Multi-degree-of-freedom spine joint quadruped robot and stiffness self-adaptive control method thereof

Abstract

The application discloses a multi-degree-of-freedom spine joint four-legged robot and a stiffness self-adaptive control method thereof, and comprises a trunk, a multi-degree-of-freedom spine joint and a mechanical leg; a front trunk is connected with a rear trunk through the multi-degree-of-freedom spine joint, and the front trunk is realized to pitch and roll relative to the rear trunk through the multi-degree-of-freedom spine joint; the multi-degree-of-freedom spine joint is arranged as three joints, contains two pitch joints and one roll joint, each joint contains a stiffness self-adaptive active adjusting assembly, and the multi-degree-of-freedom spine joint is hinged with the front and rear trunks; the mechanical leg is arranged as four groups; the application can fuse a multi-sensor system of a machine body to perceive a complex change of a self posture and a surrounding terrain, calculate the required stiffness of each joint through relevant information, reduce a violent impact of the ground on the robot, reduce joint motor loss, make the robot keep the stability of movement, and prevent the problem of overturning caused by irregular terrain space change or environmental disturbance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of robot technology, in particular to a multi-degree-of-freedom spine joint quadruped robot and a stiffness self-adaptive control method thereof. BACKGROUND

[0002] In recent years, robot technology has developed greatly, especially the foot type robot. Compared with the wheeled and tracked mobile robots, the foot type robot has significant flexibility, obstacle crossing ability and environmental adaptability. The foot type robot is generally divided into two-foot type, four-foot type, six-foot type and eight-foot type, among which the four-foot robot has simple structure, good flexibility, carrying capacity and stability, and has good application prospect in many aspects such as rescue and disaster relief, exploration and survey, entertainment and military.

[0003] At present, there are many four-foot robot research platforms at home and abroad, and many four-foot robot products have appeared on the market. However, most of the existing four-foot robots adopt rigid trunk as the body, which has simple structure and control, but is far away from the characteristics of animals. When researchers observe the movement mode of cheetah, they find that a large part of the high-speed movement ability of cheetah is related to the coordinated movement of the spine.

[0004] Therefore, it is more critical to study the stiffness self-adaptive four-foot robot with spine joint. SUMMARY

[0005] To solve at least one of the above technical problems, the present application provides a multi-degree-of-freedom spine joint quadruped robot, which can improve the flexibility of robot movement and reduce the impact generated in high-speed movement.

[0006] The technical scheme of the present application is as follows:

[0007] The multi-degree-of-freedom spine joint quadruped robot comprises a trunk, a multi-degree-of-freedom spine joint and a mechanical leg. The trunk comprises a front trunk and a rear trunk. The front trunk is connected with the rear trunk through the multi-degree-of-freedom spine joint, and the pitch and roll movements of the front trunk relative to the rear trunk are realized through the multi-degree-of-freedom spine joint.

[0008] Further, the multi-degree-of-freedom spine joint is provided as three joints, including two pitch joints and one roll joint, each joint comprising a stiffness self-adaptive active adjustment component, and the multi-degree-of-freedom spine joint is hinged with the front and rear trunks.

[0009] Further, the mechanical legs are arranged in four groups, and are arranged in a full elbow type configuration on the front torso and the rear torso, each group of mechanical legs comprises a side swing joint assembly, a hip joint assembly, and a knee joint assembly, each assembly comprises a stiffness self-adaptive active adjustment assembly, the size of the leg swing action is realized through the side swing joint assembly, the thigh rotation is realized through the hip joint assembly, and the calf rotation is realized through the knee joint assembly.

[0010] Further, the front torso comprises a front torso front plate, a front torso left plate, a front torso right plate, a front torso bottom plate, and a front torso rear plate, the front torso front plate and the front torso rear plate are fixedly connected with the front torso left plate and the front torso rear plate through screws, the front torso rear plate is fixedly connected with the multi-DOF spine joint, and the front torso front plate, the front torso rear plate, the front torso left plate, and the front torso right plate are all mounted on the front torso bottom plate.

[0011] Further, the front torso further comprises a battery, a front torso control system, and a front torso inertial measurement unit, and the battery, the front torso control system, and the front torso inertial measurement unit are fixedly mounted above the front torso bottom plate, and a camera is fixedly mounted on the front torso front plate.

[0012] Further, the rear torso comprises a rear torso front plate, a rear torso left plate, a rear torso right plate, a rear torso bottom plate, and a rear torso rear plate, the rear torso front plate and the rear torso rear plate are fixedly connected with the rear torso left plate and the rear torso rear plate through screws, the rear torso front plate is fixedly connected with the multi-DOF spine joint, and the rear torso front plate, the rear torso rear plate, the rear torso left plate, and the rear torso right plate are all mounted on the rear torso bottom plate.

[0013] Further, the rear torso further comprises a rear torso control system and a rear torso inertial measurement unit, and the rear torso control system and the rear torso inertial measurement unit are fixedly mounted above the rear torso bottom plate.

[0014] Further, the multi-DOF spine assembly specifically comprises a front torso pitch motor, a front torso pitch variable stiffness assembly, a front torso pitch joint connecting piece, a roll joint motor, a rear torso pitch joint connecting piece, a rear torso pitch variable stiffness assembly, and a rear torso pitch motor, the fixed end of the front torso pitch motor is fixedly mounted on the front torso rear plate through a bolt, the front torso pitch variable stiffness assembly is connected with the output end of the front torso pitch motor through a bolt, and is fixedly connected with the pitch joint connecting piece through a bolt, the fixed end of the roll joint motor is fixedly connected with the pitch joint connecting piece through a bolt, the output end is fixedly connected with the rear torso pitch joint connecting piece through a bolt, the rear torso pitch variable stiffness assembly is fixedly connected with the rear torso pitch joint connecting piece through a bolt, and is fixedly connected with the output end of the rear torso pitch motor through a bolt, and the rear torso pitch motor is fixedly mounted on the rear torso front plate through a bolt.

[0015] Further, the mechanical leg specifically includes a torso connecting piece, a side swing motor, a side swing connecting piece, a hip motor, a hip variable stiffness assembly, a thigh plate, a knee motor, a knee variable stiffness assembly, a lower leg plate, a spherical foot end, a magnetic encoder, and a magnet. The side swing motor fixed end is bolted to the torso connecting piece, the magnetic encoder is screwed to the side swing motor fixed end, the magnet is glued to the side swing motor shaft, the side swing connecting piece is bolted and fixed to the side swing motor output end, the hip motor fixed end is bolted to the side swing motor connecting piece, the magnetic encoder is screwed to the hip motor fixed end, the magnet is glued to the hip motor shaft, the hip variable stiffness assembly is fixed and installed to the hip motor output end, the thigh plate is fixedly connected to the hip variable stiffness assembly, the knee motor fixed end is bolted to the thigh plate, the magnetic encoder is screwed to the knee motor fixed end, the magnet is glued to the knee motor shaft, the knee variable stiffness assembly fixed end is bolted to the knee motor output end, the lower leg plate is bolted and fixedly connected to the knee variable stiffness assembly shell, and the spherical foot end is glued to the end of the lower leg plate.

[0016] Further, the stiffness self-adaptive active adjustment assembly includes a shell, a power input end, and a variable stiffness adjustment assembly, and a power output end. The shell includes a variable stiffness joint base connected with the power input end and a variable stiffness joint shell protecting the variable stiffness assembly. The power input end is used to drive the power output end to rotate around its center of rotation, which includes a joint motor assembly, a motor output flange, and an assembly composed of a motor and a reducer.

[0017] Further, the variable stiffness adjusting assembly is used to adjust the stiffness value of the joint according to the actual need of the power output end, which comprises a coil spring base arranged on the variable stiffness joint base and fixedly connected with the joint motor output shaft through bolts; a coil spring arranged in the base; a coil spring connecting piece connected with the center of the coil spring, which can rotate around the central axis and drive the coil spring to adjust the stiffness; a pair of worm gears, the worm wheel is connected with the coil spring connecting piece through a key, driving the coil spring connecting piece to rotate, and the worm is installed on the variable stiffness joint base through a bearing and engaged with the worm wheel; a motor mounting base fixedly installed on the variable stiffness joint base through screws; a stiffness adjusting motor arranged on the motor mounting base and connected with the worm through a synchronous pulley. The lower end shaft of the coil spring connecting piece is provided with a connecting groove connected with the input end of the coil spring center, and the upper end shaft is connected with the worm wheel through a flat key, driven by the worm wheel, and rotates clockwise through the connecting groove to drive the coil spring to curl inwards to increase the stiffness, and counterclockwise rotation makes the coil spring expand outward to reduce the stiffness. The coil spring base is provided with a mounting groove fixedly connected with the output end of the bent part of the outer ring of the coil spring, which can be driven by the coil spring to rotate the power output end.

[0018] Further, the spherical foot end surface is provided with a rubber cushion component.

[0019] Further, a foot end pressure sensor is attached to the rubber cushion component and is glued to the rubber cushion component.

[0020] Further, the quadruped robot works together with the camera, foot end sensor, inertial measurement unit, front and rear torso control system and other components, fuses the collected information, calculates the terrain drop height h1 and other information of the terrain in front of the robot, and then calculates the required joint stiffness of each variable stiffness joint of the quadruped robot. The front and rear torso joints are controlled to make the front and rear torso joints contract to lower the center of gravity, the stiffness adjusting motor adjusts the torsion amount of the coil spring inside the variable stiffness joint, and the stiffness of the spine and each leg joint is dynamically adjusted. After landing, the foot end pressure sensor senses the impact force of the ground on the robot foot end, combines the information collected by the camera and inertial measurement unit, and adjusts the joint stiffness again to cope with the impact of the complex concave-convex ground in high-speed motion or high-drop terrain, achieving the function of stiffness self-adaptation.

[0021] Further, the quadruped robot calculates the required joint stiffness of each joint according to the surrounding terrain information (including terrain height difference, slope angle, obstacle size, different types of ground, etc.) and the real-time center of mass of the current state of the robot, combined with the foot pressure, and the stiffness control system of the rear torso converts the stiffness into the torsion amount of the coil spring, and then calculates the angle required for the stiffness adjusting motor to rotate, and sends the angle signal to the stiffness adjusting motor in the variable stiffness joint. The stiffness adjusting motor drives the worm gear to rotate through the synchronous pulley set, which drives the coil spring connecting piece to adjust the torsion amount of the coil spring, thereby dynamically adjusting the stiffness of each joint. After the stiffness of each variable stiffness joint of the quadruped robot is adjusted, the terrain height difference and other information calculated according to the data collected by the sensor are dynamically adjusted to adapt to the complex uneven ground.

[0022] Further, when the quadruped robot needs to increase speed during running, the rear torso control system increases the control motor speed and the motor rotation angle range, so that the leg movement range becomes larger. At this time, the magnetic encoder senses the rotation of the magnet installed on the motor shaft end surface to obtain the motor speed, and the front and rear torso inertial measurement unit detects the change of the robot movement speed, and reduces the stiffness of the variable stiffness joint, thereby reducing the great impact force generated by the ground on the quadruped robot when the speed increases during the movement of the robot, and increasing the pitch joint angle signal range in the multi-degree-of-freedom spine joint to improve the leg reach range and foot landing distance of the robot. When the robot needs to reduce speed during running, the rear torso control system reduces the motor speed and the motor rotation angle range, so that the leg range becomes smaller. At this time, the magnetic encoder senses the rotation of the magnet installed on the motor shaft end surface to obtain the motor speed, and the front and rear torso inertial measurement unit detects the change of the robot movement speed, and increases the stiffness of the variable stiffness joint, and reduces the pitch joint angle signal range in the multi-degree-of-freedom spine joint, so that the foot landing distance of the robot becomes smaller. Before running starts, when the terrain information collected by the camera changes, the system judges the terrain characteristics and changes the joint stiffness according to the terrain flatness. When the front road surface is a concave-convex ground, the joint stiffness is reduced to provide cushioning for the impact of complex ground. Conversely, when the road surface is a flat ground, the joint stiffness is increased. The multi-degree-of-freedom spine joint is used to increase the movement space of the robot, and the variable stiffness joint is used to provide cushioning for the movement of the quadruped robot and reduce the impact of the impact on the joint motor and the robot torso.

[0023] Further, when the quadruped robot jumps from a high place to a low place, the front torso control system obtains real-time posture information of the robot according to the front and rear torso inertial measurement units, the joint motor magnetic encoders, and the foot end pressure sensors, adjusts the roll and pitch spine joint angles and the leg joint angle signals, so that the robot front torso tilts forward, so that the robot can look down at the front high-fall terrain, the camera and inertial measurement unit and other sensors collect terrain information, calculate the terrain fall height h1, the rear torso control system further adjusts the roll and pitch spine joint angles and the leg joint angle signals, so that the robot front and rear torso curls, reduces the robot gravity center, reaches the optimal posture calculated by the rear torso control system, and reduces the stiffness of the variable stiffness joint, reduces the impact force of the ground on the robot in the jumping motion, and when the quadruped robot lands, the foot end pressure sensor senses the force generated by the ground on the robot, combines the attitude angle detected by the inertial measurement unit, and reduces the roll spine joint angle in real time, increases the front and rear pitch joint angles, reduces the mechanical leg joint angle, and increases the stiffness of the hip joint and knee joint variable stiffness joint, so that the quadruped robot can remain stable after landing.

[0024] Further, when the terrain information (such as terrain inclination θ, step height h2, h3, h4, etc.) and the required signal calculation are completed, the rear torso control system sends angle signals to the left front leg joints, and the left front leg reaches the required height of the inclined step through the mechanical leg side swing joint, hip joint and knee joint magnetic encoder sensing the rotation position of the left front leg joint, when the left front leg foot end pressure sensor detects the pressure signal, it indicates that the left front leg has reached the step, at this time, the left front leg joint stiffness is increased, and the right front leg repeats the foregoing steps until the right front leg foot end pressure sensor detects the pressure signal. Then the rear torso control system provides angle signals for the roll and pitch spine joints, the front torso control system obtains the real-time motion posture of the robot through the magnetic encoders of the roll and pitch spine joints and the inertial measurement units of the front and rear torsos, and adjusts the posture of the quadruped robot in real time when climbing the inclined step until the optimal posture calculated is reached; at this time, the rear torso control system provides gait signals to the robot to make it normally advance, and stops sending gait signals when reaching the set distance, the rotation position of the left front leg joint is sensed through the magnetic encoder, and angle signals are sent to the right rear leg to make the right rear leg reach the required height of the inclined step, when the right rear leg foot end pressure sensor detects the pressure signal, the right rear leg joint stiffness is increased, at this time, increasing the stiffness can make the robot more stable during climbing, and the left rear leg repeats the foregoing steps. When all four foot end pressure sensors detect the pressure signal, the front torso control system changes the roll and pitch angles of the front and rear torso spines according to the foot end pressure, and combines the real-time posture information of the robot obtained by the magnetic encoders of the joint motors and the inertial measurement units of the front and rear torsos to adjust the posture of the robot in real time, constantly change the foot point and adjust the center of gravity of the robot to adapt to the inclined step, so that the quadruped robot can move stably on the step.

[0025] The present application provides a multi-degree-of-freedom spine joint quadruped robot by improvement, compared with the prior art, has the following improvements and advantages:

[0026] 1) The present application has strong carrying capacity, good stability and simple structure;

[0027] 2) The multi-degree-of-freedom robot leg driven by the joint motor ensures a certain load capacity, and the active variable stiffness component is added to provide certain shock absorption and impact resistance, which can reduce the joint motor loss, improve the service life of the robot, make the robot motion stable, and prevent the problem of overturning caused by irregular terrain space changes or environmental disturbances.

[0028] 3) The multi-degree-of-freedom spine joint robot has more extensive body deformation capability and spatial adaptability, is beneficial to trajectory optimization, increases the range of robot gravity center adjustment, can climb inclined steps, jump on high and low terrains, improves the motion and obstacle crossing capability of the robot in a complex environment, and can provide more superior running characteristics.

[0029] 4) The spine joint robot can fuse a multi-sensor system to perceive the posture of the robot and the complex changes of the surrounding terrain, collect terrain information through the multi-sensor system, obtain real-time posture and foot end contact force signals of the robot, calculate surrounding terrain information, the current posture of the robot, and the gravity center position through the front and rear trunk control system of the robot, and in combination with the foot end pressure signal, calculate the required stiffness of each joint, so that the robot can adaptively adjust the stiffness of each joint when running, jumping, and climbing in a complex terrain, and reduce the impact of the ground on the robot. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is the overall structure diagram of the robot of the present application;

[0031] Figure 2 is the trunk structure diagram of the robot of the present application;

[0032] Figure 3 is the mechanical leg structure diagram of the present application;

[0033] Figure 4 is the explosion view of the knee active variable stiffness assembly of the present application;

[0034] Figure 5 is the cross-sectional view of the knee active variable stiffness assembly of the present application;

[0035] Figure 6 is the running schematic diagram of the robot of the present application in different terrains;

[0036] Figure 7 is the schematic diagram of the robot of the present application jumping from a high place to a low place;

[0037] Figure 8 is the schematic diagram of the robot of the present application climbing an inclined step;

[0038] In the figure: 1000 - mechanical leg, 2000 - front torso, 3000 - multi-DOF spine joint, 4000 - back torso, 1 - front torso front plate, 2 - front torso inertial measurement unit, 3 - camera, 4 - front torso right plate, 5 - front torso control system, 6 - front torso back plate, 7 - front torso pitch variable stiffness assembly, 8 - front torso pitch joint connector, 9 - roll joint motor, 10 - back torso pitch joint connector, 11 - back torso right plate, 12 - back torso inertial measurement unit, 13 - back torso pitch motor, 14 - back torso back plate, 15 - back torso control system, 16 - back torso left plate, 17 - back torso bottom plate, 18 - back torso pitch joint connector, 19 - back torso front plate, 20 - front torso pitch motor, 21 - front torso left plate, 22 - battery, 23 - front torso bottom plate, 24 - lower leg plate, 25 - knee variable stiffness assembly, 26 - hip variable stiffness assembly, 27 - yaw motor, 28 - torso connector, 29 - yaw connector, 30 - hip motor, 31 - upper leg plate, 32 - knee motor, 33 - spherical foot end, 34 - foot end pressure sensor, 35 - motor flange, 36 - variable stiffness joint base, 37 - coil spring base, 38 - first coil spring, 39 - second coil spring, 40 - motor base, 41 - timing pulley set, 42 - stiffness adjustment motor, 43 - worm long end bearing, 44 - worm, 45 - coil spring connector, 46 - worm gear, 47 - variable stiffness joint housing, 48 - end cap, 49 - housing bearing, 50 - worm short end bearing, 51 - hexagonal socket cap screw A, 52 - coil spring base bearing, 53 - hexagonal socket cap screw B, 54 - motor shaft, 55 - magnet, 56 - magnetic encoder. DETAILED DESCRIPTION

[0039] The embodiments of the present application will be described below by Figures 1 to 8 The embodiments of the present application will be described below by

[0040] In the description of the present application, it needs to be understood that, if the terms "center", "middle", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. The features defined as "first", "second" are used to distinguish the feature names, not to have special meanings, and in addition, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0041] In the description of the present application, it needs to be understood that, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0042] The present application relates to a multi-degree-of-freedom spine joint quadruped robot, comprising a trunk, a multi-degree-of-freedom spine joint 3000 and a mechanical leg, the trunk comprising a front trunk 2000 and a rear trunk 4000. The front trunk 2000 is connected with the rear trunk 4000 through the multi-degree-of-freedom spine joint 3000, and the pitch and roll movements of the front trunk 2000 relative to the rear trunk 4000 are realized through the multi-degree-of-freedom spine joint 3000. The multi-degree-of-freedom spine joint 3000 is arranged as three joints, including two pitch joints and one roll joint, each joint comprising a stiffness self-adaptive active adjustment assembly 18, and the spine assembly is hinged with the front and rear trunks. The mechanical leg is arranged as four, arranged in the front trunk and the rear trunk in a full elbow type, each group of mechanical legs comprising a side swing joint assembly, a hip joint assembly and a knee joint assembly, each assembly comprising a stiffness self-adaptive active adjustment assembly, the side swing action of the large and small legs is realized through the side swing joint assembly, the thigh rotation is realized through the hip joint assembly, and the shank rotation is realized through the knee joint assembly.

[0043] The multi-degree-of-freedom spine joint is provided with two pitch degrees of freedom and one roll degree of freedom, the trunk assembly is provided with two trunks in front and back, two mechanical legs are arranged on the trunk assembly, the inside of the trunk assembly is hinged to the multi-degree-of-freedom spine joint, and the axis directions of relative rotation of the multi-degree-of-freedom spine joint and the trunk assembly and the two trunk assemblies are perpendicular to each other. The mechanical legs are installed on the trunk assembly, each mechanical leg has three degrees of freedom, the multi-degree-of-freedom spine joint has three degrees of freedom, and the mechanical legs and the joints of the spine part are each provided with a stiffness self-adaptive active adjusting assembly, thereby playing a role of shock absorption and energy storage.

[0044] As shown in Figures 1-2 The front trunk 2000 includes a front trunk front plate 1, a front trunk left plate 21, a front trunk right plate 4, a front trunk bottom plate 23 and a front trunk rear plate 6, wherein the front trunk front plate 1 and the front trunk rear plate 6 are fixedly connected with the front trunk left plate 21 and the front trunk right plate 4 through screws, the front trunk rear plate 6 is fixedly connected with the multi-degree-of-freedom spine joint 3000, and the front trunk front plate 1, the front trunk rear plate 6, the front trunk left plate 21 and the front trunk right plate 4 are installed on the front trunk bottom plate 23. The front trunk 2000 further includes a battery 22, a front trunk control system 5 and a front trunk inertial measurement unit 2, and a camera 3. The battery 15, the front trunk control system 5 and the front trunk inertial measurement unit 2 are fixedly installed above the front trunk bottom plate 23, and the camera 3 is fixedly installed on the front trunk front plate 1.

[0045] The rear trunk 4000 includes a rear trunk front plate 19, a rear trunk left plate 16, a rear trunk right plate 11, a rear trunk bottom plate 17 and a rear trunk rear plate 14, wherein the rear trunk front plate 19 and the rear trunk rear plate 14 are fixedly connected with the rear trunk left plate 16 and the rear trunk right plate 11 through screws, the rear trunk front plate 19 is fixedly connected with the multi-degree-of-freedom spine joint 3000, and the rear trunk front plate 19, the rear trunk rear plate 11, the rear trunk left plate 16 and the rear trunk right plate 11 are installed on the rear trunk bottom plate 17. The rear trunk further includes a rear trunk control system 15 and a rear trunk inertial measurement unit 12. The rear trunk control system 15 and the rear trunk inertial measurement unit 12 are fixedly installed above the rear trunk bottom plate 17.

[0046] The multi-degree-of-freedom spine assembly 3000 comprises a front torso pitch motor 20, a front torso pitch variable stiffness joint assembly 7, a front torso pitch joint connector 8, a roll joint motor 9, a rear torso pitch joint connector 10, a rear torso pitch variable stiffness joint assembly 18, and a rear torso pitch motor 13. The front torso pitch motor 20 is fixedly installed on the front torso rear plate 6. The front torso pitch variable stiffness joint assembly 7 is fixedly connected to the output end of the front torso pitch motor 20 through bolts, and is fixedly connected to the front torso pitch joint connector 8 through bolts. The fixed end of the roll joint motor 9 is fixedly connected to the front torso pitch joint connector 8 through bolts, and the output end is fixedly connected to the rear torso pitch joint connector 10 through bolts. The rear torso pitch joint connector 10 is fixedly connected to the rear torso pitch joint connector 10 through bolts, and is fixedly connected to the output end of the rear torso pitch motor 13 through bolts. The rear torso pitch motor 13 is fixedly connected to the rear torso front plate 19 through bolts.

[0047] As shown in Figure 3 The mechanical leg 1000 comprises a torso connector 28, a side swing motor 27, a side swing connector 29, a hip motor 30, a hip variable stiffness assembly 26, a thigh plate 31, a knee motor 32, a knee variable stiffness assembly 25, a lower leg plate 24, and a spherical foot end 33. The fixed end of the side swing motor 29 is fixedly installed on the torso connector 28 through bolts. The side swing connector 29 is fixedly installed on the output end of the side swing motor 27 through bolts. The fixed end of the hip motor 30 is fixedly installed on the side swing connector 29 through bolts. The hip variable stiffness assembly 26 is fixedly installed on the output end of the hip motor 30 through bolts. The thigh plate 31 is fixedly connected to the hip variable stiffness assembly 26 through bolts. The output end of the knee motor 32 is fixedly installed on the thigh plate 31 through bolts. The knee variable stiffness assembly 25 is fixedly installed on the output end of the knee motor 32 through bolts. The lower leg plate 24 is fixedly connected to the knee variable stiffness assembly 25 through bolts. The spherical foot end 33 is fixedly installed at the end of the lower leg plate 24 through gluing.

[0048] As shown in Figure 4As shown, the variable stiffness assembly includes a coil spring base 37, a coil spring 39 arranged in the base 37; a coil spring connecting piece 45, which is connected to the input end of the coil spring center bend through a clamping groove, can rotate around the center axis and drive the coil spring 39 to adjust the stiffness; a worm wheel 46 is connected with the coil spring connecting piece 45 through a key, which drives the coil spring connecting piece 45 to rotate, the coil spring connecting piece 45 is installed on the variable stiffness joint shell 47 through the shell bearing 49, the worm 44 is installed on the variable stiffness joint base through the worm long end bearing 43 and the worm short end bearing 50, and is engaged with the worm 44; a motor base 40 is arranged on the variable stiffness joint base 36; a stiffness adjusting motor 42 is fixedly installed on the motor mounting seat 40 through bolts, and is connected with the worm 44 through a synchronous belt pulley 41. Wherein the lower end shaft of the coil spring connecting piece 45 is provided with a connecting groove, which is connected with the input end of the coil spring 39 center through a clamping groove, and the upper end shaft is connected with the worm wheel 46 through a flat key, the connecting piece 45 is driven by the worm wheel 46, and the coil spring 39 is rotated through the connecting groove to realize stiffness adjustment. Wherein the coil spring base 37 is provided with a mounting groove, which is fixedly connected with the output end of the coil spring 39 outer circle bend, and can be driven by the coil spring 39 to rotate the power output end.

[0049] As shown in Figure 5 , the motor flange plate 35 in the variable stiffness assembly is fixedly connected with the knee motor 32 through a hexagonal screw A51 and a hexagonal screw B53, the motor output end is fixedly connected with the coil spring base 37, the coil spring connecting piece 45 is installed on the coil spring base 37 through a first bearing 52 and installed on the variable stiffness joint shell 47 through a third bearing 49, the coil spring base 37 is provided with a mounting groove, which is fixedly connected with the output end of the coil spring 38 outer circle bend, and the input end of the coil spring 38 center bend is connected with the coil spring connecting piece 45 through a clamping groove.

[0050] As shown in Figure 3 , 4, 5, the four-legged robot calculates the required joint stiffness of each variable stiffness joint, and then the rear torso control system 5 sends a signal to the stiffness adjustment motor 42 of the knee variable stiffness joint, the stiffness adjustment motor 42 receives the signal and drives the worm wheel 46 and worm 44 through the synchronous pulley set 41, the worm wheel 46 and worm 44 drive the coil spring connecting piece 45, and then drive the coil spring 39 to adjust the torsion, thereby achieving dynamic adjustment of the joint stiffness. After the joint stiffness of each variable stiffness joint of the four-legged robot is adjusted, the terrain height difference and other information calculated according to the data collected by the camera 3, foot pressure sensor 34, and inertial measurement unit are used to dynamically adjust the joint torsion, the joint torsion angle is measured by the magnetic encoder 56 and the magnet 55 installed on the motor shaft 54, the posture is adjusted to adapt to the complex uneven ground, and after landing, the foot pressure sensor 34 is used to sense the impact force of the ground on the robot foot, combined with the information collected by the camera 3 and the inertial measurement unit, the joint stiffness is adjusted again to cope with the impact of the new road conditions on the four-legged robot, achieving the function of stiffness self-adaptation.

[0051] As shown in Figure 6 When the four-legged robot needs to increase speed during running, the rear torso control system increases the motor speed and the motor rotation angle range, so that the leg movement range becomes larger. At this time, the magnetic encoder 56 senses the rotation of the magnet 55 installed on the end surface of the motor shaft 54 to obtain the motor speed, the front and rear torso inertial measurement units detect the change in the robot movement speed, and the stiffness of the variable stiffness joint is reduced, thereby reducing the huge impact force of the ground on the four-legged robot during the speed increase of the robot movement, and increasing the pitch joint angle signal range in the multi-degree-of-freedom spine joint 3000, thereby increasing the reachable space of the robot leg and the foot landing distance. When the robot needs to reduce speed during running, the rear torso control system reduces the motor speed and the motor rotation angle range, so that the leg range becomes smaller. At this time, the magnetic encoder 56 senses the rotation of the magnet 55 installed on the end surface of the motor shaft 54 to obtain the motor speed, the front and rear torso inertial measurement units 2 and 12 detect the change in the robot movement speed, and the stiffness of the variable stiffness joint is increased, and the pitch joint angle signal range in the multi-degree-of-freedom spine joint 3000 is reduced, so that the robot foot landing distance is reduced. Before running, when the terrain information collected by the camera 3 changes, the system judges the terrain characteristics and changes the joint stiffness according to the terrain flatness. When the front road surface is a concave-convex ground, the joint stiffness is reduced to provide cushioning for the impact of complex ground, and vice versa. The multi-degree-of-freedom spine joint 3000 is used to increase the movement space of the robot, and the variable stiffness joint is used to provide cushioning for the movement of the four-legged robot, thereby reducing the impact of the movement on the joint motor and the robot torso vibration.

[0052] AsFigure 7 As shown, when the quadruped robot jumps from a high place to a low place, the front torso control system obtains real-time posture information of the robot according to the front and rear torso inertial measurement units, the joint motor magnetic encoder 56, and the foot end pressure sensor 34, tilts the front torso 2000 of the robot forward by reducing the roll joint angle, increasing the pitch joint angle, and reducing the mechanical leg joint angle signal, so that the robot can look down at the front high-drop terrain, the camera collects terrain information, calculates the terrain drop height h1, the rear torso control system further increases the roll joint, increases the pitch joint and reduces the mechanical leg joint angle signal, so that the robot front and rear torso curls, reduces the robot's gravity center, and reaches the optimal posture calculated by the front torso control system, while reducing the stiffness of the hip and knee variable stiffness joints of the mechanical leg, reducing the impact force of the ground on the robot during the jumping movement, and when the quadruped robot lands, the foot end pressure sensor 34 senses the force generated by the ground on the robot, adjusts the angles of each leg joint and the roll and pitch spine joint in real time in combination with the posture angle detected by the front and rear torso inertial measurement units, and increases the stiffness of the variable stiffness joint, so that the quadruped robot can remain stable after landing.

[0053] As Figure 8As shown, when the quadruped robot climbs the inclined steps, after the terrain information (such as the terrain inclination θ, the step height h2, h3, h4, etc.) and the required signal calculation are completed, the rear torso control system sends angle signals to each joint of the left front leg 1000, and through the mechanical leg lateral swing joint, the hip joint and the knee joint magnetic encoder 56, the rotation position of each joint of the left front leg is sensed, so that the left front leg reaches the required height of the inclined steps. When the foot end pressure sensor 34 of the left front leg detects a pressure signal, it indicates that the left front leg has reached the step, at this time the stiffness of the left front leg joint is increased, and the right front leg repeats the above steps until the foot end pressure sensor of the right front leg detects a pressure signal. Then the rear torso control system provides angle signals for the roll joint and each pitch joint, and the front torso control system obtains the real-time motion posture of the robot through the magnetic encoders of the roll joint and each pitch joint, and the inertial measurement unit of the front and rear torso, and adjusts the posture of the quadruped robot climbing the inclined steps in real time until the optimal posture calculated is reached; At this time, the rear torso control system provides gait signals to the robot to make it normally advance, and stops sending gait signals when it reaches the set distance. Through the magnetic encoder 56, the rotation position of each joint of the left front leg is sensed, and angle signals are sent to the right rear leg of the robot, so that the right rear leg reaches the required height of the inclined steps. When the foot end pressure sensor 34 of the right rear leg detects a pressure signal, the stiffness of the right rear leg joint is increased, at this time increasing the stiffness can make the robot more stable during climbing. The left rear leg repeats the above steps. When all four foot end pressure sensors detect a pressure signal, the rear torso control system changes the roll joint and pitch joint angles of the front and rear torso spines according to the foot end pressure and in combination with the real-time posture information of the robot obtained by the magnetic encoders of the joint motors, the inertial measurement units of the front and rear torso, and adjusts the posture of the robot in real time, constantly changes the foot point, adjusts the center of gravity of the robot, to adapt to the inclined steps, so that the quadruped robot can move stably on the steps.

[0054] The embodiments of the application are described in detail above with reference to the drawings, but the application is not limited to the above-described embodiments, and various changes can be made within the knowledge of those skilled in the art in the technical field without departing from the purpose of the application.

Claims

1. A stiffness adaptive control method for a multi-degree-of-freedom spinal-jointed quadruped robot, characterized in that, The multi-degree-of-freedom spinal joint quadruped robot includes a trunk, multi-degree-of-freedom spinal joints, and mechanical legs. The trunk includes a front trunk and a rear trunk. The front trunk is connected to the rear trunk through multi-degree-of-freedom spinal joints, which enable the front trunk to perform pitch and roll movements relative to the rear trunk. The mechanical legs are configured in four groups and are respectively arranged on the front trunk and the rear trunk. Stiffness adaptive control methods include stiffness adaptive control, stiffness adaptive control under different road surfaces, and stiffness adaptive control under different motion states; The stiffness adaptive control process is as follows: The quadruped robot collects terrain information through cameras mounted on its forequarters, obtains real-time posture information through inertial measurement units mounted on its forequarters and hindquarters, acquires motor angle and speed information through magnetic encoders mounted on the joint motors, and detects foot contact force information through foot pressure sensors mounted on the ball-shaped feet. The forequarter control system uses the collected information to calculate the surrounding terrain, the robot's current posture, and the real-time center of gravity position through built-in algorithms, and then combines the foot contact force to calculate the stiffness required for each joint. The hindquarter control system converts the stiffness into spring torsion, then calculates the angle required for each stiffness adjustment motor to rotate, and sends the angle signal to each stiffness adjustment motor. The stiffness adjustment motor drives the worm gear to rotate through a synchronous pulley set, which drives the spring connecting piece, and then drives the spring to adjust the torsion, thereby realizing the dynamic adjustment of the stiffness of each joint. The specific process of stiffness adaptive control under different road surfaces is as follows: When the terrain information captured by the camera changes, the system judges the terrain characteristics and adjusts the joint stiffness according to the flatness of the terrain. When the ground in front is uneven, the stiffness of the variable stiffness components of the multi-degree-of-freedom spinal joint and the mechanical leg is reduced. The variable stiffness components are used to provide cushioning for the movement of the quadruped robot and reduce the impact of the movement on the joint motors and the robot's torso. Conversely, when the ground in front is flat, the stiffness of the variable stiffness components is increased, and the multi-degree-of-freedom spinal joint is used to increase the robot's movement space. The specific process of stiffness adaptive control under different motion states is as follows: In running motion: When the quadruped robot needs to increase its speed while running, the rear torso control system increases the motor speed and the motor rotation angle range, thus increasing the leg range of motion. At this time, the magnetic encoder senses the rotational motion of the magnet mounted on the motor shaft end face to obtain the motor speed. The front and rear torso inertial measurement units detect the change in robot speed and reduce the stiffness of the variable stiffness components of the multi-degree-of-freedom spinal joints and mechanical legs, thereby reducing the huge impact force on the quadruped robot from the ground when the robot's speed increases. At the same time, it increases the pitch angle range of the multi-degree-of-freedom spinal joints, increasing the reach of the robot's legs and the landing distance. When the robot needs to decrease its speed while running, the rear torso control system decreases the motor speed and the motor rotation angle range, thus reducing the leg range. At this time, the magnetic encoder senses the rotational motion of the magnet mounted on the motor shaft end face to obtain the motor speed. The front and rear torso inertial measurement units detect the change in robot speed and increase the stiffness of the variable stiffness joints of the multi-degree-of-freedom spinal joints and mechanical legs, while decreasing the pitch angle range of the multi-degree-of-freedom spinal joints, thus reducing the landing distance of the robot. In jumping motion: When the quadruped robot jumps from a high place to a low place, the front torso control system obtains the robot's real-time posture information based on the front and rear torso inertial measurement units. By adjusting the angles of the roll joint, each pitch joint, and each mechanical leg joint, the robot's front torso tilts forward to view the terrain difference ahead. The camera collects terrain information, calculates the height of the terrain difference, reduces the roll joint angle, increases the front and rear pitch joint angles, and decreases the mechanical leg joint angles to lower the robot's center of gravity, causing the robot's front and rear torso to curl up. At the same time, the stiffness of the variable stiffness components of the mechanical leg hips and knees is reduced to reduce the impact force of the ground on the robot during the jump. When the quadruped robot lands, the foot pressure sensor senses the force exerted on the robot by the ground. Combined with the attitude angle detected by the inertial measurement unit, the angles of each mechanical leg joint, roll joint, and each pitch joint are adjusted in real time, and the stiffness of the variable stiffness components of the mechanical leg hips and knees is increased to enable the quadruped robot to remain stable after landing. In climbing motion: When the quadruped robot is climbing an inclined step, the forequarter control system acquires terrain information via a camera and sends angle signals to each joint of the left foreleg. Magnetic encoders on the mechanical leg's lateral swing joint assembly, hip joint assembly, and knee joint assembly sense the rotational position of each joint of the left foreleg, enabling the left foreleg to reach the required height of the inclined step. When the pressure sensor at the foot of the left foreleg detects a pressure signal, it indicates that the left foreleg has reached the step. At this point, the stiffness of the left foreleg joint is increased, and the same steps are repeated for the right foreleg until the pressure sensor at the foot of the right foreleg detects a pressure signal. Next, the hindquarter control system provides angle signals to the roll and pitch joints. Through the magnetic encoders of the roll and pitch joints, as well as the inertial measurement units of the forequarter and hindquarter, the robot's real-time motion posture is obtained, and the quadruped robot's posture while climbing the inclined step is adjusted in real time until the calculated optimal posture is reached. At this point, the hindquarter... The control system provides gait signals to the robot, enabling it to move forward normally. When the set distance is reached, the gait signal transmission stops. The system senses the rotational position of each joint of the left foreleg via a magnetic encoder and sends an angle signal to the robot's right hind leg, allowing the right hind leg to reach the required height on the inclined step. When the pressure sensor at the foot of the right hind leg detects a pressure signal, the stiffness of the right hind leg joint is increased. This increased stiffness makes the robot more stable during climbing. The left hind leg repeats the above steps. When all four foot pressure sensors detect pressure signals, the rear trunk control system, based on the magnitude of the foot pressure and combined with the real-time posture information of the robot obtained from the magnetic encoders of each joint motor and the inertial measurement units of the front and rear trunks, reduces the pitch and roll joint angles of the front and rear trunks, adjusts the robot's posture in real time, continuously changes the foot placement point, and adjusts the robot's center of gravity to adapt to the inclined step, enabling the quadruped robot to move stably on the step.

2. The stiffness adaptive control method for a multi-degree-of-freedom spinal joint quadruped robot according to claim 1, characterized in that, The multi-degree-of-freedom spinal joint is configured with three joints, including anterior trunk pitch joint, posterior trunk pitch joint and roll joint. The anterior trunk pitch joint and posterior trunk pitch joint are connected by a roll joint. The anterior trunk pitch joint and posterior trunk pitch joint are hinged to the anterior trunk and posterior trunk, respectively.

3. The stiffness adaptive control method for a multi-degree-of-freedom spinal joint quadruped robot according to claim 2, characterized in that, The robotic legs are all elbow-type, and each set of robotic legs includes a lateral swing joint assembly, a hip joint assembly, and a knee joint assembly. The lateral swing joint assembly realizes the lateral swing of the thigh and calf, the hip joint assembly realizes the rotation of the thigh, and the knee joint assembly realizes the rotation of the calf.

4. The stiffness adaptive control method for a multi-degree-of-freedom spinal joint quadruped robot according to claim 1, characterized in that: The anterior trunk includes an anterior trunk front plate, an anterior trunk left plate, an anterior trunk right plate, an anterior trunk base plate, and an anterior trunk rear plate. The anterior trunk front plate, anterior trunk rear plate, anterior trunk left plate, and anterior trunk rear plate are fixedly connected to the anterior trunk left plate and the anterior trunk rear plate by screws. The anterior trunk rear plate is fixedly connected to the multi-degree-of-freedom spinal joint. The anterior trunk front plate, anterior trunk rear plate, anterior trunk left plate, and anterior trunk right plate are all mounted on the anterior trunk base plate. The anterior trunk also includes a battery, an anterior trunk control system, an anterior trunk inertial measurement unit, and a camera. The battery, the anterior trunk control system, and the anterior trunk inertial measurement unit are all fixedly mounted above the anterior trunk base plate, and the camera is fixedly mounted on the anterior trunk front plate.

5. The stiffness adaptive control method for a multi-degree-of-freedom spinal joint quadruped robot according to claim 1, characterized in that: The posterior trunk includes a front plate, a left plate, a right plate, a bottom plate, and a rear plate. The front plate, rear plate, left plate, and rear plate are fixedly connected to each other by screws. The front plate is fixedly connected to the multi-degree-of-freedom spinal joint. The front plate, rear plate, left plate, and right plate are all mounted on the bottom plate. The posterior trunk also includes a posterior trunk control system and a posterior trunk inertial measurement unit. The posterior trunk control system and inertial measurement unit are both fixedly mounted above the bottom plate.

6. The stiffness adaptive control method for a multi-degree-of-freedom spinal joint quadruped robot according to claim 3, characterized in that: The anterior trunk pitch joint of the multi-degree-of-freedom spinal joint includes an anterior trunk pitch motor, an anterior trunk pitch variable stiffness assembly, and an anterior trunk pitch joint connector; the posterior trunk pitch joint includes a posterior trunk pitch variable stiffness assembly, a posterior trunk pitch motor, and a posterior trunk pitch joint connector; the roll joint includes a roll joint motor; the fixed end of the anterior trunk pitch motor is bolted to the rear plate of the anterior trunk; the anterior trunk pitch variable stiffness assembly is bolted to the output end of the anterior trunk pitch motor and bolted to the anterior trunk pitch joint connector; the fixed end of the roll joint motor is bolted to the anterior trunk pitch joint connector and bolted to the posterior trunk pitch joint connector; the output end of the roll joint motor is bolted to the posterior trunk pitch joint connector; the posterior trunk pitch variable stiffness assembly is bolted to the posterior trunk pitch joint connector and bolted to the output end of the posterior trunk pitch motor; the posterior trunk pitch motor is bolted to the front plate of the posterior trunk.

7. The stiffness adaptive control method for a multi-degree-of-freedom spinal joint quadruped robot according to claim 6, characterized in that: The lateral swing joint assembly of the mechanical leg includes a lateral swing motor, a lateral swing connector, a magnetic encoder, and a magnet; the hip joint assembly includes a hip motor, a hip variable stiffness assembly, a thigh plate, a magnetic encoder, and a magnet; the knee joint assembly includes a knee motor, a knee variable stiffness assembly, a calf plate, a ball-shaped foot end, a magnetic encoder, and a magnet; the lateral swing motor mounting end is bolted to the torso connector, the magnetic encoder is screwed to the lateral swing motor mounting end, the magnet is glued to the lateral swing motor shaft, the lateral swing connector is bolted to the lateral swing motor output end, and the hip motor mounting end is bolted to the lateral swing motor connector. The magnetic encoder is fixed to the hip motor mounting end with screws, the magnet is fixed to the hip motor shaft with adhesive, the hip variable stiffness assembly is fixedly installed at the hip motor output end, the thigh plate is fixedly connected to the hip variable stiffness assembly, the knee motor mounting end is installed on the thigh plate with bolts, the magnetic encoder is fixed to the knee motor mounting end with screws, the magnet is fixed to the knee motor shaft with adhesive, the knee variable stiffness assembly mounting end is installed on the knee motor output end with bolts, the calf plate is fixedly connected to the knee variable stiffness assembly housing with bolts, and the ball-shaped foot end is glued to the end of the calf plate.

8. The stiffness adaptive control method for a multi-degree-of-freedom spinal joint quadruped robot according to claim 7, characterized in that: The forequarter pitch variable stiffness assembly, rearquarter pitch variable stiffness assembly, hip variable stiffness assembly, and knee variable stiffness assembly all employ a stiffness adaptive active adjustment assembly, including a housing and a variable stiffness adjustment component. The housing includes a variable stiffness joint base and a variable stiffness joint housing. The variable stiffness adjustment component includes a coil spring base, a coil spring, a coil spring connector, a worm gear, a motor base, and a stiffness adjustment motor. The coil spring base is mounted on the variable stiffness joint base and is bolted to the output shaft of the joint motor. The coil spring is housed within the coil spring base. The coil spring connector is centrally connected to the coil spring and can rotate around its central axis, driving the coil spring for stiffness adjustment. The worm gear is keyed to the coil spring connector, carrying… The rotating coil spring connector rotates, and the worm gear is mounted on the variable stiffness joint base via bearings, meshing with the worm gear. The motor base is fixedly mounted on the variable stiffness joint base with screws. The stiffness adjustment motor is set on the motor base and connected to the worm gear via a synchronous pulley. The lower shaft of the coil spring connector has a connecting groove, which connects to the center input end of the coil spring. The upper shaft is connected to the worm wheel via a flat key. The worm wheel drives the connector, and the clockwise rotation via the connecting groove causes the coil spring to coil inward to increase the joint stiffness. The counterclockwise rotation causes the coil spring to expand outward to decrease the joint stiffness. The coil spring base has a mounting groove, which is fixedly connected to the output end of the outer coil bend, and the power output end can be rotated by the coil spring.

9. The stiffness adaptive control method for a multi-degree-of-freedom spinal joint quadruped robot according to claim 7, characterized in that: The surface of the spherical foot end is provided with a rubber pad component; a foot pressure sensor is attached to the rubber pad component and is bonded to the rubber pad component by adhesive.

Images