If you had gone through the project brief, you would have realised that the brief contained fair bit of Silicon Valley flair. When we first met, our objective was to figure out what is required and what is optional and gain clarity on Minimum Performance Requirements. We decided to try and focus on the optional competitive section after getting checked off, based on the amount of time we have at that instant.
We realised that the robot must have the capability to do four basic tasks to meet the performance requirements.
1. Capability to move forward, backward and take turns
2. Capability to move along a black taped line
3. Capability to sense gray lines
4. Capability to drop balls at a specified locations (one ball per every drop)
1. Design inspiration to move forward,backward and take turns
We decided to think out of the box and came up with several ideas to create a robot that has the capability to move forward, backward and take turns. We thought of
using wheels coupled with DC motors, humanoid robot systems,robotic systems that can crawl. Among all the ideas, we felt using wheels coupled with DC motors
idea had low risk of failure and is easy with respect to design and fabrication. So, we decided to go with that system.
2. Design inspiration to move along a line
As part of ME 210, we did some laboratory assignments. We came across 'Sparki System' in one of the assignments. It had some IR sensors on its base.
We took inspiration from the Sparki System. IR sensors have a photo diode and an NPN photo-transistor. The light emitted at an angle by the photo diode collides with
the ground surface. If it hits a white surface, the light is more likely to be reflected and if it hits a black surface, it is more likely to be absorbed. The reflected light
is sensed by the photo transistor. The amount of current that flows through the photo transistor is dependent on the amount of light it receives. The current signal
can be converted into a voltage signal of desired range by allowing it to flow through a resistor and measuring potential across it.
3. Design inspiration to sense gray lines
The IR sensors mentioned above give analog signals. The amount of light that gets reflected when light is incident on a white surface, black surface and gray surface is different.
We felt we should be able to distinguish between white, black and gray if we designed the circuit mentioned above currectly
4. Design inspiration to drop one ball per drop
Again, we decided to think out of the box. We came out with several ideas. We thought of shooting the balls directly from the base location, using a linear actuator and a Slide
to drop one ball at one time. Shooting the balls directly seemed risky. We were not sure if we will have sufficient control to ensure we only drop one ball
if we use a linear actuator and a slide system.
We remembered a story from the ipod days. Ipod created a revolution in the music industry. When the the first ipod emerged (before the touch screen era), an interesting problem emerged.
Scrolling down from song one to song sixty four is not fun. They had to come up with a better way of moving from one song to another song quickly and thus
the famous ipod wheel came into the market.
We took inspiration from the ipod wheel. We decided to use a slotted wheel, turn in by stepper motor to drop one ball at one instant. We believed that the risks
associated with the design are low and hence chose it.
Based on the ideation phase, we made initial sketches and quickly made Solidworks drawings. We decided to prototype using duron, pink foam and metal fasteners. We decided to use 3D printing for shapes that required complex geometry. Duron can be formed into the desired shape using laser cutting facility available in the lab. Pink foam cutting machine is also available in Room 36 (Stanford's product realisation lab). As far as the electrical circuits are concerned, we decided to make detailed designs. We also decided to make a state space diagram once we have some base mechanical system.