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Taking a Closer Look at Steer-by-Wire Systems

( 02/27/2018 ) Written by: Jonathan Thomas

Many original equipment manufacturers are re-engineering traditional vehicle hydraulic systems with intelligent electrical systems that reduce complexity and improve performance. Fully-electric or electro-hydraulic systems are inherently clean, quiet to operate, efficient and allow for more ergonomic design and less complex installation during the manufacturing process.

A natural consequence of the electrification of vehicles is the switch from standard hydraulic steering to all electric, or Steer-by-Wire (SbW) systems. In many of these SbW applications, tactile feedback devices are gaining acceptance with design engineers who are seeking solutions to today’s trends: adopt vehicle designs based on electrical technology, while maintaining the operator/machine interface that can mimic the feel of traditional hydraulics. In SbW systems, sensing of the steering command is required; however, many engineers are finding that safety and control are enhanced with controllable steering feedback. These engineers view tactile steering feedback as a requirement in any SbW implementation since it gives the driver a heightened sense of connectedness with the vehicle and improves safety in operation.

Without a traditional mechanical or hydraulic steering linkage, developers of SbW controls found early on that the loss of tactile feedback to the driver often results in a degradation of control via over- or under-steer, thus compromising safety and reducing productivity. To overcome this problem, a controllable and proportional torque feedback device is connected to the steering wheel to produce useful tactile information back to the driver, often mimicking the feel of the conventional steering system being replaced. A controller is programmed with a tactile feedback algorithm that modulates torque feedback to the driver as a function of steering wheel rotational position, velocity, acceleration, steered wheel position, vehicle speed, or other parameters — singly or in combination. To meet this need, Tactile Feedback Devices (TFD) were developed and have been widely used in the last two decades in applications ranging from lift trucks, agricultural equipment, construction equipment, greens mowers and small industrial vehicles. Recently, this technology was commercialized specifically for a marine application with a leading marine engine manufacturer.

It is less expensive for an OEM to route wires than hydraulic hoses, and from an ergonomic standpoint, reduced-effort variable-rate steering can have the benefit of reducing whole arm and wrist fatigue that can occur from operating traditional multi-turn steering units. Integrating tactile feedback with steering sensing also provides the possibility to communicate information to the driver regarding vehicle conditions. For example, tactile pulsing (high torque to low torque) while turning the wheel may indicate a vehicle fault, or increased steering effort may indicate a potential obstruction. Vehicle warning systems, steering endstops (end of travel indication), and variable steering effort (depending on vehicle mode of operation) minimize the possibility of over- or under-steer and offer improved safety by providing more precise vehicle control. Furthermore, customization of the steering “feel” of a vehicle can be obtained simply via changes in software while leveraging the same hardware, thereby reducing engineering development lead times, simplifying the system architecture and reducing cost. 

Key to design integration is working with experts with a history of SbW and TFD experience. If you are interested in learning more about how steer-by-wire is a fit for your designs, click here for more information.

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ABOUT THE AUTHOR MORE BY THIS AUTHOR
Jonathan Thomas

Jonathan Thomas is a Business Development and Key Account Manager at LORD Corporation, with a focus on industrial equipment.

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