Control method and system based on air pressure dynamic compensation and adaptive rotary joint

Abstract

The application discloses a control method and system based on air pressure dynamic compensation and adaptive rotary joints, relates to the technical field of automatic control, and comprises the following steps: modeling the pneumatic subsystem and the mechanical subsystem of an air-driven valve-controlled rotary cylinder system; constructing an MPC controller according to the pneumatic subsystem and the mechanical subsystem; inputting a reference trajectory into an upper-layer global MPC of the MPC controller to obtain a first control quantity; inputting the first control quantity into a lower-layer pressure compensator of the MPC controller to obtain a second control quantity; controlling the movement of the air-driven valve-controlled rotary cylinder in the air-driven valve-controlled rotary cylinder system according to the second control quantity, and then driving the joint actuator to move by using the air-driven valve-controlled rotary cylinder. The application solves the problems of poor real-time performance, significant pressure lag and incapability of coping with load mutation of a single MPC controller by using a hierarchical adaptive MPC controller, and improves the robustness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of automatic control, and in particular to a control method and system based on air pressure dynamic compensation and adaptive rotary joint. BACKGROUND

[0002] In the field of robot control applications, air-driven valve-controlled rotary cylinder systems are widely used to drive the terminal motion of actuators, such as air-driven motion joint control systems. However, the existing control technology has the following defects:

[0003] (1) The existing control method has poor nonlinearity adaptability, and the PID parameters need to be manually tuned for specific working conditions, which cannot effectively deal with the problems of gas compressibility, friction nonlinearity, and insufficient precision caused by model oversimplification.(2) Single MPC (Model Predictive Control) has poor real-time performance, significant pressure lag, and cannot deal with load mutations. SUMMARY

[0004] The main purpose of the embodiments of the present application is to propose a control method and system based on air pressure dynamic compensation and adaptive rotary joint to improve the robustness of air-driven valve-controlled rotary cylinder systems.

[0005] To achieve the above-mentioned purpose, one aspect of the embodiments of the present application proposes a control method based on air pressure dynamic compensation and adaptive rotary joint, which comprises the following steps:

[0006] Modeling the pneumatic subsystem and mechanical subsystem of the air-driven valve-controlled rotary cylinder system;

[0007] Building an MPC controller according to the pneumatic subsystem and the mechanical subsystem;

[0008] Inputting a reference trajectory into the upper-layer global MPC of the MPC controller to obtain a first control quantity;

[0009] Inputting the first control quantity into the lower-layer pressure compensator of the MPC controller to obtain a second control quantity;

[0010] Controlling the air-driven valve-controlled rotary cylinder motion in the air-driven valve-controlled rotary cylinder system according to the second control quantity, and then driving the joint actuator motion by using the air-driven valve-controlled rotary cylinder.

[0011] In some embodiments, the modeling of the pneumatic subsystem and the mechanical subsystem of the air-driven valve-controlled rotary cylinder system comprises the following steps:

[0012] The gas pressure dynamic equation of the pneumatic subsystem is established as follows:

[0013]

[0014] wherein T s is the sampling time; T is the temperature; P k , P k+1 are the pressures at the k, k+1 time step; V k , V k+1 are the chamber gas volumes at the k, k+1 time step; k is the gas specific heat ratio; R is the gas constant P s is the gas source pressure; C v is the valve flow coefficient; u k is the valve opening at the k time step; V(θ) is a function of the chamber gas volume as a function of the angle;

[0015] A relationship model of the chamber volume and the rotation angle is established for the pneumatic subsystem as follows:

[0016]

[0017] wherein A is the piston effective area, r is the rotation radius, and θ is the joint angle;

[0018] A joint dynamics equation of the nonlinear friction and a joint dynamics equation of the linear viscous friction are established for the mechanical subsystem;

[0019] The joint dynamics equation of the nonlinear friction is as follows:

[0020]

[0021] τ gas = (P1-P2)Ar;

[0022] wherein J is the rotation inertia, b is the damping coefficient, are the joint angular velocity and angular acceleration, respectively, τ gas is the pneumatic torque, τ load is the external load, and P1, P2 are the pressures of the two chambers;

[0023] The joint dynamics equation of the linear viscous friction is as follows:

[0024]

[0025] wherein f c is the Coulomb friction, f s is the static friction, ω s is the stribeck velocity, and σ is the viscous friction coefficient;

[0026] State variables and system inputs of the gas-driven valve-controlled rotary cylinder system are defined to obtain a state space equation of the gas-driven valve-controlled rotary cylinder system;

[0027] The state variables and the system inputs are respectively:

[0028]

[0029] where x is the state variable, and u is the system input;

[0030] The state space equation of the gas-driven valve-controlled rotary cylinder system is:

[0031]

[0032] In some embodiments, the MPC controller is constructed according to the pneumatic subsystem and the mechanical subsystem, comprising the following steps:

[0033] The upper-layer global MPC and the lower-layer pressure compensator are constructed as the MPC controller according to the pneumatic subsystem and the mechanical subsystem;

[0034] The upper-layer global MPC is used to solve the end angle tracking and energy optimization problem of the gas-driven valve-controlled rotary cylinder system, and the lower-layer pressure compensator is used to adjust the valve opening to compensate for the nonlinear characteristics of the dynamic hysteresis of the gas-driven valve-controlled rotary cylinder system.

[0035] The first time period and the prediction period are selected when constructing the upper-layer global MPC.

[0036] The second time period is included when constructing the lower-layer pressure compensator; the second time period is one order of magnitude smaller than the prediction period.

[0037] In some embodiments, the method further comprises the following steps:

[0038] The objective function and the constraint condition of the MPC controller are constructed;

[0039] The objective function is:

[0040]

[0041] where Q, R, and P are dynamically adjusted weight matrices;

[0042] The constraint conditions include pressure range, valve opening and closing speed, and safe motion angle, respectively:

[0043] P min ≤P 1,k ,P 2,k ≤P max

[0044] |u k+1 -u k |≤Δu max

[0045] θmin ≤ θ k ≤ θ max .

[0046] In some embodiments, the method further comprises the steps of:

[0047] adopting an RLS adaptive filtering algorithm to identify parameters of the gas-driven valve-controlled cylinder system online, so as to update the parameters of the current time step according to the optimization results of the previous time step;

[0048] The RLS adaptive filtering algorithm is:

[0049]

[0050] wherein, is the parameter to be identified, φ k is a regression matrix composed of states and inputs.

[0051] In some embodiments, the inputting of the first control quantity into the lower-layer pressure compensator of the MPC controller to obtain a second control quantity comprises the steps of:

[0052] inputting the first control quantity into the lower-layer pressure compensator for feedforward compensation to obtain the second control quantity;

[0053] The expression of the lower-layer pressure compensator is:

[0054] u comp,k = u MPC,k + K p (P pred,k -P meas,k );

[0055] wherein, u comp,k is the second control quantity at the kth time step, u MPC,k is the first control quantity at the kth time step, P pred,k is a compensation periodic pressure prediction value at the kth time step based on valve opening and volume change, K p is a dynamic gain.

[0056] In some embodiments, the method further comprises the steps of:

[0057] obtaining joint angles and joint speeds of the joint actuators through an encoder, and inputting the joint angles, the joint speeds and the reference trajectory into the upper-layer global MPC to obtain the first control quantity with negative feedback;

[0058] The chamber pressure of the gas-driven valve-controlled rotary cylinder is acquired by a pressure sensor, and the chamber pressure and the first control quantity with negative feedback are input to the lower pressure compensator to obtain the second control quantity with negative feedback.

[0059] To achieve the above object, another aspect of the embodiment of the present application proposes a control system based on gas pressure dynamic compensation and adaptive rotary joint, which comprises:

[0060] a system modeling module for modeling a pneumatic subsystem and a mechanical subsystem of a gas-driven valve-controlled rotary cylinder system;

[0061] a controller construction module for constructing an MPC controller according to the pneumatic subsystem and the mechanical subsystem;

[0062] a first control quantity determination module for inputting a reference trajectory to an upper global MPC of the MPC controller to obtain a first control quantity;

[0063] a second control quantity determination module for inputting the first control quantity to a lower pressure compensator of the MPC controller to obtain a second control quantity;

[0064] a driving execution module for controlling a gas-driven valve-controlled rotary cylinder in the gas-driven valve-controlled rotary cylinder system to move according to the second control quantity, and then driving a joint actuator to move by using the gas-driven valve-controlled rotary cylinder.

[0065] To achieve the above object, another aspect of the embodiment of the present application proposes an electronic device, which comprises a memory and a processor, the memory stores a computer program, and the processor implements the above method when executing the computer program.

[0066] To achieve the above object, another aspect of the embodiment of the present application proposes a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the above method.

[0067] The embodiment of the present application at least has the following beneficial effects:

[0068] The present application can model a pneumatic subsystem and a mechanical subsystem of a gas-driven valve-controlled rotary cylinder system, construct an MPC controller according to the pneumatic subsystem and the mechanical subsystem, input a reference trajectory to an upper global MPC of the MPC controller to obtain a first control quantity, input the first control quantity to a lower pressure compensator of the MPC controller to obtain a second control quantity, control a gas-driven valve-controlled rotary cylinder in the gas-driven valve-controlled rotary cylinder system to move according to the second control quantity, and then drive a joint actuator to move by using the gas-driven valve-controlled rotary cylinder. The present application solves the problems of poor real-time performance, significant pressure lag and inability to cope with load mutation of a single MPC controller by using a hierarchical adaptive MPC controller, and improves robustness. Attached Figure Description

[0069] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0070] Figure 1 A flowchart illustrating the control method based on dynamic air pressure compensation and adaptive rotary joint provided in the embodiments of this application;

[0071] Figure 2 A simplified diagram showing the overall structural relationship of the rotary joint of the pneumatic valve-controlled rotary cylinder system provided in the embodiments of this application;

[0072] Figure 3 This is a diagram showing the components of the pneumatic valve control system for the pneumatic valve-controlled rotary cylinder system provided in the embodiments of this application.

[0073] Figure 4 Example flowchart of the control method based on dynamic air pressure compensation and adaptive rotary joint provided in the embodiments of this application;

[0074] Figure 5 This is an example diagram of the architecture of the MPC controller provided in the embodiments of this application;

[0075] Figure 6 Block diagram of a high-precision control system for rotary joints with dynamic gas pressure compensation and adaptive MPC provided in an embodiment of this application;

[0076] Figure 7 A schematic diagram of the control system based on dynamic air pressure compensation and adaptive rotary joint provided in the embodiments of this application;

[0077] Figure 8 This is a schematic diagram of the hardware structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0078] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit it. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application; they are merely examples of apparatuses and methods consistent with some aspects of the embodiments of this application as detailed in the appended claims.

[0079] It can be understood that the terms "first", "second", etc. used in the present application can be used herein to describe various concepts, but unless specifically stated, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of the present application, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information. Depending on the context, the word "if" as used herein can be interpreted as "when" or "upon determining" or "in response to determining".

[0080] The terms "at least one", "multiple", "each", "any" and the like used in the present application include one, two or more than two, multiple includes two or more than two, each refers to each of the corresponding multiple, and any refers to any one of the multiple.

[0081] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which the present application belongs. The terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0082] Before the embodiments of the present application are described in detail, first, some related technologies involved in the embodiments of the present application are described as follows:

[0083] At present, there are still great challenges in the high-precision tracking control method of the end position and trajectory of a multi-degree-of-freedom gas-driven rotary joint. Most pneumatic systems use the method of PID control combined with pneumatic auxiliary limiting to achieve position or torque control by adjusting the opening degree of a proportional valve, which can achieve high control precision. However, this method has poor nonlinear adaptability, and the PID parameters need to be manually set for specific working conditions, which cannot effectively cope with the compressibility of gas, nonlinear friction and load mutation. Some researchers apply MPC to pneumatic systems, for example, by simplifying the pneumatic model to predict the valve action to control the pneumatic manipulator, to meet the real-time performance of control effect. However, the model parameters (such as moment of inertia and friction coefficient) of this method cannot be updated online, and the control performance will decrease sharply when the load changes, and the robustness is poor. Some researchers also use a hierarchical architecture of upper computer planning + lower computer PID execution, which can ensure a certain control real-time performance, but the upper and lower models are not coupled, and the global optimization algorithm does not consider the pressure dynamics, which will cause torque fluctuations, and the corresponding speed is limited, and the overshoot is significant. A few methods also propose a pressure control strategy based on a lookup table method, which directly maps the valve opening degree according to the target torque, but this method cannot adapt to the nonlinear characteristics of gas flow, and also does not integrate a feedback correction link, which is easily affected by sensor noise such as temperature drift.

[0084] In the field of robot control application after coupling, the gas drive valve control rotary cylinder system is widely used to drive the terminal motion of the actuator, such as the gas drive motion joint control system. The technical problems to be solved by the present application in view of the following defects of the existing control technology are as follows:

[0085] In view of the poor nonlinear adaptability of the existing control method, the PID parameters need to be manually adjusted for specific working conditions, which cannot effectively cope with the problems of gas compressibility, friction nonlinearity and the like, and the precision problem caused by the over-simplified model, the application fuses the gas compressibility, the volume-angle geometric relationship of the chamber and the Stribeck friction model, which can well reduce the model prediction error range.

[0086] In view of the poor real-time performance of single MPC (Model Predictive Control), the significant pressure lag and the inability to cope with load mutation, the application proposes a hierarchical adaptive MPC architecture, which uses the upper MPC to globally optimize angle tracking and energy efficiency, and integrates online parameter identification; the lower layer designs a pressure compensator, which modifies the valve command in real time based on the predicted dynamics to offset the gas lag nonlinearity and cope with sudden disturbances.

[0087] In view of the poor robustness of the fixed parameter model system, the application designs an adaptive parameter online identification module, which updates the key parameters such as moment of inertia and friction coefficient online through recursive least squares method, so as to reduce the tracking error by using computing resources when the load changes.

[0088] Reference Figure 1 The embodiments of the application provide a control method based on gas pressure dynamic compensation and adaptive rotary joint, which can include but is not limited to S100 to S140, and the details are as follows:

[0089] S100: modeling the pneumatic subsystem and mechanical subsystem of the gas drive valve control rotary cylinder system;

[0090] S110: constructing an MPC controller according to the pneumatic subsystem and the mechanical subsystem;

[0091] S120: inputting a reference trajectory into the upper global MPC of the MPC controller to obtain a first control quantity;

[0092] S130: inputting the first control quantity into the lower pressure compensator of the MPC controller to obtain a second control quantity;

[0093] S140: controlling the gas drive valve control rotary cylinder motion in the gas drive valve control rotary cylinder system according to the second control quantity, and then driving the joint actuator motion by using the gas drive valve control rotary cylinder.

[0094] Optionally, the modeling the pneumatic subsystem and the mechanical subsystem of the gas-driven valve-controlled rotary cylinder system comprises the following steps:

[0095] The gas pressure dynamic equation of the pneumatic subsystem is established as follows:

[0096]

[0097] Where, T s is the sampling time; T is the temperature; P k , P k+1 are the pressures at the kth and (k+1)th time steps; V k , V k+1 are the chamber gas volumes at the kth and (k+1)th time steps; k is the gas specific heat ratio; R is the gas constant P s is the gas source pressure; C v is the valve flow coefficient; u k is the valve opening at the kth time step; V(θ) is a function of the chamber gas volume with respect to the angle;

[0098] The relationship model of the chamber volume and the rotation angle of the pneumatic subsystem is established as follows:

[0099]

[0100] Where, A is the effective area of the piston, r is the rotation radius, and θ is the joint angle;

[0101] The joint dynamics equation of the nonlinear friction of the mechanical subsystem and the joint dynamics equation of the linear viscous friction of the mechanical subsystem are established;

[0102] The joint dynamics equation of the nonlinear friction is as follows:

[0103]

[0104] τ gas =(P1-P2)Ar;

[0105] Where, J is the moment of inertia, b is the damping coefficient, are the joint angular velocity and angular acceleration, respectively, τ gas is the pneumatic torque, τ load is the external load, and P1 and P2 are the pressures of the two chambers;

[0106] The joint dynamics equation of the linear viscous friction is as follows:

[0107]

[0108] Where, f c is the Coulomb friction, f s is the static friction, and ωs is the stribeck velocity, and σ is the viscous friction coefficient;

[0109] defining state variables and system inputs of the gas-driven valve-controlled rotary cylinder system to obtain a state space equation of the gas-driven valve-controlled rotary cylinder system;

[0110] The state variables and the system inputs are respectively:

[0111]

[0112] wherein x is the state variable, and u is the system input;

[0113] The state space equation of the gas-driven valve-controlled rotary cylinder system is:

[0114]

[0115] Optionally, the constructing the MPC controller according to the pneumatic subsystem and the mechanical subsystem comprises the following steps:

[0116] The upper-layer global MPC and the lower-layer pressure compensator are constructed as the MPC controller according to the pneumatic subsystem and the mechanical subsystem;

[0117] The upper-layer global MPC is used to solve the end angle tracking and energy optimization problems of the gas-driven valve-controlled rotary cylinder system, and the lower-layer pressure compensator is used to adjust the valve opening to compensate for the nonlinear characteristics of the dynamic hysteresis of the gas-driven valve-controlled rotary cylinder system.

[0118] The first time period and the prediction period are selected when the upper-layer global MPC is constructed.

[0119] The second time period is included when the lower-layer pressure compensator is constructed; the second time period is one order of magnitude smaller than the prediction period.

[0120] Optionally, the method further comprises the following steps:

[0121] The objective function and the constraint condition of the MPC controller are constructed.

[0122] The objective function is:

[0123]

[0124] wherein Q, R, and P are dynamically adjusted weight matrices;

[0125] The constraint condition includes the pressure range, the valve opening and closing speed, and the safe motion angle, and is respectively:

[0126] P min ≤P1,k P 2,k ≤P max

[0127] |u k+1 -u k |≤Δu max

[0128] θ min ≤θ k ≤θ max .

[0129] Optionally, the method further comprises the following steps:

[0130] adopting an RLS adaptive filtering algorithm to identify parameters of the gas-driven valve-controlled cylinder system online, so as to update the parameters of the current time step according to the optimization results of the previous time step;

[0131] the RLS adaptive filtering algorithm is:

[0132]

[0133] wherein, is the parameter to be identified, φ k is a regression matrix composed of states and inputs.

[0134] Optionally, the method further comprises the following steps:

[0135] adopting an RLS adaptive filtering algorithm to identify parameters of the gas-driven valve-controlled cylinder system online, so as to update the parameters of the current time step according to the optimization results of the previous time step;

[0136] the expression of the lower-layer pressure compensator is:

[0137] u comp,k =u MPC,k +K p (P pred,k -P meas,k );

[0138] wherein, u comp,k is the second control quantity of the kth time step, u MPC,k is the first control quantity of the kth time step, P pred,k is a compensation periodic pressure prediction value of the kth time step based on valve opening and volume change, K p is a dynamic gain.

[0139] Optionally, the method further comprises the following steps:

[0140] The joint angle and joint speed of the joint actuator are obtained by an encoder, the joint angle, the joint speed and the reference trajectory are input to the upper layer global MPC to obtain the first control quantity with negative feedback;

[0141] The chamber pressure of the gas-driven valve-controlled rotary cylinder is obtained by a pressure sensor, and the chamber pressure and the first control quantity with negative feedback are input to the lower layer pressure compensator to obtain the second control quantity with negative feedback.

[0142] Next, the scheme of the embodiment of the present application will be described in detail with reference to specific application examples.

[0143] The existing pneumatic joint control technology has significant defects in model precision, real-time performance, self-adaptability and lag compensation. The embodiment considers control precision, response speed and robustness, and to some extent, systematically solves the above problems by gas-machine coupling modeling, hierarchical adaptive MPC architecture and embedded pressure dynamic compensator, which has innovation and industrial application value.

[0144] ①During the completion of the embodiment, the necessary parts of the gas-driven valve-controlled rotary cylinder system are: rotary encoder, pressure sensor, torque sensor, rotary cylinder, proportional valve, industrial computer, data acquisition card, etc.

[0145] ②Configuration relationship: the rotary encoder is arranged on the joint output rotary shaft, the pressure sensor is arranged near the inlet and outlet of the pneumatic chamber, and an additional torque sensor can be selected to be arranged at the end of the rotary actuator for torque experiment verification.

[0146] ③The connection circuit of the parts is completed by the air pipe; the air source passage can include some auxiliary elements for filtering, purifying and lubricating, etc.

[0147] The overall configuration relationship of the rotary joint of the gas-driven valve-controlled rotary cylinder system and the component diagram of the pneumatic valve-controlled cylinder control system are shown in Figure 2 、 Figure 3 as shown in

[0148] Referring to Figure 4 , the following specific technical implementation details cover system modeling, control design and real-time optimization methods:

[0149] 1、Firstly, the embodiment can perform dynamic modeling on the pneumatic subsystem of the single-rotary-degree-of-freedom gas-driven joint. The pneumatic subsystem is the core power source of the gas-driven rotary joint, and its dynamic characteristics directly affect the torque output and control performance of the joint. In order to obtain the mathematical relationship between the gas volume in the rotary cylinder chamber and the output rotation angle, the compressibility of the gas and the valve dynamics are first considered, and the gas pressure dynamic equation is established:

[0150]

[0151] Among them, T s Sampling time; T is temperature; P k ,P k+1 For the pressure at time steps k and k+1; V k V k+1 R represents the chamber gas volume at time steps k and k+1; k is the specific heat ratio of the gas; and R is the gas constant P. s C is the gas source pressure. v The valve flow coefficient; u k Let V(θ) be the valve opening at the k-th time step; V(θ) is the function of the gas volume in the chamber as a function of the angle.

[0152] 2. For rotary cylinders, volume changes directly affect pressure dynamics, and the rate of change reflects the coupling effect of mechanical motion and gas compression. The relationship model between chamber volume and rotation angle is established as follows:

[0153]

[0154] In the formula, A is the effective area of ​​the piston, r is the radius of rotation, and θ is the joint angle.

[0155] 3. For the single-degree-of-freedom pneumatic joint system in this design, its mechanical subsystem mainly includes the joint dynamics equations involving nonlinear friction:

[0156]

[0157] τ gas =(P1-P2)Ar (4)

[0158] In the formula, J is the moment of inertia, and b is the damping coefficient. These are the joint angular velocity and angular acceleration, respectively, τ gas For aerodynamic torque, τ load P1 and P2 are the pressures of the two chambers, which are external loads.

[0159] 4. The aforementioned nonlinear friction characteristics are mainly reflected in the following: when the joint moves at low speed, the joint friction decreases nonlinearly; at high speed, it can be approximated as linear viscous friction, as shown in the following expression:

[0160]

[0161] In the formula, f c For Coulomb friction, f s For static friction, ω s σ is the Stribeck velocity, and σ is the coefficient of viscous friction.

[0162] 5、Secondly, in order to facilitate the design of model predictive controller (MPC) in the future, the state space equation of the system needs to be obtained, so the state variable of the system, the system input (double valve opening) is defined:

[0163]

[0164] The following nonlinear continuous system model is obtained:

[0165]

[0166] 6、Finally, based on the above system model, a kind of MPC controller is constructed, which can effectively suppress the chattering problem of traditional sliding mode control, and does not need to measure the acceleration pressure signal. The specific steps are as follows:

[0167] ST1: Build a hierarchical MPC structure of MPC controller, as shown in Figure 5

[0168] The purpose of designing the upper layer (upper layer global MPC) is to solve the end angle tracking and energy optimization problems of the system, and the time period and prediction period are selected as follows:

[0169] T MPC = 10ms (8)

[0170] N = 20 steps (9)

[0171] The purpose of designing the lower layer (pressure compensator structure) is to quickly adjust the valve opening based on the simplified pressure model, compensate for the nonlinear characteristics of the dynamic lag of the system, and the time period value is generally selected to be less than or equal to the prediction period one order of magnitude, such as:

[0172] T Comp = 1ms (10)

[0173] ST2: Design the objective function and constraints.

[0174] The essence of MPC is an optimization-based real-time control method, which also needs to consider the actual constraints of the system. The objective function of the upper layer MPC is designed as follows:

[0175]

[0176] In the formula, Q, R, P are weight matrices, which are adjusted according to the system dynamics.

[0177] The single degree of freedom air drive system is also subject to the constraints of the actual physical system, such as pressure range, valve opening and closing speed, and safe motion angle, which are defined as follows:

[0178] P min ≤ P 1,k ​,P 2,k ≤P max

[0179] |u k+1 -u k |≤Δu max

[0180] θ min ≤θ k ≤θ max (12)

[0181] ST3: Adaptive parameter update.

[0182] Each step of the MPC controller requires updating the current parameters based on the optimization results of the previous step. Therefore, it is necessary to identify system parameters online. The RLS adaptive filtering algorithm is used as follows:

[0183]

[0184] In the formula Let φ be the parameter vector to be identified. k The update cycle for the regression matrix (composed of state and input) is set to 10ms, synchronized with the upper layer of MPC.

[0185] ST4: Pressure dynamic compensator.

[0186] The lower-level pressure compensator of the controller mainly utilizes feedforward compensation, with the following logic:

[0187] u comp,k =u MPC,k +K p (P pred,k -P meas,k (14)

[0188] In the formula, P pred,k Based on the compensated cyclic pressure prediction value of valve opening and volume changes, K p This is the dynamic gain.

[0189] 7. In summary, the block diagram of the high-precision control system for rotary joints with dynamic gas pressure compensation and adaptive MPC is as follows: Figure 6 As shown.

[0190] 8. To ensure signal integrity, pressure sensor and encoder signals must be transmitted through shielded cables to reduce electromagnetic interference; an RC low-pass filter can be added to the output of the DA data acquisition card to eliminate the influence of high-frequency noise on the proportional valve.

[0191] The technical solutions of the embodiment provide a feasible solution for the core problems of insufficient precision, response lag and poor robustness in the control of a pneumatic joint by means of pneumatic-mechanical coupling modeling, a hierarchical adaptive MPC architecture and a pressure dynamic compensation mechanism, and can directly bring the following technical effects:

[0192] I. Real-time performance and response speed improvement: The global optimization is processed by the upper-layer global MPC (10 ms cycle), and the high-speed compensation is performed by the lower-layer pressure compensator (1 ms cycle), so that the overall response frequency of the system is greatly improved, and the real-time demand of a high-speed proportional valve can be met.

[0193] II. Robustness and energy efficiency enhancement: The parameters such as moment of inertia and friction coefficient are updated in real time by the recursive least square method (RLS), so that the recovery time is significantly reduced when the load suddenly changes (such as 50% of the rated load), and the dynamic working condition changes are adapted. Meanwhile, a valve opening weighting term is introduced into the MPC objective function, so that the consumption of invalid gas is reduced, and the energy consumption is reduced.

[0194] Reference Figure 7 The embodiment of the application further provides a control system based on pressure dynamic compensation and adaptive rotary joint, which can implement the control method based on pressure dynamic compensation and adaptive rotary joint.

[0195] A system modeling module is configured to model a pneumatic subsystem and a mechanical subsystem of a gas-driven valve-controlled rotary cylinder system.

[0196] A controller construction module is configured to construct an MPC controller according to the pneumatic subsystem and the mechanical subsystem.

[0197] A first control quantity determination module is configured to input a reference trajectory into an upper-layer global MPC of the MPC controller to obtain a first control quantity.

[0198] A second control quantity determination module is configured to input the first control quantity into a lower-layer pressure compensator of the MPC controller to obtain a second control quantity.

[0199] A driving execution module is configured to control the movement of a gas-driven valve-controlled rotary cylinder in the gas-driven valve-controlled rotary cylinder system according to the second control quantity, and then drive the movement of a joint actuator by the gas-driven valve-controlled rotary cylinder.

[0200] It can be understood that the contents in the above method embodiments are applicable to the system embodiment, the system embodiment specifically implements the same functions as the above method embodiments, and achieves the same beneficial effects as the above method embodiments.

[0201] The embodiment of the present application further provides an electronic device, which comprises a memory and a processor. The memory stores a computer program, and the processor implements the method of the embodiment of the present application when executing the computer program. The electronic device can be any intelligent terminal, such as a tablet computer or a vehicle-mounted computer.

[0202] It can be understood that the contents in the method embodiments are applicable to the device embodiments, the device embodiments specifically implement the functions of the method of the present application, and achieve the same beneficial effects as the method of the present application.

[0203] Please refer to Figure 8 , Figure 8 The hardware structure of the electronic device of another embodiment is illustrated, and the electronic device comprises:

[0204] The processor 801 can be implemented in a general-purpose CPU (Central Processing Unit), a microprocessor, an ASIC (Application Specific Integrated Circuit), or one or more integrated circuits, and is used to execute related programs to implement the technical solutions provided by the embodiments of the present application.

[0205] The memory 802 can be implemented in the form of a ROM (Read Only Memory), a static storage device, a dynamic storage device, or a RAM (Random Access Memory). The memory 802 can store an operating system and other application programs. When the technical solutions provided by the embodiments of the present application are implemented by software or firmware, the related program codes are stored in the memory 802 and are called and executed by the processor 801 to implement the method of the present application.

[0206] The input / output interface 803 is used to realize information input and output.

[0207] The communication interface 804 is used to realize the communication interaction between the device and other devices. The communication can be realized by a wired manner (for example, a USB, a network cable, etc.) or a wireless manner (for example, a mobile network, WIFI, Bluetooth, etc.).

[0208] The bus 805 is used to transmit information between various components (for example, the processor 801, the memory 802, the input / output interface 803, and the communication interface 804) of the device.

[0209] The processor 801, the memory 802, the input / output interface 803, and the communication interface 804 are connected to each other through the bus 805 to realize the communication connection between them in the device.

[0210] The embodiment of the present application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to realize the method of the present application.

[0211] It can be understood that the contents in the above method embodiments are all applicable to the present storage medium embodiment, the present storage medium embodiment specifically realizes the functions of the above method embodiments, and achieves the same beneficial effects as the above method embodiments.

[0212] The memory is a non-transitory computer readable storage medium, and can be used to store a non-transitory software program and a non-transitory computer executable program. In addition, the memory can include a high-speed random access memory, and can also include a non-transitory memory, for example, at least one magnetic disk storage device, a flash memory device, or other non-transitory solid-state memory device. In some embodiments, the memory can optionally include a memory remotely arranged relative to the processor, and the remote memory can be connected to the processor through a network. Examples of the network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and a combination thereof.

[0213] The embodiments described in the embodiments of the present application are used to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. Those skilled in the art can know that, with the evolution of technology and the appearance of new application scenarios, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0214] Those skilled in the art can understand that the technical solutions shown in the figures do not constitute a limitation on the embodiments of the present application, and can include more or fewer steps than those shown in the figures, or combine certain steps, or different steps.

[0215] The system embodiments described above are only schematic, and the modules described as separate components can or can not be physically separate, that is, can be located in one place, or can be distributed to multiple network modules. According to actual needs, part or all of the modules can be selected to achieve the purpose of the present embodiment.

[0216] Those skilled in the art can understand that all or some of the steps in the above disclosed method, the functions of the modules / units in the system and the device can be implemented as software, firmware, hardware and their appropriate combinations.

[0217] The terms "first", "second", "third", "fourth", and the like in the description and in the claims of this application, if any, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the use of the terms so termed is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of orderly or chronological mundane operation, reverse order operation, based on circuitry availability, based on stated preference or the like, and that "default" or other orderings are thus permissible. Further, the terms "comprise", "comprising", "include", "including", and the like, are specifically intended to be open-ended. That is, references to individual steps and the like do not suhstantially exclude the presence of two or more of a given step or its integral presence in the process, method, system, article, or apparatus having been made with a wider scope. The use of notation such as "first", "second", "third", etc. does not generally limit the areas, but is used to connect like elements or to distinguish one claim from another. These terms can be used interchangeably when appropriate. Terms concerning the relative position of elements can be used to describe preferred embodiments and variations thereof, but such terms are used only to describe relative position, and do not suhstantially limit or otherwise restrict the scope of the application to a specific spatial arrangement.

[0218] It should be understood that, in the application, "at least one" refers to one or more, and "multiple" refers to two or more. "And / or" is used to describe the relationship between the associated objects, which means that there can be three relationships, for example, "A and / or B" can represent three cases: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and rear associated objects. "At least one of the following" or similar expressions means any combination of these items, including any combination of single or multiple items. For example, at least one of a, b or c can mean a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, and c can be single or multiple.

[0219] In several embodiments provided in the application, it should be understood that the disclosed system and method can be implemented in other ways. For example, the above-described system embodiments are only illustrative, for example, the division of the above-mentioned modules is only a logical function division, and actual implementation can have another division manner, for example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the displayed or discussed each other can be indirect coupling or communication connection between the systems or modules through some interfaces, which can be electrical, mechanical or other forms.

[0220] The modules described above as separate components can or can not be physically separate, and the components shown as modules can or can not be physical modules, that is, they can be located in one place, or they can be distributed on multiple network modules. Part or all of the modules can be selected according to actual needs to achieve the purpose of the embodiment.

[0221] In addition, each function module in each embodiment of the present application can be integrated in one processing module, or each module can be physically present alone, or two or more modules can be integrated in one module. The integrated module can be realized in the form of hardware or in the form of a software function module.

[0222] When the integrated module is realized in the form of a software function module and sold or used as an independent product, the integrated module can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application, essentially or in other words, the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, and includes multiple instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of the embodiments of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various program storage media.

[0223] The preferred embodiments of the embodiments of the present application are described above with reference to the accompanying drawings, and are not limited to the scope of the embodiments of the present application. Any modifications, equivalent replacements and improvements made by those skilled in the art without departing from the scope and essence of the embodiments of the present application shall be within the scope of the embodiments of the present application.

Claims

1. A control method for a pneumatic dynamic compensation and adaptive rotary joint, characterized in that, The method comprises the following steps: Modeling the pneumatic subsystem and the mechanical subsystem of the gas-driven valve-controlled rotary cylinder system; Building an MPC controller according to the pneumatic subsystem and the mechanical subsystem; Inputting a reference trajectory into an upper-layer global MPC of the MPC controller to obtain a first control quantity; Inputting the first control quantity into a lower-layer pressure compensator of the MPC controller to obtain a second control quantity; Controlling the gas-driven valve-controlled rotary cylinder movement in the gas-driven valve-controlled rotary cylinder system according to the second control quantity, and then driving the joint actuator movement by using the gas-driven valve-controlled rotary cylinder; The modeling of the pneumatic subsystem and the mechanical subsystem of the gas-driven valve-controlled rotary cylinder system comprises the following steps: The gas pressure dynamic equation of the pneumatic subsystem is established as follows: ； wherein, is the sampling time; is the temperature; is the pressure at the k, k+1 time step; is the chamber gas volume at the k, k+1 time step; is the gas specific heat ratio; is the gas constant is the gas source pressure; is the valve flow coefficient; is the valve opening at the k time step; is a function of the chamber gas volume as a function of the angle; The relationship model of the chamber volume and the rotation angle of the pneumatic subsystem is established as follows: ； wherein, Aeffis the effective area of the piston, R is the radius of rotation, θ is the joint angle; The joint dynamics equation of the nonlinear friction of the mechanical subsystem and the joint dynamics equation of the linear viscous friction are established; The joint dynamics equation of the nonlinear friction is as follows: ； ； wherein, is the moment of inertia, is the damping coefficient, are the joint angular velocity, angular acceleration, respectively, is the aerodynamic moment, is the external load, , is the pressure in the two chambers; The joint dynamics equation of the linear viscous friction is as follows: ； wherein is the coulomb friction, is the static friction, is the stribeck velocity, is the viscous friction coefficient; The state variable and the system input of the gas-driven valve-controlled rotary cylinder system are defined to obtain the state space equation of the gas-driven valve-controlled rotary cylinder system; The state variable and the system input are respectively as follows: ； Wherein, x is the state variable, and u is the system input; The state space equation of the gas-driven valve-controlled rotary cylinder system is as follows: 。 2. The control method based on barometric pressure dynamic compensation and adaptive revolute joint according to claim 1, characterized in that, The MPC controller is built according to the pneumatic subsystem and the mechanical subsystem, comprising the following steps: The upper-layer global MPC and the lower-layer pressure compensator are built as the MPC controller according to the pneumatic subsystem and the mechanical subsystem; Wherein, the upper-layer global MPC is used to solve the end angle tracking and energy optimization problems of the gas-driven valve-controlled rotary cylinder system, and the lower-layer pressure compensator is used to adjust the valve opening degree to compensate for the nonlinear characteristics of the dynamic lag of the gas-driven valve-controlled rotary cylinder system; When building the upper-layer global MPC, the first time period and the prediction period are selected; When building the lower-layer pressure compensator, the second time period is included; the second time period is smaller than the prediction period by one order of magnitude.

3. The control method based on barometric pressure dynamic compensation and adaptive revolute joint according to claim 1, wherein, The method further comprises the following steps: Building the objective function and the constraint condition of the MPC controller; The objective function is as follows: ； wherein, is a dynamically adjusted weight matrix; The constraint condition comprises the pressure range, the valve opening and closing speed and the safe movement angle, which are respectively as follows: 。 4. The control method based on barometric pressure dynamic compensation and adaptive revolute joint according to claim 1, wherein, The method further comprises the following steps: An RLS adaptive filtering algorithm is used to identify the parameters of the gas-driven valve-controlled rotary cylinder system online to update the parameters of the current time step according to the optimization results of the previous time step; The RLS adaptive filtering algorithm is as follows: ； wherein, is the parameter to be identified, is a regression matrix composed of states and inputs.

5. The control method based on barometric pressure dynamic compensation and adaptive revolute joint according to claim 1, wherein, The first control quantity is inputted into the lower-layer pressure compensator to obtain the second control quantity, comprising the following steps: The first control quantity is inputted into the lower-layer pressure compensator for feedforward compensation to obtain the second control quantity; The expression of the lower-layer pressure compensator is as follows: ； wherein u comp,k is the second control quantity at the kth time step, u MPC,k is the first control quantity at the kth time step, is the kth time step prediction of the compensated cycle pressure based on valve opening and volume change, is the dynamic gain.

6. The control method based on pneumatic dynamic compensation and adaptive revolute joint according to any one of claims 1 to 5, characterized in that, The method further comprises the following steps: The joint angle and joint speed of the joint actuator are obtained by an encoder, the joint angle, the joint speed and the reference trajectory are input to the upper-layer global MPC to obtain the first control quantity with negative feedback; The chamber pressure of the air-driven valve-controlled rotary cylinder is obtained by a pressure sensor, and the chamber pressure and the first control quantity with negative feedback are input to the lower-layer pressure compensator to obtain the second control quantity with negative feedback.

7. Control system based on dynamic compensation of gas pressure and adaptive revolute joint, characterized by, The system is applied to the control method based on air pressure dynamic compensation and adaptive rotary joint according to claim 1, and the system comprises: A system modeling module is configured to model the pneumatic subsystem and mechanical subsystem of the air-driven valve-controlled rotary cylinder system. A controller construction module is configured to construct an MPC controller according to the pneumatic subsystem and the mechanical subsystem. A first control quantity determination module is configured to input a reference trajectory to the upper-layer global MPC of the MPC controller to obtain a first control quantity. A second control quantity determination module is configured to input the first control quantity to the lower-layer pressure compensator of the MPC controller to obtain a second control quantity. A driving execution module is configured to control the air-driven valve-controlled rotary cylinder in the air-driven valve-controlled rotary cylinder system to move according to the second control quantity, and then drive the joint actuator to move by using the air-driven valve-controlled rotary cylinder.

8. An electronic device, comprising: The electronic device comprises a memory and a processor, the memory stores a computer program, and the processor implements the method according to any one of claims 1 to 6 when executing the computer program.

9. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 8. The computer program is executed by the processor to implement the method according to any one of claims 1 to 6.

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