Background
Nowadays, science and technology development is so rapid, and the robot technology slowly emerges, and becomes one of indispensable technical fields of human social progress and development due to the characteristics of wide application range, high flexibility, capability of working in a limit environment and the like. In the related art, the manipulator is widely applied to the fields of mechanical manufacturing, aerospace, medicine, atomic energy and the like, and plays a vital role in automatic production. In the stressed movement of the manipulator, the manipulator interacts with the external environment, and the specified work tasks such as grinding, drilling, polishing, grabbing and the like are completed by contact. In the stressed movement, the manipulator collects the target position through the visual sensor, then the controller sends a command to drive the armature of the manipulator to drive the manipulator to move, and the dexterous hand operates the target. By utilizing the characteristic of flexible control, the precision and the force of the manipulator meet the actual operation requirements, and the application range and the safety of the manipulator are greatly expanded.
Although the application of the manipulator is wide and the safety is high, when the manipulator is controlled by a control console of the robot system through a network, input delay in the aspect of the controller is inevitable due to the characteristics of network communication, so that the command of the controller cannot reach an execution mechanism in time, and a target is not operated and processed in time. Meanwhile, the tail end of the manipulator is limited by different motion areas when a dexterous hand is executed due to different characteristics of operation objects, so that the control performance of the controller is seriously influenced, and the manipulator system is very easy to be unstable in the operation process and even is difficult to operate according to a plan to cause the whole system to be crashed.
In the existing control algorithm, for the fuzzy controller design process based on the backstepping method of the manipulator, it is often assumed that the virtual control symbol of the previous state is known, and the assumption greatly limits the applicability of the controller. Meanwhile, when describing external disturbance, the disturbance is considered to be from certainty, and in the actual operation process, the random torque disturbance suffered by different manipulators or different operating environments is different, so that the whole system modeling can be considered to be in accordance with the actual engineering significance under the framework of a random system.
Disclosure of Invention
In view of the above, the invention provides a fuzzy controller designed based on a random system, which solves the problem of input delay and output limitation of a robot system console by introducing a Pade approximation technology and nonlinear transformation, and designs a self-adaptive algorithm and combines the designed fuzzy controller to solve the problem that the robot system can be self-adjusted under the condition that the robot system suffers from input delay and output limitation and random torque disturbance, thereby improving the control accuracy and the production efficiency.
The technical scheme of the invention is as follows:
a fuzzy control algorithm for single-link manipulator based on stochastic system under limited output and input lag is realized by fuzzy adaptive controller, visual sensor, manipulator control armature and tail end dexterous hand.
The fuzzy control algorithm is constructed by a fuzzy controller and a self-adaptive algorithm;
the fuzzy control algorithm is based on the following random Uncertain Non-strict feedback (Stochastic Uncertain Non-linear feedback) mathematical model, which can be expressed as follows:
Y(t)=X1(t)
wherein f is
i(X) denotes an unknown non-linear function in the system, X being X
1To X
nThe set of vectors of (a) is,
i.e. the various stages of the robot manipulator system, where
Indicating an unknown control gain, the sign of which is unknown; u and Y (t) are the input and output of the system and-k
c<Y(t)<k
cWherein k is
cRepresents the constraint to which the output of the system is subjected, τ being the input delay of the control signal to the robotic system;
is a random perturbation and ω is an independent standard brownian motion factor defined over the full probability space.
First order state x of the original system1I.e., Y, is constrained to the interval (-k)c,kc) The nonlinear transformation method proposed by the present invention is used for processing as follows
The reference signal is then transformed into the form
The rest of each order state xi1,2, n, in the form of x in the mathematical model described aboveiThe correspondence is equal.
The manipulator system controller input delay can be processed by the following Pade approximation technology, and is characterized in that:
wherein v is a laplace variable; for further study, another intermediate variable xn+1Is introduced and satisfies (assuming the original system order is n):
then using the inverse laplace transform one can get:
where λ is 2/τ, then the dynamic equation for the entire single link manipulator system can be simply expressed as:
the fuzzy control algorithm for converting the whole system model from input time lag to no time lag is completed through Pade approximation, and the fuzzy control algorithm comprises the following steps:
1): the visual sensor captures the operation target as a reference signal yd;
2): reference signal ydState x of the manipulator at this time1Making a difference to obtain an error z of the two1And carrying out differential solution of a dynamic equation;
3): and (2) approximating strong nonlinear terms and coupling terms in a model in the manipulator system by using a Fuzzy Logic system (Fuzzy Logic Systems), wherein the Fuzzy Logic system is established as follows:
the ith fuzzy model rule is established as follows:
R
i: if Z is
1Belong to F
1 i,……,Z
nBelong to
Then y belongs to B
i(ii) a 1,2, N is a fuzzy rule number;
after single-valued fuzzifier, product inference and center-averaged deblurring, any nonlinear function f (z) that needs to be approximated can be expressed as:
wherein Z ═ Z
1,...,Z
n]
TFor an input vector of dimension n in the real number domain,
is that
Of the membership function, theta
T=[θ
1,...,θ
N]The weight vector is a vector of weights,
and is
Wherein the input signal of the ith-order system to the fuzzy logic is
Wherein
Is represented by y
dThe ith order derivative of (a) is,
is representative of
Modeling the state x of a manipulator system
1Operation target state y of manipulator
dAnd first derivative
As input to fuzzy logic systems, output being first order systems
And contains a corresponding precision level error epsilon
1;
4): two signals theta output by using fuzzy logic system
1And
establishing information about theta
1Adaptive algorithm of
Wherein theta is
1Is theta
1 *An estimate of (d). Optimal weight vector θ
1 *The selection method comprises the following steps:
where ε >0 is the precision order constant. Here we give the invention directly as theta for each orderiThe adaptive algorithm of (1) is as follows:
is representative of
M is the custom relaxation coefficient, and i represents the order of the physical model of the manipulator system.
5): error signal z
1Input to the Nussbaum function N as the argument ξ
1And establishes an argument ξ about the function
1Adaptive algorithm of
Wherein the function N must have the following properties:
here, we directly give the function argument ξiThe adaptive algorithm at each stage is:
i denotes the order of the model of the manipulator system.
6): self-setting corresponding given parameter sigma by using the self-adaptive algorithm established by 4) and 5)1,γ1,k1,m1Design of virtual controller alpha1Here we directly give the virtual control of each step of the invention as follows:
αi=N(ξi)∈i
i represents the order of the model of the manipulator system;
7): utilizing 6) designed controller and adaptive algorithm to process the state x of the next order of the manipulator system
2Processing the data to obtain a control error signal z corresponding to the virtual controller of the previous stage system
2Inputting the 2 nd order corresponding fuzzy logic system and Nussbaum function, and outputting them respectively
And xi
2And self-assigns a corresponding given parameter sigma
2,γ
2,k
2,m
2Design of virtual controller alpha
2。
8): then the first order state x
3With the virtual control signal a derived from the 2 nd order
2Differencing to obtain a 3 rd order error signal z
3And then proceeds with the work done in 7). Repeating the above steps for each step state x of the manipulator system
iSequentially processing the control signals to obtain corresponding virtual control alpha
iAnd adaptive algorithm
And
until the last stage of the system is reached, outputting a corresponding self-adaptive algorithm and an actual fuzzy controller u;
9): and (4) continuously comparing the state of the manipulator at the next moment with the state of the operation target, returning to the step 1, and continuously circulating.
The invention has the advantages of
The invention has the advantages that: the fuzzy control algorithm is invented, so that when the manipulator system suffers input time lag and output is restricted, random disturbance of torque can be overcome, a controlled target can still be operated, self-adjustment can be realized, and the robustness and the production efficiency of the system are improved.
Detailed Description
The invention is further illustrated by the following description in conjunction with the figures and the specific embodiments.
Referring to fig. 1-3, the invention is a fuzzy control algorithm of a single link manipulator based on a stochastic system with limited output and input lag, comprising the following steps:
firstly, the output of the system is processed by utilizing nonlinear transformation:
first order state x of the original system1I.e., Y, is constrained to the interval (-k)c,kc) The nonlinear transformation method proposed by the present invention is used for processing as follows
The reference signal is then transformed into the form
Each of the remaining states is defined as xi1,2, n, in the form of x in the mathematical model described aboveiThe correspondence is equal.
The manipulator system controller input delay can be processed by the following Pade approximation technology, and is characterized in that:
where v is the laplace variable. For further study, another intermediate variable xn+1Is introduced and satisfies (assuming the original system order is n):
then using the inverse laplace transform one can get:
where λ is 2/τ, then the dynamic equation for the entire single link manipulator system can be simply expressed as:
the fuzzy control algorithm for converting the whole system model from input time lag to no time lag is completed through Pade approximation, and the fuzzy control algorithm comprises the following steps:
1): the visual sensor captures the operation target as a reference signal yd;
2): reference signal ydState x of the manipulator at this time1Making a difference to obtain an error z of the two1And carrying out differential solution of a dynamic equation;
3): and (2) approximating strong nonlinear terms and coupling terms in a model in the manipulator system by using a Fuzzy Logic system (Fuzzy Logic Systems), wherein the Fuzzy Logic system is established as follows:
the ith fuzzy model rule is established as follows:
R
i: if Z is
1Belong to F
1 i,……,Z
nBelong to
Then y belongs to B
i(ii) a 1,2, N is a fuzzy rule number;
after single-valued fuzzifier, product inference and center-averaged deblurring, any nonlinear function f (z) that needs to be approximated can be expressed as:
wherein Z ═ Z
1,...,Z
n]
TFor an input vector of dimension n in the real number domain,
is that
Of the membership function, theta
T=[θ
1,...,θ
N]The weight vector is a vector of weights,
and is
Wherein the input signal of the ith-order system to the fuzzy logic is
Wherein
Is represented by y
dThe ith order derivative of (a) is,
is representative of
An estimate of (d).
Modeling the state x of a manipulator system
1Operation target state y of manipulator
dAnd first derivative
As input to fuzzy logic systems, output being first order systems
And contains a corresponding precision level error epsilon
1;
4): two signals theta output by using fuzzy logic system
1And
establishing information about theta
1Adaptive algorithm of
Wherein theta is
1Is theta
1 *An estimate of (d). Optimal weight vector θ
*The selection method comprises the following steps:
where ε >0 is the precision order constant. Here we give the invention directly as theta for each orderiThe adaptive algorithm of (1) is as follows:
is representative of
M is the custom relaxation coefficient, γ
iAnd σ
iRepresenting the custom parameters and i representing the order of the model of the manipulator system.
5): error signal z
1Input to the Nussbaum function N as the argument ξ
1And establishes an argument ξ about the function
1Adaptive algorithm of
Wherein the function N must have the following properties:
here, we directly give the function argument ξiThe adaptive algorithm at each stage is:
i denotes the order of the model of the manipulator system.
6): self-setting corresponding given parameter sigma by using the self-adaptive algorithm established by 4) and 5)1,γ1,k1,m1Design of virtual controller alpha1Here we directly give the virtual control of each step of the invention as follows:
αi=N(ξi)∈i
i denotes the order of the model of the manipulator system.
7): utilizing 6) designed controller and adaptive algorithm to carry out mechanical control on the systemState x of the next order
2Processing the data to obtain a control error signal z corresponding to the virtual controller of the previous stage system
2Inputting the 2 nd order corresponding fuzzy logic system and Nussbaum function, and outputting them respectively
And xi
2And self-assigns a corresponding given parameter sigma
2,γ
2,k
2,m
2Design of virtual controller alpha
2.
8): then the first order state x
3With the virtual control signal a derived from the 2 nd order
2Differencing to obtain a 3 rd order error signal z
3And then proceeds with the work done in 7). Repeating the above steps for each step state x of the manipulator system
iSequentially processing the control signals to obtain corresponding virtual control alpha
iAnd adaptive algorithm
And
until the last stage of the system is reached, outputting a corresponding self-adaptive algorithm and an actual fuzzy controller u;
9): and (4) continuously comparing the state of the manipulator at the next moment with the state of the operation target, returning to the step 1, and continuously circulating.
In summary, the above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Note: in fig. 3, i is the order of the manipulator system model, the initial value is 1, the orders of different manipulators are not necessarily the same, and n represents the last order.