Initial Design
There were two main kinematic mechanisms to design which were the climbing mechanism and the tail mechanism.
The Climbing Mechanism
We needed the climbing mechanism to have a specific motion. The cycle of motion was to reach in between the rungs, pull down, move back behind the rungs, reach up, and repeat.
Figure 1. Link Lengths
The lengths of each link in the monkey arm were labeled as in Figure 1. The changing length of R3 is the result of the radius of the rotary wheel.
MATLAB Code
The Matlab Code produced the following two graphs shown as Figures 2 and 3. The first graph shows the length of R3 versus theta. The second graph shows the position of the point P for each full rotation of the rotary wheelWe used position analysis through MATLAB to get an idea of the final link lengths. The code can be found separately under this page.
Figures 2 and 3. R3 length vs. Theta, and Position of point P.
From the resulting position plot in Figure 3, the tip of the monkey arm, point P, would have 3 inches of vertical clearance. The ladder was then designed off of this clearance. The motion of point P emulates the back and forth climbing motion that we desired. The two arms needed to be 180 degrees out of phase so that two arms could be used instead of four. This also meant that only one arm would hold the weight at once.in the next section. In Figure 4, we have the initial design in CAD. The arms are 180 degrees out of phase and are connected by a single axle.
Figure 4. Two arms linked together by one axle.
The Tail Mechanism
The tail mechanism was initially the same as the climbing mechanism because we thought that the back and forth motion generated would produce a swinging motion. Figure 5 shows the CAD mockup of the internal design. From Figure 4, we added bevel gears to turn the tail mechanism, and the tail mechanism itself. It has the same mechanical implementation as the arms. For the final design however, we did not go with this tail design.
Figure 5. First Internal Design