Load sensing method and system for heavy foot type carrying platform

Abstract

The invention discloses a load sensing method and system for a heavy foot type carrying platform, and the method comprises the steps: building a dynamic model of each active leg system, designing a nonlinear disturbance observer based on the dynamic models, and observing the space equivalent force in real time through the driving motor parameters of the active leg systems; establishing a kinetic model of the fuselage, acquiring inertial measurement unit data of the fuselage, and calculating inertial force and inertial moment of the fuselage; according to the observed space equivalent force of each active leg system on the fuselage, combined with the inertia force of the fuselage, the acting force of the load on the fuselage is calculated through a moment balance relation, and the acting position of the load on the fuselage is calculated through moment balance. According to the invention, on the premise of not additionally arranging a force sensor and fully considering the dynamic influence of the large-mass leg, the dual perception of the high-precision load force and the load position of the heavy foot type carrying platform in a complex environment is realized, the system cost is effectively reduced, and the control stability of the platform is improved.

Description

Technical Field

[0001] This invention relates to the field of legged robot technology, and more specifically to a load sensing method and system for heavy-duty legged transport platforms. Background Technology

[0002] Compared to traditional wheeled vehicles, legged platforms exhibit significant advantages in terrain adaptability in complex, unstructured environments. Through flexible movement and variable gait strategies, legged platforms can effectively cope with uneven terrain and dense obstacles, thus gaining widespread attention and application in challenging operations such as rescue, exploration, and military reconnaissance. To meet the demands of heavy-duty missions, heavy-duty legged platforms are typically equipped with a large-mass Active Leg System (ALS). However, the introduction of a large-mass ALS leads to significant model uncertainties and causes torque and position response hysteresis, making it difficult to directly transfer the stabilization control methods of traditional wheeled vehicles and lightweight legged robots to such platforms. Currently, robust control research for heavy-duty legged platforms in complex environments still faces many challenges, particularly in key areas such as ground force observation and load sensing on floating bases. Limited by the cost bottleneck of large-range, high-precision multidimensional force sensors and the complexity of ALS structures, existing research urgently needs to explore load sensing methods under conditions without leg-end contact sensors to improve the platform's control performance and stability under load disturbances, ground impacts, and environmental interference.

[0003] Modeling methods for heavy-duty legged platforms typically treat them as floating bases with ground-contacting or oscillating ALS (Automatic Levitation System), constructing an overall dynamic model by stacking the generalized variables of each ALS with the body pose. However, this holistic modeling method has inherent drawbacks: First, the angular acceleration of the ALS is difficult to measure directly and accurately; acquiring this parameter by adding high-precision sensors would significantly increase system costs. Second, this modeling approach leads to overdetermined characteristics; even if the ALS angular acceleration can be accurately obtained, it is still difficult to deduce the ground forces from the body inertial forces and torques calculated solely by IMU sensors. On the other hand, lightweight legged robots often employ simplified modeling methods, ignoring the influence of the leg's inertial forces and torques on the body during movement, simplifying the problem to ground forces acting directly on the body. However, this method is unsuitable for heavy-duty legged platforms equipped with large-mass ALSs because the inertial effect of the large-mass legs cannot be ignored; using a simplified model would introduce significant errors, affecting the platform's control accuracy and stability.

[0004] Therefore, a new technological solution is needed. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a load sensing method and system for heavy-duty legged transport platforms, in order to at least solve the problems existing in the prior art.

[0006] The embodiments of the present invention provide the following technical solutions: This invention provides a load sensing method for heavy-duty legged transport platforms, comprising: A dynamic model is established for each active leg system. The dynamic model describes the spatial equivalence of the active leg system at the connection point with the fuselage during the movement. A nonlinear disturbance observer is designed based on the dynamic model, and the spatial equivalence is observed in real time using the drive motor parameters of the active leg system. Establish a dynamic model of the fuselage in the inertial coordinate system, obtain the inertial measurement unit data of the fuselage, and calculate the inertial force and inertial torque of the fuselage; Based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage inertial force, the load force on the fuselage is calculated through force balance relationships. Based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage's inertial torque, the position of the load relative to the fuselage is calculated through torque balance relationships.

[0007] Preferably, establishing the dynamic model of the active leg system includes: Based on the motion stage of the active leg system, dynamic models for the ground contact stage and the swinging stage are established respectively. During the ground contact phase, the active leg system is regarded as a robotic arm fixed to the ground. Based on the assumption that the foot is in contact with the ground point and there is no relative slippage, an inertial coordinate system is established at the foot contact point, and a dynamic equation is constructed that includes the inertial matrix of the active leg system, the Coriolis force matrix, the gravity matrix, the electric cylinder active force, the friction force, and the spatial equivalent force. During the swing phase, a non-inertial coordinate system is established at the connection between the active leg system and the fuselage, and the corresponding dynamic equations are constructed. The active force of the electric cylinder is calculated based on the electromagnetic torque of the drive motor, the transmission ratio of the electric cylinder, the inertial parameters, damping parameters, and stiffness parameters of the motor and the electric cylinder through a motor-electric cylinder coupled dynamics model.

[0008] Preferably, the method for calculating the active force of the electric cylinder includes: A dynamic model of the drive motor is established, which includes the motor's electromagnetic torque, output shaft load torque, rotor moment of inertia, damping coefficient, and the relationship between rotor speed and angular acceleration. A dynamic model of an electric cylinder considering the equivalent mass of the rotor is established. The model includes the transmission ratio from the motor to the electric cylinder, the moment of inertia of the lead screw, the mass of the electric cylinder push rod, and the relationship between the push rod position, velocity, acceleration and the electric cylinder damping coefficient, stiffness coefficient, electric cylinder active force and friction force. Substituting the dynamic model of the drive motor into the dynamic model of the electric cylinder, the correlation expression between the electric cylinder's active force and the motor's electromagnetic torque, the motor and electric cylinder's structural parameters, and motion parameters is derived. Based on the expression, the electric cylinder's active force corresponding to the upper and lower legs of the active leg system is obtained.

[0009] Preferably, the design of the nonlinear perturbation observer based on the dynamic model includes: The equivalent damping of the motor and cylinder, the cylinder stiffness, and the disturbance terms within the system in the dynamic model of the active leg system are combined into the model uncertainty terms to simplify the dynamic model, resulting in the dynamic equation of the active leg system that includes the equivalent expression of the spatial equivalent on the cylinder. When the change in the spatial equivalent force is zero within a single sampling period, and the uncertainty term of the model is negligible compared to the motor's active force and the spatial equivalent force, the basic observation model of the nonlinear disturbance observer is constructed based on the simplified dynamic equation of the active leg system. By introducing intermediate variables, defining the Lyapunov function of the spatial equivalent observation error, designing the gain matrix of the nonlinear perturbation observer, ensuring the convergence of the observer, and forming a complete nonlinear perturbation observer; The parameters of the drive motor of the active leg system are input to the nonlinear disturbance observer to obtain the equivalent expression of the spatial equivalent force on the electric cylinder. Then, through the Jacobian matrix transformation from the connection point of the active leg system and the fuselage to the generalized variable, the observed value of the spatial equivalent force at the connection point of the active leg system and the fuselage is obtained.

[0010] Preferably, establishing the dynamic model of the fuselage in the inertial coordinate system includes: The generalized variable of the fuselage is defined as a vector containing the position and attitude components of the fuselage in the inertial coordinate system. The attitude components are the roll, pitch, and yaw angles of the fuselage. Based on the generalized variable, the core equation of fuselage dynamics is established. The core equation satisfies the balance relationship between the fuselage inertia matrix, Coriolis force matrix, gravity matrix and the total external forces acting on the fuselage. The composition of the total external forces acting on the fuselage is determined, including the supporting force of each active leg system on the fuselage and the force exerted by the load on the fuselage. The supporting force of each active leg system on the fuselage is equal in magnitude and opposite in direction to the spatial equivalent force at the connection point between the corresponding active leg system and the fuselage. The supporting force is converted into an expression form in the generalized space of the fuselage through the Jacobian matrix from the fuselage to the hinge point between the active leg system and the fuselage. Based on the spatial mechanics principle of inertial coordinate system, the core equation of fuselage dynamics is expanded into the triaxial force balance equation of the fuselage along the X, Y, and Z axes, and the triaxial moment balance equation of the fuselage around the X, Y, and Z axes, forming a fuselage dynamics expansion model for calculating the load force and the load position.

[0011] Preferably, acquiring the inertial measurement unit data of the fuselage and calculating the inertial force and inertial torque of the fuselage includes: The three-axis real-time linear acceleration and three-axis real-time angular acceleration collected by the fuselage inertial measurement unit are obtained, as well as the preset structural parameters of the fuselage. The preset structural parameters include the overall mass of the fuselage and the moment of inertia of the fuselage about the X, Y, and Z axes of the inertial coordinate system. Based on Newton's second law, the overall mass of the fuselage is multiplied by the real-time linear accelerations along the X, Y, and Z axes in the inertial coordinate system to obtain the inertial force components of the fuselage along the X, Y, and Z axes. The inertial force of the fuselage is then synthesized from the inertial force components along the three axes. Based on the principle of rigid body rotational dynamics, the moment of inertia of the fuselage about the three axes of the inertial coordinate system X, Y, and Z is multiplied by the real-time angular acceleration of the corresponding axis to obtain the inertial torque components of the fuselage about the three axes of the inertial coordinate system X, Y, and Z. The inertial torque of the fuselage is synthesized from the inertial torque components of the three axes.

[0012] Preferably, the step of calculating the load's force on the fuselage based on the observed spatial equivalence of each of the active leg systems on the fuselage, combined with the fuselage's inertial force, through force balance relationships includes: The spatial equivalent force at the connection point between each active leg system and the fuselage is converted into the supporting force of the corresponding active leg system on the fuselage. The supporting force is equal in magnitude and opposite in direction to the spatial equivalent force. The components of each supporting force in the X, Y, and Z axes of the inertial coordinate system are extracted, and the sum of the supporting force components in the X, Y, and Z axes of the inertial coordinate system is calculated respectively. The inertial force components of the fuselage along the X, Y, and Z axes in the inertial coordinate system are obtained, and the gravity value of the fuselage is determined. The gravity only acts in the Z-axis direction of the inertial coordinate system. Based on the principle of triaxial force balance of the fuselage in the inertial coordinate system, the components of the load force in the X, Y, and Z axes are calculated respectively. The load force component in the X axis is the sum of the fuselage inertial force component in the X axis minus the support force component in the X axis. The load force component in the Y axis is the sum of the fuselage inertial force component in the Y axis minus the support force component in the Y axis. The load force component in the Z axis is the sum of the fuselage inertial force component in the Z axis minus the support force component in the Z axis, and then minus the weight of the fuselage. The calculated load force components of the X, Y, and Z axes are combined to obtain the total force exerted by the load on the fuselage.

[0013] Preferably, the step of calculating the position of the load relative to the fuselage based on the observed spatial equivalence of each of the active leg systems on the fuselage, combined with the fuselage's inertial torque, through torque balance relationships includes: The spatial equivalent force at the connection point between each active leg system and the fuselage is converted into the supporting force of the corresponding active leg system on the fuselage. The supporting force is equal in magnitude and opposite in direction to the spatial equivalent force. The components of each supporting force in the X, Y, and Z axes of the inertial coordinate system are extracted. Combined with the position coordinates of each active leg system and the fuselage hinge point relative to the fuselage center of mass, the supporting moment of each supporting force about the fuselage center of mass about the X, Y, and Z axes is calculated. Then, the total supporting moment of the fuselage about the X, Y, and Z axes in the inertial coordinate system is obtained by summing them. Obtain the inertial torque components of the fuselage around the three axes of the inertial coordinate system X, Y, and Z. Based on the torque balance principle of the fuselage around the three axes, calculate the load torque components of the load on the fuselage center of mass around the three axes X, Y, and Z respectively. That is, the single-axis load torque component is the inertial torque component of the corresponding axis minus the total support torque component of that axis. Extract the roll, pitch, and yaw angles of the fuselage calculated by the fuselage inertial measurement unit, derive the rotation matrix of the fuselage relative to the inertial frame based on the angles, and convert the relative distance between the load and the center of mass of the fuselage from the inertial coordinate system to the form expressed in the fuselage coordinate system. Ignoring the contact deformation between the load and the fuselage and assuming it to be point contact, the vertical distance between the load and the center of mass of the fuselage is determined to be half the thickness of the fuselage. The load torque balance equation in three-dimensional space is reduced to the XY plane of the fuselage coordinate system, eliminating the unknown vertical position. Based on the reduced XY plane torque balance relationship, a corresponding coefficient matrix and torque vector are constructed. The coefficient matrix is ​​inverted and then operated with the torque vector to obtain the X and Y position components of the load relative to the fuselage center of mass in the fuselage coordinate system. Combined with the known vertical position components, the complete position coordinates of the load relative to the fuselage center of mass are obtained.

[0014] This invention also provides a load sensing system for a heavy-duty legged vehicle platform, the heavy-duty legged vehicle platform including a fuselage and multiple active leg systems, including: The model building module is used to establish a dynamic model of each of the active leg systems, and to establish a dynamic model of the fuselage in the inertial coordinate system; The data acquisition module is used to acquire the drive motor parameters of the active leg system and the inertial measurement unit data of the fuselage; A nonlinear disturbance observer module, connected to the model building module and the data acquisition module, is designed based on the dynamic model of the active leg system and uses the parameters of the drive motor to observe the spatial equivalence of the active leg system at the connection point with the fuselage during the movement in real time. An inertial force and torque calculation module is connected to the data acquisition module and calculates the inertial force and inertial torque of the fuselage based on the data from the inertial measurement unit. The load force calculation module is connected to the nonlinear disturbance observer module and the inertial force and torque calculation module, respectively. Based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage inertial force, the load force on the fuselage is calculated through the force balance relationship. The load position calculation module is connected to the nonlinear disturbance observer module and the inertial force and torque calculation module, respectively. Based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage inertial torque, the position of the load relative to the fuselage is calculated through the torque balance relationship. The output module is used to output the force exerted by the load on the fuselage and the position of the load relative to the fuselage.

[0015] Compared with the prior art, the beneficial effects that the at least one technical solution adopted in the embodiments of the present invention can achieve include at least: This invention discloses a load sensing method for heavy-duty legged transport platforms. By establishing a decoupled dynamic model of the leg and the machine, introducing spatial equivalent force to describe the leg-machine interaction, and designing a nonlinear disturbance observer, the spatial equivalent force at the leg-machine connection point can be observed in real time using only the motor's own parameters. Furthermore, by combining data from the fuselage inertial measurement unit, the force and position of the load on the fuselage are calculated through force balance and torque balance relationships, respectively. Without the need for additional force sensors and fully considering the dynamic influence of the large-mass leg, this method achieves high-precision dual sensing of load force and load position for heavy-duty legged transport platforms in complex environments, effectively reducing system costs and improving the platform's control stability. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a load sensing method for a heavy-duty legged transport platform according to an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the relationship between the fuselage and the platform in an embodiment of the present invention; Figure 3 This is a schematic diagram of load observation according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the fuselage in an embodiment of the present invention; Figure 5 This is a structural schematic diagram of a load sensing method for a heavy-duty legged transport platform according to an embodiment of the present invention. Detailed Implementation

[0018] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0019] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0021] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0022] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0023] Heavy-duty wheeled transport platforms are widely used in industry, transportation, mining, military logistics, agriculture and other fields, especially in large-scale cargo transportation, heavy operations and tasks in extreme environments[1],[2]. However, as task requirements become more complex and environmental conditions change, the challenges and limitations of traditional wheeled vehicles are becoming increasingly apparent. First, because these platforms generally adopt traditional wheel structures, their passability on rugged terrain or ruined roads is significantly limited, making it difficult to meet the passage requirements of complex obstacles in special operating environments. Second, in order to meet load-bearing requirements, heavy-duty wheeled transport platforms usually use passive suspension systems (such as fully floating leaf springs or steel plate suspensions) as shock absorbers, which results in a lack of ability to actively adjust platform stability under extreme load conditions, thus leading to insufficient handling stability and maneuverability, and making it easy for unstable driving conditions to occur.

[0024] Compared with wheeled drive, legged drive has shown better terrain adaptability in complex environments. Legged drive can effectively cope with uneven ground through flexible movement and has excellent obstacle crossing ability, especially in rugged and obstacle-dense terrain[3]. It can not only adapt to ground with varying heights, but also cope with various dynamic obstacles by changing gait, and is widely used in high-difficulty rescue, exploration and other fields. However, in order to meet the high load-bearing requirements, heavy-duty legged vehicles are usually equipped with a heavy-duty active leg system (ALS), which causes significant model uncertainty and slow torque and position response of the system, making it difficult to directly apply the stability control methods of traditional wheeled vehicles and light-duty legged platforms. In addition, due to the structural complexity of heavy-duty legged vehicles and the LS itself, as well as the cost bottleneck of large-range, high-precision, multi-dimensional force sensors, the research on robust attitude adjustment control technology of such platforms in complex environments still faces great challenges. Especially in legged mode, heavy-duty composite drive platforms face complex challenges such as load disturbances, ground reaction force (GRF) impacts, and environmental interference. These platforms urgently need breakthroughs in key technologies such as floating base GRF observation and load sensing to effectively improve their control performance and stability in complex environments. Therefore, in-depth research into load sensing for heavy-duty legged vehicles under conditions without leg-end contact sensors is of significant theoretical and practical value for improving the adaptability and control accuracy of such platforms in complex environments and promoting the development of high-performance heavy-duty legged vehicles.

[0025] Heavy-duty legged launch platforms can be viewed as floating bases with ground-contacting or oscillating aeroids (ALS). Common overall modeling methods stack the generalized variables of each ALS with the fuselage position and attitude into a unified generalized variable to establish the platform's dynamic model. In this case, the entire system is subjected to external forces consisting of gravity and the ground-free dynamic response (GRF). However, because the angular acceleration of the ALS is difficult to measure accurately, adding high-precision sensors increases costs. Furthermore, under this modeling method, the system is overdetermined; even if the angular acceleration in the ALS can be accurately obtained, it is still difficult to calculate the GRF by combining the fuselage inertial force and moment calculated from the IMU sensor with the fuselage attitude.

[0026] On the other hand, legged robots equipped with lightweight legs can ignore the influence of the inertial force and inertial torque of the legs on the body during movement, simplifying the problem to the ground force acting directly on the body. This method is also not applicable to the heavy-duty legged transport platform mentioned in this invention.

[0027] This invention achieves decoupled modeling and analysis of a heavy-duty legged vehicle platform by introducing spatial equivalent force as a correlation variable describing the interaction between the active leg system and the fuselage. First, for the active leg system, a modeling method based on the foot contact point is proposed, treating it as an equivalent robotic arm on a fixed base, and a corresponding dynamic model is established. Based on this model, a nonlinear perturbation observer is designed to achieve real-time estimation of the spatial equivalent force. Subsequently, according to the principle of action and reaction, the force exerted by the active leg system on the fuselage is equal in magnitude and opposite in direction to the estimated spatial equivalent force. After obtaining the force exerted by each leg on the fuselage, a fuselage dynamic model is established by combining data collected by inertial sensors mounted on the fuselage. Finally, the force exerted by the load on the fuselage is calculated through force balance relationships, and the position of the load relative to the vehicle's center of gravity is determined through torque balance relationships, thereby achieving dual perception of load force and load position.

[0028] Based on this, the embodiments of this specification propose a processing solution: such as Figure 1 As shown, this invention provides a load sensing method for heavy-duty legged platforms. First, the complex "leg-machine" coupling system is decoupled, establishing independent dynamic models for the active leg system and the fuselage. A spatial equivalent force is introduced at the connection point as a connecting bridge. For the active leg system, models are created for its ground contact and swing phases, and a nonlinear disturbance observer is designed. The spatial equivalent force at the leg-machine connection point can be estimated in real time using only existing motor parameters, without the need for additional force sensors. Then, the observed leg-machine force is combined with data from the fuselage inertial measurement unit. Through force balance and torque balance relationships, the magnitude and location of the load force on the fuselage are calculated.

[0029] The technical solutions provided by the various embodiments of this application are described below with reference to the accompanying drawings.

[0030] like Figure 1-5 As shown, this embodiment of the invention provides a load sensing method for heavy-duty legged transport platforms, including: Step S102: Establish a dynamic model for each active leg system. The dynamic model describes the spatial equivalence of the active leg system at the connection point with the fuselage during motion. Based on the dynamic model, design a nonlinear disturbance observer and use the drive motor parameters of the active leg system to observe the spatial equivalence in real time.

[0031] Among them, the establishment of a dynamic model of the active leg system is the core of accurately depicting the force and motion law of the large-mass active leg in different motion stages such as ground contact and swinging, clarifying the expression relationship of the spatial equivalent force (the key coupling force connecting the active leg and the fuselage) in the leg end dynamics, and solving the problem that the inertial force of the active leg of the heavy-duty leg platform cannot be ignored and the traditional modeling method of the light platform is not applicable.

[0032] Based on the model-designed nonlinear disturbance observer (NDOB), the space is observed using only low-cost parameters such as the angle and speed of the active leg drive motor. This avoids the cost bottleneck and noise problem of high-precision multidimensional force / acceleration sensors, achieving sensorless force sensing. This eliminates the need for additional sensing equipment for subsequent load calculations on the fuselage.

[0033] Furthermore, the dynamic model of the active leg system includes: Based on the movement stage of the active leg system, dynamic models for the ground contact stage and the swinging stage are established respectively to adapt to the completely different mechanical laws of the two core movement states of the active leg: ground contact and swinging. During the ground contact phase, the active leg system is regarded as a robotic arm fixed to the ground. Based on the assumption that the foot is in contact with the ground point without relative slippage, an inertial coordinate system is established at the foot contact point. Dynamic equations are constructed that include the inertial matrix of the active leg system, the Coriolis force matrix, the gravity matrix, the active force of the electric cylinder, friction, and spatial effects, so as to accurately obtain the force and motion balance relationship of the active leg during the ground contact phase. During the swing phase, a non-inertial coordinate system is established at the connection between the active leg system and the fuselage, and the corresponding dynamic equations are constructed. The active force of the electric cylinder is calculated using a motor-electric cylinder coupled dynamics model based on the electromagnetic torque of the drive motor, the transmission ratio of the electric cylinder, the inertial parameters, damping parameters, and stiffness parameters of the motor and the electric cylinder.

[0034] By specifically adapting to the distinctly different mechanical laws of the ground contact and swing phases, the model accurately describes the force and motion balance relationship of the active leg during the ground contact phase through reasonable engineering assumptions, the establishment of a dedicated inertial coordinate system, and the construction of multi-force / matrix dynamic equations. During the swing phase, a non-inertial coordinate system is established at the fuselage connection point, and corresponding dynamic equations are constructed to achieve modeling coverage of the entire motion phase of the active leg. At the same time, the active force of the electric cylinder is accurately calculated based on the motor-cylinder coupled dynamic model, providing a reliable active force input for the dynamic equations. Finally, a dynamic model is constructed that is adapted to the characteristics of the large-mass active leg of the heavy-duty leg platform, covers all motion conditions, and accurately includes the core expression of spatial equivalence. This lays a solid and accurate model foundation for the subsequent design of nonlinear disturbance observers and sensorless real-time observation of the spatial equivalence at the connection point between the active leg and the fuselage.

[0035] Specifically, based on this assumption, the ALS can be considered as a robotic arm fixed to the ground during the ground contact phase, at which point the GRF represents the constraint force exerted by the ground base on the ALS. During the movement of the transport platform, each ALS only requires two degrees of freedom: the thigh (Thigh, T) and the lower leg (Calf, C). Therefore, an inertial coordinate system is established at the ALS contact point. ,exist The dynamic model of ALS is expressed as follows:

[0036] Among them, generalized variables The length of the electric cylinder corresponding to the upper and lower legs; , , ALS The inertia matrix, Coriolis force matrix, and gravity matrix of the calf and thigh; The electric cylinders that provide the main power for the upper and lower legs are respectively the electric cylinders. For the frictional forces and other disturbances corresponding to the calf and thigh; The point of application of VSF, the connection point between ALS and the launch platform fuselage, to the generalized variable. Jacobian matrix, The force and torque exerted by the robot body on the ALS are equivalent forces, which act at the connection between the ALS and the robot body.

[0037] During the oscillation phase, the ALS is only subjected to the fuselage force at its connection point, while the EE end oscillates freely. Therefore, the previous point contact assumption is invalid. At this point, a non-inertial coordinate system is established at the connection point between the ALS and the fuselage. },exist{ The dynamic model of ALS is expressed as follows:

[0038] In the formula, generalized variables Jacobian matrix Electric cylinder main power Disturbance The definition is the same as that in equation (1). , , For ALS The inertia matrix, Coriolis force matrix, and gravity matrix of the calf and thigh.

[0039] Furthermore, methods for calculating the driving force of an electric cylinder include: A dynamic model of the drive motor is established, which includes the motor's electromagnetic torque, output shaft load torque, rotor moment of inertia, damping coefficient, and the relationship between rotor speed and angular acceleration, laying the model foundation for the motor-cylinder coupling modeling. A dynamic model of the electric cylinder considering the equivalent mass of the rotor is established. The model includes the transmission ratio from the motor to the electric cylinder, the moment of inertia of the lead screw, the mass of the electric cylinder push rod, and the relationship between the push rod position, velocity, acceleration and the damping coefficient, stiffness coefficient, active force and friction of the electric cylinder, so as to realize the mechanical connection between the motor and the electric cylinder. By substituting the dynamic model of the drive motor into the dynamic model of the electric cylinder, the correlation expression between the electric cylinder's active force and the motor's electromagnetic torque, the motor and electric cylinder's structural parameters, and motion parameters is derived. Based on the expression, the electric cylinder's active force corresponding to the upper and lower legs of the active leg system is obtained.

[0040] This invention lays the foundation for motor-end coupling modeling by establishing a dynamic model of the drive motor, and then constructs a dynamic model of the electric cylinder that considers the equivalent mass of the rotor to achieve the connection of the mechanical characteristics of the motor and the electric cylinder. Finally, the motor model is substituted into the electric cylinder model to derive the calculation expression of the electric cylinder's active force and solve for the electric cylinder's active force corresponding to the large and small legs of the active leg. The whole process fully considers the structural parameters, motion parameters, and coupling characteristics such as inertia, damping, and stiffness of the motor and the electric cylinder, avoids the force value error caused by simplified calculation, and accurately solves for the key active force term of the electric cylinder's active force required by the dynamic equation of the active leg. This provides core power source parameter support for the numerical accuracy of the dynamic model of the active leg throughout the entire motion stage, thereby ensuring the reliability of subsequent spatial equivalent force observation work based on this model.

[0041] Specifically, the electric cylinder's main power This can be obtained by modeling the motor and the electric cylinder. The dynamic model of the motor is as follows:

[0042] In the formula, The electromagnetic torque of the motor. This refers to the load torque on the motor output shaft. Let be the moment of inertia of the motor rotor. This is the damping coefficient of the motor. , Let be the rotational speed and angular acceleration of the motor rotor. The electric cylinder push rod is driven by the motor rotor via a lead screw; therefore, the dynamic model of the electric cylinder considering the equivalent mass of the rotor is as follows:

[0043] In the formula The transmission ratio from the motor to the electric cylinder is given by: The lead screw pitch; Let be the moment of inertia of the leadscrew; The mass of the electric cylinder push rod; , , The position, velocity, and acceleration of the push rod; , For the damping and stiffness coefficient of the push rod; The electric cylinder is the main power source. The friction force of the electric cylinder. Substituting the motor model (3) into the electric cylinder model (4), we obtain:

[0044] In the formula, electromagnetic torque It can be obtained from parameters such as magnetic flux, dq current, and number of pole pairs. The above formula is the output force of the electric cylinder, taking into account disturbances such as inertia, damping, stiffness, and friction in the motor and electric cylinder. and electromagnetic torque relation.

[0045] According to equation (5), the driving force of the electric cylinder at the thigh and calf can be expressed as:

[0046] Furthermore, the design of nonlinear perturbation observers based on dynamic models includes: The equivalent damping of the motor and cylinder, the stiffness of the cylinder, and the disturbance terms within the system in the dynamic model of the active leg system are combined into the model uncertainty terms to simplify the dynamic model and obtain the dynamic equation of the active leg system that includes the equivalent expression of the spatial equivalent on the cylinder. When the change in spatial equivalent force is zero within a single sampling period, and the uncertainty term of the model is negligible compared to the proportion of the motor's active force and spatial equivalent force, a basic observation model for the nonlinear disturbance observer is constructed based on the simplified dynamic equation of the active leg system. By introducing intermediate variables, defining the Lyapunov function of spatial equivalent observation error, designing the gain matrix of the nonlinear perturbation observer, ensuring the convergence of the observer, and forming a complete nonlinear perturbation observer; The parameters of the drive motor of the active leg system are input into the nonlinear disturbance observer to obtain the equivalent expression of the spatial equivalent force on the electric cylinder. Then, through the Jacobian matrix transformation from the connection point between the active leg system and the fuselage to the generalized variable, the observed value of the spatial equivalent force at the connection point between the active leg system and the fuselage is obtained.

[0047] Specifically, by simplifying the dynamic model of the active leg system and merging the uncertainty terms, and combining reasonable assumptions to construct the basic model of the nonlinear disturbance observer, and then by introducing intermediate variables and defining the Lyapunov function to design the gain matrix to ensure the convergence of the observer, the drive motor parameters are finally input into the observer and transformed by the Jacobian matrix. This enables sensorless, accurate and real-time observation of the spatial equivalence at the connection point between the active leg system and the fuselage, providing core force data support for the subsequent calculation of load force and load position.

[0048] Specifically, by combining equations (1) and (6), we can obtain:

[0049] In the formula, Let be the equivalent mass matrix of the motor and the electric cylinder. Here is the equivalent damping matrix for the motor and the electric cylinder. Here is the stiffness matrix of the electric cylinder. This represents the transmission ratio of the motor. The electromagnetic torque of the motor. Let's consider the friction-inducing perturbation matrix for the legs. The equivalent damping of the motor and cylinder should also be taken into account. Cylinder stiffness and disturbances within the system Merging into model uncertainty Equation (7) can be rewritten as:

[0050] In the formula .

[0051] For ease of subsequent derivation, equation (8) is rewritten as follows:

[0052] in , For the expression of VSF in electric cylinders, due to the Lacking prior knowledge, we therefore assume The change is zero at each sampling time interval, that is... For the heavy-duty transport platform mentioned in this case, the disturbance term in equation (9) Compared to the main force and equivalent The proportion is relatively small, so it is estimated It can be ignored; Designed according to equation (9) for observation Nonlinear Disturbance Observation (NDOB):

[0053] Equivalent matrix in the formula It is a positive definite symmetric matrix. To obtain observation values intermediate variables, defined .

[0054] By definition or This ensures the normal convergence of NDOB. Gain matrix The expression is as follows:

[0055] definition The error between the observed and actual values ​​of VSF is due to Its derivative can be obtained as follows:

[0056] To ensure observation error Approaching zero, i.e., the observer converges, requires... Lyapunov function design or , Its partial derivative expression is as follows:

[0057] Substituting equation (13) into equation (11), we get:

[0058] Substituting equation (14) into equation (12), we get:

[0059] definition The Lyapunov function is as follows:

[0060] in for Orthogonal diagonalization decomposition:

[0061] because Since it is positive definite, therefore we have Positive definite. The derivative of the Lyapunov function is:

[0062] By selecting a suitable parameter c, the equation (18) can be optimized. The observer converges, and the VSF observations are changed from... Therefore, during the operation of the launch platform, the VSF of ALS can be obtained during both the oscillation phase and the ground contact phase.

[0063] Step S104: Establish the dynamic model of the fuselage in the inertial coordinate system, obtain the inertial measurement unit data of the fuselage, and calculate the inertial force and inertial torque of the fuselage.

[0064] Among them, a dynamic model of the fuselage in the inertial coordinate system was established, the generalized variables of the fuselage position and attitude were defined, and the core equations of force and torque balance of the fuselage were derived. This provided a standardized mechanical calculation framework for the subsequent solution of load force and load position, and solved the problem that the heavy-duty legged platform, as a floating base, has no fixed reference system and no unified basis for mechanical calculation.

[0065] Using the basic data from the fuselage inertial measurement unit (IMU), the inertial forces along the three axes and the inertial moments around the three axes are calculated, and the inertial effects generated by the fuselage's own motion (translation and rotation) are accurately quantified. The heavy load and high dynamic characteristics of the heavy platform determine that this inertial effect cannot be ignored. This step solves the problem of large load calculation deviation caused by the lack of quantification of inertial quantities.

[0066] Furthermore, establishing the dynamic model of the fuselage in the inertial coordinate system includes: The generalized variables of the fuselage are defined as vectors containing the position and attitude components of the fuselage in the inertial coordinate system. The attitude components are the roll, pitch, and yaw angles of the fuselage. Based on the generalized variables, the core equations of fuselage dynamics are established. The core equations satisfy the balance relationship between the fuselage inertia matrix, Coriolis force matrix, gravity matrix and the total external forces acting on the fuselage. The composition of the total external forces acting on the fuselage is determined, including the supporting force of each active leg system on the fuselage and the force exerted by the load on the fuselage. The supporting force of each active leg system on the fuselage is equal in magnitude and opposite in direction to the spatial equivalent force at the connection point between the corresponding active leg system and the fuselage. The supporting force is converted into an expression form in the generalized space of the fuselage through the Jacobian matrix from the fuselage to the hinge point between the active leg system and the fuselage. Based on the spatial mechanics principles of inertial coordinate systems, the core equations of fuselage dynamics are expanded into three-dimensional force balance equations along the X, Y, and Z axes, and three-dimensional moment balance equations around the X, Y, and Z axes, forming a fuselage dynamics expansion model for calculating load forces and load positions.

[0067] In this process, by defining generalized variables of the fuselage to establish the core dynamic equations, clarifying the composition of external forces and completing the coordinate transformation of forces, expanding the force and torque balance equations, and finally constructing a fuselage dynamic model for calculating the load forces and positions, thus providing a theoretical basis and calculation basis for subsequent analysis.

[0068] Furthermore, by acquiring inertial measurement unit data of the fuselage, the inertial forces and moments of the fuselage are calculated, including: The system acquires real-time linear acceleration and real-time angular acceleration of the three axes from the fuselage inertial measurement unit, as well as preset structural parameters of the fuselage, including the overall mass of the fuselage and the moment of inertia of the fuselage about the X, Y, and Z axes of the inertial coordinate system. Based on Newton's second law, the overall mass of the fuselage is multiplied by the real-time linear accelerations of the X, Y, and Z axes in the inertial coordinate system to obtain the inertial force components of the fuselage along the X, Y, and Z axes of the inertial coordinate system. The inertial force of the fuselage is then synthesized from the inertial force components of the three axes. Based on the principle of rigid body rotational dynamics, the moments of inertia of the fuselage about the X, Y, and Z axes of the inertial coordinate system are multiplied by the real-time angular acceleration of the corresponding axes to obtain the inertial torque components of the fuselage about the X, Y, and Z axes of the inertial coordinate system. The inertial torque of the fuselage is then synthesized from the inertial torque components of the three axes.

[0069] Among them, by acquiring real-time motion data (three-axis acceleration and three-axis angular acceleration) collected by the fuselage inertial measurement unit (IMU), and combining it with the fuselage's preset structural parameters (overall mass and three-axis rotational inertia), the inertial force and inertial torque of the fuselage are accurately calculated using Newton's second law and the principle of rigid body rotational dynamics. This provides key mechanical data support for subsequent fuselage dynamics analysis, load force / torque calculation, and motion control strategy formulation, and is a fundamental step in realizing fuselage dynamics modeling and precise control.

[0070] Step S106: Based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage inertial force, calculate the load force on the fuselage through force balance relationships.

[0071] First, the observed spatial equivalent force is converted into the supporting force of the active leg on the fuselage (equal in magnitude and opposite in direction). Then, combined with the fuselage inertial force calculated by S104, and based on the principle of spatial triaxial force balance in the inertial coordinate system, the supporting force of the active leg, the inertial force of the fuselage itself, and the gravity are separated from the total force on the fuselage. Finally, the force of the load on the fuselage (including X, Y, and Z axis components) is solved.

[0072] Furthermore, based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage inertial force, the load forces on the fuselage are calculated using force balance relationships, including: The spatial equivalent force at the connection point between each active leg system and the fuselage is converted into the supporting force of the corresponding active leg system on the fuselage. The supporting force is equal in magnitude and opposite in direction to the spatial equivalent force. The components of each supporting force in the X, Y, and Z axes of the inertial coordinate system are extracted, and the sum of the supporting force components in the X, Y, and Z axes of the inertial coordinate system is calculated respectively. Obtain the inertial force components of the fuselage along the X, Y, and Z axes in the inertial coordinate system, and simultaneously determine the gravity value of the fuselage, which acts only in the Z-axis direction of the inertial coordinate system; Based on the principle of triaxial force balance of the fuselage in the inertial coordinate system, the components of the load force in the X, Y, and Z axes are calculated respectively. The load force component in the X axis is the sum of the fuselage inertial force component in the X axis minus the support force component in the X axis. The load force component in the Y axis is the sum of the fuselage inertial force component in the Y axis minus the support force component in the Y axis. The load force component in the Z axis is the sum of the fuselage inertial force component in the Z axis minus the support force component in the Z axis, minus the fuselage weight. The calculated load force components of the X, Y, and Z axes are combined to obtain the total force exerted by the load on the fuselage.

[0073] Among them, by utilizing the spatial equivalence of the active leg system and the fuselage connection point, combined with the fuselage inertial force and gravity, the force exerted by the load on the fuselage (including triaxial components and total force) is accurately calculated using the force balance relationship, providing key mechanical data support for fuselage dynamics analysis, load sensing and motion control.

[0074] Step S108: Based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage inertial torque, calculate the position of the load relative to the fuselage through the torque balance relationship.

[0075] Step S108 is used to accurately determine the position of the load relative to the fuselage. It is the final step in the entire load sensing process. Together with the load force in S106, it constitutes the complete load sensing result. This solves the problem of accurately locating the load contact position on the heavy-duty foot platform and provides key positional information for subsequent platform control.

[0076] Furthermore, based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage's inertial torque, the position of the load relative to the fuselage is calculated through torque balance relationships, including: The spatial equivalent force at the connection point between each active leg system and the fuselage is converted into the supporting force of the corresponding active leg system on the fuselage. The supporting force is equal in magnitude and opposite in direction to the spatial equivalent force. The components of each supporting force in the X, Y, and Z axes of the inertial coordinate system are extracted. Combined with the position coordinates of each active leg system and the fuselage hinge point relative to the fuselage center of mass, the supporting moment of each supporting force about the fuselage center of mass about the X, Y, and Z axes is calculated. Then, the total supporting moment of the fuselage about the X, Y, and Z axes in the inertial coordinate system is obtained by summing them. Obtain the inertial torque components of the fuselage around the X, Y, and Z axes of the inertial coordinate system. Based on the torque balance principle of the fuselage around the three axes, calculate the load torque components of the load on the fuselage center of mass around the X, Y, and Z axes respectively. That is, the load torque component of a single axis is the inertial torque component of the corresponding axis minus the total support torque component of that axis. Extract the fuselage roll, pitch, and yaw angles calculated by the fuselage inertial measurement unit, derive the rotation matrix of the fuselage relative to the inertial frame based on the angles, and convert the relative distance between the load and the fuselage center of mass from the inertial coordinate system to the expression in the fuselage coordinate system. Ignoring the contact deformation between the load and the fuselage and assuming it to be point contact, the vertical distance between the load and the fuselage center of mass is determined to be half the thickness of the fuselage. The load torque balance equation in three-dimensional space is reduced to the XY plane of the fuselage coordinate system, eliminating the unknown vertical position. Based on the reduced XY plane torque balance relationship, the corresponding coefficient matrix and torque vector are constructed. After inverting the coefficient matrix, the torque vector is used to obtain the X and Y position components of the load relative to the fuselage center of mass in the fuselage coordinate system. Combined with the known vertical position components, the complete position coordinates of the load relative to the fuselage center of mass are obtained.

[0077] Specifically, by calculating the supporting force and torque of each active leg system on the fuselage, and combining the torque balance principle to solve the load torque, and then using the fuselage attitude angle to complete the coordinate system transformation and equation dimensionality reduction, the complete position coordinates of the load relative to the fuselage center of mass are finally accurately calculated, providing key position data support for fuselage dynamics analysis, motion control strategy formulation, and load status perception.

[0078] The following is a detailed explanation of the calculation method for load force and load location in this invention: Figure 3 This illustrates the stress conditions on the fuselage, showing the supporting forces from the various ALS (Air Surface Units), gravity, and load forces. ALS Support Force Its magnitude is equal to the VSF experienced by ALS, but its direction is opposite. The dynamic model of the fuselage in the inertial coordinate system {I} is as follows:

[0079] In the formula, generalized variables These are generalized variables that include the fuselage's position and attitude vectors. , , Let be the inertial matrix, Coriolis force matrix, and gravity matrix of the fuselage in the inertial coordinate system {I}, respectively. The supporting forces on the i-th ALS are:

[0080] in, The supporting force of the i-th ALS Expression within the broader space of the fuselage Let be the Jacobian matrix from the fuselage to the i-th ALS hinge point with the fuselage. The total external forces acting on the fuselage are expressed as follows:

[0081] in, For load force Expression within the generalized space of the fuselage. Substituting equation (21) into equation (19) and expanding, we have the following expression:

[0082]

[0083]

[0084]

[0085]

[0086] In the formula, Represents the coordinates of the location where the i-th ALS connects to the vehicle body; , , The inertial torque of the fuselage; This indicates the distance between the point of contact between the load and the fuselage and the center of gravity of the fuselage; This indicates the force exerted by the load on the fuselage; This represents the inertial force of the fuselage.

[0087] By rewriting equations (22) to (24), we can obtain the expression of the load force on the fuselage:

[0088] In the formula It can be calculated from the signals of the IMU sensors on the fuselage, combined with previously observed data. Load capacity You can get it immediately.

[0089] Equations (25) to (27) indicate that the torque of the fuselage is balanced, and can be rewritten as:

[0090] Among them, only the distance between the load and the center of gravity of the fuselage Unknown, the rest are known.

[0091] In addition, to facilitate subsequent control, the distance of the load relative to the center of gravity of the fuselage is... Through the rotation matrix of the fuselage relative to the inertial frame Expression of relative distance in fuselage system This means that the rewritten expression (29) is:

[0092] in, From generalized variables The attitude of the fuselage in the middle, ,Decide, These represent the roll, pitch, and yaw angles of the fuselage, expressed as follows:

[0093]

[0094] Equation (25) can be simplified to:

[0095] In the formula The load force in equation (30) is a third-order oblique symmetric matrix, which is singular and cannot be directly inverted.

[0096] To facilitate online estimation of the load forces and load locations on the fuselage, the following assumptions are made: The load and the machine body are in point contact, and the deformation of the load when in contact with the machine body is negligible.

[0097] The above assumption of point contact implies the vertical distance between the load and the center of gravity of the fuselage. The thickness is half that of the fuselage. Therefore, equation (32) can be reduced to the XY plane and the contact position of the load can be calculated. At this time, we have:

[0098] in,

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105] By combining formulas (33) to (40), the load position relative to the fuselage can be obtained.

[0106] This invention, through the design of NDOB, uses only the angle and speed sensors of the motor to complete VSF observation, without the need for additional angular velocity sensors, thus avoiding the noise introduced by acceleration sensors and controlling costs. Furthermore, for the launch platform, by modeling the ALS and fuselage separately, the influence of the inertial force and inertial torque of the large-mass ALS on the fuselage is fully considered.

[0107] This invention also provides a load sensing system for a heavy-duty legged vehicle platform. The heavy-duty legged vehicle platform includes a fuselage and multiple active leg systems. The system comprises: a model building module, a data acquisition module, a nonlinear disturbance observer module, an inertial force and torque calculation module, a load force calculation module, a load position calculation module, and an output module. The model building module is used to establish a dynamic model for each active leg system and a dynamic model of the fuselage in an inertial coordinate system. The data acquisition module is used to acquire the drive motor parameters of the active leg systems and the inertial measurement unit data of the fuselage. The nonlinear disturbance observer module is connected to the model building module and the data acquisition module. Based on the dynamic model of the active leg system, it designs and uses the drive motor parameters to observe the spatial equivalence at the connection point between the active leg system and the fuselage in real time during movement. The inertial force and torque calculation module is connected to the data acquisition module and calculates the inertial force and inertia of the fuselage based on the inertial measurement unit data. The load force calculation module is connected to both the nonlinear disturbance observer module and the inertial force and torque calculation module. Based on the observed equivalent force of each active leg system on the fuselage, combined with the fuselage inertial force, it calculates the load's force on the fuselage through force balance relationships. The load position calculation module is also connected to both the nonlinear disturbance observer module and the inertial force and torque calculation module. Based on the observed equivalent force of each active leg system on the fuselage, combined with the fuselage inertial torque, it calculates the load's position relative to the fuselage through torque balance relationships. The output module outputs the load's force on the fuselage and the load's position relative to the fuselage.

[0108] In this specification, the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for the product embodiments described later, since they correspond to the methods, the descriptions are relatively simple, and the relevant parts can be referred to the descriptions in the system embodiments.

[0109] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A load sensing method for heavy-duty legged transport platforms, characterized in that, include: A dynamic model is established for each active leg system. The dynamic model describes the spatial equivalence of the active leg system at the connection point with the fuselage during the movement. A nonlinear disturbance observer is designed based on the dynamic model, and the spatial equivalence is observed in real time using the drive motor parameters of the active leg system. Establish a dynamic model of the fuselage in the inertial coordinate system, obtain the inertial measurement unit data of the fuselage, and calculate the inertial force and inertial torque of the fuselage; Based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage inertial force, the load force on the fuselage is calculated through force balance relationships. Based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage's inertial torque, the position of the load relative to the fuselage is calculated through torque balance relationships.

2. The load sensing method according to claim 1, characterized in that, Establishing the dynamic model of the active leg system includes: Based on the motion stage of the active leg system, dynamic models for the ground contact stage and the swinging stage are established respectively. During the ground contact phase, the active leg system is regarded as a robotic arm fixed to the ground. Based on the assumption that the foot is in contact with the ground point and there is no relative slippage, an inertial coordinate system is established at the foot contact point, and a dynamic equation is constructed that includes the inertial matrix of the active leg system, the Coriolis force matrix, the gravity matrix, the electric cylinder active force, the friction force, and the spatial equivalent force. During the swing phase, a non-inertial coordinate system is established at the connection between the active leg system and the fuselage, and the corresponding dynamic equations are constructed. The active force of the electric cylinder is calculated based on the electromagnetic torque of the drive motor, the transmission ratio of the electric cylinder, the inertial parameters, damping parameters, and stiffness parameters of the motor and the electric cylinder through a motor-electric cylinder coupled dynamics model.

3. The load sensing method according to claim 2, characterized in that, The method for calculating the driving force of the electric cylinder includes: A dynamic model of the drive motor is established, which includes the motor's electromagnetic torque, output shaft load torque, rotor moment of inertia, damping coefficient, and the relationship between rotor speed and angular acceleration. A dynamic model of an electric cylinder considering the equivalent mass of the rotor is established. The model includes the transmission ratio from the motor to the electric cylinder, the moment of inertia of the lead screw, the mass of the electric cylinder push rod, and the relationship between the push rod position, velocity, acceleration and the electric cylinder damping coefficient, stiffness coefficient, electric cylinder active force and friction force. Substituting the dynamic model of the drive motor into the dynamic model of the electric cylinder, the correlation expression between the electric cylinder's active force and the motor's electromagnetic torque, the motor and electric cylinder's structural parameters, and motion parameters is derived. Based on the expression, the electric cylinder's active force corresponding to the upper and lower legs of the active leg system is obtained.

4. The load sensing method according to claim 2, characterized in that, The design of the nonlinear perturbation observer based on the dynamic model includes: The equivalent damping of the motor and cylinder, the cylinder stiffness, and the disturbance terms within the system in the dynamic model of the active leg system are combined into the model uncertainty terms to simplify the dynamic model, resulting in the dynamic equation of the active leg system that includes the equivalent expression of the spatial equivalent on the cylinder. When the change in the spatial equivalent force is zero within a single sampling period, and the uncertainty term of the model is negligible compared to the motor's active force and the spatial equivalent force, the basic observation model of the nonlinear disturbance observer is constructed based on the simplified dynamic equation of the active leg system. By introducing intermediate variables, defining the Lyapunov function of the spatial equivalent observation error, designing the gain matrix of the nonlinear perturbation observer, ensuring the convergence of the observer, and forming a complete nonlinear perturbation observer; The parameters of the drive motor of the active leg system are input to the nonlinear disturbance observer to obtain the equivalent expression of the spatial equivalent force on the electric cylinder. Then, through the Jacobian matrix transformation from the connection point of the active leg system and the fuselage to the generalized variable, the observed value of the spatial equivalent force at the connection point of the active leg system and the fuselage is obtained.

5. The load sensing method according to claim 1, characterized in that, The process of establishing the dynamic model of the fuselage in the inertial coordinate system includes: The generalized variable of the fuselage is defined as a vector containing the position and attitude components of the fuselage in the inertial coordinate system. The attitude components are the roll, pitch, and yaw angles of the fuselage. Based on the generalized variable, the core equation of fuselage dynamics is established. The core equation satisfies the balance relationship between the fuselage inertia matrix, Coriolis force matrix, gravity matrix and the total external forces acting on the fuselage. The composition of the total external forces acting on the fuselage is determined, including the supporting force of each active leg system on the fuselage and the force exerted by the load on the fuselage. The supporting force of each active leg system on the fuselage is equal in magnitude and opposite in direction to the spatial equivalent force at the connection point between the corresponding active leg system and the fuselage. The supporting force is converted into an expression form in the generalized space of the fuselage through the Jacobian matrix from the fuselage to the hinge point between the active leg system and the fuselage. Based on the spatial mechanics principle of inertial coordinate system, the core equation of fuselage dynamics is expanded into the triaxial force balance equation of the fuselage along the X, Y, and Z axes, and the triaxial moment balance equation of the fuselage around the X, Y, and Z axes, forming a fuselage dynamics expansion model for calculating the load force and the load position.

6. The load sensing method according to claim 5, characterized in that, The step of acquiring inertial measurement unit data of the fuselage and calculating the inertial force and inertial torque of the fuselage includes: The three-axis real-time linear acceleration and three-axis real-time angular acceleration collected by the fuselage inertial measurement unit are obtained, as well as the preset structural parameters of the fuselage. The preset structural parameters include the overall mass of the fuselage and the moment of inertia of the fuselage about the X, Y, and Z axes of the inertial coordinate system. Based on Newton's second law, the overall mass of the fuselage is multiplied by the real-time linear accelerations along the X, Y, and Z axes in the inertial coordinate system to obtain the inertial force components of the fuselage along the X, Y, and Z axes. The inertial force of the fuselage is then synthesized from the inertial force components along the three axes. Based on the principle of rigid body rotational dynamics, the moment of inertia of the fuselage about the three axes of the inertial coordinate system X, Y, and Z is multiplied by the real-time angular acceleration of the corresponding axis to obtain the inertial torque components of the fuselage about the three axes of the inertial coordinate system X, Y, and Z. The inertial torque of the fuselage is synthesized from the inertial torque components of the three axes.

7. The load sensing method according to claim 6, characterized in that, The calculation of the load's force on the fuselage based on the observed spatial equivalence of each of the active leg systems, combined with the fuselage's inertial force, and through force balance relationships includes: The spatial equivalent force at the connection point between each active leg system and the fuselage is converted into the supporting force of the corresponding active leg system on the fuselage. The supporting force is equal in magnitude and opposite in direction to the spatial equivalent force. The components of each supporting force in the X, Y, and Z axes of the inertial coordinate system are extracted, and the sum of the supporting force components in the X, Y, and Z axes of the inertial coordinate system is calculated respectively. The inertial force components of the fuselage along the X, Y, and Z axes in the inertial coordinate system are obtained, and the gravity value of the fuselage is determined. The gravity only acts in the Z-axis direction of the inertial coordinate system. Based on the principle of triaxial force balance of the fuselage in the inertial coordinate system, the components of the load force in the X, Y, and Z axes are calculated respectively. The load force component in the X axis is the sum of the fuselage inertial force component in the X axis minus the support force component in the X axis. The load force component in the Y axis is the sum of the fuselage inertial force component in the Y axis minus the support force component in the Y axis. The load force component in the Z axis is the sum of the fuselage inertial force component in the Z axis minus the support force component in the Z axis, and then minus the weight of the fuselage. The calculated load force components of the X, Y, and Z axes are combined to obtain the total force exerted by the load on the fuselage.

8. The load sensing method according to claim 7, characterized in that, The step of calculating the position of the load relative to the fuselage based on the observed spatial equivalence of each of the active leg systems on the fuselage, combined with the fuselage's inertial torque, and through torque balance relationships includes: The spatial equivalent force at the connection point between each active leg system and the fuselage is converted into the supporting force of the corresponding active leg system on the fuselage. The supporting force is equal in magnitude and opposite in direction to the spatial equivalent force. The components of each supporting force in the X, Y, and Z axes of the inertial coordinate system are extracted. Combined with the position coordinates of each active leg system and the fuselage hinge point relative to the fuselage center of mass, the supporting moment of each supporting force about the fuselage center of mass about the X, Y, and Z axes is calculated. Then, the total supporting moment of the fuselage about the X, Y, and Z axes in the inertial coordinate system is obtained by summing them. Obtain the inertial torque components of the fuselage around the three axes of the inertial coordinate system X, Y, and Z. Based on the torque balance principle of the fuselage around the three axes, calculate the load torque components of the load on the fuselage center of mass around the three axes X, Y, and Z respectively. That is, the single-axis load torque component is the inertial torque component of the corresponding axis minus the total support torque component of that axis. Extract the roll, pitch, and yaw angles of the fuselage calculated by the fuselage inertial measurement unit, derive the rotation matrix of the fuselage relative to the inertial frame based on the angles, and convert the relative distance between the load and the center of mass of the fuselage from the inertial coordinate system to the form expressed in the fuselage coordinate system. Ignoring the contact deformation between the load and the fuselage and assuming it to be point contact, the vertical distance between the load and the center of mass of the fuselage is determined to be half the thickness of the fuselage. The load torque balance equation in three-dimensional space is reduced to the XY plane of the fuselage coordinate system, eliminating the unknown vertical position. Based on the reduced XY plane torque balance relationship, a corresponding coefficient matrix and torque vector are constructed. The coefficient matrix is ​​inverted and then operated with the torque vector to obtain the X and Y position components of the load relative to the fuselage center of mass in the fuselage coordinate system. Combined with the known vertical position components, the complete position coordinates of the load relative to the fuselage center of mass are obtained.

9. A load sensing system for a heavy-duty legged vehicle platform, the heavy-duty legged vehicle platform comprising a fuselage and multiple active leg systems, characterized in that, include: The model building module is used to establish a dynamic model of each of the active leg systems, and to establish a dynamic model of the fuselage in the inertial coordinate system; The data acquisition module is used to acquire the drive motor parameters of the active leg system and the inertial measurement unit data of the fuselage; A nonlinear disturbance observer module, connected to the model building module and the data acquisition module, is designed based on the dynamic model of the active leg system and uses the parameters of the drive motor to observe the spatial equivalence of the active leg system at the connection point with the fuselage during the movement in real time. An inertial force and torque calculation module is connected to the data acquisition module and calculates the inertial force and inertial torque of the fuselage based on the data from the inertial measurement unit. The load force calculation module is connected to the nonlinear disturbance observer module and the inertial force and torque calculation module, respectively. Based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage inertial force, the load force on the fuselage is calculated through the force balance relationship. The load position calculation module is connected to the nonlinear disturbance observer module and the inertial force and torque calculation module, respectively. Based on the observed spatial equivalence of each active leg system on the fuselage, and combined with the fuselage inertial torque, the position of the load relative to the fuselage is calculated through the torque balance relationship. The output module is used to output the force exerted by the load on the fuselage and the position of the load relative to the fuselage.

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