Design Examples

Challenging electronic motor applications using low-profile, ultrasonic, piezoelectric motors

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Stator

The core element of an application is the stator (see figure 1 above). This part can be supplied by PCBmotor, in various diameters currently ranging from 20 mm to 90 mm, or you can download PCB layouts from our webpage. The example used in this article uses a jigsaw has an outer diameter of 30 mm and an inner diameter of 22 mm.

The stator is 2.6 mm in height and built on a 1.6 mm PCB (FR4) with 48 piezo elements on each side. Typical mechanical performance yields approximately 40 RPM and a stall torque of 18 Nmm.

Rotor

The rotor consists of two discs placed on either side of the stator. Both discs have friction tape where they will rest on top of the piezo elements.

To obtain a controlled pressure of the rotors towards the stator, one of the rotors has a center spring which will ensure an even distributed force and allow for planetary and dimensional tolerances of the stator. At the same time the spring must be able to transfer the torque from the discs to the center shaft.

The spring is etched from a steel or bronze foil of 100 – 200 micron thickness and laminated to the rotor disc. The disc/spring manufacturing is done in sheets which have 20 to 50 parts on each panel.

Motherboard

The motherboard has two functions. Firstly, it provides the electrical connections to the motor (Sin, Cos and Gnd). Secondly, it has a bearing to keep the rotor in the center position.

A unique feature of the PCBMotor is that the center position is not critical to the performance.

If the rotor is not fixed somewhere it will slide off the stator. Whether or not you need a ball bearing depends on your application. The bearing must, however, allow for a slight angular play to absorb planetary tolerances of the alignment of the stator and the motherboard.

This design example will give you a movement device with an Ø30 mm platform on one side and a more conventionally drive shaft on the other side. If you do not need the drive shaft, remember to establish the centering of the rotor by other means. 

Hollow-shaft designs

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