(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2006/0290304 A1
`Marcinkiewicz et al.
`(43) Pub. Date:
`Dec. 28, 2006
`
`US 20060290304Al
`
`(54) CONTROL SYSTEMS AND METHODS FOR
`PERMANENT MAGNET ROTATING
`MACHINES
`
`(76)
`
`Inventors: Joseph G. Marcinklewicz, St. Peters,
`MO (US); Prakash B. Shahi, St. Louis,
`MO (US); Michael I. Henderson,
`North Yorkshire (GB)
`Correspondence Address:
`HARNESS, DICKEY, & PIERCE RLIC
`9
`A
`7700 BONHOMME STF 400
`’
`ST. LOUIS, MO 63105 (US)
`
`(21) Appl_ No‘:
`
`11/293,743
`
`(22)
`
`Filed;
`
`Dec_ 2, 2005
`
`Related US, 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)
`
`Int. Cl.
`(2006.01)
`H02P 7/00
`(52) U.S. Cl.
`............................................................ .. 318/432
`
`ABSTRACT
`(57)
`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 thestator. Adrive is connected to the phase
`windings for energizing the windings. A controller outputs a
`control signal to
`drive in response to inputs of demanded
`torque, rotor position and/or speed. Control methods include
`calculating a scaled torque demand from the received torque
`demand to obtain substantially constant torque over a range
`of motor speeds, calculating an optimal dr-axis injection
`current using a cost function and a starting method that
`switches from speed control mode to torque control mode at
`a predetermined rotor speed or at predetermined start-up
`timing intervals.
`
`LQQ
`
`102
`
`104
`
`Controller
`
`
`
`
`/ PM Motor
`
`Rotor Position/Speed
`
`101
`
`BOM Exhibit 1044
`
`BOM v. Nidec
`
`|PR2014—01 121
`
`BOM Exhibit 1044
`BOM v. Nidec
`IPR2014-01121
`
`1
`
`

`
`Patent Application Publication Dec. 28, 2006 Sheet 1 of 8
`
`US 2006/0290304 A1
`
`lQ9_
`
`102
`
`104
`
`Controiler
`
`
`
`
`/ PM Motor
`
`Rotor Position/Speed
`
`101
`
`FIG. 1
`
`2
`
`

`
`Patent Application Publication Dec. 28, 2006 Sheet 2 of 8
`
`US 2006/0290304 Al
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`Patent Application Publication Dec. 28, 2006 Sheet 3 of 8
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`Patent Application Publication Dec. 28, 2006 Sheet 4 of 8
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`US 2006/0290304 A1
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`
`Patent Application Publication Dec. 28, 2006 Sheet 5 of 8
`
`US 2006/0290304 A1
`
`§_0._Q
`
`Run command
`
`Start Open Loop
`Using Predetermined
`Speed Value
`
`-
`
`502
`
`Actual Speed
`>= Predefined
`
`Value?
`
`Run Closed Loop
`Using Demanded Torque
`
`FIG. 5
`
`Improved Open Loop Starting
`
`6
`
`

`
`Patent Application Publication Dec. 28, 2006 Sheet 6 of 8
`
`US 2006/0290304 A1
`
`Run command
`
`Demanded Hz
`
`Start Open Loop V/Hz
`Run Estimator with
`
`After 2 sec
`
`
`
`Transition to psuedo-ciosed loop mode
`
`- run Estimator with demanded Hz
`
`- run speed control mode
`
`
`After 1 sec
`
`§_0_Q
`
`-602
`
`604
`
`606
`
`
`
`Transition to _true sensoriess
`- transition to torque control mode
`- run estimator with filtered caicuiated speed
`
`
`
`N0
`
`612
`
`608
`
`
`
`
`is estimator speed
`within range?
`
`
`Yes
`610
`
`Shutdown and restart
`
`Run Demanded
`Torque
`
`Lost Rotor detected
`
`FIG. 6
`
`7
`
`

`
`Patent Application Publication Dec. 28, 2006 Sheet 7 of 8
`
`US 2006/0290304 A1
`
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`
`Patent Application Publication Dec. 28, 2006 Sheet 8 of 8
`
`US 2006/0290304 A1
`
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`
`US 2006/0290304 A1
`
`Dec. 28, 2006
`
`CONTROL SYSTEMS AND METHODS FOR
`PERMANENT MAGNET ROTATING MACHINES
`
`CROSS —REFERENCE TO RELATED
`APPLICATIONS
`
`[0001] This application claims the benefit of US. 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 torque
`control of permanent magnet rotating machines.
`
`BACKGROUND OF THE INVENTION
`
`[0003] Various control systems and methods are known in
`the art for controlling the output torque of permanent magnet
`machines, such as brushless permanent magnet motors.
`Some of these machines are provided with position sensing
`devices to indicate, for motor control purposes, the rotor
`position with respect to the stator, while other machines
`detect the rotor position “sensorlessly.”As recognized by the
`present inventors, a need exists for improvements in sensor-
`based and sensorless control systems for rotating permanent
`magnet machines, including those which control the output
`torque of a PM motor.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0004] FIG. 1 is a block diagram of a rotating permanent
`magnet machine system according to one embodiment of the
`present invention.
`
`[0005] FIG. 2 is a block diagram of a sensorless imple-
`mentation of the system of FIG. 1 according to another
`embodiment of the invention.
`
`[0006] FIG. 3 is a block diagram of an exemplary embodi-
`ment of the torque scaler shown in FIG. 2.
`
`[0007] FIG. 4 is a block diagram of an exemplary embodi-
`ment of the Idr Injection block, the Torque to IQdr Map
`block and the vectorize block of FIG. 2.
`
`[0008] FIG. 5 is a flow diagram of an open loop starting
`method according to another embodiment of the present
`invention.
`
`[0009] FIG. 6 is a flow diagram of an alternative start—up
`method according to another embodiment of the invention.
`
`[0010] FIG. 7 is a graph illustrating how the optimized
`calculated value of ldr injection current varies with electrical
`speed.
`
`[0011] FIG. 8 is a graph validating the proposed solution
`for the optimized calculation of Idr.
`
`DETAILED DESCRIPTION OF EXEMPLARY
`EMBODIMENTS
`
`objectives and compliance with system-related, business-
`related and/or environmental constraints. Moreover, it will
`be appreciated that such development eiforts 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.
`
`[0013] FIG. 1 illustrates a rotating permanent magnet
`machine system 100 in accordance with one embodiment of
`the present invention. The machine system includes a rotat-
`ing permanent magnet electric machine 101, such as a
`permanent magnet alternating current (PMAC) motor or a
`permanent magnet!switched reluctance (PM/SR) motor (i.e.,
`a hybrid PM machine). 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 can have an inner rotor or an outer rotor construc-
`tion. 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 which is energized through the application
`of electric power to the motor terminals.
`
`[0014] A drive 108 is coupled to provide electric power to
`the terminals of the machine. The drive 108 receives control
`inputs from a controller 110 that receives rotor position and
`rotor speed data 112 from one or more sensors coupled to the
`machine, or energization feedback from the machine (such
`as the currents and/or voltages at the motor terminals) from
`which the rotor position and rotor speed can be determined
`(i.e., sensorlessly). As an alternative to sensing voltages at
`the motor terminals, the controller can assume the actual
`voltage supplied to the motor is that which was demanded.
`Sensorless control systems and methods suitable for use
`with the present invention are described in co-pending U.S.
`Application No. [Docket 5260-000212/US], titled Sensor-
`less Control Systems and Methods for Permanent Magnet
`Rotating Machines, filed [on even date herewith], the entire
`disclosure of which is incorporated herein by reference.
`
`[0015] The controller 110 of FIG. 1 is configured to
`operate primarily in a torque control mode, and is therefore
`shown as receiving a torque demand 114 input. It should be
`understood, however, that certain aspects of the present
`invention apply to other modes of operation, including speed
`control modes, and are therefore not
`limited to torque
`control systems.
`
`the torque
`reference to FIG. 1,
`[0016] With further
`demand 114 input may be received directly by the system 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. 1 is
`embodied in an air handler/blower for a climate control
`system).
`
`Illustrative embodiments of the invention are
`[0012]
`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
`
`[0017] While the drive of FIG. 1 is illustrated in exem-
`plary form as energizing three power terminals of a three
`phase machine, 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 (eg, with neutral connections) are used. The drive
`
`10
`
`

`
`US 2006/0290304 A1
`
`Dec. 28, 2006
`
`may be of conventional design and configured to provide,
`e.g., sine wave excitation to the motor terminals or square
`wave excitation using pulse width modulation (PWM) exci-
`tation.
`
`[0018] FIG. 2 illustrates additional details of the system
`(and primarily the controller) of FIG. 1. As shown in FIG.
`2, the input torque demand 114 is provided to a torque sealer
`202 (described further below with reference to FIG. 3) that
`produces a scaled torque demand 204. The scaled torque
`demand is provided to a Torque to IQdr Map block 206 that
`calculates an IQr demand 214 using motor-specific torque-
`to—IQr map data. The IQr demand is then concatenated with
`an ldr demand from an ldr Injection block 210 (described
`further below) into a vector quantity IQdr demand 214 by
`the vectorize block 212. As shown in FIG. 2, the value ofthe
`ldr demand 209 (i.e., dr—axis injection current) is calculated
`using the value of the DC link voltage, vdc, and the
`estimated electrical speed 216 received from a flux estimator
`228 (e.g., as described in U.S. Pat. No. 6,756,753). The
`resulting IQdr demand takes into account the torque contri-
`bution,
`if any, of the dr—axis current (e.g., as may be
`encountered in hybrid PM/SR motors).
`
`[0019] With further reference to FIG. 2, the IQdr demand
`214 from the vectorize block 212 is input to an IQr Current
`Controller 218 and an ldr Current Controller 220. These
`controllers convert
`the vector of motor currents in the
`electrical frame of reference to a vector of motor voltages in
`the electrical frame of reference. The vector of motor
`voltages is then transformed to alpha-beta-zero voltages 222
`and provided to the drive 108. The drive converts the
`rotating alpha-beta—zero voltages to three ABC stationary
`reference frame voltages 226 that are applied to the motor
`terminals to produce the demanded torque (e.g., a constant
`torque) output.
`
`[0020] The flux estimator block 228 of FIG. 2 produces
`the estimated electrical speed 216, as noted above, which is
`also provided to an input filter block 230 for smoothing the
`estimated electrical speed. The output of the input filter
`block 230 is provided to a speed clamp 232 (which defines
`minimum speed limits for stability purposes) to produce a
`filtered speed demand. The filtered speed demand 234 is
`provided to an integrator 23 6, which produces a drive angle
`command 238 for the flux estimator 228, and to a gain
`scheduler 240 (details of which are disclosed in the co-
`pending application noted above) which selects or calculates
`a gain factor as a function of the filtered speed demand and
`provides this gain factor to the flux estimator 228. The use
`of a filtered speed demand to develop the drive angle
`command 238 to the flux estimator 228 improves the torque
`stability of the machine. Using the gain factor from the gain
`scheduler 240, the drive angle command 238, and energi-
`zation feedback 242 from the PM machine, the flux estima-
`tor 228 calculates an estimated electrical angle 244 (which
`is provided to a vector controller which uses the estimated
`angle to execute transforms) and an estimated electrical
`speed 216.
`
`the
`[0021] At start-up, when the rotor speed is zero,
`controller of FIG. 2 operates in an open loop speed control
`mode using a predetermined speed value (which takes into
`account characteristics of the PM machine). The controller
`operates in this open loop speed control mode until the rotor
`speed reaches a predefined threshold value (which may also
`
`be specific to the given PM machine), and then switches to
`a closed loop torque control mode of operation using the
`input torque demand. This is further illustrated by the flow
`diagram 500 of FIG. 5, where upon receipt of a run
`command, the PM machine system starts, at step 502, in
`open loop using a predefined speed value. As the actual
`speed is sampled by the system, it is compared in step 504
`to a predefined value. If the actual speed is greater than the
`predefined value, the system switches, in step 506, to closed
`loop operation using the demanded torque. If the actual
`speed is below the predefined threshold, the system contin-
`ues open loop operation in step 502.
`
`[0022] An alternative start-up operation is illustrated by
`the flow diagram 600 of FIG. 6. As shown in step 602, the
`controller operates at start-up in an open loop mode using a
`demanded speed value. After a predetermined amount of
`time, e.g.,
`two seconds,
`the controller transitions to a
`pseudo-closed loop speed control mode in step 604. After a
`further predetermined amount of time, e.g., one second, the
`controller transitions to an sensorless control mode in step
`606, e.g., a torque control mode, and runs an estimator (such
`as the estimator 228 shown in FIG. 2) at a scheduled gain
`corresponding to the filtered estimated speed 234. In step
`608, the controller determines whether the estimated elec-
`trical speed produced by the estimator is within range. If so,
`the controller runs a demanded torque instep 610. Other-
`wise, the controller will shutdown the system and attempt a
`restart as indicated in step 612.
`
`[0023] FIG. 3 illustrates an exemplary embodiment 300 of
`the torque scaler block shown in FIG. 2. In this embodi-
`merit,
`the torque scaler 300 produces the scaled torque
`demand from input values of the rotor estimated speed 302,
`the torque demand 304, a torque multiplier 306, and a torque
`oflset 308. The torque multiplier 306 and the torque offset
`value 308 are preferably motor-specific parameters which
`compensate for individual motor characteristics. The torque
`olfset 308 is preferably the minimum torque value required
`to run the motor without a load (also referred to as free shaft
`operation) As shown in FIG. 3, the rotor speed is converted
`to a corresponding speed offset by a speed-torque depen-
`dence block 310 which may be, e.g., a look-up table con-
`taining speed-torque table values for the particular motor
`being controlled.
`
`In this embodiment of the torque scaler, the scaled
`[0024]
`torque demand 312 is calculated as the sum of three com-
`ponents:
`Speed ofl"set+(Toi-que demand)"‘(Torque multiplier)+
`Torque ofiset.
`
`Atypical torque versus motor speed operating curve of a PM
`motor or hybrid PM/SR motor exhibits a negative slope at
`higher operating speeds after attaining a maximum torque.
`To achieve a constant motor torque output with increasing
`motor speed, the value of the demanded torque is increased
`(i.e., compensated) by the control system as the motor
`operating speed increases, thereby making the torque lines
`flatter with speed. Motor-specific correction factors vary the
`torque gain factor as a function of IQr current and speed to
`achieve a substantially constant torque over the operating
`speed range of the motor. In some embodiments, estimated
`speed is used as the speed variable in the torque sealer.
`
`[0025] With further reference to FIG. 2, the ldr injection
`block 210 ensures that optimal use of the DC link voltage is
`
`11
`
`11
`
`

`
`US 2006/0290304 A1
`
`Dec. 28, 2006
`
`made in order to achieve the desired IQr current demand
`208. This is achieved by defining an optimization problem
`using several costs. These costs may include terms such as:
`required voltage to support the demanded Qr and dr axis
`currents; a bulk current
`term; and power consumption.
`Solving this optimization problem for particular operation
`conditions, such as motor speed and the value of the dc-link,
`yields a desired value of dr-axis current. In the context of the
`present discussion, the term phase advance is understood to
`be the action of setting this current value as a demand for the
`dr-axis current controller. As disclosed in the copending
`application referenced above, the value of IQr demand 208
`current is compensated for the torque contribution of the ldr
`injection current using motor-specific performance charac-
`teristics.
`
`[0026] FIG. 4 shows an exemplary embodiment of the ldr
`Injection block 210, the Torque to IQdr Map block 206, and
`the vectorize block 212 of FIG. 2. In the embodiment of
`FIG. 4, the ldr demand (i .e., the dr~axis current injection is
`calculated from a look—up table 402 (specific to the PM
`motor) that considers vdc 404, and the product ofthe current
`value Iq and estimated speed 406. The calculated value of
`ldr demand 408 is provided to a vectorize block 412, as well
`as to an Iqr compensation gain for Idr within the Torque to
`IQdr Map block 206. Although the Idr injection current in
`this embodiment is determined solely as a function of vdc,
`IQr, and rotor speed, the ldr injection current can alterna-
`tively be determined using a cost function having compo-
`nents relating to bulk current costs, power consumption
`and/or torque,
`in addition to or in lieu of components
`relating to vdc, IQr and rotor speed.
`
`[0027] Additional details of the method for calculating the
`amount of ldr injection current provided to the Torque to
`IQdr Map 206 and the vectorize 212 blocks in FIG. 2 will
`now be described. For machines controlled via a speed loop
`controller, the speed error is converted to a demanded torque
`114 by the speed loop controller and the demanded torque
`114 is provided as an input to the Torque to IQdr Map block
`206. Thus, ldr injection current can be applied within either
`a speed controlled or torque controlled machine. Idr injec-
`tion current, also described in the art as a phase advance
`current, may contribute 20% or more of the torque of a
`hybrid PM machine. When this torque component is present,
`the control system preferably compensates (i.e., adjusts) the
`magnitude of the IQr demand current to achieve the desired
`torque output.
`
`[0028] The general approach is to optimize the value of ldr
`demand using a cost function. The cost function incorporates
`values associated with utilization of the DC link; bulk
`current terms; power and torque. The goal of the optimiza-
`tion problem is to calculate the amount of injection current
`necessary so that the total voltage required to drive the
`demanded currents does not exceed that available from the
`inverter (i.e., vdc).
`
`[0029] To optimize the value of ldr injection current, the
`appropriate cost components are defined for use in the cost
`equation. With the cost expression defined, the closed form
`solution for the value of ldr becomes one of dilferentiating
`the cost expression with respect to Idr-current, setting the
`result equal to zero and solving for the roots (i.e., solutions)
`of the resulting equation (i.e., a typical maxima/minima
`calculus problem).
`
`[0030] The equation used for optimization can be derived
`in the following manner:
`
`[0031]
`
`l. Define cost component associated with volts;
`
`2. Define one or more secondary cost functions,
`[0032]
`associated with power or bulk current;
`
`3. Include a cost function associated with torque
`[0033]
`demand, particularly when dealing with a hybrid motor; and
`
`[0034]
`
`4. Optimize with respect to ldr current.
`
`[0035] The cost function associated with voltage is the
`nominal DC link value needed to support the ordered pair of
`Qr and dr currents. This is the primary component of the cost
`function. Secondary cost terms may include bulk current
`terms, indicative of efliciency, or torque or power consump-
`tion.
`
`the standard
`term,
`In each cost component
`[0036]
`approach is to normalize each individual term with respect
`to some nominal maximal value (e.g., IQr, Idr, power). This
`produces a typical range of [-1,1] for the cost. A weighting
`index can also be applied to each term that allows for a
`certain degree of fine tuning.
`
`[0037] The central component of any defined cost function
`is the term defining the required voltage. The presence of
`secondary cost components can be used to condition the
`solution in a way that may be more appropriate for a given
`PM machine. In others embodiments, greater emphasis may
`be placed on efiiciency.
`
`[0038] The fundamental electrical equation in the electri-
`cal Frame of Reference is:
`
`VQ,1,.=R-IQdr+
`
`Afwr
`O
`0
`
`d
`+(L+M)-[mIQd,]+w,‘(L+M)-G-Igd,
`
`(1)
`
`[0039] Writing the single vector equation as two coupled
`scalar equations:
`
`:1
`VQ,=R-lQ,+Afw,+(L+M)-EIQ,-+w,'(L+M)-Id,
`d
`V4,: R-Id,+(L+M)-E14,-w,-(L+M)-IQ,
`
`(2)
`
`(3)
`
`[0040] Then, the condition so that the required voltages in
`the Qdr frames of reference do not exceed that which can be
`provided by the dc-link is given by:
`
`[IQ,-R+A,t.;,+w,~(L+M)-/.,,]2 +[R-ld,.—¢u,~(L+ M)-/9,]? s
`2
`2
`§'K:mwuVac
`
`(4)
`
`12
`
`12
`
`

`
`US 2006/0290304 A1
`
`Dec. 28, 2006
`
`[0041] An exemplary voltage cost function becomes:
`
`[lQ,-R+/\f¢u,+w,-(L+M)-Id,]2+
`[R« ldr —w,-<z.+ M)-19,12
`2
`3 ‘(KpwmdVdc)z
`
`'K“*
`
`[0042] This is the central component of the optimization
`cost function.
`
`[0043] Torque can be used as part of the cost function, in
`particular to drive the proposed solution such that a torque
`demand can be met. The torque cost component can be
`expressed in a normalized form as:
`
`[0049] This optimization problem can be solved by taking
`a derivative with respect
`to the variable sought
`to be
`minimized. In one exemplary embodiment, the variable is
`the ldr-axis current.
`
`(5)
`
`[0050] With a proposed solution available, it then becomes
`necessary to substitute back into the original electrical
`equation the calculated optimized value for ldr and deter-
`mine the margin between required voltage to drive the
`desired current and the value of vdc. If such margin exists,
`then the proposed solution is useful. This checking process
`is illustrated in the example below.
`
`[0051] Equation 10 is one embodiment of a cost function,
`A, where A includes the motor-specific cost components for
`voltage, bulk current and torque:
`
`k. .,
`N
`T,,_/we] .,.,
`Tmax
`
`Nil»
`
`6
`<>
`
`A(/Qn hr. 01:. Vac. Kpwmd. Kvdca Kbulln Kiowa): =
`
`(10)
`
`-Km 4-
`
`[19,-R+A,w,+w,-(L+M)-1,,,]2 +
`[R-I...—w,~(L+ M)-19.1”
`
`'(KpwmdVdc)2
`
`2 5
`
`(1g_,, + 12,) - KM + [(o.37e3IQ, — o.oo93u,,,) — 712 ‘
`I710""
`TMOITH
`
`Ionqu:
`
`[0052] Kbmk, Kvdc and Kmque are weighting coeificients
`for the bulk current, voltage and torque cost components,
`respectively.
`
`function in Equation 10
`[0053] The exemplary cost
`includes the following motor variables:
`
`[0054] L=self inductance, M=mutual inductance, R=resis-
`lance
`
`[0055]
`[0056]
`
`IQ,=Qr axis current, ld,=dr axis current
`7t,=BEMF, (n,=elect.rical speed
`
`[0057] When the maximum current of each axes current is
`18 amperes:
`norm-
`I
`--isms?
`
`Such an expression is normalized against maximal torque
`demand Tmax and scaled according to a defined weighting
`ktorque'
`
`[0044] When the motor under consideration is a hybrid
`motor, the presence of dr-axis current itself generates more
`torque. In such applications, less IQ,-axis current is needed
`and correspondingly less vdc voltage. In one exemplary
`embodiment,
`the expression for the torque related cost
`function is:
`
`[(0-3764'1q.-0-0093'1q,‘59-Tn..x}2'/(torque
`
`(7)
`
`Such an expression as that presented in Equation
`[0045]
`(7) above replaces Equation (6) in the aggregate cost func-
`tion.
`
`[0046] A good indicator of efficiency is the bulk current
`term, or sum of the squares of current. Many of the loss
`mechanisms present in a motor manifest themselves through
`expressions involving squared current
`terms. Hence, an
`appropriate bulk current cost term, normalized to lmx, is
`given by:
`
`15.1, ‘ lQdr
`[max
`
`'kbulI<
`
`(8)
`
`[0058] Define weighting coeflicients associated with the
`optimization process:
`
`vd,,=dc-link value, Kpwm=PWM duty cycle, typi-
`[0059]
`cally 0.85 to 0.95
`
`where the lmax is the sum of squares of the maximal values
`of current expected in both axes.
`
`IQ,d‘,=voltage weighting function, Kb,,]k=bulk cur-
`[0060]
`rent weighting
`
`[0047] A variant upon the concept of bulk current as a
`component of the cost function is to use a cost function
`based upon power consumption, again normalized to Pm“:
`
`V5,, - 19,,
`Pmax
`
`. WW"
`
`(9)
`
`[0048] Atypical cost function is then expressed as the sum
`of the three cost components:
`voltage_cost_component+bL1lk_cu.rrent_cost_comp0-
`nent+required_torque_cost_component
`
`[0061] Km,que=torque weighting function
`[0062] Weighting coeflicients are used with respect to the
`vdc usage as well as an aggregate IQ, current term. The
`minimum of the exemplary cost function in Equation 10
`occurs for some value of dr-axis current such that:
`
`d
`m(A(Ig,. wr. vdc) = 0)
`
`11
`
`(
`
`)
`
`[0063] The graph 700 of FIG. 7 illustrates how the mag-
`nitude of the injection current varies with motor electrical
`
`13
`
`13
`
`

`
`US 2006/0290304 A1
`
`Dec. 28, 2006
`
`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,
`the method
`comprising:
`
`receiving a rotor torque demand; and
`
`calculating a scaled torque demand from the received
`torque demand as a function of a speed of the machine
`to obtain a substantially constant rotor torque over a
`range of rotor speeds.
`2. The method of claim 1 wherein said speed is an
`estimated speed of the machine.
`3. The method of claim 2 wherein calculating further
`includes calculating the scaled torque demand as a function
`of a torque ofi"set value.
`4. The method of claim 1 wherein calculating includes
`calculating the scaled torque demand as a function of a speed
`otfset value.
`5. The method of claim 1 wherein calculating includes
`calculating the scaled torque demand as a function of a
`torque offset value.
`6. 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 chase windings situated therein, the method
`comprising:
`
`receiving a rotor torque demand; and
`
`calculating a scaled torque demand from the received
`torque demand to obtain a substantially constant rotor
`torque over a range of rotor speeds, including calcu-
`lating the scaled torque demand such that scaled torque
`dernand=a
`torque
`ofiset
`value+the
`torque
`demand*((torque multiplier)+a speed offset value).
`7. The method of claim 6 further comprising calculating
`the torque ofiset value, the torque multiplier, and the speed
`oifset value according to characteristics of said machine.
`8. The method of claim 7 wherein calculating includes the
`torque oifset value,
`the torque multiplier, and the speed
`offset value from a speed-torque map for said machine.
`9. A permanent magnet rotating machine and controller
`assembly configured to perfonn the method of claim 1.
`10. A climate control system comprising the assembly of
`claim 9.
`
`11. The climate control system of claim 10 wherein the
`system Includes an air handler and wherein the air handler
`includes said assembly.
`12. 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,
`the method
`comprising:
`
`calculating an IQr demand from a speed or torque
`demand;
`
`calculating a dr-axis injection current demand as a func-
`tion of a speed of the rotor; and
`
`combining the IQr demand and the dr-axis injection
`current demand to produce an lQdr demand that is
`compensated for any torque contribution of dr-axis-
`current.
`
`14
`
`speed and vdc for various weighting values (702,704,706,
`708) of Kvdc, Kpwm and Kmqm. This exemplary embodiment
`uses estimated electrical speed 216 in its calculation of ldr
`injection current.
`
`[0064] Note that in both motoring and generating mode,
`the sign of the ldr current is chosen as negative. Should it
`ever become positive then there arises the possibility that the
`motor could act as a good generator, a situation which may
`not be desirable unless actually required.
`
`[0065] Having arrived at an optimized solution for injec-
`tion current, it is desirable to check its validity. This can be
`done by substituting the value for Idr injection current into
`the electrical equation and checking that the dc link value is
`sufiicient.
`
`U9,-R + Ala». + <».- <L+ M)-I,i.<w..v...>1’ +
`
`2
`[R'Idr — w.«(L+ M) - I4.(w,. mi’ = -5 - Kdvé.
`
`In such a test one may choose to deliberately round motor
`parameters and other variables or states associated with the
`problem so as to investigate the typical worst case scenario.
`
`[0066] The difference or residue between what voltage is
`needed and that which the DC link oilers is given by:
`
`(12)
`
`Re;-(19,, 1,,,, w,, vdc): = [19, - R + Afw, » (L + M) . I.,,]1 +
`[M1, —w.-(L+ M)-19,12 —
`
`' Vic
`
`2 §
`
`w,: = Lu,
`
`IQ,: = IQ,
`vdc: = V41:
`
`[0067] The graph 800 of FIG. 8 illustrates the value of the
`voltage residual with motor electrical speed about zero
`speed for two sets of values 802, 804 of IQ, and vdc (18
`amps, 340 volts) and (22 amps, 300 volts) for unity values
`of Igdc, Kpwm and Ktmquc. This plot
`indicates that the
`proposed solution is successful, even though one of the
`validation plots 802 fails at the extreme speed range when
`more than the specified current is used and there is a drop in
`bus voltage. Plot 804 illustrates that the proposed solution is
`successful throughout the expected speed of operation.
`
`[0068] The description of the invention above is merely
`exemplary in nature and, thus, variations that do not depart
`from the gist of the invention are intended to be within the
`scope of the invention. Such variations are not
`to be
`regarded as a departure from the spirit and scope of the
`invention.
`
`14
`
`

`
`US 2006/0290304 A1
`
`Dec. 28, 2006
`
`13. The method of claim 12 wherein calculating includes
`calculating the dr-axis injection current demand further as a
`function of a maximum voltage available for energizing the
`machine.
`14. The method of claim 12 wherein calculating includes
`calculating the dr-axis injection current demand as a func-
`tion of estimated speed of the rotor, a q-axis current, and a
`maximum voltage available for energizing the machine.
`15. The method of claim 12 wherein calculating includes
`calculating the dr-axis injection current demand using a cost
`function.
`16. The method of claim 12 further comprising assuming
`a maximum value of a Qr-axis current.
`17. The method of claim 12 wherein calculating includes
`defining a cost function having one or more cost components
`associated with Volts, power consumption, and/or bulk cur-
`rent, and optimizing with respect to the dr-axis injection
`current.
`
`18. The method of