Video tutorials -

• Line following

Using everything that we've learned about LEGO Education SPIKE Prime competition programming we arrive at the final boss mission - how do we consistently reach a mission model at the other end of the field. Consistently. Every time. We use line following, motion sensor, counting of lines and border alignment. All the different concepts that we've looked at separately are now implemented together.

We start a course for following a line with crosses and gaps. This is a challenge that one of the users at FLLCasts.com was trying to accomplish and asked us for advice. We present the whole challenge to you step-by-step. But first, let's also see the whole run of the line following algorithm. With this course, we also do an introduction of using State Machine as a programming pattern.

Looking at the field we must first think of a strategy of solving this line following problem. There are rules that the robot must follow and these rules should be programmed in the robot. 

We list the number of decisions that the robot is making while following the line. Then, we group them and decide on the number of sensors to be used.

In this video lesson I will show you how to follow a black line using just one sensor, but fast enough so that you could use it during any robotics competition without wasting any time.

We follow a line. We start from the Smooth Proportional Line Following program and modify it a little for this program. We follow the line with the middle sensor attached on port 2. 

It's inevitable. While following this gapped line we would reach a gap. The robot must somehow understand that there is a gap and must make a decision on what to do. For detecting the gap we use the Rotation Sensor. Not the most popular, but very convenient in many cases. Check out the video.

We've detected the gap. It's time to move over it. This is difficult because we have to detect where the line is after the 0.1 meters gap on the line following field.

Next important state is Turn Right with our robot. This happens when we detect a line on the right. 

We can Turn Right. We can Turn Left. How do we decide which way to go if there are lines both to the left and to the right. Check out the video.

Next state in our state machine programming pattern is the "Turn Left" state and the corresponding behaviour.

All worked as expected, up until know because the robot got lost. This happens when we turn right and the line does not continue to the right. Now the robot must somehow understand that it is "lost" and escape.

We discuss the state of "Lost" and the different ways we could escape this state. We also build the next step of our State machine programming pattern where the next state is determined by the previous state.

The final video from the course. The robot escapes the state where it is lost. This happens if it can not continue in any direction.

In this video tutorial we show how you can build robots that position on the field consistently and reliably by following and line and then aligning to a line. We also demonstrate the concept of "double align" which is quite powerful and even if there were some mistakes they will be handled.

In this video tutorial we demonstrate a really important concept for FIRST LEGO League competitions - you position the robot on the field with depending on timers and rotations. The issue with moving the robot for 10 seconds and then stopping is that every time it is in a different location. Same for rotations. The wheels will slip, the battery will change, something will happen and the robot will not be in the same place every time. This is not consistent and reliable.

In this video tutorial we take a next step in programming reliable and consistent robots and this is to learn how to stop at a second intersection. We need this because most of the time when we want to reach a mission model on a robotics competition field, the model will be located away from us and we must use all kind of technique to reach it. In this tutorial - we stop at a second intersection.