During the ZF Technology Days, June 26- 29, the company unveiled its ReAX EPS, the world’s first prototype of a fully electric steering system for commercial vehicles that eliminates the need for hydraulics and associated peripheral components. Its powerful electric motor offers complete servo power of up to 70 Nm. Additionally, ZF’s Electrically Powered Steering (EPS) system is designed to support steer-by-wire applications in the future. Fully electric steering is an important enabler for advanced driver assistance systems (ADAS) and automated drive functions that can help to improve safety as well as relieving drivers and improving logistics workflow. Moreover, the ZF ReAX EPS offers increased efficiency with reduced packaging space and weight, compared to traditional hydraulic steering systems.
Growing numbers of trucks delivering goods ordered online are flowing into large metropolitan areas against increased city center driving restrictions for combustion-engine vehicles. As the trend moves toward local, zero-pollution electric transport options, this will heavily impact commercial vehicles. The same can be said of automated driving. For example, truck platooning can potentially reduce traffic jams and help to increase general safety.
“With the ReAX EPS, we are presenting a prototype for a commercial vehicle steering system that can simplify and accelerate the advance of electrification, including 48V on-board vehicle power supply systems and steer-by-wire options, and do so with the high efficiency and reliability,” says Mitja Schulz, head of CV Steering Systems at ZF.
The clean E
ZF has developed the ReAX EPS, based on its well-established electromechanical steering concept designed for passenger cars, adapting the technology to trucks and buses. An actuator system powered by a 70 Nm electric motor, equipped with an integrated control unit, transmission and sensors is the critical component delivering increased power. Despite its compact size, it achieves the necessary steering forces required by commercial vehicles– and does so without an additional hydraulic pump system. This eliminates yet another energy draw from the vehicle drive system.
Compact and highly efficient
“After the first test-drives, the ReAX EPS operates more efficiently than our most advanced electro-hydraulic system to date. It also weighs significantly less, “says Schulz. The compact unit creates more installation space in the vehicle, useful for other systems, such as electric drives that interact with the new steering system. The ReAX EPS can be used with automated driving functions as it incorporates electronic controls allowing for inputs from camera, radar, and other vehicle data to influence steering for enhanced safety and autonomous operations.
Intelligent steering with and without the driver
In line with the ZF “SEE – THINK – ACT” claim, the ReAX EPS is a critical system component for enabling trucks and buses to act. Networked with control electronics such as the ZF ProAI, environmental sensors and other vehicle systems, the intelligent steering system is designed to handle many tasks, ranging from lateral control to SAE Level 4 automated driving. This means, for example, that the truck is capable of steering itself on certain sections of the highway or in loading areas, so the driver can work on other activities or rest in the meantime.
The ReAX EPS also offers comparable support for individual networked safety and comfort functions. This includes, for example, the OnTraX Lane Keeping Assist function (LKA), which helps keep vehicles in the driving lane. ReAX EPS has also effortlessly integrated other popular features from the volume-produced commercial vehicle lines, such as the active steering wheel return to the center position, compensation for road crown and cross winds as well as speed-dependent steering assist. In addition, almost any preferred steering wheel feel can be programmed as a feature for the respective OEM or as an option selection for the driver.