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In this first example a point-point fixture is used to aid the operator in bringing a point on the end effector to a point in space. As the operator moves near the fixture it activates and pulls the end-effector toward the fixture location. The fixture guides the operator's actions. In this case assisting in rotating the end-effector about a point.
Examples (continued)
Fixtures do not completely constrain the operator. For example, here the operator chooses to pull away from the fixture point. The system anticipates the operator's next desired action and activates a circle fixture.
In this second example a number of fixtures aid the operator in contacting surfaces in the environment. If the operator moves near appropriate surfaces then fixtures are activated to guide the end-effector toward flat face-face contacts.
As the operator slides the end-effector forward the system activates a fixture to discourage the operator from moving near the edge (the position of which is uncertain). The end-effector is guided up, out and around the uncertain edge...
before being pulled back into contact with the box. Again fixtures guide, but do not constrain the operator. In this case the operator chooses to rotate out and slide away from contact.
Craig Sayers (sayers@grip.cis.upenn.edu) 4 August 1994