To every Rover turn… turn… turn…

Now that we have achieved basic locomotion we are interested in adding directional control.  To explain how we’re going to do this, it would be useful to look at how we have numbered our motors.

I have created a simplified diagram of the motors for discussion.

There are two types of turns we need.

Stationary Turns

Stationary turns have the advantage of being more precise but could be less useful for chasing something down.  Because each tire has independent control we can do things your car couldn’t.  In this case we can have the tires on one side turn forward while the other side spins backward.  This should allow the rover to spin in place which means he will be able to parallel park more easily than a even a Toyota Prius.

While I have used 100% as the motor speed, I could also turn more slowly by reducing the speed of all the motors equally.

Moving Turns

We don’t have a steering column we can use to change the direction of the wheels, but by varying the speed of each tire, we can create moving turns by rotating the tires on one side faster.

Again, we can vary the percentages to create sharper or more gradual turns.  For very tight moving turns we could leave the tires on one side stationary while the others drive the rover through a tighter moving turn.

More Tests?

In our next series of test we are going to try to quantify how many pulses on each motor are required for the following stationary turns:

• 45 degrees off center
• 90 degrees off center
• 135 degrees off center
• 180 degrees off center  (turn backwards)
• 225 degrees off center
• 270 degrees off center
• 315 degrees off center
• 360 degree turn (turn completely around back to start)

Because we used a series of pulses to drive the motors we can use them to count with a good degree of accuracy.  That means once we have a good pulse count, we can be reasonable certain our rover will turn in the direction we want with good precision.