A hybrid active disturbance rejection admittance control system of cervical vertebra rehabilitation robot

Abstract

The application provides a hybrid active disturbance rejection admittance control system of a cervical vertebra rehabilitation robot, relates to the technical field of admittance control, and adopts a pneumatic artificial muscle system as a driving element, the control system comprises an outer ring admittance controller, an inner ring active disturbance rejection controller and an adaptive combination valve; the outer ring admittance controller is used for adjusting an expected trajectory according to an error between an actual feedback force and an expected tracking force; the inner ring active disturbance rejection controller comprises a tracking differentiator, an extended observer and a nonlinear feedback controller and is used for inhibiting nonlinearity and external disturbance of the pneumatic artificial muscle system; the adaptive combination valve is used for controlling the inflation and deflation flow of the pneumatic artificial muscle system; wherein the output of the outer ring admittance controller is used as the input of the inner ring active disturbance rejection controller, and the output of the inner ring active disturbance rejection controller is used for controlling the adaptive combination valve. The application realizes effective inhibition of nonlinearity and external disturbance, and simultaneously considers the accuracy of position control and the flexibility of force output.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of admittance control, in particular to a hybrid active disturbance rejection admittance control system of a cervical vertebra rehabilitation robot. BACKGROUND

[0002] As an auxiliary rehabilitation device, the cervical vertebra rehabilitation robot plays an important role in improving the function of the cervical vertebra. The traditional cervical vertebra rehabilitation robot mainly adopts motor drive to realize traction action through mechanical structure. This method can achieve the purpose of cervical vertebra rehabilitation to some extent, but still has some limitations.

[0003] With the continuous development of automation technology, the control of force and energy, mechanical technology and medical technology are constantly integrated, and researchers have developed various cervical vertebra rehabilitation robots. For example, some researchers have designed an automatic robot that can perform cervical vertebra traction in a single extension spring and a cadaver model. The device can accurately apply traction force and maintain a steady state force and corresponding linear increase in actuator displacement during operation. Some researchers have invented a horizontal cervical vertebra rehabilitation robot, which realizes the accurate adjustment of the angle, direction and traction of cervical vertebra traction. To achieve multi-degree-of-freedom rehabilitation, some researchers have designed a six-degree-of-freedom cable-driven robot platform that can realize natural head and neck movement.

[0004] However, the existing cervical vertebra rehabilitation robot still faces some challenges. First, most devices use motor-driven end effectors, which have high control accuracy but strong rigidity and small allowable misalignment. If the maximum stretching displacement and angle of the rehabilitation patient are exceeded during traction, it is easy to cause cervical vertebra injury. Second, the existing control methods mainly include PID control, fuzzy control and adaptive control, which can improve the control performance of the system to some extent, but still cannot effectively solve the problems of nonlinearity and external disturbance.

[0005] Therefore, it is of great significance to develop a new type of cervical vertebra rehabilitation robot control system to improve the performance and safety of the cervical vertebra rehabilitation robot. SUMMARY

[0006] Therefore, the present application proposes a hybrid active disturbance rejection admittance control system of a cervical vertebra rehabilitation robot, which aims to solve the deficiencies of the existing cervical vertebra rehabilitation robot in control accuracy and safety. The system uses pneumatic artificial muscle as the driving element, combines an outer ring admittance controller and an inner ring active disturbance rejection controller, and an adaptive combination valve to effectively suppress nonlinearity and external disturbance, while considering the accuracy of position control and the flexibility of force output. The system can improve the control performance of the cervical vertebra rehabilitation robot, ensure the safety and comfort during traction, and provide more accurate, safe and effective technical support for cervical vertebra rehabilitation.

[0007] The technical scheme of the present application is implemented as follows: the present application provides a hybrid active disturbance rejection admittance control system of a cervical vertebra rehabilitation robot, the cervical vertebra rehabilitation robot adopts a pneumatic artificial muscle system as a driving element, and the control system comprises:

[0008] an outer ring admittance controller, an inner ring active disturbance rejection controller and an adaptive combination valve;

[0009] The outer ring admittance controller adopts a mass-spring-damper virtual dynamics model, which is used to adjust an expected trajectory according to an error between an actual feedback force and an expected tracking force;

[0010] The inner ring active disturbance rejection controller comprises a tracking differentiator, an extended observer and a nonlinear feedback controller, which are used to suppress nonlinearities and external disturbances of the pneumatic artificial muscle system and realize position control;

[0011] The adaptive combination valve is used to control the inflation and deflation flow of the pneumatic artificial muscle system.

[0012] The output of the outer ring admittance controller is taken as the input of the inner ring active disturbance rejection controller, and the output of the inner ring active disturbance rejection controller is used to control the adaptive combination valve, so as to realize position control of the cervical vertebra rehabilitation robot in the traction process.

[0013] On the basis of the above scheme, preferably, the force equation of the mass-spring-damper virtual dynamics model is as follows:

[0014]

[0015] In the formula, m r is an expected inertia matrix, b r is an expected damping matrix, k r is an expected stiffness matrix, e w =v d -v0, v d is a reference trajectory, v0 is an expected trajectory after the outer ring admittance controller, Δf=f e -f r >0, f r is an expected tracking force, and f e is an actual feedback force.

[0016] On the basis of the above scheme, preferably, the tracking differentiator is designed as follows:

[0017]

[0018]

[0019] In the formula, r0 is a tracking differentiator speed factor; h0 is a tracking differentiator filter factor; v1 is a tracking signal of an input signal v0 obtained by the tracking differentiator; and v2 is a differential signal of v1.

[0020] On the basis of the above scheme, preferably, the expression of the extended observer is as follows:

[0021]

[0022] In the formula, x p1 , x p2 and x p3 are states of the pneumatic artificial muscle system; w is a differential of x p3 ; z1, z2 and z3 are estimated observation values of x p1 , x p2 and x p3 respectively; e1 is an error of the angle observation value z1 and the output angle x p1 ; β 01 , β 02 and β 03 are gain coefficients of the extended observer; u0 is an output duty ratio; and b0 is a polynomial coefficient.

[0023] The function expression of fal(e1, a i , δ) is as follows:

[0024]

[0025] In the formula, δ i is a linear interval length; and a i is a feedback power.

[0026] On the basis of the above scheme, preferably, the expression of the nonlinear feedback controller is as follows:

[0027]

[0028] In the formula, ε i , i = 1, 2 is an error of v i after the tracking differentiator and the estimated observation value z i ; and β1 and β2 are proportional differential coefficients.

[0029] On the basis of the above scheme, preferably, the adaptive combination valve comprises two electric proportional valves, a control unit and a pressure sensor.

[0030] The air inlet of the first electric proportional valve is connected with an air compressor, and the air outlet is connected with the pneumatic artificial muscle; the air inlet of the second electric proportional valve is connected with the pneumatic artificial muscle, and the air outlet is communicated with the atmosphere.

[0031] The control unit is configured to adjust the opening degrees of the two electric proportional valves according to the output of the inner-loop active disturbance rejection controller.

[0032] The pressure sensor is configured to detect the internal pressure of the pneumatic artificial muscle system.

[0033] On the basis of the above scheme, preferably, the cervical vertebra rehabilitation robot comprises a seat, a displacement sensor, a tension sensor, a steel cable, a cervical vertebra support and a pneumatic artificial muscle system.

[0034] The pneumatic artificial muscle system is arranged side by side with the displacement sensor, and the lower end is fixed and the upper end is connected with the tension sensor.

[0035] On the basis of the above scheme, preferably, the traction mode of the cervical vertebra rehabilitation robot comprises continuous traction and intermittent traction.

[0036] The continuous traction is realized by fixed-point position control, and the intermittent traction is realized by an intermittent cervical vertebra stretching optimal control curve.

[0037] On the basis of the above scheme, preferably, the intermittent cervical vertebra stretching optimal control curve is generated based on a minimum jerk model, and the expression is as follows:

[0038]

[0039] wherein v t is the intermittent cervical vertebra stretching optimal control curve, T is the period of the intermittent cervical vertebra traction optimal control curve, n is the number of repetitions of the intermittent cervical vertebra traction optimal control curve, t is a time value, d is an interval time, t0 is the starting time of joint movement, t f is the stopping time of joint movement, v s0 is the initial position of joint movement, and v s1 is the stopping position of joint movement.

[0040] On the basis of the above scheme, preferably, the operation process of the control system is as follows:

[0041] S1 The outer-loop admittance controller receives the actual feedback force and the expected tracking force, calculates the error and adjusts the expected trajectory.

[0042] S2 The adjusted expected trajectory is input into the inner-loop active disturbance rejection controller.

[0043] S3 The tracking differentiator generates a smooth trajectory and a differential signal.

[0044] S4 The extended observer estimates the system state and the total disturbance.

[0045] S5 The nonlinear feedback controller calculates the control amount according to the output of the extended observer.

[0046] S6 control quantity is transmitted to the adaptive combination valve to adjust the inflation and deflation flow of the pneumatic artificial muscle system;

[0047] S7 the pneumatic artificial muscle system drives the cervical vertebra rehabilitation robot to perform traction action;

[0048] S8 displacement sensors and tension sensors feed back displacement and force information in real time to form a closed-loop control.

[0049] The present application has the following beneficial effects relative to the prior art:

[0050] (1) The control system provided by the present application combines an outer loop admittance controller and an inner loop active disturbance rejection controller to effectively suppress the nonlinearity and external disturbance of the pneumatic artificial muscle system, while ensuring the accuracy of position control and the compliance of force output. The system can adaptively adjust the expected trajectory according to the error between the actual feedback force and the expected tracking force, thereby ensuring the accuracy of position control during the traction of the cervical vertebra rehabilitation robot while effectively avoiding potential damage to the cervical vertebra caused by excessive tension;

[0051] (2) The pneumatic artificial muscle system is used as the driving element in the present application, which has better compliance and continuous deformation capability compared to traditional motor driving. This driving method can play a buffering protection role on the cervical vertebra during traction, thereby improving the comfort and safety of the rehabilitation process;

[0052] (3) The tracking differentiator is introduced into the inner loop active disturbance rejection controller of the present application, which can quickly track the input signal and generate smooth trajectory and differential signal, thereby effectively improving the signal-to-noise ratio and control quality of the system;

[0053] (4) The extended observer of the present application can accurately estimate the system state and total disturbance, and in combination with the nonlinear feedback controller, effectively overcomes the inherent nonlinearity, time-varying nature and susceptibility to external disturbance of the pneumatic artificial muscle system, thereby improving the accuracy of position control;

[0054] (5) The adaptive combination valve is used to control the inflation and deflation flow of the pneumatic artificial muscle system in the present application, which realizes more precise and flexible control of the pneumatic artificial muscle system through the coordinated work of the two electrical proportional valves, thereby further improving the response speed and control accuracy of the system;

[0055] (6) The present application provides two traction modes, continuous traction and intermittent traction. The optimal control curve based on the minimum jerk model is used in intermittent traction, which can minimize the discomfort during traction while ensuring the rehabilitation effect, thereby improving the comfort and safety. BRIEF DESCRIPTION OF DRAWINGS

[0056] In order to make the technical solutions in the embodiments of the present application or the prior art clearer, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description only need to be some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative labor.

[0057] Figure 1 Control system block diagram of the present application;

[0058] Figure 2 Schematic diagram of the pneumatic artificial muscle of the present application;

[0059] Figure 3 Schematic diagram of the three-element model of the pneumatic artificial muscle system of the present application;

[0060] Figure 4 Control block diagram of the inner-loop active disturbance rejection controller of the present application;

[0061] Figure 5 Comparison diagram of the set-point position control results of the inner-loop active disturbance rejection controller and the PID controller of the present application;

[0062] Figure 6 Comparison diagram of the optimal control curves of the intermittent cervical spine stretching of the inner-loop active disturbance rejection controller and the PID controller of the present application;

[0063] Figure 7 Trajectory tracking control experimental result diagram of embodiment 1 of the present application;

[0064] Figure 8 Schematic diagram of the relationship between the expected force and the tension of embodiment 1 of the present application;

[0065] Figure 9 Trajectory tracking control experimental result diagram of embodiment 2 of the present application;

[0066] Figure 10 Schematic diagram of the relationship between the expected force and the tension of embodiment 2 of the present application. DETAILED DESCRIPTION

[0067] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0068] As Figure 1As shown, the application provides a hybrid active disturbance rejection admittance control system of a cervical vertebra rehabilitation robot, the cervical vertebra rehabilitation robot adopts a pneumatic artificial muscle system as a driving element, and the control system comprises:

[0069] an outer ring admittance controller, an inner ring active disturbance rejection controller and an adaptive combination valve;

[0070] The outer ring admittance controller adopts a mass-spring-damper virtual dynamics model, is used for adjusting an expected trajectory according to an error between an actual feedback force and an expected tracking force, and realizes position control.

[0071] The inner ring active disturbance rejection controller comprises a tracking differentiator, an extended observer and a nonlinear feedback controller, is used for suppressing nonlinearities and external disturbances of the pneumatic artificial muscle system, and realizes position control.

[0072] The adaptive combination valve is used for controlling the inflation and deflation flow of the pneumatic artificial muscle system.

[0073] The output of the outer ring admittance controller is taken as the input of the inner ring active disturbance rejection controller, and the output of the inner ring active disturbance rejection controller is used for controlling the adaptive combination valve, so that the position control of the cervical vertebra rehabilitation robot in the traction process is realized.

[0074] Specifically, the cervical vertebra rehabilitation robot of the application adopts a pneumatic artificial muscle system (PAM) as a driving element, the main body of which mainly comprises a seat, a displacement sensor, a tension sensor, a steel cable and a cervical vertebra support, the PAM is placed side by side with the displacement sensor, the lower end is fixed, the upper end is connected with the tension sensor, and the tension sensor is connected with the cervical vertebra support through the cable. In order to avoid damage to the cervical vertebra during the debugging process during the test, a group of springs are used to simulate the cervical structure, the lower end of the spring is fixed, and the upper end of the spring is connected to the tension sensor through the cable. The PAM is inflated and deflated, which can drive the up and down stretching of the spring, simulate the process of cervical traction, and the displacement sensor and the tension sensor can respectively monitor the displacement and the tension in real time.

[0075] The control system of the application controls the inflation and deflation flow of the PAM by combining the outer ring admittance controller, the inner ring active disturbance rejection controller and the adaptive combination valve, the adaptive combination valve comprises two electric proportional valves, a control unit and a pressure sensor; the air inlet of the first electric proportional valve is connected with an air compressor, and the air outlet is connected with the pneumatic artificial muscle; the air inlet of the second electric proportional valve is connected with the pneumatic artificial muscle, and the air outlet is connected with the atmosphere; the control unit is used for adjusting the opening degree of the two electric proportional valves according to the output of the inner ring active disturbance rejection controller; and the pressure sensor is used for detecting the internal pressure of the pneumatic artificial muscle system, predicting and defining data, and transmitting the pressure data to the upper computer through the control unit.

[0076] In the PAM inflation and deflation process, low noise air compressor is used to inflate the PAM, displacement sensor is used to detect the displacement of the PAM inflation and deflation (corresponding to the displacement of cervical traction), tension sensor is used to detect the tension generated by the PAM (corresponding to the tension of cervical traction), the air inlet of the electric proportional valve 1 is connected with the air compressor and the PAM respectively, when the valve 1 is opened, the air compressor sends gas into the PAM, the volume of the PAM increases, the radial shortens to generate downward tension. The air inlet of the electric proportional valve 2 is connected with the PAM, when the valve 2 is opened, the PAM expels the internal gas, the volume of the PAM decreases, the radial lengthens to generate contraction force. By adjusting the duty cycle of the input PWM wave of the valves 1 and 2, the acceleration when the displacement changes is controlled.

[0077] Please refer to Figure 2 , the PAM used in the application is a flexible controller composed of an internal rubber cylinder and an external fiber layer, which will expand radially and contract axially when inflated, and vice versa when deflated. Figure 2 In the formula, L is the length, D is the width, and the volume V of the PAM is q :

[0078]

[0079] The electric proportional valve EPV of the application has two, when modeling, Sanville flow formula is used to calculate the mass flow q of ideal gas m :

[0080]

[0081] In the formula, C q is the flow coefficient of high-speed on-off valve; A v is the effective valve port area; K=1.4 is the specific heat ratio of air, R=287 N·m / kg·k is the ideal gas constant, T is the absolute temperature of the gas source, p a , p b are the inlet and outlet pressures of the valve.

[0082] When the temperature in the electric proportional valve is constant, the flow is related to the valve opening area, and the duty cycle of the PWM wave determines the valve opening area and further affects the outlet pressure p b . Therefore, q m is equivalent to:

[0083] q m =K a u0+K b p b (3)

[0084] Where K a , K b are undetermined coefficients, and u0 is the output duty cycle.

[0085] In this invention, the adiabatic inflation / deflation process of the pneumatic artificial muscle chamber, despite its limited internal volume, still obeys the thermodynamic energy conservation equation. Therefore, the energy conservation equation for the pneumatic artificial muscle can be obtained as follows:

[0086]

[0087] In the formula, P q V is the internal driving air pressure for pneumatic artificial muscles. q q represents the volume of the pneumatic artificial muscle chamber. m1 For the net mass flow rate entering the pneumatic artificial muscle chamber, q m1 =q m2 -q m3 Where q m2 q is the mass flow rate of air inflating the chamber of the pneumatic artificial muscle. m3 The mass flow rate for venting the pneumatic artificial muscle chamber.

[0088] A schematic diagram of a pneumatic artificial muscle system is shown below. Figure 3 As shown, in the three-element model of pneumatic artificial muscle, it is equivalent to a structure consisting of a damping element, a spring element, and a contraction element connected in parallel. Based on this, a dynamic model of the pneumatic artificial muscle system is established:

[0089]

[0090] Where F t Let F be the tension force exerted by the spring on the pneumatic artificial muscle, and x be the displacement of the pneumatic artificial muscle. c (P q ), F s (x,P q The forces represented by ) represent the contractile force, damping force, and spring force of the pneumatic artificial muscle, respectively, and can be expressed as:

[0091]

[0092] In the formula, C(P) q ), K1(P q K2(P) q () represent the damping coefficient, first-order spring constant, and second-order spring constant, respectively; f1, f2, c1, c2, k 11 k 12 k 21 k 22 All are unknown polynomial coefficients. Substituting equation (6) into equation (5) and rearranging, we get:

[0093]

[0094] Substitute formula (1), formula (3) and formula (4) into formula (7), and after arrangement, the following formula is obtained:

[0095]

[0096] Substitute formula (1) into formula (7), and after arrangement, the following formula is obtained: s The expression of the total disturbance of the system is as follows:

[0097]

[0098] Substitute formula (1) into formula (7), and after arrangement, the following formula is obtained: Write the system (8) as a state space expression:

[0099]

[0100] Specifically, the inner loop active disturbance rejection controller of the application is to ensure the control accuracy of the system when facing variable load, unknown disturbance and nonlinear terms. The control block diagram is as shown in the figure. Figure 4 The inner loop active disturbance rejection controller includes a tracking differentiator, an extended observer and a nonlinear feedback controller.

[0101] The tracking differentiator can quickly track the input signal, has no overshoot and no chatter, and can improve the signal-to-noise ratio of the signal, and output a differential signal with high quality. The tracking differentiator of the application is a second-order tracking differentiator, which is designed as follows:

[0102]

[0103] In the formula, r0 is a tracking differentiator speed factor; h0 is a tracking differentiator filter factor; v1 is a tracking signal of the input signal v0 obtained by the tracking differentiator; and v2 is a differential signal of v1.

[0104] f han The specific expression of (v1-v0, v2, r0, h0) is designed as follows:

[0105]

[0106] In the formula:

[0107]

[0108] The extended observer ESO of the application is used to estimate the state variable and the total disturbance f s of the system. Expand the total disturbance f s in formula (9) into a new state The new state space expression of the system is as follows:

[0109]

[0110] In the formula, x p1 , and is the state of the pneumatic artificial muscle system; is continuously derivable, w is The differential of. The designed third-order ESO expression is as follows:

[0111]

[0112] In the formula, z1, z2 and z3 are respectively x p1 , and is the error of the angle observation z1 and the output angle x p1 ; β 01 , β 02 and β 03 are gain coefficients of the extended observer; u0 is the output duty ratio; b0 is a polynomial coefficient. The function expression of fal(e1, a i , δ) is as follows:

[0113]

[0114] In the formula, δ i is the linear interval length; a i is the feedback power.

[0115] In the application, in order to accelerate the response speed, the nonlinear feedback controller adopts a non-smooth feedback mode, so that the steady-state error decreases in an exponential form, and the specific expression is as follows:

[0116]

[0117] In the formula, ε i , i=1, 2 is the error of v i after passing through the tracking differentiator and the estimated observation z i ; β1 and β2 are proportional differential coefficients.

[0118] Finally, the ESO estimated total disturbance z3 is compensated into the control quantity, so as to improve the control performance, and the specific expression is as follows:

[0119]

[0120] The compensated u0 is taken as the input, and after passing through the dead zone nonlinear system, the input dead zone nonlinearity is eliminated, and then the high-speed on-off valve is taken as the charge and discharge control duty ratio instruction, which is recorded as u. When u0 is positive and non-zero, the control rate u=u a is taken as the duty ratio of the charging valve, and the charging amount of the PAM is controlled; when u0 is less than 0, the control rate u=-u b is taken as the duty ratio of the charging valve, and the discharge flow of the PAM is controlled.

[0121] Specifically, the output of the outer loop admittance controller of the present application is taken as the input of the inner loop active disturbance rejection controller, and the output of the inner loop active disturbance rejection controller is used to control the adaptive combination valve to realize the position control of the cervical vertebra rehabilitation robot in the traction process. That is, the control system of the present application is essentially a two-stage control system of the flexibility-adaptive cervical vertebra trajectory tracking control, in which the outer loop admittance controller is used in the high layer, the desired trajectory v d is adjusted according to the error between the actual feedback force and the expected tracking force, and the position instruction v0 is sent to the inner loop active disturbance rejection controller in the bottom layer, so as to realize the feedback force-position tracking control.

[0122] The admittance controller of the present application converts the physical system into a mass-spring-damper virtual dynamics model, and the force equation is:

[0123]

[0124] In the formula, m r is the expected inertia matrix, b r is the expected damping matrix, and k r is the expected stiffness matrix; e w =v d -v0, v d is the reference trajectory, and v0 is the expected trajectory after the outer loop admittance controller; Δf=f e -f r >0, f r is the expected tracking force, and f e is the actual feedback force.

[0125] In the present application, the traction mode of the cervical vertebra rehabilitation robot includes continuous traction and intermittent traction; wherein the continuous traction is realized by using the fixed point position control, and the intermittent traction is realized by using the intermittent cervical vertebra stretching optimal control curve.

[0126] The intermittent cervical vertebra stretching optimal control curve is generated based on the minimum jerk model, and the expression of the minimum jerk model is as follows:

[0127]

[0128]

[0129] In the formula, t0 is the starting time of joint movement, is the initial position of joint movement, t1 is the stopping time of joint movement, is the stopping position of joint movement, is the linear jerk, and is the third derivative of the displacement with respect to time.

[0130] On the basis of the minimum jerk model, the optimal cervical vertebra stretching movement curve v t is obtained by conversion through the variational method:

[0131]

[0132] In order to realize intermittent cervical spine stretching, a delay time of 1 / 4T is kept when moving to the lowest position and the highest position respectively, so that a certain time is kept when moving to the highest position for traction treatment, and the cervical spine of the patient can be rested and relaxed when moving to the lowest position, preparing for the next stretching. The optimal curve law of intermittent cervical spine stretching is finally obtained by adding the delay time in formula (19):

[0133]

[0134] Wherein, v t is the optimal control curve of intermittent cervical spine stretching, T is the period of the optimal control curve of intermittent cervical spine traction, n is the number of repetitions of the optimal control curve of intermittent cervical spine traction, t is the time value, d is the interval time, t0 is the starting time of joint movement, t f is the stopping time of joint movement, v s0 is the initial position of joint movement, v s1 is the stopping position of joint movement.

[0135] Specifically, in an embodiment of the present application, the operation process of the control system is as follows:

[0136] S1 The outer loop admittance controller receives the actual feedback force and the desired tracking force, calculates the error and adjusts the desired trajectory.

[0137] Specifically, the actual feedback force is the actual force acting on the neck measured by the tension sensor; the desired tracking force is the preset ideal traction force. The actual feedback force is compared with the desired tracking force to obtain an error value. According to the error value, the mass-spring-damper virtual dynamics model is used to adjust the desired trajectory.

[0138] S2 The adjusted desired trajectory is input into the inner loop active disturbance rejection controller.

[0139] Specifically, the adjusted desired trajectory output by the outer loop admittance controller is transmitted to the inner loop active disturbance rejection controller.

[0140] S3 The tracking differentiator generates a smooth trajectory and a differential signal.

[0141] Specifically, the tracking differentiator receives the adjusted desired trajectory. A smooth trajectory is generated: a specific algorithm is used to smooth the input signal. A differential signal is generated: the rate of change of the smoothed signal is calculated.

[0142] S4 The extended observer estimates the system state and total disturbance.

[0143] Specifically, the extended observer estimates the system state: including the position, velocity, etc. of the pneumatic artificial muscle system. Estimate the total disturbance: including system nonlinearities, external disturbances, etc.

[0144] S5 The nonlinear feedback controller calculates the control amount according to the output of the extended observer.

[0145] Specifically, the nonlinear feedback controller receives the output of the extended observer. Calculate the control amount: according to the estimated value of the system state and the total disturbance, calculate the required control signal.

[0146] S6 The control amount is transmitted to the adaptive combination valve to adjust the inflation and deflation flow of the pneumatic artificial muscle system.

[0147] Specifically, the adaptive combination valve receives the control amount of the nonlinear feedback controller. Adjust the inflation and deflation flow of the pneumatic artificial muscle system: control the opening of the two electrical proportional valves to achieve precise airflow control.

[0148] S7 The pneumatic artificial muscle system drives the cervical vertebra rehabilitation robot to perform traction action.

[0149] Specifically, the pneumatic artificial muscle system performs action, according to the change of inflation and deflation flow, the pneumatic artificial muscle contracts or relaxes. Drive the cervical vertebra rehabilitation robot to perform traction action: transmit force through steel cable and neck support, achieve traction on cervical vertebra.

[0150] S8 Displacement sensor and tension sensor feedback displacement and force information in real time, forming a closed loop control.

[0151] Specifically, in the control process, the displacement sensor measures the traction distance in real time. The tension sensor measures the force in real time. The displacement and force information is fed back to the control system, especially the outer loop admittance controller. Form a closed loop control: through continuous feedback and adjustment, ensure that the system can accurately perform traction action according to the expected trajectory and force.

[0152] In an embodiment of the present application, the inner loop active disturbance rejection controller (ADRC) proposed in the present application and the traditional PID controller are tested in two groups to compare the performance of ADRC and PID.

[0153] The first group of tests is the trajectory tracking comparison test. In this test, a step signal with a traction displacement of 30mm is given. The ADRC and PID controller parameters are set as follows:

[0154] ADRC: h0=0.01, r0=300, b0=1000, β 01 =20, β 02 =1200, β 03 =8000, β1=1, β2=2,

[0155] δ1=0.03, δ2=0.3.

[0156] PID: k p = 0.05, k i = 0.08, k d = 0.001.

[0157] The results of the first group of tests are shown in Figure 5 Fig. 1. Figure 5 Fig. 1(a) is the response curve of the ADRC control experiment, and Figure 5 Fig. 1(b) is the response curve of the PID controller. It can be seen from Figure 5 Fig. 1 that the output v1 of the tracking differentiator of the ADRC stably and quickly tracks the given signal v0. The actual output x p1 all quickly and accurately reach the required input v0. The observed value z1 is also almost consistent with x1. According to the results of the comparative test, the root mean square error of the system after reaching the steady state under the ADRC control is 0.112 mm, and the average absolute error is 0.084. In contrast, the PID controller has much larger values of the two indicators. The transition process time of the ADRC to reach the steady state is 1.02 s, while the PID takes 8.41 s. Table 1 compares the response time t, the root mean square error (RSME), and the average absolute error (MAE) of the two controllers. It can be seen that, in terms of response time, stability, and accuracy, the control effect of the ADRC is better than that of the PID.

[0158] Table 1. Response time, root mean square error (RSME), and average absolute error (MAE) of ADRC and PID

[0159] Controller Response time (s) RSME (°) MAE (°) ADRC 1.02s 0.112 0.084 PID 8.41s 1.004 1.004

[0160] The second group of tests is an intermittent cervical spine stretching optimal control curve trajectory tracking control experiment of the ADRC and the PID with a frequency of 0.01 Hz and an amplitude of 30 mm. Compared with the first group of tests, the ADRC parameters of this group of tests are adjusted to β1=1, β2=2, and the rest of the parameters are consistent with those of the first group of tests; the PID parameters are adjusted to k p = 0.2, k i = 0.5, k d = 0.001. In this group of tests, the root mean square error and the average absolute error of the intermittent cervical spine traction optimal control curve trajectory tracking control of the ADRC and the PID are shown in Table 2.

[0161] Table 2. Root mean square error (RSME) and average absolute error (MAE) of intermittent cervical spine traction optimal control curve trajectory tracking control of ADRC and PID

[0162]

[0163]

[0164] The results of the second group of tests are shown in Figure 6 wherein, Figure 6 (a) and (c) in (b) are the output control curves of ADRC and PID, Figure 6 (b) is the error curve of the output of the two controllers. It can be seen from Figure 6 that since the control curve is an intermittent curve, the tension of the external load spring on the pneumatic muscle is also intermittent, and the PID cannot well adapt to the influence of the changing force on the system. If the PID parameters are adjusted to be small, the upward movement and downward movement curves cannot be tracked quickly and accurately. In this group of tests, the parameters of the PID are adjusted to be large, although the tracking effect of the changing curve is better, but in the trough, the control accuracy is poor and easy to fluctuate. The ADRC controller of the application increases the observer ESO, which can well estimate the influence of the changing force of the spring on the system, and compensates the influence of the intermittent spring force on the system in the nonlinear controller. Therefore, in the whole trajectory tracking process, whether it is a peak or a trough, it can well track the given curve, so that the whole tracking error is smaller than that of the PID controller.

[0165] Through the two groups of tests, it is verified that the ADRC can overcome the nonlinearity of the pneumatic muscle, the disturbance of the external force on the system, etc., and realize high-precision position control. The following will provide two embodiments to verify the soft control effect of the control system of the application in cervical traction. In the embodiment 1 and the embodiment 2, the parameter settings of the outer loop admittance controller are as follows: m r = 1, b r = 0.03, k r = 8, and the expected tracking force is set to f r 20N.

[0166] Embodiment 1

[0167] The traction mode of this embodiment is continuous traction, which is realized by fixed-point position control. The control test results of this embodiment are shown in Figure 7 . Figure 7 (a) is the trajectory replanning result, Figure 7 (b) is the trajectory tracking control result of the expected position. The relationship between the expected tracking force and the feedback tension of this embodiment is shown in Figure 8 . Figure 7 and Figure 8 It can be analyzed that when the feedback tension f e ≤ 20N, the outer loop admittance controller does not work, and as the displacement increases, the feedback tension becomes larger and larger; when it is greater than the critical value 20N, it enters the outer loop admittance controller, and the displacement difference ew This will cause the reference trajectory v d The change occurs, resulting in the desired trajectory v0 (see...). Figure 7 (a) Then ADRC trajectory tracking control is performed, from Figure 7 The feedback trajectory x can be seen in (b). q1 It can track the desired trajectory v0 very well. After passing through the outer loop admittance controller, the feedback tension f can be seen. e With a tension f greater than expected r Subsequently, it will change as the feedback position changes, gradually decreasing until it eventually approaches the given tension f. r (See Figure 8 This achieves a compliant traction effect.

[0168] Example 2

[0169] The traction method in this embodiment is intermittent traction, achieved using the optimal control curve for intermittent cervical spine stretching. The control test results of this embodiment are as follows: Figure 9 As shown. Figure 9 (a) shows the replanning result of the trajectory after passing through the outer loop admittance controller. Figure 9 (b) shows the trajectory tracking curve after passing through the outer loop admittance controller. The relationship between the expected tracking force and the feedback tension in the admittance control based on the optimal control curve of intermittent cervical traction in this embodiment is as follows: Figure 10 As shown. By Figure 9 and Figure 10 Analysis shows that, firstly, the feedback pull increases continuously with the increase of displacement; then, when the feedback pull exceeds the desired pull, it enters the outer loop admittance controller, thereby changing the desired trajectory; finally, it enters ADRC to achieve the desired trajectory tracking control. Similarly, if the feedback pull is too large, it is adjusted to approach the desired pull, thus regulating the traction force of the cervical traction rehabilitation robot during rehabilitation work and avoiding damage to the cervical spine caused by excessive pull.

[0170] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hybrid active disturbance rejection admittance control system of a cervical rehabilitation robot, characterized by, The cervical vertebra rehabilitation robot adopts a pneumatic artificial muscle system as a driving element, and the control system comprises: an outer loop admittance controller, an inner loop active disturbance rejection controller and an adaptive combination valve; the outer loop admittance controller adopts a mass-spring-damper virtual dynamics model for adjusting an expected trajectory according to an error between an actual feedback force and an expected tracking force; the inner loop active disturbance rejection controller comprises a tracking differentiator, an extended observer and a nonlinear feedback controller for suppressing nonlinearity and external disturbance of the pneumatic artificial muscle system and realizing position control; the tracking differentiator is designed as follows: ； ； ； wherein is a tracking differentiator velocity factor; is a tracking differentiator filter factor; is an input signal to the tracking differentiator is a tracking signal; is a derivative signal of is a derivative signal of the extended observer is expressed as follows: ； ； wherein , and are states of the pneumatic artificial muscle system; is a differential of , and are estimated observation values of , and respectively; is an angle observation value and an error of an output angle ; , and are gain coefficients of the extended observer; is an output duty ratio; is a polynomial coefficient; The function expression is as follows: ； wherein is a linear interval length; is a feedback power. the nonlinear feedback controller is expressed as follows: ； wherein is the output of the tracking differentiator and the estimated observation error, , is the proportional differential coefficient; the adaptive combination valve is used for controlling the inflation and deflation flow of the pneumatic artificial muscle system; the adaptive combination valve comprises two electric proportional valves, a control unit and a pressure sensor; the air inlet of the first electric proportional valve is connected with an air compressor, and the air outlet is connected with the pneumatic artificial muscle; the air inlet of the second electric proportional valve is connected with the pneumatic artificial muscle, and the air outlet is communicated with the atmosphere; the control unit is used for adjusting the opening degrees of the two electric proportional valves according to the output of the inner loop active disturbance rejection controller; and the pressure sensor is used for detecting the internal pressure of the pneumatic artificial muscle system; wherein the output of the outer loop admittance controller is taken as the input of the inner loop active disturbance rejection controller, and the output of the inner loop active disturbance rejection controller is used for controlling the adaptive combination valve, so as to realize the position control of the cervical vertebra rehabilitation robot in the traction process.

2. The hybrid active disturbance rejection admittance control system of a cervical rehabilitation robot according to claim 1, wherein, the force equation of the mass-spring-damper virtual dynamics model is as follows: ； wherein is a desired inertia matrix, is a desired damping matrix, is a desired stiffness matrix; , is a reference trajectory, is a desired trajectory after the outer loop admittance controller; , is a desired tracking force, is an actual feedback force.

3. The hybrid active disturbance rejection admittance control system of a cervical rehabilitation robot according to claim 1, wherein, The cervical vertebra rehabilitation robot comprises a seat, a displacement sensor, a tension sensor, a steel cable, a cervical vertebra support and a pneumatic artificial muscle system; wherein the pneumatic artificial muscle system is placed side by side with the displacement sensor, the lower end is fixed, and the upper end is connected with the tension sensor; the tension sensor is connected with the cervical vertebra support through the cable.

4. The hybrid active disturbance rejection admittance control system of a cervical rehabilitation robot according to claim 1, wherein, The traction mode of the cervical vertebra rehabilitation robot comprises continuous traction and intermittent traction; wherein the continuous traction is realized by fixed-point position control, and the intermittent traction is realized by an intermittent cervical vertebra stretching optimal control curve.

5. The hybrid active disturbance rejection admittance control system of a cervical rehabilitation robot according to claim 4, wherein, The intermittent cervical vertebra stretching optimal control curve is generated based on a minimum jerk model, and the expression is as follows: ； ； ； ； ； wherein, is an optimal control curve for intermittent cervical spine stretching, is a period of the optimal control curve for intermittent cervical spine traction, is a number of repetitions of the optimal control curve for intermittent cervical spine traction, is a time value, is an interval time, is a joint motion start time, is a joint motion stop time, is a joint motion initial position, is a joint motion stop position.

6. The hybrid active disturbance rejection admittance control system of a cervical rehabilitation robot according to claim 1, wherein, the operation process of the control system is as follows: S1 the outer loop admittance controller receives the actual feedback force and the expected tracking force, calculates the error and adjusts the expected trajectory; S2 the adjusted expected trajectory is input into the inner loop active disturbance rejection controller; S3 the tracking differentiator generates a smooth trajectory and a differential signal; S4 the extended observer estimates the system state and the total disturbance; S5 the nonlinear feedback controller calculates the control amount according to the output of the extended observer; S6 the control amount is transmitted to the adaptive combination valve to adjust the inflation and deflation flow of the pneumatic artificial muscle system; S7 the pneumatic artificial muscle system drives the cervical vertebra rehabilitation robot to perform the traction action; S8 the displacement sensor and the tension sensor feed back the displacement and force information in real time to form a closed loop control.

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