Parallel carving robot based on visual perception and control method thereof

Abstract

The invention relates to a parallel carving robot based on visual perception and a control method thereof.The parallel carving robot comprises a frame support, a parallel mechanism and a working platform, the parallel mechanism comprises four driving branches, a middle constraint branch and a movable platform, and the first driving branch and the third driving branch in the parallel mechanism are completely the same in structure; one end of the linear module sliding table is connected with the rotating pair, and the other end of the linear module sliding table is connected with the movable platform through the hooke joint; the second driving branch and the fourth driving branch are identical and comprise hooke joints, servo electric cylinders and revolute pairs, one ends of the servo electric cylinders are connected with the frame, and the other ends of the servo electric cylinders are connected with the movable platform; the middle constraint branch chain comprises two revolute pairs and a sliding device, and the middle constraint branch chain is sequentially connected with the frame and the movable platform through the revolute pairs. According to the method, redundant drive and force-position hybrid control are fused, visual perception and sliding mode control are fused, the flutter phenomenon is effectively reduced, the system precision and robustness are improved, and the method has wide application prospects.

Description

Technical Field

[0001] The invention relates to a parallel robot, a visual perception technology and a sliding mode control technology, and in particular to a parallel engraving robot based on visual perception and applied to the processing of high-precision complex curved surface parts and a control method thereof. Background Art

[0002] With the rapid development of industrial automation and intelligent manufacturing technology, engraving robots are increasingly used in the field of precision manufacturing, especially parallel robots. Parallel robots have become important tools for high-precision engraving, cutting and processing due to their excellent rigidity, high precision and strong load capacity. However, existing engraving robot systems, whether based on series or parallel structures, still face technical challenges such as precision control, difficulty in adjusting the relative position of the workpiece and the tool, and susceptibility to vibration and error during processing.

[0003] In the field of parallel robots, some studies have introduced visual perception technology to improve the accuracy and adaptability of robots, especially control methods based on visual feedback. In the prior art, some parallel robot systems use cameras and image recognition technology to monitor the relative position between the tool and the workpiece in real time, and dynamically adjust the robot's motion trajectory through closed-loop control. The system analyzes errors by extracting image features and edge information, and corrects the position of the robot in a timely manner. However, existing visual perception systems are usually limited to static position measurement and image recognition, and there are still major deficiencies in precise control during dynamic processing, and they cannot effectively deal with complex three-dimensional spatial errors and external disturbances. Therefore, although some visual perception systems have been applied to engraving robots, there are generally problems with single visual input and lack of comprehensive perception of real-time dynamic environments.

[0004] In order to overcome the shortcomings of the prior art, the present invention proposes a parallel engraving robot based on a visual perception sensor and a control method thereof. The method can obtain the position information and posture parameters of the moving platform in real time. By introducing a robust sliding mode control algorithm, the system can effectively resist the influence of external disturbances and uncertainty factors, while effectively suppressing the chatter phenomenon in the processing process, and can significantly improve the operating accuracy of the parallel engraving robot, especially in dynamic processing and complex environments. It has higher robustness and adaptability, thereby overcoming the limitations of the prior art in dynamic precise control and environmental perception. Summary of the invention

[0005] The present invention provides a parallel engraving robot based on visual perception and a control method thereof, aiming to obtain the motion parameters of the moving platform in real time by introducing visual perception technology, and dynamically monitor and optimize the robot motion trajectory and tool position during the engraving process, thereby significantly improving the engraving accuracy and processing efficiency. The technical solution of the present invention not only overcomes the accuracy problems caused by the measurement errors of traditional sensors, but also can provide real-time feedback on dynamic processing, correct errors in real time, and effectively improve the stability and robustness of workpiece processing. By introducing a sliding mode control algorithm, the system's anti-interference ability to external disturbances and uncertain factors is enhanced, the chatter phenomenon in the processing process is suppressed, and the sustainability of high-precision engraving is ensured. The present invention is implemented using the following technical solutions:

[0006] A parallel engraving robot based on visual perception, characterized in that it includes a frame support, a parallel mechanism, and a working platform. An industrial camera is installed on the frame support. The parallel mechanism includes four drive branches, an intermediate constraint branch, and a moving platform. The first drive branch and the third drive branch in the drive branch include a linear module slide, a rotating pair, a branch chain body, and a Hooke's hinge. The linear module slide includes a servo motor, a motor bracket, a coupling, a ball screw, a bearing, a bearing seat, a mother seat, a guide rail, and a slider. The Hooke's hinge includes a T-shaft, a bearing, a nut, and a retaining spring. The linear module slide fixed on the frame support is connected to one end of the branch chain body through a rotating pair. The branch chain body The other end is connected to the moving platform through a Hooke's hinge, the second drive branch and the fourth drive branch include a Hooke's hinge, a servo electric cylinder and a rotating pair, the Hooke's hinge includes a T-shaft, a bearing, a nut and a retaining spring, the upper end of the servo electric cylinder is connected to the Hooke's hinge fixed to the frame, and the other end is connected to the moving platform through a rotating pair, the middle constraint branch includes two rotating pairs and a sliding device, one end of the sliding device is connected to the frame support through a rotating pair, and the other end is connected to the moving platform through a rotating pair, the rotation axes of the two rotating pairs connected to the sliding device are perpendicular, the moving platform includes an engraving head, a servo motor, and the working platform includes a two-degree-of-freedom movable slide rail, an engraving table and a vise.

[0007] The parallel engraving robot based on visual perception is characterized in that the second rotation axis of the Hooke's joint of the first driving branch and the third driving branch is parallel to the x-axis of the fixed coordinate system o-xyz and parallel to the rotation axis of the rotating pair, and the second driving branch and the fourth driving branch are characterized in that the second rotation axis of the Hooke's joint is parallel to the y-axis of the fixed coordinate system o-xyz and parallel to the rotation axis of the rotating pair.

[0008] The parallel engraving robot based on visual perception is characterized in that: the intermediate constraint branch is arranged in the middle of the moving platform, the rotation axis of the rotation pair connected to the frame base is parallel to the rotation axis of the first drive branch and the third drive branch, and the rotation axis of the rotation pair connected to the moving platform is parallel to the rotation axis of the second drive branch and the fourth drive branch.

[0009] A control method for a parallel engraving robot based on visual perception, characterized in that: applied to the above-mentioned parallel engraving robot, the control method comprises the following steps:

[0010] (1) Establish the kinematic equations based on the closed vector method of geometric loops:

[0011] b i +d i s i =p+Ra i

[0012] Where, d i represents the linear displacement of the driving branch, b i is the position vector of the joint point of the kinematic pair in the fixed coordinate system, R represents the rotation matrix of the moving coordinate system relative to the fixed coordinate system, and α and β represent the Euler angles of the moving coordinate system transformed around the fixed coordinate system. The inverse solution of the kinematic equation of the parallel engraving robot is expressed as:

[0013] d i =||p+Ra i -b i ||=f(z,α,β),s i =(p+Ra i -b i ) / d i

[0014] The above formula establishes a mapping equation that characterizes the spatial pose parameters of the driving joint and the moving platform, where z represents the displacement of the origin of the moving platform coordinate system relative to the fixed coordinate system and satisfies the constraint equation:

[0015] y=-ztanα

[0016] In the formula, y represents the position information of the origin of the moving platform coordinate system in the y direction;

[0017] (2) By differentiating the kinematic equation with respect to time, we can obtain the velocity of the driving joint: Independent posture parameters of the moving platform The velocity mapping equation is:

[0018]

[0019] In the formula, J0 is the velocity Jacobian matrix of the parallel engraving robot;

[0020] (3) Derivative the above equation with respect to time to establish the driving joint acceleration Independent posture parameters of the moving platform The acceleration mapping equation is:

[0021]

[0022] (4) Based on the principle of virtual work and the D'Alembert principle, the dynamic model of the parallel engraving robot is constructed to obtain the mapping representation of the dynamic equation in the operation space:

[0023]

[0024] In the formula, F X is the external force on the operating space moving platform, M(X) is the positive definite inertia matrix of the system, is the Coriolis force and centrifugal force matrix of the system, N(X) is the generalized force matrix of the system;

[0025] Using the dual relationship between the velocity Jacobian matrix and the force Jacobian matrix, the dynamic equation of the driving joint space is established:

[0026]

[0027] In the formula,

[0028] (5) Based on the visual perception sensor, the position and posture of the engraving robot's moving platform are obtained, and the position tracking error in the operating space is set to e and the speed tracking error is set to and

[0029]

[0030] Where, X d and is the expected state and velocity of the moving platform parameters in the operating space, X and for the actual state and speed;

[0031] The degree of freedom synchronization error is defined as:

[0032]

[0033] Where, e=[e1 e2 e3] T , H(t) is the mapping matrix between tracking error and synchronization error, and N is the number of degrees of freedom of the mechanism;

[0034] Taking into account the trajectory tracking error and degree of freedom synchronization error, the cross-coupling error and velocity are defined as:

[0035]

[0036] Where P and Q are positive definite matrices;

[0037] Set the reference speed of the moving platform and reference acceleration Defined as:

[0038]

[0039] The sliding surface function and its derivative are defined as:

[0040]

[0041] The sliding mode controller design consists of three parts. The first part is the dynamic compensation term:

[0042]

[0043] Y represents an n×r known regression matrix, represents an r×1 unknown parameter vector;

[0044] The second part is the mixed error compensation term:

[0045]

[0046] The third part is the robust term:

[0047]

[0048] Where u aux represents the robust control term, u aux There are three modes of behavior;

[0049] Finally, based on the requirements for system stability and precision control, the sliding mode control method under the upper limit constraint was adopted, and the mathematical model of the sliding mode controller was designed as follows:

[0050]

[0051] A control method for a parallel engraving robot based on visual perception is characterized in that: the first driving branch, the second driving branch and the third driving branch use positions as inputs of driving joints, and the fourth driving branch uses forces as inputs of joints.

[0052] Compared with the prior art, the present invention has the following advantages: (1) The combination of redundant drive and force-position hybrid control effectively reduces the vibration phenomenon in the processing process and improves the processing accuracy and stability. The redundant drive also optimizes the internal force distribution of the drive branch chain and enhances the flexibility and adaptability of the system; (2) The structural design is simple, and the load and weight distribution are optimized through fewer degrees of freedom and good symmetry, thereby improving the carrying capacity, response speed and accuracy; (3) Based on the data fusion of visual perception sensors, the dynamic platform posture is acquired in real time, and the sliding mode controller is used to improve the operating accuracy of the end effector, thereby enhancing the robustness and intelligence of the system; (4) It is suitable for high-precision engraving, personalized customization, small batch production, industrial automation and other fields, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a schematic diagram of the overall structure of a parallel engraving robot based on visual perception of the present invention;

[0054] Figure 2 It is a schematic diagram of the structure of the first driving branch and the third driving branch of a parallel engraving robot based on visual perception of the present invention;

[0055] Figure 3 It is a schematic diagram of the structure of the second driving branch and the fourth driving branch of a parallel engraving robot based on visual perception according to the present invention;

[0056] Figure 4 It is a schematic diagram of the intermediate constraint branch structure of a parallel engraving robot based on visual perception according to the present invention;

[0057] Figure 5 It is a schematic diagram of the structure of a moving platform of a parallel engraving robot based on visual perception according to the present invention;

[0058] Figure 6 It is a schematic diagram of the working platform and moving slide rail structure of a parallel engraving robot based on visual perception of the present invention;

[0059] Figure 7 The present invention is a flow chart of a parallel engraving robot control method based on visual perception.

[0060] in:

[0061] Figure 1 Middle: 1. First drive branch; 2. Second drive branch; 3. Third drive branch; 4. Fourth drive branch; 5. Middle constraint branch; 6. Moving platform; 7. Working platform; 8. Moving slide rail; 9. Frame support;

[0062] Figure 2Middle: 10. servo motor; 11. motor support; 12. revolving pair; 13. branch chain; 14. Hook hinge; 15. bearing support; 16. ball screw; 17. slider; 18. coupling; 19. slide rail;

[0063] Figure 3 Middle: 20. Electric cylinder; 21. Electric push rod; 22. Rotary pair; 23. Servo motor; 24. Hooke hinge;

[0064] Figure 4 Middle: 25. Telescopic rod; 26. Rotation pair; 27. Passive moving pair; 28. Rotation pair;

[0065] Figure 5 Middle: 51. Engraving head support; 52. Engraving head; 53. Servo motor;

[0066] Figure 6 Middle: 61. Vise; 62. Engraving platform; 63. Servo motor; 64. Moving slide rail. DETAILED DESCRIPTION

[0067] In order to further understand the parallel engraving robot based on visual perception and the control method thereof provided by the present invention, the present invention is specifically described below in conjunction with the accompanying drawings and detailed embodiments, but the present invention is not limited to the embodiments.

[0068] Figure 1 It is a schematic diagram of the overall structure of a parallel engraving robot based on visual perception of the present invention, including a frame support 9, a movable slide rail 8, a working platform 7, a moving platform 6 for installing an engraving head, and a first driving branch 1, a second driving branch 2, a third driving branch 3 and a fourth driving branch 4 connecting the moving and fixed platforms; it is characterized in that: the connection points of the four driving branches and the fixed platform 7 are evenly distributed at the vertices of a regular quadrilateral, and the kinematic joints connecting the moving platform 6 for installing a spindle head and the four driving branches are evenly distributed at the vertices of the regular quadrilateral.

[0069] Further, Figure 2 It is a schematic diagram of the structure of the first driving branch and the third driving branch of a parallel engraving robot based on visual perception of the present invention. The first driving branch 1 is completely identical in structure to the third driving branch 3, including a linear module slide, a rotating pair and a Hooke's hinge; the linear module slide includes: a servo motor 10, a motor support 11, a rotating pair 12, a branch chain body 13, a Hooke's hinge 14, a bearing support 15, a ball screw 16, a slider 17, a coupling 18, and a slide rail 19; the rotation axis of the rotating pair 12 of the driving branch connecting the branch chain body 13 is parallel to the x-axis in the fixed coordinate system o-xyz, and is parallel to the second rotation axis of the Hooke's hinge 14, and is fixed to the moving platform 6 through a connecting flange.

[0070] Further, Figure 3It is a schematic diagram of the structure of the second driving branch and the fourth driving branch of a parallel engraving robot based on visual perception of the present invention. The second driving branch 2 is completely identical in structure to the fourth driving branch 4, including a Hooke's hinge, a servo electric cylinder and a rotating pair; the servo electric cylinder includes a servo motor 23, an electric cylinder 20, and an electric push rod 21; the driving branch rotating pair 22 is parallel to the y-axis of the fixed coordinate system o-xyz, and is parallel to the second rotation axis of the Hooke's hinge 24, and the rotating pair 22 is connected to a moving platform 6 equipped with a spindle head.

[0071] Further, Figure 4 It is a schematic diagram of the intermediate constraint branch structure of a parallel engraving robot based on visual perception in the present invention. The intermediate constraint branch 5 includes a rotating pair connected to the top frame, a sliding device, and a rotating pair connected to the moving platform. The upper end of the intermediate constraint branch 5 is connected to the frame support through a rotating pair 28. The rotation axis of the rotating pair 28 is parallel to the rotation axis of the rotating pair of the first drive branch and the third drive branch, and is parallel to the x-axis in the fixed coordinate system o-xyz. The lower end of the intermediate constraint branch 5 is arranged in the middle of the moving platform and is connected to the moving platform through a rotating pair 26. The rotation axis of the rotating pair 26 is parallel to the rotation axis of the rotating pair of the second drive branch and the fourth drive branch, and is parallel to the y-axis in the fixed coordinate system o-xyz.

[0072] Furthermore, the first rotation axis of the Hooke's hinge 14 of the first drive branch 1 is collinear with the first rotation axis of the Hooke's hinge 14 of the third drive branch, the first rotation axis of the Hooke's hinge 24 in the second drive branch 2 is collinear with the first rotation axis of the Hooke's hinge 24 in the fourth drive branch 4, the revolute pair 12 in the first drive branch 1 is parallel to the revolute pair 12 of the third drive branch 3, and the revolute pair 22 in the second drive branch 2 is parallel to the revolute pair 22 of the fourth drive branch 4. One end of the first drive branch 1 and the third drive branch 3 is connected to the linear module slide through the revolute pair 12 and is vertically fixed on the frame support 9, and the other end is connected to the moving platform 6 through the Hooke's hinge 14. One end of the second drive branch 2 and the fourth drive branch 4 is connected to the frame support 9 through the Hooke's hinge 24, and the other end is connected to the moving platform through the revolute pair 22. The four drive branches are symmetrically distributed at the four vertices of the moving platform.

[0073] Further, Figure 5-Figure 6 It is a schematic diagram of the structure of a moving platform of a parallel engraving robot based on visual perception in the present invention. The moving platform includes an engraving head support 51, an engraving head 52, and a servo motor 53. The working platform and the movable slide rail include a vise 61, an engraving platform 62, a servo motor 63, and a movable slide rail 64.

[0074] Figure 7This is a flow chart of a control method of a parallel engraving robot based on visual perception of the present invention, which is characterized in that: when applied to the above-mentioned parallel engraving robot, the control method includes the following steps:

[0075] (1) Establish the kinematic equations based on the closed vector method of geometric loops:

[0076] b i +d i s i =p+Ra i

[0077] Where, d i represents the linear displacement of the driving branch, b i is the position vector of the joint point of the kinematic pair in the fixed coordinate system, R represents the rotation matrix of the moving coordinate system relative to the fixed coordinate system, and α and β represent the Euler angles of the moving coordinate system transformed around the fixed coordinate system. The inverse solution of the kinematic equation of the parallel engraving robot is expressed as:

[0078] d i =||p+Ra i -b i ||=f(z,α,β),s i =(p+Ra i -b i ) / d i

[0079] The above formula establishes a mapping equation that characterizes the spatial pose parameters of the driving joint and the moving platform, where z represents the displacement of the origin of the moving platform coordinate system relative to the fixed coordinate system and satisfies the constraint equation:

[0080] y=-ztanα

[0081] In the formula, y represents the position information of the origin of the moving platform coordinate system in the y direction;

[0082] (2) By differentiating the kinematic equation with respect to time, we can obtain the velocity of the driving joint: Independent posture parameters of the moving platform The velocity mapping equation is:

[0083]

[0084] In the formula, J0 is the velocity Jacobian matrix of the parallel engraving robot;

[0085] (3) Derivative the above equation with respect to time to establish the driving joint acceleration Independent posture parameters of the moving platform The acceleration mapping equation is:

[0086]

[0087] (4) Based on the principle of virtual work and the D'Alembert principle, the dynamic model of the parallel engraving robot is constructed to obtain the mapping representation of the dynamic equation in the operation space:

[0088]

[0089] In the formula, F X is the external force on the operating space moving platform, M(X) is the positive definite inertia matrix of the system, is the Coriolis force and centrifugal force matrix of the system, N(X) is the generalized force matrix of the system;

[0090] Using the dual relationship between the velocity Jacobian matrix and the force Jacobian matrix, the dynamic equation of the driving joint space is established:

[0091]

[0092] In the formula,

[0093] (5) Based on the visual perception sensor, the position and posture of the engraving robot's moving platform are obtained, and the position tracking error in the operating space is set to e and the speed tracking error is set to and

[0094]

[0095] Where, X d and is the expected state and velocity of the moving platform parameters in the operating space, X and for the actual state and speed;

[0096] The degree of freedom synchronization error is defined as:

[0097]

[0098] Where, e=[e1 e2 e3] T , H(t) is the mapping matrix between tracking error and synchronization error, and N is the number of degrees of freedom of the mechanism;

[0099] Taking into account the trajectory tracking error and degree of freedom synchronization error, the cross-coupling error and velocity are defined as:

[0100]

[0101] Where P and Q are positive definite matrices;

[0102] Set the reference speed of the moving platform and reference acceleration Defined as:

[0103]

[0104] The sliding surface function and its derivative are defined as:

[0105]

[0106] The sliding mode controller design consists of three parts. The first part is the dynamic compensation term:

[0107]

[0108] Y represents an n×r known regression matrix, represents an r×1 unknown parameter vector;

[0109] The second part is the mixed error compensation term:

[0110]

[0111] The third part is the robust item that enables the control system to operate stably under unknown parameter uncertainty and external disturbances:

[0112]

[0113] Where u aux represents the robust control term, u aux There are three modes of behavior;

[0114] Finally, based on the requirements for system stability and precision control, the sliding mode control method under the upper limit constraint was adopted, and the mathematical model of the sliding mode controller was designed as follows:

[0115]

[0116] Furthermore, according to a visual perception-based parallel engraving robot control method according to claim 4, it is characterized in that the first driving branch, the second driving branch and the third driving branch use position as the input of the driving joint, and the fourth driving branch uses force as the input of the joint.

[0117] The implementation manner of a parallel engraving robot based on visual perception and a control method thereof of the present invention is not intended to limit the present invention. According to the contents disclosed in the present invention, technicians in the relevant technical field can also adopt other specific methods to implement them without departing from the present invention, which all belong to the protection scope of the present invention.

Claims

1. A parallel engraving robot based on visual perception, comprising a frame support, a parallel mechanism, and a working platform, characterized in that: An industrial camera is installed on the frame support. The parallel mechanism includes four driving branches, an intermediate constraint branch and a moving platform. The first driving branch and the third driving branch in the driving branch include a linear module slide, a rotating pair, a branch chain body and a Hooke's hinge. The linear module slide includes a servo motor, a motor bracket, a coupling, a ball screw, a bearing, a bearing seat, a nut seat, a guide rail and a slider. The Hooke's hinge includes a T-shaft, a bearing, a nut and a retaining spring. The linear module slide fixed on the frame support is connected to one end of the branch chain body through a rotating pair, and the other end of the branch chain body is connected to the moving platform through a Hooke's hinge. The driving branch and the fourth driving branch include a Hooke's hinge, a servo electric cylinder and a rotating pair. The Hooke's hinge includes a T-shaped shaft, a bearing, a nut and a retaining spring. The upper end of the servo electric cylinder is connected to the Hooke's hinge fixed on the frame, and the other end is connected to the moving platform through a rotating pair. The intermediate constraint branch includes two rotating pairs and a sliding device. One end of the sliding device is connected to the frame support through a rotating pair, and the other end is connected to the moving platform through a rotating pair. The rotation axes of the two rotating pairs connected by the sliding device are perpendicular. The moving platform includes an engraving head and a servo motor. The working platform includes a two-degree-of-freedom movable slide rail, an engraving table and a vise.

2. The parallel engraving robot based on visual perception according to claim 1, characterized in that: The second rotation axis of the Hooke's joint of the first driving branch and the third driving branch is parallel to the x-axis of the fixed coordinate system o-xyz and parallel to the rotation axis of the rotating pair in its driving branch. The second rotation axis of the Hooke's joint of the second driving branch and the fourth driving branch is parallel to the y-axis of the fixed coordinate system o-xyz and parallel to the rotation axis of the rotating pair in its driving branch.

3. The parallel engraving robot based on visual perception according to claim 1, characterized in that: The intermediate constraint branch is arranged in the middle part of the moving platform, and the rotational axis of the rotational pair connected to the frame support is parallel to the rotational axis of the first drive branch and the third drive branch, and the rotational axis of the rotational pair connected to the moving platform is parallel to the rotational axis of the second drive branch and the fourth drive branch.

4. A control method for a parallel engraving robot based on visual perception, characterized in that: Applied to the above parallel engraving robot, the control method thereof comprises the following steps: (1) Establish the kinematic equations based on the closed vector method of geometric loops: b i +d i s i =p+Ra i Where, d i represents the linear displacement of the driving branch, b i is the position vector of the joint point of the kinematic pair in the fixed coordinate system, R represents the rotation matrix of the moving coordinate system relative to the fixed coordinate system, and α and β represent the Euler angles of the moving coordinate system transformed around the fixed coordinate system. The inverse solution of the kinematic equation of the parallel engraving robot is expressed as: d i =||p+Ra i -b i ||=f(z,α,β),s i =(p+Ra i -b i ) / day i The above formula establishes a mapping equation that characterizes the spatial pose parameters of the driving joint and the moving platform, where z represents the displacement of the origin of the moving platform coordinate system relative to the fixed coordinate system and satisfies the constraint equation: y=-ztanα In the formula, y represents the position information of the origin of the moving platform coordinate system in the y direction; (2) By differentiating the kinematic equation with respect to time, we can obtain the velocity of the driving joint: Independent posture parameters of the moving platform The velocity mapping equation is: In the formula, J0 is the velocity Jacobian matrix of the parallel engraving robot; (3) Derivative the above equation with respect to time to establish the driving joint acceleration Independent posture parameters of the moving platform The acceleration mapping equation is: (4) Based on the principle of virtual work and the D'Alembert principle, the dynamic model of the parallel engraving robot is constructed to obtain the mapping representation of the dynamic equation in the operation space: In the formula, F X is the external force on the operating space moving platform, M(X) is the positive definite inertia matrix of the system, is the Coriolis force and centrifugal force matrix of the system, N(X) is the generalized force matrix of the system; Using the dual relationship between the velocity Jacobian matrix and the force Jacobian matrix, the dynamic equation of the driving joint space is established: In the formula, (5) Based on the visual perception sensor, the position and posture of the engraving robot's moving platform are obtained, and the position tracking error in the operating space is set to e and the speed tracking error is set to and Where, X d and is the expected state and velocity of the moving platform parameters in the operating space, X and for the actual state and speed; The degree of freedom synchronization error is defined as: Where, e=[e1 e2 e3] T , H(t) is the mapping matrix between tracking error and synchronization error, and N is the number of degrees of freedom of the mechanism; Taking into account the trajectory tracking error and degree of freedom synchronization error, the cross-coupling error and velocity are defined as: Where P and Q are positive definite matrices; Set the reference speed of the moving platform and reference acceleration Defined as: The sliding surface function and its derivative are defined as: The sliding mode controller design consists of three parts. The first part is the dynamic compensation term: Y represents an n×r known regression matrix, represents an r×1 unknown parameter vector; The second part is the mixed error compensation term: The third part is the robust term: Where u aux represents the robust control term, u aux There are three modes of behavior; Finally, based on the requirements for system stability and precision control, the sliding mode control method under the upper limit constraint was adopted, and the mathematical model of the sliding mode controller was designed as follows:

5. The control method of a parallel engraving robot based on visual perception according to claim 4 is characterized in that: The first driving branch, the second driving branch and the third driving branch use the position as the input of driving the joint, and the fourth driving branch uses the force as the input of the joint.

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