Research on fast self-learning improvement of ADRC control algorithm for film thickness control system

This paper discusses the problem of friction disturbance compensation of tank gun servo system. For the friction uncertainties and non-model dynamics in tank azimuth gun control system, the azimuth Gun Control system model and friction model are established firstly, then considering them as a composite disturbance, and then, extended states observer (ESO), a new observer is proposed to observe and compensate this composite disturbance, and using the compensation loop of active disturbance rejection control (ADRC) as the inner loop of traditional PID controller. Finally, the simulation results show that the anti-interference ability could be improved by the designing of ADRC with traditional PID control, which has the feature of "passive anti-interference" and "active anti-interference". The stable precision of visible axis and low speed feature could be well improved.

This paper presents the development and application of an Active Disturbance Rejection Controller (ADRC) to regulate the frequency error for a three-area interconnected power system. As the interconnected power system transmits the power from one area to another, the system frequency will inevitably deviate from a scheduled frequency, resulting in a frequency error. A control system is essential to correct the deviation in the presences of external disturbances and structural uncertainties to ensure a safe and smooth operation of the power system. ADRC can extract the information of the disturbance from input and output data of the system and actively compensate for the disturbance in real time. In addition, it has the advantages of simple structure, few tuning parameters, and robustness against parameter uncertainties over the traditional PID controllers used in current power industry. The effectives of the controller are validated by both simulation results and a frequency-domain analysis of the control system.

In this paper, an Active Disturbance Rejection Controller (ADRC) is introduced into the system named the dredger cutter motion control, aiming at achieving the cutter motor synchronous speed control precisely. Because the load power of cutter motor may changes drastically at work, it is important that the parallel drive of two cutter motors is designed to keep the system secure and ensure its reliability. Previous studies have already indicated that the traditional approach by PID controller can not meet the performance index anymore. Therefore, the ADRC algorithm is presented and compared with the traditional PID in this work. A lot of comparative experiments were implemented and response curves were obtained by MATLAB, and experimental dates showed that the ADRC algorithm is feasible.

The examples of controls in a high-precision scientific laboratory are countless and most scientific applications
\nrely on controls of the powerful proportional-integral-derivative
\n(PID), first introduced by Minorsky in 1922. In recent years
\na novel Active Disturbance Rejection Control (ADRC) has been
\nproposed. The ADRC is a linear, simple, intuitive, and inherently
\nrobust form of control. It is based on a linear extended state
\nobserver (LESO) that estimates and compensates the disturbance
\nof the system in real time with a certain bandwidth. The
\nbandwidths of the control and of the observer are the only
\nparameters needed for tuning. The design of the ADRC is model
\nindependent and requires only some approximate knowledge of
\nthe fast frequency response of the system. We applied the ADRC
\nto the stabilization of the temperature of optical ultra-stable
\ncavities. Such cavities are used for laser frequency stabilization
\nfor high-resolution spectroscopy and in optical clocks. In our case
\na 578 nm yellow laser is locked to the cavities and it will be used
\nfor the spectroscopy of ytterbium atoms. The temperature of the
\ncavities has to be stabilized to prevent drift in their length and
\nthus in the frequency of the laser. We will present the details
\nof the ADRC and show the performance of the temperature
\nstabilization. The ADRC shows attractive features that motivates
\nour choice: it is easy to design and to implement digitally,
\ninsensitive to environmental changes, and avoids typical problems
\nencountered with PID like overshoots and integral windup.

Usually, the order of active disturbance rejection control (ADRC) is equal to the relative order of the plant. To improve the control performance, a robust reduced-order method for ADRC is investigated in this paper. Firstly, frequency domain analysis shows that the lower-order extended state observer (ESO) has a smaller disturbance estimation error, so disturbance attenuation capability can be improved by reducing the order of ADRC. However, using only reduced-order ADRC will worsen the robustness of closed-loop systems. Therefore, a robust ADRC method based on a modified noise reduction disturbance observer (MNRDOB) is proposed. The main role of the MNRDOB is to improve the control performance of the closed-loop system by modifying the structure of the controlled object. In addition, the robust stability of the closed-loop control system based on the MNRDOB is discussed. Moreover, some simulations are used to demonstrate the robustness and noise suppression effects of the compound control method reduced-order ADRC with MNRDOB, and the parameter tuning method for the MNRDOB to improve the robustness of the system is given. Finally, some experiments on speed control of a one-dimensional gimbal are performed, and the results show that the proposed method is excellent in overshoot, tracking accuracy, and disturbance attenuation.

According to the unstable and nonlinear performances of the servo valve-controlled hydraulic motor, classical control methods based on linear theory are gradually unable to meet the high-performance requirements of the system. Using the servo valve-controlled hydraulic motor based on the third-order active disturbance rejection control (ADRC) to improve the dynamic performance of the system is feasible. The mathematical model and the simulation model of the third-order ADRC for the servo valve-controlled hydraulic motor system are established respectively. For the phase lag caused by the third-order ADRC controller, the control performance of the ADRC controller is significantly improved using the advance forecast. The simulation experiment results show that the designed ADRC controller has good tracking performance and stronger robustness of the system than the traditional PID controller.

Five-phase induction motors have the characteristics of high torque density, low torque ripple, and flexible control, making them suitable for medium- and low-voltage power supply situations. However, with the expansion of application scenarios, five-phase motors need to cope with increasingly complex operating conditions. Five-phase motors for propeller propulsion will face various complex sea conditions during actual use, and five-phase motors for electric vehicles will also face various complex road conditions and operating requirements during use. Therefore, as a propulsion motor, its speed control system must have strong robustness and anti-disturbance performance. The use of traditional PI algorithms has problems, such as poor adaptability and inability to adapt to various complex working conditions, but the use of an active disturbance rejection controller (ADRC) can effectively solve these problems. However, due to the significant coupling between the variables of induction motors and the large number of parameters in the ADRC, tuning the parameters of the ADRC is complex. Traditional empirical tuning methods can only obtain a rough range of parameter values and may have significant errors. Therefore, this paper uses ADRC based on genetic algorithm(GAADRC) to tune the parameters of the control and design an objective function based on multi-objective optimization. The parameters to be adjusted were obtained through multiple iterations. The simulation and experimental results indicate that GAADRC has lower startup overshoot, faster adjustment time, and lower load/unload speed changes compared to the empirically tuned PI controller and ADRC. Meanwhile, using a genetic algorithm for motor ADRC parameter tuning can obtain optimal control parameters while the control parameter range is completely uncertain; therefore, the method proposed in this paper has strong practical value.

In order to effectively control the water level of steam generator (SG), SG water level control objects mathematically are derived in the paper, in the context of cascade PID control system proposed two-order active disturbances rejection control(ADRC), and on this basis to further put forward a variable structure sliding mode control (SMC) strategy to replace the nonlinear state feedback control error rate of ADRC. Performance of SMC-ADRC control system demonstrated is better than ADRC control systems, time and location to reach steady-state may slip regulation, transient and steady-state performance are better, robustness and strong anti-jamming capability.

A closed-loop neuromodulation automatically adjusts stimuli according to brain response in real time. It is viewed as a promising way to control medically intractable epilepsy. A suitable closed-loop modulation strategy, which is robust enough to unknown nonlinearities, dynamics, and disturbances, is in great need in the clinic. For the specialization of epilepsy, the Jansen’s neural mass model is utilized to simulate the undesired high amplitudes epileptic activities, and active disturbance rejection control is designed to suppress the high amplitudes of epileptiform discharges. With the help of active disturbance rejection control, closed-loop roots of the system are far from the imaginary axis. Time domain response shows that active disturbance rejection control is able to control seizure no matter whether disturbances exist or not. At the same time, frequency domain response presents that enough stability margins and a broader range of tunable controller parameters can be obtained. Stable regions have also been presented to provide guidance to choose the parameters of active disturbance rejection control. Numerical results show that, compared with proportional-integral control, more accurate modulation with less energy can be achieved by active disturbance rejection control. It confirms that the active disturbance rejection control-based neuromodulation solution is able to achieve a desired performance. It is a promising closed-loop neuromodulation strategy in seizure control.

Quadrotor trajectory tracking and obstacle avoidance by chaotic grey wolf optimization-based active disturbance rejection control

A tracking control algorithm based on active disturbance rejection controller (ADRC) is proposed to overcome the telescope’s mount fluctuation. The fluctuations are caused by internal and external disturbance when the large aperture telescope runs at ultra-low speed with direct drive. According to the high-precision and high-stability requirements of a large aperture telescope, the ADRC position controller is designed based on segmented arc Permanent Magnet Synchronous Motors (arc PMSMs). The tracking differentiator of ADRC is designed to undergo a transition process to avoid overshoot in the position loop. The speed of target tracking process is observed by the extended state observer and the position information in the system is estimated in real time. The current control variable of the segmented arc PMSM is generated by implementing a non-linear state error feedback control law. The simulation results demonstrate that the proposed control strategy can not only accurately estimate the position and speed of the tracking target, but also estimate the disturbance to compensate the control variables. Experiments showed that the speed error is less than 0.05′ s−1 when using the ADRC, and it can realize high tracking performance when compared with PID controller, which improves the robustness of a large aperture telescope control system.

This paper presents a high-precision control scheme based on active disturbance rejection control (ADRC) to improve the stabilization accuracy of an inertially stabilized platform (ISP) for aerial remote sensing applications. The ADRC controller is designed to suppress the effects of the disturbance on the stabilization accuracy that consists of a tracking differentiator, a nonlinear state error feedback, and an extended state observer. By the ADRC controller, the effects of both the internal uncertain dynamics and the external multisource disturbances on the system output are compensated as a total disturbance in real time. The disturbance rejection ability of the ADRC is analyzed by simulations. To verify the method, the experiments are conducted. The results show that compared with the conventional PID controller, the ADRC has excellent capability in disturbance rejection, by which the effect of main friction disturbance on the control system can be weakened seriously and the stabilization accuracy of the ISP is improved significantly.

ABSTRACTAn account is given of the ultrastructure and optical properties of the structural colour scales of Papilio karna and P.palinurus. The scales are Urania‐type multilayers of 10 lamellae separated by air‐spaces. A theoretical model is elaborated to account for the results and it is concluded that colour variation between species is achieved through control of film thickness. It is proposed that the surface structure functions as an anti‐reflection coating. A generalised functional basis for the structural difference between Urania‐type and Morpho‐type scales is suggested.

Atomic layer deposition (ALD) has been proven to be a versatile method for the deposition of thin films of various materials. It yields films with exceptional conformality and allows tunable film compositions with control of film thickness at the atomic level. Thin films of Al oxide, nitride, and oxynitride are deposited via ALD using Al(CH3)3 (TMA)/AlCl3 with H2O/NH3. Herein, surface chemical reactions are examined using density functional theory calculations to elucidate the adsorption, oxidation, and nitridation of precursors [TMA and AlCl3] as well as the mechanism controlling the composition of Al oxynitride thin films obtained through ALD. The hydrogen-terminated substrate surface is transformed into a CH3/Cl-terminated surface after the reaction with the TMA/AlCl3 precursors. The molecular adsorption of TMA occurs through a spontaneous reaction, whereas that of AlCl3 requires a slight energy input. Although the adsorption energy of AlCl3 is higher than that of TMA, the activation energy and energy change of AlCl3 adsorption are higher and lower than those of TMA, respectively; furthermore, the use of AlCl3 results in the generation of a corrosive by-product (HCl). A similar tendency is observed in the second ALD half reaction, which is oxidation. Nitride formation is endothermic for molecularly adsorbed AlCl3 but exothermic for TMA. Furthermore, the investigation of the exchange reactions between surface moieties and excess gaseous reactants reveals a preference for the substitution of N by O, which is attributed to differences in bond energies between the surface moieties and the surface metal atom, as well as between H2O and NH3.

A system was developed that significantly improves the accuracy of molecular-beam epitaxial flux calibration and provides ±1.0% run-to-run control of film thickness as demonstrated by double-crystal x-ray diffraction analysis of 980 nm GaAs/AlAs Bragg reflector stacks. The system combines PC-based data acquisition and analysis of reflection high-energy electron diffraction (RHEED) wave forms and beam flux gauge signals with mechanical improvements in RHEED sample preparation and mounting. In developing this system, an extensive series of experiments were performed to determine the sources and magnitudes of error in RHEED flux measurements. Proper flux transient corrections, precisely centered 1 mm×1 mm RHEED slices, and improved signal processing and analysis of RHEED wave forms were found to significantly enhance run-to-run flux control.