Compensation for delay of scheduled gearshifts in automatic transmissions

Abstract

A control for producing ratio changes in an automatic transmission includes sensors producing signals from which vehicle speed, throttle position, vehicle acceleration, and the time rate of throttle position are determined. Electronic memory accessible to a microprocessor contains functions relating vehicle speed to throttle position, one function being related to each upshift and downshift. Shift solenoids are energized and deenergized according to the output of a control algorithm executed by the microprocessor. A hydraulic circuit contains shift valves, servos, brakes and clutches activated by the servos selectively to produce the various gear ratios of the transmission. Shift delays for each upshift and downshift are predetermined and stored as constants in memory. A shift schedule relating throttle position, vehicle speed and the current transmission gear ratio is stored in memory. Control variables compensating for shift delay on the basis of vehicle acceleration and throttle rate are calculated. A vehicle acceleration compensation value is substituted for vehicle speed and a throttle rate compensation value is substituted for throttle position. Signals produced by the microprocessor upon executing the control algorithms alter the state of shift solenoids in accordance with a predetermined schedule of the solenoid states that produces the commanded gear ratio.