The rotor also carries the secondary of the rotary transformer that is used to excite the rotor of the resolver. The stator consists of the two output windings spaced 90 electrical degrees apart and the primary of a rotary transformer. In order to dispense with the need for sliprings, a separate rotary transformer is used to provide power to the rotating primary winding. The signals from the resolver are therefore relatively insensitive to an electrically noisy environment, and they can be transmitted over considerable distances with little loss in accuracy. By having two windings ninety electrical degrees apart and considering only the ratio of the outputs ( Fig. 4.13B), the variations due to the input voltage and the frequency changes become unimportant. As the relative positions of the primary and secondary windings change, the output varies as the sine of the angle. Resolvers are based on similar principles to LVDTs, but the primary winding moves relative to the two secondary windings rather than having a moving solid core, as shown in Fig. 4.13A.
Based on this discrepancy a new concept for optical low cost high resolution angular resolvers is developed. Thus traditional optical angular resolvers usually show the disadvantage that high resolution is hard to combine with low manufacturing costs. High resolution optical angular resolvers mostly work with very cost intensive solid measures made of glass with lithographic structured coatings. While magnetic sensors with limited resolution are mostly found in the low cost sector and for absolute encoded systems, optical sensors are provided as absolute or incremental encoded systems and can reach highest resolutions. Optical and magnetic sensors have the highest economical weight.
įor a contact free determination of the angular position normally capacitive, magnetic-inductive or optical sensors are used. Examples are the detection of steering angle in cars for driving assistant systems or the position sensing of rotating units in machines. Kück, in 4M 2006 - Second International Conference on Multi-Material Micro Manufacture, 2006 1 IntroductionĪngular resolvers are used in many industrial applications for the detection of the angular position of rotary motions.