Smart Electric Scooter Lock
During this project, my teammates and I worked with the venture Mount to create a smart electric scooter lock. I was tasked among my team to design and develop the locking mechanism that will go onto this modular scooter lock. After some discussions with the client and the team, a few design constraints were laid out.
1. This must be a retractable lock design
2. The lock will need to be able to passively lock when tip is inserted
3. The lock will need to be electronically unlocked
There are a number of designs that fulfill these constraints, but after some research online on other smart door locks, regular retractable locks, and smart bike locks, I decide to move forth with a design utilizing a solenoid actuator.
Lock Version 1
This lock was based on my research into retractable locks and their common design with their reel head tips. The tips are have these mushroom head like shapes where another spring loaded component is ready to snap into place to "lock" the tip from moving backwards. This design allows for a passive locking system because regardless of the actuator, a solenoid in this instance, the tip of the reel can be pressed in and locked into place. Only when the solenoid is activated can the arm move and release the pin.
Issues with Prototype V1 Design
After prototyping this design without the implementation of a spring, most likely a torsion spring, I quickly understood the flaw with this specific iteration. The placement of the pivot point for the arm rotating arm that is meant to lock the pin is in a position where any sort of pulling on the pin head would result in the arm rotating so that the pin can be freed. An analysis of free body diagram of the force interactions with this design show that any pulling on the pin results in a moment on the arm that can only really be prevented by adding a torque opposing the direction of the moment created. For this specific design layout, this would mean a very strong torsion spring would need to be placed if the lock is to prevent any accidental unlocks, but then this would correlate to needing a actuator that can pull or push against this torque to open the arm to release the lock. So to solve this problem easily, I just moved the pivot point of the arm so that the moment generated from pulling on the pin will not induce the arm to rotate open.
Lock Version 2
The biggest changes in this iteration of the lock design include moving the pivot point of the arm so that a moment can not be created to open the arm when the pin is pulled on, the arm shape, the addition of a torsion spring, and a locating feature for the solenoid.
Passive Locking and Electronic Unlocking
The videos below demonstrate the active unlocking and passive locking features design. Once the pin is inserted, the arm locks on and traps the pin until the solenoid is powered on, pulling on the arm and pivoting open to release the pin.
Retractable Reel Cut Protection
In the event that the retractable reel on the smart scooter lock is cut, the team agreed that having a signal wire adjacent to the steel wire will allow the device to understand whether the reel has been cut, or if pinhead is properly locked. With this in mind, I incorporated a signal wire through the pinhead by using a spring loaded pin connected to a wire and an accompanying copper plate to press against. Below are photos and videos showcasing these adjustments.
Below is a video demonstrating the ability for the pinhead to pass a signal through it.