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Chapter 2 _1_ - Vehicle Dynamics Basic Principles of Road...

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Vehicle Dynamics: Basic Principles of Road Vehicle Interaction and Performance
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ECI 161 Winter 2012 2 Why we learn this? head2right Safety head2right Highway design (sight distance, stopping distance, lane widths, vertical/horizontal curves, grades, speed limits) head2right Traffic analysis (flow capacity, delay, traffic signal timing) head2right Fuel economy
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ECI 161 Winter 2012 3 What are involved? head2right Vehicle performance head2right Straight-line performance (Accl/decl/max_v/grades) head2right Corner performance head2right Tractive Effort (engine-generated) head2right Resistance square4 Aerodynamic square4 Rolling square4 Grade (Gravitational Resistance)
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ECI 161 Winter 2012 4 Tractive Effort and Resistance Moving direction A Four-Wheel Drive Vehicle with acceleration a on flat road
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ECI 161 Winter 2012 5 Resistance is defined as the force impeding vehicle motion 1. Aerodynamic resistance: R a 2. Rolling resistance: R rl 3. Grade resistance: R g If F denotes tractive force, then Where was R g on last slide? Tractive Effort and Resistance
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ECI 161 Winter 2012 6 Tractive Effort and Resistance On a slope with angle θ g
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ECI 161 Winter 2012 7 Aerodynamic Resistance R a (lb|N) Composed of: 1. Turbulent air flow around vehicle body (85%) 2. Friction of air over vehicle body (12%) 3. Vehicle component resistance, from radiators and air vents (3%) 2 2 V A C R f D a ρ = from National Research Council Canada What are C D , A f , and V? A f : Frontal area of the vehicle
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ECI 161 Winter 2012 8 Aerodynamic Resistance: Air density The dry air density gradient in mid-latitudes Source: http://www.auf.asn.au/meteorology/section1a.html
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ECI 161 Winter 2012 9 Aerodynamic Resistance: drag coefficient C D (unitless)
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ECI 161 Winter 2012 10 Aerodynamic Resistance: drag coefficient C D (unitless)
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ECI 161 Winter 2012 11 Guess your Drag Coe.
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