Design & Safety Considerations for Electrical Power Steering (EPS) Systems Based on Automotive Safety Integrity Levels

Recently, Electric Power Steering (EPS) Systems are gaining popularity and acceptance among the auto manufacturers and consumers. When compared to the hydraulic power steering systems, increased fuel efficiency is one of the most deserving advantages of the EPS systems. However, elimination of hydraulic fluid is an environmentally safer alternative. In a hydraulic power steering system, hydraulic pump is turned on when the engine is running and power is consumed regardless the vehicle is steered or not. The hydraulic pump, piping and hoses add extra weight and labor cost to the system. In a vehicle with electric power steering, the steering system can be tuned easily for steering feel and the ability to return to the center position. It can also be easily adapted to various road conditions including the highway and city driving conditions. Moreover, the electric power steering is an integral part of the vehicle dynamics and stability control systems. A highly safe and reliable EPS system is essential for the successful implementation of advanced steering functions including the automated park assist, lane departure warning, lane keeping, adaptive cruise control, smooth road shake control and automated stability controls.