Solenoid Actuation for Electronically Controlled Valve Control
Advanced Actuators Research Group
Joe Bonivel
Advisor: Dr. David Rocheleau
Mechanical Engineering
(803)777-5648
Our Mission
Typical 4 stroke engines have fixed intake and exhaust valve timing and the designer of the engine chooses the timing to achieve certain performance goals. Once the valve characteristics are designed and mounted, the timing is fixed unless a major mechanical change is made. Honda Automotive has recently introduced a new form of mechanical variable valve timing that changes the cam profile at different speeds. BMW automotive valvetronic is another mechanical variable valve timing method that uses a cam profile to move the cam into different positions at certain speeds. Both mechanical approaches still have their limitations due to the cam profiles that are used. Electronic variable valve control or camless engines offer the possibility of unlimited variations in valve timing. Our concept is to use solenoids to actuate the valves and a micro-controller to implement algorithms to open or close the valves at the right time. With electronic control, the designer is no longer constrained to fixed cam profiles to achieve desired performance goals. Electronic control offers the possibility of engines having the performance of a Coverette with the fuel economy of a Honda Civic.
My Research
To help convert the existing engine into a camless engine, a microcontroller was needed in order to implement electronically controlled valve timing. I used Matlab/Simulink and controlDesk/Dspace as a median between the input and output for control of the solenoids actuating the valves on the Honda GX 31 engine. The inputs were in the form of a square wave, 5 volts high and 0 volts low, coming from the BEI optical encoder. The optical encoder had a resolution of 1800 cycles/revolutions that correlates to 5 cycles for every degree of rotation. Matlab/Simulink processed this information from the optical encoder to determine the position of the shaft and, thereby, the cycle so that it can facilitate the firing of the solenoids to open the valves. MatLab/Simulink was also be tasked with controlling the duration of the valves opening through the computation of the area under the curve of the cam profile resulting from benchmark testing of the engine from crank angle versus valve lift. The program in Matlab/Simulink will have to output to two simultaneous switches, one for the exhaust valve and one for the intake valve. The exact output from Matlab/Simulink was the 5 volts sent through a relay to the solenoids. The 5 volts was sent to pins 43 &44 on the Dspace board, this pins directly controlled the voltage to the solenoids.
Links
Advanced Actuators Research Group (AARG) specializing in Mechatronics research and development projects.
University of South Carolina Mechanical Engineering
How typical 4 stroke cycle engines work