External-force-interference-resistant gait control method for hydraulic quadruped robot

Abstract

The invention provides an external force interference resisting gait control method of a hydraulic quadruped robot. The external force interference resisting gait control method comprises the steps that firstly, a stable walking controller of the quadruped robot is built; comprising an impedance controller of a swing phase and a virtual force controller of a support phase; secondly, when the quadruped robot walks, the foot end contact force of the robot is processed through an impedance controller in the swing phase, the position compensation amount is output, the position output amount of a single position control closed loop is corrected through the compensation amount, and impedance closed loop control is conducted; the supporting phase adopts a virtual force control method through the virtual force controller, and the posture of the quadruped robot is adjusted from crossing gait planning and posture angle adjustment so as to be switched to a normal gait. Thirdly, the swing phase is controlled in a closed-loop mode according to impedance, and the supporting phase conducts stable walking of the robot according to the adjusted normal gaits. The stability of the hydraulic quadruped robot when the hydraulic quadruped robot is disturbed by the outside is improved, and the risks of rollover and toppling are reduced; the energy loss is reduced by reducing the impact force at the foot end and optimizing the gait.

Description

Technical Field

[0001] The invention relates to the technical field of quadruped robot control, and in particular to a gait control method of a hydraulic quadruped robot that resists external force interference. Background Art

[0002] The duty cycle of a quadruped robot is the ratio of the time the robot is in the support phase to the time it is in the swing phase. The trot gait of a quadruped robot requires the robot to achieve gait movement at a duty cycle of 0.5. However, in the existing electro-hydraulic servo-driven quadruped robot control technology, it is difficult for the robot to accurately achieve trot gait movement at a duty cycle of 0.5. This is manifested in the inconsistent time points at which the diagonal legs enter the support phase, that is, in a certain period of time, the robot's three legs will be in the support phase at the same time.

[0003] Due to the nonlinearity of the robot's hydraulic system, drastic load changes, and high stiffness during position servo control, the robot is prone to having three legs in the supporting phase at the same time, causing rollovers and tipping. Existing technologies mainly focus on compliant control of the legs and feet to reduce the impact of high hydraulic pressure bursts during walking. However, under the influence of external disturbances, the robot's stability judgment point will more easily cross the stability critical line, causing the robot to tip over and tip over.

[0004] Therefore, a single position controller is difficult to meet the requirements of stable walking of a quadruped robot. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a gait control method for a hydraulic quadruped robot that resists external force interference, which can solve the existing problems.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] The present invention is realized by the following technical scheme: a gait control method for a hydraulic quadruped robot against external force interference comprises the following steps:

[0008] Step 1: Build a stable walking controller for the quadruped robot, including building an impedance controller for the swing phase of the quadruped robot and a virtual force controller for the support phase;

[0009] Step 2: When the quadruped robot is walking, the foot contact force of the robot is processed by the impedance controller during the swing phase and a position compensation is output, and the position output of a single position control closed loop is corrected by the compensation to perform impedance closed loop control;

[0010] In the support phase, the virtual force controller adopts a virtual force control method to adjust the posture of the quadruped robot from the straddling gait planning and posture angle adjustment to switch to the normal gait.

[0011] Step 3: The swing phase is controlled according to the impedance closed loop, and the support phase is controlled according to the normal gait after adjustment to make the robot walk stably.

[0012] Furthermore, the swing phase processes the foot contact force of the robot through the impedance controller and outputs a position compensation amount, and corrects the position output of a single position control closed loop through the compensation amount to perform impedance closed loop control; comprising the following steps:

[0013] S1, trajectory planning: The controller first completes the foot trajectory planning and outputs the desired foot position (x r );

[0014] S2, PID adjustment: Use PID controller and position closed loop system to adjust and output the actual position (x) of the foot end;

[0015] S3, Environmental contact force calculation: According to the actual position (x), environmental position (x e ) and the environmental model to calculate the environmental contact force (F e );

[0016] S4, force deviation processing: the environmental contact force (F e ) and expected power (F r ) The force deviation value formed is brought into the impedance controller;

[0017] S5, position compensation amount calculation: calculate the position compensation amount (Δx) in the impedance controller;

[0018] S6, expected position correction: Use the position compensation (Δx) to correct the expected position (x r ) is corrected to achieve impedance closed-loop control.

[0019] Furthermore, the actual position (x), the environment position (x e ) and the environmental model to calculate the environmental contact force (F e ), where the calculation formula is:

[0020] F e The established environment model is used to represent:

[0021]

[0022] In formula (2): M e Represents environmental inertia; B e represents environmental damping; K e represents the environmental stiffness; Δxe Indicates the amount of deviation in the foot end environment position.

[0023] Furthermore, the environmental contact force (F e ) and expected power (F r ) is calculated as:

[0024] The impedance control model in the form of a second-order linear differential equation is used to express the force-position deviation relationship:

[0025]

[0026] In formula (1): M d represents the expected inertia coefficient; B d represents the expected damping coefficient; K d represents the expected stiffness coefficient; x represents the actual position of the foot end; x r Indicates the desired position of the foot; F r F represents the expected force at the foot end; e Represents the environmental contact force at the foot end.

[0027] Furthermore, the support phase uses a virtual force control method through the virtual force controller to adjust the posture of the quadruped robot from the straddling gait planning and posture angle adjustment to switch to the normal gait, including:

[0028] S1. Virtual force control: The virtual force control method is used to adjust the attitude angle of the quadruped robot using the virtual force generated by the virtual mechanism based on the spring damping system;

[0029] S2. Yaw angle control: The attitude angle adjustment strategy of the quadruped robot is designed through the virtual force control theory, and the gait control is combined with the attitude angle control to enhance the anti-interference and stable walking ability of the quadruped robot;

[0030] S3, determine whether the quadruped robot is disturbed by external forces. If so, perform stability margin planning under external force disturbance: when disturbed by external forces, plan the stability margin of the robot and design a gait control strategy; then proceed to the next step;

[0031] If not, return to S1;

[0032] S4, lateral stepping motion: When the robot has a tendency to roll over, control the affected leg to perform lateral stepping motion and land at a reasonable position to support the body;

[0033] S5, posture adjustment: The controller adjusts the robot's posture, and after the robot regains balance and has sufficient stability margin, it switches back to normal gait for movement.

[0034] Furthermore, the specific process of the yaw angle control includes:

[0035] The virtual mechanism is preset to be located at the center of gravity (COG) of the robot, and there is a virtual torque M around the Z axis (perpendicular to the XY horizontal plane). The torque can be expressed as:

[0036]

[0037] In formula (3): K θ represents the virtual stiffness coefficient; B θ represents the virtual damping coefficient; θ r represents the expected yaw angle; θ represents the actual yaw angle;

[0038] According to theoretical mechanics, the virtual torque M acting on the COG can be converted into a pair of planar couples, and this pair of couples can be equivalent to one of the diagonal legs of the robot. When this pair of diagonal legs is in the supporting phase, the virtual torque M can be converted into a pair of planar couples through the virtual force F. y To express it, as shown in the formula:

[0039] M=2F y ·L (4)

[0040] Substituting equation (4) into equation (3), we can get the virtual force F y With yaw angle θ r Relationship:

[0041]

[0042] In formula (5), L represents half of the total length of the fuselage; F y It represents the force on the robot's side swing joint and can be directly measured with the help of the force sensor on the side swing cylinder.

[0043] Furthermore, when the robot has a tendency to roll over, the affected leg is controlled to perform a lateral stepping motion, and the specific calculation process includes:

[0044] Determine the critical speed v0 at which the robot is about to roll over. According to the law of conservation of energy, we have:

[0045]

[0046] After simplification, we get:

[0047]

[0048] Where: W1 represents the vertical distance between the original foot contact point P1 and the ground projection point of COG in the Y direction; H represents the height of COG;

[0049] According to Equation (7), when v < v0, the robot still has a stability margin and can continue to move forward stably in a trot gait; when v > v0, the robot is about to tip over; the foot touchdown point will change from P1 to P2, and the distance between the touchdown point and the projection of the COG will change from W1 to W2. During this process, the lateral step speed v1 of the affected leg needs to meet the condition:

[0050]

[0051] Assuming the lateral step speed is v1' (v1' ≥ v1), then the stride length S of the straddle gait w is:

[0052]

[0053] And the swing joint angle α is:

[0054]

[0055] In the formula: L represents the total length of a single leg of the robot in the Y-Z plane;

[0056] It can be seen from Equation (9) and Equation (10) that by selecting a reasonable straddle speed v 1' the straddle stride length S can be determined w and the swing joint angle α, thereby optimizing the anti-interference ability of the robot from the perspective of gait control.

[0057] Furthermore, the stable walking controller of the quadruped robot is built, and the swing phase also includes building an environment model module, a PID controller, a position controller I, a position controller II, and a hydraulic actuator;

[0058] The virtual force controller is connected to the trajectory planning module and the controller switching module.

[0059] An anti-external force interference gait control device for a hydraulic quadruped robot, including a processor and a memory; the memory is used to store programs; the processor executes the programs to implement the method described in any one of the above.

[0060] A computer-readable storage medium, the storage medium stores a program, and the program is executed by a processor to implement the method described in any one of the above.

[0061] Compared with the prior art, the beneficial effects of the present invention include:

[0062] The present invention improves the stability of the hydraulic quadruped robot when subjected to external disturbances and reduces the risk of rollover and tipping over by designing an anti-external force interference gait control algorithm. The robot's attitude angle is adjusted by a virtual force control method, and the gait control is combined with the attitude angle control to enhance the robot's anti-interference stable walking ability. When a rollover tendency is detected, the robot can adjust its own posture and center of gravity through reasonable gait changes and return to a normal forward walking posture. Through precise gait planning and attitude angle adjustment, the robot's anti-interference ability is optimized, so that it can remain stable when subjected to external force disturbances. Through reasonable lateral stride speed and step length selection, the robot's stride strategy when subjected to lateral impact force is optimized, and the robot's stability and adaptability are improved. The critical speed at which the robot is about to roll over is calculated using the law of conservation of energy, providing a theoretical basis for gait control.

[0063] The present invention uses the foot end force sensor to provide real-time feedback on the force on the sole of the foot, so that the robot can quickly respond to external interference and adjust its gait in time. The introduction of an impedance controller based on the position inner loop reduces the impact force on the foot end, achieves smooth contact between the foot end and the environment, and enhances movement stability.

[0064] By adjusting the system inertia, stiffness and damping variables, the dynamic performance of the robot is optimized to adapt to different walking environments. The entire swing phase impedance control process is concise and clear, easy to implement and maintain. The control method of the present invention enables the robot to adapt to complex and changeable environments, and improves its applicability and reliability in practical applications. By reducing the foot end impact force and optimizing the gait, energy loss is reduced and the energy efficiency of the robot is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The disclosure of the present invention is described with reference to the accompanying drawings. It should be understood that the drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In the drawings, the same reference numerals are used to refer to the same components. Among them:

[0066] Figure 1 It is a schematic flow chart of a gait control method for a hydraulic quadruped robot that resists external force interference according to the present invention;

[0067] Figure 2 Schematic diagram of virtual force controlling yaw angle in an embodiment of the present invention;

[0068] Figure 3 Schematic diagram of the gait strategy for resisting external force interference in an implementation case of the present invention;

[0069] Figure 4 This is a schematic diagram of the lateral stepping of the LF embodiment of the present invention;

[0070] Figure 5 This is a principle block diagram of a stable walking controller according to an implementation example of the present invention. DETAILED DESCRIPTION

[0071] It is easy to understand that according to the technical solution of the present invention, without changing the essential spirit of the present invention, a person skilled in the art can propose a variety of interchangeable structural modes and implementation modes. Therefore, the following specific implementation modes and drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction to the technical solution of the present invention.

[0072] The present invention provides a method for controlling the gait of a hydraulic quadruped robot against external force interference, and a stable walking control algorithm that controls the support phase and the swing phase of the robot respectively through different controllers: when the robot walks, the force sensor at the foot end will provide real-time feedback on the current force situation of the sole. If it is detected that the robot has three legs supporting it at this time, the controller will switch, and the leg that touches the ground first will maintain the phase unchanged at this moment, and wait for its diagonal leg to fall before performing the next set of gait movements. The present invention provides a method for controlling the gait of a hydraulic quadruped robot against external force interference, and its process is as follows: Figure 1 As shown, the following steps are included:

[0073] Step 1: Build a stable walking controller for the quadruped robot, including building an impedance controller for the swing phase and a virtual force controller for the support phase. Specifically, the system block diagram of the stable walking controller is as follows: Figure 5 As shown,

[0074] Wherein: in the swing phase: the impedance controller is connected to the environment model module, the impedance controller is connected to the PID controller, and the PID controller is connected to the hydraulic actuator through the position controller 1, and the position controller 2 is also connected between the impedance controller and the PID controller connection line;

[0075] The virtual force controller is also connected to the trajectory planning module and the control switching module.

[0076] Step 2:

[0077] During the swing phase when the quadruped robot walks, the foot end contact force of the robot is processed by the impedance controller and a position compensation amount is output, and the position output amount of a single position control closed loop is corrected by the compensation amount to perform impedance closed loop control;

[0078] The swing phase module in the stable walking controller uses an impedance controller based on the position inner loop. When a simple rigid leg contacts the ground, the foot end will be subjected to a large impact from the environment, which will not only cause energy loss, but also have a great impact on the robot's motion stability. The introduction of the impedance controller is to solve this problem. The principle of position-based impedance control is to process the robot's foot contact force through the impedance controller and output the position compensation. The compensation can be used to correct the position output of a single position control closed loop, thereby reducing the robot's foot impact force, achieving smooth contact between the foot end and the environment, and achieving the purpose of enhancing motion stability.

[0079] S1, trajectory planning: The controller first completes the foot end trajectory planning, which is mainly planned through the trajectory planning module, and outputs the desired position of the foot end (x r );

[0080] S2. PID regulation: Use the PID controller and the position closed-loop system to adjust and output the actual position (x) of the foot end; the position closed-loop system is used to accurately control the position of each joint to ensure that the robot can move according to the predetermined trajectory or posture; the position closed-loop system usually includes three main parts: sensors, controllers and actuators, and belongs to the existing technology of existing quadruped robots.

[0081] S3, Environmental contact force calculation: According to the actual position (x), environmental position (x e ) and the environmental model to calculate the environmental contact force (F e );

[0082] S4, force deviation processing: the environmental contact force (F e ) and expected power (F r ) is substituted into the impedance controller;

[0083] In S3 and S4, the impedance control model requires that the robot's single leg be regarded as a spring damping system, and the desired dynamic performance is obtained by adjusting the system inertia, stiffness and damping variables. In this design, the impedance control model in the form of a second-order linear differential equation is used to represent the force-position deviation relationship:

[0084]

[0085] In formula (1): M d represents the expected inertia coefficient; B d represents the expected damping coefficient; K d represents the expected stiffness coefficient; x represents the actual position of the foot end; x r Indicates the desired position of the foot; F r F represents the expected force at the foot end; e Represents the environmental contact force at the foot end.

[0086] The foot end environmental contact force F e The established environmental model can be used to express:

[0087]

[0088] In formula (2): M d Represents environmental inertia; B d represents environmental damping; K d represents the environmental stiffness; Δx e Indicates the amount of deviation in the foot end environment position.

[0089] S5, position compensation amount calculation: calculate the position compensation amount (Δx) in the impedance controller;

[0090] S6, expected position correction: Use the position compensation (Δx) to correct the expected position (x r ) is corrected to achieve impedance closed-loop control.

[0091] The support phase uses a virtual force control method through the virtual force controller to adjust the posture of the quadruped robot from the lateral gait planning and posture angle adjustment to switch to the normal gait. Therefore, for the support phase, a virtual force control method is adopted, and its core idea is to use the virtual force generated by a virtual mechanism based on a spring damping system to adjust the robot's posture angle. The robot's posture angle adjustment strategy is designed based on virtual force control theory, aiming to combine gait control with posture angle control to further enhance the robot's anti-interference and stable walking ability. It mainly includes the following steps:

[0092] S1. Virtual force control: The virtual force control method is used to adjust the attitude angle of the quadruped robot using the virtual force generated by the virtual mechanism based on the spring damping system;

[0093] S2. Yaw angle control: The attitude angle adjustment strategy of the quadruped robot is designed through the virtual force control theory, and the gait control is combined with the attitude angle control to enhance the anti-interference and stable walking ability of the quadruped robot;

[0094] Exemplarily, the relationship between the virtual force and the yaw angle is calculated as:

[0095] according to Figure 2 , we assume that the virtual mechanism is located at the center of gravity (COG) of the robot, and there is a virtual torque M around the Z axis (perpendicular to the XY horizontal plane), then the torque can be expressed as:

[0096]

[0097] Where: K θ represents the virtual stiffness coefficient; Bθ represents the virtual damping coefficient; θ r represents the desired yaw angle; θ represents the actual yaw angle.

[0098] According to theoretical mechanics, the virtual torque M acting on the COG can be converted into a pair of planar couples, and this pair of couples can be equivalent to the RF-LB diagonal legs of the robot. When this set of diagonal legs is in the supporting phase, the virtual torque M can be converted into a pair of planar couples through the virtual force F y To express it, as shown in the formula:

[0099] M=2F y ·L (4)

[0100] Substituting equation (4) into equation (3), we can get the virtual force F y With yaw angle θ r Relationship:

[0101]

[0102] Where: L represents half of the total length of the fuselage; F y It represents the force on the robot's side swing joint and can be directly measured with the help of the force sensor on the side swing cylinder.

[0103] S3, determine whether the quadruped robot is disturbed by external forces. If so, perform stability margin planning under external force disturbance: when disturbed by external forces, plan the stability margin of the robot and design a gait control strategy; then proceed to the next step;

[0104] If not, return to S1;

[0105] Schematic diagram of the gait strategy to resist external interference Figure 3 As shown. Assume that when the robot is walking in a trot gait, the right side is subjected to an instantaneous interference force F in a direction perpendicular to the forward direction. At this time, in order to prevent the body from rolling over, the center of gravity of the robot will shift to the left front, and its left single leg (such as the LF leg) will adopt a strategy to perform a lateral step movement and fall at a reasonable position to support the body. Then the other three legs of the robot will also be adjusted accordingly. At the same time, the controller adjusts the robot's posture. After the robot recovers its balance and has sufficient stability margin, it will switch back to the trot gait for movement.

[0106] The YZ plane coordinate system is established based on the front view of the robot. When the robot is subjected to an instantaneous external force disturbance, the lateral step diagram of its LF is as follows: Figure 4As shown in the figure. In the figure, COG represents the center of gravity of the robot, and F represents the instantaneous lateral impact force. Under the action of this force, the fuselage will generate a velocity v in the left direction. When the robot has a tendency to roll over, in order to maintain the balance of the fuselage, the controller will control the three cylinders of LF to move simultaneously, so that the touchdown point of the LF foot changes from the original P1 to P2, so as to support the fuselage.

[0107] In order to formulate a striding strategy, it is first necessary to find out the critical velocity v0 at which the robot is about to roll over. According to the law of conservation of energy, we have:

[0108]

[0109] Integrating both sides simultaneously, we get:

[0110]

[0111] In the formula: W1 represents the vertical distance in the Y direction between the original touchdown point P1 of the foot and the ground projection point of the COG; H represents the height of the COG.

[0112] According to Equation (7), when v < v0, the robot still has a stability margin and can continue to move forward stably in a trot gait; when v > v0, the robot is about to roll over, and the touchdown point of the foot will change from P1 to P2, and the distance between the touchdown point and the COG projection changes from W1 to W2. During this process, the lateral striding velocity v1 of LF needs to meet the condition:

[0113]

[0114] Assume that the lateral striding velocity is v1' (v1' ≥ v1), then the striding gait length S w is:

[0115]

[0116] And the lateral swing joint angle α is:

[0117]

[0118] In the formula: L represents the total length of a single leg of the robot in the Y-Z plane.

[0119] It can be seen from Equation (9) and Equation (10) that by selecting a reasonable lateral striding velocity v1', the striding gait length Sw and the lateral swing joint angle α can be determined, thereby optimizing the anti-interference ability of the robot from the perspective of gait control.

[0120] S4. Lateral striding motion: When the robot has a tendency to roll over, control the affected leg to perform a lateral striding motion and land at a reasonable position to support the fuselage;

[0121] S5, posture adjustment: The controller adjusts the robot's posture, and after the robot regains balance and has sufficient stability margin, it switches back to normal gait for movement.

[0122] Step 3: The swing phase is controlled according to the impedance closed loop, and the support phase is controlled according to the normal gait after adjustment to make the robot walk stably.

[0123] The advantages of the anti-external force interference gait control method of the hydraulic quadruped robot of the present invention are as follows:

[0124] The present invention improves the stability of the hydraulic quadruped robot when subjected to external disturbances and reduces the risk of rollover and tipping over by designing an anti-external force interference gait control algorithm. The robot's attitude angle is adjusted by a virtual force control method, and the gait control is combined with the attitude angle control to enhance the robot's anti-interference stable walking ability. When a rollover tendency is detected, the robot can adjust its own posture and center of gravity through reasonable gait changes and return to a normal forward walking posture. Through precise gait planning and attitude angle adjustment, the robot's anti-interference ability is optimized, so that it can remain stable when subjected to external force disturbances. Through reasonable lateral stride speed and step length selection, the robot's stride strategy when subjected to lateral impact force is optimized, and the robot's stability and adaptability are improved. The critical speed at which the robot is about to roll over is calculated using the law of conservation of energy, providing a theoretical basis for gait control.

[0125] The present invention uses the foot end force sensor to provide real-time feedback on the force on the sole of the foot, so that the robot can quickly respond to external interference and adjust its gait in time. The introduction of an impedance controller based on the position inner loop reduces the impact force on the foot end, achieves smooth contact between the foot end and the environment, and enhances movement stability.

[0126] By adjusting the system inertia, stiffness and damping variables, the dynamic performance of the robot is optimized to adapt to different walking environments. The entire swing phase impedance control process is concise and clear, easy to implement and maintain. The method of the present invention enables the robot to adapt to complex and changeable environments, and improves its applicability and reliability in practical applications. By reducing the foot-end impact force and optimizing the gait, energy loss is reduced and the energy efficiency of the robot is improved.

[0127] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this article.

[0128] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0129] In the several embodiments provided herein, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, or it can be an electrical, mechanical or other form of connection.

[0130] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of this article.

[0131] In addition, each functional unit in each embodiment of this invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit may be implemented in the form of hardware or in the form of software functional unit.

[0132] If the integrated unit is implemented in the form of 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 article is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of this article. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program code.

[0133] Specific embodiments are used in this article to illustrate the principles and implementation methods of this article. The description of the above embodiments is only used to help understand the methods and core ideas of this article. At the same time, for general technicians in this field, according to the ideas of this article, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on this article.

Claims

1. A gait control method for a hydraulic quadruped robot with resistance to external force interference, characterized in that: The following steps are involved: Step 1: Build a stable walking controller for the quadruped robot, including building an impedance controller for the swing phase of the quadruped robot and a virtual force controller for the support phase; Step 2: During the swing phase when the quadruped robot walks, the foot end contact force of the robot is processed by the impedance controller and a position compensation amount is output, and the position output amount of a single position control closed loop is corrected by the compensation amount to perform impedance closed loop control; In the support phase, the virtual force controller adopts a virtual force control method to adjust the posture of the quadruped robot from the straddling gait planning and posture angle adjustment to switch to the normal gait. Step 3: The swing phase is controlled according to the impedance closed loop, and the support phase is controlled according to the normal gait after adjustment to make the robot walk stably.

2. The method for controlling the gait of a hydraulic quadruped robot against external interference according to claim 1, characterized in that: The swing phase processes the foot end contact force of the robot through the impedance controller and outputs a position compensation amount, and corrects the position output of a single position control closed loop through the compensation amount to perform impedance closed loop control; comprising the following steps: S1, trajectory planning: The controller first completes the foot trajectory planning and outputs the desired foot position (x r ); S2, PID adjustment: Use PID controller and position closed loop system to adjust and output the actual position (x) of the foot end; S3, Environmental contact force calculation: According to the actual position (x), environmental position (x e ) and the environmental model to calculate the environmental contact force (F e ); S4, force deviation processing: the environmental contact force (F e ) and expected power (F r ) is substituted into the impedance controller; S5, position compensation amount calculation: calculate the position compensation amount (Δx) in the impedance controller; S6, expected position correction: Use the position compensation (Δx) to correct the expected position (x r ) is corrected to achieve impedance closed-loop control.

3. The method for controlling the gait of a hydraulic quadruped robot against external interference according to claim 2, characterized in that: According to the actual position (x), the environmental position (x e ) and the environmental model to calculate the environmental contact force (F e ), where the calculation formula is: F e The established environment model is used to represent: In formula (2): M e Represents environmental inertia; B e represents environmental damping; K e represents the environmental stiffness; Δx e Indicates the amount of deviation in the foot end environment position.

4. The method for controlling the gait of a hydraulic quadruped robot against external interference according to claim 2, characterized in that: The environmental contact force (F e ) and expected power (F r ) is calculated as: The impedance control model in the form of a second-order linear differential equation is used to express the force-position deviation relationship: In formula (1): M d represents the expected inertia coefficient; B d represents the expected damping coefficient; K d represents the expected stiffness coefficient; x represents the actual position of the foot end; x r Indicates the desired position of the foot; F r F represents the expected force at the foot end; e Represents the environmental contact force at the foot end.

5. The method for controlling the gait of a hydraulic quadruped robot against external interference according to claim 1, characterized in that: The supporting phase uses a virtual force control method through the virtual force controller to adjust the posture of the quadruped robot from the straddling gait planning and posture angle adjustment to switch to a normal gait, including: S1. Virtual force control: The virtual force control method is used to adjust the attitude angle of the quadruped robot using the virtual force generated by the virtual mechanism based on the spring damping system; S2. Yaw angle control: The attitude angle adjustment strategy of the quadruped robot is designed through the virtual force control theory, and the gait control is combined with the attitude angle control to enhance the anti-interference and stable walking ability of the quadruped robot; S3, determine whether the quadruped robot is disturbed by external forces. If so, perform stability margin planning under external force disturbance: when disturbed by external forces, plan the stability margin of the robot and design a gait control strategy; then proceed to the next step; If not, return to S1; S4, lateral stepping motion: When the robot has a tendency to roll over, control the affected leg to perform lateral stepping motion and land at a reasonable position to support the body; S5, posture adjustment: The controller adjusts the robot's posture, and after the robot regains balance and has sufficient stability margin, it switches back to normal gait for movement.

6. The method for controlling the gait of a hydraulic quadruped robot against external force interference according to claim 5, characterized in that: The specific process of the yaw angle control includes: The virtual mechanism is located at the center of gravity (COG) of the robot, and there is a virtual torque M around the Z axis (perpendicular to the XY horizontal plane). The torque can be expressed as: In formula (3): K θ represents the virtual stiffness coefficient; B θ represents the virtual damping coefficient; θ r represents the expected yaw angle; θ represents the actual yaw angle; According to theoretical mechanics, the virtual torque M acting on the COG can be converted into a pair of planar couples, and this pair of couples can be equivalent to one of the diagonal legs of the robot. When this pair of diagonal legs is in the supporting phase, the virtual torque M can be converted into a pair of planar couples through the virtual force F. y To express it, as shown in the formula: M=2F y ·L (4) Substituting equation (4) into equation (3), we can get the virtual force F y With yaw angle θ r Relationship: In formula (5), L represents half of the total length of the fuselage; F y It represents the force on the robot's side swing joint and can be directly measured with the help of the force sensor on the side swing cylinder.

7. The method for controlling the gait of a hydraulic quadruped robot against external interference according to claim 5, characterized in that: When the robot has a tendency to roll over, the affected leg is controlled to perform a lateral stepping motion. The specific calculation process includes: Determine the critical speed v0 at which the robot is about to roll over. According to the law of conservation of energy, we have: After simplification, we get: Where: W1 represents the vertical distance between the original foot contact point P1 and the ground projection point of COG in the Y direction; H represents the height of COG; According to Equation (7), when v < v0, the robot still has a stability margin and can continue to move forward stably in a trot gait; when v > v0, the robot is about to tip over; the foot touchdown point will change from P1 to P2, and the distance between the touchdown point and the projection of the COG will change from W1 to W2. During this process, the lateral striding speed v1 of the affected leg needs to meet the condition: Assuming the lateral stride speed is v1' (v1' ≥ v1), the lateral stride length S w for: And the lateral swing joint angle α is: Where: L represents the total length of a single leg of the robot in the Y-Z plane; From equations (9) and (10), we can see that by choosing a reasonable traverse speed v 1' The step length S can be determined w and the lateral swing joint angle α, thereby optimizing the robot's anti-interference ability at the angle of gait control.

8. The method for controlling the gait of a hydraulic quadruped robot against external force interference according to claim 1, characterized in that: The constructed stable walking controller for the quadruped robot, and the swing phase thereof further includes an environment model module, a PID controller, a position controller I, a position controller II, and a hydraulic actuator; The virtual force controller is connected to the trajectory planning module and the controller switching module.

9. A gait control device for a hydraulic quadruped robot that resists external force interference, characterized in that: It includes a processor and a memory; the memory is used to store programs; the processor executes the programs to implement the method described in any one of claims 1-8.

10. A computer-readable storage medium, characterized in that: The storage medium stores a program, and the program is executed by the processor to implement the method described in any one of claims 1-8.

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