1990-10-01

Advanced Controls for Heavy Duty Transmission Applications 901157

Allison Transmission Division of General Motors Corporation is currently developing an electronically controlled automatic transmission system utilizing advanced technologies in microprocessors, application specific integrated circuits (ASICs), sensors, actuators, displays, and direct electronic clutch pressure control. The transmission system has been designated the World Transmission (WT). Included is a complete family of heavy duty automatic transmissions which will become part of the Allison Transmission product line starting in 1991. The WT design provides expanded capabilities over present transmission technology and results in improved performance with benefits in life cycle cost. A key advancement in the state-of-art of transmission shift quality has been achieved with the WT transmission through use of a fully automatic self calibration feature. Implementation of this feature is achieved through use of an adaptive closed-loop clutch pressure control system. The microprocessor based controller is a second generation Allison Transmission Electronic Control system (ATEC II). The system utilizes the Motorola MC 68HC11 microcomputer which provides increased computational speed for enhanced transmission control, on-chip functions for expanded diagnostics and communication, and input/output capability to meet current and future customer needs.In the following sections, the WT transmission system concept is presented together with a description of the ATEC II system. Included is an overview of the electronic hardware components, the system operating features, and the adaptive clutch control system. The electronic control unit interfaces associated with the operator, transmission, and vehicle systems are also addressed as a part of this description. Standardized serial data links provide digital communication with a remote shift selector, vehicle displays, diagnostic equipment, and other vehicle systems. Various adaptive shift control test results are also provided to illustrate the transmission system operating benefits.

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