Formula Hybrid is a design and engineering challenge for undergraduate and graduate college and university students. The competition is organized by Thayer School of Engineering at Dartmouth and carries the endorsement of the Society of Automotive Engineers, Inc. (SAE) and the Institute of Electrical and Electronics Engineers, Inc. (IEEE).
Each team must design, build, and compete an open-wheel, single-seat, plug-in hybrid racecar. This car must conform to a formula that emphasizes drive train innovation and fuel efficiency in a high-performance application.
The emphasis of the Formula Hybrid Competition is on the engineering of the hybrid drive system and vehicle dynamics to maximize performance in three different tests, acceleration, autocross and endurance.
The LPC1768 mbed
This year Tufts Hybrid Racing will debut a brand new vehicle, the THR12. Since the THR12 is designed specifically for the Formula Hybrid competition, and not a retrofitted Formula SAE vehicle, it is built from the ground up to capitalize on the unique advantage of a hybrid electric drivetrain.
To control the integration of the drivetrains, however, requires high-speed data acquisition, sophisticated control systems and reliable safety fallbacks. The THR12 must integrate data from a multitude of digital and analog sensors along with information from motor controller and battery management systems. The THR12 then dispatches power to the internal combustion engine or electric motor depending on vehicle speed and stored energy reserves.
What makes this possible is a hardware and software platform from NXP and ARM called the LPC1768 mbed. The LPC1768 mbed is composed of an NXP-based system on a chip hardware platform and high-level libraries developed specifically for the mbed. The heart of the mbed hardware platform is the NXP LPC1768 microcontroller; an ARM Cortex-M3 processor with a high clock speed, plenty of memory and flash and a multitude of peripherals, including full-speed USB2.0 and CAN-interfaces.
The THR12 features four independent mbeds: a Control Node, a Human-Computer Interaction Node and two Sensor Nodes. These nodes communicate over the industry standard CANbus. CAN communication is required for the THR12 since the battery management systems and motor controller both use CAN. We selected the LPC1768 because it has two independent CAN controllers, allowing for safety-critical redundant communication.
The THR12 features two LPC1768 mbed boards specifically for sensor data acquisition and DSP. The sensor nodes record speed from all four wheels, accelerator and brake pedal travel, up and downshift signals, and many other parameters from the motor controller and battery management systems. These sensor nodes filter sensor data before sending data via CAN to the control node for processing. The LPC1768’s onboard 12-bit ADCs and high-speed digital-pin interrupts also reduce external components and overall complexity.
While the LPC1768 microcontroller provides the THR12 with high performance potential, the mbed software libraries unlock it. The provided high-level C++ libraries and user-generated code enable rapid prototyping, a boon for student developers without much embedded C or Assembly experience. In addition, the online compiler and drag-and-drop programming eliminate any cross platform issues, especially on a team with Windows, Linux and Macintosh computers.
Recap + Conclusion
The THR12 integrates many cutting edge technologies and does so with the mbed at its core. Implementing such advanced communication and control systems would likely be out of reach for a student-engineering project without the powerful embedded hardware and easy to use software libraries that the mbed platform provides.
More information on the THR12 can be found on our website, sites.tufts.edu/hybridracing, and be sure to check out the LPC1768 microcontroller at www.nxp.com/microcontrollers .
William Jessup Salisbury, Lead Electrical and Computer Engineer, Tufts Hybrid Racing Team, Tufts University, Somerville, MA. William will graduate from Tufts University in May with a BS in Computer Engineering. He currently serves as the Lead Electrical and Computer Engineer for the Tufts Hybrid Racing Team and is charter member of the Tufts Robotics Club.
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The ARM Connected Community (CC) is an extensive ecosystem covering all aspects of ARM processor-based design, from chip implementation through to system and device design. The CC provides a platform for collaborative innovation, with multiple types of forums for members to work with one another, and with customers, to solve industry challenges, all with the purpose of enabling designers to focus on differentiating features and an accelerated time-to-market for ARM powered solutions.
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