IVK – Institut für Verbrennungsmotoren und Kraftfahrwesen Virtual Testing and Subjective Evaluation of Chassis Components in the Stuttgart Driving Simulator IPG Apply & Innovate, Karlsruhe September 20 – 21, 2016 Dipl.-Ing. Minh-Tri Nguyen
Overview I. Motivation and Purpose II. Principle of Driving Dynamics Evaluation in the Simulator III. Implementation of the Driving Scenario IV. Human’s Perception of Vehicle Motion V. Evaluation of Chassis Components VI. Summary University of Stuttgart 9/21/2016 2
I. Motivation and Purpose
Motivation and Purpose • Integration of the driving simulator in the process of chassis development and driving dynamics Vision: Holistic approach for vehicle development Vehicle IVK Driving Aeroacoustics Dynamics Wind Tunnel Test Bench Stuttgart Driving Simulator University of Stuttgart 9/21/2016 4
Motivation and Purpose • Improving system understanding in early stages of the development process by subjective evaluation Definition, Simulation Concept Prototype Building, Tuning, Validation Optimization SOP Subjective Evaluation Objective Data Simulation Testing University of Stuttgart 9/21/2016 5
Motivation and Purpose • Approach for driving dynamics evaluation in the driving simulator Use Case, Customized - Subjective Benefits, Modeling driving Limits. and impression Simulation - Comparison to Reality University of Stuttgart 9/21/2016 6
II. Principle of Driving Dynamics Evaluation in the Simulator
Principle of Driving Dynamics Evaluation in the Simulator • Common process for subjective and objective evaluation of driving dynamics Disturbances ψ, ϑ, φ, … Obj. Data Driver’s reaction Vehicle’s reaction ? Vehicle δ Correlation subj.- obj. Subj. Evaluation Driver University of Stuttgart 9/21/2016 8
Principle of Driving Dynamics Evaluation in the Simulator • Driving Simulator process for subjective evaluation of driving dynamics Disturbances On/Off Model’s reaction Ψ mod , ϑ mod , φ mod Ψ‘, ϑ‘, φ‘ Driver’s reaction Simulator’s reaction Model Simulator Motion Cueing Correlation subj.- obj. δ Subj. Evaluation Driver University of Stuttgart 9/21/2016 9
III. Implementation of the Driving Scenario
Implementation of the Driving Scenario Requirements for the Vehicle Model Accuracy of Modeling Limit of Real Time Capability Computing Time Subjective improvement due to model complexity University of Stuttgart 9/21/2016 11
Implementation of the Driving Scenario IPG CarMaker Vehicle Model for Driving Dynamics Evaluation 0,6 Enhanced Damper- 0,4 Topmount-Model 0,2 0,0 -15,0 -5,0 5,0 15,0 Force-distance-graph damper Force-velocity-graph damper Aerodynamic Coeff. 2000 2000 1500 1500 1000 1000 Pfeffer Steering 500 500 0 0 0 0 0 0 -1.5 -1 -0.5 0 0.5 1 1.5 -30 -20 -10 0 10 20 30 5-Mass Model With Rigid Body Suspension Elements Kin./ Elakin. (.skc) Parameterized MF 5.2 University of Stuttgart 9/21/2016 12
Implementation of the Driving Scenario Transferring On-Road Scenario to Virtual Reality • Scenario Driving on Autobahn with road impact, e.g. bumps, bridge joints and road unevenness Focus on: VR in the Simulator Exact reproduction of vehicle’s body motion Autobahn Test Run Subjective driving impression comparable to reality University of Stuttgart 9/21/2016 13
Implementation of the Driving Scenario Structure of Excitation Superposition of synthetic road spectrum and impulses on vehicle body 0 10 0.1 Heave Motion CG Heave (f) [m²/Hz] 0.05 Heave [m] -10 10 0 -0.05 -20 10 -0.1 -2 0 2 4 10 10 10 10 0 1000 2000 3000 4000 5000 Frequency [Hz] Length [m] Synthetic Road Spectrum 𝐺 𝑏 𝑦 𝑦 Excitation 𝑏 𝑧 𝐺 𝑧 𝐺 𝑏 𝑨 CG 𝑨 𝜒 𝑁 𝑦 Measured Forces and 𝑁 𝑧 𝜘 Vehicle’s Motion Moments 𝑁 𝑨 after Vertical 𝜚 Referred to CG Impact University of Stuttgart 9/21/2016 14
IV. Human’s Perception of Vehicle Motion
Human’s Perception of Vehicle Motion “Threshold of Perception” and the “Just Noticeable Difference” Using defined excitation to generate criteria of perception: • General statements about the “Threshold of Perception” regarding to the Autobahn scenario • Evaluating the “Just Noticeable Difference” due to impulses Threshold of Perception Noticeable Difference Excitation Driver Virtual Vehicle Model University of Stuttgart 9/21/2016 16
Human’s Perception of Vehicle Motion Driver’s Task to Evaluate the Threshold of Perception (ToP) • Experimental measuring of detected impulses • Correlation between the intensity of impulses and the stochastic road excitation ToP 𝑏 𝐽𝑛𝑞 = 𝒒 ∗ 𝑏 𝑠𝑝𝑏𝑒 + 𝒓 5 Correlation AMP / RMS Correlation - Impulse - Excitation 4 5 Body Acc. in m/s² 4.5 3 AMP Impulse 4 Amplitude Impulse [m/s²] 2 3.5 Vertical Acc. [m/s²] 3 1 2.5 2 0 1.5 -1 1 0.5 -2 0 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 -3 RMS of Vertical Excitation [m/s²] RMS Vertical Road Excitation -4 -5 200 205 210 215 220 225 230 Time [s] Time in s University of Stuttgart 9/21/2016 17
Human’s Perception of Vehicle Motion Results of the ToP Linear correlation between impulse amplitudes and RMS of vehicle’s vertical acceleration due to road disturbances. Threshold of Perception 5 Amplitude of Vertical impacts in m/s² ● detected ● non-detected Separation of 4 Vehicle Motion Threshold of Perception .7 .5 5 3 .6 4 2 .5 3 .5 .4 .3 2 1 .2 2 1 .5 .1 0 0 0 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 Threshold of Perception 5 .7 .5 .6 4 2 1 .5 3 .5 .4 .3 1 2 .2 1 .5 .1 0 0 0 0 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 RMS of vehicle`s vertical acc. due to road disturbance in m/s² University of Stuttgart 9/21/2016 18
Human’s Perception of Vehicle Motion Driver’s Task to Evaluate t he Just Noticeable Difference (JND) • Experimental measuring of three impulses in a row (3AFC-Method) • Probability of detecting a difference between two impulses JND > 2 Psychometric Function 1 st 2 nd 3 rd 1.5 Probability in % 1 Body Acc. in m/s² 0.9 1 1 0.8 0.7 𝑄(𝑦) = 0.5 0.6 𝑦−𝒅 𝒕 0.5 0 0.4 1 + 𝑓 𝒃 𝒕 0.3 -0.5 0.2 0.1 𝒃 𝒕 = JND -1 0 0 0.5 1 1.5 2 2.5 < 𝒅 𝒕 = x(P50%) -1.5 AMP Impulse -2 540 541 542 543 544 545 546 547 548 549 550 Time in s University of Stuttgart 9/21/2016 19
Human’s Perception of Vehicle Motion Results of the JND • Fitting the psychometric function based on the probability of perceived impulses • Calculation the JND by evaluating the impulse intensity at the probability of 50% and 75% Psychometric Function - Vertical Dynamics Impulse 1 Probability of Perception in 100% 0.8 75% 0.6 50% JND 0.4 0.2 * measured impulse - Fitted sigmoid fun. 0 0 0.5 1 1.5 2 2.5 Relative Stimulus Intensity University of Stuttgart 9/21/2016 20
V. Evaluation of Chassis Components
Evaluation of Chassis Components Comparison of Vehicle Variants by the Perception of Road Impacts ToP and JND of vertical impulses 4 4 Threshold of Perception 3 3 2 2 Body Acc.z in m/s 2 Body Acc.z in m/s 2 1 1 0 0 ● Vehicle 1 (orig.) ● Vehicle 1 -1 -1 • + 20 % Stiffness • + 20 % Damping -2 -2 -3 -3 Perceptible as impulse -4 -4 60 62 64 66 60 62 64 66 Time in s Time in s University of Stuttgart 9/21/2016 22
Evaluation of Chassis Components Comparison of Vehicle Variants by the Perception of Road Impacts ToP and JND of vertical impulses 4 4 2 3 3 2 Body Acc.z in m/s 1.9 > JND 2 2 Body Acc.z in m/s 2 Body Acc.z in m/s 2 1 1 1.8 0 0 1.7 61.75 61.8 61.85 61.9 61.95 -1 -1 Time in s Noticeable as difference -2 -2 -3 -3 -4 -4 60 62 64 66 60 62 64 66 Time in s Time in s University of Stuttgart 9/21/2016 23
VI. Summary
Summary • Improved system understanding by subjective evaluation of driving dynamics in early stages of the development process. • Thresholds of perceptions can be used to evaluate driving dynamics topics to get additional objective data and better correlations. • Compared to real on-road tests new approaches and analysis can be implemented. • With this simulation environment the evaluation of driving dynamics can be more experienced. University of Stuttgart 9/21/2016 25
Thank you! Dipl.-Ing. Minh-Tri Nguyen e-mail Minh-Tri.Nguyen@ivk.uni-stuttgart.de phone +49 (0) 711 685- 65889 fax +49 (0) 711 685- 65710 University of Stuttgart IVK – Institute of Internal Combustion Engines and Automotive Engineering Pfaffenwaldring 12 D-70569 Stuttgart
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