Casting cleaning robot force control method based on self-adaptive impedance control

Abstract

The invention discloses a casting cleaning robot force control method based on self-adaptive impedance control, and the method comprises the steps: collecting and obtaining a plurality of groups of characterization working forces of a casting cleaning robot end tool under different poses through a six-dimensional force sensor, so as to obtain the actual working force of the casting cleaning robot end tool; obtaining a given position and a given workload of the casting cleaning robot, and obtaining a force deviation value of the casting cleaning robot based on the constructed force adaptive control model; and constructing a force impedance control model, obtaining the position deviation of the end tool of the casting cleaning robot according to the force deviation value, compensating the position deviation to a given position of the casting cleaning robot by adopting an inverse kinematics method, and adjusting according to the end tool track of the casting cleaning robot. And the working force of the tail end tool of the casting cleaning robot is controlled until the position deviation is completely eliminated. The problems that in an existing casting cleaning process, the tail end working force cannot be accurately controlled, and the casting robot is poor in casting cleaning quality and low in casting cleaning efficiency are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of robot casting cleaning, and particularly relates to a force control method for a casting cleaning robot based on adaptive impedance control. Background Art

[0002] With the development of the times, people have put forward higher and higher usage requirements for castings. At the same time, in order to improve work efficiency and the quality of castings, people have gradually started to use robots to replace manual labor for cleaning castings. In order to ensure that the entire cleaning process is efficient and controllable, it is necessary to measure and adjust the working force of the robot in real time during the cleaning process, so as to realize real-time control of the workload of the robot, and finally improve the work efficiency of the robot and the quality of the cleaned castings.

[0003] However, during the cleaning process, it is difficult to achieve precise control of the force generated by the contact between the end of the robot and the casting. For example, if this force is too small, it will lead to insufficient cleaning of the casting, affecting the surface accuracy of the product; if this force is too large, it will exceed the bearing range of the product, resulting in damage to the casting. Furthermore, due to the inability to precisely control the movement and output force of the robot, the work efficiency of the robot is low and the quality accuracy of the cleaned castings is poor. Therefore, during the cleaning process, the force control and motion control of the robot are very important issues. Summary of the Invention

[0004] The present invention provides a force control method for a casting cleaning robot based on adaptive impedance control to overcome the above technical problems.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A force control method for a casting cleaning robot based on adaptive impedance control specifically includes the following steps:

[0007] S1: Collect and obtain the representative working forces of the end tool of the casting cleaning robot in multiple different poses through a six-axis force sensor, and perform gravity compensation on the representative working forces to obtain the actual working force of the end tool of the casting cleaning robot;

[0008] S2: Obtain the given position and given workload of the casting cleaning robot, and based on the constructed force adaptive control model, obtain the force deviation amount of the casting cleaning robot according to the actual working force;

[0009] S3: Construct a force impedance control model, obtain the position deviation of the end tool of the casting cleaning robot according to the force deviation amount, and use the inverse kinematics method to compensate the position deviation to the given position of the casting cleaning robot to adjust the trajectory of the end tool of the casting cleaning robot and obtain the new working position of the end tool of the robot;

[0010] The new working position is used as the given position of the casting cleaning robot, and step S2 is repeatedly performed until the position deviation is completely eliminated, so as to realize the working force control of the end tool of the casting cleaning robot.

[0011] Furthermore, the S1 specifically includes the following steps:

[0012] S11: collecting and obtaining the representative working force of the end tool of the casting cleaning robot in multiple groups of different positions through a six-dimensional force sensor, and the representative working force is the sum of the zero point data with error of the sensor itself and the force generated by the gravity of the end tool of the robot;

[0013] The calculation formula for characterizing the working force is:

[0014]

[0015] Where: f x ,f y ,f z They respectively represent the components of the force sensor data in the x-axis, y-axis and z-axis directions in the preset sensor base coordinate system; G represents the gravity of the robot end tool; U and V represent the angles between the robot base coordinates and the world coordinates; It represents the zero point data of the sensor in the x-axis, y-axis and z-axis directions in the preset sensor base coordinate system; α, β, γ represent the angles between the robot end tool and the x-axis, y-axis and z-axis directions of the preset sensor base coordinate system;

[0016] S12: Solve multiple sets of calculation formulas representing the working force jointly, that is, the component force and sensor zero point data of the robot end tool gravity in the preset sensor base coordinate system can be obtained, so as to realize the gravity compensation of the end tool for the representing working force and obtain the actual working force of the casting cleaning robot end tool.

[0017] Furthermore, the S2 specifically includes the following steps:

[0018] S21: Obtaining a given position and a given workload of the casting cleaning robot, and performing differential transformation on the given position to obtain a motion speed;

[0019] S22: constructing a force adaptive control model, wherein the force adaptive control model includes a processing parameter estimation model and an expected grinding force measurement model;

[0020] And the expression of the processing parameter estimation model is

[0021]

[0022] Where: a erepresents the output of the processing parameter estimation model, i.e., the actual processing amount of the casting cleaning robot; F represents the actual working force of the robot; V w represents the actual processing speed of the robot; represents the expression of the environmental stiffness of the casting cleaning robot;

[0023] The expression of the expected grinding force measurement model is

[0024]

[0025] In the formula: F q represents the output of the expected grinding force measurement model, i.e., the expected working force of the casting cleaning robot; K m represents the mass matrix of the casting cleaning robot; V represents the movement speed of the casting cleaning robot obtained by differentiating the given position;

[0026] S23: Based on the processing parameter estimation model, obtain the deviation amount Δa of the workload according to the given workload, and Δa = a - a e , where a represents the given workload; a e represents the actual processing amount of the casting cleaning robot;

[0027] S24: Based on the expected grinding force measurement model, obtain the expected working force F according to the deviation amount Δa of the workload and the movement speed V q , and combine with the actual working force F to obtain the force deviation amount ΔF, and ΔF = F q -F.

[0028] Further, the specific steps of S3 are as follows:

[0029] S31: Substitute the force deviation amount into the constructed force impedance control model to obtain the position deviation of the end tool of the casting cleaning robot;

[0030] S32: Use the inverse kinematics method to compensate the position deviation to the given position of the casting cleaning robot, adjust the trajectory of the end tool of the casting cleaning robot, and obtain the new working position of the end tool of the robot;

[0031] S33: Take the new working position as the given position of the casting cleaning robot, and repeat step S2 until the position deviation is completely eliminated to achieve the working force control of the end tool of the casting cleaning robot.

[0032] Further, the expression of the force impedance control model constructed in S31 is

[0033]

[0034] Where: ΔF represents the difference between the desired working force and the actual working force; ΔX represents the position deviation; M d represents the inertia parameter of the casting cleaning robot; B d represents the damping parameter of the casting cleaning robot; K d represents the stiffness parameter of the casting cleaning robot.

[0035] Beneficial effects: The present invention provides a force control method for a casting cleaning robot based on adaptive impedance control. By installing a six-axis force sensor at the end of the robot to obtain the actual working force, the force deviation of the casting cleaning robot is obtained based on the constructed force adaptive control model, and it is compared with the desired force in the force impedance control model. Thus, the force deviation is converted into the displacement offset of the casting cleaning robot, and the inverse kinematics method is used to compensate the position deviation to the given position of the casting cleaning robot, and the working force of the end tool of the casting cleaning robot is adjusted until the position deviation is completely eliminated, so as to realize the working force control of the end tool of the casting cleaning robot, making the working force generated by the contact between the end of the robot and the casting more accurate, and greatly improving the quality and efficiency of the casting robot for cleaning the casting. Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 is the flow chart of the force control method for the casting cleaning robot based on adaptive impedance control of the present invention;

[0038] Figure 2 is the structural diagram of the adaptive impedance control model in this embodiment;

[0039] Figure 3 is the schematic block diagram of the force adaptive control model in this embodiment. Detailed Embodiments

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0041] This embodiment provides a casting cleaning robot force control method based on adaptive impedance control, such as Figures 1 to 3 As shown, the specific steps include:

[0042] S1: The six-dimensional force sensor is used to collect and obtain the representative working force of the end tool of the casting cleaning robot in multiple different positions, and the gravity compensation of the end tool is performed on the representative working force to obtain the actual working force of the end tool of the casting cleaning robot, which specifically includes the following steps:

[0043] S11: collecting and obtaining the representative working force of the end tool of the casting cleaning robot in multiple groups of different positions through a six-dimensional force sensor, and the representative working force is the sum of the zero point data with error of the sensor itself and the force generated by the gravity of the end tool of the robot;

[0044] The calculation formula for characterizing the working force is:

[0045]

[0046] Where: f x ,f y ,f z They respectively represent the components of the force sensor data in the x-axis, y-axis and z-axis directions in the preset sensor base coordinate system; G represents the gravity of the robot end tool; U and V represent the angles between the robot base coordinates and the world coordinates; It represents the zero point data of the sensor in the x-axis, y-axis and z-axis directions in the preset sensor base coordinate system; α, β, γ represent the angles between the robot end tool and the x-axis, y-axis and z-axis directions of the preset sensor base coordinate system;

[0047] S12: Solving multiple groups of calculation formulas representing the working force jointly, that is, obtaining the component force and sensor zero point data of the gravity of the end tool of the casting cleaning robot in the preset sensor base coordinate system, so as to realize the gravity compensation of the end tool for representing the working force, and obtain the actual working force of the end tool of the casting cleaning robot; wherein, the gravity compensation: summing the component force and sensor zero point data of the gravity of the end tool of the casting cleaning robot in the preset sensor base coordinate system, and then directly subtracting the data obtained by summing the component force and sensor zero point data from the actual sensor reading, that is, completing the gravity compensation, and obtaining the actual working force of the end tool of the casting cleaning robot;

[0048] In this embodiment, the actual working force of the robot is collected by a six-axis force sensor. To ensure the accuracy of the collected data, it is necessary to collect multiple groups of data obtained by the six-axis force sensor when the robot is in different poses, and then substitute the data into the formula for characterizing the working force to form a system of equations with more than two groups. Furthermore, by solving the system of equations for the formula characterizing the working force, the gravity compensation for the sensor measurement data is realized, and thus the true working force at the end of the casting cleaning robot during operation is obtained;

[0049] S2: Obtain the given position and given workload of the casting cleaning robot, and based on the constructed force adaptive control model, obtain the force deviation of the casting cleaning robot according to the actual working force. The specific steps are as follows:

[0050] S21: Obtain the given position and given workload of the casting cleaning robot, and perform differential transformation on the given position to obtain the motion speed;

[0051] S22: Construct a force adaptive control model, and the force adaptive control model includes a processing parameter estimation model and an expected grinding force calculation model;

[0052] And the expression of the processing parameter estimation model is

[0053]

[0054] In the formula: a e represents the output of the processing parameter estimation model, that is, the actual processing amount of the casting cleaning robot; F represents the actual working force of the robot, that is, the value that can be directly read from the sensor after gravity compensation; V w represents the actual processing speed of the robot, that is, obtained by integrating the acceleration of the robot through the inverse kinematics method of the robot (the inverse kinematics method is a common method in the field of robots and will not be elaborated here); represents the expression of the environmental stiffness of the casting cleaning robot, and is a constant value in a determined working environment;

[0055] The expression of the expected grinding force calculation model is

[0056]

[0057] In the formula: F q represents the output of the expected grinding force calculation model, that is, the expected working force of the casting cleaning robot; K m represents the mass matrix of the casting cleaning robot, and its specific expression is related to the model parameters of the robot body; V represents the motion speed of the casting cleaning robot obtained by differentiating the given position;

[0058] S23: Based on the processing parameter estimation model, obtain the deviation amount Δa of the workload according to the given workload, and Δa = a - a e , where a represents the given workload; a e represents the actual processing amount of the casting cleaning robot;

[0059] S24: Based on the expected grinding force measurement model, obtain the expected working force F according to the deviation amount Δa of the workload and the movement speed V q , and combine with the actual working force F to obtain the force deviation amount ΔF, and ΔF = F q - F;

[0060] S3: Construct a force impedance control model, obtain the position deviation of the end tool of the casting cleaning robot according to the force deviation amount, and use the inverse kinematics method to compensate the position deviation to the given position of the casting cleaning robot, so as to adjust the trajectory of the end tool of the casting cleaning robot and obtain the new working position of the end tool of the robot;

[0061] And use the new working position as the given position of the casting cleaning robot, and repeat step S2 until the position deviation is completely eliminated, so as to realize the working force control of the end tool of the casting cleaning robot.

[0062] Specifically, it includes the following steps:

[0063] S31: Substitute the force deviation amount into the constructed force impedance control model to obtain the position deviation of the end tool of the casting cleaning robot. The constructed force impedance control model has the following expression

[0064]

[0065] In the formula: ΔF represents the difference between the expected working force and the actual working force; ΔX represents the position deviation; M d represents the inertia parameter of the casting cleaning robot; B d represents the damping parameter of the casting cleaning robot; K d represents the stiffness parameter of the casting cleaning robot; and the inertia parameter, damping parameter, and stiffness parameter of the casting cleaning robot. These three parameters need to be adjusted through experiments in combination with the actual working conditions on site. Through the force impedance model, the position deviation of the actual work of the robot can be calculated, that is, the compensation amount of the robot position. Then, combined with the existing robot inverse kinematics, the end position q, speed acceleration and the change amount of the joint torque τ (and the inverse kinematics obtains the end position q, speed acceleration The method for the change amount of the joint torque τ is a common method in the field of robotics and is not the inventive point of this application, so it will not be elaborated here), and finally adjust the end trajectory of the robot to eliminate the position deviation;

[0066] S32: Use the inverse kinematics method to compensate the position deviation to the given position of the casting cleaning robot, adjust the end tool trajectory of the casting cleaning robot, and obtain the new working position of the end tool of the robot;

[0067] S33: Take the new working position as the given position of the casting cleaning robot, and repeat step S2 until the position deviation is completely eliminated, so as to realize the working force control of the end tool of the casting cleaning robot.

[0068] In this embodiment, for the complete force adaptive control model and force impedance control model, as Figure 2 shown, first input the given position and given workload of the casting cleaning robot, and then perform differential transformation on the given position to obtain the motion speed After that, compare the given workload a with the a obtained from the parameter estimation model e to obtain the deviation amount Δa of the workload, and input the deviation amount Δa and the motion speed into the expected force calculation model to obtain the expected working force F q , calculate the force deviation ΔF by subtracting the compensated actual working force F from the expected working force, input the force deviation into the adjusted impedance control model to calculate the position deviation ΔX, compensate the position deviation to the given position of the robot, and substitute it into the position control inner loop (i.e., the calculation process using the inverse kinematics method mentioned above) to adjust the end trajectory of the robot, obtain the new working position of the end of the robot, and at the same time generate a new contact force. Then compare the new contact force with the expected force, and perform a similar position correction process again according to the force deviation to realize the closed-loop control of the force, so that the working force in the actual cleaning process of the robot is infinitely close to the expected value set by humans, and finally realize the accurate control of the force of the robot during the entire casting cleaning process.

[0069] Compared with the prior art, the beneficial effects of this embodiment are as follows: By designing a force adaptive control model and a force impedance control model, and combining with the position control of the robot itself to form an adaptive impedance force control model, the gravity compensation is performed on the six-axis force sensor to obtain the accurate actual working force of the robot, and then the deviation of the force is obtained by comparing with the desired force. Then, the ideal impedance model is obtained by adjusting the impedance parameters. The deviation of the force is input into the force impedance control model to generate a position deviation, and then the existing inverse kinematics of the robot is used for calculation to adjust the end position of the robot, so as to eliminate the position deviation, make the actual working force of the robot continuously approach the desired force, and realize the accurate control of the force during the cleaning of the casting by the casting cleaning robot, and improve the quality and efficiency of cleaning the casting.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A casting cleaning robot force control method based on adaptive impedance control, characterized in that: The specific steps include: S1: The six-dimensional force sensor is used to collect and obtain the representative working force of the end tool of the casting cleaning robot in multiple different positions, and the gravity compensation of the end tool is performed on the representative working force to obtain the actual working force of the end tool of the casting cleaning robot; S2: obtaining a given position and a given workload of the casting cleaning robot, and obtaining a force deviation of the casting cleaning robot according to the actual working force based on the constructed force adaptive control model; S3: Construct a force impedance control model, obtain the position deviation of the end tool of the casting cleaning robot according to the force deviation, and use the inverse kinematics method to compensate the position deviation to the given position of the casting cleaning robot, so as to adjust the trajectory of the end tool of the casting cleaning robot and obtain the new working position of the end tool of the robot; The new working position is used as the given position of the casting cleaning robot, and step S2 is repeatedly performed until the position deviation is completely eliminated, so as to realize the working force control of the end tool of the casting cleaning robot.

2. The method for controlling the force of a casting cleaning robot based on adaptive impedance control according to claim 1, characterized in that: The S1 specifically includes the following steps: S11: collecting and obtaining the representative working force of the end tool of the casting cleaning robot in multiple groups of different positions through a six-dimensional force sensor, and the representative working force is the sum of the zero point data with error of the sensor itself and the force generated by the gravity of the end tool of the robot; The calculation formula for characterizing the working force is: Where: f x ,f y ,f z They respectively represent the components of the force sensor data in the x-axis, y-axis and z-axis directions in the preset sensor base coordinate system; G represents the gravity of the robot end tool; U and V represent the angles between the robot base coordinates and the world coordinates; It represents the zero point data of the sensor in the x-axis, y-axis and z-axis directions in the preset sensor base coordinate system; α, β, γ represent the angles between the robot end tool and the x-axis, y-axis and z-axis directions of the preset sensor base coordinate system; S12: Solve multiple sets of calculation formulas representing the working force jointly, that is, the component force and sensor zero point data of the robot end tool gravity in the preset sensor base coordinate system can be obtained, so as to realize the gravity compensation of the end tool for the representing working force and obtain the actual working force of the casting cleaning robot end tool.

3. The method for controlling the force of a casting cleaning robot based on adaptive impedance control according to claim 2, characterized in that: The S2 specifically includes the following steps: S21: Obtaining a given position and a given workload of the casting cleaning robot, and performing differential transformation on the given position to obtain a motion speed; S22: constructing a force adaptive control model, wherein the force adaptive control model includes a processing parameter estimation model and an expected grinding force measurement model; And the expression of the processing parameter estimation model is Where: a e represents the output of the processing parameter estimation model, that is, the actual processing volume of the casting cleaning robot; F represents the actual working force of the robot; V w Indicates the actual processing speed of the robot; Expression for the environmental stiffness of the foundry cleaning robot; The expression of the expected grinding force calculation model is: Where: F q represents the output of the expected grinding force calculation model, that is, the expected working force of the casting cleaning robot; K m represents the mass matrix of the casting cleaning robot; V represents the motion speed of the casting cleaning robot obtained by differentiating a given position; S23: Based on the processing parameter estimation model, obtain the deviation of the workload Δa according to the given workload, and Δa=aa e , where a represents the given workload; a e Indicates the actual processing volume of the casting cleaning robot; S24: Based on the expected grinding force calculation model, the expected working force F is obtained according to the deviation Δa of the workload and the movement speed V. q , and combined with the actual working force F to obtain the force deviation ΔF, and ΔF=F q -F.

4. The method for controlling the force of a casting cleaning robot based on adaptive impedance control according to claim 3, characterized in that: The S3 specifically includes the following steps: S31: Bring the force deviation into the constructed force impedance control model to obtain the position deviation of the end tool of the casting cleaning robot; S32: using an inverse kinematics method to compensate the position deviation to a given position of the casting cleaning robot, adjusting the trajectory of the end tool of the casting cleaning robot, and obtaining a new working position of the end tool of the robot; S33: taking the new working position as the given position of the casting cleaning robot, and repeating step S2 until the position deviation is completely eliminated, so as to realize the working force control of the end tool of the casting cleaning robot.

5. The method for controlling the force of a casting cleaning robot based on adaptive impedance control according to claim 4, characterized in that: The force impedance control model constructed in S31 is expressed as follows: Where: ΔF represents the difference between the expected working force and the actual working force; ΔX represents the position deviation; M d represents the inertia parameter of the casting cleaning robot; B d represents the damping parameter of the casting cleaning robot; K d Represents the stiffness parameters of the casting cleaning robot.

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