Lower Bound Testing

SUMMARY

 The Hot Box

The Hot Box

This week we were able to streamline our hardware setup because of the “Hot Shocks’ Hot Box,” designed and laser cut by Justin. With 5W oil in the shock, we established maximum, minimum and optimal temperature set points for shock operation at different RPMs and verified that the hysteresis controller works under varying conditions. Our maximum operating temperature was determined to be 80℃ based on the potential operating temperature for an actual shock and because of issues Alex had with shock modifications for the next lab group when the oil was beyond 80℃.

As can be seen in the figure below, our controller stabilizes the forces within the shock by forcing decreasing the time required for the oil to reach steady state temperature. Once the oil has reached the set temperature, the forces have much less variation, which was one of our original goals.

Force(green) and Temperature(blue) vs. Time

Next week is our final week in lab, and we are hoping to test Eric’s PID controller, which could decrease the slight temperature ripples that have been present in recent tests at lower RPMs. We are also hoping to implement a version of the hysteresis controller that does not involve a micro-controller so that future groups can utilize our system more easily. Although we will miss our time together in lab, we are very happy with everything we have accomplished so far and are looking forward to collecting as much data as possible next week.

Thanks for reading!
-The Hot Shocks

INDIVIDUAL THOUGHTS

GRACE

This week I worked with Les, Turner, Justin, and Christy to characterize the optimal setpoint for 30 and 90 RPM. We attempted to not only determine the optimal setpoint, but also estimate minimum and maximum set points for the given RPMs.

Additionally, for next week, Justin and I are working on creating a panel within the box for a potentiometer. The potentiometer will be used to easily adjust the temperature setpoint. Currently to adjust the setpoint, we have to adjust the arduino code, and re-upload it to the arduino. Using the potentiometer, we can simply program the arduino to read the voltage input from the potentiometer, and map that value to a given temperature. This is a more realistic user friendly option. We will laser cut the panel so that it fits within the box.

TURNER

Before lab this week, I edited the LabView VI to display plots of oil pressure and nitrogen pressure vs. time. Although we did not export this data after our tests this week, it was interesting to note that, although the pressures increased with temperature, the pressure variations decreased with more constant temperatures. During lab, I ran the LabVIEW VI and helped the rest of the group collect data for maximum, minimum, and optimal set points at different RPMs. In the coming week, I plan to help Les eliminate the Arduino from the hysteresis controller and continue working on the final report. I’ve been very satisfied with the way the Hot Shocks have worked together this semester, and I’m a little sad to see our time in lab come to an end next week.

LES

Circuit diagram for the hysteresis controlle

This week we determined more operating setpoints for the heater, this time with 5W oil at 30 RPM and 90 RPM. We found that the lowest operating temperature for the heater with 5W oil at 30 RPM was 37℃ - coincidentally, the homeostatic temperature of the human body. The upper limits for both 30 and 90 RPM were determined by safety constraints rather than the physical limits. Most of this week’s lab session was data collection, but for next week I plan on having a complete hardware controller developed for the hysteresis thermostat. This new controller will eliminate the Arduino and allow the user to change the reference temperature by adjusting a knob.

CHRISTY

I worked with Justin, Grace, Turner, and Les in lab this week to gather more data about the operation of the controller with 5W oil under different conditions. We began by running the shock at 30 RPM and modifying the temperature set point until we determined the minimum value that allows the controller to function properly. We determined that the lowest that the shock should be set at for 30 RPM is 37℃. We then repeated the process for 90 RPM. Outside of lab, I have been working with Turner on our final report and presentation. Next week, we plan to gather our final data that will help verify the success of our hysteresis controller and test out the functionality of our PID controller.

ERIC

This week I used the characterized model of our shock dyno plant and our PID controller to test different PID tunings in simulation.  From the initial simulations it  became apparent that the integral gain needed to be limited otherwise the control input would saturate.  Several tunings were simulated showing the ability to control for a variety of factors including: rise time, settling time, and percent overshoot.  At Spencer’s suggestion, noise was added to our simulation.  After simulating several different tunings, the steady state error, rise time, settling time, and percent overshoot were analyzed.  These results will be discussed in detail in our final report.

JUSTIN

Before lab this week, I remade the wiring harness to include longer leads for the heaters and a box to contain the setup. In lab it seemed that the setup took much less time because the hardware was already set up in the box and only needed the wires to be plugged in and the heaters to be ziptied to the shock. I’m happy with how the box came out and think it will help the final presentation look better.