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The last few years have been an exciting time for alternative vehicle development. New concerns about the environmental impact of personal transportation and about the United States' dependence on imported oil have pushed energy efficient, ultra-low, and zero emissions vehicles to the forefront of automotive design. California's own mandate for Zero Emissions Vehicles (ZEV) takes effect in 1998, creating a tremendous push towards the difficult goal of producing a commercially viable, practical electric vehicle for sale in 1998. Beyond California, most of the world's automakers are simultaneously committing tremendous research and development resources towards the technology necessary for a viable electric vehicle. The University of California at Davis is one of seven California universities participating in the 1993 Ford Hybrid Electric Vehicle Challenge.

Test methods and data acquisition system specifications are described for measurements of the energy consumption of the control system of a servo-pump continuously variable transmission (CVT). Dynamic measurements of the power consumption of the servo-pump CVT control system show that the control system draws approximately 18.9 W-hrs of electrical energy over the HWFET cycle and 13.6 W-hrs over the 505 cycle. Sample results are presented of the dynamic power consumption of the servo-pump system under drive cycle conditions. Steady state measurements of the control power draw of the servo-pump CVT show a peak power consumption of 271 W, including lubrication power. The drive-cycle averaged and steady state energy consumption of the servo-pump CVT are compared to conventional CVT pump technologies.

In an effort to improve the Continuously Variable Transmission and evaluate its performance with different modifications, a conventional CVT was redesigned to incorporate an energy efficient Servo Hydraulic Control (SHC) system and to substitute a different torque transmitting element, a Gear Chain Industry (GCI) chain for the Van Doorne Transmissie (VDT/Bosch) belt. Various loaded and unloaded tests were performed on the CVT while using the GCI Chain and VDT Belt in the Stock and Servo Hydraulic configuration. An analysis of the various configurations was made and key features of each element have been outlined.

The objective of the advanced transmission system concepts such as the Continuously Variable Transmission (CVT) and Hybrid Electric Drives is to improve fuel efficiency, lower emissions and reduce powertrain part count while not impacting cost. The control of the system, however, can greatly affect the final fuel consumption, performance and emissions for any of the possible configurations. This paper describes an engine control philosophy for a hybrid electric CVT powertrain concept with the fewest number of mechanical parts but with many modes of operation such as: 1. All electric operation 2. Regenerative braking to maintain the battery charge at a desired level. 3. Engine charge for maintaining the battery state of charge 4. Highway cruise efficiency. 5. Power enhancement by use of the electrical energy for passing and highway maneuvers. 6.

The standard vehicle propulsion system and its controls are compared with a flywheel propulsion system. Different concepts of control and various system configurations are explored. Some considerations for the design of a general purpose automatic flywheel transmission vehicle are presented and discussed. Specifications required for a flywheel transmission system which can achieve substantial mileage improvements and provide high performance are presented. The resulting vehicle would have performance of 0–60 mph in less than 10 seconds and achieve 50 miles per gallon on the Federal Urban Driving Cycle (FUDC) at an inertia weight of 3,000 lb. Higher mileages are possible for lighter vehicles. Fuel economy is achieved by (1) engine operation only at minimum BSFC, (2) elimination of engine idle, (3) recovery of energy from braking and (4) minimizing transmission losses.

Hybrid vehicles, i.e., those containing two or more sources of power, have the potential of increased fuel economy under certain types of driving conditions. Systems currently being investigated include combinations of heat engines, electric drives, fly-wheels, and accumulators. In order to obtain fuel economy improvements over conventional vehicles, efficient components are required as well as a good system design. Hybrid powerplants appear more promising for heavier vehicles.

The flywheel energy-storage unit is examined as a tool for engine load management. The control decision to store or retrieve energy is formulated and discussed. Vehicle dynamics are simulated on a digital computer in combination with dynamic programming techniques to obtain optimal operation policy. The simplified algorithm is explained, as well as the cost-function criteria and optimization constraints. The sensitivity of the optimal path and the vehicle gas-mileage improvements are elaborated. The study of losses indicates that the transmission is the largest energy sink in the power train. The result of this study provides an indication of the appropriate real-time control policy.

Four hybrid powertrain designs are compared for a refuse collection truck driven over approach, loading and return segments of a representative route. Appropriate matching of component characteristics, drivetrain design and control strategy is shown to reduce fuel consumption by 39% to 56% compared to a conventional vehicle. Concurrently, brake usage is reduced 54% to 85% and the number of engine revolutions is reduced 66% to 84%. The four hybrid powertrains consist of “Integrated” and “Add-On” designs using flywheel or accumulator energy storage to recover braking energy and optimize engine efficiency. The average engine efficiency for each design is comparable and the vehicle fuel economy depends on the ability of each design and control strategy to minimize parasitic losses and use of the service brakes.

The design and evaluation of a control system for a continuously variable transmission (CVT) vehicle is presented in this paper. Studied and simulated are the following three topics: design and evaluation of the control system with a CVT vehicle in acceleration, deceleration and to the sensitivity of the system with respect to changing characteristics of the engine (hot, cold, age). It is shown that the control system proposed here could insure good stability and controllability not only for acceleration of the system but also for deceleration operation, provided that a pulse width modulated (PWM) fuel control scheme for the engine is employed in the system. It seems that the control system designed in this paper is not complicated and does not have large sensitivity with respect to variation of the characteristics of the components of the system and provides the best possible fuel efficiency.