Many vehicles today have electric power steering systems. Electric power steering (EPS) systems typically use an electric motor to provide a steering assist to a driver of the vehicle, thereby reducing effort by the driver in steering the vehicle.
Smooth road shake (SRS) is one of the vibrations leading to customers complaints. SRS is caused by internal periodic excitation such as tire/wheel imbalance, tire irregularities, brake rotor imbalance and lack of precision piloting of the rotating members. SRS typically occurs over a band of frequencies extending from 8 to 22 Hz depending on vehicle speed.
In certain vehicles equipped with EPS it is possible to actively attenuate relatively narrowband torsional vibrations that are typical of SRS. When these features are implemented without any additional controls for other lower frequency bands, they also can produce unwanted effects at these lower frequencies, influencing the perception of the steering performance of the vehicle. Even the presence of the mechanical torsional vibrations originating in the periodic excitation by the corners at lower orders of tire rotation (SRS) without any intervention by the EPS motor can result in a degradation in the perception of the steering response. Mechanical vibrations originating in the periodic corner road wheel excitation and the active vibratory actions of the EPS motor can both affect the stiction and friction responses of the steering system thereby producing the perceptions of steering feel degradation. Although not influencing the operation of the vehicle, these perception nuances can be large enough to convey a degree of dissatisfaction with the feel of the steering system as the steering wheel is rotated during mild steering maneuvers.
Accordingly, it is desirable to provide methods for improved steering perception in vehicles, for example that provide an improved feel for the steering system during vibratory conditions as with SRS attenuation by an EPS. It is also desirable to provide program products and systems for improved steering perception in vehicles, for example that provide an improved feel for the steering system during vibratory conditions as with SRS attenuation by an EPS. Furthermore, other desirable features and characteristics of the present disclosure will be apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.