RGV-based load workpiece centroid detection and anti-collision control method

Abstract

The application discloses a load workpiece centroid detection and anti-collision control method based on RGV and a three-axis RGV. The method establishes a fixed coordinate system and a workpiece clamping coordinate system, records the tare weight of a workpiece carrier when no workpiece is installed, carries out first weighing and calculates a plane centroid after a workpiece is installed, carries out second weighing after the workpiece is rotated by 90 degrees around a predetermined coordinate axis in the workpiece clamping coordinate system, and obtains a three-dimensional centroid of the workpiece in combination with the two plane centroids and a coordinate rotation transformation relationship. Three-axis kinetic models in loaded and unloaded states are established based on the mass and centroid of the RGV body, the workpiece carrier and the workpiece, theoretical driving force and theoretical driving torque are calculated, torque abnormality alarm is realized by comparing a servo feedback torque with a theoretical torque, a safety distance is calculated according to real-time speed, maximum deceleration, real-time position and limit position, and three-stage limit position early warning is executed. The application can improve the operation stability and anti-collision safety in the workpiece carrying process of a complex shape.

Description

Technical Field

[0001] This invention relates to the field of automated handling equipment control technology, specifically to a load workpiece centroid detection and anti-collision control method based on RGV and a three-axis RGV. Background Technology

[0002] RGV (Rail Guided Vehicle) is a common material handling equipment in automated logistics systems and flexible production lines, capable of transferring workpieces, tooling, or materials between different workstations along a track. For a three-axis RGV with X-axis travel, Y-axis extension, and Z-axis lifting functions, its operational stability depends not only on the track positioning accuracy and servo control accuracy, but also closely on the load mass distribution and the position of the load center of gravity.

[0003] In handling scenarios involving complex-shaped workpieces, eccentric workpieces, or workpieces combined with carriers, the center of gravity of the loaded workpiece often deviates from the geometric center of the telescopic assembly or the entire machine. If the control system still drives the load based on a fixed load or an ideal centered load, it is easy to cause inaccurate estimation of the required driving force and driving torque for each motion axis, resulting in problems such as equipment vibration, increased positioning error, impact on the drive mechanism, and accelerated wear of structural components.

[0004] Existing RGV collision avoidance solutions typically employ mechanical limits, proximity switches, laser rangefinders, or contact sensors for safety protection. While these solutions can limit the equipment's overtravel or detect obstacles to some extent, most do not incorporate load center of gravity changes into the dynamic control model, making it difficult to promptly identify torque anomalies caused by load eccentricity, motion jamming, or the initial stages of a collision. Furthermore, single-stroke limit methods usually only trigger protection when approaching the limit position, offering limited warning levels and failing to adequately address early warning, active deceleration, and emergency braking.

[0005] Therefore, it is necessary to provide a technical solution that can measure the three-dimensional centroid of the loaded workpiece and use the centroid results for the triaxial dynamic model and anti-collision control of the RGV, so as to improve the operational stability, positioning reliability and safety of the RGV in the process of handling complex workpieces. Summary of the Invention

[0006] The purpose of this invention is to provide a load workpiece centroid detection and anti-collision control method and a three-axis RGV based on RGV, so as to at least solve the problems of traditional RGV not fully considering the influence of load workpiece eccentricity, resulting in reduced motion accuracy, inaccurate driving torque estimation and insufficient collision risk prediction.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] A method for detecting the center of mass of a loaded workpiece and preventing collisions based on an RGV (Remotely Reinforcing Vehicle) is applied to a triaxial RGV. The triaxial RGV includes an X-axis moving base (9), a column assembly, a telescopic insertion assembly, and a weighing center of mass measurement system. The X-axis moving base (9) and the ground rail (13) form a translational motion pair along the X-axis; the column assembly is connected to the X-axis moving base (9) and forms a translational motion pair along the Z-axis; the telescopic insertion assembly is connected to the column assembly and forms a translational motion pair along the Y-axis; the weighing center of mass measurement system includes multiple weighing units disposed on the X-axis moving base (9).

[0009] The method includes: establishing a fixed coordinate system O-XYZ and a workpiece clamping coordinate system Oj-XjYjZj; with the workpiece unloaded, applying the workpiece carrier to the weighing center of mass measurement system and recording the readings of each weighing unit as the tare weight; after installing the workpiece, applying the load composed of the workpiece carrier and the workpiece to the weighing center of mass measurement system, subtracting the tare weight to obtain the weighing reading in the first posture, and calculating the planar center of mass coordinates of the workpiece in the first posture based on the torque balance relationship; rotating the workpiece 90° around a predetermined coordinate axis in the workpiece clamping coordinate system with the workpiece carrier, weighing again, and calculating the second posture. The planar centroid coordinates under the given state are calculated; the three-dimensional centroid coordinates of the workpiece are obtained based on the two planar centroid coordinates and the coordinate rotation transformation relationship, and then transformed to a fixed coordinate system O-XYZ; a three-axis dynamic model is established based on the mass and centroid coordinates of the three-axis RGV body, workpiece carrier and workpiece, under loaded and unloaded states, and the theoretical driving force and theoretical driving torque of each axis are calculated; the three-axis motion parameters and servo motor feedback torque are collected in real time, and torque abnormality alarm is performed based on the theoretical driving torque, and the safety distance is calculated based on the real-time speed, maximum deceleration, real-time position and limit position to perform travel limit warning.

[0010] Furthermore, the weighing center of mass measurement system includes weighing units 1 (7), 2 (8), 3 (11), and 4 (12), arranged in a rectangular array. The planar center of mass in both the first and second postures can be obtained by weighted averaging of the coordinates of each weighing unit and its reading.

[0011] Furthermore, in the triaxial dynamics model, the total driving force of each axis is obtained by superimposing inertial force, eccentric coupling force, viscous friction force and Coulomb friction force, and is converted into theoretical driving torque through the torque radius of the corresponding axis.

[0012] Furthermore, the torque anomaly alarm compares the servo motor feedback torque with the corrected theoretical drive torque. When the difference between the two exceeds a preset ratio and the duration exceeds a preset time, it is determined that there is a risk of collision or jamming and a shutdown alarm is triggered.

[0013] Furthermore, the travel limit warning is set into three levels: Level 1, Level 2, and Level 3, based on the safe distance, remaining travel distance, and real-time speed. Among them, Level 1 warning provides a prompt, Level 2 warning performs deceleration braking when the remaining travel distance enters the safe distance range and the actual operating speed meets the Level 2 warning speed conditions, and Level 3 warning performs emergency braking.

[0014] The present invention also provides a three-axis RGV, including a control system, an X-axis moving base (9), a column assembly, a telescopic insertion assembly, and a weighing center of mass measurement system, wherein the control system is configured to execute the above-described RGV-based load workpiece center of mass detection and anti-collision control method.

[0015] Compared with existing technologies, the present invention has at least the following beneficial effects: First, the three-dimensional centroid of the loaded workpiece is obtained through weighing, 90° rotation, and coordinate transformation, without relying on visual recognition and less affected by illumination and occlusion; Second, the centroid result can participate in the triaxial dynamics calculation under loaded and unloaded states, making the theoretical driving force and theoretical driving torque more consistent with the actual load state; Third, a dual anti-collision strategy is formed through torque anomaly alarm and three-level stroke limit warning, which can take into account early collision identification, active deceleration, and emergency braking at extreme positions; Fourth, the weighing centroid measurement system is integrated into the RGV body, and centroid detection and safety control can be completed on the handling equipment without the need for additional independent centroid detection equipment. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the three-axis RGV composition in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the establishment of the fixed coordinate system O-XYZ in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the establishment of the workpiece clamping coordinate system Oj-XjYjZj in an embodiment of the present invention.

[0017] The components are: 1. Column 1; 2. Telescopic plug 1; 3. Telescopic plug base 1; 4. Telescopic plug mounting plate; 5. Telescopic plug 2; 6. Telescopic plug base 2; 7. Weighing device 1; 8. Weighing device 2; 9. X-axis moving base; 10. Column 2; 11. Weighing device 3; 12. Weighing device 4; 13. Ground rail. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Where there is no conflict, the technical features in the following embodiments can be combined with each other.

[0019] like Figure 1As shown, a triaxial RGV includes an X-axis movable base (9), a column assembly, a telescopic plug assembly, and a weighing center of mass measurement system. The X-axis movable base (9) serves as the mounting base for the entire machine, and it cooperates with the ground rail (13) to form a translational motion pair along the X-axis. The column assembly includes a column 1 (1), a column 2 (10), and a telescopic plug mounting plate (4). The columns 1 (1) and 2 (10) are fixedly connected to the upper surface of the X-axis movable base (9), and the telescopic plug mounting plate (4) is slidably connected to the columns 1 (1) and 2 (10), thereby forming a lifting motion pair along the Z-axis.

[0020] The telescopic connector assembly includes a telescopic connector base 1 (3), a telescopic connector base 2 (6), a movable telescopic connector 1 (2), and a movable telescopic connector 2 (5). The telescopic connector base 1 (3) and the telescopic connector base 2 (6) are fixedly connected to the telescopic connector mounting plate (4). The movable telescopic connector 1 (2) and the movable telescopic connector 2 (5) are slidably connected to their respective telescopic connector bases and are driven by a transmission mechanism to form a synchronous telescopic structure, thereby constituting a telescopic motion pair along the Y-axis. The movable telescopic connector is used to carry or transfer workpiece carriers and workpieces.

[0021] The weighing center of mass measurement system includes weighing units 1 (7), 2 (8), 3 (11), and 4 (12), which are arranged in a rectangular array on the X-axis moving base (9). The four weighing units are used to acquire pressure distribution data of the workpiece carrier and the workpiece under different postures in order to calculate the position of the workpiece center of mass.

[0022] I. Establishment of Coordinate System like Figure 2 As shown, a fixed coordinate system O-XYZ is established. The projection of the intersection of the zero position of the X-axis and the zero position of the Y-axis on the upper surface of the X-axis moving base (9) is taken as the origin O. The X-axis is parallel to the extension direction of the ground rail (13), the Y-axis is perpendicular to the X-axis and parallel to the upper surface of the X-axis moving base (9), and the Z-axis is perpendicular to the upper surface of the X-axis moving base (9).

[0023] like Figure 3 As shown, a workpiece clamping coordinate system Oj-XjYjZj is established. Its origin Oj has coordinates (0,0,d) in the fixed coordinate system O-XYZ. The Xj, Yj, and Zj axes are parallel to the X, Y, and Z axes of the fixed coordinate system O-XYZ, respectively. The load includes the workpiece carrier and the workpiece; when the Y and Z axes are at their zero positions, the coordinates of the workpiece carrier's center of mass can be denoted as (0,0,e).

[0024] II. Calculation of the Centroid of RGV To facilitate dynamic modeling, the RGV body can be divided into structure 1, structure 2, and structure 3. Structure 1 includes an X-axis movable base (9), column 1 (1), column 2 (10), and a weighing center of mass measurement system with a mass of m1. In the initial state, the center of mass coordinates are (0,0,c). Structure 1 only moves with the X-axis. Structure 2 includes a telescopic mounting plate (4), telescopic base 1 (3), and telescopic base 2 (6) with a mass of m2. When the Z-axis is at the zero position, the center of mass coordinates are (0,0,2c). Structure 2 moves with the X-axis and Z-axis. Structure 3 includes a movable telescopic plug 1 (2) and a movable telescopic plug 2 (5) with a mass of m3. When the Y-axis and Z-axis are at the zero position, the center of mass coordinates are (0,0,2c+c'). Structure 3 moves with the X-axis, Y-axis, and Z-axis.

[0025] Let the real-time positions of the X-axis, Y-axis, and Z-axis be qx, qy, and qz, respectively. Based on the motion axes involved in each structure, the initial centroid coordinates of each structure can be superimposed with the displacement of the corresponding axis to obtain the real-time centroid coordinates of each structure; then, based on the mass-weighted average relationship, the real-time centroid coordinates of the RGV body in the unloaded state can be obtained.

[0026] When loading a workpiece, the movable telescopic plug, the workpiece carrier, and the workpiece together constitute the loading part that moves with the Y and Z axes. The control system updates the total mass and real-time centroid under the loading state based on the workpiece carrier mass, the workpiece mass, and the three-dimensional centroid coordinates of the workpiece.

[0027] III. Center of gravity detection of the loaded workpiece The detection of the center of mass of the loaded workpiece is achieved by combining the weighing method, 90° rotation, and coordinate transformation.

[0028] First, with the workpiece not installed, control the Z-axis to drive the telescopic mounting plate (4) to descend, so that the telescopic assembly drives the workpiece carrier to fully act on weighing 1 (7), weighing 2 (8), weighing 3 (11) and weighing 4 (12). After the readings of the four weighing units stabilize, record the readings of each weighing unit as tare weight.

[0029] Secondly, after installing the workpiece, the load consisting of the workpiece carrier and the workpiece is fully applied to the four weighing units. After the readings stabilize, the tare weight is subtracted from the weighing readings to obtain the weighing readings W1, W2, W3, and W4 in the first posture. Let the coordinates of the four weighing units in the fixed coordinate system O-XYZ be P1(x1,y1,0), P2(x2,y2,0), P3(x3,y3,0), and P4(x4,y4,0), respectively. Then, the workpiece mass M and the plane centroid coordinates (xa,ya) in the first posture can be calculated using the following formula: M = W1 + W2 + W3 + W4 xa=(W1·x1+W2·x2+W3·x3+W4·x4) / M ya=(W1·y1+W2·y2+W3·y3+W4·y4) / M Next, the tooling fixture is controlled to rotate the loaded workpiece 90° around the predetermined coordinate axes in the workpiece clamping coordinate system Oj-XjYjZj, while keeping the workpiece fully engaged with the weighing center of mass measurement system; after deducting the tare weight, the weighing readings W1', W2', W3', and W4' in the second posture are obtained, and the planar center of mass coordinates (xb, yb) in the second posture are calculated using the torque method: M'=W1'+W2'+W3'+W4' xb=(W1'·x1+W2'·x2+W3'·x3+W4'·x4) / M' yb=(W1'·y1+W2'·y2+W3'·y3+W4'·y4) / M' Then, based on the planar centroid coordinates in the first posture, the planar centroid coordinates in the second posture, and the rotation transformation matrix for rotating 90° around a predetermined coordinate axis, the three-dimensional centroid coordinates of the workpiece in the workpiece clamping coordinate system Oj-XjYjZj are solved. Taking a 90° rotation around the Xj axis as an example, if the centroid of the workpiece before flipping is (xj, yj, zj) in the workpiece clamping coordinate system, and the coordinates after rotation are (xj', yj', zj'), then the following rotation relationship can be used: xj'=xj, yj'=-zj, zj'=yj This allows us to correlate the planar coordinates obtained from the first and second weighings to obtain the three-dimensional centroid coordinates (xj, yj, zj). Finally, based on the translation relationship between the workpiece clamping coordinate system Oj-XjYjZj and the fixed coordinate system O-XYZ, the workpiece centroid coordinates are converted into the actual centroid coordinates in the fixed coordinate system.

[0030] IV. Dynamic Modeling The control system establishes dynamic models for the X, Y, and Z axes under both unloaded and loaded states. Model parameters include: constraint stiffness coefficients kx, ky, and kz for each axis; torque radii rx, ry, and rz for each axis; viscous drag coefficients bx, by, and bz for each axis; Coulomb friction coefficients μx, μy, and μz for each axis; normal forces Nx, Ny, and Nz for each axis; and real-time position, velocity, and acceleration of the three axes.

[0031] For any axis of motion i, where i is any one of x, y, and z, its total driving force Fi is obtained by superimposing the inertial force Fmi, the eccentric coupling force Fei, the viscous friction force Fvi, and the Coulomb friction force Fci: Fi = Fmi + Fei + Fvi + Fci Fmi=m·ai Fei=ki·ei Fvi=bi·vi Fci=μi·Ni Where m is the mass of the corresponding moving part, ai is the acceleration of the corresponding axis, ei is the eccentricity of the corresponding axis determined by the center of mass offset, and vi is the velocity of the corresponding axis. The theoretical driving torque Ti of the corresponding axis can be obtained by the following formula: Ti=Fi·ri The control system selects the corresponding total mass, real-time centroid, and eccentricity for calculation based on whether the system is under load. In the unloaded state, the model uses the mass and centroid of the RGV body; in the loaded state, the model further incorporates the mass, centroid, and centroid offset of the workpiece carrier and the workpiece.

[0032] V. Torque Abnormality Alarm Torque anomaly alarm is used to identify collisions, jamming, or abnormal forces during motion. The control system divides the three-axis RGV motion into acceleration, constant speed, and deceleration phases, and can employ trapezoidal acceleration / deceleration control. The control system collects the position, velocity, acceleration, deceleration, and servo motor feedback torque of the X, Y, and Z axes in real time at a preset sampling period.

[0033] In one implementation, the preset sampling period is 50ms. The control system determines whether the workpiece is currently under load based on the weighing center of mass measurement system; if it is under load, it first calculates the three-dimensional center of mass of the workpiece based on the detection results of the center of mass of the loaded workpiece, and selects the dynamic model under the loaded state; if it is under unloaded state, it selects the dynamic model under the unloaded state.

[0034] The control system inputs real-time motion parameters into the corresponding dynamic model to obtain the theoretical drive torque for each axis. Then, it calculates a theoretical torque correction coefficient based on the servo motor feedback torque and the theoretical drive torque, and uses this coefficient to correct the theoretical drive torque. Subsequently, the control system compares the servo motor feedback torque with the corrected theoretical drive torque in real time. When the difference exceeds a preset ratio and persists for a preset duration, it determines that the equipment has a risk of collision or jamming.

[0035] In one implementation, the preset ratio is 10% and the preset duration is 100ms. When abnormal conditions are met, the control system cuts off the power output of the corresponding axis or three-axis servo motor, triggers an audible and visual alarm, and saves the current motion parameters to the system log for subsequent traceability.

[0036] VI. Trip Limit Warning The travel limit warning is used to initiate graded actions before the equipment approaches the limit position. For any motion axis, the control system calculates the safe distance s required to decelerate to 0 at the current speed based on the real-time speed v and the maximum deceleration amax. s = v² / (2·amax) The control system obtains the current position p and the limit position plim of the device in real time, and calculates the remaining stroke L: L = |plim - p| According to the relationship between the safety distance s and the remaining stroke L, the control system sets a three - level warning mechanism: when L > s, it is a first - level warning, and the system displays a prompt message on the human - machine interface without interfering with the movement of the device; when αs < L ≤ s and the actual running speed v is greater than sqrt[2·amax·(1 - α)·s], it is a second - level warning, and the system controls the device to decelerate and issues a prompt; when L ≤ αs, it is a third - level warning, and the system immediately executes an emergency brake until the device stops completely, locks the movement permission, and can only continue to run after manual reset. α is a safety factor greater than 0 and less than 1, and can take 0.4 in one implementation; sqrt[] represents the square - root operation.

[0037] VII. Embodiment The following takes a set of parameters as an example to illustrate the implementation process of the present invention. The size of the X - axis moving base (9) is 1000mm×800mm; the heights of the column 1 (1) and the column 2 (10) are 1500mm, and the cross - section size is 80mm×80mm; the scales 1 (7) to 4 (12) adopt strain - type sensors with a measuring range of 0kg to 500kg, are distributed in a 600mm×600mm rectangle, and communicate with the control system through Modbus RTU; the power of the X - axis servo - drive system is 2.2kW, and the powers of the Y - axis and Z - axis servo - drive systems are both 1.5kW, and the servo motors are equipped with absolute encoders.

[0038] The structural masses can be set as: m1 = 500kg, m2 = 100kg, m3 = 50kg, and the mass of the workpiece carrier is 50kg; when each axis is at the motion zero - position, the relevant centroid coordinates are (0mm, 0mm, 200mm), (0mm, 0mm, 400mm), (0mm, 0mm, 420mm), and (0mm, 0mm, 450mm) respectively. The viscous - resistance coefficient can take 10N·s / m, the Coulomb - friction coefficient can take 0.02, the constraint stiffness coefficient of each axis can take 1×10 5 N / m, and the torque radius of each axis can take 0.01m.

[0039] After placing the complex - shaped part on the workpiece carrier, through two weighings and a 90° flip, the centroid coordinates of the loaded workpiece in the fixed coordinate system O - XYZ are measured as (10mm, 5mm, 550mm), and the mass of the workpiece is 60kg. When the X - axis moves with the loaded workpiece, the total mass is 760kg, and the X - axis acceleration is 0.5m / s². After calculating the inertial force, eccentric coupling force, viscous friction force, and Coulomb friction force, the total driving force and driving torque of the X - axis can be obtained.

[0040] In the limit collision warning, if the X-axis limit position is 26000mm, the maximum deceleration is 1000mm / s², and the safety factor α is 0.4, when the current position is 25500mm and the speed is 0.5m / s, the remaining travel is greater than the safety distance, triggering a level one warning; when the current position is 25900mm and the speed is 0.5m / s, the remaining travel is less than or equal to the safety distance, and the actual running speed is greater than the speed threshold corresponding to sqrt[2·amax·(1-α)·s], triggering a level two warning and reducing speed; when the current position further approaches the limit position and satisfies L≤αs, triggering a level three warning and emergency braking.

[0041] The above embodiments are merely preferred embodiments of the present invention and do not limit the present invention. Those skilled in the art can make equivalent substitutions or modifications to the above embodiments without departing from the concept of the present invention, and all such substitutions or modifications should fall within the protection scope of the present invention.

Claims

1. A method for detecting the center of mass of a loaded workpiece and preventing collisions based on an RGV (Remotely Reinforcing Vehicle), applied to a triaxial RGV, wherein the triaxial RGV includes an X-axis moving base, a column assembly, a telescopic insertion assembly, and a weighing center of mass measurement system; the X-axis moving base and the ground rail form a translational kinematic pair along the X-axis; the column assembly is connected to the X-axis moving base and forms a translational kinematic pair along the Z-axis; the telescopic insertion assembly is connected to the column assembly and forms a translational kinematic pair along the Y-axis; and the weighing center of mass measurement system includes multiple weighing units disposed on the X-axis moving base; characterized in that... The method includes: S1, establish a fixed coordinate system O-XYZ and a workpiece clamping coordinate system Oj-XjYjZj; S2, with the workpiece not installed, the workpiece carrier is applied to the weighing center of mass measurement system, and the readings of each weighing unit are recorded as the tare weight; S3, after the workpiece is installed, the load consisting of the workpiece carrier and the workpiece is applied to the weighing center of mass measurement system, and the weighing reading of each weighing unit under the first posture is obtained after deducting the tare weight. S4. Calculate the plane centroid coordinates of the workpiece in the first posture based on the weighing readings and torque balance relationship of each weighing unit in the first posture. S5, rotate the workpiece 90° around a predetermined coordinate axis in the workpiece clamping coordinate system along with the workpiece carrier; S6, after rotating 90°, apply the load to the weighing center of mass measurement system again, and obtain the weighing readings of each weighing unit in the second posture after deducting the tare weight; S7. Calculate the planar centroid coordinates of the workpiece in the second posture based on the weighing readings of each weighing unit in the second posture. S8. Based on the two planar centroid coordinates and the coordinate transformation relationship of rotating 90° around the predetermined coordinate axis, the three-dimensional centroid coordinates of the workpiece in the workpiece clamping coordinate system are obtained. S9, convert the three-dimensional centroid coordinates into the workpiece centroid coordinates in the fixed coordinate system; S10, Based on the mass and centroid coordinates of the three-axis RGV body, workpiece carrier and workpiece, establish dynamic models of the X-axis, Y-axis and Z-axis in the unloaded state and the loaded state respectively; S11, Calculate the theoretical driving force and theoretical driving torque of each shaft according to the dynamic model; S12, real-time acquisition of motion parameters of X-axis, Y-axis and Z-axis and feedback torque of servo motor, comparison of the feedback torque of servo motor with the theoretical driving torque of the corresponding axis to execute torque abnormality alarm; S13, calculate the safe distance based on real-time speed, maximum deceleration, real-time position and limit position, and execute travel limit warning; S14, based on the judgment results of the abnormal torque alarm and the travel limit warning, execute prompt, deceleration braking or emergency stop.

2. The method for detecting the centroid of a loaded workpiece and preventing collisions based on RGV according to claim 1, characterized in that, The weighing center of mass measurement system includes weighing units 1, 2, 3, and 4, which are arranged in a rectangular array on the X-axis movable base. Let the coordinates of the four weighing units in the fixed coordinate system O-XYZ be P1(x1,y1,0), P2(x2,y2,0), P3(x3,y3,0), and P4(x4,y4,0), respectively. Let the weighing readings after deducting the tare weight in the first posture be W1, W2, W3, and W4, respectively. Then, the mass M of the workpiece in the first posture satisfies: M = W1 + W2 + W3 + W4; The planar centroid coordinates (xa, ya) in the first attitude satisfy: xa=(W1·x1+W2·x2+W3·x3+W4·x4) / M; ya=(W1·y1+W2·y2+W3·y3+W4·y4) / M.

3. The method for detecting the centroid of a loaded workpiece and preventing collisions based on RGV according to claim 2, characterized in that, In the second posture, the weighing readings after deducting the tare weight are W1', W2', W3', and W4', respectively. The mass M' of the workpiece in the second posture satisfies M' = W1' + W2' + W3' + W4'. The planar centroid coordinates (xb, yb) in the second posture satisfy: xb=(W1'·x1+W2'·x2+W3'·x3+W4'·x4) / M'; yb=(W1'·y1+W2'·y2+W3'·y3+W4'·y4) / M'.

4. The method for detecting the centroid of a loaded workpiece and preventing collisions based on RGV according to claim 1, characterized in that, The fixed coordinate system O-XYZ takes the projection of the intersection of the zero position of the X-axis and the zero position of the Y-axis on the upper surface of the X-axis moving base as its origin O. The X-axis is parallel to the extension direction of the ground rail, the Y-axis is perpendicular to the X-axis and parallel to the upper surface of the X-axis moving base, and the Z-axis is perpendicular to the upper surface of the X-axis moving base. The coordinates of the origin Oj of the workpiece clamping coordinate system Oj-XjYjZj in the fixed coordinate system O-XYZ are (0,0,d), and the Xj, Yj, and Zj axes are parallel to the X, Y, and Z axes, respectively.

5. The method for detecting the centroid of a loaded workpiece and preventing collisions based on RGV according to claim 4, characterized in that, The triaxial RGV body is divided into structure 1, structure 2, and structure 3. Structure 1 includes an X-axis movable base, a column in the column assembly, and a weighing center of mass measurement system with a mass of m1 and an initial center of mass coordinate of (0,0,c), which moves with the X-axis. Structure 2 includes a telescopic mounting plate and a telescopic base with a mass of m2. When the Z-axis is at the zero position, the initial center of mass coordinate of the telescopic base is (0,0,2c), which moves with the X-axis and Z-axis. Structure 3 includes a movable telescopic plug with a mass of m3. When the Y-axis and Z-axis are at the zero position, the initial center of mass coordinate of the telescopic plug is (0,0,2c+c'), which moves with the X-axis, Y-axis, and Z-axis. Based on the real-time positions of the X-axis, Y-axis, and Z-axis, the center of mass coordinates of structures 1, 2, and 3 are updated, and the real-time center of mass of the triaxial RGV body is calculated.

6. The method for detecting the centroid of a loaded workpiece and preventing collisions based on RGV according to claim 1, characterized in that, In the aforementioned dynamic model, the total driving force Fi of each axis is obtained by superimposing the inertial force Fmi, the eccentric coupling force Fei, the viscous friction force Fvi, and the Coulomb friction force Fci, satisfying: Fi = Fmi + Fei + Fvi + Fci; Where Fmi = m·ai, Fvi = bi·vi, Fci = μi·Ni, Fei = ki·ei; m is the mass of the corresponding moving part, ai is the acceleration of the corresponding shaft, bi is the viscous drag coefficient of the corresponding shaft, vi is the velocity of the corresponding shaft, μi is the Coulomb friction coefficient of the corresponding shaft, Ni is the normal force of the corresponding shaft, ki is the constraint stiffness coefficient of the corresponding shaft, ei is the eccentricity of the center of mass on the corresponding shaft, and i is any one of x, y, z; the theoretical driving torque Ti of the corresponding shaft satisfies Ti = Fi·ri, where ri is the torque radius of the corresponding shaft.

7. The method for detecting the centroid of a loaded workpiece and preventing collisions based on RGV according to claim 1, characterized in that, The torque anomaly alarm includes: dividing the movement of the three-axis RGV into an acceleration stage, a constant-speed stage, and a deceleration stage; collecting the position, speed, acceleration, deceleration, and servo motor feedback torque of the X-axis, Y-axis, and Z-axis in real time according to a preset sampling period; selecting a dynamic model in the unloaded state or the loaded state according to the loading state, and calculating the theoretical driving torque; calculating a theoretical torque correction coefficient based on the servo motor feedback torque and the theoretical driving torque, and using the corrected theoretical driving torque as the judgment benchmark; when the difference between the servo motor feedback torque and the corrected theoretical driving torque exceeds a preset ratio and the duration exceeds a preset time length, it is determined that there is a risk of collision or jamming, and the power output of the corresponding servo motor is cut off and an alarm is given.

8. The method for detecting the centroid of a loaded workpiece and preventing collisions based on RGV according to claim 7, characterized in that, The preset sampling period is 50 ms; the preset ratio is 10%; the preset time length is 100 ms.

9. The method for detecting the centroid of a loaded workpiece and preventing collisions based on RGV according to claim 1, characterized in that, The travel limit warning includes: calculating the safe distance s required to decelerate to 0 at the current speed according to the real-time speed v of the corresponding axis and the maximum deceleration amax, where s = v² / (2·amax); calculating the remaining travel L = |plim - p| according to the real-time position p of the corresponding axis and the limit position plim; when L > s, execute a first-level warning and give a prompt; when αs < L ≤ s and the actual running speed v is greater than sqrt[2·amax·(1 - α)·s], execute a second-level warning and control the equipment to decelerate; when L ≤ αs, execute a third-level warning and perform an emergency brake, where α is a safety factor greater than 0 and less than 1, and sqrt[] represents the square root operation.

10. A triaxial RGV, characterized in that, It includes a control system, an X-axis moving base, a column assembly, a telescopic plug assembly, and a weighing centroid measurement system; the X-axis moving base and the ground rail form a translational motion pair along the X-axis; the column assembly includes column 1, column 2, and a telescopic plug mounting plate. Column 1 and column 2 are fixedly connected to the X-axis moving base, and the telescopic plug mounting plate is slidably connected to column 1 and column 2 to form a translational motion pair along the Z-axis; the telescopic plug assembly includes a telescopic plug base and a movable telescopic plug. The telescopic plug base is fixedly connected to the telescopic plug mounting plate, and the movable telescopic plug is slidably connected to the telescopic plug base to form a translational motion pair along the Y-axis; the weighing centroid measurement system is arranged on the X-axis moving base and is used to collect load pressure distribution data; the control system is respectively communicatively connected to the weighing centroid measurement system and the servo drive systems of the X-axis, Y-axis, and Z-axis, and is configured to execute the RGV-based load workpiece centroid detection and anti-collision control method according to any one of claims 1 to 9.

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