Car Suspensions

Car suspension modeling using simscapeby: karim ahmed abuamo

Car Suspensions:

Definition:

Suspension system: a mechanical system of springs and shock absorbers that connect the wheels and axles to the chassis of a wheeled vehicle

The Function of suspension system:

- to carry the static weight of the vehicle. - to maximize the friction between the tires and the road surface. - to provide steering stability with good handling (minimize body roll).- to ensure the comfort of the passengers (ability to smooth out a bumpy road).

The Function of Spring and Shock Absorber:The Function of Spring: to absorb shock energy from road bump and convert it into potential energy of springThe Function of Shock Absorber: to dissipate shock energy from road bump without causing undue oscillation in the vehicle.

Car suspension types:Passive suspension:Traditional springs and dampers are referred to as passive suspensions

Active suspensions:active suspension works by constantly sensing changes in the road surface and feeding that information, via the ECU, to the outlying components. These components then act upon the system to modify its character, adjusting shock stiffness, spring rate and the like, to improve ride performance, drivability, responsiveness, etc.

Analysis of Suspension System using SimscapeSimscape extends Simulink with tools for modeling and simulating multidomain physical systems, such as those with mechanical, hydraulic, and electrical components. Simscape can be used for a variety of automotive, aerospace, defense, and industrial-equipment applications

With Simscape you build a model of a system just as you would assemble a physical system. This approach lets you describe the physical structure of a system rather than the underlying mathematics.From your model, which closely resembles a schematic, Simscapeautomatically constructs equations that characterize the behavior of the system. These equationsare integrated with the rest of the Simulink model.

Here are some common used Continuous Blocks:PS-Simulink Converter

The PS-Simulink Converter block converts a physical signal into a Simulink output signal. Use this block to connect outputs of a Physical Network diagram to Simulink scopes or other Simulink blocks.

Each physical network represented by a connected Simscape block diagram requires solver settings information for simulation. The Solver Configuration block specifies the solver parameters that your model needs before you can begin simulation.Solver Configuration

The Ideal Force Source block represents an ideal source of mechanical energy that generates force proportional to the input physical signal.Ideal Force SourceIdeal Translational Motion Sensor

The Ideal Translational Motion Sensor block represents a device that converts an across variable measured between two mechanical translational nodes into a control signal proportional to velocity or position.Mass

The Mass block represents an ideal mechanical translational mass , described with the following equation:

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Mechanical Translational Elements

The Mechanical Translational Reference block represents a reference point, or frame, for all mechanical translational ports. All translational ports that are rigidly clamped to the frame (ground) must be connected to a Mechanical Translational Reference block.Translational DamperThe Translational Damper block represents an ideal mechanical translational viscous damper, described with the following equations:

Translational Spring

The Translational Spring block represents an ideal mechanical linear spring, described with the following equations:

The Scope block displays its input with respect to simulation time. Scope

Signal BuilderThe Signal Builder block allows you to create interchangeable groups of piecewise linear signal sources and use them in a model.

Problem(1) Forced vibration

Equation Of Motion:f(t)=Kx+Rx'+Mx''

Signal I/p Mass Displacement

Problem(2)Base excited vibration

Equation Of Motion:K(x-y)+R(x-y)+Mx'=0

Signal I/p Mass Displacement

Model parameters are:

Mse-seat and driver mass (90 kg)Ms-is the quarter of the vehicle sprung mass (250kg)Mu-is the quarter of the vehicle unsprung mass (40kg)Bs-Damping ratio of the vehicle suspension (2000Ns/m)Bse-Damping ratio of the seat suspension (3000Ns/m)Kt=Tire stiffness (125000N/m)Ks-vehicle susspension stiffness (28000N/m)Kse-seat suspension spring stiffness (8000N/m)

Equation of motion for drive and seat mass is:

Equation of motion for sprung mass is:

Equation of motion for sprung mass is:

Signal I/p , Zse Zs,Zu

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Thank you