Polishing robot proportional damping control method and system based on force sensor

Abstract

The application provides a polishing robot proportional damping control method and system based on a force sensor. The method comprises a mechanical arm and a polishing head. The method collects the force and torque received by the end of the mechanical arm in real time, filters the high-frequency noise in the force and torque, and obtains the actual contact force signal measured by the current force sensor. The expected force under the current polishing condition of the polishing robot is calculated, and the difference between the expected force and the actual contact force signal is the current force deviation. The current force deviation is converted into an electric signal required for the polishing robot to generate the expected force. The change amount of each joint angle of the mechanical arm is calculated to obtain the movement speed of the end of the mechanical arm, and the electric signal required for the polishing robot to generate the damping force of the current movement speed is calculated. The robot completes proportional damping control according to the electric signal. The control system applies the above control method, and comprises a polishing robot mechanical arm, a clamping mechanism, a polishing head, an angle sensor and a force sensor.

Description

Technical Field

[0001] This invention belongs to the field of grinding robot control technology, specifically relating to a proportional damping control method for surface grinding robots based on force sensors. Background Technology

[0002] Polishing and grinding are essential processes in many industrial production processes. Traditional polishing and grinding processes are often mainly manual operations. The dust and noise generated during the operation threaten the physical and mental health of the operators. In addition, a large amount of repetitive work requires a high level of skill and concentration from the practitioners, which poses a risk of processing errors.

[0003] The application of robots to replace humans in performing repetitive tasks requiring high precision is imperative. Current industrial robot grinding primarily involves fixing the cutting tool (or grinding wheel) to a worktable and having a robotic arm grasp the workpiece and bring it close to the tool (or wheel) for grinding. Due to limitations in sensor accuracy, this grinding method can only perform rough processing on regularly shaped workpieces. It cannot accurately control the contact force between the grinding tool and the workpiece surface, easily generating significant impact forces at the moment of contact, leading to internal damage or other issues. Furthermore, the high-frequency vibrations generated by the high-speed rotation of the grinding drill bit itself make it difficult for sensors installed in the grinding system to accurately detect and measure these vibrations, further complicating the precise control of the robot.

[0004] Given this current technological state, automated robotic grinding requires higher precision sensors to accurately perceive the contact force between the grinding head and the workpiece surface, high-frequency signal filtering to reduce the interference of grinding head vibration on control, and optimized control strategies to mitigate the impact force on the workpiece at the moment of contact. Ultimately, it is necessary to accurately control the tool to grind the workpiece according to the desired force. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a proportional damping control method for a surface grinding robot using a force sensor, which solves the problem that existing robots cannot accurately control the contact force during the grinding process.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a proportional damping control method for a surface polishing robot based on a force sensor, comprising a robot base and a robotic arm, and a polishing head.

[0007] The system collects the forces and torques acting on the end effector of the robotic arm in real time. When the grinding drill bit is working, the vibrations generated by its high-speed rotation will affect the forces and torques directly collected by the force sensor. The data causes interference. To solve this problem, a low-pass filter is applied to filter the force and torque. High-frequency noise in the signal is filtered out to obtain the actual contact force signal measured by the current force sensor. The expected force of the grinding robot under the current grinding conditions is The difference between the expected force and the actual contact force signal is the deviation of the current force. The calculation formula is as follows:

[0008]

[0009] The deviation of the current force is controlled by the proportional controller. This is converted into the electrical signal needed to control the grinding robot to generate the desired force. The proportional controller model is as follows:

[0010]

[0011] In the formula, k f These are the parameters of the proportional controller for the grinding robot. The value of the proportional controller parameters is adjusted according to the on-site control effect.

[0012] The speed of the grinding head at the end of the robotic arm is calculated based on the changes in the angles of each joint of the robotic arm. The damping controller calculates the electrical signal required for the grinding robot to generate the damping force at its current movement speed. To counteract the impact of the robot's motion on the workpiece under the proportional controller, the damping controller model is as follows:

[0013]

[0014] In the formula, k b These are the damping controller parameters for the grinding robot.

[0015] Furthermore, during the grinding process, the force output by the grinding head at the end of the robotic arm changes in real time. Therefore, the parameters of the damping controller also need to be adjusted in real time according to the force error during the adjustment process. The damping controller parameter k at time t... b The adjustment value Δk b (t) is:

[0016]

[0017] λ is the sampling period for the movement speed of the grinding head at the end of the grinding robot system, and Δk b (t-λ) represents the adjustment value of the controller parameters at the previous moment, and η represents the update frequency of the force sensor's acquired signal.

[0018] The robot's control signal at this time is:

[0019]

[0020] The control signal is sent to the grinding robot to complete the proportional damping control.

[0021] Furthermore, when the grinding robot is working, the actual position of the grinding head is obtained through the image acquisition module. The desired grinding location of the grinding robot is The difference between the desired grinding position and the actual position is the deviation of the current position. The calculation formula is as follows:

[0022]

[0023] The desired polishing range is (-x) s ,x s ), where x s >0; when When the position of the grinding head is within the desired grinding range, the grinding head motor is activated to begin grinding; when When the setting is reached, it indicates that the position and depth of the grinding head do not meet the set requirements, and grinding will stop. This avoids over-processing and reduces motor idling, saving energy.

[0024] Furthermore, by observing the noise spectrum, it can be found that the vibration noise is mainly concentrated above 200Hz. Applying a low-pass filter to filter out the force and torque... To address the interference of high-frequency noise of 200Hz and above present in the grinding head, the vibration of the grinding head is used to resolve the signal interference of the force sensor's contact force acquisition.

[0025] Sending control signals to the grinding robot completes one instance of proportional damping control. During the contact between the grinding head and the workpiece, the robotic arm's end effector moves at a relatively high speed, where the damping mechanism plays a significant role in mitigating impact and preventing damage. During the grinding process, the system feeds back the motion speed of the robot's end effector and the magnitude of force and torque collected by force sensors to the control system, forming a feedback loop. Repeating these steps allows the system to control the grinding operation based on the desired position of the robot. and expected force Continuously adjust the robot's current position The feed rate of the grinding head during the grinding process is controlled by proportional damping, thereby achieving impact-free automatic grinding of the components to be processed.

[0026] The present invention also provides a proportional damping control system for a grinding robot based on force sensors, including a grinding robot arm, a gripping mechanism, a grinding head, and also including an angle sensor and a force sensor; and applies the proportional damping control method for a grinding robot based on force sensors as described above.

[0027] An angle sensor is fixedly mounted on the joint of the robotic arm to collect the angle information of the joint in real time. A force sensor is fixedly mounted on the end of the robotic arm to collect the contact force and torque at the end of the robotic arm. A clamping mechanism is fixedly mounted on the force transmission shaft of the force sensor and connected to the grinding head for processing the component to be processed.

[0028] Force sensors mounted on the end effector of the robotic arm collect the applied forces and torques in real time.

[0029] Furthermore, the filtering force and torque of the low-pass filter are applied. The high-frequency noise in the signal is used to obtain the actual contact force signal measured by the current force sensor. The deviation of the current force is controlled by the proportional controller. This is converted into the electrical signal needed to control the grinding robot to generate the desired force.

[0030] The change in angle of each joint is calculated based on the encoder at the joint of the robotic arm, thereby calculating the end effector speed of the robotic arm. The damping controller calculates the electrical signal required for the grinding robot to generate the damping force at its current movement speed.

[0031] The grinding robot performs proportional damping control based on the control signal.

[0032] Furthermore, the proportional damping control method for a grinding robot based on a force sensor as described in claim 2 also includes an image acquisition module; the image acquisition module acquires image information of the grinding head and the component to be processed, and obtains the actual position of the current grinding head.

[0033] The present invention has the following beneficial effects: (1) The proportional damping control method is used to control the grinding robot, which reduces the impact force at the moment of contact between the cutting head and the component, ensures the smooth contact between the grinding head and the component to be processed, and enables more accurate force control during the grinding process, reducing the damage to the component.

[0034] (2) A force sensor was installed at the end of the grinding robot to accurately and completely acquire the contact force and torque data between the grinding head and the workpiece during the grinding process.

[0035] (3) After obtaining the force sensor data, a low-pass filter was added to filter the high-frequency noise generated by the rotation of the grinding head, thereby reducing the interference to the controller input signal.

[0036] (4) The image acquisition module collects the position information of the grinding head and the component to be processed in real time, and judges whether the grinding depth and position meet the set requirements. This is used as a switch quantity to control the on and off of the grinding motor, avoiding unnecessary processing and improving production efficiency. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the proportional damping control system for a surface polishing robot based on a force sensor, according to an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram illustrating the control principle of the proportional damping control method for a surface polishing robot based on a force sensor, according to an embodiment of the present invention.

[0039] Among them: 1 is the robotic arm, 2 is the angle sensor, 3 is the force sensor, 4 is the clamping mechanism, 5 is the grinding head, 6 is the component to be processed, and 7 is the industrial camera. Detailed Implementation

[0040] To facilitate understanding by those skilled in the art, the present invention will be further described below in conjunction with embodiments and accompanying drawings.

[0041] The proportional damping control system for a surface polishing robot based on force sensors includes a robot base and robotic arm 1, an angle sensor 2, a force sensor 3, a clamping mechanism 4, a polishing head 5, the component to be processed 6, and an industrial camera 7 (i.e., an image acquisition module).

[0042] Angle sensors 2 are fixedly installed on each joint of the robotic arm 1 to collect the angle information of each joint in real time. Force sensors 3 are fixedly installed at the end of the robotic arm 1 to collect the contact force and torque at the end of the robotic arm. Clamping mechanism 4 is fixedly installed on the force transmission shaft of force sensor 3 and connected to grinding head 5 to process the workpiece 6. Industrial camera 7 is fixedly installed outside the processing area to collect image information of grinding head 5 and workpiece 6.

[0043] like Figure 2 As shown, the robot's desired position at a certain moment during the polishing process is... The expected force under the current polishing conditions is The desired polishing range is (-x) s ,x s (x) s >0).

[0044] The actual position of the robotic arm 1 is obtained using industrial camera 7. The difference between the robot's desired grinding position and the actual grinding head position is The calculation formula is as follows:

[0045]

[0046] when When the position of grinding head 5 is within the desired grinding range, the motor of grinding head 5 is switched on to begin grinding; when When the position and depth of the grinding head 5 do not meet the set requirements, the motor of the grinding head 5 is turned off to stop grinding, thus avoiding over-processing and reducing motor idling, saving energy.

[0047] The force sensor 3, installed at the end of the robot arm 1, collects the forces and torques acting on it in real time along the X, Y, and Z axes in a three-dimensional coordinate system. When the grinding head 5 is working, the vibrations generated by its high-speed rotation will affect the forces and torques directly collected by the force sensor 3. The data causes interference, therefore a low-pass filter is applied to filter out force and torque. High-frequency noise in the signal is filtered out to obtain the actual contact force signal measured by the current force sensor.

[0048] The difference between the robot's expected force and the actual force was calculated to be... The calculation formula is as follows:

[0049]

[0050] The deviation of the current force is controlled by the proportional controller. This is converted into the electrical signal needed to control the robot to generate the desired force. The proportional controller model is as follows:

[0051]

[0052] In the formula, k f These are the proportional controller parameters that are tuned based on the robot's actual performance parameters.

[0053] The encoders at the joints of the robotic arm provide feedback to calculate the changes in the angles of each joint in real time. The velocity of the grinding head at the end effector of the robot arm 1 was obtained by forward kinematics calculation. This parameter is the same as the movement speed of the robotic arm's end effector and can be directly obtained from the robot development SDK. A damping controller can be designed to calculate the electrical signal required to generate the damping force needed for the robot to reach its current movement speed. To counteract the impact of the robot's motion on the workpiece under the proportional controller, the damping controller model is as follows:

[0054]

[0055] In the formula, k b These are damping controller parameters that are tuned based on the robot's actual performance parameters.

[0056] During the grinding process, the force output by the grinding head at the end of the robotic arm changes in real time. Therefore, the parameters of the damping controller also need to be adjusted in real time according to the force error during the adjustment process. The damping controller parameter k at time t... b The adjustment value Δk b (t) is:

[0057]

[0058] In the formula, λ is the sampling period of the grinding head movement speed at the end of the grinding robot system, and Δk b (t-λ) represents the adjustment value of the controller parameters at the previous moment, and η represents the update frequency of the force sensor's acquired signal.

[0059] The robot's control signal at this time is:

[0060]

[0061] Sending control signals to the grinding robot completes one instance of proportional damping control. During the contact between the grinding head 5 and the workpiece 6, the end effector of the robotic arm 1 moves at a relatively high speed, resulting in a significant damping effect that effectively reduces the impact on the workpiece 6 during contact, preventing damage. During the grinding process, the robot's current end effector speed and the force and torque magnitudes collected by the force sensor 3 are fed back to the control system, forming a feedback loop. Repeating these steps allows the system to control the grinding operation based on the desired position of the robot. and expected force Continuously adjust the robot's current position The feed rate of the grinding head 5 during the grinding process is controlled by proportional damping, thereby achieving impact-free automatic grinding of the component 6 to be processed.

[0062] The above embodiments are merely illustrative of the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A force sensor based polishing robot proportional damping control method, characterized by: Includes robotic arms and grinding heads; Real-time acquisition of forces and torques acting on the end effector of the robotic arm. Filtering force and torque High-frequency noise in The actual contact force signal measured by the current force sensor The expected force of the grinding robot under the current grinding conditions is: The difference between the expected force and the actual contact force signal is the deviation of the current force. Calculation formula: ; The deviation of the current force This is converted into the electrical signal needed to control the grinding robot to generate the desired force. The proportional controller model is as follows: ; In the formula, is the proportional controller parameter of the polishing robot; The speed of the grinding head at the end of the robotic arm is calculated based on the changes in the angles of each joint of the robotic arm. The electrical signal required to calculate the damping force needed for the grinding robot to generate its current motion speed. The damping controller model is as follows: ; In the formula, is the damping controller parameter of the polishing robot; The control signal of the robot at this time is: ; The control signal is sent to the grinding robot to complete the proportional damping control; During the polishing process, the damping controller parameters Adjustments are made in real time based on the force error during the adjustment process. Time-of-flight damping controller parameters Adjustment value for: , To determine the sampling period for the movement speed of the grinding head at the end of the grinding robot system, These are the adjustment values ​​of the controller parameters from the previous moment. This refers to the update frequency of the signals acquired by the force sensor.

2. The proportional damping control method for a grinding robot based on a force sensor according to claim 1, characterized in that: When the grinding robot is working, obtain the actual position of the grinding head currently connected to the robotic arm. The desired grinding location of the grinding robot The difference between the expected grinding position and the actual position is the deviation of the current position. Calculation formula: The desired polishing area is ,in ;when At that time, the grinding head performs grinding; when At that time, the grinding head stops grinding.

3. The force sensor based polishing robot proportional damping control method of claim 1, wherein: The filtered high-frequency noise is 200Hz and above.

4. A force sensor based polishing robot proportional damping control system characterized by: This includes a grinding robot arm, a gripping mechanism, a grinding head, as well as angle sensors and force sensors; The proportional damping control method for a grinding robot based on a force sensor as described in claim 1 is applied. An angle sensor is fixedly mounted on the joint of the robotic arm to collect the angle information of the joint in real time. A force sensor is fixedly mounted on the end of the robotic arm to collect the contact force and torque at the end of the robotic arm. A clamping mechanism is fixedly mounted on the force transmission shaft of the force sensor and connected to the grinding head for processing the component to be processed. The force sensor installed at the end of the mechanical arm collects the force and torque in real time .

5. The proportional damping control system for a grinding robot based on a force sensor according to claim 4, characterized in that: Applying low-pass filter filtering force and torque The high-frequency noise in the signal is used to obtain the actual contact force signal measured by the current force sensor. ; The deviation of the current force is converted by a proportional controller into an electrical signal needed to control the polishing robot to generate the desired force ;​ The change in the angle of each joint is calculated based on the encoder at the joint of the robotic arm, thereby calculating the speed of the grinding head at the end of the robotic arm. The damping controller calculates the electrical signal required for the grinding robot to generate the damping force at its current speed. ; The grinding robot performs proportional damping control based on the control signal.

6. The force sensor based polishing robot proportional damping control system of claim 4 or 5, wherein: The proportional damping control method for a grinding robot based on a force sensor, as described in any one of claims 2 to 3, is applied. Also comprising an image acquisition module; the image acquisition module acquires image information of the polishing head and the element to be processed, and obtains the actual position of the current polishing head .

Images