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

Abstract

The invention discloses a control method and system based on air pressure dynamic compensation and a self-adaptive rotary joint, and relates to the technical field of automatic control. The method comprises the steps that a pneumatic subsystem and a mechanical subsystem are modeled for a gas-driven valve control rotary cylinder system; an MPC controller is constructed according to the pneumatic subsystem and the mechanical subsystem; inputting the reference trajectory into an upper global MPC of an 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; and according to the second control quantity, a gas-driven valve-controlled rotary cylinder in the gas-driven valve-controlled rotary cylinder system is controlled to move, and then the gas-driven valve-controlled rotary cylinder is used for driving a joint actuator to move. Through the hierarchical adaptive MPC controller, the problems that a single MPC controller is poor in real-time performance, significant in pressure lag and incapable of coping with sudden load change are solved, and the robustness is improved.

Description

Technical Field

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

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

[0003] (1) The existing control methods have poor nonlinear adaptability, and the PID parameters need to be manually adjusted for specific working conditions. They cannot effectively deal with problems such as gas compressibility and friction nonlinearity, as well as the lack of accuracy caused by over-simplification of the model. (2) Single MPC (Model Predictive Control) has poor real-time performance, significant pressure lag, and cannot cope with sudden load changes. Summary of the invention

[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 joints to improve the robustness of the air-driven valve-controlled rotary cylinder system.

[0005] To achieve the above object, an embodiment of the present application provides a control method based on air pressure dynamic compensation and adaptive rotary joint, the method comprising the following steps:

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

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

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

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

[0010] The movement of the air-driven valve-controlled rotary cylinder in the air-driven valve-controlled rotary cylinder system is controlled according to the second control amount, and then the air-driven valve-controlled rotary cylinder is used to drive the joint actuator to move.

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

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

[0013]

[0014] Among them, T s is the sampling time; T is the temperature; P k ,P k+1 is the pressure at the kth and k+1th time steps; V k ,V k+1 is the chamber gas volume at the kth and k+1th 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 the function of the chamber gas volume changing with the angle;

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

[0016]

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

[0018] Establishing joint dynamics equations of nonlinear friction and joint dynamics equations of linear viscous friction for the mechanical subsystem;

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

[0020]

[0021] τ gas =(P1-P2)Ar;

[0022] Where J is the moment of inertia, b is the damping coefficient, are the joint angular velocity and angular acceleration, τ gas is the aerodynamic torque, τ load is the external load, P1 and P2 are the pressures in the two chambers;

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

[0024]

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

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

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

[0028]

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

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

[0031]

[0032] In some embodiments, constructing an MPC controller according to the pneumatic subsystem and the mechanical subsystem comprises the following steps:

[0033] Constructing the upper global MPC and the lower pressure compensator as the MPC controller according to the pneumatic subsystem and the mechanical subsystem;

[0034] The upper 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 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] Constructing the upper global MPC includes selecting a first time period and a prediction period;

[0036] The construction of the lower layer pressure compensator includes a second time period; 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] Constructing the objective function and constraints of the MPC controller;

[0039] The objective function is:

[0040]

[0041] Among them, Q, R, P are dynamically adjusted weight matrices;

[0042] The constraints include pressure range, valve opening and closing speed, and safe movement angle, which are:

[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 following steps:

[0047] The parameters of the gas-driven valve-controlled rotary cylinder system are identified online using an RLS adaptive filtering algorithm, so as to update the parameters of the current time step according to the optimization result of the previous time step;

[0048] The RLS adaptive filtering algorithm is:

[0049]

[0050] in, is the parameter to be identified, φ k is the regression matrix consisting of state and input.

[0051] In some embodiments, the step of inputting the first control variable into the lower pressure compensator of the MPC controller to obtain the second control variable comprises the following steps:

[0052] Inputting the first control amount into the lower layer pressure compensator for feedforward compensation to obtain the second control amount;

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

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

[0055] Among them, 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 the predicted value of the compensated cycle pressure based on valve opening and volume change at the kth time step, K p is the dynamic gain.

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

[0057] Acquire the joint angle and joint velocity of the joint actuator through an encoder, input the joint angle, the joint velocity and the reference trajectory into the upper-layer global MPC, and obtain the first control quantity with negative feedback;

[0058] The chamber pressure of the air-driven valve-controlled rotary cylinder is obtained through a pressure sensor, and the chamber pressure and the first control amount with negative feedback are input into the lower pressure compensator to obtain the second control amount with negative feedback.

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

[0060] System modeling module, used to model the pneumatic subsystem and mechanical subsystem of the air-driven valve-controlled rotary cylinder system;

[0061] A controller building module, used for building an MPC controller according to the pneumatic subsystem and the mechanical subsystem;

[0062] A first control amount determination module is used to input the reference trajectory into the upper global MPC of the MPC controller to obtain a first control amount;

[0063] A second control amount determination module, used for inputting the first control amount into the lower pressure compensator of the MPC controller to obtain a second control amount;

[0064] The driving execution module is used to control the movement of the air-driven valve-controlled rotary cylinder in the air-driven valve-controlled rotary cylinder system according to the second control amount, and then use the air-driven valve-controlled rotary cylinder to drive the joint actuator to move.

[0065] To achieve the above objective, another aspect of an embodiment of the present application provides an electronic device, the electronic device comprising a memory and a processor, the memory storing a computer program, and the processor implementing the above method when executing the computer program.

[0066] To achieve the above objective, another aspect of an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and the computer program implements the above method when executed by a processor.

[0067] The embodiments of the present application include at least the following beneficial effects:

[0068] The present application can model the pneumatic subsystem and mechanical subsystem of the air-driven valve-controlled rotary cylinder system; construct an MPC controller based on the pneumatic subsystem and the mechanical subsystem; input the reference trajectory into the upper global MPC of the MPC controller to obtain a first control quantity; input the first control quantity into the lower pressure compensator of the MPC controller to obtain a second control quantity; control 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 use the air-driven valve-controlled rotary cylinder to drive the movement of the joint actuator. The present application solves the problems of poor real-time performance, significant pressure hysteresis, and inability to cope with sudden load changes of a single MPC controller through a hierarchical adaptive MPC controller, thereby improving robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0070] Figure 1 A flow chart of a control method based on air pressure dynamic compensation and adaptive rotary joint provided in an embodiment of the present application;

[0071] Figure 2 A simplified diagram of the overall structural relationship of the rotary joint of the air-driven valve-controlled rotary cylinder system provided in an embodiment of the present application;

[0072] Figure 3 A diagram of components of a pneumatic valve-controlled cylinder control system of an air-driven valve-controlled rotary cylinder system provided in an embodiment of the present application;

[0073] Figure 4 An example flow chart of a control method based on air pressure dynamic compensation and adaptive rotary joint provided in an embodiment of the present application;

[0074] Figure 5 An example diagram of the architecture of an MPC controller provided in an embodiment of the present application;

[0075] Figure 6 A block diagram of a high-precision control system for a rotary joint with dynamic compensation of gas pressure and adaptive MPC provided in an embodiment of the present application;

[0076] Figure 7 A schematic diagram of the structure of a control system based on air pressure dynamic compensation and adaptive rotary joint provided in an embodiment of the present application;

[0077] Figure 8 A schematic diagram of the hardware structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0078] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. When the following description refers to the 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 the embodiments of the present application. They are only examples of devices and methods consistent with some aspects of the embodiments of the present application as detailed in the attached claims.

[0079] It is understood that the terms "first", "second", etc. used in this application can be used to describe various concepts in this article, but unless otherwise specified, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another concept. For example, without departing from the scope of the embodiment of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the words "if" and "if" as used herein can be interpreted as "at the time of" or "when" or "in response to determination".

[0080] The terms "at least one", "multiple", "each", "any", etc. used in this application, at least one includes one, two or more, multiple includes two or more, 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 those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0082] Before describing the embodiments of the present application in detail, some related technologies involved in the embodiments of the present application are first 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 multi-degree-of-freedom gas-driven rotary joints. Most pneumatic systems use PID control combined with pneumatic assisted limiting methods to achieve position or torque control by adjusting the opening of the proportional valve, which can achieve high control accuracy. However, this method has poor nonlinear adaptability, and the PID parameters need to be manually adjusted for specific working conditions, which cannot effectively deal with gas compressibility, friction nonlinearity and load mutations. Some studies apply MPC to pneumatic systems, such as predicting valve movements by simplifying pneumatic models to control pneumatic manipulators to meet the real-time control effect. However, the model parameters of this method are fixed (such as moment of inertia and friction coefficient) and cannot be updated online. When the load changes, the control performance drops sharply and the robustness is poor. Some researchers also use a hierarchical architecture of upper computer planning + lower computer PID execution. This method can ensure a certain degree of control real-time performance, but the upper and lower models are not coupled, and its global optimization algorithm does not consider pressure dynamics, which will lead to torque fluctuations. At the same time, it relies on the lower PID feedback gas hysteresis correction, the corresponding speed is limited, and the overshoot is significant. There are also a few methods that propose pressure control strategies based on the table lookup method, which directly maps the valve opening according to the target torque. However, this method not only cannot adapt to the nonlinear characteristics of gas flow, but also does not integrate feedback correction links, and is easily affected by sensor noise, such as temperature drift.

[0084] In the field of rigid-coupled robot control applications, air-driven valve-controlled rotary cylinder systems are widely used to drive actuator terminal motion, such as air-driven motion joint control systems. In view of the following defects of existing control technologies, the technical problems that this patent application intends to solve are as follows:

[0085] In view of the poor nonlinear adaptability of existing control methods, PID parameters need to be manually adjusted for specific working conditions, and cannot effectively deal with problems such as gas compressibility and friction nonlinearity, as well as the problem of insufficient accuracy caused by over-simplification of the model. This application integrates gas compressibility, chamber volume-angle geometric relationship and Stribeck friction model, which can effectively reduce the model prediction error range.

[0086] In response to the problems of poor real-time performance, significant pressure lag and inability to cope with sudden load changes in a single MPC (Model Predictive Control), this application proposes a hierarchical adaptive MPC architecture, which uses the upper-level MPC to globally optimize angle tracking and energy efficiency and integrates online parameter identification; the lower-level pressure compensator is designed to correct valve instructions in real time based on predicted dynamics, offset gas lag nonlinearity, and cope with sudden interference.

[0087] To address the poor robustness of fixed parameter model systems, this application designs an adaptive parameter online identification module, which updates key system parameters such as moment of inertia and friction coefficient online through the recursive least squares method to ensure that tracking errors can be reduced by utilizing computing resources when the load changes.

[0088] Reference Figure 1 The embodiment of the present application provides a control method based on air pressure dynamic compensation and adaptive rotary joint, which may include but is not limited to S100 to S140, as follows:

[0089] S100: Modeling the pneumatic subsystem and mechanical subsystem of the air-driven valve-controlled rotary cylinder system;

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

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

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

[0093] S140: 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 amount, and then utilizing the air-driven valve-controlled rotary cylinder to drive the joint actuator to move.

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

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

[0096]

[0097] Among them, T s is the sampling time; T is the temperature; P k ,P k+1 is the pressure at the kth and k+1th time steps; V k ,V k+1 is the chamber gas volume at the kth and k+1th 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 the function of the chamber gas volume changing with the angle;

[0098] The relationship model between the chamber volume and the rotation angle is established for the pneumatic subsystem 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] Establishing joint dynamics equations of nonlinear friction and joint dynamics equations of linear viscous friction for the mechanical subsystem;

[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, τ gas is the aerodynamic torque, τ load is the external load, P1 and P2 are the pressures in the two chambers;

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

[0107]

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

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

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

[0111]

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

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

[0114]

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

[0116] Constructing the upper global MPC and the lower pressure compensator as the MPC controller according to the pneumatic subsystem and the mechanical subsystem;

[0117] The upper 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 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] Constructing the upper global MPC includes selecting a first time period and a prediction period;

[0119] The construction of the lower layer pressure compensator includes a second time period; the second time period is one order of magnitude smaller than the prediction period.

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

[0121] Constructing the objective function and constraints of the MPC controller;

[0122] The objective function is:

[0123]

[0124] Among them, Q, R, P are dynamically adjusted weight matrices;

[0125] The constraints include pressure range, valve opening and closing speed, and safe movement angle, which are:

[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] The parameters of the gas-driven valve-controlled rotary cylinder system are identified online using an RLS adaptive filtering algorithm, so as to update the parameters of the current time step according to the optimization result of the previous time step;

[0131] The RLS adaptive filtering algorithm is:

[0132]

[0133] in, is the parameter to be identified, φ k is the regression matrix consisting of state and input.

[0134] Optionally, the step of inputting the first control variable into a lower pressure compensator of the MPC controller to obtain a second control variable comprises the following steps:

[0135] Inputting the first control amount into the lower layer pressure compensator for feedforward compensation to obtain the second control amount;

[0136] The expression of the lower pressure compensator is:

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

[0138] Among them, 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 the predicted value of the compensated cycle pressure based on valve opening and volume change at the kth time step, K p is the dynamic gain.

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

[0140] Acquire the joint angle and joint velocity of the joint actuator through an encoder, input the joint angle, the joint velocity and the reference trajectory into the upper-layer global MPC, and obtain the first control quantity with negative feedback;

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

[0142] Next, the solution of the embodiment of the present application will be introduced and explained in detail with reference to specific application examples.

[0143] The existing pneumatic joint control technology has significant defects in model accuracy, real-time performance, adaptability and hysteresis compensation. This embodiment systematically solves the above problems to a certain extent by considering control accuracy, response speed and robustness through gas-machine coupling modeling, hierarchical adaptive MPC architecture and embedded pressure dynamic compensator, and has innovation and industrial application value.

[0144] ① In the process of completing this embodiment, the necessary components of the air-driven valve-controlled rotary cylinder system include: a rotary encoder, a pressure sensor, a torque sensor, a rotary cylinder, a proportional valve, an industrial computer, a data acquisition card, etc.

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

[0146] ③The connection circuits of components are all completed through air pipes; the air source path may include some auxiliary components for filtering, purification, lubrication, etc.

[0147] The simplified diagram of the overall structure of the rotary joint of the above-mentioned air-driven valve-controlled rotary cylinder system and the components of its air pressure valve-controlled cylinder control system are shown in Figure 2 , Figure 3 As shown:

[0148] Reference Figure 4 ,The following specific technical solution implementation details cover system modeling, control design and real-time optimization methods:

[0149] 1. First, this embodiment can perform dynamic modeling on the pneumatic subsystem of the gas-driven joint with a single rotational degree of freedom. 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 and the output angle of the rotary cylinder chamber, the gas compressibility and valve dynamics are first considered, and the gas pressure dynamic equation is established:

[0150]

[0151] Among them, T s is the sampling time; T is the temperature; P k ,P k+1 is the pressure at the kth and k+1th time steps; V k ,V k+1 is the chamber gas volume at the kth and k+1th 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 the function of the chamber gas volume changing with the angle.

[0152] 2. For the rotating cylinder, the volume change directly affects the pressure dynamics, and its change rate 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] Where A is the effective area of ​​the piston, r is the rotation radius, and θ is the joint angle.

[0155] 3. For the single-degree-of-freedom air-driven joint system designed in this paper, its mechanical subsystem mainly includes the joint dynamics equation with nonlinear friction:

[0156]

[0157] τ gas =(P1-P2)Ar (4)

[0158] Where J is the moment of inertia, b is the damping coefficient, are the joint angular velocity and angular acceleration, τ gas is the aerodynamic torque, τ load is the external load, P1 and P2 are the pressures in the two chambers.

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

[0160]

[0161] In the formula, 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.

[0162] 5. Secondly, in order to facilitate the subsequent design of the model predictive controller (MPC), it is necessary to obtain the system state space equation, so the system state variables and system input (dual valve opening) are defined:

[0163]

[0164] The following nonlinear continuous system model is rewritten as:

[0165]

[0166] 6. Finally, based on the above system model, an MPC controller is constructed, which can effectively suppress the chattering problem of traditional synovial control without measuring the acceleration pressure signal. The specific steps are as follows:

[0167] ST1: Build the hierarchical MPC structure of the MPC controller, as shown in the following figure. Figure 5 shown.

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

[0169] T MPC =10ms (8)

[0170] N=20step (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 to compensate for the nonlinear characteristics of the system dynamic hysteresis. The time period value is generally selected to be less than or equal to one order of magnitude of the prediction period, such as:

[0172] T Comp =1ms (10)

[0173] ST2: Design objective function and constraints.

[0174] The essence of MPC is a real-time control method based on optimization, which also needs to take into account the actual constraints of the system. The objective function of the upper-level MPC is designed as follows:

[0175]

[0176] Where Q, R, and P are weight matrices, which are adjusted dynamically according to the system.

[0177] The single-degree-of-freedom gas 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. The above constraints 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 needs to update the current parameters according to the optimization results of the previous step, so it is necessary to identify the system parameters online. The RLS adaptive filtering algorithm is used as follows:

[0183]

[0184] In the formula is the parameter vector to be identified, φ k It is the regression matrix (consisting of states and inputs), and the update period is set to be synchronized with the MPC upper layer to 10ms.

[0185] ST4: Pressure dynamic compensator.

[0186] The lower pressure compensator of the controller mainly uses feedforward compensation, and the logic is as follows:

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

[0188] Where, P pred,k Compensated cycle pressure prediction based on valve opening and volume change, K p is the dynamic gain.

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

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

[0191] The technical solution of this embodiment systematically proposes feasible solutions to the core problems such as insufficient precision, delayed response, and poor robustness in pneumatic joint control through pneumatic-mechanical coupling modeling, hierarchical adaptive MPC architecture, and pressure dynamic compensation mechanism, which can directly bring the following technical effects:

[0192] I. Improved real-time performance and response speed: The upper-level global MPC (10ms cycle) processes global optimization, and the lower-level pressure compensator (1ms cycle) performs high-speed compensation. The overall response frequency of the system is greatly improved, which can adapt to the real-time needs of high-speed proportional valves.

[0193] II. Enhanced robustness and energy efficiency: The recursive least squares method (RLS) is used to update the moment of inertia, friction coefficient and other parameters in real time. When the load changes suddenly (such as 50% of the rated load), the recovery time is significantly reduced to adapt to the dynamic working conditions. At the same time, the valve opening weighted term is introduced into the MPC objective function to reduce the ineffective gas consumption and reduce energy consumption.

[0194] Reference Figure 7 The embodiment of the present application also provides a control system based on air pressure dynamic compensation and adaptive rotary joint, which can implement the above-mentioned control method based on air pressure dynamic compensation and adaptive rotary joint. The device includes:

[0195] System modeling module, used to model the pneumatic subsystem and mechanical subsystem of the air-driven valve-controlled rotary cylinder system;

[0196] A controller building module, used for building an MPC controller according to the pneumatic subsystem and the mechanical subsystem;

[0197] A first control amount determination module is used to input the reference trajectory into the upper global MPC of the MPC controller to obtain a first control amount;

[0198] A second control amount determination module, used for inputting the first control amount into the lower pressure compensator of the MPC controller to obtain a second control amount;

[0199] The driving execution module is used to control the movement of the air-driven valve-controlled rotary cylinder in the air-driven valve-controlled rotary cylinder system according to the second control amount, and then use the air-driven valve-controlled rotary cylinder to drive the joint actuator to move.

[0200] It can be understood that the contents of the above method embodiments are all applicable to the present system embodiments, the functions specifically implemented by the present system embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0201] The embodiment of the present application also provides an electronic device, the electronic device includes 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 including a tablet computer, a car computer, etc.

[0202] It can be understood that the contents of the above method embodiments are all applicable to the embodiments of the present device, the functions specifically implemented by the embodiments of the present device are the same as those of the method of the present application, and the beneficial effects achieved are also the same as those achieved by the method of the present application.

[0203] See also Figure 8 , Figure 8 The hardware structure of an electronic device of another embodiment is illustrated, and the electronic device includes:

[0204] The processor 801 may be implemented by a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of the present application;

[0205] The memory 802 can be implemented in the form of a read-only memory (ROM), a static storage device, a dynamic storage device, or a random access memory (RAM). The memory 802 can store an operating system and other application programs. When the technical solutions provided in the embodiments of this specification are implemented by software or firmware, the relevant program codes are stored in the memory 802, and the processor 801 calls and executes the methods of the embodiments of this application;

[0206] Input / output interface 803, used to implement 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 through a wired manner (such as USB, network cable, etc.) or a wireless manner (such as mobile network, WIFI, Bluetooth, etc.);

[0208] A bus 805 that transmits information between the various components of the device (e.g., the processor 801, the memory 802, the input / output interface 803, and the communication interface 804);

[0209] The processor 801 , the memory 802 , the input / output interface 803 and the communication interface 804 are connected to each other in communication within the device via a bus 805 .

[0210] An embodiment of the present application further provides a computer-readable storage medium, which stores a computer program, and the computer program implements the method of the present application when executed by a processor.

[0211] It can be understood that the contents of the above method embodiments are all applicable to the present storage medium embodiments, the functions specifically implemented by the present storage medium embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0212] The memory, as a non-transient computer-readable storage medium, can be used to store non-transient software programs and non-transient computer executable programs. In addition, the memory may include a high-speed random access memory, and may also include a non-transient memory, such as at least one disk storage device, a flash memory device, or other non-transient solid-state storage device. In some embodiments, the memory may optionally include a memory remotely disposed relative to the processor, and these remote memories may be connected to the processor via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0213] The embodiments described in the embodiments of the present application are intended 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 in the embodiments of the present application. Those skilled in the art will appreciate that with the evolution of technology and the emergence of new application scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

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

[0215] The system embodiment described above is merely illustrative, wherein the modules described as separate components may or may not be physically separated, i.e., may be located in one place, or may be distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment.

[0216] Those skilled in the art will appreciate that all or some of the steps in the methods disclosed above, and the functional modules / units in the systems and devices may be implemented as software, firmware, hardware, or a suitable combination thereof.

[0217] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or modules is not necessarily limited to those steps or modules clearly listed, but may include other steps or modules that are not clearly listed or inherent to these processes, methods, products or devices.

[0218] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: 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 indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural 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, c can be single or multiple.

[0219] In the several embodiments provided in the present application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are only schematic. For example, the division of the above modules is only a logical function division. There may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of systems or modules, which can be electrical, mechanical or other forms.

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

[0221] In addition, each functional module in each embodiment of the present application can be integrated into a processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The above integrated modules can be implemented in the form of hardware or software functional modules.

[0222] If the integrated module is implemented in the form of a software function module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including multiple instructions to enable a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of various embodiments of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory, referred to as ROM), random access memory (Random Access Memory, referred to as RAM), disk or optical disk and other media that can store programs.

[0223] The preferred embodiments of the present invention are described above with reference to the accompanying drawings, but the scope of the rights of the present invention is not limited thereto. Any modification, equivalent substitution and improvement made by a person skilled in the art without departing from the scope and essence of the present invention should be within the scope of the rights of the present invention.

Claims

1. A control method based on air pressure dynamic compensation and adaptive rotary joint, characterized in that: The method comprises the following steps: Model the pneumatic subsystem and mechanical subsystem of the air-driven valve-controlled rotary cylinder system; Constructing an MPC controller according to the pneumatic subsystem and the mechanical subsystem; Inputting the reference trajectory into the upper global MPC of the MPC controller to obtain a first control variable; Inputting the first control variable into the lower pressure compensator of the MPC controller to obtain a second control variable; The movement of the air-driven valve-controlled rotary cylinder in the air-driven valve-controlled rotary cylinder system is controlled according to the second control amount, and then the air-driven valve-controlled rotary cylinder is used to drive the joint actuator to move.

2. The control method based on air pressure dynamic compensation and adaptive rotary joint according to claim 1, characterized in that: The method of modeling the pneumatic subsystem and the mechanical subsystem of the air-driven valve-controlled rotary cylinder system comprises the following steps: The gas pressure dynamic equation for the pneumatic subsystem is established as follows: Among them, T s is the sampling time; T is the temperature; P k ,P k+1 is the pressure at the kth and k+1th time steps; V k ,V k+1 is the chamber gas volume at the kth and k+1th 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 the function of the chamber gas volume changing with the angle; The relationship model between the chamber volume and the rotation angle is established for the pneumatic subsystem as follows: Where A is the effective area of ​​the piston, r is the rotation radius, and θ is the joint angle; Establishing joint dynamics equations of nonlinear friction and joint dynamics equations of linear viscous friction for the mechanical subsystem; The joint dynamics equation of the nonlinear friction is as follows: t gas =(P1-P2)Ar; Where J is the moment of inertia, b is the damping coefficient, are the joint angular velocity and angular acceleration, τ gas is the aerodynamic torque, τ load is the external load, P1 and P2 are the pressures in the two chambers; The joint dynamics equation of linear viscous friction is as follows: Among them, f c is the Coulomb friction, f s is the static friction, ω s is the stribeck velocity, σ is the viscous friction coefficient; Defining the state variables and system inputs of the gas-driven valve-controlled rotary cylinder system to obtain the state space equation of the gas-driven valve-controlled rotary cylinder system; The state variables and the system inputs are: Wherein, x is the state variable, and u is the system input; The state space equation of the air-driven valve-controlled rotary cylinder system is:

3. The control method based on air pressure dynamic compensation and adaptive rotary joint according to claim 1, characterized in that: The method of constructing an MPC controller according to the pneumatic subsystem and the mechanical subsystem comprises the following steps: Constructing the upper global MPC and the lower pressure compensator as the MPC controller according to the pneumatic subsystem and the mechanical subsystem; The upper 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 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. Constructing the upper global MPC includes selecting a first time period and a prediction period; The construction of the lower layer pressure compensator includes a second time period; the second time period is one order of magnitude smaller than the prediction period.

4. The control method based on air pressure dynamic compensation and adaptive rotary joint according to claim 1, characterized in that: The method further comprises the following steps: Constructing the objective function and constraints of the MPC controller; The objective function is: Among them, Q, R, and P are dynamically adjusted weight matrices; The constraints include pressure range, valve opening and closing speed, and safe movement angle, which are: P min ≤P 1,k ,P 2,k ≤P max |in k+1 -in k |≤Δu max i min ≤θ k ≤θ max 。 5. The control method based on air pressure dynamic compensation and adaptive rotary joint according to claim 1, characterized in that: The method further comprises the following steps: The parameters of the gas-driven valve-controlled rotary cylinder system are identified online using an RLS adaptive filtering algorithm, so as to update the parameters of the current time step according to the optimization result of the previous time step; The RLS adaptive filtering algorithm is: in, is the parameter to be identified, φ k is the regression matrix consisting of state and input.

6. The control method based on air pressure dynamic compensation and adaptive rotary joint according to claim 1, characterized in that: The step of inputting the first control variable into the lower pressure compensator of the MPC controller to obtain the second control variable comprises the following steps: Inputting the first control amount into the lower layer pressure compensator for feedforward compensation to obtain the second control amount; The expression of the lower pressure compensator is: in comp,k =in MPC,k +K p (P pred,k -P meas,k ); Among them, 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 the predicted value of the compensated cycle pressure based on valve opening and volume change at the kth time step, K p is the dynamic gain.

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

8. A control system based on air pressure dynamic compensation and adaptive rotary joint, characterized in that: The system comprises: System modeling module, used to model the pneumatic subsystem and mechanical subsystem of the air-driven valve-controlled rotary cylinder system; A controller building module, used for building an MPC controller according to the pneumatic subsystem and the mechanical subsystem; A first control amount determination module is used to input the reference trajectory into the upper global MPC of the MPC controller to obtain a first control amount; A second control amount determination module, used for inputting the first control amount into the lower pressure compensator of the MPC controller to obtain a second control amount; The driving execution module is used to control the movement of the air-driven valve-controlled rotary cylinder in the air-driven valve-controlled rotary cylinder system according to the second control amount, and then use the air-driven valve-controlled rotary cylinder to drive the joint actuator to move.

9. An electronic device, characterized in that: 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 7 when executing the computer program.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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