Method for detecting the angular position of a rotor in a brushless electric motor
First Claim
1. A method for detecting the angular position of a brushless electric motor, of the type in which the emission of a polarity signal of the back electromotive force by a detection circuitry associated with the motor is provided, comprising:
- detecting a polarity signal of a back electromotive force from a winding of the motor using a detection circuit;
using a bi-directional counter to count a difference in residence time of logic states ‘
0’ and
‘
1’
at an output of said detection circuitry; and
enabling the bi-directional counter around an expected zero-crossing of said back electromotive force with a counting window having an arbitrary duration.
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Accused Products
Abstract
A method for detecting the angular position of a rotor in a brushless electric motor, of the type in which the emission of a polarity signal of the back electromotive force by a detection circuitry associated with the motor, includes the using a bi-directional counter for counting the residence time difference of the logic states ‘0’ and ‘1’ at the output of the detection circuitry. The method is aimed at improving the detection of the instantaneous position of the rotor in a brushless motor through the detection of the zero-crossing signal.
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Citations
29 Claims
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1. A method for detecting the angular position of a brushless electric motor, of the type in which the emission of a polarity signal of the back electromotive force by a detection circuitry associated with the motor is provided, comprising:
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detecting a polarity signal of a back electromotive force from a winding of the motor using a detection circuit; using a bi-directional counter to count a difference in residence time of logic states ‘
0’ and
‘
1’
at an output of said detection circuitry; andenabling the bi-directional counter around an expected zero-crossing of said back electromotive force with a counting window having an arbitrary duration. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A method for detecting a rotor position in a brushless electric motor, comprising:
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detecting a back electromotive force in a winding of the motor; determining a polarity of the back electromotive force; incrementing a counter up or down according to the polarity of the back electromotive force; repeating the determining and incrementing steps at a selected frequency during a selected time period; and establishing a true point of zero crossing based upon a count of the counter at the end of the selected time period. - View Dependent Claims (16, 17, 18)
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14. A method for detecting a rotor position in a brushless electric motor, comprising:
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detecting a back electromotive force in a winding of the motor; estimating a point of zero crossing of the back electromotive force; determining a polarity of the back electromotive force; incrementing a counter up or down according to the polarity of the back electromotive force; and repeating the determining and incrementing steps at a selected frequency during a selected time period. - View Dependent Claims (15)
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19. A method, comprising:
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estimating a point of zero crossing of a back electromotive force of a winding of a motor; establishing a time period beginning a first selected period prior to the estimated zero crossing, and ending a second selected period after the estimated zero crossing, the first and second selected periods being equal; incrementing a counter repeatedly at a selected frequency during the time period; determining, at each increment of the counter, a polarity of the back electromotive force; incrementing the counter in a first direction if the polarity of the back electromotive force is positive; incrementing the counter in a second direction if the polarity of the back electromotive force is negative; and establishing a true point of zero crossing based upon a value of the counter at the end of the time period. - View Dependent Claims (22, 24)
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20. A system, comprising:
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a comparator module configured to detect a back electromotive force in a motor winding and supply a digital signal at an output based upon a polarity of the detected back electromotive force; a counter module configured to increment up or down at a selected frequency according to a digital value at the output of the comparator module; a position detector module configured to estimate a point of zero crossing of the back electromotive force, and to determine a true position of a rotor of the motor based upon a count of the counter module at an end of a selected time period; and an enable module configured to select the time period such that the estimated zero crossing occurs at a midpoint of the time period, and to enable the counter module during the selected time period. - View Dependent Claims (21)
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23. A method for detecting the angular position of a brushless electric motor, comprising:
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detecting a polarity signal of a back electromotive force from a winding of the motor, using a detection circuit; using a bi-directional counter to count a difference in residence time of logic states ‘
0’ and
‘
1’
at an output of said detection circuitry during counting windows; andzeroing the counter at a start of each counting window, or at an arbitrary moment before such a time period. - View Dependent Claims (25)
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26. A method for detecting the angular postion of a brushless electric motor, comprising:
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detecting a polarity signal of a back electromotive force from a winding of the motor using a detection circuit; using a bi-directional counter to count a difference in residence time of logic states ‘
0’ and
‘
1’
at an output of said detection circuitry during counting windows;varying a counting frequency of the counter during various driving phases of the motor; and zeroing the counter at a start of each counting window, or at an arbitrary moment before such a time period.
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27. A method for detecting the angular postion of a brushless electric motor, comprising:
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detecting a polarity signal of a back electromotive force from a winding of the motor using a detection circuit; using a bi-directional counter to count a difference in residence time of logic states ‘
0’ and
‘
1’
at an output of said detection circuitry during each of succession of counting windows;using a value assumed by the counter at an end of each counting window in formulas to estimate an instantaneous position of the rotor, a period between two zero-crossings, and a speed of rotation; estimating a zero crossing based on previously determined zero crossings; and establishing a counting window such that the estimated zero crossing is at a midpoint of the counting window.
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28. A method for detecting the angular position of a brushless electric motor, comprising:
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detecting a polarity signal of a back electromotive force from a winding of the motor using a detection circuit; using a bi-directional counter to count a difference in residence time of logic states ‘
0’ and
‘
1’
at an output of said detection circuitry during each of a succession of counting windows; andcomputing a period between two zero-crossings according to the algorithm
Period(n)=Period(n−
1)+K1*Delta(n−
1)where; “
Period(n−
1)”
results from a calculation carried out at an end of a previous window,Delta is the calculation carried out at the end of the previous window and is a filtered value of position information of a real zero-crossing with respect to the expected zero crossing at the base; “
Period(n)”
is the period which separates one zero crossing from a previous zero-crossing calculated at the end of a previous counting window; andK1 and K2 are generic parameters whose value can be established according to filtering requirements. - View Dependent Claims (29)
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Specification