In addition to desired force applied by a vehicle operator, an input control for a vehicle, such as an accelerator pedal, is subject to, and may be influenced by, one or more undesired forces from a variety of sources. Such forces may include, but are not limited to, extra-vehicular inertial forces, such as inertial forces encountered when a vehicle traverses a pathway obstacle such as a bump or dip, and intra-vehicle forces, such as vibrations generated by other parts of the vehicle, such as a wheel out of balance. Such forces may also include forces unintentionally generated by the operator due to, for example, muscle fatigue, inattention, or poor driving habits.
As well as a potential generator of undesired force, a vehicle operator may also be affected by one or more such forces, particularly extra-vehicular and vehicle-generated forces. Individually or in combination such forces may undesirably influence an operator's application of force to an input control, such as an accelerator pedal. Moreover, the effects of such forces on an operator may lag slightly behind the effect on the input control, which in turn may generate independent, desynchronized motions between an operator and an input control.
Due to the influence of such undesired forces individually and in combination, an input control may depart from a desired state or, alternately, fail to approach a desired state in the manner intended by the vehicle operator. For example, an operator may unintentionally apply pressure to an accelerator pedal when a land vehicle encounters a bump on a pathway. In another example, an operator of a high-torque land vehicle under load, such as a tractor, may unintentionally change a force applied to an accelerator pedal when experiencing “power hop,” a type of dynamic instability characterized by “porpoising”-like forward motion. In yet another example, an operator of a tractor may unintentionally change a force applied to an accelerator pedal when experiencing road lope, which includes a vehicle vibration caused at least in part by out-of-round tires rolling at a speed that generates a rotational input frequency at or near a vehicle harmonic.
Several approaches have been employed to mitigate or reduce unintentional inputs and/or their effects:
U.S. Pat. No. 5,775,293, assigned to Cummins Engine Co., Inc. relates to a lag filter, which has the effect of filtering small changes in throttle input, while allowing large changes. However, indiscriminately filtering all small changes does not distinguish between intentional and unintentional small changes.
U.S. Pat. No. 6,589,135, assigned to Deere & Company relates to managing fuel flow using an on-board accelerometer to reduce bouncing of a vehicle due to road lope. Issues related to on and off road conditions, as well as unintentional forces generated by the operator are not addressed.
U.S. Pat. No. 7,720,583, assigned to Toyota Jidosha Kabushiki Kaisha and Denso Corporation, relates to setting a target driving force based on at least one of instructions from a driver and from a second processor and correcting the target driving force to suppress vibration on a spring of the vehicle. Correcting the target driving force does not however account for the effects of such forces on an operator, and the resulting unintentional forces generated by the operator.
U.S. Patent Publication No. 2011/0022286A1, assigned to Honda Motor Co., LTD., references an engine control unit that corrects an output signal of an accelerator pedal that governs the output of the engine according to detected vertical acceleration of the vehicle so that the unintended change in the output of the engine which is caused by an external force applied to the accelerator pedal and may cause an unintended acceleration or deceleration of the engine can be canceled. However, the engine control unit is only enabled when in an economy mode of operation. For other modes of operation, the responsiveness and performance are negatively impacted by enabling the engine control unit, and it is therefore disabled.