Informations to RoboSim

This program has been generated for a software practical course by Johannes Schützner, under the direction of Dr.Thomas Bräunl, University of Stuttgart, in 1996. It is based on the 'Studienarbeit' by Rainer Pollak, made in 1992 and programmed in C.

Introduction

RoboSim is a program which simulates a six-link robot. You can control the robot in several ways and manipulate it, for example giving the links new lengths or changing the weights belonging to the indicated angles. It's also possible to make the robot save pre-allocated positions and to teach the robot a sequence of movements. Also, this software can be used to control a real robot. This robot is a Lynxmotion manipulator, available from Joker Robotics. In the following passage the possible commands are explained in more detail.

Useful Advice

This Java applet needs a reserved place of 920x670 pixels. Otherwise parts of the drawing are hidden by the panel on the right side. If you can't see a robot between the control panels, it's useful to click several times between the panels. If the robot seems to stop while doing a move and the scrollbar labels disappear, it might be helpful to move the mouse across the robot.

Restrictions

• Since there exist a lot of security restrictions, the loading and producing of control programs can only be done with the Java interpreter. Unfortunately, applets started with Netscape are not allowed to do this.
• The real robot can only be controlled by a special RoboSim version, because its control needs C-code which has to be integrated into this Java program. This integration would make it impossible for this program to run on every computer system. So the integration has been realized only on a limited version.

The Commands

• Forward Kinematics: This command is used to control the robot and its rotation links directly by modifying the angles corresponding to these links. The angles' values are restricted to sensible ranges which are shown above the scollbars. They are as follows:
  • Angle 1: 180.0 degree to -180.0 degree
  • Angle 2: 30.0 degree to -210.0 degree
  • Angle 3: 30.0 degree to -210.0 degree
  • Angle 4: 180.0 degree to -180.0 degree
  • Angle 5: 90.0 degree to -90.0 degree
  • Angle 6: 180.0 degree to -180.0 degree
  The real robot has not got the facilities of angles 4 and 6, so these angles are not available to the user.

• Inverse Kinematics: You can control the robot by giving it a target position (x-, y-, and z-value) with this command. The movement is executed after a click on the execute, button just below the scrollbars of the inverse kinematics. If a target point is unreachable, the robot stops. By pushing on the other button in the inverse kinematics area, you can select, whether the robot should move in a straight line or on an arbitrary tra- jectory.

• Determination of the arm lengths: This command allows you to vary the length of the arms of the robot. Also there exists a test for col- lision. If a collision is detected, the change of the arm lengths is not executed. The execution is only performed, if the corresponding execute button is pushed. The possible new lengths are limited to sensible ranges shown above each scrollbar. They are as follows:
  • Arm 1: 15.0 to 4.5
  • Arm 2: 15.0 to 2.5
  • Arm 3: 15.0 to 2.5
  If the real robot is controlled, this command can't be selected, because the real robot has got fixed arm lengths.

• Angle weights: Again, the values given to the text fields are only accepted after pushing the execute button. Then you have new angle weights. They are needed to obtain the best solution of the inverse kinematics. The values have to be positve integers.

• Point of view: You can change the point of view by dragging the robot with the mouse to any direction. By using the zoom scrollbar, you are able to increase and decrease the size ofthe robot.

• Speed: You can select your required speed with the corresponding scrollbar. By switching off the double buffering mode, the robot motion is much faster.

• Define/Go to positions: Three positions can be defined simply by pushing the define pos button of your choice. By doing this, the six actual angles of the robot and the actual open/close state of the hand are saved. This position can be restored by pushing the equivalent go to button. The first button (Go to Init) holds the angles of the robot at the beginning. If you want to see an example movement, push the example button.

• Virtual/Real robot: You can choose between the virtual robot as shown in the middle of your screen and a real robot (Lynxmotion manipula- tor). Selecting the real robot, the arm lengths and the angles four and six can't be changed, since the real robot consists of only four links.

• Open File: By selecting this button, you can load a file which either has been written "by hand" or has been produced with the Teach button. How to write executable files and use the Teach button, see the following links.

• Teach: After having activated this button, a file dialog window appears in which you can choose the name and the directory of the file which will be produced and written automatically. By doing this, the Teach button will be replaced by the Enter button and the Stop button will be enabled. Now you can control the robot as usual, but every time you push the Enter button, the actual robot angles and the actual open/close state of the hand are written into the indicated file. This mode is only stopped, if the Stop button is pushed. At the beginning of this mode, the actual linklengths,speed, and zooming factor are stored.

• Writing own control programs: You can write control programs such like these ones being produced by the Teach button, but you have got more command power. Every command starts with a command character and is completed by the arguments needed for this command. Every input, e.g. command character and arguments, must be in a seperate line. Otherwise the required motion of RoboSim cannot be guaranteed. The possible commands are:
  • f This character stands for forward kinematics. It has to be followed by six numbers in double format representing the new angles. Remember that every command and every number has to be in a row of its own.
  • i indicates inverse kinematics. In the next three lines there must be the three coordinates of the target point.
  • l By choosing this character, which represents linklengths, you can determine new lengths for the links. These lengths has to be in the allowed ranges.
  • w is the abbreviated form for angle weights . The arguments of this command are the six new angle weights wich are integers.
  • s represents speed. It has only one argument - the new speed. The range of possible values starts at 1 (slow) and goes up to 82 (fast).
  • h signifies that the content of the following line should be regarded as the open/close state of the robot's hand. 0.0 means a fully open hand and 1.0 a totally closed one.
  • z indicates the zooming factor. The zooming factor range is between 0.1 (very tiny) and 3.5 (large).
  • e must be the last command of every control program and means end.
  • # Comments start with # and last till the end of line.
  The system is not case sensitive.

  Example:

  # Automatic generated file (Mon Jul 29 15:31:00 MET DST 1996)
  l
  13.5
  10
  10
  s
  35
  z
  1.0
  f
  0
  -51.5662
  -76.3944
  0
  0
  0
  h
  0.3
  f
  -66.8451
  -53.4761
  -11.4592
  0
  0
  0
  h
  0.5
  z
  2.8
  f
  38.1972
  0
  0
  0
  45.8366
  0
  h
  0
  z
  1.5
  f
  38.1972
  0
  0
  0
  45.8366
  0
  h
  0
  f
  -66.8451
  -53.4761
  -11.4592
  0
  0
  0
  h
  0
  f
  0
  0
  -76.3944
  0
  0
  0
  h
  1
  f
  0
  0
  0
  0
  0
  0
  h
  0
  e
  
  

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