Harmonic Drive
Passenger Aircraft Position Pick-Up Unit
Lightweight component set
Harmonic Drive® gearing is extensively used in measuring devices. This position pick-up unit is used to measure the position of control surfaces in the wing of a commercial aircraft. Here a high reduction ratio, excellent accuracy and above all, light weight and small envelope are the key requirements dictating the use of this unique gear principle.
In this design example a HDUF component set is used to drive two brushless resolvers. This gear type is used because of the limited torque requirement and most importantly because of the limited space available. A splined input shaft is connected via a bevel gear to the drive shaft driving the control surface. This input shaft is connected to the Wave Generator.
The Circular Spline is the fixed gear element and the Dynamic Spline drives the resolvers via a spur gear and split pinion arrangement. The Harmonic Drive® gear is thus used in combination with the spur gear stage to reduce the angle of rotation of the drive shaft to an angle of less than 360° at the input to the resolvers.
The resolvers are mounted in parallel for safety reasons in this critical application. The component set is manufactured from stainless steel to avoid corrosion and also features a special grease for low temperature operation.
