Objective

• The client teamed up with Generate to design a smart cable lock for dockless e-scooters that deterred theft and reduced urban clutter

• The client was a past Generate client who had then teamed up with another professional product development firm to further develop the lock

• By the end of the semester we were responsible for creating a pre-production prototype

• My role in the project was as the project lead. I was responsible for scoping the project, creating and executing a project plan, and interfacing with the client as well as support in technical work wherever necessary.

Design Path

• The design started with me creating a scope for the project and establishing a product requirements document (PRD) with the client

• After receiving a hand-off design from another product design firm we began work reverse engineering it and identifying areas of improvement

• It became apparent there was little to no engineering intent many of the design decisions made on the initial model. The team began redesigning the lock in accordance with the PRD from the ground up to add functionality and improve the design to make it more intuitive.

• The module modified the most was the locking chamber. The redesign changed the design from one that used a motor and complex linkages to a single action system actuated by a solenoid. The new design provided more security and durability while reducing the amount of moving parts.

• The firmware and software were also designed from the ground up built fundamentally on the user story developed early in the project. The user story I created heavily guided the development of the state machine and influenced the functionality of the software application.

• Most of the electronics came to creating a custom PCB and integrating the functionality of a number of electrical systems. Another major change over the last model was the addition of a tripwire. Managing the connection of a tripwire ended up being much more difficult than originally thought. The wire routed from one terminal on the PCB to a slip-ring in the reel assembly around the cable (under the poly-urea jacketing) and into the locking pin. The locking pin made contact with a conductive plate inside the locking chamber which in turn connected to the other terminal on the PCB. Managing the integrity of the signal while avoiding false positives proved to be a challenge for the electrical team

• All the subsystems were contained in a redesigned enclosure. While the final model was 3D printed, the design could be easily injection molded. Throughout the design process the team maintained a constant wall thickness, minimized additional actions, and avoided thicker geometries as well as other pitfalls in injection molding design

Challenges

• The biggest challenge posed in this project was the fact that we had to redesign the project from the ground up. We initially thought the scope of the project would entail making minor design changes to get the lock ready for manufacturing but given the functionality that the client was looking for, it was clear that the given design was not sufficient. On the tight timeline of a Generate semester, any setback can be costly to accomplishing the scope of a project. That being said the team was able to quickly adapt achieve all deliverables. By taking a manufacturing first approach to the redesign we were able to make a new, better, more produceable product.

• Another significant challenge we faced was deciding on a communication protocol between bluetooth, NFC and cellular. Each protocol had its advantages and drawbacks. In our initial vision for bluetooth, the system had a number of security vulnerabilities. Cellular posed challenges ensuring a consistent signal along with mixed reports as to the dependability of the signal. NFC was more secure and reliable, however lacked widespread adoption amongst the cell-phone users. After further research the team devised a secure and simple way to use bluetooth to accomplish our goals.