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Dynamic Traction Dynamic Traction ControlControl
By: Thiago Avila, Mike Sinclair & Jeffrey McLarty
MotivationMotivation
Drastically improve vehicle performance and safety by maintaining optimal wheel traction in all road conditions
MotivationMotivation
Needs AssessmentNeeds Assessment
FSAE car is currently traction limited and would benefit from the use of a traction control system
System must follow FSAE guidelines
Minimal cost solution should be pursued
Design Criteria and ConstraintsDesign Criteria and Constraints
◦Meet FSAE Guidelines
◦Predict slip with enough time to adjust engine output
◦Reduced FSAE 75m acceleration times
◦Improve FSAE skid pad testing results
Problem FormulationProblem Formulation
The traction control system is required to prevent driver error from overloading any of the four wheels and causing slip, through either throttle or brake application
AbstractionAbstraction
Physics model sensors◦3-axis Accelerometer◦Linear Potentiometer Cost & Complexity
Engine Power Control◦Cutting Spark Difficult to Predict Power
◦Limiting Fuel Improper Fuel Ratio
◦Drive by wire throttle Infringes FSAE rules
◦Electronic Air Restrictor
Proposed Solution BreakdownProposed Solution Breakdown
Slip Model◦Vehicle Dynamics and Sensing
Vehicle Control◦Electronic Restrictor
Proposed SolutionProposed Solution
Slip Model
◦Dynamic Physics Model
◦Dynamic Coefficient of Friction
◦Understeer Detection
Design LayoutDesign Layout
Physics Model
(Saturator)
ECU
RPMThrottle Pos.
Driver Pedal
Slip AngleRadius
External Sensors
X/Y/Z
Acceleration
+- CBR 600 F4i
EngineWheels
Wheel Slip
Detector
μs/μk
Physics Model Physics Model
Torque MapTorque Map
InterpolationInterpolation
Interpolate Between Four Points on Torque Map•Interpolate between Engine Speeds at Throttle 1
InterpolationInterpolation
Interpolate Between Four Points on Torque Map•Interpolate between Engine Speeds at Throttle 1•Interpolate between Engine Speeds at Throttle 2
InterpolationInterpolation
Interpolate Between Four Points on the Torque Map•Interpolate between Engine Speeds at Throttle 1•Interpolate between Engine Speeds at Throttle 2•Interpolate between results at different Throttles
InterpolationInterpolation
Interpolate Between Four Points on the Torque Map•Interpolate between Engine Speeds at Throttle 1•Interpolate between Engine Speeds at Throttle 2•Interpolate between results at different Throttles
InterpolationInterpolation
Interpolate Between Four Points on the Torque Map•Interpolate between Engine Speeds at Throttle 1•Interpolate between Engine Speeds at Throttle 2•Interpolate between results at different Throttles•Engine Power from 4 point Interpolation = Done
Physics Model Physics Model
Data AcquisitionData Acquisition
Installed Sensors◦Steering Wheel Angle◦2-D Acceleration◦Suspension Deflection◦Wheel Velocity◦Brake Pressure◦Engine RPM◦Throttle Position◦Air Mass Flow Rate
Physics Model SimulationPhysics Model Simulation
Model Validation – FL TireModel Validation – FL Tire
Slip ConditionSlip Condition
Dynamic Coefficient of Friction Dynamic Coefficient of Friction CalculatorCalculator
Slip Detected
Calculate Engine Torque @ T(0)
Calculate Vertical Force @
T(0)
Calculate Coefficient of Friction and Update Model
μs
Optimize PerformanceOptimize Performance
No Slip Detected
Is μs at the limit?
Maintain current
μs
Increase μs
Yes
No
New Limit
Initial Value
Calculated Values
Understeer DetectionUndersteer Detection
Turning Radius:◦Desired vs. Actual
Major Factor:◦Wheel Slip Angle
Slip Angle Slip Angle
Proposed SolutionProposed Solution
Vehicle Control
◦Electronic Restrictor
◦Brake Pressure Controller
Electronic RestrictorElectronic Restrictor
Electronic RestrictorElectronic Restrictor
Electronic RestrictorElectronic Restrictor
Electronic RestrictorElectronic Restrictor
Electronic RestrictorElectronic Restrictor
Electronic RestrictorElectronic Restrictor
Electronic RestrictorElectronic Restrictor
Electronic RestrictorElectronic Restrictor
ServoRotary
Potentiometer
Gears
Butter-Fly-Valve
Electronic RestrictorElectronic Restrictor
)()(
ss
KsP
))((
)()(
bsas
psGsC
0
%5..%
sec5.0
sec1.0
esteadystate
SO
Tsettle
Tpeak
PatentsPatents
Physics Model
(Saturator)
ECU
RPMThrottle Pos.
Driver Pedal
Slip AngleRadius
External Sensors
X/Y/Z
Acceleration
+- CBR 600 F4i
EngineWheels
Wheel Slip
Detector
μs/μk
PatentsPatents
Physics Model
(Saturator)
ECU
RPMThrottle Pos.
Driver Pedal
Slip AngleRadius
External Sensors
X/Y/Z
Acceleration
+- CBR 600 F4i
EngineWheels
Wheel Slip
Detector
μs/μk
Possibly patentable:Continuously Improving
Predictive Traction Control
1 day
2 weeks 1 week
2.5 weeks4 weeks
CommissioningThe Plan
StartStart
Create Controller based on Design Criterion
Create Controller based on Design Criterion
Finish
Finish Install
RestrictorInstall
Restrictor
Order Parts & MaterialsOrder Parts & Materials
Build Restrictor
Build Restrictor
Test & OptimizeTest &
Optimize
Critical Path ~10 weeks
3.5 weeks
Program PSoC with Physics Model &
Interpolation
Program PSoC with Physics Model &
Interpolation
Questions?Questions?Comments?
The EndThe EndThank you!
