Electro-optical Tracking System Research Articles

A Multi-Channel Data Simulator Based on the Time Unification System

In satellite and airborne electro-optical tracking systems, there are numerous processing devices and complex data flows. To ensure the coordinated operation of the system, the multiple devices within the target system must operate under unified time control for data acquisition, computation, and output. This study introduces a multi-channel data simulator based on a time unification system. The complete simulation system includes the host computer, simulator, target system, and time reference generator. The simulator has programmable input and output interfaces for multi-channel protocols and has storage and real-time working modes. In the storage mode, the simulated data are pre-transmitted to the simulator’s storage and sent to the target system according to the time reference generator. The simulator simultaneously stores the target system results. In the real-time mode, the host computer generates simulated data based on the target system’s results and outputs the data through the simulator in real time. The main contribution of the simulator is that it achieves system-level closed-loop simulation and completes the functional and performance verification of the target system. Through experimental verification, it is found that the simulator can achieve 4.2 Gbps of simulated data transmission and 1.6 Gbps of data reception and storage, with a closed-loop delay of 39.9 µs.

An adaptive error-based observer method in electro-optical tracking system

Electro-optical tracking system which is used to track and aim at targets, is a key equipment in long-distance laser communication, astronomical observation, and so on. And the motion state of the target and the complicated external disturbance often limit the tracking accuracy of the system. In previous studies, target tracking and disturbance suppression are usually discussed separately. In this paper, in order to solve the tracking and disturbance problems together, the error-based observer (EOB) structure was proposed. It is a feedforward control method that only needs an error signal to observe the target trajectory and external disturbances. And it can be used to improve the tracking and anti-disturbance performance of the system without additional sensors. However, in the actual scene, the target motion and external disturbance faced by the electro-optical tracking system are often variable. So an adaptive error-based observer (AEOB) structure based on signal identification and adaptive compensation was proposed, which can reduce the effect of time-varying target motion and narrowband disturbance on tracking accuracy. And the adaptive process of AEOB contains AR parameter model identification with high precision and adaptive feedforward of variable parameter Q filter. In addition, an improved notch Q filter is proposed, which had stronger feedforward capabilities for narrowband signals. Finally, the effectiveness is verified by simulations and experiments of the electro-optical tracking system.

The RSLQR Control Method Based on the Linear Extended State Observer in the Electro-Optical Tracking System

The RSLQR Control Method Based on the Linear Extended State Observer in the Electro-Optical Tracking System

Multi-Channel Phase-Compensated Active Disturbance Rejection Control with an Improved Backstepping Strategy for Electro-Optical Tracking Systems

A multi-channel phase-compensated active disturbance rejection control (MPADRC) incorporating an improved backstepping strategy is proposed in this paper to handle the phase lag in the extended state observer (ESO) and the residual uncertainty in the system. Firstly, a multi-channel phase-compensated ESO (MPESO) is constructed by adding phase-advanced networks to all output channels of the ESO, which allows disturbances and system states to be compensated and feedback in a more timely manner, respectively. Then, to estimate and offset the residual uncertainty in the system, an improved backstepping control method is employed and a Lyapunov function is designed to verify the convergence of the error between the estimated and actual values of the residual uncertainty. After that, the improved backstepping control is combined with MPADRC, and comparisons with the conventional linear active disturbance rejection control (LADRC) are conducted for a range of cases. Finally, on an inertial stabilization platform in the electro-optical tracking system (ETS), simulation and experimental results verified the effectiveness of the proposed method.

Extended State Kalman Filter-Based Model Predictive Control for Electro-Optical Tracking Systems with Disturbances: Design and Experimental Verification

A modified Extended State Kalman Filter (ESKF)-based Model Predictive Control (MPC) algorithm is introduced to tailor the enhanced disturbance suppression in electro-optical tracking systems. Traditional control techniques, although robust, often struggle in scenarios with concurrent internal, external disturbances, and sensor noise. The proposed algorithm effectively overcomes these limitations by precisely estimating system states and actively mitigating disturbances, thus significantly boosting noise and perturbation control resilience. The primary contributions of this study include the integration of ESKF for accurate system state and disturbance estimation in noisy environments, the embedding of an ESKF estimation-compensation loop to simulate an improved disturbance-free system, and a simplified modeling approach for the controlled device. This designed structure minimizes the reliance on extensive system identification, easing the predictive control model-based constraints. Moreover, the approach incorporates total disturbance estimation into the optimization problem, safeguarding against actuator damage and ensuring high tracking accuracy. Through rigorous simulations and experiments, the ESKF-based MPC has demonstrated enhanced model error tolerance and superior disturbance suppression capabilities. Comparative analyses under varying model parameters and external disturbances highlight its exceptional trajectory tracking performance, even in the presence of model uncertainties and external noise.

Design of Backstepping Control Based on a Softsign Linear–Nonlinear Tracking Differentiator for an Electro-Optical Tracking System

To address the problems of a low tracking accuracy and slow error convergence in high-order single-input, single-output electro-optical tracking systems, a backstepping control method based on a Softsign linear–nonlinear tracking differentiator is proposed. First, a linear–nonlinear tracking differentiator is designed in conjunction with the Softsign excitation function, using its output as an approximate replacement for the conventional differentiation process. Then, this is combined with backstepping control to eliminate the “explosion of complexity” problem in conventional backstepping procedures due to repeated derivation of virtual control quantities. This reduces the workload of parameter tuning, takes into account the rapidity and stability of signal convergence, and improves the trajectory tracking performance. This method can ensure the boundedness of the system signal. The effectiveness and superiority of this control method are verified through simulations and experiments.

A novel fuzzy extended state observer-based control for electro-optical tracking system with disturbances and measurement noises: Design, analysis and experiments

In the electro-optical tracking system (ETS), the stability of line-of-sight (LOS) is usually limited by low and medium-frequency disturbances and measurement noises. Conventionally, the active disturbance rejection control (ADRC) strategy is an effective method to improve the stability of LOS; however, it is limited by the fixed observer bandwidth, which is the parameter of the extended state observer (ESO). Besides that, for conventional ESO, the conflict exists between disturbance rejection ability and noise attenuation ability. In this paper, this problem is tackled by transforming the ESO which is the core element of ADRC, into a novel fuzzy self-tuning observer structure. The proposed method is experimentally validated to effectively ensure the stability of the LOS after obtaining an optimal trade-off between disturbance rejection ability and noise attenuation ability.

Disturbance-Observer-Based LQR Tracking Control for Electro-Optical System

To improve the dynamic property and the disturbance suppression ability of an electro-optical tracking system, this paper presents a disturbance-observer-based LQR tracking control method. The disturbance-observer-based robust controller is composed of three parts: one is the LQR tracking controller, one is the reference model controller and the other is a compensatory controller designed with the output of the disturbance observer. The uncertainty and disturbances are considered in the controller design. By Lyapunov stability theory and linear matrix inequality (LMI) technique, the sufficient conditions for observer gain and controller gain of the tracking reference model of the electro-optical system are given. Simulation and experimental results show that the proposed method in this paper not only improved the disturbance suppression ability of the electro-optical tracking system but also improved the dynamic property of the electro-optical tracking system, such as rise time, settling time and system overshoot. Specially, compared with other methods in this paper, the tracking accuracy and the disturbance suppression ability of the proposed method are about two to three times higher. The method presented in this paper has important reference value in the field of electro-optical system applications. But, with the development of electro-optical system applications, the tracking accuracy and disturbance suppression ability of the proposed method cannot meet the actual requirements of an electro-optical system. The next step of this paper will consider a variety of practical requirements, such as the controller saturation problem and tracking reference target with strong maneuverability, and further optimize the proposed method.

Improved Particle Swarm Optimization Fractional-System Identification Algorithm for Electro-Optical Tracking System

When an electro-optical tracking system (ETS) needs higher control precision, system identification can be considered to improve the accuracy of the system, so as to improve its control effect. The fractional system model of ETS can describe the characteristics of the system better and improve the accuracy of the system model. Therefore, this paper presents a fractional system identification algorithm for ETS that is based on an improved particle swarm optimization algorithm. The existence of the fractional order system of ETS was verified by identification experiments, and the fractional order system model was obtained. Under the same conditions, PI controllers were designed based on a fractional order system and an integer order system, respectively. The results verify the superiority of fractional order system in ETS.

LOS Stabilization Controller Design of EOTS and Performance Prediction Using Disturbance Model

The EOTS(Electro Optical Tracking System) must have stabilization performance to provide high-quality images under disturbance environment. In this paper, we present a controller that can minimize the LOS error and has a simple structure. Hence, to evaluate the performance of this controller, analysis in the frequency domain and LOS error measurement are performed. In order to measure the LOS error without a ‘rate table’ that requires a lot of facility investment, we propose a design method for disturbance model that considers the operating environment of the EOTS. Finally, the performance of the stabilization algorithm is evaluated by the proposed disturbance model.

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The cover image is based on the Research Article A target anti-occlusion method based on image processing and trajectory prediction in electro-optical tracking system by Yao Mao et al., https://doi.org/10.1049/rsn2.12235

A target anti‐occlusion method based on image processing and trajectory prediction in electro‐optical tracking system

In the electro-optical tracking system, due to the full occlusion of clouds or buildings, the traditional tracking algorithm fails to work effectively. In the authors’ study, a dual-channel anti-occlusion scheme based on image processing and trajectory prediction is proposed. On the one hand, the image-processing unit plays a significant role in evaluating the occlusion state of the target. An improved image occlusion judgement method based on Bhattacharyya coefficient occlusion judgement is proposed, and the ability to resist background interference and rapidity of the algorithm is enhanced. On the other hand, according to the different occlusion states, the dual operation modes of tracking and prediction are usually set. When the target is completely occluded, the prediction mode based on a robust predictive filtering method is investigated to predict the real-time trajectory of the target more accurately. Image occlusion judgement and trajectory prediction can solve the occlusion problems in tracking control. Otherwise, the feasibility and effectiveness of the proposed method are verified by experiments. The cover image is based on the Research Article A target anti-occlusion method based on image processing and trajectory prediction in electro-optical tracking system by Yao Mao et al., https://doi.org/10.1049/rsn2.12235.

Development of Sliding Mode Controller Based on Internal Model Controller for Higher Precision Electro-Optical Tracking System

The electro-optical tracking system (ETS) on moving platforms is affected by the vibration of the moving carrier, the wind resistance torque in motion, the uncertainty of mechanisms and the nonlinear friction between frames and other disturbances, which may lead to the instability of the electro-optical tracking platform. Sliding mode control (SMC) has strong robustness to system disturbances and unknown dynamic external signals, which can enhance the disturbance suppression ability of ETSs. However, the strong robustness of SMC requires greater switching gain, which causes serious chattering. At the same time, the tracking accuracy of SMC has room for further improvement. Therefore, in order to solve the chattering problem of SMC and improve the tracking accuracy of SMC, an SMC controller based on internal model control (IMC) is proposed. Compared with traditional SMC, the proposed method can be used to suppress the strongest disturbance with the smallest switching gain, effectively solving the chattering problem of the SMC, while improving the tracking accuracy of the system. In addition, to reduce the adverse influence of sensor noise on the control effect, lifting wavelet threshold de-noising is introduced into the control structure to further improve the tracking accuracy of the system. The simulation and experimental results verify the superiority of the proposed control method.

Development of ship-borne electro-optical tracking and fire control system

舰载光电跟踪与火控系统是一种远距离监视、跟踪与火力打击装置，按照体系结构可以分为分立式和综合式两类。对比分析了德国MSP500、意大利“梅杜莎MK4”、英国2500型、以色列Toplite、美国SeaFLIR 280-HD和380-HD、瑞典EOS 500、法国EOMS NG和PASEO等典型光电指向器的结构形式、传感器配置、作用距离及与火控系统的关系。指出光电指向器的结构由“T型”逐渐发展为“U型”，光电传感器的波段由单一波段发展为多个波段，光电跟踪系统的功能由单一功能向综合多功能转变。随着现代海战对抗加剧，舰载光电跟踪与火控系统将朝着多传感器协同探测、信息融合、多目标识别、智能跟踪、使命任务多样化方向发展。

측정치 시간지연을 가진 전자광학 추적장비의 초기 자세 결정 알고리즘

In order to have accurate target positions of the EOTS(Electro-Optical Tracking System), more accurate navigation outputs are required. An IMU(Inertial Measurement Unit) can be attached to the EOTS to have high rate INS ouputs. Due to the time-delay of the vehicle’s navigation outputs, it is not easy to have accurate target positions. When the vehicle moves at high speed and with high maneuverability, the accuracy becomes even worse. In this paper, an initial attitude determination algorithm of the EOTS with measurement time-delay is proposed. In order to compensate the measurement time-delay, the time-delay variable is augmented into the integrated Kalman filter for the IMU of EOTS and vehicle’s measurement output. The proposed algorithm was evaluated for sensor’s model-based measurement generator outputs, and a land vehicle experiments were performed. The evaluation results show that the proposed algorithm compensates the measurement time-delay well and gives more accurate initial attitude.

Multi-order cascade lag control for high precision tracking systems

Error attenuation capacity of a target tracking system is the key indicator for the system’s tracking precision. Without changing the system’s feedback control structure, the traditional first order integral control, which is widely used in traditional tracking systems, cannot meet a higher precision for those fast targets with high mobility. The work described in this paper concerns about this problem, and proposes a cascade lag control scheme with one or more order to level up the system’s active error suppression capacity in low-frequency range. By substituting the cascade lag controllers for additional integral operator, a higher amplitude ratio system, which implies higher tracking precision, is obtained without loss of stability. As a difficult task for massive parameters’ designing, a concept of relative order and a configuration proportion law is proposed to simplify the analysis as well as parameters tuning. Relationship between the relative order and system performance is given. The multi-order cascade lag control scheme’s efficiency is proved in both theoretical analysis and experiments in an electro-optical tracking system.

Non-singleton interval type-2 fuzzy PID control for high precision electro-optical tracking system

In this paper, two non-singleton interval type-2 fuzzy PID (NIT2F-PID) controllers for the high precision electro-optical tracking system (ETS) are presented to improve anti-interference ability. Specifically, two types of non-singleton fuzzifiers, including type-1 (T1) and type-2 (T2), are considered to construct the proposed NIT2F-PID (N1IT2F-PID and N2IT2F-PID) controllers. Faced with the optimization problem of parameters, particle swarm optimization (PSO), quantum-behaved PSO (QPSO), weighted QPSO (WQPSO) and improved QPSO with adaptive coefficients (LTQPSO) are employed for comparison of convergence performance to optimize the parameters of controllers. In addition, to demonstrate the superiority of the proposed NIT2F-PID controllers, PID, singleton T1 fuzzy PID (ST1F-PID), singleton interval T2 fuzzy PID (SIT2F-PID), T1 non-singleton interval T2 fuzzy (N1IT2F) and T2 non-singleton interval T2 fuzzy (N2IT2F) controllers are also designed. All of these controllers are tested under the circumstances of step disturbance and sinusoidal disturbance. At last, a series of simulation analyses and experimental results explicitly show performance of proposed NIT2F-PID controllers are superior to their counterparts.

Trajectory tracking control for electro-optical tracking system based on fractional-order sliding mode controller with super-twisting extended state observer

This paper investigates a trajectory tracking control scheme for electro-optical tracking systems subject to friction and other nonlinear disturbances. The proposed approach is based on a super-twisting extended state observer (ESO) and a fractional-order nonsingular terminal sliding mode (FONTSM) with a switching-type reaching law. The novel hybrid control scheme exhibits the following advantageous characteristics. First, the extended state observer injected with a super-twisting algorithm is capable of simultaneously estimating the friction and other nonlinear disturbances without detailed knowledge of the precise friction and disturbance models. Second, the FONTSM surface enhances the control accuracy and robustness, and provides a more flexible controller structure than its integer counterpart. Third, a novel switching-type reaching law is utilized to achieve fast response, constraining chattering in the system. Additionally, the finite-time convergence of the adopted ESO and the finite-time stability of the control system are demonstrated based on the rigorous Lyapunov criteria. Finally, the effectiveness of the proposed hybrid control scheme is demonstrated for an electro-optical tracking system via trajectory tracking experiments.

Add-on integration module-based proportional-integration-derivative control for higher precision electro-optical tracking system

This paper concerns the improvement on proportional-integration-derivative (PID) control for the electro-optical tracking system for high-mobility targets. To achieve higher tracking precision and stronger disturbance rejection while fully utilizing the existing PID loop, the add-on integration module is proposed and seamlessly integrated into the conventional PID loop. It is proven that for any given conventional PID controller parameters, the add-on integration module based PID control can improve the ability of error attenuation at low frequency and keep the stability of resulting closed-loop system. More importantly, the feasible set of all parameters in the added module is explicitly given. Based on the feasible set, the non-dominated sorting genetic algorithm II (NSGA-II) is adopted to obtain the globally optimal controller’s parameter under certain performance indices. The experiments are carried out for a typical electro-optical tracking test bed with several reference signals. It is shown that the proposed method has much smaller tracking errors than the existing PID method.

Trajectory Tracking Control for Electro-Optical Tracking System Using ESO Based Fractional- Order Sliding Mode Control

In this study, to achieve high trajectory tracking performance in electro-optical tracking systems under strong nonlinear disturbances and uncertainties, we develop a nonlinear extended state observer (ESO) based fractional-order sliding mode control. When compared with previous work, the new compound control strategy is attractive in terms of the following three points. First, a novel controller is developed that integrates the advantages of a nonlinear ESO, a fractional-order nonsingular terminal sliding mode (FONTSM) manifold, and a super-twisting algorithm. Second, the nonlinear ESO is employed to estimate the disturbances and uncertainties without explicit knowledge of the system model. Third, a FONTSM manifold-based super-twisting algorithm is integrated into the controller to enhance the system robustness. The FONTSM manifold has a faster dynamical response, more flexible sliding manifold structure, and better control results than its integer-order NTSM counterpart. The finite-time convergences of the ESO and controller are both proved by the Lyapunov method. Finally, the comparative experimental results demonstrate the effectiveness and superiority of the developed control strategy with respect to existing approaches.