When trying to accomplish the missions, the name of the game is consistency. In order to achieve consistency, you have to have a way to know where your robot is.
When your robot executes your program, it won’t move exactly the same each time. Even though you program your robot to move forward 300 degrees, it could stop plus or minus a few degrees each time. If you turn and move again, each turn and movement could be off a little each time. As you can guess, the errors compound and you could end up in a much different location than you expect.
The reason for this is that as you use your mat, the friction on your mat will change. Your robot will be running on your mat dozens, if not hundreds of times. This will change your mat ever so slightly, changing how the wheels (or other components) rub against the mat. Also keep in mind that your mat will not be the one you will be using at competition. You’ll be using the mat provided at the competition. It may have a completely different friction than yours.
Not being in an exact spot not always a problem, but when a mission requires precision, an inch here or there will determine whether or not a mission is accomplished.
So how do you maintain consistency across all mats? There are several ways to do this:
Start in the Same Place
In order to make sure your robot ends at the same spot each mission, you have to make sure it starts in the same place each mission. It doesn’t have to start in the same place for all the missions, but you should try to start your robot in a consistent spot for each mission. You can accomplish this by using a wall, using the tick marks or logos in base, or build a jig.
In woodworking, a jig is used as a pattern to recreate a pattern in multiple pieces of wood. Here, a jig would keep you starting in the exact same spot each time. You can build a structure out of LEGOs that could be set against the corner of base that you can then set your robot against.
Use the Walls
The walls are a good point of reference because they surround the mat. It’s a good way to determine that your robot is at the edge of the mat. If you need to travel from base to 6 inches short of the East wall, using the rotation sensors is one way to get there. But if you let your robot go all the way until you touch the East wall, then back up 6 inches, you’ll likely hit the mark a lot more often.
Walls are also straight lines. If you need to get to a certain spot on the board, why not use the wall as a guide and then make turns as necessary.
Look for black or white
To maintain consistency while your robot is out in the field, use landmarks. Take note of the design of the mat. Everything was put on there for a reason. Some graphics are there to fool the robot, others are put there to help it. There are always black lines on the mat. More often then not, they are there to help direct the robot where it should go. Mind you, the designers will also thrown in a few extra black lines to confuse your robot, but if you program your robot right, you’ll be able to avoid the “black herrings.”
Use points of reference whereever you can whether it be a wall or something on the mat itself. Travel the shortest amount of distance from a point of reference to reduce your errors and reach your goal with the most consistency.
If my team is able to accomplish a mission, I have them run it again. I don’t consider their mission a success unless it works three times in a row. It’s harder than you think. But if it can run three times in a row during practice, they’ll be more likely to be consistent during the competition.