A miniature pan-tilt actuator: the spherical pointing motor
Bederson, B.B.; Wallace, R.S.; Schwartz, E.L.
Robotics and Automation, IEEE Transactions on
Volume 10, Issue 3, Jun 1994 Page(s):298 - 308
Digital Object Identifier 10.1109/70.294205
Summary:A pan-tilt mechanism is a computer-controlled actuator designed to
point an object such as a camera sensor. For applications in active
vision, a pan-tilt mechanism should be accurate, fast, small,
inexpensive and have low power requirements. The authors have designed
and constructed a new type of actuator meeting these requirements, which
incorporates both pan and tilt into a single, two-degree-of-freedom
device. The spherical pointing motor (SPM) consists of three orthogonal
motor windings in a permanent magnetic field, configured to move a small
camera mounted on a gimbal. It is an absolute positioning device and is
run open-loop. The SPM is capable of panning and tilting a load of 15
grams, for example a CCD image sensor, at rotational velocities of
several hundred degrees per second with a repeatability of .15°. The
authors have also built a miniature camera consisting of a single CCD
sensor chip and miniature lens assembly that fits on the rotor of this
motor. In this paper, the authors discuss the theory of the SPM, which
includes its basic electromagnetic principles, and derive the
relationship between applied currents and resultant motor position. The
authors present an automatic calibration procedure and discuss open- and
closed-loop control strategies. Finally, the authors present the
physical characteristics and results of their prototype
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