Control method and control device for single-leg hydraulic power-assisted exoskeleton under heavy load and exoskeleton

Abstract

The invention relates to a single-leg hydraulic power-assisted exoskeleton control method and device under heavy load and an exoskeleton. The control method for the single-leg hydraulic power-assisted exoskeleton under the heavy load comprises the steps that pump valve flow distribution of all the joints is conducted according to the expected flow alpha2p of a rod cavity and the expected flow Q1m of a rodless cavity of a hydraulic cylinder in all the joints, then the control voltage of a variable-speed pump and a servo valve corresponding to all the joints is obtained, and the action of the single-leg hydraulic power-assisted exoskeleton is controlled; the pump valve flow distribution method comprises the steps that the control voltage of the variable-speed pump corresponding to the hydraulic cylinder i and the control voltage of the servo valve corresponding to the hydraulic cylinder i are determined, and the pump control part and the valve control part are controlled according to the control voltages. According to the heavy-load single-leg hydraulic power-assisted exoskeleton control method, the scheme that the pump provides low-frequency flow and the valve provides high-frequency flow is adopted for flow distribution, the problem of flow distribution caused by non-negligible oil compressibility under the heavy load is solved, and system energy consumption under the heavy load is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of exoskeletons, and in particular to a control method, a control device and an exoskeleton for a single-leg hydraulically assisted exoskeleton under heavy load. Background Art

[0002] The wearable lower limb power-assisted exoskeleton is a human-machine integrated device that enhances the wearer's load-bearing capacity and can be used in emergency rescue, national defense and military industries. Hydraulic actuators are very suitable for compact and heavy systems such as lower limb power-assisted exoskeletons because of their advantages such as large output force and torque and high power-to-weight ratio. In the power-assisted exoskeleton system, the exoskeleton can accurately track human movements by reducing the human-machine force, so that the wearer can easily bear weight. Therefore, the design of a high-precision human-machine force control algorithm is an important guarantee for realizing the power-assisted function of the exoskeleton. On the other hand, the energy supply system of the lower limb power-assisted exoskeleton must be carried with you, and the energy source is very limited. In order to ensure a longer working time, the energy efficiency of the system cannot be ignored. How to simultaneously achieve high-precision and high-energy efficiency control of the lower limb hydraulic power-assisted exoskeleton is a key technology to improve the performance of the exoskeleton.

[0003] When realizing high-precision and high-energy efficiency control of hydraulic exoskeleton, two problems need to be solved. The first is the design of high-precision and high-efficiency electro-hydraulic system for hydraulic exoskeleton. Traditional electro-hydraulic system of hydraulic power-assisted exoskeleton for lower limbs often adopts valve control system solution. Due to the throttling loss and overflow loss of valve control system, the energy efficiency level of traditional hydraulic exoskeleton is low. Secondly, it is necessary to design the corresponding high-precision and high-energy efficiency control algorithm of exoskeleton based on the selected electro-hydraulic system. The existing control method of hydraulic power-assisted exoskeleton focuses on solving the inherent strong coupling high-order nonlinearity of hydraulic exoskeleton system and the influence of modeling uncertainty. It can only achieve high-precision force control, and does not consider energy consumption, resulting in high energy consumption of the system. In addition, especially under heavy load, the compressibility of hydraulic oil cannot be ignored, which brings difficulties to the flow distribution of pump valve. Summary of the invention

[0004] Based on this, it is necessary to provide a single-leg hydraulic assisted exoskeleton control method, control device and exoskeleton under heavy load to address the problem that under heavy load, the hydraulic oil has oil compressibility, which makes pump valve flow distribution difficult.

[0005] A method for controlling a single-leg hydraulically assisted exoskeleton under heavy load, wherein the three hydraulic systems of the ankle joint, knee joint and hip joint of the exoskeleton all adopt a parallel pump-valve coordinated electro-hydraulic system; each parallel pump-valve coordinated electro-hydraulic system includes a parallel coordinated pump control part and a valve control part; the pump control part includes a variable speed pump and two switch valves SV1 and SV2 that determine the flow direction of the variable speed pump outlet; the valve control part includes four servo valves PV1, PV2, PV3 and PV4; according to the expected flow α of the rod chamber of the hydraulic cylinder in each joint2p 、Expected flow rate of rodless cavity Q 1m , distribute the pump and valve flow of each joint, and then obtain the control voltage of the variable speed pump and servo valve corresponding to each joint to control the action of the single-leg hydraulic power-assisted exoskeleton;

[0006] The method for distributing pump and valve flow includes determining a control voltage u of a variable speed pump corresponding to a hydraulic cylinder i pi and determine the control voltage u of the servo valve corresponding to the hydraulic cylinder i pv1i ,u pv2i ,u pv3i ,u pv4i , the pump control part and the valve control part are controlled according to the control voltage;

[0007] Among them, determine the control voltage u of the variable speed pump corresponding to the hydraulic cylinder i pi The method comprises the following steps:

[0008] Determine whether the variable speed pump provides flow to the rodless chamber of hydraulic cylinder i or the rod chamber of hydraulic cylinder i, and control the switch state of the corresponding switch valve accordingly:

[0009] Calculate Q 1madi and α 2padi :Let Q 1mad =[Q 1mad1 Q 1mad2 Q 1mad3 ] T ;

[0010]

[0011] If Q 1mi Q 1madi ≤0, then Q 1madi =0;

[0012] If α 2pi α 2padi ≤0, then α 2padi =0;

[0013] In the formula, Q 1madi It's Q 1mad The i-th element of Q 1madi and α 2padi They represent the expected flow of the low-frequency part of the hydraulic cylinder rodless cavity compensation and the expected flow of the low-frequency part of the hydraulic cylinder rod cavity compensation using the joint reference trajectory of the i-th joint, respectively. di represents the motion reference trajectory of hydraulic cylinder i, is x di about The first partial derivative of V 1di =V h1i +A1i x di and V 2di =V h2i -A 2i x di are the compressible volume V at the i-th hydraulic cylinder. 1i and V 2i Using motion reference trajectory x di Replace x Li The expression form, is an estimate of the elastic modulus,

[0014] N 1d =diag{A 11 / V 1d1 ,A 12 / V 1d2 ,A 13 / V 1d3},N 2d =diag{A 21 / V 2d1 ,A 22 / V 2d2 ,A 23 / V 2d3},

[0015] α 2pad =[α 2pad1 α 2pad2 α 2pad3 ] T ,

[0016]

[0017] φ 4cd =[0 3×7 0 3×3 0 3×3 N 2d α 2pad -q vd I 3×3 ] T , is the estimated value of the exoskeleton system parameters, F Ldad is the expected compensating driving force of the hydraulic cylinder at each joint, and F Ldad about and the partial derivatives of t, is the estimated value of the constant part of the uncertainty of the rod cavity model in hydraulic cylinder i, is the derivative of the desired pressure in the rod chamber of the i-th hydraulic cylinder, Q 1mi is the expected flow rate of the rodless cavity of the ith joint, α 2pi is the expected flow rate of the rod cavity of the ith joint;

[0018] Calculate the expected output flow Q of the variable speed pump corresponding to hydraulic cylinder i pdi :Q pdi =sw 1i Q 1madi -sw 2i α 2padi ;

[0019] If 0≤Q pdi ≤Q pbound , then Q pdi =0;

[0020] In the formula, Q pbound Indicates the minimum boundary flow rate for using a variable speed pump;

[0021] Calculate the control voltage of the variable speed pump corresponding to hydraulic cylinder i as follows: In the formula, k p is the flow gain coefficient.

[0022] The present invention also provides a heavy-loaded single-leg hydraulic-assisted exoskeleton control device, which adopts the heavy-loaded single-leg hydraulic-assisted exoskeleton control method as described above; the control device comprises:

[0023] A plurality of parallel pump-valve coordinated electro-hydraulic systems; each parallel pump-valve coordinated electro-hydraulic system comprises a parallel coordinated pump control part and a valve control part; the pump control part comprises a variable speed pump PS1 and two two-way switch valves SV1 and SV2 that determine the outlet flow direction of the variable speed pump PS1; the valve control part comprises four two-way electro-hydraulic servo valves PV1, PV2, PV3 and PV4 and a hydraulic oil source PS2, the electro-hydraulic servo valves PV1 and PV2 control the flow of the hydraulic oil source PS2 to the two chambers of the corresponding hydraulic cylinder, and the electro-hydraulic servo valves PV3 and PV4 control the flow of the two chambers of the corresponding hydraulic cylinder to the oil tank;

[0024] The flow acquisition module is used to coordinate the electro-hydraulic system of the parallel pump valves of each joint of the single-leg hydraulic assisted exoskeleton according to the reference rotation angle of each joint. Reference angular velocity Reference angular acceleration Actual driving force F of hydraulic cylinder L , actual rotation angle q, actual rotation angular velocity Get the expected flow rate α of the rod cavity of each joint 2p =[α 2p1 α 2p2 α 2p3 ] T and the rodless chamber expected flow rate Q 1m =[Q 1m1 Q 1m2 Q1m3 ] T ; where i represents the serial number of the three joints, the expected flow rate of the rod cavity of the i-th joint is α 2pi , the expected flow rate of the rodless cavity of the i-th joint is Q 1mi ;

[0025] The control voltage acquisition module is used to obtain the voltage according to α 2p , Q 1m Calculate the control voltages of PS1, PV1, PV2, PV3, and PV4 corresponding to each joint to distribute the pump and valve flow of each joint.

[0026] The present invention also provides a heavy-loaded single-leg hydraulically-assisted exoskeleton, which adopts the heavy-loaded single-leg hydraulically-assisted exoskeleton control method as described above.

[0027] Compared with the existing exoskeleton control method, the heavy-load single-leg hydraulic-assisted exoskeleton control method and device of the present invention has the following beneficial effects:

[0028] 1. The single-leg hydraulic-assisted exoskeleton control method under heavy load adopts a hydraulic drive system, which has the characteristics of being able to output large force or torque, sensitive action response, easy control, small size, and compact structure.

[0029] 2. The control method of the single-leg hydraulic assisted exoskeleton under heavy load adopts a parallel pump-valve coordinated electro-hydraulic system solution for the hydraulic system, constructs independently operated pump control part and valve control part, allows the pump control part to provide the main flow, and the valve control part to provide a small flow, without losing accuracy, improving the energy efficiency level of the lower limb assisted exoskeleton electro-hydraulic system.

[0030] 3. The sensor system of this single-leg hydraulic assisted exoskeleton control method under heavy load is mainly composed of back force sensors and joint encoders to achieve more reliable human-computer interaction.

[0031] 4. The control method of the single-leg hydraulic-assisted exoskeleton under heavy load adopts a force control method. The upper and lower layer controllers are designed using the adaptive robust control algorithm (ARC), which effectively overcomes the influence of high-order nonlinearity and model uncertainty of the single-leg hydraulic-assisted exoskeleton. The rodless chamber of the hydraulic cylinder in the lower layer controller adopts position tracking control, and the rod chamber of the hydraulic cylinder adopts pressure tracking control, so that the pressure of one chamber of the hydraulic cylinder is always in the minimum pressure state. It solves the technical problem of high energy consumption of the existing exoskeleton control method, not only enables the hydraulic-assisted exoskeleton to follow and assist human movement well, but also reduces system energy consumption and achieves a longer endurance time, which has a strong application value.

[0032] 5. The control method of the single-leg hydraulic assisted exoskeleton under heavy load adopts a flow distribution scheme in which a pump provides low-frequency flow and a valve provides high-frequency flow, which solves the problem of flow distribution caused by the non-negligible compressibility of oil under heavy load and reduces the system energy consumption under heavy load.

[0033] 6. This heavy-load single-leg hydraulic-assisted exoskeleton control method uses human motion as the external input of the entire exoskeleton system, ensuring the balance state during walking. In addition, the upper and lower layer cascade force control algorithm is adopted to achieve the exoskeleton following the trajectory of the person. The control method is simple to implement, easy to implement in engineering, and flexible to control.

[0034] 7. The heavy-loaded single-leg hydraulic-assisted exoskeleton control device and the heavy-loaded single-leg hydraulic-assisted exoskeleton have the same beneficial effects as the above-mentioned heavy-loaded single-leg hydraulic-assisted exoskeleton control method. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the overall shape and structure of a single-leg hydraulically assisted exoskeleton provided in a preferred embodiment of the present invention;

[0036] Figure 2 for Figure 1 Schematic diagram of the single-joint parallel pump-valve coordinated electro-hydraulic system used in the single-leg hydraulic power-assisted exoskeleton;

[0037] Figure 3 for Figure 1 The design concept block diagram of the control method of the single-leg hydraulic power-assisted exoskeleton under heavy load adopted by the single-leg hydraulic power-assisted exoskeleton;

[0038] Figure 4 for Figure 1 Control flow chart of the control method of the single-leg hydraulically assisted exoskeleton under heavy load adopted by the medium single-leg hydraulically assisted exoskeleton. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more of the related listed items.

[0041] See also Figure 1 , which is a schematic diagram of the overall shape and structure of a single-leg hydraulic power-assisted exoskeleton provided by a preferred embodiment of the present invention. Figure 1 It can be seen that the single-leg hydraulic power-assisted exoskeleton includes a foot 1, an ankle joint encoder 2, an ankle joint hydraulic cylinder rod cavity pressure sensor 3, an ankle joint hydraulic cylinder 4, an ankle joint hydraulic cylinder rodless cavity pressure sensor 5, a calf rod 6, a knee joint encoder 7, a knee joint hydraulic cylinder rod cavity pressure sensor 8, a thigh rod 9, a knee joint hydraulic cylinder 10, a knee joint hydraulic cylinder rodless cavity pressure sensor 11, a hip joint encoder 12, a hip joint hydraulic cylinder rod cavity pressure sensor 13, a hip joint hydraulic cylinder rodless cavity pressure sensor 1 4. Base plate 15, hip joint hydraulic cylinder 16, switch valve 17 of ankle joint pump control part, servo valve 18 of ankle joint valve control part, switch valve 19 of knee joint pump control part, servo valve 20 of knee joint valve control part, switch valve 21 of hip joint pump control part, servo valve 22 of hip joint valve control part, back plate 23, back force sensor 24, back strap 25, waist strap 26, servo amplifier board (not shown in the figure), variable speed pump corresponding to each joint (not shown in the figure), and real-time controller (not shown in the figure).

[0042] The foot 1 of the exoskeleton is the contact part with the ground, and the entire exoskeleton is supported by the foot, and its function is similar to that of a human foot. The bottom end of the calf rod 6 is rotatably connected to the foot 1, and can be a hinge connection. The bottom end of the thigh rod 9 is rotatably connected to the top of the calf rod 6, and can also be a hinge connection. The ankle joint hydraulic cylinder 4 is used to drive the foot 1 and the calf rod 6 to rotate relative to each other. The ankle joint encoder 2 is installed at the ankle joint (can be installed at the hinge connection). The knee joint hydraulic cylinder 10 is used to drive the calf rod 6 and the thigh rod 9 to rotate relative to each other. The knee joint encoder 7 is installed at the knee joint (can be installed at the hinge connection). The top of the thigh rod 9 is rotatably connected to the base plate 15, and the hip joint hydraulic cylinder 16 is used to drive the thigh rod 9 and the base plate 15 to rotate relative to each other. The hip joint encoder 12 is installed at the hip joint (can be installed at the hinge connection). The bottom plate 15 is connected to the back plate 23 by bolts, the back force sensor 24 is installed between the back plate 23 and the back strap 25 , and the waist strap 26 is connected to the lower end of the back plate 23 .

[0043] The rod cavity pressure sensor 3 of the ankle joint hydraulic cylinder is used to detect the rod cavity pressure of the ankle joint hydraulic cylinder 4, and the rodless cavity pressure sensor 5 of the ankle joint hydraulic cylinder is used to detect the rodless cavity pressure of the ankle joint hydraulic cylinder 4. The ankle joint encoder is used to detect the rotation angle at the ankle joint. The rod cavity pressure sensor 8 of the knee joint hydraulic cylinder is used to detect the rod cavity pressure of the knee joint hydraulic cylinder 10, and the rodless cavity pressure sensor 11 of the knee joint hydraulic cylinder is used to detect the rodless cavity pressure of the knee joint hydraulic cylinder 10. The knee joint encoder is used to detect the rotation angle at the knee joint. The rod cavity pressure sensor 13 of the hip joint hydraulic cylinder is used to detect the rod cavity pressure of the hip joint hydraulic cylinder 16, and the rodless cavity pressure sensor 14 of the hip joint hydraulic cylinder is used to detect the rodless cavity pressure of the hip joint hydraulic cylinder 16. The hip joint encoder is used to detect the rotation angle at the hip joint.

[0044] The switch valve 17 of the ankle joint pump control part and the servo valve 18 of the ankle joint valve control part are used to control the ankle joint hydraulic cylinder 4, the switch valve 19 of the knee joint pump control part and the servo valve 20 of the knee joint valve control part are used to control the knee joint hydraulic cylinder 10, and the switch valve 21 of the hip joint pump control part and the servo valve 22 of the hip joint valve control part are used to control the hip joint hydraulic cylinder 16. The real-time controller is electrically connected to the ankle joint encoder 2, the ankle joint hydraulic cylinder rod cavity pressure sensor 3, the ankle joint hydraulic cylinder rodless cavity pressure sensor 5, the knee joint encoder 7, the knee joint hydraulic cylinder rod cavity pressure sensor 8, the knee joint hydraulic cylinder rodless cavity pressure sensor 11, the hip joint encoder 12, the hip joint hydraulic cylinder rod cavity pressure sensor 13, the hip joint hydraulic cylinder rodless cavity pressure sensor 14, the switch valve 17 of the ankle joint pump control part, the servo valve 18 of the ankle joint valve control part, the switch valve 19 of the knee joint pump control part, the servo valve 20 of the knee joint valve control part, the switch valve 21 of the hip joint pump control part, the servo valve 22 of the hip joint valve control part and the back force sensor 24. The real-time controller model can be selected from NI cRIO-9031, but is not limited thereto. The amplifier board of the servo valve can be the Star WO36829 / 1 product, but is not limited thereto.

[0045] In order to overcome the problem of high energy consumption of the electro-hydraulic system of the single-leg hydraulic-assisted exoskeleton, the hydraulic system adopts a parallel pump-valve coordinated electro-hydraulic system solution, constructs an independently operated pump control part and valve control part, and allows the pump control part to provide the main flow and the valve control part to provide a small flow. In order to overcome the influence of high-order nonlinearity and model uncertainty of the single-leg hydraulic-assisted exoskeleton, the adaptive robust control algorithm (ARC) is used to design the upper and lower layer controllers to achieve good following and assisting effects of the single-leg hydraulic-assisted exoskeleton on human movement. In order to overcome the problem of flow distribution caused by the non-negligible compressibility of oil under heavy load, the flow distribution adopts a solution in which the pump provides low-frequency flow and the valve provides high-frequency flow, which reduces the system energy consumption under heavy load.

[0046] In this embodiment, the present invention changes the original power system of the ankle joint, knee joint and hip joint, and improves the original power system of each joint into a parallel pump-valve coordinated electro-hydraulic system. Figure 2 Each parallel pump-valve coordinated electro-hydraulic system includes a parallel coordinated pump control part and a valve control part; the pump control part includes a variable speed pump PS1 and two two-way switch valves SV1 and SV2 that determine the outlet flow direction of the variable speed pump PS1; the valve control part includes four two-way electro-hydraulic servo valves PV1, PV2, PV3 and PV4 and a hydraulic oil source PS2. The electro-hydraulic servo valves PV1 and PV2 control the flow of the hydraulic oil source PS2 to the two chambers of the corresponding hydraulic cylinder, and the electro-hydraulic servo valves PV3 and PV4 control the flow of the two chambers of the corresponding hydraulic cylinder to the oil tank.

[0047] Of course, the present invention not only improves the power system of the ankle joint, knee joint and hip joint, but also needs to cooperate with the required single-leg hydraulic power-assisted exoskeleton control method to complete the corresponding coordinated actions between the three joints. In the present invention, the single-leg hydraulic power-assisted exoskeleton control method under heavy load adopts an adaptive robust control algorithm (ARC) that can well overcome the influence of model uncertainty. The principle is to continuously adjust the parameters of the system model by designing an adaptive law, make feedforward compensation to the control model to ensure zero tracking error under static conditions, and design robust feedback to ensure the dynamic characteristics and stability of the single-leg hydraulic power-assisted exoskeleton system. At the same time, using the cascade force control method, the upper controller is designed to obtain the reference trajectory of the single-leg exoskeleton joint, and the lower rodless cavity position tracking controller, the lower rod cavity pressure planner and the lower rod cavity pressure tracking controller realize the tracking of the joint reference trajectory and reduce the system energy consumption. In addition, the flow distribution adopts a scheme in which the pump provides low-frequency flow and the valve provides high-frequency flow, which reduces the system energy consumption under heavy load. The control algorithm is simple to implement, easy to implement in engineering, and flexible to control.

[0048] When the single-leg hydraulic power-assisted exoskeleton control method is applied in a specific application, it can be applied in the form of software, such as being designed as an independently running program and installed on a computer terminal, which can be a computer, a smart phone, a control system, and other Internet of Things devices; it can also be designed as an embedded running program and installed on a computer terminal, such as being installed on a single-chip microcomputer. A computer terminal generally includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the single-leg hydraulic power-assisted exoskeleton control method under heavy load are implemented. When the single-leg hydraulic power-assisted exoskeleton control method under heavy load is applied, it can be applied in the form of software, such as being designed as a program that can be independently run on a computer-readable storage medium, which can be a U disk, which can be designed as a U shield, and the U disk is designed to start the entire method through an external trigger. The U disk is a type of computer-readable storage medium, and a computer program is stored on the computer-readable storage medium. When the program is executed by the processor, the steps of the single-leg hydraulic power-assisted exoskeleton control method are implemented.

[0049] Regardless of the application mode of the single-leg hydraulic power-assisted exoskeleton control method under heavy load, it can be classified as a single-leg hydraulic power-assisted exoskeleton device in terms of functional design. The single-leg hydraulic power-assisted exoskeleton device mainly includes a flow acquisition module, a control voltage acquisition module, a hydraulic cylinder actual driving force acquisition module, a joint actual driving torque acquisition module, and a rotation angular velocity acquisition module.

[0050] Next, combine Figure 3 and Figure 4 The present invention provides a detailed description of the single-leg hydraulic power-assisted exoskeleton control method under heavy load. When the single-leg hydraulic power-assisted exoskeleton control method under heavy load is applied, the exoskeleton needs to be prepared in advance as follows:

[0051] (1) The exoskeleton is fixed to the human body by means of the back strap 25 and the waist strap 26, and the sampling period T of the real-time controller is initialized according to the actual situation, and the sampling period T is set in the range of 10 to 20 milliseconds;

[0052] (2) Rotate the foot 1 to a horizontal position, and rotate the calf rod 6, thigh rod 9, and back plate 23 to a vertical position. At this time, initialize the ankle joint encoder 2, knee joint encoder 7, and hip joint encoder 12, and set the values ​​of the joint encoders to zero;

[0053] (3) Initializing the back force sensor 24 and adjusting the value of the back force sensor 24 to zero;

[0054] (4) Design a schematic diagram of the pump-valve coordinated electro-hydraulic system for a single-leg hydraulically assisted exoskeleton.

[0055] The principle scheme of the pump-valve coordination electro-hydraulic system of the single-leg hydraulic assisted exoskeleton is as follows Figure 2 As shown, Figure 2 This is the schematic diagram of the single-joint parallel pump-valve coordinated electro-hydraulic system. The principle scheme of the pump-valve coordinated electro-hydraulic system for the single-leg hydraulic assisted exoskeleton is to apply the single-joint parallel pump-valve coordinated electro-hydraulic system to the ankle joint, knee joint and hip joint of the exoskeleton respectively.

[0056] The structure of the parallel pump-valve coordinated electro-hydraulic system is mainly divided into the pump control part and the valve control part. The pump control part consists of a variable speed pump PS1 and two two-way switch valves SV1 and SV2. The outlet flow direction of its oil source is determined by the switch valve. The valve control part consists of four two-way electro-hydraulic servo valves PV1, PV2, PV3 and PV4 and a hydraulic oil source PS2. The electro-hydraulic servo valves PV1 and PV2 control the flow of the oil source to the two chambers of the hydraulic cylinder, and the electro-hydraulic servo valves PV3 and PV4 control the flow of the two chambers of the hydraulic cylinder to the oil tank. Among them, the oil source of the pump control part is not limited to the variable speed pump. The variable pump with similar functions and the combination of the variable speed pump and the variable pump can also be used in the pump control part, which needs to adjust the output flow in real time according to the given input signal; PV1, PV2, PV3 and PV4 are not limited to the electro-hydraulic servo valve. The proportional servo valve and proportional cartridge valve with similar functions can also be used in the valve control part. Its basic function is to realize continuous adjustment of the flow through the valve port, and the bandwidth is higher than that of the pump control part. The flow of the pump control part and the flow of the valve control part are superimposed in parallel at N1 and N2 to jointly control the flow to the two chambers of the hydraulic cylinder.

[0057] (5) Establishing a physical model of a single-leg hydraulically assisted exoskeleton and converting it into a state equation; wherein the physical model includes a human-machine interface model, a motion model of the exoskeleton mechanical body, and a dynamic model of the hydraulic actuator;

[0058] The upper-level human-machine interface model expression is:

[0059]

[0060] Among them, F hm =[F hmx F hmy τ hmz ] T is the human-machine force at the contact point between the human and the exoskeleton robot, x, y, z are the symbols of the three coordinate axes of the world coordinate system; K = diag{K x ,K y ,K z} is the stiffness of the human-machine interface, x h =[x hx x hy x hz ] T is the Cartesian coordinate position of the contact point of the strap 25 on the back of the person, x e =[xex x ey x ez ] T is the Cartesian position of the contact point of the exoskeleton back plate 23; It is about concentrated interference and modeling uncertainty at the human-machine interface.

[0061] When transforming the physical model, the integration of human-machine forces Replace F hm , the state equation is obtained as:

[0062]

[0063] The motion model of the exoskeleton mechanical body is:

[0064]

[0065] In the formula, τ act =[τ1 τ2 τ3] T is the joint driving torque at the ankle, knee and hip joints, J is the Jacobian matrix of the system at the force sensor, q = [q1 q2 q3] T are the rotation angles of the ankle joint, knee joint and hip joint, M sp3 (q) is the inertia matrix of the system, is the centrifugal force and Coriolis force matrix of the system, G sp3 (q) is the gravity matrix of the system, B = diag{B1, B2, B3} is the damping matrix of the system, It is a concentrated disturbance of the system;

[0066] The dynamic model of the hydraulic actuator is:

[0067]

[0068] Q 1i =Q 1vi +Q 1pi , Q 2i =Q 2vi -Q 2pi

[0069] Q 1vi =Q pv1i -Q pv3i , Q 2vi =-Q pv2i +Q pv4i

[0070]

[0071] ΔP pv1i =P s -P1i , ΔP pv2i =P s -P 2i , ΔP pv3i =P 1i -P r , ΔP pv4i =P 2i -P r

[0072] x pvji =u pvji ,i=1,2,3

[0073] Q 1pi =sw 1i Q pi , Q 2pi =sw 2i Q pi

[0074]

[0075] Q pi =k pi u pi ,i=1,2,3

[0076] Where x Li is the displacement of hydraulic cylinder i, is x Li About q i The first-order partial derivative of 1i and P 2i A represents the actual pressure of the rodless chamber and the rod chamber in hydraulic cylinder i. 1i and A 2i Represents the effective area of ​​the rodless cavity and the rod cavity in hydraulic cylinder i. V 1i =V h1i +A 1i x Li and V 2i =V h2i -A 2i x Li are the total volume of the two chambers in hydraulic cylinder i, V h1i ,V h2i Yes i = 0, the volume of the two chambers of hydraulic cylinder i, β e Represents the bulk elastic modulus. Q 1i , Q 2i are the oil flow rate in the rodless chamber and the oil flow rate out of the rod chamber in hydraulic cylinder i, respectively. and represents the concentrated modeling error and uncertain disturbance in the hydraulic actuator dynamics model, Q 1vi and Q 2viThey represent the oil flow rate from the rodless chamber to the valve-controlled part and the oil flow rate from the rod chamber to the hydraulic cylinder i, respectively. 1pi and Q 2pi They represent the oil flow rate of the rodless chamber and the rod chamber from the pump control part in the hydraulic cylinder i, respectively, and Q pvji represents the flow rate of the jth servo valve corresponding to hydraulic cylinder i, k qpvji is the flow gain coefficient of the jth servo valve corresponding to hydraulic cylinder i, x pvji is the valve core displacement of the jth servo valve corresponding to hydraulic cylinder i, P s With P r They are the oil supply pressure of the valve control part and the pressure of the oil tank, ΔP pv1i and ΔP pv2i Respectively represent the oil supply pressure P of the valve control part in the hydraulic cylinder i s The actual pressure P of the rodless chamber 1i and the actual pressure of the rod chamber P 2i The pressure difference, ΔP pv3i and ΔP pv4i Respectively represent the actual pressure P of the rodless chamber in hydraulic cylinder i 1i and the actual pressure of the rod chamber P 2i With tank pressure P r The pressure difference, u pvji is the control voltage of the jth servo valve corresponding to hydraulic cylinder i, Q pi represents the output flow of the variable speed pump corresponding to hydraulic cylinder i, k pi and u pi They respectively represent the flow gain coefficient and control voltage of the variable speed pump corresponding to the hydraulic cylinder i.

[0077] The method of converting the physical model into the state equation includes the following steps:

[0078] (5.1) Define state variables:

[0079]

[0080] x2=q

[0081]

[0082] x4=P1=[P 11 P 12 P 13 ] T

[0083] x5=P2=[P 21 P 22 P 23 ] T

[0084] x=[x1T x2 T x3 T x4 T x5 T ] T

[0085] The concentrated model uncertainty is defined as:

[0086]

[0087] (5.2) The centralized model uncertainty is divided into two parts: a constant and a time-varying function, and we get Δ in and Δ i Respectively represent The constant part and the time-varying part of

[0088] (5.3)Assume θ q =[β T B θ T Δ 2n T β e Δ 3n T ] T ,θ p2i =[β e Δ 4ni ] T ,in, Δ 1n =[Δ 1nx Δ 1ny Δ 1nz ] T ,β=[Y2 Y3 Y4 X4 J2 J3 J4] T is the system parameter of the exoskeleton single leg, B θ =[B1 B2 B3] T is the system damping, Δ 2n =[Δ 2n1 Δ 2n2 Δ 2n3 ] T , Δ 3n =[Δ 3n1 Δ 3n2 Δ 3n3 ] T , Δ 4n =[Δ 4n1 Δ 4n2 Δ 4n3 ] T .

[0089] The state equation of the physical model of the single-leg hydraulic assisted exoskeleton is:

[0090]

[0091]

[0092]

[0093] in, A2=diag{A 21 ,A 22 ,A 23} , F L =A1P1-A2P2, Q v =N1Q1+N2Q2, Q v =[Q 11 A 11 / V 11 +Q 21 A 21 / V 21 ,Q 12 A 12 / V 12 +Q 22 A 22 / V 22 ,Q 13 A 13 / V 13 +Q 23 A 23 / V 23 ] T , Q1=[Q 11 ,Q 12 ,Q 13 ] T ,Q2=[Q 21 ,Q 22 ,Q 23 ] T ,N1=diag{A 11 / V 11 ,A 12 / V 12 ,A 13 / V 13},

[0094] (6) Connecting the wearer to the back force sensor 24 through the back strap 25, measuring the human-machine force of the back force sensor 24, and obtaining the reference rotation angle of each joint of the single-leg hydraulic power-assisted exoskeleton through the upper controller;

[0095] According to the state equation of the physical model in step (5), let the first tracking error z1 = x1-x 1d , where x 1d is the integral of the desired human-machine forces in the x, y, and z directions, which is zero;e As a virtual control input, x e Design control law x m Make the first tracking error z1 of the human-machine force quickly approach zero;

[0096] Let x m =x ma +x ms +x msn ,in x ms =K1z1, and By x ma After parameter linearization, we get is the desired human-machine force in the x, y, and z directions, K1 = diag{K 1x ,K 1y ,K 1z} is the linear feedback gain, in this example, K1 = diag{8,8,8}; is θ F The estimated value of is in the range of: In this embodiment, the initial value is in is the parameter θ F Estimated value of The minimum value of is the parameter θ F Estimated value of In this embodiment, take Estimated value In the upper controller, the adaptive law It is obtained that Γ1 is a positive definite gain matrix. In this embodiment, Γ1=diag{0,0,0,2,15,2} is taken. The mapping function is:

[0097]

[0098] In the formula, i is the independent variable, the nonlinear robust feedback term x msn satisfy:

[0099]

[0100] in, It is an estimate Subtract the actual value θ F , ε1 is a threshold value and is any non-negative number. In this example, ε1 =

[111] T , x msn=

[000] T .

[0101] According to the design x m , and the inverse kinematics model of the single-leg hydraulic assisted exoskeleton to obtain the expected rotation angle q of each joint of the exoskeleton m =[q m1 q m2 q m3 ] T :

[0102] q m =invkine(x m )

[0103] Where invkine stands for inverse kinematics. According to the expected rotation angle q of each joint of the exoskeleton mi , i = 1, 2, 3, and smoothed by a fourth-order filter to obtain the reference rotation angle, reference rotation angular velocity, reference rotation angular acceleration and reference rotation angular jerk of each joint of the exoskeleton; wherein the state equation of the fourth-order filter is as follows:

[0104]

[0105] i=1,2,3

[0106] In the formula, Respectively represent the reference rotation angle, reference rotation angular velocity, reference rotation angular acceleration and reference rotation angular jerk after filtering, from q mi to η 1i The transfer function is:

[0107]

[0108] Through the above transfer function, we can obtain q mi Transformed into the required smooth reference rotation angle η of each joint of the exoskeleton 1i ; Wherein, a1, a2, a3, and a4 in the transfer function are obtained by pole configuration. In this embodiment, the closed-loop pole is set to 20 radians per second, and the values ​​of a1, a2, a3, and a4 are respectively a1=80, a2=2400, a3=32000, and a4=160000, but the actual value is not limited thereto.

[0109] (7) The actual rotation angle values ​​of the joints of the single-leg hydraulic power-assisted exoskeleton are obtained through the ankle joint encoder 2, the knee joint encoder 7 and the hip joint encoder 12; the reference rotation angles of the joints are obtained according to step (6), and the actual rotation angles and the reference rotation angles are used as inputs of the lower-layer rodless cavity position tracking controller, and the outputs of the lower-layer rodless cavity position tracking controller are the desired driving forces at the ankle joint hydraulic cylinder 4, the knee joint hydraulic cylinder 10 and the hip joint hydraulic cylinder 16 in the single-leg hydraulic power-assisted exoskeleton and the desired flow rate of the rodless cavity; the design method of the lower-layer rodless cavity position tracking controller includes the following steps:

[0110] Assume the second tracking error in Define a transformation equation:

[0111]

[0112] Where K2 is the positive feedback gain matrix. In this example, K2=diag{85,85,85}. z3 is the third tracking error. The transfer function of z2 and z3 is G p (s)=z2(s) / z3(s)=diag{1 / (s+K 2i ),i=1,2,3},

[0113]

[0114] Let Bx3 = Y B B θ , Where β=[Y2 Y3 Y4 X4 J2 J3 J4] T , Y2, Y3, Y4, X4, J2, J3, J4 are all model parameters of the mechanical structure. B θ =[B1B2 B3] T is the damping of the system;

[0115] (7.1) L As a virtual control input, F L Design control law F Ld Make the second tracking error z2 quickly approach zero;

[0116] Let F Ld =F Lda +F Lds +F Ldsn ,in, F Lds =-h -1 K3z3, K3 is the linear feedback gain. In this example, K3=diag{85,85,85}; is the parameter β,Bθ ,Δ 2n An estimate of θ q =[β T B θ T Δ 2n T β e Δ 3n T ] T In this example, take the initial value

[0117] is θ q The estimated value of is in the range of: in is the parameter θ q Estimated value of The minimum value of is the parameter θ q Estimated value of In this example, take the maximum value of

[0118]

[0119] Estimated value In the lower rodless cavity position tracking controller, the adaptive law We get, τ4 is obtained by step (7.3), Γ2 is a positive definite gain matrix. In this example, we take Γ2 = diag{10,0,0,0,10,0,0,0,0,0,0,0,0,0,0}, The mapping function is:

[0120]

[0121] In the formula, i As the independent variable, let φ3=[-YY B I 3×3 0 3×1 0 3×3 ] T , where I 3×3 =diag{1,1,1},0 3×1 =

[000] T , 0 3×3 =diag{0,0,0},F Ldsn satisfy:

[0122]

[0123] In the formula, It is an estimate Subtract the actual value θq , ε2 is a threshold value and is any non-negative number; in this example, ε2 =

[111] T , F Ldsn =

[000] T .

[0124] (7.2) Design an adaptive robust observer to estimate the angular velocity and angular acceleration of the joint rotation.

[0125] Assume that the observation error e o1 =x2-y, where y is the estimated value of the joint angle, and a transformation equation is defined:

[0126]

[0127] Among them, K o1 is the positive feedback gain matrix. In this example, K o1 =[606060] T ; is the estimated value of the angular velocity of the joint rotation, and the estimated value of the angular acceleration of the joint rotation Designed for:

[0128]

[0129] in, is to use θ q Another set of parameter estimates for The obtained M sp3 , C sp3 , G sp3 The estimated value of K o2 is the linear positive definite feedback gain matrix. In this example, K o2 =[400200200] T ; K o2s is the nonlinear positive definite feedback gain matrix. In this example, K o2s =

[000] T ; T os is the robust feedback term of the observer error; let In this example, the initial value is The range of estimated values ​​that can be obtained is: make φ o =[-Y o -Y Bo I 3×3 0 3×1 0 3×3 ] T ; Estimated value In the adaptive robust observer, the adaptive law We get, where Γ o is a positive definite gain matrix. In this example, we take Γ o =diag{10,0,0,0,2,0,0,0,0,0,0,0,0,0,0,0}, The mapping function is:

[0130]

[0131] In the formula, i is the independent variable,

[0132] The following two conditions are met:

[0133]

[0134] In the formula, It is an estimate Subtract the actual value θ q , ε o is a threshold value and is any non-negative number. In this embodiment, ε is selected o =

[111] T , select T os =

[000] T .

[0135] Defining the fourth tracking error in, That is, in the control law F Ld Medium replace To calculate

[0136] (7.3) Consider Q1 as a virtual control input and design the control law Q for Q1. 1m The fourth tracking error Rapidly approaches zero;

[0137] Let Q 1m =Q 1ma +Q 1ms +Q 1msn ,in,

[0138] φ 4c =[0 3×7 0 3×3 0 3×3 N2α 2p -q v I 3×3 ] T , α 2p From step (9), K4>0 is the linear feedback gain. In this example, K4=[858585] T Let φ4=[0 3×7 0 3×3 0 3×3 QUR 1ma +N2α 2p -q v I 3×3 ] T , Q 1msn The following two conditions must be met:

[0139]

[0140] In the formula, It is an estimate Subtract the actual value θ q , ε3 is a threshold value and is any non-negative number; in this embodiment, ε3=

[111] T , select Q 1msn =

[000] T .

[0141] (8) The desired driving force of the ankle joint hydraulic cylinder 4, the knee joint hydraulic cylinder 10 and the hip joint hydraulic cylinder 16 in the single-leg hydraulic power-assisted exoskeleton obtained in step (7) is used as the input of the lower-layer rod cavity pressure planner, and the output of the lower-layer rod cavity pressure planner is the desired rod cavity pressure of the ankle joint hydraulic cylinder 4, the knee joint hydraulic cylinder 10 and the hip joint hydraulic cylinder 16 of the single-leg hydraulic power-assisted exoskeleton; the design of the lower-layer rod cavity pressure planner includes the following steps:

[0142] Considering that good control design can ensure that the system error is within a small range, the model compensation term F in step (7.1) Lda Can basically characterize the expected driving force F Ld In addition, in order to obtain a more continuous and smooth desired pressure in the rod cavity and to avoid the negative influence of noise, the joint reference trajectory is used instead of the measurement signal of the state quantity.

[0143] set up

[0144] Among them, F Ldad =[F Ldad1 F Ldad2 F Ldad3 ] T .

[0145] The expected pressure P of the rod chamber of the i-th hydraulic cylinder2di Designed for:

[0146]

[0147] Where P c is the minimum working pressure. In this example, P c =0.1×10 6 Pa. The derivative of the desired pressure in the rod chamber of the i-th hydraulic cylinder Designed for:

[0148]

[0149] (9) The actual pressure values ​​of the rod chambers of the ankle joint hydraulic cylinder 4, the knee joint hydraulic cylinder 10 and the hip joint hydraulic cylinder 16 are obtained through the ankle joint hydraulic cylinder rod chamber pressure sensor 3, the knee joint hydraulic cylinder rod chamber pressure sensor 8 and the hip joint hydraulic cylinder rod chamber pressure sensor 13; according to the expected rod chamber pressures of the ankle joint hydraulic cylinder 4, the knee joint hydraulic cylinder 10 and the hip joint hydraulic cylinder 16 in the single-leg hydraulic power-assisted exoskeleton obtained in step (8), the expected rod chamber pressures and the actual rod chamber pressures are used as inputs of the lower-level rod chamber pressure tracking controller, and the output of the lower-level rod chamber pressure tracking controller is the expected rod chamber flow of the ankle joint hydraulic cylinder 4, the knee joint hydraulic cylinder 10 and the hip joint hydraulic cylinder 16. In this example, the lower-level rod chamber pressure tracking controller method includes the following steps:

[0150] Define the fifth tracking error z 5i =p 2i -p 2di , Q 2i As a virtual control input, Q 2i Design control law α 2pi The fifth tracking error z 5i =p 2i -p 2di Rapidly approaches zero;

[0151] Let α 2pi =α 2pai +α 2ps1i +α 2ps2i ,in α 2p =[α 2p1 α 2p2 α 2p3 ] T ,K p2i >0 is the linear feedback gain. In this example, K p21 =200,K p22 =100,K p23 =100; They are β e , Δ4ni The estimated value of θ p2i =[β e Δ 4ni ] T , is θ p2i In this example, the initial value is taken And the estimated values ​​range from: in is the parameter θ p2i Estimated value of The minimum value of is the parameter θ p2i Estimated value of In this example, take the maximum value of make Estimated value In the lower pressure tracking controller, the adaptive law Get, Γ p2i is a positive definite gain matrix. In this example, we take Γ p2i =

[00] T , The mapping function is:

[0152]

[0153] In the formula, i is the independent variable, the nonlinear robust feedback term α 2ps2i The following two conditions must be met:

[0154]

[0155] in, It is an estimate Subtract the actual value θ p2i , ε p2i is a threshold value and is any non-negative number. In this embodiment, ε is selected p2i =1, select α 2ps2i =0.

[0156] (10) The expected flow rates of the rodless chambers of the ankle joint hydraulic cylinder, the knee joint hydraulic cylinder and the hip joint hydraulic cylinder in the single-leg hydraulic power-assisted exoskeleton obtained in step (7) and the expected flow rates of the rod chambers of the ankle joint hydraulic cylinder, the knee joint hydraulic cylinder and the hip joint hydraulic cylinder in the single-leg hydraulic power-assisted exoskeleton obtained in step (9) are used as inputs of a pump-valve flow distribution module, and the output of the pump-valve flow distribution module is the control voltage of the electro-hydraulic servo valve of each hydraulic cylinder and the control voltage of the variable speed pump; the pump-valve flow distribution includes the following steps:

[0157] (10.1) Determine the control voltage u of the variable speed pump corresponding to hydraulic cylinder i pi.

[0158] Step 1: Determine whether the pump provides flow to the rodless chamber of the hydraulic cylinder or to the rod chamber of the hydraulic cylinder.

[0159] If Q 1mi >0,α 2pi ≥0, then sw 1i =1, sw 2i =0;

[0160] If Q 1mi >0,α 2pi <0;

[0161] If |Q 1madi |≥|α 2padi |, sw 1i =1, sw 2i =0;

[0162] If |Q 1madi |<|α 2padi |, sw 1i =0, sw 2i =1;

[0163] If Q 1mi ≤0,α 2pi ≥0, then sw 1i =0, sw 2i =0;

[0164] If Q 1mi ≤0,α 2pi <0, then sw 1i =0, sw 2i =1;

[0165] Among them, sw 1i and sw 2i They represent the switch state of the switch valve when the flow of the pump control part in the hydraulic cylinder i enters the rodless chamber of the hydraulic cylinder and the switch state of the switch valve when entering the rod chamber of the hydraulic cylinder, respectively. Q 1madi and α 2padi They represent the expected flow of the low-frequency part of the hydraulic cylinder without rod cavity compensation and the expected flow of the low-frequency part of the hydraulic cylinder with rod cavity compensation using the joint reference trajectory of the i-th joint. The joint reference trajectory includes the reference rotation angle after the above filtering Reference angular velocity and the reference angular acceleration The expected flow rate of the low-frequency part is the value calculated by removing the part directly related to the measurement error from the compensation term of the expected flow model of each joint, and replacing the actual trajectory with the joint reference trajectory for the remaining part. Specifically, for the rodless cavity expected flow rate Q 1m =Q 1ma +Q1ms +Q 1msn , the desired flow Q of the low-frequency part required by the rodless chamber pump control part of each joint 1mad is the compensation term Q for the above adaptive model 1ma The part directly related to the measurement error is removed (i.e., the term related to the third tracking error z3 is removed, because it is directly related to the measurement error and has a higher frequency), and the remaining part is calculated using the joint reference trajectory instead of the actual trajectory. Similarly, the expected flow rate of the low-frequency part required for the rod cavity pump control part can be analogous to the rodless cavity.

[0166] Step 2: Determine the expected output flow rate Q of the pump pdi .

[0167] 1) Calculate Q 1madi and α 2padi ;

[0168] Let Q 1mad =[Q 1mad1 Q 1mad2 Q 1mad3 ] T ;

[0169]

[0170]

[0171] If Q 1mi Q 1madi ≤0, then Q 1madi =0;

[0172] If α 2pi α 2padi ≤0, then α 2padi =0;

[0173] Among them, Q 1madi It's Q 1mad The i-th element of Q 1madi and α 2padi They represent the expected flow of the low-frequency part of the hydraulic cylinder rodless cavity compensation and the expected flow of the low-frequency part of the hydraulic cylinder rod cavity compensation using the joint reference trajectory of the i-th joint, respectively. di represents the motion reference trajectory of hydraulic cylinder i, is x di about The first partial derivative of V 1di =V h1i +A 1i x di and V 2di =V h2i -A 2i x diare the compressible volume V at the i-th hydraulic cylinder. 1i and V 2i Using motion reference trajectory x di Replace x Li The expression form, is an estimate of the elastic modulus, N 1d =diag{A 11 / V 1d1 ,A 12 / V 1d2 ,A 13 / V 1d3},N 2d =diag{A 21 / V 2d1 ,A 22 / V 2d2 ,A 23 / V 2d3}, α 2pad =[α 2pad1 α 2pad2 α 2pad3 ] T ,

[0174] φ 4cd =[0 3×7 0 3×3 0 3×3 N 2d α 2pad -q vd I 3×3 ] T , is the estimated value of the exoskeleton system parameters, F Ldad is the expected compensating driving force of the hydraulic cylinder at each joint, and F Ldad about and the partial derivatives of t, is the estimated value of the constant part of the uncertainty of the rod cavity model in hydraulic cylinder i, is the derivative of the desired pressure in the rod chamber of the i-th hydraulic cylinder, Q 1mi is the expected flow rate of the rodless cavity of the ith joint, α 2pi is the expected flow rate of the rod chamber of the i-th joint. It is worth mentioning that the values ​​in the above formulas are calculated using the joint reference trajectory instead of the actual trajectory. The reason for using the joint reference trajectory for calculation is that on the one hand, it can avoid the influence of state measurement noise, and on the other hand, it avoids the state being related to the measured quantity, so the frequency is low. Since the pump can only receive the low-frequency signal, the filtered joint reference trajectory is used here.

[0175] 2) Calculate Q pdi .

[0176] Q pdi =sw 1i Q 1madi -sw 2i α 2padi ;

[0177] If 0≤Q pdi ≤Q pbound , then Q pdi =0;

[0178] Among them, Q pbound Indicates the minimum boundary flow rate of the variable speed pump. In this example, Q pbound =1×10 - 6 m 3 / s,Q pdi Represents the expected output flow of the variable speed pump corresponding to hydraulic cylinder i.

[0179] Step 3: Calculate the control voltage of the pump.

[0180] The control voltage of the variable speed pump corresponding to hydraulic cylinder i is Among them, the flow gain coefficient k p =8.3×10 -5 m 3 / (s·V).

[0181] (10.2) Determine the control voltage u of the servo valve corresponding to hydraulic cylinder i pv1i ,u pv2i ,u pv3i ,u pv4i .

[0182] Q 1pdi =sw 1i Q pdi , Q 2pdi =sw 2i Q pdi , Q 1vdi =Q 1mi -Q 1pdi , Q 2vdi =α 2pi +Q 2pdi ,

[0183] Where Q 1pdi and Q 2pdi They represent the expected oil flow rate of the rodless chamber and the rod chamber from the pump control part in the hydraulic cylinder i, respectively, and Q 1vdi and Q 2vdi They respectively represent the expected oil inlet flow rate of the rodless chamber and the expected oil outlet flow rate of the rod chamber from the valve control part in the hydraulic cylinder i.

[0184] If Q 1vdi >0, then u pv3i =0;

[0185] If Q 1vdi <0, then u pv1i =0,

[0186] If Q 1vdi =0, then u pv1i =0,u pv3i =0;

[0187] If Q 2vdi >0, then u pv2i =0,

[0188] If Q 2vdi <0, then u pv4i =0;

[0189] If Q 2vdi =0, then u pv2i =0,u pv4i =0;

[0190] in,

[0191] In summary, the control input signals of the pump control part and the valve control part can be obtained.

[0192] (11) converting the control voltage of the electro-hydraulic servo valve obtained in step (10) into a control current of the corresponding servo valve through an amplifier board of an ankle joint electro-hydraulic servo valve, an amplifier board of a knee joint electro-hydraulic servo valve, and an amplifier board of a hip joint electro-hydraulic servo valve;

[0193] (12) The valve core opening displacement of the corresponding servo valve 18 of the ankle joint valve control part, the servo valve 20 of the knee joint valve control part and the servo valve 22 of the hip joint valve control part is controlled by the control current of each servo valve, and the speed of the servo motor of the corresponding variable speed pump of the ankle joint pump control part, the variable speed pump of the knee joint pump control part and the variable speed pump of the hip joint pump control part is controlled by the control voltage of each variable speed pump, so as to control the pressure at both ends of the hydraulic cylinder, promote the movement of each hydraulic cylinder, and then drive the rotation of each joint of the single-leg hydraulic power-assisted exoskeleton to achieve the following movement of the single-leg hydraulic power-assisted exoskeleton. Compared with the prior art, the flow of the existing exoskeleton pump control part adopts the distribution method of "hydraulic cylinder speed × area", which does not take into account the compressibility of the oil. In the present invention, the flow of the pump control part is calculated based on the low-frequency part of the model compensation term, taking into account the compressibility of the oil. Under heavy load conditions, the compressibility of the oil cannot be ignored. At this time, the flow rate of the two chambers of the hydraulic cylinder and the speed of the hydraulic cylinder cannot be simply regarded as an algebraic relationship, but there is a dynamic relationship. At this time, the existing flow distribution scheme will no longer be applicable. The control method provided by the present invention solves this problem, so that under heavy load conditions, the variable speed pump can provide most of the flow rate and achieve energy saving.

[0194] In summary, in this embodiment, the single-leg hydraulic-assisted exoskeleton control method of the present invention can be summarized into the following steps.

[0195] In the first step, the three hydraulic systems respectively applied to the ankle joint, knee joint and hip joint of the exoskeleton all adopt parallel pump-valve coordinated electro-hydraulic systems. Each parallel pump-valve coordinated electro-hydraulic system includes a parallel coordinated pump control part and a valve control part. The pump control part includes a variable speed pump PS1 and two two-way switch valves SV1 and SV2 that determine the outlet flow direction of the variable speed pump PS1. The valve control part includes four two-way electro-hydraulic servo valves PV1, PV2, PV3 and PV4 and a hydraulic oil source PS2. The electro-hydraulic servo valves PV1 and PV2 control the flow of the hydraulic oil source PS2 to the two chambers of the corresponding hydraulic cylinder, and the electro-hydraulic servo valves PV3 and PV4 control the flow of the two chambers of the corresponding hydraulic cylinder to the oil tank.

[0196] This step requires the installation of three corresponding hydraulic systems on the exoskeleton for the ankle, knee and hip joints.

[0197] The second step is to coordinate the electro-hydraulic system of the parallel pump valves of each joint of the single-leg hydraulic assisted exoskeleton according to the reference rotation angle of each joint. Reference angular velocity Reference angular acceleration Actual driving force F of hydraulic cylinder L , actual rotation angle q, actual rotation angular velocity Get the expected flow rate α of the rod cavity of each joint2p =[α 2p1 α 2p2 α 2p3 ] T and the rodless chamber expected flow rate Q 1m =[Q 1m1 Q 1m2 Q 1m3 ] T ; where i represents the serial number of the three joints, the expected flow rate of the rod cavity of the i-th joint is α 2pi , the expected flow rate of the rodless cavity of the i-th joint is Q 1mi .

[0198] This step can be performed by the traffic acquisition module.

[0199] Among them, (1) The method for obtaining includes the following steps:

[0200] According to the human-machine force F hm and the Cartesian position x of the exoskeleton at the contact point e Design an upper-layer controller, which is x m =x ma +x ms +x msn , thus obtaining the Cartesian expected position x of the exoskeleton at the contact point m ; In the formula, x ma For x m The adaptive model compensation term, x ms For x m The linear robust feedback term, x msn For x m The nonlinear robust feedback term of ;

[0201] According to the design x m , based on the inverse kinematics model of the single-leg hydraulically assisted exoskeleton m =invkine(x m ), and thus the expected rotation angle q of each joint of the single-leg hydraulic power-assisted exoskeleton is obtained m =[q m1 q m2 q m3 ] T ,q mi represents the expected rotation angle of the i-th joint;

[0202] The expected rotation angle q of the i-th joint of the single-leg hydraulic assisted exoskeleton mi, i = 1, 2, 3, and smoothed by a fourth-order filter to obtain the reference rotation angle, reference rotation angular velocity, reference rotation angular acceleration and reference rotation angular jerk of the i-th joint of the exoskeleton; wherein the state equation of the fourth-order filter is as follows:

[0203]

[0204] i=1,2,3

[0205] In the formula, Respectively represent the reference rotation angle, reference rotation angular velocity, reference rotation angular acceleration and reference rotation angular jerk of the i-th joint of the exoskeleton after filtering, from q mi to η 1i The transfer function is:

[0206]

[0207] Through the above transfer function, we can obtain q mi Transformed into the required smooth reference rotation angle η of the i-th joint of the exoskeleton 1i ; Among them, a1, a2, a3, and a4 in the transfer function are obtained by pole configuration;

[0208] The reference rotation angles of each joint of the single-leg hydraulic assisted exoskeleton are obtained. Reference angular velocity Reference angular acceleration

[0209] (2) Expected flow rate Q of the rodless cavity of each joint of the single-leg hydraulic assisted exoskeleton 1m =[Q 1m1 Q 1m2 Q 1m3 ] T The calculation method includes the following steps:

[0210] according to q. α 2p 、F L Design a rodless cavity position tracking controller, the rodless cavity position tracking controller is Q 1m =Q 1ma +Q 1ms +Q 1msn , thus the expected flow rate Q of the rodless cavity of each joint of the single-leg hydraulic power-assisted exoskeleton is obtained 1m , where Q 1ma Q 1m The adaptive model compensation term, Q 1ms Q 1m The linear robust feedback term, Q 1msn Q1m The nonlinear robust feedback term.

[0211] (3) Expected flow rate α of the rod chamber of each joint of the single-leg hydraulic assisted exoskeleton 2p =[α 2p1 α 2p2 α 2p3 ] T The calculation method includes the following steps:

[0212] according to q. α 2p 、F L Design a rodless cavity position tracking controller, the rodless cavity position tracking controller is F Ld =F Lda +F Lds +F Ldsn , thus obtaining the expected driving force F of the hydraulic cylinder of each joint of the single-leg hydraulic power-assisted exoskeleton Ld Where, F Lda F Ld The adaptive model compensation term, F Lds F Ld The linear robust feedback term, F Ldsn F Ld The nonlinear robust feedback term of ;

[0213] According to F Ld =[F Ld1 F Ld2 F Ld3 ] T Design the rod cavity pressure planner for each joint. Considering that a good control design can ensure that the system error is within a small range, the adaptive model compensation term F Lda Can basically characterize the expected driving force F of the hydraulic cylinder Ld In addition, in order to obtain a more continuous and smooth desired pressure in the rod chamber and avoid the negative impact of noise, the joint reference trajectory is used instead of the measurement signal of the state quantity, that is, the desired compensation driving force F of the hydraulic cylinder Ldad =[F Ldad1 F Ldad2 F Ldad3 ] T , the expected compensation driving force of the hydraulic cylinder of the i-th joint is F Ldadi ;

[0214] For the F at the i-th joint Ldadi , the rod cavity pressure planner of the i-th joint is The expected pressure P of the rod cavity of the i-th joint is obtained 2di Where, P c is the set minimum working pressure, A1i and A 2i They represent the effective areas of the cavity without rod and the cavity with rod in the i-th joint respectively;

[0215] According to P 2di and the actual pressure P of the rod cavity of the i-th joint 2i , design the rod cavity pressure tracking controller of the i-th joint, the rod cavity pressure tracking controller of the i-th joint is α 2pi =α 2pai +α 2ps1i +α 2ps2i , thus we get the expected flow rate α of the rod cavity of the i-th joint 2pi ; In the formula, α 2pai is α 2pi The adaptive model compensation term, α 2ps1i is α 2pi The linear robust feedback term, α 2ps2i is α 2pi The nonlinear robust feedback term of ;

[0216] Thus, the expected flow rate α of the rod cavity of each joint of the single-leg hydraulic power-assisted exoskeleton is obtained 2p =[α 2p1 α 2p2 α 2p3 ] T .

[0217] The third step is to 2p , Q 1m Calculate the control voltages of PS1, PV1, PV2, PV3, and PV4 corresponding to each joint to distribute the pump and valve flow of each joint.

[0218] This step can be performed by the control voltage acquisition module. Thus, the technical problems of high-order nonlinearity, model uncertainty, and high energy consumption of the existing single-leg hydraulic power-assisted exoskeleton can be solved.

[0219] (1) The calculation method of the control voltages of PS1, PV1, PV2, PV3, and PV4 corresponding to each joint includes the following steps:

[0220] According to α 2p , Q 1m Distribute pump and valve flow to each joint;

[0221] For the i-th joint, the control voltage u of the variable speed pump PS1 of the i-th joint pi for:

[0222] Step 1: Determine whether the pump provides flow to the rodless chamber of the hydraulic cylinder or to the rod chamber of the hydraulic cylinder.

[0223] If Q 1mi >0,α2pi ≥0, then sw 1i =1, sw 2i =0;

[0224] If Q 1mi >0,α 2pi <0;

[0225] If |Q 1madi |≥|α 2padi |, sw 1i =1, sw 2i =0;

[0226] If |Q 1madi |<|α 2padi |, sw 1i =0, sw 2i =1;

[0227] If Q 1mi ≤0,α 2pi ≥0, then sw 1i =0, sw 2i =0;

[0228] If Q 1mi ≤0,α 2pi <0, then sw 1i =0, sw 2i =1;

[0229] Among them, sw 1i and sw 2i They represent the switch state of the switch valve when the flow of the pump control part in the hydraulic cylinder i enters the rodless chamber of the hydraulic cylinder and the switch state of the switch valve when entering the rod chamber of the hydraulic cylinder, respectively. Q 1madi and α 2padi They respectively represent the expected flow of the low-frequency part of the hydraulic cylinder rodless cavity compensation and the expected flow of the low-frequency part of the hydraulic cylinder rod cavity compensation for the i-th joint using the joint reference trajectory.

[0230] Step 2: Determine the expected output flow rate Q of the pump pdi .

[0231] 1) Calculate Q 1madi and α 2padi .

[0232] Let Q 1mad =[Q 1mad1 Q 1mad2 Q 1mad3 ] T ;

[0233]

[0234]

[0235] If Q 1mi Q 1madi ≤0, then Q 1madi =0;

[0236] If α 2pi α 2padi ≤0, then α 2padi =0;

[0237] Among them, Q 1madi It's Q 1mad The i-th element of Q 1madi and α 2padi They represent the expected flow of the low-frequency part of the hydraulic cylinder rodless cavity compensation and the expected flow of the low-frequency part of the hydraulic cylinder rod cavity compensation using the joint reference trajectory of the i-th joint, respectively. di represents the motion reference trajectory of hydraulic cylinder i, is x di about The first partial derivative of V 1di =V h1i +A 1i x di and V 2di =V h2i -A 2i x di are the compressible volume V at the i-th hydraulic cylinder. 1i and V 2i Using motion reference trajectory x di Replace x Li The expression form, N 1d =diag{A 11 / V 1d1 ,A 12 / V 1d2 ,A 13 / V 1d3},N 2d =diag{A 21 / V 2d1 ,A 22 / V 2d2 ,A 23 / V 2d3}, α 2pad =[α 2pad1 α 2pad2 α 2pad3 ] T ,

[0238] φ 4cd =[0 3×7 0 3×3 0 3×3 N 2d α2pad -q vd I 3×3 ] T , is the estimated value of the exoskeleton system parameters, F Ldad is the expected compensating driving force of the hydraulic cylinder at each joint, and F Ldad about and the partial derivatives of t, is the estimated value of the constant part of the uncertainty of the rod cavity model in hydraulic cylinder i, is the derivative of the desired pressure in the rod chamber of the i-th hydraulic cylinder, Q 1mi is the expected flow rate of the rodless cavity of the ith joint, α 2pi is the expected flow rate of the rod cavity of the ith joint.

[0239] 2) Calculate Q pdi .

[0240] Q pdi =sw 1i Q 1madi -sw 2i α 2padi ;

[0241] If 0≤Q pdi ≤Q pbound , then Q pdi =0;

[0242] Among them, Q pbound Indicates the minimum boundary flow rate of the variable speed pump. In this example, Q pbound =1×10 - 6 m 3 / s,Q pdi Represents the expected output flow of the variable speed pump corresponding to hydraulic cylinder i.

[0243] Step 3: Calculate the control voltage of the pump.

[0244] The control voltage of the variable speed pump corresponding to hydraulic cylinder i is Among them, the flow gain coefficient k p =8.3×10 -5 m 3 / (s·V).

[0245] The control voltage u of the servo valve of the i-th joint pv1i ,u pv2i ,u pv3i ,u pv4i for:

[0246] Q 1pdi =sw1i Q pdi , Q 2pdi =sw 2i Q pdi , Q 1vdi =Q 1mi -Q 1pdi , Q 2vdi =α 2pi +Q 2pdi , where Q 1pdi and Q 2pdi They represent the expected oil flow rate of the rodless chamber and the rod chamber from the pump control part in the i-th joint, respectively, and Q 1vdi and Q 2vdi They represent the expected oil inlet flow rate of the rodless chamber and the expected oil outlet flow rate of the rod chamber from the valve control part in the i-th joint respectively;

[0247] If Q 1vdi >0, then u pv3i =0;

[0248] If Q 1vdi <0, then u pv1i =0,

[0249] If Q 1vdi =0, then u pv1i =0,u pv3i =0;

[0250] If Q 2vdi >0, then u pv2i =0,

[0251] If Q 2vdi <0, then u pv4i =0;

[0252] If Q 2vdi =0, then u pv2i =0,u pv4i =0;

[0253] Among them, the control voltage of PV1 in the i-th joint is u pv1i ; The control voltage of PV2 in the i-th joint is u pv2i ; The control voltage of PV3 in the i-th joint is u pv3i ; The control voltage of PV4 in the i-th joint is u pv4i ;

[0254] Thus, the control voltages of PS1, PV1, PV2, PV3, and PV4 corresponding to each joint are obtained.

[0255] The fourth step is to determine the dynamic model of the hydraulic actuator in the i-th joint according to the control voltages of PS1, PV1, PV2, PV3, and PV4 corresponding to each joint. Thus, the actual pressure P of the rod chamber corresponding to the hydraulic cylinder in the i-th joint is obtained 2i Where Q 2i is the oil flow rate out of the rod chamber of the hydraulic cylinder in the i-th joint; x Li is the displacement of the hydraulic cylinder in the ith joint, is x Li About q i The first partial derivative of V 2i =V h2i -A 2i x Li is the total volume of the rod chamber of the hydraulic cylinder in the ith joint, V h2i Yes i = 0, the volume of the rod chamber of the hydraulic cylinder in the i-th joint, β e represents the bulk elastic modulus; represents the concentrated modeling error and uncertain interference in the dynamic model of the hydraulic actuator in the i-th joint; thereby, the actual pressure P2 of the rod cavity corresponding to the hydraulic cylinder in each joint of the single-leg hydraulic assisted exoskeleton is obtained; according to the actual pressure P2 of the rodless cavity corresponding to the hydraulic cylinder in the i-th joint 1i and the actual pressure P in the rod chamber 2i , get the actual driving force F of the hydraulic cylinder in the i-th joint Li =P 1i A 1i -P 2i A 2i ; Thus, the actual driving force F of the hydraulic cylinder of each joint of the single-leg hydraulic power-assisted exoskeleton is obtained L =[F L1 F L2 F L3 ] T .

[0256] This step can be performed by the hydraulic cylinder actual driving force acquisition module.

[0257] Step 5: According to the actual driving force F of the hydraulic cylinders of each joint of the single-leg hydraulic power-assisted exoskeleton L ; For the i-th joint, the actual joint driving torque τ of the i-th joint is obtained i =F Li h i ; In the formula, h i represents the force arm between the i-th joint rotation point and the hydraulic cylinder; thus, the actual joint driving torque τ of each joint of the single-leg hydraulic power-assisted exoskeleton is obtained act =[τ1 τ2τ3] T .

[0258] This step can be performed by the joint actual driving torque acquisition module.

[0259] Step 6: According to τ act , and based on the motion model of the exoskeleton mechanical body Thus, the actual rotation angle q and the actual rotation angular velocity of each joint are obtained. Among them, τ act =[τ1τ2τ3] T is the actual joint driving torque at the ankle, knee and hip joints, J is the Jacobian matrix of the system at the force sensor, M sp3 (q) is the inertia matrix of the system, is the centrifugal force and Coriolis force matrix of the system, G sp3 (q) is the gravity matrix of the system, B = diag{B1, B2, B3} is the damping matrix of the system, It is a concentrated interference of the system.

[0260] This step can be performed by the rotation angular velocity acquisition module. Among them, the fourth, fifth and sixth steps are the steps after the pump valve flow distribution of each joint.

[0261] The single-leg hydraulic power-assisted exoskeleton control method under heavy load of the present invention is suitable for single-leg use. The power system adopted is a hydraulic system with small size, light weight, flexible layout, compact structure, and can output large force or torque, sensitive action response, easy control and other characteristics. The hydraulic system adopts a parallel pump-valve coordinated electro-hydraulic system solution, allowing the pump control part to provide the main flow and the valve control part to provide a small flow, thereby improving the energy efficiency level of the lower limb power-assisted exoskeleton electro-hydraulic system. The single-leg hydraulic power-assisted exoskeleton control method of the present invention adopts a force control method, and uses the adaptive robust control algorithm (ARC) to design the upper and lower layer controllers, effectively overcoming the influence of high-order nonlinearity and model uncertainty of the single-leg hydraulic power-assisted exoskeleton. The rodless cavity of the hydraulic cylinder in the lower layer controller adopts position tracking control, and the rod cavity of the hydraulic cylinder adopts pressure tracking control, which solves the technical problem of high energy consumption of the existing exoskeleton control method. The flow distribution adopts a solution in which the pump provides low-frequency flow and the valve provides high-frequency flow, which solves the problem of flow distribution caused by the non-negligible compressibility of the oil under heavy load. The invention not only realizes good following and assistance of the hydraulically assisted exoskeleton to human motion under heavy load, but also reduces the energy consumption of the system, realizes longer battery life, and has strong application value. The invention effectively overcomes the influence of the strong coupling of multiple joints, the high-order nonlinearity of the hydraulic drive and the model uncertainty of the single-leg hydraulically assisted exoskeleton, and not only realizes good following and assistance of the hydraulically assisted exoskeleton to human motion under heavy load, but also reduces the energy consumption of the system, and realizes longer battery life.

[0262] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0263] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for controlling a single-leg hydraulically assisted exoskeleton under heavy load, wherein the three hydraulic systems of the exoskeleton's ankle joint, knee joint and hip joint all adopt a parallel pump-valve coordinated electro-hydraulic system; each parallel pump-valve coordinated electro-hydraulic system includes a parallel coordinated pump control part and a valve control part; the pump control part includes a variable speed pump and two switch valves SV1 and SV2 that determine the flow direction of the variable speed pump outlet; the valve control part includes four servo valves PV1, PV2, PV3 and PV4; according to the desired flow rate α of the rod chamber of the hydraulic cylinder in each joint 2p 、Expected flow rate of rodless cavity Q 1m , distribute the pump and valve flow of each joint, and then obtain the control voltage of the variable speed pump and servo valve corresponding to each joint to control the action of the single-leg hydraulic power-assisted exoskeleton; It is characterized in that The method for distributing pump and valve flow includes determining a control voltage u of a variable speed pump corresponding to a hydraulic cylinder i pi and determine the control voltage u of the servo valve corresponding to the hydraulic cylinder i pv1i ,u pv2i ,u pv3i ,u pv4i , the pump control part and the valve control part are controlled according to the control voltage; Among them, determine the control voltage u of the variable speed pump corresponding to the hydraulic cylinder i pi The method comprises the following steps: Determine whether the variable speed pump provides flow to the rodless chamber of hydraulic cylinder i or the rod chamber of hydraulic cylinder i, and control the switch state of the corresponding switch valve accordingly: Calculate Q 1madi and α 2padi :Let Q 1mad =[Q 1mad1 Q 1mad2 Q 1mad3 ] T ; If Q 1mi Q 1madi ≤0, then Q 1madi =0; If α 2pi α 2padi ≤0, then α 2padi =0; In the formula, Q 1madi It's Q 1mad The i-th element of Q 1madi and α 2padi They represent the expected flow of the low-frequency part of the hydraulic cylinder rodless cavity compensation and the expected flow of the low-frequency part of the hydraulic cylinder rod cavity compensation using the joint reference trajectory of the i-th joint, respectively. di represents the motion reference trajectory of hydraulic cylinder i, is x di about The first-order partial derivative of 1i and A 2i V represents the effective area of ​​the rodless cavity and the rod cavity in hydraulic cylinder i, 1di =V h1i +A 1i x di and V 2di =V h2i -A 2i x di are the compressible volume V at the i-th hydraulic cylinder. 1i and V 2i Using motion reference trajectory x di Replace x Li The expression form, is an estimate of the elastic modulus, N 1d =diag{A 11 / V 1d1 ,A 12 / V 1d2 ,A 13 / V 1d3 },N 2d =diag{A 21 / V 2d1 ,A 22 / V 2d2 ,A 23 / V 2d3 }, α 2pad =[α 2pad1 α 2pad2 α 2pad3 ] T , φ 4cd =[0 3×7 0 3×3 0 3×3 N 2d α 2pad -q vd I 3×3 ] T , is the estimated value of the exoskeleton system parameters, F Ldad is the expected compensating driving force of the hydraulic cylinder at each joint, and F Ldad about and the partial derivatives of t, is the estimated value of the constant part of the uncertainty of the rod cavity model in hydraulic cylinder i, is the derivative of the desired pressure in the rod chamber of the i-th hydraulic cylinder, Q 1mi is the expected flow rate of the rodless cavity of the ith joint, α 2pi is the expected flow rate of the rod cavity of the ith joint; Calculate the expected output flow Q of the variable speed pump corresponding to hydraulic cylinder i pdi :Q pdi =sw 1i Q 1madi -sw 2i α 2padi ; If 0≤Q pdi ≤Q pbound , then Q pdi =0; In the formula, Q pbound Indicates the minimum boundary flow rate for using a variable speed pump; Calculate the control voltage of the variable speed pump corresponding to hydraulic cylinder i as follows: In the formula, k p is the flow gain coefficient.

2. The method for controlling a single-leg hydraulically assisted exoskeleton under heavy load according to claim 1, characterized in that: The method for controlling the switching state of the corresponding switching valve comprises the following steps: If Q 1mi >0,α 2pi ≥0, then sw 1i =1, sw 2i =0; If Q 1mi >0,α 2pi <0; If |Q 1madi |≥|α 2padi |, sw 1i =1, sw 2i =0; If |Q 1madi |<|α 2padi |, sw 1i =0, sw 2i =1; If Q 1mi ≤0,α 2pi ≥0, then sw 1i =0, sw 2i =0; If Q 1mi ≤0,α 2pi <0, then sw 1i =0, sw 2i =1; Among them, sw 1i and sw 2i They respectively represent the switching state of the switch valve when the flow of the pump control part in the hydraulic cylinder i enters the rodless chamber of the hydraulic cylinder and the switching state of the switch valve when entering the rod chamber of the hydraulic cylinder.

3. The method for controlling a single-leg hydraulically assisted exoskeleton under heavy load according to claim 1, characterized in that: The joint reference trajectory includes the reference rotation angle of each joint Reference angular velocity and the reference angular acceleration 4. The method for controlling a single-leg hydraulically assisted exoskeleton under heavy load according to claim 1, characterized in that: The expected flow of the low-frequency part is the value calculated by replacing the actual trajectory with the joint reference trajectory for the remaining part after removing the part directly related to the measurement error from the compensation item of the expected flow model of each joint.

5. The method for controlling a single-leg hydraulically assisted exoskeleton under heavy load according to claim 1, characterized in that: Determine the control voltage u of the servo valve corresponding to the hydraulic cylinder i pv1i ,u pv2i ,u pv3i ,u pv4i The method is: Q 1pdi =sw 1i Q pdi ,Q 2pdi =sw 2i Q pdi ,Q 1vdi =Q 1mi -Q 1pdi ,Q 2vdi =α 2pi +Q 2pdi In the formula, Q 1pdi and Q 2pdi They represent the expected oil flow rate of the rodless chamber and the rod chamber from the pump control part in the hydraulic cylinder i, respectively, and Q 1vdi and Q 2vdi They represent the expected oil inlet flow rate of the rodless chamber and the expected oil outlet flow rate of the rod chamber from the valve control part in the hydraulic cylinder i respectively; If Q 1vdi >0, then u pv3i =0; If Q 1vdi <0, then u pv1i =0, If Q 1vdi =0, then u pv1i =0,u pv3i =0; If Q 2vdi >0, then u pv2i =0, If Q 2vdi <0, then u pv4i =0; If Q 2vdi =0, then u pv2i =0,u pv4i =0; In the formula, k qpv1i , k qpv2i , k qpv3i , k qpv4i are the flow gain coefficient of a servo valve corresponding to hydraulic cylinder i, ΔP pv1i and ΔP pv2i They represent the pressure difference between the oil supply pressure of the valve-controlled part of the hydraulic cylinder i and the actual pressure of the rodless chamber and the actual pressure of the rod chamber, ΔP pv3i and ΔP pv4i They respectively represent the pressure difference between the actual pressure of the rodless chamber and the actual pressure of the rod chamber in hydraulic cylinder i and the tank pressure.

6. The method for controlling a single-leg hydraulically assisted exoskeleton under heavy load according to claim 1, characterized in that: The control voltage u of the servo valve is increased by the amplifier board pv1i ,u pv2i ,u pv3i ,u pv4i Converted into the control current of the corresponding servo valve, the valve core opening displacement of the corresponding servo valve is controlled by the control current; the control voltage u of the variable speed pump is pi Controls the speed of the servo motor of the variable speed pump.

7. The method for controlling a single-leg hydraulically assisted exoskeleton under heavy load according to claim 1, characterized in that: Expected flow rate Q of the rodless chamber in each joint hydraulic cylinder 1m The calculation method includes the following steps: According to the reference rotation angle of each joint Reference angular velocity Reference angular acceleration Actual driving force F of hydraulic cylinder L 、Expected flow rate of the rod chamber of the hydraulic cylinder α 2p , actual rotation angle q, actual rotation angular velocity Design a rodless cavity position tracking controller; the rodless cavity position tracking controller is Q 1m =Q 1ma +Q 1ms +Q 1msn , thus the expected flow rate Q of the rodless cavity of each joint of the single-leg hydraulic power-assisted exoskeleton is obtained 1m , where Q 1ma Q 1m The adaptive model compensation term, Q 1ms Q 1m The linear robust feedback term, Q 1msn Q 1m The nonlinear robust feedback term.

8. The method for controlling a single-leg hydraulically assisted exoskeleton under heavy load according to claim 1, characterized in that: The expected flow rate α in the rod chamber of each joint hydraulic cylinder 2p The calculation method includes the following steps: According to the reference rotation angle of each joint Reference angular velocity Reference angular acceleration Actual driving force F of hydraulic cylinder L 、Expected flow rate of the rod chamber of the hydraulic cylinder α 2p , actual rotation angle q, actual rotation angular velocity Design a rodless cavity position tracking controller, the rodless cavity position tracking controller is F Ld =F Lda +F Lds +F Ldsn , thus obtaining the expected driving force F of the hydraulic cylinder of each joint of the single-leg hydraulic power-assisted exoskeleton Ld Where, F Lda F Ld The adaptive model compensation term, F Lds F Ld The linear robust feedback term, F Ldsn F Ld The nonlinear robust feedback term of ; According to F Ld =[F Ld1 F Ld2 F Ld3 ] T Design the rod cavity pressure planner for each joint. Considering that a good control design can ensure that the system error is within a small range, the adaptive model compensation term F Lda Can basically characterize the expected driving force F of the hydraulic cylinder Ld In addition, in order to obtain a more continuous and smooth desired pressure in the rod chamber and avoid the negative impact of noise, the joint reference trajectory is used instead of the measurement signal of the state quantity, that is, the desired compensation driving force F of the hydraulic cylinder Ldad =[F Ldad1 F Ldad2 F Ldad3 ] T , the expected compensation driving force of the hydraulic cylinder of the i-th joint is F Ldadi ; For the F at the i-th joint Ldadi , the rod cavity pressure planner of the i-th joint is The expected pressure P of the rod cavity of the i-th joint is obtained 2di Where, P c is the set minimum working pressure, A 1i and A 2i They represent the effective areas of the rodless cavity and the rod-containing cavity in the i-th joint respectively; According to P 2di and the actual pressure P of the rod cavity of the i-th joint 2i , design the rod cavity pressure tracking controller of the i-th joint, the rod cavity pressure tracking controller of the i-th joint is α 2pi =α 2pai +α 2ps1i +α 2ps2i , thus we get the expected flow rate α of the rod cavity of the i-th joint 2pi ; In the formula, α 2pai is α 2pi The adaptive model compensation term, α 2ps1i is α 2pi The linear robust feedback term, α 2ps2i is α 2pi The nonlinear robust feedback term of ; Thus, the expected flow rate α of the rod cavity of each joint of the single-leg hydraulic power-assisted exoskeleton is obtained 2p =[α 2p1 α 2p2 α 2p3 ] T .

9. A heavy-load single-leg hydraulically assisted exoskeleton control device, characterized in that: It adopts the heavy-load single-leg hydraulic-assisted exoskeleton control method according to any one of claims 1 to 8, and the control device includes: A plurality of parallel pump-valve coordinated electro-hydraulic systems; each parallel pump-valve coordinated electro-hydraulic system comprises a parallel coordinated pump control part and a valve control part; the pump control part comprises a variable speed pump PS1 and two two-way switch valves SV1 and SV2 that determine the outlet flow direction of the variable speed pump PS1; the valve control part comprises four two-way electro-hydraulic servo valves PV1, PV2, PV3 and PV4 and a hydraulic oil source PS2, the electro-hydraulic servo valves PV1 and PV2 control the flow of the hydraulic oil source PS2 to the two chambers of the corresponding hydraulic cylinder, and the electro-hydraulic servo valves PV3 and PV4 control the flow of the two chambers of the corresponding hydraulic cylinder to the oil tank; The flow acquisition module is used to coordinate the electro-hydraulic system of the parallel pump valves of each joint of the single-leg hydraulic assisted exoskeleton according to the reference rotation angle of each joint. Reference angular velocity Reference angular acceleration Actual driving force F of hydraulic cylinder L , actual rotation angle q, actual rotation angular velocity Get the expected flow rate α of the rod cavity of each joint 2p =[α 2p1 α 2p2 α 2p3 ] T and the rodless chamber expected flow rate Q 1m =[Q 1m1 Q 1m2 Q 1m3 ] T ; where i represents the serial number of the three joints, the expected flow rate of the rod cavity of the i-th joint is α 2pi , the expected flow rate of the rodless cavity of the i-th joint is Q 1mi ; The control voltage acquisition module is used to obtain the voltage according to α 2p , Q 1m Calculate the control voltages of PS1, PV1, PV2, PV3, and PV4 corresponding to each joint to distribute the pump and valve flow of each joint.

10. A heavy-load single-leg hydraulically assisted exoskeleton, characterized in that: It adopts the single-leg hydraulic-assisted exoskeleton control method under heavy load as described in any one of claims 1 to 8.

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