What I Contributed:

Initially, I considered using a small spring to achieve low or zero preload. Still, it led to instability in the helicopter mast. I shifted gears and experimented with a small torque wrench, which introduced a more significant preload while stabilizing the mast. Seeking an optimal solution, I devised a gravity offloader to counteract the preload caused by the small spring and the helicopter's mass.

The gravity offloader was designed with coarse and fine adjustment features to meet customization requirements on the helicopter mast. Surgical tubing and a force gauge were employed to address the critical need to avoid adding inertia to the system. The device also incorporated several off-the-shelf components, but two custom adapter plates were necessary. I designed and provided the detailed GD&T drawings for these adapter plates. These parts were crafted in-house within our machine shop. 

Challenges Encountered:

• Initially faced challenges with a substantial preload between the helicopter interface and the spring stack system during development testing. This interface on mars when in use would have zero pre-load. 

Solutions Implemented:

• Experimented with using a small spring to achieve low or zero preload, but encountered instability in the helicopter mast.

• Shifted focus to experimenting with a small torque wrench, which introduced a more significant preload while stabilizing the mast.

• Devised a gravity offloader to counteract the preload caused by the small spring and the helicopter's mass. Designed the gravity offloader with coarse and fine adjustment features to meet customization requirements on the helicopter mast. Employed surgical tubing and a force gauge to avoid adding inertia to the system.

• Designed and provided detailed drawings for two custom adapter plates necessary for integration and fabricated the custom adapter plates in-house within our machine shop.

Lessons Learned:

• Gained experience in experimenting with different solutions and adapting to unforeseen challenges.

• Developed proficiency in designing and fabricating custom components to meet specific project requirements.

• Enhanced understanding of system dynamics and the importance of stability in mechanical designs.

What I Contributed:

During the final phase of my summer project, I helped run the spring stack shock testing. To facilitate the process, I provided detailed instructions on IBAT for assembling and resetting the test stand between tests. My primary responsibilities involved operating the IMUs and accelerometers and conducting in-depth IMU and video data analysis.

Below are two IMU088 runs. The top graph, representing run 13, utilized crushable C and felt as damping materials. My focus was on detecting saturation in the IMU, and the abrupt stop of the green line at the 24 g mark indicated saturation. In contrast, the bottom graph, representing run 11 with 45 millimeters of felt as damping material, showed a clear data range without saturation, signifying successful testing.

Post-test, I delved into video data analysis. Using Trackr, a program designed for motion tracking, I uploaded the videos to track the motion of the springs as they unfurled. This verification process ensured we achieved the targeted impact velocity of approximately five m/s. The bottom photo provides a snapshot of the Trackr program during run 13. This comprehensive analysis was pivotal in confirming the success and accuracy of our spring stack testing.

Challenges Encountered:

• The IMU was saturating due to poor damping materials.

• There was no physical way to measure final velocity before impact to ensure repeatability.

Solutions Implemented:

• Utilized unconventional materials for damping which led to smaller shocks to the IMU

• Employed Trackr program for video data analysis to track spring motion and ensure targeted impact velocity.

Lessons Learned:

• Importance of selecting appropriate damping materials to prevent IMU saturation and ensure accurate data collection.

• Proficiency in utilizing motion tracking software like Trackr for comprehensive video data analysis and verification purposes.

What I Contributed:

The device I was modeling operates sequentially: first, a pin, powered by a spring, moves downward and clears the path for a component. Once the element is free from contact with the pin, it descends, also driven by a spring. The overall module is released with both components in motion, propelling the helicopter into the air.

To conduct the dynamic analysis, I began by defining the spring characteristics for the pin and component, both disc springs, and the overall module, which is a compression spring. In addition to spring characteristics, I needed initial inputs for position and velocity. While velocity was straightforward since it started at rest, choosing the position was more complex. I opted for displacement, measuring the distance from the top of the spring to where the spring is neutral. This choice simplified coding and resulted in more user-friendly and readable output.

The logic for coding the springs in MATLAB also posed challenges, as they didn't start simultaneously and had a staggered start. I implemented a function in the code to initiate a spring only when the preceding spring had moved 3 millimeters. Additionally, I incorporated a function in the code to shift the hard stops by 45 millimeters to explore the impact of moving the springs' end positions. It's worth noting that the springs, due to their length, couldn't accelerate throughout the entire motion. After reaching their neutral state, I assumed they continued to move at a velocity influenced only by friction.

The three graphs below illustrate displacement versus time, velocity versus time, and acceleration versus time plots for the three springs. Vertical lines in the displacement versus time plots indicate the positions of the overall module when the pin and component reach their hard stops. This dynamic analysis provides valuable insights into the complex interplay of components within the mechanism.

Challenges Encountered:

• Sequential operation of the device with multiple components driven by different types of springs posed challenges in conducting a dynamic analysis.

• Complexities in defining initial inputs for position and velocity, especially considering the staggered start of the springs.

Solutions Implemented:

• Defined the spring characteristics for each component, including disc springs for the pin and component and a compression spring for the overall module.

• Chose displacement as the measure for position, simplifying coding and enhancing output readability.

• Implemented logic in the code to initiate springs sequentially based on movement thresholds and adjusted hard stops to explore end position impacts.

• Accounted for the limited acceleration of springs due to their length, assuming constant velocity post-neutral state influenced by friction.

Lessons Learned:

• Gained proficiency in defining spring characteristics and establishing initial inputs for dynamic analysis.

• Overcame coding challenges related to staggered spring starts and integrated functions for accurate simulation.