Rigid-flexible coupled climbing robot for space pipe: vacuum weightlessness adaptation design and path planning

Abstract

The present application relates to rigid-flexible coupling climbing robot for space pipe body: vacuum weightlessness adaptive design and path planning, belongs to space robot technical field. In order to solve the technical problems of poor pipe adaptability and insufficient load capacity of existing robots in space vacuum weightlessness environment, the following technical scheme is adopted: including modular body structure, rigid-flexible coupling driving system, control system and autonomous path planning module. Among them, the rigid-flexible coupling driving system is composed of rigid joint and flexible cable driving unit, realizes the self-adaptive deformation of pipe diameter;The control system is embedded with segmented constant curvature dynamics model, and the fuzzy PID, adaptive sliding mode control and deep reinforcement learning algorithm are fused;The autonomous path planning module adopts deep deterministic policy gradient algorithm and integrates dynamics constraint. The present application realizes load ratio ≥1:2 under self weight ≤3kg, positioning error ≤±0.5mm, vibration suppression time ≤0.3s, and is used for pipe inspection and maintenance under weightlessness condition.

Description

Technical Field

[0001] This invention relates to the field of space robot technology, and more specifically, to a rigid-flexible coupling climbing robot for use in space tubes. Background Technology

[0002] Space pipe structures are widely used in critical equipment such as spacecraft propulsion systems, space station life support systems, and deep space probe fuel delivery systems. These pipes operate for extended periods in complex environments characterized by high vacuum, microgravity, and extreme temperature variations, requiring regular inspections, maintenance, and troubleshooting. Currently, such operations primarily rely on extravehicular activity (EVA) by astronauts or the use of rigid robots, but this approach has significant limitations: EVAs are high-risk, costly, and time-constrained; traditional rigid robots have fixed configurations and struggle to adapt to the complex topologies of space pipes, such as diameter changes, bends, and branches, and their sealing and power transmission efficiency in a vacuum environment cannot meet the demands of long-term operations.

[0003] In recent years, cable-driven technology and rigid-flexible coupling configurations have provided new ideas for the development of space robots. Cable-driven systems offer advantages such as lightweight design, long stroke, and flexible transmission; rigid-flexible coupling configurations combine the high precision of rigid structures with the adaptive characteristics of flexible structures. However, existing research mainly focuses on conventional ground environments, and systematic research on material properties (such as sealing and lubrication), cable-driven dynamics (such as tension transmission and vibration suppression), and path planning (such as attitude stabilization and complex path search) in vacuum and weightless environments is still insufficient. Therefore, there is an urgent need for a rigid-flexible coupling climbing robot that can adapt to complex spatial pipe environments, has a high load-to-weight ratio, and autonomous operation capabilities. Summary of the Invention

[0004] This invention aims to solve the technical problems of existing space pipeline robots, such as poor adaptability, insufficient load capacity, and weak autonomous operation capability in vacuum weightlessness environments.

[0005] This invention provides a rigid-flexible coupling climbing robot for space tubes, comprising the following technical solutions: A rigid-flexible coupling climbing robot for use in space tubes, characterized in that it comprises: The modular body structure adopts a three-level modular configuration of "drive-connection-execution", and all modules are connected through standardized interfaces. The drive module has built-in servo motors and cable drive elements, which are used to drive the robot to extend and retract along the pipe axis and rotate circumferentially. The connection module serves as the skeleton, connecting the drive module and the execution module. The execution module is equipped with standardized interfaces for mounting working tools or sensors.

[0006] The rigid-flexible coupling drive system includes a rigid joint and a flexible cable drive unit; the rigid joint provides high-precision positioning support; the flexible cable drive unit uses a steel wire rope and is controlled by a servo motor in the drive module to drive the robot to achieve a wide range of movements and adaptive deformation of the tube diameter.

[0007] The control system includes a sensing unit, a control unit, and a communication unit; the sensing unit is used to collect robot posture, position, and pipeline environment information; the control unit receives the information from the sensing unit and generates control commands based on a dynamic model and intelligent control algorithm; the communication unit is used to exchange data with a host computer.

[0008] Fourth, the autonomous path planning module, built into the control unit, is used to integrate robot dynamics constraints and pipeline environment models to generate collision-free, executable optimized motion paths.

[0009] Preferred technical solution 1: The connecting module uses a carbon fiber rod as a skeleton and is wrapped with a 3D printed ABS shell, which balances lightweight and structural strength.

[0010] Preferred technical solution 2: The cable drive element of the drive module is a stainless steel wire rope with a diameter of 1mm, which is matched with an MG996R servo motor to realize a telescopic stroke of 0-100mm between modules.

[0011] Preferred technical solution 3: The standardized interface of the execution module is compatible with laser displacement sensors and miniature cameras, and is designed to bear a load of not less than 3kg.

[0012] Preferred technical solution four: The control system adopts an STM32F103 main control chip and is equipped with a rigid-flexible coupling dynamic model based on a piecewise constant curvature model.

[0013] Preferred technical solution five: The intelligent control algorithm integrates fuzzy PID control, adaptive sliding mode control and deep reinforcement learning algorithm to suppress flexible vibration and realize autonomous obstacle avoidance and path optimization in the pipeline.

[0014] Preferred technical solution six: The autonomous path planning module adopts a deep deterministic strategy gradient algorithm, which incorporates the robot's attitude angle range and cable tension constraints as dynamic constraints into the path planning model.

[0015] Preferred technical solution seven: The robot's self-weight does not exceed 3kg, the load ratio (load weight / self-weight) is not less than 1:2, the motion positioning error does not exceed ±0.5mm, and the flexible vibration suppression time does not exceed 0.3s.

[0016] By adopting the above technical solution, the present invention has the following beneficial effects: 1. Strong environmental adaptability: Through a "rigid-flexible integration and tube-shaped deformation" configuration design, combined with cable-driven and rigid joint coordinated control, the robot can adapt to the changing diameter, bending and branching structure of spatial pipes, and achieve flexible climbing of complex pipes.

[0017] 2. Lightweight and high load ratio: Using lightweight materials such as carbon fiber and 3D-printed ABS, and combined with the flexible transmission characteristics of cable drive, it achieves a self-weight of ≤3kg while ensuring a load ratio of ≥1:2, meeting the stringent requirements of spacecraft for payloads, and providing the capability to carry inspection and maintenance tools.

[0018] 3. High control precision: Based on the piecewise constant curvature model, the rigid-flexible coupling dynamic model accurately describes the motion characteristics of the robot under pipeline constraints. Combined with fuzzy PID and adaptive sliding mode control, it effectively suppresses flexible vibration and achieves high-precision positioning of ±0.5mm.

[0019] 4. Strong ability to work independently: By integrating dynamics models and deep reinforcement learning algorithms, the robot has achieved autonomous path planning and obstacle avoidance in complex pipeline environments, enabling it to complete inspection tasks autonomously without human intervention.

[0020] 5. Broad prospects for space applications: The robot of this invention can be applied to pipeline inspection, cleaning, and simple maintenance tasks in on-orbit services such as space stations and spacecraft, providing key technical support for solving long-term on-orbit maintenance of pipelines in extreme space environments. Attached Figure Description

[0021] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic cross-sectional view of the overall structure of the robot in an embodiment of the present invention; Figure 2 This is a structural engineering drawing of the present invention; Figure 3 This is an exploded view of the robot structure in an example of the present invention; Figure 4 This is a schematic diagram of the mating of the quadrupedal telescopic gear rack parts of the robot according to an example of the present invention. Detailed Implementation 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] Please see Figures 1 to 4 This embodiment provides a rigid-flexible coupling climbing robot for space tubes.

[0023] The robot includes a modular body structure, a rigid-flexible coupling drive system, a control system, and an autonomous path planning module.

[0024] 1. Drive module: The dimensions are 50mm×50mm×30mm. It has a built-in MG996R servo motor and uses a 1mm diameter stainless steel wire rope as the cable drive element to achieve a telescopic stroke of 0-100mm between modules.

[0025] 2. Connection module: The frame is made of T300 grade carbon fiber rod with a diameter of 8mm, and the outer layer is a 3D printed ABS shell with a wall thickness of 2mm, which takes into account both lightweight and impact and vibration absorption performance.

[0026] 3. Execution module: The dimensions are 40mm×40mm×25mm. It is equipped with a standardized interface and is compatible with laser displacement sensors, miniature cameras, etc. It is designed to bear a load of no less than 5kg to meet the needs of pipeline inspection and operation.

[0027] The rigid-flexible coupling drive system consists of rigid joints and flexible cable drive units working together. The rigid joints ensure the robot's high-precision positioning capability at critical work points; the flexible cable drive units, driven by servo motors, enable the robot's extension, retraction, and bending, thus adapting to changes in pipe diameter and curvature. The cable drive system uses lightweight, flexible materials to replace traditional rigid, heavy structures, effectively reducing the robot's weight.

[0028] The control system is the core of this invention, and its interaction relationship is as follows: Figure 2 As shown, the sensing unit includes a tension sensor and a laser displacement sensor, which collects information on the robot's posture, cable tension, and distance from the inner wall of the pipe in real time. The control unit uses an STM32F103 as the main control chip and embeds a rigid-flexible coupling dynamic model based on a piecewise constant curvature model (PCC). This model can accurately describe the nonlinear deformation and vibration characteristics of the flexible arm under vacuum, weightlessness, and constraints from the inner wall of the pipe. Based on this, the control unit integrates fuzzy PID control and adaptive sliding mode control algorithms to suppress the vibration of the flexible structure, ensuring that the motion positioning error does not exceed ±0.5mm and the vibration suppression time does not exceed 0.3s.

[0029] The autonomous path planning module is built into the control unit. For example... Figure 4 As shown, this module employs the Deep Deterministic Policy Gradient (DDPG) algorithm for path planning. Unlike traditional geometric search methods, this module incorporates the robot's dynamic constraints (such as attitude angle range and cable tension limits) as one of the optimization objectives into the path planning model. Combined with prior knowledge of the pipeline environment provided by the digital twin system, the robot can plan autonomous inspection paths in real time that meet dynamic feasibility requirements and are collision-free in complex pipeline networks with varying diameters, bends, and obstacles.

[0030] To verify the performance of the present invention, a prototype was prepared and tested according to the following steps: 1. Configuration design and simulation: SolidWorks was used for full parametric modeling, and ANSYS was used to perform topology optimization and static analysis on key load-bearing components to ensure that the load ratio is ≥1:2 under the premise that the self-weight is ≤3kg.

[0031] 2. Prototype Integration: Based on the optimized design, complete the processing, procurement, and final assembly of the drive module, connection module, and execution module.

[0032] 3. Environmental simulation test: Component testing: Test the scaling accuracy and load capacity of the drive module.

[0033] Algorithm testing: The positioning accuracy and vibration suppression effect of the control algorithm were tested inside a simulated pipeline on the ground.

[0034] Vacuum environment testing: The space environment is simulated in a vacuum chamber to test the force transmission efficiency of the cable drive system and the robot's autonomous obstacle avoidance capability in a vacuum.

[0035] Comprehensive inspection test: Perform continuous inspection tasks in a simulated pipeline including straight pipes, bends, and variable diameter pipe sections to comprehensively verify the robot's motion accuracy, load capacity, autonomous planning, and obstacle avoidance performance.

[0036] Test results show that the robot prototype proposed in this invention has a weight of 2.8 kg, a maximum load capacity of 1.5 kg, and a load ratio better than 1:2. Within a simulated pipeline, the motion positioning error is ±0.45 mm, the flexible vibration suppression time is 0.28 s, and it can autonomously complete path planning and obstacle avoidance tasks in complex pipeline networks.

Claims

1. An eight-legged rigid-flexible coupled robot, characterized in that, The system includes a main body module, a foot module, a telescopic drive module, and a locking drive module. The main body module includes a front main body base and a rear main body base spaced apart. The front and rear main body bases are detachably connected by at least four connecting columns arranged in an array. The connecting columns are helical screw structures, and the locking drive module is sleeved on the connecting columns. The foot module includes eight sets of telescopic feet symmetrically arranged around the main body module. Each set of telescopic feet includes a fixed leg and a telescopic leg. One end of the fixed leg is fixedly connected to the main body module, and the telescopic leg is slidably inserted inside the fixed leg. The telescopic leg is driven by a motor gear rack. The locking drive module includes a fixed pulley assembly sleeved on the connecting columns. The fixed pulley assembly is fixedly connected to both the upper and lower main body bases. The fixed pulley assembly is connected to the core control unit of the main body module via a traction rope to achieve linkage locking between the main body module and the telescopic foot module.

2. The eight-legged rigid-flexible coupling robot according to claim 1, characterized in that, Both the front and rear main body bases of the main body module are square hollow structures. The corners of the front and rear main body bases are provided with mounting grooves for mounting the fixing legs. The mounting grooves and the fixing legs are detachably connected by bolts.

3. The eight-legged rigid-flexible coupling robot according to claim 1, characterized in that, The number of connecting columns is four, and the four connecting columns are located at the four corners of the front main body base and the rear main body base, respectively. The two ends of the connecting columns are fixedly connected to the upper main body base and the lower main body base through fixed pulleys. The fixed leg of the telescopic leg module is a hollow rectangular tubular structure. The inner wall of the fixed leg is provided with a guide rail along its length direction, and the outer wall of the telescopic leg is provided with a slider adapted to the guide rail. The slider is slidably connected to the guide rail.

4. The eight-legged rigid-flexible coupling robot according to claim 1, characterized in that, The motor gear rack transmission mechanism includes a drive motor fixed inside the main module, a drive gear keyed to the output shaft of the drive motor, and a transmission rack arranged parallel to the length direction of the telescopic leg. The transmission rack is fixedly connected to the telescopic leg, and the drive gear meshes with the transmission rack.

5. The eight-legged rigid-flexible coupling robot according to claim 1, characterized in that, The fixed pulley assembly includes a fixed base, a fixed pulley, and a connecting ear. The fixed base is fixedly connected to the outer shell of the upper main body base / lower main body base. The fixed pulley is rotatably connected to the fixed base via a rotating shaft. The connecting ear is disposed on the side wall of the fixed base and is used to connect to the traction rope.

6. The eight-legged rigid-flexible coupling robot according to claim 1, characterized in that, The core control unit includes a controller, a power module, and a wireless communication module. The controller is electrically connected to the drive motor, the power module, and the wireless communication module, respectively. The wireless communication module is used to receive external control commands to realize remote control of the robot.

7. The eight-legged rigid-flexible coupling robot according to claim 1, characterized in that, A pressure sensor is installed at the end of the telescopic leg. The pressure sensor is electrically connected to the controller and is used to detect the contact pressure between the telescopic leg and the inner wall of the pipe.

8. A drive control method for an eight-legged rigid-flexible coupled robot according to any one of claims 1-7, characterized in that, Includes the following steps: S1. In the initial state, the fixed pulley assembly of the locking drive module is in a relaxed state, and the telescopic leg of the telescopic foot module is retracted inside the fixed leg; S2. When a walking command is received, the core control unit controls the drive motor of the telescopic drive module to start. The drive motor drives the transmission rack through the active gear, thereby pushing the telescopic leg to extend from the fixed leg until the telescopic leg contacts the inner wall of the pipe and reaches the preset support force. S3. After the pressure sensor detects that the contact pressure has reached the preset value, the core control unit sends a locking command to control the fixed pulley assembly of the locking drive module to tighten the traction rope, thereby locking and fixing the connecting column to the main module. S4. Repeat steps S2-S3 to control multiple sets of telescopic leg modules to sequentially complete the extension, support, and locking actions, thereby realizing the robot's walking movement; S5. When a retraction command is received, the fixed pulley assembly of the locking drive module releases the traction rope, the drive motor reverses, and the telescopic leg is retracted into the fixed leg, completing the reset.

9. The drive control method according to claim 8, characterized in that, In step S3, the preset support force ranges from 50N to 200N, and the pressure sensor feeds back the contact pressure signal to the core control unit in real time to achieve closed-loop control.

10. The drive control method according to claim 8, characterized in that, In step S4, the sequence of actions of the multiple sets of telescopic leg modules is as follows: first, control the two sets of telescopic leg modules on the front side to complete the support and locking, then control the two sets of telescopic leg modules on the rear side to complete the support and locking, and so on, to realize the robot's forward / backward / turning.

Images