US 4,746,859 A · Power and temperature independent magnetic position sensor for a rotor

Abstract

In order to optimize the electrical performance in motors in terms of improved efficiency, power factor, and reduced current, a power and temperature magnetic position sensor for a rotor utilizes first and second magnetic sensing devices for accurately determining the angular position of the rotor. The first and second magnetic sensing devices include at least one target operatively associated with the rotor so as to rotate therewith, a first sensor disposed at a variable distance from the target dependent upon the angular position of the rotor to define a first air gap therebetween, and a second sensor disposed at a variable distance from the target dependent upon the angular position of the rotor to define a second air gap therebetween. The first and second sensors cooperate with the target to detect magnetic field intensity in the first and second air gaps, respectively, and produce output signals indicative of the magnetic field intensity which, at any point in time, is dependent upon the length of the first and second air gaps as determined by the position of the first and second sensors relative to the target at that point in time. The first and second sensors are also operatively associated with a compensating circuit which includes an electronic adder for adding the output signals produced by the first and second sensors, an electronic subtractor for subtracting the output signals produced by the first and second sensors, and an electronic divider for dividing the added output signals by the subtracted output signals. Since the output signals change in magnitude in a manner indicative of the magnetic field intensity by reason of changes in the length of the first and second air gaps, the electronic divider produces a numerical value representative of the accurate angular position of the rotor which is independent of power supply and temperature variations.

Claims43

Dependent claims

A power and temperature independent magnetic position sensor for a rotor, comprising:

first and second magnetic sensing means for accurately determining the angular position of said rotor, said first and second magnetic sensing means including at least one disk shaped target means having a continuously increasing radial dimension and being fixedly mounted in operatively associated relation to said rotor so as to rotate therewith, first sensor means fixedly mounted in spaced relation to the periphery of said target means and disposed at a variable distance from said target means dependent upon the angular position of said rotor to define a first air gap therebetween, and second sensor means fixedly mounted in spaced relation to the periphery of said target means and disposed at a variable distance from said target means dependent upon the angular position of said rotor to define a second air gap therebetween, said first and second sensor means cooperating with said target means to detect magnetic field intensity in said first and second air gaps, respectively;
said first and second sensor means producing output signals indicative of said magnetic field intensity in said first and second air gaps, said magnetic field intensity in said first and second air gaps at any point in time being dependent upon the length of said first and second air gaps as determined by the position of said first and second sensor means relative to said target means at that point in time, said output signals changing in magnitude in a manner indicative of said magnetic field intensity by reason of changes in the length of said first and second air gaps;
and
compensating means operatively associated with said first and second sensor means, said compensating means including means for adding said output signals produced by said first and second sensor means, means for subtracting said output signals produced by said first and second sensor means, and means for dividing said added output signals by said subtracted output signals to produce a numerical value representative of the accurate angular position of said rotor, said numerical value being independent of power supply and temperature variations.

1 more element

A power and temperature independent magnetic position sensor for a rotor, comprising:

first and second magnetic sensing means for accurately determining the angular position of said rotor, said first and second magnetic sensing means including first and second disk shaped target means each having a continuously increasing radial dimension and each being fixedly mounted in operatively associated relation to said rotor so as to rotate therewith, first sensor means fixedly mounted in spaced relation to the periphery of said first target means and disposed at a variable distance from said first target means dependent upon the angular position of said rotor to define a first linearly variable air gap therebetween, and second sensor means fixedly mounted in spaced relation to the periphery of said second target means and disposed at a variable distance from said second target means dependent upon the angular position of said rotor to define a second linearly variable air gap therebetween, said first and second sensor means cooperating with said first and second target means to detect magnetic field intensity in said first and second air gaps, respectively;
said first and second sensor means producing output signals indicative of said magnetic field intensity in said first and second air gaps, said magnetic field intensity in said first and second air gaps at any point in time being dependent upon the length of said first and second air gaps as determined by the position of said first and second sensor means relative to said first and second target means at that point in time, said output signals changing in magnitude in a manner indicative of said magnetic field intensity by reason of changes in the length of said first and second air gaps;
the length of said first air gap always being less than the length of said second air gap so that the magnitude of said output signal produced by said first sensor means is always greater than the magnitude of said output signal produced by said second sensor means;
and
compensating means operatively associated with said first and second sensor means, said compensating means including means for adding said output signals produced by said first and second sensor means, means for subtracting said output signals produced by said first and second sensor means, and means for dividing said added output signals by said subtracted output signals to produce a numerical value representative of said accurate angular position of said rotor, said numerical value being independent of power supply and temperature variations.

2 more elements

A power and temperature independent magnetic position sensor for a rotor comprising:

first and second magnetic sensing means for accurately determining the angular position of said rotor, said first and second magnetic sensing means including single disk shaped target means having a continuously increasing radial dimension and being fixedly mounted in operatively associated relation to said rotor so as to rotate therewith, first sensor means fixedly mounted in spaced relation to the periphery of said target means in a manner so as to be disposed at a variable distance from said target means dependent upon the angular position of said rotor to define a first linearly variable air gap therebetween, and second sensor means fixedly mounted in spaced relation to the periphery of said target means in a manner so as to be disposed at a variable distance from said target means dependent upon the angular position of said rotor to define a second linearly variable air gap therebetween, said first and second sensor means cooperating with said target means to detect magnetic field intensity in said first and second air gaps, respectively;
said first and second sensor means producing output signals indicative of said magnetic field intensity in said first and second air gaps, said magnetic field intensity in said first and second air gaps at any point in time being dependent upon the length of said first and second air gaps as determined by the position of said first and second sensor means relative to said target means at that point in time, said output signals changing in magnitude in a manner indicative of said magnetic field intensity by reason of changes in the length of said first and second air gaps;
the length of said first air gap normally being less than the length of said second air gap so that the magnitude of said output signal produced by said first sensor means is normally greater than the magnitude of said output signal produced by said second sensor means;
and p1 compensating means operatively associated with said first and second sensor means, said compensating means including means for adding said output signals produced by said first and second sensor means, means for subtracting said output signals produced by said first and second sensor means, and means for dividing said output signals by said subtracted output signals to produce a numerical value representative of the accurate angular position of said rotor, said numerical value being independent of power supply and temperature variations.

1 more element

In a compensating circuit for accurately determining the angular position of a rotor with a magnetic position sensor independent of power supply and temperature variations, said magnetic position sensor including first and second magnetic sensing means for accurately determining the annular position of said rotor, said first and second magnetic sensing means including at least one disk shaped target means having a continuously increasing radial dimension and being fixedly mounted in operatively associated relation to said rotor so as to rotate therewith, first sensor means fixedly mounted in spaced relation to the periphery of said target means and disposed at a variable distance from said target means dependent upon the angular position of said rotor to define a first air gap therebetween, and second sensor means fixedly mounted in spaced relation to the periphery of said target means and disposed at a variable distance from said target means dependent upon the angular position of said rotor to define a second air gap therebetween, said first and second sensor means cooperating with said target means to detect magnetic field intensity in said first and second air gaps, the improvement comprising:

means for adding output signals from said first and second sensor means of said magnetic position sensor, said output signals being indicative of said magnetic field intensity in said first and second air gaps and said adding means being operatively associated with said first and second sensor means;
means for subtracting said output signals from said first and second sensor means of said magnetic position sensor, said output signals changing in magnitude with changes in the length of said first and second air gaps and said subtracting means being operatively associated with said first and second sensor means;
and
means operatively associated with said adding and subtracting means for dividing said added output signals by said subtracted output signals to produce a numerical value representative of the accurate angular position of said rotor;
said numerical value being independent of power supply and temperature variations.

2 more elements

A method for accurately determining the angular position of a rotor with a magnetic position sensor, said magnetic position sensor including first and second ensor means disposed relative to target means operatively associated with said rotor to rotate therewith to define first and second air gaps therebetween, respectively, the angular position being determined independent of power supply and temperature variations, comprising the steps of:

adding rotor angle-related linearly variable output signals from said first and second sensor means of said magnetic position sensor, said output signals being indicative of said magnetic field intensity in said first and second air gaps;
subtracting said rotor angle-related linearly variable output signals from said first and second sensor means of said magnetic position sensor, said output signals changing in magnitude with changes in the length of said first and second air gaps;
said output signals being dependent upon the angular position of said rotor at any point in time;
and
dividing said added output signals by said subtracted output signals to produce a numerical value representative of the accurate angular position of said rotor;
said numerical value being independent of power supply and temperature variations.

3 more elements

Dependencies are inferred from the claim text.

Power and temperature independent magnetic position sensor for a rotor

Life of this patent

Power and temperature independent magnetic position sensor for a rotor

Life of this patent

Abstract

Claims43