# DOC-20220923-WA0025..pptx

31 de May de 2023
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### DOC-20220923-WA0025..pptx

• 1. VEHICLE DYNAMICS • PRESENTED BY • NIKHIL PAWAR • (2130331612031) • F.Y. MECHANICAL ENGINEERING
• 3. 2. INTRODUCTION It is the study of how the vehicle will react to driver inputs on a given road. Vehicle dynamics is a part of engineering primarily based on classical mechanics. Vehicles • Wheels • Motion • Self-powered Dynamics • Greek “DYNAMIS” • power • Vehicle Ride and Handling • Ride is associated with comfort and grip • Handling is associated with path following • Driving task has two components: Command and control
• 4. 2. ASPECTS OF VEHICLE DYNAMICS Some attributes or aspects of vehicle dynamics are purely dynamic. These include: 1.Body flex 2.Body roll 3.Bump Steer 4.Bundorf analysis 5.Directional stability 6.Understeer, oversteer 7.Pitch 8.Roll 9.Yaw 10. Noise, vibration, and harshness 11. Ride quality 12. Speed wobble 13. Weight transfer and load transfer
• 5. 3.POWER AND TORQUE CHARACTERISTICS OF AUTOMOBILE
• 6. 4. ENGINE POWER OUTPUT Following types of powers are being quoted with reference to engines. 1. INDICATED POWER The power developed inside the cylinder by combustion of gases is called indicate horsepower.Anindicating device an oscilloscope is used to determine IP. IP = pLANK/1000×kW 2. BRAKE POWER The power available at the crankshaft (for onward transmission to drive the vehicle) is called thebrake power. Rating of automotive engines is done m terms of BP. Brake power can be measured by dynamometer. BHP = 2πNT/4500 where N is in rpm and T in kgf-m. If N is in rps and T in Nm, then 4500 will be replaced by 1000 and power will be kW. Then it will be calculated by, BP = 2πNT/1000 3. FRICTION POWER A larger proportion of brake horsepower goes waste in overcoming various resistances in a movingvehicle. Rest of the Power is utilized to propel the vehicle. This power which is utilized to propel thevehicle is known as drawbar horsepower (DHP). FP = IP-BP
• 7. 4. TAXABLE HORSEPOWER It is also used to categorize engines on a uniform basis. To illustrate, we consider a race event of auto vehicles in which all types of vehicles ranging from mopeds, scooters, motorcycles, cars etc. are thep participants. Question arises whether all these vehicles should run together, or they be grouped indifferent categories. THD = D^2N/2.5 5. DRAWBAR HORSEPOWER A larger proportion of brake horsepower goes waste in overcoming various resistances in a movingvehicle. Rest of the Power is utilized to propel the vehicle. This power which is utilized to propel the vehicle is known as drawbar horsepower (DHP). DHP = BHP - RESISTANCES
• 8. 5. AUTOMOTIVE RESISTANCES AND PROPULSIVE POWER The brake horsepower available at the crankshaft of an automotive engine is not fully utilized to Speed up the vehicle much of it goes waste to overcome various resistances which are given as under. 1. ROAD RESISTANCE (A) ROLLING RESISTANCE It mainly occurs due to the deformation of road and tyre, and dissipation of energy through impact.The rolling resistance depends upon, • Mass of the vehicle • Material of the road surface such as; asphalt, macadam, gravel, clay, wood or sand. • Nature (quality) of the road surface such as poor, good, dry or wet. • Material of the tyres • Inflation of the tyres The rolling resistance R, can be expressed by, R r = C r mg Where Cri is rolling resistance constant and m is mass of the vehicle. The value of Cr, depends upon the condition of tyre and road surfaces in contact.. (B) FRICTIONAL RESISTANCES Another kind of road resistance is frictional resistance that includes resistance due to transmissionlosses also. Such losses are owing to • Lower gear efficiencies in first, second, and top gears. • Churning of oil in gearbox and the rear axle system. • Adhesion of tyre which is about 65% of the total losses in chassis. The frictional resistance R can be approximated by R f = 132.5 + 50.5 m
• 9. 2. ROAD GRADIENT RESISTANCE Slope (Gradient) of the road has considerable effect on the resistance to motion of the vehicle. The gradient resistance depends upon • mass of the vehicle • slope of the Road on which vehicle is moving The road gradient resistance Rg is expressed by . R g = mg sin θ 3. AIR (or WIND) RESISTANCE The air resistance faced by an automobile depends upon • Speed of the vehicle • Size and shape of the vehicle • Speed of moving air • Direction of wind with respect to direction of the vehicles motion Ra is expressed by : R a = C a AV^2 Gradeability of vehicle Effect of Speed on Aur Resistance
• 10. 7. MEASUREMENT OF THE TEST VEHICLES 7.1 BENCH TESTS (A) LOCATION OF CENTRE OF GRAVITY The location of centre of gravity of the test vehicle is determined in a longitudinal, lateral and verticaldirection. Below, the longitudinal direction is called the x coordinate, the lateral direction y coordinate andthe vertical direction z coordinate. The location of centre of gravity in the x and y directions is determinedby measuring the four wheel loads by means of wheel-load scales, onto which the vehicle is placed. Alongside the overall weight of the vehicle determined in this way, the position of the centre of gravity in an x and y direction can be calculated with the known wheel base and track width variables by productionof torque equilibria. The height of the centre of gravity is determined by weight displacement when lifting an axle. In thisprocess, the brakes are released and the transmission is in neutral, through which the wheels can be freelyturned. The efficiency lines of the axle loads pass through the wheel centre lines. To detect the axle load of the axle which has not been lifted, two wheel- load scales are used. As a function of the inclination of the vehicle, the axle loads on the front and rear axle change. The height h of the centre of gravity above the level passing through the front and rear wheel centre linecan be calculated via the torque equilibrium around the rear wheel centre line from the difference of the axle loads and the angle of inclination of the vehicle in question . H cog = (∆G.I)/[tan(a) Measurement of the vehicle’s centre of gravity height H cog
• 11. (B) MOMENT OF INERTIA The moment of inertia, otherwise known as the angular mass or rotational inertia, of a rigidbody is a quantity that determines the torque needed for a desired angular acceleration about arotational axis; similar to how mass determines the force needed for a desired acceleration. It dependson the body's mass distribution and the axis chosen, with larger moments requiring more torque tochange the body's rotation rate. Now that the location of centre of gravity is known, the moments of inertia (MOI) around the longitudinal, lateral and vertical axes can be measured. This is done by the vehicle oscillating aroundthe corresponding axes at the centre of gravity of the vehicle against springs of a known stiffness. Bymeasurement of the oscillation time T, the moments of inertia can be calculated with known spring stiffness. To determine the moments of inertia around the lateral axis of the vehicle, the vehicle is placed on a cutting line transverse to the direction of travel. The cutting line is aligned in such a way that theCentre of gravity of the vehicle in a horizontal position of the vehicle is vertically above the cuttingline. In the longitudinal direction of the vehicle, springs on which the vehicle supports itself via the auxiliary frame are clamped in at identical distances Euler's theorem is used to calculate the moment of inertia of the vehicle/frame unit around the cuttingb line axis from the frequency of the oscillations of this system: ,Frame from the overall moment of inertia around the cutting line Θy, total, the moment of inertia of the vehicle alone around the cutting line axis. Θ y,Veh = Θ y,total – Θ y,Frame The second item having an influence on the moment of inertia around the lateral axis is the so-called “Steiner ratio” of the vehicle. . Θy,CoG = Θy,Veh -mVeh ∆h2
• 12. 7.2 BRAKE FORCE DISTRIBUTION These measurements are done on the “ABS test bench” of the ika. The ABS test bench has four sets of rollers driven independently of one another onto which the vehicle is placed. Thanks to a movable frame for the rollers for the rear axle, the test bench can be adjusted to various wheel bases. All four wheels are driven evenly via the rollers with a speed corresponding to a traction of 6.5 kph. The reaction torque and thus the effective brake power up to a maximum of 5 kN are measured by a force transmitter interposed between the drive unit support and the frame. A detection roller measures the actual wheel speed in order to switch the test bench off automa- tically in the event of excessive slip between the rollers and the wheel. A principal diagram of the ABS test bench is shown in Figure. ABS Test Bench
• 13. 7.3 DRIVING TESTS Driving Test Instruments
• 14. 8. CONCLUSION 1. Enhance vehicle steerability and stability Steerability is enhanced in normal driving condition. Braking is involved only when the vehicle tends to instability 2. Precise steering control requires understanding of interaction between tyre and road. Treated as disturbance to be cancelled out. 3. Vehicle state estimation uses interaction between tire and road as source of information. Seen by observer as force that govern vehicle’s motion. 4. Vehicle dynamics are important to enable a good overall design of such a complex product as a vehicle intended for mass production at affordable cost for the customers.
• 15. 9. REFERENCES 1. K.M. Gupta, “Automobile Engineering” by Umesh Publications, Third Edition, Page no. 78-84, 87-90,. 2. R.S. Khurmi, J.K. Gupta, “ Theory Of Machines” by S. Chand Publications, Third Edition Page no. 253-255. 3. K.M. Moeed, “Automobile Engineering” by Katson Publications, Revised Edition 2016, Page no. 63-64. 4. J. J. Uicker; G. R. Pennock; J. E. Shigley (2003). Theory of Machines and Mechanisms (3rd ed.). New York: Oxford University Press. ISBN 9780195155983. 5. Marion, JB; Thornton, ST (1995). Classical dynamics of particles & systems (4th ed.). Thomson. ISBN 0-03-097302-3.
• 16. THANK YOU