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MAK 4045E- Vehicle Dynamics and Control Assoc. Prof.Dr. PΔ±nar Boyraz 12 May-25 May 2015 Q1. Aerodynamic drag coefficient (Cd) and rolling resistant coefficient (f) of a vehicle will be calculated using coast-down test. Fort his aim, two different coast down tests have been done in a flat surface. In first experiment, the vehicleβs speed has been increased to 20m/s, then without any throtlle or brake command and in neutral gear position the vehicle stops after 40 seconds. In the second experiment vehicle stops from 30m/s speed in 45 seconds at same conditions. What are the coefficients Cd and f ? Vehicle Mass (M) : 500kg Front projection area (A) : 5π2 Air density (π) : 1.2ππ/π3 Gravitational acceleration (g) : 9.8π/π 2 Rolling resistant force: π π₯ = π β π β π Aerodynamic drag force: π·π = 0.5 β π β πΆπ β π΄ β π 2 Q2. a) Sketch a typical time-speed graphic of a vehicle in which ABS (Antilock Braking System) is activated from 50km/h until it stops. b) Following speed data is collected from vehicle in every 0.5 seconds. ABS of the vehicle is programmed to be activated at β2π/π 2 deceleration. According to the data, does ABS activated, if yes when it happens? π1 =24.6m/s π2 =26 m/s π3 =25.2 m/s π4 =24.5 m/s π5 =23.4 m/s π6 =22.8 m/s Q3. (a) Explain the reason(s) why driver models are important in developing the vehicles? In what type of systems is necessary to obtain and use driver model? (b) Sketch the blockdiagram of the human-driver controlled vehicle system. Q4. Draw the block-diagram of an Air-to-Fuel Ratio control loop. What does EGR stands for and why do we have to apply EGR in internal combustion engines?
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