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Methods for determining the take-off speed of launchers for unmanned aerial vehicles

Jastrzębski G., Ułanowicz L.

Journal of KONES

2018

Vol. 25, No. 1

170--176

Unmanned aerial vehicles (UAV) are currently a very rapidly developing type of aviation. The problem of support during the take-off with the use of, i.e. take-off launchers arose along with their development, especially for UAVs with weights and dimensions preventing manual take-off. One of the major issues associated with UAV take-off launchers is for its UAV accelerating element to obtain its initial speed. The article presents three methods of determining launcher take-off speeds for unmanned aerial vehicles, i.e. the concentrated very oblique projection method, the high-speed camera methods, and the acceleration recorder method. The take-off launcher carriage speed in the oblique projection method is determined from a formula. This method involves “ejections” of concentrated masses from the UAV mass range and measuring the component values resulting from the used formula, which contains the range of the oblique projection, the elevation of the projection and its angle. The method using the high-speed camera involves recording the course of ejections of the concentrated mass from the launcher. The average take-off speed is determined on the basis of a take-off run length (section of the launcher race, where the unit accelerates) and defining the start and end frame of the carriage movement. The third method for the determination of the take-off speed utilizes an acceleration recorder. The method with the recorder involves registering a change in the accelerations when the take-off carriage is being accelerated by a system fixed on the carriage or the accelerated object. The article presents the methodology of dynamic tests of object acceleration on a launcher, necessary for the determination of speed with the mentioned methods. Selected results from actual tests with the use of the 01/WS/2015 launcher, which is an element of the ZOCP JET2 set, were presented. The test results are presented in a tabular form. The methods for the determination of the take-off speed were compared on the basis of performed tests. Based on the obtained results, the factors impacting the accuracy of each of the methods were identified.

Impact of opening time of the take-off pneumatic launcher main valve on take-off pressure losses

Jastrzębski G.

Journal of KONES

2016

Vol. 23, No. 4

175--182

This publication presents UAV rope and pneumatic launchers constructed and operated in the Air Force Institute of Technology. The construction and operating principle were presented, and functional properties of the UAV take-off pneumatic launcher were characterised. Furthermore, a detailed diagram of the take-off pneumatic launcher was shown, and an operating principle of the launcher take-off system and pneumatic control of the take-off procedure were discussed. The operation parameters of the most important operational elements (main ball valve, semi-rotary actuator, pneumatic valves controlling the flow) from the launcher pneumatic system were specified. On the basis of data sheets of pneumatic elements, a calculation model of the mass flow (volumetric flow rate) of compressed air flowing through the main valve (ball valve in the take-off cylinder supply line) of the take-off pneumatic launcher was designed. The possible cracks, through which compressed air leaks and the take-off cylinder dead sections during the main valve opening and shot, were characterised and discussed. The calculation model designed for individual leaks and total compressed air leaks in the take-off line of the pneumatic launcher was presented. Based on the mass flow model (volumetric flow rate) of compressed air flowing through the main valve, and total compressed air leaks, the relationship of compressed air energy losses depending on opening time of the main valve of the take-off pneumatic launcher was determined. In the paper, the results of simulation studies for the times shorter than data sheets of the main valve opening were presented. In addition, the change of the compressed air disposable energy losses was defined. Based on the results of simulation studies, the opening time of the take-off launcher main valve for the acceptable disposable energy loss level of the take-off pneumatic launcher was specified.