Vehicle automatic transmission control system for controlling the speed change ratio based on driving resistance

A system for controlling a gear ratio of a multi-step geared or continuously variable automatic transmission of a vehicle based on determined parameters indicative of operating conditions of said vehicle including a driving resistance calculated by driving resistance calculating means;

• wherein the improvement comprises:
• said driving resistance calculating means comprising:
• first means for determining output torque generated by a vehicle engine at least from an engine speed and an engine load in accordance with a predetermined characteristic;
• second means for adjusting said determined output torque by subtracting torque consumption of a least one device including an oil pump to be driven by said vehicle defined with respect to an engine speed and adjusting for transmission lag, deeming the lag as the first order, and for calculating motive force said vehicle generates by multiplying said adjusted torque by overall gear ration and transmission efficiency and by dividing the product by vehicle tire radius;
• third means for determining a vehicle acceleration from a frequency signal less than a determined frequency and by multiplying said determined vehicle acceleration by vehicle mass, to determine force required for acceleration, and then to determine a driving resistance by subtracting the determined force from the motive force;
• fourth means for determining a steering angle of said vehicle;
• and
• fifth means for adjusting said determined driving resistance in response to the magnitude of said detected steering angle in such a manner that said determined driving resistance decreases with increasing magnitude of said detected steering angle.