E-CVT

The goal of this project is to create a electronic actuated CVT for Chico State's SAE Baja team to give the car more control over its transission gearing and power output. Using a linear stepper actuator and a pivot arm the hope is to accurately and quickly cycle through the gear ratios with a drivers input. This project is fully designed, a 1:1 3d printed model is being made and a full prototype has been machined.

Below is the code structured to enable easy tuning for the transmission. The number of gears, steps taken per gear and gear shift speed can be easily changed internally in the code or also externally with dials. The code is safely coded to where no errors can be made to overtravel the transmission out of its operating region and bind against itself. If the system ever looses power it will automatically home to the nuetral position when power is restored to regain its known position. In order to get consistant 100ft acceleration runs a launch sequence was integrated into the system to minimize driver errors. If both the Up and Down shift buttons are pressed within 20ms of eachother the system goes into a luanch mode. The driver will press full throttle and the vehicle will take off the line when the driver releases the buttons. The rate at which the transmission goes throughout the gear range is driven by the excel plot shown below. 10,000 points from that plot are converted to an array format and uploaded to the arduino's internal memory. While this system has been very succesful more tuning can still be done to obtain a better time.