Here I present an idea for the design of a printed circuit board Linear Induction motor that contains no ferrous magnet core and hence, introduces no or very little hysteresis properties into the magnet circuit.

Being that this design possesses no iron constrains this device to have little ability to produce a significant linear force. In addition, this device would be limited to horizontal linear motion only. Hence, I classify this device as a positioner instead of a motor.

Also, for stability the movable and stationary members of this device (stage) would be supported by an air or magnetic bearing.

Finally, it should be noted that there is no discussion here as to the type of position feedback mechanism used. I would be assumed that this feedback would be provided by a high resolution (multiplying) linear encoder or laser interferometer.

A summary of the main components of this device, referring to Figure 1.

1 – An array of multilayer PC boards attached to the base of the stage interspersed between an array of aluminum fins integrated into the movable member of the stage. The PC boards contain only arranged layers of copper traces.

2 – The movable member of the stage supported by an air or magnetic bearing.

3 – A compartment attached to the stage that houses all control and power electronics. Close proximity of the electronics to the stage is of paramount importance for reasons of stability.

A slice view of the stage is shown in Figure 2.

4 – The array of multilayer PC boards press fit into the aluminum base of the stage. In reality this would be a tricky process affected by the height and length of travel of the stage. The higher density or number of boards would aid in the production of linear force. However, since there has to be an interleaving of aluminum fin between each of the boards, holding separation over the travel length of the stage becomes problematic.

5 – The aluminum fins which are machined out of block of aluminum acting as the movable member fo the stage.

6 – The air or magnetic bearing separating the base from the movable member of the stage.

Each printed circuit board contains a series of layers containing two sets of hairpin windings traversing the length of the board, connect to the next layer and traversing back. This back and forth layering can be done N / 2 times where N is the number of PC board layers. In the example shown in Figure 3A and Figure 3B, a 12-layer board is used.

One set of winding defines a overlapping for Phase A, B, C motor connections. The other set is for a single-phase coil used to provide controlled damping.

7 – For the example of Phase A connection, the winding starts at Layer 1 and returns at Layer 4 (Figure 3A). A feedthrough (via) connection is made between Layer 4 and Layer 7 (Figure 3B).

9 – For the given PC board, Phase A ends on Layer 10. An external connection will then be made between this point and point “7” of the next adjacent board. The process is similar for Phase B and C, and repeats for K number of PC boards making up the array.