Disclosure of Invention
The technical problem solved by the invention is as follows: based on the difficult problems, the patent provides a time-varying output-limited robot teleoperation limited time control method, and a feasible scheme is provided for a teleoperation system to carry out actual work.
The technical scheme of the invention is as follows: a time-varying output constraint robot teleoperation finite time control method based on width neural learning is characterized by comprising the following steps:
step 1: performing dynamic modeling on the mechanical arm;
step 2: estimating the force of an operator and the environmental force by a width neural learning algorithm and an inverse dynamics observer;
and step 3: and designing a time-varying output constraint finite time control law, eliminating uncertain influence of a model, and realizing high-precision tracking and rapid convergence of the teleoperation robot.
The further technical scheme of the invention is as follows: the system is a pair of n-degree-of-freedom mechanical arms, and the model expression is as follows:
wherein j belongs to { m, s }, and is respectively a master-slave robot identifier.
q
j∈R
n×1Acceleration, velocity and position of the joint space, respectively;
x
j∈R
n×1acceleration, velocity and position of the operating space, respectively; m
xjIs a matrix of inertia quantities, C
xjIs a matrix of centrifugal and Coriolis forces, g
xjIs a gravity term matrix, u
xjRepresenting a control input, F
mν=F
hIndicating operator applied force, F
sν=F
eRepresenting the contact force between the slave robot and the environment.
The further technical scheme of the invention is as follows: the step 2 comprises the following substeps:
step 2.1: the model was linearized as:
in the formula
Is a linear regression matrix, eta is a parameter vector related to the mechanical arm, theta belongs to R
n×1Is the product of the two;
step 2.2: evaluating external force by using a deep neural learning algorithm:
wherein q is
j,
Is an input to the neural network;
step 2.3: based on the inverse dynamics observer, the dynamics model (15) of the mechanical arm is further linearized
In the formula
Is a linear regression matrix, eta is a parameter vector related to the mechanical arm, theta belongs to R
n×1Is the product of the two;
step 2.4: the external force is estimated by designing a deep neural learning algorithm:
the input of the neural network is q
j,
The estimation of the interaction force can be realized through a width neural learning algorithm.
The further technical scheme of the invention is as follows: the step 3 comprises the following substeps:
step 3.1: by designing the controller u
xjRealize the reference track
Tracking for a limited time while guaranteeing an output x
η1Within a restricted area, i.e.
The control law of the master-slave robot is
In formula (22):
is composed of
Satisfies the following conditions
The update law in equation (22) is selected as follows:
error variable e in equation (22)j1,ej2J is as { m, s }
In the formula:
is a reference track of the master and slave terminals, alpha
j1Is a virtual control quantity to be designed.
Equation (10) then generates a reference trajectory for the master based on the operator behavior,
formula (27) wherein
Representing estimates of operator force and environmental force, respectively, wherein:
acceleration, speed and position of the main end reference track respectively;
scaling factors for the operator force estimate and the environmental force estimate, respectively; m
r,C
r,g
rTarget impedance parameters for operator behavior, respectively;
step 3.2: the reference trajectories of the slave end are:
T
f(t) network transmission delay from the master to the slave; designing a virtual control quantity alpha
j1:
In the formula, 0 < xi
j<1,
And gamma
j1Respectively as follows:
in formula (22):
respectively operator force and contact force between robot and environment, k
j1,k
j2,χ
j,b
jIs a normal number, and is,
is opposite to the angular array. The weight vector of the neural network is W obtained by the step 2 width neural learning algorithm
j,
Effects of the invention
The invention has the technical effects that: the invention focuses on solving the problems of system instability caused by time delay and uncertainty in a teleoperation system, difficulty in external force perception of interaction between a robot and an unknown environment, limited operation space and operation time of the robot and the like, and provides a time-varying output constraint robot teleoperation limited time control method based on width neural learning. The wide neural learning algorithm effectively combines incremental learning and an RBF neural network, realizes the estimation of operator force and environmental force, and simultaneously resolves the negative influence caused by the uncertainty of a system model; the time-varying output constraint algorithm ensures that the tail end position of the robot does not exceed a time-varying boundary, and the operation safety is improved; the limited time control method ensures the rapid tracking capability of the robot track. The method does not need a force sensor, the model of the system does not need to be known accurately, and the high-precision tracking and the rapidity control of the teleoperation robot are realized on the premise of ensuring the safe operation of the system.
Compared with the prior art, the invention has the following advantages:
(1) the invention designs a width neural learning algorithm to realize the estimation of operator force and environmental force; while eliminating the effect of model uncertainty in the controller design. Compared with the traditional neural network, the network can ensure higher estimation accuracy, simultaneously saves a large amount of calculation pressure and does not need sufficient learning conditions;
(2) a limited time controller with strong robustness is designed, and limited time control of the robot under the condition that the operation time is limited is realized. The invention has faster convergence speed and achieves the aim of efficient interaction between the robot and the environment.
(3) The invention considers the safety problem of the operation process, constrains the output of the robot, and the constraint boundary is a time-varying boundary, while the constant boundary is a special form of the time-varying boundary, so the method has stronger practicability and practical significance.
Detailed Description
Referring to fig. 1-4, the method comprises the following steps:
the method comprises the following steps: dynamic modeling of a system
Step two: designing a width neural learning algorithm, and then estimating the force of an operator and the environmental force based on an inverse dynamics observer;
step three: designing a time-varying output constraint finite time control law, eliminating uncertain influence of a model, realizing high-precision tracking and rapid convergence of the teleoperation robot (the master end is similar to the slave end control law, so that a variable j is in accordance with { m, s } in a unified way)
The steps are integrated, so that stable, safe and efficient interaction between the teleoperation system and the environment can be realized.
Teleoperation systems are complex and an overview of the overall framework is necessary to more clearly expand the subsequent discussion.
The method comprises the following steps: the system consists of a pair of n-degree-of-freedom mechanical arms, the dynamics form in an operation space is as follows, and for the sake of simplicity, the dynamics of a master end and a slave end are uniformly written as follows:
in the formula: j belongs to { m, s }, and is respectively a master-slave robot identifier.
q
j∈R
n×1Acceleration, velocity and position of the joint space, respectively.
x
j∈R
n×1Acceleration, velocity and position of the operating space, respectively. M
xjIs a matrix of inertia quantities, C
xjIs a matrix of centrifugal and Coriolis forces, g
xjIs a gravity term matrix, u
xjRepresenting a control input, F
mν=F
hIndicating operator applied force, F
sν=F
eRepresenting the contact force between the slave robot and the environment.
Step two: based on an inverse dynamics observer, a wide neural learning algorithm is designed to estimate the interaction force (the contact force between a main-end operator and a main-end robot, and the contact force between a slave-end robot and the environment). The dynamic model (15) of the mechanical arm can be linearized
In the formula
Is a linear regression matrix, eta is a parameter vector related to the mechanical arm, theta belongs to R
n×1Is the product of the two. Because the mechanical arm cannot be accurately modeled and the model has certain deviation, the traditional inverse dynamics observer cannot realize accurate estimation of the external force. Therefore, designing a deep neural learning algorithm enables estimation of external forces:
the input of the neural network is q
j,
The estimation of the interaction force can be realized through a width neural learning algorithm. Due to the change of the external environment and the uncertainty of the system, the traditional algorithm needs to adjust and retrain the neural network parameters, but the wide neural learning algorithm designed by the invention combines RBF and incremental learning, and obtains a better training network by setting threshold deviation and increasing nodes in a self-adaptive manner, as shown in figure 2. Based on an inverse dynamics observer, the estimation of the interaction force can be realized by utilizing the wide neural network algorithm; while the broad neural learning algorithm can compensate for uncertainty in the system model. The pseudo code is shown in table one based on the width neural learning algorithm.
TABLE-learning algorithm based on breadth nerve
In the table: x is heel q
j,
Related input vector, W, beta are weight vector and radial basis of RBF neural network respectivelyVector, A
mAnd A
m+1Are all defined mode matrices.
In the formula: d ═ am)+Hm+1,
Wherein C is Hm+1-AmD, so the weight can be:
Wei=(λI+(Am)TAm)-1(Am)TY (20)
step three: in order to ensure the safety of the operation, the position output of the robot needs to be limited, namely the end position of the robot is within the time-varying boundary. The method adopts direct barrier Lyapunov function (IBLF), a breadth neural learning algorithm and a finite time theory, and firstly provides a time-varying output constraint finite time control method based on breadth neural learning.
A control target: by designing the controller u
xjRealize the reference track
Tracking for a limited time while guaranteeing an output x
η1Within a restricted area, i.e.
The control law of master-slave robot is designed as
In formula (22):
is composed of
Satisfies the following conditions
The update law in equation (22) is selected as follows:
error variable e in equation (22)j1,ej2J is as { m, s }
In the formula:
is a reference track of the master and slave terminals, alpha
j1Is a virtual control quantity to be designed.
Equation (26) then generates a reference trajectory for the master based on the operator behavior,
formula (27) wherein
Representing the estimated values of the operator force and the environmental force, respectively (without force measuring means, estimated in step one using a neuro-learning algorithm, see step two), in which:
acceleration, speed and position of the main end reference track respectively;
scaling factors for the operator force estimate and the environmental force estimate, respectively; m
r,C
r,g
rRespectively, target impedance parameters for operator behavior.
The reference trajectories of the slave end are:
T
fand (t) is the network transmission delay from the master end to the slave end. Equation (22), designed virtual control quantity α
j1
In the formula, 0 < xi
j<1,
And gamma
j1Respectively as follows:
in formula (22):
respectively operator force and contact force between robot and environment, k
j1,k
j2,χ
j,b
jIs a normal number, and is,
is opposite to the angular array. Here the weight vector of the neural network is step 2 width neurologyW obtained by learning algorithm
j,
Aiming at the teleoperation system (15), virtual control quantity (28), control quantity (22) and updating law (24) are selected, so that the closed-loop stability of the teleoperation system is ensured, and meanwhile, the safe and efficient interaction between the robot and the environment is realized.
Overall process framework of the system: a teleoperational system control framework based on time-varying output constraints is shown in fig. 1. Position signal x of the master
m(t) transmitting to the slave end through the communication link to obtain the reference signal of the slave end
Then designing a time-varying output constraint finite time controller u based on the width neural learning
xs(see step 3), the reference signal can be realized by the slave robot
High precision and fast tracking. Meanwhile, the environment force of the slave end is estimated by using a width neural learning algorithm (see step 2), and virtual environment parameters are transmitted to the master end. And at the master end, reconstructing the environment force of the slave end at the master end by utilizing the motion information of the master end and the virtual environment parameters of the slave end. In order to provide better force perception for the operator, the reference trajectory of the main terminal is generated based on the behavior of the operator. Then designing a time-varying output constraint finite time controller u based on the width neural learning at the main end
xm(see step 3), realize the master robot to the master reference signal
High precision and fast tracking. (due to master control law u
xmAnd slave control law u
xsThe same form, so unify the expression)
In conclusion, the invention discloses a finite time control method of a time-varying output constraint robot for width neural learning. Lyapunov function based on integral obstacle and breadth neural learningAn algorithm and a finite time theory creatively provide a time-varying output constraint finite time controller based on the width neural learning. The direct integral barrier Lyapunov function ensures that the output of the system is in a time-varying boundary; the width neural learning algorithm integrates the advantages of the traditional neural network and the width learning, based on the inverse dynamics observer, solves the external force perception problem by using the width learning algorithm, and simultaneously resolves the control rate uxjModel uncertainty in the design process; the finite time theory ensures high precision and rapidity tracking of the reference signal by the robot. In conclusion, the algorithm ensures stable, safe and efficient interaction between the robot and the environment, and improves the reliability and the efficiency of the teleoperation system.