HEXA

Anti-lock Braking System(ABS) 1 1. GENERAL INFORMATION : A. NECCESSITY OF ABS WITH EBD : Whenever the brakes are applied, the road wheels transmit this braking force to the road surface. To achieve optimal deceleration each wheel should be braked to the point of imminent lock. In this manner maximum possible braking force would be imparted to the road surface. However if a wheel is braked beyond this level it will lock which can result in the vehicle skidding and the driver loosing control. EBD : During normal braking there is always a level of load transfer from the rear axle to the front. Due to this occurrence it is necessary to ensure that the rear axle wheels do not reach the point of lock before the front axle wheels. On vehicles without ABS and EBD this is achieved through the use of a pressure conscious regulating valve (PCRV) which limits the pressure to the rear axle to give a front first locking sequence. The PCRV allows only a predetermined pressure to the rear wheels to avoid locking of the rear axle wheels before the front axle wheels. As a mechanical fixed ratio component it cannot adapt to the condition of the vehicle brakes, tyres, road or the vehicle load conditions, and hence it cannot achieve ideal braking at the rear axle To enable optimum braking at the rear axle while maintaining vehicle stability during braking, EBD is provided. It enables the distribution of brake force between the front and rear axle brakes to be adjusted at any point of time, depending on the condition of the vehicle brakes, tyres; the road, or vehicle load conditions. In the case of EBD failure the driver will be alerted .It is unsafe to drive the vehicle with EBD not working. ABS : In emergency braking conditions and when driving on wet or slippery road surfaces like snow and Ice, gravel, steel plates and bridges etc.., it is possible that the braking forces at the wheel exceed those possible to transmit to the road surface. This will result in wheel locking (stopping rotating). If one or more wheels lock under braking the vehicle can go into a skid and no longer be controlled by the driver as he will have lost steerability. To avoid the wheels from locking and prevent the vehicle from skidding ABS is provided. It prevents the wheels from locking and maintains the steerability of the vehicle thereby helping the driver to maintain stability of the vehicle while bringing it to a stop in the safest possible way. In case of ABS failures the driver will be alerted and the conventional braking circuit will still be operational. ENGINE DRAG CONTROL (EDC) : Engine braking is an act of using engine compression as braking force instead of service brakes. This is done when prolonged and continuous brakes have to be applied. The efficiency of the service brakes reduces in such applications as they are subjected to high temperatures. In such situations engine braking is preferred as engine has a system to dissipate the heat generated. During such braking the vehicle will be running in gear such that the wheels are connected to the engine. Hence there are chances that the engine may get stalled if the speed is very less resulting in the drive wheels getting locked. EDC avoids such situation by slightly increasing the engine torque to avoid engine stalling and thus avoids the wheel slipping. In case of EDC failure the ABS will still be working. Cornering Stability Control(CSC) : CSC Stabilizes the vehicle in bends by pressure reduction at the inner wheels during partial braking, Countermeasure to ensure stability while braking in curves. Rough Road ABS : With rough Road ABS mode Special Braking performance is offered to support Rough road surfaces as compared to other drive modes. The braking interval is increased and will cause wheels lock up in a controlled manner so that small wedges of material from the ground (such as gravel or sand) build up in front of each wheel. This can substantially reduce the stopping distance of the vehicle. NOTE :  ABS ECU in all the variants of vehicle calculates the Vehicle Speed and Odometer signals. If ABS ECU fails or CAN bus fails vehicle speed and odometer will not function.  In all the 4x4 variants of vehicle ABS ECU interacts and controls the TOD functionality. If the ABS communication with TOD ECU is lost, standard ABS functions shall continue operating normally unless there is no other fault.  If Rough Road ABS switch fails ABS mode will shift to default mode and ABS functions shall continue operating normally unless there is no other fault in the system.