Target Velocity Estimation Research Articles

Temporal Evolution of 2-Dimensional Direction Signals Used to Guide Eye Movements

The smooth pursuit system must integrate many local motion measurements into a coherent estimate of target velocity. Several laboratories have studied this integration process using eye movements elicited by targets, such as tilted bars, containing conflicts between local motion signals measured along contours [one dimensional (1D)] and those measured at the bar's endpoints, or terminators [two dimensional (2D)]. The general finding is that 1D signals dominate early responses, whereas later components of the behavior are determined by 2D signals. We studied the dynamics of the integration process in macaque monkeys by systematically varying the relative proportions of 1D and 2D signals and the retinal eccentricities at which they appeared. Predictably, longer bars produced greater and longer-lasting contour-induced deviations. The evolution of the 2D response occurred over a period of 50-400 ms, depending on the relative proportions of 1D and 2D signals. As contours were displaced from the fovea the deviation decreased but much less so for early (1st 40 ms) than for late (subsequent 40 ms) pursuit initiation. These bottom-up effects could be overcome to a limited extent by the top-down influence of predictability. Finally, we observed that when animals were free to track any part of the bar, they spontaneously made short-latency saccades to the terminators on most trials, especially when the bars were tilted. This suggests an increased saliency of moving terminators, particularly when discrepancies exist among local motion signals.

Prediction-related activity of smooth-pursuit neurons in the periarcuate cortex: Estimate of target velocity

Prediction-related activity of smooth-pursuit neurons in the periarcuate cortex: Estimate of target velocity

Target tracking with bearings – Only measurements

The estimation of target position and velocity is attempted on the basis of angular measurements only. This topic is of interest for: airborne radar and sonar in passive listening mode, and electronic warfare systems; in these cases the target radiates either an electro-magnetic (e.m.) or an acoustic wave. The measurements are affected by white Gaussian noise; the presence of outliers is also considered. Two types of tracking filters are presented: (i) one processes a batch of data, (ii) the other recursively processes the data. The estimation of the target kinematic co-ordinates in the filter (i) is obtained by minimising a suitable quadratic cost function of measurement error. The closed form expression of the Cramer–Rao lower bound of the estimate is evaluated in a number of operational cases of practical interest; comparison with Monte Carlo simulation results is also shown. The filter (ii) is determined on the basis of the so-called modified polar co-ordinates. Monte Carlo simulation demonstrates the performance of this filter for straight line and accelerating moving targets.

A new MTI-SAR approach using the reflectivity displacement method

A new method for moving target detection, localization, and velocity estimation using SAR raw data is presented which allows the determination of the target's complete velocity vector. The method is applicable if the target has either a tangential velocity (/spl mu//sub T//spl ne/0) or a radial acceleration (/spl nu//spl dot//sub R//spl ne/0), or both. It is based on the analysis of the Doppler rate map which is obtained from the range compressed raw data, applying the reflectivity displacement method (RDM). The tangential velocity of each moving target is obtained from its own Doppler rate and the radial velocity from its own linear range migration. A velocity accuracy better than 3 m/s can be achieved for the airborne case. The method is validated experimentally by the use of real SAR data obtained by DLR's E-SAR. The paper gives a short description of the state of the art of moving target velocity measurements, introduces the RDM for stationary targets and its extension to the application for moving targets. It furthermore shows experimental results. >

Target velocity estimation with FM and PW echo ranging Doppler systems I. Signal analysis

The theoretical foundation is presented for velocity estimation with a pulsed wave (PW) Doppler system transmitting linear FM signals. The Doppler system possesses echo ranging capabilities and is evaluated in the context of Doppler ultrasound for blood velocity measurement. The FM excitation signal is formulated and the received signal is derived for a single moving particle. This signal is similar to the transmitted signal, but with modified parameters due to Doppler effect and range. The demodulated received signal is subsequently derived and analyzed. It is shown that, due to the Doppler effect, this is a linear sweep signal as well. The velocity and range information obtainable from one and two consecutively received signals are described. The latter case establishes the basis for an FM Doppler system for blood velocity measurements.

Target velocity estimation with FM and PW echo ranging Doppler systems. II. Systems analysis

For part I see ibid., vol.40, no.4, pp.366-372 (1993). In Part I, the encoding of the velocity and range information into the received and demodulated signals based on transmission of coherent repetitive linear sweep signals, was discussed. In the present work, two different implementations of FM Doppler systems that can be used to obtain velocity profiles are presented. The first implementation is similar to the implementation of a conventional pulsed wave (PW) Doppler system, based on measurement of phase shift (correlation based system): the second implementation is a frequency-domain analog to the PW Doppler system, based on time shift measurements (cross correlation-based system).

Controller Design for High-Performance Visual Servoing

This paper describes the design of a control architecture for robot visual servoing, in particular high-performance tracking control. A 50Hz vision system in conjunction with an end-effector mounted camera is used to close the robots position loop. The limitations of pure feedback control are discussed, and an approach based on estimated target velocity feedforward is introduced. Experimental results are provided.

Optical track initiator for multitarget tracking

An optical processor for multitarget track initiation is presented. It uses the Hough transform to detect target tracks in a fixed time independent of the number of tracks present. In new results, we describe how the system produces target position and velocity estimates in linear time (with the number of targets). Tests of the system are presented for multiple targets with various velocities and target detection probabilities. A new thresholded Hough transform algorithm to reduce the effects of noise and false tracks in single data frames is introduced and tested. The optical implementation of these Hough transform track initiation algorithms is discussed.

Pattern recognition applications in underwater acoustics

Pattern recognition application to underwater acoustics is a relatively less explored area, even though much study has been made of sonar signal detection. Recently, significant effort has been made of submarine transient signal analysis and classification. Various spectral and time domain features are considered for detection and event classification. Effective recognition requires signal segmentation. The use of entropy distance measure for waveform segmentation is then examined. The next pattern recognition application is the target motion analysis by using pattern matching idea in the estimation of target range, velocity, and bearing. Another application is in multipath ranging. An image processing technique is used to extract the significant tracks from the correlograms to provide a continuous estimate of time delay or range under a multipath environment. Major computer results reported earlier [C. H. Chen, Pattern Recog. J. 16 (6) (1983)] along with further results on transient signal analysis are presented. Other applications such as sonar recognition in fisheries are also examined. While the trend continues to be digital processing and system integration, the basic recognition issue remains to be the extraction of effective features from the preprocessed underwater acoustical data. [Work partially supported by NUSC at Newport, RI.]

Bearings-Only Target Tracking via Partitioning Estimation Algorithms

The bearings-only estimation of target velocity and position has been reformulated and treated as a combined estimation and identification problem which has been tackled through partitioning. Certain advantages of the partition estimation algorithm have been exploited to improve convergence. Here a different numerical realization which reduces the amount of computation is presented. Simulation examples are given.