We always know what motors we want to use before we CAD the robot. Sometimes the choice will change due to cost, size, or weight problems, and we will change it in CAD or after-the-fact.
We will either:
- Know the exact amount of power required for our mechanism, and select our motor and gear reduction that way, or
- Make a best guess based on past experience and looking at other robots.
Many of our mechanisms are first made out of plywood, using the same size, motors, wheels, etc. as the final robot. This way we can change the motors and transmissions before we commit to drawing it in CAD, buying the metal, and manufacturing the final robot.
If we think it will work without prototyping, we will CAD the mechanism without a prototype, but the designer or controls team will have already chosen what motor they want to use.
If you’d like see more information about calculating power requirements and choosing motors, see how much you can get from the video and the other links, then ask any questions you have from what you’ve learned there.