Method for attenuating smooth road shake in an electric power steering system
First Claim
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1. A method for attenuating smooth road shake at a steering wheel of a steering column of a motor vehicle having an electric power steering system including an electric motor and a rack, comprising the steps of:
- determining a frequency range of the smooth road shake during predetermined driving conditions of the motor vehicle;
mechanically tuning an electric power steering motor assembly of the motor vehicle electric power steering system to a predetermined frequency to thereby provide a tuned vibration absorber having a mechanically tuned resonance frequency substantially proximate the frequency range of the smooth road shake; and
damping the tuned vibration absorber to maximize rack stiffness at the frequency range of the smooth road shake so as to thereby minimize smooth road shake at the steering wheel over a range of vehicle speeds.
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Abstract
A method to reduce vehicular sensitivity to torsional smooth road shake (SRS) at the steering wheel provided by selectively increasing reverse driven-impedance of the steering system via an effective dynamic tuned vibration absorber comprising the existing power steering motor inertia supported on the torsional stiffness of the gearing to the rack in the case of a REPS system, or of the column rotary shaft in the case of a CEPS system.
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Citations
27 Claims
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1. A method for attenuating smooth road shake at a steering wheel of a steering column of a motor vehicle having an electric power steering system including an electric motor and a rack, comprising the steps of:
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determining a frequency range of the smooth road shake during predetermined driving conditions of the motor vehicle; mechanically tuning an electric power steering motor assembly of the motor vehicle electric power steering system to a predetermined frequency to thereby provide a tuned vibration absorber having a mechanically tuned resonance frequency substantially proximate the frequency range of the smooth road shake; and damping the tuned vibration absorber to maximize rack stiffness at the frequency range of the smooth road shake so as to thereby minimize smooth road shake at the steering wheel over a range of vehicle speeds. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method for attenuating smooth road shake at a steering wheel of a steering column of a motor vehicle having an electric power steering system including an electric motor and a rack, comprising the steps of:
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a) determining a frequency range of the smooth road shake during predetermined driving conditions of the motor vehicle; b) mechanically tuning an electric power steering motor assembly of the motor vehicle electric power steering system to a predetermined frequency to thereby provide a tuned vibration absorber having a mechanically tuned resonance frequency; c) determining smooth road shake frequency at an operating velocity of the vehicle, determined from at least one of;
1) a predetermined relationship between motor vehicle velocity and smooth road shake frequency, and
2) periodic dynamic content of a torque signal of the electric power steering system;d) dynamically tuning the tuned vibration absorber to the frequency of the smooth road shake at the velocity responsive to the relationship for all frequencies of the frequency range except the mechanically tuned resonance frequency; and e) minimizing damping of the tuned vibration absorber to maximize rack stiffness at the frequency of the smooth road shake so as to thereby minimize smooth road shake at the steering wheel; wherein said steps of d) and e) comprise controlling current in the electric motor of the electric power steering system to provide an equivalent of an inertia of the electric power steering assembly which effects the dynamic tuning of said step d) and to provide a torque which effects the minimized damping of said step e). - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification