Electro-optical Tracking System Research Articles

Line-of-Sight Stabilization System Based on Fractional-Order Control

The line-of-sight (LOS) stabilization control is required to isolate LOS from the movement and vibration of carrier and ensure pointing and tracking for target in electro-optical tracking system. In this paper, a fractional-order PI (FOPI) controller is applied in the design of stabilization loop of LOS stabilization system based on the analysis of the fractional calculus theory. This controller exhibits excellent performance even in presence of nonlinearity and uncertainty. Details of this controller along with the performance comparisons between FOPI and conventional integer-order PI (IOPI) are presented. Simulation results indicate that the FOPI controller can improve the carrier disturbance rejection performance of LOS stabilization system.

Design and Optimal Control of Line of Sight Stabilization of Moving Target

The Line-of-Sight stabilization and tracking control based on gyro stabilized platform is required to isolate Line of sight from the movement and vibration of carrier and ensure pointing and tracking for target in electro-optical tracking system. This work describes the design of a high performance controller for an electromechanical target tracking system with an optical sensor for sighting. The control law has been obtained using a linear model of the electro mechanical system. The modelling of the system has been carried out using the experimental frequency response data. The PID adesigning of control system methodology has been used to design the controller and study the comparative analysis using both controller and optimized tuned performance is also seeing by using the designing the PID controller in different loop analysis and study responses of system by using step response and frequency response analysis by using the bode diagram so as to stabilize the line of sight stabilization and tracking control system. The mixed sensitivity optimisation problem has been posed and weighting functions are selected by using the gradient and dissent method having more numbers of iterations so that they not only encapsulate all the design goals but also accommodate the modelling uncertainties. A stabilising controller with excellent robustness properties has been obtained. Investigator has used MATLAB for the designing of controller and simulated the system for a required criterion of the system.

외부짐발 선구동에 의한 EOTS의 기동성 개선

An EOTS (Electro-Optical Tracking System) provides stabilized images while tracking a moving target. This paper presents a novel concept of driving the outer gimbal first for improving the maneuverability of an EOTS, contrary to the conventional inner gimbal mode. It has the advantages of faster positioning performance and stable operation in Nadir-point. Analysis of frequency responses reveal that the present scheme results in a wider control bandwidth and larger gain margin, compared to those of the previous one. The actual experimental results confirm that the maneuvering is stable although the input command has a large angular acceleration.

Research of Sliding Mode Control in Electro-Optical Tracking System

as the foundation and critical part of the free Space optical communication, the electro-optical tracking system is a typical nonlinear system. However, the angular accuracy should be better than a few micro-radians to meet the requirement of the communication link construction between two terminals. To get more control precision, the mathematic model of the coarse pointing system is founded, and sliding mode variable structure controller with approach law is designed. Finally, the simulation is done separately for a typical PID controller and the variable structure controller. Simulation results are showed that the sliding mode control can finely control the attitude of coarse pointing system, and can get higher precision by contrasted to the conventional PID controller.

Transmission backlash of precise cable drive system

Precise cable drive has been developed as an alternative transmission element to gears, belts and pulleys, chains and sprockets in electro-optical tracking system. The analytical method is developed to predict the transmission backlash of precise cable drive to enable designers to better assess the precision performance in the design study phase. Slip angle of precise cable drive is studied, and the effect of the rotational velocity and inertia of cable on the force equilibrium of contact region is considered. The deformation of cable in slip region and free region is calculated respectively and theoretical formulation of transmission backlash for precise cable drive system is carried out. Parametric sensitivity is investigated to evaluate the relationship between the transmission backlash and precise cable drive parameters including preload tension, load tension, friction coefficient, center distance and output drum radius. Experimental setup is built and the transmission backlash is tested. Effect of preload tension on the transmission backlash is tested. Results show that the experimental value and the theoretical curve of the transmission backlash fit well, which validates the theoretical method developed in this article.

光电跟踪系统的共轴跟踪控制技术研究

光电跟踪系统的共轴跟踪控制技术研究

Transverse Oscillation of Precise Cable Drive System

Precise cable drive has been developed as an alternative transmission element to gearbox, belt and pulleys, chains and sprocket in Electro-Optical Tracking system. Precise cable drive has several significant advantages including backlash free, high stiffness, high efficiency, no lubrication etc. This paper develops analytical methods to predict the transverse oscillation frequency of precise cable drive to enable designers to better assess dynamic performance in the design study phase. Theoretical formulation of transverse oscillation equation for precise cable drive is carried out based on Hamiltons principle taking into account flexural rigidity of cable. Furthermore, the transverse oscillation frequency is obtained from the transverse oscillation equation assuming small and linear vibration. Parametric studies are conducted to evaluate the relationship between the oscillation properties and cable drive parameters.

Sensor Calibration using In-Situ Celestial Observations to Estimate Bias in Space-Based Missile Tracking

The work presented here demonstrates a new methodology of using star observations and advanced nonlinear estimation algorithms to improve the ability of a space-based electro-optical (EO) tracking system to track targets in space. Nominally, the tracking system consists of two satellites flying in a lead-follower formation tracking a ballistic or space target. Each satellite is equipped with a narrow-view EO sensor that provides azimuth and elevation measurements to the target. The tracking problem is made more difficult due to a constant, nonvarying or slowly varying bias error present in each sensor's line of sight (LOS) measurements. The conventional sensor calibration process occurs prior to the start of the tracking process and does not account for subsequent changes in the sensor bias. This study develops a technique to estimate the sensor bias from celestial observations while simultaneously tracking the target. As stars are detected during the target tracking process, the instantaneous sensor pointing error can be calculated as the difference between a measurement of the celestial observation and the known position of the star. The system then utilizes a bias filter to estimate the bias value based on these measurements and correct the target line of sight measurements. After bias correction, we compare the ability of three advanced nonlinear state estimators to update the target state vector: a linearized Kalman filter (LKF); an extended Kalman filter (EKF); and an unscented Kalman filter (UKF). The bias correction-state estimation algorithm is validated with a number of scenarios that were created using The Satellite Toolkit (STK). The target position error resulting from the nonlinear estimation filters are compared to the Cramer-Rao lower bound (CRLB) and a filter consistency check. The results of this research provide a potential solution to sensor calibration while simultaneously tracking a space target with a space-based sensor system.

Research on High Dynamic Target Electro-Optical Tracking Based Improved Robust Disturbance Observer

The compound axis control technique is an effective means to improve the accuracy and bandwidth of high precision electro-optical tracking systems. However, traditional methods of lead and lag correction can not achieve ideal performance. The robust control method based on the disturbance observer (DOB) is introduced in this paper, and the method is applied to the electro-optical tracking system together with the Kalman Filter. Compared to the traditional method of lead and lag correction, the method based on DOB can inhibit high-frequency noise and compensate for low-frequency interference better, such as frictions, and achieve better precision finally.

Design Consideration for Precise Cable Drive

A brief overview of previously built Electro-Optical Tracking system reveals a trend toward smaller, more agile systems. Steel cable drive technology is an alternative to gearbox, belt and pulleys, chains and sprocket and other currently available transmission for several significant advantages, which includes backlash free, high stiffness, high efficiency, no lubrication etc.. As a new type of drive form, there were several key tradeoffs for the cable drive application, which will be developed and subjected in detail in this paper. Firstly Transmission principle and properties of cable drive is studied. Secondly, related design considerations of cable drive will be implemented and researched in detail, including the cable selection and capstan design, cable-groove matching strategy and cable tensioning design. Finally, actual application example of precise steel cable drive is presented for an Electro-Optical tracking gimbals, and performances tested validate the significant advantages of precise cable drive technology.

Low Observable Moving Target Tracking Based on Modified PDA-AI

During tracking low observable moving target in electro-optical (EO) imaging tracking system, multiple false alarms resulted from low signal-to-noise rate (SNR) would seriously debase the performance of target tracking. Probabilistic data association with amplitude information (PDA-AI) assumes that amplitude of target is not correlative among different sampling instants and larger amplitude is, greater the probability of validated measurement being target of interest would be. In EO imaging tracking system, amplitude and motion of target of interest are consistent and highly correlative. A modified PDA-AI is discussed and developed to resolve the inconsistency between PDA-AI and EO tracking system in this paper, which analyzes target motion by means of modeling amplitude and motion as well as their consistency as stationary random signal. The theory analysis with Cramer-Rao lower bound (CRLB) and experiments results show that the performance of low observable target tracking of the modified PDA-AI would be more accurate and more reliable than that of the original PDA-AI.

Adaptive fuzzy PID composite control with hysteresis-band switching for line of sight stabilization servo system

The line of sight (LOS) stabilization control based on gyro stabilized platform is required to isolate the LOS from the disturbance and vibration of carrier and ensure pointing and tracking for target in electro-optical tracking system. A composite adaptive fuzzy proportional-integral-derivative (PID) control with hysteresis-band switching is developed to achieve real-time and high stabilization precision for this nonlinear uncertainty servo system. First of all, in the adaptive fuzzy controller, the pre-designed self-tuning factors are able to modify the parameters of fuzzy controller online, and a new learning algorithm of fuzzy rules modifier is proposed to adjust control efforts. Then, an improved PID controller is chosen to restrain motor saturation and eliminate the static error originated from the fuzzy controller, and fulfill non-error control. The hysteresis-band switching strategy is given to deal with jitter caused by single-point switching condition. The experimental results in four-axis servo turntable show that the proposed method can achieve nice control performance and is proved to be effective in bating carrier disturbances within the scope of definite noise and sensitivity to acceleration.

A FULL MISSILE HOMING SYSTEM DESIGN BASED ON PROPORTIONAL NAVIGATION GUIDANCE LAW AND ELECTRO-OPTICAL TRACKING SYSTEM

Generally, the homing systems are majorly constructing from three components: the guidance law, the target tracking system, and the missile flight control system. Therefore, in this paper, we construct our homing system from the following components: the proportional navigation guidance law which is considered as the guidance scheme for most homing missile systems, the electro-optical tracking system, and a tail controlled missile. And subsequently complete mathematical derivations and the demand transfer function formulations of all these three components have been introduced. The proposed homing system is capable to pursuit and hit any target just by specifying the required missile flight time. A SIMULINK software program has been built mainly from four subsystems to simulate the operation of this homing system, and the simulation results show clearly the efficient performance of the proposed homing system under any probable disturbance

Novel approach for tracking and recognizing dim small moving targets based on probabilistic data association filter

While tracking dim and small moving targets in the electro-optical (EO) tracking system, the numerous false alarms resulted from the low signal-to-noise ratio would seriously debase the performance of target recognition and tracking. The probabilistic data association filter in conjunction with a maximum likelihood approach (PDAF-ML) has been applied effectively to low observable or dim target motion analysis. Whereas, the PDAF-ML supposes that the amplitude of target is not correlative among different sampling instants, and that the greater the amplitude value is, the greater the probability of being the target of interest would be. In the EO imaging tracking system, the amplitude information and the motion of target are consistent and highly correlative in a short period. To resolve the problem that the PDAF-ML is inconsistent with the EO imaging tracking system, the two features, namely, the amplitude information and the motion as well as their consistency, are modeled as Markov stationary random signals and are fused by means of PDAF. Experiments are carried out, and the results show that, with the proposed approach, the uncertainty of trajectory association would be largely decreased, and the performance of target recognition and tracking could be significantly improved.

전자광학추적장비의 좌표추적기 구현 및 헬리콥터 탑재 레이더 연동시험에 관한 연구

This paper describes the realization of a coordinates tracking algorithm for an EOTS (Electro-Optical Tracking System). The EOTS stabilizes the image sensors, tracks targets automatically, and provides navigation capability for vehicles. The coordinates tracking algorithm calculates the azimuth and the elevation angle of an EOTS using the inertial navigation system and the attitude sensors of the vehicle, so that LOS designates the target coordinates which are generated by a Radar. In the error analysis, the unexpected behaviors of an EOTS due to the time delay and deadbeat of the digital signals of the vehicle equipments are anticipated and the countermeasures are suggested. The application of this algorithm to an EOTS will improve the operational capability by reducing the time which is required to find the target and support flight especially in the night time flight and the poor weather condition.

Transmission characteristics of axial waves in blood vessels

The elastic behavior of blood vessels can be quantitatively examined by measuring the propagation characteristics of waves transmitted by them. In addition, specific information regarding the viscoelastic properties of the vessel wall can be deduced by comparing the observed wave transmission data with theoretical predictions. The relevance of these deductions is directly dependent on the validity of the mathematical model for the mechanical behavior of blood vessels used in the theoretical analysis. Previous experimental investigations of waves in blood vessels have been restricted to pressure waves even though theoretical studies predict three types of waves with distinctly different transmission characteristics. These waves can be distinguished by the dominant displacement component of the vessel wall and are accordingly referred to as radial, axial and circumferential waves. The radial waves are also referred to as pressure waves since they exhibit pronounced pressure fluctuations. For a thorough evaluation of the mathematical models used in the analysis it is necessary to measure also the dispersion and attenuation of the axial and circumferential (torsion) waves. To this end a method has been developed to determine the phase velocities and damping of sinusoidal axial waves in the carotid artery of anesthetized dogs with the aid of an electro-optical tracking system. For frequencies between 25 and 150 Hz the speed of the axial waves was between 20 and 40 m/sec and generally increased with frequency, while the natural pressure wave travelled at a speed of about 10 m/sec. On the basis of an isotropic wall model the axial wave speed should however be approximately 5 times higher than the pressure wave speed. This discrepancy can be interpreted as an indication for an anisotropic behavior of the carotid wall. The carotid artery appears to be more elastic in the axial than in the circumferential direction.