• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1915-1920
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• 2015

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.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.1
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• pp.85-95
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• 2013

As the conventional hydraulic power steering system in the passenger vehicles is being rapidly replaced by EPS (Electric Power Steering) system, performance evaluation of the EPS system has become an important issue in the automotive industries. But the evaluation process takes significant expertise since steering conditions in the test protocols must be implemented with high accuracy. EPS HILS (Hardware-In the-Loop Simulation) system is developed together with robot steering system in this study. Main components of EPS HILS system include: C-EPS hardware, CarSim vehicle model, and road reaction force generation system powered by servo motor. The robot steering system, operated by another servo motor, was combined with EPS HILS system to substitute for steering efforts of human driver. The road reaction force generation system and the robot steering system were carefully validated by using the data obtained from vehicle tests. An on-center handling test was conducted by using EPS HILS system combined with the robot steering system. In the result of this study, robot-steered EPS HILS system developed with its high reliability and no need of skilled driver's, can be widely adopted to evaluate any performance of EPS system.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.72-80
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• 2006

Electric Power Steering (EPS) mechanism has become widely equipped in passenger vehicle due to the increasing environmental concerns and higher fuel efficiency. This paper describes the development of concurrent simulation technique and simulation integration technique of EPS control system with a dynamic vehicle system. A full vehicle model interacting with EPS control algorithm was concurrently simulated on a single bump road condition. The dynamic responses of vehicle chassis and steering system resulting from road surface impact were evaluated and compared with proving ground experimental data. The comparisons show reasonable agreement on tie-rod load, rack displacement, steering wheel torque and tire center acceleration. This concurrent simulation capability was employed fur EPS performance evaluation and calibration as well as for vehicle handling performance integration and synthesis.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.154-161
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• 2004

A new column type electric power steering system (EPS-TT) is proposed in this study. The remarkable features of EPS-TT are its opto-isolated torque sensor and assist torque control methodology. EPS-TT uses a uni-directional motor and two clutches. Full order and simplified models for EPS-TT are developed to evaluate the EPS-TT. A full car model is also used to investigate the vehicle responses. A PID control logic is designed to control the torque of the assist motor. Various sinusoidal inputs are applied to the system and the resulting performances are analyzed. The results prove that the performances achieved by the EPS-TT are improved compared to those of a conventional EPS-TT across the frequency domain. In addition, it is inexpensive and easy to control the motor. The results of the full order steering system model are similar to those simplified model, but the vehicle responses are slightly different.

• Journal of Mechanical Science and Technology
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• v.19 no.3
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• pp.792-801
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• 2005

This paper discusses a dc motor equipped electric power steering (EPS) system and demonstrates its advantages over a typical hydraulic power steering (HPS) system. The tire-road interaction torque at the steering tires is calculated using the 2 d.o.f. bicycle model, in other words by using a single-track model, which was verified with the J-turn test of a real vehicle. Because the detail parameters of a steering system are not easily acquired, a simple system is modeled here. In previous EPS systems, the assisting torque for the measured driving torque is developed as a boost curve similar to that of the HPS system. To improve steering stiffness and return-ability of the steering system, a third-order polynomial as a torque map is introduced and modified within the preferred driving torques researched by Bertollini. Using the torque map modification sufficiently improves the EPS system.

• Journal of Magnetics
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• v.17 no.4
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• pp.285-290
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• 2012

Electric Power Steering (EPS) system is superior to conventional Hydraulic Power Steering (HPS) system in aspect of fuel economy and environmental concerns. The EPS system consists of torque sensor, electric motor, ECU (Electric Control Unit), gears and etc. Among the elements, the torque sensor is one of the core technologies of which output signal is used for main input of EPS controller. Usually, the torque sensor has used torsion bar to transform torsion angle into torque and needs linear characteristic in terms of flux variation with respect to rotation angle of permanent magnet. The torsion angle of both ends of a torsion bar is measured by a contact variable resistor. In this paper, the sensor is accurately analyzed using 3D finite element method and its characteristics with respect to four different shapes of the stator teeth are compared. The four shapes are rectangular, triangular, trapezoidal and circular type.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4083-4094
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• 2011

The Electric Power Steering (EPS) has been applied to the vehicles due to its better fuel efficiency, better steering feel, and the compact volume compared to the hydraulic power steering. The brushed PM (Permanent Magnet) DC motors had been adopted in most of the EPS systems until several years ago due to its easy control and a simple hardware configuration of the power converter, but nowadays the BLAC (Brushless AC) motor is becoming more popular for the EPS system because of its high efficiency and long lifetime. This paper reviews the configuration of the EPS system and the BLAC motor and drive technologies based on the papers published recently. The torque ripple reduction for steering feel and the fault detection algorithms for safety are also reviewed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.11
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• pp.1511-1518
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• 2014

Demand for high fuel efficiency and smart features of the vehicles, research has been intensified. Hence, research and development on electric power steering (EPS) system to replace the existing hydraulic steering system has been actively conducted. Permanent magnet motors are widely used in automotive applications due to their high power density and high efficiency. However, increasing price and limited production of rare-earth permanent magnets has recently prompted the auto parts makers to substitute permanent magnet motors by non- or less rare earth magnet motors. Switched reluctance motors SRMs), known as typical non-rare earth motors have simple structure, low manufacturing cost, and high reliability. This paper discusses design, modeling, simulation, and experimental verification of a prototype SRM drive for electric power steering system.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.1
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• pp.53-60
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• 2012

As enforced by the regulation on the improving fuel efficiency and increased the demand on green technology, many interests are focused on electric vehicles and hybrid vehicles. Thus the technology development in electrification of vehicle operation system, including steering and braking field, is actively progressive. Especially electric power steering substitutes for hydraulic power steering rapidly in the market, which is more complex and bigger in packaging volume compared with electric power steering system. The core component in electric power steering system is a motor, which is required to be silent and powerful to guarantee required system performance. Brushless synchronous motors are widely used and many variations of the motors are introduced in the market, while the performance of each type is not well defined or studied for electric power steering system. In this paper, recent developments in brushless synchronous motor are reviewed and compared applying finite element analysis in electromagnetic field. As results, each characteristic of different types of brushless synchronous motors is compared and summarized for optimized selection in electric power steering system.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.121-126
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• 2005

This paper describes the attributes, performance and development status of a high performance capacitive torque sensor intended for use in a electric power steering (EPS) system. The EPS system is composed of torque sensor, ECU, motor, gears and etc. Among the elements, torque sensor in the steering column is one of the core technologies. The new capacitive torque sensor in this paper is developed differently from working principle and mechanical structure compare to extant torque sensors in market and patent. Based on the result of numerical analysis, a experimental equipment is made which is composed of a test jig and a capacitive sensor and validity of numerical analysis and feasibility of the torque sensor are verified.