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Lund University Formula Student Engineering - Nordic Comp

Contact Information

University: Lund University

Team Members (with year of graduation): Dennis Honkanen (2016), Sebastian Brand (2016), Måns Fällman (2016)

Faculty Advisers: Krister Olsson

Email Address: dennishonkanen@gmail.com, njs.brand@gmail.com,elt11mfa@student.lu.se

Submission Language: English


Project Information

Title: Designing and implementing a Chassis Control Module for a Formula Type Vehicle Using myRIO

Description:

Using the myRIO device as the main unit in a rugged and high-performing system that continuously logs data from 27 sensors and performs real-time analysis and control to simplify driver interaction and ultimately improve lap times at competitions.

Products:

NI Hardware used:

NI myRIO 1900

NI Software used:

LabVIEW myRIO package

Other Hardware:

XMOS XK1A


The Challenge:

Designing and implementing a chassis control module for a formula student vehicle that offers easy driver interaction, shift and clutch control, and high-performance data logging.


The Solution:

20140802_18-57-38_8528_singh-L.jpg

Figure 1: The LUR6 competing at Hockenheimring in August 2014.
               (Picture, Courtesy of Formula Student Germany)

Students at Lund University were building their team’s sixth formula student vehicle to compete at Silverstone and Hockenheim in the summer of 2014. They needed a chassis control module (CCM) that could complement the engine control unit (ECU) and offer extensive data logging and rugged control capabilities.

We followed three design criteria for the CCM: extensive data logging, simplified driver interaction, and extreme reliability. Due to the amount of vehicle testing planned, data logging and data management were important to simplifying and optimizing test procedures. By easing and minimizing driver interaction with the vehicle, the driver can focus on the track and improve lap times. For reliability, driver input and control must work flawlessly during operation. Shift and clutch control are essential for vehicle operation. If shifting or clutch actuation fails, the vehicle might have to forfeit the race.

System Description

The system consists of two parts with different requirements. The real-time control part, responsible for clutch control, gear engagement with spark cut, brake light triggering, and driver interfacing, focuses on response time and stability. Alongside that part is a high-rate data acquisition system that logs and, to some extent, processes data from 27 sensors for wheel speed, damper movement, accelerometers, and driver behavior, among others. The main focus is to handle all incoming data in an effective way.

Schematic.png

Figure 2: System Schematic

Hardware Considerations

Embedded systems with different requirements are often separated in hardware to make sure that the timing requirements for the real-time control are met regardless of variations in data rate from the sensors. We considered other solutions, including a simpler ~20 MHz microprocessor running the real-time control due to its deterministic properties and running the data acquisition on a CompactRIOcontroller. Because of the real-time properties, we realized we could use the LabVIEW reconfigurable I/O (RIO) architecture to run both subsystems with no timing problems or deadlocks. Since weight is a major concern in formula student cars, we decided not to use CompactRIO and instead  chose the myRIO embedded device and LabVIEW software for our final deployment since the myRIO is lighter.

Our systems use 33 of the ports on the myRIO, excluding power and ground connections, which makes the hardware connector types important. They must be reliable and easy to connect. The standard connectors on the myRIO meant that we could connect the PCB containing all sensor prescaling and filtering using a flat cable connector. This simplified installation, alterations, and reparations significantly.

An automotive system must withstand quite an amount of physical abuse, including vibrations, impacts, and a wide temperature range. This creates other hardware concerns. We were most concerned about the vibration part of the system since the 450 cc one-cylinder engine produced substantial vibrations in the chassis, and every component on the control system must withstand this. Several miles of testing showed that the myRIO fulfilled these criteria.

Ratt.JPG

Figure 3: Steering wheel model, with shift paddles & several button inputs visible.

Versatility, Compatibility, and Fast Software Iterations

The versatility and compatibility of the myRIO unit helped us integrate it alongside the ECU using CAN. This opened up the possibility of interfacing with engine parameters in a much more coherent and efficient way. We took advantage of the LabVIEW environment for fast software development and easy reconfiguration between software iterations. This was crucial during testing when we needed to make small software changes in between testing runs. This is partly due to the workability in the LabVIEW environment, but also due to the WiFi capability of the myRIO. We did not have to open up enclosures and physically connect the myRIO with the development laptop, which decreased the time between code iterations out in the field.

Conclusion

The hardware properties of physical robustness, computational power, and embedded functions (A/D converters, selectable pull-up resistors, and more) for the myRIO definitely meets the requirements for our system. From the software side, LabVIEW offered a fast development process (days) with easy debugging and many built-in real-time programming considerations that probably lowered the bug count substantially. By using the NI myRIO in the LUR6, we successfully showed that is possible to use an educational tool such as the NI myRIO in real hostile environments.

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Figure 4: The LUR6 racecar during the wet skidpad event at Hockenheimring in August 2014.
             (Picture, Courtesy of Formula Student Germany)

logging.jpg

Figure 5: Logging data from some of the sensors during testing. The data is from a bit more than one lap on a test track.

Contributors