Patent ID: 6571631
Filing Date: 2003-06-03
Classification: G01P

Abstract:
A displacement sensor comprising:a moving member composed of a magnetic material; a first stator and a second stator each composed of a magnetic material and arranged opposed to each other with respect to said moving member, said first stator comprising a first driving coil and a first position detector corresponding to said first driving coil, and said second stator comprising a second driving coil and a second position detector corresponding to said second driving coil; and a control unit operable to: drive at least one of said first and second driving coils, based on a detection output coming from at least one of said first and second position detectors, with an electric power corresponding to a first interval between said first stator and said moving member and a second interval between said second stator and said moving member so as to balance said moving member at an intermediate position between said first and second stators; and compute a force or acceleration applied to said moving member with a driving electric power of said first and second driving coils, said control unit comprising: a phase comparator circuit operable to supply a comparing signal to said first and second position detectors and to detect an unbalance between the first and second intervals as a difference in phase of the comparing signal; a pulse generating circuit operable to supply a driving pulse of a constant pulse-width to one of said first and second driving coils in accordance with the detected phase difference; a driver circuit operable to drive said first and second driving coils with the driving pulse; a counter circuit operable to count the number of driving pulses; and computing means for computing a force or acceleration applied to said moving member based on the number counted by said counter circuit.