Analysis of detailed electric vehicle data in electrical engineering education
There is a large quantity of data available on the CAN bus of the Chevrolet Volt that can be obtained through the OBD2 connectors on both the passenger and driver side of the vehicle. Although much of this is not available on the console of the vehicle to passengers, it can be logged and collected to analyse various vehicle performance measures and behaviours as well as charging characteristics. A set of pertinent data has been collected simultaneously for approximately 40 vehicle parameters for numerous trips and charging events for the 2012 Chevrolet Volt. Some of the key parameters are battery voltage, battery current, motor currents, state of charge, engine rpm, vehicle speed, longitude, latitude, altitude, battery power, motor power, etc. This data has been used as a learning tool in the electrical engineering classroom for senior students in both advanced machine courses and in sustainable energy courses. Through analysis the students develop a better understanding of general electric vehicle operation principles and energy useage and management. They also develop problem solving skills and experience with analysing large data sets (certain trips have over 15 million data points) and using appropriate tools to perform large but repetitive tasks.
Characterizing energy usage of Chevrolet Volt versus speed
There is a large quantity of data available on the CAN bus of the Chevrolet Volt that can be obtained through the OBD2 connectors on both the passenger and driver side of the vehicle. Although much of this is not available on the console of the vehicle to passengers, with additional equipment it can be logged and collected to analyze various vehicle performance measures and behaviors as well as charging characteristics. Average energy usage is determined for a constant speed portion of a trip over a range of speeds from 30 mph to 75 mph. The energy usage ranges from 170 Wh/mile at 30 mph to the high of 369 Wh/mile at 75 mph. The segment used for evaluation was selected to have the smallest practical elevation change to reduce the dependency of the energy usage on this factor. The optimum speed for energy efficiency over this range has been determined experimentally and is found to be the lowest speed of 30mph. The average energy usage for a variety of complete trips is also given as a comparison of the usage over a variety of speeds and elevations as well as potential driving behavior effects.
Applied Engineering With Labview: Experiences From A Plug In Hybrid Project
In this paper we discuss a primarily undergraduate project conducted during the 2006-2007 academic year with the goals of converting a stock Toyota Prius to a plug-in hybrid having enhanced electric only range capability. This project afforded the author with an opportunity to help with the utilization of National Instrument’s Laboratory Virtual Instrument Engineering Workbench (LabVIEW) and a National Instruments compact RIO (Reconfigurable Input/Output) embedded controller in an applied engineering design project. This is a relatively new embedded system controller which, through the use of LabVIEW software applications, can be used as a stand alone real-time controller. This paper provides a background of the project and the role of LabVIEW and the compact RIO device. It also provides a description of some experiences related to introducing this system to undergraduate students, and later graduate students, having little background in rapid prototyping, real-time controllers, and the HS-CAN (High Speed Controller Area Network) communication protocol and standard. This type of automotive conversion project provided an excellent venue for introducing the students to a systems oriented approach to engineering design, from sensor measurement and vehicle interfacing to electrical energy consumption and strategy implementation on some of the most advanced vehicle technology available today. Introduction and Background A unique and successful degree program at Minnesota State University, Mankato is the Automotive Engineering Technology (AET) undergraduate program. Unique in that it is one of the only, if not the only, ABET accredited program of its type in the United States with numerous graduates each year pursuing primarily automotive technology and engineering test and development careers in industry. As part of the program, undergraduates complete a two semester (one year) senior design project related to an automotive system development, student competition or other automotive related research effort. During the 2006-2007 academic year, a group of students chose a project to modify and enhance the capability of the Toyota Prius Hybrid vehicle. Specifically, their goals P ge 13211.2 included converting the vehicle fuel system to accept Ethanol blended fuels, enhancing the on-board battery capacity, modifying the vehicle for electric-only operation beyond launch and overall improvement of fuel economy with a target of around 100 mpg. With the use of a 2006 year Prius and a strong team effort, many of the project goals were accomplished. Modifying the on-board battery pack posed some challenges. Due to the lack of detailed knowledge of the operational characteristics of the Prius battery control unit (BCU), the students decided to interface the modified battery pack such that the Prius vehicle was not aware of the modification (i.e. masking the change to the BCU). There are numerous Prius conversion projects across the United States in various stages of development. A search through the internet yielded a similar endeavor: The CalCARS PriusPlus project [1]. In this conversion the stock Nickel Metal-Hydride (Ni-MH) battery pack was replaced with a Lead-Acid (Pb-Acid) chemistry pack with the same pack voltage as the stock battery pack. The BCU was sent similar fractional-pack voltage measurements from the new pack as provided by the stock pack in an effort to mask the battery pack change from the BCU. However since the charge and discharge curves for the two different battery chemistries are different, the voltage measurements provided to the BCU were supplemented with offsets to avoid alarm conditions in the Prius. The PriusPlus project integrated these voltage offsets via supplemental electronics and manually adjustable analog controls. A similar conversion methodology was attempted by the AET students. A Pb-Acid chemistry pack was developed with approximately six times the energy capacity as compared to the stock battery pack. Implementing a similar auxiliary controller interfaced to the BCU was considered excessively challenging given the limited student expertise gained in the AET degree program for developing integrated circuits and in working with electronic components. Therefore an alternative was considered which incorporated an embedded systems approach and provided an opportunity for the students to learn about applied high speed automotive communication and system control combined using the LabVIEW application. The National Instruments cRIO was chosen as the embedded system platform based on its low relative cost and the capability to interface the tool with LabVIEW. In this way an automated control strategy could be implemented removing the necessity for operator-based manual adjustments. All of the project objectives were not achieved at the completion of the senior design project period. Two graduate students from the Manufacturing Engineering Technology (MET) program, under the guidance of the project advisors, continued working on the remaining project objectives. Their experiences, to date, are also summarized in this paper. The paper is organized in multiple sections. Section 2 introduces LabVIEW and describes its use in the Prius conversion project. Section 3 introduces the cRIO hardware, describes its intended use on the project and discusses the outcomes of the student efforts put toward this system. Section 4 compares and contrasts the capability of the AET undergraduate students and the graduate Manufacturing Engineering Technology (MET) students (having an AET undergraduate degree) to incorporate the cRIO system into the conversion project. Section 5 provides some concluding remarks. P ge 13211.3 The entire scope of the conversion project will not be discussed in this paper, however aspects of the project related to the use of LabVIEW and the cRIO system will be discussed. Additional background on the entire project can be found in the project’s final report [2]. Refer to figure 1 for an overview of the conversion project scope. Figure 1: Diagram of the components of the conversion project. LabVIEW and Real-Time I/O The intent to incorporate LabVIEW into the AET curriculum has existed prior to the 2006-2007 academic year and this project provided an avenue to fulfill that intent. LabVIEW is a graphical development environment software package which runs on a personal computer and allows the user to interface with data acquisition and control systems hardware, external to the computer, using a block diagram interface and Virtual Instruments (or VIs). The software was originally intended to interface multiple instruments but has expanded to incorporate data acquisition, signal conditioning, real-time control and communication and simulation as well as providing an interface for embedding various types of programming language code. LabVIEW VIs have a front panel P ge 13211.4 interface with virtual knobs, switches and data entry along with graphs and other data output constructs. The VIs also have a block diagram which details the interconnections between various blocks to execute some set of desired tasks. Some blocks also link the processing occurring in the block diagram to the I/O occurring in the front panel. To facilitate the processing or simple I/O of data to and from the VIs, hardware which digitizes the data external to the computer must be used in concert with LabVIEW. Various options are available, one of which is the cRIO and is available through National Instruments. The cRIO will be discussed in more detail in the next section. A significant portion of the student project involved measurement of key vehicle data. This data included periodic high voltage battery pack voltage measurements, battery pack currents, battery pack temperature measurements from multiple surfaces of the battery pack and other vehicle operational data. In the case of the Toyota Prius vehicle, most of this information is internally measured by the vehicle and transferred between vehicle subsystems through the high speed controller area network (HS-CAN). This communication network is prevalent in many passenger vehicles built within the past ten years. The communication standard, originally designed by Bosch, has been around for a longer period but its widespread adoption did not occur immediately. The HS-CAN within the Prius vehicle provides a real-time representation of important vehicle measureables and status data. The student project team used a CANUSB interface cable and hardware specific software drivers to process the serial data within LabVIEW. A screen shot of an earlier version of a VI used to read HS-CAN data is shown in Figure 2. CAN-related training in the AET curriculum prior to this project was limited only to the use of standard diagnostic tools. The training did not discuss the CAN protocols, message structure nor timing. In addition, topics related to microprocessors, microcontrollers or embedded systems are also not covered as part of the AET degree coursework. This project provided an opportunity to expose the students to these topics to gain some appreciation for what is happening behind the diagnostic tools and vehicle computers. The undergraduate students were directed to complete tutorials on the LabVIEW software package and develop, starting with example VIs, usable VIs which measure and display vehicle parameters considered important and available on the CAN. Data specific to the operation and architecture of the Prius CAN is available from multiple public sources on the internet and these sources were leveraged to parse the particular messages containing desired vehicle data. For many of the students involved in the project, this was their first exposure to CAN communication. The author provided a short workshop (approximately 2 hours) for the group to review binary and hexadecimal number systems, introduce high speed communication and the CAN protocol and data frame structure, a