CN103365210A - Control method and control system for communication-limited network - Google Patents

Abstract

The invention relates to a control method and control system for a communication-limited network. The control system comprises a controller, a performer, a sensor and a controlled object which are connected in a closed loop. The control method comprises the following steps: a real-time state signal obtained by the sensor through sampling is transmitted to the controller through a control network with packet loss and random communication time delay, wherein there are certain probabilities of sensor faults; the controller, according to corresponding controller gain matrix obtained from the controller object and corresponding network state parameters, outputs control information to the performer; the performer executes corresponding actions so as to finish the real-time control of the controlled object and guarantee the stability of the system. Compared with the prior art, the provided method and system solve the control problems of a networked control system with packet loss, random communication time delay and probable sensor faults, and real-time online control may be provided for the controlled object.

Description

The control method and the control system that are used for the communication limited network

Technical field

The present invention relates to field of wireless communication, especially relate to a kind of control method for the communication limited network and control system.

Background technology

Along with the develop rapidly of computer technology and the communication technology, later 1980s, computer network progresses into the field of automatic control.The development of the technology such as control network, intelligence sensor, actuator and driving arrangement has caused network control system (Networked Control System is called for short NCS) to produce and caused widely and has paid close attention to.Thereby all be to connect the feedback system that forms closed loop by the control network between the sensor of this type systematic, controller and the actuator.NCS is the product of computing machine, the communication technology and control technology development and fusion, and it can be applied to any with controller, need to carry out the distributed occasion of exchanges data.Embodied the development trend of control system to integrated, distribution, node intelligent.NCS is the new stage of current control system development, compare with the control system of traditional point to point connect, plurality of advantages such as having that cost is low, efficient is high, be easy to expansion, be convenient to maintenance, high reliability, realization information resources are shared has effectively been avoided some shortcomings that exist in the traditional control system.These factors have promoted the widespread use of NCS at control fields such as industrial automation, device fabrication, process control, intelligent transportation, robot and Aero-Space.

Although network control system is compared traditional control system many advantages are arranged, because the intervention of network, the exchanges data of carrying out between the network control system node all needs to transmit by network, yet network is not a kind of reliable communication media.Bandwidth of network is always limited, the transmission of information needs timesharing to take network communication circuit, this must cause information obstruction, wait in line and the phenomenon such as re-transmission occurs, inevitably caused network transfer delay, data packet loss, wrapped transmission more, the problems such as shake and sequential entanglement.These network factors all may have influence on the stability of NCS and the control effect of control law.

In the most related network control system design process, only considered the subnetwork factor, to existing the network environments such as packet loss, random delay, probability sensor fault all to be assumed to be perfect condition with the control network, so that these control system are for can not carry out well in real time control at the communication limited network.

Summary of the invention

Purpose of the present invention is exactly to provide a kind of for the defective that overcomes above-mentioned prior art existence can carry out the control method of effectively in real time control and the control system of using the method to controlled device in the communication limited network.

Purpose of the present invention can be achieved through the following technical solutions:

A kind of control method for the communication limited network may further comprise the steps:

1) controller is sent to actuator according to the original state output initial control signal of system via the control network, and by actuator control controlled device;

2) sensor carries out periodic sampling to the status signal of controlled device, and by control network input control device;

3) controller is processed the status signal of input by the ride gain matrix, outputs control signals to actuator;

4) actuator is controlled controlled device according to the control signal that receives, and then execution in step 2) realize the closed-loop control of system.

Described ride gain matrix obtains by finding the solution corresponding LMI according to the state parameter of control network and the model parameter of controlled device.

The state parameter of described control network comprises the failure rate of the maximum packet loss upper bound, the time delay upper bound and sensor.

A kind of control system of using above-mentioned control method, comprise controller, actuator, sensor and controlled device, described controlled device connects respectively actuator and sensor, and described controller connects respectively actuator and sensor by the control network, forms closed-loop system.

Compared with prior art, the present invention has the following advantages:

1) control structure is simple, only need to according to the failure rate of system matrix and network condition parameter and the sensor of controlled device, by finding the solution given LMI, can obtain the ride gain matrix of corresponding controllers.

2) control strategy is easy to realize, the status signal that this controller only need to provide controlled device to obtain by sensor sample can be realized control, does not need other parameters of controlled device.

3) control network model meets realistic situation more, in traditional control system, the general impact of not considering to control network, namely be assumed to be the network under the ecotopia, there is not time delay, the behaviors such as packet loss, and the present invention has considered the factors such as failure rate of data packet loss, random delay and the sensor of control network existence are met reality more.

Description of drawings

Fig. 1 is the process flow diagram of control method of the present invention;

Fig. 2 is the structural representation of control system of the present invention;

Fig. 3 is system state analogous diagram of the present invention.

Embodiment

The present invention is described in detail below in conjunction with the drawings and specific embodiments.

Embodiment

The present invention mainly is controller's design, for a certain controlled device, supposes that this plant model is described below:

$\left\{\begin{array}{c}\stackrel{\·}{x}\left(t\right)=\mathrm{Ax}\left(t\right)+\mathrm{Bu}\left(\mathrm{kT}\right)+\mathrm{E\ω}\left(t\right)\\ z\left(t\right)=\mathrm{Cx}\left(t\right)+\mathrm{D\ω}\left(t\right),t\∈[\mathrm{kT},(k+1)T)\end{array}\right.---\left(1\right)$

Wherein,

The expression system state;

The discrete control inputs of expression;

The disturbance input of expression system;

Represent output to be estimated; T represents the sampling period.A, B, C, D, E is suitable dimension matrix.Here, the controller u (kT) that we adopt is the Static Sampling controller, and the ride gain matrix is K.Hypothesis matrix (A, B) can be calmed.

Controlled device, sensor, controller and actuator all connect by network.This network configuration is as follows: sensor-controller end is connected the actuator end and is all connected by network with controller, and sensor is to drive the time, and controller and actuator are event driven.In addition, suppose within each sampling period to only have a data packet transmission on the network channel.Then to behind this discrete model construction, its state space equation is as follows:

$\left\{\begin{array}{c}x(k+1)=\mathrm{Gx}\left(k\right)+\mathrm{Hu}\left(k\right)+\mathrm{F\ω}\left(k\right)\\ z\left(k\right)=\mathrm{Cx}\left(k\right)+\mathrm{D\ω}\left(k\right)\end{array}\right.---\left(2\right)$

Wherein, G=G (T)=e ^AT, $H=H\left(T\right)={\∫}_0^T{e}^{\mathrm{As}}\mathrm{dsB},$ $F=F\left(T\right)={\∫}_0^T{e}^{\mathrm{As}}\mathrm{dsE},$ T is the sampling period of system.

The network control system that will contain the packet loss factor among the present invention is modeled as the discrete system that contains the Makovian jumping parameters, compares in the existing document methods such as the most of Bernoulli of employing stochastic distribution, and the model that this method is set up is more near real network environment.

Following definition set ζ={ i ₁, i ₂, i ₃... }, this set for the discrete time step- length 1,2,3 ... } and a subset.To be packet successfully be transferred to the time point of actuator from sensor to Element of a set, and then the mathematical description of packet loss process is as described below:

η _k＝{i _k+1-i _k，i _k∈ζ}(3)

Wherein, η _kThe set Ψ=1,2 ... σ in value, σ is called the maximum packet loss upper bound, namely works as η _k=1 o'clock, the expression network did not have packet loss at current time; Work as η _k=2 o'clock, there was 1 packet loss in the expression network, by that analogy.

For the network control system that contains random loss in the network, according to discrete model construction method above-mentioned it is carried out discretize, its time-varying sampling period is The state space equation of system is as follows after the discretize:

$\left\{\begin{array}{c}x(k+{\mathrm{\η}}_k)=G\left({\mathrm{\η}}_k\right)x\left(k\right)+H\left({\mathrm{\η}}_k\right)u\left(k\right)+F\left({\mathrm{\η}}_k\right)\mathrm{\ω}\left(k\right)\\ z\left(k\right)=\mathrm{Cx}\left(k\right)+\mathrm{D\ω}\left(k\right)\end{array}\right.---\left(4\right)$

Wherein, $G\left({\mathrm{\η}}_k\right)=e^{A{\mathrm{\η}}_{k}T},$ $H\left({\mathrm{\η}}_k\right)={\∫}_0^{{\mathrm{\η}}_{k}T}{e}^{\mathrm{As}}\mathrm{dsB},$ $F\left({\mathrm{\η}}_k\right)={\∫}_0^{{\mathrm{\η}}_{k}T}{e}^{\mathrm{As}}\mathrm{dsE}.$

In addition, the controller of the nonmodal dependence of the present invention's design is

u(k)＝K∏x(k-τ _k)，(0≤τ _k≤τ _M)(5)

Wherein,

In the formula (5), matrix K is ride gain to be asked.τ _kThe expression sensor is to the random delay of actuator, τ _MBe the time delay upper bound.ρ _i(i=1 ..., n) be n uncorrelated random variables, and also uncorrelated with disturbance input ω (t).In the present invention, ρ _iEach sensor fault situation in the expression network is supposed ρ _iProbability density function be F (ρ _i), span is [0,1], and ρ _iMathematical expectation and variance be respectively α _iWith

The above has introduced respectively the modeling situation of packet loss, random delay and three kinds of network environments of probability sensor fault, when considering that simultaneously when having three kinds of network factors in the network control system, the state space equation of closed-loop system can be rewritten as:

$\left\{\begin{array}{c}x(k+{\mathrm{\η}}_k)=G_{i}x\left(k\right)+H_i\mathrm{K\Πx}(k-{\mathrm{\τ}}_k)+F_i\mathrm{\ω}\left(k\right)\\ =G_{i}x\left(k\right)+H_{i}K(\mathrm{\Π}-\stackrel{\‾}{\mathrm{\Π}})x(k-{\mathrm{\τ}}_k)+\\ H_{i}K\stackrel{\‾}{\mathrm{\Π}}x(k-{\mathrm{\τ}}_k)+F_i\mathrm{\ω}\left(k\right)\\ z\left(k\right)=\mathrm{Cx}\left(k\right)+\mathrm{D\ω}\left(k\right)\\ x\left(k\right)=X\left(k\right),l=-{\mathrm{\τ}}_M,-{\mathrm{\τ}}_M+1,...,0.\end{array}\right.$

Wherein, X (k) is the original state of system,

$G_i=G_{{\mathrm{\η}}_k=i},H_i=H_{{\mathrm{\η}}_k=i},F_i=F_{{\mathrm{\η}}_k=i},i=1,...,\mathrm{\σ}.$

According to the Lyapunov stability theory, analyze the stochastic stability of closed-loop system, final design has gone out satisfactory state feedback controller, and has H _∞The disturbance fade performance.The controller design need to be found the solution one group of corresponding LMI.

For given closed-loop system (6), if there is the matrix P with suitable dimension _i＞0, Q＞0, R＞0, X _i＞0, Y＞0, Z＞0 and ride gain matrix K are so that the establishment of following MATRIX INEQUALITIES:

$\left[\begin{array}{ccccc}{\widetilde{\mathrm{\&Gamma;}}}_1& *& *& *& *\\ {\mathrm{\&Theta;}}_{21}& -X_i& *& *& *\\ {\mathrm{\&Theta;}}_{21}& 0& -Y& *& *\\ {\mathrm{\&tau;}}_M{\mathrm{\&Theta;}}_{22}& 0& 0& -{\mathrm{\&tau;}}_{M}Z& *\\ {\widetilde{\mathrm{\&Gamma;}}}_2& 0& 0& 0& {\widetilde{\mathrm{\&Gamma;}}}_3\end{array}\right]<0,---\left(7\right)$

$\stackrel{\&OverBar;}{P}{\mathrm{\&Lambda;}}_i{X}_i=I,$ QY＝I，RZ＝I.(8)

Wherein,

${\widetilde{\mathrm{\&Gamma;}}}_1=\left[\begin{array}{cccc}{\mathrm{\&Gamma;}}_{11}& *& *& *\\ {\mathrm{\&Gamma;}}_{21}& {\mathrm{\&Gamma;}}_{22}& *& *\\ D^{T}C& 0& -{\mathrm{\&gamma;}}^{2}I+D^{T}D& *\\ -{\mathrm{\&tau;}}_M({\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="HDA0000149566600000021.png"\; state="\{\{state\}\}">M</figure-callout>}}_1+N_1)& -{\mathrm{\&tau;}}_M({\mathrm{<figure-callout\; id="2"\; label="M"\; filenames="HDA0000149566600000021.png"\; state="\{\{state\}\}">M</figure-callout>}}_2+N_2)& 0& -{\mathrm{\&tau;}}_{M}R\end{array}\right]$

${\mathrm{\&Gamma;}}_{11}=M_1+M_1^T+{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="HDA0000149566600000021.png"\; state="\{\{state\}\}">N</figure-callout>}}_1+N_1^T-P_i+C^{T}C,$

Γ ₂₁＝-M ₁+M ₂-N ₁+N ₂，

${\mathrm{\&Gamma;}}_{22}=-M_2-M_2^T-N_2-N_2^T-Q,$

${\mathrm{\&Theta;}}_{21}=\left[\begin{array}{cccc}{G}_i& H_{i}K\stackrel{\&OverBar;}{\mathrm{\&Pi;}}& F_i& 0\end{array}\right],$

${\mathrm{\&Theta;}}_{22}=\left[\begin{array}{cccc}{G}_i-I& H_{i}K\stackrel{\&OverBar;}{\mathrm{\&Pi;}}& F_i& 0\end{array}\right],$

${\widetilde{\mathrm{\&Gamma;}}}_2={\left[\begin{array}{ccc}{\mathrm{\&Phi;}}^T& {\mathrm{\&Phi;}}^T& {\mathrm{\&tau;}}_M{\mathrm{\&Phi;}}^T\end{array}\right]}^T,\mathrm{\&Phi;}={\left[\begin{array}{cccc}{\mathrm{\&phi;}}_1^T& {\mathrm{\&phi;}}_1^T& ...& {\mathrm{\&phi;}}_n^T\end{array}\right]}^T,$

φ _j＝[0?β _jH _iKγ _j?0?0]，i＝1，2，...，n，

${\stackrel{\&OverBar;}{P}}^T=\left[\begin{array}{ccc}{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="HDA0000149566600000021.png"\; state="\{\{state\}\}">P</figure-callout>}}_1& ...& P_{\mathrm{\&sigma;}}\end{array}\right],$ Λ _i＝[λ _i1I _n…λ _iσI _n】，i＝1，...，σ.

The controller (5) that then exists a nonmodal to rely on so that closed-loop system (6) is stable at random, and satisfies given H _∞The disturbance fade performance.

Can obtain as shown in Figure 1 a kind of control method for the communication limited network according to above-mentioned principle, specifically may further comprise the steps:

1) controller is sent to actuator according to the original state output initial control signal of system via the control network, and by actuator control controlled device;

2) sensor carries out periodic sampling to the status signal of controlled device, and by control network input control device;

3) controller is processed the status signal of input by the ride gain matrix, outputs control signals to actuator;

4) actuator is controlled controlled device according to the control signal that receives, and then from step 2) begin to carry out, realize the real-time control of closed-loop system.

Wherein, the ride gain matrix is according to the control state parameter of network and the model parameter of controlled device, and utilizes the line style MATRIX INEQUALITIES to obtain, and the state parameter of control network comprises the failure rate of the maximum packet loss upper bound, the time delay upper bound and sensor.

Said method can be applicable to control system as shown in Figure 2, comprise controller 2, actuator 3, sensor 1 and controlled device 4, controlled device 4 connects respectively actuator 3 and sensor 1, and controller 2 connects respectively actuator 3 and sensor 1 by the control network, forms closed-loop system.

Controller to above-mentioned control system carries out analogue simulation, supposes that system model is following inverted pendulum simplified model:

$\stackrel{\&CenterDot;}{x}\left(t\right)=\left[\begin{array}{cc}0& 1\\ 1& 0\end{array}\right]x\left(t\right)+\left[\begin{array}{c}0\\ 1\end{array}\right]u=\left(\mathrm{kT}\right)+\left[\begin{array}{c}0\\ 0.1\end{array}\right]\mathrm{\&omega;}\left(t\right),$

$z\left(t\right)=\left[\begin{array}{cc}1& 0\\ 1& 1\end{array}\right]x\left(t\right)+\left[\begin{array}{c}0\\ 1\end{array}\right]\mathrm{\&omega;}\left(t\right),t\&Element;[\mathrm{kT},(k+1)T).$

According to above-mentioned model as can be known, this system of systems eigenwert is 1 and-1, so this system is unsettled.Below we will be according to above-mentioned controller design method CONTROLLER DESIGN so that this system is stable at random, and satisfy given H _∞Performance index.

Given following systematic parameter.The sampling time of supposing this system is T=0.2s, scalar γ=1.2, and the packet loss upper bound of network is σ=3, namely δ={ 1,2,3}, the maximum delay upper bound is τ _M=2.Transition probability matrix between the system mode is

$\mathrm{\&Lambda;}=\left[\begin{array}{ccc}0.5& 0.5& 0\\ 0.3& 0.6& 0.1\\ 0.1& 0.6& 0.3\end{array}\right].$

In addition, ρ _iProbability density function be

$F\left({\mathrm{\&rho;}}_1\right)=\left\{\begin{array}{cc}0.1,& {\mathrm{\&rho;}}_1=0\\ 0.2,& {\mathrm{\&rho;}}_1=0.5\\ 0.7,& {\mathrm{\&rho;}}_1=1\end{array}\right.$ $F\left({\mathrm{\&rho;}}_2\right)=\left\{\begin{array}{cc}0.2,& {\mathrm{\&rho;}}_2=0\\ 0.2,& {\mathrm{\&rho;}}_2=0.5\\ 0.6,& {\mathrm{\&rho;}}_2=1\end{array}\right.$

Hence one can see that, ρ ₁And ρ ₂Mathematical expectation and variance be respectively α ₁=0.71,

And α ₂=0.61, ${\mathrm{\&beta;}}_2^2=0.17.$

Utilize above-mentioned system discretization method, the inverted pendulum model in discrete this example, the stochastic systems that can obtain having three kinds of mode.According to above-mentioned parameter with based on the controller design method of LMI, utilize cone to mend iterative algorithm, the controller of design is as follows:

K＝[-3.6132-3.7836].

In order to verify the validity of method for designing, the curvilinear path of any given one group of Markovian packet loss process and random delay.The original state of supposing the system is x ₀=[0 0] ^T, and the disturbance input of system is

This controller can be controlled the reversible pendulum system that has packet loss, random delay and probability sensor fault in the network, the state trajectory of system as shown in Figure 3, as we know from the figure, the Effective Raise Systems balanth according to the present invention.

Claims (4)

1. a control method that is used for the communication limited network is characterized in that, may further comprise the steps:

1) controller is sent to actuator according to the original state output initial control signal of system via the control network, and by actuator control controlled device;

2) sensor carries out periodic sampling to the status signal of controlled device, and by control network input control device;

3) controller is processed the status signal of input by the ride gain matrix, outputs control signals to actuator;

4) actuator is controlled controlled device according to the control signal that receives, and then execution in step 2) realize the closed-loop control of system.

2. a kind of control method for the communication limited network according to claim 1 is characterized in that, described ride gain matrix obtains by finding the solution corresponding LMI according to the state parameter of control network and the model parameter of controlled device.

3. a kind of control method for the communication limited network according to claim 1 is characterized in that, the state parameter of described control network comprises the failure rate of the maximum packet loss upper bound, the time delay upper bound and sensor.

4. control system of using control method as claimed in claim 1, it is characterized in that, comprise controller, actuator, sensor and controlled device, described controlled device connects respectively actuator and sensor, described controller connects respectively actuator and sensor by the control network, forms closed-loop system.

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