Bio Inspired Robot

Bio Inspired Robot

The last project for my MMAE 232 class was to make a bio inspired robot. The requirements are as follows:

1) Autonomously travels 4.9m on the designed track. The track will have a slight incline and decline on it. The change in height will be no more than 3.1 mm. Autonomous means you cannot touch it once you start it. After your robot completes its first 4.9m, you must pick it up and move it to the start line to complete its second trial.

2) The design must be bio inspired. 

3) Has the ability to be disassembled. No electronics can be glued down to anything.

We started by creating 2 sketches of a robot design, each inspired by a different animal. We chose the bear and the ostrich. In order to analyze this, we had to create a Hildebrand Gait Plot for each design, Identify the posture of each design, Identify the convex polygon for each of the gaits, Prove that the center of gravity is always within the polygon, and identify tourque requirements.

We chose to make the bear design. We used an Epilog 50W laser to cut out the frame from 1/4" MDF. After making our robot, we found out that it would not work because the center of gravity shifts outside of the polygon when the robot moves up the hill. We decided to modify the design by moving all servos inward toward the center of the frame. We created new legs that had a small contact surface. We modeled it after the sea turtle because it was meant to walk like one. 

We had issues with the battery packs coming loose. Videos looking at the walk of this robot can be found here. We were not able to tweak it in time to meet the deadline. 

Here is the link to the full report.

Trebuchet

Trebuchet

The next project after the Sustainable Chair Design was the Trebuchet. The goal of this project was to launch a rubber ball weighing 27 grams more than 12.5 meters. The material restrictions are as follows:

1. 10 pieces or less of 24" x 18" x 1/4" MDF
2. 10 pieces or less of 24" x 18" x 1/8" MDF
3. 1/4" acrylic rod
4. Wood screws
5. Wood glue
6. Rope or string of our choice
7. Fabric of our choice

The difference between a catapult and a trebuchet is simple.

Catapults are any device that throws an object, although it commonly refers to the medieval siege weapon. Trebuchets are a TYPE of catapult, using gravity (with a counterweight) or traction (men pulling down), to propel the arm and often employing a sling at the end of the arm for greater distance. This is different from other catapults in that it doesn't use built up tension for it's throwing force. 

We made a quick sketch of the trebuchet. It was composed of 2 main pillars, an axle, a release mechanism, an arm, a counterweight, and ribs made for balancing. 

A crucial part of this trebuchet was the computerized calculations used to see if our design was optimized. What I mean by this is that the length of the arm to the pivot, the length of the sling ,etc We were given Matlab scripts to modify our design. The Matlab scripts were modified based on the following diagram.

We changed the values of L, l, n, and r. As a result of the scripts, we had an ourput of a general imae of the trebuchet, distance graph, and a distance vs l vs L graph.

The max distance was predicted to be about 26 meters. This varied largely from our actual results because this design does not account for many things such as friction, air resistance, and wind. We went ahead and created a design on Autodesk Inventor for our trebuchet. 

Our next task was to make a release mechanism. We decided to make a hook release mechanism. We used simple force and moment equations in order to create an analysis of the release mechanism. The mechanism will be powered by a 250 N*mm servo.

After we analyzed these components, we created the actual trebuchet. We used an Epilog Laser Cutter 50W. We cut out each piece and used wood glue to put them all together.

After finishing our design, we attached the servo to a battery pack for power and an Arduino Mega 2560.

We ended up launching the ball 16.7 meters. Here is the video.