Ottos legs

Robots can move in many ways: by wheels, tracks (like tanks) or legs, as is the case with Zowi. But which way of moving is the most useful? Keep reading and you know it.

In reality, there is no better or worse way, each has its advantages and disadvantages.

The wheels are faster and easier to control, but only while on level ground. As soon as there are stones or the ground is rough, they will be at a disadvantage.
The tracks are also easy to control and much better on difficult terrain, however they tend to be slower.
The legs … well, we better see it in the next experiment.
However, they all have one characteristic in common. They are actuators of the robot because they allow it to do something, in this case, move.

Experiment 1
Bipedal robots

A leg-based movement system is one of the most complicated that can be. You, as a human, are very used to moving your legs to walk. But remember what it cost you when you were a baby. You do not remember? Well, nothing happens.

Do you remember reading an algorithm for walking in the Robot Choreography project? Now imagine having to make an algorithm (that is, a list of instructions) to move each muscle in your legs as you walk. Actually, your brain does this automatically, but with a robot, it doesn’t do it alone. To take a step, precise commands must be executed on each motor in the robot’s leg. This is quite complicated, but not impossible.

Human legs Zowi’s legs
But not all are disadvantages! If the robot’s legs have enough motors, they can climb stairs, sit in a chair, get up off the ground and much more that, with wheels or tracks, would be impossible.

Let’s experiment with Zowi’s movements

Put Zowi doing a handstand, so that the legs are up and the head is down.
Now, enter the game 3,2,1 Action! and create an algorithm that is to make Zowi walk forward 100 times. You can alternate medium, slow, and fast speeds.
Observe how the four motors in Zowi’s legs move.
You can repeat the experiment with some Zowi dance passes. Thus, you will see the difference between dancing and walking. You will also see that some of these movements do not need to move the four motors.
As you can see, the motors are synchronized with each other to allow Zowi’s movement and make him walk. If not, Zowi would fall over and the leg motors could collide with each other, causing it to break.

Experiment 2
What is a servo?

Until now we were talking about engines, but … can you imagine Zowi with the same engine as a car? The legs would twist and turn without stopping, at full speed.

To prevent that from happening, different types of robot motors have been invented. Zowi uses a type of motor called a servo. Servos differ from car engines in that they need electricity (instead of gasoline).

Also, a car engine can go faster or slower, but it cannot go exactly half a wheel turn and stop. With a servo, you can tell it to go exactly half a turn. This is how programmers can make legged robots move.

However, the servos have a disadvantage, they cannot turn more than half a turn (maybe a little more). That is, Zowi’s legs cannot be fully turned (just like your legs).

Zowi servos

we’ll see if it’s true

Turn Zowi off and put him on a handstand, as in the previous experiment.
With Zowi off, move one of its legs. Can you make a complete turn?
Try now with one foot. Can this one go all the way around?
Servos are very useful actuators that allow robots to move easily. You will see how you use many of them when you build your own robot!
Did you know…?
Also, there are different types of servos. Other widely used are continuous rotation servos, which can turn full turns, but in a more controlled way than car motors.

Inspiration moment!
If you were to build a robot… what sensors and actuators would it have? How would it move and what things could it do? Make a drawing of your imaginary robot in which you indicate what components it has and where they are placed.