Student Projects
Contact Information
Competition Year: 2016
University: University of Sheffield
Team Members (with year of graduation): Dylan Tomlinson (2018)
Faculty Advisers: Dr Tom Slatter
Email Address:
Country: UK
Project Information
Title:
Description: An electronic throttle control (ETC) system for use on an FSAE racing car
Products:
NI Hardware:
NI MyRIO
NI Software:
LabVIEW 2014
LabVIEW FPGA Module 2014
LabVIEW Real-Time Module 2014
LabVIEW control and simulation 2014
LabVIEW MyRIO 2014
Other Hardware:
Brushless DC motor
Brushless DC motor driver
Various rotary and linear analogue absolute position sensors
ECU
The Challenge:
The ETC system is a drive-by-wire system that controls the throttle valve of an FSAE racing car; it is designed to meet the technical requirements provided by FSAE. The system includes a throttle valve actuator and hardware that runs the control software. It is envisaged to be highly reliable and able to detect faults in case of malfunction to ensure complete safe operation. This is achieved using multiple redundant sensors and incorporating plausibility laws in the control software. The ultimate aim is to interpret the torque requested by the driver through the accelerator pedal, control the position of the throttle valve and give an ability to control the engine speed.
The use of drive-by-wire systems are common place in the commercial automotive industry however it has only been recently allowed within the FSAE competition rules, thus this application of the technology is in its infancy. The system is a safety critical system and so steps have to be taken to ensure a safe and robust system. Appropriately, the rules for student designed ETC systems are strict and the system must meet a set of technical standards for their use to be allowed.
The ETC system must be able to detect any faults that may compromise its safe operation, such as inaccurate sensor data and remove power to the actuator in which it will mechanically return to the closed position. The hardware – a MyRIO - must assimilate all sensor data and continuously poll for plausibility errors while providing real-time control of the throttle valve actuator and control the engine speed during a gear change.
The Solution:
Through using the MyRio, a PID controller can be used to control the actuation of the throttle valve using the FPGA and a RT environment can be used for plausibility error polling and handling the driver accelerator input to send to the FPGA – taking command and controlling the engine speed in gear changes. The MyRio is ideal as it is lightweight and has low form factor, with its complement of digital and analogue inputs for the various sensors used plus it is simple to compile code to using the LabVIEW MyRio software offering a quick turnaround during prototyping.
As this type of project is a first for the Sheffield Formula Racing team, it was decided to use analogue outputting sensors in efforts to simplify their integration to the MyRio device. The accelerator pedal position sensors and throttle position sensors all output a variable analogue signals, there are two sensors for both applications as to compare signals and make sure they are credible this is done consistently in the RT environment amongst other checks to ensure the device’s safe operation. The FSAE rules give several other plausibility checks that if failed, will remove power from the unit.
The FPGA is tasked with PID control of the actuator valve, the PID values of the control system are written to it from the RT host to allow for tuning during integration to the race car. The FPGA script writes to an analogue output to the brushless dc motor driver.
When the driver disengages the clutch for a gear change it is detected by the RT host script and the system then ignores the drivers throttle request and attempts to match the engine speed to the transmission speed, to do so the RT script receives car speed and engine RPM data through serial communication with the engine control unit. It then uses a second PID feedback control system to control the engine speed. When the driver reengages the clutch the driver throttle request is then obliged, this will help smooth quick gear changes.
In efforts to push the performance envelope of the race car, it was decided to develop an in house roller barrel throttle valve, having better flow properties than the currently used butterfly valve types. This can be seen in figure 1. Using LabVIEW control and simulation toolbox we have taken steps to model the proposed throttle body actuator, helping to finalise the design.
Figure 1: Electronic Throttle Control Assembly
Currently the first iteration of code for control of the actuator valve is completed and is ready to be tested at an alpha stage. The code for controlling engine speed during gear changes is still under development. The manufacture of the throttle body design is delayed as it was originally designed to be manufactured using additive manufacturing techniques, but unfortunately these services ceased to be available. It has been redesigned to be manufactured using traditional machining processes. Assembly of the throttle body and tuning of the control system can begin following the manufacturing of throttle body. A phase of testing to verify the system works as it designed and a working first prototype should be ready to be showcased at the FSAE UK 2015-2016 competition and integration onto the SFR007 car, for the 2016-2017 FSAE UK competition.
