Electric Power Steering

Electric power steering (EPS) is a key technology for highly automated driving. The EPS has an electric motor which controls the vehicle steering. With an electric motor the EPS controls and assists vehicle steering and provides an optimal and enjoying steering feel. 

An Electronic Power Steering (EPS) system’s advantage over a hydraulic system is if the engine stalls, you will still have steering assist. This advantage can also be a disadvantage if the system should shut down while the engine is running you lose steering assist.

Electronic power steering systems eliminate the need for a pump, hoses and a drive belt connected to the engine using variable amounts of power. The configuration of an EPS system can allow the entire power assist system to be packaged on the rack and pinion steering gear or in the steering column.

The system does not drag on the engine from either a power steering pump or alternator because it will not provide assist until required by driver input. Also, there is no hydraulic fluid.

Main Types of EPS Electronics Failure Modes 

There are three main types of electronics system failures that you are likely to see when inspecting and repairing current EPS systems: motor, electronics board, and torque sensor problems. Here's a quick rundown of the types of errors associated with each of these service categories. These failure modes related to the electronic column drive system with a mounted electric motor and manual rack and pinion.

Today's electronic power steering can fail due to problems with the built-in electric motor. Excessive heat in the engine in particular is likely to cause the failure modes. The ingress of water, dirt, or other contaminants into the system environment is also likely to cause EPS failure. Also, carbon contamination can cause steering failure only on brushed systems. In general, the brushed style is more prone to failure than the brushless.

Another area of ??concern is electronic boards and circuits. The EPS board processes the electrical signals passed through the system and is a communication hub between the sensors and the system circuitry.Types of failures to look out for include particular thermal and power cycling over time (MOSFETs, relays, capacitors, resistors). These are more of a problem when they are near engine and exhaust components. Water, dirt or other contaminants entering the system can also cause the
EPS to fail. However, microprocessors do not typically fail and should not be a major concern during diagnosis and repair.

Finally, another common type of fault relates to the torque sensor.Torque sensor failure is actually the most common failure in spinal assist and a contact torque sensor has a much higher failure rate than non-contact sensors. When in contact with the sensors, the metallic contact points wear out over time.

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