Method for calculating forward acoustic scattering doppler frequency shift of underwater moving target under irregular trajectory

A method for calculating the forward acoustic scattering doppler frequency shift of an underwater moving target under irregular trajectory is characterized by comprising:

• (1) converting earth longitude and latitude coordinates of a transmitter, a irregular trajectory of the underwater moving target under irregular trajectory and a receiver into Cartesian coordinates, and marking as (xS, yS), (xT, yT), and (xR, yR), respectively, and designating a baseline connecting the transmitter and receiver as a transceiver line;
• (2) denoting a target trajectory sequence of the underwater moving target under irregular trajectory as (xT(ti), yT(ti)), i=1, 2, . . . , N, and directly calculating a motion velocity v of the underwater moving target under irregular trajectory between any two adjacent moments ti and ti+1;
• v
• i
• =
• [
• x
• T
• (
• t
• i
• +
• 1
• )
• -
• x
• T
• (
• t
• i
• )
• ]
• 2
• +
• [
• y
• T
• (
• t
• i
• +
• 1
• )
• -
• y
• T
• (
• t
• i
• )
• ]
• 2
• t
• i
• +
• 1
• -
• t
• i
• ,
• i
• =
• 1
• ,
• 2
• ,
• …
• ⁢
• N
• -
• 1
• ,
• calculating an arithmetic average of the velocities in all time periods to obtain
• v
• _
• =
• 1
• N
• -
• 1
• ⁢
• ∑
• i
• =
• 1
• N
• -
• 1
• v
• i
• ;
• (3) smoothing the target trajectory of the underwater moving target under the irregular trajectory, and performing piecewise linear approximation on the smoothed target trajectory of the underwater moving target under irregular trajectory so that a motion trajectory of the underwater moving target under irregular trajectory between any two adjacent moments ti and ti+1 is a straight line, and using the straight line as a virtual straight line trajectory, calculating horizontal distances from the underwater moving target under irregular trajectory and the receiver to an intersection point of the target trajectory of the underwater moving target under irregular trajectory on the transceiver line, and an included angle between the virtual straight line trajectory and the transceiver line;
• wherein the smoothing is performed using a smoothing method, the smoothing method comprising using a time window with a length of lw points to successively intercept the target trajectory sequence with a step of tw points, and regarding an arithmetic mean of trajectory coordinates within each window as the equivalent target trajectory coordinate in the interval and the smoothed target trajectory coordinates are given by the following formula:
• x
• ~
• T
• (
• t
• w
• )
• =
• 1
• l
• w
• ⁢
• ∑
• t
• =
• t
• w
• ⁢
• i
• w
• -
• 1
• 2
• t
• w
• -
• I
• w
• -
• 1
• 2
• x
• T
• (
• t
• )
• ,
• y
• ~
• T
• (
• t
• w
• )
• =
• 1
• l
• w
• ⁢
• ∑
• t
• =
• t
• w
• ⁢
• I
• w
• -
• 1
• 2
• t
• w
• +
• I
• w
• -
• 1
• 2
• y
• T
• (
• t
• )
• ;
• (4) calculating the acoustic forward-scattering Doppler-shift of the underwater moving target under irregular trajectory at each moment by using the parameters obtained in steps (2) and (3).