Aerospace Technic and Technology

The main advantages of helicopters include the ability to reduce altitude and flight speed, hover in the air, unscheduled landings, and low sensitivity to weather conditions. These advantages over the aircraft allow the use of helicopters for civilian and military purposes. Simultaneously, the problem of landing the helicopter on an unequipped area with unknown terrain in bad weather conditions, in low visibility, at night, and in smoky areas remains unsolved. This research optimizes the algorithm of terrain formation from a helicopter. To achieve this goal, the radio wave range is used, which allows to operate the system regardless of external conditions and lighting. The geometry of the problem assumes that the distance to each point of the surface is measured by the pulse method. In the bow of the helicopter, there are two antennas, which due to the spatial diversity form two patterns that overlap some areas of the underlying surface. The summary and differential channels are formed from the antenna outputs. During the formation of the input data, mathematical models of the probing signal and the received observations are given, considering the influence of the atmosphere on the propagation of waves and the internal noise of the system. A theoretical study of the optimal algorithm for forming the surface relief by on-board helicopter radar was performed within the method of maximum likelihood. The obtained analytical expressions help calculate the angular position of the pulse volume, which can then be used in the formation of the surface of the area to be landed. Because of the analysis, a structural scheme of the onboard sum-difference system of measurement of range and the angular position of the scattered radar pulses is proposed. The block diagram clarifies the principle of operation of the optimal algorithm and implements the construction of relief. In accordance with the developed algorithm, a simulation was performed, which resulted in angular positions in degrees. The obtained initial data prove the efficiency of the presented on-board radar for the formation of the underlying surface.

helicopter radar; unequipped area; relief measurements; algorithm optimization; radar block diagram

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