Modeling and Analysis of an Electric Power Steering System

Badawy, Aly; Zuraski, Jeff; Bolourchi, Farhad; Chandy, Ashok

doi:10.4271/1999-01-0399

Cited by 119 publications

(57 citation statements)

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“…Linear models were derived to study chattering and a nonlinear model to study catch-up. The same approach to modelling the mechanical subsystem is also used in EPAS systems, as shown by Badawy, Zuraski, et al (1999). A column-assisted EPAS was modelled and a higher and a lower degree model were compared to show similar results.…”

Section: Mechanical Submodelmentioning

confidence: 90%

On Electrohydraulic Pressure Control for Power Steering Applications : Active Steering for Road Vehicles

Dell’Amico¹

2016

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This thesis deals with the Electrohydraulic Power Steering system for road vehicles, using electronic pressure control valves. With an ever increasing demand for safer vehicles and fewer traffic accidents, steering-related active safety functions are becoming more common in modern vehicles. These are functions that aim at assisting the driver in more or less critical situations and could be anything from applying a guiding steering torque to taking over the steering completely. Future road vehicles will also evolve towards autonomous vehicles, with several safety, environmental and financial benefits. A key component in realising such solutions is active steering. This refers to the possibility to control the steering angle or steering torque with an electronic signal.The power steering system was initially developed to ease the driver's workload by assisting in turning the wheels. This is traditionally done through an open-centre hydraulic system and heavy trucks must still rely on fluid power, due to the heavy work forces. The system provides a robust solution but suffers from poor energy efficiency and lacks the possibility of active control. Since the purpose of the original system is to control the assistive pressure, one way would be to use proportional pressure control valves. Since these are electronically controlled, active steering is possible and with closed-centre, energy efficiency can be significantly improved on.In this work, such a system is analysed in detail with the purpose of investigating the possible use of the system for Boost curve control, the most common control strategy in power steering systems, and position control for autonomous driving. Commercially available valves are investigated since they provide an attractive solution. A model-based approach is adopted, where simulation of the system is an important tool. Detailed models at both a component level and a system level are developed and form the basis of the analysis and control design. Another important tool is hardware-in-the-loop simulation. A test rig of the system, that also includes the original system, is developed. The rig supports the modelling and validation process, as it also makes it possible to verify control concepts on a real system. This work has shown how proportional pressure control valves can be used for Boost curve control and position control and what implications this has i on a system level. As it turns out, the valves add a great deal of phase shift and with the high gain from the Boost curve, this creates a control challenge. The problem can be handled by tuning the Boost gain, pressure response and damping and has been effectively shown through simulation and experiments. For position control, there is greater freedom to design the controller to fit the system. The pressure response can be made fast enough for this case and the phase shift is much less critical.Keywords: Electrohydraulic power steering, pressure control, closed-centre steering, Boost curve control, autonomous driving, hardware-...

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Section: Mechanical Submodelmentioning

confidence: 90%

On Electrohydraulic Pressure Control for Power Steering Applications : Active Steering for Road Vehicles

Dell’Amico¹

2016

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“…Steering torque is defined as the torque a driver applies on the steering column while turning the steering wheel. When an appropriate assistant torque by an assist motor is applied in the same direction as the driver's steering direction, the amount of steering torque required for steering can be significantly reduced [3][4][5][6]. In addition, adjustment of the characteristics of the assistant torque allows the driver to experience various steering feels [7].…”

Section: Introductionmentioning

confidence: 99%

“…ISO 26262 outlines the process of assessing risks and hazardous events by evaluating three factors: severity of potential harm to individuals (S), probability of exposure in the driving and operating situations (E), and the controllability by the driver to control the hazardous situation (C). For the EPS system, the majority of hazard caused by malfunctions in the city could be allocated to ASIL D as shown in Table 1 [2,3]. Here, a request means that the driver operates the system in a vehicle.…”

Section: Hazard Analysis/risk Assessment Of Eps Systemmentioning

confidence: 99%

“…In addition, adjustment of the characteristics of the assistant torque allows the driver to experience various steering feels [7]. Many research and technical papers on the EPS system have been published: basic principle and control algorithms were introduced in [3], a reference model based control strategy was proposed in [8], and a fuzzy logic based control method was presented in [9]. The EPS system has a mechanical steering, an ECU, and an assist motor, as illustrated in Fig.…”

Section: Introductionmentioning

confidence: 99%

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Design and Development of a Functional Safety Compliant Electric Power Steering System

Lee¹,

Lee²,

Moon³

et al. 2015

Journal of Electrical Engineering and Technology

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-ISO 26262 is an international standard for the functional safety of electric and electronic systems in vehicles, and this standard has become a major issue in the automotive industry. In this paper, a functional safety compliant electronic control unit (ECU) for an electric power steering (EPS) system and a demonstration purposed EPS system are developed, and a software and hardware structure for a safety critical system is presented. EPS is the most recently introduced power steering technology for vehicles, and it can improve driver's convenience and fuel efficiency. In conformity with the design process specified in ISO 26262, the Automotive Safety Integrity Level (ASIL) of an EPS system is evaluated, and hardware and software are designed based on an asymmetric dual processing unit architecture and an external watchdog. The developed EPS system effectively demonstrates the fault detection and diagnostic functions of a functional safety compliant ECU as well as the basic EPS functions.

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“…Linear models were derived to study chattering [34], and a nonlinear model to study catchup [35]. The same approach to model the mechanical subsystem is also used for EPAS systems, as shown by Badawy et al [36], where they…”

Section: Mechanical Modellingmentioning

confidence: 99%

Pressure Control in Hydraulic Power Steering Systems

Dell’Amico¹

2013

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There is a clear trend in the vehicle industry to implement more safetyrelated functions, where the focus is on active safety systems and today the steering system is also involved. Steering-related active safety functions can only be realised with a steering system that allows electronic control of either the road wheel angle or the torque required to steer the vehicle, called active steering. The high power requirement of heavy vehicles means they must rely on hydraulic power to assist the driver. The system is a pure hydro-mechanical system with an open-centre circuit activated by the driver's steering action and suffers from poor energy efficiency. The main task of the hydraulic system is to control the pressure in the assistance cylinder in such a way that it eases the load on the driver.This work suggests a way to design and evaluate a self-regulating pressure control valve for use as actuator in the steering system. This valve can be made small and fast and is electronically controlled to enable active steering. It is based on a closed-centre circuit and has therefore the potential to improve energy efficiency. The aim of this work has been to investigate the possibility for the valve to perform as the original open-centre valve. The suggested approach is a model-based design and evaluation process where an optimisation routine is used to design the valve. Together with a validated model of the steering system, the new concept is compared with the original system. A hardware-inthe-loop simulation test rig has also been designed and built with the possibility to test a closed-centre steering system. It has partly been used to support the modelling process and partly to verify that a closedcentre steering system is a feasible solution. The simulation results have shown that the designed valve can perform sufficiently well compared to the original system.

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Modeling and Analysis of an Electric Power Steering System

Cited by 119 publications

References 0 publications

On Electrohydraulic Pressure Control for Power Steering Applications : Active Steering for Road Vehicles

On Electrohydraulic Pressure Control for Power Steering Applications : Active Steering for Road Vehicles

Design and Development of a Functional Safety Compliant Electric Power Steering System

Pressure Control in Hydraulic Power Steering Systems

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