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Vehicle Program The Texas Electric Vehicle (EV) Program The University of Texas at Center for Electromechanics (UT-CEM), the Texas Energy Conservation Office, and the Texas Department of Commerce have jointly organized an electric and hybrid-electric vehicle program in Texas. The program capitalizes on the advanced technical position in four key dual-use technologies that has been established by UT-CEM and focuses on technology development and transfer to firms capable of production. The program also involves innovative linkages with users and customers during the development process to simultaneously develop initial market interest, attract investment, and identify user test platforms. The program is intended to serve as a beginning, with an expanding number of participants and technologies in future years. Funds are being provided by Federal Agencies, State Agencies, utility companies, industrial project partners, a metropolitan transportation authority, and commercial investors. The Texas Electric Vehicle Program consists of four interdependent projects to develop: efficient low-cost homopolar EV traction motors; small flywheel batteries for vehicle power management; large flywheel batteries for utility power management (such as would be required for practical electric vehicle recharge stations) and hybrid electric railroad locomotives; and improved electromechanical active vehicle suspensions. The breadth and scope of the principal organizations (over a dozen) participating in the projects provide the strength of the program — the interaction of the manufacturers, the developers, and the users during the development process. Similarly, the program’s complexity and the diverse requirements of the 10 different organizations that are providing funds has heightened the dependencies of the projects. For example, the Texas Office of State-Federal Relations is primarily interested in job creation in Texas. The Advanced Research Projects Agency (ARPA), on the other hand, is primarily interested in electric vehicle technology development for both military and commercial applications. Technical inter-dependencies also exist. For example, the utility flywheel battery program relies on the vehicular flywheel battery project to solve flywheel battery manufacturing cost issues and flywheel battery containment and safety problems. Small Flywheel Battery Systems For Vehicle Power Management The primary objective of the project is to develop dual-use stand alone flywheel battery systems, for military and commercial applications. Future military requirements for power averaging are more demanding than commercial applications, and will demand the advanced rotor technology being applied in this project. This becomes even more critical with the next generation of combat vehicles, employing EM guns, EM suspensions and EM countermeasures. Until now, flywheel battery systems have either been low risk and low performance devices or expensive, high risk, moderate performance designs. Under this ARPA program, UT-CEM is providing the advanced composite rotor technology, developed in DoD programs, for the most demanding high performance flywheels. Additionally UT-CEM is developing techniques to reduce costs for the high performance rotor to be as low as or lower than conventional wet wound filament technology. With conservative operating stresses UT-CEM’s predicted power density is in excess of 1,600 W/kg, and energy density over 30 W-hr/kg. These are appropriate and attractive performance parameters for this load leveling application where power averaging and reliability are the objectives. This project, to fabricate a moderate-cost high-performance composite flywheel battery system, capitalizes on an alliance of mass transit providers, university technology developers, and commercial manufacturing entities. For this reason, the program structure encompasses the elements necessary to develop the required production technology, formulate component manufacturing plans which are guided by customer-driven system designs, and introduce the technology to the marketplace. Each member of the alliance has a vested interest in producing these systems in large numbers and is investing considerable resources to insure the success of the program with the ultimate goal of producing a commercially viable unit. Commercial viability will also be enhanced by the composite rotor manufacturing tasks to reduce fabrication costs in the project. Efficient Low-Cost Homopolar EV Traction Motors Work on this project began in May 1995, and a prototype motor design has been completed. This design uses a four-pass armature and operates at a peak current of 5,000 A from a 48 V battery pack. Full power efficiency is currently at 87% with the majority of losses (about 10%) coming from the brushes. Brush testing is in progress to address efficiency improvements, document wear rates, and confirm operation of several new low-cost and compact actuator designs. Test data obtained so far shows excellent operation of a constant force spring-actuated brush and brush holder design. Brush wear rates at normal driving conditions appear to be far less than those obtained from worst case speed and current loading conditions cited in previous studies. This is very encouraging considering the typical duty cycle of the bus. To regulate power flow to the motor, UT-CEM is developing a high-current pulse width modulator (PWM) controller based on a highly parallel array of MOSFET switching devices. For low voltage systems, MOSFETs are an ideal choice given their low on-state resistance, high switching frequency, low switching losses, and ease of parallel operation. A 300 A prototype has been assembled, and testing is under way to confirm operation with a low impedance load. The final tasks for this program requires setting up a manufacturing line to produce homopolar traction motors, controllers, and gearboxes. Private funds support this portion of the program. Electromechanical Active Vehicle Suspensions In phase two, the concept was adapted from a trailing arm suspension system, as is found in the M1 MBT, to a dual A-arm suspension, as is found in a HMMWV. Control strategies were expanded from the single wheel station approach developed under the current TACOM project, to a four wheel vehicle. To reduce cost and to reduce the project duration, the four wheel "vehicle," designed to simulate the important characteristics of a HMMWV. This allowed (1) development and refinement of control algorithms on an adaptable test platform, (2) maximum use of "off-the-shelf" components at a stage in the program when it is difficult to totally specify required component performance, and (3) development of necessary specifications and information needed to design a system optimized for a HMMWV. Phase three of the EM Suspension program has developed customized actuators and control systems to allow installation of a complete system on a HMMWV and a transit bus. Sponsors For further information please contact: |