Milestone 7: Electric Clutch Verification
Electric Clutch Verification
Last year's drivetrain design used an Ogura general purpose clutch as seen in the image to the left. The clutch maintains 100% efficiency, with zero slipping. The current configuration of the clutch introduces a problem upon engagement. As the clutch is engaged, the tractor accelerates at a rapid rate, and this introduces safety concerns and discomfort for the driver. Rapid acceleration is also an issue when competing in the maneuverability performance event at the annual competition where the driver must stop and go repeatedly to maneuver through the tight course. The verification testing was performed to determine if this issue could be resolved by reprogramming the clutch or if this electric clutch will have to be totally omitted from the new design. The "Physics Toolbox Accelerometer" App was used to record data of the acceleration of the driver during the clutch engagement process. During the test, the coding of the electric clutch was changed using the Danfoss Plus+1 system. The values changed to the code were the ramp duration and the maximum duty cycle. The ramp duration is the time frame from when the clutched is initiated and when it actually engages, and the maximum duty cycle is for the pulse width modulation (PWM) output to the clutch. The accelerometer app recorded the data for each variation of code tested on the tractor.
Wildcat 3122 Code
The testing was conducted using the Plus+1 code from last year's Wildcat 3122 tractor. As mentioned above, the testing variables were the maximum PWM duty cycle and ramp duration. Both of theses parameters are defined with the ramp function block of the code. Modifying these parameters changes the electrical input to the clutch which should alter how the timing and speed of engagement.
Testing Results
100% Max Duty Cycle, 2 Sec Ramp
100% Max Duty Cycle, 5 Sec Ramp
50% Max Duty Cycle, 5 Sec Ramp
25% Max Duty Cycle, 5 Sec Ramp
10% Max Duty Cycle, 2 Sec Ramp
Summary
The five trials of different ramp duration and maximum duty cycle variations as shown above were conducted and data was recorded using the accelerometer app. Analysis of the testing results proved that decreasing the magnitude of the acceleration felt by the driver is possible through tuning the activating algorithm for the clutch. However, all configurations tested resulted in an acceleration spike of some sort. This sudden surge results in degraded controllability and manueverability. In conclusion, the testing indicates that using the electric clutch in a stand alone configuration is possible, but it might not be the best option. Further testing will need to be conducted in which the electric clutch is compared with other types of clutches in order to determine which component is best suited for the application.
