Investigation

It’s time to do the first exercise. And this is about working out how you need to command the robot to move around.

This is the web page you will use. It’s got a title, it tells you a little about what’s going on, and it gives you the tasks to do. It also tells you how you can use the keyboard to do the particular controls. The web page is looking like this, but if your browser is different orientation, you might see it moved around. But I’ll demonstrate things like this. What you do in this particular exercise is to specify what the speed should be of the left motor and for the right motor, and to see what actually happens. Now when you specify a speed, as you view the robot from the outside, a positive speed means the wheel will turn clockwise.

To explain what I mean I quickly go over to this web page. And here you can see the two wheels of the ERIC Robot. You’re looking at the right wheel from the outside, so you see that the wheel here is in front of the circuit board, the motors, and the battery pack. Whereas for the left wheel, it is behind them. Both wheels have a positive voltage, so you see the right wheel is turning clockwise, but the left one is going anti-clockwise. So I need to make the left motor not a positive voltage for them both to be going in the same direction. And this might be more clear if we view the robot in 3D, like so.

And I can by now click left motor positive. So both positive. You see one wheel is going that way, the other wheel is going in the opposite direction. Now you should understand what the direction of the wheel is determined by whether the voltage is positive or negative.

So back to the web page. And what you need to do is to put numbers in these two boxes here. And the numbers you put in should be integers between minus 40 and plus 40. So if I put in 4, I press start, we see the robot turning. If I change that to minus 4, it goes in the opposite direction. I can also put in 4 for the other one. And we see– press start– and it’s going like so. Stop it. If I change– click this so it’s reversed, the motor we now find it, and it turns around.

You play like that. What you see is your robot moving around, and when it hits the end, it stops. But if you click there, it will reposition itself. In addition to using the mouse, you could use a keyboard. So you press L, and then you’re into the field where you could type in the number. You can press I, J, K, or M to move the robot around. So I M, moving down, K to the right, and so forth.

So what you need to do in this particular exercise is to see what happens when you try different values for the left and the right motor. Work out what you have to do to make the robot go forward or go backwards, or spin to the left or to the right, and investigate the reverse left motor option. Have fun.