Movable base type hybrid robot machining system for high-precision milling of large structural parts

Abstract

The invention relates to the technical field of industrial robots, and solves the technical problems that the working space is insufficient, the tail end rigidity is low, the milling vibration is large, and the machining precision and the surface quality are difficult to guarantee when an existing robot system is used for machining a large structural part. The movable base type series-parallel robot machining system comprises a movable base unit, a multi-degree-of-freedom series mechanical arm, a high-rigidity parallel module, an end effector, an active composite vibration reduction module and a cooperative control system. A series-parallel connection structure is combined with the movable base, the effective machining range and flexibility of the robot are remarkably expanded, meanwhile, the local rigidity of a machining point is improved through the parallel modules, milling vibration is greatly reduced through the active composite vibration reduction technology, and the machining precision is improved. Therefore, high-efficiency and high-precision five-axis linkage milling machining can be performed on large complex structural parts, and the machining quality and the surface smoothness are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial robots, and particularly to a mobile base hybrid serial-parallel robot machining system for high-precision milling of large-scale structural parts. Background Art

[0002] Large-scale structural parts, such as aircraft skins, fuselage frames, ship sections, wind turbine blade molds, etc., usually have the characteristics of large size and complex shape. High-precision machining of them is an important challenge faced by modern manufacturing industry, especially milling. At present, there are still many problems in the existing technical means for machining large and complex structural parts. Large gantry numerically controlled machine tools have the advantages of high stiffness and high precision, and can meet the requirements of high-quality machining. However, they are costly, occupy a huge area, have a heavy structure, a long installation and commissioning cycle, and for particularly complex curved surfaces, the flexibility of their five-axis machining is sometimes limited and it is difficult to reach some machining areas.

[0003] Traditional industrial robots (serial robots) have the advantages of large working space and high flexibility, and relatively low cost. However, their serial open-chain structure results in relatively low stiffness at the end, usually between 0.1 and 1 N / μm (the public literature is: International Journal of Mechanical Sciences, 2022, DOI: 10.1016 / j.ijmecsci.2022.107638). When bearing large loads such as milling forces, they are prone to deformation and vibration, and it is difficult to ensure the high precision and surface quality requirements of large-scale structural parts.

[0004] The stiffness of parallel robots (such as Tricept T9000) can reach 100 N / μm (the public literature is: SAE Technical Papers, 2007, DOI: 10.4271 / 2007-01-3820), and they have the advantage of high precision. However, their working space is usually small, and it is difficult to independently cover all machining areas of large-scale structural parts.

[0005] In recent years, some studies have attempted to install robots on AGV mobile platforms (such as the Chinese invention patent with announcement number CN114770602B) or ground rails (public document: Chinese Journal of Aeronautics, 2014, DOI:10.1016 / j.cja.2014.10.028) to expand the working range, but this does not solve the problem of insufficient rigidity and vibration of the serial robot body. For example, the public document: Precision Engineering, 2023, DOI: 10.1016 / j.precisioneng.2022.09.007 proposed a hybrid robot structure, aiming to combine the advantages of both, but the existing solutions still have shortcomings in how to effectively adapt to large workpiece processing.

[0006] Moreover, in the milling process of large structural parts, the interaction between the tool and the workpiece will generate complex cutting forces, which can easily excite the robot structure, especially high-frequency and low-frequency vibrations (chatter) near the end effector, seriously affecting the quality of the machined surface (such as chatter marks), reducing tool life, and even damaging the workpiece. Traditional passive vibration reduction measures have limited effects, and active vibration reduction technology for robot milling, especially efficient composite vibration reduction solutions that can effectively suppress broadband vibrations at the same time, is still a technical problem that needs to be solved urgently.

[0007] Therefore, it is urgent to develop a new type of robot processing system that can combine a large working range, high flexibility, high rigidity, high processing accuracy, and effectively suppress milling vibration to meet the high-efficiency and high-quality processing requirements of large and complex structural parts. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention provides a mobile base-type hybrid robot processing system for high-precision milling of large structural parts, which solves the technical problems faced by existing robot systems when processing large structural parts, such as insufficient working space, low end stiffness, large milling vibration, and difficulty in ensuring processing accuracy and surface quality.

[0009] In order to solve the above technical problems, the present invention provides the following technical solutions: a mobile base type hybrid robot processing system for high-precision milling of large structural parts, comprising: Mobile base unit. This unit is set on the ground or on a track, such as a linear guide or an autonomous mobile platform (AGV), and can carry the robot body and perform a large range of linear or planar movements along a predetermined path to expand the reach of the entire system. Preferably, if a linear guide is used, its surface can be coated with a wear-resistant ceramic layer to improve durability and precision.

[0010] Multi-DOF tandem robot. For example, a tandem arm with at least four rotational degrees of freedom, whose base is mounted on a mobile base unit. The tandem arm is responsible for achieving a wide range of posture adjustment and rough positioning of the robot end in the workspace. Its joints can adopt a hollow shaft structure with built-in coolant circulation pipelines to effectively dissipate the heat of the generator and reducer to ensure long-term high-precision operation.

[0011] High-rigidity parallel module. For example, a parallel mechanism with at least two degrees of freedom, whose static platform is connected to the end flange of the serial robot arm, and the dynamic platform is used to install the end effector. The parallel module has a closed-loop structure, which can provide local stiffness and accuracy far higher than the end of the serial arm near the processing point, and undertakes the main precision feed movement. The surface of its drive screw can be ceramic coated and matched with a dynamic preload nut to improve the transmission stiffness and accuracy.

[0012] End effector. Installed on the parallel module dynamic platform, it is usually a high-speed electric spindle for milling. Its interface can adopt a quick-change structure, allowing it to be quickly replaced with a grinding head, drilling head, riveting tool, etc. as needed, increasing the flexibility of the system.

[0013] Active composite vibration reduction module. This module is integrated between the parallel module dynamic platform and the end effector, or directly integrated inside the end effector. It is characterized by including both a magnetorheological damper and a piezoelectric ceramic actuator. The magnetorheological damper changes the damping force in real time by controlling the excitation current (for example, 0-1500mA adjustable, response time ≤8ms), effectively absorbing medium and low frequency, large amplitude vibration energy; the piezoelectric ceramic actuator (for example, in a specific spatial distribution) uses the inverse piezoelectric effect to generate high-frequency micro-displacement, actively compensating or offsetting high-frequency vibrations. The two work together to achieve active and efficient suppression of wide-band vibrations during milling.

[0014] Collaborative control system. This system uses a distributed architecture such as PC+PLC+motion control module, and connects and controls the mobile base unit, the joints of the serial robot arm, the drive branches of the parallel module, and the active composite vibration reduction module through a high-speed real-time industrial Ethernet bus (such as EtherCAT). The control system can achieve: High-precision synchronization and coordinated motion planning and control of all motion axes (including mobile base, tandem arm joints, parallel module branches) enable the end effector to accurately mill along a predetermined five-axis trajectory on large and complex surfaces; According to the processing status (such as real-time cutting force and acceleration sensor signal feedback), the damping force of the magnetorheological damper in the active vibration reduction module and the compensation signal of the piezoelectric ceramic actuator are dynamically adjusted to achieve real-time active suppression of milling vibration.

[0015] Further, the high-rigidity parallel module is a parallel mechanism with two degrees of freedom, including: a parallel static platform, a parallel linkage platform, a parallel module upper cover plate, a parallel module side arm, a first branch chain and a second branch chain; One end of the first branch chain is connected to the parallel static platform through a rotating pair, and the other end is connected to the parallel linkage platform through a rotating pair. The parallel linkage platform and the end effector are detachably fixedly connected.

[0016] Furthermore, the first branch chain includes an A bracket, an A bearing seat, a nut, a bearing connector, a bolt, a first lead screw, a B bearing seat, a B bracket, and a first motor, and one end of the first motor is connected to the parallel static platform through a revolute pair; The nut in the ball screw nut pair is fixed to the rotor of the first motor, and the first motor is mounted on the first screw, so that the first screw has a rotational freedom around the axis of the nut and a linear movement freedom along the axis direction, so as to form a cylindrical kinematic pair; The first lead screw is connected to the parallel linkage platform through a rotating pair, the end of the first lead screw is fixedly connected to the A bearing seat, the A bracket is connected to the A bearing seat to form a rotating pair, the bearing connecting piece is connected to the first lead screw through nuts and bolts, and the B bracket is connected to the B bearing seat to form a rotating pair.

[0017] Furthermore, the second branch chain has the same structural setting as the first branch chain, the first branch chain is connected between the parallel static platform and the parallel linkage platform, the second branch chain is connected between the parallel static platform and the parallel module upper cover plate, and the parallel module upper cover plate is connected to the parallel linkage platform through a rotating pair to form a closed-loop double-chain parallel structure.

[0018] Furthermore, the mobile base unit adopts any one of an autonomous mobile platform or a linear guide rail with a wear-resistant ceramic layer coated on the surface.

[0019] Furthermore, the multi-degree-of-freedom serial robot is a serial arm with at least four rotational degrees of freedom, including a robot base mounted on a mobile base unit, a robot waist providing a first degree of freedom of rotation around the Z axis, a first link group, a second link group, a robot upper arm and a robot joint.

[0020] Furthermore, at least one joint of the multi-degree-of-freedom serial robot arm adopts a hollow shaft structure and has a built-in coolant circulation pipeline.

[0021] Furthermore, the damping force of the magnetorheological damper can be dynamically adjusted according to the processing load, the excitation current thereof is continuously adjustable within a preset range, and the response time is not greater than a specific value.

[0022] Furthermore, the piezoelectric ceramic actuators are distributed in multiple predetermined positions to achieve active suppression of multi-directional vibrations.

[0023] Furthermore, the collaborative control system is based on the EtherCAT bus architecture, and is capable of driving the mobile base unit, the multi-degree-of-freedom serial robot arm and the high-rigidity parallel module to perform collaborative movement, thereby realizing five-axis linkage machining path tracking of the entire curved surface of a large structural part in one clamping.

[0024] By means of the above technical solution, the present invention provides a mobile base type hybrid robot processing system for high-precision milling of large structural parts, which has at least the following beneficial effects: 1. Large working range and high flexibility. Combining the large-range mobility of the mobile base unit and the posture adjustment capability of the multi-degree-of-freedom serial robot arm, the robot can cover and process various areas of super-large structural parts without multiple moves or re-clamping of the workpiece, thus improving processing efficiency and flexibility.

[0025] 2. High local stiffness and precision. The introduction of a high-rigidity parallel module at the end of the multi-DOF serial robot significantly improves the structural stiffness of the end effector near the processing point, reduces the deformation caused by the cutting force, and ensures the dimensional accuracy and shape accuracy of the milling process.

[0026] 3. Strong vibration suppression capability. The innovative active composite vibration reduction module can actively and in real time suppress the medium, low-frequency and high-frequency vibrations generated during the milling process, significantly reducing the amplitude of machining chatter. Compared with the case of no vibration reduction or only passive vibration reduction, the vibration amplitude can be greatly reduced, thereby greatly improving the machining surface quality, extending the tool life, and allowing the use of higher cutting parameters to improve efficiency.

[0027] 4. High efficiency and automation. Through collaborative control to achieve linkage of various parts, the full-surface five-axis machining of large and complex structural parts can be completed in one clamping, reducing auxiliary time and improving automation and production efficiency.

[0028] 5. Multifunctionality and flexibility. The design of the quick-change interface enables the system to easily switch between different end tools, adapting to a variety of processing tasks such as milling, drilling, grinding, riveting, etc., improving the flexibility and utilization of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 It is a structural schematic diagram of a hybrid robot processing system without a mobile base in the present invention; Figure 2 Schematic structural diagram of a hybrid robot machining system with a linear guide rail as a moving base in the present invention; Figure 3 Schematic structural diagram of a hybrid robot machining system with an automated guided vehicle as a moving base in the present invention; Figure 4 Schematic structural diagram of a four-degree-of-freedom serial module in the present invention; Figure 5 Schematic structural diagram of a two-degree-of-freedom parallel module in the present invention; Figure 6 Exploded view of the first branch chain of the two-degree-of-freedom parallel module in the present invention; Figure 7 Schematic structural diagram of a composite vibration damping module in the present invention; Figure 8 Principle block diagram of a collaborative control system in the present invention.

[0030] In the figure: 1. Four-degree-of-freedom serial robotic arm module; 2. Robot connection flange; 3. Two-degree-of-freedom parallel module; 4. Linear guide rail; 5. First six-degree-of-freedom hybrid robotic arm; 6. Automated guided vehicle; 7. Second six-degree-of-freedom hybrid robotic arm; 8. Robotic arm base; 9. Robotic arm waist; 10. First link group; 11. Second link group; 12. Robotic arm upper arm; 13. Robotic arm joint; 14. Parallel static platform; 15. First branch chain; 16. Parallel moving platform; 17. End effector; 18. Second branch chain; 19. Support; 20. Parallel module side arm; 21. Parallel module upper cover; 22. A bracket; 23. A bearing seat; 24. Nut; 25. Bearing connecting piece; 26. Bolt; 27. First lead screw; 28. B bearing seat; 29. B bracket; 30. First motor; 31. Magnetorheological damper; 32. Piezoelectric ceramic actuator. Detailed implementation manners

[0031] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners. Thereby, the implementation process of how the present application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0032] A mobile base type hybrid robot machining system for high-precision milling of large structural parts provided in this embodiment, as Figure 1As shown in the figure, it mainly includes a mobile base unit composed of a linear guide rail 4 or an automated guided vehicle 6, a four-degree-of-freedom serial manipulator module 1 installed on the mobile base unit, and a two-degree-of-freedom parallel module 3 installed at the end of the four-degree-of-freedom serial manipulator module 1 through a robot connection flange 2. The robot connection flange 2 can be selected from standard flange interfaces, such as the GB / T9125 standard. For example, the end effector 17 of a high-speed milling spindle is installed on the parallel moving platform 16, as well as an active vibration damping module and a cooperative control system.

[0033] In this embodiment, as Figure 2 shown, the mobile base unit can adopt a high-precision linear guide rail 4. The linear guide rail 4 is laid along the length direction of the large workpiece, and bears the entire first six-degree-of-freedom hybrid manipulator 5 composed of the four-degree-of-freedom serial manipulator module 1 and the two-degree-of-freedom parallel module 3 for long-distance linear movement. The surface of the linear guide rail 4 is preferably coated with a wear-resistant ceramic layer, and is matched with a high-precision rolling linear guide pair to ensure the smoothness and positioning accuracy of the movement. Or, as Figure 3 shown, in occasions where greater flexibility is required, the mobile base unit can adopt an automated guided vehicle 6 (AGV), which bears the entire second six-degree-of-freedom hybrid manipulator 7 composed of the four-degree-of-freedom serial manipulator module 1 and the two-degree-of-freedom parallel module 3 to move freely on the factory floor.

[0034] As Figure 4 shown, the four-degree-of-freedom serial manipulator module 1 provides the main motion range and posture adjustment ability of the robot. It includes a manipulator base 8 installed on the mobile base unit, a manipulator waist 9 that provides the first degree of freedom of rotation around the Z axis, a first link group 10, a second link group 11, a manipulator upper arm 12, and a manipulator joint 13, etc. By rotating these joints (for example, a total of 4 rotational degrees of freedom are provided), the two-degree-of-freedom parallel module 3 at the end can be driven to reach the target position and posture in the working space. The joints preferably adopt a hollow shaft design, with a built-in coolant circulation pipeline, and the heat generated by the motor is taken away by an external cooling system to ensure the thermal stability during long-term operation.

[0035] As Figure 5 and Figure 6 shown, the two-degree-of-freedom parallel module 3 is the key to improving local stiffness and accuracy. As Figure 5As shown, it includes a parallel static platform 14, a first branch chain 15, a parallel linkage platform 16, an end effector 17, a second branch chain 18, a support 19, a parallel module side arm 20 and a parallel module upper cover plate 21. One end of the first branch chain 15 is connected to the parallel static platform 14 through a rotating pair, and the other end is connected to the parallel linkage platform 16 through a rotating pair. The parallel linkage platform 16 and the end effector 17 are fixedly connected; the second branch chain 18 has the same structure as the first branch chain 15, one end is connected to the parallel static platform 14 through a rotating pair, and the other end is connected to the parallel module upper cover plate 21 through the support 19. After the parallel module upper cover plate 21 is fixed to the parallel module side arm 20, it is connected to the parallel linkage platform 16 through a rotating pair. The first branch chain 15 and the second branch chain 18 are both connected between the parallel static platform 14 and the parallel linkage platform 16 to form a closed-loop double-chain parallel structure.

[0036] Specifically, Figure 6 As shown, the first branch chain 15 includes an A bracket 22, an A bearing seat 23, a nut 24, a bearing connector 25, a bolt 26, a first lead screw 27, a B bearing seat 28, a B bracket 29, and a first motor 30. The first motor 30 is mounted on the first lead screw 27, and the rotor of the first motor 30 is fixedly connected to the nut in the ball screw nut pair, so that the first lead screw 27 has a rotational freedom around the axis of the nut and a linear movement freedom along the axis direction, forming a cylindrical motion pair. The lead screw surface of the ball screw nut pair is coated with ceramic, and the nut preload is dynamically adjusted by a disc spring group. The end of the first lead screw 27 is fixedly connected to the A bearing seat 23; the A bracket 22 is connected to the A bearing seat 23 to form a rotation pair, the bearing connector 25 is connected to the first lead screw 27 through the nut 24 and the bolt 26, and the B bracket 29 is connected to the B bearing seat 28 to form a rotation pair. The second branch chain 18 has the same structure as the first branch chain 15, and both realize the control of their own branches and form a parallel closed loop structure. This parallel closed loop structure makes the two-degree-of-freedom parallel module 3 have high rigidity and load-bearing capacity. The surface of the ball screw nut pair is preferably coated with ceramic, and the nut is dynamically preloaded by a disc spring group to eliminate clearance, improve transmission rigidity and precision, and resist the impact of milling force.

[0037] End effector 17 and active composite vibration reduction module: The end effector 17, such as a high-speed electric spindle, is installed on the parallel platform 16 of the two-degree-of-freedom parallel module 3. The quick-change interface for connecting the end effector 17 and the parallel platform 16 can use a standard tool handle interface (such as an HSK tool handle interface). The key is that an active composite vibration reduction module is set between the parallel platform 16 and the end effector 17 (or integrated inside the end effector). Figure 7 As shown, this module integrates: The magnetorheological damper 31 utilizes the property that the viscosity of the magnetorheological fluid can be varied under the action of a magnetic field. The control system, based on the vibration signals (mainly low-frequency and large-amplitude) detected by the sensors, adjusts in real time the excitation current applied to the magnetorheological damper (for example, continuously adjustable from 0 to 1500 mA), rapidly (response time ≤ 8 ms) changes its damping force, effectively dissipates the vibration energy, and suppresses the mid-low frequency vibrations.

[0038] The piezoelectric ceramic actuator 32 utilizes the inverse piezoelectric effect to generate small but rapid telescopic deformations under the action of an electric field. The control system, according to the detected high-frequency vibration signals, drives the piezoelectric ceramic stack (for example, arranged radially and axially according to a specific spatial distribution to cope with vibrations in different directions) to generate high-frequency micro-displacements opposite in phase to the vibrations, actively canceling or compensating for the high-frequency chatter.

[0039] The magnetorheological damper 31 and the piezoelectric ceramic actuator 32 work in coordination under the coordination of the cooperative control system. The magnetorheological damper 31 is responsible for "absorbing" the low-frequency vibrations with large energy, and the piezoelectric ceramic actuator 32 is responsible for "canceling" the high-frequency vibrations that affect the surface quality, thereby achieving efficient active suppression of the broadband vibrations throughout the milling process.

[0040] As Figure 8 shown, the cooperative control system is the "brain" of the entire system. It uses a high-performance PC as the upper computer (responsible for human-computer interaction, task planning, and trajectory generation), the PLC is responsible for logic control and auxiliary equipment management, and the high-performance multi-axis motion control module (either integrated in the PLC / PC) is responsible for the underlying servo drive control. All these hardware units (including the mobile base driver, the servo drivers of each joint of the serial arm, the servo drivers of each branch of the parallel module, the magnetorheological damper controller, the piezoelectric ceramic drive power supply, etc.) are connected through the high-speed, real-time, and deterministic EtherCAT bus. The EtherCAT bus ensures the microsecond-level precise synchronization between all axes and between motion control and vibration damping control. The control software contains complex kinematic and dynamic models, which can calculate the cooperative motion commands of all drive axes of the mobile base unit, the multi-degree-of-freedom serial manipulator, and the high-stiffness parallel module under the given five-axis tool trajectory. At the same time, it also contains advanced vibration suppression algorithms, which dynamically adjust the working states of the magnetorheological damper and the piezoelectric ceramic actuator according to the real-time feedback signals to achieve the best vibration damping effect.

[0041] Example of the working process When milling a large and complex curved surface part is required, the working process is as follows: 1. The operator imports the part model and the machining program through the PC interface.

[0042] 2. The cooperative control system plans the global path and first drives the mobile base unit to move the robot body near the area to be machined of the part.

[0043] 3. Then, the cooperative control system coordinates the joint movements of the multi-degree-of-freedom serial manipulator, moves the high-stiffness parallel module and the end effector (milling cutter) to the machining starting point, and adjusts the initial posture.

[0044] 4. Start milling. If large-range tracking is required, the cooperative control system precisely coordinates the movements of the mobile base unit, the multi-degree-of-freedom serial manipulator for posture adjustment, and the high-stiffness parallel module for precise five-axis linkage feeding, so that the tool tip moves precisely along the complex trajectory of the part surface.

[0045] 5. During the entire milling process, the active composite vibration damping module works continuously. Sensors (such as accelerometers and force sensors) monitor the vibration of the machining point in real time. The cooperative control system dynamically adjusts the current of the magnetorheological damper and the driving voltage of the piezoelectric ceramic actuator according to the feedback signal, and actively suppresses various vibrations caused by changes in cutting force.

[0046] 6. After machining is completed, the robot retracts the tool and moves to the next area or ends the task.

[0047] Other embodiments 1. The high-stiffness parallel module can adopt other configurations, such as 3-PSS (providing three translational degrees of freedom in X, Y, and Z) or other hybrid-degree-of-freedom configurations, to adapt to different machining requirements.

[0048] 2. The structure and integration method of the active vibration damping module can be diversified. For example, the magnetorheological damper 31 and the piezoelectric ceramic actuator 32 can be integrated at different positions, or different types of sensors can be used for feedback.

[0049] 3. The end effector 17 can be replaced with a grinding head, drill bit, etc. through a quick-change device to perform different machining tasks.

[0050] Through the ingenious combination of the mobile base, serial arm, and parallel module, as well as the integrated application of the active composite vibration damping technology, the present invention has successfully constructed a hybrid robot system capable of achieving high-stiffness, high-precision, and low-vibration milling machining within a large range. It overcomes the limitations of the prior art and provides an innovative solution for the efficient and high-quality automated machining of large and complex structural parts.

[0051] The present invention combines the hybrid structure with the mobile base, significantly expanding the effective machining range and flexibility of the robot. At the same time, the local stiffness of the machining point is improved by using the parallel module, and the milling vibration is greatly reduced by the active composite vibration damping technology. Thus, it can perform five-axis linkage milling machining of large and complex structural parts with high efficiency and high precision, significantly improving the machining quality and surface finish.

[0052] Those of ordinary skill in the art can understand that all or part of the steps in implementing the above-described embodiment methods can be completed by instructing relevant hardware through a program. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memory, CD-ROM, optical memory, etc.) containing computer-usable program code.

[0053] Each embodiment in this specification is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other. For the above embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and reference can be made to the corresponding parts of the method embodiments for the relevant content.

[0054] The above embodiments have introduced the present invention in detail. Specific examples are used herein to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only for helping to understand the method and its core idea of the present invention. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A mobile base hybrid serial-parallel robot machining system for high-precision milling of large structural parts, characterized in that include: a mobile base unit for providing a first set of degrees of freedom of motion along a predetermined path to extend the effective working range of the robot; A multi-degree-of-freedom serial robot arm, the base of which is mounted on the mobile base unit, providing a second set of degrees of freedom for large-scale posture adjustment of the robot; A high-rigidity parallel module, wherein the parallel static platform is connected to the end of the multi-degree-of-freedom serial robot arm, and the parallel linkage platform provides a third group of motion degrees of freedom for local high-precision feeding motion; the first group of motion degrees of freedom, the second group of motion degrees of freedom, and the third group of motion degrees of freedom constitute at least six degrees of freedom of the robot during operation; The end effector is installed on the parallel linkage platform of the multi-degree-of-freedom parallel module and is used for five-axis linkage processing of large structural parts, including milling, grinding and drilling; An active composite vibration reduction module, integrated between the parallel linkage platform and the end effector or integrated into the end effector, the active composite vibration reduction module comprising a magnetorheological damper and a piezoelectric ceramic actuator for actively suppressing vibration during processing; The collaborative control system connects and controls the mobile base unit, the multi-degree-of-freedom serial robot arm, the high-rigidity parallel module and the active composite vibration reduction module through a high-speed real-time bus, realizes the collaborative movement of the components to complete the five-axis linkage processing of large structural parts, and controls the active composite vibration reduction module in real time to reduce vibration.

2. The mobile base type hybrid serial-parallel robot machining system according to claim 1, wherein, The high-rigidity parallel module is a parallel mechanism with two degrees of freedom, comprising: a parallel static platform, a parallel linkage platform, a parallel module upper cover plate, a parallel module side arm, a first branch chain and a second branch chain; One end of the first branch chain is connected to the parallel static platform through a rotating pair, and the other end is connected to the parallel linkage platform through a rotating pair. The parallel linkage platform and the end effector are detachably fixedly connected.

3. The mobile base type hybrid serial-parallel robot machining system according to claim 2, characterized in that, The first branch chain includes an A bracket, an A bearing seat, a nut, a bearing connector, a bolt, a first lead screw, a B bearing seat, a B bracket, and a first motor, and one end of the first motor is connected to the parallel static platform through a revolute pair; The nut in the ball screw nut pair is fixed to the rotor of the first motor, and the first motor is mounted on the first screw, so that the first screw has a rotational freedom around the axis of the nut and a linear movement freedom along the axis direction, so as to form a cylindrical kinematic pair; The first lead screw is connected to the parallel linkage platform through a rotating pair, the end of the first lead screw is fixedly connected to the A bearing seat, the A bracket is connected to the A bearing seat to form a rotating pair, the bearing connecting piece is connected to the first lead screw through nuts and bolts, and the B bracket is connected to the B bearing seat to form a rotating pair.

4. The mobile base type hybrid serial-parallel robot machining system according to claim 3, characterized in that The second branch chain has the same structural setting as the first branch chain. The first branch chain is connected between the parallel static platform and the parallel linkage platform. The second branch chain is connected between the parallel static platform and the parallel module upper cover plate. The parallel module upper cover plate is connected to the parallel linkage platform through a rotating pair to form a closed-loop double-chain parallel structure.

5. The mobile base type hybrid serial-parallel robot machining system according to claim 1, wherein, The mobile base unit adopts any one of an autonomous mobile platform or a linear guide rail with a wear-resistant ceramic layer coated on the surface.

6. The mobile base type hybrid serial-parallel robot machining system according to claim 1, characterized in that The multi-degree-of-freedom serial manipulator is a serial arm with at least four rotational degrees of freedom, including a manipulator base mounted on a mobile base unit, a manipulator waist providing the first degree of freedom of rotation about the Z axis, a first link group, a second link group, a manipulator upper arm, and a manipulator joint.

7. The mobile base type hybrid serial-parallel robot machining system according to claim 6, characterized in that At least one joint of the multi-degree-of-freedom serial manipulator adopts a hollow shaft structure and is internally provided with a coolant circulation pipeline.

8. The mobile base type hybrid serial-parallel robot machining system according to claim 1, characterized in that, The damping force of the magnetorheological damper can be dynamically adjusted according to the machining load, its excitation current is continuously adjustable within a preset range, and the response time is not greater than a specific value.

9. The mobile base type hybrid serial-parallel robot machining system according to claim 1, characterized in that, The piezoelectric ceramic actuators are distributed at multiple predetermined positions to achieve active suppression of multi-directional vibrations.

10. The mobile base type hybrid serial-parallel robot machining system according to claim 1, characterized in that, The collaborative control system is based on the EtherCAT bus architecture and can drive the mobile base unit, the multi-degree-of-freedom serial manipulator, and the high-rigidity parallel module to perform collaborative motion, and realize the five-axis linkage machining path tracking of the full curved surface of large structural parts in one clamping.

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