in one embodiment of the present invention, the expression for the probability of the target fixture's offset at the current moment can be specifically as follows:

[0068] C = tanh(A × σ)

[0069] Where C represents the probability of the target clamp's offset at the current moment; A represents the offset coefficient of the target clamp at the current moment; σ represents the standard deviation of the pressure data of the target clamp at all moments within the preset time period before the current moment, i.e., the vibration disturbance degree of the target clamp at the current moment; tanh() represents the hyperbolic tangent function, used for normalization processing.

[0070] In actual welding, the area being welded acts as the vibration origin, and the resulting vibration spreads to both sides of the workpiece. The vibration originates at the welding position on the workpiece and propagates along the workpiece towards the clamping position. As the vibration spreads from one end to the other, the amplitude of the oscillation at the clamping position increases with the distance between the welding position and the clamping position. Furthermore, since welding is a process involving rotation, and the workpiece rotates along with the clamp, the centrifugal force generated during rotation can also cause the clamping position to shift, which may be mistakenly attributed to the clamping mechanism. Improper clamping can cause the fixture to shift. The effect of centrifugal force generated by rotation on the fixture depends on the distance between the center of the fixture and the center of the workpiece. Therefore, the difference between the distance from the welding position to the target fixture and the distance from the target fixture to the center of the target workpiece at the current moment can be analyzed. The obtained clamping offset dominance reflects the correlation between the clamping offset phenomenon caused by the clamping condition of the target fixture itself. The greater the clamping offset dominance, the more likely the offset of the target fixture is caused by improper clamping of the target fixture under the premise of welding vibration, and the less likely it is caused by centrifugal force generated by rotation.

[0071] Preferably, in one embodiment of the present invention, the method for obtaining the dominance of the clamping offset of the target fixture at the current moment specifically includes:

[0072] If the distance from the current welding position to the target fixture is less than the distance from the target fixture to the center of the target workpiece, it indicates that the influence of welding vibration at the current moment is less than the influence of rotational centrifugal force. The greater the difference between the two distances, the more likely the offset of the target fixture is due to rotational centrifugal force. This further indicates that the correlation between the target fixture's own clamping condition and the clamping offset phenomenon is lower. Therefore, the absolute value of the difference between the current welding position to the target fixture and the distance from the target fixture to the center of the target workpiece can be used as the numerator, and the distance from the target fixture to the center of the target workpiece can be used as the denominator. The values ​​are then normalized with negative correlation, and the calculation results are limited to the range of [0,1] to obtain the dominance of the clamping offset of the target fixture at the current moment.

[0073] If the distance from the current welding position to the target fixture is not less than the distance from the target fixture to the center of the target workpiece, it indicates that the influence of welding vibration is greater than the influence of centrifugal force at the current moment. The greater the difference between the two distances, the more likely the offset of the target fixture is caused by welding vibration. This further indicates that the correlation between the target fixture and the clamping offset phenomenon caused by its own clamping condition is higher. Therefore, the absolute value of the difference between the current welding position to the target fixture and the distance from the target fixture to the center of the target workpiece can be used as the numerator, and the current welding position to the target fixture can be used as the denominator. The values ​​are then normalized, and the calculation results are limited to the range of [0,1] to obtain the dominance of the clamping offset of the target fixture at the current moment.

[0074] As an example, in one embodiment of the present invention, the expression for the dominant clamping offset of the target clamp at the current moment can be specifically, for example, as follows:

[0075]

[0076] Where E represents the dominance of the clamping offset of the target fixture at the current moment; D represents the distance from the welding position to the target fixture at the current moment; D ′ This represents the distance from the center of the target fixture to the center of the target workpiece; tanh() represents the hyperbolic tangent function, used for normalization, while 1-tanh() is used for normalization of negative correlations.

[0077] The clamping offset dominance of each clamp holding the target workpiece at the current moment can be obtained by using the same method described above.

[0078] When a workpiece is offset while being held by a fixture, two main vibration trajectories are formed. One is a unidirectional vibration, in which the workpiece's vibration return point is more likely to pass through the center of the brake drum, and it still passes through the center of the brake drum when the fixture rotates, only the vibration direction changes with the direction of fixture rotation. Therefore, the centrifugal effect of the vibration caused by rotation is smaller, and the influence of centrifugal force generated by rotation is smaller. The other is a vibration return point that does not pass through the center of the brake drum and is more irregular. In this case, even a small centrifugal force can easily cause the fixture to loosen under vibration. Therefore, this embodiment of the invention obtains the clamping offset interference degree of the target fixture at the current moment based on the possibility of the target fixture offset at the current moment and the clamping offset dominance of each fixture holding the target workpiece at the current moment. The clamping offset interference degree reflects the possibility that the target fixture offset is due to improper clamping during the welding process, thereby eliminating the influence of rotational centrifugal force and improving the control accuracy of the clamping pressure of the target fixture in the future.

[0079] Preferably, in one embodiment of the present invention, the method for obtaining the clamping offset interference degree of the target clamp at the current moment specifically includes:

[0080] First, the smaller the dominance of the clamping offset of a certain clamp holding the target workpiece at the current moment, the more likely the loosening and offset phenomenon of the clamp at the current moment is caused by the centrifugal force generated by rotation. Therefore, based on the dominance of the clamping offset of each clamp holding the target workpiece at the current moment, the rotation offset clamp can be screened from all the clamps holding the target workpiece.

[0081] Preferably, in one embodiment of the present invention, among all the clamps holding the target workpiece, the clamp with a clamping offset dominance less than a preset offset threshold can be used as the rotation offset clamp at the current moment. The preset offset threshold ranges from (0,1). In one embodiment of the present invention, the preset offset threshold is set to 0.5. The specific value of the preset offset threshold can also be set by the implementer according to the specific implementation scenario, and is not limited here.

[0082] Then, the smaller the distance distribution between each rotary offset fixture and the more rotary offset fixtures there are, the greater the centrifugal force generated by the rotation on the fixture holding the target workpiece at the current moment. Therefore, the degree of rotational influence at the current moment can be obtained based on the distance between each rotary offset fixture and the number of rotary offset fixtures at the current moment.

[0083] Preferably, in one embodiment of the present invention, the method for obtaining the degree of rotational influence at the current moment specifically includes:

[0084] The average distance between any two rotating offset fixtures at the current moment is taken as the rotation influence factor at the current moment. The rotation influence factor and the number of rotating offset fixtures at the current moment are combined and normalized. The calculation result is limited to the range of [0,1] to obtain the degree of rotation influence at the current moment.

[0085] As an example, in one embodiment of the present invention, the expression for the degree of influence of rotation at the current moment can be specifically as follows:

[0086] W = tanh(K × S)

[0087] Where W represents the degree of rotational influence at the current moment; K represents the average distance between any two rotational offset fixtures at the current moment, i.e., the rotational influence factor at the current moment; S represents the number of rotational offset fixtures at the current moment; tanh() represents the hyperbolic tangent function, used for normalization.

[0088] Furthermore, based on the degree of rotational influence at the current moment, the dominance of the clamping offset of the target fixture at the current moment is adjusted, thereby eliminating the interference of the centrifugal force generated by rotation on the improper clamping analysis of the target fixture. Combined with the possibility of the target fixture offset at the current moment, the clamping offset interference degree of the target fixture at the current moment is obtained.

[0089] Preferably, in one embodiment of the present invention, the method for obtaining the clamping offset interference degree of the target clamp at the current moment further includes:

[0090] The product of the degree of rotational influence at the current moment and the dominance of the clamping offset at the current moment is used as the clamping offset adjustment amount of the target fixture at the current moment. The difference between the dominance of the clamping offset at the current moment and the clamping offset adjustment amount is used as the adjustment of the clamping offset dominance of the target fixture at the current moment. The adjustment of the clamping offset dominance reflects the possibility that the target fixture will deviate at the current moment due to improper clamping after eliminating the interference of centrifugal force generated by rotation.

[0091] Then, the dominant force and probability of the target fixture's adjustment clamping offset at the current moment are combined and normalized, and the calculation results are limited to the range of [0,1], so as to obtain the clamping offset interference degree of the target fixture at the current moment.

[0092] As an example, in one embodiment of the present invention, the expression for the clamping offset disturbance degree of the target clamp at the current moment can be specifically as follows:

[0093] Q = tanh(C × E) ′ )

[0094] E′ =EW×E

[0095] Where Q represents the clamping offset disturbance degree of the target clamp at the current moment; C represents the offset probability of the target clamp at the current moment; E ′ E represents the dominance of the target fixture's clamping offset adjustment at the current moment; W represents the dominance of the target fixture's clamping offset at the current moment; W×E represents the amount of clamping offset adjustment of the target fixture at the current moment; tanh() represents the hyperbolic tangent function, used for normalization.

[0096] The clamping offset interference degree of each clamp holding the target workpiece at the current moment can be obtained by using the same method described above, as well as the clamping offset interference degree of each clamp holding each type of workpiece of the composite brake drum at the current moment.

[0097] Step S3: Take another workpiece as a reference workpiece, and take the clamping fixture that is closest to the target fixture and holds the reference workpiece as the reference fixture of the target fixture. Based on the difference in clamping offset interference between the target fixture and the reference fixture at the current moment, obtain the clamping imbalance of the target fixture at the current moment.

[0098] Because the different workpieces of the composite brake drum are made of different materials, their response to welding vibration varies, leading to different offsets. If the clamping offset interference obtained above is directly used to adjust the clamping pressure of the target fixture, it will increase the distance between the welds of different workpieces during subsequent welding, reducing the final welding effect. Therefore, it is necessary to analyze the differences in clamping offset interference between the fixtures holding different workpieces at the current moment. In this embodiment of the invention, another workpiece of the composite brake drum is first used as a reference workpiece, and the clamping reference workpiece closest to the target fixture is... The fixture for the target fixture serves as a reference fixture for the target fixture. The target fixture and the reference fixture each hold different workpieces, and the distance between them is the shortest, making them the most reliable references. The difference in clamping offset interference between the target fixture and the reference fixture at the current moment is analyzed to obtain the clamping imbalance of the target fixture at the current moment. The greater the clamping imbalance of the target fixture at the current moment, the greater the difference in offset tendency between the target fixture and the reference fixture when clamping different workpieces. This indicates that the clamping pressure applied by the target fixture at the current moment is more unbalanced, and therefore, the clamping pressure of the target fixture needs to be adjusted to a greater extent in the future.

[0099] Preferably, in one embodiment of the present invention, the method for obtaining the clamping imbalance of the target clamp at the current moment specifically includes:

[0100] The absolute value of the difference between the clamping offset interference degree between the target fixture and the reference fixture at the current time is normalized, and the calculation result is limited to the range of [0,1], so as to obtain the clamping imbalance degree of the target fixture at the current time.

[0101] As an example, in one embodiment of the present invention, the expression for the clamping imbalance of the target clamp at the current moment can be specifically as follows:

[0102] U = tanh(|QQ) ′ |)

[0103] Where U represents the clamping imbalance of the target clamp at the current moment; Q represents the clamping offset disturbance of the target clamp at the current moment; Q ′ This represents the clamping offset disturbance of the reference fixture at the current moment; tanh() represents the hyperbolic tangent function, used for normalization.

[0104] Step S4: Based on the clamping imbalance, control the clamping pressure of the target clamp at the next moment.

[0105] The greater the clamping imbalance of the target fixture at the current moment, the greater the difference in the offset tendency between the target fixture and the reference fixture when clamping different workpieces. This indicates that the clamping pressure applied by the target fixture at the current moment is more unbalanced, resulting in a smaller clamping pressure and requiring a greater increase in the clamping pressure applied by the target fixture. Therefore, the clamping pressure of the target fixture at the next moment can be controlled based on the clamping imbalance to avoid clamping offset of the target fixture during subsequent welding processes and improve the clamping effect of the target fixture.

[0106] Preferably, in one embodiment of the present invention, the method for controlling the clamping pressure of the target clamp at the next moment specifically includes:

[0107] The product of the clamping imbalance and pressure data of the target clamp at the current moment is used as the clamping pressure adjustment amount of the target clamp at the current moment. The sum of the pressure data of the target clamp at the current moment and the clamping pressure adjustment amount is used as the clamping pressure of the target clamp at the next moment.

[0108] As an example, in one embodiment of the present invention, the expression for the clamping pressure of the target clamp at the next moment can be specifically as follows:

[0109] F ′ =F + U × F

[0110] Among them, F ′F represents the clamping pressure of the target clamp at the next moment; F represents the pressure data of the target clamp at the current moment, that is, the clamping pressure of the target clamp at the current moment; U represents the clamping imbalance of the target clamp at the current moment.

[0111] By using the same method described above, the clamping pressure of each fixture holding each type of workpiece can be obtained at the next moment. Then, when welding enters the next moment, the clamping pressure of each fixture can be adjusted to avoid positional displacement of each fixture during the welding process.

[0112] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0113] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A pressure control method for a multi-station positioning fixture used in welding composite brake drums, characterized in that, The method includes: During the welding process of the two workpieces of the composite brake drum, the pressure data applied by each fixture of different workpieces is acquired in real time; Using any type of workpiece of the composite brake drum as the target workpiece, and any clamp holding the target workpiece as the target clamp, the displacement probability of the target clamp at the current moment is obtained based on the distribution of pressure data of the target clamp at each moment in a preset time period before the current moment, and the difference in pressure data between the target clamp and other clamps holding the target workpiece at the current moment. Based on the difference between the distance from the welding position to the target clamp and the distance from the target clamp to the center of the target workpiece at the current moment, the clamping displacement dominance of the target clamp at the current moment is obtained. Based on the displacement probability of the target clamp at the current moment, and the clamping displacement dominance of each clamp holding the target workpiece at the current moment, the clamping displacement interference degree of the target clamp at the current moment is obtained. Using another workpiece as a reference workpiece, and the clamping fixture that is closest to the target fixture and holds the reference workpiece as the reference fixture of the target fixture, the clamping imbalance of the target fixture at the current moment is obtained based on the difference in the clamping offset disturbance between the target fixture and the reference fixture at the current moment. Based on the clamping imbalance, the clamping pressure of the target clamp at the next moment is controlled.

2. The pressure control method for a multi-station positioning fixture for welding composite brake drums according to claim 1, characterized in that, The possible offsets of the target fixture at the current moment include: The average of the absolute values ​​of the pressure differences between the target workpiece and all other clamps (excluding the target clamp) at the current moment is taken as the pressure difference characteristic value of the target clamp at the current moment. The offset coefficient of the target fixture at the current moment is obtained based on the difference in the characteristic value of the pressure difference between the target fixture and other fixtures that hold the target workpiece. The dispersion of pressure data of the target fixture at all times within a preset time period before the current time is analyzed to obtain the vibration disturbance degree of the target fixture at the current time. After combining the vibration disturbance degree and the offset coefficient and performing normalization, the offset probability of the target fixture at the current moment is obtained.

3. The pressure control method for a multi-station positioning fixture for welding composite brake drums according to claim 2, characterized in that, The offset coefficient of the target fixture at the current moment includes: The average of the absolute values ​​of the differences in the pressure difference characteristic values ​​between the target workpiece and all other clamps (excluding the target clamp) at the current moment is taken as the offset coefficient of the target clamp at the current moment.

4. The pressure control method for a multi-station positioning fixture for welding composite brake drums according to claim 1, characterized in that, The dominance of the clamping offset of the target fixture at the current moment includes: If the distance from the current welding position to the target fixture is less than the distance from the target fixture to the center of the target workpiece, then the absolute value of the difference between the current welding position to the target fixture and the distance from the target fixture to the center of the target workpiece is used as the numerator, and the distance from the target fixture to the center of the target workpiece is used as the denominator. The values ​​are then compared and normalized with negative correlation to obtain the clamping offset dominance of the target fixture at the current moment. If the distance from the current welding position to the target fixture is not less than the distance from the target fixture to the center of the target workpiece, then the absolute value of the difference between the current welding position to the target fixture and the distance from the target fixture to the center of the target workpiece is used as the numerator, and the current welding position to the target fixture is used as the denominator. The values ​​are then normalized to obtain the clamping offset dominance of the target fixture at the current moment.

5. The pressure control method for a multi-station positioning fixture for welding composite brake drums according to claim 1, characterized in that, The obtained clamping offset disturbance of the target fixture at the current moment includes: Based on the dominance of the clamping offset of each fixture holding the target workpiece at the current moment, the rotational offset fixture at the current moment is selected from all the fixtures holding the target workpiece. The degree of rotational influence at the current moment is obtained based on the distance between each of the rotational offset fixtures and the number of rotational offset fixtures. Based on the degree of rotational influence at the current moment, the dominance of the clamping offset of the target fixture at the current moment is adjusted, and combined with the offset probability of the target fixture at the current moment, the clamping offset interference degree of the target fixture at the current moment is obtained.

6. The pressure control method for a multi-station positioning fixture for welding composite brake drums according to claim 5, characterized in that, The step of selecting the rotational offset fixture from all fixtures holding the target workpiece at the current moment includes: Among all the fixtures holding the target workpiece, the fixture whose clamping offset dominance is less than a preset offset threshold is selected as the rotation offset fixture at the current moment.

7. The pressure control method for a multi-station positioning fixture for welding composite brake drums according to claim 5, characterized in that, The degree of rotational influence at the current moment includes: The average distance between any two rotation offset fixtures at the current moment is taken as the rotation influence factor at the current moment. The degree of rotational influence at the current moment is obtained by combining and normalizing the rotational influence factor and the number of rotational offset fixtures.

8. The pressure control method for a multi-station positioning fixture for welding composite brake drums according to claim 5, characterized in that, The step of adjusting the dominance of the clamping offset of the target clamp at the current moment based on the degree of rotational influence at the current moment, and combining the offset probability of the target clamp at the current moment to obtain the clamping offset interference degree of the target clamp at the current moment includes: The product of the degree of rotational influence at the current moment and the dominance of the clamping offset of the target fixture at the current moment is used as the clamping offset adjustment amount of the target fixture at the current moment; The difference between the dominant clamping offset of the target fixture at the current moment and the clamping offset adjustment amount is taken as the dominant clamping offset adjustment of the target fixture at the current moment. The clamping offset interference degree of the target fixture at the current moment is obtained by combining and normalizing the dominant force of the clamping offset adjustment and the probability of the offset at the current moment.

9. The pressure control method for a multi-station positioning fixture for welding composite brake drums according to claim 1, characterized in that, The obtained clamping imbalance of the target fixture at the current moment includes: The absolute value of the difference between the clamping offset interference degree between the target fixture and the reference fixture at the current time is normalized to obtain the clamping imbalance degree of the target fixture at the current time.

10. The pressure control method for a multi-station positioning fixture for welding composite brake drums according to claim 1, characterized in that, The control of the clamping pressure of the target clamp at the next moment based on the clamping imbalance includes: The product of the clamping imbalance of the target clamp at the current moment and the pressure data is used as the clamping pressure adjustment amount of the target clamp at the current moment. The sum of the pressure data of the target clamp at the current moment and the clamping pressure adjustment amount is used as the clamping pressure of the target clamp at the next moment.

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