[Defense Column] Precisely Shooting Down 'Smaller Drones' with This Method

[Image source=Yonhap News]

[Agency for Defense Development]The methods by which guided weapons recognize and track targets vary depending on the guidance method and tracking form. Among them, the method of irradiating a target with a laser and tracking the target using the reflected laser wave is called the Semi-Active Laser (SAL) homing guidance method. The SAL method has many advantages, such as enabling the production of guided weapons at a relatively low cost and allowing precise strikes by selectively targeting in densely populated areas like cities. However, it has the disadvantage of requiring a separate laser designator to irradiate the target and being limited in use against moving targets. In particular, for moving targets, there are limitations in tracking the target while the operator continuously irradiates the laser as in the conventional method. Therefore, a video-tracking laser designator is needed that can recognize and track the target through video, and use the target information obtained from the video to irradiate the laser while tracking with a pan/tilt gimbal device combined with the laser designator.

▲ Video-Tracking Laser Designator, Technical Operational Concept = As recent cases of North Korea’s small unmanned aerial vehicles (UAVs) invading South Korean territory show, threats from miniaturized high-speed UAVs, high-speed maneuvering vessels, and vehicles are increasing. As a countermeasure weapon system against these, low-cost, high-precision SAL guided weapons can be an alternative. To apply SAL guided weapons to small, high-speed maneuvering targets, it is necessary to irradiate the laser stably on the target. For this, automatic target tracking and irradiation are required.

In the case of conventional fixed or low-speed maneuvering targets, even if gimbal tracking is performed using information obtained from video, the difference in the target’s position change was negligible, so there was no problem. However, as the target’s speed increases, the difference in the target’s position change during the time required for gimbal tracking becomes larger, causing difficulties in irradiating the laser on small targets such as high-speed maneuvering targets and UAVs. The Agency for Defense Development (ADD) developed and applied video-tracking laser designator technology that calculates a corrected target position during the time required for gimbal tracking, enabling laser irradiation at the center of the target.

▲ Technology for Faster and More Accurate Targeting = To track targets by video, additional devices capable of measuring distance, angle, speed, etc., are generally required, along with algorithms for accurate video tracking calculations. Also, to ensure device mobility, low cost, and response to high-speed maneuvering targets such as UAVs, the calculation time must be reduced. To solve this, the video-tracking laser designator is configured to acquire target information using only video, without separate devices for measuring distance, speed, or angle. Furthermore, to minimize calculation speed, an algorithm was developed that performs calculations without converting target information from video pixel coordinates to spatial coordinates and integrates correction coefficients into distance and speed calculations.

The operational procedure of this technology is as follows. The video-tracking laser designator acquires video of a high-speed maneuvering target, tracks it to calculate the target’s position, and analyzes previous video information. Then, it calculates correction coefficients and corrects the target’s speed and position values. Using this information, the gimbal moves and tracks while irradiating the laser source onto the target.

▲ Application Fields of the Video-Tracking Laser Designator = In the defense sector, the SAL method is expected to be applicable to guided weapon systems on various platforms such as air defense, ground attack, and anti-ship due to its low cost and high precision. If video-tracking laser designator technology is applied to the SAL method, it is expected to effectively respond to fast and small threats like small UAVs through rapid and accurate targeting. Furthermore, this technology can be applied to autonomous driving collision avoidance systems in civilian sectors including defense, and is expected to be utilized in systems monitoring moving objects on airport runways or ports. The ADD plans to improve the technology maturity level in the future to resolve future asymmetric threats and contribute to domestic industrial development.