Drive control for engagement and disengagement of axles of a vehicle
AssigneeZF Friedrichshafen AG
InventorDitmar Salg
Life of this patent
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Abstract
The invention concerns a drive control for motor and utility vehicles. The speeds of the wheels and the steering angle are measured by means of sensors. Driving axle slip is determined by comparing the average peripheral wheel speeds of the driven and non driven axles and by taking into account the steering geometry. Driving force and finally chassis efficiency are determined by the slip with the assistance of standard characteristic lines. The efficiencies of all-wheel drive and rear-wheel drive are compared. The drive with the higher degree of efficiency is engaged.
Claims26
A drive control for a power train of a motor vehicle having a constantly driven axle and an engageable axle, the drive control comprising:
- an electronic control unit for receiving data from first and second speed sensors positioned on a steerable axle for determining a peripheral speed of a pair of wheels supported by the steerable axle and a third speed sensor positioned on the driven axle for measuring a peripheral speed of a pair of wheels supported by the driven axle,
- wherein the electronic control unit includes means for determining engagement and disengagement of the engageable axle and the means for determining including:
- means for obtaining from the first, the second and the third speed sensors initial data comprising an actual peripheral speed of the wheels of both the driven axle and the engageable axle;
- means for determining a steering angle from one of a peripheral wheel speed ratio of each of the wheels of the steered axle and a steering angle sensor;
- means for calculating from the steering angle a theoretical ratio of a relative peripheral speed of the wheels without slip for the driven axle and the engageable axle;
- means for comparing the actual peripheral speed of the wheels of the driven axle and the engageable axle obtained from the first, the second and the third speed sensors with the theoretical ratio of the peripheral wheel speeds to determine slip of the driven axle;
- means for generating, in the electronic control unit, initial characteristic lines from the determined slip to obtain a coefficient of driving force and a coefficient of rolling friction;
- means for calculating a theoretical chassis efficiency of the driven axle via a first mathematical equation corresponding to a physical model using the coefficient of driving force, the coefficient of rolling friction, the steering angle, the slip and one of a preset axle load distribution and a measured axle load distribution;
- means for obtaining further data via the first sensor, the second sensor and the third sensor from the driven axle and the engageable axle;
- means for generating further characteristic lines to determine an actual slip value and an actual coefficient of driving force and an actual coefficient of rolling friction based upon a condition where a drive traction of the driven axle is equal to a drive traction of at least one additional driving axle;
- means for calculating an actual chassis efficiency via a second mathematical equation and the further characteristic lines;
- means for obtaining a ratio of the calculated chassis efficiency and the theoretical chassis efficiency, to be used by the electronic control unit as engagement criterion for determining engagement of the engageable axle;
- and
- means for engaging the second engageable axle when the engagement criterion is greater than 1 and in the event of positive slip, and, disengaging the engageable axle when the engagement criterion is less than 1 and in the event of negative slip.
A method of controlling a drive control for a power train of a motor vehicle having a constantly driven axle and an engageable axle, the drive control comprising an electronic control unit for receiving data from first and second speed sensors positioned on a steerable axle for determining a peripheral speed of a pair of wheels supported by the steerable axle and a third speed sensor positioned on the driven axle for measuring a peripheral speed of a pair of wheels supported by the driven axle, wherein the electronic control unit determines engagement and disengagement of the engageable axle, and the method comprises the steps of:
- obtaining from the first, the second and the third speed sensors initial data comprising an actual peripheral speed of the wheels of both the driven axle and the engageable axle;
- determining a steering angle from one of a peripheral wheel speed ratio of each of the wheels of the steered axle and a steering angle sensor;
- calculating from the steering angle a theoretical ratio of a relative peripheral speed of the wheels without slip for the driven axle and the engageable axle;
- comparing the actual peripheral speed of the wheels of the driven axle and the engageable axle obtained from the first, the second and the third speed sensors with the theoretical ratio of the peripheral wheel speeds to determine slip of the driven axle;
- generating, in the electronic control unit, initial characteristic lines from the determined slip to obtain a coefficient of driving force and a coefficient of rolling friction;
- calculating a theoretical chassis efficiency of the driven axle via a first mathematical equation corresponding to a physical model using the coefficient of driving force, the coefficient of rolling friction, the steering angle, the slip and one of a preset axle load distribution and a measured axle load distribution;
- obtaining further data via the first sensor, the second sensor and the third sensor from the driven axle and the engageable axle;
- generating further characteristic lines to determine an actual slip value and an actual coefficient of driving force and an actual coefficient of rolling friction based upon a condition where a drive traction of the driven axle is equal to a drive traction of at least one additional driving axle;
- calculating an actual chassis efficiency via a second mathematical equation and the further characteristic lines;
- obtaining a ratio of the calculated chassis efficiency and the theoretical chassis efficiency, to be used by the electronic control unit as engagement criterion for determining engagement of the engageable axle;
- and
- engaging the engageable axle when the engagement criterion is greater than 1 and in the event of positive slip, and, disengaging the engageable axle when the engagement criterion is less than 1 in the event of negative slip.
Dependencies are inferred from the claim text.