Automotive Engineer

Driver safety systems are receiving increased coverage as tighter regulations are proposed and OEMs look to highlight the safety virtues of their vehicles. 

The European Parliament has called for electronic stability control (ESC) to be mandatory on all passenger vehicles from 2014. EuroNCAP has also played a part in highlighting the need for better active safety technologies.

ESC is a closed-loop system that can intervene in the brake system, stopping wheel spin and brakes locking, and helping vehicles to maintain stability. Variants of the system have been used since the 1980s, but early versions were large and heavy. Basic anti-lock brake system modules weighed as much as 8kg. Today the entire ESC module, which includes traction control and anti-lock brakes, weighs less than 2kg.

Research by Tier One suppliers such as TRU will focus on shrinking the systems further. And, as powertrain development work concentrates on improved efficiency and fuel economy, Tier Ones will also have to produce new ESC systems that will work with future brake technology.

1. Motor
Rotates the eccentric bearings that drive the six pump elements. The electromechanical motor drives the pump which delivers fluid into the system. The motor power can vary depending on application, but is typically above 300W

2. 3 Pressure transducer (redundant)
The transducer is a standard component. Within the sense element there are two outputs that provide failsafeing. The sense element diagnoses whether the pressure transducer is in range, between zero and 180bar

3. Analogue ABS ISO valve, digitally controlled 
As current is passed into the coil the armature can be moved to differing states, which give differing effective openings, therefore different flow rates. Current can vary between zero and 2A

4. Analogue traction control ISO valve
This valve controls the amount of pressure allowed in the brake system. The valve is closed with a coil. Pressure is increased in the system until a given force level is met at which point the valve opens and the excess fluid is sent to the master cylinder, regulating the pressure

5. Electric control unit
The ECU comprises a PCB and the coils that interface with the valve stems. Valves will be connected either using an assuaging or clinching method to prevent fluid damaging the electronic components

6. Digital supply valve
When fluid is needed in the system, but the brake hasn't been pushed, the valve allows the pumps to move fluid from the master cylinder reservoir, delivering it to the brakes being activated

7. Digital dump valve
Allows the release of fluid from the brakes. When the coil in the ECU is energised it opens the valve and allows fluid from the brakes to release into the LPA. The primary concern is preventing leakage

8. Low-pressure accumulator
This consists of an aluminium piston with a spring inside. The spring lifts the piston and closes it. When the piston is reopened while the motor’s running, the pumps draw fluid out of the low-pressure accumulator (LPA) and put it into the brakes. When fluid is released from the brake calipers, it is sent to the LPA

9. Half-sleeved pump
The pump delivers fluid from the reservoir and pushes it into the brakes. The aluminium half-sleeve design around the pump gives better durability. Durability is dictated by the number of ABS cycles or how many ESC events the motor is turned on for