CN115816453A - TDE-based adaptive supercoiled multivariate fast terminal sliding mode control method - Google Patents

TDE-based adaptive supercoiled multivariate fast terminal sliding mode control method Download PDF

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CN115816453A
CN115816453A CN202211531085.7A CN202211531085A CN115816453A CN 115816453 A CN115816453 A CN 115816453A CN 202211531085 A CN202211531085 A CN 202211531085A CN 115816453 A CN115816453 A CN 115816453A
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mechanical arm
tde
supercoiled
constraint
joint
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商巍
邹宇晗
李立军
章正飞
李靖
刘宇帆
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Zhejiang Qiantang Robot And Intelligent Equipment Research Co ltd
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Zhejiang Qiantang Robot And Intelligent Equipment Research Co ltd
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Abstract

The invention provides a TDE-based adaptive supercoiled multivariate rapid terminal sliding mode control method, which ensures high-precision trajectory tracking control of a cable-driven mechanical arm under a complex unknown uncertainty condition. Firstly, designing an error range of a joint, ensuring that the deviation between the position of the joint and an expected contour is not too large while ensuring the safety performance of a manipulator, and estimating and compensating the residual lumped system dynamics by using time-lag estimation. Secondly, carrying out design analysis on the angle error expectation by using a safety constraint function, and processing the constraints of different sections in a unified system architecture; through strict analysis, the problem of the motion trail of the mechanical arm with output constraint and uncertainty is solved. The supercoiled adaptive control effectively ensures the algorithm to meet the rapid, accurate and robust convergence under all constraint conditions in operation, and the stability of the closed-loop control system is analyzed by utilizing the Lyapunov method.

Description

TDE-based adaptive supercoiled multivariate fast terminal sliding mode control method
Technical Field
The invention belongs to the technical field of mechanical arm control, and relates to a TDE-based adaptive supercoiled multivariable rapid terminal sliding mode control method for a cable-driven mechanical arm with error safety constraint.
Background
Aiming at the problem of control precision of the mechanical arm, a great deal of research is carried out by a plurality of scholars, han S I designs a robust PID controller by combining robust control and PID control to realize the track tracking control [ 1 ] of the mechanical arm, J.xu provides a specified performance controller based on a Linear Extended State Observer (LESO), the problem of stabilization of a complex transformation system is solved, and the control precision [ 2 ] is further improved. Xu provides an orthogonal fuzzy PID intelligent control method [ 3 ], and compared with fuzzy PID orthogonal fuzzy PID, the accuracy of the system can be further improved. Most of the work in the literature that considers the joint tracking problem does not address the problem of error constraints during operation. However, to ensure accurate and safe operation of the cable driven robot, error constraints are required to be non-negligible. In the case of normal control, the control objective can be indicated when the error of the system can be gradually reduced from the initial position to the desired position to a very small value, i.e. the error is within the control range. Some positional ranges are unsafe due to mechanical control structure limitations, and the range is time-varying. If an emergency occurs, a huge deviation is caused, the error floats in an unpredictable range, and people cannot react in time, so that an overlarge movement error of a mechanical system can be caused, the mechanical system collides with the outside, and safety problems and economic losses are caused.
To solve the error constraint problem and to ensure the specified position tracking performance of the robot manipulator, zhou proposes a new constraint error variable [ 4 ] similar to a sliding mode surface. Li Y et al solved the output constraint problem due to physical and environmental limitations by constructing the Lyapunov function of the integral barrier [ 5 ]. And designing a controller by using the traditional logarithm Lyapunov function in the W.He to realize the track tracking control of the robot arm under the full-state constraint. 【6】 However, most of these approaches focus on input or output security constraints, and do not meet time-varying and asymmetric security constraints for position errors.
The control method based on the asymmetric constraint of the mechanical arm has many achievements, and Z.Kai provides a neural adaptive tracking control method aiming at an uncertain robot manipulator constrained in an asymmetric and time-varying holostate under the condition of not relating to feasible conditions, and the scheme can adapt to the asymmetric but time-varying motion constraint [ 7 ]. Xu presents a new Iterative Learning Control (ILC) scheme for tracking the non-repetitive reference trajectory problem of robotic manipulators over iterative domains with different trial lengths, subject to the asymmetric constraint requirements of joint angles [ 8 ]. Zhu proposes a self-adaptive timing estimation algorithm for an uncertain robot, and can avoid measuring acceleration signals (9) in the estimation process.
Overall, residual linkage dynamics, motor dynamics and collective uncertainty in the model parameters are difficult to obtain with conventional methods, and using TDE can be subject to estimation errors, especially when the system contains fast time-varying dynamics, which can lead to degradation of control performance. It is therefore necessary to develop a TDE-based control scheme with fast convergence and high control accuracy.
The relevant references are as follows:
【1】Han S I,Lee J M.Decentralized neural network control for guaranteed tracking error constraint of a robot manipulator[J].International Journal of Control,Automation and Systems,2015,13(4):906-915.
【2】Xu J,Qiao L.Robust Adaptive PID Control of Robot Manipulator with Bounded Disturbances[J].Mathematical Problems in Engineering,2013,2013(pt.13):1-13.
【3】Xu B,Ji S,Zhang C,et al.Linear-extended-state-observer-based prescribed performance control for trajectory tracking of a robotic manipulator[J].Industrial Robot,2021,ahead-of-print(ahead-of-print).
【4】Zhou,Chen,Liu.Design and Analysis of a Drive System for a Series Manipulator Based on Orthogonal-Fuzzy PID Control[J].Electronics,2019,8(9):1051-
【5】Li Y,Yang C,Yan W,et al.Admittance-based adaptive cooperative control for multiple manipulators with output constraints[J].IEEE transactions on neural networks and learning systems,2019,30(12):3621-3632.
【6】He W,Chen Y,Yin Z.Adaptive neural network control of an uncertain robot with full-state constraints[J].IEEE transactions on cybernetics,2015,46(3):620-629.
【7】Kai Z,Song Y.Neuroadaptive Robotic Control Under TimeVarying Asymmetric Motion Constraints:A Feasibility-Condition-Free Approach[J].IEEE Transactions on Cybernetics,2018,PP:1-10.
【8】Xu J.Iterative Learning Control for Robot Manipulators with NonRepetitive Reference Trajectory,Iteration Varying Trial Lengths,and Asymmetric Output Constraints[C]//2020American Control Conference(ACC).2020.
【9】Zhu C,Jiang Y,Yang C.Fixed-time Parameter Estimation and Control Design for Unknown Robot Manipulators with Asymmetric Motion Constraints[J].International Journal of Control,Automation and Systems,2022,20(1):268-282.
disclosure of Invention
In order to overcome the defects of the prior art, the invention designs the supercoiled controller based on asymmetric error constraint by adopting a time delay estimation method aiming at the problem of high-precision track tracking of the cable driving mechanical arm. According to the method, the error range is controlled by utilizing safety constraint, and the supercoiled design of the controller ensures that the mechanical arm meets the safety constraint in the aspect of control error. Meanwhile, joint position error constraints are designed by utilizing barrier functions. The method reduces the position error of the mechanical arm, and the track of the mechanical arm can be overlapped with the expected track to a great extent.
The technical scheme adopted by the invention is as follows: a TDE-based adaptive supercoiled multivariate fast terminal sliding mode control method comprises the following steps:
step 1, establishing a dynamic model of a mechanical arm, wherein the dynamic model is used for describing the state of the mechanical arm of a machine;
step 2, parameters in the dynamic model are estimated by using TED delay;
step 3, designing the slide film surface to facilitate the design of the next control method, and the method comprises the following substeps;
step 3.1, introducing safety constraint on joint position errors, and setting a safety range for the errors between the actual joint position and the expected joint position, so that the safety range has an upper limit and a lower limit to ensure the accurate and normal operation of the cable-driven mechanical arm;
step 3.2, designing and analyzing the angle error expectation by utilizing a safety constraint function and combining a barrier function, and processing the constraints of different sections in a unified system structure;
3.3, designing a slip form surface according to the joint position kinematics principle of the mechanical arm;
and 4, designing the terminal sliding mode controller by using the sliding film surface.
Further, the dynamical model of the mechanical arm with n degrees of freedom established in step 1 is represented as:
Figure BDA0003976051090000031
Figure BDA0003976051090000032
Figure BDA0003976051090000033
wherein J and d m Is the motor inertia and damping matrix, q and theta are the joint and motor position vectors,
Figure BDA0003976051090000034
representing the first and second derivatives of q and theta, respectively, M (q) is an inertia matrix,
Figure BDA0003976051090000035
is the coriolis/centrifuge matrix, g (q) is the attractive force,
Figure BDA0003976051090000036
is the friction vector, τ m And τ s Control torque and joint compliance torque, d, respectively, given to the motor s To damp the matrix, k s Is a joint stiffness matrix, τ d Representing a lumped unknown uncertainty;
to facilitate the use of the TDE scheme, substitute (2) into (1), apply constant parameters
Figure BDA0003976051090000037
Obtaining:
Figure BDA0003976051090000038
wherein the expression of f is:
Figure BDA0003976051090000039
further, in step 2, the TED scheme is used to obtain an estimated value of f
Figure BDA00039760510900000310
Figure BDA0003976051090000041
Where Δ t is the delay time, the kinetic model (4) is substituted into (6) and is available:
Figure BDA0003976051090000042
as can be seen from (6) and (7), the purpose of the TED scheme is to estimate the lumped system dynamics using only the time-lag values of the control and acceleration signals, and then to give a model-free scheme;
in engineering applications, u s (t- Δ t) may be represented by u s Is obtained by numerical differentiation
Figure BDA0003976051090000043
Figure BDA0003976051090000044
Wherein, the time node t 0 At ≧ 2 Δ t, t ≦ 2 Δ t at the initial stage, q (t) has the actual measurement value, and q (t-2 Δ t) will be manually zeroed, possibly resulting in strong fluctuations, and therefore (8) is used to mitigate the strong fluctuations that may exist.
Further, the specific implementation manner of step 3.1 is as follows;
defining the attitude tracking error of the mechanical arm as follows:
e Q =[e q1 ,e q2 ]=Q-Q di (10)
wherein, Q = [ Q ] 1 ,q 2 ] T ,e q1 ,e q2 Refer to errors of joint one and joint two, Q, respectively di (t)=[q d1 (t),q d2 (t)] T According to the starting and stopping position, the speed, the acceleration and the ballistic time t, 6 equations can be constructed, 6 coefficients of 5-order polynomial are solved, and Q is obtained di (t);
The attitude tracking error must satisfy the following condition:
Li (t)<e qi (t)<Ω Hi (t) (11)
wherein, for all t ≧ 0, the constraint function Ω Li And Ω Hi Is a second order derivative function, satisfies
Figure BDA0003976051090000045
Safety constraints (10) - (12) require that the attitude tracking error does not exceed a range defined by a user, wherein constraint functions on the profiles of all degrees of freedom are different, and if the constraint requirements (10) are violated, the motion performance of the mechanical arm is influenced, so that the dynamic system of the mechanical arm is unstable, and the system fails;
in this step, the error e of the joint angle Q of the robot arm is defined Q It satisfies e Q =Q-Q di Equation (a) of (b), q d Is an artificial expected joint position, and the value range of q is-pi<q i <π;
Defining ω as the derivative of q, obtaining- π by a back-stepping method<q i <π,e ω Error of ω, whose derivative is:
Figure BDA0003976051090000051
further, the barrier function in step 3.2 is designed as follows;
introducing a transformed error variable for the attitude tracking error constraint condition of the mechanical arm:
Figure BDA0003976051090000052
Ω qL lower bound for asymmetric constraints, \8230 qH Is an upper bound of asymmetric constraints, η qi Can realize the error e qi Is asymmetrically constrained, η qi A barrier function representing the ith degree of freedom;
in this step, the barrier function η takes into account the safety constraints of the joint position error qi The derivatives of (c) are as follows:
Figure BDA0003976051090000053
wherein the content of the first and second substances,
Figure BDA0003976051090000054
defining an asymmetric constraint function:
Figure BDA0003976051090000055
Figure BDA0003976051090000056
Figure BDA0003976051090000057
further, the slip film surface in step 3.3 is designed to:
Figure BDA0003976051090000058
Figure BDA0003976051090000059
Figure BDA00039760510900000510
for parameters, two-sided derivation of the equation (21)
Figure BDA00039760510900000514
For convenience of expression, let:
Figure BDA00039760510900000512
Figure BDA00039760510900000513
is an external disturbance in which, among other things,
Figure BDA0003976051090000061
Figure BDA0003976051090000062
further, the controller in step 4 is designed as follows:
Figure BDA0003976051090000063
Figure BDA0003976051090000064
ξ 1 (S) and xi 2 (S) is as follows:
Figure BDA0003976051090000065
Figure BDA0003976051090000066
k q1 ,k q2 are adaptive gains and are all greater than 0, k q3 Is a constant parameter;
Figure BDA0003976051090000067
k q2 =ηk q1 (27)
in summary, (25) can be expressed as:
Figure BDA0003976051090000068
Figure BDA0003976051090000069
wherein, the ratio of mu to mu,
Figure BDA00039760510900000610
eta and epsilon are parameters.
Further, the method for designing the controller is proved by adopting a Lyapunov method.
Compared with the prior art, the invention has the following beneficial effects:
(1) A novel TDE-based adaptive over-torque multivariable rapid terminal sliding mode control scheme is provided, and the scheme has high control precision and robustness.
(2) Asymmetric error constraint is considered, a supercoiling algorithm is improved, and rapid convergence and high control precision are guaranteed.
(3) A general barrier function is employed to address the safety constraints of time-varying and asymmetric position errors.
(4) By using time delay estimation and compensating for overall system dynamics, the error between the actual position and the desired position is reduced.
Detailed Description
The technical solution of the present invention is further explained below.
The invention provides a TDE-based adaptive supercoiled multivariable rapid terminal sliding mode control method, which comprises the following steps:
step 1: establishing a system model for describing the state of the mechanical arm of the machine;
the kinetic model of a mechanical arm with n degrees of freedom is expressed as:
Figure BDA0003976051090000071
Figure BDA0003976051090000072
Figure BDA0003976051090000073
wherein J and d m Is the motor inertia and damping matrix, q and theta are the joint and motor position vectors,
Figure BDA0003976051090000074
representing the first and second derivatives of q and theta, respectively, M (q) is an inertia matrix,
Figure BDA0003976051090000075
is the coriolis/centrifuge matrix, g (q) is the attractive force,
Figure BDA0003976051090000076
is the friction vector, τ m And τ s Control torque and joint compliance torque, d, respectively, given to the motor s To damp the matrix, k s Is a joint stiffness matrix, τ d Representing the lumped unknown uncertainty.
To facilitate the use of the TDE scheme, substitute (2) into (1), apply constant parameters
Figure BDA0003976051090000077
Obtaining:
Figure BDA0003976051090000078
wherein the expression of f is:
Figure BDA0003976051090000079
f, three main components including residual link dynamics, motor dynamics and total uncertainty, which are difficult to obtain using traditional methods, are subsequently estimated using TED.
Step 2: using TED delay time estimation to find the estimated value of f
Figure BDA00039760510900000710
f is particularly complex and difficult to solve, in this part we will solve using TED scheme
Figure BDA00039760510900000711
The value:
Figure BDA00039760510900000712
where Δ t is the delay time, the integrated system dynamics (4) is brought into (6) and is available:
Figure BDA00039760510900000713
as can be seen from (6) and (7), the main purpose of the TED scheme is to estimate the lumped system dynamics using only the time-lag values of the control and acceleration signals, and then to give a model-free scheme.
In engineering applications, u s (t- Δ t) may be represented by u s Is obtained by numerical differentiation
Figure BDA00039760510900000714
Figure BDA0003976051090000081
Wherein, the time node t 0 2 Δ t, t ≦ 2 Δ t at the initial stage, q (t) has the actual measured value, and q (t-2 Δ t) is manually zeroed, possibly leading to strong fluctuations, so (8) is used to mitigate the strong fluctuations that may be present, and in addition (8) and its initial versions are noted:
Figure BDA0003976051090000082
t>0 (9)
it is widely applied to many robust control schemes based on TDE. If no action is taken, the numerical differentiation (9) can significantly amplify the noise effect, thereby degrading control performance. However, it has been theoretically demonstrated that the gain can be reduced
Figure BDA0003976051090000083
Or an additional low pass filter may be used to solve this problem.
From (8), the current value of the dynamic model (4) is estimated by the TDE scheme using the time-lag system state, so that the estimation error of the method becomes large when a large disturbance occurs, but the method proposed by the inventor can effectively reduce the estimation error.
And step 3: designing a slide film surface of the system model to facilitate the design of a control method in the next step, wherein the design comprises the following substeps;
and 3.1, introducing safety constraint on joint position errors in a control link, and setting a safety range for the errors between the actual joint position and the expected joint position to enable the safety range to have an upper limit and a lower limit. This upper limit may be given by the actual situation, may be asymmetric, or may vary with time. The purpose of our control is to make it meet safety constraints to ensure accurate and proper operation of the cable driven robotic arm.
Defining the attitude tracking error of the mechanical arm as follows:
e Q =[e q1 ,e q2 ]=Q-Q di (10)
wherein, Q = [ Q ] 1 ,q 2 ] T ,e q1 ,e q2 Refer to errors of joint one and joint two, Q, respectively di (t)=[q d1 (t),q d2 (t)] T According to the starting and stopping position, the speed, the acceleration and the trajectory time t, 6 equations can be constructed, 6 coefficients of 5-order polynomial are solved, and Q is obtained di (t);
The attitude tracking error must satisfy the following condition:
Li (t)<e qi (t)<Ω Hi (t) (11)
wherein, for all t ≧ 0, the constraint function Ω Li And Ω Hi Is a second order derivative function, satisfies
Figure BDA0003976051090000084
The safety constraints (10) - (12) require that the attitude tracking error does not exceed a user-defined range, where the constraint functions on the respective degree of freedom profiles may be different, the above-mentioned constraint functions may also be time-varying and asymmetric. If the constraint requirement (10) is violated, the motion performance of the mechanical arm is affected, the dynamic system is unstable, and the system fails.
In this step, we define the error e of the joint angle Q of the mechanical arm Q It satisfies e Q =Q-Q di Equation (a) of (b), q d Is an artificial expected joint position, and the value range of q is-pi<q i <π;
Defining ω as the derivative of q, obtaining- π by a back-stepping method<q i <π,e ω Error of ω, whose derivative is:
Figure BDA0003976051090000091
step 3.2, carrying out design analysis on the angle error expectation by using a safety constraint function, and processing the constraints of different sections in a unified system structure;
in order to meet the safety constraint, a barrier function is introduced, the barrier function is a continuous function, an inequality constraint can be replaced by a more easily processed item in an objective function of constraint optimization, and asymmetric constraint is facilitated;
first, the error variables are introduced as follows:
Figure BDA0003976051090000092
Ω Lij lower bound of asymmetric constraints, Ω Hij Is an upper bound of asymmetric constraints, η ij Can realize the error e ij The asymmetric constraint of (2). It is obvious that if and only if e ij η =0 ij And =0. Furthermore, when e ij →Ω Hij ,η ij → + ∞, or when e ij →Ω Lij Has η ij →-∞;
For the general barrier function V ij If the constraint function is symmetric, i.e. Ω Hij =Ω Lij =Ω ij Time, barrier function η ij Comprises the following steps:
Figure BDA0003976051090000093
when e is ij When there is no constraint condition, it can be equivalent to Ω Hij =Ω Lij =Ω ij → + ∞, at this time:
Figure BDA0003976051090000094
the above reasoning shows that we can treat a system without output constraint requirements as a special case of the general case of asymmetric constraint requirements.
Introducing a transformed error variable for the attitude tracking error constraint condition of the mechanical arm:
Figure BDA0003976051090000095
Ω qL lower bound of asymmetric constraints, Ω qH Is an upper bound of asymmetric constraints, η qi Can realize the error e qi The asymmetric constraint of (2). Eta qi A barrier function representing the ith degree of freedom;
in this step, we consider the safety constraint of joint position error, the barrier function eta qi The derivatives of (c) are as follows:
Figure BDA0003976051090000101
wherein the content of the first and second substances,
Figure BDA0003976051090000102
defining an asymmetric constraint function:
Figure BDA0003976051090000103
Figure BDA0003976051090000104
3.3, designing a slip form surface according to the joint position kinematics principle of the mechanical arm;
in this step, we consider the joint position kinematics problem of the cable-driven mechanical arm, and design the synovial surface as:
Figure BDA0003976051090000105
Figure BDA0003976051090000106
Figure BDA0003976051090000107
for parameters, two-sided derivation of the equation (21)
Figure BDA0003976051090000108
The symbol ° represents the hadamard product, i.e. the product between the elements of two matrices having the same dimension, given by:
Figure BDA00039760510900001012
Figure BDA0003976051090000109
is an external disturbance in which, among other things,
Figure BDA00039760510900001011
and 4, step 4: design of controller by using slide film surface
In this step, the overall controller design will proceed, the overall control scheme is as follows:
Figure BDA0003976051090000111
Figure BDA0003976051090000112
ξ 1 (S) and xi 2 (S) is as follows:
Figure BDA0003976051090000113
Figure BDA0003976051090000114
k q1 ,k q2 are adaptive gains and are all greater than 0, k q3 Is a constant parameter;
Figure BDA0003976051090000115
k q2 =ηk q1 (27)
in summary, (25) can be expressed as:
Figure BDA0003976051090000116
Figure BDA0003976051090000117
theorem 1 inIn a system with gain (27), a suitable parameter mu is selected,
Figure BDA0003976051090000118
η,ε,
Figure BDA0003976051090000119
the sliding surface S of the system can converge to 0 within a limited time.
And 5: making valid proof of the above controller
For the system (10), the analysis was performed using the Lyapunov method, and the Lyapunov candidate function was chosen as follows:
Figure BDA00039760510900001110
in the formula, k q1
Figure BDA00039760510900001111
Is a constant greater than 0:
Figure BDA00039760510900001112
is a symmetric positive definite matrix, in which λ>0,ε>0;
Derivation on both sides of equation (29):
Figure BDA00039760510900001113
order to
Figure BDA0003976051090000121
Can be converted into:
Figure BDA0003976051090000122
wherein, Q is a symmetric matrix,
Figure BDA0003976051090000123
wherein:
c 1 =k q1 λ 2 +4k q1 ε-λk 2 =a 1 k q1 -λk 2
Figure BDA0003976051090000124
c 3 =λ
if it is not
Figure BDA0003976051090000125
Negative, then the matrix Q is positive with a determinant greater than zero. If det (Q) is to be guaranteed>0, then the root discriminant λ k 2 (k q1 -λ)>0. And because of
Figure BDA0003976051090000126
So k 2 >0, thereby
Figure BDA0003976051090000127
k q1 >λ。
Wherein k is 2 The value range is as follows:
Figure BDA0003976051090000128
let k q1 = λ + τ, where τ>0, then det [ Q ]]The solution of =0 is:
Figure BDA0003976051090000129
if ρ 1 Has a value range of
Figure BDA00039760510900001210
At this time det [ Q ]]>0. When in use
Figure BDA00039760510900001211
The existence of the root can be guaranteed. Let k 2 =κ 2 Obtaining:
Figure BDA00039760510900001212
thereby pushing to
Figure BDA00039760510900001213
Thus, it is possible to provide
Figure BDA00039760510900001214
Let λ max { P } and λ min { P } is the maximum eigenvalue and minimum eigenvalue of the matrix, then (33) can be:
Figure BDA00039760510900001215
in the formula, xi 1 Is xi 1 The amount of the characteristic(s),
Figure BDA00039760510900001216
thus, it is possible to provide
Figure BDA00039760510900001220
(35) The method can be characterized in that:
Figure BDA00039760510900001218
in the formula, beta η =min{η 112 },
Figure BDA00039760510900001219
Figure BDA0003976051090000131
To ensure k q1 And k q2 Are respectively represented by k q1 - | S | and η k q1 The slope of | S | is increased to satisfy | S! non-calculation>ε, when the following conditions are met:
Figure BDA0003976051090000132
can obtain zeta 1 >0 and ζ 2 >0;
Thus, it is possible to provide
Figure BDA0003976051090000133
Therefore | S | can converge to the interval | S | in a limited time<ε 2 Internal; if | S |<ε 2 Then ζ 1 <0,ζ 2 <0,
Figure BDA0003976051090000134
Is unknown, the rate of change of gain becomes-k q1 - | S | and-. Eta.k q1 G | S | when the gain is reduced to the interval | S |, the Y ray<ε 2 The gain will be at k q1 - | S | and η · k q1 The slope of | S | increases.

Claims (8)

1. The TDE-based adaptive supercoiled multivariate fast terminal sliding mode control method is characterized by comprising the following steps of:
step 1, establishing a dynamic model of a mechanical arm, wherein the dynamic model is used for describing the state of the mechanical arm of a machine;
step 2, parameters in the dynamic model are estimated by using TED delay;
step 3, designing the slide film surface to facilitate the design of the next control method, and the method comprises the following substeps;
step 3.1, introducing safety constraint on joint position errors, and setting a safety range for the errors between the actual joint position and the expected joint position, so that the safety range has an upper limit and a lower limit to ensure the accurate and normal operation of the cable-driven mechanical arm;
step 3.2, designing and analyzing the angle error expectation by utilizing a safety constraint function and combining a barrier function, and processing the constraints of different sections in a unified system structure;
3.3, designing a slip form surface according to the joint position kinematics principle of the mechanical arm;
and 4, designing the terminal sliding mode controller by using the sliding film surface.
2. The TDE-based adaptive supercoiled multivariate fast terminal sliding-mode control method according to claim 1, characterized in that: the kinetic model of the mechanical arm with n degrees of freedom established in step 1 is represented as:
Figure FDA0003976051080000011
Figure FDA0003976051080000012
Figure FDA0003976051080000013
wherein J and d m Is the motor inertia and damping matrix, q and theta are the joint and motor position vectors,
Figure FDA0003976051080000014
representing the first and second derivatives of q and theta, respectively, M (q) is an inertia matrix,
Figure FDA0003976051080000015
is the Coriolis/centrifuge matrix, g (q) is the gravitational force,
Figure FDA0003976051080000016
is the friction vector, τ m And τ s Control torque and joint compliance torque, d, respectively, given to the motor s To damp the matrix, k s Is a joint stiffness matrix, τ d Representing a lumped unknown uncertainty;
to facilitate the use of the TDE scheme, substitute (2) into (1), apply constant parameters
Figure FDA0003976051080000017
Obtaining:
Figure FDA0003976051080000018
wherein the expression of f is:
Figure FDA0003976051080000019
3. the TDE-based adaptive supercoiled multivariate fast terminal sliding-mode control method according to claim 2, characterized in that: step 2, using TED scheme to obtain f estimation value
Figure FDA00039760510800000110
Figure FDA0003976051080000021
Where Δ t is the delay time, the kinetic model (4) is substituted (6) to obtain:
Figure FDA0003976051080000022
as can be seen from (6) and (7), the purpose of the TED scheme is to estimate the lumped system dynamics using only the time-lag values of the control and acceleration signals, and then to give a model-free scheme;
in engineering applications, u s (t- Δ t) may be represented by u s Is obtained by numerical differentiation
Figure FDA0003976051080000023
Figure FDA0003976051080000024
Wherein, the time node t 0 At ≧ 2 Δ t, t ≦ 2 Δ t at the initial stage, q (t) has the actual measurement value, and q (t-2 Δ t) will be manually zeroed, possibly resulting in strong fluctuations, and therefore (8) is used to mitigate the strong fluctuations that may exist.
4. The TDE-based adaptive supercoiled multivariate fast terminal sliding-mode control method according to claim 3, characterized in that: the specific implementation of step 3.1 is as follows;
defining the attitude tracking error of the mechanical arm as follows:
e Q =[e q1 ,e q2 ]=Q-Q di (10)
wherein, Q = [ Q ] 1 ,q 2 ] T ,e q1 ,e q2 Refer to errors of joint one and joint two, Q, respectively di (t)=[q d1 (t),q d2 (t)] T According to the starting and stopping position, the speed, the acceleration and the ballistic time t, 6 equations can be constructed, 6 coefficients of 5-order polynomial are solved, and Q is obtained di (t);
The attitude tracking error must satisfy the following condition:
Li (t)<e qi (t)<Ω Hi (t) (11)
wherein, for all t ≧ 0, the constraint function Ω Li And Ω Hi Is a second order derivative function, satisfies
Figure FDA0003976051080000025
Safety constraints (10) - (12) require that the attitude tracking error does not exceed a range defined by a user, wherein constraint functions on the profiles of all degrees of freedom are different, and if the constraint requirements (10) are violated, the motion performance of the mechanical arm is influenced, so that the dynamic system of the mechanical arm is unstable, and the system fails;
in this step, the error e of the joint angle Q of the robot arm is defined Q It satisfies e Q =Q-Q di Equation (a) of (b), q d Is an artificial expected joint position, and the value range of q is-pi<q i <π;
Defining ω as the derivative of q, obtaining- π by a back-stepping method<q i <π,e ω Error at ω, whose derivative is:
Figure FDA0003976051080000031
5. the TDE-based adaptive supercoiled multivariate fast terminal sliding-mode control method of claim 4, characterized in that: the barrier function in step 3.2 is designed as follows;
introducing a transformed error variable for the attitude tracking error constraint condition of the mechanical arm:
Figure FDA0003976051080000032
Ω qL lower bound of asymmetric constraints, Ω qH Is an upper bound of asymmetric constraints, η qi Can realize the error e qi Is asymmetrically constrained, η qi A barrier function representing the ith degree of freedom;
in this step, the barrier function η takes into account the safety constraints of the joint position error qi The derivatives of (c) are as follows:
Figure FDA0003976051080000033
wherein the content of the first and second substances,
Figure FDA0003976051080000034
defining an asymmetric constraint function:
Figure FDA0003976051080000035
Figure FDA0003976051080000036
Figure FDA0003976051080000037
6. the TDE-based adaptive supercoiled multivariate fast terminal sliding-mode control method according to claim 5, characterized in that: in step 3.3 the slip film surface is designed as follows:
Figure FDA0003976051080000038
Figure FDA0003976051080000039
Figure FDA00039760510800000310
for parameters, two-sided derivation of the equation (21)
Figure FDA00039760510800000311
For convenience of expression, let:
Figure FDA0003976051080000041
Figure FDA0003976051080000042
is an external disturbance in which, among other things,
Figure FDA0003976051080000043
Figure FDA0003976051080000044
7. the TDE-based adaptive supercoiled multivariate fast terminal sliding-mode control method according to claim 6, characterized in that: the controller in step 4 is designed as follows:
Figure FDA0003976051080000045
Figure FDA0003976051080000046
ξ 1 (S) and xi 2 (S) is as follows:
Figure FDA0003976051080000047
Figure FDA0003976051080000048
k q1 ,k q2 are adaptive gains and are all greater than 0, k q3 Is a constant parameter;
Figure FDA0003976051080000049
k q2 =ηk q1 (27)
in summary, (25) can be expressed as:
Figure FDA00039760510800000410
Figure FDA00039760510800000411
wherein the content of the first and second substances,
Figure FDA00039760510800000412
are all parameters.
8. The TDE-based adaptive supercoiled multivariate fast terminal sliding-mode control method according to claim 1, characterized in that: the method also comprises the step of proving the design method of the controller by adopting a Lyapunov method.
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Publication number Priority date Publication date Assignee Title
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116141339A (en) * 2023-04-19 2023-05-23 珞石(北京)科技有限公司 Seven-degree-of-freedom mechanical arm preset time track tracking control method

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