Module 1.pptx

MEC2017 Vehicle Dynamics Presented by Dr. Santosh Kumar Sahu 8/20/24 1  NEW Course Code: MEC2017 Course Titl...

MEC2017 Vehicle Dynamics Presented by Dr. Santosh Kumar Sahu 8/20/24 1  NEW Course Code: MEC2017 Course Title TPC 4 0 4 Vehicle Dynamics Version No. 1.0 Course Pre-requisites/ Co- Theory of Machines requisites/ anti-requisites (if any). Otherwise, please indicate as ‘None’ Objectives: The objectives of this course are 1. Introduce different forces on vehicles. 2. Explain concept of resistance to motion. 3. Give information about stability of a vehicle on a curved track. 4. Explain transient response characteristics of a vehicle. 5. Give information about riding characteristics of a vehicle CO's Mappingwith PO's and PEO's Course Course Outcome Statement Outcomes PO's / PEO's Understand the dynamics of the automotive systems CO1 PO1/ PEO3 and its performance parameters. Analyse the driving/ braking resistances and their CO2 PO3/ PSO1/ PEO1 influences on vehicle dynamics CO3 Identify ride characteristic of vehicle. PO2/ PEO1 CO4 Analyse the longitudinal and lateral dynamics PO2/ PSO1 Total hours of instructions: 45 8/20/24 2 Module No. 1 Introduction to Vehicle 9 Hours Dynamics Fundamental and types of suspension system, Single, Half and full car wheel models, passive, semi active and active suspension, Influence of suspension stiffness, suspension damping, and tyre stiffness, Different types of forces on suspension. Module No. 2 Tiresand Resistance to motion 9 Hours Resistance to motion, air gradient and friction resistance, Tractive effort draw bar pull, Tractive effort vs speed graph, Gear ratio selection, power calculation of vehicle. Tire forces and moments, Tire structure, Longitudinal and Lateral force at various slip angles, rolling resistance, Tractive and cornering property of tire. Ride property of tires. Conicity and Ply Steer, Tire models, Estimation of tire road friction. Module No. 3 Longitudinal Dynamics 9 Hours Forces acting in longitudinal direction, load distribution, acceleration, tractive effort and reactions for different drives, stability of a vehicle on a curved track, slope, and a banked road. 8/20/24 3 Module No. 4 Lateral Dynamics 9 Hours Forces acting in lateral direction, steady state handling characteristics. Transient response characteristics, Direction control of vehicles. Roll center, Roll axis, Vehicle under side forces. Effect of suspension on cornering. Module No. 5 RidingCharacteristics 9 Hours Slip angle, Over steer and under steer and its relationship with slip angle, Ackerman angle, Steady state and transient cornering, Lateral force developed during cornering. Cornering stiffness, Dynamic axle loads. Anti-squat, anti-pitch and anti-dive suspension geometry. Text Books 1. Thomas D. Gillespie, "Fundamentals of Vehicle Dynamics", 2013, Society of Automobile Engineers Inc., 2. J. Y. Woung , "Theory of Ground Vehicles", John Willey & Sons, 4th edition 2008 References 1. Rajesh Rajamani , "Vehicle dynamics and control", 2nd edition, Springer publication 2. W. Steed -Mechanics of Road Vehicles, Illefe Books Ltd. London 3. Martin Meywer, Vehicle Dynamics (Automotive Series), Wiley; 1st edition (2015) Mode of Evaluation Continuous Assess Continuous Assessment (CATs and FAT – 60%; CAT-1: 15 (50), CAT-2: 15 (50), FAT: 40 (100), QUIZ/Digital Quizzes, Assignments, Projects, etc. – 40%;). assignment: 30 8/20/24 4  Module 1 Introduction to Vehicle Dynamics 8/20/24 5  Vehicle constitutes number of sub-sytems Power Chassis Body module module module (provides comfort to occupant) Engine Suspension Power system transmission Frame Steering system Tire/wheels Requirement of vehicle Carry people- Safely, comfortably, economically NotDriver Safety: discussinginteraction with on the crash, rather safety vehicle when vehicle moves or turns Comfort: How road profile affects comfort. Economic: How tire affects economic 8/20/24 6  Driver Vehicl e Effect on Respon occupan ds cy Input Mathematical Outpu model t Steering Mass Lane change Accelerating Moment of inertia of vehicle Overtake De-Accelerating Stiffness Stopping Damping 8/20/24 7  Vehicle dynamics Longitudinal dynamics Lateral dynamics Vertical dynamics 8/20/24 8 8/20/24 9 8/20/24 10 8/20/24 11 8/20/24 12 Functions of Suspension 8/20/24 13 Requirements of Suspension system 8/20/24 14  Rotation around the front-to-back axis is called roll. Rotation around the side-to-side axis is called pitch. Rotation around the vertical axis is called yaw. 8/20/24 15  Roll is the movement of a car about its longitudinal axis. When a vehicle is cornering, centrifugal forces and other lateral forces cause the transfer of weight from the inside to the outer side of the vehicle. The amount of roll motion in a car is generally higher than the pitch as more load is transferred sideways. This can be felt as a swaying motion from side to side. Wind in a sideways direction can also cause roll motion. The suspension system has a major role in controlling these forces and enabling a stable turn. A car with a softer suspension has more roll than the one with a stiffer suspension. 8/20/24 16  Pitch is the movement of a car about its transverse/ lateral axis. This is basically a swaying motion of the car forward and backward. The pitch motion happens due to weight transfer to the front/ rear of the car under braking/ acceleration. Under braking, the weight of the car is transferred to the front, making the car sway forward- This is called a dive. And under acceleration, the weight transfer happens towards the rear of the car- Squat. A car with a softer suspension will have more pitch than the one with a stiffer suspension. The pitch motion helps the tires to get better traction 8/20/24 17 (grip), but anything in excess is harmful.  Yaw is the movement of a car about its vertical axis. That is basically the left-to-right motion of the car's front. When you steer/ turn a car, the yaw of the car is changed. This motion needs to be well in control for the driver to feel confident behind the wheel. Cornering forces can affect the yaw angle- If you dive into a corner with too much speed, there will be a loss of traction at the front tires, causing the car to understeer. Traction availability also depends on the road condition- a car on a wet surface will have low traction at the tires. Loss of traction at the front tires causes understeer, and loss of traction at the rear tires causes oversteer. https://www.youtube.com/watch?v=fPjOWekzeGI 8/20/24 18  https://www.youtube.com/watch?v=iMqE- NCrWIg&list=PLWnsX7VKWk_0Yh5Y8LBNmyCsdS9lylNAr&index=2 8/20/24 19 tps://www.youtube.com/watch?v=PDnyfrMy1iA A dependent suspension is one with a solid axle between the two wheels. When one wheel moves, the other is affected due to the solid axle between them. Independent suspensions generally handle better because when one wheel loses traction due to a bump, the other wheel isn't affected. In an Independent suspension system, as the name suggests, when the vehicle encounters a bump or pothole, the wheels react independently to the obstruction rather than engaging the other wheel, too thereby disturbing the passenger’s ride quality (figure for reference). Advantage of independent suspension: It offers better Ride Comfort. Better traction. No reaction of steering even if there is a large deflection in tire orientation vertically. Greater distance for resistance rolling friction. Minimum vibration of tires. 8/20/24 20  Example: Leaf spring used in vans, trucks, SUVs, and railway carriages https://www.youtube.com/watch?v=B00moGNbbgc 8/20/24 21  Coil/Helical Springs A coil spring is made out of a long piece of metal that is wound around itself. Coil springs can be either compression springs, tension springs, or torsion springs depending on how they are wound. A coil spring is a mechanical device that is typically used to store energy and subsequently release it, absorb shock, or maintain a force between contacting surfaces. They are made of an elastic material formed into the shape of a helix which returns to its natural length when unloaded. They are commonly used in mattresses, automotive suspensions, and residential plumbing. Coil springs come in a variety of sizes and shapes and can be used for a variety of applications. Small coil springs are often used in electronic devices, while larger ones are used in automobile suspensions. Coil springs can be made from various materials, including steel, brass, and bronze. Example: Sports cars, heavy-duty trucks, compact cars, etc. https://www.youtube.com/watch?v=3nWNFHLh1a 8/20/24 22  Torsion bar ample: Older military vehicles like Jeeps and Humvees, etc. rrations=surface https://www.youtube.com/watch?v=PDnyfrMy1iA&t=406s 8/20/24 23 Torsion bar 8/20/24 24 Wheel Alignment https://www.youtube.com/watch?v=7d2K_mKgsZ0 8/20/24 25  Independent Suspension systems  Double Wishbone (or) Parallel link type 8/20/24 https://www.youtube.com/watch?v=_wUSd-OVZX8 26  Double Wishbone (or) Parallel link type 8/20/24 27  Independent Suspension systems  Mac-Pherson Strut type 8/20/24 28  Mac-Pherson Strut type https://www.youtube.com/watch?v=X6JejXjGQiQ 8/20/24 29  Mac-Pherson Strut type Advantages Simple in construction Low manufacturing cost Lighter than double wishbone https://www.youtube.com/watch?v=BbU269DsMyM suspension 8/20/24 30  Independent Suspension systems  Vertical guide Suspension 8/20/24 31  Independent Suspension systems  Trailing arm/link This suspension employs two Suspension trailing arms which are pivoted to the car body at the arm's front edge. The arm is relatively large compare with other suspensions The arm is a single piece and its upper surface supports the coil spring. It is rigidly fixed to the wheel at the other end. This suspension only allows the wheel to move up and down to deal with bump. 8/20/24 32   Trailing arm/link When the car rolls into a corner, the Suspension trailing arm rolls for the same degree as the car body, thus changes camber angle. Here both the wheels lean towards the outside of the corner, thus lead to understeer. Because of this reason, pure trailing arm was forgotten by car makers long ago. Instead of it, they adopted semi-trailing arm. Semi-trailing arm suspension has the trailing arm pivoted at inclined angles - about 50 to 70 degrees. 8/20/24 33  Swing arm Suspension 8/20/24 34 Types of Suspension systems Passive: This suspension is provided by large springs where the movement is determined entirely by the road surface Semi-active: This suspension has an electrically controlled damping valve along with the springs to just the damping Active: This active suspension is a type of automotive suspension on a vehicle. It uses an onboard system to control the vertical movement of the vehicle's wheels relative to the chassis  BMW 5 Series.  Ford Focus.  Genesis GV80.  Land Rover Defender.  Mercedes S-Class. magnetic  Porsche 911. Electro-  Tesla Model S.  Volkswagen Polo. 8/20/24 35 8/20/24 36  https://www.youtube.com/watch? v=jE8s1qZy61Q&list=PLZ9pcD2vw_bskSNH0T7Wx 8/20/24 PBa7LOVQzMIR 37 8/20/24 38 8/20/24 39 8/20/24 40 Single/Quarter Car model 8/20/24 41 Single/Quarter Car model in passive Suspension system 8/20/24 42 8/20/24 43 8/20/24 44 8/20/24 45 8/20/24 46 8/20/24 47 8/20/24 48 8/20/24 49 8/20/24 50 8/20/24 51 8/20/24 52 8/20/24 53 8/20/24 54 8/20/24 55 Matlab code 8/20/24 56  Matlab ttps://www.youtube.com/watch?v=RJgTRkjCemE amp= amplitude of excitation omega= frequency associated with it. Initial variable is assumed zero as major excitation offered by road Ode45 functionality which gives final solution, ode45 solves the first order differential equation 8/20/24 57 8/20/24 58 Single/Quarter Car model in Active Suspension system 8/20/24 59 8/20/24 60 8/20/24 61 8/20/24 62 8/20/24 63 8/20/24 64 8/20/24 65 8/20/24 66 8/20/24 67 Single Car model Natural frequencies 8/20/24 68 Single Car model 8/20/24 69  Influence of suspension parameters on sprung mass vibrations 1. Spring Stiffness (k): o High Stiffness (Large k): The vehicle will have less vertical displacement when hitting a bump, leading to a "stiffer" ride. High stiffness can reduce the comfort but improves handling and stability. o Low Stiffness (Small k): The vehicle will have more vertical displacement, leading to a "softer" ride. This improves comfort but can reduce handling and stability. 2. Damping Coefficient (c): o High Damping (Large c): The oscillations of the sprung mass will die out quickly. This reduces the duration and intensity of vibrations, leading to a smoother ride. However, too much damping can make the vehicle feel sluggish (slow-moving or inactive). o Low Damping (Small c): The oscillations will last longer and the ride can feel "bouncy". 8/20/24 This might improve handling responsiveness but can make the ride uncomfortable. 70  Influence of suspension parameters on un-sprung mass vibrations Tire Stiffness (kt): Higher kt​increases the force transmitted from the road to the un-sprung mass, increasing vibrations. Lower kt​ provides better isolation from road irregularities, reducing vibrations but may lead to instability. 8/20/24 71 Single Car model in Semi-Active Suspension System 8/20/24 72 Advantages of Semi-active Suspension System  Compared to fully active suspension systems, semi-active systems consume significantly less power.  The power consumption in a semi-active system is only for purposes of changing the real-time dissipative force characteristics of the semi-active device. For example, power is used to change the area of the piston orifice in a variable opening damper or to change the current in the electromagnetic coil of a damper.  External power is not directly used to counter vibratory forces. Another advantage of semi-active systems over active systems is that they cannot cause the suspension system to become unstable.  This is due to the fact that they do not actively supply energy to the 8/20/24 73 Half Car model in Passive Suspension System Front Rear wheel wheel 8/20/24 74 Half Car model in Passive Suspension System https://www.youtube.com/watch?v=259KmgQ40Q8 8/20/24 75 Functions of Suspension 8/20/24 76 Full Car Automotive Suspension model 8/20/24 77