Control method based on foot end and hydraulic drive unit equivalent stiffness damping mapping

Abstract

This invention provides a control method based on the equivalent stiffness and damping mapping between the foot and the hydraulic drive unit, comprising the following steps: constructing a hydraulic leg model, obtaining the equivalent stiffness mapping relationship between the foot and the rotary joint, obtaining the equivalent stiffness mapping relationship between the rotary joint and the hydraulic drive unit, further establishing the equivalent stiffness mapping relationship between the foot and the hydraulic drive unit; establishing the equivalent damping mapping relationship between the foot and the hydraulic drive unit, further establishing the equivalent stiffness and damping mapping relationship between the foot of the hydraulically driven leg and the hydraulic drive unit, and performing control. This invention can accurately solve the compliance parameters of the rotary joint and the hydraulic drive unit based on the stiffness, damping, and compliance parameters of the foot of the hydraulic robotic arm and hydraulic leg. Compared with pure position control or compliance control with passive springs, the stiffness and damping parameters of the hydraulic leg foot can be accurately controlled by the hydraulic drive cylinder without the need for additional design of passive springs or other mechanical structures, resulting in low cost and high reliability.

Description

Technical Field

[0001] This invention belongs to the field of robot control, specifically relating to a control method based on the equivalent stiffness damping mapping between the foot and the hydraulic drive unit. Background Technology

[0002] With the increasingly widespread application of robots in various fields, many situations require robots to interact compliantly with the environment, possessing the ability to sense and control contact forces. For example, in operations such as precision assembly, scraping or grinding workpiece surfaces, polishing, and cleaning, it is necessary to maintain compliant contact between the end effector and the environment. Therefore, robots must possess compliant control capabilities over end forces to complete these tasks. Hydraulic legged robots are an important branch of robotics technology. Due to the high power density of hydraulic servo drives, the mass ratio of the drive system in the robot body can be minimized. Legged robots rely on their discrete foot-ground contact to achieve flexible adaptation to terrain, and are widely used in fields such as terrain exploration, weaponry, and material transportation. These diverse new application areas also place higher demands on the compliance of robots.

[0003] Traditional active compliance control is generally divided into impedance control and admittance control. Their basic working principle involves identifying stiffness and damping parameters in the compliance control model through empirical formulas or estimation. However, current technologies lack a complete theoretical formula to establish the mapping relationship between the foot and joint stiffness and damping parameters, making it difficult to achieve precise foot compliance performance through joint compliance control. This has become a technical barrier and challenge for legged robots to adapt to stiffness environments. Therefore, how to achieve precise end-effector compliance control performance through joint compliance control is an urgent problem to be solved. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a control method based on the equivalent stiffness and damping mapping between the foot and the hydraulic drive unit. It establishes the mapping relationship between the stiffness and damping of the robot foot and the hydraulic drive unit through the force-position transfer equation of the foot-joint-hydraulic drive unit, and uses a position-based impedance control method to control the hydraulic drive unit, which greatly improves the accuracy of controlling the compliance performance of the foot with the drive cylinder.

[0005] Specifically, the present invention provides a control method based on the equivalent stiffness-damping mapping between the foot and the hydraulic drive unit, which includes the following steps:

[0006] S1. Construct a hydraulic leg model based on the leg configuration of the hydraulic drive mechanism;

[0007] S2. Based on the generalized force and positional relationship between the foot and the rotating joint of the hydraulic drive unit, the equivalent stiffness mapping relationship between the foot and the rotating joint is obtained.

[0008] S3. Based on the generalized force and positional relationships between the rotary joint and the hydraulic drive unit, the equivalent stiffness mapping relationship between the rotary joint and the hydraulic drive unit is obtained. Combined with the equivalent stiffness mapping relationship between the foot and the rotary joint from step S1, the equivalent stiffness mapping relationship between the foot and the hydraulic drive unit is established. The expression for the equivalent stiffness mapping relationship between the foot and the hydraulic drive unit is:

[0009] k hx =inv(L)*(J θ T K c J θ +K g )*inv(W);

[0010] Among them, K c K is the foot stiffness matrix. θ k is the joint stiffness matrix. hx Let J be the stiffness matrix of the hydraulic drive unit, L be the lever arm matrix between the hydraulic drive unit and the joint torque, inv() represents the inversion of the matrix, and J be the stiffness matrix of the hydraulic drive unit. θ Let be the Jacobian matrix; W is the length matrix obtained by differentiating the mapping relationship between joint angle and elongation of hydraulic drive unit, (·). T Transpose of a matrix or vector; f represents the generalized force at the foot. For differentiation, θ represents the generalized joint displacement;

[0011] S4. Based on the generalized force and positional relationship between the foot and the rotating joint of the hydraulic drive unit, the equivalent damping mapping relationship between the foot and the rotating joint is obtained.

[0012] S5. Based on the generalized force and positional relationships between the rotary joint and the hydraulic drive unit, the equivalent damping mapping relationship between the rotary joint and the hydraulic drive unit is obtained. Combined with the equivalent damping mapping relationship between the foot and the rotary joint from step S4, the equivalent damping mapping relationship between the foot and the hydraulic drive unit is established. The expression for the equivalent damping mapping relationship between the foot and the hydraulic drive unit is:

[0013]

[0014] Among them, B hx B is the damping matrix of the hydraulic drive unit. c Here, A is the foot-end damping matrix, and A is the matrix representing the minimum change in the extension length of the hydraulic drive unit.

[0015] S6. Combining the equivalent stiffness mapping relationship and equivalent damping mapping relationship established in steps S5 and S3, the impedance control model of the hydraulic drive unit based on the stiffness-damping mapping relationship is obtained, and the foot is subjected to compliant control. The impedance control model of the hydraulic drive unit based on the stiffness-damping mapping relationship is as follows:

[0016]

[0017] In the formula, Fhx is the joint output force matrix of the hydraulic drive unit, and Xp is the extension length matrix of the hydraulic drive unit;

[0018] S7. Solve the hydraulic drive unit impedance control model based on the stiffness-damping mapping relationship obtained in step S6 to obtain the extension length of the hydraulic drive unit, and perform position-based impedance control, thereby controlling the foot stiffness-damping precisely by controlling the hydraulic drive unit.

[0019] Preferably, the mapping relationship between the foot end and the generalized force of the joint is as follows:

[0020]

[0021] The mapping relationship between the minimum change in the generalized force of the foot and the joint is expressed as follows:

[0022]

[0023] In the formula, d(·) represents a very small change, and (·) T Let τ be the transpose of a matrix or vector, and τ be the generalized torque of the joint; the mapping relationship between the foot end and the minimal change in the generalized position of the joint is as follows:

[0024] dp = J θ (dθ)

[0025] In the formula, p is the generalized displacement of the foot end, and θ is the generalized displacement of the joint.

[0026] The stiffness relationships between the foot end and the joint generalized force, and between the foot end and the generalized position, are as follows:

[0027] f = K c (dp ref -dp)

[0028] τ=K θ (dθ ref -dθ)

[0029] Therefore, the mapping relationship between the foot end and the minimum change in the generalized force of the joint can be expressed as:

[0030]

[0031] Simultaneously eliminating dθ, the equivalent stiffness mapping relationship between the foot end and the joint of the hydraulically driven leg is obtained as follows:

[0032]

[0033] in

[0034]

[0035] Preferably, the equivalent stiffness mapping relationship between the hydraulically driven leg joint and the hydraulic drive unit is obtained through the following steps:

[0036] At the joint, the relationship between the joint torque and the force on the hydraulic drive unit is as follows:

[0037] τ=LF

[0038] In the formula, F is the output force matrix of the joint hydraulic drive unit;

[0039] in

[0040] F=khxdxp

[0041] The stiffness relationships between the joint torque and the hydraulic drive unit and the generalized position are expressed as follows:

[0042] τ=K θ (dθ)

[0043] F = K hx (dxp)

[0044] The positions of the hydraulic drive unit and the joint are obtained by differentiating the mapping relationship between the joint angle and the elongation of the hydraulic drive unit. The simplified expression is as follows:

[0045] dxp = Wdθ;

[0046] The mapping relationship between the joint and the generalized force of the hydraulic drive unit is expressed as follows:

[0047] kθ(dθ)=LkhxW(dθ)

[0048] After eliminating dθ, the mapping relationship between the stiffness of the hydraulic drive unit and the equivalent stiffness of the joint is obtained as follows:

[0049] k hx =invL*k θ *invW.

[0050] Preferably, the equivalent damping mapping relationship between the foot and the joint is obtained through the following steps:

[0051] The damping relationships between the generalized force and the minimal change in generalized position of the foot and joint are as follows:

[0052] f = B c (dp ref -dp)

[0053] τ=B θ (dθ ref -dθ)

[0054] In the formula, the subscript (·) ref This is the expected value;

[0055] Based on the mapping relationship between the foot end and the joint generalized force, and substituting the damping relationship between the foot end and the joint generalized force and the minimum change in generalized position, the mapping relationship between the foot end and the joint generalized force with the damping parameter is obtained:

[0056]

[0057] Substituting the mapping relationship between the foot tip and the minimal change in the generalized position of the joint, the above formula is expressed as:

[0058]

[0059] Simultaneously eliminate (dθ) ref -dθ) yields the equivalent damping mapping relationship between the foot end and joint of the hydraulically driven leg as follows:

[0060]

[0061] Preferably, the derivation process of the equivalent damping mapping relationship between the hydraulically driven leg joint and the hydraulic drive unit is as follows:

[0062] The damping relationships between the generalized force of the joint and the generalized force of the hydraulic drive unit and the minimum change in generalized position are as follows:

[0063] τ=B θ (dθ ref -dθ)

[0064] F = B hx (dxp ref -dxp)

[0065] The relationship between the hydraulic drive unit and the minimum change in joint position is expressed as follows:

[0066] (dxp ref -dxp)=A(dθ ref -dθ)

[0067] In the formula, B θ This represents the joint damping matrix, with subscripts (·). re f is the expected value;

[0068] Based on the relationship between joint torque and joint output force, and substituting the derivative of the mapping relationship between the hydraulic drive unit position and joint position through the joint angle and the elongation of the hydraulic drive unit, the mapping relationship between the generalized joint force with the damping parameter and the generalized force of the hydraulic drive unit is obtained:

[0069] B θ (dθ ref -dθ)=LB hx A(dθ ref -dθ)

[0070] Simultaneously eliminate (dθ) ref -dθ) yields the equivalent damping mapping relationship between the hydraulically driven leg joint and the hydraulic drive unit as follows:

[0071] B θ =LB hx A.

[0072] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0073] (1) The stiffness damping method proposed in this invention can accurately solve the precise compliance parameters of the rotating joints of the robotic arm and the hydraulic drive unit of the hydraulic robot leg, laying the foundation for impedance control of each joint using different compliance parameters, so as to match different parameters to achieve better compliance control effect; the application range of the whole method is very wide and can be applied to serial robots such as two-degree-of-freedom or multi-degree-of-freedom robotic arms and hydraulic legged robots.

[0074] (2) This invention does not limit the impedance stiffness damping. During the application process, the desired stiffness damping can be changed arbitrarily to improve the adaptability to the environment and the safety of human-computer interaction. It is very convenient and quick to use, and the control process is accurate.

[0075] (3) Compared with passive compliance adjustment, the method of the present invention can solve for accurate compliance parameters without the need for additional hardware and without the need for additional components, which can significantly save manufacturing costs. Moreover, the entire control process is more accurate and controllable, reducing the difficulty of subsequent control. Attached Figure Description

[0076] Figure 1 This is a schematic diagram of the structure of the hydraulic leg for controlling and testing according to the present invention;

[0077] Figure 2 This is a schematic diagram of the equivalent structure of the hydraulic leg used for control and testing in this invention.

[0078] Figure 3 This is a schematic diagram of the method flow of the present invention;

[0079] Figures 4a-4c This is a comparison chart of the simulation curves of the force output of the leg hydraulic unit and the calculated joint force based on the stiffness in an embodiment of the present invention.

[0080] Some of the attached labels in the figure are as follows:

[0081] 1-Base, 2-Hip joint, 3-Thigh, 4-Knee joint, 5-Lower leg, 6-Ankle joint, 7-Hydraulic drive unit, 8-Foot component, 9-Moving pair, 10-Guide rail. Detailed Implementation

[0082] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0083] This invention provides a control method based on the equivalent stiffness-damping mapping between the foot and the hydraulic drive unit, such as... Figure 3 As shown, it includes the following steps:

[0084] S1. Construct a hydraulic leg model based on the leg configuration of the hydraulic drive mechanism.

[0085] S2. Based on the generalized force and positional relationship between the foot and the rotating joint of the hydraulic drive unit, the equivalent stiffness mapping relationship between the foot and the rotating joint is obtained.

[0086] S3. Based on the generalized force and positional relationships between the rotary joint and the hydraulic drive unit, the equivalent stiffness mapping relationship between the rotary joint and the hydraulic drive unit is obtained. Combined with the equivalent stiffness mapping relationship between the foot and the rotary joint from step S1, the equivalent stiffness mapping relationship between the foot and the hydraulic drive unit is established. The expression for the equivalent stiffness mapping relationship between the foot and the hydraulic drive unit is:

[0087] k hx =inv(L)*(J θ T K c J θ +K g )*inv(W);

[0088] Among them, K c K is the foot stiffness matrix. θ k is the joint stiffness matrix. hx Let J be the stiffness matrix of the hydraulic drive unit, L be the lever arm matrix between the hydraulic drive unit and the joint torque, inv() represents the inversion of the matrix, and J be the stiffness matrix of the hydraulic drive unit. θ Let be the Jacobian matrix; W is the length matrix obtained by differentiating the mapping relationship between joint angle and elongation of hydraulic drive unit, (·). T Transpose of a matrix or vector; f represents the generalized force at the foot. For differentiation, θ represents the generalized joint displacement;

[0089] S4. Based on the generalized force and positional relationship between the foot and the rotating joint of the hydraulic drive unit, the equivalent damping mapping relationship between the foot and the rotating joint is obtained.

[0090] S5. Based on the generalized force and positional relationships between the rotary joint and the hydraulic drive unit, the equivalent damping mapping relationship between the rotary joint and the hydraulic drive unit is obtained. Combined with the equivalent damping mapping relationship between the foot and the rotary joint from step S4, the equivalent damping mapping relationship between the foot and the hydraulic drive unit is established. The expression for the equivalent damping mapping relationship between the foot and the hydraulic drive unit is:

[0091]

[0092] Among them, B hx B is the damping matrix of the hydraulic drive unit. c Here, A is the foot-end damping matrix, and A is the matrix representing the minimum change in the extension length of the hydraulic drive unit.

[0093] S6. Combining the equivalent stiffness mapping relationship and equivalent damping mapping relationship established in steps S5 and S3, the impedance control model of the hydraulic drive unit based on the stiffness-damping mapping relationship is obtained, and the foot is subjected to compliant control. The impedance control model of the hydraulic drive unit based on the stiffness-damping mapping relationship is as follows:

[0094]

[0095] In the formula, Fhx is the joint output force matrix of the hydraulic drive unit, and Xp is the extension length matrix of the hydraulic drive unit;

[0096] S7. Solve the hydraulic drive unit impedance control model based on the stiffness-damping mapping relationship obtained in step S6 to obtain the extension length of the hydraulic drive unit, and perform position-based impedance control, thereby controlling the foot stiffness-damping precisely by controlling the hydraulic drive unit. Specific Implementation

[0098] This embodiment provides a control method based on the equivalent stiffness-damping mapping between the foot and the hydraulic drive unit, establishing an equivalent model of the single-leg test platform to obtain... Figure 1 and Figure 2 The diagram showing the leg structure serves as an example of a specific expression in the mapping method embodiment. Figure 1 In the middle, the base 1 is respectively provided with a hip joint 2, thigh 3, knee joint 4, lower leg 5, ankle joint 6, hydraulic drive unit 7, and foot component 8. Figure 2 In the middle, the base 1 is also connected to the sliding joint 9 and the guide rail 10.

[0099] Specifically, such as Figure 3As shown, the implementation steps of the stiffness-damping mapping method include the following steps:

[0100] S1. Based on the leg configuration of the hydraulically driven robot, the mapping relationship between the generalized forces at the foot and joints and the mapping relationship between the minimum changes in the generalized positions of the foot and joints are obtained using the Jacobian matrix. The stiffness relationships between the generalized forces and generalized positions of the foot and joints are then constructed, and the foot stiffness K of the hydraulically driven leg is derived. c Equivalent stiffness K of the joint θ The mapping relationship between them.

[0101] The mapping relationship between the foot and the generalized force of the joint is as follows:

[0102]

[0103] Among them, J θ Let be a Jacobian matrix, (·) T τ is the transpose of a matrix or vector, f is the generalized torque of the joint, and f is the generalized force at the foot.

[0104]

[0105]

[0106]

[0107] Among them, f x For the force acting on the foot in the X direction, f y τ1 represents the force acting on the foot in the Y direction, τ2 represents the torque acting on the hip joint, τ3 represents the torque acting on the knee joint, and τ4 represents the torque acting on the ankle joint.

[0108] The mapping relationship between the minimum changes in the generalized force at the foot and joint can be expressed as:

[0109]

[0110] In the formula, d(·) is a very small change;

[0111] The mapping relationship between the foot tip and the minimum change in the generalized position of the joint is as follows:

[0112] dp = J θ (dθ)

[0113] In the formula, p is the generalized displacement of the foot end, and θ is the generalized displacement of the joint.

[0114] The stiffness relationships of the foot end and joint generalized force and generalized position are as follows:

[0115] df = K c dp

[0116] dτ=K θ dθ

[0117] In the formula, K c K is the foot stiffness matrix. θ Here is the joint stiffness matrix;

[0118]

[0119] The mapping relationship between the minimum change in generalized force at the foot and joint can be expressed as:

[0120]

[0121] Simultaneously eliminating dθ yields the equivalent stiffness mapping relationship between the foot end and joint of the hydraulically driven leg:

[0122]

[0123] in:

[0124]

[0125] The specific expression is:

[0126]

[0127] k g θ11=-(l1cosθ1+l2cos(θ1+θ2)+l3cos(θ1+θ2+θ3))*fx

[0128] -(l1sinθ1+l2sin(θ1+θ2)+l3sin(θ1+θ2+θ3))*f y

[0129] k g θ 12 =k gθ21

[0130] =-(l2cos(θ1+θ2)+l3cos(θ1+θ2+θ3))*f x

[0131] -(l2sin(θ1+θ2)+l3sin(θ1+θ2+θ3))*fy

[0132] k g θ 13 =k g θ 31 =-l3cos(θ1+θ2+θ3)*fx-l3sin(θ1+θ2+θ3)*fy

[0133] k gθ22=-(l2cos(θ1+θ2)+l3cos(θ1+θ2+θ3))*fx-(l2sin(θ1+θ2)

[0134] +l3sin(θ1+θ2+θ3))*fy

[0135] k gθ23 =k gθ32 =-l3cos(θ1+θ2+θ3)*fx-l3sin(θ1+θ2+θ3)*fy.

[0136] S2. Based on the generalized force and positional relationship between the foot and the rotating joint of the hydraulic drive unit, the equivalent stiffness mapping relationship between the foot and the rotating joint is obtained.

[0137] S3. Derive the mapping relationship between the equivalent stiffness Kθ of the hydraulically driven leg joint and the equivalent stiffness Khx of the hydraulic drive unit: k hx =inv(L)*k θ *inv(W) establishes the mapping relationship between the equivalent stiffness of the foot and the equivalent stiffness of the hydraulic drive unit, combining the mapping relationship between the joint and the equivalent stiffness of the foot. x Mapping relationship:

[0138] k h x=inv(L)*(J θ TKcJ θ +Kg)*inv(W);

[0139] At the joint, the relationship between the joint torque and the force on the hydraulic drive unit is as follows:

[0140] τ=LF

[0141] F=khxd xp

[0142]

[0143] In the formula, τ is the generalized torque of the joint, and F is the output force matrix of the joint hydraulic drive unit, specifically as follows: k hx Let d be the stiffness matrix of the hydraulic drive unit. xp L represents the minimum change in the generalized position of the hydraulic drive unit, and L is the lever arm matrix between the hydraulic drive unit and the joint torque.

[0144] The relationships between joint torque and hydraulic drive unit output force and the stiffness of the generalized position are as follows:

[0145] τ=Kθ(dθ)

[0146] F = K hx (dxp)

[0147] The positions of the hydraulic drive unit and the joints are obtained by differentiating the mapping relationship between the joint angle and the elongation of the hydraulic drive unit. The simplified expression is as follows:

[0148] d xp =Wdθ

[0149] In the formula, W is the length matrix obtained by differentiating the mapping relationship between the joint angle and the elongation of the hydraulic drive unit.

[0150] Specifically:

[0151] The mapping relationship between the joint and the generalized force of the hydraulic drive unit can be expressed as:

[0152] k θ (dθ)=Lk hx W(dθ)

[0153] Simultaneously eliminating dθ, the mapping relationship between the stiffness of the hydraulically driven leg hydraulic drive unit and the equivalent stiffness of the joint is obtained as follows:

[0154] k hx =inv(L)*k θ *inv(W)

[0155] In the formula, kh x Here, Kθ is the stiffness matrix of the hydraulic drive unit, Kθ is the joint stiffness matrix, L is the joint structure lever arm matrix, which is determined according to the robot's leg structure, and d... xp Let be the minimum change in the generalized position of the hydraulic drive unit, and inv() represents the inversion of the matrix.

[0156] In summary, the stiffness K of the hydraulically driven leg foot end... c Equivalent stiffness K of the joint θ Mapping relationship:

[0157]

[0158] S4. Construct the damping relationships between the generalized forces and the minimum changes in generalized position at the foot and joint, respectively. Combine this with the mapping relationships between the minimum changes in generalized forces and the minimum changes in generalized position at the foot and joint based on the Jacobian matrix, and derive the equivalent damping B at the foot of the hydraulically driven leg. c Equivalent damping of joint B θ Mapping relationship:

[0159] The damping relationships between the generalized force and the minimal change in generalized position of the foot and joint are as follows:

[0160] f = B c (dp ref -dp)

[0161] τ=B θ (dθ ref -dθ)

[0162] In the formula, B c B is the foot-end damping matrix. θ This represents the joint damping matrix, with subscripts (·). ref This is the expected value;

[0163] Based on the mapping relationship between the generalized forces of the foot and joints, and substituting the damping relationship between the generalized forces of the foot and joints and the minimal change in generalized position, the mapping relationship between the generalized forces of the foot and joints with damping parameters can be derived:

[0164]

[0165] Substituting the mapping relationship between the foot tip and the minimal change in the generalized position of the joint, the above formula can be expressed as:

[0166]

[0167] Simultaneously eliminate (dθ) ref -dθ) can be used to derive the equivalent damping mapping relationship between the foot end and joint of the hydraulically driven leg as follows:

[0168]

[0169] Constructing the joint equivalent damping B θ Equivalent damping B of hydraulic drive unit hx Mapping relationship: B θ =LB hx A. Based on the mapping relationship between equivalent damping at the foot and equivalent damping at the joint, establish the mapping relationship between equivalent damping at the foot and equivalent damping at the hydraulic drive unit:

[0170]

[0171] The damping relationships between the generalized force of the joint and the generalized force of the hydraulic drive unit and the minimum change in generalized position are as follows:

[0172] τ=B θ (dθ ref -dθ)

[0173] F = B hx (dxp ref -dxp)

[0174] The relationship between the hydraulic drive unit and the minimum change in joint position is expressed as follows:

[0175] (dxp ref -dxp)=A(dθ ref -dθ)

[0176] In the formula, B hx B is the damping matrix of the hydraulic drive unit. θ This represents the joint damping matrix, with subscripts (·). ref This is the expected value;

[0177] Based on the relationship between joint torque and joint output force, and substituting the derivative of the mapping relationship between the position of the hydraulic drive unit and the joint position through the joint angle and the elongation of the hydraulic drive unit, the mapping relationship between the generalized force of the joint with damping parameters and the generalized force of the hydraulic drive unit can be derived:

[0178] B θ (dθ ref -dθ)=LB hx A(dθ ref -dθ)

[0179] In the formula, L is the lever arm matrix between the hydraulic drive unit and the joint torque, and A is the matrix of the minimum change in the extension length of the hydraulic drive unit.

[0180] Specifically

[0181] Simultaneously eliminate (dθ) ref -dθ) can be used to derive the equivalent damping mapping relationship between the hydraulically driven leg joint and the hydraulic drive unit as follows:

[0182] B θ =LB hx A

[0183] This establishes a mapping relationship between the equivalent damping at the foot and the equivalent damping of the hydraulic drive unit:

[0184]

[0185] S5. Based on the generalized force and positional relationships between the rotary joint and the hydraulic drive unit, the equivalent damping mapping relationship between the rotary joint and the hydraulic drive unit is obtained. Combined with the equivalent damping mapping relationship between the foot and the rotary joint from step S4, the equivalent damping mapping relationship between the foot and the hydraulic drive unit is established. The expression for the equivalent damping mapping relationship between the foot and the hydraulic drive unit is:

[0186]

[0187] Among them, B c Let L be the foot end damping matrix, L be the lever arm matrix between the hydraulic drive unit and the joint torque, and A be the matrix of the minimum change in the extension length of the hydraulic drive unit.

[0188] S6. Combining the equivalent stiffness mapping relationship and equivalent damping mapping relationship established in steps S5 and S3, an impedance control model for the hydraulic drive unit is developed based on the stiffness-damping mapping relationship, and compliant control is applied to the foot. The impedance control model for the hydraulic drive unit based on the stiffness-damping mapping relationship is as follows:

[0189]

[0190] In the formula, Fhx is the joint output force matrix of the hydraulic drive unit, Xp is the extension length matrix of the hydraulic drive unit, and B... hx This is the damping matrix of the hydraulic drive unit.

[0191] S7. Solve the hydraulic drive unit impedance control model based on the stiffness-damping mapping relationship obtained in step S6, determine the extension length of the hydraulic drive unit, and perform position-based impedance control, thereby controlling the foot stiffness-damping precisely by controlling the hydraulic drive unit.

[0192] Based on the above control model and mapping method theory, this method is applied to the leg of a two-degree-of-freedom hydraulic robot. Impedance control is performed on the foot end and the joint of the hydraulic drive unit, respectively. Finally, the output force of the hydraulic drive unit joint is used as an indicator for comparison to complete the verification. Figures 4a-4c The simulation curves compare the output of the hydraulic drive unit after applying the mapping method and applying the mapping method with impedance at the foot. The comparison shows that the calculated force curve of the hydraulic drive unit using the mapping method almost overlaps with the measured output force curve of the hydraulic drive unit, thus demonstrating the correctness of the mapping method.

[0193] In this embodiment, impedance control of the joint is performed based on a mapping method. The specific control process is as follows:

[0194] After determining the target foot-end impedance stiffness and damping, the equivalent stiffness damping is calculated to the hydraulic drive unit using the equivalent stiffness-damping mapping method. Then, using a position-based impedance control mathematical model, the extension length of the hydraulic drive unit is calculated, achieving impedance position control of the hydraulic joint with the desired foot-end stiffness damping.

[0195] The invention method achieves impedance control of the specific joint stiffness damping with the desired end stiffness damping, and can further adjust the stiffness damping parameters of different joints, which has broad application prospects.

[0196] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A control method based on foot end and hydraulic drive unit equivalent stiffness damping mapping, characterized by: It comprises the following steps: S1, constructing a hydraulic leg model according to the leg configuration of the hydraulic drive mechanism; S2, obtaining the equivalent stiffness mapping relationship between the foot end and the rotary joint based on the generalized force relationship and the position relationship between the foot end and the rotary joint of the hydraulic drive unit; S3, obtaining the equivalent stiffness mapping relationship between the rotary joint and the hydraulic drive unit based on the generalized force relationship and the position relationship between the rotary joint and the hydraulic drive unit, and combining the equivalent stiffness mapping relationship between the foot end and the rotary joint in step S1 to establish the equivalent stiffness mapping relationship between the foot end and the hydraulic drive unit, the expression of the equivalent stiffness mapping relationship between the foot end and the hydraulic drive unit is: ； wherein, is the foot end stiffness matrix, is the joint stiffness matrix; is the hydraulic drive unit stiffness matrix, is the force arm matrix between the hydraulic drive unit and the joint torque, denotes the inversion of a matrix, is the Jacobian matrix; is the length matrix obtained by differentiating the mapping relationship between the joint angle and the hydraulic drive unit elongation, is the transpose of a matrix or vector; , is the foot end generalized force, is the differentiation, is the joint generalized displacement; S4, obtaining the equivalent damping mapping relationship between the foot end and the rotary joint based on the generalized force relationship and the position relationship between the foot end and the rotary joint of the hydraulic drive unit; S5, obtaining the equivalent damping mapping relationship between the rotary joint and the hydraulic drive unit based on the generalized force relationship and the position relationship between the rotary joint and the hydraulic drive unit, and combining the equivalent damping mapping relationship between the foot end and the rotary joint in step S4 to establish the equivalent damping mapping relationship between the foot end and the hydraulic drive unit, the expression of the equivalent damping mapping relationship between the foot end and the hydraulic drive unit is: ； wherein B hx is a hydraulic drive unit damping matrix, is a foot end damping matrix, is a hydraulic drive unit extension length minimum change amount matrix; S6, combining the equivalent stiffness mapping relationship and the equivalent damping mapping relationship between the foot end and the hydraulic drive unit established in steps S5 and S3 to obtain the hydraulic drive unit impedance control model of the stiffness-damping mapping relationship, and performing compliant control on the foot end; the hydraulic drive unit impedance control model based on the stiffness-damping mapping relationship is as follows: ； wherein is the hydraulic drive unit joint output matrix, is the hydraulic drive unit extension length matrix; S7, solving the hydraulic drive unit impedance control model of the stiffness-damping mapping relationship obtained in step S6 to obtain the extension length of the hydraulic drive unit, and performing position-based impedance control, so as to control the foot end stiffness-damping by controlling the hydraulic drive unit.

2. The control method based on foot end to hydraulic drive unit equivalent stiffness damping mapping of claim 1, wherein: The mapping relationship of the foot end and the joint generalized force is: ； The mapping relationship of the minimum change amount of the foot end and the joint generalized force is: ； wherein is a very small change, is the joint generalized moment; The mapping relationship of the minimum change amount of the foot end and the joint generalized position is: ； wherein is the foot end generalized displacement and θ is the joint generalized displacement. The stiffness relationship of the foot end and the joint generalized force and the generalized position is: ； Therefore, the mapping relationship of the minimum change amount of the foot end and the joint generalized force is: ； simultaneous elimination The equivalent stiffness mapping relationship of the hydraulic-driven leg foot end and joint is obtained as ； Wherein 。 3. The control method based on foot end to hydraulic drive unit equivalent stiffness damping mapping of claim 2, wherein: The equivalent stiffness mapping relationship between the hydraulic drive type leg joint and the hydraulic drive unit is obtained through the following steps: At the joint, the relationship between the joint torque and the force of the hydraulic drive unit is: ； In the formula, is the output matrix of the joint hydraulic drive unit; Wherein The relationship between the joint torque and the generalized position and the stiffness of the hydraulic driving unit is respectively expressed as ； Wherein, the position of the hydraulic drive unit and the position of the joint are derived by the mapping relationship between the joint angle and the extension amount of the hydraulic drive unit, and the relationship is simply written as: ； The mapping relationship of the joint and the hydraulic drive unit generalized force is: ； After the elimination The mapping relationship between the stiffness of the hydraulic driving unit and the equivalent stiffness of the joint is obtained as 。 4. The control method based on foot end to hydraulic drive unit equivalent stiffness damping mapping of claim 3, wherein: The equivalent damping mapping relationship between the foot end and the joint is obtained through the following steps: The damping relationship of the minimum change amount of the foot end and the joint generalized force and the generalized position is: ； wherein is the joint damping matrix, subscript is the expected value; Based on the mapping relationship of the foot end and the joint generalized force, the damping relationship of the minimum change amount of the foot end and the joint generalized force and the generalized position is brought in to obtain the mapping relationship of the foot end and the joint generalized force with damping parameters: ； With the mapping relationship of the foot end and the joint generalized position small change amount, the above formula is expressed as: ； simultaneous elimination The equivalent damping mapping relationship of the hydraulic drive type leg foot end and joint is obtained as follows: 。 5. The control method based on foot end to hydraulic drive unit equivalent stiffness damping mapping of claim 4, wherein: The equivalent damping mapping relationship derivation process of the hydraulic drive type leg joint and the hydraulic drive unit is as follows: The damping relationship of the joint generalized force and the hydraulic drive unit generalized force and the generalized position small change amount is respectively: ； The relationship of the hydraulic drive unit and the joint position small change amount is expressed as: ； Based on the joint torque and the joint output relationship, the mapping relationship of the joint generalized force and the hydraulic drive unit generalized force with the damping parameter is obtained by substituting the hydraulic drive unit position and the joint position into the joint angle and the hydraulic drive unit elongation mapping relationship derivation relationship: ； simultaneous elimination The equivalent damping mapping relationship between the hydraulic drive type leg joint and the hydraulic drive unit is obtained as follows: 。

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