Problem Statement

The basic idea behind the study of the Fischer Technik robot design was to

evaluate the APIs and to measure the temporal properties for all operations.

The Fisher robot can be used as a design tool for the preliminary stage

evaluation of industrial sized projects which require temporal properties to be satisfied.

Including the real time properties into the initial phases itself will provide

a better tool for the designers to evaluate their initial design and provide them

with the evaluation tool required for verification without developing the expensive

prototypes.

Introduction

Because of it's unlimited usability, fischertechnik is superbly suited for simulation

and training in industrial applications. Very often, industry models are built to plan

plants and machines so you are able to detect and solve problems in advance.

Fischertechnik can be used to simulate very complex factory automation projects;

this makes planning the real plant much easier and will save money. 

H/W specification

This active interface is the kernel of the Computing kits. It controls communication

between the PC and the models. Its function is to convert the software commands

so that a motor will run when you operate a button on the model. The interface

has eight digital inputs where pushbutton signals (0 or 1) or phototransistor and

Reed contact signals can be evaluated. There are also two analog inputs which

can read resistances ranging from 0 to 5 kilohms. There are four reversible motor

outputs to control lamps, motors or d.c. relays. This means that you can change

the motor's direction of rotation (by program) at any time. We supply a battery

holder to power the interface. You can also use any mains adapter with a direct

current of about 9 Volts and a power of about 5 Watts.

This computer interface hardware for FischerTechniks Computing series building

kits include components at par with any PLC control system.

Specification:

• 16-bit microcontroller
• USB and serial interfaces
• 128 kByte of flash memory for downloading 2 different programs which are

        retained even if the power supply is disconnected.

• Four 9V/250mA (max. 1A) motor outputs now with variable speed control
• 8 digital inputs
• 2 analog inputs for resistances from 0-5kOhm
• 2 analog inputs for voltages from 0-10V
• 2 inputs for digital distance sensors
• Connection for ROBO RF Data Link radio interface(available soon)
• Connection for Fischertechnik Robo Controller I/O Extender
• Interface to Fischertechnik IR Control Set 
• Additional 26-pole male connector strip - to which all inputs and outputs

        are brought out - for convenient connection of finished models through

        a single 26-pole connector

3-axis robot with grabber claw, 4 DC motors operating with either 9V or 24V, 4 limit

switches, 4 pulse counters for travel measurement, all counters are zero-potential.

Model mounted on stable wooden panel, packed in a wooden box.

Degrees of freedom -

Axis 1: 180° of rotation
Axis 2: 100 mm back and forth
Axis 3: 160 mm raise/lower
 

External Interfaces

The Robot provides 2 interfaces for programming the Robot .The first interface

provides support for programming the board which has been divided into 3 basic programs.

The RAM space is left free for the user to download

the program onto the microcontroller and execute.The RAM is refreshed each time the

power supply is reset from the board provided with the Fischer Technik robot.

The other interface works in an online mode where an external microcontroller/microcomputer

controls the robot through a serial port/USB port supported by the Board provided with the

Robot.The ports provide I/O operations though which an external logic controller can provide the

control logic.

C Compiler

Fischer robot also provides a C compiler and an IDE is provided to directly program the

board provided with fischer robot.

Case Study

For the first step into the evaluation process the Robo interface provided with the

Fischer Teknic was used for programming.The USB interface provides an online mode of controlling the robot.

JavaFish

The class JavaFish contains a number of methods and properties to access the

fischertechnik Interfaces. JavaFish uses the Wrapper-DLL javaFish.DLL for access to

the common umFish20.DLL via JNI. To obtain all changes of the E-Inputs, umFish20.DLL polls

them with high priority (using the MultiMediaTimer) in intervals of about 10 msec. In addition

to the polling a refresh of the M-Outputs is done. If requested, it reads EX / EY too. The

state is stored in an internal control block (can be determinined with instancing). The changes

of the E-Inputs are counted and stored in special counter fields. These counters can be used for

determining the position of an model (look for "impulse wheel" on the Industry Robots). 

Sample code

 Link to code

Robot motion video

 Link to video

Results

The simple design of the fischer teknic robot makes it easy to program and control the robot.Also

high levels of precision can be achieved by additional design changes to fischer robot.The 3 axes

provide free motion on all three axes with relative ease. The C / Java language interface provided with the robot

makes it easy to program the robot.

Future Work

In future 2 possibilities can be explored further -

1) Fischer robot can be controlled by a RT operating system using the serial or USB

    interface and the model can be programmed to include real time properties.

2) The C compiler provided by one of the software providers can be used to provide a measure

    of the timing constraints between each subsequent action/command.Also a library than can

    be built to provide the necessary temporal properties that are required.