Introduction
Have you ever observed a busy bar counter where the bartenders not only need to interact with customers while preparing various cocktails but also have to open a bunch of cans manually in a short time? Have you ever experienced the inconvenience of a hand or finger injury/trauma that made the can-opening task suddenly hard? Do you or your friends always want to keep good condition of your vulnerable nails? The can-opening task can be bothering or inconvenient in many cases. To solve this, the automated robotic can-opener of our project aims to eliminate manpower and make our lives much easier!
Problem Statement
Many currently used automated can openers require user input to open a can. We need a can-opener mechanism that will autonomously locate the tab of a can and to open it with adequate force. The complexity of our design stems from determining the correct link lengths, angles, and force such that the 'end-effector' of our mechanism will consistently translate and rotate to pull the tab of the can open. The use of simple joints is not suitbale to accomplish this task because we need linkages that have enough compliance to achieve desired angles while maintaining structural integrity to lift the tab and open the can.
Mechanism
Our team has identified that an 8-bar mechanism, similar to a Jansen’s linkage, could be used to achieve the positional profile for this project. The Jansen mechanism is a planar combination of 4-bar linkages that involves the use of one motor to drive the position of the entire system. This mechanism creates complex motion from a circular input. These mechanisms are commonly used to generate walking motions. Pictured below is an example of a combination of 4-bars that we could use to generate the sliding mechanism to get under the tab of the can and then sequentially pull upward. We will edit the ratio of the linkages to generate the desired path profile. The end link will be pushed underneath the tab before moving in a semi-circular path that will generate a moment about the tab, pushing it upwards, before sliding back out from under it.
Example of a Jansen Mechanism used for walking.
Proposed Scope
The proposed solution to our unique problem statement will revolve around developing a motion pattern with an appropriate force to lift the tab of a canned beverage. The movement that the solution follows should orient the end effector to be under the tab of a 12 ounce can. Additionally, the end effector should have enough force to lift the tab and open the can. Our plan to create a solution for this unique problem will include the following steps:
- Perform position and force analysis on the 4-bar mechanism to position the end effector to be under the tab of the can and lift the tab
- Fabricating mechanism and develop hardware and software systems to achieve the proposed motion
Analysis will focus on determining the kinematics of the linkages and the joints needed to move to the tab, as well as the force to lift the tab. Since there will be multiple mechanisms connected in series, the workspace of each joint and the end effector will determine the dimensions of the fabrication for the solution. The force of the end effector should be able to only lift the tab and not add any other force to disturb the system. In addition to the mechanical structure of the solution, the code for the electronics must account for both the position and the force applied. This will be determined once the relationship between the motor’s properties and the desired parameters for our system are clearly defined.
Currently, our team is eager to fabricate this solution with the goal of finding a certain fabrication technique that is best to maintain durability while performing this unique movement pattern. We hope to find a solution that best suits our needs for this project as well as the needs for using this solution in the real world. Additionally, [Pull something from the intro and summarize] We strive to complete this solution and hope to improve on certain areas for future iterations.
Preliminary Design
We have utilized MotionGen to mock up a few potential 8-bar geometries that could generate the position profile that would scoop under the tab and push it upward. In addition to this 8-bar, the end effector link would have a tip that can be pushed back when the link meets the top of the can, and as the link meets the tab the interaction locks the tip into place.
