Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
2001-08-23
2003-05-20
Nguyen, Tan Q. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S124000, C702S173000
Reexamination Certificate
active
06567734
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to systems for estimating the mass of a vehicle carrying an internal combustion engine, and more specifically to such systems operable to dynamically estimate vehicle mass based on engine/vehicle operating conditions.
BACKGROUND OF THE INVENTION
Systems for estimating vehicle mass or weight are known and typically used in medium and heavy duty truck applications wherein such information is useful for optimizing any of a number of engine and/or transmission operating conditions. One particular class of such systems makes use of Newton's second law of motion by estimating mass in accordance with an equation of the form m=F/A, where m is the mass of the vehicle, F is the vehicle driving force and A is the vehicle acceleration.
Unfortunately, known systems for estimating vehicle mass based on the foregoing equation have a number of drawbacks associated therewith. For example, the vehicle driving force, F, is oftentimes determined in known systems as a rough estimation of the actual driving force of the vehicle that occurs at the vehicle wheels. Many force factors, both additive and resistive, contribute to the actual driving force seen at the vehicle wheels, and the use of inaccurate vehicle driving force values may lead to gross errors in the estimated vehicle mass values.
As another example, known systems for estimating vehicle mass generally fail to optimize conditions under which vehicle driving force and vehicle acceleration data is sampled, resulting in non-linearities and other data measurement inaccuracies. As a specific example, driveline windup effects at the onset of a vehicle acceleration event can contribute to inaccurate driving force and acceleration measurements, although known vehicle mass estimating systems typically do not compensate for such effects. As another specific example, while most known vehicle mass estimating systems require certain operating conditions to be satisfied prior to computing mass estimate values, e.g., vehicle acceleration above an acceleration threshold, transmission gear engaged, etc., such systems generally fall short in providing for optimal operating conditions for computing such estimates.
As yet another example, known systems for estimating vehicle mass are generally operable to compute vehicle mass estimates upon satisfaction of certain operating conditions as just described, but fail to either discontinue computing or disregard such estimates under operating conditions that may grossly corrupt the data. For example, any of a number of typically unaccounted for environmental factors may impart forces, either additive or resistive, on the vehicle that may at the very least corrupt the estimated mass values, and more often render such estimated values highly inaccurate. As a specific example, road grade conditions greater than only a few percent or less, wind conditions, road surface conditions, and the like, can each contribute to vehicle mass estimates that so remote from the true vehicle mass so as to render such estimates unusable.
Unfortunately, known vehicle mass estimating systems typically include such highly inaccurate estimates in their vehicle mass computations, and as a result must employ filtering techniques designed to minimize the impact of such poor estimates on final or running mass estimate values. One popular filtering technique is to maintain as a vehicle mass estimate the running average of several tens, hundreds or thousands of individual vehicle mass estimate values in hopes that this running average will “absorb” poor estimates and more closely reflect the true vehicle mass. However, this approach is generally undesirable, particularly in systems that require a responsive indication of instantaneous vehicle mass changes, such as when an operator either drops or picks up a trailer and/or loads or unloads cargo. With known vehicle mass estimating systems of the type just described, the running vehicle mass average value will generally not provide such a responsive indication of instantaneous mass changes, but will instead provide only a gradual indication over an extended time period.
What is therefore needed is an improved system for estimating vehicle mass that provides accurate vehicle mass information and that is highly responsive to instantaneous changes in actual vehicle mass.
SUMMARY OF THE INVENTION
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a system for estimating vehicle mass comprises a speed sensor producing a vehicle speed signal indicative of road speed of a vehicle carrying an internal combustion engine having a transmission coupled thereto, means for determining a gear ratio of the transmission, and a control circuit determining a vehicle driving force, computing a vehicle acceleration as a function of the vehicle speed signal and estimating a mass of the vehicle as a function of the vehicle driving force and the vehicle acceleration only if the gear ratio is between predefined high and low gear ratio values.
In accordance with another aspect of the present invention, a method of estimating vehicle mass comprises determining a road speed of a vehicle carrying an internal combustion engine coupled to a transmission, determining a gear ratio of the transmission, determining a vehicle driving force, computing a vehicle acceleration value as a function of the road speed, and estimating a mass of the vehicle as a function of the vehicle driving force and the vehicle acceleration value only if the gear ratio is between first and second predefined gear ratio values.
In accordance with yet another aspect of the present invention, a system for estimating vehicle mass comprises a first sensor producing a vehicle speed signal indicative of road speed of a vehicle carrying an internal combustion engine, a second sensor producing an engine speed signal indicative of rotational speed of the engine, a fuel system responsive to a fueling signal to supply fuel to the engine, and a control circuit producing the fueling signal and computing an engine driving force as a function thereof, the control circuit responsive to the engine speed signal to determine a first resistance force associated with at least one accessory driven by the engine and to compute a net driving force as a function of the engine driving force and the first resistance force, the control circuit determining a vehicle acceleration value as a function of the vehicle speed signal and estimating a mass of the vehicle as a function of the vehicle acceleration value and the net driving force.
In accordance with still another aspect of the present invention, a method of estimating vehicle mass comprises determining a road speed of a vehicle carrying an internal combustion engine, determining a rotational speed of the engine, computing a vehicle acceleration value as a function of the road speed, determining an engine driving force, determining a first resistance force as a function of the rotational speed, the first resistance force corresponding to a force required to overcome a load resistance of at least one accessory driven by the engine, computing a net driving force as a function of the engine driving force and the first resistance force, and estimating a mass of the vehicle as a function of the vehicle acceleration value and the net driving force.
In accordance with a further aspect of the present invention, a system for estimating vehicle mass comprises a speed sensor producing a vehicle speed signal indicative of road speed of a vehicle carrying an internal combustion engine, and a control circuit responsive to the vehicle speed signal to compute a vehicle acceleration value, the control circuit responsive to the vehicle acceleration value exceeding an acceleration threshold to execute a data collection sequence by periodically computing instantaneous vehicle mass values as functions of instantaneous vehicle driving force and vehicle acceleration value pairs, and to the v
Bellinger Steven M.
Kalill John F.
Tyler Brian C.
Barnes & Thornburg
Cummins Inc.
Nguyen Tan Q.
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