A robot seam grinding system and method based on contact sensing

Abstract

The application discloses a robot welding seam polishing system based on contact sensing, and relates to the field of welding seam polishing.The robot welding seam polishing system comprises an EHA constant force floating end effector, an EHA constant force floating end control cabinet, an industrial robot, an industrial computer and a workbench.The industrial computer sends instructions to the industrial robot control cabinet to control the movement of the industrial robot, and the EHA constant force floating end effector polishes the welding seam of the workpiece under the control of the industrial robot.The EHA constant force floating end effector is provided with a force sensor, a displacement sensor, a polishing tool and an end contact wheel.The application further discloses a polishing method using the above welding seam polishing system.The surface topography is obtained through contact sensing, the polishing removal height can be monitored in real time in the polishing process, no additional visual sensor is needed, self-adaptive process parameter optimization can be realized, and the application has the advantages of high precision, low cost and high efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of weld polishing, in particular to a robot weld polishing system and method based on contact sensing. BACKGROUND

[0002] Weld polishing has a large number of applications in the shipbuilding, automobile, aviation, aerospace and other industries. At present, most of the weld polishing is still completed by manual work. Due to the poor polishing environment, unstable quality of manual polishing, rising labor costs and other reasons, it is urgent to realize robot polishing of welds to replace manual work.

[0003] Using traditional teaching methods has certain feasibility for simple welds, but for complex welds with spatial curved surfaces, manual teaching cannot be applied on a large scale due to its operation errors and long time consumption. In addition, using pure force control polishing method, it is difficult to polish flat due to the unevenness of the weld, and there are often over-polishing or under-polishing quality problems, so that position control mode is needed, similar to machine tool machining method, to realize flat polishing of welds, but it is difficult for machine tools to realize flexible and intelligent processing similar to robots. The surface morphology of the weld is a non-structured environment, and the pure position mode needs to increase external vision sensing for accurate measurement of the weld surface position, and then slice the road milling and cutting. Therefore, force control and position control mode are needed to mill flat the unevenness in position mode, and then polish in force control mode combined with parameter library to realize weld polishing.

[0004] At present, the existing robot automatic weld polishing basically is based on laser vision guidance or 3D vision guidance. The weld area is photographed by a laser camera or a 3D camera, the point cloud of the weld area is obtained, the point cloud related algorithm is used to process the weld to segment, and then the polishing trajectory is planned to obtain the polishing trajectory. However, this method cannot realize high-precision weld polishing due to the problems of expensive laser camera or 3D camera, poor imaging effect caused by complex polishing site environment, hand-eye calibration, and self-positioning error of the robot. It is these problems that greatly limit the actual use of robot automatic polishing in the factory.

[0005] Therefore, the skilled in the art is committed to developing a robot weld polishing system and method based on contact sensing, which does not need additional vision sensors and obtains high-precision weld polishing effect at low cost. The weld surface topography is obtained by using an electro-hydraulic actuator EHA constant force floating end effector combined with an end contact wheel, and then a trajectory planning algorithm is used to generate a weld polishing trajectory. SUMMARY

[0006] In view of the above defects of the prior art, the technical problems to be solved by the present application are high cost of weld area shooting, poor imaging effect caused by complex polishing site, poor stability, high polishing cost, and poor precision, etc.

[0007] To achieve the above object, the present application provides a robot weld polishing system based on contact sensing, comprising an EHA constant force floating end effector, an EHA constant force floating end control cabinet, an industrial robot, an industrial robot control cabinet, an industrial computer, and a workbench, wherein the EHA constant force floating end effector is connected to the end of the industrial robot and plays a role in polishing the weld, the industrial computer sends instructions to the industrial robot control cabinet to control the movement of the industrial robot, the workpiece is placed on the workbench, and the EHA constant force floating end effector polishes the weld of the workpiece under the control of the industrial robot; the EHA constant force floating end effector is a constant force floating actuator driven by EHA hydraulic pressure, and is provided with a force sensor, a displacement sensor, a polishing tool, and an end contact wheel; the polishing tool and the end contact wheel are installed at the end of the EHA constant force floating end effector in a mutually replaceable manner, the end contact wheel is used when initially measuring the morphology of both sides of the weld, and the polishing tool is replaced during the polishing process.

[0008] Further, the EHA constant force floating end effector comprises a main shaft motor, an EHA hydraulic servo motor, a force sensor, a connecting rod, a displacement sensor, a rotating main shaft, a polishing tool, an end contact wheel, and a floating part.

[0009] Further, a constant output force is first set, a constant force closed-loop control part is composed of the force sensor and the EHA hydraulic servo motor to ensure constant output force, the connecting rod transmits the constant force drive to the floating part, the displacement sensor collects the displacement data of the floating part in real time, the floating part is connected to the rotating main shaft, and the rotating main shaft is driven to rotate by the main shaft motor; the EHA hydraulic servo motor is connected to the floating part through the connecting rod, and the position of the floating part is adjusted through closed-loop control under the feedback of the force sensor to realize constant force output.

[0010] Further, the topography detection method based on contact sensing is realized by the cooperation of the force sensor, displacement sensor and the end contact wheel; first, the constant output force is set by the EHA constant force floating end control cabinet, and the constant output force is guaranteed by the force sensor and the EHA hydraulic servo motor, and the end contact wheel rolls in contact with the surface of the weld workpiece; then the displacement sensor is used to collect the displacement information of the floating part, and then the surface topography information of the weld is converted; in the grinding process, the end contact wheel is replaced by the grinding tool to contact the surface of the grinding area to realize real-time monitoring of the removal height of the weld.

[0011] Further, the end contact wheel is a metal roller with a radius of 5mm, and before topography detection, the initial position of the floating part is set to zero, the EHA servo hydraulic motor is disabled, and TCP calibration is performed at zero, and the TCP is calibrated at the end of the end contact wheel.

[0012] The application also provides a robot weld grinding method based on contact sensing, using the above-mentioned robot weld grinding system based on contact sensing, the method comprising the following steps:

[0013] Step 1, calibrate the TCP of the industrial robot and the end contact wheel respectively;

[0014] Step 2, measure the topography of the two sides of the weld;

[0015] Step 3, calculate the midpoint of the topography measurement points;

[0016] Step 4, generate a grinding track according to the target preview;

[0017] Step 5, perform grinding work;

[0018] Step 6, optimize the grinding parameters in real time;

[0019] Step 7, determine whether the grinding work is completed, if not, jump to step 5, if completed, end the grinding.

[0020] Further, the step 1 specifically calibrates the TCP of the industrial robot at the grinding position of the grinding tool, and calibrates the TCP of the end contact wheel at the end of the end contact wheel; the step 2 is to measure the topography of the two sides of the weld by the topography detection method based on contact sensing, and obtain two groups of position points L1[P 11 ,P 12 ,P 13 ,P 14 ,…,P 1n ] and L2[P 21 ,P 22 ,P 23 ,P24 ..., P 2n The midpoint of the two measuring base surfaces is calculated by step 3, and in order to ensure the accuracy of the center point track, a cubic B-spline difference method is used to interpolate the two groups of position points L1 and L2 in step 3, and the interpolated curve track point is solved, and the midpoint P is solved from the interpolated track curve m That is, the polishing track.

[0021] Further, the polishing track position point composed of the midpoint obtained in step 3 in the polishing track processing step 4 further includes the normal direction of polishing, and the two together constitute the polishing track file.

[0022] Further, in the polishing process, by calculating the change Δd f The polishing height that needs to be removed at this point can be obtained.

[0023] Further, by dividing the weld reinforcement into two parts to remove and realize adaptive optimization of process parameters, after detecting the weld height, the first part removal height and the second part removal height are calculated by the target reinforcement and the weld height, the first part removal height is the uneven part of the weld, and the second part removal height is the difference between the weld height and the first part; for the first part removal height, generate polishing parameters through the process parameter library, adjust the polishing process parameters to remove the uneven part to be flat; after each polishing, the remaining height after polishing is monitored in real time, and the comparison between the monitored removal height and the target removal height of this polishing is made to adjust the polishing process parameters; for the second part removal height, generate appropriate polishing parameters through the process parameter library, if the second part removal height is within the range of the process parameter library, the second part removal height can be removed by one polishing, if the second part removal height exceeds the maximum removal amount that can be removed by the polishing tool once, the second part removal height is divided into multiple removals;

[0024] The specific calculation method is as follows:

[0025]

[0026] In the formula, h r2 represents the height removed each time in the second polishing, h r2 The process parameter library is queried to obtain the polishing parameters, h2 represents the second part removal height, h gmax represents the maximum removal amount that can be removed by the polishing tool once; set the error value σ of the polishing reinforcement, judge whether the polishing operation is completed according to whether the monitored reinforcement is within the range of δ±σ, if not, execute the polishing operation again according to the adjusted polishing process parameters until the polishing operation is completed.

[0027] In a preferred embodiment of the present application, the EHA constant force floating end effector can realize the measurement of the surface topography by connecting the polishing tool or the end contact wheel, but due to the initial polishing track being obtained according to the topography on both sides of the weld, the initial weld topography detection is performed by the end contact wheel due to the interference problem. During the polishing process, the removal height in the polishing depth direction can also be monitored in real time through the TCP position of the polishing tool. During the polishing process, by calculating the change Δd of the displacement sensor relative to the initial zero point f , the polishing height that needs to be removed at this point can be obtained. The polishing tool is a louver or a diamond wheel, etc.

[0028] Compared with the prior art, the present application has the following beneficial technical effects:

[0029] 1. The present application uses a contact measurement method based on constant force control, and the surface topography is obtained by contact sensing, which can detect the actual contact position of the robot in real time, and can monitor the polishing removal height in real time during the polishing process, so as to realize high-precision surface measurement of the weld surface. The function of the end contact wheel is to facilitate the detection of the weld surface topography. Due to the high roughness and large difference of the weld surface, the traditional probe type topography detection structure is prone to collision and fracture, etc., and the contact wheel form can effectively roll on the weld workpiece surface.

[0030] 2. The present application uses automatic weld polishing without manual teaching, does not need laser sensors and 3D cameras, and the weld polishing track generation method based on contact sensing can effectively generate point information and robot pose of weld polishing based on the surfaces on both sides of the weld, so as to realize low-cost automatic polishing of the robot.

[0031] 3. In view of the problem that the traditional method cannot adaptively adjust the process parameters, the present application realizes adaptive process parameter optimization, and the process parameter adjustment and adaptive process parameter optimization according to the weld detection height can realize the surface flatness after weld polishing. After optimizing the parameters, the surface after weld polishing is flat, and the polishing efficiency is higher.

[0032] The concept, specific structure and technical effects of the present application will be further described below with reference to the accompanying drawings, so as to fully understand the purpose, features and effects of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a schematic diagram of a robot weld polishing system based on contact sensing of a preferred embodiment of the present application;

[0034] Figure 2 is a schematic diagram of the internal structure of an EHA constant force floating end effector of a preferred embodiment of the present application;

[0035] Figure 3 Figure 1 is a working principle diagram of an EHA constant force floating end effector of a preferred embodiment of the present application;

[0036] Figure 4 Figure 2 is a topography detection principle diagram based on contact sensing of a preferred embodiment of the present application;

[0037] Figure 5 Figure 3 is a flow chart of a welding seam polishing method based on contact sensing of a preferred embodiment of the present application;

[0038] Figure 6 Figure 4 is a welding seam polishing topography measurement schematic diagram of a preferred embodiment of the present application;

[0039] Figure 7 Figure 5 is a polishing trajectory and polishing direction generation principle schematic diagram of a preferred embodiment of the present application;

[0040] Figure 8 Figure 6 is a polishing depth direction removal height real-time monitoring principle diagram of a preferred embodiment of the present application;

[0041] Figure 9 Figure 7 is a flow chart of a high-efficiency polishing method of a preferred embodiment of the present application for adaptive optimization of process parameters;

[0042] Figure 10 Figure 8 is a welding seam polishing sub-removal schematic diagram of a preferred embodiment of the present application for adaptive optimization of process parameters of a high-efficiency polishing method;

[0043] Figure 1 is a working principle diagram of an EHA constant force floating end effector of a preferred embodiment of the present application; 1-EHA constant force floating end effector; 2-industrial robot; 3-industrial robot control cabinet; 4-industrial computer; 5-workpiece; 6-EHA constant force floating end control cabinet; 7-end contact wheel; 8-polishing tool; 9-EHA hydraulic servo motor; 10-force sensor; 11-connecting rod; 12-main shaft motor; 13-floating part; 14-displacement sensor; 15-rotary main shaft; 16-welding seam; 17-substrate; 18-welding seam measurement area. DETAILED DESCRIPTION

[0044] The preferred embodiments of the present application are described below with reference to the accompanying drawings, so that the technical content of the present application is more clear and easy to understand. The present application can be embodied in many different forms, and the protection scope of the present application is not limited to the embodiments described herein.

[0045] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0046] like Figure 1 The diagram shows a tactile sensing-based robotic weld grinding system. It includes an EHA constant-force floating end effector 1, an EHA constant-force floating end effector control cabinet 6, an industrial robot 2, an industrial robot control cabinet 3, an industrial computer 4, and a worktable. The end effector contact wheel 7 and grinding tool 8 are replaceable and mounted on the end of the EHA constant-force floating end effector 1. Unlike pneumatic end effectors typically used in robotic grinding, the EHA constant-force floating end effector 1 is a constant-force floating actuator driven by EHA hydraulics. Its internal structure is shown below. Figure 2 As shown. The main structure includes a spindle motor 12, an EHA hydraulic servo motor 9, a force sensor 10, a connecting rod 11, a displacement sensor 14, a rotary spindle 15, an end contact wheel 7, a grinding tool 8, and a floating part 13. Its working principle is as follows: Figure 3 As shown. First, a constant output force is set. A constant force closed-loop control system, consisting of force sensor 10 and EHA hydraulic servo motor 9, ensures a constant output force. The constant force drive is transmitted to the floating part 13 via connecting rod 11. Displacement sensor 14 can collect the displacement data of the floating part 13 in real time. The floating part 13 is connected to the rotating spindle 15, which is driven to rotate by spindle motor 12. EHA hydraulic servo motor 9 is connected to the floating part 13 via connecting rod 11. Under the feedback of force sensor 10, the position of the floating part 13 is adjusted through closed-loop control to achieve constant force output.

[0047] A schematic diagram of the principle of the contact sensing-based topography detection method is shown below. Figure 4 The end-sensing wheel 7 is a metal roller with a radius of 5mm. The initial position of the floating part 13 is set to zero. The EHA servo hydraulic motor is disabled, and TCP calibration is performed at the zero position, with the TCP calibration set at the tip of the CNC probe.

[0048] During morphology measurement, a constant output force is set at the end, and the output position of displacement sensor 14 is collected to achieve the end-effector morphology detection function. For example... Figure 4 As shown, the actual contact position of the end contact wheel is P[X, Y, Z], while the calibrated TCP position is P. tcp [X tcp Y tcp Z tcp A tcp B tcp C tcp] at this time, the displacement sensor 14 relative to the initial zero change is Δd f , the position change of the floating part in the world coordinate system is written as [Δx f Δy f Δz f ]Then there is a relationship as follows:

[0049]

[0050] Written as the coordinate form under the robot world coordinate system is as follows:

[0051]

[0052] According to the principle of robotics, the following relationship can be obtained: (for convenience, where α is A tcp , β is B tcp , γ is C tcp )

[0053]

[0054] Solving the matrix, the following relationship can be obtained:

[0055]

[0056] So far, the actual contact position P of the robot end TCP has been solved. The measurement point composed by calculating the actual contact position can realize the surface topography measurement.

[0057] A welding seam polishing method based on contact sensing, the polishing method mainly includes welding seam topography measurement and trajectory planning part. The polishing process is shown in Figure 5 , including the following steps:

[0058] Step 1, calibrate the TCP of the industrial robot and the end contact wheel respectively;

[0059] Step 2, measure the topography of the two sides of the welding seam;

[0060] Step 3, calculate the midpoint of the topography measurement point;

[0061] Step 4, generate polishing trajectory according to target preview;

[0062] Step 5, polishing work;

[0063] Step 6, real-time optimization of polishing parameters;

[0064] Step 7, determine whether the polishing work is completed, if not, jump to step 5, if completed, end polishing.

[0065] Weld grinding is usually to remove the weld to the same height as the two sides of the base surface, so it is necessary to measure the profile of the two sides of the base surface first. The detection schematic diagram is shown in Figure 6 .

[0066] The profile measurement area shown in the end contact wheel pair Figure 6 is measured, the TCP of the industrial robot is calibrated at the grinding position of the grinding tool, and the TCP of the end contact wheel is calibrated at the end of the end contact wheel. The profile of the two sides of the weld is measured by the contact sensing based profile measurement principle described above. After measuring on both sides, two groups of position points L1[P 11 , P 12 , P 13 , P 14 , …, P 1n ] and L2[P 21 , P 22 , P 23 , P 24 , …, P 2n ] are obtained. The grinding track is composed of the midpoint of the two measured base surfaces. However, since the points generated by the measurement are not uniform, directly solving the midpoint will affect the accuracy of the center point track. Here, the cubic B-spline interpolation method is used to interpolate the two groups of position points L1 and L2. The cubic B-spline interpolation method is as follows:

[0067] The curve of cubic B-spline interpolation is defined as follows:

[0068]

[0069] In the formula, C(u) is the B-spline interpolation function, L is the point measured by the two sides of the base surface, i.e. the control node of B-spline interpolation, N i,3 (u) is the basis function. The node vector U is defined as follows:

[0070] U = {0, 0, 0, 0, u4, u5, …, u n , 1, 1, 1, 1} (6)

[0071] The cubic B-spline interpolation curve can be calculated by giving the control points and the node vector. The interpolation points of the node vector can be expressed as follows:

[0072] u i+3 = u i+2 + |Δm i-1 |, i = 1, 2, 3, …, n-3 (7)

[0073]

[0074] In the formula, m i (i = 0, 1, …, n-2), wherein the basis function Ni,3 (u) can be defined as follows:

[0075]

[0076] In the above formula, the fourth column means that when the numerator or denominator is 0, the fraction is 0.

[0077] Substituting equation (8) into equation (5), we can obtain the cubic B-spline interpolation formula and the key contact point m. i The relationships (i = 0, 1, ..., n-2) are as follows:

[0078]

[0079] Equation (11) can be rewritten in the following matrix form:

[0080]

[0081] As shown in equation (11), solving this cubic B-spline interpolation equation involves n+1 control points and n-1 equations. The boundary conditions, namely that the first and last control points coincide with the interpolation points, can be expressed as follows:

[0082]

[0083] The interpolated curve trajectory points can be solved using equations (11) and (12). By calculating the node vectors at equal intervals, the interpolated trajectory curves C1 and C2 of the measurement points on both base surfaces can be obtained. Then, the midpoint P can be solved from the interpolated trajectory curve. m This refers to the polishing path, such as... Figure 7 As shown in (2), the calculation method is as follows:

[0084]

[0085] For weld grinding, in addition to obtaining the grinding trajectory location points, it is also necessary to calculate the normal direction of the grinding. A schematic diagram of the grinding direction is shown below. Figure 7 (3) shows the calculation method for the grinding normal direction as follows:

[0086] To calculate the direction of the normal vector for polishing, a plane of the polishing target must first be established. For example... Figure 7 As shown, point sets C1(u) and C2(u) can be obtained by performing cubic B-spline interpolation on the weld substrate positions detected on both sides of the weld. Then, from point C1(u) i C2(u) i It can generate position vectors. The calculation formula is as follows:

[0087]

[0088] For the calculation of , the first derivative of the cubic B-spline curve can be used, and the calculation formula is as follows:

[0089]

[0090] Then the calculation of is as follows:

[0091]

[0092] For the polishing trajectory C that needs to reserve the excess height δ δ The generation method is as follows:

[0093]

[0094] After the polishing trajectory points and the polishing normal vector are generated, they are arranged in the data format of [X, Y, Z, A, B, C] to generate a polishing trajectory file. During the polishing process, the removal height in the polishing depth direction can also be monitored in real time through the TCP position of the polishing tool, and the principle is as shown in Figure 8 .

[0095] During the polishing process, by calculating the change Δd f of the displacement sensor relative to the initial zero point, the polishing height that still needs to be removed at the point can be obtained.

[0096] On this basis, an adaptive optimization process parameter welding seam efficient polishing method is proposed, which realizes adaptive optimization process parameter efficient polishing by dividing the welding seam excess height into two parts for removal. The process is as shown in Figure 9 , and the schematic diagram of welding seam polishing division removal is as shown in Figure 10 .

[0097] After detecting the welding seam height, the first part removal height and the second part removal height are calculated by the target excess height and the welding seam height. The first part removal height is the uneven part of the welding seam, and the second part removal height is the difference between the welding seam height and the first part. For the first part removal height, the polishing parameters are generated through the process parameter library, and the polishing process parameters are adjusted to remove the uneven part. After each polishing, the excess height after polishing is monitored in real time, and the removal height and the target removal height of this polishing are compared to adjust the polishing process parameters. For the second part removal height, appropriate polishing parameters are generated through the process parameter library. If the second part removal height is within the range of the process parameter library, the second part removal height can be removed by one polishing. If the second part removal height exceeds the maximum removal amount that can be removed by the polishing tool at one time, the second part removal height is divided into multiple removals. The specific calculation method is as follows:

[0098]

[0099] In the formula, h r2 represents the height removed each time the second polishing is performed, and h r2 The polishing parameters are obtained by querying a process parameter library, h2 represents the height removed in the second part, and h gmax represents the maximum removal amount that can be removed by the polishing tool once;

[0100] An error value σ of the remaining height allowed by polishing is set, and whether the polishing operation is completed is determined according to whether the monitored remaining height is within the range of δ±σ. If the polishing operation is not completed, the polishing operation is performed again according to the adjusted polishing process parameters until the polishing operation is completed. The polishing target remaining height is achieved by removing the weld in two parts.

[0101] The welding seam polishing method based on contact force position sensing provided by the present application does not require an additional visual sensor, and high-precision welding seam polishing effects are obtained at low cost. The method for obtaining the welding seam topography and performing polishing track planning based on contact force position sensing obtains the welding seam surface topography through the constant force floating end effector of the electro-hydraulic actuator EHA combined with the end contact wheel, and then generates the welding seam polishing track through the track planning algorithm. The present application also provides a robot absolute positioning correction method based on tactile servo, which corrects the robot position through tactile servo to improve the positioning accuracy of the robot, and realizes high-precision welding seam polishing.

[0102] The preferred embodiments of the present application are described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and changes to the present application without creative labor based on the concept of the present application. Therefore, any technical solutions obtained by logical analysis, reasoning or limited experiments by those skilled in the art based on the concept of the present application and the prior art shall be within the protection scope defined by the claims.

Claims

1. A robot seam grinding system based on contact sensing, characterized by, The application relates to an EHA constant force floating end effector, an EHA constant force floating end control cabinet, an industrial robot, an industrial robot control cabinet, an industrial computer and a workbench, wherein the EHA constant force floating end effector is connected to the end of the industrial robot and plays a role of polishing a weld, the industrial computer sends instructions to the industrial robot control cabinet to control the movement of the industrial robot, a workpiece is placed on the workbench, and the EHA constant force floating end effector polishes the weld of the workpiece under the control of the industrial robot; the EHA constant force floating end effector is a constant force floating execution mechanism driven by an EHA hydraulic system, the EHA constant force floating end effector is provided with a force sensor, a displacement sensor, a polishing tool and an end contact wheel, the polishing tool and the end contact wheel are alternately installed at the end of the EHA constant force floating end effector, the end contact wheel is used when the appearance of both sides of the weld is measured at the beginning, and the polishing tool is replaced in the polishing process; the EHA constant force floating end effector comprises a main shaft motor, an EHA hydraulic servo motor, a force sensor, a connecting rod, a displacement sensor, a rotating main shaft, a polishing tool, an end contact wheel and a floating part; firstly, a constant output force is set, a constant force closed loop control part is formed by the force sensor and the EHA hydraulic servo motor, the constant output force is ensured, the connecting rod transmits the constant force to the floating part, the displacement sensor collects floating part displacement data in real time, and the floating part is connected to the rotating main shaft and is driven to rotate by the main shaft motor; the EHA hydraulic servo motor is connected to the floating part through the connecting rod, the position of the floating part is adjusted through closed loop control under the feedback of the force sensor, and constant force output is realized; an appearance detection method based on contact sensing is realized through the cooperation of the force sensor, the displacement sensor and the end contact wheel; firstly, a constant output force is set through the EHA constant force floating end control cabinet, the constant output force is ensured by the force sensor and the EHA hydraulic servo motor, and the end contact wheel rolls and contacts on the surface of a weld workpiece; then, the displacement sensor is used to collect floating part displacement information, and the information is converted into surface appearance information of the weld; in the polishing process, the end contact wheel is replaced by the polishing tool to contact the surface of a polishing area, and the polishing height of the weld is monitored in real time; the end contact wheel is a metal roller with a radius of 5 mm, the initial position of the floating part is set as zero before appearance detection, the EHA hydraulic servo motor is disabled, TCP calibration is carried out at zero, and the TCP is calibrated at the end of the end contact wheel; the TCP of the industrial robot is calibrated at the polishing position of the polishing tool, in the polishing process, the polishing height of the weld at the point is obtained by calculating the change of the displacement sensor relative to the initial zero f . When the topography measurement is performed, a constant output force is set at the end, the output position of the displacement sensor is collected, and the end topography detection function is realized; the actual contact position of the end contact wheel is , and the TCP position of the calibration is , at this time, the change of the displacement sensor relative to the initial zero point is , and the position change of the floating part in the world coordinate system is written as Then there is a relationship as follows: The coordinates in the robot world coordinate system are written as follows: According to the principles of robotics, the following relationship can be obtained: wherein is , is , is , The matrix is solved to obtain the following relationship: Thus, the actual contact position P of the robot end TCP is obtained; the surface topography measurement can be realized by calculating the measurement points composed of the actual contact position.

2. A robot seam grinding method based on contact sensing, characterized by, The method using the contact sensing based robot weld seam grinding system according to claim 1 comprises the following steps: Step 1, calibrate the TCP of the industrial robot and the end contact wheel respectively; Step 2, measure the topography of the area on both sides of the weld seam; Step 3, calculate the midpoint of the topography measurement points; Step 4, generate a grinding track according to the target preview; Step 5, perform the grinding operation; Step 6, optimize the grinding parameters in real time; Step 7, determine whether the grinding operation is completed, if not, jump to step 5, if completed, end the grinding.

3. The contact-sensing based robotic weld seam grinding method of claim 2, wherein, Step 1 specifically involves calibrating the TCP of the industrial robot at the grinding position of the grinding tool, and calibrating the TCP of the end contact wheel at the end of the end contact wheel; Step 2 involves measuring the morphology on both sides of the weld seam using a morphology detection method based on contact sensing, thereby obtaining two sets of position points. and Then, in step 3, the points formed by the midpoints of the two measuring base surfaces are calculated. To ensure the accuracy of the center point trajectory, step 3 uses the cubic B-spline interpolation method to calculate the two sets of position points. L 1 and L 2 Perform interpolation to obtain the points on the interpolated curve trajectory, and then determine the midpoint from the interpolated trajectory curve. P m This refers to the polishing trajectory.

4. The contact-sensing based robotic weld seam grinding method of claim 2, wherein, The grinding track in step 4 includes the normal direction of grinding in addition to the grinding track position points composed of the midpoint obtained in step 3, and the two together constitute the grinding track file.

5. The contact-sensing based robotic weld seam grinding method of claim 2, wherein, In the grinding process, by calculating the change of the displacement sensor relative to the initial zero point The grinding height that still needs to be removed at this point is obtained.

6. The contact-sensing based robotic weld seam grinding method of claim 5, wherein, The welding seam height is divided into two parts to remove to realize the efficient grinding of adaptive optimization process parameters, after detecting the welding seam height, the first part removal height and the second part removal height are calculated by the target height and the welding seam height, the first part removal height is the uneven part of the welding seam, and the second part removal height is the difference between the welding seam height and the first part; for the first part removal height, the grinding parameters are generated by the process parameter library, and the grinding process parameters are adjusted to remove and smooth the uneven part; after each grinding, the remaining height after grinding is monitored in real time, and the comparison between the monitored removal height and the target removal height of this grinding is made to adjust the grinding process parameters; for the second part removal height, appropriate grinding parameters are generated by the process parameter library, if the second part removal height is within the range of the process parameter library, the second part removal height can be removed by one grinding, if the second part removal height exceeds the maximum removal amount that can be removed by one grinding of the grinding tool, the second part removal height is divided into multiple removals; The specific calculation method is as follows: In the formula, represents the height removed each time the second polishing is performed, and is determined by Inquiring a process parameter library to obtain polishing parameters, represents the second part of the height removed, represents the maximum removal amount that can be removed by the polishing tool once; an error value allowed by the polishing residual height is set σ According to whether the monitored residual height is within δ ± σ range, it is judged whether the polishing operation is completed, and if not, the polishing operation is performed again according to the adjusted polishing process parameters until the polishing operation is completed.

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