Increased Hydraulic Power Assisted Steering Functionality Using the Active Pinion Concept
2006 (English)In: Proceedings of 5th International Fluid Power Conference Aachen, IFK2006, Aachen, Germany, 20th-22nd March, 2006Conference paper (Other academic)
The traditional way of assisting car drivers during steering is with the help of hydraulic power assisted steering (HPAS) systems, which were introduced in the 1960's. In these systems, the torque the driver applies to the steering wheel is used to open a spool valve, which then modulates the load pressure in a hydraulic piston in the steering gear, thus assisting the driver. Such systems are regarded as cost effective and robust, but at the same time associated with limited flexibility. Since the broad introduction of electric power assisted steering (EPAS) systems during past years, the possibility to freely control steering wheel torque has been achieved. Steering wheel torque control is utilized both by comfort and safety functions, such as park assist systems and lane keeping assist systems or the next generation of active yaw control functions. In this paper, a solution to the controllability problem is presented for conventional HPAS systems. The solution is based on a traditional hydraulic power steering unit with modification to the valve. Added to the valve is an extra pilot motor, which enables the valve to be actuated electrically without compromising the basic robust mechanical solution of a traditional hydraulic power steering unit. Control strategies for position control and offset torque control have been presented together with test results carried out in a hardware in the loop test rig. An important advantage of the proposed solution is its low electric energy consumption. The electric motor has to compensate for the tiny sealing friction in the hydraulic spool valve. In other respects it relies on the power gain capability of the hydraulic system. This concept is called Active Pinion.
Place, publisher, year, edition, pages
Hydraulic, Power Steering System, Lane Keeping Aid, Parking Pilot, Active Pinion
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-14255OAI: oai:DiVA.org:liu-14255DiVA: diva2:23025