Control System Architecture for an Advanced Electric Vehicle Powertrain

Reduced complexity, improved driveability, and increased energy efficiency are among the advantages which can be obtained through Con-board) computer control of powertrains in both conventional and electric vehicles. This paper describes the design and implementation of a control system for an advanced electric vehicle powertrain, incorporating an integrated induction motor and two speed automatic transaxle. The control system employs a distributed computer architecture utilizing a fiber optic communication system for computer coordination. The software architecture utilizes a unique combination of standard multitasking concepts and finite state automata techniques. This approach allows individual tasks to be defined and prioritized and permits data and system resources to be shared effectively. Through the use of torque and gear shift scheduling, internal combustion engine torque characteristics can be duplicated to improve driveability. Direct computer control of the clutches in the transmission results in smooth gear shifts without requiring a torque converter. Control of regeneration as a function of master cylinder pressure allows power brake emulation while reducing energy consumption. Continuous calculation of the battery state of charge allows better operator awareness of the current range capability of the vehicle. The architecture used accommodated system design changes and allowed successful completion of the control system on schedule. Final testing and evaluation of the vehicle has verified the effectiveness of this control system in providing excellent driveability while maintaining good energy efficiency.