Parallel biped robot with waist structure and walking method

Abstract

The parallel biped robot with the waist structure is characterized by comprising a parallel double-leg structure, the waist structure and an upper body structure which are arranged from bottom to top and can move independently; the parallel double-leg structure comprises a leg structure cross beam, the two ends of the leg structure cross beam are downwards connected with leg structures, and the upper portion of the leg structure cross beam is fixedly connected with the waist structure; the waist structure is a six-degree-of-freedom Stewart mechanism, a lower platform of the waist structure is rigidly connected with a cross beam of the leg structure, an upper platform of the waist structure is rigidly connected with the upper body structure, and six telescopic rods are connected between the upper platform and the lower platform; the invention further discloses a walking method of the robot, through introduction of the six-degree-of-freedom waist structure, the robot can adjust the position and posture of the upper body in real time in the walking process, active compensation of mass center deviation is achieved, and compared with a traditional serial connection type waist mass center adjusting range is larger, the corresponding speed is higher, and the robot can walk more stably. And the advancing stability is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of robots. More specifically, the present invention relates to a parallel biped robot with a waist structure and a walking method. Background Art

[0002] Biped robots can simulate the walking mode of the human body, and their motion modes are less restricted by the environment, with high mobility and a wide range of applications. They have also become a hot research topic in recent years. However, biped robots are still limited by the technical problem of dynamic balance control in practical applications.

[0003] Currently, most biped robots include lower limb structural components and upper limb structural components. The upper limb structural components have functions such as assisting walking and carrying objects. Robots with upper limb structures face difficulties in quickly responding to the deviation of the center of mass during walking. Especially during the single-leg support phase, the range of center of gravity adjustment of the robot is limited. For example, when moving in a straight line, the robot is in a single-leg support state. At this time, if the upper limb suddenly makes a certain posture change, resulting in the deviation of the robot's center of gravity, in the existing technical solutions, traditional biped robots generally adopt the method of directly fixedly connecting the body and the lower limb structure. Adjusting the overall center of mass position of the robot is completely determined by the movement of the lower limbs. When the posture of the upper body changes and causes the center of gravity to deviate, only compensation can be made through the adjustment of the leg joints. This adjustment method has a lag response and a limited range, and there is a transmission gap in the motor drive. The maximum adjustment range of the center of mass is small and the response time is long, making it difficult to cope with sudden changes in the upper body structure.

[0004] Currently, for the waist design of robots, most designs adopt the scheme of fixedly connecting the upper body structure and the lower body structure or low-degree-of-freedom hinged connections. Even if some biped robots use a double-motor group to simulate the pitch and yaw movements of the waist between the upper body structure and the lower body structure, although this design can provide limited trunk posture adjustment capabilities, limited by the motor performance and series design, the response speed is slow. When the waist adopts a series structure, the motion coupling effect is significant. When multiple degrees of freedom need to be adjusted simultaneously, the control complexity increases sharply, easily causing system oscillations.

[0005] In the prior art, for the central control of robots, the most commonly used method is to improve flexibility by increasing the degrees of freedom of the legs or introducing elastic elements. However, this method still cannot solve the problem of coordinated control between the upper body structure and the legs of the robot. Another method is to set movable counterweights between the upper body structure and the lower body mechanism to adjust the overall center of gravity of the robot. However, no matter which method is used, the coordinated control between the upper body structure and the parallel leg structure cannot be directly achieved. Therefore, it is necessary to propose a new robot structure. Summary of the Invention

[0006] An object of the present invention is to provide a parallel biped robot with a waist structure and a walking method, which can better simulate the waist characteristics of the human body, and during the forward movement of the robot, the waist structure can adjust the overall center of mass position of the robot according to the movement of the upper body structure to ensure the balance of the robot during walking.

[0007] In order to achieve these objects and other advantages of the present invention, in a first aspect, the present invention provides a parallel biped robot with a waist structure, including a parallel leg structure, a waist structure, and an upper body structure that are arranged from bottom to top and can move independently of each other; the parallel leg structure includes a leg structure cross beam, both ends of the leg structure cross beam are connected downward to the leg structure, and the upper part of the leg structure cross beam is fixedly connected to the waist structure; the waist structure is a six-degree-of-freedom Stewart mechanism, its lower platform is rigidly connected to the leg structure cross beam, the upper platform is rigidly connected to the upper body structure, and six telescopic rods are connected between the upper platform and the lower platform; the upper body structure is fixedly connected to the upper platform.

[0008] In a second aspect, the present invention provides a walking method for a parallel biped robot with a waist structure, applying the above-mentioned parallel biped robot with a waist structure, including the following steps: S1. Plan the movement trajectory of the robot's two feet and formulate a stepping strategy, the stepping strategy includes the foot landing position, the state of the parallel leg structure at any time, and the state of the lower platform at any time, to obtain the center of mass position of the parallel leg structure; S2. According to the foot landing position of the robot, formulate the overall center of mass position planning value γ0(t) of the robot; S3. When the parallel leg structure of the robot and the lower platform move forward according to the stepping strategy, the upper platform remains horizontal, and the current actual value γ1(t) of the robot's center of mass is detected and calculated in real time, and it is judged whether it is equal to the overall center of mass position planning value of the robot. If not, adjust the position of the upper platform so that the actual center of mass position of the robot returns to the center of mass position planning value until the robot completes this section of the movement trajectory.

[0009] Preferably, the overall center of mass position planning value is calculated by calculating the support polygon range through the foot contact point position in the robot's stepping strategy, and using the midpoint of the support polygon and the geometric median line of the support polygon in the single-foot support state as the center of mass design reference trajectory to obtain the relationship between the center of mass position planning value and time.

[0010] Preferably, step S1 includes: S11. Formulate the stepping strategy of the robot, including the stepping distance and the stepping frequency, and plan the gait trajectory of the biped robot on the traveling route, and the result includes the foot touchdown point; S12. Discretize the walking cycle into several time points, calculate the foot motion trajectory through quintic polynomial interpolation, and calculate the relationship between the rotational positions and time of each joint in the parallel double-leg structure through inverse kinematics to obtain the relationship between the position of the center of mass of the parallel double-leg structure and time; S13. Obtain the relationship between the position, center of mass of the lower platform and time.

[0011] Preferably, step S3 includes the following steps: S31. At a time point, calculate the position of the center of mass of the upper body structure and the position of the center of mass of the waist structure; S32. Calculate the actual value of the center of mass of the robot at this time point; S33. According to the difference in the horizontal displacement between the planned value of the center of mass position and the actual value of the center of mass, the waist structure adjusts the position of the upper platform according to the difference; S34. Enter the next time point, and repeat steps S31 - S34 until the movement trajectory of this section is completed.

[0012] Preferably, step S33 includes the following steps; S331. The upper platform is directly adjusted according to the position difference between the actual value of the center of mass and the planned value of the center of mass position; S332. Calculate whether the deviation between the adjusted actual value of the center of mass and the planned value of the center of mass position meets the stability margin based on the planned value of the center of mass position. If it meets, no further adjustment is made. If not, repeat steps S31 - S33.

[0013] Preferably, in step S332, the stability margin is determined based on the formula Δ = α·D, where D is the minimum lateral span of the current support polygon, α is a preset stability coefficient, and the value range is 0.05 ≤ α ≤ 0.15. The value of the stability coefficient α is related to the gait phase, taking 0.10 - 0.15 in the single - foot support phase and 0.05 - 0.10 in the double - foot support phase.

[0014] Preferably, attitude sensors are installed on the upper body structure and the waist structure to obtain the pose data of the upper body structure and the waist structure in real time. Combining with the preset mass distribution parameters, the position of the center of mass of the upper body structure and the position of the center of mass of the waist structure are calculated through the mass - weighted formula.

[0015] The present invention has at least the following beneficial effects: First, by introducing the six - degree - of - freedom Stewart waist structure, the robot can adjust the upper body pose in real time during walking, realizing active compensation for the center - of - mass offset. Compared with the traditional series - type waist design, due to the high rigidity and multi - degree - of - freedom characteristics of the Stewart platform, the range of center - of - mass adjustment is larger, significantly improving the traveling stability.

[0016] Second, through the control of centroid planning and real-time feedback, the present invention ensures the stability of the robot's center of gravity during walking; the horizontal holding function of the upper platform reduces attitude disturbances and improves the smoothness of movement.

[0017] Other advantages, objectives, and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. Brief Description of the Drawings

[0018] Figure 1 It is a flowchart of the walking method in a technical solution of the present invention; Figure 2 It is a flowchart of the waist structure adjustment process in a technical solution of the present invention; Figure 3 It is a schematic diagram of a parallel biped robot with a waist structure in a technical solution of the present invention. Detailed Embodiments

[0019] The following further elaborates on the present invention in conjunction with the drawings and specific embodiments, enabling those skilled in the art to implement it with reference to the description in the specification.

[0020] It should be understood that terms such as "having", "comprising", and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0021] It should be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the structures and components can be obtained from commercial channels unless otherwise specified; in the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "set" should be understood in a broad sense. For example, they can be fixedly connected and set, or detachably connected and set, or integrally connected and set. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The orientation or positional relationships indicated by terms such as "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0022] Such as Figures 1 to 3As shown in the figure, the present invention provides a parallel biped robot with a waist structure, which is characterized in that it includes a parallel double-leg structure 3, a waist structure 2, and an upper body structure 1 that are arranged from bottom to top and can move independently of each other; the parallel double-leg structure 3 includes a leg structure cross beam 31, and both ends of the leg structure cross beam 31 are connected downward to the leg structure, and the upper part of the leg structure cross beam 31 is fixedly connected to the waist structure 2; the waist structure 2 is a six-degree-of-freedom Stewart mechanism, its lower platform 23 is rigidly connected to the leg structure cross beam 31, the upper platform 21 is rigidly connected to the upper body structure 1, and six telescopic rods 22 are connected between the upper platform 21 and the lower platform 23; the upper body structure 1 is fixedly connected to the upper platform 21. In this technical solution, the parallel biped robot consists of three core parts with independent movements: the parallel double-leg structure 3, the waist structure 2 composed of a six-degree-of-freedom Stewart structure, and the upper body structure 1. Among them, the parallel double-leg structure 3 realizes a left-right symmetric layout through the leg structure cross beam 31. Both ends of the leg structure cross beam 31 are connected to the hip joints of the leg structure through multiple series-connected motors or other forms of ball joints. The hip joints allow the legs to perform pitching, yawing, and rolling movements in three-dimensional space. The lower platform 23 of the waist structure 2 is rigidly fixed to the leg structure cross beam 31, and the upper platform 21 is connected to the lower platform 23 through six telescopic rods 22. Each telescopic rod 22 can independently adjust its length. The upper body structure 1 is directly fixed to the upper platform 21 of the waist and changes its posture as it moves. Optionally, the waist structure 2 can also adopt other forms of six-degree-of-freedom devices. In this technical solution, the parallel double-leg structure 3 supports the whole machine and implements walking. The waist structure 2 adjusts the upper body pose in real time through the telescopic rods 22. When the robot walks, the hip joints, knee joints, and ankle joints in the parallel double-leg structure 3 move along a preset trajectory, and the waist structure 2 dynamically adjusts the position of the upper platform 21 according to the sensor feedback to ensure that the overall center of mass is always within the support polygon range.

[0023] In existing technical solutions, traditional biped robots generally adopt a direct fixed connection between the body and the lower limb structure. Adjusting the overall center of mass position of the robot is completely determined by the movement of the lower limbs. When the upper body posture changes and causes the center of gravity to shift, compensation can only be achieved through the adjustment of leg joints. This adjustment method has a lagging response and a limited range. When using a series motor to simulate the pitching and yaw functions of the waist, due to the low stiffness of the series structure and the transmission gap in the motor drive, the maximum adjustment range of the center of mass is small and the response time is long, making it difficult to cope with sudden changes in the upper body structure. When the waist adopts a series structure, the motion coupling effect is significant. When multiple degrees of freedom need to be adjusted simultaneously, the control complexity increases sharply, easily triggering system oscillations. In this technical solution, a Stewart mechanism is used as the waist structure 2. Through the coordinated movement of six telescopic rods 22, precise translation control of the upper body structure 1 in three-dimensional space can be achieved, breaking through the limitation of traditional series waists that can only achieve limited degrees of freedom such as pitching and yaw. Moreover, the waist structure 2 in this solution is a closed-frame formed by the upper platform 21, the lower platform 23, and the telescopic rods 22. The stiffness of the waist structure 2 has been greatly improved compared to the motor series waist structure. The waist structure 2 has a large load-bearing capacity and can effectively reduce the elastic deformation during movement compared to conventional designs, ensuring the immediacy of force transmission. The waist structure 2 can quickly compensate for sudden center of mass offsets caused by the movement of the upper body structure 1. By means of the parallel double-leg structure 3 focusing on supporting movement, the waist structure 2 actively adjusting the center of mass, and the upper body structure 1 making various actions as required, a hierarchical control strategy is achieved, reducing the dynamic torque requirements of the leg joints and making the robot perform better in scenarios such as complex terrain adaptation and dynamic load handling.

[0024] In another technical solution, the walking method of the parallel biped robot with the waist structure described above includes the following steps: S1. Plan the motion trajectory of the robot's two feet and formulate a stepping strategy. The stepping strategy includes the foot landing position, the state of the parallel double-leg structure 3 at any time, and the state of the lower platform 23 at any time, to obtain the center of mass position of the parallel double-leg structure 3. Specifically, the motion trajectory of the robot's two feet is generated through a gait planning algorithm, the foot landing position is determined, and the foot trajectory of the robot is converted into an angle sequence of each joint using inverse kinematics according to the foot landing position, providing precise control instructions for each servo motor in the parallel double-leg structure 3. Finally, the change relationship of the center of mass position of the parallel double-leg structure 3 over time is calculated for subsequent calculations, providing a smooth and stable walking gait plan for the robot.

[0025] S2. Based on the foot landing position of the robot, formulate the overall centroid position planning value γ0(t) of the robot. Specifically, the support polygon range can be calculated based on the foot landing position. Taking the midpoint and geometric median line of the support polygon during single-foot support as the reference, generate the target centroid position planning value γ0(t) of the robot during the entire walking cycle to provide a stable centroid reference trajectory for the robot during this movement process, calculate the centroid trajectory in advance, reduce the real-time calculation burden, improve the control response speed, and ensure that when the upper body structure 1 makes any movement during walking, the center of gravity of the robot is always within the safety margin range.

[0026] S3. When the parallel double-leg structure 3 of the robot and the lower platform 23 move forward according to the stepping strategy, the upper platform remains horizontal, and the actual value γ1(t) of the current robot centroid is detected and calculated in real time, and it is judged whether it is equal to the overall centroid position planning value of the robot. If not, the position of the upper platform 21 is adjusted so that the actual centroid position of the robot returns to the centroid position planning value until the robot completes this section of the motion trajectory. Specifically, during the movement of the robot, the attitude data of the upper body mechanism 1 and the waist structure 2 are monitored in real time, and the actual centroid γ1(t) is calculated. If there is a deviation from the planned value γ0(t), the position of the upper platform 21 is adjusted through the Stewart mechanism to make the overall centroid of the robot return to the target trajectory. While keeping the upper platform 21 horizontal, the position is adjusted to reduce the influence of attitude disturbance on the motion smoothness.

[0027] In this technical solution, the three steps of S1~S3 form a closed-loop control system of "planning - execution - feedback". Combining the high rigidity and multi-degree-of-freedom characteristics of the Stewart mechanism, the robot can still maintain stability under complex working conditions, reduce the dynamic torque requirements of the leg joints, and extend the mechanical life.

[0028] In another technical solution, for the overall centroid position planning value, the support polygon range is calculated through the foot contact point position in the robot stepping strategy. Taking the midpoint of the support polygon and the geometric median line of the support polygon in the single-foot support state as the centroid design reference trajectory, the relationship between the centroid position planning value and time is obtained. In this technical solution, according to the position information of the foot touchdown point in the robot stepping strategy, the support polygon range is calculated. The support polygon is the set of contact points between the robot sole and the ground, forming the smallest convex polygon area. In the single-foot support state, the support polygon is composed of the single-foot effective support area; in the double-foot support state, the support polygon is the geometric figure formed by the connection line of the two-foot ground contact points and its extended area. Extract the geometric median line of the support polygon (i.e., the symmetric axis connecting the polygon vertices or the midpoints of the sides) and the polygon midpoint (geometric center), and use the combination of the two as the centroid design reference trajectory.

[0029] In this technical solution, first, it can be assumed that the upper body structure and the waist structure of the robot remain in a relatively static state, and the centroid positions of the upper body structure 1 and the waist structure 2 remain relatively static with respect to the parallel double-leg structure 3. According to the single-leg support phase and the double-leg support phase of the robot, a support polygon is constructed. When in single-leg support, the minimum convex polygon of the sole contact surface is generated with the contact point of the supporting foot as the center. When in double-leg support, the two foot contact points are combined and extended into a geometric figure covering the area of the two feet. For the single-leg support state, the geometric center point is extracted as the reference trajectory; when in double-leg support, the bisector of the line connecting the two feet is used as the midline, and a transition trajectory is generated in combination with the geometric center of the two feet. The centroid target position moves smoothly along the combined path of the midline and the midpoint. In the single-leg phase, an interpolation algorithm is used to generate a continuous trajectory, and in the double-leg phase, a uniform transition is made to ensure balanced force. Optionally, for the determination of the planned value of the centroid position, the centroid trajectory can also be indirectly derived by controlling the relationship between the zero moment point and the support polygon, or methods such as model predictive control technology can be used for planning and determination.

[0030] In another technical solution, step S1 includes: S11. Formulate the stepping strategy of the robot, including the stepping distance, stepping frequency, and plan the gait trajectory of the biped robot on the traveling route. The result includes the foot contact points. Specifically, determine the basic parameters of the robot's walking and plan the movement trajectory of the two feet on the traveling route, clarify the positions and sequences of the foot contact points, provide a gait plan that meets the target path for the robot, and ensure the rationality of the foot movement in contact with the ground.

[0031] S12. Discretize the walking cycle into several time points, calculate the foot movement trajectory through quintic polynomial interpolation, calculate the relationship between the rotational positions of each joint in the parallel double-leg structure and time through inverse kinematics, obtain the relationship between the centroid position of the parallel double-leg structure 3 and time, the centroid γ2(t) of the parallel double-leg structure, and generate a smooth foot trajectory and joint movement curve through inverse kinematics to ensure no impact and no jamming during the robot's walking process.

[0032] S13. Obtain the relationship between the position, centroid of the lower platform 23 and time. The movement of the lower platform 23 in the waist structure 2 is synchronized with the parallel double-leg structure 3, providing a reference for the dynamic adjustment of the waist structure 2.

[0033] In another technical solution, step S3 includes the following steps: S31. At a certain time point, calculate the centroid position of the upper body structure 1 and the centroid position of the waist structure 2. Specifically, through the attitude sensors installed on the upper body structure 1 and the waist structure 2, the pose data of both are obtained in real time, and in combination with the preset mass distribution parameters, the centroid positions γ3(t) of the upper body structure and γ4(t) of the waist structure are calculated respectively.

[0034] S32. Calculate the actual value of the robot's centroid at this time point. Specifically, at this time, given γ2(t), γ3(t), and γ4(t), the actual value of the robot's centroid γ1(t) can be calculated through the mass-weighted formula.

[0035] S33. According to the difference in the horizontal displacement between the planned value of the centroid position and the actual value of the centroid, the waist structure 2 adjusts the position of the upper platform 21 according to the difference. Among them, the centroid deviation can be decomposed into lateral and longitudinal displacement components. Since the upper platform 21 needs to remain horizontal, the vertical displacement can be 0, and only the planar position of the upper platform 21 needs to be adjusted. At this time, the positions of the lower platform 23 and the new position of the upper platform 21 are both known values, and the connection positions at both ends of each telescopic rod 22 are also known. The length adjustment amount of each telescopic rod 22 is determined through inverse kinematics and geometric relationships, and each telescopic rod 22 expands and contracts according to the length adjustment amount. This solution utilizes the structural characteristic of the Stewart mechanism that can only adjust the horizontal position, decouples the parallel double-leg structure 3 that advances according to the stepping strategy and the upper body structure that continuously makes various movements, adopts a horizontal holding strategy, and significantly reduces the control and calculation difficulty on the premise of ensuring stability, avoiding the problem of high calculation complexity and easy occurrence of attitude oscillation in the process of adjusting the centroid of a conventional robot with a waist, which requires simultaneous processing of coupled motions of pitch, yaw, and translation.

[0036] S34. Enter the next time point, and repeat steps S31 - S34 until the movement trajectory of this section is completed, forming a closed-loop control system to ensure that the centroid always tracks the planned value of the centroid position γ0(t) throughout the movement process.

[0037] In this technical solution, the waist structure 2 only compensates for the centroid deviation by adjusting the x and y direction displacements of the upper platform, avoiding the complex calculations in a robot with a waist using a series motor. Since the position of the lower platform 23 is known and fixed, the strategy of directly compensating for the horizontal centroid deviation makes the control target more focused, avoiding the multi-objective coordinated control that other types of robots may require. By quickly calculating the length change of the telescopic rod 22 through the inverse kinematics of the Stewart mechanism, more direct servo drive control can be achieved, with a faster response speed. The two-dimensional adjustment of the upper platform significantly simplifies the inverse kinematics model, reduces the calculation amount, and improves the efficiency of real-time control.

[0038] In another technical solution, step S33 includes the following steps; S331. The upper platform 21 is directly adjusted according to the position difference between the actual value of the centroid and the planned value of the centroid position; S332. Calculate whether the deviation between the adjusted actual value of the centroid and the planned value of the centroid position meets the stability margin based on the planned value of the centroid position. If it meets, no further adjustment is made. If not, repeat steps S31 - S33.

[0039] In this technical solution, after the Stewart mechanism directly adjusts the position of the upper platform, the change in the center of mass of the waist structure 2 causes the actual value of the center of mass γ1(t) after the change to still deviate from the planned value of the center of mass position γ0(t). The adjusted center of mass fails to completely return to the target trajectory. Therefore, a clear margin standard is used to quickly judge whether the adjustment is in place, avoiding excessive adjustment. The adjustment can be terminated in time under the premise of meeting stability, greatly reducing the calculation complexity and reducing the computing power consumption in real-time control. Among them, the formulation of the margin standard can adopt the method of limiting the center of mass deviation to a certain proportion of the area of the supporting polygon.

[0040] In another technical solution, in step S332, the stability margin is determined based on the formula Δ=α·D, where D is the minimum lateral span of the current support polygon, α is a preset stability coefficient, and the value range is 0.05≤α≤0.15. The value of the stability coefficient α is related to the gait phase, and is 0.10-0.15 in the single-leg support phase and 0.05-0.10 in the double-leg support phase. In this technical solution, the minimum lateral span is the minimum span passing through the center point of the current support polygon, corresponding to the weakest direction of the robot's stability. α is used as the stability coefficient, and its value is dynamically adjusted according to the gait phase.

[0041] In another technical solution, posture sensors are installed on the upper body structure 1 and the waist structure 2 to obtain the posture data of the upper body structure 1 and the waist structure 2 in real time. In combination with preset mass distribution parameters, the center of mass position of the upper body structure 1 and the center of mass position of the waist structure 2 are calculated through a mass-weighted formula. Herein, posture sensors such as IMU are installed on the upper body structure 1 and the waist structure 2 respectively, and acceleration and angular velocity data are collected in real time. In combination with a preset kinematic model, the three-dimensional posture of the upper body and waist is solved. Through physical modeling and experimental calibration of the upper body structure and the waist structure, the center of mass position of each component in the upper body structure 1 and the waist structure 2 is determined. Through multi-sensor fusion and mass-weighted calculation, the real-time and accuracy of the center of mass position of the upper body structure and the waist structure are ensured.

[0042] According to one embodiment of the present invention, a parallel biped robot with a waist structure, the upper body structure is simplified to a torso m t =8kg, left arm m la =3kg, right arm m ra =3kg, waist structure adopts stewart mechanism, waist structure m w =6kg, parallel double-leg structure m l =6kg.

[0043] S11. Develop a stepping strategy. The robot adopts a straight-line walking strategy with a step length L = 0.5 m, a step frequency T = 1 s, a single-foot width of 0.3 m for the robot, a lateral span of the support polygon during single-foot support phase regarded as 0.3 m, and a stability coefficient of 0.13. Consider the waist structure and the upper body structure as relatively stationary counterweights to obtain the foot landing positions when the robot walks in a straight line.

[0044] S12. Set the time step to 0.1 s and generate the foot trajectory through quintic polynomial interpolation. The quintic polynomial uses , and determine the polynomial coefficients a0~a5 according to the starting position, target position, and time nodes of the foot, and obtain the motion trajectory of the corresponding foot. Perform inverse kinematics calculations based on the foot trajectory to obtain the joint angles of the parallel double-leg structure, and obtain the centroid trajectory γ2(t) of the parallel double-leg structure, where γ2(0.4)=(0.25,0,0.32).

[0045] S13. The lower platform moves in coordination with the parallel double-leg structure, and the connection point coordinates of each telescopic rod in the waist structure and the lower platform can be known.

[0046] S2. Based on the foot landing positions of the robot, use the midpoint and geometric median line of the support polygon as the centroid design reference trajectory, and the centroid planning value γ0(t) when the robot walks in this gait with the waist structure and the upper body structure stationary. When t = 0.4 s, γ0(0.4)=(0.3,0,0.72) m. [[ID=!3]]

[0047] S31. At t = 0.4, the upper body structure changes its posture from the static state. According to the measurement by the attitude sensors in the upper body structure, the centroid of each component in the upper body structure is: for the torso γ t (0.4) = (0.15,0,0.95), for the left arm γ la (0.4)=(0.1,0,1), for the right arm γ ra (0.6,0,1.1). Through mass weighting, the centroid of the upper body structure γ3(0.4)=(0.236,0,0.993) can be obtained. According to the measurement by the attitude sensors in the waist attitude, the centroid of the waist structure γ4(0.4)=(0.28,0,0.72).

[0048] S32. Calculate the actual value of the robot's centroid through the mass weighting formula. The calculation formula is as follows: ; S331. The centroid position planning value γ0(0.4)=(0.3,0,0.45). The upper platform adjusts according to the position difference and remains horizontal, with a vertical displacement of 0. The bottom coordinates of each telescopic rod in the Stewart mechanism remain unchanged, and the updated top coordinates of each telescopic rod can be known. The calculation formula for the adjusted length of each telescopic rod is: ; where A X , A y , A z are respectively the coordinate values of the top end of the telescopic rod after the upper platform is adjusted on the X, Y, and Z axes in the global coordinate system, and A X , A y , A z are respectively the coordinate values of the bottom end of the telescopic rod. By driving the telescopic rod to adjust its length according to this calculation result, the updated position of the upper platform adjustment value can be obtained.

[0049] S332. Determine the stability margin based on Δ = α·D, where α = 0.13, D = 0.3, and Δ = 0.039 m. Recalculate the actual value of the center of mass after adjustment . The deviation of the actual value of the center of mass from the planned value of the center of mass position in the horizontal direction is 0.005, which is less than the stability margin, so no further adjustment is required.

[0050] It should be noted that although the above steps are described in a specific order, it does not mean that the steps must be executed in the above specific order. In fact, some of these steps can be executed concurrently or even in a different order, as long as the required functions can be achieved. The number of devices and the processing scale described here are used to simplify the description of the present invention, and it is obvious to those skilled in the art for the application, modification, and variation of the present invention.

[0051] Although the embodiments of the present invention have been disclosed above, it is not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details and the illustrated and described examples here.

Claims

1. A parallel biped robot with a waist structure, characterized in that, It includes a parallel leg structure, a waist structure, and an upper body structure that are arranged from bottom to top and can move independently of each other; the parallel leg structure includes a leg structure cross beam, and both ends of the leg structure cross beam are connected downward to the leg structures, and the upper part of the leg structure cross beam is fixedly connected to the waist structure; the waist structure is a six-degree-of-freedom Stewart mechanism, its lower platform is rigidly connected to the leg structure cross beam, the upper platform is rigidly connected to the upper body structure, and six telescopic rods are connected between the upper platform and the lower platform; the upper platform is fixedly connected to the upper body structure.

2. Walking method of a parallel biped robot with a waist structure, applied to the parallel biped robot with a waist structure according to claim 1, characterized in that, It includes the following steps: S1. Plan the biped motion trajectory of the robot and formulate a stepping strategy, where the stepping strategy includes the foot landing position, the state of the parallel leg structure at any time, and the state of the lower platform at any time, to obtain the centroid position of the parallel leg structure; S2. According to the foot landing position of the robot, formulate the overall centroid position planning value γ0(t) of the robot; S3. When the parallel leg structure of the robot and the lower platform move forward according to the stepping strategy, the upper platform remains horizontal, and the actual value γ1(t) of the current robot centroid is detected and calculated in real time, and it is judged whether it is equal to the overall centroid position planning value of the robot. If not, the position of the upper platform is adjusted so that the actual centroid position of the robot returns to the centroid position planning value until the robot completes this section of the motion trajectory.

3. The walking method of the parallel biped robot with a waist structure according to claim 2, characterized in that, The overall centroid position planning value calculates the support polygon range through the foot contact point position in the robot stepping strategy, and uses the midpoint of the support polygon and the geometric median line of the support polygon in the single-foot support state as the centroid design reference trajectory to obtain the relationship between the centroid position planning value and time.

4. The walking method of the parallel biped robot with a waist structure according to claim 2, characterized in that Step S1 includes: S11. Formulate the robot stepping strategy, including the stepping distance and the stepping frequency, and plan the gait trajectory of the biped robot on the travel route, and the result includes the foot touchdown point; S12. Discretize the walking cycle into several time points, calculate the foot motion trajectory through quintic polynomial interpolation, and calculate the relationship between the rotational position of each joint in the parallel leg structure and time through inverse kinematics to obtain the relationship between the centroid position of the parallel leg structure and time; S13. Obtain the relationship between the position, centroid of the lower platform and time.

5. The walking method of the parallel biped robot with a waist structure according to claim 4, characterized in that, Step S3 includes the following steps: S31. Calculate the centroid position of the upper body structure and the centroid position of the waist structure at a time point; S32. Calculate the actual value of the robot centroid at this time point; S33. According to the difference in the horizontal displacement between the centroid position planning value and the actual centroid value, the waist structure adjusts the position of the upper platform according to the difference; S34. Enter the next time point, and repeat steps S31~S34 until this section of the motion trajectory is completed.

6. The walking method of the parallel biped robot with a waist structure according to claim 5, characterized in that, Step S33 includes the following steps; S331. The upper platform is directly adjusted according to the position difference between the actual centroid value and the centroid position planning value; S332. Calculate whether the deviation between the adjusted actual centroid value and the centroid position planning value meets the stability margin based on the centroid position planning value. If it meets, no further adjustment is made. If not, repeat steps S31~S33.

7. The walking method of the parallel biped robot with a waist structure according to claim 6, characterized in that, In step S332, the stability margin is determined based on the formula Δ = α·D, where D is the minimum lateral span of the current support polygon, α is a preset stability coefficient, and the value range is 0.05 ≤ α ≤ 0.

15. The value of the stability coefficient α is related to the gait phase, taking 0.10 - 0.15 in the single-leg support phase and 0.05 - 0.10 in the double-leg support phase.

8. The walking method of the parallel biped robot with a waist structure according to claim 5, characterized in that, Pose sensors are installed on the upper body structure and the waist structure to obtain the pose data of the upper body structure and the waist structure in real time. Combining with the preset mass distribution parameters, the centroid positions of the upper body structure and the waist structure are calculated through the mass weighting formula.

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