Parallel biped robot ankle with rotational center separation, control method and device

Abstract

The application provides a parallel double-leg robot ankle joint with separated rotation centers, a control method and a device, and relates to the technical field of robot motion control. The ankle joint comprises: a parallel crank linkage mechanism, including two drive chains, each drive chain comprising a drive motor, a crank and a connecting rod; an ankle joint motion component connected with the two connecting rods respectively; the pitch rotation center is separated from the roll rotation center; the foot of the common perpendicular of the connecting line of the two rotation centers and the connecting line of the connecting points of the two connecting rods is the coordinate origin of the reference coordinate system; the reference coordinate system is fixed relative to the ankle joint. The structural design of the application breaks through the traditional ideal assumption of "coincidence of rotation centers", significantly improving the universality of the mechanism; at the same time, the reference coordinate system defined based on the structure lays a geometric foundation for directly deriving the inverse solution formula in an analytical form, thereby reducing the complex calculation of relying on numerical iteration, and further meeting the demand of universality and real-time solution.

Description

Technical Field

[0001] This application relates to the field of robot motion control technology, and in particular to an ankle joint of a parallel bipedal robot with a separated rotation center, a control method, and a device. Background Technology

[0002] The ankle joint of a bipedal robot is the core actuator for achieving stable dynamic walking, and its motion control accuracy and response speed directly affect the overall motion performance of the robot. To meet the demands of high-dynamic walking for high rigidity, high load-bearing capacity, and rapid response, the use of a parallel crank-connecting rod mechanism driven by two motors as the ankle joint's actuation method has become an important technological direction. This type of mechanism uses two motor-crank-connecting rod drive chains to jointly control the composite motion of the ankle joint's pitch and roll degrees of freedom. In motion control, it is necessary to solve for the target rotation angles of the two drive motors based on the desired joint posture (pitch angle, roll angle), i.e., solving the inverse kinematics problem of the mechanism. The real-time performance and accuracy of this solution process are crucial to determining whether the robot can achieve high-frequency, stable walking control.

[0003] In related technologies, the following two types of solutions are typically used to solve the inverse kinematics problem of the aforementioned parallel crank-connecting rod mechanism. The first type is an analytical method based on specific geometric assumptions. This method first assumes that the pitch and roll rotation centers of the ankle joint coincide in space. Under this ideal model, a closed analytical formula for solving the motor rotation angle is derived through geometric relationships, achieving rapid calculation. However, this type of solution relies on the ideal assumption of "coincidence of rotation centers," resulting in poor versatility. The second type is a general numerical iterative method (such as the Newton-Raphson method). This method does not rely on the assumption of coincidence of rotation centers. It constructs a target error function for the motor rotation angle and iteratively approximates it until the required accuracy is met, at which point the solution is output. However, this type of solution lacks real-time performance, making it difficult to meet the real-time calculation requirements of high-dynamic walking control for bipedal robots. In other words, existing solutions struggle to achieve a balance between "versatility" and "real-time solution performance."

[0004] Therefore, a solution scheme for the ankle joint of a parallel bipedal robot with a separated rotation center and its inverse kinematics is needed to achieve both versatility and real-time solution. Summary of the Invention

[0005] This application provides a parallel bipedal robot ankle joint with a separated rotation center, a control method, and a device to improve the problem that solutions in related technologies are difficult to achieve simultaneously in terms of "versatility" and "real-time solution".

[0006] In a first aspect, this application provides a parallel bipedal robot ankle joint with a rotation center separated, comprising:

[0007] A parallel crank-connecting rod mechanism includes a first drive chain and a second drive chain, each drive chain comprising a drive motor, a crank connected to the output shaft of the drive motor, and a connecting rod connected to the crank;

[0008] Ankle joint motion component, with the links of the two drive chains connected to the ankle joint motion component respectively;

[0009] The center of flexion and extension rotation of the ankle joint is separated from the center of tumbling rotation;

[0010] The origin of the reference coordinate system is the foot of the common perpendicular line connecting the pitch rotation center and the roll rotation center, and the line connecting the two link connection points; the two link connection points are the connection points between the links of the two drive chains and the ankle joint moving parts; the reference coordinate system is fixed relative to the ankle joint.

[0011] In one possible implementation, the connecting rod lengths of the two drive chains are respectively equal to the distance from the axis of their respective drive motors to the origin of the coordinate system, the crank lengths of the two drive motors are equal, and the installation offset of the drive motors is equal to the installation offset of the connecting rods.

[0012] In one possible implementation, the ankle joint has two mirror-symmetric configurations: in the first configuration, the pitch rotation center is located on the positive z-axis of the reference coordinate system, and the roll rotation center is located on the negative z-axis of the reference coordinate system; in the second configuration, the pitch rotation center is located on the negative z-axis of the reference coordinate system, and the roll rotation center is located on the positive z-axis of the reference coordinate system.

[0013] Secondly, this application provides a bipedal robot, comprising:

[0014] The robot itself;

[0015] The ankle joint of a parallel bipedal robot, with its rotation center separated from any of the first aspects, is set on the robot body;

[0016] The controller, connected to the drive motor in the ankle joint, is used to control ankle joint movement.

[0017] Thirdly, this application provides a method for controlling the ankle joint of a parallel bipedal robot with a separated rotation center, applied to a controller in a bipedal robot as described in the second aspect, the control method comprising:

[0018] Obtain the target attitude angles of the ankle joint, which include the target pitch angle and the target roll angle;

[0019] Obtain the preset analytical formula, which is used to determine the target drive motor rotation angle based on the target attitude angle. The analytical formula is obtained by solving the kinematic constraint equation, which is an equation between the drive motor rotation angle and the attitude angle based on the reference coordinate system, which is fixed relative to the ankle joint.

[0020] The target drive motor rotation angle corresponding to the target pitch angle and target roll angle is determined according to the analytical formula, and control commands are sent to the corresponding drive motor to drive the ankle joint to move to the target posture.

[0021] In one possible implementation, the first drive chain and the second drive chain in the ankle joint are the upper drive chain and the lower drive chain, respectively. The kinematic constraint equations are determined as follows: based on a reference coordinate system, the coordinates of the first connection point between the link in the upper drive chain and the ankle joint moving part in the ankle joint, and the coordinates of the second connection point between the link in the lower drive chain and the ankle joint moving part are determined respectively. Based on the determined coordinates of the first and second connection points, and according to the constraint that the link lengths in the upper and lower drive chains remain unchanged, a first geometric relationship between the rotation angle of the drive motor and the attitude angle in the upper drive chain, and a second geometric relationship between the rotation angle of the drive motor and the attitude angle in the lower drive chain are established respectively, as the kinematic constraint equations.

[0022] In one possible implementation, determining the coordinates of the first connection point between the link in the upper drive chain and the ankle joint moving component in the ankle joint, and the coordinates of the second connection point between the link in the lower drive chain and the ankle joint moving component, includes: determining the coordinates of the first and second connection points along the x-axis of the reference coordinate system based on the target pitch angle; determining the coordinates of the first and second connection points along the y-axis of the reference coordinate system based on the target roll angle; and determining the coordinates of the first and second connection points along the z-axis of the reference coordinate system based on the target pitch angle and the target roll angle.

[0023] In one possible implementation, solving the kinematic constraint equations includes: constructing a first trigonometric equation regarding the rotation angle of the drive motor in the upper drive chain based on a first geometric relationship; constructing a second trigonometric equation regarding the rotation angle of the drive motor in the lower drive chain based on a second geometric relationship; and analytically solving the first and second trigonometric equations respectively to obtain analytical formulas for the rotation angles of the drive motors in the upper and lower drive chains with respect to attitude angles.

[0024] In one possible implementation, the analytical solution of the first trigonometric equation and the second trigonometric equation is further included: based on the actual assembly structure of the parallel crank-connecting rod mechanism in the ankle joint, a unique physically feasible solution is selected from the general mathematical solution of the first trigonometric equation as the analytical formula for the rotation angle of the drive motor in the upper drive chain; based on the actual assembly structure of the parallel crank-connecting rod mechanism, a unique physically feasible solution is selected from the general mathematical solution of the second trigonometric equation as the analytical formula for the rotation angle of the drive motor in the lower drive chain.

[0025] In one possible implementation, when determining the target drive motor angle corresponding to the target pitch angle and target roll angle according to the analytical formula, different joint configurations are adapted in the following way: A first preset angle and a second preset angle are obtained; wherein, the first preset angle is the arctangent of the ratio of the crank length of the drive motor to the distance from the pitch rotation center to the coordinate origin; the second preset angle is the arctangent of the ratio of the installation offset of the drive motor to the distance from the roll rotation center to the coordinate origin; when the ankle joint is in the first configuration, the target pitch angle and target roll angle are directly substituted into the analytical formula to obtain the target... The target drive motor rotation angle is determined. When the ankle joint is in a second configuration that is mirror-symmetrical to the first configuration, the angle terms in the analytical formula are replaced with signs. The target pitch angle and the target roll angle are substituted into the analytical formula after the sign replacement to obtain the target drive motor rotation angle. The sign replacement includes: replacing the sum of the pitch angle and the first preset angle with the difference between the pitch angle and the first preset angle in the attitude angle; replacing the difference between the roll angle and the second preset angle in the attitude angle with the sum of the roll angle and the second preset angle; and replacing the sum of the roll angle and the second preset angle with the difference between the roll angle and the second preset angle.

[0026] In one possible implementation, after determining the target drive motor rotation angle corresponding to the target pitch angle and the target roll angle according to the analytical formula, the method further includes: normalizing the target drive motor rotation angle to a preset control angle range to obtain a normalized angle value; and generating a control command based on the normalized angle value.

[0027] In one possible implementation, after sending control commands to the corresponding drive motor, the method further includes: receiving the actual rotation angle fed back by the drive motor through an encoder; comparing the actual rotation angle with the target drive motor rotation angle to determine the angle deviation; and performing closed-loop adjustment of the drive motor based on the angle deviation to correct the ankle joint's movement posture.

[0028] Fourthly, this application provides a parallel bipedal robot ankle joint control device with a separated rotation center, applied to a controller in a bipedal robot as described in the second aspect, the control device comprising:

[0029] The attitude acquisition module is used to acquire the target attitude angle of the ankle joint, which includes the target pitch angle and the target roll angle.

[0030] The processing module is used to obtain a preset analytical formula, which is used to determine the target drive motor rotation angle based on the target attitude angle. The analytical formula is obtained by solving the kinematic constraint equation, which is an equation between the drive motor rotation angle and the attitude angle established based on the reference coordinate system, which is fixed relative to the ankle joint.

[0031] The control module is used to determine the target drive motor rotation angle corresponding to the target attitude angle according to the analytical formula, and send control commands to the corresponding drive motor to drive the ankle joint to move to the target attitude.

[0032] Fifthly, this application provides a controller, including: a processor, and a memory communicatively connected to the processor;

[0033] Memory is used to store instructions executed by the computer;

[0034] A processor is used to execute computer-executable instructions stored in memory to implement any of the methods in the third aspect.

[0035] In a sixth aspect, this application provides a computer-readable storage medium storing computer-executable instructions, which, when executed, are used to implement the method of any one of the third aspects.

[0036] In a seventh aspect, this application provides a computer program product, including a computer program that, when executed, implements the method of any one of the third aspects.

[0037] The present application provides a parallel bipedal robot ankle joint with a separated rotation center, a control method, and a device. The ankle joint of the parallel bipedal robot with a separated rotation center includes: a parallel crank-link mechanism, including a first drive chain and a second drive chain, each drive chain including a drive motor, a crank connected to the output shaft of the drive motor, and a connecting rod connected to the crank; an ankle joint motion component, with the connecting rods of the two drive chains respectively connected to the ankle joint motion component; the pitch rotation center and the tumble rotation center of the ankle joint are separated; the foot of the perpendicular of the common perpendicular line connecting the pitch rotation center and the tumble rotation center and the line connecting the connection point of the two connecting rods is the origin of the reference coordinate system; the connection point of the two connecting rods is the connection point between the connecting rods of the two drive chains and the ankle joint motion component; the reference coordinate system is fixed relative to the ankle joint.

[0038] This application separates the pitch rotation center and roll rotation center in space and establishes a reference coordinate system with the foot of the common perpendicular of the line connecting the two centers and the connection point of the two links as the origin. This provides a precise and universal geometric benchmark for subsequent inverse kinematics solutions. This structural design breaks through the traditional ideal assumption of "coincidence of rotation centers," allowing the joints to flexibly adapt to different mechanical optimization and interference avoidance requirements, significantly improving the mechanism's versatility. Simultaneously, based on the fixed reference coordinate system defined by this structure, a geometric foundation is laid for directly deriving the analytical inverse kinematics formula, thereby reducing complex calculations relying on numerical iterations. This creates conditions for achieving high real-time motion control, further improving the real-time performance, stability, and configuration adaptability of inverse kinematics solutions under complex mechanism configurations, and is more conducive to meeting the millisecond-level control requirements of bipedal robots. Attached Figure Description

[0039] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0040] Figure 1 A schematic diagram of a parallel bipedal robot ankle joint with a separated rotation center, provided as an exemplary embodiment of this application;

[0041] Figure 2 Another structural schematic diagram of a parallel bipedal robot ankle joint with a separated rotation center, provided as an exemplary embodiment of this application;

[0042] Figure 3 A flowchart illustrating a method for controlling the ankle joint of a parallel bipedal robot with a separated rotation center, provided as an exemplary embodiment of this application;

[0043] Figure 4 A schematic diagram of the projection of the pitch of the ankle joint (first configuration) of a parallel bipedal robot with a separated rotation center provided for an exemplary embodiment of this application in the XZ plane;

[0044] Figure 5 A schematic diagram of the projection of the ankle joint (first configuration) roll of a parallel bipedal robot with a separated rotation center provided for an exemplary embodiment of this application onto the YZ plane;

[0045] Figure 6 A schematic diagram of the projection of the pitch of the ankle joint (second configuration) of a parallel bipedal robot with a separated rotation center provided for an exemplary embodiment of this application in the XZ plane;

[0046] Figure 7 A schematic diagram of the projection of the ankle joint (second configuration) roll of a parallel bipedal robot with a separated rotation center provided for an exemplary embodiment of this application onto the YZ plane;

[0047] Figure 8 A schematic diagram of a parallel bipedal robot ankle joint control device with a separated rotation center provided as an exemplary embodiment of this application;

[0048] Figure 9 A schematic diagram of the controller provided for an exemplary embodiment of this application.

[0049] In the figure, 10—ankle joint of a parallel bipedal robot with its rotation center separated; 11—parallel crank-connecting rod mechanism; 111—first drive chain; —The drive motor of the first drive chain; —The crank of the first drive chain; —Link of the first drive chain; 112—Second drive chain; —The drive motor of the second drive chain; —The crank of the second drive chain; —Link of the second drive chain; 12—Ankle joint moving parts; —Pitch rotation center; —The center of tumbling rotation; —The origin of the reference coordinate system.

[0050] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0051] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0052] The terms “first,” “second,” etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, products, or apparatus.

[0053] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties. Furthermore, the collection, use and processing of the relevant data must comply with relevant laws, regulations and standards, and corresponding operation entry points are provided for users to choose to authorize or refuse.

[0054] In related technologies, numerical iteration methods or analytical methods based on specific geometric assumptions are mainly employed. While numerical iteration methods have a relatively wide range of applications, they often rely on initial value selection and the iterative convergence process. Under high-frequency control cycles, they are prone to problems such as fluctuating solution time, unstable convergence, and even local failures. Once computational delays enter the control link, they affect the timing of foot landing and the effectiveness of posture correction. On the other hand, while analytical methods are faster, they are usually based on the premise that the ankle joint's pitch and roll rotation centers coincide or satisfy fixed geometric relationships. When actual mechanisms adopt more complex rotational relationships to avoid mechanical interference, optimize force paths, or adapt to compact layouts, the original model is often difficult to apply directly, requiring remodeling and re-deriving, resulting in a lack of a unified description method across different configurations. Especially in parallel mechanisms, there is significant spatial coupling between the two drive chains and moving parts. Without a stable and unified reference relationship, inverse kinematics modeling becomes cumbersome, increasing the difficulty of engineering implementation and weakening the reusability of control algorithms under different mechanical layouts. Therefore, it is difficult to simultaneously meet the requirements of real-time performance, versatility, and engineering adaptability under complex configurations.

[0055] In view of this, how to establish a clear, unified, and easily solvable spatial relationship for the ankle joint of a parallel bipedal robot under the condition that the pitch and roll rotation centers of the ankle joint do not coincide has become an urgent technical problem to be solved. To address this problem, a parallel bipedal robot ankle joint with separated rotation centers is provided. This ankle joint adopts a parallel crank-connecting rod mechanism and sets up a first drive chain and a second drive chain. The connecting rods of the two drive chains are respectively connected to the ankle joint moving parts, enabling the ankle joint moving parts to achieve posture adjustment under the coordinated action of the two drive chains. Simultaneously, the pitch and roll rotation centers of the ankle joint are designed to be separated from each other, and the origin of the reference coordinate system is constructed using the foot of the perpendicular line connecting the pitch and roll rotation centers and the line connecting the two connecting rod points. This structure and reference relationship provide a unified basis for describing the mechanism under the separated rotation center configuration, thereby improving the problem of the difficulty in clearly representing the ankle joint motion relationship under complex configurations and providing support for subsequent efficient and stable control.

[0056] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0057] Figure 1 A schematic diagram of a parallel bipedal robot ankle joint with a separated rotation center, provided as an exemplary embodiment of this application. Figure 1As shown, the ankle joint 10 of the parallel bipedal robot with a detached rotation center includes:

[0058] The parallel crank-connecting rod mechanism 11 includes a first drive chain 111 and a second drive chain 112;

[0059] The first drive train 111 includes a drive motor. and drive motor Crank connected to the output shaft and the crank Connecting rods ;

[0060] The second drive train 112 includes a drive motor. and drive motor Crank connected to the output shaft and the crank Connecting rods ;

[0061] Ankle joint moving parts 12, connecting rod ,link Each is connected to the ankle joint movement component 12;

[0062] The center of flexion and extension rotation of the ankle joint 10 With the center of tumbling rotation Separation;

[0063] Pitch Rotation Center With the center of tumbling rotation The line connecting the two links and the line connecting the two links to their connection points. The foot of the common perpendicular is the origin of the reference coordinate system. ; Connection point of two links , Link ,link The connection point with the ankle joint moving part 12; the reference coordinate system is fixed relative to the ankle joint 10.

[0064] Among them, the parallel crank-connecting rod mechanism 11 refers to a parallel transmission mechanism composed of two independent and cooperative drive chains, used to drive the motor Drive motor The rotational input is converted into a composite posture output of the ankle joint motion component 12, providing the ankle with pitch and roll direction linkage control capabilities during bipedal robot walking, hopping, cushioning, and posture maintenance. It is typically positioned on either side or opposite to the ankle joint body to form a symmetrical or quasi-symmetrical force path, and applies constraint and driving forces to the ankle joint motion component 12 via the first drive chain 111 and the second drive chain 112, respectively. In one possible embodiment, the parallel crank-connecting rod mechanism 11 can adopt a symmetrical plate frame structure; in another possible embodiment, a box-type encapsulation structure can be used to enclose the crank... and connecting rod and crank ,link Arranged inside the housing, in another exemplary embodiment, a lightweight frame structure can be employed to reduce the overall inertia of the ankle joint; wherein, the drive motor Drive motor Servo motors, brushless DC motors, or integrated motor modules can be selected, cranks and connecting rod and crank ,link Aluminum alloy, titanium alloy, alloy steel, carbon fiber composite material or engineering plastic reinforcement can be selected. The overall size of the mechanism is usually arranged compactly according to the ankle envelope space of the robot, and the crank length is generally less than the connecting rod length, so as to obtain sufficient motion stroke and output adjustment capability in a limited space.

[0065] The first drive chain 111 refers to an independent transmission branch in the parallel crank-connecting rod mechanism 11, which is used to receive motor drive commands from the controller and transmit rotational motion through the crank. and connecting rod The transmission is sent to the ankle joint motion component 12, thereby participating in the formation of a complex posture of pitch and roll during ankle posture adjustment; it is typically positioned on one side of the ankle joint 10 and forms a spatially distributed support relationship with the second drive chain 112, with the motor output shaft and crank... The connecting rods can be connected by rigid couplings, keyed connections, or spline connections. The ankle joint moving component 12 can be connected by a pin hinge, ball joint, or universal joint to accommodate angular deflection and assembly errors during movement; in terms of shape, the drive motor... It can be a cylindrical, flat, or integrated reducer with a single-piece structure, crank. It can be a plate-shaped, arm-shaped, or eccentric wheel structure, with connecting rods It can be a solid rod, a hollow tube, or a rod-shaped structure with reinforcing ribs; in terms of size, the length of the connecting rod of the first drive chain 111, the length of the crank, and the distance from the motor shaft to the connecting rod connection point together determine its reachable working space, which usually meets the installation spacing between it and the second drive chain 112, the swing envelope of the ankle joint moving part 12, and the space avoidance requirements after the separation of the rotation center.

[0066] The second drive chain 112 refers to another independent transmission branch corresponding to the first drive chain 111. It works in conjunction with the first drive chain 111 to act on the ankle joint moving component 12, achieving dual-degree-of-freedom adjustment of the ankle joint posture through mutual cooperation. At its output end, it forms a synchronous or differential drive relationship with the first drive chain 111 to achieve continuous correction of the foot posture. Its installation position is generally located on the other side of the ankle joint 10, symmetrically or approximately symmetrically distributed with the first drive chain 111 about the centerline of the mechanism to improve force balance and reduce local off-center loads, driving the motor. ,crank and connecting rods The connection method can adopt the same or similar mechanical interface form as the first drive chain 111 to facilitate unified manufacturing and assembly; in one possible embodiment, the drive motor of the second drive chain 112 With crank It can be arranged at different height levels to further avoid interference with the internal mechanisms of the ankle joint. In another possible embodiment, the link of the second drive chain 112... An adjustable length structure can be used to facilitate mechanism calibration. In another exemplary embodiment, the second drive chain 112 can be made of lightweight material to reduce the overall lower limb swing mass. Its size and proportions are generally matched or mirrored with the first drive chain 111 to ensure symmetrical motion response when outputting the same or complementary control quantities.

[0067] The ankle joint motion component 12 refers to the component that receives the output action of the first drive chain 111 and the second drive chain 112, and converts the driving force and constraint relationship between the two into a common force and motion component for ankle joint posture changes. As the output end of the ankle joint 10, it forms a posture transmission interface with the foot support structure or the upper leg structure, and is used to realize the adaptive adjustment of the foot contact surface with the ground during the robot's standing, swinging and landing processes. This component is usually located between the two drive chains or within the working area enclosed by the output ends of the two drive chains, and is provided with two linkage connection points respectively. , With the connecting rod ,link The ankle joint is articulated, allowing it to receive combined action in two directions. In one possible embodiment, the ankle joint motion component 12 can be a one-piece load-bearing turntable; in another possible embodiment, it can be a connecting seat structure with ear plates; and in yet another exemplary embodiment, it can be a lightweight frame-type turntable or a closed box-type rotating seat structure. Its material can be aluminum alloy, magnesium alloy, titanium alloy, or high-strength composite material to balance rigidity, weight, and processing performance. Its dimensions are typically adapted to the spacing between the two link connection points and the envelope of the ankle joint body, and the two connection points... , The position should match the travel range of the drive chain to avoid interference or dead points at the maximum attitude swing angle.

[0068] Pitch Rotation Center With the center of tumbling rotation Separation refers to the fact that the rotational axes of the ankle joint 10 around the pitch and roll directions do not coincide in space. This allows the two rotational movements to have independent geometric reference bases, thus reserving more flexible force paths and avoidance space for the mechanism layout; furthermore, the pitch rotation center The instantaneous center of rotation of the ankle joint 10 around the pitch axis (anteroposterior direction), the center of tumbling rotation. The instantaneous center of rotation of the ankle joint around the roll axis (left-right direction); the center of pitch rotation. , Tumbling rotation center Drive motor axis center and drive motor The four axes are collinear. Structurally, this separate arrangement usually means that the pitch rotation center is collinear. With the center of tumbling rotation There is a predetermined bias between them. When the robot performs foot lifting, foot landing, ramp fitting, or lateral balance correction, the ankle joint can couple the two rotations through the differential output of the parallel crank-connecting rod mechanism 11. In one possible embodiment, the two rotation centers after separation can be arranged in different spatial directions. In another possible embodiment, it can be achieved through an offset joint seat, a stepped bearing seat, or an out-of-plane rotating shaft structure. In yet another exemplary embodiment, the relative position can also be defined by the geometric arrangement of the connecting rod connection point and the shape of the moving part. The dimensional constraints of this separation relationship are usually related to the overall thickness of the ankle joint, the width of the foot, and the motor installation space, and must meet the spatial avoidance requirements within the range of crank swing and connecting rod swing angle to ensure continuous movement of the mechanism.

[0069] The reference coordinate system refers to the geometric coordinate system fixed on the ankle joint 10 body. This is because the ankle joint 10 has a pitch and rotation center. With the center of tumbling rotation The connection line and the connection point between the two links , The line connecting the two hinge balls of the driven joint (i.e., the two hinge balls) is a straight line with skew lines, and the line segment is... With a straight line The foot of the perpendicular is the origin of the coordinate system. Establish a local coordinate system for the ankle joint; this coordinate system is defined as follows: using vectors... The direction is the positive z-axis, and the vector is... The direction of x is the positive x-axis, and the positive y-axis direction is determined according to the right-hand rule; point For line segments The midpoint; in this coordinate system, the center of rotation of the pitch axis (i.e., the center of pitch rotation). The coordinates of ) are The coordinates of the rotation center F of the roll axis are ,in, = and = From the center of rotation to the origin The distance. This reference coordinate system is used to uniformly characterize the spatial positional relationships and kinematic parameters under the ankle joint separation rotation center configuration, thereby providing a stable reference basis for the subsequent controller to solve the drive motor angle, crank attitude, and connecting rod position. This coordinate system is fixed relative to the ankle joint 10, which means that during the attitude change of the ankle joint 10 relative to the body or the ground, the coordinate system moves together with the ankle joint as a whole and does not change with the external environment, making it easy to solidify the geometric relationship of the mechanism into a reusable modeling condition. In one possible embodiment, the coordinate system can be a Cartesian coordinate system with the origin located at the vertical foot position, and the coordinate axes corresponding to the main structural direction, pitch direction, and roll direction of the ankle joint, respectively. In another possible embodiment, one of the coordinate axes can be aligned with the direction of the line connecting the two connecting rods according to the control requirements. In yet another exemplary embodiment, a local inertial coordinate system or an engineering coordinate system consistent with the assembly reference plane can also be used. The establishment of this coordinate system transforms the complex spatial relationship of the separation rotation center into a unified geometric constraint, enabling the mechanism parameters under different configurations to be expressed within the same reference frame.

[0070] Based on the above analysis, it can be seen that the ankle joint of the parallel bipedal robot with a separated rotation center provided in this embodiment adopts a dual-motor drive structure, including a drive motor. (i.e., the upper motor) and the drive motor (i.e., the lower motor); drive motor The output shaft is connected to a crank. With connecting rod (i.e., the upper connecting rod) one end ( (Point) connection, drive motor The output shaft of the (lower motor) is connected to a crank. With connecting rod (i.e., the lower connecting rod) one end ( (2 points) Connection, upper connecting rod With connecting rod The other end (respectively) Point and The points (points) are jointly connected to the ankle joint motion component 12. When the system is started, the drive motors in the first drive chain 111 and the second drive chain 112 are activated. Drive motor Each receives control commands and outputs rotary motion; the crank... With drive motor The output shaft rotates synchronously, and the crank... With drive motor The output shafts rotate synchronously, which in turn drives the respective connecting rods to oscillate. ,link Pushing and pulling forces are applied to the ankle joint moving component 12 through the connection points respectively; due to the pitch and rotation center of the ankle joint 10 With the center of tumbling rotation Separated from each other, and referencing the origin of the coordinate system. Established at the foot of the common perpendicular line connecting the two rotation centers and the connection point of the two links, the controller can describe and solve the pose relationship of the two drive chains under a unified geometric reference, so that the drive outputs on both sides form a clear correspondence in space; when the ankle joint 10 performs pitch adjustment, the two drive chains can output the same direction or differential angle, so that the ankle joint moving part 12 revolves around the pitch rotation center. The expected rotation is generated, and during the roll adjustment, the two drive chains can adjust relative to each other to form lateral attitude correction, thereby allowing the foot to better fit the ground or adapt to changes in terrain.

[0071] Since the relationships between the drive chain, connection points, and rotation centers are all defined in a reference coordinate system fixed to the ankle joint, the geometric relationships of the mechanism can be consistently represented regardless of whether the robot is standing, swinging, or in a landing cushioning phase. The control algorithm can complete inverse kinematics calculations without relying on frequently changing external references. This helps reduce the complexity of model reconstruction and repeated calibration, and reduces the uncertainty in the solution caused by configuration changes. Meanwhile, the separate rotation center design makes the pitch and roll spatial layout easier to avoid interference between motors, cranks, and connecting rods, and can also optimize the drive chain arrangement according to the force path, thereby improving structural compactness and assembly adaptability. Based on this, this embodiment can provide a clearer spatial modeling foundation, a more stable attitude control interface, and greater engineering versatility for parallel bipedal robots without changing the basic functions of the two-degree-of-freedom ankle joint, enabling the ankle joint to obtain more reliable motion output during high-dynamic walking and complex terrain adaptation. It should be understood that the above examples are merely illustrative and not limiting. Those skilled in the art can make equivalent substitutions or modifications to the drive form, connection method, material selection, and coordinate system refinement method without departing from the spirit of this application.

[0072] In this embodiment, the pitch rotation center and roll rotation center are spatially separated, and a reference coordinate system is established with the foot of the common perpendicular of the line connecting the two centers and the line connecting the two link connection points as the origin. This provides a precise and universal geometric reference for subsequent inverse kinematics solutions. This structural design breaks through the traditional ideal assumption of "coincidence of rotation centers," allowing the joints to flexibly adapt to different mechanical optimization and interference avoidance requirements, significantly improving the versatility of the mechanism. At the same time, based on the fixed reference coordinate system defined by this structure, a geometric foundation is laid for directly deriving the analytical inverse kinematics formula, thereby reducing the complex calculations that rely on numerical iterations. This creates conditions for achieving high real-time motion control, thereby improving the real-time performance, stability, and configuration adaptability of inverse kinematics solutions under complex mechanism configurations, and is more conducive to meeting the millisecond-level control requirements of bipedal robots.

[0073] In some embodiments, the connecting rod lengths of the two drive chains are respectively equal to the distance from the axis of their respective drive motors to the origin of the coordinate system, the crank lengths of the two drive motors are equal, and the mounting offset of the drive motors is equal to the mounting offset of the connecting rods.

[0074] Accordingly, to achieve decoupled control of the pitch and roll movements of the ankle joint and optimize torque output, this embodiment employs a specific set of geometric constraints, the key dimensions of which are defined as follows: upper and lower drive links (i.e., links) ,link The lengths of ) are defined as follows: and And there are , This equal-length relationship is one of the key conditions for ensuring motion decoupling. A connecting rod is a rod-shaped component used to transmit displacement and force between the crank and the ankle joint moving parts. Its function is to convert the rotational motion of the drive motor output shaft into spatial attitude changes of the ankle joint moving parts, and to jointly form the ability to adjust the ankle joint attitude in both pitch and roll directions. The connecting rods in the two drive chains are respectively arranged on both sides of the ankle joint moving parts or distributed in a mirror relationship at corresponding connection positions on the ankle joint moving parts. One end of the connecting rod is connected to the end of the corresponding crank through a hinge joint, and the other end is connected to the connecting rod connection point on the ankle joint moving parts through a hinge joint. Since the origin of the reference coordinate system is defined in this application as the foot of the perpendicular of the line connecting the pitch rotation center and the roll rotation center, and the line connecting the two connecting rod connection points, when the length of the connecting rod is equal to the distance from the axis of each drive motor to the origin of the coordinate system, a fixed-length geometric relationship is established between the drive motor axis, the connecting rod connection point, and the origin of the reference coordinate system, thus forming a directly corresponding analytical model in the spatial arrangement of the two drive chains.

[0075] The crank arm length of the drive motor is defined as ,Right now The fact that the crank lengths of the two drive motors are equal indicates that the lever arm parameters of the drive inputs on both sides are consistent. The crank can be understood as an eccentric arm or swing arm mounted on the output shaft of the drive motor. Its length is determined by the distance from the motor shaft center to the hinge point at the end of the crank. When the same size is used on both sides, the two drive chains can produce similar displacement responses under the same input conditions, which facilitates the unified solution of pitch and roll attitudes during the control process.

[0076] The installation offset of the drive motor is equal to the installation offset of the connecting rod, defined as follows: ,Right now This design achieves structural symmetry and simplifies the kinematic model. The installation offset of the drive motor is equal to that of the connecting rod, indicating the offset of the drive motor's mounting reference relative to the ankle joint's fixed reference coordinate system. This offset corresponds dimensionally to the mounting offset of the connecting rod on the ankle joint's moving parts, and is typically defined by the center distance, eccentricity, or normal offset between the motor mount and the connecting rod connector to maintain the mirror symmetry of the left and right drive chains. It should be understood that the aforementioned installation offset can be achieved through symmetrically arranged motor brackets, eccentric flanges, stepped mounting plates, or offset pads. The connecting rod can be constructed using linear members with spherical bearings, plate-reinforced connecting rods, or lightweight hollow members. The crank can be a single-piece arm, a double-layer clamping arm, or a hub-integrated eccentric arm. Materials can include aluminum alloy, alloy steel, titanium alloy, carbon fiber reinforced composite materials, or metal-core-clad engineering plastic structures to adapt to different load and inertia requirements.

[0077] The positioning dimension of the ankle joint rotation center is defined as follows: and These two dimensions directly determine the instantaneous rotation center position of the ankle joint, affecting its range of motion and dexterity. Regarding dimensions and proportions, the connecting rod length is usually consistent with the distance from the drive motor shaft center to the coordinate origin. These two can be set to the same value or approximately equal within a predetermined tolerance range, depending on the mechanism's unfolded space and the ankle joint's envelope dimensions. When the crank lengths on both sides are equal, the output characteristics of the two drive chains have high consistency. When the installation offset is equal to the connecting rod installation offset, their difference is usually controlled within the allowable error of the mechanism assembly to ensure that the analytical relationship does not deviate significantly due to offset errors. Based on the above analysis, this set of symmetrical constraints not only facilitates the unification of the geometric expression of the drive chains on both sides but also makes it easier to decompose the complex spatial motion of the ankle joint into calculable mirror parameter relationships, thereby reducing the difficulty of inverse kinematics modeling and parameter calibration.

[0078] When the system starts, the controller establishes a geometric mapping relationship between the two drive chains based on the robot's current posture and the target ankle joint's pitch and roll angles, according to a reference coordinate system fixed to the ankle joint body. Utilizing the constraint that the link length equals the distance from the axis of each drive motor to the origin, the target posture is converted into the target rotation angle of the two drive motors. Since the crank lengths on both sides are equal and their installation offsets are equal to the link installation offsets, the two drive chains can form a consistent kinematic response under the same control input. After the drive motor output shaft drives the cranks to rotate, the rotational motion is converted into push-pull displacements on the ankle joint's moving parts via the link, thereby causing the ankle joint's moving parts to perform a composite posture adjustment around the separately set pitch and roll rotation centers. In this process, the geometric symmetry of the two drive chains makes the correspondence between the linkage motion trajectory, crank angle and ankle joint posture change clearer. The controller does not need to establish different models for the left and right drive chains to complete unified solution and synchronous control. Therefore, it can reduce the amount of inverse kinematics calculation, reduce the solution fluctuation caused by parameter coupling, improve the calculation stability within the control cycle, and help maintain the continuity and consistency of foot posture correction during high dynamic walking, cushioned footing or terrain adaptation.

[0079] It should be understood that the above examples are merely illustrative and not limiting. Without departing from the technical concept of this application, the specific structural forms and material configurations of the connecting rod, crank, and installation offset can be replaced with equivalent ones. As long as the correspondence between length and offset is still satisfied, the same or similar kinematic constraint effects can be achieved.

[0080] Based on the foregoing embodiments, in some embodiments, the ankle joint has two mirror-symmetric configurations: in the first configuration, the pitch rotation center is located on the positive z-axis of the reference coordinate system, and the roll rotation center is located on the negative z-axis of the reference coordinate system; in the second configuration, the pitch rotation center is located on the negative z-axis of the reference coordinate system, and the roll rotation center is located on the positive z-axis of the reference coordinate system.

[0081] In one possible embodiment, the two mirror-symmetric configurations mentioned above refer to two mutually mirror-image installation forms of the parallel crank-connecting rod mechanism of the same ankle joint in spatial layout. The pitch rotation center and roll rotation center are arranged along the positive and negative half-axis of the reference coordinate system, respectively, or their positive and negative half-axis positions are interchanged in another corresponding arrangement. This allows the ankle joint to adapt to both symmetrical installation requirements for the left and right feet and assembly requirements under conditions of limited front-to-back and left-to-right space on the robot body. Based on the above analysis, it can be seen that the first and second configurations maintain the same topological relationship, that is, the connection methods of the first drive chain, the second drive chain, and the ankle joint moving parts remain unchanged. The mirror arrangement is achieved only by flipping the z-axis sign of the pitch rotation center and roll rotation center relative to the origin of the reference coordinate system. Therefore, different assembly directions can be switched without changing the overall kinematic model framework. It should be understood that the above examples are merely illustrative and not limiting.

[0082] In one possible embodiment, the mirror-symmetric configuration can be defined as a symmetrical spatial arrangement for the ankle joint of a bipedal robot. The pitch rotation center provides the reference for the ankle joint's swing about the pitch direction, and the roll rotation center provides the reference for the ankle joint's swing about the roll direction. Their alternating arrangement on the positive and negative z-axis ensures that the mechanism maintains the same motion direction convention and control input logic even after mirror assembly. Its function is that when the robot's left and right feet adopt the first and second configurations respectively, the control system can still use the same set of angle decomposition and drive solution methods. Coordinated movements of both ankle joints can be achieved simply by symbolic mapping or coordinate transformation of the output target, thereby reducing the cost of repetitive design of the control software. The positions and relationships are such that in the first configuration, the pitch rotation center is located on the positive z-axis of the reference coordinate system, and the roll rotation center is located on the negative z-axis. In the second configuration, the arrangement is reversed. The relative geometric relationships between the two rotation centers, the two link connection points, and the drive chain installation positions remain consistent, ensuring that the link swing angle range, crank rotation angle range, and ankle joint motion component attitude range are comparable under both configurations. This configuration is typically achieved through mirror mounting brackets, flip-up bases, or interchangeable left and right mounting plates. The brackets can be made of aluminum alloy, magnesium alloy, or high-strength steel to balance lightweight, rigidity, and durability. In another exemplary embodiment, a one-piece cast frame, a split bolted frame, or a rotatable mounting frame can also be used to form a mirror assembly interface, facilitating switching between different airframe layouts. Regarding dimensions and proportions, the key external dimensions of the two configurations are generally consistent. The distances of the pitch and roll rotation centers relative to the origin of the reference coordinate system satisfy a mirror correspondence. Furthermore, the mounting hole positions, flange reference surfaces, and connecting rod connection points of the two drive chains should remain equidistant after mirroring to avoid introducing additional eccentric loads due to different structural offsets. During the movement, after the first and second configurations receive the same type of motor angle command, the drive motor drives the ankle joint moving parts to rotate via the crank and connecting rod. If the first configuration is used, the direction of spatial attitude change corresponding to the pitch and roll motion on the positive and negative half axes of the z-axis is opposite to that of the second configuration. The control system uses a pre-established mirror mapping relationship to uniformly constrain the two, so that the moving parts can obtain the target ankle posture.

[0083] For example, still refer to Figure 1 , Figure 1 The ankle joint of the parallel bipedal robot with a separated rotation center shown is the first configuration, as... Figure 1 As shown, pitch rotation center Located on the positive z-axis of the reference coordinate system, the center of roll rotation The negative z-axis of the reference coordinate system. Accordingly, Figure 2 Another structural schematic diagram of a parallel bipedal robot ankle joint with a separated rotation center, provided as an exemplary embodiment of this application. (See diagram below.) Figure 2 As shown, the ankle joint of the parallel bipedal robot with its rotation center separated is in the second configuration, with the pitch rotation center... Located on the negative z-axis of the reference coordinate system, the center of roll rotation The positive z-axis of the reference coordinate system.

[0084] In this embodiment, the mirror symmetry configuration can meet the requirements of symmetrical assembly of the left and right feet, compact layout avoidance and modular design while ensuring the consistency of the mechanism topology and control logic. It is also conducive to improving the versatility, replaceability and engineering adaptability of the ankle joint mechanism.

[0085] The above embodiments illustrate the implementation of a parallel bipedal robot ankle joint with a separated rotation center. The following describes the application of the parallel bipedal robot ankle joint with a separated rotation center.

[0086] This application provides a bipedal robot, comprising: a robot body; a parallel bipedal robot ankle joint with a rotation center separated as in any of the above embodiments, disposed on the robot body; and a controller connected to a drive motor in the ankle joint for controlling the movement of the ankle joint.

[0087] By integrating the parallel bipedal robot's ankle joint, with its rotation center separated, into the robot body, the robot can perform combined pitch and roll posture adjustments at its feet, thus adapting to the needs of climbing slopes, traversing obstacles, and contacting uneven ground. After the controller is connected to the drive motor in the ankle joint, it can output control quantities based on gait planning results, driving the parallel mechanism to complete target posture tracking, making the ankle joint's motion response more direct. Because the ankle joint itself establishes a unified reference relationship for the rotation center-separated configuration, the controller can more easily solve the kinematics during control, thereby improving control real-time performance and posture adjustment accuracy. Therefore, this is beneficial for improving the bipedal robot's walking stability, foot landing cushioning ability, and overall motion performance in complex terrain.

[0088] Figure 3 This is a flowchart illustrating a method for controlling the ankle joint of a parallel bipedal robot with a separated rotation center, provided as an exemplary embodiment of this application. The ankle joint control method for a parallel bipedal robot with a separated rotation center provided in this embodiment is applied to the controller of the bipedal robot as described above. Figure 3 As shown, the ankle joint control method for the parallel bipedal robot with a separated rotation center includes:

[0089] S301. Obtain the target attitude angle of the ankle joint, which includes the target pitch angle and the target roll angle.

[0090] In this embodiment, the controller can communicate with the upper-level gait planning module, the body posture estimation module, and the motion task management module, and receive ankle joint posture commands corresponding to the current gait stage in each control cycle. Specifically, in the scenario of robot walking on flat ground, the upper-level gait planning module outputs the target pitch angle and the target roll angle according to the swing phase and the support phase, respectively, so that the sole of the foot is aligned with the predetermined landing point at the end of the swing and maintains the contact relationship between the sole of the foot and the ground during the support phase. In scenarios of walking uphill or downhill, crossing slopes, or crossing obstacles, the controller can also combine the posture information output by the body inertial measurement unit, the contact state fed back by the foot contact sensor, and the terrain tilt angle estimated by the environmental perception unit to correct the original posture command and generate a target posture angle suitable for the current control cycle. For example, the target posture angle can be directly output by the upper-level planning module, or it can be synthesized in real time by the controller based on the foot height, the body pitch compensation amount, and the lateral balance compensation amount, wherein the pitch angle is used to adjust the tilt state of the foot in the forward and backward direction, and the roll angle is used to adjust the tilt state of the foot in the left and right direction.

[0091] In one possible embodiment, the controller first reads the robot's current gait status word from the communication bus, identifies whether the foot with the ankle joint is in the swing phase or the support phase, and then reads the current sampling point in the corresponding attitude trajectory based on the status word to obtain the target pitch angle and target roll angle. To facilitate subsequent analytical calculations, the controller can uniformly convert the angle data into radians and simultaneously add an angle sign convention, such as setting clockwise rotation around a preset axis of the reference coordinate system as positive and counterclockwise rotation as negative, or using the opposite convention, as long as it remains consistent throughout the entire control flow. Based on the above processing, the controller obtains a set of target attitude angle data valid within the current control cycle and triggers the subsequent reading of analytical formulas.

[0092] S302. Obtain the preset analytical formula. The analytical formula is used to determine the target drive motor rotation angle based on the target attitude angle. The analytical formula is obtained by solving the kinematic constraint equation. The kinematic constraint equation is the equation between the drive motor rotation angle and the attitude angle established based on the reference coordinate system. The reference coordinate system is fixed relative to the ankle joint.

[0093] The analytical formula refers to a closed-form mathematical expression obtained by mathematically transforming and solving the kinematic constraint equations, which can directly calculate the target rotation angle of each drive motor based on the target attitude angle. This analytical formula is pre-stored in the controller's storage unit, and its derivation and storage are completed during the robot initialization phase or when the system is powered on. It can be directly read and used in each subsequent control cycle without repeating the equation establishment and solving calculations.

[0094] Specifically, the kinematic constraint equations are equations established based on a reference coordinate system to describe the geometric relationship between the drive motor rotation angle and the ankle joint attitude angle. Since the reference coordinate system is fixed relative to the ankle joint, and the pitch and roll rotation centers of the ankle joint are spatially separated, the kinematic constraint equations accurately reflect the spatial geometric relationship under the separated rotation center configuration. By performing mathematical transformations on these kinematic constraint equations (such as substituting mechanism geometric parameters, unfolding distance formulas, and rearranging trigonometric function terms), and solving them analytically (such as using auxiliary angle formulas and solving trigonometric equations), an explicit functional expression of the drive motor rotation angle with respect to the target attitude angle can be obtained, i.e., the analytical formula. The analytical formula is a closed-form expression, meaning that it only contains a finite number of basic operations (such as addition, subtraction, multiplication, division, trigonometric functions, arctangent functions, etc.) and does not include iterative loops or numerical approximation processes. Therefore, after obtaining the target attitude angle, the controller only needs to substitute the target pitch angle and the target roll angle into the analytical formula to directly calculate the corresponding target rotation angle of the drive motor. There is no need to perform complex numerical iteration solutions, which significantly reduces the calculation time of each control cycle and meets the real-time control requirements of bipedal robot high dynamic walking.

[0095] In one possible embodiment, during the initialization phase, the controller pre-establishes kinematic constraint equations based on the fixed geometric parameters of the ankle joint (such as link length, crank length, mounting offset, rotation center distance, etc.) and the definition of the reference coordinate system. The controller then solves these equations using symbolic computation or algebraic elimination methods to obtain analytical formulas. These analytical formulas are then stored in non-volatile memory in functional form or in lookup table form. During robot operation, the controller directly reads these analytical formulas from memory and performs numerical calculations within each control cycle.

[0096] In another possible embodiment, the analytical formula can also be pre-derived and converted into executable code by an offline calculation tool, and then burned into the controller's program memory. When the controller executes the control method, it directly calls this code segment to perform calculations, without needing to derive the equations or solve them online.

[0097] In yet another exemplary embodiment, the analytical formula can be pre-calculated and stored for different mechanism configurations (such as different rotation center separation distances, different link size ratios, etc.). When the mechanical configuration of the ankle joint changes, the controller can call the matching analytical formula version through a parameter switching mechanism to ensure calculation accuracy and mechanism adaptability.

[0098] Based on the above processing, the controller only needs to perform simple algebraic operations in each control cycle to complete the inverse kinematics solution, thus providing a computational basis for the real-time output of high-frequency control commands.

[0099] S303. Determine the target drive motor rotation angle corresponding to the target pitch angle and target roll angle according to the analytical formula, and send control commands to the corresponding drive motor to drive the ankle joint to move to the target posture.

[0100] In this embodiment, the controller uses the target pitch angle and target roll angle obtained in step S301 as input variables, substitutes them into the analytical formula obtained in step S302, and performs numerical calculations to obtain the target drive motor rotation angle corresponding to the current target attitude angle. The target drive motor rotation angle refers to the angle value that the upper drive motor and the lower drive motor need to rotate to, which directly reflects the motor position command required to make the ankle joint reach the desired attitude within the current control cycle.

[0101] Specifically, since the analytical formula already includes the ankle joint's geometric parameters (such as link length, crank length, mounting offset, rotation center position, etc.) and the definition of the reference coordinate system, the controller only needs to substitute the specific values ​​of the target pitch angle and the target roll angle into the formula to calculate the target rotation angles of the upper and lower drive motors respectively. This calculation process does not involve iterative approximation or numerical convergence judgment, and the calculation speed is fast and the result is uniquely determined.

[0102] After calculating the target rotation angle of the drive motor, the controller converts the calculation result into an executable instruction format for the drive motor and sends it to the corresponding motor driver via a communication interface such as EtherCAT, Controller Area Network (CAN) bus, or a dedicated drive interface. Upon receiving the instruction, the drive motor executes rotational motion according to the target rotation angle, transmitting the motion to the ankle joint moving parts via the crank and connecting rod, driving the ankle joint to move to the target posture.

[0103] In one possible embodiment, before sending control commands, the controller can also perform a validity check on the calculated target drive motor angle (e.g., whether it exceeds the motor's allowable rotation range, whether it is close to the mechanical limit, etc.), and perform limiting or correction processing if necessary to protect the mechanism's safety. In another possible embodiment, the controller can smooth and filter the target drive motor angle sequence over multiple control cycles to avoid motor speed shocks caused by sudden changes in posture commands, thereby improving the smoothness of ankle joint movement and dynamic response quality.

[0104] Based on the above steps, the controller completes the mapping from posture commands to motor commands within each control cycle, enabling the ankle joint to follow the target posture planned by the upper layer in real time, achieving high-precision motion control. Because analytical formulas are used for direct calculation, the computational delay throughout the process is extremely short, thus meeting the millisecond or even sub-millisecond real-time control requirements during bipedal robot walking.

[0105] The ankle joint control method for a parallel bipedal robot with a separated rotation center provided in this application obtains the target posture angle of the ankle joint and a preset analytical formula. Based on the analytical formula, the target drive motor rotation angle corresponding to the target posture angle is determined and a control command is sent. Since the analytical formula does not require iterative calculation, only a finite number of algebraic operations are needed to complete the inverse kinematics solution in each control cycle, significantly reducing the calculation time of a single control cycle. This meets the requirements of high-dynamic bipedal robot walking for millisecond or even sub-millisecond real-time control. At the same time, since the reference coordinate system is fixed relative to the ankle joint, the establishment of kinematic constraint equations and analytical formulas does not depend on the ideal assumption of "coincidence of rotation centers". It can be directly applied to the actual parallel mechanism configuration with separated pitch and roll rotation centers, thus effectively overcoming the technical defects of poor versatility of existing analytical methods and insufficient real-time performance of numerical iterative methods. It takes into account both model versatility and real-time solution performance, thereby providing a reliable technical foundation for accurate and stable control of the bipedal robot ankle joint in high-frequency control cycles.

[0106] In some embodiments, the first drive chain and the second drive chain in the ankle joint are the upper drive chain and the lower drive chain, respectively. The kinematic constraint equations are determined as follows: based on a reference coordinate system, the coordinates of the first connection point between the link in the upper drive chain and the ankle joint moving part in the ankle joint, and the coordinates of the second connection point between the link in the lower drive chain and the ankle joint moving part are determined respectively. Based on the determined coordinates of the first and second connection points, and according to the constraint that the link lengths in the upper and lower drive chains remain unchanged, the first geometric relationship between the drive motor rotation angle and the attitude angle in the upper drive chain, and the second geometric relationship between the drive motor rotation angle and the attitude angle in the lower drive chain are established respectively, as the kinematic constraint equations.

[0107] For example, Figure 4 A schematic projection of the pitch of the ankle joint (first configuration) of a parallel bipedal robot with a separated rotation center, provided as an exemplary embodiment of this application, onto the XZ plane. (See reference) Figure 4 To analyze ankle joint pitch motion, the pitch rotation angle is defined as... Its center of rotation is the pitch rotation center. The geometric dimensions defined according to the above embodiments. and The driving point can be determined. To the pitch rotation center The constant distance is In the initial configuration, connect the lines. With axis The included angle is The constant The relationship indicates that the driving point In pitch motion, the center of rotation is the pitch rotation. Center of the circle The geometric constraint of making circular motion with a radius simplifies the calculation of inverse kinematics and helps to achieve decoupled control of motion in the pitch direction.

[0108] For example, Figure 5 A schematic diagram of the projection of the ankle joint (first configuration) roll of a parallel bipedal robot with a separated rotation center, provided as an exemplary embodiment of this application, onto the YZ plane. (See reference) Figure 5 To analyze the ankle joint roll motion, its rotation around the x-axis (passing through...) is defined. The rotation angle of point () is ;point and Projection point on the y-axis , y coordinate ( ) Changes constitute the driving input for the roll motion. Accordingly, based on the symmetrical design presented in the figure, under the initial configuration, there are... This allows us to determine two key geometric constraints: the projection point. To the center of tumbling rotation The distance is constant Initial angle The constant Relationships and pitch movement The relationship is symmetrical in form, forming the design basis for achieving a geometrical decoupling between ankle joint pitch and roll movements; the roll movement ultimately passes through the coordinates of the projection point. , The changes are driven by the upper and lower connecting rods, which in turn drive the drive motors. Drive motor accomplish.

[0109] Accordingly, based on Figure 1 , Figure 4 and Figure 5 The ankle joint geometry shown is used to define the following kinematic relationships for joint control and position calculation. Specifically, based on the fixed geometric dimensions of the ankle joint, the following four intermediate constants are first defined: 1) the initial angle related to the roll motion. ;2) Initial angle related to pitch motion 3) Constant radius in pitch motion ;4) Constant radius in roll motion Among them, the dimensional parameters , , , Definition and Figure 1 Consistent.

[0110] In some embodiments, determining the coordinates of the first connection point between the link in the upper drive chain and the ankle joint moving component in the ankle joint, and the coordinates of the second connection point between the link in the lower drive chain and the ankle joint moving component, includes: determining the coordinates of the first connection point and the second connection point along the x-axis of the reference coordinate system based on the target pitch angle; determining the coordinates of the first connection point and the second connection point along the y-axis of the reference coordinate system based on the target roll angle; and determining the coordinates of the first connection point and the second connection point along the z-axis of the reference coordinate system based on the target pitch angle and the target roll angle.

[0111] For example, based on the constraint that the link length remains constant, the coordinates of each key point in the reference coordinate system can be derived from the target attitude angle. (pitch) (roll) and target drive motor rotation angle , Calculations show that That is, the target pitch angle. This is the target roll angle. Specifically, the crank end point in the upper drive chain... The coordinates satisfy the following formula: , , The first connection point between the connecting rod in the upper drive chain and the ankle joint moving parts. The coordinates satisfy the following formula: , , Crank end in the lower drive chain The coordinates satisfy the following formula: , , The second connection point between the link in the lower drive chain and the ankle joint moving parts. The coordinates satisfy the following formula: , , .

[0112] Correspondingly, based on the determined coordinates of the first and second connection points, and according to the constraint that the link lengths in the upper and lower drive chains remain unchanged ( , Establish kinematic constraint equations, specifically as follows:

[0113]

[0114]

[0115] Accordingly, in order to achieve precise control of the ankle joint, it is necessary to determine the desired joint angle and the target posture angle. The input angles of the two drive motors, i.e., the rotation angle of the target drive motor, are obtained by inverse solving. .

[0116] In this embodiment, by modeling the upper and lower drive chains separately, a clear mapping can be established between the spatial posture of the ankle joint moving parts and the rotation angles of the two drive motors, enabling the controller to stably solve the target drive motor rotation angle and output control commands. Due to the use of a fixed reference coordinate system and fixed-length constraints, the model has good uniformity and reusability, which is beneficial for improving the efficiency of inverse kinematics solving and reducing the modeling complexity under different mechanism layouts.

[0117] In some embodiments, solving the kinematic constraint equations includes: constructing a first trigonometric equation for the rotation angle of the drive motor in the upper drive chain based on a first geometric relationship; constructing a second trigonometric equation for the rotation angle of the drive motor in the lower drive chain based on a second geometric relationship; and solving the first and second trigonometric equations analytically to obtain analytical formulas for the rotation angles of the drive motors in the upper and lower drive chains with respect to their respective attitude angles.

[0118] For example, based on constraints respectively , Construct and solve for about and The trigonometric equation. Specifically, for the drive motor. Target drive motor rotation angle Its solution equation is determined by constraints. Ultimately, this boils down to solving trigonometric equations of the following form:

[0119]

[0120] Among them, coefficient Uniquely determined by the target state of the ankle joint and known geometric parameters: , , ;definition Correspondingly, the general solution to the first trigonometric equation is: .

[0121] Accordingly, for the drive motor Target drive motor rotation angle Its solution process is the same as Symmetry, based on constraints We obtain the trigonometric equation:

[0122]

[0123] The coefficient is defined as follows: , , ;definition Correspondingly, the general solution to the second trigonometric equation is: .

[0124] In some embodiments, the analytical solution of the first trigonometric equation and the second trigonometric equation is further included: based on the actual assembly structure of the parallel crank-connecting rod mechanism in the ankle joint, a unique physically feasible solution is selected from the general mathematical solution of the first trigonometric equation as the analytical formula for the rotation angle of the drive motor in the upper drive chain; based on the actual assembly structure of the parallel crank-connecting rod mechanism, a unique physically feasible solution is selected from the general mathematical solution of the second trigonometric equation as the analytical formula for the rotation angle of the drive motor in the lower drive chain.

[0125] Among them, the general mathematical solution is used to represent all candidate solutions obtained after analyzing the trigonometric equations, and the physical feasible solution is used to represent the only valid solution that satisfies the requirements of link length, installation offset, rotation direction constraint and assembly interference.

[0126] Specifically, considering the actual mechanical configuration of the ankle joint and the linkage assembly relationship, the drive motor... Target drive motor rotation angle The physically feasible solution is selected from the general mathematical solution of the first trigonometric equation, and its expression is: For drive motors Target drive motor rotation angle The physically feasible solution can be selected from the general mathematical solution of the second trigonometric equation, and its expression is: .

[0127] In this embodiment, by constructing first and second trigonometric equations regarding the rotation angles of the drive motors in the upper and lower drive chains based on first and second geometric relationships, respectively, and analytically solving these equations, the complex inverse kinematics problem can be transformed into standard trigonometric equations, allowing for direct solution using analytical methods and reducing computational delays caused by numerical iterations. Furthermore, by selecting a unique physically feasible solution from the general mathematical solution of the trigonometric equations based on the actual assembly structure of the parallel crank-connecting rod mechanism, the ambiguity caused by multiple solutions to the trigonometric equations can be effectively resolved. This ensures that the motor rotation angle output by the analytical formula is consistent with the actual motion state of the mechanism, reducing the likelihood of invalid motor commands or abnormal mechanism motion due to incorrect solution selection. Simultaneously, the selection of the physically feasible solution is predetermined in the analytical formula. Subsequent control cycles do not require online judgment or iterative filtering; the unique effective motor rotation angle can be calculated directly by substituting the target attitude angle. This further improves the real-time performance of control while ensuring the uniqueness of the solution, providing a reliable guarantee for high-precision and high-stability control of the ankle joint of a bipedal robot during high-dynamic walking.

[0128] Based on the above embodiments, in some embodiments, after determining the target drive motor rotation angle corresponding to the target pitch angle and the target roll angle according to the analytical formula, the method further includes: normalizing the target drive motor rotation angle to a preset control angle range to obtain a normalized angle value; and generating a control command based on the normalized angle value.

[0129] The control angle range is used to limit the effective control range of the drive motor angle after normalization, so that the controller can uniformly map angles of different amplitudes into standardized data; the normalized angle value is used to represent the result of the original drive motor angle after range mapping, and serves as the direct input for the generation of subsequent control commands; the control command is used to convert the angle value into command data that can drive the corresponding drive motor to perform motion.

[0130] For example, the calculated angle value , Normalization to intervals, such as Within this range, a normalized angle value is obtained for easier processing. This angle value is then converted into a pulse quantity, position loop target value, or bus message data corresponding to the first or second drive chain, and sent to the corresponding drive motor to make the ankle joint moving parts run according to the target posture. In practical applications, the control angle range and control command format can also be adjusted according to the drive motor model, driver protocol, and mechanism assembly relationship. This application embodiment does not limit this.

[0131] In this embodiment of the application, by normalizing the motor rotation angle obtained from the analysis before generating control commands, the control data can be kept within a uniform effective range, reducing the impact of angle out-of-bounds on the driver input, improving the consistency and portability of control commands under different configurations, and helping to improve the response stability and posture tracking accuracy of the ankle joint in the high-frequency control process.

[0132] In some embodiments, after sending control commands to the corresponding drive motor, the method further includes: receiving the actual rotation angle fed back by the drive motor through the encoder; comparing the actual rotation angle with the target drive motor rotation angle to determine the angle deviation; and performing closed-loop adjustment of the drive motor based on the angle deviation to correct the ankle joint's movement posture.

[0133] The encoder is used to provide feedback on the actual rotation state of the drive motor, and its feedback value corresponds to the actual rotation angle. The actual rotation angle is used to characterize the angular position information after the actual output of the motor. The angle deviation is used to represent the difference between the actual rotation angle and the target drive motor rotation angle. The closed-loop adjustment is used to correct the motor output based on this difference, thereby compensating for ankle joint movement errors.

[0134] In actual control, after sending control commands to the drive motors of the first or second drive chain, the controller continuously reads the angle signal output by the encoder and compares it with the target drive motor rotation angle obtained by the analytical formula to form an error signal. Based on this error signal, the controller updates the motor compensation amount, using one or more adjustment methods such as proportional, integral, and derivative, to gradually bring the drive motor output closer to the target angle, thereby driving the crank and connecting rod to correct the posture of the ankle joint moving parts. The encoder can be set as an incremental encoder or an absolute encoder to improve the real-time performance and anti-interference capability of the angle feedback. In practical applications, other models of this component can also be selected, and this application embodiment does not limit this.

[0135] This closed-loop control method ensures that the actual rotation angle of the drive motor is consistent with or nearly consistent with the target rotation angle. The controller then dynamically corrects the motor output accordingly, thereby suppressing the effects of mechanical backlash, load fluctuations, and assembly errors on the ankle joint posture. This approach improves the ankle joint's angle tracking accuracy and motion stability, reduces the deviation between the target posture and the actual posture, and helps enhance the reliability of bipedal robots in footing cushioning, terrain adaptation, and dynamic balance control.

[0136] Based on the above embodiments, in some embodiments, when determining the target drive motor rotation angle corresponding to the target pitch angle and target roll angle according to the analytical formula, the following method is used to adapt to different joint configurations: A first preset angle and a second preset angle are obtained; wherein, the first preset angle is the arctangent of the ratio of the crank length of the drive motor to the distance from the pitch rotation center to the coordinate origin; the second preset angle is the arctangent of the ratio of the installation offset of the drive motor to the distance from the roll rotation center to the coordinate origin; when the ankle joint is in the first configuration, the target pitch angle and target roll angle are directly substituted into the analytical formula. The target drive motor rotation angle is obtained; when the ankle joint is a second configuration that is mirror-symmetrical to the first configuration, the angle terms in the analytical formula are replaced with signs, and the target pitch angle and the target roll angle are substituted into the analytical formula after the sign replacement to obtain the target drive motor rotation angle; wherein, the sign replacement includes: replacing the sum of the pitch angle and the first preset angle with the difference between the pitch angle and the first preset angle in the attitude angle; replacing the difference between the roll angle and the second preset angle in the attitude angle with the sum of the roll angle and the second preset angle; replacing the sum of the roll angle and the second preset angle with the difference between the roll angle and the second preset angle.

[0137] For example, Figure 6 A schematic projection of the pitch of the ankle joint (second configuration) of a parallel bipedal robot with a separated rotation center, provided as an exemplary embodiment of this application, onto the XZ plane. (See reference) Figure 6 The pitch motion projection relationship in this embodiment is related to Figure 4 (First configuration) is mirror symmetric, and the core geometric constraints (such as the radius of circular motion) remain unchanged. However, due to changes in the position of the rotation center and the direction of the coordinate system, the analysis and adjustment of the coordinate component expressions and the signs of the angle relationship terms are as follows:

[0138] 1) The motion characteristics of the circular arc remain unchanged: with Figure 4 Similarly, point (i.e., line segment) The midpoint of the pitch axis is the center of rotation about the pitch axis (i.e., the pitch rotation center). It moves in a circular arc, with the radius remaining the same. ( for To the origin distance, for To the origin The x-direction distance is consistent with the dimension definition in the first configuration); 2) The initial included angle definition logic is consistent: under the initial configuration, the connecting lines With axis The included angle is still ( For acute angles, only the direction is affected. (3) The position changes and reverses); Reverse the position: such as Figure 6 As shown, since the z-axis direction of the coordinate system of the first configuration is... ( (at the positive z-axis), pitch rotation center Located on the negative z-axis (coordinate is Therefore, in the projection onto the XZ plane, Point from Figure 4 The positive z-axis ( ) becomes the negative half-axis of the z-axis ( ); 4) Angle relationship terms from " "becomes " In the initial configuration, Figure 4 middle Located on the axis "Front and lower" (with) (Since the rotation directions are the same), the angles are superimposed as follows: ,and Figure 6 middle The point is located on the negative z-axis. The initial position is located on the axis. "Above and in front" (and) (rotation direction reversed), therefore the angular relationship is adjusted to... ( (Direction reversed, canceled out by minus sign); 5) The x-coordinate formula is corrected to: Considering the first configuration, (The negative sign indicates the negative x-direction). In this embodiment, the angle term becomes " "Initial configuration (Since the negative x-direction sign is already included), the formula simplifies to: (No extra negative sign needed, directly obtain the negative x-coordinate, as in the initial configuration) When =0, ,and The point is at the origin. (The negative x-direction is consistent); 6) Adjust the sign of the z-coordinate components (" "becomes " "): In the first configuration The z-coordinate of the point is ( exist (the negative z-direction, with negative projection) In this embodiment On the negative z-axis, lie in The positive z-direction (above). arrive Since the z-axis projection is positive, the z-coordinate formula is adjusted to: (“ "for z-coordinate, "for arrive The z-axis orthographic projection, such as the initial configuration When =0, ,and The definition is consistent on the x-axis (Z=0).

[0139] Accordingly, Figure 7 A schematic diagram of the projection of the ankle joint (second configuration) roll of a parallel bipedal robot with a separated rotation center, provided as an exemplary embodiment of this application, onto the YZ plane. (See reference) Figure 7 The roll motion projection relationship in this embodiment is related to Figure 5 (First configuration) is mirror symmetric, with core geometric constraints (such as the radius of circular motion) remaining unchanged. However, due to changes in the position of the rotation center and the direction of the coordinate system, the analysis and adjustment of the coordinate component expressions and the signs of the angle relationships are as follows: 1) The characteristics of circular motion remain unchanged: with Figure 5 similar, , Point (end of the roll shaft drive rod) around the roll rotation center (i.e., the tumbling rotation center) It moves in a circular arc, with the radius remaining the same. ( for To the origin distance, for To the origin The y-direction distance is consistent with the first configuration dimension definition); 2) The initial included angle definition logic is consistent: under the initial configuration, the connecting lines , With axis The included angle is still ( For acute angles, only the direction is affected. 3) The position changes and the rotation is reversed; Position reversal and " "Take the negative": such as Figure 7 As shown, because the z-axis direction of the second configuration coordinate system is ( (at the positive z-axis), the center of tumbling rotation The actual coordinates are (Right now Using a negative sign in the coordinate formula reflects the center of rotation during tumbling. Relative to the origin (The z-axis position is reversed), therefore, in the YZ plane projection, the center of tumbling rotation is... from Figure 5 The positive z-axis ( ) becomes the negative half-axis of the z-axis ( ); ); 4) Angle relationship items: and The included angle is " " and The included angle is " ": In the initial configuration, Figure 5 middle lie in "Front and lower" of the axis (and) (Rotation direction is the same), with an included angle of 1 / 2. ;and Figure 7 Center of tumbling rotation After the position is reversed, The initial position is located at "Above the front" of the axis (and) (Rotation direction reversed), therefore the included angle relationship is adjusted to ( (This is the rotation angle of the roll axis, superimposed on the α direction); similarly, and The angle between the axes is from Figure 5 of" "Adjusted to " ",make sure , Geometric constraints regarding y-axis symmetry; 5) Formula for y-coordinate: Pick" " Pick" In the first configuration, The y-coordinate is In this embodiment, the included angle becomes " "Initial configuration When =0, Therefore The formula for the y-coordinate is (Directly reflects the positive y-direction, such as in the initial configuration) ,and At the origin The positive y-direction is the same, and similarly, Located in the negative y-direction, its y-coordinate formula is: (No extra minus sign needed, because) When the initial configuration is a negative angle, the sine value is negative, directly reflecting the negative y-direction, such as the initial configuration. When =0, ,and At the origin (The negative y-direction is consistent); 6) The z-coordinate formula is uniformly adjusted to " ": In the first configuration, the center of tumbling rotation" On the positive z-axis (coordinate) ), Located at the center of tumbling rotation The negative z-direction, the z-coordinate is In this embodiment, the center of tumbling rotation On the negative z-axis (coordinate) ), , All are located at the center of tumbling rotation. Since the z-direction is positive (upward), and the projection of the z-direction is positive, the z-coordinate formula is uniformly adjusted to: , (Initial configuration) When =0, , ,and , Passing through the origin The definition on the y-axis (Z=0) is consistent.

[0140] Accordingly, based on Figure 2 , Figure 6 and Figure 7 Geometric constraints, key coordinate points of the ankle joint ( , , , The kinematic expression is as follows:

[0141] upper drive chain crank end The coordinates satisfy the following formula:

[0142]

[0143] The first connection point between the link in the upper drive chain and the ankle joint moving parts The coordinates satisfy the following formula:

[0144]

[0145] Crank end in the lower drive chain The coordinates satisfy the following formula:

[0146]

[0147] The second connection point between the link in the lower drive chain and the ankle joint moving parts The coordinates satisfy the following formula:

[0148]

[0149] Considering that the two joint configurations mentioned above are mirror-symmetric, the difference in their kinematic relationship is only caused by the reversal of the position of the rotation center. The specific symmetry principle and parameter substitution rules are as follows: 1) The essence of symmetry is the reversal of the position of the rotation center: The core difference between the two joint configurations lies in the reversal of the z-axis position of the pitch / roll rotation center. Among them, the pitch rotation center of the first configuration is... Located on the positive z-axis (coordinate is ), Tumbling Rotation Center Located on the negative z-axis (coordinate is ); Pitch rotation center of the second configuration Located on the negative z-axis (coordinate is ), Tumbling Rotation Center Located on the positive z-axis (coordinate is This reversal results in a systematic adjustment of the coordinate projection direction, angle term direction, and parameter signs, but the joint topology and drive chain constraints (such as fixed drive chain length) remain unchanged. For example, Table 1 provides an example of the parameter and angle term substitution rules provided in an exemplary embodiment of this application.

[0150]

[0151] As shown in Table 1, the kinematic formula of the second configuration can be directly obtained from the kinematic formula of the first configuration by using the above substitution rules, and vice versa.

[0152] For example, in the first configuration The x-coordinate is According to the replacement rules Replace with ,Will Replace with ,get:

[0153]

[0154] As can be seen, the result obtained by replacing the rules The x-coordinate and the second configuration The x-coordinate expression is completely consistent, thus verifying the correctness of the replacement rule.

[0155] Correspondingly, although the coordinate expressions for the two joint configurations differ in sign due to symmetry, the form of the inverse kinematics formula remains unchanged. The core of the inverse kinematics solution is based on the constraint of "fixed drive chain length". , Establish the equation, specifically as follows:

[0156]

[0157]

[0158] Correspondingly, regardless of whether it is the first configuration or the second configuration, the solution logic remains the same: both are solved by substituting coordinate expressions, expanding equations, and eliminating variables. Then substitute back to solve The solution steps are exactly the same, only the parameter signs are adjusted. Specifically, the coefficients in the inverse solution formula (such as...) ) and angle items (such as , The formulas need to be adjusted according to the replacement rules in Table 1 above, while the formula structure (such as trigonometric equation form and addition / subtraction relationship) remains unchanged.

[0159] In this embodiment, a first preset angle and a second preset angle are obtained, and differentiated processing is performed according to the configuration type of the ankle joint: when the ankle joint is in the first configuration, the analytical formula is directly substituted; when the ankle joint is in the mirror-symmetric second configuration, the angle terms in the analytical formula are replaced with signs before being substituted into the calculation. This approach achieves design reusability, that is, the second configuration can be directly derived from the kinematic model of the first configuration by replacing the symmetric parameters, without the need for remodeling and derivation, significantly reducing the workload of repetitive development; at the same time, it achieves unified control algorithm, that is, the form of the analytical formula remains unchanged, and only the parameter signs need to be switched to adapt to the two mirror-symmetric configurations, which greatly simplifies the development and maintenance of the controller and effectively reduces the software version management cost; in addition, it ensures kinematic consistency, that is, mirror symmetry ensures that the range of motion and singular point distribution of the two configurations are completely symmetrical, improving the flexibility and engineering adaptability of joint design, and enabling the same set of control algorithms to be seamlessly applied to robot ankle joints with different mechanical layouts.

[0160] Furthermore, based on the above embodiments, the correctness and effectiveness of the above inverse kinematics solution scheme were verified. For example, when the ankle joint of the parallel bipedal robot is in the first configuration, the corresponding Embodiment 1 is as follows:

[0161] First, set the system parameters. For example, the mechanical dimensions of the decoupled ankle joint are set as follows: length of the upper drive chain link. mm, length of lower drive chain link mm, crank length mm, lateral mounting offset mm, ankle joint pitch axis rotation center offset mm, ankle joint roll axis rotation center offset mm; Set the target pose angle of the ankle joint, i.e., the rotation angle around the pitch axis. Rotation angle around the roll axis .

[0162] II. Calculate the intermediate constants and the target point coordinates. Specifically, based on the aforementioned formula, the intermediate constants are calculated as follows: rad, rad, mm, mm; then the ankle joint connection point under the target configuration is calculated. and Key coordinate components: mm, mm, mm, mm.

[0163] Third, perform inverse kinematics calculations, substituting the above parameters and target coordinates into the inverse kinematics formula to calculate the target drive motor rotation angle. The solution specifically includes: 1) Calculating the coefficients: , , , ;2) According to the formula Solving for rad (i.e.) ). Targeting the rotation angle of the drive motor The solution specifically includes: 1) Calculating the coefficients: , , , ;2) According to the formula Solving for rad (i.e.) ).

[0164] In summary, this embodiment 1 demonstrates that when it is desired to achieve ankle joint... and During the combined motion, the inverse kinematics solution scheme disclosed in this application can uniquely and definitively calculate the corresponding target drive motor rotation angle. and The results verify the correctness of the inverse kinematic model and formula, as well as the feasibility and effectiveness of the above control method, which can accurately map high-level joint space commands to low-level motor drive commands.

[0165] Accordingly, when the ankle joint of the parallel bipedal robot is in the second configuration, the corresponding embodiment 2 is as follows:

[0166] First, the system parameters are set. For example, the mechanical dimensions of the decoupled ankle joint are completely consistent with those of Embodiment 1 above (reflecting the reusability of the symmetrical design): the length of the upper drive chain link. mm, length of lower drive chain link mm, motor crank length mm, lateral mounting offset mm, ankle joint pitch axis rotation center offset mm, ankle joint roll axis rotation center offset mm; The target posture angle of the ankle joint is set to be the same as in Example 1, that is, the rotation angle around the pitch axis. Rotation angle around the roll axis .

[0167] II. Calculate the intermediate constants and target point coordinates. Specifically, based on the kinematic relationships and trigonometric function values ​​of the second configuration, the intermediate constants are calculated as follows:

[0168]

[0169]

[0170] mm

[0171] mm

[0172] Trigonometric function values ​​for angle terms: rad, , ; rad, , ; rad, , .

[0173] Then, the ankle joint connection point under the target configuration is calculated. and The coordinates, specifically:

[0174]

[0175]

[0176]

[0177]

[0178]

[0179]

[0180] Among them, due to the symmetry of the pitch axis x-axis projection, x-axis coordinates and Their x-axis coordinates are the same.

[0181] Third, perform inverse kinematics calculations, substituting the above parameters and target coordinates into the inverse kinematics formula to calculate the target drive motor rotation angle. The solution specifically includes: based on the driving chain length constraint mm, The coordinate formula is:

[0182]

[0183] Substitution coordinate( mm, mm, mm), unfolding distance formula:

[0184]

[0185] Substituting and rearranging, we get:

[0186]

[0187] After simplification, we get about The equation:

[0188]

[0189] Solving using the trigonometric auxiliary angle method, we get: .

[0190] Accordingly, for the target drive motor rotation angle The solution specifically includes: based on the driving chain length constraint mm, The coordinate formula is:

[0191]

[0192] Substitution coordinate( mm, mm, mm), unfolding distance formula:

[0193]

[0194] Substituting and rearranging, we get:

[0195]

[0196] After simplification, we get about The equation:

[0197]

[0198] Solving using the trigonometric auxiliary angle method, we get: .

[0199] In summary, this embodiment 2 demonstrates that when it is desired to achieve ankle joint... and During the combined motion, the inverse kinematics solution scheme disclosed in this application can uniquely and definitively calculate the corresponding drive motor control command. and The results verify the correctness of the inverse kinematic model and formula, as well as the feasibility and effectiveness of the control method, which can accurately map high-level joint space commands to low-level motor drive commands.

[0200] The following are embodiments of the apparatus described in this application, which can be used to execute the embodiments of the method described in this application. For details not disclosed in the apparatus embodiments of this application, please refer to the embodiments of the method described in this application.

[0201] Figure 8 This is a schematic diagram of a parallel bipedal robot ankle joint control device with a separated rotation center, provided as an exemplary embodiment of this application. The ankle joint control device with a separated rotation center provided in this embodiment is applied to the controller of the bipedal robot as described above. Figure 8 As shown, the parallel bipedal robot ankle joint control device 80 with a separated rotation center includes an attitude acquisition module 81, a processing module 82, and a control module 83, wherein:

[0202] The attitude acquisition module 81 is used to acquire the target attitude angle of the ankle joint, which includes the target pitch angle and the target roll angle.

[0203] Processing module 82 is used to obtain a preset analytical formula, which is used to determine the target drive motor rotation angle based on the target attitude angle. The analytical formula is obtained by solving the kinematic constraint equation, which is an equation between the drive motor rotation angle and the attitude angle established based on the reference coordinate system, which is fixed relative to the ankle joint.

[0204] The control module 83 is used to determine the target drive motor rotation angle corresponding to the target attitude angle according to the analytical formula, and send control commands to the corresponding drive motor to drive the ankle joint to move to the target attitude.

[0205] In one possible implementation, the first drive chain and the second drive chain in the ankle joint are the upper drive chain and the lower drive chain, respectively. The processing module 82 can be specifically used to: determine the coordinates of the first connection point between the link in the upper drive chain and the ankle joint moving part in the ankle joint, and the coordinates of the second connection point between the link in the lower drive chain and the ankle joint moving part, respectively, according to the reference coordinate system; based on the determined coordinates of the first connection point and the second connection point, and according to the constraint that the length of the link in the upper drive chain remains unchanged, establish the first geometric relationship between the rotation angle of the drive motor in the upper drive chain and the attitude angle, and the second geometric relationship between the rotation angle of the drive motor in the lower drive chain and the attitude angle, respectively, as kinematic constraint equations.

[0206] In one possible implementation, the processing module 82 can also be used to: determine the coordinates of the first connection point and the second connection point along the x-axis of the reference coordinate system according to the target pitch angle; determine the coordinates of the first connection point and the second connection point along the y-axis of the reference coordinate system according to the target roll angle; and determine the coordinates of the first connection point and the second connection point along the z-axis of the reference coordinate system according to the target pitch angle and the target roll angle.

[0207] In one possible implementation, the processing module 82 can also be used to: construct a first trigonometric equation for the rotation angle of the drive motor in the upper drive chain based on a first geometric relationship; construct a second trigonometric equation for the rotation angle of the drive motor in the lower drive chain based on a second geometric relationship; and perform analytical solutions on the first and second trigonometric equations respectively to obtain analytical formulas for the rotation angles of the drive motor in the upper and lower drive chains with respect to the attitude angle.

[0208] In one possible implementation, the processing module 82 can also be used to: select a unique physically feasible solution from the general mathematical solution of the first trigonometric equation as the analytical formula for the rotation angle of the drive motor in the upper drive chain, based on the actual assembly structure of the parallel crank-connecting rod mechanism in the ankle joint; and select a unique physically feasible solution from the general mathematical solution of the second trigonometric equation as the analytical formula for the rotation angle of the drive motor in the lower drive chain, based on the actual assembly structure of the parallel crank-connecting rod mechanism.

[0209] In one possible implementation, the control module 83 can be specifically used to: obtain a first preset angle and a second preset angle; wherein, the first preset angle is the arctangent of the ratio of the crank length of the drive motor to the distance from the pitch rotation center to the origin of the coordinate system; the second preset angle is the arctangent of the ratio of the installation offset of the drive motor to the distance from the roll rotation center to the origin of the coordinate system; when the ankle joint is in the first configuration, the target pitch angle and the target roll angle are directly substituted into the analytical formula to obtain the target drive motor angle; when the ankle joint is in the second configuration that is mirror-symmetrical to the first configuration, the angle terms in the analytical formula are replaced with signs, and the target pitch angle and the target roll angle are substituted into the analytical formula after the sign replacement to obtain the target drive motor angle; wherein, the sign replacement includes: replacing the sum of the pitch angle and the first preset angle with the difference between the pitch angle and the first preset angle in the attitude angle; replacing the difference between the roll angle and the second preset angle in the attitude angle with the sum of the roll angle and the second preset angle; and replacing the sum of the roll angle and the second preset angle with the difference between the roll angle and the second preset angle.

[0210] In one possible implementation, the control module 83 can also be used to: normalize the target drive motor angle to a preset control angle range to obtain a normalized angle value; and generate a control command based on the normalized angle value.

[0211] In one possible implementation, the control module 83 can also be used to: receive the actual rotation angle fed back by the drive motor through the encoder; compare the actual rotation angle with the target drive motor rotation angle to determine the angle deviation; and perform closed-loop adjustment of the drive motor according to the angle deviation to correct the movement posture of the ankle joint.

[0212] The ankle joint control device for parallel bipedal robot with rotation center separation provided in this application embodiment can execute the technical solution shown in the above embodiment of the ankle joint control method for parallel bipedal robot with rotation center separation. Its implementation principle and beneficial effects are similar, and will not be repeated here.

[0213] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily essential to this application.

[0214] It should be further noted that although the steps in the flowchart are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowchart may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0215] It should be noted that the above-described device embodiments are merely illustrative, and the device of this application can also be implemented in other ways; and it should be understood that the division of the various modules of the above device is only a logical functional division, and in actual implementation, they can be fully or partially integrated into a single physical entity, or they can be physically separated. Furthermore, these modules can all be implemented in software through processing element calls; they can all be implemented in hardware; or some modules can be implemented by processing element calls to software, and some modules can be implemented in hardware. For example, a processing module can be a separately established processing element, or it can be integrated into a chip of the above device. Alternatively, it can be stored as program code in the memory of the above device, and its functions can be called and executed by a processing element of the above device. The implementation of other modules is similar. In addition, these modules can be fully or partially integrated together, or they can be implemented independently. The processing element here can be an integrated circuit with signal processing capabilities. In the implementation process, each step of the above method or each of the above modules can be completed by the integrated logic circuit in the hardware of the processor element or by software instructions.

[0216] For example, these modules can be one or more integrated circuits configured to implement the above methods, such as one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), or one or more Field Programmable Gate Arrays (FPGAs). As another example, when a module is implemented using processing element scheduler code, the processing element can be a general-purpose processor, such as a Central Processing Unit (CPU) or other processor capable of calling program code. Furthermore, these modules can be integrated together as a System-On-a-Chip (SOC).

[0217] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available media can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., Digital Video Discs, DVDs), or semiconductor media (e.g., solid-state disks (SSDs)).

[0218] Figure 9 A schematic diagram of the controller provided for an exemplary embodiment of this application. (See attached diagram.) Figure 9 As shown, the controller 90 in this embodiment includes:

[0219] At least one processor 91; and a memory 92 communicatively connected to the at least one processor;

[0220] The memory 92 stores instructions that can be executed by at least one processor 91 to cause the controller to perform the method as described in any of the above embodiments.

[0221] Alternatively, the memory 92 can be either standalone or integrated with the processor 91.

[0222] The memory 92 may include high-speed random access memory (RAM) and may also include non-volatile memory, such as at least one disk storage device.

[0223] The processor 91 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application. Specifically, in implementing the ankle joint control method for a parallel bipedal robot with a separated rotation center as described in the foregoing method embodiments, the controller may be, for example, an electronic device with processing capabilities such as a server.

[0224] Optionally, the controller may also include a communication interface 93. In specific implementations, if the communication interface 93, memory 92, and processor 91 are implemented independently, they can be interconnected via a bus to communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc., but this does not imply that there is only one bus or one type of bus.

[0225] Optionally, in a specific implementation, if the communication interface 93, memory 92, and processor 91 are integrated on a single chip, then the communication interface 93, memory 92, and processor 91 can communicate through an internal interface.

[0226] Accordingly, based on the above controller structure, during specific operation, the processor 91 loads the kinematic model parameters and control program from the memory 92, combines them with the intermediate data in memory, and determines the target attitude angle according to the upper-level plan. The inverse kinematics algorithm was executed to calculate the rotation angle of the target drive motor. The processor 91 transmits the target drive motor rotation angle via the bus. The control commands are transmitted to the communication interface 93, which uses the EtherCAT protocol to send the control commands to the parallel motor driver in a high real-time (e.g., communication cycle ≤1ms) and low-latency manner to drive the drive motor. With drive motor Precise rotation drives the ankle joint to achieve the desired posture through a parallel crank-connecting rod mechanism. At the same time, the processor 91 receives the actual rotation angle (θ1 actual, θ2 actual) fed back in real time from the motor encoder through the communication interface 93, compares the actual angle with the target drive motor rotation angle, and adjusts subsequent commands through closed-loop control (such as proportional, integral, and derivative adjustment) to ensure the accuracy and real-time performance of the ankle joint movement.

[0227] The implementation principle and technical effects of the controller provided in this embodiment can be found in the foregoing embodiments, and will not be repeated here.

[0228] This application also provides a computer program product, including a computer program, which, when executed, implements the method steps as described in the above method embodiments. The specific implementation and technical effects are similar and will not be repeated here.

[0229] This application also provides a computer-readable storage medium storing computer-executable instructions. When the computer-executable instructions are executed, they are used to implement the method steps as described in the above method embodiments. The specific implementation methods and technical effects are similar and will not be repeated here.

[0230] The aforementioned computer-readable storage media can be implemented from any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Read Only Memory (PROM), Read Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0231] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an application-specific integrated circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in a parallel bipedal robot ankle joint control device with a separate rotation center.

[0232] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0233] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0234] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0235] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0236] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0237] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A parallel bipedal robot ankle joint with a separated rotation center, characterized in that, include: A parallel crank-connecting rod mechanism includes a first drive chain and a second drive chain, each of the drive chains including a drive motor, a crank connected to the output shaft of the drive motor, and a connecting rod connected to the crank; An ankle joint motion component, wherein the two links of the drive chain are respectively connected to the ankle joint motion component; The pitch rotation center and roll rotation center of the ankle joint are separated; The foot of the perpendicular line connecting the pitch rotation center and the roll rotation center, and the line connecting the two link connection points, is the origin of the reference coordinate system; the two link connection points are the connection points between the two drive chain links and the ankle joint motion component; the reference coordinate system is fixed relative to the ankle joint. In this configuration, the connecting rod lengths of the two drive chains are respectively equal to the distance from the shaft center of their respective drive motors to the origin of the coordinate system, the crank lengths of the two drive motors are equal, and the installation offset of the drive motors is equal to the installation offset of the connecting rods.

2. The ankle joint of a parallel bipedal robot with a separated rotation center according to claim 1, characterized in that, The ankle joint has two mirror-symmetrical configurations: In the first configuration, the pitch rotation center is located on the positive z-axis of the reference coordinate system, and the roll rotation center is located on the negative z-axis of the reference coordinate system. In the second configuration, the pitch rotation center is located on the negative z-axis of the reference coordinate system, and the roll rotation center is located on the positive z-axis of the reference coordinate system.

3. A bipedal robot, characterized in that, include: The robot itself; The ankle joint of the parallel bipedal robot with a rotation center separation as described in claim 2 is disposed on the robot body; A controller, connected to a drive motor in the ankle joint, is used to control the movement of the ankle joint.

4. A method for controlling the ankle joint of a parallel bipedal robot with a separated rotation center, characterized in that, The controller applied in the bipedal robot as described in claim 3, the control method comprising: Obtain the target posture angle of the ankle joint, the target posture angle including the target pitch angle and the target roll angle; A preset analytical formula is obtained, which is used to determine the target drive motor rotation angle based on the target attitude angle; the analytical formula is obtained by solving the kinematic constraint equation, which is an equation between the drive motor rotation angle and the attitude angle established based on the reference coordinate system; The target drive motor rotation angle corresponding to the target pitch angle and the target roll angle is determined according to the analytical formula, and control commands are sent to the corresponding drive motors to drive the ankle joint to move to the target posture.

5. The ankle joint control method for a parallel bipedal robot with a separated rotation center according to claim 4, characterized in that, The first and second kinetic chains in the ankle joint are the upper and lower kinetic chains, respectively; the kinematic constraint equations are determined as follows: Based on the reference coordinate system, determine the coordinates of the first connection point between the link in the upper drive chain and the ankle joint motion component in the ankle joint, and the coordinates of the second connection point between the link in the lower drive chain and the ankle joint motion component. Based on the determined coordinates of the first and second connection points, and according to the constraint that the link lengths in the upper and lower drive chains remain unchanged, a first geometric relationship between the rotation angle of the drive motor and the attitude angle in the upper drive chain, and a second geometric relationship between the rotation angle of the drive motor and the attitude angle in the lower drive chain are established as the kinematic constraint equations.

6. The ankle joint control method for a parallel bipedal robot with a separated rotation center according to claim 5, characterized in that, The step of determining the coordinates of the first connection point between the link in the upper drive chain and the ankle joint motion component in the ankle joint, and the coordinates of the second connection point between the link in the lower drive chain and the ankle joint motion component, includes: Based on the target pitch angle, determine the coordinates of the first connection point and the second connection point along the x-axis of the reference coordinate system; Based on the target roll angle, determine the coordinates of the first connection point and the second connection point along the y-axis of the reference coordinate system; Based on the target pitch angle and the target roll angle, the coordinates of the first connection point and the second connection point along the z-axis of the reference coordinate system are determined respectively.

7. The ankle joint control method for a parallel bipedal robot with a separated rotation center according to claim 5, characterized in that, Solving the kinematic constraint equations includes: Based on the first geometric relationship, construct a first trigonometric equation regarding the rotation angle of the drive motor in the upper drive chain; Based on the second geometric relationship, construct a second trigonometric equation regarding the rotation angle of the drive motor in the lower drive chain; The first trigonometric equation and the second trigonometric equation are solved analytically to obtain the analytical formulas for the rotation angle of the drive motor in the upper drive chain and the rotation angle of the drive motor in the lower drive chain with respect to the attitude angle.

8. The ankle joint control method for a parallel bipedal robot with a separated rotation center according to claim 7, characterized in that, The analytical solution of the first trigonometric equation and the second trigonometric equation also includes: Based on the actual assembly structure of the parallel crank-connecting rod mechanism in the ankle joint, a unique physically feasible solution is selected from the general mathematical solution of the first trigonometric equation as the analytical formula for the rotation angle of the drive motor in the upper drive chain. Based on the actual assembly structure of the parallel crank-connecting rod mechanism, a unique physically feasible solution is selected from the general mathematical solution of the second trigonometric equation as the analytical formula for the rotation angle of the drive motor in the lower drive chain.

9. The ankle joint control method for a parallel bipedal robot with a separated rotation center according to claim 4, characterized in that, When determining the target drive motor rotation angle corresponding to the target pitch angle and the target roll angle according to the analytical formula, the following method is used to adapt to different joint configurations: Obtain a first preset angle and a second preset angle; wherein, the first preset angle is the arctangent of the ratio of the crank length of the drive motor to the distance from the pitch rotation center to the coordinate origin; the second preset angle is the arctangent of the ratio of the installation offset of the drive motor to the distance from the roll rotation center to the coordinate origin; When the ankle joint is in the first configuration, the target pitch angle and the target roll angle are directly substituted into the analytical formula to obtain the target drive motor rotation angle; When the ankle joint is a second configuration that is mirror-symmetrical to the first configuration, the angle terms in the analytical formula are replaced with signs, and the target pitch angle and the target roll angle are substituted into the analytical formula after the sign replacement to obtain the target drive motor rotation angle; wherein, the sign replacement includes: replacing the sum of the pitch angle and the first preset angle with the difference between the pitch angle and the first preset angle in the attitude angle; replacing the difference between the roll angle and the second preset angle in the attitude angle with the sum of the roll angle and the second preset angle; and replacing the sum of the roll angle and the second preset angle with the difference between the roll angle and the second preset angle.

10. The ankle joint control method for a parallel bipedal robot with a rotation center separation according to any one of claims 4 to 9, characterized in that, After determining the target drive motor rotation angle corresponding to the target pitch angle and the target roll angle according to the analytical formula, the method further includes: The target drive motor rotation angle is normalized to a preset control angle range to obtain the normalized angle value; The control command is generated based on the normalized angle value.

11. The ankle joint control method for a parallel bipedal robot with a rotation center separation according to any one of claims 4 to 9, characterized in that, After sending the control command to the corresponding drive motor, the method further includes: Receive the actual rotation angle of the drive motor fed back by the encoder; The actual rotation angle is compared with the target drive motor rotation angle to determine the angle deviation; The drive motor is adjusted in a closed loop based on the angle deviation to correct the movement posture of the ankle joint.

12. A parallel bipedal robot ankle joint control device with a separated rotation center, characterized in that, A controller applied in a bipedal robot as described in claim 3, the control device comprising: The attitude acquisition module is used to acquire the target attitude angle of the ankle joint, the target attitude angle including the target pitch angle and the target roll angle; The processing module is used to obtain a preset analytical formula, which is used to determine the target drive motor rotation angle based on the target attitude angle. The analytical formula is obtained by solving the kinematic constraint equation, which is an equation between the drive motor rotation angle and the attitude angle established based on the reference coordinate system. The control module is used to determine the target drive motor rotation angle corresponding to the target posture angle according to the analytical formula, and send control commands to the corresponding drive motor to drive the ankle joint to move to the target posture.

13. A controller, characterized in that, include: A processor, and a memory communicatively connected to the processor; The memory is used to store computer-executed instructions; The processor is configured to execute the computer execution instructions to implement the method as described in any one of claims 4-11.

14. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed, are used to implement the method as described in any one of claims 4-11.

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