Disclosure of Invention
The embodiment of the invention provides a reliable control method of an information physical system facing malicious attack, which can ensure that the system output is accurately tracked to ideal output in a limited time. The technical scheme is as follows:
The embodiment of the invention provides a reliable control method of an information physical system facing malicious attack,
Establishing a control-oriented dynamic model of an information physical system with external disturbance under malicious attack;
based on the established dynamic model, determining tracking error according to the actual output and the ideal output of the system, and designing a system switching surface required in the variable structure control method;
Constructing a Gaussian radial basis function neural network, and carrying out online real-time estimation and reconstruction on malicious attack and external disturbance based on the determined tracking error;
Based on Lyapunov stability theorem, the adaptive rule of the Gaussian radial basis function neural network is determined, and the adaptive neural network finite time controller is designed according to the determined adaptive rule and the switching surface, so that reliable control of an information physical system under malicious attack is realized.
Further, the established dynamic model of the information physical system with external disturbance under the malicious attack is as follows:
Where t represents time, ζ (t) represents an information physical system state variable,.., Ζ(n-1)(t)、ξ(n) (t) denote in sequence the first, second, third, etc. derivative of ζ (t) with respect to time t, where n denotes that the system is an n-th order nonlinear system, p (-) and q (-) are known real continuous nonlinear functions with respect to system state variables, y (t) denotes the actual output of the system, C denotes the coefficient matrix, ua (t) denotes the malicious attack, u (t) denotes the system input, the malicious attacker intends to achieve the purpose of the malicious attack by superimposing ua (t) on the system input u (t), d (t) denotes the external disturbance present in the control object, |d (t) | < β, β is a positive constant;
Converting the kinetic model into the following form:
Wherein,The n-dimensional state vector of the information physical system after conversion is represented, ζ1 (t) and ζ (t) represent the same meaning, each represent 1 st dimension in n-dimensional state variables of the information physical system, ζ2(t)、ξ3(t)、ξ4(t)、…、ξn (t) respectively represent first derivative, second derivative, third derivative and third derivative of ζ (t) with respect to time t, n-1 th derivative, and a (t) =ψ (xi, t) =q (xi) ua (t) represents the energy of malicious attack suffered by the information physical system;
according to the attack energy bounded theory, the method comprises the following steps:
Wherein phii >0, i=1, 2,..n represents the upper energy bound for malicious attacks to the information physical system,.., Ψ(n) (xi, t) represent, in order, the first derivative, the second derivative, the third derivative, the fourth derivative of ψ (xi, t) with respect to time t.
Further, the determining tracking error according to the actual output and the ideal output of the system based on the established dynamics model, and designing the system switching surface required in the variable structure control method includes:
based on the established dynamics model, determining the tracking error of the system according to the actual output and the ideal output of the system as follows:
Wherein,Representing the tracking error of the system, yd (t) representing the ideal output of the system, and y (t) representing the actual output of the system;
the tracking error dynamics of the system are described as:
Wherein,Representing the nth derivative of the ideal output yd (t) with respect to time t,Respectively representFirst derivative, second derivative, and third derivative of time t third derivative, n-1, n derivative,Respectively representFirst, second, third, n-1 derivatives over time t;
the control targets of the system are described as:
wherein, pi (t) is in a shorthand form,The expression of the expression vector is European norms, T represents the adjustment time of the system, and epsilon represents the preset tracking precision;
defining a switching surface as:
Wherein W (t) represents the switching surface and v represents the conversion rate of the switching surface;
according to the newton's expansion formula, the switching surface is written specifically as follows:
Wherein,Respectively representFirst derivative, second derivative, n-3, n-2, n-1 derivatives over time t;
converting the switching surface into, according to the tracking error dynamics of the system:
Wherein,Representing a tracking error of the system;
after the first derivative of the switching surface with respect to time t is obtained, the following steps are obtained:
Further, the constructing the gaussian radial basis function neural network, based on the determined tracking error, performing online real-time prediction and reconstruction on the malicious attack and the external disturbance comprises:
constructing a Gaussian radial basis function neural network;
will track errorsTraining weights Q between hidden layers and output layers in the constructed Gaussian radial basis function neural network as input so as to estimate the sum of malicious attack and external disturbance by the trained Gaussian radial basis function neural network
Wherein S (-) represents a Gaussian function,Respectively representing the weights between the estimated hidden layer and the output layer, the center of the hidden layer neuron and the standard deviation of the hidden layer neuron, X (t) represents the input vector of the Gaussian radial basis function neural network,
Defining the estimated error of the weight Q between the hidden layer and the output layer of the Gaussian radial basis function neural networkThe method comprises the following steps:
Wherein,The estimated weight of the Gaussian radial basis function neural network constructed in the embodiment is Q*, and the existing weight between the optimal hidden layer and the output layer is the estimated weight.
Further, the adaptive rule of the gaussian radial basis function neural network is expressed as:
Based on Lyapunov stability theorem, determining the adaptive rule of the Gaussian radial basis function neural network:
Wherein,Representation ofFor the first derivative of time t, μ=μ*,τ=τ*, μ, τ represent the center μ* of the optimal hidden layer neuron and the standard deviation τ* of the optimal hidden layer neuron, respectively.
Further, the designed adaptive neural network finite time controller is expressed as:
wherein sgn (·) represents a sign function, k is a normal number, k is equal to or greater than α+β, β is an upper bound of external disturbance d (t) existing in the system, α is a normal number, and q (Σ) is not equal to 0.
The technical scheme provided by the embodiment of the invention has the beneficial effects that at least:
1) Aiming at an information physical system with external disturbance under malicious attack, a reliable control method of the information physical system is provided to ensure that the system output is accurately tracked to ideal output in a limited time;
2) The Gaussian radial basis function neural network constructed in the embodiment is a self-adaptive neural network predictor, and can realize online prediction and reconstruction of external disturbance and malicious attack existing in a system;
3) The reliable control method of the information physical system provided by the embodiment is designed aiming at the n-order nonlinear information physical system, so that the method can be applied to the safety control of various nonlinear information physical systems;
4) The embodiment fuses the Lyapunov stabilization theory, ensures the stability of the information physical system, and effectively improves the control performance.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
In this embodiment, the structure diagram of the information physical system with external disturbance under the malicious attack is shown in fig. 1, the communication mode in the system is wireless communication, the controller sends a control instruction to the actuator through the wireless communication network, the actuator acts on the control object, the external disturbance exists in the control object all the time, the sensor measures the signal in the control object and sends the signal to the controller through the wireless communication network, the malicious attack intends to send the control instruction u (t) (i.e. system input) to the actuator through the wireless communication network, and then the malicious attack signal ua (t) is added, so that the purpose of the malicious attack is achieved.
S101, establishing a control-oriented dynamic model of an information physical system with external disturbance under malicious attack so as to mathematically characterize the malicious attack and the existing external disturbance of the information physical system;
In this embodiment, the dynamic model of the information physical system with external disturbance under the malicious attack is:
Where t represents time, ζ (t) represents information physical system state variables such as vehicle speed, vehicle-to-vehicle distance, etc.,.., Ζ(n-1)(t)、ξ(n) (t) denote in order that ζ (t) is a first derivative, a second derivative, a third derivative, a.i., n-1 order, n-order derivative of time t, n denotes that the system is an n-order nonlinear system, p (, q () is a known real continuous nonlinear function of system state variables, y (t) denotes an actual output of the system, such as vehicle speed, vehicle acceleration, etc., C denotes a coefficient matrix, c= [1, 0]T,ua (t) denotes a malicious attack, u (t) denotes a system input, a malicious attacker intends to achieve the purpose of the malicious attack by superimposing ua (t) on the system input u (t), d (t) denotes an external disturbance present in the control object, |d (t) | < β, β is a positive constant;
Converting the kinetic model into the following form:
Wherein,The n-dimensional state vector of the information physical system after conversion is represented, ζ1 (t) and ζ (t) represent the same meaning, each represent 1 st dimension in n-dimensional state variables of the information physical system, ζ2(t)、ξ3(t)、ξ4(t)、...、ξn (t) respectively represent first derivative, second derivative, third derivative and third derivative of ζ (t) with respect to time t, n-1 th derivative, and a (t) =ψ (xi, t) =q (xi) ua (t) represents the energy of malicious attack suffered by the information physical system;
according to the attack energy bounded theory, the method comprises the following steps:
Wherein phii >0, i=1, 2,..n represents the upper energy bound for malicious attacks to the information physical system,.., Ψ(n) (xi, t) represent, in order, the first derivative, the second derivative, the third derivative, the fourth derivative of ψ (xi, t) with respect to time t.
S102, determining tracking errors according to actual output and ideal output of a system based on the established dynamic model, and designing a system switching surface required in a variable structure control method;
In this embodiment, the tracking error of the system is:
Wherein,Representing the tracking error of the system, yd (t) representing the ideal output of the system, and y (t) representing the actual output of the system;
the tracking error dynamics of the system are described as:
Wherein,Representing the nth derivative of the ideal output yd (t) with respect to time t,...、Respectively representFirst derivative, second derivative, and third derivative of time t third derivative, n-1, n derivative,Respectively representFirst, second, third, n-1 derivatives over time t;
The control objective of this embodiment is to ensure that, for any initial state of the system, the system output can be accurately tracked to the ideal output within a limited time, and the control objective of the system can be written as:
wherein, pi (t) is in a shorthand form,The expression vector is European norms, T >0 represents the adjustment time of the system, and epsilon >0 represents the preset tracking precision;
defining a switching surface as:
Wherein W (t) represents the switching surface, and v >0 represents the conversion rate of the switching surface;
according to the newton's expansion formula, the switching surface is written specifically as follows:
Wherein,Respectively representFirst derivative, second derivative, n-3, n-2, n-1 derivatives over time t;
converting the switching surface into, according to the tracking error dynamics of the system:
Wherein,Representing a tracking error of the system;
after the first derivative of the switching surface with respect to time t is obtained, the following steps are obtained:
S103, constructing a Gaussian radial basis function neural network, and carrying out online real-time prediction and reconstruction on malicious attacks and external disturbance based on the determined tracking error, so as to realize the purposes of online prediction and reconstruction on the external disturbance and the malicious attacks of the system;
In this embodiment, according to the global approximation theorem, for the sum of external disturbance and malicious attack, ad (t) =a (t) +d (t), there is always a gaussian radial basis function neural network, so that for any approximation accuracy, the following equation always holds:
Wherein S (-) represents a Gaussian function,Representing the estimated result of the Gaussian radial basis function neural network constructed in the embodiment, specifically, the sum of external disturbance and malicious attack, χ >0 represents the approximation accuracy, Q*、μ*、τ* represents the weight between the optimal hidden layer and the output layer, the center of the hidden layer neuron and the standard deviation of the hidden layer neuron respectively, X (t) represents the input vector of the Gaussian radial basis function neural network,
The above equation indicates that there is always an optimal Q*,μ*,τ* so that the above equation is satisfied, and for the Gaussian radial basis function neural network constructed in this embodiment, the estimated result of Ad (t)Can be expressed as follows:
Wherein,Respectively representing the weights between the predicted hidden layer and the output layer, the center of the hidden layer neuron and the standard deviation of the hidden layer neuron;
It is worth noting that the gaussian radial basis function neural network constructed in the embodiment is trained only for the weight Q between the hidden layer and the output layer, and the designed gaussian radial basis function neural network is used as a self-adaptive neural network predictor, so as to realize online prediction and reconstruction of external disturbance and malicious attack existing in the system.
In this embodiment, the following estimation error is defined with respect to the weight Q between the hidden layer and the output layer of the Gaussian radial basis function neural networkThe method comprises the following steps:
Wherein,The estimated weight of the Gaussian radial basis function neural network constructed in the embodiment is Q*, and the existing weight between the optimal hidden layer and the output layer is the estimated weight.
S104, based on the Lyapunov stability theorem, determining the self-adaptive rule of the Gaussian radial basis function neural network, and designing a finite time controller of the self-adaptive neural network according to the determined self-adaptive rule and the switching surface to realize reliable control of an information physical system under malicious attack. Therefore, the Lyapunov stability theory is fused, the stability of the information physical system is ensured, and the control performance is effectively improved.
In this embodiment, based on the lyapunov stability theorem, an adaptive rule of the gaussian radial basis function neural network is determined:
Wherein,Representation ofFor the first derivative of time t, since the present embodiment only trains for weights between hidden layer to output layer, μ, τ represent the center of the optimal hidden layer neuron and the standard deviation of the optimal hidden layer neuron, i.e., μ=μ*,τ=τ*, respectively;
According to the global approximation theorem, an optimal Gaussian radial basis function neural network always exists and can accurately approximate Ad (t), namely the following formula holds:
Ad(t)=Q*TS(X(t),μ,τ)
therefore, an adaptive neural network finite time controller is designed as follows:
wherein sgn (·) represents a sign function, k is a normal number, k is equal to or greater than α+β, β is an upper bound of external disturbance d (t) existing in the system, α is a normal number, and q (Σ) is not equal to 0.
The system stability proving process is as follows:
The following form of lyapunov function was selected:
deriving the Lyapunov function to obtain:
Will beSubstituting the formula:
the finite time controller of the adaptive neural network constructed by the embodiment is brought into the formula to obtain:
Further simplification of the above formula can be obtained:
according to the global approximation theorem:
Then willThe simplification is as follows:
Substituting the adaptive rule determined in this embodiment into the above formula yields:
further simplifying and obtaining:
according to the lyapunov theorem, the system output can accurately track the ideal output in a limited time.
The reliable control method for the information physical system facing malicious attack provided by the embodiment of the invention has at least the following advantages:
1) Aiming at an information physical system with external disturbance under malicious attack, a reliable control method of the information physical system is provided to ensure that the system output is accurately tracked to ideal output in a limited time;
2) The Gaussian radial basis function neural network constructed in the embodiment is a self-adaptive neural network predictor, and can realize online prediction and reconstruction of external disturbance and malicious attack existing in a system;
3) The reliable control method of the information physical system provided by the embodiment is designed aiming at the n-order nonlinear information physical system, so that the method can be applied to the safety control of various nonlinear information physical systems;
4) The embodiment fuses the Lyapunov stabilization theory, ensures the stability of the information physical system, and effectively improves the control performance.
For better understanding of the present invention, the reliable control method for the information physical system under malicious attack provided by the embodiment of the present invention is described with ζ (t) =v (t), where v (t) represents the vehicle speed of the heavy-duty car, as shown in fig. 3, in this embodiment,
y(t)=v(t),u(t)=Te(t)
Wherein,Ma=40000kg,ma denotes the mass of the car, mt denotes the total mass of the heavy vehicle system, Jw=32.9kgm2,Jw denotes the rotational inertia of the car tyre, rw=0.5m,rw denotes the radius of the vehicle wheel,In relation to the wheel inertia, lambdaG=1,λG denotes the gearbox, lambdaF=2.71,λF denotes the transmission ratio of the main transmission gear, etaG=0.97,ηG denotes the gearbox, etaF=0.97,ηF denotes the main transmission efficiency factor,In relation to the inertia of the flywheel,Representing the transmission coefficient of the force generated by the engine,Za denotes an air resistance coefficient, cd denotes a resistance coefficient, aa=10m2,Aa denotes a front area of the vehicle, ρa=1.29kg/m3,ρa denotes an air density, zr=crmag,cr=0.007,cr denotes a sliding friction coefficient, g=9.82, g denotes a gravitational constant, zr denotes a resistance coefficient due to vehicle gravity, zg=mag,zg denotes vehicle gravity, Je=3.5kgm2, α(s) denotes a slope road angle (which is a function of a position s on a road where the vehicle is located), Te (T) denotes an engine torque, v (T) denotes a speed of the vehicle, y (T) =v (T) denotes a speed of the vehicle as a system output, and a (T) and d (T) respectively denote a malicious attack and an external disturbance suffered by the vehicle;
firstly, establishing a control-oriented dynamic model of an information physical system with external disturbance under malicious attack, wherein the control-oriented dynamic model comprises the following steps:
y(t)=v(t)
Wherein a (t) and d (t) are shown in fig. 4 and 5, respectively.
Secondly, determining the tracking error as follows:
wherein yd (t) represents the ideal speed, yd (t) =22.2 m/s;
Then, the switching surface of the system is determined as:
Thirdly, constructing a Gaussian radial basis function neural network to estimate the sum of malicious attack and external disturbance, wherein the input of the neural network is thatThe output isThe number of neurons of an hidden layer of the designed neural network is 5, the Gaussian radial basis function neural network constructed in the embodiment is trained only for the weight Q between the hidden layer and an output layer, and the designed Gaussian radial basis function neural network is used as a self-adaptive neural network estimator to realize online estimation and reconstruction of external disturbance and malicious attack existing in a system.
Fourth, the following adaptive rules are determined:
then, an adaptive neural network finite time controller is designed as follows:
wherein k is equal to or greater than α+β, β is the upper bound of the external disturbance d (t) present in the system, α=0.5, and q (Σ) noteq0.
In this embodiment, the built adaptive neural network predictor performs online prediction on external disturbance and malicious attack existing in the system, the prediction result is shown in fig. 6, and obviously, the adaptive neural network predictor built in this embodiment can accurately estimate and reconstruct the malicious attack and the external disturbance, in addition, the automobile speed v (t) and the operation curve result of the switching surface W (t) obtained by simulating the heavy automobile system implementation case are shown in fig. 7 and 8, it is known from fig. 7 and 8 that the automobile speed v (t) tracks to the ideal speed vcc =22.2 m/s in a limited time, and the switching surface W (t) is converted into 0 in a limited time.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.