# Curb to Curb Diameter and Ackerman 1 and 2

Branch ID: 290

Request Number: 80000290

Table 1.
.plt Files .abf, .mrf Files Component Unit Comment
F1 RESULT(1) Not Used Not Used Not Used
F2 RESULT(2) Curb to Curb Diameter (Method 1) m The first method of calculating the approximate diameter of the circle the vehicle would move around at the current steer angles assuming no rear wheel steer.
When the Vehicle is Steering Right

outer = abs((left toe-in)/rtod)

inner = abs((right toe-in)/rtod)

turn radius = (wheel base)/tan((inner+outer)/2)

ctoc diam = 2*sqrt(((turn radius)+track/2)^2+ (wheel base)^2)/1000

When the Vehicle is Steering Left

inner = -(left toe-in)/rtod

turn radius = (wheel base)/tan((inner+outer)/2)

ctoc diam = 2*sqrt(((turn radius)+track/2)^2+ (wheel base)^2)/1000

F3 RESULT(3) Percent Ackerman (Method 1) % The first method of calculating percent Ackerman. Ackerman is used to quantify the amount of scrubbing occurring on the front of the vehicle during a turn assuming no rear wheel steer. A vehicle whose front wheels are parallel (the same steer angle) has 0% Ackerman. Conversely a vehicle is said to be 100% Ackerman when the lines through the left and right spindle axes intersect in the top view at a lateral line passing through the rear wheel centers. The following equation is used to calculate percent Ackerman with Method 1. See F2/RESULT(2) above for intermediate term calculations.
When the Vehicle is Steering Right

percent Ackerman = 100*((wheel base)/tan(outer)-(turn radius))/ (right spindle at kingpin y)

When the Vehicle is Steering Left

percent Ackerman = 100*((wheel base)/tan(outer)-(turn radius))/-(left spindle at kingpin y)

F4 RESULT(4) Ackerman Deviation (Method 1) deg The first method of calculating Ackerman deviation. Ackerman deviation, like percent Ackerman, is used to quantify the amount of scrubbing occurring on the front of the vehicle during a turn assuming no rear wheel steer. Zero Ackerman deviation means that lines through the left and right spindle axes intersect in the top view at a lateral line passing through the rear wheel centers. The following equation is used to calculate Ackerman deviation with Method 1. See F2/RESULT(2) above for intermediate term calculations.

alpha = atan((wheel base)/((turn radius)+track/2))

deviation = (outer-alpha)*rtod

F5 RESULT(5) Not Used Not Used Not Used
F6 RESULT(6) Curb to Curb Diameter (Method 2) m The second method of calculating the approximate diameter of the circle the vehicle would move around at the current steer angles assuming no rear wheel steer.
When the Vehicle is Steering Right

outer = abs((left toe-in)/rtod)

inner = abs((right toe-in)/rtod)

turn radius = track/2+(wheel base)/tan(inner)

ctoc diam = 2*sqrt(((turn radius)+track/2)^2+ (wheel base)^2)/1000

When the Vehicle is Steering Left

inner = -(left toe-in)/rtod

turn radius = track/2+(wheel base)/tan(inner)

ctoc diam = 2*sqrt(((turn radius)+track/2)^2+ (wheel base)^2)/1000

F7 RESULT(7) Percent Ackerman (Method 2) %

The second method of calculating percent Ackerman. See F3/RESULT(3) above for an explanation of Percent Ackerman. See F6/RESULT(6) above for intermediate term calculations.

alpha = atan((wheel base)/((turn radius)+track/2))

percent Ackerman = (inner-outer)/(inner-alpha)*100

F8 RESULT(8) Ackerman Deviation (Method 2) deg The second method of calculating Ackerman deviation. See F4/RESULT(4) above for an explanation of Ackerman deviation. See F6/RESULT(6) and F7/RESULT(7) above for intermediate term calculations.

deviation = (outer-alpha)*rtod