Data processing: measuring – calibrating – or testing – Measurement system – Weight
Reexamination Certificate
1999-01-25
2002-01-15
Assouad, Patrick (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Weight
C701S070000, C701S090000
Reexamination Certificate
active
06339749
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German application no. 198 02 630.7, filed Jan. 24, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a device for determining the weight of a motor vehicle which is being moved in its longitudinal direction by propulsive forces.
Knowledge of the current values of the weight of the vehicle and grade of the road are of considerable importance for optimizing the function of a plurality of regulating and/or control devices which influence various vehicle subsystems. Such vehicle subsystems (in which the weight of the vehicle and/or road grade form a regulating and/or control parameter) include, for example, a speed regulating system and a driving dynamics regulating strategy, such as ABS (anti-lock braking systems), for example. Such vehicle systems may also include ASR (anti-slip regulating) systems, a rear-wheel steering system, a front-wheel steering system, systems for adjusting the optimum tire pressure, a transmission control with various shift strategies and a suspension system, for example.
During downhill travel, these systems are particularly important in trucks having a trailer or semitrailer for preventing disadvantageous effects, for example, on the steering behavior of the tractor when the tractor is pushed by the trailer or semitrailer.
In buses, knowledge of the current total weight of the vehicle is also of great importance for optimizing the drive, suspension and brake systems, since the weight of the vehicle can change considerably at each bus stop. Articulated buses with rear drive require data regarding the weight of the vehicle for controlling and/or regulating damping members in the articulation area, in order to prevent the rear of the vehicle from breaking loose.
In a device disclosed in German patent document DE-OS 42 28 413 A1, the weight of the vehicle is determined by detecting at least two longitudinal accelerations at at least two different points in time and detecting the propulsive forces which exist at these points in time. The weight of the vehicle is then determined from the difference between the propulsive forces and the difference between the longitudinal accelerations. The accuracy of this disclosed method requires a significant difference to exist between the two acceleration values measured in succession. Additionally, the driving resistances such as the air-resistance, rolling resistance and descending force, for example, must not have changed significantly between the successive points in time. An increase in the accuracy of this method is sought by repeating the determination of the weight of the vehicle, with each increase in the acceleration of the vehicle.
German patent document DE 38 43 818 C1 discloses a device for determining an average value of the weight of a motor vehicle. The determination of a relatively accurate value of the weight of the vehicle is performed by determining the driving resistance of the vehicle while the clutch is disengaged from the drive train and by repeatedly determining (by averaging) the engine torque and simultaneously repeatedly measuring (by averaging) the acceleration of the vehicle with the clutch engaged, as well as by taking into account the transmission ratio of the transmission. In order to successfully determine the weight of the vehicle with this device, a shifting process is necessary. Hence, when shifts during trips which last a long time do not occur, the weight of the vehicle cannot be updated.
EP 0 111 636 A2 discloses a device for determining the weight of a vehicle. Here, the weight is determined based on the knowledge that the driving torque of a vehicle engine is determined by multiplying the vehicle weight by the vehicle acceleration and adding the resistance moments that oppose the forward movement of the vehicle. When the resistance moments, vehicle acceleration and drive torque are measured at different points in time, two equations can be produced which can be solved for the vehicle weight. In order to successfully calculate a usable value of the weight of the vehicle from this equation, a sufficient difference between the drive torques must be measured. This device teaches the selection of one measuring point in time while the vehicle is in a drive-less state. Such a drive-less state exists when the drive train is disconnected from the engine, for example, when a gear shift occurs.
WO 93/18 375 A1 discloses another device for determining the weight of a vehicle. Here, two operating states of the vehicle are compared with one another. During each of these driving states, a series of successive pulses is determined. By integrating these pulses, an average value is obtained for the change in momentum that takes place in each of the operating states. From the changes in momentum of the two operating states, the weight of the vehicle is then determined, but on the assumption that the vehicle is traveling on a horizontal road. This calculation method is especially suitable for calculating the weight of ships.
It is therefore an object of the present invention to provide a device for determining the weight of a vehicle which is being moved in its longitudinal direction by propulsive forces such that during travel, highly accurate values for the weight of the vehicle and grade of the road can be obtained as simply as possible.
This and other objects and advantages are achieved by the device according to the invention, in which signals which correspond to the propulsive force and the corresponding vehicle longitudinal acceleration are recorded continuously and stored in time sequences, for example, in a memory. To produce a signal that corresponds to the current vehicle weight, a certain number of successive elements or values in this series are used for the signals of the propulsive forces, and the corresponding values from the time sequence are used for the signals of the vehicle longitudinal accelerations. In this manner, a continuously updated signal which correlates with the weight of the vehicle is available for optimizing the regulating and/or control systems of the vehicle. This enables these systems to react especially rapidly to changes in the weight of the vehicle.
In addition, with the knowledge of the current weight of the vehicle, the current values for the propulsive force and the vehicle longitudinal acceleration, a signal can be generated which represents the current grade of the road.
The present invention is based on the knowledge that to determine the weight of the vehicle and grade of the road, only the propulsive force Z
TRL
acting on the vehicle, the corresponding vehicle longitudinal acceleration b
Fzg
and the corresponding descending force Z
HA
are required. The initial situation is formed by the generally known relationship:
Z
TRLi
=m
Fzg
*b
Fzi
+Z
HA
.
The propulsive force Z
TRL
is composed of the driving or braking force Z
T
acting on the vehicle minus the rolling resistance Z
R
and minus the air resistance Z
L
:
Z
TRL
=Z
T
−Z
R
−Z
L
.
The propulsive force Z
TRL
of the vehicle can be determined, for example, from the engine torque, transmission ratio, axle ratio and the wheel radius. This is true if, for example, the engine torque is stored in the form of measured characteristic maps as a function of certain engine parameters such as pedal position, rpm, etc. The engine torque is already available in vehicles in a plurality of engine controls that are now conventional. The longitudinal acceleration of the vehicle can be calculated, for example, from the wheel rpm in conjunction with the wheel radius, with a distance traveled in a unit time being derived twice as a function of time. The values required for this purpose are provided, for example, by an ABS and/or ASR system and thus are available in many contemporary vehicles.
The terms which are provided with subscript i are the values that are detected in sequence and stored in the time sequences. When the time interval &Dgr;t between the
Rieker Heinz
Schuetzner Paul
Stoll Josef
Assouad Patrick
Bui Bryan
Crowell & Moring LLP
Daimler-Chrysler AG
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