Nexteer can 'tune' vehicle steering feel to suit local driver expectations
25 June 2012
Specialist electric power steering supplier Nexteer Automotive is enabling global vehicle manufacturers to create custom steering calibrations to suit different local market requirements. The company has provided the first customers with electric power steering (EPS) systems 'tuned' to provide certain markets with different levels of feel, feedback and refinement.
“The perceived quality of a vehicle’s steering by drivers in key markets is a critical part of any global vehicle platform’s commercial success,” says Laurent Bresson, Nexteer’s president and COO. “Drivers in some markets, such as the UK, expect higher levels of road-feedback than drivers in other markets. Nexteer’s high precision mechanical design and the strength of our in-house software expertise is making it viable for manufacturers to commission custom steering set-ups for some markets.”
A vehicle’s steering feel is influenced by a range of parameters, including suspension geometry, tyre and bushing stiffness, spring rates and mass distribution, but the quality of the EPS system is critical. The basis for good steering feel is a mechanical system with low levels of inertia and friction, combined with a high-resolution steering sensor and a smooth assist motor. With intelligent control algorithms, it is then possible to create custom set-ups that meet both global brand characteristics and local market requirements.
“Designing the complete system and developing the software entirely in-house gives Nexteer precise control of all the variables, allowing us to calibrate the steering more quickly,” says Nexteer's EPS technology manager, Bertram Moeller. “Using our own specialist software, a custom set-up for a specific local market can be very fast. Much of the driver’s perception of the vehicle’s behaviour and the road’s surface is communicated through the steering system, so the effect on the finished vehicle can be significant, helping to ensure a successful model launch and higher levels of customer satisfaction.”
While the algorithms define the system’s functionality, the calibration determines the actual timings and levels of the key system outputs, such as damping levels and the filtration of unwanted vibration.
“Our development process begins by creating the necessary mechanical properties in the system to ensure that no unwanted vibrations can interfere with the system’s response,” says Moeller. “The mechanical tuning is defined early in the programme, when interfaces, bearings and the mechanical links that determine the system’s friction levels are all specified. The subjective tuning of the vehicle’s steering feel then takes place behind the wheel with a laptop.”
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