Introduction
There already exists a multitude of walking linkage mechanisms, from the Jensen linkage to the Klann linkage, there is no shortage of mechanisms that achieve this profile. Instead of replicating what many other linkage systems have done, we wanted to tackle a problem more complex while still keeping the theme of walking linkage systems. Therefore, we turned to nature and looked at how other organisms moved. We were particularly fascinated with the spider, with movements that seemed to pivot and shift rather than strut like a typical walking linkage system, and so for our project we decided to mimic the movements as best we can. The biggest issue, is the fact that a spider leg moves with multiple degrees of freedom and in different directions, as such a direct copy would involve knowledge beyond the scope of this class. Instead be decided to approach this goal by combining two different 1 DOF linkage systems in different phases to achieve a similar 3D motion, limiting the scope to contents of our class and also creating a challenge that not only involves the design of linkages, but also the fine tuning of the relationship between multiple linkages using just one input. In summary, our goal is to create the closest representation of a spider as we can, capturing the complex motion profile of the legs using two 2-D linkage systems in parallel to create a more realistic walking motion.
Complexities
Many complexities arise from replicating the walking profile of a spider. Because a spider's leg has multiple degrees of freedom, they are able to move in very complex position profile. Furthermore there are very few resources that are applicable to this situation, and therefore our solution will have to be relatively novel. In order to replicate a spider as closely as possible, there will also be 8 individual legs. Each leg would add another layer of friction and possibility of error, potentially creating issues for actuation, troubleshooting, among many others.
Description of Proposed Mechanism
Scope of Work
Preliminary Design Ideas
Our first task was to decide on a leg mechanism that both visually represented a spider leg and had a position profile that fit our application. After a bit of research we were between the Jansen Linkage, Klann Linkage, and a custom 4 bar linkage. We ruled out the custom 4 bar linkage as we could not get it to have a motion profile that could go down to the ground and remain their with relatively little up and down motion for approximately 50% of its cycle. When it came to choosing between the Jansen and Klann linkages, we saw more potential in the manipulability of the Klann linkage to achieve our target motion profile. Additionally, the Klann linkage appeared visually skinnier and more "spider-like" so we figured it would be the best for both functionality and aesthetic.
As for the oscillating linkage, we always knew we wanted a linkage system that could oscillate back and forth but we were not entirely sure how to achieve that. Our first idea was a double linear slider linkage system but we decided against that because the production and analysis of the system would be overly complicated and we felt there was likely a simpler solution. Eventually we came across a diagram of a windshield wiper mechanism that we realized was very close to what we were looking for. So inspired by this mechanism we figured our a simple 4 bar linkage that we could manipulate to achieve our desired oscillating motion that had a link that the Klann linkage could be mounted to.
Combining the two systems through 1 actuator was a pretty big obstacle to overcome. Though we quickly decided on a bevel gear, we struggled to find a bevel gear set that was both the right size and had the proper tolerances to allow for the pivoting that Klann linkage would do. We were also weary of attempting to produce our own bevel gears as they would likely have a lot of inconsistencies and resistance.
Project Video