Abstract
Acceleration is frequently used in motion control. It is usually obtained as a time derivative of position, which is measured by an encoder. A time derivative is corrupted by high frequency noise and is not reliable at low rotational speed. Since there is no appropriate angular acceleration sensor available at present, we propose a new type of angular acceleration sensor which has unlimited rotational sensing range and sufficient sensitivity to be used in motion control. The proposed sensor is composed of two discs. One of them is a spring-inertia acceleration transducer and the other is a disc similar to the discs of pulse encoders. A pair of optical pick-ups is used to measure a relative angular displacement between the two discs. In this way non-contact and speed independent angular acceleration sensing is realized. Some basic performances of the sensor are discussed in this paper: it is shown that linearity of the sensor can be improved by slits with a shape of Archimedes' spiral; eccentricities of the shaft and the discs are analyzed and a sufficient but not ideal compensation is provided by two optical pick-ups that are placed diametrically on the opposite sides of the discs. Experimental results show that the sensor's output excellently matches with the calculated acceleration.
