(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2006/0290302 A1
`Marcinkiewicz et al. Dec. 28, 2006 (43) Pub. Date:
`
`
`
`US 20060290302Al
`
`(54) SENSORLESS CONTROL SYSTEMS AND
`METHODS FOR PERMANENT MAGNET
`ROTATING MACHINES
`
`(52) U.S. Cl.
`
`................................................................ 318/66
`
`(75)
`
`Inventors: Joseph G. Marcinkiewicz, St. Peters,
`MO (US); Prakash B. Shahi, St. Louis,
`MO (US); Michael 1. Henderson,
`North Yorkshire (GB)
`
`57
`
`(
`
`)
`
`ABSTRAC
`
`T
`
`Correspondence Address:
`HARNESS DICKEY & PIERCE PILIC
`7700 BONIEOMME’ gr]-E 400
`’
`ST_ LOUIS’ MO 63105 (US)
`
`(21) App], No;
`
`11/293,744
`
`(22) Filed:
`
`Dec. 2, 2005
`
`Related U-S- Application Data
`
`(60) Provisional application No. 60/694,077, filed on Jun.
`24, 2005. Provisional application No. 60/694,066,
`filed on Jun. 24, 2005.
`
`Publication Classification
`
`(51) mt, C],
`H02P 5/00
`
`(2006.01)
`
`Systems and methods for controlling a rotating electromag-
`.
`.
`.
`.
`netic machine. The rotating machine, such as a permanent
`magnet motor or hybrid switched reluctance motor, includes
`a stator having a plurality of phase windings and a rotor that
`rotates relative to the stator. A drive is connected to the phase
`
`windings for energizing the windings. A controller outputs a
`control signal to the drive in response to an input demand
`such as a demanded speed or torque. Control methods
`(which can be implemented separately or in combination)
`include varying the gain of an estimator as a function of a
`demanded or estimated speed to position control system
`poles at desired locations, decoupling control system cur-
`rents to achieve a constant torque with motor speed, com-
`pensating flux estimates of the estimator for saturation
`operation of the stator, estimating rotor position using aver-
`ages of sample values of energization feedback, and calcu-
`lating a trim adjusted speed error from a plurality of speed
`estimates.
`
`1 O0
`
`2
`
`102
`
`114
`
`
`Controller
`
`Feeback
`
`112
`
`BOM Exhibit 1045
`
`BOM v. Nideo
`
`|PR2014—01 121
`
`BOM Exhibit 1045
`BOM v. Nidec
`IPR2014-01121
`
`1
`
`

`
`Patent Application Publication Dec. 28, 2006 Sheet 1 of 13
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`
`FIG. 4
`
`5
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`

`
`Patent Application Publication Dec. 28, 2006 Sheet 5 of 13
`
`US 2006/0290302 A1
`
`m:_m>ENG
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`_-______L____--__L
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`Motor Electrical Speed (radians per second)
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`-1000
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`-2000
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`FIG. 5a
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`-_______L_____-__
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`
`FIG
`
`.5b
`
`6
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`
`Patent Application Publication Dec. 28, 2006 Sheet 6 of 13
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`US 2006/0290302 A1
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`Patent Application Publication Dec. 28, 2006 Sheet 7 of 13
`
`US 2006/0290302 A1
`
`716
`
`Update observer
`states
`
`71 8
`
`Calculate electrical angle
`
`720
`
`Calculate electrical speed
`
`
`
`
`
`722
`
`724
`
`Filter speed
`estimate
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`angle
`
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`
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`
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`
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`
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`
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`Estimator gains
`
`FIG. 7
`
`8
`
`

`
`Patent Application Publication Dec. 28, 2006 Sheet 8 of 13
`
`US 2006/0290302 A1
`
`800
`
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`
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`
`electrical speed
`
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`
`electrical speed
`
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`error
`
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`action
`
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`
`injection
`
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`
`814
`
`
`
`Output Or and dr currents to
`the current control loops
`
`FIG. 8
`
`9
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`Patent Application Publication Dec. 28, 2006 Sheet 9 of 13
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`US 2006/0290302 A1
`
`Dec. 28, 2006
`
`SENSORLESS CONTROL SYSTEMS AND
`METHODS FOR PERMANENT MAGNET
`ROTATING MACHINES
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`[0001] This application claims the benefit of U.S. Provi-
`sional Applications No. 60/694,077 and No. 60/694,066
`filed Jun. 24, 2005,
`the entire disclosures of which are
`incorporated herein by reference.
`
`FIELD OF THE INVENTION
`
`[0002] The present invention relates generally to control
`of rotating machines, including but not limited to sensorless
`control of permanent magnet rotating machines.
`
`BACKGROUND OF THE INVENTION
`
`[0003] Permanent magnet machines, such as brushless
`permanent magnet motors, have been conventionally pro-
`vided with position sensing devices. Such devices indicate,
`for use in controlling the motor,
`the rotor position with
`respect to the stator. However, rotor position sensors can be
`quite expensive, occupy space within a motor housing, and
`sometimes fail. To eliminate the need for position sensors,
`various “sensorless” motor constructions and methods have
`been developed with varying degrees of success. As recog-
`nized by the present inventors a need exists for improve-
`ments in sensorless control systems for rotating permanent
`magnet machines.
`
`SUMIVIARY OF THE INVENTION
`
`In one aspect of the present invention, a method is
`[0004]
`provided for controlling a permanent magnet
`rotating
`machine. The machine includes a stator having a plurality of '
`energizable phase windings situated therein, a rotor situated
`to rotate relative to the stator, and an estimator having at
`least one gain value and employing an observer. The method
`includes varying the gain of the estimator as a function of
`either a demanded rotor speed or an estimated rotor speed to
`thereby position poles of the observer at desired locations.
`
`In another aspect of the invention, a method is
`[0005]
`provided for controlling a permanent magnet
`rotating
`machine. The machine includes a stator having a plurality of
`energizable phase windings situated therein, and a rotor
`situated to rotate relative to the stator. The method includes
`determining a value of Idr-axis current to be injected, and
`selecting a value of IQr-axis current that, in conjunction with
`the value of Idr-axis current, will produce a desired rotor
`torque.
`
`In still another aspect of the invention, a method is
`[0006]
`provided for controlling a permanent magnet
`rotating
`machine. The machine includes a stator having a plurality of
`energizable phase windings situated therein, and a rotor
`situated to rotate relative to the stator. The method includes
`receiving energization feedback from the machine, and
`producing a flux estimate compensated for saturation in the
`stator.
`'
`
`one another. It should also be understood that the detailed
`description and drawings, while indicating certain exem-
`plary embodiments of the invention, are intended for pur-
`poses of illustration only and should not be construed as
`limiting the scope of the invention.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0008] FIG. 1 is a block diagram of a rotating permanent
`magnet (PM) machine system according to one exemplary
`embodiment of the invention.
`
`[0009] FIG. 2 is a block diagram of a PM machine system
`configured to operate primarily in a torque control mode
`according to another exemplary embodiment of the inven-
`tion.
`
`[0010] FIG. 3 is a block diagram of a PM machine system
`configured to operate primarily in a speed control mode
`according to another exemplary embodiment of the inven-
`tion.
`
`[0011] FIG. 4 is a graph illustrating how gain values can
`be varied with respect to rotor speed so as to maintain the
`poles of an observer employed by the estimators of FIGS.
`2 and 3 in desired locations.
`
`[0012] FIGS. 5a and 5b illustrate how estimator gain
`values approach excessive values as
`the rotor
`speed
`approaches zero.
`
`[0013] FIG. 6 is a block diagram illustrating how estima-
`tor gain values can be stored in and accessed fiom lookup
`tables.
`
`[0014] FIG. 7 is a flow diagram of a method implemented
`by the gain schedulers of FIGS. 2 and 3 according to
`another exemplary embodiment of the invention.
`
`[0015] FIG. 8 is a flow diagram of a method of calculating
`a Qr-axis current based on a given dr-axis current injection
`to produce a desired rotor torque according to another
`exemplary embodiment of the invention.
`
`[0016] FIG. 9 is a block diagram of a speed loop control-
`ler, a torque to IQdr Map block, and a Idr injection block
`according to another exemplary embodiment of the inven-
`tion.
`
`[0017] FIG. 10 is a block diagram of the torque and Idr to
`IQr map block of FIG. 9 according to another exemplary
`embodiment.
`
`[0018] FIG. 11 is a block diagram illustrating how satu-
`ration effects can be compensated for in the measurement
`path of an observer according to another exemplary embodi-
`ment.
`
`[0019] FIG. 12(a) is graph illustrating how two energiza-
`tion feedback samples are collected at the beginning and end
`of an exemplary sampling interval according to the prior art.
`
`[0020] FIG. 12(1)) is a graph illustrating how two energi-
`zation feedback samples can be collected and averaged to
`produce an estimated rotor position/angle according to
`another embodiment of the invention.
`
`[0007] Further aspects of the present invention will be in
`part apparent and in part pointed out below. It should be
`understood that various aspects of the invention may where
`suitable be implemented individually or in combination with
`
`[0021] FIG. 13 is a block diagram of an exemplary speed
`trim mechanism for producing a speed trim value that can be
`provided to the estimator of FIG. 3 according to another
`exemplary embodiment of the invention.
`
`15
`
`15
`
`

`
`US 2006/0290302 A1
`
`Dec. 28, 2006
`
`[0022] Like reference symbols indicate like elements or
`features throughout the drawings.
`
`DETAILED DESCRIPTION OF EXEMPLARY
`EMBODIMENTS
`
`Illustrative embodiments of the invention are
`[0023]
`described below. In the interest of clarity, not all features of
`an actual implementation are described in this specification.
`It will be appreciated that in the development of any actual
`embodiment, numerous implementation-specific decisions
`must be made to achieve specific goals, such as performance
`objectives and compliance with system-related, business-
`related and/or environmental constraints. Moreover, it will
`be appreciated that such development efforts may be com-
`plex and time-consuming, but would nevertheless be a
`routine undertaking for those of ordinary skill
`in the art
`having the benefit of this disclosure.
`
`[0024] FIG. 1 illustrates a rotating permanent magnet
`machine system 100 according to one embodiment of the
`present
`invention. The machine system 100 includes a
`rotating permanent magnet electric machine 101, such as a
`permanent magnet alternating current (PMAC) motor or a
`hybrid permanent magnet/switched reluctance (PM/SR)
`motor. For simplicity, the term “motor” is often used in this
`specification. However, one skilled in the art having the
`benefit of this disclosure will understand that the present
`invention is applicable to other types of rotating electric
`machines,
`including generators. The PM machine 101
`shown in FIG. 1 includes a stationary component (stator)
`102 and a rotating component (rotor) 104. The machine 101
`can have an inner rotor or an outer rotor construction. In this
`exemplary embodiment, the PM machine 101 is a three
`phase machine having an inner rotor construction with
`energizable phase windings 106A, 106B, 106C wound about
`the stator 102, which are energized through the application
`of electric power to the motor terminals.
`,
`
`[0025] A drive 108 is coupled to the terminals of the
`machine for providing electric power. The drive 108
`receives control inputs from a controller 110 that receives
`energization feedback 112 from the machine (such as the
`currents and/or voltages at the motor terminals), or that .
`assumes the actual voltage supplied to the motor is that
`which was demanded by the controller 110 (e.g., in the form
`of PWM duty cycle), from which the electrical angle and
`electrical speed can be determined (i.e., estimated sensor-
`lessly). From these estimates, rotor speed can be inferred, as
`can rotor angle (to the extent the estimates are based upon
`electrical angle). The controller 110 of FIG. 1 is shown as
`receiving an input demand 114 that may be, for example, a
`torque demand or a speed demand.
`
`[0026] While the drive 108 of FIG. 1 is illustrated in
`exemplary form as energizing three power terminals of a
`three phase machine 101, it should be understood that more
`or fewer power terminals may be provided to accommodate
`machines with greater or less than three phases, or if various
`types of inverters (e.g., with neutral connections) are used.
`The drive may be of conventional design and configured to
`provide, for example., sine wave excitation to the motor
`terminals or square wave excitation using conventional
`pulse width modulation (PWM) excitation.
`
`[0027] FIG. 2 illustrates additional details ofthe system of
`FIG. 1 as configured to operate primarily in a torque control
`
`mode. For this reason, a torque demand input 214 is shown
`in FIG. 2. The torque demand input may be received directly
`by the system 200 as an external command or alternatively,
`may be derived from an external command. For example,
`the torque demand input may be derived from a speed
`demand input or from an air flow demand input (e.g., where
`the system of FIG. 2 is embodied in an air handler/blower
`for a climate control system). Additional details regarding
`the embodiment of FIG. 2 are provided in U.S. application
`Ser. No. [Docket No. 5260-000211/US filed on Dec. 2,
`2005] titled Control Systems and Methods for Permanent
`Magnet Rotating Machines and filed [on even date here-
`with], the entire disclosure of which is incorporated herein
`by reference.
`
`[0028] FIG. 3 illustrates additional details of the system of
`FIG. 1 as configured to operate primarily in a speed control
`mode. Further information regarding operating in speed
`control modes is set forth in U.S. Pat. No. 6,756,753.
`
`[0029] Described below are several additional improve-
`ments in controlling a PM machine according to various
`aspects of the present invention. It should be understood that
`each improvement can be advantageously implemented by
`itself or in combination with one or more other improve-
`ments disclosed herein.
`
`[0030] As shown in FIGS. 2 and 3, the controller of FIG.
`1 can include an estimator 202, 302 for estimating the
`machine’s electrical speed and angle. In some embodiments,
`the estimators 202, 302 employ a Luenberger Observer.
`However, other types of observers, including the Kalman
`Estimator, may be employed.
`
`[0031] According to one aspect of the present invention,
`the gain of an estimator——such as the estimators 202, 302
`shown in FIGS. 2 and 3—can be varied (e.g., using the gain
`schedulers 204, 304 shown in FIGS. 2 and 3) as a function
`of either a demanded rotor speed (including a filtered
`demanded speed) or an estimated rotor speed. In this man-
`ner, control system poles (i.e., poles of the observer) can be
`positioned at desired locations, including maintaining the
`poles at desired and not necessarily fixed locations to
`improve control system and machine stability.
`
`In a torque control mode of operation, there is no
`[0032]
`demanded speed. Therefore, the estimator gains are prefer-
`ably varied as a function of the estimated rotor speed so as
`to position the control system poles at desired locations. The
`estimated rotor speed used in the gain scheduling may be
`pre-processed in a suitable manner before being used in the
`gain scheduling scheme, typically being passed through a
`low pass filter.
`
`In one embodiment of a speed control mode of
`[0033]
`operation, the pole locations of the estimators 202, 302 are
`increased as speed increases, with the slowest pole locations
`occurring as the system is switched from open loop opera-
`tion to closed loop operation.
`
`[0034] The gain values can be calculated for a range of
`speeds. This may be done on the fly by the gain scheduler
`204, 304 of FIG. 2 or 3 using a closed form set of equations.
`Alternatively, the gain values may be retrieved by the gain
`scheduler from one or more look—up tables or from a fitted
`curves characterizing the gain-speed profile for a specific
`motor.
`
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`[0035] FIG. 4 illustrates how gain values are varied with
`respect to the electrical speed in one exemplary embodiment
`so as to maintain observer poles at desired locations.
`
`[0036] FIGS. 5a and 5b illustrate how gain values
`approach excessive values as the electrical speed approaches
`zero. For this reason, gain values are preferably not calcu-
`lated as described within a range of values around zero
`electrical speed. At low or zero speeds, predetermined gain
`values which are suificiently high, but not excessive, are
`preferably used, thereby improving control system stability.
`
`[0037] FIG. 6 illustrates how gain values may be stored in
`and accessed from lookup tables. In the particular embodi-
`ment of FIG. 6, two columns of gain values are constructed
`through a multiplexer and then concatenated together to
`form a 4x2 gain matrix.
`
`[0038] FIG. 7 is a flow diagram 700 illustrating one
`preferred implementation of the gain schedulers 204, 304 of
`FIGS. 2 and 3 in which the speed used by the gain
`scheduler, referred to as the scheduled speed, is set to the
`drive speed (i.e., a demanded rotor speed) at lower rotor
`speeds and to the estimated electrical speed at higher rotor
`speeds.
`
`In step 702, the controller transforms state vari-
`[0039]
`ables into a rotating frame of reference. In step 704, the
`controller reads the estimated electrical speed and then reads
`the drive speed (i.e., the demanded speed) in step 706. In
`step 708,
`the controller compares the drive speed to a
`predetermined threshold speed. The predetermined speed
`threshold parameter can be selected, as needed, for any
`given PM machine.
`
`If the drive speed is greater than the predetermined
`[0040]
`threshold speed,
`the scheduled speed used by the gain
`schedulers 204, 304 (FIGS. 2 and 3) is set equal to the
`estimated electrical speed in step 710. If the drive speed is
`less than the predetermined threshold speed, the scheduled
`speed used by the gain schedulers 204, 304 is set equal to the
`drive speed in step 712. Subsequent to controller selection of
`the appropriate scheduled speed, the selected schedule speed
`is used by gain schedulers 204, 304 to look up or calculate
`the estimator gains in step 714 to maintain the system poles
`at desired positions. The estimator uses the scheduled gain
`factors and the updated observer states in step 716 to
`calculate an updated estimated electrical angle in step 718
`and an updated estimated electrical speed in step 720. The
`updated electrical speed estimate is filtered in step 722 and
`the filtered speed estimate is integrated in step 724 to
`produce an updated electrical angle demand.
`
`[0041] According to another aspect of the present inven-
`tion, a Qr-axis current can be selected that, in conjunction
`with a given value of dr—axis current, will produce a desired
`rotor torque. This aspect is particularly well suited to hybrid
`PM/SR motors, where the dr—axis current component con-
`tributes to the amount of torque produced, and especially
`hybrid PIVI/SR motors employing a dr—axis injection current.
`
`[0042] FIG. 8 is a flow diagram 800 illustrating a method
`of calculating a Qr-axis current based on a given dr—axis
`current injection to produce a desired rotor torque according
`to one exemplary embodiment. In this embodiment, the
`dr—axis current injection is calculated ofllline in accordance
`with a dr—axis current injection method described in co-
`pending US. application Ser. No. [Docket 5260-000211/US
`
`filed on even date herewith] noted above. These values are
`typically stored in a lookup table but may also be described
`as a mathematical function in alternative embodiments. The
`motor speed and the value of the dc—link are used to calculate
`the value of the dr—axis injection current to be applied at any
`given moment in time.
`
`In step 802, the controller reads the demanded
`[0043]
`electrical speed 802 and then reads the estimated electrical
`speed in step 804. In step 806, the controller calculates a
`speed error. The controller uses the calculated speed error
`from step 806 to update the control action in step 808. After
`updating the control action, the controller reads the intended
`dr—axis injection current in step 810, calculates the Qr—axis
`current required to produce a demanded torque in step 812
`and outputs the demanded Qr- and dr—axis currents in step
`814 to a pair of current controllers, such as current control-
`lers 206, 208 of FIG. 2 or current controllers 306, 308 of
`FIG. 3.
`
`[0044] FIG. 9 is a block diagram of a speed loop control-
`ler 902, a torque to IQdr Map block 904, and a Idr injection
`block 906 according to another exemplary embodiment. As
`shown in FIG. 9, the selected Qr-axis current and the dr—axis
`injection current are multiplexed and provided to a pair of
`current controllers, preferably as a multiplexed demand
`signal, IQdr demand 908. In this embodiment of the Idr
`injection block 906, the required Idr current is calculated
`from the speed error, assuming that Idr is for the moment
`nominally zero.
`
`[0045] FIG. 10 is a block diagram of the Torque and Idr
`to IQr map block of FIG. 9 according to another exemplary
`embodiment of the invention. In this embodiment, using the
`motor-specific constants noted, the Iqr_demand is calculated
`as:
`
`Iqr;dema.nd=(S4.5"Torque
`(22.54—Idr)
`
`dema.nd+0.4373*Idr)/
`
`[0046] The decoupling of IQdr components in the produc-
`tion of torque can be applied within either a sensorless
`control system or a sensor-controlled system. If a given
`motor does not show any discernible hybrid behavior, the
`control technique can default to that classically used with a
`PM motor (i.e., Idr torque contribution is assumed to be
`zero) where the torque contribution comes from IQr.
`
`[0047] According to another aspect of the invention, the
`flux estimate produced by a flux estimator 202, 302, such as
`the estimators shown in FIGS. 2 and 3, can be compensated
`for saturation eifects when the motor operates in the non-
`linear saturation regions of stator magnetic flux. In this
`manner, errors in the flux estimate can be reduced, thus
`reducing errors in rotor position and/or rotor speed estimates
`produced from the flux estimate. As a result, the stability of
`the control system is improved under stator saturation oper-
`ating conditions. This improvement is particularly important
`when the structure of the drive control
`is based upon
`manipulating variables generated using transformations hav-
`ing values dependent on the machine electrical angle. This
`aspect of the invention is particular well suited for hybrid
`PM machines, PM machines having embedded rotor mag-
`nets, and PM machines employing highly magnetized mate-
`rial.
`
`[0048] The compensated flux estimate can be produced
`using nonlinear correction terms including, for example,
`
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`
`dominant angle invariant terms associated with saturation,
`including cubic terms. Dominant angle-varying terms may
`also be used to produce the compensated flux estimate.
`Tenns may also be present that include quadratic current
`expressions when they have a dominant effect on the flux
`estimate. In one embodiment of the invention directed to an
`air handler for a climate control system, the dominant terms
`are cubic.
`
`In one exemplary embodiment, a flux estimate is
`[0049]
`first produced using energization feedback 112 from the
`machine. This flux estimate is then compensated for satu-
`ration effects, with the flux estimate becoming significant as
`the saturation effects themselves become significant
`
`[0050] FIG. 11 is a block diagram illustrating how satu-
`ration effects are compensated for in the measurement path
`of an Observer (e.g., embodied in a flux estimator) according
`to one exemplary embodiment of the invention. When the
`controller detects saturation operation of the stator,
`the
`compensated flux estimate is used by the estimator to
`estimate rotor speed and rotor position.
`
`[0051] According to another aspect of the present inven-
`tion, a rotor position (i.e., angle) estimator-such as the
`estimators 202, 302 shown in FIGS. 2 and 3—<:an average
`samples of the energization feedback 112 from the machine
`and estimate the rotor position using the average sample
`values. In this manner, the magnitude of the potential error
`within each sampling interval is reduced in half, resulting in
`more accurate control of the machine when control of the
`machine is dependent on accurately estimating the rotor
`position. Although the magnitude of the potential error
`within each sampling interval increases as the sampling rate
`decreases, it should be understood that this aspect of the
`present invention can be advantageously used with any
`sampling rate to improve the accuracy of the estimated rotor
`position. The estimate calculation eifectively compensates
`for time delays resulting from use of the angle estimate in
`the drive.
`
`samples
`each successive pair of
`[0052] Preferably,
`(including the second sample from the immediately preced-
`ing successive sample pair) is averaged to produce a series
`of average sample values which are used to estimate the
`rotor position.
`
`[0053] FIG. 12(a) illustrates how two samples are col-
`lected at the beginning and end of an exemplary sampling
`interval according to the prior art, where each sample is
`treated as representing the actual rotor position/angle at the
`time such sample was obtained. FIG. 12(b) illustrates how
`two samples are collected and averaged to produce an
`estimated rotor position/angle. Collectively, FIGS. 12(a) and
`12(1)) illustrate that while the range of error (2e) remains the
`same, the absolute value of the potential error about the
`average angle estimate in FIG. 12(b) is reduced in half
`(+/—e) as compared to FIG. 12(a), where the angle error
`estimate could be as large as 2e.
`
`[0054] According to another aspect of the present inven-
`tion, a trim-adjusted speed error can be calculated and
`provided, e.g.,
`to a speed contro]ler—such as the speed
`controller shown in FIG. 3. An exemplary method includes
`producing a first rotor speed estimate, producing a second
`rotor speed estimate, and calculating a trim-adjusted speed
`error using the first rotor speed estimate and the second rotor
`
`speed estimate. Preferably, a trim value is produced by
`calculating a difference between the first rotor speed esti-
`mate and the second rotor speed estimate. Additionally, a
`raw speed error is preferably produced by calculating a
`difference between a demanded rotor speed and an estimated
`rotor speed (which may be the first rotor speed estimate or
`the second rotor speed estimate, and preferably the more
`reliable one of such estimates, which may depend, e.g., on
`the PWM rate of the motor drive). The trim-adjusted speed
`error is preferably calculated by adding the trim value to the
`raw speed error.
`
`[0055] The first rotor speed estimate carrbe produced
`using modeled motor parameters, and the second rotor speed
`estimate can be produced using zero crossings detected from
`energization feedback from the machine. In this manner, the
`trim value and thus the trim-adjusted speed error can
`account for potential variations between modeled motor
`parameters and actual parameters of a production motor.
`
`[0056] FIG. 13 is a block diagram of an exemplary trim
`mechanism for producing a trim value that can be provided,
`e.g., to an estimator such as the estimator shown in FIG. 3.
`In this embodiment, the trim error 1302 is filtered using a
`first order low pass filter 1304. The filtered trim error signal
`1306 is then added directly to the error signal driving the
`speed loop controller. FIG. 9, discussed above, illustrates an
`exemplary speed controller that includes an input 910 for
`such a trim value. The trim mechanism can be used to
`improve the performance of an estimator-based sensorless
`control system.
`
`1. A method of controlling a permanent magnet rotating
`machine, the machine including a stator and a rotor situated
`to rotate relative to the stator, the stator having a plurality of
`energizable phase windings situated therein, and an estima-
`tor having at
`least one gain value and employing an
`observer, the method comprising:
`
`varying the gain of the estimator as a function of either a
`demanded rotor speed or an estimated rotor speed to
`thereby position poles of the observer at desired loca-
`tions.
`2. The method of claim 1 wherein varying includes
`varying the estimator gain while operating in a closed loop
`control mode.
`3. The method of claim 1 wherein varying includes
`varying the estimator gain with respect to the demanded
`rotor speed when the actual rotor speed is outside a pre-
`defined range, and varying the estimator gain with respect to
`the estimated electrical speed when the actual rotor speed is
`within the predefined range.
`4. The method of claim 1 further comprising calculating
`estimator gains for one or more rotor speed ranges.
`5. The method of claim 4 wherein the one or more rotor
`speed ranges exclud