Table of Contents
Testing Results and Analysis
ME Test #1-Force Output of Cylinder
Solenoid was unable to meet the required 37.5 lbs on the bench test. Only once was the solenoid able to provide 24 lbs. Therefore, the cylinder fails the bench testing. Failure could be due to the inability to switch the cylinder on using the clean signal provided to the mosfets by the microcontroller. We were just touching the wires to the battery terminals which does not provide a clean switching signal to the mosfet and since the ability to flow current through the mosfet is dependent on the gate voltage, then we might have not been able to provide enough current flow to the electric solenoid. Force is directly proportional to current flow through the cylinder. Additionally, we were basing the opposing force on Bimba power factor of 0.4 for our cylinder. Foutput = 0.4 x Air Pressure. This was an assumption and could have been wrong. Finally, we were using a poppet style relief valve to relieve the cylinder of pressure during solenoid activation. This style of relief valve is not very accurate and it would have been much more accurate to use a ball and seat style valve that is more sensitive to pressure changes. This valve was not readily available.
ME Test #2- Shift TimeSolenoid shift time was under the required 0.1s on the bench. Using the force test stand the opposing cylinder was pressurized and a magnetic reed switch was used to determine when the cylinder had reached the full shift position. An oscilloscope was used to measure the activation voltage across the gate and the turn on voltage of the reed switch. These graphs were overlayed the time to activate and full stroke of the solenoid were determined to be the full shift time. The results provide a consistent 50 ms of shift time which is half of the customer requirement.
ME Test #3- TorqueShift Torque without Spark Cutout:
- Shift force without spark cutout was determined during MSD I with the rear wheels raised providing no loading on the wheels. The force was determined to be 37.5 lbs.
Shift Torque with Spark Cutout:
- Spark cutout was provided by momentarily switching the off/run/off with the rear wheels raised and a torque wrench placed on the shift lever mounting bolt. After performing a trial test this was determined to difficult to time the spark cutout and get a measurement with the torque wrench during this short period of time. Since you were required to move the torque wrench slowly to hear the clicking
EE Test #1The RPM and TPS signals were not actually recorded due to a lack of data acquisition equipment available. The data that was used was based off of data given from Polaris. The system functionality was tested successfully in the lab on a bench. The cylinder responded to different signals supplied from a function generator and the program functionality was verified. When integrated on the ATV the program was tested by applying scenarios to test several up and down shifts and points in the program were modified to optimize the points. The RPM/TPS relationship was read from the graph pictured below.
EE Test #2The amount of current that is able to be drawn from the battery is important to ensure that the system can get the required amperage to complete a shift. The battery proved to draw over the 40A required and therefore was sufficient for the system without having to add an aftermarket stator.
Gear IndicatorFactory gear indicator was removed and fabricated by the team members. Four additional copper contact posts were fabricated as well as an additional contact for the transmission drum. A resistor was placed inline with the 5 volt supply to 1st post, then resistors were wired in series between each remaining post to provide a changing output signal voltage. The original wires were reused as well as the waterproof connector to retain serviceability. With the indicator installed, resistance was checked for each gear position and then 5 volts was supplied and output voltage was checked for each gear position to verify a difference in voltage at each gear. The gear indicator works properly, but if slightly out of gear the voltage will automatically ground completely and read a voltage output equal to the neutral position. The following voltages were recorded for each gear:
Gear DisplayThe gear display was installed to notify the user which gear the ATV is and what exactly the system is doing. Using the signal from the gear indicator mounted in the transmission the display reads out the gear whether it is changed manually, with button or automated. The display is wired but not yet integrated to flash a up or down arrow when the system is completing an up or down shift during button or auto shift. The bad shift indicator, also not successfully operational as of yet, is there to show the user that a button input at a certain point would not be safe for shifting the transmission. The stock indicators could not be tested as the failure modes that would require them to light up could not be simulated.
Full System Functionality Testing
Button ShiftingAll five gears were tested using button shift mode. The following requirements were met during all up and down shifts during button mode:
- -Spark was cut
- -Shifting remained smooth
- -Downshift at a very high RPM is not possible
- -Downshift from 1st gear not possible
- -All upshifting 1-5 and Downshifting 5-1 possible
Modifications were made to program regarding downshifting. A TPS value was required and when decelerating the user often removes input to the throttle which was keeping the program from completing a shift. This limitation was adjusted due to this scenario.