Study of On-Board Calculation of Road Gradient

Abstract

It is desirable to change the shift schedule of an automatic transmission according to the road gradient. We previously developed a drive torque calculation method, and used it to calculate the gradient of a road as which a car was traveling. Gradient resistance torque is calculated by subtraction of the acceleration torque and road load torque from the drive torque. By improvement of the detection method for determining vehicle speed and the masking method for eliminating interruption by braking, a gradient calculation accuracy of ±20% is obtained. This is not a as good as in the case of use of the conventional sensing method, but the new method can be implemented without a torque sensor. We studied the possibility of applying this control with the presnt ±20% error. Control can be realized when this road gradient calculation method is used together with another parameter to judge the control situation.