TECHNICAL NOTE NADS Vehicle Dynamics Typical Modeling Data Document ID: N06-017 Author(s): Chris Schwarz Date: August 2006 National Advanced Driving Simulator 2401 Oakdale Blvd. Iowa City, IA 52242-5003 Fax (319) 335-4658 Copyright 2005 by the National Advanced Driving Simulator, The University of Iowa. All rights reserved.
TABLE OF CONTENTS 1 Introduction... 3 2 Vehicle Data... 3 2.1 Inertia Measurements... 3 2.2 Suspension Kinematics and Compliance... 3 2.3 Steering Component Geometric and Inertia Measurements... 3 2.4 Tire Data (For STI Tire Model)... 3 3 Sample Vehicle Tests for Subsystem Validation... 4 3.1 Constant Radius Test... 4 3.2 Increasing Steer Test...4 3.3 J-turn Test... 4 3.4 Double Lane Change... 5 3.5 Pulse Test... 5 3.6 Sine with Dwell Test... 5 3.7 On-center Weave Test... 5 3.8 On-center Transition Test... 5 3.9 Steer and Brake Tests... 5 3.10 Brake Tests... 6 3.11 Acceleration Tests... 6 3.12 Coast Down Tests...6 4 Vehicle Instrumentation for Sample Tests... 6 2
1 INTRODUCTION The National Advanced Driving Simulator (NADS) vehicle dynamics models are highfidelity multi-body models. Suspension elements are modeled as bodies, in addition to the chassis; and non-linear relations such as suspension stiffness are captured in look-up tables. Moreover, vehicle subsystem models are provided for accurate vehicle behaviors in response to driver inputs. Modeled vehicle subsystems include the tires, steering, brake, engine, torque converter, transmission, and aerodynamics subsystems. For these reasons, the development of an accurate NADS vehicle model requires a lot of vehicle and test track data. A list of such data is given in this document. 2 VEHICLE DATA 2.1 Inertia Measurements Vehicle Weight Vehicle Center of Gravity (Longitudinal, Lateral, and Vertical) Vehicle Roll Mass Moment of Inertia Vehicle Pitch Mass Moment of Inertia Vehicle Yaw Mass Moment of Inertia 2.2 Suspension Kinematics and Compliance Front Ride Rate (Vertical Force vs. Suspension Deflection) Rear Ride Rate (Vertical Force vs. suspension Deflection) Front Roll Camber (Wheel Camber Angle vs. Roll Angle) Overall Front Roll Rate (Roll Moment vs. Roll Angle) Rear Roll Camber (Wheel Camber Angle vs. Roll Angle) Overall Rear Roll Rate (Roll Moment vs. Roll Angle) Front Steering Compliance (Applied Steering Torque vs. Steer Angle) Aligning Moment Compliance (Applied Aligning Moment vs. Steer Angle) Steering Ratio (Steering Wheel Angle vs. Wheel Steer Angle) Shock Absorbers (Force vs. Displacement curves) 2.3 Steering Component Geometric and Inertia Measurements Suspension Component (Geometry 3D locations of component connection points) Suspension Components (Weights and C.G. Locations) 2.4 Tire Data (For STI Tire Model) Tire Manufacturer 3
Tire Size Wheel Size Inflation Pressure Lateral Force vs. Slip Angle Aligning Moment vs. Slip Angle Longitudinal Force vs. Slip Ratio, Braking and Driving Lateral Friction Coefficients Longitudinal Friction Coefficients Lateral Force Stiffness Aligning Moment Stiffness Overturning Moment Stiffness Tire Longitudinal Stiffness Tire Vertical Stiffness Tire Inclination (Camber) Effect Frequency Response 3 SAMPLE VEHICLE TESTS FOR SUBSYSTEM VALIDATION 3.1 Constant Radius Test Use the 200-foot radius circle. From stop, accelerate slowly until the vehicle can no longer follow the circle (or a wheel lifts). Manually stop data recording. Run once in each direction. Driver controls throttle. 3.2 Increasing Steer Test Arm and drive straight ahead for 4 seconds before turning. Set the steering controller for a rate of 10 degrees/second. Stop recording when unable to maintain speed or vehicle begins to plow. Hold turn for 2 seconds before slowing or straightening wheels. Manually stop data recording. Run once in each direction at 25, 50, and 65 mph (11, 22, and 29 m/s). Use cruise control when possible. Driver maintains constant throttle when unable to use cruise control. 3.3 J-turn Test Set the steering controller based on desired g-level and speed. Use 750 degrees/sec for 25 mph runs; 500 degrees/sec for 50 mph and higher. When up to speed, arm and wait 3 seconds and initiate turn. Test lasts 12 seconds. Run 5 tests for each condition. Use cruise control when possible. Driver maintains constant throttle when unable to use cruise control. 4
3.4 Double Lane Change Place optical event reflecting stripe at gate for the first turn. Obtain test speed and arm data system 4 seconds before entering gate. Data recording starts with turning the wheel. Data will be recorded for 15 seconds or until manually stopped. First run is at 25 mph (11 m/s). Increase speed by 5 mph until course can no longer be traversed or a top speed of 50 mph (22 m/s) is reached. Use cruise control when possible. Driver maintains constant throttle when unable to use cruise control. 3.5 Pulse Test Set the steering controller for 3 m/s 2 turn. When up to speed, arm and wait 3 seconds and initiate turn. The pulse should be no wider than ½ second (1/3 second is better). End test four seconds after returning the steering wheel. Run 5 tests in each direction at 25, 50, and 65 mph (11, 22, and 29 m/s). Use cruise control when possible. Driver maintains constant throttle when unable to use cruise control. 3.6 Sine with Dwell Test Set the steering machine program for Sine with Dwell. The vehicle speed is 50 mph (22 m/s). Approach course at a speed slightly above desired speed and use drop-throttle trigger. Run one test each at the following angles (all left steer): 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, and 300. 3.7 On-Center Weave Test The course of the vehicle is straight ahead, but the driver slowly weaves back and forth in the lane. Obtain test speed and trigger data collection. Maintain straight course for 3 seconds and then begin weave. The amount of steering input should be such to produce a lateral acceleration of 2 m/s 2 (0.2g). One cycle of weaving (center-left-center-rightcenter) should take 5 seconds. Perform 2 cycles and return to straight ahead. Wait 1 second and stop recording. Perform 5 tests each at 25, 50, and 65 mph (11, 22, and 29 m/s). Use cruise control when possible. Driver maintains constant throttle when unable to use cruise control. 3.8 On-Center Transition Test The desired test speed is reached, and the data system is armed. Once the vehicle is moving straight and as the data system is armed, remove hands from the steering wheel. Wait 3 seconds and lightly place the palms on the steering wheel and slowly turn it until a lateral acceleration of 2 m/s 2 (0.2g) is reached. Data is recorded for 15 seconds. Perform 5 tests in each direction at 25, 50, and 65 mph (11, 22, and 29 m/s). Use cruise control when possible. Driver maintains constant throttle when unable to use cruise control. 3.9 Steer and Brake Tests The steering machine will be set to achieve the desired lateral acceleration. Use 750 degrees/sec for 25 mph runs; 500 degrees/sec for 50 mph and higher. Arm the data system. Approach course at a speed slightly above desired speed and use drop-throttle trigger. Allow 3 seconds of coast before the system triggers. Apply the brakes and hold at 5
a steady force until data system stops recording. The data system will stop after 15 seconds or until the driver stops it. See test sheet for test conditions. Perform 5 tests for each condition. 3.10 Brake Tests The cruise control will be used to obtain the desired test speed of 50 mph (22 m/s). Arm the data system. Wait 3 seconds and apply the brakes. Do not resume until the data system stops recording. The data system will stop after 15 seconds or until the driver stops it. There will be 4 tests per decel (2, 3, and 5 m/s 2, and max with ABS) except for the last set. The last set will consist of 6 best-effort stops with ABS off and no wheel lockup. Then 4 will be without ABS and more pedal force so that at least one wheel locks. Hold for 1 second and then back off the brake pedal to allow the stop to proceed without lockup. 3.11 Acceleration Tests The vehicle will be started at rest with 3 seconds of pre-trigger. The data system triggers off the throttle. When the vehicle reaches 70 mph (31 m/s), end test. If top speed is not reached in 45 seconds, end test. Three tests at each of 5 throttle positions (10, 25, 50, 75, and 100%) will be performed. Driver controls throttle. 3.12 Coast Down Tests The coast down tests will consist of one set of coast down runs in gear and four sets of different loading conditions in neutral. The set of coast down runs in gear will consist of two runs while each set of the runs in neutral will consist of four runs. Before starting, make sure the tires have been warmed up. The runs will alternate directions on the skid pad (or on different sides of the HSTT). Each run will begin at 70 mph and end at 15 mph (or until room on the skid pad runs out). Data collection will begin and end through manual start and stop. 4 VEHICLE INSTRUMENTATION FOR SAMPLE TESTS Longitudinal acceleration - forward positive (+/- 10 m/s 2 ) Lateral acceleration - right positive (+/- 10 m/s 2 ) Vertical acceleration - down positive (-20 to 0 m/s 2 ) Distance traveled Brake pedal force (0 800 N) Length of right front suspension (full travel) Length of left front suspension (full travel) Length of right rear suspension (full travel) Length of left rear suspension (full travel) Steering wheel torque - clockwise positive (50 N-m) 6
Transmission selector position Engine speed (0 600 rad/s) Steering wheel angular rate clockwise (+/- 300 deg/s) Wheel speed - right front (0 100 rad/s) Wheel speed - left front (0 100 rad/s) Wheel speed - right rear (0 100 rad/s) Wheel speed - left rear (0 100 rad/s) Throttle position (0-100 %) Distance from ground to right side of vehicle Distance from ground to left side of vehicle Roll rate - roll to right positive (+/- 1.0 rad/s) Pitch rate - front end rising positive (+/- 1.0 rad/s) Yaw rate - right turn positive (+/- 1.0 rad/s) Speed (0 35 m/s) Steering wheel angle - clockwise positive (lock to lock) Brake light switch (0 12V) ESC icon illuminated 7