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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
The proposed mechanism is a combination of two different linkages, a 4-bar oscillator and a Klann linkage. Each leg will combine both linkages in sync in order to facilitate the desired position profile. Both linkages will also be modified to better fit our desired position profile. The Klann linkage will be heavily modified to create a more vertical path while the 4-bar oscillator will be modified to match the phases of the Klann linkage and to create the desired distance of travel. These mechanisms will be built using gears serving as the crank arm to save space and reduce complexity. The gear driving the 4-bar oscillator will drive a bevel gear driving the Klann linkage. Both gears will be the same size to better sync the motion of each respective linkage. There will be 8 legs in total all with the same size gears. These gears will the be connected to the outside perimeter of a big actuator gear that will actuate all of the legs at once. Each leg can then synchronized by placing each gear in different position or different times in their phases.
Scope of Work
- While our primary goal would be to completely replicate the walking motion of a spider, realistically it would likely be outside of our scope. As such, instead of creating a mechanism that can actually walk on its own, our main goal will be to simply create a working mechanism combining two linkages to create the more complex 3D motion profile. So instead of focusing on the functional purpose of the robot, we want to lean in to the artistic purpose of the robot and demonstrate the possibility of the combination of the two linkages.
- Prior to fabrication we will need to analyze and modify each individual linkage. While we do not need to consider mechanical advantage and thus do not need to worry about velocity or acceleration analysis, it is important to perform a position analysis to ensure that the linkages work well together and would fit the motion need for lateral motion.
- It will be exciting to work on the novel solutions we will need to come up with to combine each linkage and the way will need to connect them together. It will likely be most challenging to actually manufacture the robot, since there would be so many components and small parts.
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.
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