A quadruped robot based on joint coupling and momentum wheel and a control method thereof

Abstract

The application discloses a kind of four-legged robot based on joint coupling and momentum wheel and control method thereof, belong to the field of foot type robot structure design and motion control. Robot includes fuselage, four leg mechanisms, pitch and roll momentum wheel module, main control and perception system. Each leg mechanism adopts differential bevel gear coupling hip drive, is moved by two hip motors through synchronous pulley and bevel gear set to realize hip joint pitch, side swing;Knee joint drive unit is arranged in proximal femur and is transmitted through synchronous belt, reduces the inertia of leg distal end. Two orthogonal momentum wheel modules are arranged in the middle of fuselage, and the pitch and roll attitude adjustment torque is outputted by the change of angular momentum. Control method uses body-momentum wheel collaborative framework, generates mass center trajectory and contact force reference by NMPC, distributes leg joint torque by WBC, and LQR controls momentum wheel output high-frequency attitude compensation torque, so as to improve dynamic response and attitude stability under complex terrain, weak support and external disturbance.

Description

Technical Field

[0001] This invention relates to the field of robotics, specifically to a quadruped robot based on joint coupling and momentum wheels and its control method, belonging to the fields of legged robot mechanical structure design, inertial attitude adjustment and motion control technology.

[0002] In this invention, the "momentum wheel" refers to an inertial rotor assembly driven by a motor and outputting a reaction attitude adjustment torque to the machine body through changes in angular momentum. Its function is equivalent to the reaction wheel commonly referred to in the field of robot attitude control. Background Technology

[0003] Quadruped robots offer advantages such as good stability, strong terrain mobility, and flexible movement patterns, making them suitable for tasks like inspection, transportation, rescue, and exploration in complex environments. Most existing quadruped robots employ a tandem leg structure, with each joint typically driven by an independent motor in a single-degree-of-freedom manner. While this structure offers relatively simple control, the actuators and transmission components are often distributed near the various joints of the legs, potentially resulting in a large distal mass and equivalent moment of inertia, limiting high-speed leg swing, rapid gait switching, and dynamic response capabilities in complex terrain.

[0004] On the other hand, traditional tandem leg structures lack power coupling and torque sharing mechanisms between their joints. When a robot needs to simultaneously perform hip lateral movement, hip pitch, and knee swing, each actuator can typically only independently bear the load of its corresponding degree of freedom, making it difficult to achieve power redundancy between different degrees of freedom. Under conditions of high-speed motion, asymmetric loads, or external disturbances, individual joint motors are more prone to problems such as torque saturation, increased temperature rise, or increased tracking errors.

[0005] Meanwhile, the attitude adjustment of quadruped robots typically relies primarily on the ground reaction force at the feet. When the robot is in states such as weak support, diagonal support, single-leg support, narrow support area, low-speed quasi-static adjustment, or transient airborne state, the foot contact constraint is insufficient, and the ability to generate restoring torque based on contact force is significantly limited, resulting in insufficient attitude recovery performance in the roll and pitch directions. Momentum wheels can directly affect the body attitude through their own angular momentum changes, providing additional inertial torque when foot contact force is insufficient. However, existing quadruped robots typically lack a unified structural integration and cooperative control scheme between momentum wheels and leg drive systems.

[0006] Therefore, there is a need for a quadruped robot system and control method that takes into account low leg inertia, joint torque coupling and modular maintenance in terms of mechanical structure, and low-frequency support of legs and high-frequency attitude compensation of momentum wheels in terms of control method. Summary of the Invention

[0007] The purpose of this invention is to provide a quadruped robot based on joint coupling and momentum wheels and its control method, so as to solve the problems of large distal inertia of the legs, insufficient joint drive power coupling, insufficient posture recovery ability under weak support state, and difficulty in coordinating momentum wheels and leg control in existing quadruped robots.

[0008] To achieve the above objectives, the quadruped robot provided by this invention includes a body structure, four leg mechanisms, a pitch momentum wheel module, a roll momentum wheel module, a battery, a main control unit, an electrical system, and a sensing system. The four leg mechanisms are symmetrically arranged at the four corners of the body structure. Each leg mechanism includes two hip joint drive units, a knee joint drive unit, a thigh structure, a lower leg structure, and a foot end structure. The two hip joint drive units form a joint-coupled drive mechanism via synchronous pulleys, synchronous belts, idler pulleys, and a differential bevel gear set. The co-directional output of the two hip motors generates hip joint pitch motion, while the differential output generates hip joint lateral movement, thereby achieving dual-degree-of-freedom coupled drive in a compact structure.

[0009] The knee joint drive unit adopts a semi-in-place layout, installed on the proximal lateral aspect of the thigh, and directly transmits power to the knee joint axis via a synchronous belt pulley mechanism. The thigh structure uses a double-plate load-bearing structure composed of a carbon fiber inner and outer plate, the lower leg structure uses lightweight carbon fiber components, and the foot end uses a rubber elastic structure. This arrangement concentrates the drive mass in the proximal leg, shortens the knee joint drive chain, reduces the rotational inertia of the distal leg, and improves the swing response speed.

[0010] The fuselage structure adopts a modular frame-type load-bearing structure, with leg mounting areas at the four corners, a pitch momentum wheel module, a roll momentum wheel module, and an inertial measurement unit in the middle, a battery at the front, and a main control unit and interface area at the rear. The pitch and roll momentum wheel modules each include a carbon fiber mounting plate, a momentum wheel motor, a motor output flange, a momentum wheel connector, a drive shaft, and a momentum wheel. The two momentum wheel modules are orthogonal to each other and arranged close to the fuselage's center of gravity, respectively outputting attitude adjustment torques in the pitch and roll directions.

[0011] This invention also provides a control method. The method first acquires information from the IMU, joint encoder, motor drive module, and depth camera, and performs state estimation. Then, nonlinear model predictive control optimizes the center of mass trajectory, base attitude, and contact force distribution based on the current state, gait pattern, and target speed. Next, whole-body control transforms the planning results into twelve-dimensional leg joint torques based on floating base dynamics, friction cones, and task priorities. Simultaneously, a linear quadratic regulator outputs momentum wheel compensation torque based on roll and pitch attitude errors and momentum wheel speed. Finally, leg motor commands and momentum wheel motor commands are sent to the drive module via the CAN bus, and closed-loop collaborative control is formed based on feedback.

[0012] Compared with the prior art, the present invention has at least the following beneficial effects: (i) The output of the two hip motors is mapped to the hip joint pitch and lateral swing two-degree-of-freedom motion through the differential bevel gear set, so as to achieve motor power sharing and joint torque redistribution while maintaining the compact structure.

[0013] (ii) The knee joint motor adopts a semi-in-place proximal arrangement and directly drives the knee joint axis via a synchronous belt, avoiding excessively long transmission chains and complex spatial universal transmission, reducing transmission losses, assembly errors and maintenance difficulties.

[0014] (iii) The carbon fiber thigh side plates, carbon fiber calf and rubber foot end work together to reduce the mass of the distal leg while ensuring support rigidity and impact resistance, thereby improving foot trajectory tracking and rapid leg swing performance.

[0015] (iv) The dual-axis orthogonal momentum wheel module is installed close to the fuselage center of mass. It can output pitch and roll attitude compensation torque to the fuselage without relying on significant changes in foot position, thereby enhancing attitude stability under weak support and disturbance conditions.

[0016] (v) The control method integrates NMPC, WBC and LQR in a hierarchical and coordinated manner to form a control system with low-frequency global planning, mid-frequency leg torque distribution and high-frequency momentum wheel attitude compensation, thereby improving the robot's dynamic balance capability in complex terrain and underactuated conditions.

[0017] (vi) The momentum wheel control channel is independent of the WBC contact force optimization process, does not occupy foot contact force resources, can quickly compensate for attitude disturbances when foot support margin is insufficient, and can unload angular momentum after support conditions are restored.

[0018] (vii) The fuselage, battery, momentum wheel, main control unit, IMU and leg mechanism are all modularly installed, which facilitates processing, assembly, disassembly, debugging and subsequent hardware upgrades. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the quadruped robot of the present invention.

[0020] Figure 2 This is a schematic diagram of the overall structure of the quadruped robot of the present invention from another perspective.

[0021] Figure 3 This is a schematic diagram of the leg mechanism and the driving structure of the hip and knee joints of the present invention.

[0022] Figure 4 This is a schematic diagram of the momentum wheel module structure and installation method of the present invention.

[0023] Figure 5 This is a block diagram of the control system of the present invention.

[0024] Explanation of reference numerals in the attached drawings: 1. Body structure; 2. Leg mechanism; 3. Motor mounting box; 4. Depth camera; 5. Camera support frame; 6. Front protective shell; 7. Side protective shell; 8. Battery cover; 9. Rear protective shell; 10. Pitch momentum wheel module; 11. Roll momentum wheel module; 12. Battery; 13. Main control unit; 14. Carbon fiber base plate; 15. First hip joint drive unit; 16. Second hip joint drive unit; 17. Knee joint drive unit; 18. Knee joint motor mounting cover; 19. Synchronizing pulley; 20. (The last part is incomplete and likely refers to a different component or element.) 21. Walking belt; 22. Synchronizing pulley; 23. Idler pulley; 24. Carbon fiber inner thigh plate; 25. Carbon fiber outer thigh plate; 26. Lower leg fixation component; 27. Knee joint shaft; 28. Carbon fiber lower leg; 29-31. Foot end; 32-34. Hip joint positioning plate; 35. Bevel gear; 36. Motor output shaft; 37-39. Gear power output shaft; 40. Angle iron structure; 41. Carbon fiber fixing plate; 42. Momentum wheel motor; 43. Motor output flange; 44. Momentum wheel connector; 45. Drive shaft; 46. Momentum wheel.

[0025] Detailed Implementation

[0026] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Any equivalent substitutions or conventional adjustments made by those skilled in the art to structural dimensions, material specifications, installation methods, control parameters, and actuator models without departing from the principles of the present invention should fall within the scope of protection of the present invention.

[0027] like Figure 1 and Figure 2 As shown, the quadruped robot in this embodiment adopts a configuration with the body centered and the four legs symmetrically arranged. The body structure (1) serves as the main load-bearing platform of the whole machine. The carbon fiber base plate (14) is connected to the body frame and is used to support the leg mechanism (2), pitch momentum wheel module (10), roll momentum wheel module (11), battery (12), main control unit (13), electrical module and sensing module. The four leg mechanisms (2) are respectively installed at the four corners of the body structure (1), so that the robot has twelve active degrees of freedom, that is, each leg has three active degrees of freedom: hip joint lateral swing, hip joint pitch and knee joint pitch.

[0028] The fuselage structure (1) adopts a modular frame structure. The motor mounting box (3) is used to fix and protect the hip drive components; the depth camera (4) is mounted on the front of the fuselage via a camera support bracket (5) to acquire depth information of the environment in front; the front protective shell (6), side protective shell (7), battery cover (8), and rear protective shell (9) are used to protect the internal electrical components and provide an external mounting interface. The battery (12) is located at the front of the fuselage, and the main control unit (13) is located at the rear or mid-rear of the fuselage. Together with the mass distribution of the momentum wheel module, the two adjust the center of gravity of the whole machine, so that the center of gravity is close to the geometric center of the fuselage. The inertial measurement unit is preferably installed in the middle of the fuselage and fixedly connected to the fuselage to reduce the influence of local vibration and installation offset on attitude measurement.

[0029] like Figure 3 As shown, each leg mechanism (2) includes a first hip joint drive unit (15), a second hip joint drive unit (16), a knee joint drive unit (17), a knee joint motor fixing cover (18), synchronous pulleys (19, 21), a synchronous belt (20), an idler pulley (22), a carbon fiber inner thigh plate (23), a carbon fiber outer thigh plate (24), a calf fixation piece (25), a knee joint shaft (26), a carbon fiber calf (27), and a foot end (28). The first hip joint drive unit (15) and the second hip joint drive unit (16) are mounted on the proximal end of the leg and close to the fuselage. The two are connected by synchronous pulleys (19, 21), a synchronous belt (20), an idler pulley (22), and a bevel gear set (32-34) to form a differential coupling drive mechanism.

[0030] In the hip differential coupling drive mechanism, the first hip joint drive unit (15) and the second hip joint drive unit (16) drive corresponding input bevel gears through the motor output shaft (35), respectively. The two input bevel gears mesh with the output bevel gear, and the output bevel gear is connected to the gear power output shaft (36). When the two hip motors output at the same speed in the same direction, the motion of the two input bevel gears is superimposed to form the hip joint pitch motion; when there is a speed difference between the outputs of the two hip motors, the differential motion of the two input bevel gears forms the hip joint lateral swing motion. Therefore, the hip joint pitch angle can be expressed as the proportionality of the algebraic sum of the rotation angles of the two hip motors, and the hip joint lateral swing angle can be expressed as the proportionality of the difference in rotation angles of the two hip motors. This structure enables the two hip motors to share the hip load and redistribute torque between different degrees of freedom of motion.

[0031] The knee joint drive unit (17) is mounted on the proximal lateral side of the thigh via a knee joint motor mounting cover (18) and transmits power to the knee joint axis (26) via a synchronous belt pulley mechanism. The knee joint axis (26) is fixedly connected to the carbon fiber calf (27) via a calf fixation piece (25), enabling the output of the knee joint drive unit (17) to drive the carbon fiber calf (27) to swing. Compared to the scheme of arranging the knee joint motor near the calf or foot, this semi-integrated arrangement concentrates the driving mass in the proximal end of the leg, reducing the distal rotational inertia; compared to the fully integrated long drive chain scheme, this arrangement does not require passing through the hip via multi-stage universal joints, resulting in a shorter transmission path, simpler control modeling, and higher transmission efficiency and assembly reliability.

[0032] The carbon fiber inner thigh plate (23) and the carbon fiber outer thigh plate (24) constitute a double-side plate load-bearing structure. The double-side plates connect the hip output end and the knee joint axis (26) and provide mounting bases for the knee joint drive unit (17), timing belt (20), timing pulleys (19, 21), idler pulleys (22), and tensioning connectors. Weight-reduction openings can be provided on the double-side plates to reduce the leg mass while ensuring bending resistance, torsion resistance, and installation stiffness. The carbon fiber calf (27) mainly undertakes the functions of foot end support and motion transmission. The foot end (28) is preferably a rubber elastic round bottom or spherical structure to improve ground adaptability and cushion the impact of foot landing.

[0033] like Figure 4 As shown, both the pitch momentum wheel module (10) and the roll momentum wheel module (11) consist of a carbon fiber mounting plate (40), a momentum wheel motor (41), a motor output flange (42), a momentum wheel connector (43), a drive shaft (44), and a momentum wheel (45). The carbon fiber mounting plate (40) serves as a sub-module support and is detachably connected to the fuselage structure (1). The momentum wheel motor (41) is fixed on the carbon fiber mounting plate (40), and the momentum wheel (45) is coaxially connected to the output end of the momentum wheel motor (41) via the motor output flange (42), the momentum wheel connector (43), and the drive shaft (44). The momentum wheel (45) is preferably made of 45 steel to obtain a large moment of inertia within a limited size.

[0034] The rotation axis of the pitch momentum wheel module (10) corresponds to the pitch axis of the fuselage, and the rotation axis of the roll momentum wheel module (11) corresponds to the roll axis of the fuselage. The two modules are orthogonal to each other and installed in the middle of the fuselage, close to the center of gravity of the whole machine, in order to reduce the additional torque and structural coupling caused by the installation offset. The momentum wheel motor (41) changes its angular momentum by accelerating or decelerating the momentum wheel (45). According to the principle of conservation of angular momentum, the fuselage is subjected to a reaction torque in the opposite direction. This reaction torque can quickly compensate for roll and pitch attitude errors when the foot support margin is insufficient or the fuselage attitude disturbance is large.

[0035] The electrical system includes a battery (12), a power distribution module, a main control unit (13), a leg joint motor drive module, a momentum wheel motor drive module, and sensors. The battery (12) is preferably a 24V power battery, which supplies power to the joint motor, momentum wheel motor, and control computing platform via an anti-spark switch and a power distribution board. The leg joint motor can be an integrated brushless servo motor, and the momentum wheel motor can be an integrated hub motor that supports speed, position, torque, or MIT control modes. The leg joint motor and momentum wheel motor communicate with the main control unit (13) via a CAN bus. Each drive module has a unique CAN ID to achieve independent control and unified scheduling. The depth camera (4) can be connected to the main control unit via a USB interface, and the IMU can be connected to the main control unit via a serial port or other buses.

[0036] like Figure 5 As shown, the control system of this invention adopts a body-momentum wheel cooperative control framework. The sensor and state estimation layer collects IMU attitude angles and angular velocities, joint encoder positions and velocities, estimated motor currents or torques, and environmental information from the depth camera, and publishes a unified state to each control layer. The NMPC planning layer optimizes the center of mass trajectory, base attitude trajectory, and foot contact force distribution within a finite prediction time domain based on the current state, gait contact pattern, and target motion speed, preferably operating at a frequency of around 100 Hz. The WBC torque layer receives the NMPC output and, based on the floating base dynamics model, contact friction cone constraints, joint torque limiting, and swing foot trajectory task, converts the desired motion into twelve-dimensional joint torque commands, preferably operating at a frequency above 200 Hz. The LQR attitude layer directly receives IMU attitude feedback and momentum wheel speed feedback, outputting momentum wheel attitude compensation torques in the roll and pitch directions, preferably operating at a frequency of around 500 Hz.

[0037] Specifically, the NMPC planning layer uses centroid dynamics as the prediction model, comprehensively considering constraints such as the contact force of the supporting foot, the motion of the swinging foot, the friction cone at the foot tip, the foot tip distance, and the range of motion of the joints, and outputs the desired centroid trajectory, the base attitude trajectory, the reference contact force, and the reference joint velocity. The WBC torque layer is solved using hierarchical quadratic programming, with the floating base dynamics equation, joint torque limit, friction cone, and zero acceleration at the contact point of the supporting foot as hard constraints; base acceleration tracking and swinging foot trajectory tracking as motion tasks; and approximation of the contact force to the NMPC reference value as a low-priority optimization objective, thereby ensuring that high-priority physical constraints are not violated by low-priority tasks.

[0038] The LQR attitude layer establishes a single-axis discrete state-space model for the roll and pitch axes. The state variables include the fuselage tilt angle, angular velocity, and momentum wheel angular velocity for the corresponding axes. The controller solves the discrete Riccati equation offline to obtain the state feedback gain and outputs the motor torque online based on the attitude error and momentum wheel speed. To balance attitude recovery speed, overshoot suppression, and momentum wheel speed management, tilt angle weight, angular velocity weight, momentum wheel speed weight, and control torque weight are set in the performance indicators, respectively. When the momentum wheel speed approaches the limit, the main control unit (13) adjusts the fuselage attitude through reverse momentum wheel control or, when support conditions permit, through the ground reaction force of the legs to unload the angular momentum of the momentum wheel.

[0039] During the control command conversion process, the hip joint pitch torque and hip joint lateral torque output by WBC are converted into the motor torque or MIT control target of the first hip joint drive unit (15) and the second hip joint drive unit (16) through differential coupling mapping; the knee joint torque is directly converted into the control target of the knee joint drive unit (17); the pitch momentum wheel torque and roll momentum wheel torque output by LQR are sent to the pitch momentum wheel module (10) and the roll momentum wheel module (11) respectively. Each motor drive module performs low-level closed-loop control and feeds back position, speed, torque, temperature and fault status. The main control unit (13) updates the state estimation and control output of the next control cycle according to the feedback.

[0040] Under conditions of weak support, diagonal support, single-leg support, airborne operation, or external disturbance, the leg mechanism (2) may not be able to provide sufficient restoring torque on its own. In this case, the momentum wheel module prioritizes outputting high-frequency attitude compensation torque to quickly suppress attitude deviations in the roll and pitch directions. Once the robot regains stable support, the WBC adjusts the foot contact force distribution in conjunction with the momentum wheel control to unload angular momentum. Through the synergy of the low-frequency leg support and high-frequency momentum wheel compensation, the robot can achieve higher dynamic stability in complex terrain and underactuated conditions.

[0041] The motor model, control frequency, material specifications, dimensional parameters, and sensor type mentioned in the above embodiments are all preferred examples. Those skilled in the art can replace them with equivalent components or adjust parameters according to the load level, overall size, controller computing power, and application environment. As long as the joint-coupled leg mechanism, orthogonal momentum wheel attitude adjustment mechanism, and body-momentum wheel cooperative control concept are still adopted, they fall within the protection scope of this invention.

Claims

1. A quadruped robot based on joint coupling and momentum wheels, characterized in that, The system includes a fuselage structure (1), four leg mechanisms (2), a motor mounting box (3), a depth camera (4), a camera support frame (5), a front protective shell (6), a side protective shell (7), a battery cover (8), a rear protective shell (9), a pitch momentum wheel module (10), a roll momentum wheel module (11), a battery (12), a main control unit (13), and a carbon fiber base plate (14). The four leg mechanisms (2) are respectively installed at the four corners of the fuselage structure (1). The pitch momentum wheel module (10) and the roll momentum wheel module (11) are installed in the middle area of ​​the fuselage structure (1) and arranged orthogonally to each other. The main control unit (13) is electrically connected to the leg mechanisms (2), the pitch momentum wheel module (10), and the roll momentum wheel module (11) for controlling leg movements and the machine's motion. The body posture is coordinated for control; each of the leg mechanisms (2) includes a first hip joint drive unit (15), a second hip joint drive unit (16), a knee joint drive unit (17), a knee joint motor fixing cover (18), synchronous pulleys (19, 21), a synchronous belt (20), an idler pulley (22), a carbon fiber inner thigh plate (23), a carbon fiber outer thigh plate (24), a calf fixation piece (25), a knee joint shaft (26), a carbon fiber calf (27), and a foot end (28); wherein, the first hip joint drive unit (15) and the second hip joint drive unit (16) form a differential coupling drive mechanism through synchronous pulleys (19, 21), a synchronous belt (20), an idler pulley (22), and a bevel gear set (32-34) to coordinate the generation of hip joint pitch freedom and hip joint lateral swing freedom.

2. The quadruped robot according to claim 1, characterized in that, The bevel gear set (32-34) includes two input bevel gears and one output bevel gear. The two input bevel gears are respectively connected to the motor output shafts (35) of the first hip joint drive unit (15) and the second hip joint drive unit (16). The output bevel gear is connected to the gear power output shaft (36). The same rotational component of the two input bevel gears is mapped to the hip joint pitching motion, and the differential rotational component of the two input bevel gears is mapped to the hip joint lateral swinging motion, so that the two hip motors share the output power and output torque between the two degrees of freedom. The differential coupling drive mechanism satisfies the following motion mapping relationship: the pitch angle of the hip joint is proportional to the algebraic sum of the rotation angles of the two hip motors, and the lateral swing angle of the hip joint is proportional to the difference between the rotation angles of the two hip motors; when the robot performs high-speed gait, lateral disturbance compensation or asymmetric load tasks, the main control unit (13) dynamically adjusts the output ratio of the two hip motors according to the expected hip output torque, so as to reduce the risk of torque saturation of a single motor and improve the joint's anti-disturbance capability.

3. The quadruped robot according to claim 1, characterized in that, The knee joint drive unit (17) is installed on the outer side of the proximal thigh in a semi-in-wall arrangement and is connected to the knee joint shaft (26) through a synchronous belt pulley mechanism; the knee joint shaft (26) is fixedly connected to the carbon fiber calf (27), and the knee joint drive unit (17) drives the carbon fiber calf (27) to swing around the knee joint via synchronous belt drive, thereby shortening the power transmission path of the knee joint and reducing the inertia of the distal calf. The carbon fiber inner thigh plate (23) and the carbon fiber outer thigh plate (24) constitute a double-side plate bearing structure. A synchronous wheel, support shaft, idler wheel and tensioning connector are provided between the double side plates or on the outer side of the double side plates. The double side plates are provided with weight reduction openings and connect the hip output end to the knee joint shaft (26) to improve the leg bending stiffness, torsional stiffness and installation stiffness when bearing ground reaction force and external load.

4. The quadruped robot according to claim 1, characterized in that, The carbon fiber calf (27) is made of carbon fiber tube or carbon fiber sheet, and the foot end (28) is a rubber round bottom or spherical elastic foot end, which is set at the end of the carbon fiber calf (27) to improve ground contact adaptability, buffer the impact of foot landing and reduce the impact load on the leg transmission mechanism.

5. The quadruped robot according to claim 1, characterized in that, The fuselage structure (1) is a modular frame-type load-bearing structure with symmetrical leg mounting areas on the left and right sides. The front end is equipped with a battery (12) and a battery cover (8), the rear end is equipped with a main control unit (13), and the middle part is equipped with a pitch momentum wheel module (10), a roll momentum wheel module (11), and an inertial measurement unit. The front and rear mass distributions of the battery (12), the main control unit (13), and the momentum wheel module are balanced with each other, so that the center of mass of the whole machine is close to the geometric center of the fuselage.

6. The quadruped robot according to claim 1, characterized in that, Both the pitch momentum wheel module (10) and the roll momentum wheel module (11) include a carbon fiber fixing plate (40), a momentum wheel motor (41), a motor output flange (42), a momentum wheel connector (43), a drive shaft (44), and a momentum wheel (45). The momentum wheel (45) is coaxially connected to the output end of the momentum wheel motor (41). The momentum wheel motor (41) changes the angular momentum by accelerating or decelerating the momentum wheel (45) to output an attitude adjustment torque in the opposite direction to the fuselage according to the principle of conservation of angular momentum. The rotation axis of the pitch momentum wheel module (10) corresponds to the pitch axis of the fuselage, and the rotation axis of the roll momentum wheel module (11) corresponds to the roll axis of the fuselage. The two momentum wheel modules are independent of each other in terms of mechanical structure, electrical drive and control commands, and are used to adjust the pitch attitude of the fuselage and the roll attitude of the fuselage respectively. The momentum wheel (45) is made of 45 steel and is used to increase the moment of inertia in a compact size. The carbon fiber fixing plate (40) is detachably connected to the fuselage structure (1) to reduce the weight of the momentum wheel module and facilitate independent disassembly, debugging and maintenance.

7. The quadruped robot according to claim 1, characterized in that, The main control unit (13) adopts a hierarchical control architecture with upper and lower computers. The upper computer is used to execute gait command generation, foot trajectory planning, state estimation, nonlinear model predictive control, whole-body control and task logic management. The lower computer is composed of motor drive modules, which are used to receive desired position, desired speed, desired torque or speed control quantity and complete motor closed-loop control. The upper computer communicates with twelve leg joint motors and two momentum wheel motors through the CAN bus, and achieves independent addressing and unified scheduling through different CAN IDs.

8. A control method for a quadruped robot based on joint coupling and momentum wheels, applied to the quadruped robot according to any one of claims 1 to 11, characterized in that, The process includes the following steps: S1, acquiring state information from the inertial measurement unit, joint encoder, joint motor drive module, and depth camera to obtain body attitude angle, angular velocity, acceleration, joint position, joint velocity, motor output state, and environmental information; S2, performing state estimation and gait pattern determination based on the state information and task instructions; S3, using nonlinear model predictive control to optimize the rolling motion of the center of mass, base attitude, and foot contact force within a finite time domain, outputting the desired center of mass trajectory, base attitude trajectory, reference contact force, and reference joint velocity; S4, employing whole-body control to... The desired center of mass trajectory, base attitude trajectory, and reference contact force are mapped to torque commands for each leg joint; S5, a linear quadratic regulator is used to generate momentum wheel attitude compensation torque based on the fuselage roll angle, pitch angle, angular velocity, and momentum wheel speed; S6, the leg joint torque commands are converted into coordination commands for the two hip motors and the knee motor of the differential coupling drive mechanism, and the momentum wheel attitude compensation torque is simultaneously sent to the corresponding momentum wheel motor; S7, the control commands are updated based on feedback from the motor drive module and sensors to form a closed-loop coordinated control of leg movement and momentum wheel attitude compensation; In step S3, the nonlinear model predictive control uses the centroid dynamics model as the predictive model, and the supporting foot contact force, joint velocity and body state as optimization variables or state variables. It sets constraints on the contact friction cone, swing foot off the ground, supporting foot zero velocity, foot end distance and joint range of motion, and outputs reference quantities for whole-body control at a frequency of about 100 Hz. In step S4, the whole-body control adopts a hierarchical quadratic programming solution. The floating base dynamic equation, joint torque limit, friction cone constraint and zero acceleration of the support foot contact point are taken as the highest priority hard constraints. The base acceleration tracking and swing foot trajectory tracking are taken as the motion task layer. The approximation of the contact force to the nonlinear model predictive control reference value is taken as the force tracking layer. Thus, the torque commands of each joint are obtained without destroying the high-level constraints. In step S5, the linear quadratic regulator uses the single-axis body tilt angle, single-axis angular velocity, and corresponding momentum wheel angular velocity as state variables, solves the Riccati equation offline based on the discrete state space model to obtain the feedback gain, and outputs the momentum wheel motor torque at a frequency of about 500 Hz. The momentum wheel attitude compensation torque does not participate in the contact force optimization in the whole body control, so as to form a high-frequency angular momentum regulation channel that is decoupled from the foot contact force distribution.

9. The control method according to claim 12, characterized in that, The leg mechanism (2) undertakes low-frequency support force and motion execution functions, while the pitch momentum wheel module (10) and the roll momentum wheel module (11) undertake high-frequency attitude disturbance compensation functions. When the robot is in a weak support, diagonal leg support, single-leg support, airborne or external disturbance condition, the attitude compensation torque is output first through the momentum wheel, and after the support condition is restored, the angular momentum of the momentum wheel is unloaded through the ground reaction force of the legs or the reverse momentum wheel control to avoid the momentum wheel speed saturation.

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