07.6 - Conclusions and Future Work

This project successfully demonstrated that we could mechanically power Jansen Legs by a manual gear transmission system. We used the manual gear transmission system to control how fast the Jansen legs would move. Kinematic analysis was conducted to evaluate how the leg motion and the gear system behaved together. Unlike Theo Jansen’s original Strandbeest, which is wind-powered, our design is powered by manually operating the gear transmission to generate the desired walking motion.  

Our main goal was to prove that we could change the speed of the Jansen legs by implementing a manual gear transmission system with a dog clutch. We were able to successfully verify that we could vary the speed of the legs by choosing different gear engagements. Overall, the gear system and the Jansen Legs functioned together as intended.

Lessons Learned

1. Time Management in Design and Manufacturing Phases: This project really demonstrated the importance of allocating a sufficient amount of time to the manufacturing process and not just the initial design. While the CAD worked perfectly fine, manufacturing constraints such as tolerancing and materials can impact the design if not looked at earlier. For example, we spent a lot of time sanding the inner diameter of the blue support because of tolerancing issues. We also had really tight joint fits for our Jansen Legs, so we had to add lubrication oil. We learned that things like this arise very quickly in the manufacturing process, so allowing more time for manufacturing allows for design adjustment and verification before assembly.

2. Gear Manufacturing: This project also highlighted the importance of considering the best manufacturing methods for functional requirements. For components that require high precisions, such as gears, we realized that using commercially manufactured parts could significantly improve our integration issues for the automatic transmission and the manual transmission. We quickly learned that additive manufacturing is better suited for custom or low-precision.

3. Selecting the Right Component: We also learned how essential it is to select joint mechanisms that promote the quality of motion. We used 3D printed rotational joints for convenience and quick manufacturing. However, they did introduce friction and inconsistent motion due to uneven surfaces. Lubrication was a solution, but we quickly learned that excessive lubrication can reduce the grip of certain components and lead to variability in joint behavior. This really brought home the concept of choosing the right components. Bearings would have been a better solution since they provide low friction with their built-in lubrication. Although bearings can be heavy-weight, this can be dealt with by using lightweight bearings.

Future Work Ideas

1. Integrate Electromechanical System: The current design is purely mechanical, but it has the ability to be integrated with a electronic control system. This electronic system would have an Arduino as a microcontroller that would process user input and send respective commands to the system. We could also implement a push button that would be pressed by a person. By using the push button, the user has the ability to toggle the system from OFF to ON when the motor is running. The stepper motor and the stepper motor driver would then go through with these commands and rotate the motor to then drive the Jansen legs.  We did implement a portion of this in our project, but since we didn’t have access to a high torque stepper motor at the time, we weren’t able to conduct as much of testing as we wanted.

2. Integrating Bearings and Commercially Manufactured Gears: In the future, we could switch the 3D-printed joints with bearings. Integrating bearings would allow smoother motion of the Jansen legs and also get rid of the need for any additional lubrication because bearings are already pre-lubricated. We can account for additional weight by making sure the weight is equally distributed across the mechanism as well as try to purchase smaller bearings. We could also order commercial gears and integrate them into the system instead of sticking to our 3D-printed ones because manufactured gears are more precise, leading to better meshing of teeth, reduced friction, and increased efficiency of the system overall.

3. Four Leg Configuration vs Two Leg Configuration: In our current design, the Jansen mechanism is stationary for the sake of demonstration. To enable forward motion, we could add an additional pair of Jansen Legs to the opposite side. The 2 pairs of Jansen Legs on either side would be in alternating phases to produce a gait-like motion and promote stability while moving forward.

Tips for Future Students

1. Print Backup Parts: If you have small parts that are 3D printed, be sure to print at least 2 backups, especially if they are delicate. Since they have a higher chance of breaking during assembly, printing extras can serve to your advantage.

2. Keep Team Roles Flexible: It can be beneficial to have multiple team members working on each subsystem, especially when you have to troubleshoot hardware, electronics, or code. This way you can troubleshoot as a team instead of waiting on one person to fix it. The shared ownership reduces delays and allows everyone to grow in different knowledge bases.

3. Start Early and Try to Follow Timeline: We highly recommend starting the project as soon as possible. Creating a timeline is easy, but sticking to it is not so easy. Be sure to make a timeline that has checkpoints for CAD, manufacturing, and assembly. Even though it is not possible to always follow the timeline, be open and communicate with your team members if you cannot get something in before a deadline so they have enough time to find another solution.

Acknowledgements

This project was challenging but incredibly rewarding. We would like to thank Professor Petlowany, Cade Wetherill, Min Geun Kim, and the Texas InventionWorks Team for their guidance, feedback, and access to fabrication tools. Their support in 3D printing, laser cutting, electronics, and prototyping was invaluable to the success of this project.