Introduction Flashcards
What is the ISO 8855 standard, and why is it important in vehicle dynamics?
The standard ISO 8855 provides a standardized set of terms and definitions related to vehicle dynamics, including coordinate systems, motion variables, and forces.
Define the earth-fixed axis system ((X_E, Y_E, Z_E)).
Coordinated system fixed in space. The plane X-Y is parallel to ground and Z axis positive is pointing upwards
What is the vehicle reference point, and where is it typically located?
Point fixed in the sprung mass in order to set the origin of the vehicle reference system. It is typically located in the sprung total center of gravity
How is the wheelbase of a vehicle defined?
It is the distance between the contact center of the tires of the front axle and the rear axle in the same side, measured with 0 steering angle and at rest
What is the track distance, and how is it measured?
The track distance is measured in the middle point of the contact surface of the tires in the same axle
Define the terms “camber angle” and “toe angle” in the context of vehicle dynamics.
Camber angle is the angle between the wheel plane and the Zv axis measured about the Xv axis
What is the difference between sprung mass and unsprung mass?
Sprung mass the one supported by the suspension. Unsprung mass is not supported by the suspension, it is common to allocate a part of the suspension, drive shaft, brakes mass to the unsprung mass and the rest to the sprung mass
What are the primary functions of a vehicle’s suspension system?
-Provide vertical compliance tp allow the wheels follow the uneven road
-Keep the correct steer and camber of the wheels
-React to control forces produced by tires longitudinal and lateral forces
-Load transfer
-Keep the tires in contact with the road
What is the roll center, and how is it defined?
The roll center is the imaginary point in the plane containing the two wheel centers of an axle at which a lateral force would produce no suspension roll angle
What is the pitch center, and how does it affect vehicle dynamics?
The pitch center is the imaginary point located in the plane of the lateral center of the vehicle (Y-Z) at which a longitudinal force applied to the vehicle body will not produce a suspension jounce.
What is the wheel plane, and how is it related to the wheel-spin axis?
The wheel plane is defined as the plane normal to the wheel spinning axis Yw located halfway between the rim flanges
Define the tire axis system ((X_T, Y_T, Z_T)) and its relationship to the wheel plane.
Axis formed
What is the significance of the road plane in tire dynamics?
It is the plane that represent the road surface within the tyre contact patch
How is the vehicle reference frame ((X_V, Y_V, Z_V)) defined, and what is its origin?
The vehicle coordinate system is based on the vehicle axis system fixed with the body and its origin is located at the vehicle reference point
What is the difference between the earth-fixed axis system and the intermediate axis system?
The intermediate axis system has its X axis a
How are multi-unit combinations (e.g., tractor-trailer) represented in the vehicle axis system?
Asigning each unit a reference system attached to it
What is the ground plane, and how does it relate to the vehicle’s motion?
The plane assigned to the road surface. It is the reference for the speed and the place where the earth system of reference is placed
What is the difference between the front track and the rear track of a vehicle?
The front track measures the distance between the center of contact points of the front wheels, the rear track does the same for the rear. This distances can be different.
How is the overall width of a vehicle measured?
It is the distance between furthest points of the car in the YZ plane
What is the significance of the wheel-spin axis in tire dynamics?
It is really important as serves as the reference for other dimensions.
What are the main subsystems that make up a vehicle?
Chassis, suspension. Powertrain, steering system, wheels and tires, braking system
How do suspensions contribute to vehicle dynamics?
Suspension are important for vehicle dynamics as contribute in great measure to the kinematic behaviour of the car, as well as its response to forces and moments that must be transmited by the tires to the chassis
What are the differences between solid axles and independent suspensions?
Solid axles connect one wheel to the other by a solid beam so when one wheel moves, this movement affect directly the other. Independent suspension, as the name says, has the advantage that each wheel in the axle move independetly
What is the role of the steering system in vehicle dynamics?
The steering system allows the driver to turn (steer) the front wheels of the car to provide overall directional control of the car. It is related to VDYN because we are interested in the control of the “car” system which is in part achieved thanks to the steering system
How does the design of the steering system influence the directional response of a vehicle?
The steer angles are modified by the dynamics of the car.
What are the key properties of a suspension system that affect vehicle dynamics?
Its kinematic (motion) behaviour and its response to the forces and moments that it must transmit from the tires to the chassis
What is the significance of the pitch center in suspension design?
It is important to minimize the squat and diving behaviour of the car under acceleration and braking
How does the roll center affect the handling of a vehicle?
It is importat for the weight distribution during cornering
What is the purpose of the damper and spring in a suspension system?
The function of the spring in the suspension is to support the weight of the car and maintain ride height, absorb impacts coming from the road and keep the tires in contact with the road surface. The function of the damper is to disipate energy from the system which traduces in a smoother ride. This is accomplish by regulating the movement of the spring
What is the function of the stabilizer bar in a suspension system?
The stabilizer bar reduces the body roll and improve stability during cornering maintaining better tire contact with the road. In general, it is used to improve handling
How does the suspension system react to longitudinal and lateral forces from the tires?
It deflects and/or compresses or extends depending on the direction of the forces
What is the role of the suspension in maintaining tire contact with the road?
One of the main purposes of the suspension system is to keep tyre contact as much as possible while compressing or extending according to the load transfer during the vehicle motion
What is the difference between bump and jounce in suspension terminology?
Jounce and bump are synonims and refers to the position in compression of the suspension (spring and shock absorber)
How does the suspension system resist roll of the chassis during cornering?
Throug the suspension stiffness and the stabilizer bar settings
What is the significance of the kinematic chain in suspension design?
It is a critical concept for vehicle dynamics and suspension design as defines how the different suspension components interact during the motion of the wheels with respect to the sprung mass
How does the suspension geometry affect the vehicle’s handling during acceleration and braking?
According to the suspension configuration there will be certain amount of weight transfer from the front to the rear axle or viceversa during acceleration and braking.
What is the role of the steering system in maintaining proper wheel alignment?
The steering system is crucial to keep proper wheel alignment through the camber and toe angles and the caster
How does the steering system modify the actual steer angles achieved by the wheels?
Through geometry and design principles: Ackerman, steering ratio. Caster angle
What is the purpose of the kingpin angle in steering geometry?
The kingpin angle is a fundamental aspect of steering geometry that enhances vehicle stability, reduces steering effort, improves handling, and minimizes tire wear. By optimizing the kingpin angle, engineers ensure that the vehicle responds predictably to steering inputs and maintains optimal contact with the road, contributing to a safe and comfortable driving experience
What are the three Cardanic angles, and how do they define the orientation of a vehicle?
The three cardanic angles are yaw (letter psi), pitch (letter theta), roll (letter phi)
How is the vehicle sideslip angle calculated?
it is the arctang(Vy/Vx)
What is the relationship between vehicle horizontal velocity and centripetal acceleration?
The relation is the Path radius Rp=Vh^2/Ac (path radius equal to horizontal velocity squared divided by the centripetal aceleration)
