Antilock or Antiskid Device | Anti-lock Breaking System

Antilock or antiskid device

The vehicle will stop more quickly if the brakes are applied just hard enough to get maximum static friction between the tyres and road. If the brakes are applied harder than this then the wheels will lock, the tyres will skid or slide on the road and a lesser kinetic friction will result. Then braking the vehicle is much less effective.


To prevent skidding and thus provide maximum effective braking several devices have been proposed. Mostly skid control of the rear wheels only is provided. Some others provide control at all the four wheels. What is meant by “control” is this. As long as the wheels are rotating the antiskid device permits normal application of the brakes. But if the brakes are applied so tough that the wheels tend to stop turning and thus a skid starts to develop the device comes into operation and partly release the brakes so that the wheels continue to rotate. Still intermittent braking continues. But it is held to just below the point where a skid would start. The result is maximum braking effect.

Antilock brake system: The hydraulic unit is the central component of an ABS system. Each of the four wheels has a speed sensor, which measures the rotational speed of the wheel. This information is monitored by an Electronic Control Unit: which opens and closes the magnetic valves at the right time. If a wheel is about to lock under heavy braking, the system continues to reduce the hydraulic pressure on that wheel alone, till the threat of locking is past. Once the wheel is turning freely again, the hydraulic pressure is increased. This increase and release of pressure continues until the driver reduces the force on the brake pedal or until the tendency to lock is overcome. ABS is incorporated in some of the cars to prevent skidding and to rove braking.


Senstronic braking control (SBC) Senstronic Braking Control is basically a brake-by-wire system which eliminates the need for mechanical linkage between the brake pedal and brake master cylinder. SBS also work in conjunction with ABS to enhance braking.

It was developed by Mercedes in association with Robert Bosch GmbH. Among its most important performance features are the dynamic building up of brake pressure and the precise monitoring of driver and vehicle behavior using sensors. In an emergency situation, SBC increases brake line pressure and readies the brakes, so that they can grip instantly with full force when the brakes are applied.

Additionally, variable brake proportioning offers enhanced safety when braking on bends. SBC controls each wheel individually. When in corners, they apply varying degree of pressure on the inside and outside wheels of a car, and in the wet road condition. The SBC is found in Mercedes Benz E cars.

Power Steering | Electronic Power Steering

Power steering

In heavy duty (dump) trucks and power tractors the effort applied by the driver is inadequate to turn the wheels. In this case a booster arrangement is incorporated in the steering system. The booster is set into operation when the steering wheel is turned. The booster then takes over and does most of the work for steering. This system called power steering uses compressed air, electrical mechanisms, and hydraulic pressure. Hydraulic pressure is used on a vast majority of power steering mechanism today.


When the steering wheel is turned, the worm turns the sector of the worm wheel and the arm. The arm turns the road wheel by means of the drag link. If the resistance offered to turn the wheels is too high and the effort applied by the driver to the steering wheel is too weak, then the worm, like a screw in a nut will be displaced axially together with the distributor slide valve. The axial movement of the distributor slide valve in the cylinder will admit oil into the booster cylinder through the pipe line. The piston in the booster cylinder will turn the road wheels via the gear rack, the toothed worm sector, arm and drag link. At the same time, the worm sector will act upon the work and will shift it together with the distribution slide valve to its initial position and stop the piston travel in the boost cylinder. When the steering wheel is turned in the other direction, the wheels will be turned appropriately in the same sequence.


The more the steering mechanism and wheels resist turning, the more the control valve is displaced. Hence, power assistance is always supplied in proportion to the effort needed to turn the wheels.

Electronic power steering

Electrically assisted power steering is used in some cars. The assistance can be applied directly by an electric stepper motor integrated with the steering column, or the steering mechanism, or it can be applied indirectly with hydraulic assistance pressurized by electric pump. EPS attached to the rack and pinion-steering-exists in Honda-City vehicles.


Electronic power steering Improves steering feel and power saving effectiveness and increases steering performance. It does so with control mechanisms that reduce steering effort. Nissan’s Blue Bird passenger car series use an electronically controlled three way power steering. This power steering is responsive to vehicle speed, providing maximum assistance as the speed rises. The driver can also select his or her own performance from three levels of assistance that make the steering effort heavy, normal or light.