Amt off-highway downshift logic

A method for controlling an automated transmission system for vehicles having a fuel-controlled engine having a maximum engine speed, a throttle controlling means for controlling the amount of fuel supplied to the engine and a transmission having a plurality of gear ratio combinations selectively engagable between a transmission input shaft and a transmission output shaft, said transmission input shaft being operatively connected to said engine by a coupling device, said transmission system comprising, an information processing unit having means for receiving a plurality of input signals including (1) an input signal indicative of the position of said throttle controlling means and (2) an input signal indicative of the speed of said vehicle, said processing unit including means for processing said input signals in accordance with a program to provide a predetermined selected gear ratio for a given combination of input signals and for generating command output signals whereby said transmission system is operated in accordance with said program, and means associated with said transmission effective to actuate said transmission to effect engagement of one of said gear ratio combinations in response to said output signals from said processing unit, the method including sensing vehicle conditions indicative of the desirability of a downshift and determining a value indicative of vehicle acceleration, and calculating an expected engine speed value indicative of the expected rotational speed of the engine at selected vehicle speeds in selected gear ratio combinations, said method comprising:

• sensing operator selection of a performance enhancing mode of operation;
• sensing conditions indicative of a desirable downshift;
• comparing throttle controlling means position to a predetermined first reference value and the value indicative of vehicle deceleration to a second reference value and, if throttle position is greater than said first reference value and the value indicative of vehicle acceleration is less than said second reference value;
• calculating expected vehicle speed at completion of a downshift assuming constant vehicle acceleration for a period of time greater than the time required to complete a single downshift from the currently engaged gear ratio;
• calculating expected engine speeds at each of the Nth lower gear ratios, at expected vehicle speed, where N is an integral greater than one until at least the expected engine speed in the Nth lower gear ratio is greater than said maximum allowable engine speed;
• and
• commanding a downshift directly into the lowest gear ratio having an expected engine speed less than said maximum allowable engine speed.