# TuSeSy: An Intelligent Turntable Servo System for Tracking Aircraft and Parachutes Automatically
## 1 Introduction  
In modern warfare, due to changes in combat styles, airborne troops are important forces used to achieve strategic campaign goals. Therefore, the construction and development of airborne troops have received great attention globally. It makes sense to conduct in-depth research on issues regarding airdropping combat personnel or materials to designated locations using a large transport aircraft as a platform. Parachutes play vital roles in airdrops; it is necessary to study the parachute open state and parachute flight trajectory [1]. When a large transport aircraft is airdropped, after the fighters or materials are separated from the airframe, the parachute generally has four stages, from opening the parachute bag to fully opening the parachute and then falling smoothly: the free fall phase from leaving the transport aircraft to opening the parachute bag (Figure 0(a)); from the parachute, pulling the parachute out of the bag to the straightening stage of the parachute and the parachute line (Figure 0(b)); pulling the parachute and the parachute line until the parachute is inflated (Figure 0(c)); the parachute is full of air to the steady landing stage of stable descent (Figure 0(d)). Regarding an airdrop involving heavy equipment such as tanks and infantry fighting vehicles, a pilot chute is usually added to guide the main chute to open. Research shows that airdrop failures often occur during the first threestages [2]. Therefore, if the attitude changes of the parachute in these three stages can be obtained, it will play an important role in the later design and improvement of the parachute. In the fourth stage of the airdrop, if the flight trajectory of the parachute can be accurately obtained, it can provide an effective reference for the design of the fixed-point airdrop program. Regarding the above problems, more scholars are focusing on how to efficiently and accurately obtain parachute deformation data and trajectory data. At present, the actual data collection mainly involves experimenters holding high-definition high-speed cameras to track and shoot a parachute to obtain the image sequences of the parachute during the entire airdrop process. These images save detailed information such as parachute attitude, which can be used for subsequent research and analysis. However, manual shooting has many disadvantages [3,4]. First, the trajectory of parachutes cannot be obtained. Second, when the parachute leaves the plane, it is a free fall motion and the speed of descent is very fast. For inexperienced photographers, they will often lose the target. Third, shooting for a long time requires a lot of physical strength, resulting in instability during shooting. Then the quality of the shooting picture is significantly reduced; in severe cases, the target will be lost. In 2004, [PERSON] et al. developed the parachute drop test system, which mainly collects the parachute data by means of photoelectric tracking and records the real landing images for subsequent research [5]. [PERSON] et al. proposed a parachute measurement method based on the Kalman filter. This method is carried out in semi-physical simulations and airdrop experiments; the parachute motion parameters are measured at the same time [6]. The system can track multiple targets simultaneously, with high reliability of airborne equipment and resistance to shock. [PERSON] and [PERSON] applied GPS to the parachute airdrop test, mainly using global positioning system (GPS) positioning principles, the spatial distributions of satellites, and the distances between satellites and ground points to rendezvous the ground point location method. The distance of the test point relative to the satellite is continuously and synchronously measured to calculate the space position of the parachute target, and then the flight trajectory of the parachute is obtained [7,8]. [PERSON] et al.