Electronic throttle pedal nonlinear filter

Abstract

An electronic throttle pedal nonlinear filter. During throttle control of a vehicle's all speed governor, a nonlinear prefilter is used to modify the reference command. This prefilter can be used to heavily filter small throttle corrections, while allowing large throttle changes to have little or no filtering. By heavily filtering small throttle corrections, throttle sensitivity can be reduced, helping the throttle 'feel' when driving over bumpy roads or when making small throttle changes. Little filtering when making large throttle changes helps to give a fast governor response when a large acceleration or deceleration is desired. The filter works by comparing the past value of the all speed governor reference speed (or throttle position) to a rate limited value of the current reference speed (or throttle position). This difference is used to look up a filter coefficient in a table. This coefficient is used in a conventional first-order digital lag filter to produce the filter output. The table can be calibrated such that if the difference was small (a small change in throttle position), a large filter coefficient (large time constant) can be selected. If the difference was large (a big change in throttle position), a small filter coefficient (or none at all) can be used to lightly filter the throttle.