Autonomous, Self-Assembling Robots

Step 3 Actuators overview

The robot has two electromagnetically-actuated latches. The red arm of the latch has a 3mm cube magnet (NdFeB type) press-fit into it, while the yellow base of the robot has a cylindrical coil press-fit into it. The coils were custom-made to the following specifications: 700 turns of 42-guage magnet wire, 4mm length, wound on a 2mm spindle. This resulted in a diameter of approximately 4mm OD, 2mm ID. We selected these coil specifications so that we could drive them directly from the robot power source and have a reasonable amount of power. We originally tried to put a magnetic core in the coil, which makes it much more powerful, but we could not find a core which did not remain magnetized after the coil turned off, and we did not have the capability to reverse the coil polarity (this requires 4 FET's per actuator instead of 1).