Continuous tracking control method of network control system under control framework

Abstract

The invention discloses a continuous tracking control method of a network control system under a control framework. The network control system belongs to a nonlinear system with strict feedback. A filter is added to an actuator end, the filter is combined with a controlled object to serve as a new extension system, and then the extension system is subjected to tracking controller design. The technical scheme provided by the invention has the beneficial effects that the saturation quantizer is introduced, so that the occupation of communication resources is reduced, and the requirement on communication bandwidth is reduced; a filter is introduced into an actuator end, transmitted discontinuous control signals are converted into continuous signals to act on the actuator, and continuous control is guaranteed; compared with the prior art, the algorithm provided by the invention can realize remote continuous control on the controlled object while reducing the communication burden.

Description

Technical Field

[0001] This invention belongs to the field of nonlinear system control technology and relates to a continuous tracking control method for a network control system under a new control framework. Background Technology

[0002] Due to the widespread application of networked control systems in remote control of drones, unmanned vehicles, and robots, they have attracted considerable attention in the control field. In networked control systems, control signals often need to be transmitted to the actuator via a controller-actuator channel. Quantizing the signal before transmission maps a continuous signal to a finite number of discrete values, significantly reducing the bandwidth requirements and alleviating communication burden. However, in practical applications such as machine tool systems, chemical production systems, and water treatment systems, signal jumps in actuators can cause negative effects such as mechanical wear and excessive impact loads. Therefore, designing a continuous control method based on signal quantization transmission has become increasingly important to researchers. Summary of the Invention

[0003] To address the aforementioned problems in the existing technology, this invention proposes a continuous tracking control method for network control systems under a new control framework.

[0004] This invention designs a continuous tracking control method for a networked control system under a novel control framework, ensuring that the signal acting on the controlled object is continuous and can accurately track the desired trajectory during long-distance transmission of control signals. Compared with traditional remote tracking control, the innovation lies mainly in two aspects: 1) By introducing a saturation quantizer, the quantization layer can be determined in advance, reducing the demand for transmission bandwidth and alleviating the communication burden. 2) By adding a low-pass filter at the actuator end and integrating the extended system into a single design, the continuity of the signal acting on the controlled object is guaranteed.

[0005] The technical solution adopted in this invention is a continuous total control method for a networked control system under a new control framework, comprising the following steps:

[0006] S1. For a class of network control systems, the following strict feedback nonlinear system model is established:

[0007] In the formula x i ,i=1,...,n are the system states, y is the system output, g i (·), i=1,...,n are known smooth functions, θ i ,i=1,...,n is an unknown constant vector, and u represents the control signal.

[0008] S2. Design a first-order filter for the saturated quantized signal transmitted in the controller-actuator channel;

[0009]

[0010] S3. Based on the controlled object and the designed first-order filter, establish an extended system with a new dimension.

[0011] S4. Based on the new extended system, an adaptive quantization tracking control protocol is constructed using adaptive back-propagation control technology:

[0012] In the formula, η is a positive design parameter. It is an adaptive law, where w is an intermediate variable and z is an adaptive variable. n+1 Let n+1 be the error variable;

[0013] S5. Verify the stability and tracking performance of the control system using Lyapunov stability theory.

[0014] Compared with existing methods, the beneficial effects of the present invention are as follows: by introducing a saturable quantizer, the quantization layer can be determined in advance, while reducing the demand for transmission bandwidth and alleviating the communication burden; by adding a low-pass filter at the actuator end and designing the extended system as an integrated whole, the continuity of the signal acting on the controlled object is guaranteed. Attached Figure Description

[0015] Figure 1 This is a flowchart of the invention;

[0016] Figure 2 This is a new control framework diagram according to an embodiment of the present invention;

[0017] Figure 3 These are simulation results of the tracking control in an embodiment of the present invention;

[0018] Figure 4 These are simulation results of the quantized signal in an embodiment of the present invention;

[0019] Figure 5 These are simulation results of the continuous actuator signals in an embodiment of the present invention. Detailed Implementation

[0020] In existing network control systems, the number of quantization layers for transmitted signals is often unknown in advance, and the actuator signals acting on the controlled object are discontinuous and step-like. This can easily have a negative impact on the system.

[0021] To address the above problems, the present invention provides the following approach:

[0022] 1) Based on the quantization transmission of control signals, a saturated quantization controller is introduced, which reduces the communication burden while ensuring that the number of quantization layers can be determined in advance.

[0023] 2) By adding a low-pass filter at the actuator end and designing the extended system as a whole, a continuous actuator signal can be obtained based on quantized transmission.

[0024] Based on the above research ideas, the structural block diagram of the continuous tracking control method based on a new control framework of this invention is as follows: Figure 2 As shown, the controller design steps include the following:

[0025] 1) Determine the saturation quantizer model as follows:

[0026] In the formula, v M It is the saturation threshold, and q(v) is a commonly used hysteresis quantizer.

[0027] 2) Design a first-order low-pass filter for saturated quantized signals.

[0028]

[0029] For the extended system combining (1) and (5), the original control signal u becomes a state signal, and we need to design a new control signal v that needs to be quantized before transmission at the controller. Here we define the (n+1)th surface error.

[0030]

[0031] 3) Design a new tracking controller by adopting adaptive back-pull control technology.

[0032]

[0033] In the formula, η is a positive design parameter, and the adaptive law for unknown parameters is designed as follows:

[0034]

[0035] In the formula, τ n It is the parameter tuning rate obtained using adaptive back-calculation technique for the first n steps.

[0036] For unknown gain The adaptive law design is as follows:

[0037]

[0038] In the formula, γ p and σ p These are design parameters, and

[0039]

[0040] 4) To meet the control performance requirements, verify the stability of the closed-loop signal of the network control system, and demonstrate that the tracking performance with arbitrarily small tracking error can be achieved by adjusting the parameters.

[0041] To check the stability and tracking performance of the control system, firstly, based on the definition of the (n+1)th surface error in 3), we can obtain...

[0042]

[0043] Define the Lyapunov function as:

[0044]

[0045] Combining the control law and the adaptive law mentioned above, V can be obtained. n+1 The differential satisfies:

[0046]

[0047] Further simplification yields,

[0048]

[0049] In the formula

[0050] κ=min{2c1,…,2c n+1 ,γσ,γ p σ p}(15)

[0051]

[0052] By solving equation (14), we can obtain:

[0053]

[0054] From the above equation, we can deduce that the signal z i , α i The boundedness of u, w, v further leads to

[0055]

[0056] Therefore, by appropriately selecting design parameters, and ensuring that b remains unchanged in equation (16), the value of κ in equation (15) can be increased, thus ensuring that the tracking error converges to an arbitrarily small set.

[0057] The following is a numerical simulation example: The method proposed in this invention will be illustrated below with a numerical simulation.

[0058] Consider a second-order nonlinear system, whose model is as follows:

[0059]

[0060] Referring to system (1), where x1 and x2 are the system states, and y = x1 is the system output. The nonlinear function is g1(x1) = 0, g2(x1, x2) = [x1... 2 The unknown constant vectors are θ1 = 0 and θ2 = [0.2, 2]. T Our control objective is to propose a control based on... Figure 2 The continuous control signals of the control framework enable the output y to track the desired trajectory y very well. r =sint.

[0061] According to the design scheme proposed in 3), the virtual control law and control signal are selected as follows:

[0062] α1=-5z1(20)

[0063]

[0064]

[0065]

[0066]

[0067]

[0068] The initial conditions are set to [x1(0), x2(0)]. T =[0.2,0] T , And select the saturation quantizer parameters as δ = 0.3, v M =60.

[0069] Figure 3-5 The stability and tracking performance of the nonlinear system (19) under the control framework and control scheme proposed in this specification are shown. It can be seen that, based on reducing the communication burden by quantizing the transmission of control signals, a good tracking effect can be guaranteed by adding a low-pass filter while ensuring the continuity of the actuator signal.

[0070] The present invention has been described above by way of examples. Those skilled in the art should understand that the present disclosure is not limited to the examples described above, and various changes, modifications and substitutions can be made without departing from the scope of the present invention.

Claims

1. A continuous tracking control method for a networked control system under a control framework, comprising adding a filter at the actuator end, combining it with the controlled object as an extended system, and then designing a tracking controller for the extended system; characterized in that: Specifically, the following steps are included: S1. Establish a mathematical model for the network control system; For a class of networked control systems, the following strict feedback nonlinear system model is established: In the formula x i ,i=1,...,n are the system states, y is the system output, g i (·), i=1,...,n are known smooth functions, θ i ,i=1,...,n is an unknown constant vector, and u represents the control signal; S2. Design a first-order filter for the saturated quantized signal transmitted in the controller-actuator channel; S3. Based on the controlled object and the designed first-order filter, establish a new dimension of extended system; S4. Based on the new extended system, an adaptive quantization tracking control protocol is constructed using adaptive back-propagation control technology: In the formula, η is a positive design parameter. It is an adaptive law, where w is an intermediate variable and z is an adaptive variable. n+1 Let n+1 be the error variable; S5. Verify the stability and tracking performance of the control system using Lyapunov stability theory.

2. The continuous tracking control method for a networked control system under a new control framework according to claim 1, characterized in that: After the control signal is quantized, it is transmitted through the controller-actuator channel, which reduces the burden on network communication.

3. The continuous tracking control method for a networked control system under a new control framework according to claim 1, characterized in that: By adding a filter to the actuator and integrating it into the extended system, the signal acting on the actuator is made continuous, thus avoiding the impact damage to the actuator caused by discontinuous action.

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