ProtoDrive: An Experimental Platform for Electric Vehicle Energy Scheduling and Control

Source Organization:
University:University of Pennsylvania
Principal Investigator:Rahul Mangharam
PI Contact Information:200 S. 33rd Street, 203 Moore Building, University of Pennsylvania, Philadelphia, PA 19104.
Tel: 215-573-3636.
Project Manager:Courtney Ehrlichman
Funding Source(s) and Amounts Provided (by each agency or organization):UTC
Total Dollars:
Agency ID/Contract/Grant Number:DTRT12GUTC11
Start and End Dates:1/1/12 – 12/31/13
Project Status:Complete
Subject Categories:Control
Abstract:The focus of this project is to ensure safe and efficient hybrid energy storage systems for future vehicle architectures. The project is developing control and scheduling algorithms to ensure battery systems are safe by minimizing peak current draw. This is achieved by using a supercapacitor to buffer charge and flatten peak current draws from the battery. The result is an extension in the lifetime of the battery and operation in the safe power density regime. We are developing the circuits, system models and control/scheduling algorithms that require minimal drive cycle information.

We are developing Protodrive, an experimental platform enabling rapid prototyping and simulation of electric vehicle powertrains. The powertrain is modeled at the small-scale in hardware, making it low-cost and compact enough to fit on a desk. It consists of a physical model of an electric vehicle powertrain coupled to an active dynamometer, making it possible to run the powertrain through its full speed and torque range. The fact that this system has been constructed in hardware allows it to capture intricacies in vehicle operation that may be missed by simulation in software alone.

Protodrive can be used for a wide range of simulation tasks, and presently the benefits of a battery/supercapacitor powertrain are being investigated. Protodrive runs a scaled version of an actual commute drive cycle with various battery/super capacitor charging/discharging schedules with the goal of maximizing the battery’s life time and the vehicle’s range. Protodrive has a number of interesting applications that will further EV development:
  • Enabling rapid prototyping and evaluation of novel powertrain architectures
  • Simulating federal drive cycles to determine a vehicle’s fuel consumption and MPGe rating (Miles Per Gallon equivalent)
  • Predicting range, when coupled with elevation data from Google maps and a driver control strategy
To investigate battery-supercapacitor charge/discharge control and scheduling strategies for range maximization, peak current draw minimization and maintaining the battery temperature in the efficient operating region we begin with an energy-efficient hybrid system that comprises of both, the batteries and the supercapacitors connected through a DC/DC converter to achieve optimal performance. The inputs to the system are the EPA’s Federal Drive Cycle and real vehicle model information from the EPA, the U.S. Department of Energy (DoE) and the National Renewable Energy Laboratory (NREL). Various power distribution schedules will be implemented over the drive cycle, enabling the comparison of a hybrid system to a battery-only system, and the comparison of various current distribution algorithms. The output will show the current load on the battery and the super capacitor, which can be used to determine the battery’s State of Charge and the efficiency of the vehicle. Ultimately, we aim to determine if a battery/supercapacitor system offers significant benefits over a battery-only system, by simulating real commuting routes in hardware.
Describe Implementation of Research Outcomes (or why not implemented):
Impacts/Benefits of Implementation (actual, not anticipated):In the past few months, ProtoDrive won the 3rd Prize in 11th World Embedded Systems Competition, Seoul, Korea. It won the Distinguished Recognition Award at the Intel/Cornell Embedded Systems Competition. The ProtoDrive team demonstrated at the ITS Showcase in DC on June 26, 2013.

In President Obama's, Jan 2011 State of Union Address, he mentioned - "We can replace our dependence on oil with biofuels and become the first country to have a million electric vehicles on the road by 2015." Electric Vehicles (EVs) have had a recent resurgence in popularity and are showing promise as a future mainstream means of transportation. However, the low energy density, high cost and long recharging time of batteries are formidable obstacles to mass consumer acceptance. There are a number of things that can be done to increase the viability of EVs, such as:
  • Powertrain system optimization to extract the maximum range
  • Development of better tools to predict range and reduce “range anxiety”
  • Optimal fuel control and driver behavior influence to increase range
An electric vehicle powertrain consists of all the components necessary to deliver power to the wheels. This typically consists of a battery, motor controller, motor, gearbox and differential. Currently, EV powertrains are modeled and simulated in software and then prototyped and tested in a full-scale vehicle. While software can provide decently accurate predictions of performance, it may fail to miss some of the detailed intricacies of a real system. Full-scale models obviously demonstrate all real problems, however, iterating on a full-scale vehicle is time consuming and expensive.

Protodrive is a small-scale electric vehicle prototyping platform that attempts to find a middle ground between simulating purely in software, and prototyping at full scale. It is a real hardware system, representative of a real powertrain, however, it is implemented at a scale small enough to fit on a desktop. The hope is that it will allow the quick and cost effective characteristic of simulating in software, while still being able to capture the intricacies of real hardware performance.
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