Proportional navigation missile guidance using image recognition
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: FLIGHT DYNAMICS
GNC
AVIONICS
EQUIPMENT
IMAGE PROCESSING

description: Proportional Navigation Guidance (PNG) is the most frequently used guidance scheme in missiles control systems. Since the time it was first described, many modifications have been developed to enhance its effectiveness. In its basic formulation, it requires only the information about the missiles closing velocity and a rate of change of the targets relative angular position. The location of the missile\'s target is usually not known a priori with high precision, which makes target detection an important aspect of any guided missile. Various target detection methodologies like radar, lidar or electro-optics are used.
This paper will study the impact point precision and control quality of a guided missile equipped with vision-based navigation. The control scheme utilizing various types of image recognition algorithms and methods of converting its output to the input of control algorithms will be investigated. A nonsymmetrical ArUco marker of 4 by 4 units size was chosen as a mission target. Target detection will be performed using algorithms based on basic image processing methods, such as thresholding, morphological operations and edge detection, as well as using deep neural networks. Guidance towards the target will utilize the three-loop acceleration autopilot using proportional navigation for generating commands. The control signals will be converted to four independent forward control surfaces deflections.
In order to achieve satisfying control effectiveness, the commands from the guidance system to the control effectors should be generated with a high frequency. This requires a high computational power of the on-board computer to perform both the image recognition and generating control commands. Designing a small and cost-effective missile presents significant challenges. The bottleneck is the output frequency of the visual navigation system, as a powerful dedicated computer for image analysis requires a significant amount of space and power supply.
There exist several ways of overcoming this problem. One of them is the estimation of the targets absolute position, which allows to utilize this information in the control algorithm in longer timespans, as the target might be considered stationary. This can be achieved by combining the absolute position of the rocket - obtained from the inertial navigation and satellite systems - with the targets position relative to the rocket. Targets relative position is determined from a single camera frame using targets visual features, such as size, shape, or angular orientation.
The research described in this paper is a part of the FOK project. FOK is an aerodynamically controlled rocket being developed by the Rocketry Division of the Students Space Association at the Warsaw University of Technology since 2017. The rocket, 70 mm in diameter, 1.4 m long, equipped with four canards, was designed as a cheap and fully reusable platform intended for studying guidance, navigation and control algorithms.