ADAS Parameter Definitions - VBOX 3i (FW 2.8)

The following tables provide a list of channels capable of being calculated in each vehicle within an ADAS test.

• For 1 Vehicle Target testing, Racelogic refers to each vehicle as the ‘Subject Vehicle’ or the ‘Target Vehicle’. For example, under testing for adaptive cruise control, the lead vehicle will be the Target Vehicle, whilst the following vehicle (where the adaptive cruise control is being tested) is referred to as the Subject Vehicle.
   
• For 2 Target Vehicle testing, channel naming now changes such to indicate channels calculated with respect to, Target Vehicle 1 and Target Vehicle 2. As there are now three vehicles involved with this testing, the number of channels increases at the Subject Vehicle, this is reflected in the table below:

The vehicle separation channels calculated at the Target vehicle are essentially exactly the same as the channels calculated at the subject vehicle, except for the channels highlighted in yellow.

The channels highlighted in grey are not used in Static Point testing. These are listed to ensure continuity of the Racelogic report generator application, which uses channel ordering as its sort function.
 

Channel name definition. Where the channel name is not obvious, then it is made up of three parts:
 

• The first part is the parameter type i.e. LngR = Longitudinal Range
• The second part indicates which vehicle heading is being used in the calculation of this parameter i.e. sv = subject vehicle
• The last part indicates which vehicle is parameter is being calculated with reference to, i.e. tg1 = Target Vehicle 1
   

A number of the parameters shown in the table above are outlined in schematics below in order to give a clear visualisation of how they are calculated.

Longitudinal and Lateral Range with respect to subject vehicle heading.
 

Lng Range and Lat Range between Subject Vehicle and Target 1 Vehicle using Subject Vehicle heading example
 

Note: The LngRsv and LatRsv values are calculated from offset points on each respective vehicle. Details of how to apply these offsets is provided in the Quick Start Guide.

Longitudinal and lateral difference between two vehicles based on an external reference heading.
 

It is a requirement of the National Highway Traffic Safety Administration “Forward Collision Warning System NCAP Confirmation Test March 2012” confirmation tests that the Subject Vehicle (SV) remains within 0.6 m of the centre line of the Target Vehicle (in the standard referred to as Principle Other Vehicle - POV).
 

Range calculations using a reference lane for NHTSA FCWS confirmation test
 

If this Lateral Range channel was based purely on vehicle heading then the resultant value would be extremely susceptible to noise. Small fluctuations in the Subject or Target Vehicle heading will results in fluctuations in Lateral Range greater than the NHTSA standard, the following example demonstrates this principle:
 

Heading fluctuation of 0.5° over a vehicle separation of 100 m:
 

By using a Reference lane heading, a very stable Lateral Range channel is generated. Please click here for details on how to record a reference lane.

Lat Range between Subject Vehicle and Target 1 Vehicle using Reference Line heading example

Longitudinal and Lateral Range with respect to target vehicle heading.
 

Lng Range and Lat Range between Subject Vehicle and Target 1 Vehicle using Target 1 Vehicle heading example

Note: Target Heading is a standard channel logged in the Target Vehicle, but only used in calculations at the Subject Vehicle. 

Angle to the Target Vehicle with respect to the heading of the Subject Vehicle.
 

Angle between Subject Vehicle and Target 1 Vehicle using Subject Vehicle heading example

Time to collision based on Longitudinal Range from Subject Vehicle to Target Vehicle based on Subject Vehicle heading and Longitudinal Speed.
 

T2Csv_tg1 example:

Time to collision taking into account a decelerating target vehicle

NHTSA provide the following equation to account for a decelerating target vehicle in test 2 of their FCWS NCAP confirmation test.
 

T2C2sv_tg1 example:

• V_pov = Velocity of Principle Other Vehicle (Target Speed)
• V_sv = Velocity of Subject Vehicle (Speed)
• a_pov = Acceleration of Principle Other Vehicle (Target Accel)
• a_sv = Acceleration of Subject Vehicle (Accel)
• S_sv = Longitudinal distance from Subject Vehicle to Target Vehicle (LngRange)

Time to collision based on Longitudinal Range from Subject Vehicle to Target Vehicle based on Target Vehicle heading and Target Vehicle longitudinal Speed.
 

T2Ctg_tg1 example:

This channel is a time based incremental value based on Target Vehicle UTC time. A good link will show a trace incrementing every 10 ms with no drops to zero. Once this value reaches 65535 it is reset to zero.

Link Time is a good indicator of ADAS radio link quality, If this incremental count drops out and falls to zero then it is a likely indication that the ADAS radio link has intermittently failed.

The VBOX ADAS system will suffer occaisional single sample drops outs, which are acceptable but larger periods of time with full or intermittent drop outs are an indicator of a Radio problem that needs addressing.

See also section Radio Link

This channel indicates the current operating mode of the VBOX.

For Adaptive Cruise control testing; time it would take the Subject Vehicle to travel across the Vehicle separation distance at its current speed.
 

SepTim_tg1 example: