Method and device for determining torque of parallel ankle joint mechanism with rotation center separation

Abstract

This application provides a method and apparatus for determining the torque of a parallel ankle joint mechanism with a separated rotation center. The method includes: obtaining the target posture angle of the ankle joint in the parallel ankle joint mechanism; obtaining analytical expressions for each element of the inverse kinematics Jacobian matrix derived from the geometric parameters of the parallel ankle joint mechanism by applying the chain rule to the inverse kinematics equations of the parallel ankle joint mechanism; determining the inverse kinematics Jacobian matrix corresponding to the target posture angle based on the analytical expressions; and realizing a bidirectional conversion between the drive motor torque and the ankle joint load torque using the inverse kinematics Jacobian matrix, based on the static mapping formula between the drive motor torque and the ankle joint load torque. The static mapping formula is constructed based on the principle of virtual work. This application can improve the accuracy and computational efficiency of the mapping between the drive motor torque and the ankle joint load torque, and enhance the real-time control, state assessment, and operational stability of the robot's ankle joint.

Description

Technical Field

[0001] This application relates to the field of robot kinematics and statics analysis technology, and in particular to a method and apparatus for determining the torque of a parallel ankle joint mechanism with a separated rotation center. Background Technology

[0002] In the field of robotics, to meet the demands for high precision, high load-bearing capacity, and high rigidity in motion performance, an increasing number of bionic ankle joints are employing parallel crank-connecting rod mechanisms driven by dual motors. These mechanisms, through two "drive motor-crank-connecting rod" drive chains, jointly control the flexible composite motion of the ankle joint's pitch and roll degrees of freedom. For bionic ankle joints using parallel mechanisms, under static or quasi-static conditions, it is necessary to establish a mapping relationship between the drive motor torque and the ankle joint load torque—that is, the static analysis problem of the parallel ankle joint mechanism—for load state assessment, fault diagnosis, and control optimization.

[0003] Currently, robot systems are typically defined using the Unified Robot Description Format (URDF) in engineering deployments. However, URDF is essentially a tree-structured description format designed for serial mechanisms, and the joint torque data it provides corresponds to serial joints. For parallel ankle joint mechanisms, the geometry is complex, especially in configurations with separated rotation centers (i.e., the pitch and roll rotation centers of the ankle joint are separated). A strong nonlinear mapping exists between the output torque of the drive motor and the load torque borne by the ankle joint. Therefore, existing static analysis methods based on serial mechanisms are difficult to directly apply to such parallel mechanisms.

[0004] In summary, there is an urgent need for a static analysis scheme applicable to parallel ankle joint mechanisms with separated rotation centers, in order to achieve a precise mapping between the drive motor torque and the ankle joint load torque, and to provide a theoretical basis for load assessment, fault diagnosis and control optimization of the mechanism. Summary of the Invention

[0005] This application provides a method and apparatus for determining the torque of a parallel ankle joint mechanism with a separated rotation center, in order to solve the technical problem in the related art of lacking a static analysis scheme for a parallel ankle joint mechanism with a separated rotation center, thus making it impossible to accurately establish the mapping relationship between the drive motor torque and the ankle joint load torque.

[0006] In a first aspect, this application provides a method for determining the torque of a parallel ankle joint mechanism with a separated rotation center, including:

[0007] Obtain the target attitude angle of the ankle joint in the parallel ankle joint mechanism. The target attitude angle includes the target pitch angle and the target roll angle.

[0008] Obtain the analytical expressions of each element in the pre-established inverse kinematics Jacobian matrix. The analytical expressions are derived by applying the chain rule to the inverse kinematics equations of the parallel ankle joint mechanism based on the geometric parameters of the parallel ankle joint mechanism. Each analytical expression is a closed function of pitch and roll angles.

[0009] Based on the analytical expression, the inverse kinematics Jacobian matrix corresponding to the target attitude angle is determined. The kinematics Jacobian matrix is ​​used to describe the velocity mapping from the ankle joint space to the drive motor space.

[0010] Based on the static mapping formula between the drive motor torque and the ankle joint load torque, the known drive motor torque is converted into the actual load torque of the ankle joint using the inverse kinematic Jacobian matrix, or the known target load torque is converted into the output torque of the drive motor in the parallel ankle joint mechanism; the static mapping formula is constructed based on the principle of virtual work.

[0011] In one possible implementation, the analytical expressions for each element in the inverse kinematics Jacobian matrix are determined as follows:

[0012] Based on geometric parameters, coordinate expressions for the first connection point between the link on the first drive chain and the ankle joint moving part in the parallel ankle joint mechanism, and coordinate expressions for the second connection point between the link on the second drive chain and the ankle joint moving part are established respectively. The coordinate expressions are functions of pitch angle and roll angle.

[0013] Based on the coordinate expression of the first connection point and the inverse kinematic equation of the first drive chain, the analytical expressions of the partial derivatives of the first drive motor angle with respect to the pitch angle and roll angle are derived by applying the chain rule.

[0014] Based on the coordinate expression of the second connection point and the inverse kinematic equation of the second drive chain, the analytical expressions of the partial derivatives of the second drive motor angle with respect to the pitch and roll angles are derived by applying the chain rule.

[0015] In one possible implementation, the static mapping formula satisfies:

[0016] The drive motor torque vector is equal to the transpose of the inverse kinematics Jacobian matrix multiplied by the ankle joint load torque vector;

[0017] Alternatively, the ankle joint load torque vector is equal to the transpose of the kinematic Jacobian matrix multiplied by the drive motor torque vector;

[0018] Among them, the kinematic Jacobian matrix is ​​the inverse of the inverse kinematic Jacobian matrix, the drive motor torque vector includes the output torque of the first drive motor and the second drive motor, and the ankle joint load torque vector includes the rolling torque and pitching torque of the ankle joint.

[0019] In one possible implementation, determining the inverse kinematic Jacobian matrix corresponding to the target attitude angle based on the analytical expression includes:

[0020] Substitute the target pitch angle and target roll angle into the analytical expression of each element of the inverse kinematics Jacobian matrix to calculate the value of each element;

[0021] The calculated values ​​of each element are combined according to a preset matrix form to obtain the inverse kinematics Jacobian matrix corresponding to the target attitude angle.

[0022] In one possible implementation, after converting the known drive motor torque into the actual load torque of the ankle joint, the method further includes:

[0023] Obtain the target load torque of the ankle joint;

[0024] Determine the torque deviation between the actual load torque and the target load torque;

[0025] When the torque deviation exceeds the preset deviation threshold, the parallel ankle joint mechanism is determined to be in an abnormal operating state.

[0026] When the torque deviation is less than or equal to the preset deviation threshold, the parallel ankle joint mechanism is determined to be in normal operating condition.

[0027] In one possible implementation, after converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, the method further includes:

[0028] Use the output torque as a feedforward control command;

[0029] Based on feedforward control commands, the corresponding drive motor is controlled to output torque to drive the ankle joint movement of the parallel ankle joint mechanism.

[0030] In one possible implementation, after converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, the method further includes:

[0031] When the output torque is determined to be greater than the rated torque of the drive motor, the limiting process is triggered to limit the output torque of the drive motor to within the rated torque range;

[0032] Output overload warning signal.

[0033] Secondly, this application provides a torque determination device for a parallel ankle joint mechanism with a separated rotation center, comprising:

[0034] The acquisition module is used to acquire the target attitude angle of the ankle joint in the parallel ankle joint mechanism. The target attitude angle includes the target pitch angle and the target roll angle.

[0035] The acquisition module is also used to acquire the analytical expressions of each element in the pre-established inverse kinematics Jacobian matrix. The analytical expressions are derived by applying the chain rule to the inverse kinematics equations of the parallel ankle joint mechanism based on the geometric parameters of the parallel ankle joint mechanism. Each analytical expression is a closed function of pitch angle and roll angle.

[0036] The determination module is used to determine the inverse kinematics Jacobian matrix corresponding to the target attitude angle based on the analytical expression. The kinematics Jacobian matrix is ​​used to describe the velocity mapping from the ankle joint space to the drive motor space.

[0037] The conversion module is used to convert the known drive motor torque into the ankle joint load torque, or convert the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, based on the static mapping formula between the drive motor torque and the ankle joint load torque and using the inverse kinematic Jacobian matrix; the static mapping formula is constructed based on the principle of virtual work.

[0038] In one possible implementation, the analytical expressions for each element in the inverse kinematics Jacobian matrix are determined as follows: Based on geometric parameters, coordinate expressions are established for the first connection point between the link on the first drive chain and the ankle joint moving component in the parallel ankle joint mechanism, and for the second connection point between the link on the second drive chain and the ankle joint moving component, respectively. These coordinate expressions are functions of pitch and roll angles. Based on the coordinate expressions of the first connection points and the inverse kinematic equations of the first drive chain, the chain rule is applied to derive the analytical expressions for the partial derivatives of the first drive motor angle corresponding to the first drive chain with respect to the pitch and roll angles, respectively. Based on the coordinate expressions of the second connection points and the inverse kinematic equations of the second drive chain, the chain rule is applied to derive the analytical expressions for the partial derivatives of the second drive motor angle corresponding to the second drive chain with respect to the pitch and roll angles, respectively.

[0039] In one possible implementation, the static mapping formula satisfies: the drive motor torque vector is equal to the transpose of the inverse kinematic Jacobian matrix multiplied by the ankle joint load torque vector; or, the ankle joint load torque vector is equal to the transpose of the kinematic Jacobian matrix multiplied by the drive motor torque vector; wherein, the kinematic Jacobian matrix is ​​the inverse of the inverse kinematic Jacobian matrix, the drive motor torque vector includes the output torques of the first drive motor and the second drive motor, and the ankle joint load torque vector includes the rolling torque and pitching torque of the ankle joint.

[0040] In one possible implementation, the determining module is specifically used to: substitute the target pitch angle and the target roll angle into the analytical expression of each element of the inverse kinematics Jacobian matrix to calculate the value of each element; and combine the calculated values ​​of each element according to a preset matrix form to obtain the inverse kinematics Jacobian matrix corresponding to the target attitude angle.

[0041] In one possible implementation, the torque determination device for the parallel ankle joint mechanism with a separated rotation center further includes a diagnostic module for: obtaining the target load torque of the ankle joint after converting the known drive motor torque into the actual load torque of the ankle joint; determining the torque deviation between the actual load torque and the target load torque; determining that the parallel ankle joint mechanism is in an abnormal operating state when the torque deviation is greater than a preset deviation threshold; and determining that the parallel ankle joint mechanism is in a normal operating state when the torque deviation is less than or equal to the preset deviation threshold.

[0042] In one possible implementation, the torque determination device for the parallel ankle joint mechanism with a separated rotation center further includes a control module for: converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, and using the output torque as a feedforward control command; and controlling the corresponding drive motor to output torque based on the feedforward control command to drive the ankle joint movement of the parallel ankle joint mechanism.

[0043] In one possible implementation, the torque determination device for the parallel ankle joint mechanism with a separated rotation center further includes a processing module for: after converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, triggering a limiting process when it is determined that the output torque is greater than the rated torque of the drive motor, so as to limit the output torque of the drive motor within the rated torque range; and outputting an overload warning signal.

[0044] Thirdly, this application provides a controller, including: a processor, and a memory communicatively connected to the processor;

[0045] Memory is used to store instructions executed by the computer;

[0046] A processor is used to execute computer execution instructions to implement the torque determination method for a parallel ankle joint mechanism with a separation of rotation centers, as described above.

[0047] Fourthly, this application provides a bipedal robot, comprising:

[0048] The robot itself;

[0049] Controller;

[0050] And, a parallel ankle joint mechanism with a rotation center separated from the robot body;

[0051] The controller is connected to the drive motor in the parallel ankle joint mechanism.

[0052] Fifthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed, are used to implement the torque determination method for a parallel ankle joint mechanism with rotation center separation provided above.

[0053] Sixthly, this application provides a computer program product, including a computer program that, when executed by a processor, implements the torque determination method for a parallel ankle joint mechanism with a separation of rotation centers as described above.

[0054] The method and apparatus for determining the torque of a parallel ankle joint mechanism with a separated rotation center provided in this application include: obtaining the target attitude angle of the ankle joint in the parallel ankle joint mechanism, the target attitude angle including the target pitch angle and the target roll angle; obtaining the analytical expression of each element in a pre-established inverse kinematics Jacobian matrix, the analytical expression being derived by applying the chain rule to the inverse kinematic equation of the parallel ankle joint mechanism based on the geometric structural parameters of the parallel ankle joint mechanism, each analytical expression being a closed function of the pitch angle and the roll angle; determining the inverse kinematics Jacobian matrix corresponding to the target attitude angle according to the analytical expression, the kinematics Jacobian matrix being used to describe the velocity mapping from the ankle joint space to the drive motor space; based on the static mapping formula between the drive motor torque and the ankle joint load torque, using the inverse kinematics Jacobian matrix, converting the known drive motor torque into the actual load torque of the ankle joint, or converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism; the static mapping formula is constructed based on the principle of virtual work. In this process, by acquiring the target pitch and roll angles of the ankle joint and combining them with the analytical expressions of each element of the inverse kinematics Jacobian matrix derived from the mechanism's geometric parameters, the velocity mapping relationship between the ankle joint space and the drive motor space can be quickly determined for the target posture. Since the analytical expression is a closed function, the value of the Jacobian matrix can be directly calculated by substituting the current posture angle, eliminating the need for online iterative solution of the inverse kinematics equations, significantly reducing online computational complexity and meeting the computational efficiency requirements of real-time robot control. Furthermore, this application does not rely on the URDF model for mechanism description, but directly starts from the geometric parameters of the parallel ankle joint mechanism, deriving the analytical expression by applying the chain rule to the inverse kinematics equations, effectively solving the problem that URDF, due to its tree structure, cannot describe the closed-loop topology of parallel mechanisms. Based on this, a static mapping formula is constructed based on the principle of virtual work, using the determined inverse kinematics Jacobian matrix to achieve bidirectional conversion between the drive motor torque and the actual load torque of the ankle joint, thereby improving the accuracy and real-time performance of torque mapping in the parallel ankle joint mechanism and providing a reliable basis for mechanism operation status evaluation and control. Attached Figure Description

[0055] 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.

[0056] Figure 1 A schematic diagram of the ankle joint mechanism of a parallel bipedal robot separated by a rotation center;

[0057] Figure 2 A flowchart illustrating the torque determination method for a parallel ankle joint mechanism with a separated rotation center provided in this application embodiment;

[0058] Figure 3 A schematic diagram of the torque determination device for a parallel ankle joint mechanism with a separated rotation center provided in this application embodiment. Figure 1 ;

[0059] Figure 4 A schematic diagram of the torque determination device for a parallel ankle joint mechanism with a separated rotation center provided in this application embodiment. Figure 2 ;

[0060] Figure 5 A schematic diagram of the torque determination device for a parallel ankle joint mechanism with a separated rotation center provided in this application embodiment. Figure 3 ;

[0061] Figure 6 This is a schematic diagram of the controller provided in an embodiment of this application.

[0062] 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

[0063] 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.

[0064] The terms “first,” “second,” etc., used in this application’s specification 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.

[0065] 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.

[0066] Ankle joint control and force analysis technology is widely used in bipedal robots, exoskeleton robots, bionic robotic legs, and some highly mobile service robots. In these devices, the ankle joint typically performs functions such as foot posture adjustment, ground contact cushioning, maintaining center of gravity balance, and load transfer. Its control accuracy directly affects the stability, safety, and energy consumption of the entire device. Especially when using parallel ankle joint mechanisms with separate rotation centers, the ankle joint is often driven by multiple drive motors via different drive chains, working together to achieve compound movements in both pitch and roll directions. Accordingly, the system architecture generally includes at least the ankle joint body (i.e., the joint motion component), drive motors, linkages, cranks, posture acquisition units, and a controller. The controller calculates the mapping relationship between the drive motors and the ankle joint based on the ankle joint's posture requirements, combined with the mechanism's geometric parameters and drive-side feedback information, thereby supporting real-time control during applications such as walking, standing, obstacle crossing, and rehabilitation assistance.

[0067] In related technologies, the analysis of robot joint torque relationships is mostly based on the modeling of serial mechanisms. The approach typically involves establishing kinematic equations based on the serial joint chain structure and then converting the driving torque to the end effector load. This approach is applicable to serial mechanisms with simple structures and relatively straightforward joint relationships. However, when the object is transformed into a parallel ankle joint mechanism with separate rotation centers, the ankle joint posture is determined by multiple drive chains through geometric constraints, resulting in a significant nonlinear coupling between the drive motor space and the ankle joint space. This makes the existing modeling approach difficult to directly adapt. Firstly, existing solutions do not accurately express inverse kinematic relationships, particularly failing to clearly characterize the continuous changes in pitch angle, roll angle, and various drive motor variables. This leads to a large mapping error between the driving torque and the ankle joint load torque, making it easier to accumulate control deviations under conditions such as foot impact, slope support, or single-leg weight-bearing. Secondly, the related calculations often rely on iterative solutions, resulting in a large computational load, which is difficult to meet the real-time control requirements of robots in scenarios such as rapid gait switching and dynamic balance adjustment. Furthermore, when the mechanism experiences overload, jamming, or abrupt changes in contact state, the inability to obtain accurate load torque information in a timely manner weakens the control system's ability to judge the operating status, thereby affecting the safety and stability of the equipment. Therefore, existing background technologies generally suffer from insufficient mapping accuracy, low computational efficiency, and inadequate support for state assessment in parallel ankle joint mechanism scenarios.

[0068] Therefore, improving the accuracy and real-time performance of the mapping between the drive motor torque and the ankle joint load torque in a parallel ankle joint mechanism with a separated rotation center has become an urgent technical problem to be solved.

[0069] To address the aforementioned issues, this application provides a method for determining the torque of a parallel ankle joint mechanism with a separated rotation center. During ankle joint operation, the target attitude angles of the ankle joint are first obtained, including the target pitch angle and the target roll angle. Then, the analytical expressions for each element in a pre-established inverse kinematics Jacobian matrix are obtained. These expressions are derived from the geometric parameters of the parallel ankle joint mechanism by applying the chain rule to the inverse kinematic equations, and each element is a closed-form function of the pitch and roll angles. Subsequently, the inverse kinematics Jacobian matrix corresponding to the target attitude angle is determined based on the analytical expressions. This matrix represents the velocity mapping from the ankle joint space to the drive motor space. Finally, based on a static mapping formula constructed according to the principle of virtual work, the known drive motor torque is converted into the actual load torque of the ankle joint, or the known target load torque is converted into the output torque of the drive motor. This technical approach provides a more suitable solution basis for the torque analysis and control of parallel ankle joint mechanisms, taking into account their structural characteristics.

[0070] To facilitate a better understanding of the technical solution of this application, the mechanical features of the parallel ankle joint mechanism with a separated rotation center to which this application applies will be described first. This mechanism has the characteristic of a separated rotation center.

[0071] Figure 1 A schematic diagram of the ankle joint mechanism of a parallel bipedal robot separated by a rotation center. (See diagram below.) Figure 1 As shown, the parallel bipedal robot ankle joint mechanism with a separate rotation center includes: a parallel crank-connecting rod mechanism 11 and an ankle joint motion component 12.

[0072] The parallel crank-connecting rod mechanism 11 includes a first drive chain 111 and a second drive chain 112, wherein the first drive chain 111 includes a drive motor. and drive motor Crank connected to the output shaft and the crank Connecting rods The second drive train 112 includes a drive motor. and drive motor Crank connected to the output shaft and the crank Connecting rods ;link ,link Connected to the ankle joint motion component 12; the pitch and rotation center of the ankle joint motion component 12 With the center of tumbling rotation Separation.

[0073] 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 Connection point with ankle joint motion component 12; reference coordinate system fixed relative to the ankle joint mechanism of parallel bipedal robot.

[0074] Parallel crank-connecting rod mechanism 11 refers to a parallel transmission mechanism consisting of two independent but cooperating drive chains, used to drive motors Drive motor The rotational input is converted into a composite posture output of the ankle joint motion component 12. It is typically positioned on either side of the ankle joint body or in a relatively opposite location 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.

[0075] 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 It is transmitted to the ankle joint motion component 12, thereby participating in the formation of a composite posture of pitching and rolling during ankle posture adjustment.

[0076] The second drive chain 112 refers to another independent transmission branch that is set in accordance with the first drive chain 111. It is used to work together with the first drive chain 111 to act on the ankle joint moving part 12. Through mutual cooperation, it realizes the dual-degree-of-freedom adjustment of the ankle joint posture and forms a synchronous or differential drive relationship with the first drive chain 111 at the output end to realize the continuous correction of the foot posture.

[0077] 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 parallel ankle joint mechanism, 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. , to connect with the link ,link The hinged connection allows it to receive combined action in two directions.

[0078] Pitch Rotation Center The instantaneous center of rotation (forward and backward) of the ankle joint moving component 12 about the pitch axis (i.e., the pitch axis, located in the positive half of the Z-axis), and the center of tumbling rotation. The instantaneous center of rotation (left-right direction) of the ankle joint moving component 12 around the roll axis (i.e., the roll axis, located in the negative half of the Z-axis); the center of pitch rotation. , Tumbling rotation center Drive motor axis center and drive motor The four axes are collinear.

[0079] The reference coordinate system refers to the geometric coordinate system fixed on the parallel ankle joint mechanism. This is because the ankle joint moving component 12 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 parallel ankle joint mechanism; the 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.

[0080] To achieve motion decoupling and torque optimization, the parallel ankle joint mechanism design must satisfy the following constraints:

[0081] link ,link The lengths are defined as follows: and And there are , This equal length relationship is one of the key conditions for ensuring motion decoupling.

[0082] 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.

[0083] The installation offset of the drive motor is equal to the installation offset of the connecting rod, defined as follows: ,Right now , , The crankshaft of the motor is the center of rotation. This design makes the structure symmetrical and simplifies the kinematic model.

[0084] Radius of moving parts (ankle joint moving parts 12 around the center of tumbling rotation) The radius of the circular arc motion is defined as follows: , , , They are points and The projection point on the y-axis, the radius of the moving part (ankle joint moving part 12 around the pitch rotation center). The radius of the circular arc motion is defined as follows: , , yes and The projection point on the x-axis.

[0085] 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.

[0086] Figure 2 This is a flowchart illustrating the torque determination method for a parallel ankle joint mechanism with a separated rotation center provided in an embodiment of this application. Figure 2 As shown, the method for determining the torque of the parallel ankle joint mechanism with a separated rotation center includes:

[0087] S201. Obtain the target attitude angle of the ankle joint in the parallel ankle joint mechanism. The target attitude angle includes the target pitch angle and the target roll angle.

[0088] In this embodiment, the parallel ankle joint mechanism with a separated rotation center serves as the execution object and can be installed in a bipedal robot, exoskeleton robot, bionic mechanical leg, or other robotic device with foot posture adjustment requirements. This mechanism is implemented through multiple drive chains (such as... Figure 1 As shown, (including 2 drive chains) work together at the end of the ankle joint, causing the ankle joint (i.e. Figure 1 The ankle joint moving component 12) performs compound motion in the pitch and tumble directions. The target attitude angle, also known as the desired attitude angle, refers to the expected pitch and tumble angle values ​​of the ankle joint, rather than the current actual joint angles. This target attitude angle is used to characterize the target ankle joint attitude for which torque analysis or control calculations are required. The target pitch angle represents the angular component of the ankle joint about the pitch axis, and the target tumble angle represents the angular component of the ankle joint about the tumble axis. Together, they constitute the input variables for subsequent inverse kinematics Jacobian matrix calculations.

[0089] For example, the target attitude angle can be determined by the controller based on control instructions issued by the gait planner, balance controller, or host computer. For instance, during the robot's walking phase, the target pitch angle and target roll angle can be given based on the landing requirements of the swing leg or the posture adjustment requirements of the supporting leg in the current gait cycle; or, the target angle instructions can be received from the outside through a human-machine interface. The controller can be an embedded main control board, motion controller, industrial computer, or dedicated processing chip.

[0090] In one possible embodiment, the controller receives ankle joint posture input signals according to a preset sampling period. This sampling period can be consistent with the robot's underlying servo control period to ensure consistency between the target posture angle and the driving torque data on the time base. Upon receiving the posture input, the controller performs coordinate system transformation, zero-point correction, and unit unification processing on the raw posture data, converting the posture quantities into the joint space expression of the parallel ankle joint mechanism. Then, it extracts the pitch and roll angles as the target posture angle at the current moment. If the target posture angle originates from the motion planning module, the controller can directly read the angle setting value output by the planning module. If the target posture angle originates from a feedback sensor, low-pass filtering, complementary filtering, or Kalman filtering can be further applied after reading the angle information to suppress sensor noise and improve the stability of subsequent Jacobian matrix calculations.

[0091] Based on the above analysis, this step, by explicitly providing the attitude input directly related to the nonlinear mapping process of the parallel ankle joint mechanism, enables subsequent matrix elements to be evaluated in a closed loop around the target pitch angle and the target roll angle. This transforms the real-time torque analysis problem of the complex mechanism into a deterministic calculation process with the target attitude angle as the core index, which is beneficial to improving the real-time performance and consistency of ankle joint load assessment and drive control.

[0092] S202. Obtain the analytical expressions of each element in the pre-established inverse kinematics Jacobian matrix. The analytical expressions are derived by applying the chain rule to the inverse kinematics equations of the parallel ankle joint mechanism based on the geometric parameters of the parallel ankle joint mechanism. Each analytical expression is a closed function of pitch and roll angles.

[0093] In this embodiment, the inverse kinematics Jacobian matrix is ​​used to describe the velocity mapping from the ankle joint space (pitch angle, roll angle) to the drive motor space (angles of the two motors). Its matrix elements essentially reflect the partial derivatives of each drive motor variable with respect to the pitch and roll angles; that is, each element is the partial derivative of the motor angle with respect to the ankle joint angle. To accurately establish this inverse kinematics Jacobian matrix, it is necessary to first establish inverse kinematic equations based on the geometric parameters of the parallel ankle joint mechanism. Geometric parameters may include the link lengths of each drive chain, crank arm lengths, mounting offsets, pitch axis rotation center positions, roll axis rotation center positions, etc. Based on these geometric parameters, spatial coordinate expressions for each key connection point of the foot or ankle joint moving parts under pitch and roll posture changes can be constructed, and further, inverse kinematic equations between the drive motor rotation angle and the ankle joint posture angle can be established. Since the inverse kinematics equations typically represent composite functions under the combined influence of multiple geometric constraints, the chain rule is used to derive the inverse kinematics Jacobian matrix by calculating the partial derivatives of each drive motor angle with respect to the pitch and roll angles, thus forming the elements of the matrix. Each analytical expression is constructed as a closed-form function with respect to the pitch and roll angles, meaning it can be directly calculated through a finite number of algebraic operations, trigonometric function operations, and constant parameter substitution, without relying on online iterative searches or numerical approximations. The chain rule ensures the accuracy of the analytical expressions for partial derivatives, while the introduction of geometric parameters further enhances the consistency between the inverse kinematics Jacobian matrix and the actual kinematics of the mechanism.

[0094] For example, in the specific implementation process, the establishment of the inverse kinematics equations can be completed in the offline modeling stage. First, the geometric parameters of the parallel ankle joint mechanism are obtained based on the mechanism design drawings, 3D model, or calibration results. All key points (including connection points) are represented in a fixed reference coordinate system. Then, the positions of the connection points in the reference coordinate system are determined based on the rotational transformation relationship formed by the pitch and roll angles. Combined with the drive chain length constraint, the analytical relationship of each drive motor variable is obtained. Based on this, the inverse kinematics equations are differentiated in a chain with respect to the target attitude angle to obtain the analytical expression for each element in the Jacobian matrix. These expressions are stored in the controller's memory as symbolic expressions, function libraries, lookup table models, or compiled calculation modules for direct runtime invocation. If the mechanism has multiple specifications, corresponding sets of analytical expressions can be established for different parameter configurations and loaded according to the mechanism model or calibration parameters at system startup.

[0095] Based on the above analysis, it can be seen that by deriving the closed-form analytical expressions of each element of the inverse kinematics Jacobian matrix in advance, it is possible to avoid repeatedly performing inverse kinematics differential derivation and numerical iteration for complex parallel mechanisms during robot operation, thereby reducing the amount of online computation and improving the response speed under rapid gait switching, sudden attitude changes and impact contact conditions. At the same time, the closed-form function makes the relationship between the matrix elements and the target pitch angle and target roll angle clearer, which is conducive to reducing the mapping error caused by traditional approximate modeling, thereby improving the accuracy of the conversion between the drive side torque and the ankle joint load torque.

[0096] S203. Based on the analytical expression, determine the inverse kinematics Jacobian matrix corresponding to the target attitude angle. The kinematics Jacobian matrix is ​​used to describe the velocity mapping from the ankle joint space to the drive motor space.

[0097] In this embodiment of the application, the analytical expression of each element of the inverse kinematics Jacobian matrix takes pitch angle and roll angle as inputs and outputs the numerical values ​​of the corresponding matrix terms.

[0098] For example, the inverse kinematics Jacobian matrix corresponding to the target attitude angle is determined according to the analytical expression. Specifically, this includes: substituting the target pitch angle and the target roll angle into the analytical expression of each element of the inverse kinematics Jacobian matrix to calculate the value of each element; and combining the calculated values ​​of each element according to a preset matrix form to obtain the inverse kinematics Jacobian matrix corresponding to the target attitude angle.

[0099] The preset matrix form is used to limit the row and column positions of each element in the matrix, so that the values ​​of each element can be combined according to the arrangement relationship corresponding to the first drive chain, the second drive chain, and the pitch and roll directions, thereby forming an inverse kinematic Jacobian matrix that can be directly used for subsequent torque mapping.

[0100] In other words, after obtaining the analytical expressions for the target attitude angle and each element of the inverse kinematics Jacobian matrix, the controller substitutes the target pitch angle and target roll angle into the closed-form function corresponding to each element, calculates the matrix element values ​​under the target attitude angle item by item, and assembles them into the inverse kinematics Jacobian matrix according to the correspondence between the number of drive motors and the ankle joint degrees of freedom. For Figure 1In a typical two-degree-of-freedom parallel ankle joint mechanism, this matrix can characterize the mapping relationship between the two drive chain variables and the pitch and roll angular velocities. For mechanisms with redundant drives or auxiliary constraints, a higher-dimensional matrix expression can also be formed. Here, the inverse kinematics Jacobian matrix represents the velocity mapping relationship from the ankle joint space to the drive motor space, that is, the proportional relationship of the corresponding changes of the variables on each drive motor side when the ankle joint posture undergoes small changes in the pitch and roll directions. Therefore, this matrix is ​​not only a tool for velocity solving, but also the core foundation for subsequent torque mapping based on the principle of virtual work.

[0101] In one possible embodiment, the controller reads the target pitch and roll angles at the current moment in each control cycle, inputs these two angles into a pre-stored analytical expression calculation module, directly calculates the partial derivatives, and fills the results into the corresponding positions in the matrix. To ensure numerical stability, the controller can also perform a validity check after forming the matrix, such as determining whether matrix elements exceed the physical limits allowed by the mechanism, whether there is an abnormal increase in the condition number due to near-singular attitudes, and whether the current attitude falls within the reachable workspace of the mechanism. When the target attitude angle is detected to be in a near-singular region, the controller can trigger protection strategies, such as limiting the rate of attitude change, switching control gain, enabling the nearest neighbor attitude interpolation matrix, or outputting an anomaly flag for use by the upper-level control module. If no anomaly occurs, the obtained inverse kinematics Jacobian matrix is ​​used as the valid mapping matrix for the current control cycle for subsequent static mapping.

[0102] Based on the above analysis, this step achieves rapid calculation of the Jacobian matrix of the inverse kinematics of the parallel ankle joint mechanism by directly associating the target attitude angle with the pre-established closed-form analytical expression. This avoids error accumulation caused by improper step size selection in traditional numerical difference methods and also avoids computational delays caused by online iterative differentiation. Since the matrix directly represents the local mapping relationship from the ankle joint space to the drive motor space, it can more accurately reflect the nonlinear coupling characteristics between pitch and roll under the rotation center separation structure, providing a mapping basis consistent with the current attitude for subsequent bidirectional torque conversion.

[0103] S204. Based on the static mapping formula between the drive motor torque and the ankle joint load torque, the known drive motor torque is converted into the actual load torque of the ankle joint using the inverse kinematic Jacobian matrix, or the known target load torque is converted into the output torque of the drive motor in the parallel ankle joint mechanism; the static mapping formula is constructed based on the principle of virtual work.

[0104] In this embodiment, the static mapping formula is used to establish the mathematical relationship between the drive motor torque and the ankle joint load torque, based on the principle of virtual work. The principle of virtual work reflects the balance between the virtual work done by external forces and the generalized force under ideal constraints and arbitrary compatible virtual displacements. Based on this principle, a linear relationship can be derived between the drive motor torque vector and the ankle joint load torque vector, thus achieving bidirectional torque mapping between the drive motor and the ankle joint, providing a reliable basis for mechanism operation status evaluation and control. Since the inverse kinematics Jacobian matrix describes the differential motion mapping between the ankle joint space and the drive motor space, the torque mapping relationship can be further derived from the velocity mapping. For scenarios where the drive motor torque vector is known, the controller inputs the motor-side torque into the static mapping formula related to the inverse kinematics Jacobian matrix to obtain the actual load torque vector in the ankle joint space. This actual load torque can include pitch load torque and roll load torque, used to characterize the force state of the ankle joint under support, collision, push-off, or center-of-gravity adjustment conditions. For scenarios where the target load torque vector is known, the torque values ​​required to be output by each drive motor can be calculated in reverse according to the same mapping relationship, serving as the setting input for the motor controller. The drive motor torque can originate from motor current estimation, torque sensor measurement, or driver feedback; the ankle joint load torque can serve as a status monitoring quantity, impedance control input, balance control feedback, or fault diagnosis basis.

[0105] In the specific implementation process, the controller can first construct the motor-side torque vector and the ankle-side load torque vector, and then complete the conversion between them based on the transpose of the inverse kinematics Jacobian matrix. For example, when the drive motor torque is known, the generalized force in the motor space can be mapped to the ankle joint space through the transpose of the Jacobian matrix based on the virtual work conservation relationship, thereby obtaining the equivalent actual load torque of the ankle joint under the current posture; when the target load torque is known, the corresponding drive motor output torque can be calculated based on the load torque vector and the Jacobian matrix, and this output torque can be sent to the servo driver to execute closed-loop control. Optionally, if the system also considers factors such as transmission efficiency, reducer speed ratio, friction compensation, and motor constant, the controller can add corresponding correction terms before and after the static mapping to make the calculation results closer to the actual force conditions of the mechanism. To ensure real-time performance, the entire conversion process can be completed within each control cycle, and since the Jacobian matrix has been directly obtained from a closed function, the static mapping only involves matrix multiplication, transpose operation, and necessary linear solutions, making it suitable for deployment in a real-time controller.

[0106] Based on the above analysis, this step establishes a structurally consistent bidirectional mapping relationship between the ankle joint load torque, which was originally difficult to measure directly, and the drive motor torque, which is easier to obtain. This allows the system to quickly obtain current force information or reverse-engineer control output without relying on complex iterative solutions, effectively solving the problems of insufficient mapping accuracy, low computational efficiency, and inadequate state assessment support in existing technologies for parallel ankle joint mechanisms with separated rotation centers. Especially under conditions such as foot impact, ramp support, single-leg load bearing, and dynamic balance adjustment, this static mapping method can reflect ankle joint load changes more promptly, improve the control system's ability to identify overload, jamming, and sudden changes in contact state, and enhance the overall stability and safety of the robot's operation.

[0107] It should be noted that the torque determination method for the parallel ankle joint mechanism provided in this application embodiment can be applied to static working conditions, quasi-static working conditions, or low-speed motion working conditions. Under these working conditions, dynamic terms such as inertial force, Coriolis force, and friction force can be ignored, and the system is in a state of force equilibrium. Therefore, the static mapping formula has sufficient engineering accuracy.

[0108] In this embodiment, by obtaining the target pitch and roll angles of the ankle joint and combining them with the analytical expressions of each element of the inverse kinematics Jacobian matrix derived from the mechanism's geometric parameters, the velocity mapping relationship between the ankle joint space and the drive motor space can be quickly determined for the target posture. Since the analytical expression is a closed function, the value of the Jacobian matrix can be directly calculated by substituting the current posture angle, eliminating the need for online iterative solution of the inverse kinematics equations, significantly reducing online computational complexity and meeting the computational efficiency requirements of real-time robot control. Furthermore, this application does not rely on the URDF model for mechanism description, but directly starts from the geometric parameters of the parallel ankle joint mechanism, deriving the analytical expression by applying the chain rule to the inverse kinematics equations, effectively solving the problem that URDF, due to its tree structure, cannot describe the closed-loop topology of parallel mechanisms. Based on this, a static mapping formula is constructed based on the principle of virtual work, using the determined inverse kinematics Jacobian matrix to achieve bidirectional conversion between the drive motor torque and the actual load torque of the ankle joint, thereby improving the accuracy and real-time performance of torque mapping in the parallel ankle joint mechanism and providing a reliable basis for mechanism operation status evaluation and control.

[0109] Based on the foregoing embodiments, in some embodiments, the analytical expressions of each element in the inverse kinematics Jacobian matrix are determined in the following way: Based on geometric structural parameters, coordinate expressions are established for the first connection point between the link on the first drive chain and the ankle joint moving component in the parallel ankle joint mechanism, and coordinate expressions are established for the second connection point between the link on the second drive chain and the ankle joint moving component, where the coordinate expressions are functions of pitch and roll angles; based on the coordinate expressions of the first connection points and the inverse kinematic equations of the first drive chain, the chain rule is applied to derive the analytical expressions for the partial derivatives of the first drive motor angle corresponding to the first drive chain with respect to pitch and roll angles; based on the coordinate expressions of the second connection points and the inverse kinematic equations of the second drive chain, the chain rule is applied to derive the analytical expressions for the partial derivatives of the second drive motor angle corresponding to the second drive chain with respect to pitch and roll angles.

[0110] In this embodiment of the application, the inverse kinematics Jacobian matrix is ​​2. 2. A matrix, defined as follows:

[0111]

[0112] in, Indicates the pitch angle; Indicates the roll angle; Indicates the angle of the first drive motor; This indicates the angle of the second drive motor.

[0113] For example, still refer to Figure 1 Based on the constraint that the link length remains constant, the coordinates of each key point in the reference coordinate system can be determined by the pitch angle. Roll angle The geometric parameters were calculated. Among them, the first connection point... The coordinates satisfy the following expression:

[0114]

[0115]

[0116] Second connection point The coordinates satisfy the following expression:

[0117]

[0118]

[0119] In the formula, Indicates the ankle joint's moving parts rotating around the center of rotation. The radius when moving in a circular arc. ; Indicates the ankle joint's moving parts rotating around the center of pitch. The radius when moving in a circular arc. ; Indicates the initial angle associated with the roll motion. ; Indicates the initial angle associated with the pitch motion. ; Indicates the center distance of the pitch axis rotation. ; Indicates the center distance of the roll axis rotation. .

[0120] Understandable Since all of these are known geometric parameters, the coordinate expression is essentially a function of the pitch and roll angles.

[0121] Based on the constraint that the link lengths in the first and second drive chains remain constant, the inverse kinematic equation of the first drive chain can be defined as: The inverse kinematic equation of the second driving chain can be defined as: .

[0122] in, It can be regarded as an intermediate variable. , , , , , ;definition ,definition ; Given the known geometric parameters, define with Figure 1 Consistent.

[0123] Further, calculate the first connection point. Coordinate expression for pitch angle Roll angle Partial derivatives:

[0124]

[0125] Calculate the intermediate variables for the roll angle Partial derivatives:

[0126]

[0127] Calculate the intermediate variables for pitch angle Partial derivatives:

[0128]

[0129] According to the chain rule, based on the inverse kinematic equations of the first driving chain, the pitch angle... Differentiate:

[0130]

[0131] Based on the inverse kinematic equations of the first drive chain, the roll angle is... Differentiate:

[0132]

[0133] Accordingly, calculate the second connection point. Coordinate expression for pitch angle Roll angle Partial derivatives:

[0134]

[0135] Calculate the intermediate variables for the roll angle Partial derivatives:

[0136]

[0137] Calculate the intermediate variables for pitch angle Partial derivatives:

[0138]

[0139] Based on the chain rule for differentiation and the inverse kinematic equations of the second driving chain, the pitch angle is... Differentiate:

[0140]

[0141] Based on the inverse kinematic equations of the second drive chain, the roll angle is... Differentiate:

[0142]

[0143] Based on the above derivation and calculation, it can be seen that by substituting the known geometric parameters into the corresponding formulas, the analytical expressions of each element in the final inverse kinematics Jacobian matrix are only functions of pitch and roll angles.

[0144] Therefore, by substituting the target pitch angle and target roll angle into the analytical expression of each element of the inverse kinematics Jacobian matrix, the value of each element can be calculated, thus obtaining the inverse kinematics Jacobian matrix corresponding to the target attitude angle.

[0145] The embodiments of this application avoid the high-cost numerical iteration solution for parallel ankle joint mechanisms, enabling the Jacobian matrix construction process to have high analytical accuracy and computational efficiency. Since each element is directly derived from the geometric parameters of the mechanism, the mapping error under attitude angle changes can be reduced, the stability of the conversion between the output torque of the drive motor and the load torque of the ankle joint can be improved, and thus the control reliability of the robot under dynamic walking, load support and contact impact conditions can be enhanced.

[0146] In some embodiments, the static mapping formula satisfies: the drive motor torque vector is equal to the transpose of the inverse kinematic Jacobian matrix multiplied by the ankle joint load torque vector; or, the ankle joint load torque vector is equal to the transpose of the kinematic Jacobian matrix multiplied by the drive motor torque vector.

[0147] Among them, the kinematic Jacobian matrix is ​​the inverse of the inverse kinematic Jacobian matrix, the drive motor torque vector includes the output torque of the first drive motor and the second drive motor, and the ankle joint load torque vector includes the rolling torque and pitching torque of the ankle joint.

[0148] The drive motor torque vector is used to represent the set of output torques of the first drive motor and the second drive motor at the target attitude angle. The ankle joint load torque vector is used to represent the rolling torque and pitch torque borne by the ankle joint when supporting the ground, being impacted, or maintaining the attitude.

[0149] The matrix transpose operation reflects the energy conservation relationship between the drive motor and the ankle joint, while the introduction of the inverse matrix ensures the bidirectional reversibility of the torque mapping, thereby improving the accuracy and real-time performance of torque mapping in parallel ankle joint mechanisms.

[0150] In practical implementation, the controller can obtain the inverse kinematics Jacobian matrix based on the target attitude angle. This is used as the fundamental matrix for static transformation. If the output torque on the drive motor side is known, then this torque vector is compared with the inverse kinematic Jacobian matrix. Multiplying by the transposes yields the actual load torques on the ankle joint in the roll and pitch directions, for example... , Represents the torque vector of the drive motor, defined as follows: , The output torque of the first drive motor, This is the output torque of the second drive motor. Represents the ankle joint load torque vector, defined , For rolling torque, This is the pitching moment.

[0151] If the target load torque that the ankle joint needs to withstand is known, the kinematic Jacobian matrix is ​​first obtained by inverting the inverse kinematic Jacobian matrix. Then, its transpose is multiplied by the load torque vector to calculate the torque that the first and second drive motors should output. For example... .

[0152] It should be noted that the matrix inversion and transpose operations can be performed by the numerical calculation module in the controller. In practical applications, other models of this component can also be selected, and this application embodiment does not limit this.

[0153] In practical applications, changes in the ankle joint's posture will cause changes in the geometric relationship of the drive chain, which in turn will cause changes in the values ​​of the elements of the inverse kinematics Jacobian matrix. The controller can realize the bidirectional mapping between the drive motor torque and the ankle joint load torque by substituting the inverse kinematics Jacobian matrix calculated under the target posture angle into the static mapping formula based on the principle of virtual work. This ensures that the motor output torque matches the actual force requirements of the ankle joint.

[0154] Understandably, the static mapping formula only involves matrix multiplication and transpose operations, without including complex iteration or numerical solution processes. The computational load is extremely small and can be completed in milliseconds, meeting the needs of real-time robot control.

[0155] By adopting the embodiments of this application, the conversion relationship between the ankle joint load torque and the drive motor output torque can be kept consistent with the actual kinematics of the mechanism, reducing the error caused by approximate modeling, and improving the real-time performance and stability of the rolling torque and pitch torque solutions. This is beneficial to improving the control accuracy and safety of the parallel ankle joint mechanism in the process of dynamic support, foot landing cushioning and posture adjustment.

[0156] Furthermore, in some embodiments, after converting the known drive motor torque into the actual load torque of the ankle joint, the method further includes: obtaining the target load torque of the ankle joint; determining the torque deviation between the actual load torque and the target load torque; determining that the parallel ankle joint mechanism is in an abnormal operating state when the torque deviation is greater than a preset deviation threshold; and determining that the parallel ankle joint mechanism is in a normal operating state when the torque deviation is less than or equal to the preset deviation threshold.

[0157] The target load torque characterizes the torque value that the parallel ankle joint mechanism is expected to withstand under target posture angles and external load conditions. It is typically determined by control commands, a dynamic model, or external environmental input. The actual load torque represents the ankle joint load result calculated from the drive motor torque and is the fundamental quantity for comparison with the target load torque. Torque deviation is defined as relative error, used to quantify the degree of deviation between the actual load torque and the target load torque. A preset deviation threshold is used to limit the acceptable deviation range and serves as the boundary for judging normal and abnormal states. The preset deviation threshold can be pre-set based on the rated load capacity, operating conditions, and control accuracy requirements of the parallel ankle joint mechanism, such as 15%, and stored in the controller parameter area.

[0158] For example, in a specific implementation, after the controller completes the mapping from the drive motor torque to the actual load torque, it reads the target load torque from the host computer control commands, the attitude controller output, or the force control module, and performs a difference calculation between it and the actual load torque at the current moment. The difference calculation can be in absolute value form to avoid the positive and negative directions affecting the judgment result. When the calculated torque deviation exceeds the preset deviation threshold, the controller outputs an abnormal operating status signal to indicate that the mechanism may have overload, jamming, sudden changes in contact conditions, or excessive torque mapping deviation, and can also trigger corresponding alarms or maintenance commands; when the torque deviation does not exceed the preset deviation threshold, it outputs a normal operating status signal to indicate that the mechanism is operating within an acceptable range.

[0159] This state judgment mechanism performs a closed-loop comparison between the torque mapping result and the target load requirement, enabling the parallel ankle joint mechanism to not only obtain the current force information, but also to complete the operational health identification based on the magnitude of the deviation, thereby providing a basis for subsequent amplitude limiting control, protection shutdown, or parameter correction.

[0160] In this embodiment, the mechanism's operating status is determined directly based on the torque conversion result, which improves the ability to identify abnormal loads, mechanism jamming, and control deviations, and enhances the safety and stability of the parallel ankle joint mechanism in dynamic load scenarios. It also helps to reduce control inaccuracies caused by the accumulation of torque deviations.

[0161] In some embodiments, after converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, the method further includes: using the output torque as a feedforward control command; and controlling the corresponding drive motor to output torque based on the feedforward control command to drive the ankle joint movement of the parallel ankle joint mechanism.

[0162] The output torque is the motor-side torque calculated from the target load torque through static mapping. The feedforward control command is used to directly convert this motor-side torque into an executable control quantity and send it to the drive motor.

[0163] In practical implementation, after the controller converts the target load torque into the output torque of the drive motor, it writes the output torque into the current loop or torque loop control command to generate the corresponding drive signal, thereby controlling the output torque of the first and second drive motors. Since this output torque already reflects the force requirements of the ankle joint in the target posture, the drive motor can directly establish a compensating torque after receiving the feedforward control command, thereby reducing the hysteresis error caused by posture changes or external load changes, enabling the ankle joint to complete the coordinated movement in the pitch or roll direction, and improving the response speed and tracking accuracy of the ankle joint movement.

[0164] The core of the aforementioned feedforward control method lies in first determining the required torque on the motor side using the static mapping results, and then directly applying this torque to the drive chain. This allows the ankle joint to obtain torque compensation matching the target load during start-up, foot landing, support, or posture correction. Its function is to enable the control system to provide the main driving force before feedback correction, thereby improving the ankle joint's motion response speed and reducing control deviation.

[0165] In this embodiment, by directly using the output torque as a feedforward quantity to participate in the control, the error accumulation caused by model lag, sensor sampling delay and load abrupt change is reduced, making the torque output of the drive motor more consistent with the actual force of the parallel ankle joint mechanism, thereby improving the stability of ankle joint movement, tracking accuracy and dynamic response performance.

[0166] In some embodiments, after converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, the method further includes: triggering a limiting process when it is determined that the output torque is greater than the rated torque of the drive motor, so as to limit the output torque of the drive motor within the rated torque range; and outputting an overload warning signal.

[0167] Rated torque is the upper limit of the drive motor's allowable output under specified heat dissipation, continuous operating conditions, and rated operating conditions. Limiting is a protective mechanism that constrains and corrects calculations exceeding this upper limit. Overload warning signals are used to indicate that the drive motor is approaching or exceeding its safe operating boundary.

[0168] In its implementation, after converting the target load torque to the output torque, the controller compares the output torque with the pre-stored rated torque parameters. If the output torque exceeds the rated torque, the controller calls the limiting module to cut off the upper limit of the output torque, ensuring that the torque command sent to the drive motor does not exceed the rated torque range. The limiting module can be integrated into the controller's software logic or implemented by a hardware protection unit. Its internal limiting threshold is matched to the drive motor model. For example, corresponding boundaries are set based on the continuous rated torque, peak rated torque, and allowable duration of the first and second drive motors, thereby ensuring the continuity of ankle joint movements while preventing the motor from operating under overload for extended periods. For example, the limiting process can be implemented in any of the following ways: directly cut off the output torque exceeding the rated torque to the rated torque value; when the output torque of both drive motors exceeds their respective rated torque, reduce them synchronously to a safe range in equal proportion; adopt different processing strategies according to the degree of over-limit, for example, when the over-limit ratio is less than 10%, only record the warning information but do not limit the torque; when the over-limit ratio is greater than or equal to 10%, perform saturation limiting.

[0169] At the same time as or after triggering the amplitude limiting process, the controller generates an overload warning signal. The overload warning signal can be output through the communication bus, indicator lights, upper computer pop-up window or status flag, enabling the control system to further reduce the target attitude change rate, switch to safe control mode or limit the ankle joint output range.

[0170] This processing mechanism intervenes in the torque command channel immediately after the torque mapping result is generated. Through comparison, trimming, and alarm linkage, it ensures that the output torque is always limited within the load-bearing capacity of the drive motor. Therefore, when the ankle joint experiences high load demands under conditions such as slope support, foot impact, or single-leg weight-bearing, the system can promptly identify potential overload states while ensuring basic motion control and issue warnings to the upper-level control logic.

[0171] It should be noted that the rated torque of the two drive motors can be the same, or they can be set to different values ​​according to differences in mechanism design. The rated torque value can be pre-stored in the controller's non-volatile memory, or set by maintenance personnel through the human-machine interface.

[0172] In this embodiment, the limiting processing and early warning mechanism can effectively improve the over-output of the drive motor due to excessive target load torque, reduce the risk of motor overheating, demagnetization, stalling or mechanical damage, thereby improving the safety, reliability and operational stability of the parallel ankle joint mechanism under complex working conditions, and providing clear status basis for subsequent protection control.

[0173] Next, a specific embodiment will be used to illustrate the method for determining the torque of a parallel ankle joint mechanism with a separated rotation center. The geometric parameters of the parallel ankle joint mechanism used in this embodiment are shown in Table 1.

[0174] Table 1

[0175]

[0176] The method for determining the torque of the parallel ankle joint mechanism with its rotation center separated includes the following steps:

[0177] Step 1.1: Calculate the first connection point The coordinates.

[0178] Target attitude angle ( , )

[0179] Substitute the parameters from Table 1 above into the first connection point. In the coordinate expression: , , , , ,but:

[0180]

[0181]

[0182] therefore, .

[0183] Step 1.2: Calculate the second connection point The coordinates.

[0184] Substitute the parameters from Table 1 above into the second connection point. In the coordinate expression: , , ,but:

[0185]

[0186] (and symmetry)

[0187] therefore, .

[0188] Step 1.3: Kinematic chain analysis and inverse kinematics Jacobian matrix solution.

[0189] Step 1.3.1, Analysis of the upper kinetic chain (M1-P1-Q1):

[0190] Calculate intermediate variables:

[0191]

[0192]

[0193]

[0194]

[0195] calculate Partial derivatives of coordinates with respect to target attitude angle ( ):

[0196]

[0197] Calculate intermediate variable pairs Partial derivatives ( ):

[0198]

[0199] Calculate intermediate variable pairs Partial derivatives ( ):

[0200]

[0201] Solve and ( ):

[0202] Substitute the relevant values ​​obtained from the above calculations into the following formula:

[0203]

[0204]

[0205] You will then receive:

[0206] ,

[0207] Step 1.3.2, Analysis of the upper kinetic chain (M2-P2-Q2):

[0208] Calculate intermediate variables:

[0209]

[0210]

[0211]

[0212]

[0213] calculate Partial derivatives of coordinates with respect to target attitude angle ( ):

[0214]

[0215] Calculate intermediate variable pairs Partial derivatives ( ):

[0216]

[0217] Calculate intermediate variable pairs Partial derivatives ( ):

[0218]

[0219] Similarly, the solution can be found. and ( ):

[0220] ,

[0221] Step 1.3.3: Construct the Jacobian matrix.

[0222] Based on the combined analysis results of the upper and lower kinetic chains, the results from the joint space ( ) to drive space ( The inverse velocity kinematics Jacobian matrix :

[0223]

[0224] Step 1.4, Static transformation.

[0225] According to the principle of virtual work, the joint space torque With motor drive space torque The following relationship must be satisfied:

[0226]

[0227]

[0228] Scenario 1: Given the joint torque (i.e., the target load torque of the ankle joint), calculate the motor torque (i.e., the output torque of the drive motor).

[0229] set up ,but .

[0230] Scenario 2: Given the motor torque (i.e., the drive motor torque), find the joint torque (i.e., the actual load torque of the ankle joint).

[0231] set up ,but .

[0232] Step 1.5, Mechanism status diagnosis.

[0233] In application, let the desired joint torque (target load torque) be: Based on the measured drive motor torque, the actual load torque is calculated as follows: If the torque deviation is approximately 0.1%, which is less than the deviation threshold (15%), it can be determined that the parallel ankle joint mechanism is in normal operating condition.

[0234] Conversely, if If the torque deviation is approximately 18%, which is greater than the deviation threshold (15%), then the parallel ankle joint mechanism is judged to be in an abnormal operating state.

[0235] This application provides a dedicated static analysis method for parallel mechanisms with separated ankle joint rotation centers, filling the gaps in the URDF series model's ability to handle static problems of such parallel mechanisms. Through rigorous mathematical derivation, the calculation steps for the analytical solution of the inverse kinematics Jacobian matrix are presented, demonstrating high accuracy and applicability for real-time calculations or offline analysis. Furthermore, this method is highly practical, directly utilizing existing drive motor torque information from the robot control system to calculate the actual load torque of the end effector ankle joint, providing an effective tool for robot status monitoring, safety protection, and performance evaluation.

[0236] Figure 3 A schematic diagram of the torque determination device for a parallel ankle joint mechanism with a separated rotation center provided in this application embodiment. Figure 1 ,like Figure 3 As shown, the torque determination device 30 for a parallel ankle joint mechanism with a separated rotation center provided in this embodiment includes: an acquisition module 31, a determination module 32, and a conversion module 33. Wherein:

[0237] The acquisition module 31 is used to acquire the target attitude angle of the ankle joint in the parallel ankle joint mechanism. The target attitude angle includes the target pitch angle and the target roll angle.

[0238] The acquisition module 31 is also used to acquire the analytical expressions of each element in the pre-established inverse kinematics Jacobian matrix. The analytical expressions are derived by applying the chain rule to the inverse kinematics equations of the parallel ankle joint mechanism based on the geometric parameters of the parallel ankle joint mechanism. Each analytical expression is a closed function of pitch angle and roll angle.

[0239] The determination module 32 is used to determine the inverse kinematics Jacobian matrix corresponding to the target attitude angle based on the analytical expression. The kinematics Jacobian matrix is ​​used to describe the velocity mapping from the ankle joint space to the drive motor space.

[0240] The conversion module 33 is used to convert the known drive motor torque into the ankle joint load torque, or convert the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, based on the static mapping formula between the drive motor torque and the ankle joint load torque and using the inverse kinematic Jacobian matrix; the static mapping formula is constructed based on the principle of virtual work.

[0241] In one possible implementation, the analytical expressions for each element in the inverse kinematics Jacobian matrix are determined as follows: Based on geometric parameters, coordinate expressions are established for the first connection point between the link on the first drive chain and the ankle joint moving component in the parallel ankle joint mechanism, and for the second connection point between the link on the second drive chain and the ankle joint moving component, respectively. These coordinate expressions are functions of pitch and roll angles. Based on the coordinate expressions of the first connection points and the inverse kinematic equations of the first drive chain, the chain rule is applied to derive the analytical expressions for the partial derivatives of the first drive motor angle corresponding to the first drive chain with respect to the pitch and roll angles, respectively. Based on the coordinate expressions of the second connection points and the inverse kinematic equations of the second drive chain, the chain rule is applied to derive the analytical expressions for the partial derivatives of the second drive motor angle corresponding to the second drive chain with respect to the pitch and roll angles, respectively.

[0242] In one possible implementation, the static mapping formula satisfies: the drive motor torque vector is equal to the transpose of the inverse kinematic Jacobian matrix multiplied by the ankle joint load torque vector; or, the ankle joint load torque vector is equal to the transpose of the kinematic Jacobian matrix multiplied by the drive motor torque vector; wherein, the kinematic Jacobian matrix is ​​the inverse of the inverse kinematic Jacobian matrix, the drive motor torque vector includes the output torques of the first drive motor and the second drive motor, and the ankle joint load torque vector includes the rolling torque and pitching torque of the ankle joint.

[0243] In one possible implementation, the determining module 32 is specifically used to: substitute the target pitch angle and the target roll angle into the analytical expression of each element of the inverse kinematics Jacobian matrix to calculate the value of each element; and combine the calculated values ​​of each element according to a preset matrix form to obtain the inverse kinematics Jacobian matrix corresponding to the target attitude angle.

[0244] like Figure 4As shown, in one possible implementation, the torque determination device 30 for the parallel ankle joint mechanism with a separated rotation center further includes a diagnostic module 34, used for: obtaining the target load torque of the ankle joint after converting the known drive motor torque into the actual load torque of the ankle joint; determining the torque deviation between the actual load torque and the target load torque; determining that the parallel ankle joint mechanism is in an abnormal operating state when the torque deviation is greater than a preset deviation threshold; and determining that the parallel ankle joint mechanism is in a normal operating state when the torque deviation is less than or equal to the preset deviation threshold.

[0245] like Figure 5 As shown in one possible implementation, the torque determination device 30 for the parallel ankle joint mechanism with a separated rotation center further includes a control module 35, which is used to: after converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, use the output torque as a feedforward control command; and based on the feedforward control command, control the corresponding drive motor to output torque to drive the ankle joint movement of the parallel ankle joint mechanism.

[0246] In one possible implementation, the control module 35 is further configured to: after converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, trigger a limiting process when it is determined that the output torque is greater than the rated torque of the drive motor, so as to limit the output torque of the drive motor within the rated torque range; and output an overload warning signal.

[0247] The torque determination device for the parallel ankle joint mechanism with a separated rotation center provided in this embodiment can execute the method provided in the above method embodiment. Its implementation principle and technical effect are similar, and will not be described in detail here.

[0248] Figure 6 This is a schematic diagram of the controller provided in an embodiment of this application. Figure 6 As shown, the controller 60 provided in this embodiment includes at least one processor 601 and a memory 602. Optionally, the controller 60 further includes a communication component 603. The processor 601, memory 602, and communication component 603 are connected via a bus 604.

[0249] In a specific implementation, at least one processor 601 executes computer execution instructions stored in memory 602, causing at least one processor 601 to perform the above-described method.

[0250] The specific implementation process of processor 601 can be found in the above method embodiments, and its implementation principle and technical effect are similar. It will not be repeated here.

[0251] In the above embodiments, it should be understood that the processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules within the processor.

[0252] The memory may include random access memory (RAM) and may also include non-volatile memory (NVM), such as at least one disk storage device.

[0253] 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. For ease of illustration, the buses shown in the accompanying drawings are not limited to a single bus or a single type of bus.

[0254] This application also provides a bipedal robot, including: a robot body; a controller; and a parallel ankle joint mechanism with a rotation center separated from the robot body; the controller is connected to a drive motor in the parallel ankle joint mechanism.

[0255] By setting up parallel ankle joint mechanisms with separate rotation centers on the robot body, and having the controller directly connected to the drive motors in these mechanisms, the controller can combine the target pitch and roll angles of the ankle joints, and call upon the analytical expression of the inverse kinematics Jacobian matrix pre-established based on the mechanism's geometric parameters to determine the mapping relationship between the ankle joint space and the drive motor space in real time. This allows for a more accurate conversion between the drive motor torque and the ankle joint load torque. Because the mapping relationship is expressed as a closed function, it reduces errors and delays caused by iterative solutions and empirical corrections. This enables the bipedal robot to obtain ankle joint force information more promptly during standing, walking, foot landing cushioning, and slope support, thereby improving posture control accuracy, dynamic balance capability, and operational safety. Consequently, it helps reduce energy consumption and improve overall robot stability.

[0256] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0257] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0258] The aforementioned readable storage medium can be implemented by 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.

[0259] 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 the device.

[0260] 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.

[0261] 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.

[0262] 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.

[0263] 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.

[0264] 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.

[0265] 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.

Claims

1. A method for determining the torque of a parallel ankle joint mechanism with a separated rotation center, characterized in that, include: Obtain the target posture angle of the ankle joint in the parallel ankle joint mechanism, wherein the target posture angle includes the target pitch angle and the target roll angle; Obtain the analytical expressions of each element in the pre-established inverse kinematics Jacobian matrix. The analytical expressions are derived by applying the chain rule to the inverse kinematics equations of the parallel ankle joint mechanism based on the geometric parameters of the parallel ankle joint mechanism. Each analytical expression is a closed function of pitch angle and roll angle. Based on the analytical expression, the inverse kinematics Jacobian matrix corresponding to the target attitude angle is determined. The kinematics Jacobian matrix is ​​used to describe the velocity mapping from the ankle joint space to the drive motor space. Based on the static mapping formula between the drive motor torque and the ankle joint load torque, the known drive motor torque is converted into the actual load torque of the ankle joint using the inverse kinematic Jacobian matrix, or the known target load torque is converted into the output torque of the drive motor in the parallel ankle joint mechanism; the static mapping formula is constructed based on the principle of virtual work.

2. The method for determining the torque of a parallel ankle joint mechanism with a separated rotation center according to claim 1, characterized in that, The analytical expressions for each element in the inverse kinematics Jacobian matrix are determined in the following way: Based on the geometric parameters, coordinate expressions for the first connection point between the link on the first drive chain and the ankle joint moving part in the parallel ankle joint mechanism, and coordinate expressions for the second connection point between the link on the second drive chain and the ankle joint moving part are established respectively. The coordinate expressions are functions of pitch angle and roll angle. Based on the coordinate expression of the first connection point and the inverse kinematic equation of the first drive chain, the analytical expressions of the partial derivatives of the first drive motor angle with respect to the pitch angle and roll angle are derived by applying the chain rule. Based on the coordinate expression of the second connection point and the inverse kinematic equation of the second drive chain, the analytical expressions of the partial derivatives of the second drive motor angle with respect to the pitch angle and roll angle are derived by applying the chain rule.

3. The method for determining the torque of a parallel ankle joint mechanism with a separated rotation center according to claim 1, characterized in that, The static mapping formula satisfies: The drive motor torque vector is equal to the transpose of the inverse kinematics Jacobian matrix multiplied by the ankle joint load torque vector; Alternatively, the ankle joint load torque vector is equal to the transpose of the kinematic Jacobian matrix multiplied by the drive motor torque vector; Wherein, the kinematic Jacobian matrix is ​​the inverse of the inverse kinematic Jacobian matrix, the drive motor torque vector includes the output torque of the first drive motor and the second drive motor, and the ankle joint load torque vector includes the rolling torque and pitching torque of the ankle joint.

4. The method for determining the torque of a parallel ankle joint mechanism with a separated rotation center according to any one of claims 1 to 3, characterized in that, The step of determining the inverse kinematics Jacobian matrix corresponding to the target attitude angle based on the analytical expression includes: Substitute the target pitch angle and the target roll angle into the analytical expression of each element of the inverse kinematics Jacobian matrix to calculate the value of each element; The calculated values ​​of each element are combined in a preset matrix form to obtain the inverse kinematic Jacobian matrix corresponding to the target attitude angle.

5. The method for determining the torque of a parallel ankle joint mechanism with a separated rotation center according to any one of claims 1 to 3, characterized in that, After converting the known drive motor torque into the actual load torque of the ankle joint, the method further includes: Obtain the target load torque of the ankle joint; Determine the torque deviation between the actual load torque and the target load torque; When the torque deviation is greater than a preset deviation threshold, it is determined that the parallel ankle joint mechanism is in an abnormal operating state; When the torque deviation is less than or equal to the preset deviation threshold, the parallel ankle joint mechanism is determined to be in normal operating condition.

6. The method for determining the torque of a parallel ankle joint mechanism with a separated rotation center according to any one of claims 1 to 3, characterized in that, After converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, the method further includes: The output torque is used as a feedforward control command; Based on the feedforward control command, the corresponding drive motor is controlled to output torque to drive the ankle joint movement of the parallel ankle joint mechanism.

7. The method for determining the torque of a parallel ankle joint mechanism with a separated rotation center according to any one of claims 1 to 3, characterized in that, After converting the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, the method further includes: When it is determined that the output torque is greater than the rated torque of the drive motor, a limiting process is triggered to limit the output torque of the drive motor within the rated torque range; Output overload warning signal.

8. A torque determining device for a parallel ankle joint mechanism with a separated rotation center, characterized in that, include: The acquisition module is used to acquire the target posture angle of the ankle joint in the parallel ankle joint mechanism, the target posture angle including the target pitch angle and the target roll angle; The acquisition module is also used to acquire the analytical expressions of each element in the pre-established inverse kinematics Jacobian matrix. The analytical expressions are derived by applying the chain rule to the inverse kinematics equations of the parallel ankle joint mechanism based on the geometric parameters of the parallel ankle joint mechanism. Each analytical expression is a closed function of pitch angle and roll angle. The determination module is used to determine the inverse kinematics Jacobian matrix corresponding to the target attitude angle based on the analytical expression. The kinematics Jacobian matrix is ​​used to describe the velocity mapping from the ankle joint space to the drive motor space. The conversion module is used to convert the known drive motor torque into the load torque of the ankle joint, or to convert the known target load torque into the output torque of the drive motor in the parallel ankle joint mechanism, based on the static mapping formula between the drive motor torque and the ankle joint load torque, using the inverse kinematic Jacobian matrix; the static mapping formula is constructed based on the principle of virtual work.

9. 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 torque determination method for a parallel ankle joint mechanism with a rotation center separation as described in any one of claims 1 to 7.

10. A bipedal robot, characterized in that, include: The robot itself; The controller as described in claim 9; And, a parallel ankle joint mechanism separated from the rotation center on the robot body; The controller is connected to the drive motor in the parallel ankle joint mechanism.

11. 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 torque determination method for the parallel ankle joint mechanism with rotation center separation as described in any one of claims 1 to 7.

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