2.1: Advanced Driving Commands

When we walk around, we are always sensing our environment. We need to be able to sense obstacles that come up along the way and take action. While humans can do this easily, this is a problem for Zumi. So far, Zumi cannot check her sensors or her surroundings while driving using the forward block. Imagine walking around with your eyes closed, and only opening your eyes when you have stopped moving to decide your next move. In this lesson, you will learn how to use a new function that will let Zumi drive while checking her sensors and respond to the changing environment.

When you are walking, what actions are being repeated? Right foot, left foot, right foot, left foot…hmm…sounds like a loop! Zumi can also take “steps” forward by driving a tiny bit at a time. When these small steps are put in a loop, Zumi will drive forward. Begin by placing a repeat block in the workspace that will repeat 50 times.

In the past, you have used the Junior driving functions to drive Zumi. This time, you will be using the forward “step” block from the Senior driving menu. Click on the Senior tab and take a look at the functions. What do you notice?

The Senior block functions look a little bit different! You will notice some parentheses (), underscores _ , and commas , on the blocks. This is because it is more similar to the Python code that is running in the background. Notice that each block has a name and parameters inside of the parentheses. This is what Python code looks like!

Now that you’ve taken a look at some of the advanced commands, let’s tell Zumi to take 50 “steps”. Grab the forward_step() block and include it in the loop.

Finally, add a stop command at the end of the loop. This can be found in the Junior commands menu. Do not skip the stop! Unlike the forward block, forward_step() has no stop that is built in. You will have to tell Zumi to stop when the loop is done, or else she will drive forever!

Now try running the loop. What happens? Try changing some of the values, too. Increase the iterations, change the speed, or change the angle. How does this change the driving behavior?

By now you should know that you can control how long Zumi drives by increasing how many times the code repeats and that you can change the speed Zumi drives at. There is a new parameter for driving forward called “angle” that will determine Zumi’s heading. When you are telling Zumi which angle to drive at, it is relative to the direction where Zumi began, which is 0 degrees. The direction “0 degrees” will always stay the same, just like how North, South, East, and West are always the same directions, no matter how many times you turn.

In this case, think of “North” as 0 degrees. North or 0 is set when the code starts. Let’s try driving Northwest. What angle or heading corresponds to that direction? Try changing the angle to 30.

To prove that the angle does not mean “turn that many degrees”, repeat that whole code twice with a repeat block.

Did you notice that it continued in the same direction instead of turning another 30 degrees the second time? This is because the headings will always stay the same relative to where Zumi started facing.

Remember when you wrote a square code but used the turn function? This time, you are going to use the forward_step() function and change the angle headings. Let’s brainstorm what each heading will need to be.

Now, you will have four repeat blocks back-to-back. Each loop will be one side of the square. Make sure you repeat each loop the same number of times so that the sides are equal! Don’t forget to stop!

If you need to make right turns, you can set heading to negative values. Look at this example for a right square.

You did it! You learned how to use the Senior driving command forward_step(). Remember the rules for using this block:

• Forward_step() must be used in a loop
• The angle determines the heading, which is fixed and is set when you start the program. Think of North as being 0 degrees. North doesn’t move around!
• Always add a stop command after the loop is done. Unlike the forward block, there is no stop command. If you forget to add a stop command, use the red stop sign button at the top of Blockly.