A dual closed-loop controller for motion control of rigid-soft coupled dexterous hand and its design method

Abstract

The present invention belongs to the field of controller design technology, and specifically relates to a dual closed-loop controller for motion control of a rigid-soft coupled dexterous hand and its design method. The pneumatic loop is an inner loop, using a sliding mode controller; the position loop is an outer loop, using a feedforward + PID controller; the pneumatic loop includes a data processing module for the pneumatic loop and a sliding mode controller; the position loop includes a data processing module for the position loop and a feedforward + PID controller; the data processing module for the pneumatic loop is respectively connected to an IMU sensor and a data processing module for the position loop; the sliding mode controller is respectively connected to a feedforward + PID controller, an air pressure sensor, and an electromagnetic valve, and the data processing module for the position loop also receives joint angle target trajectory data. The present invention is used to achieve motion control of soft dexterous fingers.

Description

Technical Field

[0001] The present invention belongs to the technical field of controller design, and in particular relates to a dual closed-loop controller for motion control of a rigid-soft coupled dexterous hand and a design method thereof. Background Art

[0002] In recent years, research on soft dexterous hands has yielded a series of achievements, demonstrating outstanding performance in tasks such as adaptive grasping of object shapes, grasping in special environments, and compliant grasping. With advances in manufacturing processes and actuation technologies, soft dexterous hands have demonstrated potential for practical applications. Currently, one of the greatest challenges in soft robotics is motion control, yet the motion control of soft dexterous hands has received insufficient attention. Furthermore, their multi-joint and small size present additional challenges.

[0003] Current motion control methods for soft robots can be divided into model-based and machine learning-based approaches. Some researchers have also attempted to combine soft robot body sensors with PID controllers, but these efforts have not focused on dynamic processes.

[0004] Model-based methods require building an effective mathematical and physical model for a specific soft robot and controlling it based on the mapping relationship between air pressure and angle. Some results have verified the effectiveness of this method. However, the main problems with this method are as follows:

[0005] 1) It is difficult to establish an accurate mathematical model, and silicone materials have creep characteristics;

[0006] 2) Static models are only applicable to low-speed conditions, while dynamic models rely on a large amount of experimental data;

[0007] At the same time, researchers have proposed a control method based on machine learning, using a data-driven mapping approach and have achieved excellent results on some soft actuators. However, this method also has certain limitations:

[0008] 1) A large amount of data sets need to be collected for training, which is difficult to obtain through experiments;

[0009] 2) Errors in the manufacturing process are unavoidable, resulting in different mechanical properties for different fingers;

[0010] Furthermore, pneumatic soft fingers are prone to significant vibration due to the low stiffness of flexible materials and the difficulty in dynamically controlling airflow. This vibration can lead to dramatic changes in sensor data, further exacerbating the vibration, making air pressure control crucial.

[0011] Given the aforementioned background, existing methods for achieving good motion control in soft dexterous hands face numerous limitations. Therefore, this paper proposes a novel approach, systematically addressing these challenges through both sensing and control approaches. We utilize proprioceptive sensing to provide posture information for the control system. A dual-loop controller employs proprioceptive sensing and air pressure, enabling stable posture control within the position loop using simple, traditional control methods. Summary of the Invention

[0012] The present invention provides a dual closed-loop controller for motion control of a rigid-soft coupled dexterous hand, which is used to solve the above technical problems and realize motion control of soft dexterous fingers.

[0013] The present invention provides a design method for a dual closed-loop controller for rigid-soft coupled dexterous hand motion control, thereby obtaining a dual closed-loop controller for rigid-soft coupled dexterous hand motion control.

[0014] The present invention provides a computer-readable storage medium for realizing a design method of a dual closed-loop controller for rigid-soft coupled dexterous hand motion control.

[0015] The present invention provides a motion control method for a soft dexterous finger, which is realized by applying a dual closed-loop controller for motion control of a rigid-soft coupled dexterous hand.

[0016] The present invention is achieved through the following technical solutions:

[0017] A dual closed-loop controller for motion control of a rigid-soft coupled dexterous hand, comprising a pneumatic loop and a position loop, wherein the pneumatic loop is an inner loop and uses a sliding mode controller; the position loop is an outer loop and uses a feedforward + PID controller;

[0018] The pneumatic ring includes a data processing module and a sliding mode controller of the pneumatic ring; the position loop includes a data processing module and a feedforward + PID controller of the position loop;

[0019] The data processing module of the pneumatic ring is respectively connected to the data processing modules of the IMU sensor and the position loop; the sliding mode controller is respectively connected to the feedforward + PID controller, the air pressure sensor and the solenoid valve, and the data processing module of the position loop also receives the joint angle target trajectory data.

[0020] Furthermore, the data processing module of the air pressure ring receives the posture data of the IMU sensor, and the sliding mode controller receives the feedback data of the air pressure of the air pressure sensor;

[0021] The data processing module of the position loop receives the posture data transmitted by the data processing module of the air pressure ring. The data processing module of the position loop also receives the joint angle target value trajectory data. The data processing module of the position loop sends the feedback data of the joint angle and the target data of the joint angle, and the feedforward + PID controller sends the target air pressure value to the sliding mode controller. The sliding mode controller controls the duty cycle of the PWM signal of the solenoid valve based on the feedback data of the air pressure and the target air pressure value.

[0022] A design method for a dual closed-loop controller for rigid-soft coupled dexterous hand motion control, the design method comprising:

[0023] Step 1: Establish solenoid valve and aerodynamic models;

[0024] Step 2: Based on the solenoid valve and aerodynamic model in step 1, design a pneumatic ring controller based on sliding mode control;

[0025] Step 3: Based on the solenoid valve and aerodynamic model in step 1, design a PID position loop controller with feedforward compensation.

[0026] Step 4: Combine the pneumatic loop controller of sliding mode control in step 2 and the PID position loop controller of feedforward compensation in step 3 to form a complete dual closed-loop controller for rigid-soft coupled dexterous hand motion control.

[0027] Furthermore, the step 1 is specifically as follows: for the air in the gas path, there is an ideal gas state equation:

[0028] S P P in V=mR g (T0+T) (1)

[0029] Where, P in is the driving pressure of the air cavity; V is the volume of the compressible gas in the channel; m is the mass of the compressible gas in the channel; R g is the ideal gas constant of air; T is the gas temperature; S P is a constant;

[0030] By taking the derivative of formula (1), we can get:

[0031]

[0032] Formula (2) can be simplified as:

[0033]

[0034]

[0035] The relationship between gas pressure change and flow rate is obtained, where is the average mass flow rate of the gas.

[0036] Furthermore, the upstream and downstream pressure ratio P ratio Above the critical pressure ratio b o When , the air produces subsonic flow in the valve:

[0037]

[0038] Where, P ratio is the upstream and downstream pressure ratio; P u is the pressure upstream of the valve port; P d is the pressure downstream of the valve port; P a is the atmospheric pressure;

[0039] Based on the small hole model under standard conditions, the air volume flow rate Q of the solenoid valve port can be calculated separately when there is no gas leakage and the valve port is fully open. vo (P u ,P d ) and mass flow rate Q mo :

[0040]

[0041] Q mo (P u ,P d )=ρQ vo (P u ,P d ) (7)

[0042] Where, ρ is the air density under standard conditions; C f is the pressure downstream of the valve port;

[0043] T a is the standard state temperature; T is the actual temperature of the gas; C o is the sonic conductance at the valve port; b o is the critical pressure ratio of the valve port;

[0044] Use a solenoid valve opening ratio C r To describe the actual average flow:

[0045] Q m =C r Q mo (8)

[0046] In the formula, the solenoid valve opening ratio C r >0 indicates the inflation process, the ratio C r <0 indicates exhaust process;

[0047] Simplified description of the solenoid valve opening ratio:

[0048]

[0049] Where k v is the linear ratio of valve opening; u in is the duty cycle of the PWM valve control signal; u dz It is the dead zone of the solenoid valve.

[0050] Furthermore, the step 2 is specifically to establish the state equation of the system from formulas (4) to (9):

[0051]

[0052]

[0053] Where, P in Input pressure of the air cavity; u in is the duty cycle of the PWM valve control signal; Δ(t) is the disturbance term; Simplify Equation (11) appropriately and let k v -1 =1-u dz sgn(u dz ), the gas source pressure is P s , G(u, x1) in formula (11) is calculated by formula (12):

[0054]

[0055] Where, Inflate the dead zone of the solenoid valve; is the dead zone of the solenoid valve deflation; sta represents the system charging and deflation mode;

[0056] Here, it is agreed that sta=0 means that the solenoid valve is in the stopped state within the forward and reverse dead zone, sta=1 means that the charging solenoid valve is open, the exhaust solenoid valve is closed, and the solenoid valve group works in the charging state, and sta=2 means that the charging solenoid valve is closed, the exhaust solenoid valve is open, and the solenoid valve group works in the exhaust state:

[0057]

[0058] Furthermore, the integral sliding surface is designed:

[0059]

[0060] Where c>0, e=x1-x d , set the target pressure x d =P d As the state tracking target value; the design goal is s→0, at this time,

[0061] The construction index approaches the sliding mode as Using the hyperbolic tangent instead of the sign function reduces jitter:

[0062]

[0063] Taking the derivative of (12) we get

[0064] Combining (13) and (14) we get

[0065] Combining (4)(9)(10)(15), the control law of SMC control can be calculated according to formulas (16) to (18):

[0066]

[0067]

[0068]

[0069] Where u in is the control law of SMC control; u eq is the equivalent controller of SMC control; u sw is the SMC control robust term.

[0070] Furthermore, when judging the system's inflation and deflation working mode, it is necessary to first calculate the controller control laws in the two modes according to the inflation and deflation modes, which are the controller output u in the inflation state and u in the deflation state. inflate and the controller output u in the deflated state deflate ; Then inflate the dead zone according to the debugging parameters and deflation dead zone Determine the working mode.

[0071] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method described above is implemented.

[0072] A motion control method for a soft dexterous finger is disclosed. The control method uses a dual closed-loop controller for motion control of a rigid-soft coupled dexterous hand as described above to achieve motion control of the soft dexterous finger.

[0073] The beneficial effects of the present invention are:

[0074] The present invention has good dynamic and static performance under different working conditions.

[0075] When multiple joints move simultaneously, the average error of each joint is less than 1 degree, and the root mean square error is about 2 degrees.

[0076] The present invention simplifies the soft hand motion control. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 It is a structural schematic diagram of the present invention.

[0078] Figure 2 These are the dynamic and static experimental results of the controller of the present invention under different working conditions, among which (a) is a schematic diagram of the trapezoidal response curve with a target value of 60 degrees and a speed of 10 degrees / second, (b) is a schematic diagram of the trapezoidal response curve with a target value of 60 degrees and a speed of 20 degrees / second, (c) is a schematic diagram of the trapezoidal response curve with a target value of 60 degrees and a speed of 30 degrees / second, (d) is a schematic diagram of the trapezoidal response curve of the coordinated action of multiple finger joints, (e) is a schematic diagram of the sinusoidal response curve with a target value of 60 degrees, and (f) is a schematic diagram of the step response curve with target values ​​of 40 degrees and 60 degrees. DETAILED DESCRIPTION

[0079] In the following description, specific details such as specific system structures and technologies are provided for illustration rather than limitation to facilitate a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obstructing the description of the present application with unnecessary details.

[0080] It will be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0081] It should also be understood that the terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0082] The following is attached to this application specification Figure 1-2 , clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of this application.

[0083] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0084] Implementation Method 1

[0085] This embodiment provides a dual closed-loop controller for motion control of a rigid-soft coupled dexterous hand. The dual closed-loop controller is a pressure-position dual closed-loop controller. The dual closed-loop controller includes a pressure loop and a position loop. The pressure loop is an inner loop and uses a sliding mode controller; the position loop is an outer loop and uses a feedforward + PID controller.

[0086] The pneumatic ring includes a data processing module and a sliding mode controller of the pneumatic ring; the position loop includes a data processing module and a feedforward + PID controller of the position loop;

[0087] The data processing module of the pneumatic ring is respectively connected to the data processing modules of the IMU sensor and the position loop; the sliding mode controller is respectively connected to the feedforward + PID controller, the air pressure sensor and the solenoid valve, and the data processing module of the position loop also receives the joint angle target trajectory data.

[0088] Furthermore, the data processing module of the air pressure ring receives the posture data of the IMU sensor, and the sliding mode controller receives the feedback data of the air pressure of the air pressure sensor;

[0089] The data processing module of the position loop receives the posture data transmitted by the data processing module of the air pressure ring. The data processing module of the position loop also receives the joint angle target value trajectory data. The data processing module of the position loop sends the feedback data of the joint angle and the target data of the joint angle, and the feedforward + PID controller sends the target air pressure value to the sliding mode controller. The sliding mode controller controls the duty cycle of the PWM signal of the solenoid valve based on the feedback data of the air pressure and the target air pressure value.

[0090] Specifically, the present invention designs a dual closed-loop controller for rigid-soft coupled dexterous hand motion control. The controller can be divided into a pneumatic loop and a position loop, wherein the pneumatic loop is an inner loop and uses a sliding mode controller; the position loop is an outer loop and uses a feedforward + PID controller. During operation, the host computer generates joint angle targets at a certain frequency based on the given finger joint trajectory and transmits them to the position loop controller. The latter can continuously adjust the desired air pressure target value of the relevant air chamber as the control quantity according to the data fed back by the IMU sensor, and transmit it to the pneumatic loop; the desired air pressure target value is the target value of the pneumatic loop. The pneumatic loop controller adjusts the solenoid valve PWM duty cycle according to the information fed back by the air pressure sensor to control the gas flow, so that the finger moves. Then the IMU sensor detects the change in joint angle and transmits it to the position loop again to enter the next control cycle.

[0091] From the perspective of the entire control system, effective pneumatic control is fundamental. Due to the low stiffness of the rigid-soft coupled finger and the rapid changes in air pressure caused by the on-off valve, jitter during finger joint movement is unavoidable. Failure to achieve fast and stable control in the pneumatic control loop will result in the transmission of undesirable angle data to the position loop, resulting in unreasonable target air pressure values ​​and ultimately exacerbating jitter.

[0092] The miniature electromagnetic switch valve used in the present invention is a typical nonlinear element. The air pressure in an air cavity is controlled by two solenoid valves, one for inflation and the other for deflation. The air circuit formed by this combination of solenoid valves is a discontinuous nonlinear system. Due to factors such as the solenoid valve dead zone and gas leakage, the air circuit system is difficult to accurately model. For such a system, model-free controllers such as PID and physical model methods that require precise modeling are difficult to achieve ideal results. Therefore, the present invention proposes a sliding mode controller based on inflation and deflation rules for controlling the air pressure loop.

[0093] Implementation Method 2

[0094] This embodiment provides a design method for a dual closed-loop controller for rigid-soft coupled dexterous hand motion control, the design method comprising:

[0095] Step 1: Establish solenoid valve and aerodynamic models;

[0096] Step 2: Based on the solenoid valve and aerodynamic model in step 1, design a pneumatic ring controller based on sliding mode control (SMC);

[0097] Step 3: Based on the solenoid valve and aerodynamic model in step 1, design a PID position loop controller with feedforward compensation.

[0098] Step 4: Combine the pneumatic loop controller of sliding mode control in step 2 and the PID position loop controller of feedforward compensation in step 3 to form a complete dual closed-loop controller for rigid-soft coupled dexterous hand motion control.

[0099] Furthermore, the step 1 is specifically as follows: first, the present invention derives the relationship between the pressure change in the gas path and the PWM duty cycle during the movement of the solenoid valve core. For the air in the gas path, there is an ideal gas state equation:

[0100] S P P in V=mR g (T0+T) (1)

[0101] Where, P in is the driving pressure of the air cavity (kPa); V is the volume of the compressible gas in the channel (m 3 ); m is the mass of the compressible gas in the channel (g); R g is the ideal gas constant of air (R g =287Nm / (kg·K)); T is the gas temperature (K, T0=273.15K); S P is a constant (S P =1000).

[0102] By taking the derivative of formula (1), we can get:

[0103]

[0104] There are terms related to finger dynamics in formula (2): This term is not only related to the driving torque of the gas on the air cavity, but also to mechanical factors such as structural inertia, external force, and external torque. In order to obtain a controller that is robust to external forces, this term is ignored in the control, and the error caused by ignoring this term is regarded as a system interference. Therefore, Equation (2) can be simplified to:

[0105]

[0106]

[0107] The relationship between gas pressure change and flow rate is obtained, where is the average mass flow rate of the gas.

[0108] Furthermore, the orifice model can be used to describe the gas flow state at the valve port; for the sonic conductance C o and critical pressure ratio b o To describe the flow characteristics of a high-speed switch solenoid valve, the flow of gas in the valve can be divided into two flow states. When the upstream and downstream pressures P ratioRatio is less than the critical pressure ratio b o When the air velocity at the valve port reaches the speed of sound, the air will flow in the valve in a blocked manner. At this time, the mass flow rate of the gas has nothing to do with the downstream pressure. ratio Above the critical pressure ratio b o When , the air produces subsonic flow in the valve:

[0109]

[0110] Where, P ratio is the upstream and downstream pressure ratio; P u is the pressure upstream of the valve port (kPa); P d is the pressure downstream of the valve port (kPa); P a is the atmospheric pressure (kPa);

[0111] Based on the orifice model under standard conditions (ANR), the air volume flow rate Q at the solenoid valve port can be calculated when there is no gas leakage and the valve port is fully open. vo (P u ,P d ) and mass flow rate Q mo :

[0112]

[0113] Q mo (P u ,P d )=ρQ vo (P u ,P d ) (7)

[0114] Where ρ is the air density under standard conditions (ρ = 1.205 kg / m 3 );C f is the pressure downstream of the valve port (C f =10); T a is the standard state temperature (T a =20℃); T is the actual temperature of the gas (℃); C o is the valve port sonic conductance (dm 3 / (s·bar));b o is the critical pressure ratio of the valve port;

[0115] The system uses SMC high-speed solenoid valve S070C-5BC, whose sonic flow conductance is C o =0.042dm 3 / (s·bar), critical pressure ratio b o =0.27. Standard conditions (ANR) refer to temperature T = 20 ° C, atmospheric pressure P a=101.325kPa, relative humidity of air is 65%.

[0116] The switching response time of the S070C-5BC solenoid valve is less than 3ms. The present invention uses a PWM drive with a carrier frequency of 180Hz and an amplitude of 24V to drive the solenoid valve to operate in a fully open or fully closed state. Therefore, a solenoid valve opening ratio C can be used. r To describe the actual average flow:

[0117] Q m =C r Q mo (8)

[0118] In the formula, the solenoid valve opening ratio C r >0 indicates the inflation process, the ratio C r <0 indicates exhaust process;

[0119] The solenoid valve has a large dead zone. When the PWM duty cycle exceeds this dead zone, the average flow rate is proportional to the PWM duty cycle, and a linear ratio k is used. v >0 approximates this relationship, and the solenoid valve opening ratio can be simplified as follows:

[0120]

[0121] Where k v is the linear ratio of valve opening; u in is the duty cycle of the PWM valve control signal ( in ∈[-1, 1]); u dz It is the dead zone of the solenoid valve.

[0122] Parameter u dz and k v The size of is related to the structure of the solenoid valve itself, the current valve opening and closing state, friction, upstream and downstream pressure difference, temperature and PWM signal carrier frequency. These characteristics are difficult to be accurately calibrated. Therefore, when designing the controller, the influence of the hysteresis characteristics of the solenoid valve is ignored.

[0123] The unknown parameters of the solenoid valve are bounded. Among them, k v max The upper and lower limits of the linear ratio of the valve opening of the switch valve are related to the actual characteristics of the solenoid valve and are obtained from actual tests. The dead zone of the solenoid valve is also bounded. The upper and lower bounds of the dead zone estimation of the solenoid valve are obtained from actual tests.

[0124] Furthermore, the step 2 is specifically to use two high-speed switch valves on the hardware to control the inflation and exhaust of the air cavity respectively in the actual air pressure control. The parameters related to the inflation valve are marked as (+), and the parameters related to the exhaust valve are marked as (-). According to the above analysis of the gas dynamics model in the air path, the system is a nonlinear discontinuous first-order system with uncertain parameters. In the design of the air pressure SMC controller, the air cavity pressure P is used as the input. in As the control target, the PWM signal duty cycle u in is the controller output. From formulas (4) to (9), the state equation of the system can be established:

[0125]

[0126]

[0127] Where, P in is the air cavity input pressure (kPa); u in is the duty cycle of the PWM valve control signal; Δ(t) is the disturbance term; the unmodeled dynamic Δ(t) includes the influence of external interference, inertia, material hysteresis characteristics and other factors, is the sum of modeling error and parameter estimation error, and is a nonlinear function of time t; the uncertain parameter k v and u dz There is a strong correlation between them, making it difficult to achieve online identification of these two parameters at the same time; therefore, Equation (11) is simplified appropriately, and k v -1 =1-u dz sgn(u dz ), the gas source pressure is P s , G(u, x1) in formula (11) is calculated by formula (12):

[0128]

[0129] Where, It is the positive dead zone of the solenoid valve (the state of the solenoid valve group being inflated); is the reverse dead zone of the solenoid valve (the solenoid valve group is in the deflation state); sta represents the system charging and deflation mode;

[0130] Here, it is agreed that sta=0 means that the solenoid valve is in the stopped state within the forward and reverse dead zone, sta=1 means that the charging solenoid valve is open, the exhaust solenoid valve is closed, and the solenoid valve group works in the charging state, and sta=2 means that the charging solenoid valve is closed, the exhaust solenoid valve is open, and the solenoid valve group works in the exhaust state:

[0131]

[0132] Furthermore, for the first-order nonlinear system of the present invention, an integral sliding surface is designed:

[0133]

[0134] Where c>0, e=x1-x d , set the target pressure x d =P d As the state tracking target value; the design goal is s→0, at this time,

[0135] The construction index approaches the sliding mode as Using the hyperbolic tangent instead of the sign function reduces jitter:

[0136]

[0137] Taking the derivative of (12) we get

[0138] Combining (13) and (14) we get

[0139] Combining (4)(9)(10)(15), the control law of SMC control can be calculated according to formulas (16) to (18):

[0140]

[0141]

[0142]

[0143] Where u in is the control law of SMC control; u eq is the equivalent controller of SMC control; u sw is the SMC control robust term.

[0144] C, K, and E are design parameters greater than 0 and can be selected through parameter adjustment. Increasing C and K can accelerate convergence and obtain smaller deviations. Excessively large C, K, and E can exacerbate oscillations.

[0145] Furthermore, the controller's control law calculation requires prior knowledge of the system's inflation and deflation operating mode. The system's operating mode is determined by both the target value and the current system state. To determine the inflation and deflation operating mode while reducing system jitter caused by frequent state switching, the present invention establishes the inflation and deflation rules shown in Table 1.

[0146] Table 1 Inflating and deflation rules

[0147]

[0148] When judging the system's inflation and deflation working mode, it is necessary to first calculate the controller control laws in the two modes according to the inflation and deflation modes, which are the controller output u in the inflation state and u in the deflation state. inflate and the controller output u in the deflated state deflate ; Then inflate the dead zone according to the debugging parameters and deflation dead zone Determine the working mode. Table 1 is the specific inflation and deflation rules table, where e min is the controller dead zone.

[0149] Specifically, for a motor-driven rigid manipulator, finger position control is relatively easy due to joint angle sensors and motor current loop control. However, for a pneumatic soft manipulator, the control method becomes more complicated due to limitations in sensor integration and difficulties in gas control.

[0150] Specifically, we first take the trapezoidal planning task with the target value of the MCP joint bending at 60 degrees as an example and test the performance at different planning speeds. We compare the joint angle curve calculated by the IMU sensor with the target joint angle curve, and also give the curve of the control value of the position loop (target air pressure value). Figure 2 As can be seen in the figure, the controller exhibits excellent dynamic and static performance under different operating conditions. To further verify the controller's ability to control the entire finger, the IP, MCPB, and MCPA joints were simultaneously driven to achieve coordinated motion of multiple joints. The results showed that when multiple joints were simultaneously actuated, the average error for each joint was less than 1 degree, and the root mean square error was approximately 2 degrees. Sine programming experiments and step response experiments were also conducted using the MCP joint as an example.

[0151] Table 2 Position control error of MCP joint bending motion

[0152]

[0153] Table 3 Finger motion position control error

[0154]

[0155] Table 4 Sinusoidal response results of position loop controller

[0156]

[0157] Implementation Method 3

[0158] An embodiment of the present invention provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. The memory is used to store software programs and modules, and the processor executes various functional applications and data processing by executing the software programs and modules stored in the memory. The memory and processor are connected via a bus. Specifically, the processor implements any step of the first embodiment described above by executing the computer program stored in the memory.

[0159] It should be understood that in the embodiments of the present invention, the processor referred to may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor, etc.

[0160] The memory may include a read-only memory, a flash memory, and a random access memory, and provides instructions and data to the processor. A portion or all of the memory may also include a non-volatile random access memory.

[0161] It should be understood that if the above-mentioned integrated modules / units are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The above-mentioned computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, it can implement the steps of the above-mentioned various method embodiments. Among them, the above-mentioned computer program includes computer program code, and the above-mentioned computer program code can be in source code form, object code form, executable file or some intermediate form. The above-mentioned computer-readable medium may include: any entity or device capable of carrying the above-mentioned computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium. It should be noted that the content contained in the above-mentioned computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction.

[0162] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

[0163] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the above-mentioned device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the implementation method can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method implementation method, and will not be repeated here.

[0164] It should be noted that the methods and detailed examples provided in the above embodiments can be combined with the devices and equipment provided in the embodiments, and references can be made to each other, and no further details will be given.

[0165] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0166] In the embodiments provided by the present invention, it should be understood that the disclosed apparatus / terminal equipment and methods can be implemented in other ways. For example, the apparatus / device embodiments described above are merely illustrative. For example, the division of the modules or units described above is merely a logical functional division. In actual implementation, other division methods may be used. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not implemented.

[0167] Implementation Method 4

[0168] This embodiment provides a motion control method for a soft dexterous finger. The control method uses a dual closed-loop controller for motion control of a rigid-soft coupled dexterous hand as described in embodiment 1 to achieve motion control of the soft dexterous finger.

[0169] The comprehensive solution proposed by the present invention makes it possible to simplify the motion control of the soft hand. The aforementioned posture sensing system and air pressure control play the roles of the joint angle sensor and current loop control in the rigid manipulator, respectively. The present invention applies a PID controller based on feedforward compensation to position loop control. The feedforward control establishes the air pressure-angle relationship of the joint under no-load state according to the experimental data, avoids the establishment of the main body mathematical model, and makes full use of the prior information provided by the main body posture sensor to achieve rapid response. However, the mapping relationship fitted by the experimental data is not completely accurate, and is affected by the time-lag characteristics of the material. The feedforward control cannot avoid the generation of errors, while the PID link can correct the errors in real time to ensure the accuracy of the control results.

[0170] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A dual closed-loop controller for rigid-soft coupled dexterous hand motion control, characterized in that: The dual closed-loop controller includes a pressure loop and a position loop, wherein the pressure loop is an inner loop and uses a sliding mode controller; the position loop is an outer loop and uses a feedforward + PID controller; The pneumatic ring includes a data processing module and a sliding mode controller of the pneumatic ring; the position loop includes a data processing module and a feedforward + PID controller of the position loop; The data processing module of the pneumatic ring is respectively connected to the data processing modules of the IMU sensor and the position ring; the sliding mode controller is respectively connected to the feedforward + PID controller, the air pressure sensor and the solenoid valve, and the data processing module of the position ring also receives the joint angle target trajectory data; The data processing module of the air pressure ring receives the posture data of the IMU sensor, and the controller receives the feedback data of the air pressure of the air pressure sensor; The data processing module of the position loop receives the posture data transmitted by the data processing module of the air pressure ring. The data processing module of the position loop also receives the joint angle target value trajectory data. The data processing module of the position loop sends the feedback data of the joint angle and the target data of the joint angle, and the feedforward + PID controller sends the target air pressure value to the controller. The sliding mode controller controls the duty cycle of the PWM signal of the solenoid valve based on the feedback data of the air pressure and the target air pressure value.

2. A design method for a dual closed-loop controller for rigid-soft coupled dexterous hand motion control, characterized in that: The design method includes: Step 1: Establish solenoid valve and aerodynamic models; Step 2: Based on the solenoid valve and aerodynamic model in step 1, design a pneumatic ring controller based on sliding mode control; Step 3: Based on the solenoid valve and aerodynamic model in step 1, design a PID position loop controller with feedforward compensation. Step 4: Combine the air pressure loop controller of the sliding mode control in step 2 and the PID position loop controller of the feedforward compensation in step 3 to form a complete dual closed-loop controller for the motion control of the rigid-soft coupled dexterous hand; Specifically, step 1 is as follows: for the air in the gas path, there is an ideal gas state equation: (1) Where, It is the air cavity driving air pressure; is the volume of compressible gas in the channel; is the mass of compressible gas in the channel; is the ideal gas constant for air; is the gas temperature; is a constant; By taking the derivative of formula (1), we can get: (2) Formula (2) can be simplified as: (3) (4) The relationship between gas pressure change and flow rate is obtained, where is the average mass flow rate of the gas.

3. The design method according to claim 2, characterized in that: Upstream and downstream pressure ratio Above critical pressure ratio When , the air produces subsonic flow in the valve: (5) Where, is the upstream and downstream pressure ratio; is the pressure upstream of the valve port; is the pressure downstream of the valve port; is the atmospheric pressure; Based on the small hole model under standard conditions, the air volume flow rate of the solenoid valve port when there is no gas leakage and the valve port is fully open can be calculated separately and mass flow : (6) (7) Where, is the air density under standard conditions; is the pressure downstream of the valve port; is the standard state temperature; is the actual temperature of the gas; is the sonic conductance of the valve port; is the critical pressure ratio of the valve port; Use a solenoid valve opening ratio To describe the actual average flow: (8) In the formula, the solenoid valve opening ratio Indicates the inflation process, the ratio Indicates the exhaust process; Simplified description of the solenoid valve opening ratio: (9) Where, is the linear ratio of valve opening; is the duty cycle of the PWM valve control signal; It is the dead zone of the solenoid valve.

4. The design method according to claim 2, characterized in that: Specifically, the step 2 is to establish the state equation of the system from formulas (4) to (9): (10) (11) Where, Input air pressure to the air cavity; is the duty cycle of the PWM valve control signal; is the disturbance term; simplify Equation (11) appropriately and let , the gas source pressure is , in formula (11) Calculated by formula (12): (12) Where, Inflate the dead zone of the solenoid valve; Bleed the dead zone of the solenoid valve; Represents the system charging and discharging mode; Agreement here Indicates that the solenoid valve is in a stopped state within the forward and reverse dead zone. Indicates that the charging solenoid valve is open, the exhaust solenoid valve is closed, and the solenoid valve group is working in the charging state. Indicates that the charging solenoid valve is closed, the exhaust solenoid valve is open, and the solenoid valve group is working in the exhaust state: (13)。 5. The design method according to claim 4, characterized in that: Design the integral sliding surface: (14) in, , , set the target pressure As the state tracking target value; the design goal is ,at this time, ; The construction index approaches the sliding mode as , using the hyperbolic tangent instead of the sign function reduces jitter: (15) Taking the derivative of (12) we get (16) Combining (13) and (14) we get (17) Combining (4)(9)(10)(15), the control law of SMC control can be calculated according to formulas (16) to (18): (18) (19) (20) In the formula is the control law of SMC control; It is the equivalent controller of SMC control; is the SMC control robust term.

6. The design method according to claim 5, characterized in that: When judging the system's inflation and deflation working mode, it is necessary to first calculate the controller control laws in the two modes according to the inflation and deflation modes, which are the controller outputs in the inflation state and and the controller output in the deflated state ; Then inflate the dead zone according to the debugging parameters and deflation dead zone Determine the working mode.

7. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 2 to 6 is implemented.

8. A method for controlling the motion of a soft dexterous finger, characterized in that: The control method uses a dual closed-loop controller for motion control of a rigid-soft coupled dexterous hand as described in claim 1 to achieve motion control of a soft dexterous finger.

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