Method of operating an electronic automatic transmission system

In a vehicle having an engine with throttle means and a transmission system including an input member with a plurality of teeth, a torque converter assembly for transmitting torque between the engine and the input member, the torque converter assembly having a turbine, an output member, a gear assembly for changing the ratio of torque between the input member and output member, a plurality of friction elements for shifting the gear assembly, a fluid actuating device being moveable to engage and disengage at least one friction element, at least one solenoid-actuated valve being moveable in response to the presence or absence of electrical power for directing fluid-flow between a fluid source and the fluid actuating device, a plurality of sensors providing signals indicative of measurement data for predetermined conditions, a controller having memory for processing and storing the signals and predetermined values and providing signals to control the actuation of the solenoid-actuated valve, a method of controlling the transmission system for the vehicle, said method comprising the steps of:

• powering and initializing the controller;
• reading a sensor by the controller to determine the tooth count of the input member in a predetermined time period;
• calculating an input speed based on the tooth count of the input member for the predetermined time period;
• reading a sensor by the controller to determine the shift lever position of the driver-selected operating mode of the transmission;
• reading a sensor by the controller to determine the position of the throttle means in the engine of the vehicle;
• determining the gear the transmission should be operating in by the controller based on the calculated input speed and shift lever position and throttle position;
• comparing the determined gear to the gear the transmission is presently operating in by the controller to determine whether a gear change is required;
• executing predetermined monitoring routines by the controller to determine if a failure of the transmission system has occurred;
• determining by the controller whether a gear change is required;
• identifying and executing the proper gear change by the controller if a gear change is required;
• determining by the controller whether a lock-up of the torque converter assembly is required;
• determining by the controller whether the torque converter assembly is presently in lock-up if lock-up is required;
• executing a predetermined mode of lock-up by the controller if the torque converter assembly is not presently in lock-up;
• determining by the controller the desired acceleration of the input member;
• calculating by the controller the actual speed and acceleration of the input member;
• comparing by the controller the calculated acceleration and the desired acceleration of the input member to each other;
• and
• outputting signals by the controller to the solenoid-actuated valves and controlling the friction elements such that the calculated acceleration approximates the desired acceleration for completing the gear change.