20.1 Project Proposal

Introduction

The inspiration for wanting to make a stair-climbing robot came when we noticed we hadn’t seen many walking robots able to successfully traverse stairs. Many walking robots are only made for the ground without obstacles. Putting a common obstacle in the way like a staircase to travel between stories would be awesome. We believe this can be an interesting problem to solve because even though it seems simple, there are other factors than just the linkages to consider. It is also enticing that this problem has room for lots of creative freedom. For our project, we plan to create a robot that is able to consistently go up and down stairs.

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Problem Statement

The motion required to actually move the joints into positions where it can climb stairs will be fairly complicated to achieve, especially with a one actuator. The actuator used is also going to need to generate enough force to lift the legs of the bot against its own weight high enough to clear the next step, but not too high as to be non-functional on the way down. The path of the leg must be able to clear each step while moving forward laterally so as to climb the stairs. The bot also needs to be stable enough to not slip or tip and tumble when it transitions from step to step.

Mechanism

We will design a mechanism very similar to the Jansen linkage. We will have to find an adjusted link combination that creates a path that fits the geometry of the stairs we want to climb. Both vertically and horizontally, the path will have to match each step while providing the mechanical advantage on contact necessary for the actuator to lift the whole robot. The mechanism will likely follow a similar path to the Jansen linkage but with an adjusted ground angle that allows for the correct height to be reached each cycle. Since the point of contact relative to the stairs is constant, we can model the stairs as a simple angle where the step size is the distance between adjacent stairs, thus we will have to create a path that is scaled to that step size as well.

Scope of Work

We aim to design and build a fully functioning stair climbing spider-like robot mechanism. The robot will not necessarily be able to transition from a flat position onto the stairs, but will be made to start on the stair steps in a slanted position. The robot will be able to travel both up and down the stairs. Additionally, we have decided to design our robot around and test it on the steps in TIW. In order to successfully build this robot mechanism, we will need to analyze the range of output paths and mechanical advantage that is optimal for climbing stairs. We will need to also analyze the effects of the center of gravity on the overall stability as it climbs steep stairs. The major obstacles to overcome are clearance of each stair, and stability from slipping or tipping. Another step we will need to take into consideration is the shape and material of the robot’s feet to grip the stair steps. Overall, there are many parts in the development of the final product, many of which will include complex analysis.

Preliminary Design Ideas

To form our robot mechanism, we plan on customizing the Jansen Mechanism. We will be changing the link lengths to produce a path profile fitting the TIW stair case. The main dimension is the horizontal spacing of the stairs and we just have to confirm that it clears the height of each stair. After we have the proper linkage, we will need to prevent our robot from slipping or tipping over.

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We will also have a set of these legs on each side of the robot, left and right. Each set will include at least 4 to always have legs on the steps holding the weight as well as to create a smooth transition between each step. In term of length, the mechanism should always be on two steps and will be accordingly sized.