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In this study, a class of linear system, which is with no exogenous input and suffered from constant measurement delay and uncertain model‐parameter errors, is under consideration. To combat both the parametric uncertainties and constant measurement delay, a novel robust state estimator is proposed. Accounting for the constant measurement delay, a clever approach is utilised to expand the state vector and the system model is converted into an augmented delay‐free model. Considering the deterioration of estimation performance caused by stochastic model‐parameter errors, the sensitivity penalisation function of model‐parameter errors is defined and introduced into the objective function of the regularised least‐squares (RLS) problem, whose solution is the standard Kalman filter. Furthermore, by restricting the range of introduced parameter, the objective function of the modified RLS problem is converted into a strict convex function. Then, the recursive procedure of the proposed estimator is derived. The asymptotic stability conditions of the proposed estimator and the conditions for boundness of the estimation error matrix are given. Numerical simulations show the effectiveness of the estimator proposed in this paper.

In this paper, to enhance the tracking ability of a charge-coupled device (CCD) and micro-electro-mechanical-system (MEMS) accelerometer based low-cost tracking control system, an acceleration feed-forward control method based on fusion of model output and sensor data is proposed. To achieve the acceleration feed-forward control, the target acceleration is fed into the traditional acceleration-position dual closed-loop. Considering the CCD can only detect the line-of-sight (LOS) error of the target, the double integration of accelerometer measurement is regarded as the platform's position and is combined with the LOS error to build the target trajectory. The target acceleration is predicted by a Kalman filter, in which the combined target trajectory is used as the observed value. However, the basic acceleration feed-forward control method fails to improve the tracking ability at low frequencies due to inaccuracy of the accelerometer measurement caused by drift and noise. To solve this problem, we further propose to calculate an acceleration using the system acceleration model, and then use this calculated acceleration to fuse with the measured acceleration to obtain a new acceleration. The new acceleration, which is more accurate than the original measured acceleration in low frequency, is utilized to rebuild the target trajectory and predict the target acceleration again. Experimental results confirm the effectiveness of the proposed method.

The electro-optical tracking system with speedability and maneuverability based on stationary platform is confronted with some problems such as external physical disturbance and detector delay. To obtain better stability, which is the key to achieving high tracking precision, a modified Smith predictor method for inertia stabilization loop control is introduced. This method proposes the Smith predictor control scheme based to compensate delay time caused by the signal filtering of fiber gyroscope sensor in the velocity feedback control, and it utilizes disturbance feedforward control to improve the stability of stabilization platform simultaneously. The design of control structure and analysis of the theory are reported. The experiment results indicate convincingly that the proposed method can effectively improve the bandwidth of velocity closed-loop. Moreover, it can drastically enhance the disturbance suppression performance of tracking platform.

For the high precise tracking control task in quantum communications, this paper introduces a fractional-order control scheme to resolve the confliction between error rejection capacity and stability margin. In the system and controller design, a system preprocessing, including phase margin compensation and controller structure amelioration, is introduced to make the controller realizable. And in order to obtain the global optimum in controller parameter tuning, a visual version method is also imported. This innovative control scheme could effectively equilibrate the system's demands for high error suppression capacity and enough phase margin, and makes it possible for a class of systems' high precision control. The innovative control method is experimented in an electro-optical system, which could help to obtain a better beam tracking performance in quantum communications.

Research has been focused on the pointing control of the two-axis gimbal system (TGS) which plays a significant role in many different tasks. The pointing accuracy is one of the most concerning performance in practical application, which is, to a large extent, affected by the pointing controller design. Often, the three-loop (current-velocity-position) control scheme is applied to suppress the disturbance and point reference signal. In this paper, the PID type-III control loop is proposed for TGSs and the controller parameters tuning rules are given explicitly. Concretely, the friction compensation based on the LuGre model is carried out first to the velocity inner loop. A greater system rigidity is achieved for the position loop. Secondly, based on frequency domain modeling, the PID type-III control loop is designed according to the position-controlled plant, which is characterized by the presence of three integrators in the open-loop transfer function to achieve zero steady-state position, velocity and acceleration error. Then, considering the system design complexity and practical application, the explicit tuning rules of the PID type-III control loop are derived using magnitude optimum criterion. The parameters are finally designed by stability margin and error suppression ability, which is more appropriate for practical systems. Besides, a pre-filter is also added outside the closed-loop structure when set-point tracking is carried out. Finally, to justify verily the efficiency of the proposed control law, the simulations and experiments in a two-axis pod gimbal system are investigated. The dynamic and stationary performances compared with another type-III control loop method, indicating that the proposed tuning rules have higher positioning accuracy.

Classic servo systems typically use Dual Closed-loop Feedback (DCF) control as the tracking control method. When the system tracks the large position deviation signal, the DCF often has too much overshoot problem due to the integral failure (Windup), which is unacceptable for some precision equipment. Based on this, this paper proposes a control method for large position deviation signals (CLPS) by adding transition signals based on DCF, in which the transition signal is used to smooth the input and makes the jumping large position deviation signal become to a slowly changing one. And the transition signal is time optimal, this reduces the settling time while decreasing the overshoot. Finally, the control algorithm is verified in the electro-optical tracking (EOT) system and the experimental results show that the fast and smoothness of the system reach the expected goal, and the control method has obvious tracking effect improvement compared with the DCF.

The optimal estimation of the target movement state is the key technology of target tracking. The single-model predictive filtering algorithm cannot satisfy the requirement of accuracy when the system is tracking a strong maneuver target. Because the estimation algorithm is inaccurate when the target's motion state and model do not match. The multi-model algorithm is proposed to solve this problem and it does effectively improve the estimation accuracy. However, it is hard to apply to the actual engineering due to the large calculation quantity. In this paper, a feedforward method based on SVM is proposed. This method uses SVM to classify the target's motion state and gets the most suitable motion model to the targets current state. This model is utilized to predict and estimate the motion parameters of the target in the way of single model. Therefore, the contradiction between calculation quantity and precision is alleviated. Then, the target motion parameters are fed into the system, and the target is tracked with high precision.

Set-point tracking servo systems encounter the problem of the trade-off between the swiftness and smoothness in tracking task. To deal with this problem, the proximate time-optimal servomechanism based on transition process (PTSTP) is proposed in this paper. The PTSTP control scheme incorporates a transition process (TP) into the framework of proximate time-optimal servomechanism (PTOS) to eliminate the conservatism of the original PTOS without the controller changing. The target position signal amplitude and the ultimate ability of actuator are utilized to design the time-optimal TP to make the jumping target position signal turns to a smooth signal, which can significantly reduce system overshoot. Therefore, the system swiftness and smoothness performance are guaranteed by PTSTP. Then, the stability of the proposed method is analyzed theoretically. Finally, the experimental results show that the controlled system is able to track the target position signal with different amplitude fast and smoothly in an electro-optical set-point tracking servo system.

In the mobile optoelectronic tracking system (MOTS) based on charge-coupled device (CCD) and fiber-optic gyroscope (FOG), the tracking performance (TP) and anti-disturbance ability (ADA) characterized by boresight error are of equal importance. Generally, the position tracking loop, limited by the image integration time of CCD, would be subject to a non-negligible delay and low-sampling rate, which could not minimize the boresight error. Although the FOG-based velocity loop could enhance the ADA of the system, it is still insufficient in the case of some uncertain disturbances. In this paper, a feedforward control method based on the results of error and disturbance observation was proposed. The error observer (EOB) based on the CCD data and model output essentially combined the low-frequency tracking feedforward and closed-loop disturbance observer (DOB), which could simultaneously enhance the low-frequency TP and ADA. In addition, in view of the poor low-frequency performance of the FOG due to drift and noise that may result in the inaccuracy of the observed low-frequency disturbance, the FOG-based DOB was used to improve the relatively high-frequency ADA. The proposed method could make EOB and DOB complementary and help to obtain a high-precision MOTS, for in practical engineering, we give more attention to the low-frequency TP and full-band ADA. Simulations and experiments demonstrated that the proposed method was valid and had a much better performance than the traditional velocity and position double-loop control (VPDC).