We designed two different actuators and tested their performance. The following picture shows the Dipole-Quadrapole Actuator (left) and the Quad-U-Core Actuator (right). They are both designed to suspend tubes with diameters within 0.5in.

 

Dipole-Quadrapole Actuator
The dipole-quadrapole actuator uses a bias field to impose a dipole on the steel tube.  A quadrapole field is then added to exert a force on the tube (now a magnetic dipole) which is linear with current and decoupled with the perpindicular direction of motion.

Quad-U-Core Actuator
The quad-U-core actuator consists of 4 U shaped electromagnets, performing a pull-push action on the tube in both X and Y directions. The testing result shows this actuator has a higher power efficiency than the dipole-quadrapole actuator, and it is easier to build. This actuator is chosen to be the 8 actuators used in the final experiment.

    Experimental Results

The following figure shows the testing result of the dipole-quadrapole actuator. The force is linear with input current, and decoupled in x and y directions.  This means that the control system can command a force directly by commanding a current, rather than computing a square root as required by standard electromagnets (which takes valuable time).  Also, the fact that the x- and y-forces are decoupled means that the control system can be much simpler; a single-input single-output system rather than a multi-input, multi-output system. The quad-U-core actuator also shows similar results, and with even larger force output. The testing result is to be attached later.