Downloads / Mechanisms

 

Mechanisms is a skeleton of a program that contains a simple 2D kinematic simulator suitable for demonstrating simple kinematics and for carrying out experiments in evolutionary robotics. The simulator is simple and robust, and can be easily extended.

You should play around with the simulator first to get a feeling for its capabilities. Here are some tips. Run the program, then

  1. Move an exiting mechanism: Grab and drag on one of the joints to see how a mechanism moves.
  2. Delete a mechanism: Use ‘Select All’ (or Ctrl+A) to select the entire mechanism, or drag a rectangle around the entire mechanism. The Select ‘Delete’ (or hit the Delete button) to delete the current model. You can also drag a rectangle to select a region, or click on individual elements to select/deselect them.
  3. Create new mechanisms by holding down the Shift key and dragging the mouse to sketch a new links. Each stroke is a single link, and only the endpoint locations matter. Sketch, for example, a four-bar mechanism. When done, click on the background and the sketch will turn into rigid links. Drag the joints around, and sketch more stuff. Select individual links and delete them, and see what happens.
  4. Ground elements by Select a joint or a link and then select ‘Ground’. Pull hard on a joint to see how the color of links changes. Red means the link is in tension, and blue means compression.
  5. Change lengths of links by selecting a link or several links, and then using the mouse wheel. You can make various active mechanisms this way. This is an actuator. Changing lengths of several bars simultaneously can create complex actuation patterns, such as curved motion.
  6. Hide a link or set of links by selecting them and hitting ‘Hide’. Now you can create structures that appear to behave in complex ways.
  7. Turn on gravity. Now objects fall to the floor, and have more realistic behavior. The floor is frictionless. It is usually difficult to draw new mechanisms ‘in the air’ while gravity is on, so you usually turn gravity off while editing.
  8. Switch on friction. Under simulator, select different types of friction: None (slippery), some, or infinite (sticky). Then sketch a nearly-vertical bar and let it fall down, and check out what happens. Friction has effect only when gravity is turned on.
  9. Copy results to the clipboard. Use view|Copy Snapshot to copy a bitmap of the current view to the clipboard. Use copy metafile to copy the current image as vector graphics, and paste them as a metafile. This vector format can be edited by right-selecting ‘edit image’ in MS Word, for example.

Download the simulator

Revised: November 11, 2006 .