Steer by Wire

Praveen.V Chethana. J

STEER-BY-WIRE

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What is By Wire ?

Replace Mechanical and Hydraulic Control system with an electronic system. Technology first appeared in aviation. Today many civil and most military aircraft rely on Fly-By-Wire. Revolutionized aircraft design due to improved performance and safety over conventional flight control system.

Automotive Applications of By Wire ?

Steer-By-WireBrake-By-Wire Throttle-By-Wire Fly-By-Wire

Brake-By-Wire ?

Throttle-By-Wire ?

Why Do Accidents Accur ?

42% of fatal crashes result from loss of control. In most conditions, a vehicle under proper control is very safe. However, every vehicle has thresholds beyond which control

becomes extremely difficult.

Handling Characteristics

Under steering Over steeringneutral steering

less responsive more responsive

-+ Kus

Negative real roots at low speed. As speed increases, poles move off real axis. Under steering vehicle is always stable, but yaw becomes

oscillatory at higher speed.

Under steering

Single negative real root due to pole zero cancellation. Always stable with first order response. This is the ideal handling case. Not practical to design this way: small changes in operating conditions

(passengers or cargo, tire wear) can make it over steering.

Neutral steering

Negative real roots at low speed. As speed increases, one pole moves into right half plane. At higher speed, over steering vehicle becomes unstable! Analogy to unstable aircraft: the more over steering a vehicle is, the

more responsive it will be.

Over steering

Full load of passengers shifts weight distribution rearward. Vehicle becomes over steering, unstable while still in linear

handling region. Full load also raised center of gravity height, contributing to

rollover.

15 passenger van rollovers

Real World Example

Most vehicles designed to be under steering (by tire selection, weight distribution, suspension kinematics). Provides safety margin. Compromises responsiveness.

What if we could arbitrarily change handling characteristics? Don’t need such a wide safety margin. Can make vehicle responsive without crossing over to

instability.

Can in fact do this with combination of steer-by-wire and state feedback!

How are Vehicles Designed

What is Steer-By-Wire ?

Unlike the conventional steering system where a hand-operated steering wheel is used to turn the front wheels through the steering column, steer-by-wire technology removes the mechanical and physical links between the driver (steering wheel) and the front wheels, and replace them with electronic actuators and other components.

Control

Driver’s Request

Filtering

Conventional Steering System Steer-by-Wire System

Difference Between conventional and Steer-By-Wire

Control

Driver’s Request

Filtering

Difference Between conventional and Steer-By-Wire

How It Works

How It Works

Advantages

No-Steering Column –Simplify the design of car’s interior giving the driver more space Better safety in case of crash (No Intrusion of Steering Column) The Absence of Steering shaft and gear reduction mechanism allows much better utilization of the engine’s compartment. Decreases the total weigh of the car issuing better energy reduction effectiveness. Easier implementation of left or right-hand driving. No Noise or Vibration can reach the Driver’s Hands. The Most Significant benefit is the ability to electronically augment the driver’s steering input depending on driver’s conditions, also called Active Steering.

STUDENTS WILL NOT ASK WHICH PEDAL IS THE BRAKE PEDAL IN THIS VEHICLE…Future Holds New Concepts

Conclusion