A six-degree-of-freedom robotic arm system based on modular joint modules and its control method

Abstract

This invention discloses a six-degree-of-freedom robotic arm system and its control method based on modular joint modules. The system includes replaceable end effectors, a lightweight arm, integrated drive and control joint modules, an embedded main control base, and a host computer. The end effector of the robotic arm is designed with a standardized quick-replacement interface, which can be equipped with various tools and occupies little space. It adopts a six-degree-of-freedom serial structure, and each joint module integrates a motor, reducer, encoder, and drive control unit, which communicates with the embedded main control base via an FDCAN bus. The embedded main control base integrates a core board main control unit, which receives commands from the host computer, performs trajectory planning, joint control, status feedback, and safety management. The host computer completes human-computer interaction, task parameter configuration, motion command issuance, and operation status detection. Through the coordinated optimization of structure and control, the foldability, load efficiency, and task execution capability of the robotic arm are improved, making it suitable for scenarios such as on-orbit maintenance, space assembly, and confined space operations.

Description

Technical Field

[0001] This invention belongs to the fields of end-effector tool replacement, mechatronics equipment, modular joint drive and control, and bus communication control, and relates to a six-degree-of-freedom robotic arm system based on modular joint modules and its control method. Background Technology

[0002] Existing robotic arm systems are mostly used in ground-based industrial production or laboratory operations, often employing fixed bases. Their structural design, control systems, and end-effector forms are typically geared towards repetitive handling, assembly, welding, or inspection tasks in ground environments. However, in applications such as space structure assembly, spacecraft external component replacement, and fuel loading for small space platforms, robotic arms are required to be lightweight, have a high folding and storage ratio, and a high load-to-weight ratio to reduce space occupation during launch, ensure reliable on-orbit deployment, facilitate module replacement, provide independent and autonomous control, and offer adaptability for end-effectors. Existing robotic arm systems have the following main shortcomings in these scenarios: 1. The overall size of the device is too large and its folding and storage capabilities are insufficient: Existing robotic arms are mostly used for fixed ground installations, typically employing distributed motors, cascaded reducers, and additional drive cabinets. This results in a bulky system structure, complex wiring, and difficult installation and maintenance. Furthermore, insufficient consideration is given to the envelope size during launch, folding and storage configuration, and space utilization. Lightweight robotic arms also limit load capacity and suffer from insufficient strength in the arm and joints.

[0003] 2. Insufficient modularity and inconvenient on-orbit maintenance: To reduce weight at the end effector or joints, some robotic arms employ synchronous belts, wire ropes, and linkage mechanisms to distribute the motors, reducers, and encoders, improving weight distribution. However, this introduces longer transmission links. In space orbit operations, robotic arms must withstand extreme conditions such as launch vibrations, on-orbit temperature cycles, and vacuum. Complex transmission links increase potential failure points, hindering fault location and rapid on-orbit replacement.

[0004] 3. The end-effectors lack adaptability and are insufficient for tasks such as drilling and sawing. Traditional robotic arms often employ specialized tools at the end effector for a single task. When task switching is required, manual replacement or a quick-change device is often necessary. For on-orbit maintenance tasks in space, tools should be more flexible and adaptable, the replacement process should be simple and reliable, and the tool's start and stop should be coordinated with the robotic arm's movement trajectory.

[0005] 4. Insufficient independent operation capability: Current robotic arms largely rely on external control cabinets and industrial computers for trajectory planning, motion control, and mission management. This architecture increases system size, cabling complexity, and computing power consumption. For small spacecraft, onboard computing resources are scarce, and power and communication resources are limited. Over-reliance on satellite main control computing power or ground telemetry platform mission management may increase the difficulty of overall satellite system integration and mission risks.

[0006] 5. Insufficient feedback and control capabilities for complex tasks: Traditional robotic arms rely solely on a single encoder for simple position feedback. During operation, the end effector is subjected to periodic cutting forces, impacts, and other disturbances. Coupled with issues such as the flexible deformation of the joint drive chain and the backlash of the reducer, positioning accuracy is affected. The system lacks a unified state management mechanism for motion control, interference suppression, and command parsing, making it prone to problems such as joint malfunctions, tool mis-starts, and delayed fault handling.

[0007] Therefore, there is an urgent need for a lightweight, mechatronic, multi-degree-of-freedom robotic arm system suitable for space on-orbit services. This system should have a smaller envelope size and a better folding and storage form to reduce the cost of on-orbit launch and deployment. Furthermore, modular components, strong independent operation capabilities, mission management, and operation feedback should ensure the execution of on-orbit missions, thereby reducing the burden on satellite platforms in terms of computing power, power supply, and communication. Summary of the Invention

[0008] The purpose of this invention is to provide a lightweight mechatronic robotic arm system and its control method based on modular joint modules, in order to solve the problems of existing robotic arms in space operation scenarios, such as insufficient overall folding and storage capacity, difficulty in balancing lightweight and load capacity, low modularity of joints and arms, reliance on external computing power for control systems, insufficient adaptability of end-effectors, and lack of unified state management for task control.

[0009] This invention employs a six-degree-of-freedom serial configuration, providing complete spatial orientation adjustment capabilities. It utilizes high-strength aluminum alloy, reinforcing ribs, and a weight-reduction design to ensure rigidity and load-bearing capacity while reducing mass. An integrated planetary joint module combines the motor, reducer, drive control board, dual encoders, and communication interface. The module is mounted on the FDCAN bus, with control and feedback executed by an embedded main control unit encapsulated in the base. A replaceable interface consisting of a tensioning sleeve, coupling, and drive motor allows for tool selection based on the task. A state machine, planning and teaching module, control module, and safety interlocks enable multi-functional unified scheduling.

[0010] This invention provides a six-degree-of-freedom robotic arm based on modular joint modules. An aluminum alloy CNC engraving base serves as the supporting foundation for the entire device, and an embedded main control unit is installed inside. This main control unit runs a real-time operating system and communicates with each joint module via an FDCAN bus communication interface. Six integrated drive and control joint modules are arranged in series. Each joint module integrates a motor, a planetary reduction mechanism, a drive control board, a first encoder, and a second encoder. The joint modules are arranged sequentially according to the following configuration: shoulder: joint one, joint two; elbow: joint three; wrist: joint four, joint five, joint six, and connected by connectors to form a six-degree-of-freedom structure. The drive control board integrates an FDCAN communication interface and an XT30 power socket, which are used to receive commands from the main control unit and drive the motor. The first encoder is located on the motor output shaft side of each joint module, and the second encoder is located on the reduction mechanism output side of each joint module. A high-precision joint output angle value is obtained by differential calculation of the signals from the two encoders. The boom assembly is made of high-strength aluminum alloy and features a reinforced rib design. It includes the boom arm, forearm arm, first and second joint connecting rods, fourth and fifth joint connecting rods, and fifth and sixth joint connecting rods. Each boom arm has countersunk holes at both ends and is fixed to the joint module without protruding from the surface by M3*10 / 12 / 14 socket head cap screws. A 3D-printed pull-out shell is fitted onto the rear of the CNC-carved base and fixed to the base with M3*12 socket head cap screws. The STM32H750VBT6 core board is installed inside a 3D printed pull-out shell and serves as the core of the embedded main control unit, communicating with the drive control boards of each joint module. The FDCAN integrated debugging board is installed inside a 3D-printed pull-out shell and connects to the communication terminal of the STM32H750VBT6 core board for debugging FDCAN bus communication. The robotic arm has a replaceable tool interface at its end, including an end coupling, a tensioning sleeve, and a front lock. The tensioning sleeve is fitted onto the outer end of the end coupling and is connected to the tool through the front lock. A standard cylindrical shank is used as a universal interface. The axial and circumferential fixation between the tool and the coupling is achieved by the friction generated by the tensioning sleeve on the inner and outer cylindrical surfaces. The host computer communicates with the STM32H750VBT6 core board via a serial port.

[0011] Preferably, the embedded main control unit sends control commands to each joint module sequentially via the FDCAN bus and receives sensor data fed back by each joint module. It supports multiple control modes, including joint spatial position / velocity control, circular trajectory interpolation, teaching playback, and single joint control. It has safety interlock logic, which can immediately stop joint movement and put the system into a safe state when it detects loss of communication with the host computer, joint abnormality, or error emergency stop signal.

[0012] Preferably, the host computer is compatible with Windows / Linux systems, and displays the position, speed, torque and deviation from the target value of the six joints in real time. It also compares and displays the difference between the PID control torque and the dynamic feedforward torque, and records the main control status for easy error backtracking. Manual teaching can be performed through the host computer to record joint trajectory data. During playback, the main control board performs smooth interpolation processing on the teaching acquisition points and then controls the movement of each joint.

[0013] Preferably, the folded dimensions of the robotic arm are no more than 162mm x 341mm x 80mm, the arm span is no less than 485mm, the reachable working space radius is no less than 385mm, the total weight without tools is no more than 2.3kg, and the load capacity is no less than 1kg; the base and arm are made of high-strength aluminum alloy CNC machined, and the arm is a plate structure with reinforcing ribs provided along the length of the arm inside the plate.

[0014] Preferably, the tool is fixed to the outer end of the tension sleeve by the locking mechanism of the front lock. The tension sleeve is fitted onto the outer end of the end coupling. One end of the end coupling is connected to the output shaft of the joint six drive motor, and the other end is connected to the tension sleeve. One end of the front lock is connected to the outer end of the tension sleeve, and the other end is connected to the handle of the tool. The handle of the tool is inserted into the inner hole of the front lock and fixed by the locking mechanism of the front lock.

[0015] Preferably, the joint-1 drive motor is fixedly mounted on the base, one end of the first-second joint connecting rod is connected to the output shaft of the joint-1 drive motor, and the other end is connected to the input end of the joint-2 drive motor; the joint-2 drive motor is fixed to the other end of the first-second joint connecting rod by an M310 hexagon socket head cap screw; the joint-3 drive motor is fixed to the upper end of the upper arm rod by an M314 hexagon socket head cap screw, the lower end of the upper arm rod is connected to the output shaft of the joint-2 drive motor, and the upper end is connected to the input end of the joint-3 drive motor; the joint-4 drive motor is fixed to the forearm rod by an M312 hexagon socket head cap screw. The upper end of the forearm arm is connected to the output shaft of the joint three drive motor at its lower end and to the input end of the joint four drive motor at its upper end. One end of the fourth and fifth joint connecting rod is connected to the output shaft of the joint four drive motor and the other end is connected to the input end of the joint five drive motor. The joint five drive motor is fixed to the other end of the fourth and fifth joint connecting rod with an M312 hexagon socket head cap screw. One end of the fifth and sixth joint connecting rod is connected to the output shaft of the joint five drive motor and the other end is connected to the input end of the joint six drive motor. The joint six drive motor is fixed to the other end of the fifth and sixth joint connecting rod with an M3*12 hexagon socket head cap screw.

[0016] Preferably, the 3D-printed pull-out shell is located at the rear of the CNC engraving base and is fixed to the base with M3*12 hexagon socket head cap screws; the STM32H750VBT6 core board is installed inside the 3D-printed pull-out shell and is connected to the control terminals of each drive motor; the FDCAN integrated debugging board is installed inside the 3D-printed pull-out shell and is connected to the communication terminal of the STM32H750VBT6 core board.

[0017] Preferably, the aluminum alloy CNC engraving base serves as the supporting foundation for the entire device. The joint-1 drive motor is fixedly mounted on the base. One end of the first-to-second joint connecting rod is connected to the output shaft of the joint-1 drive motor, and the other end is connected to the input end of the joint-2 drive motor. The joint-2 drive motor is fixed to the other end of the first-to-second joint connecting rod using M310 socket head cap screws. The joint-3 drive motor is fixed to the upper end of the upper arm using M314 socket head cap screws. The lower end of the upper arm is connected to the output shaft of the joint-2 drive motor, and the upper end is connected to the input end of the joint-3 drive motor. The joint-4 drive motor is fixed to the upper end of the forearm using M312 socket head cap screws. The lower end of the forearm is connected to the output shaft of the joint-3 drive motor, and the upper end is connected to the input end of the joint-4 drive motor. One end of the fourth-to-fifth joint connecting rod is connected to the output shaft of the fourth joint drive motor, and the other end is connected to the input end of the joint-5 drive motor. The joint-5 drive motor is fixed to the fourth-to-fifth joint connecting rod using M312 socket head cap screws. At the other end of the rod, one end of the fifth and sixth joint connecting rod is connected to the output shaft of the fifth joint drive motor, and the other end is connected to the input end of the sixth joint drive motor. The sixth joint drive motor is fixed to the other end of the fifth and sixth joint connecting rod by an M312 hexagon socket head cap screw. One end of the end coupling is connected to the output shaft of the sixth joint drive motor, and the other end is connected to the tension sleeve. The tension sleeve is fitted onto the outer end of the end coupling and is connected to the tool through a front lock. One end of the front lock is connected to the outer end of the tension sleeve, and the other end is connected to the handle of the tool. The handle of the tool is inserted into the inner hole of the front lock and fixed by the locking mechanism of the front lock. The 3D printed pull-out shell is installed on the rear of the CNC carving base and fixed to the base by an M3*12 hexagon socket head cap screw. The STM32H750VBT6 core board is installed inside the 3D printed pull-out shell and is connected to the control end of each drive motor. The FDCAN integrated debugging board is installed inside the 3D printed pull-out shell and is connected to the communication end of the STM32H750VBT6 core board.

[0018] This invention provides a control method for a six-degree-of-freedom robotic arm, comprising the following steps: S1. The embedded main controller initializes control parameters and filters and wakes up periodically. S2. Receive and parse the data fed back by each joint sensor via the FDCAN bus; S3. Based on the instructions issued by the host computer or the preset trajectory on the board, call the kinematic algorithm to generate the target joint position and velocity; S4. PID control is used to generate the driving torque command for each joint; S5. Send the above control commands to the corresponding joints for execution via FDCAN; S6. Control the start and stop of end tools (such as drill bits or saw blades) according to task requirements; S7. Record and smoothly replay the joint trajectory in teaching mode; S8. Real-time monitoring of displacement, velocity, and torque errors of each joint. When any parameter exceeds the set threshold, safety protection measures such as emergency stop or torque release are triggered. S9. Periodically upload joint status and communication information to the host computer for debugging and status monitoring.

[0019] The beneficial effects achieved by this invention are as follows: Suitable for on-orbit space service scenarios: The robotic arm has a small envelope size, good folding and storage form, high load-to-weight ratio, is suitable for on-orbit operation, and has low deployment cost.

[0020] Highly modular and easy to maintain on track: Power supply and communication functions are completed through a 24V DC power supply and FDCAN bus integrated interface. The joint motor integrates a planetary reducer, dual encoders, and a drive and control integrated circuit board. It is highly modular, and the bolts are easy to install and remove, making it easy to maintain on track in case of failure.

[0021] The toolkit is comprehensive and suitable for a variety of on-orbit tasks: the robotic arm end effector uses a universal tool handle, tension sleeve, and coupling design, and the toolkit includes tools such as drill bits, grippers, saw blades, and welding torches, with high centering accuracy. Tools can be quickly changed to meet task requirements, and software interlocking logic ensures safe coordination between tool start / stop and robotic arm movement.

[0022] Rich motion control modes: Supports multiple control modes such as base, tool system motion, single joint motion, circular interpolation and teach playback.

[0023] Real-time status acquisition and reporting: The system collects joint position, speed and torque feedback in real time, and combines state machine management and information frame parsing to ensure stable execution of different operation modes.

[0024] High system compatibility: Written in C / C++, it is compatible with Windows or Linux systems and can control multiple systems simultaneously.

[0025] The user-friendly interface features a host computer that displays joint status in real time, reflecting the control effect. Users can record teaching trajectories, control coordinate systems, and set tool parameters via the host computer, making debugging and use convenient.

[0026] Independent control with low external computing power requirements: The base is embedded with a core board, equipped with kinematic and dynamic functions, and has a high control frequency. It does not rely on external computing resources, thus reducing the integration of the satellite system. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope.

[0028] Figure 1 This is an exploded view of the mechanical structure of the mechatronic robotic arm system of the present invention. Figure 2 This is an isometric assembly drawing of the overall structure of the present invention; Figure 3 This is a block diagram illustrating the control system principle of the mechatronic robotic arm system of the present invention. Figure 4 This is a diagram of the host computer interface of the present invention; Figure 1 The components include: 1. Tool; 2. Front lock; 3. Tensioning sleeve; 4. End coupling; 5. Joint 6 drive motor; 6. Joint 5-6 connecting rod; 7. Joint 5 drive motor; 8. Joint 4-5 connecting rod; 9. M3*12 socket head cap screw; 10. Forearm arm; 11. Joint 3 drive motor; 12. Arm arm; 13. M3*14 socket head cap screw; 14. Joint 4 drive motor; 15. M3*10 socket head cap screw; 16. Joint 2 drive motor; 17. Joint 1-2 connecting rod; 18. Joint 1 drive motor; 19. 3D printed pull-out shell; 20. STM32H750VBT6 core board; 21. FDCAN integrated debugging board; 22. Aluminum alloy CNC engraved base. Figure 2 In the left image, the tool is a drill bit; in the right image, the tool is a saw blade. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0032] To facilitate the explanation of the overall technical structure of the method of this invention, the current embodiment first summarizes and describes the main functional modules included in this invention. It should be noted that the following functional module division is only used to clearly illustrate the technical concept and implementation logic of this invention and does not constitute a limitation on the scope of protection of this invention. Each functional module can be executed independently in sequence, or it can be implemented collaboratively in combination by a unified bearing defect detection system.

[0033] This invention provides a six-degree-of-freedom robotic arm based on modular joint modules. An aluminum alloy CNC engraving base serves as the supporting foundation for the entire device, and an embedded main control unit is installed inside. This main control unit runs a real-time operating system and communicates with each joint module via an FDCAN bus communication interface. Six integrated drive and control joint modules are arranged in series. Each joint module integrates a motor, a planetary reduction mechanism, a drive control board, a first encoder, and a second encoder. The joint modules are arranged sequentially according to the following configuration: shoulder: joint one, joint two; elbow: joint three; wrist: joint four, joint five, joint six, and connected by connectors to form a six-degree-of-freedom structure. The drive control board integrates an FDCAN communication interface and an XT30 power socket, which are used to receive commands from the main control unit and drive the motor. The first encoder is located on the motor output shaft side of each joint module, and the second encoder is located on the reduction mechanism output side of each joint module. A high-precision joint output angle value is obtained by differential calculation of the signals from the two encoders. The boom assembly is made of high-strength aluminum alloy and features a reinforced rib design. It includes the boom arm, forearm arm, first and second joint connecting rods, fourth and fifth joint connecting rods, and fifth and sixth joint connecting rods. Each boom arm has countersunk holes at both ends and is fixed to the joint module without protruding from the surface by M3*10 / 12 / 14 socket head cap screws. A 3D-printed pull-out shell is fitted onto the rear of the CNC-carved base and fixed to the base with M3*12 socket head cap screws. The STM32H750VBT6 core board is installed inside a 3D printed pull-out shell and serves as the core of the embedded main control unit, communicating with the drive control boards of each joint module. The FDCAN integrated debugging board is installed inside a 3D-printed pull-out shell and connects to the communication terminal of the STM32H750VBT6 core board for debugging FDCAN bus communication. The robotic arm has a replaceable tool interface at its end, including an end coupling, a tensioning sleeve, and a front lock. The tensioning sleeve is fitted onto the outer end of the end coupling and is connected to the tool through the front lock. A standard cylindrical shank is used as a universal interface. The axial and circumferential fixation between the tool and the coupling is achieved by the friction generated by the tensioning sleeve on the inner and outer cylindrical surfaces. The host computer communicates with the STM32H750VBT6 core board via a serial port.

[0034] Preferably, the embedded main control unit sends control commands to each joint module sequentially via the FDCAN bus and receives sensor data fed back by each joint module. It supports multiple control modes, including joint spatial position / velocity control, circular trajectory interpolation, teaching playback, and single joint control. It has safety interlock logic, which can immediately stop joint movement and put the system into a safe state when it detects loss of communication with the host computer, joint abnormality, or error emergency stop signal.

[0035] Preferably, the host computer is compatible with Windows / Linux systems, and displays the position, speed, torque and deviation from the target value of the six joints in real time. It also compares and displays the difference between the PID control torque and the dynamic feedforward torque, and records the main control status for easy error backtracking. Manual teaching can be performed through the host computer to record joint trajectory data. During playback, the main control board performs smooth interpolation processing on the teaching acquisition points and then controls the movement of each joint.

[0036] Preferably, the folded dimensions of the robotic arm are no more than 162mm x 341mm x 80mm, the arm span is no less than 485mm, the reachable working space radius is no less than 385mm, the total weight without tools is no more than 2.3kg, and the load capacity is no less than 1kg; the base and arm are made of high-strength aluminum alloy CNC machined, and the arm is a plate structure with reinforcing ribs provided along the length of the arm inside the plate.

[0037] Preferably, the tool is fixed to the outer end of the tension sleeve by the locking mechanism of the front lock. The tension sleeve is fitted onto the outer end of the end coupling. One end of the end coupling is connected to the output shaft of the joint six drive motor, and the other end is connected to the tension sleeve. One end of the front lock is connected to the outer end of the tension sleeve, and the other end is connected to the handle of the tool. The handle of the tool is inserted into the inner hole of the front lock and fixed by the locking mechanism of the front lock.

[0038] Preferably, the joint-1 drive motor is fixedly mounted on the base, one end of the first-second joint connecting rod is connected to the output shaft of the joint-1 drive motor, and the other end is connected to the input end of the joint-2 drive motor; the joint-2 drive motor is fixed to the other end of the first-second joint connecting rod by an M310 hexagon socket head cap screw; the joint-3 drive motor is fixed to the upper end of the upper arm rod by an M314 hexagon socket head cap screw, the lower end of the upper arm rod is connected to the output shaft of the joint-2 drive motor, and the upper end is connected to the input end of the joint-3 drive motor; the joint-4 drive motor is fixed to the forearm rod by an M312 hexagon socket head cap screw. The upper end of the forearm arm is connected to the output shaft of the joint three drive motor at its lower end and to the input end of the joint four drive motor at its upper end. One end of the fourth and fifth joint connecting rod is connected to the output shaft of the joint four drive motor and the other end is connected to the input end of the joint five drive motor. The joint five drive motor is fixed to the other end of the fourth and fifth joint connecting rod with an M312 hexagon socket head cap screw. One end of the fifth and sixth joint connecting rod is connected to the output shaft of the joint five drive motor and the other end is connected to the input end of the joint six drive motor. The joint six drive motor is fixed to the other end of the fifth and sixth joint connecting rod with an M3*12 hexagon socket head cap screw.

[0039] Preferably, the 3D-printed pull-out shell is located at the rear of the CNC engraving base and is fixed to the base with M3*12 hexagon socket head cap screws; the STM32H750VBT6 core board is installed inside the 3D-printed pull-out shell and is connected to the control terminals of each drive motor; the FDCAN integrated debugging board is installed inside the 3D-printed pull-out shell and is connected to the communication terminal of the STM32H750VBT6 core board.

[0040] Preferably, the aluminum alloy CNC engraving base serves as the supporting foundation for the entire device. The joint-1 drive motor is fixedly mounted on the base. One end of the first-to-second joint connecting rod is connected to the output shaft of the joint-1 drive motor, and the other end is connected to the input end of the joint-2 drive motor. The joint-2 drive motor is fixed to the other end of the first-to-second joint connecting rod using M310 socket head cap screws. The joint-3 drive motor is fixed to the upper end of the upper arm using M314 socket head cap screws. The lower end of the upper arm is connected to the output shaft of the joint-2 drive motor, and the upper end is connected to the input end of the joint-3 drive motor. The joint-4 drive motor is fixed to the upper end of the forearm using M312 socket head cap screws. The lower end of the forearm is connected to the output shaft of the joint-3 drive motor, and the upper end is connected to the input end of the joint-4 drive motor. One end of the fourth-to-fifth joint connecting rod is connected to the output shaft of the fourth joint drive motor, and the other end is connected to the input end of the joint-5 drive motor. The joint-5 drive motor is fixed to the fourth-to-fifth joint connecting rod using M312 socket head cap screws. At the other end, one end of the fifth and sixth joint connecting rod is connected to the output shaft of the fifth joint drive motor, and the other end is connected to the input end of the sixth joint drive motor. The sixth joint drive motor is fixed to the other end of the fifth and sixth joint connecting rod by an M312 hexagon socket head cap screw. One end of the end coupling is connected to the output shaft of the sixth joint drive motor, and the other end is connected to the tension sleeve. The tension sleeve is fitted onto the outer end of the end coupling and is connected to the tool through a front lock. One end of the front lock is connected to the outer end of the tension sleeve, and the other end is connected to the handle of the tool. The handle of the tool is inserted into the inner hole of the front lock and fixed by the locking mechanism of the front lock. The 3D printed pull-out shell is covered on the rear of the CNC carving base and fixed to the base by an M3*12 hexagon socket head cap screw. The STM32H750VBT6 core board is installed inside the 3D printed pull-out shell and is connected to the control end of each drive motor. The FDCAN integrated debugging board is installed inside the 3D printed pull-out shell and is connected to the communication end of the STM32H750VBT6 core board.

[0041] This invention provides a control method for a six-degree-of-freedom robotic arm, comprising the following steps: S1. The embedded main controller initializes control parameters and filters and wakes up periodically. S2. Receive and parse the data fed back by each joint sensor via the FDCAN bus; S3. Based on the instructions issued by the host computer or the preset trajectory on the board, call the kinematic algorithm to generate the target joint position and velocity; S4. PID control is used to generate the driving torque command for each joint; S5. Send the above control commands to the corresponding joints for execution via FDCAN; S6. Control the start and stop of end tools (such as drill bits or saw blades) according to task requirements; S7. Record and smoothly replay the joint trajectory in teaching mode; S8. Real-time monitoring of displacement, velocity, and torque errors of each joint. When any parameter exceeds the set threshold, safety protection measures such as emergency stop or torque release are triggered. S9. Periodically upload joint status and communication information to the host computer for debugging and status monitoring. Example

[0042] like Figure 1 As shown, the robotic arm system in this embodiment includes an end effector assembly, six integrated drive and control joint modules, six lightweight arm rods, and a base. The end effector assembly includes a saw blade, a front lock, a tension sleeve, and an end coupling. The saw blade has a standardized cylindrical shank that can be inserted into the inner cavity of the tension sleeve. The inner cylindrical surface of the tension sleeve tightens the saw blade shank, and the outer cylindrical surface engages the inner hole of the coupling, achieving axial and radial fixation of the tool. The front lock locks the saw blade and shank with bolts, providing a large contact area and good centering. Each joint module includes a high-speed motor and a planetary gear reduction mechanism, as well as an integrated drive and control circuit board (integrating XT30 and FDCAN communication interfaces). Wrist joints are connected by short links; joint one and joint two are connected by a connecting rod; joint two and joint three, and joint three and joint four are connected by the upper arm rod and lower arm rod, respectively, achieving six degrees of freedom combined motion. The lightweight arm rods are made of high-strength aluminum alloy plates, with reinforcing ribs added to the plate edges to improve bending stiffness. The arm is equipped with countersunk screws of M310, M312, and M3*14 sizes for mounting and securing the joint modules, ensuring a smooth, protrusion-free outer surface. The base cavity houses an STM32H750VBT6 embedded main control development board and an FDCAN debugging control board, capable of receiving sensor data from each joint. Example

[0043] like Figure 2 As shown, the robotic arm base has an XT30 power supply port and a USB data cable interface. The XT30 provides 24V regulated DC power to the joint motor module through the input port, and then powers the next joint module through the output port on the other side of the module. The USB data cable provides a data communication channel between the embedded development board and the onboard host computer, and also provides a 5V regulated power supply to meet the power requirements of the development board. The robotic arm's end effector operates using the 24V DC power provided by the end effector module's output port, and is equipped with a voltage regulator / buck converter module as needed to provide logic power to the tool control board chip and wireless communication module. Example

[0044] like Figure 3As shown, the development board runs the FreeRTOS real-time operating system. This embodiment employs a two-level state machine architecture: the communication receiving state machine is responsible for receiving instructions from the spaceborne platform or ground system and performing data verification, parsing, and distribution; the instruction execution state machine is responsible for calling relevant modules to perform trajectory planning and PID torque control according to the current control mode (joint spatial motion, end-effector spatial motion, single-joint control, circular interpolation, teach playback, etc.), and generating commands to be sent to each joint, periodically sending control frames to drive the joints via the FDCAN bus. Simultaneously, the main control board continuously monitors the feedback signals from each joint and uploads the status to the host computer or ground platform to form a complete closed-loop control and status monitoring system. If the joint position, speed, or torque exceeds a safety threshold, the instruction execution state machine will trigger emergency stop or fault protection logic to ensure equipment and personnel safety. Example

[0045] like Figure 4 As shown, the host computer program is developed in C / C++, supports Windows and Linux system platforms, and communicates with the base main controller via serial port. The host computer interface displays the position, velocity, torque, and deviations from the target values ​​of the six joints in real time, and compares the difference between the PID control torque and the dynamic feedforward torque, facilitating controller parameter adjustment. Users can manually teach the system via the host computer, recording joint trajectory data. During playback, the main control board performs smooth interpolation processing on the taught data points before controlling the movement of each joint. Furthermore, the host computer supports translational and rotational control of the base coordinate system and end-effector coordinate system, automatic trajectory import, emergency stop command execution, and diagnostic information viewing, improving the system's operational convenience and maintainability.

[0046] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A six-degree-of-freedom robotic arm based on a modular joint module, characterized in that, An aluminum alloy CNC engraving base (22) serves as the supporting foundation for the entire device. It contains an embedded main control unit that runs a real-time operating system and communicates with each joint module via the FDCAN bus communication interface. Six drive-control integrated joint modules are connected in series. Each joint module integrates a motor, a planetary reduction mechanism, a drive control board, a first encoder, and a second encoder. The joint modules are arranged according to shoulder: joint one, joint two. Elbow: Joint 3; Wrist: Joints four, five, and six are arranged sequentially and connected by connectors to form a six-degree-of-freedom structure; The drive control board integrates an FDCAN communication interface and an XT30 power socket, which are used to receive commands from the main control unit and drive the motor. The first encoder is located on the motor output shaft side of each joint module, and the second encoder is located on the reduction mechanism output side of each joint module. A high-precision joint output angle value is obtained by differential calculation of the signals from the two encoders. The boom assembly is made of high-strength aluminum alloy and features a reinforced rib design. It includes the boom arm (12), the forearm arm (10), the first and second joint connecting rods (17), the fourth and fifth joint connecting rods (8), and the fifth and sixth joint connecting rods (6). Each boom arm has countersunk holes at both ends and is fixed to the joint module without protruding from the surface by M3*10 / 12 / 14 socket head cap screws (9 / 13 / 15). A 3D printed pull-out shell (19) is set at the rear of the CNC engraving base (22) and fixed to the base by an M3*12 socket head cap screw (9); The STM32H750VBT6 core board (20) is installed inside the 3D printed pull-out shell (19) and serves as the core of the embedded main control unit, communicating with the drive control boards of each joint module. The FDCAN integrated debugging board (21) is installed inside the 3D printed pull-out shell (19) and connected to the communication end of the STM32H750VBT6 core board (20) for debugging FDCAN bus communication. The end of the robotic arm is provided with a replaceable tool interface, including an end coupling (4), a tensioning sleeve (3) and a front lock (2). The tensioning sleeve (3) is sleeved on the outer end of the end coupling (4) and connected to the tool (1) through the front lock (2). A standard cylindrical shank is used as a universal interface. The axial and circumferential fixation between the tool and the coupling is achieved by the friction force generated by the tensioning sleeve (3) on the inner and outer cylindrical surfaces. The host computer communicates with the STM32H750VBT6 core board (20) via serial port.

2. The six-degree-of-freedom robotic arm according to claim 1, characterized in that, The embedded main control unit sends control commands to each joint module sequentially via the FDCAN bus and receives sensor data fed back by each joint module. It supports multiple control modes, including joint spatial position / velocity control, circular trajectory interpolation, teaching playback, and single joint control. It has safety interlock logic, which can immediately stop joint movement and put the system into a safe state when it detects loss of communication with the host computer, joint abnormality, or error emergency stop signal.

3. The six-degree-of-freedom robotic arm according to claim 1, characterized in that, The host computer is compatible with Windows / Linux systems and displays the position, velocity, torque, and deviation from the target values ​​of the six joints in real time. It also compares and displays the difference between the PID control torque and the dynamic feedforward torque, and records the main control status for easy error backtracking. Manual teaching can be performed through the host computer to record joint trajectory data. During playback, the main control board performs smooth interpolation processing on the teaching acquisition points before controlling the movement of each joint.

4. The six-degree-of-freedom robotic arm according to claim 1, characterized in that, The folded dimensions of the robotic arm are no more than 162mm x 341mm x 80mm, the arm span is no less than 485mm, the reachable working space radius is no less than 385mm, the total weight without tools is no more than 2.3kg, and the load capacity is no less than 1kg. The base and arm are made of high-strength aluminum alloy CNC machined. The arm is a plate structure with reinforcing ribs along the length of the arm inside the plate.

5. The six-degree-of-freedom robotic arm according to claim 1, characterized in that, The tool (1) is fixed to the outer end of the tension sleeve (3) by the locking mechanism of the front lock (2). The tension sleeve (3) is sleeved on the outer end of the end coupling (4). One end of the end coupling (4) is connected to the output shaft of the joint six drive motor (5), and the other end is connected to the tension sleeve (3). One end of the front lock (2) is connected to the outer end of the tension sleeve (3), and the other end is connected to the handle of the tool (1). The handle of the tool (1) is inserted into the inner hole of the front lock (2) and fixed by the locking mechanism of the front lock (2).

6. The six-degree-of-freedom robotic arm according to claim 1, characterized in that, The joint-1 drive motor (18) is fixedly mounted on the base (22). One end of the first-second joint connecting rod (17) is connected to the output shaft of the joint-1 drive motor (18), and the other end is connected to the input end of the joint-2 drive motor (16). The joint-2 drive motor (16) is fixed to the other end of the first-second joint connecting rod (17) by an M310 socket head cap screw (15). The joint-3 drive motor (11) is fixed to the upper end of the boom arm (12) by an M314 socket head cap screw (13). The lower end of the boom arm (12) is connected to the output shaft of the joint-2 drive motor (16), and the upper end is connected to the input end of the joint-3 drive motor (11). The joint-4 drive motor (14) is fixed to the small joint arm (22) by an M312 socket head cap screw (9). The upper end of the arm lever (10) and the lower end of the forearm lever (10) are connected to the output shaft of the joint three drive motor (11), and the upper end is connected to the input end of the joint four drive motor (14); one end of the four-five joint connecting rod (8) is connected to the output shaft of the joint four drive motor (14), and the other end is connected to the input end of the joint five drive motor (7); the joint five drive motor (7) is fixed to the other end of the four-five joint connecting rod (8) by an M312 internal hexagonal head screw (9); one end of the five-six joint connecting rod (6) is connected to the output shaft of the joint five drive motor (7), and the other end is connected to the input end of the joint six drive motor (5); the joint six drive motor (5) is fixed to the other end of the five-six joint connecting rod (6) by an M3*12 internal hexagonal head screw (9).

7. The six-degree-of-freedom robotic arm according to claim 1, characterized in that, The 3D printed pull-out shell (19) is placed over the rear of the CNC engraving base (22), forming a closed cavity with the base, and is fixed to the base by M3*12 hexagon socket head cap screws (9); the STM32H750VBT6 core board (20) is installed inside the 3D printed pull-out shell (19) and connected to the control terminals of each drive motor (18, 16, 11, 14, 7, 5); the FDCAN integrated debugging board (21) is installed inside the 3D printed pull-out shell (19) and connected to the communication terminal of the STM32H750VBT6 core board (20).

8. The six-degree-of-freedom robotic arm according to claim 1, characterized in that, The aluminum alloy CNC engraving base (22) serves as the supporting foundation for the entire device. The joint drive motor (18) is fixedly installed on the base (22). One end of the first and second joint connecting rod (17) is connected to the output shaft of the joint drive motor (18), and the other end is connected to the input end of the joint drive motor (16). The joint drive motor (16) is fixed to the other end of the first and second joint connecting rod (17) by an M310 socket head cap screw (15). The joint drive motor (11) is fixed to the upper end of the upper arm (12) by an M314 socket head cap screw (13). The lower end of the upper arm (12) is connected to the joint. The output shaft of the second drive motor (16) is connected, and its upper end is connected to the input end of the third drive motor (11). The fourth drive motor (14) is fixed to the upper end of the forearm arm (10) by an M312 socket head cap screw (9). The lower end of the forearm arm (10) is connected to the output shaft of the third drive motor (11), and its upper end is connected to the input end of the fourth drive motor (14). One end of the fourth and fifth joint connecting rod (8) is connected to the output shaft of the fourth drive motor (14), and the other end is connected to the input end of the fifth drive motor (7). The fifth drive motor (7) is fixed by an M312 socket head cap screw (9). One end of the fourth and fifth joint connecting rod (8) is connected to the output shaft of the fifth joint drive motor (7), and the other end is connected to the input end of the sixth joint drive motor (5). The sixth joint drive motor (5) is fixed to the other end of the fifth and sixth joint connecting rod (6) by an M312 socket head cap screw (9). One end of the end coupling (4) is connected to the output shaft of the sixth joint drive motor (5), and the other end is connected to the tension sleeve (3). The tension sleeve (3) is fitted on the outer end of the end coupling (4) and connected to the tool (1) through the front lock (2). One end of the front lock (2) is connected to the outer end of the tension sleeve (3). The other end is connected to the handle of the tool (1). The handle of the tool (1) is inserted into the inner hole of the front lock (2) and fixed by the locking mechanism of the front lock (2). The 3D printed pull-out shell (19) is covered on the CNC carving base (22). The STM32H750VBT6 core board (20) is installed inside the 3D printed pull-out shell (19) and connected to the control terminals of each drive motor (18, 16, 11, 14, 7, 5). The FDCAN integrated debugging board (21) is installed inside the 3D printed pull-out shell (19) and connected to the communication terminal of the STM32H750VBT6 core board (20).

9. A control method for controlling the six-degree-of-freedom robotic arm according to any one of claims 1-8, characterized in that, Includes the following steps: S1. The embedded main controller initializes control parameters and filters and wakes up periodically. S2. Receive and parse the data fed back by each joint sensor via the FDCAN bus; S3. Based on the instructions issued by the host computer or the preset trajectory on the board, call the kinematic algorithm to generate the target joint position and velocity; S4. PID control is used to generate the driving torque command for each joint; S5. Send the above control commands to the corresponding joints for execution via FDCAN; S6. Control the start and stop of end tools (such as drill bits or saw blades) according to task requirements; S7. Record and smoothly replay the joint trajectory in teaching mode; S8. Real-time monitoring of displacement, velocity, and torque errors of each joint. When any parameter exceeds the set threshold, safety protection measures such as emergency stop or torque release are triggered. S9. Periodically upload joint status and communication information to the host computer for debugging and status monitoring.

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