Field compensation method of six-dimensional force sensor for special grinding and polishing machine

Abstract

The invention discloses a field compensation method of a six-dimensional force sensor for a special grinding and polishing machine, which comprises the following steps of: S1, operating the special grinding and polishing machine, reading force and torque data of the six-dimensional force sensor in a static state under the condition that the six-dimensional force sensor works normally, and executing a zero clearing instruction on the six-dimensional force sensor; s2, the six-dimensional force sensor is controlled to move on a plane composed of the x axis and the y axis, grinding and polishing are started, data of the six-dimensional force sensor are read, the acceleration at each moment and the data of the six-dimensional force sensor are recorded, the pseudo-inverse of the acceleration data is solved through a least square method, and the load inertia force is obtained through the acceleration data obtained after the pseudo-inverse is solved; and S3, in the step S2, the six-dimensional force sensor data is subjected to load compensation according to the load inertia force, real grinding force is obtained, the accuracy of force feedback in the whole grinding and polishing process is guaranteed, and the working performance and reliability of the special grinding and polishing machine are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of special grinding and polishing machines, and particularly to an on-site compensation method for a six-axis force sensor used in a special grinding and polishing machine. Background Art

[0002] As a key equipment in modern manufacturing, special grinding and polishing machines play an important role in fields such as metal processing, aerospace, automotive manufacturing, and electronics. With the continuous development of automation and intelligent technologies, special grinding and polishing machines are evolving towards being more efficient, precise, and adaptable.

[0003] Due to its ability to simultaneously measure three-dimensional space forces and torques, a six-axis force sensor can sense the contact force between the grinding tool and the workpiece in real time. It can accurately control the grinding force and angle according to the workpiece material, shape, and processing requirements, improve the grinding and polishing accuracy and quality, reduce the scrap rate, and can also adapt to workpieces with complex shapes, ensuring that the grinding tool can closely fit the processing surface whether it is a curved surface, concave-convex surface or other irregular surfaces, achieving uniform and efficient grinding. Thus, it has become a key sensing element for realizing automated grinding and polishing.

[0004] Currently, in the improvement of special grinding and polishing machines, the following solutions exist: In the patent with publication number CN116833866A and invention name "A Special Polishing Machine for Conductive Sheets", a special polishing machine for conductive sheets is proposed. It uses a sanding belt grinding method to meet the chamfer grinding requirements of conductive sheets and the grinding requirements for the precise dimension b value of conductive sheets, and can achieve the grinding requirements for different chamfers of conductive sheets, ensuring that the edges of the gold sheets of conductive sheets are straight and the b value dimension of the gold sheets of conductive sheets is processed to meet the specified indicators.

[0005] In the method with authorization number CN110802585B and invention name "Robot End Sensor Compensation Method and Contact Force / Torque Measurement", a robot end sensor compensation method is provided, which can eliminate the influence of the zero point of the six-axis force sensor and the load gravity on force perception, and accurately obtain the external forces and torques acting on the load at the end of the robot. A robot end sensor contact force / torque measurement method is also disclosed. When the load contacts the external environment and generates contact forces and torques, the robot end sensor compensation method compensates for the zero point error of the six-axis force sensor and the gravity of the load. Using this compensation method can make the measurement value of the six-axis force sensor more accurate.

[0006] However, a series of complex problems still need to be solved in the above solutions.

[0007] 1) During the grinding and polishing process, the load carried by the six-axis force sensor has a high degree of complexity and variability, and there is a lack of effective means to accurately identify such complex loads; 2) The force coordinate system direction of the six-axis force sensor itself is often inconsistent with the grinding coordinate system direction, which will cause deviations in the measurement data during conversion and application to the grinding process control; 3) In a long-term complex working environment, the six-axis force sensor may fail, but there is a lack of a timely and accurate failure judgment method. Summary of the Invention

[0008] In view of the above three problems, the present invention proposes a field compensation method for a six-axis force sensor used in a grinding and polishing special machine. By controlling the grinding and polishing special machine to perform a series of movements, load compensation and coordinate system relationship calibration are carried out on the six-axis force sensor. At the same time, during the working process of the grinding and polishing special machine, by monitoring the data of the six-axis force sensor and the grinding and polishing special machine, it is judged whether the six-axis force sensor is working properly, ensuring the accuracy of force feedback in the whole grinding and polishing process, and improving the working performance and reliability of the grinding and polishing special machine. It is realized through the following technical solutions: A field compensation method for a six-axis force sensor used in a grinding and polishing special machine. The grinding and polishing special machine includes a workpiece, a fixture, an A-axis motor, an A-axis, an acceleration sensor, a six-axis force sensor, and an A-axis divider. The acceleration sensor is mounted on the upper end of the six-axis force sensor. The first end of the six-axis force sensor is connected to the workpiece through the fixture, and the second end of the six-axis force sensor is connected to the A-axis divider. The A-axis divider is driven by the A-axis motor. The load includes the workpiece and the fixture. During the rotation process, the forces and torques sensed by the six-axis force sensor include the gravity and inertial forces received by the load, as well as the grinding force received by the workpiece. Below the A-axis, there is a servo mechanism for controlling the movement of the spindle in the x and y directions. The A-axis assembly, the six-axis force sensor, the fixture, and the workpiece will all move in the x and y directions along with the spindle.

[0009] During grinding, the workpiece will be ground or polished by the grinding disc above. The grinding head can move up and down in the z-axis direction. The z-axis coincides with the axial direction of the A-axis, and the grinding head can rotate around the A-axis to achieve the purpose of switching multiple grinding heads.

[0010] A field compensation method for a six-axis force sensor used in a grinding and polishing special machine includes the following steps: S1: Construct a grinding and polishing special machine coordinate system with the geometric center of the grinding and polishing special machine as the origin, the z-axis vertically upward, control the x-axis and y-axis to be parallel to the upper plane of the workpiece to be ground, run the grinding and polishing special machine, and under the condition that the six-axis force sensor is working properly, read the forces 、 、 and torque data 、 、 of the six-axis force sensor in the static state, and execute a zeroing instruction on the six-axis force sensor to make the forces and torques of the six-axis force sensor in the static state both zero; where, , , and respectively represent the original forces in the x-axis, y-axis, and z-axis directions of the six-axis force sensor in the static state. , , respectively represent the original torques of the six-axis force sensor rotating around the x-axis, y-axis, and z-axis; S2: After executing the zero-clearing instruction in step S1, control the six-axis force sensor to move on the plane formed by the x-axis and y-axis, start grinding and polishing, read the data of the six-axis force sensor, and record the data of the six-axis force sensor as , obtain the acceleration at each moment according to the acceleration sensor, find the pseudo-inverse of the acceleration data by the least squares method, and obtain the load inertial force from the pseudo-inverted acceleration data ; S3: In step S2, perform load compensation on the six-axis force sensor data based on the load inertial force in step S2 to obtain the grinding force after compensating for the load inertial force , , obtain the true grinding force through the following formula. The formula for obtaining the true grinding force is as follows: ; where represents that the six-axis force sensor performs load compensation to obtain the true grinding force, T represents the transformation matrix from the six-axis force sensor coordinate system to the grinding and polishing machine coordinate system, represents the initial reading of the six-axis force sensor in the no-load state.

[0011] By compensating for the load inertial force, the actual grinding force between the tool and the workpiece can be measured more accurately, the interference of the load inertial force can be avoided, the accuracy of the force feedback in the entire grinding and polishing process can be ensured, and the working performance and reliability of the grinding and polishing machine can be improved.

[0012] Preferably, in step S2, reading the data of the six-axis force sensor includes the following steps: 1) Construct a six-axis force sensor coordinate system with the geometric center of the six-axis force sensor as the origin, control the z-axis of the grinding and polishing machine to coincide with the A-axis of the A-axis divider and point to the workpiece, and control the x-axis and y-axis to be parallel to the upper plane of the workpiece to be ground; 2) After constructing the six-axis force sensor coordinate system, move the grinding disc to the edge of the workpiece to be ground, control the plane of the grinding disc to be perpendicular to the upper plane of the workpiece to be ground, and the plane of the grinding disc to be perpendicular to the y-axis, control the axis of the grinding disc to intersect the perpendicular bisector of the six-axis force sensor, and apply a force to the workpiece along the y-axis direction of the grinding and polishing machine coordinate system , and record the data of the six-axis force sensor; 3) After recording the data in the y-axis direction of the six-axis force sensor, move the grinding disc to the edge of the workpiece to be ground. The plane of the grinding disc is perpendicular to the upper plane of the workpiece to be ground and perpendicular to the x-axis. Control the axis of the grinding disc to intersect with the perpendicular bisector of the six-axis force sensor, and apply a force to the workpiece along the x-axis direction of the grinding and polishing machine coordinate system. , and record the data of the six-axis force sensor; 4) After recording the data in the x-axis direction of the six-axis force sensor, move the grinding disc to the upper plane of the workpiece to be ground. The plane of the grinding disc is in contact with the upper plane of the workpiece to be ground and perpendicular to the z-axis. Control the axis of the grinding disc to coincide with the perpendicular bisector of the six-axis force sensor, and apply a force to the workpiece along the z-axis direction of the grinding and polishing machine coordinate system. , and record the data of the six-axis force sensor; 5) Repeat steps 2)-4), repeat the test 3 times, and each time control the distance between the axis of the grinding disc and the perpendicular bisector of the six-axis force sensor to be different from that in the previous cycle, and keep the distance of the perpendicular bisector unchanged in each cycle.

[0013] Through systematic calibration steps and multi-directional repeated tests, the accuracy of force measurement in the grinding and polishing process can be significantly improved.

[0014] Preferably, record the data read from the six-axis force sensor in step S2 as , , , and substitute and into the formula to obtain the element values in the transformation matrix; where represents the force and moment vector matrix in the six-axis force sensor coordinate system, represents the force and moment vector matrix in the grinding and polishing machine coordinate system; , , respectively represent the force vectors in the x-axis, y-axis, and z-axis directions in the six-axis force sensor coordinate system, , , respectively represent the moment vectors of the x-axis, y-axis, and z-axis of the six-axis force sensor; , , respectively represent the force vectors in the x-axis, y-axis, and z-axis directions in the grinding and polishing machine coordinate system, , , respectively represent the moment vectors in the x-axis, y-axis, and z-axis directions in the grinding and polishing machine coordinate system.

[0015] This method converts the data in the six-axis force sensor coordinate system to the grinding and polishing machine coordinate system through coordinate transformation, eliminating the measurement error caused by inconsistent coordinates.

[0016] Preferably, in step S1, after running the special grinding and polishing machine, it is necessary to determine whether the six-axis force sensor is working properly. The determination steps are as follows: Determine whether the special grinding and polishing machine is in a steady state. If it is in a steady state, read the grinding force sensed by the six-axis force sensor, read and observe the motor current, and determine whether the motor current changes within a certain time. If it does not change, it is abnormal; if it changes, determine whether the motor current is greater than . If it is greater, the six-axis force sensor is considered to be working properly; if it is not greater, the six-axis force sensor is working abnormally; where represents the normal motor current, represents the no-load current, and n represents a multiple, where n > 2; If the special grinding and polishing machine is in a non-steady state, read the grinding force data sensed by the six-axis force sensor, and determine whether the grinding force is stable. If the grinding force is in an unstable state, it is considered abnormal; if the grinding force is in a stable state, read the motor current data and determine whether the current is stable. If the current is unstable, it is considered abnormal; if the current is stable, the six-axis force sensor is working properly.

[0017] The method for judging the working state of the six-axis force sensor realizes the rapid diagnosis of the six-axis force sensor fault through multi-condition joint detection including steady state, non-steady state, force data, and motor current.

[0018] Preferably, when the special grinding and polishing machine is in a stable state and the grinding force sensed by the six-axis force sensor is less than , the difference between the motor current and the no-load current is within a specific range I; where, represents a set critical force value; the specific range I is related to the current and the torque coefficient of the motor; If the special grinding and polishing machine is in a stable state and the grinding force sensed by the six-axis force sensor is greater than or equal to , the difference between the motor current and the no-load current is stable within a specific range I of a fixed value; the specific range I and the fixed value are related to the current and the torque coefficient of the motor.

[0019] By introducing the dual criteria of the critical force value and the specific range I of the current difference, a more refined fault detection mechanism is provided for the on-site compensation of the six-axis force sensor.

[0020] Preferably, when there is a large change in the current, if the motor current changes from the normal to , where n > 2, it is considered a fault of the six-axis force sensor. Introducing the fault determination mechanism for the sudden change of the motor current can significantly improve the reliability and safety of the system.

[0021] Preferably, when determining whether the six-axis force sensor is working properly, an external step force needs to be applied to the six-axis sensor to determine the response time of the motor current. It is determined whether it meets the preset value. If the current response time does not meet the preset value, it is regarded that there is a problem with the data of the six-axis force sensor; if it meets, it is regarded that the data of the six-axis force sensor is normal. This provides a quantitative standard for the dynamic performance of the six-axis force sensor in judging its working state.

[0022] Preferably, in step S2, the acceleration data a obtained after obtaining the pseudo-inverse is based on the formula to obtain the load inertia force , where m represents the load mass.

[0023] The beneficial effects of the present invention compared with the prior art are as follows: By controlling the grinding and polishing special machine to perform a series of movements, load compensation and coordinate system relationship calibration are carried out on the six-axis force sensor. At the same time, during the working process of the grinding and polishing special machine, through the data monitoring of the six-axis force sensor and the grinding and polishing special machine, it is judged whether the six-axis force sensor is working properly, ensuring the accuracy of force feedback throughout the grinding and polishing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a flowchart of a field compensation method for a six-axis force sensor used in a grinding and polishing special machine; Figure 2 are the specific steps for calibrating the conversion relationship between the coordinate system of the six-axis force sensor and the coordinate system of the grinding and polishing special machine; Figure 3 is a logic diagram for judging whether there is a problem with the data of the six-axis force sensor. DETAILED DESCRIPTION OF THE INVENTION

[0025] Next, the technical solutions in the embodiments of the present invention will be described in detail in conjunction with the accompanying Figures 1 to 3 drawings of the embodiments of the present invention.

[0026] As Figure 1 shown, it is a flowchart of a field compensation method for a six-axis force sensor used in a grinding and polishing special machine. This method is based on the actual working site of the grinding and polishing special machine. By controlling the grinding and polishing special machine to perform a series of movements, load compensation and coordinate system relationship calibration are carried out on the six-axis force sensor. At the same time, during the working process of the grinding and polishing special machine, through the data monitoring of the six-axis force sensor and the grinding and polishing special machine, it is judged whether the six-axis force sensor is working properly, ensuring the accuracy of force feedback throughout the grinding and polishing process.

[0027] First, describe the installation position and working mode of the six-axis force sensor. The six-axis force sensor is installed at the upper end of the A-axis divider. The six-axis force sensor is connected to the workpiece via a jig. The A-axis motor is used to drive the A-axis divider. Then, the acceleration sensor is mounted on the upper end of the six-axis force sensor. The acceleration sensor is used to read the acceleration of the six-axis force sensor at each moment. The data read by the six-axis force sensor includes force and torque. The A-axis and the z-axis are axially coincident and both point vertically upward. The A-axis is a key rotating axis used to realize the rotational movement of the workpiece and the jig, and at the same time cooperate with the x, y, and z-axis movements to achieve multi-angle grinding. The A-axis divider is a high-precision indexing and positioning device used to control the rotation angle and pause position of the A-axis. Its core function is to convert continuous rotational movement into precise intermittent indexing movement to ensure that the workpiece can stop accurately at the set angle for operations such as grinding, polishing, or tool change. During the grinding and polishing process, the six-axis force sensor will rotate with the A-axis together with the workpiece and the jig. The load includes the workpiece and the jig. The force and torque sensed by the six-axis force sensor during the rotation process include the inertial force received by the load and the grinding force received by the workpiece. The A-axis assembly, the six-axis force sensor, the jig, and the workpiece will all move in the x-direction and y-direction along with the spindle. When grinding, the workpiece will be ground or polished by the grinding disc above. The grinding head can move up and down in the z-axis direction and can rotate around the A-axis, so as to achieve the purpose of switching multiple grinding heads.

[0028] Secondly, describe the steps for the six-axis force sensor to perform load compensation on the grinding and polishing machine. In step S1: Construct a coordinate system for the grinding and polishing machine with the geometric center of the grinding and polishing machine as the origin, the z-axis pointing vertically upward, control the x-axis and y-axis to be parallel to the upper plane of the workpiece to be ground, run the grinding and polishing machine. When the six-axis force sensor is working normally, read the force 、 、 and torque data 、 、 of the six-axis force sensor in the stationary state. The data of the six-axis force sensor mainly includes these six data. Execute a zero-clear instruction on the six-axis force sensor to make the force and torque of the six-axis force sensor in the stationary state both zero. Among them, 、 、 and respectively represent the original forces in the x-axis, y-axis, and z-axis directions of the six-axis force sensor in the stationary state, 、 、 respectively represent the original torques of the six-axis force sensor rotating around the x-axis, y-axis, and z-axis; Step S2: After executing the clearing instruction in Step S1, control the six-axis force sensor to move on the plane formed by the x-axis and the y-axis. Start grinding and polishing, read the data of the six-axis force sensor, record the acceleration and the six-axis force sensor data at each moment, obtain the pseudo-inverse of the acceleration data by the least squares method, and obtain the load inertia force from the pseudo-inversed acceleration data ; The least squares method is a method for solving the linear equation system Ax = b, where A is an m×n matrix, m > n, x is the unknown vector, and b is the observed vector; the least squares solution minimizes the sum of the squares of the residuals ; Obtaining the pseudo-inverse is to perform an inverse operation on the matrix composed of the acceleration data; Establish the relationship between the load inertia force and the acceleration by the least squares method, that is, solve the least squares solution of the following equation: ; Organize the acceleration data a(t) and the corresponding force data (t) into matrix form: ; Taking the x-axis as an example here, the y-axis and the z-axis are the same by analogy, , , and the obtained pseudo-inverse solution is , that is, the mass m is fitted by the least squares method. After obtaining m, the load inertia force is: ; represents the load inertia force, m represents the load mass, and a represents the acceleration; S3: In Step S2, perform load compensation on the six-axis force sensor data according to the load inertia force in Step S2 to obtain the grinding force after compensating for the load inertia force , , represents the original data of the six-axis force sensor, represents the load inertia force obtained from the acceleration data, and the + and - signs are related to the defined direction of the inertia force. The true grinding force is obtained through the following formula. The formula for obtaining the true grinding force is as follows: ; Among them, represents obtaining the true grinding force by performing load compensation on the six-axis force sensor, T represents the transformation matrix from the six-axis force sensor coordinate system to the grinding and polishing special machine coordinate system, represents the grinding force after compensating for the load inertia force, represents the initial reading of the six-axis force sensor in the no-load state. It is the zero drift or initial deviation of the six - axis force sensor under no load, no grinding force, and no movement. Subtracting this value can eliminate the zero - bias error of the six - axis force sensor itself and ensure that reflects the true grinding force.

[0029] By compensating for the inertial force, the actual grinding force between the tool and the workpiece can be measured more accurately, avoiding the interference of the inertial force, ensuring the accuracy of force feedback during the entire grinding and polishing process, and improving the working performance and reliability of the special grinding and polishing machine.

[0030] As Figure 2 shown, it is a specific step for calibrating the conversion relationship between the coordinate system of the six - axis force sensor and the coordinate system of the special polishing and grinding machine; combined with Figure 2 shown, in step S1, reading the data of the six - axis force sensor includes the following steps: 1) Construct a six - axis force sensor coordinate system with the geometric center of the six - axis force sensor as the origin. Control the z - axis of the special grinding and polishing machine to coincide with the A - axis of the A - axis divider and point to the workpiece, and control the x - axis and y - axis to be parallel to the upper plane of the workpiece to be ground. 2) After constructing the six - axis force sensor coordinate system, move the grinding disc to the edge of the workpiece to be ground. Control the grinding disc plane to be perpendicular to the upper plane of the workpiece to be ground, and the grinding disc plane to be perpendicular to the y - axis. Control the axis of the grinding disc to intersect the perpendicular bisector of the six - axis force sensor, and apply a force to the workpiece along the y - axis direction of the special grinding and polishing machine coordinate system , and record the data of the six - axis force sensor. 3) After recording the data in the y - axis direction of the six - axis force sensor, move the grinding disc to the edge of the workpiece to be ground. The grinding disc plane is perpendicular to the upper plane of the workpiece to be ground, and the grinding disc plane is perpendicular to the x - axis. Control the axis of the grinding disc to intersect the perpendicular bisector of the six - axis force sensor, and apply a force to the workpiece along the x - axis direction of the special grinding and polishing machine coordinate system , and record the data of the six - axis force sensor. 4) After recording the data in the x - axis direction of the six - axis force sensor, move the grinding disc to the upper plane of the workpiece to be ground. The grinding disc plane is in contact with the upper plane of the workpiece to be ground, and the grinding disc plane is perpendicular to the z - axis. Control the axis of the grinding disc to coincide with the perpendicular bisector of the six - axis force sensor, and apply a force to the workpiece along the z - axis direction of the special grinding and polishing machine coordinate system , and record the data of the six - axis force sensor. 5) Repeat steps 2) - 4), repeat the test 3 times. Each time, control the distance between the axis of the grinding disc and the perpendicular bisector of the six - axis force sensor to be different from that in the previous cycle, and keep the distance of the perpendicular bisector unchanged in each cycle. Read the final data of the six - axis force sensor.

[0031] This method can significantly improve the accuracy of force measurement during the grinding and polishing process through systematic calibration steps and multi - direction repeated tests.

[0032] The coordinate system of the six-axis force sensor may not be consistent with that of the grinding and polishing special machine, such as rotation or translation. The transformation matrix T converts the data of the six-axis force sensor from the six-axis force sensor coordinate system to the grinding and polishing special machine coordinate system to ensure the correct direction of the force.

[0033] Denote the data read from the six-axis force sensor in step S2 as , , , substitute and into the formula to obtain the values of each element in the transformation matrix; where, represents the force and torque vector matrix in the six-axis force sensor coordinate system, represents the force and torque vector matrix in the grinding and polishing special machine coordinate system; , , respectively represent the force vectors in the x-axis, y-axis, and z-axis directions in the six-axis force sensor coordinate system, , , respectively represent the torque vectors of the x-axis, y-axis, and z-axis of the six-axis force sensor; , , respectively represent the force vectors in the x-axis, y-axis, and z-axis directions in the grinding and polishing special machine coordinate system, , , respectively represent the torque vectors in the x-axis, y-axis, and z-axis directions in the grinding and polishing special machine coordinate system.

[0034] This method converts the data of the six-axis force sensor coordinate system to the grinding and polishing special machine coordinate system through coordinate transformation to eliminate the measurement error caused by inconsistent coordinates.

[0035] In step S1, after running the grinding and polishing special machine, it is necessary to judge whether the six-axis force sensor is working properly. The judgment steps are as follows: When the grinding and polishing special machine is in a stable state and the grinding force sensed by the six-axis force sensor is less than , the difference between the motor current and the no-load current is within a specific range I; where, represents a set critical force value, = 3N, N represents the unit of force, Newton; the specific range I is related to the current and the torque coefficient of the motor; the range of the difference between the motor current and the no-load current is within 10% - 30% of the motor current. The difference between the no-load current and the actual current I needs to satisfy .

[0036] If the special grinding and polishing machine is in a stable state and the grinding force sensed by the six-axis force sensor is greater than or equal to When this occurs, the difference between the motor current and the no-load current stabilizes within a specific range I of a fixed value; the specific range I and the fixed value are related to the current and the torque coefficient of the motor. In this solution, the fixed value is 2A, where A represents the unit of current, Ampere.

[0037] This method provides a more refined fault detection mechanism for on-site compensation of the six-axis force sensor by introducing the dual criteria of the critical force value and the specific range I of the current difference.

[0038] When an external force acts on the six-axis force sensor, the motor current will change. However, if the current suddenly changes significantly, such as instantaneously exceeding several times the rated current, it indicates that the six-axis force sensor has a fault. When the six-axis force sensor is working properly, if it is suddenly detected that the motor current changes from the normal to , where n > 2 and n represents the multiple, it means that there is a problem with the feedback of the six-axis force sensor, resulting in a sharp increase in the motor load, or there is an electrical fault in the motor itself, such as a short circuit.

[0039] Since the special grinding and polishing machine is an application scenario of a six-axis force sensor that requires rapid response to external force changes, the response time of the motor current is also an important judgment index. When a known, rapidly changing external force is applied, the motor current should respond within a reasonable time. When a step external force is applied to the six-axis force sensor, a step external force refers to a force that instantaneously increases from zero to a certain constant value and remains unchanged in a very short time, theoretically instantaneously. The motor current should start to change within , and reach near a new stable value. If the current response time is too long or too short, it means that there is a problem with the data of the six-axis force sensor.

[0040] As Figure 3 shown, it is a logic diagram for judging whether there is a problem with the data of the six-axis force sensor. The specific steps for judging whether the six-axis force sensor is working properly during the operation of the special grinding and polishing machine are as follows: Judge whether the special grinding and polishing machine is in a steady state. If it is in a steady state, read the grinding force sensed by the six-axis force sensor, read and observe the motor current, and judge whether the motor current changes within . If it does not change, it is abnormal; if it changes, judge whether the motor current is greater than . If it is greater, the six-axis force sensor is considered to be working properly; if it is not greater, the six-axis force sensor is working abnormally; where represents the normal motor current, It represents the no-load current, n represents the multiple, and n > 2; If the special grinding and polishing machine is in an unsteady state, read the grinding force data sensed by the six-axis force sensor to determine whether the grinding force is stable. If the grinding force is in an unstable state, it is regarded as abnormal; if the grinding force is in a stable state, read the motor current data and determine whether the current is stable. If the current is unstable, it is regarded as abnormal; if the current is stable, the six-axis force sensor is working properly. Introducing a fault determination mechanism for sudden changes in motor current can significantly improve the reliability and safety of the system. It provides a quantitative standard for the dynamic performance of the six-axis force sensor working state judgment.

[0041] In summary, the present invention performs load compensation and coordinate system relationship calibration on the six-axis force sensor by controlling the special grinding and polishing machine to execute a series of movements. At the same time, during the working process of the special grinding and polishing machine, by monitoring the data of the six-axis force sensor and the special grinding and polishing machine, it is determined whether the six-axis force sensor is working properly, ensuring the accuracy of force feedback in the entire grinding and polishing process, and having significant progressiveness.

[0042] The above embodiments are only used to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the present invention.

Claims

1. An on-site compensation method for a six-axis force sensor for a grinding and polishing machine, the grinding and polishing machine comprises a workpiece, a fixture, an A-axis motor, an A-axis, an acceleration sensor, a six-axis force sensor, and an A-axis divider, the first end of the six-axis force sensor is connected to the workpiece through the fixture, the second end of the six-axis force sensor is connected to the A-axis divider, and the A-axis divider is driven by the A-axis motor, characterized in that: The method comprises the following steps: S1: Construct the coordinate system of the grinding and polishing machine with the geometric center of the grinding and polishing machine as the origin, with the z-axis pointing vertically upward, and the x-axis and y-axis controlled to be parallel to the upper plane of the workpiece being polished. Run the grinding and polishing machine, and read the force of the six-dimensional force sensor in a static state when the six-dimensional force sensor is working normally. , , and torque data , , , execute the zeroing instruction on the six-axis force sensor, so that the force and torque of the six-axis force sensor in the static state are both zero; where, , , They represent the original forces of the six-dimensional force sensor in the x-axis, y-axis, and z-axis directions in a static state. , , Respectively represent the original torque of the six-dimensional force sensor rotating around the x-axis, y-axis, and z-axis; S2: After executing the reset instruction of step S1, control the six-dimensional force sensor to move on the plane formed by the x-axis and the y-axis, start grinding and polishing, read the data of the six-dimensional force sensor, and record the data of the six-dimensional force sensor as , the acceleration at each moment is obtained from the acceleration sensor, the pseudo-inverse of the acceleration data is obtained by the least squares method, and the load inertia force is obtained from the acceleration data after pseudo-inverse. ; S3: In step S2, load compensation is performed on the six-dimensional force sensor data according to the load inertia force in step S2 to obtain the grinding force after the load inertia force has been compensated. , , the real grinding force is obtained by the following formula, and the formula for obtaining the real grinding force is as follows: ， in, It indicates that the six-dimensional force sensor performs load compensation to obtain the real grinding force, and T indicates the conversion matrix from the six-dimensional force sensor coordinate system to the grinding and polishing machine coordinate system. Indicates the initial reading of the six-axis force sensor in the no-load state.

2. The on-site compensation method of a six-dimensional force sensor for a grinding and polishing machine according to claim 1 is characterized in that: In step S2, reading the six-dimensional force sensor data includes the following steps: 1) Construct a six-dimensional force sensor coordinate system with the geometric center of the six-dimensional force sensor as the origin, control the z-axis of the grinding and polishing machine to coincide with the A-axis of the A-axis divider and point to the workpiece, and control the x-axis and y-axis to be parallel to the upper plane of the workpiece being ground; 2) After constructing the six-dimensional force sensor coordinate system, move the grinding disc to the edge of the workpiece being polished, control the plane of the grinding disc to be perpendicular to the plane on the workpiece being polished, and the plane of the grinding disc to be perpendicular to the y-axis, control the axis of the grinding disc to intersect with the mid-perpendicular line of the six-dimensional force sensor, and apply force to the workpiece along the y-axis direction of the coordinate system of the polishing machine , record six-dimensional force sensor data; 3) After recording the data of the six-dimensional force sensor in the y-axis direction, move the grinding disc to the edge of the workpiece being polished, so that the plane of the grinding disc is perpendicular to the plane on the workpiece being polished, and the plane of the grinding disc is perpendicular to the x-axis. Control the axis of the grinding disc to intersect with the mid-perpendicular line of the six-dimensional force sensor, and apply force to the workpiece along the x-axis direction of the coordinate system of the polishing machine. , record six-dimensional force sensor data; 4) After recording the data of the six-dimensional force sensor in the x-axis direction, move the grinding disc to the upper plane of the workpiece being polished, so that the grinding disc plane contacts the upper plane of the workpiece being polished and the grinding disc plane is perpendicular to the z-axis. Control the grinding disc axis to coincide with the mid-perpendicular line of the six-dimensional force sensor, and apply force to the workpiece along the z-axis direction of the coordinate system of the polishing machine. , record six-dimensional force sensor data; 5) Repeat steps 2) to 4) and repeat the test 3 times. Each time, the distance between the grinding disc axis and the mid-perpendicular line of the six-dimensional force sensor is controlled to be different from that in the previous cycle, and the distance between the mid-perpendicular lines remains unchanged in each cycle.

3. The on-site compensation method of a six-dimensional force sensor for a grinding and polishing machine according to claim 1 is characterized in that: The data of the six-dimensional force sensor read in step S2 is recorded as , , ,Will and Substitute into the formula , get the values ​​of each element in the transformation matrix; where, represents the force and torque vector matrix in the six-dimensional force sensor coordinate system, Represents the force and torque vector matrix in the coordinate system of the grinding and polishing machine; , , They represent the force vectors in the x-axis, y-axis, and z-axis directions in the six-dimensional force sensor coordinate system. , , Respectively represent the x-axis, y-axis, and z-axis moment vectors of the six-dimensional force sensor; , , They represent the force vectors in the x-axis, y-axis, and z-axis directions in the coordinate system of the grinding and polishing machine. , , They respectively represent the torque vectors in the x-axis, y-axis, and z-axis directions in the coordinate system of the grinding and polishing machine.

4. The on-site compensation method of a six-dimensional force sensor for a grinding and polishing machine according to claim 1 is characterized in that: In step S1, after the grinding and polishing machine is running, it is necessary to determine whether the six-dimensional force sensor is working normally. The determination steps include: When the grinding and polishing machine is in a steady state, read the grinding force sensed by the six-dimensional force sensor, read and observe the motor current, and determine whether the motor current is Does it change within the time? If it does not change, it is abnormal; if it changes, judge the motor current Is it greater than , if it is greater than, the six-dimensional force sensor is considered to be working normally; if it is not greater than, the six-dimensional force sensor is considered to be working abnormally; Indicates the normal motor current, Represents no-load current, n represents multiple, n>

2.

5. The on-site compensation method of a six-dimensional force sensor for a grinding and polishing machine according to claim 4 is characterized in that: The judgment step also includes: when the grinding and polishing machine is in a non-steady state, reading the grinding force data sensed by the six-dimensional force sensor to determine whether the grinding force is stable. If the grinding force is in an unstable state, it is considered abnormal; if the grinding force is in a stable state, reading the motor current data and determining whether the current is stable. If the current is unstable, it is considered abnormal; if the current is stable, the six-dimensional force sensor is working normally.

6. The on-site compensation method of a six-dimensional force sensor for a grinding and polishing machine according to claim 4 is characterized in that: When the grinding and polishing machine is in a stable state and the grinding force sensed by the six-dimensional force sensor is less than When , the difference between the motor current and the no-load current is within a specific range I; where, Indicates a critical force value to be set; the specific range I is related to the current and the torque coefficient of the motor.

7. The on-site compensation method of a six-dimensional force sensor for a grinding and polishing machine according to claim 4 is characterized in that: If the grinding and polishing machine is in a stable state and the grinding force sensed by the six-dimensional force sensor is greater than or equal to When the motor current is 0.05V, the difference between the motor current and the no-load current is stabilized at a fixed value within a specific range I; the specific range I and the fixed value are related to the current and the torque coefficient of the motor.

8. The on-site compensation method of a six-dimensional force sensor for a grinding and polishing machine according to claim 4 is characterized in that: When the current changes greatly, if the motor current changes from normal becomes , n>2, it is considered as a six-dimensional force sensor failure.

9. The on-site compensation method of a six-dimensional force sensor for a grinding and polishing machine according to claim 4, characterized in that: When judging whether the six-dimensional force sensor is working properly, it is also necessary to apply a step external force to the six-dimensional sensor to judge the response time of the motor current. Whether the preset value is met. If the current response time does not meet the preset value, it is considered that there is a problem with the data of the six-dimensional force sensor; if it meets the preset value, it is considered that the data of the six-dimensional force sensor is normal.

10. The on-site compensation method of a six-dimensional force sensor for a grinding and polishing machine according to claim 1, characterized in that: In step S2, the acceleration data a obtained by calculating the pseudo-inverse is based on the formula Get the load inertia force , m represents the load mass.

Images