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A study was conducted to investigate the subjective responses to steering wheel vibration caused by the electric power steering. The objective was to correlate the subjective responses to a measurable parameter that can be used to assess various design alternatives. Evaluations of six steering wheel vibration levels were performed in a stationary vehicle. Two rating methods were used. Results showed a wide range of acceptability of steering wheel vibration over the conditions evaluated. RMS angular acceleration and peak to peak torque at the steering wheel shaft correlated best with subjective ratings.

An Electric Power Steering (EPS) System will be considered in this report. The modeling of this dynamic system will be achieved with both simplicity and usability taken into account. As such, a Reduced Order Model that reveals the important dynamic distinctions of the system will be developed from a more complex one. This model will be used to analyze various closed loop effects such as torque performance, disturbance rejection, noise rejection, road feel, and stability. These fundamental effects (compromises) are used toward the design of a desired control system. This modeling philosophy together with a comprehensive understanding of system compromises is essential to an optimized EPS system.

Hydraulic rack and pinion power steering system is a high bandwidth servo with stringent performance requirements on accuracy, reliability, and cost. Design of such a system can be best achieved by using a validated and user friendly computer simulation program. Hydraulic integrated power steering ( HIPS ) program has been developed using basic concepts from science and engineering. HIPS provides a design and test environment for the integrated steering and suspension system subjected to disturbance forces, which may be induced by pump flow oscillations and tire loads. Two real-world automotive hydraulic steering systems are simulated with HIPS. The simulation results agree closely with the dynamometer test results. The application of HIPS for design optimization is also demonstrated.

Thermal duty cycle requirements in an electric power steering (EPS) system are a major cost driver. In order to develop these requirements, a technique has been developed to analyze load and time data from a vehicle level schedule and condense the load and time data into a compact specification for thermal duty cycle. This allows the duty cycle requirement to be determined at the vehicle level by the end customer and flowed down appropriately to the steering system and its components. In addition, a method which mimics the requirement process is used by the EPS algorithm to provide duty cycle enforcement and hence thermal protection, reducing the need for temperature measurement sensors.