SERF inertial measurement air chamber temperature self-adaptive decoupling control method and system based on double-sampling and double-control

Abstract

The invention provides an SERF inertial measurement air chamber temperature self-adaptive decoupling control method and system based on double-sampling and double-control aiming at the characteristics of large time lag and strong coupling of an SERF inertial measurement alkali metal air chamber double-sampling and double-control heating system. Phase angle lag caused by system time lag is suppressed by adopting Smith pre-estimation control, and Smith pre-estimation control deviation caused by double-loop coupling and internal model mismatch is regarded as lumped disturbance to be suppressed by utilizing linear active disturbance rejection control (LADRC). Further dynamically adjusting the bandwidth of a system controller and an observer according to the tracking error through an adaptive linear quadratic regulator (ALQR) so as to enhance the anti-interference capability and the response speed of the system; the method improves the long-term stability and disturbance suppression capability of the alkali metal gas chamber double-production and double-control heating system, has the advantages of fast dynamic parameter response, strong robustness and the like, and can be used for high-precision temperature control of an SERF inertial measurement gas chamber.

Description

Technical Field

[0001] The present invention relates to a SERF inertial measurement chamber temperature adaptive decoupling control method and system based on dual sampling and dual control, which can be used in the field of SERF inertial measurement instruments. Background Art

[0002] Atomic sensors based on the spin-exchange relaxation-free (SERF) effect have been widely studied and applied in cutting-edge scientific research, inertial navigation, and biomedical imaging due to their ultra-high sensitivity at the sub-fetrate level. To suppress the longitudinal temperature gradient in the gas chamber introduced by the asymmetric heat transfer in the oven, a dual-sampling and dual-control scheme is adopted to reduce the longitudinal temperature distribution gradient of the heating system by separately controlling the heating power in the high-temperature and low-temperature zones of the oven.

[0003] The alkali metal gas chamber is the core of the SERF inertial measurement system. Its temperature stability is an important factor affecting the system drift. After the dual-sampling and dual-control scheme is adopted for the SERF inertial measurement gas chamber heating system, the strong coupling and large time lag characteristics of the heating system make the traditional PID control unable to meet the high-precision temperature control requirements of the SERF inertial measurement instrument. Therefore, it is necessary to improve the anti-interference ability and stable control accuracy of the gas chamber dual-sampling and dual-control system by designing a new decoupling control scheme. Summary of the Invention

[0004] The present invention designs a SERF inertial measurement chamber temperature adaptive decoupling control method and system based on dual sampling and dual control to solve the problems of decreased steady-state accuracy and slow system response introduced by the strong coupling and large time lag characteristics of dual sampling and dual control of chamber temperature. The Smith predictor controller is used to compensate for the phase lag introduced by the system response delay. The LADRC is used to suppress the coupling between the two temperature control loops and the disturbance caused by ambient temperature fluctuations, and to compensate for the influence of system modeling errors on the Smith predictor control effect, ultimately realizing the estimation and suppression of the lumped disturbance inside and outside the system. On this basis, in order to optimize the anti-disturbance capability of the system, the present invention combines the ALQR control system controller and observer parameters to improve the dynamic response effect and long-term stability of the system.

[0005] The technical solution of the present invention is as follows

[0006] A dual-sampling and dual-control SERF inertial measurement chamber temperature adaptive decoupling control method and system is proposed. By separately controlling the two longitudinally distributed heating membranes of the SERF inertial measurement heating system, the temperature gradient problem introduced by the asymmetric heat transfer structure of the system is suppressed. At this time, there is a strong coupling between the two temperature control loops of the system. At the same time, considering the inherent time lag of the heat transfer system, traditional PID control cannot guarantee the long-term temperature control accuracy and disturbance suppression capability of the system.

[0007] First, in order to solve the problem that the time delay of the heating system causes the output response to lag, the present invention proposes a Smith predictive control scheme. By constructing a predictive function containing a time delay, the system output is predicted, thereby compensating for the influence of the lag link on the system stability. However, this scheme is highly dependent on the model accuracy. If there is a parameter mismatch between the constructed predictive function and the original controlled object model, it will affect the effect of the predictive control and even cause oscillation; further, to solve the problem of strong coupling of the system, the present invention adopts the LADRC method. On the one hand, this scheme regards the coupling between the temperature control loops as external interference and achieves decoupling by suppressing the interference. On the other hand, it suppresses the internal interference introduced by inaccurate modeling, thereby compensating for the influence of the model parameter mismatch on the Smith predictive controller; finally, in order to improve the anti-disturbance effect of the system, ALQR optimizes the controller bandwidth and observer bandwidth of LADRC in real time according to the tracking error, so that the system achieves the optimal control effect. Finally, through experimental tests, the use of the adaptive decoupling control method has significantly improved the dynamic response characteristics of the system compared with the traditional PID control scheme.

[0008] The advantages of the present invention over the prior art are:

[0009] 1. To address the phase lag problem caused by the inherent pure hysteresis characteristics of the heating system, the present invention adopts Smith predictive control. By constructing an internal model that includes time delays, this strategy accurately predicts and compensates for the hysteresis effect, effectively suppressing the phase lag and significantly improving the speed and stability of the system's closed-loop response.

[0010] 2. The present invention introduces LADRC to uniformly regard the complex system coupling and model uncertainty caused by heat transfer in the dual-source dual-control system as a lumped disturbance. By constructing a linear extended state observer (LESO), the total disturbance is estimated with high precision and fed-forward compensation is provided. On the one hand, this mechanism achieves effective decoupling between the various regions of the system. On the other hand, its powerful disturbance suppression capability effectively compensates for the impact of model parameter mismatch on Smith predictor control, thereby enhancing the robustness of the system.

[0011] 3. This invention innovatively incorporates an adaptive mechanism based on the LQR optimal control framework. This scheme increases the bandwidth of the regulation controller and observer according to the real-time tracking error when external disturbances occur, thereby improving the system response speed and anti-disturbance capability. Under steady-state conditions, the controller bandwidth and observer bandwidth are kept small to avoid the introduction of high-frequency interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a SERF inertial measurement chamber temperature adaptive decoupling control method and system algorithm optimization diagram based on dual sampling and dual control.

[0013] Figure 2This is a control block diagram of a SERF inertial measurement chamber temperature adaptive decoupling control method and system based on dual sampling and dual control.

[0014] Figure 3 Temperature fluctuation diagram of the two control loops of the alkali metal gas chamber heating system under PID algorithm control

[0015] Figure 4 Temperature fluctuation diagram of the two control loops of the alkali metal gas chamber heating system under the adaptive decoupling control algorithm DETAILED DESCRIPTION

[0016] In order to facilitate understanding of the present invention, the present invention is described in more detail below with reference to specific embodiments and comparative examples:

[0017] Due to the influence of heat conduction characteristics, the two temperature outputs of the alkali metal gas chamber heating system based on dual sampling and dual control are affected by the heating signal of the other channel respectively, which makes the system have strong coupling characteristics. At the same time, the inherent time lag characteristics of the heat transfer system make it impossible to achieve high-precision control using the traditional PID algorithm. Therefore, a SERF inertial measurement gas chamber temperature adaptive decoupling control method and system based on dual sampling and dual control are designed. The characteristics are: in view of the strong coupling and large time lag characteristics of the system, an adaptive decoupling control algorithm is proposed to improve the system stability and anti-interference ability. The optimization ideas are as follows Figure 1 shown.

[0018] Step 1: Establish a controlled object model under dual sampling and dual control, and analyze the system characteristics; According to the test modeling method, the present invention obtains a system model described by a 2×2 transfer function matrix. Each transfer function component G in the matrix ij (s) are all first-order inertia links with time delay. The static coupling coefficient of the two loops is close to 1, and the system is a strongly coupled system. On the other hand, the system is affected by the time delay, and its stability margin is small, which makes it sensitive to external ambient temperature fluctuations and has a weak interference capability.

[0019] Step 2: Based on the above system characteristics, optimize the control algorithm to improve the anti-interference ability and control accuracy of the alkali metal gas chamber temperature dual sampling and dual control system.

[0020] First, in view of the strong coupling characteristics of the system, the present invention chooses to use linear active disturbance rejection control, treating the coupling between the two loops as interference. Through the expansion observer, the total disturbance of the system is observed and suppressed. At this time, the state space expression of the system is written as:

[0021]

[0022] where the matrix and matrix are the system matrix and input matrix of the dual-input and dual-output system respectively. The state variables and output variables of the system are:

[0023]

[0024]

[0025] Where x1 and x2 are the state variables of control loop 1 and control loop 2 respectively, and y1 and y2 are the temperature outputs of the two control loops. The extended observer of the system state is further constructed

[0026]

[0027] Among them, matrix A and matrix B are the state matrix and control matrix of the system after state expansion, and the system state variables and output variables are as follows:

[0028]

[0029] in and are the estimates of the total disturbances received by the two control loops, and the corresponding feedback control rate designs are:

[0030]

[0031] in K is the feedback control matrix.

[0032] In addition, the temperature control system has a significant time delay, which causes the system response to have a hysteresis characteristic, thus affecting the system stability. At this time, the system transfer function component is written as:

[0033] G ij (s)=G0(s)e -τs

[0034] Where τ is the delay time. Therefore, in combination with this delay characteristic, the present invention further adopts a Smith predictive control scheme based on active disturbance rejection. On the one hand, Smith predictive control compensates for the delay effect introduced in the heat transfer process by connecting a compensator shunt in parallel with the controlled object, so that the output y and the control variable u can be synchronized on the time axis, so that the forward path of the system will no longer be affected by the delay. At this time, the open-loop transfer function of the system will become:

[0035] G(s)=G c (s)[G0(s)e -τs +G m (s)]=G c (s)G0(s)

[0036] The Smith predictor controller constructed in the formula is G m (s) = G0(s)(1-e -τm s);

[0037] Ultimately, the optimized system closed-loop transfer function eliminates the effect of delay and becomes as follows:

[0038]

[0039] During the application process, the effect of the Smith predictive controller depends on the accuracy of the model establishment, but the actual modeling often cannot obtain a completely accurate object model, that is, a model mismatch occurs. At this time, the application of the Smith predictive controller may even cause system instability. The present invention combines LADRC with Smith predictive control. On the one hand, LADRC is used to simultaneously suppress the disturbance effects caused by the coupling of the two loops and ambient temperature fluctuations. On the other hand, the characteristic of LADRC in estimating the total disturbance is used to compensate for the system modeling error, thereby reducing the impact of model mismatch on the Smith predictive controller.

[0040] Step 3: In order to improve the system's suppression effect on external disturbances, the present invention proposes an adaptive control rate based on the LQR optimal control framework, which adjusts the system's controller bandwidth and observer bandwidth in real time according to the tracking error. The control block diagram of the system under the final solution is as follows: Figure 2 shown.

[0041] To construct the linear quadratic regulator of the dual-sampling and dual-control system, the system tracking error is first defined as:

[0042]

[0043] Further according to the state equation of the system, the state equation of the system error is derived as follows:

[0044]

[0045] At this time, the cost function of the system is written as follows, where Q and R are the weight matrices of the state and control variables respectively:

[0046]

[0047] In order to improve the performance of the controller and observer, the error state can be transformed to specify the controller pole position to be smaller than the controller bandwidth ω. c ,make

[0048]

[0049] Substitute the above coordinate transformation expression into the original system error equation and we get

[0050]

[0051] At the same time, after the coordinate transformation, the cost function of the system LQR becomes

[0052]

[0053] Wherein, the transformation forces the new system matrix All eigenvalues ​​of the real part are less than zero, and the lower bound of the convergence rate of the original system state ε(t) is constrained to ω c , that is, satisfy Thus, the controller poles are configured to the complex plane Re(s)≤-ω c In the region, the lower bound of its convergence rate is given by ω c Direct control; at this time, the controller bandwidth ω can be changed c To improve the control accuracy and anti-interference ability of the alkali metal chamber temperature dual sampling and dual control system under environmental interference, the present invention adjusts the control effect of the system according to the size of the real-time tracking error of the system for the controller bandwidth ω c Design the adaptive control rate as follows:

[0054]

[0055] Among them, α and β are adaptive gains, which determine the system's sensitivity to errors. The larger their values, the faster the adjustment rate, but it may cause oscillations. β is the damping term of adaptive adjustment. In an adaptive system, if the parameters are driven only by the error term, when the system is subjected to a small continuous disturbance or measurement noise, the adaptive parameter change rate will always be greater than zero, which means that the adaptive parameters will grow infinitely, resulting in an excessively large control signal and system instability. Therefore, a damping term is added to the adaptive parameter change rate to avoid unbounded parameter growth. For the expanded observer in the present invention, in order to ensure the control effect, the observer bandwidth is usually 2 to 10 times the controller bandwidth. The present invention stipulates that the observer bandwidth is 3 times the controller bandwidth.

[0056] Finally, the control effects of PID control and the proposed adaptive decoupling control algorithm on the air chamber temperature are compared; the experimental conditions are: the target temperature of the two loops is set to 180℃, and when there is a ±1℃ sinusoidal ambient temperature fluctuation, the long-term stability of the system is as follows: Figure 3 、 Figure 4 shown.

[0057] In the presence of periodic interference, the long-term temperature fluctuation of control loop one is reduced from 16mK to 5mK, and the long-term temperature fluctuation of control loop two is reduced from 20mK to 5mK; the adaptive decoupling control method designed in the present invention enhances the disturbance suppression capability of the system, improves the long-term stability of the gas chamber heating system, and ensures the high-precision temperature control requirements of SERF inertial measurement.

[0058] The contents not described in detail in the specification of the present invention belong to the prior art known to those skilled in the art.

Claims

1. A dual-sampling, dual-control, SERF inertial measurement chamber temperature adaptive decoupling control method and system based on dual sampling and dual control. A dual sampling, dual-control scheme is proposed for the alkali metal chamber heating system in SERF inertial measurement. The chamber temperature gradient problem introduced by uneven heat transfer is suppressed by separately adjusting the temperatures of the upper and lower halves of the oven. Due to the influence of contact heat conduction, the temperatures of the two control loops of the controlled system influence each other, giving the system a coupled characteristic. At the same time, the inherent pure hysteresis characteristic of the heating system causes problems such as phase lag in the system. For the strongly coupled, large time-delay system, the present invention proposes an adaptive decoupling control method: First, the system time delay problem is addressed through Smith predictor control. Furthermore, the linear active disturbance rejection control (LADRC) is used to treat the Smith predictor control deviation caused by dual-loop coupling and internal model mismatch as a lumped disturbance for suppression. Finally, an adaptive linear quadratic regulator (ALQR) is combined to optimize the controller bandwidth and observer bandwidth of the LADRC according to the magnitude of the observation error to improve the dynamic response characteristics of the system.

2. The Smith predictive controller according to claim 1 addresses the time lag problem in the SERF inertial measurement alkali metal chamber heating dual-sampling and dual-control system. A predictive controller is designed using a controlled object model and connected in parallel with the controlled object to compensate for the phase lag caused by the heat transfer process, ensuring that the system output and control input are synchronized on the time axis, ultimately eliminating the delay component in the system's closed-loop transfer function.

3. The LADRC according to claim 1 addresses the coupling problem introduced by contact heat conduction in the SERF inertial measurement alkali metal chamber heating dual-sampling and dual-control system. By utilizing the LADRC's characteristic of suppressing lumped disturbances, on the one hand, the coupling between the two temperature control loops is regarded as interference, which is observed in real time by the extended observer in the LADRC and fed-forward compensated. On the other hand, the LADR is used to suppress the Smith Predictor control deviation caused by modeling errors. In this case, the LADRC not only compensates for the coupling interference between the control loops, but also compensates for the impact of model parameter mismatch on the Smith Predictor controller, thereby ensuring the long-term stability of the system.

4. The ALQR according to claim 1, in the optimal control framework of LQR, by introducing a controller bandwidth ω c Scale the coordinate transformation by the exponential of the argument: Thus the original error dynamic system Convert to The original cost function Convert to in, The system will form a control law by solving the optimized LQR problem, forcing the real part of the controller pole to satisfy Re(s)≤-ω c , and the convergence lower bound is given by ω c Direct control. Furthermore, the adaptive control rate is used to adjust the LADRC controller bandwidth and observer bandwidth in real time according to the tracking error, and the LQR algorithm is combined to calculate the optimal ADRC and observer parameters at the desired bandwidth. The adaptive algorithm is designed as follows: The parameter α is the adaptive gain, which determines the system's sensitivity to error. However, if its value is too large, it may cause oscillation. The parameter β is the damping term in the adaptive control, which is used to avoid unbounded parameter growth. At the same time, according to the LADRC design principle, the observer bandwidth needs to be larger than the controller bandwidth to achieve fast state estimation. To simplify the calculation and algorithm design, the present invention fixes the observer bandwidth value to 3 times the controller bandwidth value. oh o (t)=3ω c (t)。

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