BMW F97 - Page 51

F97/F98�Complete�Vehicle
5.�Chassis�and�Suspension
47
M�Servotronic�is�that�3�stages�can�be�selected�in�comparison�to�2�stages�in�the�production�vehicles,
and�it�has�a�separate�button�in�the�M�driving�dynamics�button�panel�in�the�center�console.�Using�the
button�or�via�the�M1/M2�buttons,�the�driver�can�switch�between�"Comfort",�"Sport"�and�"Sport+".
Here�the�corresponding�characteristic�curve�is�activated�and�in�Sport�direction�the�power�steering
support�is�also�noticeably�withdrawn.�The�program�selection�can�also�be�preconfigured�in�the�head
unit�HU�and�selected�using�the�M1/M2�buttons�on�the�steering�wheel.
M�drive�dynamic�control�switch,�program�description,�M�Servotronic:
• “COMFORT”:�Focus�on�light�and�comfortable�steering�torques�with�perfect�feedback�from�the
road�surface�at�the�same�time.
• "SPORT":�Greater�rise�in�the�steering�force�and�perceptibly�more�feedback�for�sporty�M
dynamic�driving,�both�for�every�day�use�and�at�the�dynamic�driving�limit.
• "SPORT+":�Even�greater�rise�in�the�steering�force�and�high�steering�force�level�for�the�greatest
possible�feedback�and�clear�sporty�steering�sensation.
5.1.3.�Steering�angle�sensor
The�information�on�the�steering�angle�in�the�F97/F98�is�not�recorded�by�the�Electronic�Power�Steering
(EPS)�and�not�via�a�separate�sensor�on�the�steering�wheel�and�instead�is�computed�based�on�the
motor�position�angle�of�the�EPS�motor�in�relation�to�the�steering�wheel.
The�EPS�delivers�the�position�of�the�rack�via�FlexRay�to�the�M�Dynamic�Stability�Control�(M�DSC).
During�this�process,�the�EPS�calculates�the�absolute�position�of�the�rack�based�on�the�current�motor
position�of�the�EPS�motor�and�the�number�of�complete�revolutions�performed�by�the�motor�starting
from�the�zero�position�(straight-ahead�driving�position).
Taking�this�position�as�the�starting�point,�the�M�Dynamic�Stability�Control�(M�DSC)�determines�the
wheel-specific�steering�angle�among�other�things�using�the�stored�ratio�parameters�(rack�to�wheel-
specific�steering�angle)�and�transmits�this�via�FlexRay.�This�wheel-specific�steering�angle�is�used
by�the�M�Dynamic�Stability�Control�(M�DSC)�among�other�things�as�a�reference�variable�for�internal
control�functions.
In�cases�where�the�absolute�value�is�not�available�from�the�EPS�(loss�of�terminal�30,�flash�process),�the
absolute�value�is�determined�through�interaction�between�the�M�Dynamic�Stability�Control�(M�DSC)
and�EPS�using�an�adaption�function�in�which�the�steering�wheel�is�turned�from�end�stop�to�end�stop
(e.g.�straight-ahead�position�->�left�->�right�->�straight-ahead�position).