First Steps - fischertechnik Mobile Robots II Manual De Instrucciones

is an ideal basis for this. We can combine the mechanical parts in an
almost unlimited variety and build sturdy robotic vehicles. Using the
associated "Intelligent Interface" (Art. no. 30402, which must be purchased
separately), we also have sufficient computing power to design demanding
programs. Numerous different sensors and actuators are linked and
evaluated via this interface. The sensors convert physical quantities such as
light quantity or temperature into electrically recordable values. This includes
both analog and digital quantities. Digital quantities are those that can be
either logically true or false. These states are identified with 0 or 1. A switch
is a good example of a digital sensor.
But many quantities change continually between their maximum and
minimum values; these are called analog values. They cannot be displayed
simply as 0 or 1. For a computer to be able to process these quantities,
they must be converted into corresponding numeric values. The fischer-
technik interface provides two analog inputs EX and EY. The resistance value
applied to these terminals is stored in a numeric value. The measured values
of a temperature sensor, for example 0...5 kE, are recorded in a range
from 0 to 1024 and are available for subsequent processing. The most im-
portant function of the interface is in the logical linkage of input values. The
interface requires a program for this. The program decides how the sensor
signals, corresponding output data, motor control signals, etc. are created
from input data.
A graphic work sheet exists, so that we can write programs necessary for
the interface as effectively as possible. There is a software program behind
the term "work sheet," which makes it possible for us to create our
programs on a very high level. In fact, we can design programs and
algorithms using graphic symbols. The computer of the Intelligent Interface
can actually only execute commands from its machine command set. These
are essentially simple logical or arithmetic control structures, whose use is
extremely difficult for beginners. Consequently, the PC software LLWin (Art.
no. 30407, not included in the construction kit) provides graphic elements,
which can then be translated into a language that the interface can use.
We will proceed step-by-step into the fascinating world of mobile robots.
We will begin with a simple test construction to check the basic functions
of interface and sensor technology. Then we will start with simple models,
to which specific tasks are allocated. Later we will try out increasingly
complicated systems. To ensure that any errors, which occur, do not result
in permanent dissatisfaction, we will get to know the properties and special
characteristics of sensors and actuators in one chapter. There is a "Trou-
bleshooting" section at the end for very "stubborn" cases.
It is very important to take a great deal of care when setting up and
starting operation of our robots. We are dealing with complex machines,
whose only difference to other robot systems in use throughout the world
is their comparatively small size. When we assemble electric components,
we should follow the guidelines carefully and check two or three times
to make certain that everything is correct. In mechanical constructions,
including our own creations, we should pay a lot of attention to softunning
and lack of play in gears and attachments. We should never use "force"
during assembly.
Writing new programs and consequently defining new "behavior," whose
complexity is only limited by the available resources for memory and
computing power, depends on our own creativity. The following examples
should provide some ideas for this.

2 First Steps

Following the theoretical considerations, we now want to finally begin our
own experiments. Some of you would certainly like to start immediately,
maybe even with the complicated automatic forklift. This is of course
possible, and if you follow the construction instructions carefully, you can
construct the model right away.
But what can you do if it doesn't work? In such cases, you must search for
the cause of the error systematically. When you do this, questions inevitably
arise about the mode of operation and the properties of the components
used. A certain degree of basic knowledge about sensors and actuators is
apparently indispensable. But before we start to learn about these things,
we should check the interaction between computer and interface.
Install the control software on your PC in line with the guidelines from the
LLWin manual.
Using the interface diagnosis (Check Interface),
we can test the different sensors and
actuators. For example, we can connect a
pushbutton with two lines at input E1 and
then see which logical switching state the in-
terface detects. When you press the pushbut-
ton, the state must change at the corresponding input.
We can check the outputs by connecting
a motor with a motor output, e.g., M1.
Using the mouse, we can change the
rotation of the motor. If we want to
test the analog input, we can use a
phototransistor as an analog sensor.
While the polarity does not play any role for motor or pushbuttons (the mo-
tor rotates in the reverse direction in an
unfavorable case), the correct connection
of the phototransistor is imperative for
correct functioning. One contact of the
transistor is identified with a red
marking; we connect this one with a
red connection plug, and the contact not marked with a green plug.
The second red plug is inserted in the socket closer to the edge of the inter-
face of the EX input; the second green plug is inserted in the socket of EX
placed further inside. Then we can vary the lighting strength of the photo-
transistor using a flashlight and consequently change the pointer deflection.
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