Arc turn explained
If you need to make the robot turn left, you must make the right wheel turn much more compared to the left wheel of the robot.
Move Tank block allows us to set small power to the left wheel, e.g. 10%, and large power to the right wheel, e.g. 90%.
In the software
Move Tank block has two power settings. The left one is for the first motor in the ports section - motor B by default. The right-hand side power setting in the Move Tank block is for the second motor in the ports section - motor C by default.
In the picture
One of the motors is moving faster than the other one. Let motor B moves faster than motor C. The robot moves as shown on the scheme:
We will use this way of turning when we want the robot to turn smoothly. When the difference between the power settings of the two motors is greater, the turn will be sharper. And vice versa – when the difference is smaller, the turn will be broader.
There is a block in the EV3 software called the tank block. And in this video we'll use it. Why? Because this block allows us to control the power of the different motors and at the end the robot will work like this. Move forward, turn, return back. The tank block allows us to set different power to the different motors and in real life you can see examples for this in many different cases. For example, cars. When cars are moving you can have different power to the different wheels, examples like traction control or four-wheel drives. So, you control the power to the different wheels so that you can turn or you can make the car more stable. Now, our goal for this task is just to make the robot turn.
There are different ways for turning. You have a robot with two wheels. First wheel, second wheel. Left wheel, right wheel. Now, if you need to make the robot turn left what you should do is rotate the right wheel more than the left wheel. So, the right wheel should make a lаrger turn than the left wheel. So, the left side of the robot, the right side of the robot. And if the left wheel moves for this distance and the right wheel moves for this distance you can see that the left wheel will move much less than the right wheel. And this is what we'll do with the tank block. The tank block allows us to set a different power to the different wheels and we can set this wheel to rotate with small power like 10 or 20% and this wheel with large power like 90 or 100% from the power for turning for the motors. And then at the end we'll have one of the wheels turning slower the other turning faster and we have our robot turning. In the EV3 software we use the block that we know the steering block and we move forward for one rotation with motors B and C. Then we drag and drop the tank block. And I'll just zoom this a little more so that you can see it and here we have different power to the different motors. This power,the left icon and the left value is the power for motor B.
If you take the robot and look it in your hands you can see that B is our left motor and C is our right motor. And what we need to do is set the left motor to rotate slower like 10% and the right motor to rotate faster like 90%. And this will be the block that makes the robot turn left. Then I'll just download and see the program.
What you see is that the robot moves forward then turns left but while turning left it is not enough the duration for the turn. It should turn even further. And you saw that if we set the power to the right motor to 90% and this to 10% the left motor moves slower, the right motor moves faster and the whole robot turns left.