Avnish Kumar

Image stabilization for moving platform surveillance

Line of sight jitter degrades the image/real time video quality of a high performance sighting system, resulting in reduced detection/recognition/identification ranges. Line of sight jitter results from residual dynamics on the sighting system from the host platform. A scheme for fine image/video stabilization, in presence of high magnitude line of sight jitter, has been presented in this paper. The proposed scheme is a combination of conventional gyro stabilization of payload line of sight (i.e. Mechanical Image Stabilization-MIS) and Digital Image Stabilization (DIS). Gyro stabilization technique is used to minimize the computation requirement of DIS technique. The proposed technique has been implemented and evaluated using standard hardware (SMT8039). Inclusion of DIS algorithms has given an additional disturbance isolation of at least 10 dB in our experiments, while image smoothness index also improved by a factor of four or more. The proposed method also indicated that higher image smoothness and disturbance isolation are possible at comparatively higher frequencies (limited by computation capability of the computing platform).

Fast steering and quick positioning of large field-of-regard, two-axis, four-gimbaled sight

Abstract. Fast steering and quick positioning are prime requirements of the current electro-optical tracking system to achieve quick target acquisition. A scheme has been proposed for realizing these features using two-axis, four-gimbaled sight. For steering the line of sight in the stabilization mode, outer gimbal is slaved to the gyro stabilized inner gimbal. Typically, the inner gimbals have direct drives and outer gimbals have geared drives, which result in a mismatch in the acceleration capability of their servo loops. This limits the allowable control bandwidth for the inner gimbal. However, to achieve high stabilization accuracy, high bandwidth control loops are essential. This contradictory requirement has been addressed by designing a suitable command conditioning module for the inner gimbals. Also, large line-of-sight freedom in pitch axis is required to provide a wide area surveillance capacity for airborne application. This leads to a loss of freedom along the yaw axis as the pitch angle goes beyond 70 deg or so. This is addressed by making the outer gimbal master after certain pitch angle. Moreover, a mounting scheme for gyro has been proposed to accomplish yaw axis stabilization for 110-deg pitch angle movement with a single two-axis gyro.

Quick Reaction Target Acquisition and Tracking System

The most relevant application of visual tracking is in the field of surveillance and defense, where precision tracking of target with minimal reaction time is of prime importance. This paper examines an approach for reducing the reaction time for target acquisition. Algorithm for auto detection of potential targets under dynamic background has been proposed. Also, the design considerations for visual tracking and control system configuration to achieve very fast response with proper transient behavior for cued target position have been presented which ultimately leads to an integrated quick response visual tracking system.

Sliding mode control based line-of-sight (LOS) stabilization of electro-optical sighting system

Electro-optical sighting systems are used for surveillance, target acquisition and tracking. The stabilization of the line of sight (LOS) against vehicle-induced disturbances is an essential feature of the electro-optical gimbaled sighting systems, mounted on mobile platforms. Due to factors like host platform dynamics, friction, cable restraint and noise, the pointing and tracking accuracy of the gimbaled system degrades substantially. This work presents control law design for LOS stabilization of a gimbaled electro-optical sighting system, using sliding mode controller (SMC). Other controllers like proportional-integral (PI) controller (conventional frequency domain approach) and linear quadratic gaussian with loop transfer recovery (LQG/LTR) controller (state-space based optimal control) are also compared with SMC for such application. SMC is a non-linear controller that is modified in this work which further reduces the chatter so as to achieve better steady state accuracy. All these controllers meet the stringent requirements of disturbance attenuation and command following.