fischertechnik COMPUTING ROBO MOBILE SET 8 Mode D'emploi page 53

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■ After concentrating on wheeled robots we now turn to another method of locomotion that we can use
for mobile robots, walking.
The gait of insects lends itself perfectly as model for the movement of "mechanical six-legged walkers".
During the so-called tripod walk three of the six legs always lift off the floor simultaneously. The front
and back legs on one side lift together with the middle leg of the other side.
Tripod Walk
Die Beine, die auf dem Boden stehen (schwarz dargestellt), bilden ein stabiles
Dreibein, so dass das Modell immer sicher steht und beim Laufen nicht umkippt.
The legs that remain on the floor (shown in black), form a stable tripod, so the model always has a solid
stance and does not tip over when walking.
The legs of the fischertechnik Walking Robot are constructed as so-called four-joint gears. The design of
the four-joints used here is called a "crank-rocker mechanism". Driven by a crank, the floating members
of the gears make oscillating movements. The distance between the individual joints and the position of
the nadir (this is the bottom of the leg), are arranged in such a way that the foot performs an elliptical
movement when the drive crank is turning. This results in a movement resembling a walking step.
The 6 cranks driving the legs have to be adjusted exactly as shown in the construction manual. The three
legs that touch the floor at the same time have the same crank position. The cranks of the 3 legs that
are in the air at that time are rotated 180° against the other three. The correct position of the
cranks in relation to each other ensures that the model is able to walk with the correct
sequence of steps, the tripod walk.
The hub nuts used to secure the gears on the shafts have to be screwed in tightly,
so the cranks won't become misaligned during walking motion.
One motor each drives the right and the left side of the model (this is necessary for walking
curves). For this reason you have to make sure that the middle leg on one side is always
in the same position as the two outer legs on the other side. The software controls this
synchronization via the pushbutton sensors I1 and I2.
First assemble the model according to the construction manual. Double-check all
sensors and motors using the Interface test, to make sure they are connected accurately.
Rotational direction of the motors: rotational direction left = straight ahead.
A s s i g n m e n t 1 ( L e v e l 1 ) :
Teach the robot how to walk.
● Program the model to walk straight ahead using the tripod walk.
● Use the pushbutton sensors I1 and I2 to synchronize the left and right legs.
● When doing so make sure that the two outer legs on one side and the middle leg on
the other side are in the same position.
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The Walking
Robot
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