Instant Lateral Offset Correction in RT-Range

Software Releases

June 14, 2010

Using the new lateral offset feature of the RT-Range saves a lot of setup time. Line the vehicles up accurately so that they are perfectly in line and use the quick configuration to “zero” the lateral range for this configuration.

Measuring the position of the sensor and the bulls-eye accurately with a tape measure is difficult. When two people try to measure it they invariably come up with measurements that are different by a few centimetres. This error is usually larger than the measurement error of the RT and is a major contribution to the overall error in the RT-Range.

The latest version of the RT-Range fixes this problem by including a lateral offset in the calculations. (Longitudinal offsets have already been added.) Once the measurement points for the sensor and the bulls-eye have been entered, a lateral offset can be added or subtracted from the lateral range in order to make quick adjustments.

There are several reasons why the lateral range can be incorrect, mostly due to configuration problems.

300_tape-measure-errorsWhen measuring a car you can never use a tape measure in one straight line. The sensor and bulls-eye positions are invariably measured using several steps and added together. Each step causes the error to grow.

 

 

300_sensor-misaligned-RT

Even with a co-ordinate measurement machine, small angle differences still cause unexpected errors. You may think that the RT-Range is measuring from point A, but it will be measuring from point B. The solution here is to use the Slip Angle Offset feature in Enginuity to correct the RT mounting angle.

200_antenna-pos-misalign

If the GPS antenna position is not known properly then this will also cause problems. Small rotations of the RT can mean co-ordinate measurement machines measure the antenna position differently to the way that the RT is expecting. This results in a displacement of the RT’s position measurement. The RT can fix this problem during the warm-up period.

 

 

300_importance-of-bulls-eye

It is still important to measure the position of the sensor and the bulls-eye as accurately as possible so that the algorithms can take heading, pitch and roll in to account correctly. Small adjustments to the lateral range using the lateral offset will not affect the overall error budget but relying on the lateral offset and longitudinal offset completely will give unexpected results.

In this example the lateral range to the bulls-eye and to the RT’s position are different. Using the longitudinal and lateral offsets to correct the range measurements will not work when the target vehicle is rotated compared to the hunter vehicle.

The RT-Range is the most comprehensive tool available for evaluating sensors in Advanced Driver Assistance Systems (ADAS) applications. For more information contact OxTS.