Instantaneous and Discrete-Time Sensorless Insertion Applet
The following applet demonstrates an instantaneous and discrete-time analysis of a sensorless insertion strategy for rigid planar parts. It allows a user to draw a shape using B-Splines and to specify the contact locations. The applet then calculates a sensorless insertion plan which guarantees the user's drawn part will be seated (gain and remain in contact with all contact points) with the specified contact points. The calculated area to push upon the object with a frictionless pusher is drawn in blue (if it exists).
Sun's JRE version 1.4 or greater is needed to view this applet. (It use Java's new implementation of double buffering and the now easy ability to determine which mouse button caused the event).
This applet is based upon research by Jeff Trinkle and Devin Balkcom, Computing Wrench Cones for Planar Rigid Body Contact Tasks. I am currently working to extend the model developed in their paper to allow for a dynamic analysis incorporating the distance between the object and the fixels using a semi-implicit time stepping scheme.
Directions for use:
1)Draw the object to be fixtured.
This applet uses B-Spline to draw the desired shape. Left clicking the mouse will place a control point of the spline (Note: it takes 4 control points to specify one line segment). Note, the center of mass of the object is located by the large black dot in the middle of the applet. The center of mass is considered to be at coordinate (0,0). When you have finished placing the control points, you must close the object for the calculations to take place. This is accomplished my pressing and holding the shift key while left clicking the mouse. This procedure will connect the last control with the first. Once the object has been closed you can no longer add control points.
2)Place the desired contact points (fixels)
Right clicking the mouse will place a fixel. Although a drawn fixel may not lie on the edge of the object, for the instantaneous analysis all fixels must lie on the edge. To accomplish this requirement, the closest point on the object to the fixel is used in the calculations. This point is shown as a red pixel on the object. Once one or more fixels have been placed, the applet will calculate where a frictionless finger can push on the object to seat it (or perform any of the other desired modes selected in the drop down menu), this area of the object is drawn in blue. You can drag around existing fixels and spline control points by depressing the left mouse button over an existing point and moving the mouse around keeping the button depressed. You can also delete an existing fixel by pressing the Ctrl key and left clicking over and existing fixel. You cannot delete a spline control point.
Explanation of drop-down menu
This menu updates itself accordingly with the number of fixels. The possible drop-down selection (with the exception of seat) are string representations of the possible modes to analyze. "S" is Separate, "L" is Slide Left, "R" is Slide Right, and "N" is Roll. The index of the the letter in the string refers to which fixel that mode is applied. For example "SL" would be Separate from fixel 0 and Slide Left on Fixel 1. The fixel indices are displayed next to the fixel for easy correlation.
Explanation of Friction Slider
The friction constant "mu" at the fixels can be adjusted with the slider. At this time, the boundary location calculated for a given mode is assuming a frictionless pusher. Friction only exists at the fixels.