Ship Radar Antenna Velocity Compensation
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Solution Overview
Problem
Conventional ship radar systems inaccurately measure the ground velocity of target objects due to unaccounted antenna velocities caused by complex rocking and drifting motions of the ship, leading to errors in velocity estimation.
Innovation Solution
A ship radar apparatus with an antenna installed on a ship body, equipped with sensors to detect roll and pitch angles, calculates and compensates for antenna velocities relative to the ship's center of gravity, thereby reducing errors in relative velocity measurements between the ship and target objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional velocity correction methods using GPS and other measuring instruments are employed, then the ground velocity of target objects can be calculated, but measurement precision deteriorates due to unaccounted antenna velocities caused by ship rocking and drifting
Solution Approach 1:
The patent replaces the conventional mechanical/GPS-based velocity measurement system with a radar-based electromagnetic wave system. By using the radar antenna's own transmission signals and received echo signals, the system calculates velocity through signal processing rather than relying on external mechanical measuring instruments like GPS or LOG, thereby eliminating the inconsistency between antenna position and ship body position.
Solution Approach 2:
The patent introduces the radar antenna as an intermediary element that serves dual purposes: both as the platform for observation and as the reference frame for velocity measurement. By using the antenna's own motion characteristics (derived from ship motion data) to correct the velocity measurements it takes, the system eliminates the need for separate reference systems and resolves the positional inconsistency problem.
2Measurement precision
If the velocity of the ship is corrected using GPS and other instruments, then ground velocity can be obtained, but device complexity increases due to multiple measuring instruments
Solution Approach 1:
The patent makes the radar antenna multi-functional by using it both for target detection and for velocity measurement reference. The same antenna that detects target objects also serves as the reference point for calculating relative velocity, eliminating the need for separate GPS receivers, LOG devices, and gyrocompasses, thereby simplifying the overall system configuration.
Solution Approach 2:
The patent merges the velocity measurement function with the target detection function by using the same radar antenna and signal processing system. Instead of having separate systems for navigation (GPS) and velocity measurement (LOG, gyrocompass), the invention combines these functions into the radar system itself, reducing the number of components and simplifying system integration.
3Measurement precision
If multiple measuring instruments are used for velocity correction, then velocity data can be obtained, but ease of operation deteriorates due to coordinate system alignment requirements
Solution Approach 1:
Instead of transforming the velocity vector from GPS/LOG coordinates to radar antenna coordinates (the conventional approach), the patent inverts the approach by using the antenna's own coordinate system as the reference frame from the beginning. This eliminates the need for complex coordinate transformations and angle calculations, as the velocity is directly measured in the antenna's reference frame.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The compensation of antenna velocities due to roll and pitch motions effectively reduces errors in estimating the relative velocity between the ship and target objects, enhancing the accuracy of ground velocity calculations.
Implementation Method 1
an antenna (21) installed on a ship body (10) and configured to transceive electromagnetic waves
Implementation Method 2
a sensor configured to detect a roll angle and a pitch angle of the ship body
Implementation Method 3
a Doppler frequency caused by a movement of the movable body itself is generated
Data Source
AI summary
Error that occurs when an absolute velocity of a target object is measured by using an antenna installed on a ship body that rocks and drifts in a complex manner since it floats on the sea is reduced. An antenna is installed on a ship body and transceives electromagnetic waves. A roll angle and a pitch angle of the ship body are detected by using an inclination sensor. An antenna velocity calculator calculates an antenna velocity of the antenna by using the detected roll and pitch angles of the ship body. An antenna velocity compensator compensates the antenna velocity of the antenna for a relative velocity between the ship body and a target object, the antenna velocity calculated by the antenna velocity calculator, the relative velocity obtained based on reflection waves received by the antenna.