Control method and system based on bolt fastening operation

Abstract

The invention discloses a control method and system based on bolt fastening operation, and relates to the technical field of mechanical assembly automation and intelligent control. Compliant control is performed based on a force sensor; the influence of the load borne by the inner hexagonal sleeve at the tail end of bolt fastening operation on the torque is analyzed; a bolt fastening torque control strategy is obtained, and a torque coefficient control method is used for control. According to one scheme of the control method based on the bolt fastening operation, errors caused by human intervention are reduced, and the bolt fastening precision is improved; a torque coefficient control method is combined with the relation between system rigidity and pre-tightening force, torque is automatically adjusted, motor current is monitored in real time, the bolt fastening process is intelligently controlled, accurate torque control is achieved, mechanical faults caused by deviation are avoided, and operation safety and system stability are improved. Accurate matching of the bolt and the sleeve is ensured by actively / passively adjusting postures and positions, and different working conditions are adapted.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical assembly automation and intelligent control, and in particular to a control method and system based on bolt tightening operations. Background Art

[0002] In transmission lines, bolts have become widely used connecting components due to their simple structure and low cost. Since transmission lines are located outdoors, complex climatic conditions can cause transmission lines to vibrate, expand or contract, which can lead to loose bolts and cause safety hazards in transmission lines. An important guarantee for safe and reliable operation. At present, the tightening of transmission line bolts is still basically completed by manual live operations. Under high-risk conditions of high altitude, high voltage and harsh environment, manual operation efficiency is low. In addition, due to the widespread application of UHV power grids and multi-circuit towers, the voltage level is getting higher and higher, and the phase-to-phase distance is getting closer and closer. Manual live operations are extremely dangerous. It is urgent to develop bolt tightening robots to replace manual labor to achieve safe and efficient live operations on lines. Summary of the invention

[0003] In view of the above-mentioned problems, the present invention is proposed.

[0004] Therefore, the technical problem solved by the present invention is that the existing voltage level is getting higher and higher, the phase-to-phase distance is getting closer and closer, manual live work is extremely dangerous, and the problem of bolt tightening needs to be developed urgently.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions: a control method based on bolt tightening operation, comprising:

[0006] Collect data and calculate the nut rotation;

[0007] Compliant control based on force sensors;

[0008] Analyze the effect of load on torque borne by the hexagon socket at the end of bolt tightening operation;

[0009] The bolt tightening torque control strategy is obtained and controlled using the torque coefficient control method.

[0010] As a preferred solution of the control method based on bolt tightening operation described in the present invention, wherein: the calculation of the nut rotation includes calculating the angle of nut rotation and the angle of nut creep. There are three cases of the angle of the sleeve relative to the bolt. The first is that the sleeve has no deviation relative to the bolt, and then it is directly fed and rotated; the second is that the sleeve is relative to the bolt θ (|θ|≤θ max ) deviation, the feed amount should be monitored before rotation; the third is that the sleeve has too large deviation relative to the bolt (|θ|>θ max ), continue adjusting the robot arm alignment.

[0011] As a preferred solution of the control method based on bolt tightening operation described in the present invention, the flexible control based on force sensor includes: performing force analysis on the nut that can already rotate, discussing the critical situation of the flexible angle, calculating the flexible angle during the process of the bolt entering the sleeve, and completing the alignment of the bolt.

[0012] As a preferred solution of the control method based on bolt tightening operation described in the present invention, wherein: the compliance control based on force sensor also includes that a three-dimensional force sensor is installed at the end of the robot arm, and the force sensor is responsible for adjusting the position error, and the posture error is adjusted by passive compliance; the bolt is assembled in the active compliance occasion, because the posture of the bolt is basically unchanged, when the sleeve posture is known, only the three-dimensional force sensor is used for active compliance assembly;

[0013] During the process of assembling and aligning the position adjustment bolts, there is no force on the axis and the axial direction, only the axis has a feed force, the three-dimensional force is measured by the force sensor, and the control algorithm for adjusting the position is obtained according to the impedance control algorithm;

[0014] Perform posture adjustment, and obtain the coordinates of the unit vector of the z-axis in the base coordinate system based on the known current posture of the robot's manipulator end; in the process of bolt alignment, continuously adjust the axis of the sleeve at the end of the robot manipulator so that its z-axis coincides with the z-axis of the coordinate system with a bolt as the reference target, obtain the posture adjustment control algorithm, and actively adjust the posture.

[0015] As a preferred solution of the control method based on bolt tightening operation described in the present invention, wherein: the bolt tightening torque control strategy includes considering overcoming the thread resistance torque of the thread pair, the friction torque of the head bearing surface, and the total system stiffness of the thread pair and the connected space as prior conditions; combining multiple experiments, obtaining the slope of the torque change with time and the stiffness of the system, analyzing the two, and obtaining the control torque corresponding to the corresponding pre-tightening force; then converting the obtained control torque into a specific current and putting it into the program as a constraint condition. When the current of the motor reaches the set current, the motor is automatically sent to stop, realizing intelligent control.

[0016] As a preferred solution of the control method based on bolt tightening operation described in the present invention, wherein: the analysis of the influence of the load borne by the hexagon socket at the end of the bolt tightening operation on the torque includes that there is a deviation angle in the process of transmitting torque, and the hexagon socket and the cross coupling will generate a pair of lateral loads of equal size and opposite direction; and the lateral load is calculated and analyzed to determine whether there is an influence;

[0017] During the rotation process, it is assumed that the motor rotates to drive the rotating shaft to rotate, that is, the active shaft I rotates at an angular velocity ω iRotation, the angular velocity of the driven shaft II is ω2; the relationship between ω1 and ω2 is derived as follows:

[0018] ω2=[cosα / (1-sin 2 αcos 2 ψ1)]ω1

[0019] Among them, ψ i represents the rotation angle of axis I; α represents the angle between axis I and axis II;

[0020] Ignore the friction loss of the cross hinge transmission and assume the efficiency is 1; if the torque acting on the driving shaft is M1 and the transmitted torque of the driven shaft is M2, the formula is expressed as:

[0021] M1ω1=M2ω2

[0022]

[0023] The circumferential force generated by M2 on the driven shaft II is:

[0024] P2=M2 / 2R

[0025] Wherein, R represents the radius of the hexagon socket.

[0026] As a preferred solution of the control method based on bolt tightening operation described in the present invention, the torque coefficient control method includes: according to the classical theory, the tightening torque τ is the thread resistance torque τ that overcomes the thread pair i The friction torque T2 of the head bearing surface and the friction resistance T3 of the gasket are obtained, and the preload-torque calculation formula is expressed as:

[0027] T=T1+T2+T3=KdF

[0028] The preload force F is linearly related to the nut rotation angle θ. At this time, the preload force on the connected part is:

[0029]

[0030] Among them, C s represents the total stiffness of the thread pair and the connected system, P represents the thread pitch, and K t =dT / dt, we can get:

[0031]

[0032] The relationship between torque and preload can be obtained as follows:

[0033]

[0034] Among them, K t and C ζThe core variable representing the torque coefficient, C s =F / δ, where F represents the force on the bolt and δ represents the internal deformation of the bolt. If the slope of the torque changing with time and the stiffness of the system are obtained, the control torque corresponding to the corresponding preload force is obtained; K t Including the relationship with the friction coefficient, different control torques are obtained for bolts of different masses.

[0035] A system adopting any of the control methods for bolt tightening operations according to the present invention, wherein: a data collection module is responsible for collecting various data generated during the operation;

[0036] The compliance control module implements compliance control based on force sensors to ensure that the bolts are aligned and rotated during tightening;

[0037] Torque analysis module, which analyzes the influence of load on the hexagon socket on torque during bolt tightening operation;

[0038] The torque control module realizes intelligent control of bolt tightening based on the torque coefficient control method.

[0039] A computer device includes a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of a control method based on a bolt tightening operation.

[0040] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a control method based on a bolt tightening operation.

[0041] Beneficial effects of the invention: The invention provides a control method for bolt tightening operation, which reduces the error caused by human intervention and improves the accuracy of bolt tightening. The torque coefficient control method is combined with the relationship between system stiffness and preload to automatically adjust the torque, monitor the motor current in real time, and intelligently control the bolt tightening process to achieve precise torque control, avoid mechanical failures caused by deviations, and improve the safety of the operation and the stability of the system. By actively / passively adjusting the posture and position, the bolt and sleeve are accurately matched to adapt to different working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0043] Figure 1An overall flow chart of a control method based on bolt tightening operation provided for the first embodiment of the present invention.

[0044] Figure 2 A schematic diagram of the deflection angle of a sleeve relative to a bolt in a control method for a bolt tightening operation provided in a second embodiment of the present invention.

[0045] Figure 3 A force analysis diagram before rotating the nut of a control method for bolt tightening operation provided in the second embodiment of the present invention.

[0046] Figure 4 A critical diagram of a flexibility angle of a control method based on a bolt tightening operation provided in accordance with a second embodiment of the present invention.

[0047] Figure 5 A curve diagram showing the change of torque over time based on a control method for a bolt tightening operation provided in a second embodiment of the present invention.

[0048] Figure 6 A curve diagram showing the variation of Kt over time for a control system based on a bolt tightening operation provided in accordance with the second embodiment of the present invention.

[0049] Figure 7 A curve diagram showing the change of pre-tightening force over time of a control system based on a bolt tightening operation provided in the second embodiment of the present invention.

[0050] Figure 8 A diagram showing changes in deformation with force sensors of a control system based on bolt tightening operations provided in accordance with the second embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0052] Example 1, reference Figure 1-Figure 4 , as an embodiment of the present invention, provides a control method based on a bolt tightening operation, comprising:

[0053] S1: Collect data and calculate the nut rotation.

[0054] Furthermore, for the calculation of the angle of rotation of the nut, there are three cases of the angle of deviation of the sleeve relative to the bolt. The first is that the sleeve has almost no deviation relative to the bolt, and it is directly fed and rotated; the second is that the sleeve is relative to the bolt θ (|θ|≤θ max ) deviation, in this case, the feed amount should be monitored before rotation; the third is that the sleeve has too large a deviation relative to the bolt (|θ|>θ max ), continue to adjust the robot arm alignment.

[0055] Furthermore, if the sleeve has almost no angle deviation relative to the nut, but only the hexagonal deviation, the robot arm is directly controlled to feed and rotate the nut to align the hexagons of the nut and the sleeve. When the spring recovers its deformation, the bolt tightening strategy is implemented. In the actual alignment process, the sleeve will have a certain deviation in all directions relative to the nut. This article takes the angle of the sleeve downward deviation of θ1 relative to the bolt as an example. In the process from the sleeve contacting the bolt to feeding, at what angle θ1 changes the sleeve starts to rotate and align, and analyzes the number of turns of the nut fed to determine whether the alignment is successful. If not, the robot arm is controlled to make fine adjustments based on the camera and then re-align the bolt.

[0056] Furthermore, if Figure 2 As shown, the sleeve is deviated downward by θ1 relative to the nut. When the sleeve contacts the nut, the angle of deviation is θ1. From the figure, we can get:

[0057] S=l * sinθ1

[0058]

[0059] Furthermore, at this moment, the motor is controlled to feed and the mobile spring is compressed, thus:

[0060] δ=Δl

[0061] Δl=P * n

[0062] Where P is the pitch of the internal thread of the nut, and n is the number of turns of the internal thread of the nut. In actual operation, if the sleeve is fed too many turns, the upper nut will deviate too much from the sleeve, making it difficult to align. If the sleeve is fed too few turns, it will also be difficult to align.

[0063] Furthermore, we can get Δl in 0<Δl≤l max Alignment can be guaranteed within the range of 0<δ≤l max During the feeding process, the value of θ2 is used to determine whether to rotate. From the above, the relationship formula about θ2 can be obtained:

[0064]

[0065] It should be noted that during the bolt feeding process, θ1 and θ2 can be measured by the angle sensor. Within the range specified by δ, according to different θ l The value of θ2 is calculated and monitored. Once it reaches the target value range, the socket rotates the bolt to align the hexagon of the nut with the inner hexagon of the socket.

[0066] S2: Compliant control based on force sensors.

[0067] Furthermore, in order to reduce the damage to the nut during the rotation process, this paper adopts a compliant control method to adjust the position and posture of the manipulator. First, the force analysis of the nut that can already rotate is carried out. Since the force is mutual, the force of the sleeve is the reaction force of the nut.

[0068] Furthermore, the geometric compatibility equation is:

[0069]

[0070] Furthermore, the force balance equation is:

[0071]

[0072] Going further, the physical equation is:

[0073]

[0074] Furthermore, we can get:

[0075]

[0076] in, u-u0=Rrl p (θ-θ0)-u0, the radius of the sleeve is R, the radius of the bolt is r, u is the compliance center, C is the translation error along the X-axis, x is the translation error of the shaft end center along the X-axis, and θ is the angular error of the shaft axis relative to the Z-axis.

[0077] Furthermore, when the bolt enters the sleeve, if the deflection angle is too large and exceeds its flexibility range, the bolt alignment work cannot be completed. Figure 3 As shown, the critical case of the flexibility angle is discussed.

[0078] 2(Rr) / tanθ e =2rtanθ e

[0079] The solution is:

[0080]

[0081] l max =tanθ e *2r

[0082] Among them, κ is the radius of the sleeve; r is the radius of the nut; l is the depth of the sleeve entering the nut.

[0083] Furthermore, a three-dimensional force sensor is installed at the end of the robot arm. The force sensor is mainly responsible for adjusting the position error, while the attitude error is adjusted by passive compliance. However, in some active compliance occasions, bolt assembly is performed. Since the attitude of the bolt is basically unchanged, it is feasible to use only a three-dimensional force sensor for active compliance assembly when the sleeve attitude is known.

[0084] Furthermore, during the assembly and alignment process, the position adjustment bolt is not subjected to force in the x-axis and y-axis directions, and only has a feed force F in the z-axis. r , so the expected force value is F0 = [0 0F r ] T , if the force sensor measures a three-dimensional force F m =[F x F y F z ] T ,According to the impedance control algorithm, the control algorithm for adjusting the position is:

[0085]

[0086] Furthermore, the posture adjustment assumes that the posture of the bolt is:

[0087]

[0088] Furthermore, assuming that the bolt is used as the reference target coordinate system {L}, the unit vector of its Z axis in the base coordinate system is

[0089] Furthermore, in {B}:

[0090]

[0091] Furthermore, it is known that the current robot arm end posture is:

[0092]

[0093] Furthermore, the unit vector of the Z axis in the base coordinate system {B} is:

[0094]

[0095] Furthermore, during the bolt alignment process, the axis of the sleeve at the end of the robot manipulator must be constantly adjusted so that its Z axis coincides with the Z axis of the coordinate system with the bolt as the reference target. e When , the posture should be actively adjusted, and the control algorithm for posture adjustment is:

[0096]

[0097] In summary, the compliant control algorithm for bolt alignment is: when |θ|≤θ e hour:

[0098]

[0099] When |θ|>θ e hour:

[0100]

[0101] S3: Analyze the effect of the load on the hexagon socket at the end of the bolt tightening operation on the torque.

[0102] Furthermore, in the process of transmitting torque, due to the existence of the deviation angle, the hexagon socket and the cross coupling will generate a pair of lateral loads of equal magnitude and opposite direction. In order to verify whether it has an impact on the final experimental results, this paper makes the following calculations. During the rotation process, assuming that the motor rotates to drive the rotating shaft, that is, the driving shaft I rotates at an angular velocity of ω1, then the angular velocity of the driven shaft II is ω2. The relationship between ω1 and ω2 is derived as follows:

[0103] ω2=[cosα / (1-sin 2 αcos 2 ψ1)]ω1

[0104] Among them, ψ1 is the rotation angle of axis I; α is the angle between axis I and axis II. The friction loss of the cross hinge transmission is small and can be ignored, and the efficiency is considered to be 1. If the torque acting on the driving shaft is M1 and the transmitted torque of the driven shaft is M2, then:

[0105] M1ω1=M2ω2

[0106]

[0107] Furthermore, the circumferential force generated by M2 on the driven shaft II is:

[0108] P2=M2 / 2R

[0109] Where R is the radius of the hexagon socket.

[0110] Furthermore, due to the existence of the interaxial angle α, when transmitting torque, the rotating shaft and the hexagon socket are also subjected to an additional bending moment MU1 、M U2 ,At different positions, the rotating shaft, the hexagon socket and the cross coupling will generate a pair of lateral loads of equal size and opposite direction.

[0111] Furthermore, taking ψ1=0 as an example, the torque is M1, and the additional bending moment M U1 =0, at this time the torque of the driven shaft II is M2, and the additional bending moment generated is M U2 =M1sinα.

[0112] Furthermore, M U2 The driven shaft 2 generates a periodically changing lateral load F1:

[0113] F1=M1sinα / L

[0114] Where L is the distance from the cross coupling to the sleeve support.

[0115] S4: Get the bolt tightening torque control strategy and use the torque coefficient control method.

[0116] Furthermore, the commonly used bolt tightening control methods currently include "torque control method, torque angle control method, yield point control method, bolt elongation control method" and the like.

[0117] Furthermore, the torque control method is the most initial and simplest control method. It is based on the fact that the axial clamping force F is proportional to the tightening torque T during threaded connection. The formula T = K * F is used to represent the κ, which is the torque coefficient. During assembly, the tightening torque specified by the process department is used to tighten the nut to the specified torque range at one time with a tool, which indirectly controls the axial preload. Since the torque coefficient κ will fluctuate due to the influence of the screw hole itself and temperature, the tightening torque of the bolt has a range value. If the tightening torque is between the minimum torque and the maximum torque, it is considered to be tightened. The advantages of this control method are low cost and easy detection of tightening quality. However, the disadvantage of using the torque control method is that the friction force of the thread pair is uncertain, so the consistency of the preload cannot be guaranteed.

[0118] Furthermore, the torque angle control method is a control method that first tightens the bolt to a large torque, and then starts from there to tighten it to a specified angle. This method is based on a certain angle, which is a certain axial elongation of the bolt and compression of the connector, so the influence of friction resistance on the axial clamping force does not exist. Therefore, the nut of the bolt should be screwed to a position close to the gasket at the beginning, so as to avoid some surface unevenness factors, and the axial clamping force required later is all generated by the angle. The core point of the torque control method is to determine when to start the angle control. Once this problem is solved, the accuracy of bolt tightening will be higher. Therefore, the advantage of using the torque angle control method is that the accuracy of the preload can be higher. But its disadvantage is that the angle control is difficult to be accurate, which will cause certain errors.

[0119] Furthermore, the yield point control method uses the concept of torque-angle increment ratio. When the nut is attached to the gasket, the torque is linearly related to the angle. When the ratio continues to decline, the highest value point is the yield point of the bolt. The advantage of the yield point control method is that the preload accuracy is very high and the quality of the clamping force can be guaranteed. The disadvantage is that the range of the bolt yield point needs to be determined by a large number of experiments using computers, and when the yield point is reached, the tightening equipment is controlled to stop tightening the bolt to ensure the tightening accuracy. This places high demands on the material, structure and heat treatment of the bolt.

[0120] Furthermore, the bolt elongation control method means that the natural length of the bolt needs to be measured during the tightening process. Since the elongation of the bolt is only related to the preload, the bolt tightening work can be completed as long as there is a precise instrument to measure the elongation of the bolt. The advantage of this method is that the preload accuracy is very high, and it can be used to determine whether the screw is deformed based on the elongation for monitoring. However, the disadvantage is that the equipment is expensive.

[0121] Furthermore, the specific control principle is as follows: Considering the prior conditions such as overcoming the thread resistance torque of the thread pair, the friction torque of the head support surface, the total stiffness of the system between the thread pair and the connected space, and combining multiple experiments, the slope of the torque change over time and the stiffness of the system are obtained, and the two are analyzed to obtain the control torque corresponding to the corresponding preload. The obtained control torque is then converted into a specific current and put into the program as a constraint. When the current of the motor reaches the set current, the motor is automatically stopped to achieve intelligent control. According to classical theory, the tightening torque τ is used to overcome the thread resistance torque τ1 of the thread pair, the friction torque T2 of the head support surface, and the friction resistance τ of the gasket. s The obtained preload-torque calculation formula is as follows:

[0122] T=T1+T2+T3=KdF

[0123] Furthermore, the preload force F is linearly related to the nut rotation angle θ. At this time, the preload force on the connected part is:

[0124]

[0125] Among them, C s is the total stiffness of the thread pair and the connected system, and P is the thread pitch. t =dT / dt, we can get:

[0126]

[0127] Furthermore, the relationship between torque and preload can be obtained as follows:

[0128]

[0129] Among them, K t and C s There are two variables, which are also the core of the torque coefficient, C s =F / δ, F is the force applied to the bolt, and δ is the internal deformation of the bolt.

[0130] It should be noted that if we can obtain the slope of the torque changing with time and the stiffness of the system, we can calculate the control torque corresponding to the corresponding preload. t It includes the relationship with the friction coefficient, so different control torques can be obtained for bolts of different masses, ensuring the consistency of preload force when assembling bolts.

[0131] Example 2, reference Figure 5-Figure 8 , which is an embodiment of the present invention, provides a control method based on bolt tightening operation. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0132] When analyzing the effect of the load on the torque of the hexagon socket at the end of the bolt tightening operation, the interaxial angle α has no effect on the circumferential force of the hexagon socket, but affects the size of the lateral load caused by the additional bending moment, and is positively correlated with the lateral load. Assuming that the angle of the socket away from the nut is small during the tightening of the nut, assuming α = 10°, R = 22nm, L = 28mm, the calculated lateral load is relatively small relative to the circumferential force and can be ignored. Therefore, during rotation, different circumferential forces can be calculated according to different ψ1 and α. At this moment, the circumferential force is the friction force overcome by the socket relative to the nut, which is the minimum torque that the motor needs to feed.

[0133] During the process of tightening the bolt, the image is nonlinear before the nut and the gasket are close together, and then it becomes a linear image after they are close together. Finally, the control torque is reached and the motor stops running. When the linear stage is reached, the slope κ of the torque and time can be calculated.t However, in actual measurement, there is a slight fluctuation in this torque, so this paper adopts the least squares method to fit it, such as Figure 5 The corresponding preload curve is shown in Figure 7 As shown, the slope is used as the slope of torque changing with time to reduce the error. At the same time, κ can also be calculated t The curve changes with time, and it can be seen that it gradually stabilizes as time increases, such as Figure 6 shown.

[0134] In this paper, the motor moves at a constant speed, and a force sensor is placed on the bolt head. When the nut contacts the gasket to generate preload, the internal deformation of the bolt is much smaller than the deformation of the force sensor. Therefore, this paper uses the stiffness of the force sensor as the stiffness of the system and puts it into the above formula for calculation. At the same time, the curve of the preload changing with time can also be detected, such as Figure 8 shown.

[0135] Embodiment 3 is an embodiment of the present invention, which provides a control system based on bolt tightening operation, including:

[0136] The data collection module is responsible for collecting various data generated during the operation process.

[0137] The compliance control module implements compliance control based on force sensors to ensure that the bolts are aligned and rotated during tightening.

[0138] The torque analysis module analyzes the effect of the load on the hexagon socket on the torque during the bolt tightening operation.

[0139] The torque control module realizes intelligent control of bolt tightening based on the torque coefficient control method.

[0140] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0141] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0142] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering, or processing in another suitable manner as necessary, and then stored in a computer memory.

[0143] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc. It should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not limited. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

[0144] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A control method based on bolt tightening operation, characterized in that: include: Collect data and calculate the nut rotation; Compliant control based on force sensors; Analyze the effect of load on torque borne by the hexagon socket at the end of bolt tightening operation; The bolt tightening torque control strategy is obtained and controlled using the torque coefficient control method.

2. The control method based on bolt tightening operation according to claim 1, characterized in that: The calculation of the nut rotation includes calculating the angle of the nut rotation and the angle of the nut creeping. There are three cases of the angle of the sleeve relative to the bolt. The first case is that the sleeve has no deviation relative to the bolt, and then it is directly fed and rotated; the second case is that the sleeve is relative to the bolt θ (|θ|≤θ max ) deviation, the feed amount should be monitored before rotation; the third is that the sleeve has too large deviation relative to the bolt (|θ|>θ max ), continue adjusting the robot arm alignment.

3. The control method based on bolt tightening operation according to claim 2, characterized in that: The flexible control based on the force sensor includes: performing a force analysis on the nut that is already capable of rotating, discussing the critical situation of the flexible angle, calculating the flexible angle during the process of the bolt entering the sleeve, and completing the alignment of the bolt.

4. The control method based on bolt tightening operation according to claim 3, characterized in that: The compliance control based on the force sensor also includes that a three-dimensional force sensor is installed at the end of the robot arm, and the force sensor is responsible for adjusting the position error, while the posture error is adjusted by passive compliance; in the case of active compliance, the bolt is assembled, and since the posture of the bolt is basically unchanged, when the sleeve posture is known, only the three-dimensional force sensor is used for active compliance assembly; During the process of assembling and aligning the position adjustment bolts, there is no force on the axis and the axial direction, only the axis has a feed force, the three-dimensional force is measured by the force sensor, and the control algorithm for adjusting the position is obtained according to the impedance control algorithm; Perform posture adjustment, and obtain the coordinates of the unit vector of the z-axis in the base coordinate system based on the known current posture of the robot's manipulator end; in the process of bolt alignment, continuously adjust the axis of the sleeve at the end of the robot manipulator so that its z-axis coincides with the z-axis of the coordinate system with a bolt as the reference target, obtain the posture adjustment control algorithm, and actively adjust the posture.

5. The control method based on bolt tightening operation according to claim 4, characterized in that: The bolt tightening torque control strategy includes taking into account the thread resistance torque of the thread pair, the friction torque of the head bearing surface, and the total stiffness of the system between the thread pair and the connected space as prior conditions; By combining multiple experiments, we obtain the slope of the torque changing with time and the stiffness of the system. We analyze the two and get the control torque corresponding to the corresponding preload. Then we convert the obtained control torque into a specific current and put it into the program as a constraint. When the running current of the motor reaches the set current, the motor stops automatically to realize intelligent control.

6. The control method based on bolt tightening operation according to claim 5, characterized in that: The analysis of the influence of the load on the hexagon socket at the end of the bolt tightening operation on the torque includes that there is a deviation angle in the process of transmitting torque, and the hexagon socket and the cross coupling will generate a pair of lateral loads of equal size and opposite direction; and the lateral load is calculated and analyzed to determine whether there is an influence; During the rotation process, it is assumed that the motor rotates to drive the rotating shaft to rotate, that is, the active shaft I rotates at an angular velocity ω i Rotation, the angular velocity of the driven shaft II is ω2; the relationship between ω1 and ω2 is derived as follows: ω2=[cosα / (1-sin 2 acos 2 ψ1)]ω1 Among them, ψ i represents the rotation angle of axis I; α represents the angle between axis I and axis II; Ignore the friction loss of the cross hinge transmission and assume the efficiency is 1; if the torque acting on the driving shaft is M1 and the transmitted torque of the driven shaft is M2, the formula is expressed as: M1ω1=M2ω2 The circumferential force generated by M2 on the driven shaft II is: P2=M2 / 2R Wherein, R represents the radius of the hexagon socket.

7. The control method based on bolt tightening operation according to claim 6, characterized in that: The torque coefficient control method includes: according to the classical theory, the tightening torque τ is the thread resistance torque τ that overcomes the thread pair i The friction torque T2 of the head bearing surface and the friction resistance T3 of the gasket are obtained, and the preload-torque calculation formula is expressed as: T=T1+T2+T3=KdF The preload force F is linearly related to the nut rotation angle θ. At this time, the preload force on the connected part is: Among them, C s represents the total stiffness of the thread pair and the connected system, P represents the thread pitch, and K t =dT / dt, we can get: The relationship between torque and preload can be obtained as follows: Among them, K t and C ζ The core variable representing the torque coefficient, C s =F / δ, where F represents the force on the bolt and δ represents the internal deformation of the bolt. If the slope of the torque changing with time and the stiffness of the system are obtained, the control torque corresponding to the corresponding preload force is obtained; K t Including the relationship with the friction coefficient, different control torques are obtained for bolts of different masses.

8. A system using the control method based on bolt tightening operation according to any one of claims 1 to 7, characterized in that: The data collection module is responsible for collecting various data generated during the operation; The compliance control module implements compliance control based on force sensors to ensure that the bolts are aligned and rotated during tightening; Torque analysis module, which analyzes the influence of load on the hexagon socket on torque during bolt tightening operation; The torque control module realizes intelligent control of bolt tightening based on the torque coefficient control method.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the control method based on the bolt tightening work according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the control method based on the bolt tightening work according to any one of claims 1 to 7 are implemented.

Images