Method and apparatus for brushless motor control
阅读说明:本技术 用于无刷电机控制的方法和设备 (Method and apparatus for brushless motor control ) 是由 J.T.穆拉 N.斯皮克 A.高利克 J.克里什纳萨米 于 2014-11-13 设计创作,主要内容包括:一种可变磁阻马达负载绘制设备包括:框架;界面,所述界面设置在构造用于安装可变磁阻马达的框架上;静态负载单元,所述静态负载单元安装至所述框架并且联接至所述可变磁阻马达;以及控制器,所述控制器可通信地联接至所述静态负载单元和所述可变磁阻马达,所述控制器构造为:选择所述可变磁阻马达的至少一个马达相位、给所述至少一个马达相位供能、以及从至少所述静态负载单元接收马达操作数据,用于绘制和生成一批马达操作数据查阅表。(A variable reluctance motor load mapping apparatus comprising: a frame; an interface disposed on a frame configured for mounting a variable reluctance motor; a static load unit mounted to the frame and coupled to the variable reluctance motor; and a controller communicably coupled to the static load unit and the variable reluctance motor, the controller configured to: selecting at least one motor phase of the variable reluctance motor, energizing the at least one motor phase, and receiving motor operation data from at least the static load unit for mapping and generating a batch of motor operation data look-up tables.)
1. A brushless electric machine, comprising:
a passive rotor having at least one rotor pole;
a stator having at least one stator pole and a phase coil associated with each of the at least one stator pole;
wherein the phase coils are configured to establish flux in a magnetic circuit between the rotor and stator, wherein the rotor and stator define a predetermined motor form factor; and
a controller configured to control current flow to each phase coil to generate a predetermined rotor torque, the controller programmed with at least a predetermined constant torque value and a phase current value for each phase coil corresponding to a predetermined constant torque value combination and a corresponding combination of adjacent phase coils, such that the controller determines a current for each phase coil generating a required rotor torque based on the predetermined constant torque value and the phase current value for each phase coil and the corresponding combination of adjacent phase coils.
2. The brushless electric machine of claim 1, wherein the predetermined constant torque values and associated phase current values are empirically generated values.
3. The brushless electric machine of claim 1, wherein the predetermined constant torque values and associated phase current values of the brushless electric machine are generated from a system modeling analysis comprising one of a numerical modeling analysis or a finite element analysis.
4. The brushless electric machine of claim 1, further comprising a variable reluctance motor of either a rotary or linear configuration.
5. The brushless electric machine of claim 1, further comprising a variable reluctance motor configured to operate in a vacuum environment.
6. The brushless electric machine of claim 1, wherein the passive rotor is a non-coil and non-magnet rotor.
7. The brushless electric machine of claim 1, wherein the associated phase current values are a batch of phase current values, such that each phase current vector produces a predetermined constant torque value common to the batch of phase current values.
8. The brushless electric machine of claim 1, wherein the controller is programmed with a minimum power value associated with each of the predetermined constant torque values.
9. The brushless electric machine of claim 8, wherein the predetermined constant torque value and associated power and phase current values are commutative for each electric machine having a similar form factor as the predetermined electric machine form factor.
10. The brushless electric machine of claim 1, wherein the correlated phase current values are pre-measured current values.
11. The brushless electric machine of claim 1, wherein the constant torque values and associated phase current values form one or more commutation tables relating phase current strengths to torque, rotor position, and motor phase.
12. A brushless electric machine, comprising:
a passive rotor having at least one rotor pole;
a stator having at least one stator pole and a phase coil associated with each of the at least one stator pole;
wherein the phase coils are configured to establish flux in a magnetic circuit between the rotor and stator, wherein the rotor and stator define a predetermined motor form factor; and
a controller configured to control current to each phase coil so as to generate a predetermined rotor torque, the controller programmed to provide a non-zero phase current to each phase coil at a zero-torque motor output.
13. The brushless electric machine of claim 12, wherein the non-zero phase current provided to each phase coil achieves a net torque substantially equal to zero.
14. The brushless electric machine of claim 12, wherein the non-zero phase current enables a reduction in a dynamic response time of the brushless electric machine.
15. A variable reluctance motor load mapping apparatus, comprising:
a frame;
an interface disposed on a frame configured for mounting a variable reluctance motor;
a static load unit mounted to the frame and coupled to the variable reluctance motor; and
a controller communicatively coupled to the static load unit and the variable reluctance motor, the controller configured to: selecting at least one motor phase of the variable reluctance motor, energizing the at least one motor phase, and recording, using the controller, a static motor torque at a static load unit corresponding to a segment of the at least one motor phase to characterize a relationship between values of the static motor torque with respect to a motor rotor position and a corresponding phase current of one of the selected at least one motor phase of the variable reluctance motor in operation.
16. The apparatus of claim 15, wherein at least the static load unit generates motor operation data comprising at least one of static motor torque, respective phase current for each at least one respective motor phase, and motor rotor position for mapping and generating a motor operation data look-up table.
17. The apparatus of claim 16 wherein the controller receives motor operation data from at least a static load unit for mapping and generating a look-up table of motor operation data.
18. The apparatus of claim 15, wherein the controller is configured to receive motor operation data from the static load unit and the variable reluctance motor, wherein the motor operation data comprises at least one of a static motor torque, a respective phase current for each at least one respective motor phase, and a motor rotor position.
19. The apparatus of claim 15 wherein the controller is configured to generate a constant torque value from the motor operation data as a function of the motor rotor position and the phase current of the adjacent motor phase.
20. The apparatus of claim 19 wherein the controller is configured to generate a minimum power value associated with each constant torque value and provide the minimum power values in a look-up table.
21. The apparatus of claim 15 wherein the controller is configured to generate a look-up table of motor operation data, wherein each look-up table of motor operation data comprises a collection of constant torque values and corresponding phase currents for a given rotor position.
22. The apparatus of claim 15 wherein the controller is configured to energize adjacent motor phases at a range of predetermined current combinations for a range of predetermined motor rotor positions corresponding to each motor predetermined rotor position, and to receive a resultant static torque for each of the predetermined current combinations from the static load unit.
23. The apparatus of claim 22, wherein the controller is configured to vary the additional motor phase current or any suitable combination of additional phase currents for each predetermined motor rotor position and predetermined first motor phase current.
24. The apparatus of claim 22 wherein the controller is configured to generate torque values from the resultant static torque and plot the torque values and associated phase current combinations for each predetermined motor rotor position to form a batch of motor operation data look-up tables.
25. A variable reluctance motor controller, the controller comprising:
one or more sensors configured to measure predetermined operating characteristics of the variable reluctance motor;
a current loop module configured to provide a phase voltage to the variable reluctance motor; and
a torque ripple estimator configured to generate a substantially real-time phase voltage correction signal based on predetermined operating characteristics and to apply the substantially real-time phase voltage correction signal to the phase voltage in order to attenuate a torque ripple effect of the variable reluctance motor.
26. A variable reluctance motor controller according to claim 25, wherein the predetermined operating characteristics include: one or more of motor rotor position, motor rotor angular velocity, phase current per motor phase, flux linkage rate, and inductance per phase.
27. The variable reluctance motor controller of claim 26 wherein the flux linkage rate is determined from a measured value.
28. The variable reluctance motor controller of claim 26 wherein the inductance is an estimated inductance obtained by the controller from a look-up table or a motor model.
29. A variable reluctance motor controller according to claim 25, wherein the one or more sensors comprise: a coupler coil disposed at or adjacent each motor phase coil, the coupler coil configured to measure a flux linkage associated with the respective motor phase coil.
30. The variable reluctance motor controller of claim 25 further comprising an inductance module configured to determine a change in inductance of the motor relative to the motor rotor position and phase current.
31. The variable reluctance motor controller of claim 25 wherein the torque ripple estimator comprises a real time comparator between the desired motor torque and the actual motor torque such that the phase voltage correction signal causes the actual motor torque to approach the desired motor torque.
32. A method for characterizing a relationship between determining a torque, a current, and a position of a motor load of a variable reluctance motor, the method comprising:
providing a static load unit;
coupling a variable reluctance motor to a static load unit;
selecting at least one motor phase of the variable reluctance motor;
energizing the at least one motor phase;
receiving, using a controller, motor operation data from at least a static load unit; and
the controller is used to map and generate a set of look-up tables of motor operation data.
33. The method of claim 32, further comprising receiving, using the controller, motor operation data from the static load unit and the variable reluctance motor, wherein the motor operation data comprises at least one of a static motor torque, a respective phase current for each of at least the respective motor phases, and a motor rotor position.
34. The method of claim 33, further comprising generating a constant torque value from the motor operation data as a function of the phase current and the rotor position using the controller.
35. The method of claim 32 wherein the controller is configured to generate a minimum power value associated with each constant torque value and provide the minimum power values in a look-up table.
36. The method of claim 32, wherein each motor operation data look-up table comprises: a set of constant torque values and corresponding phase currents for a given rotor position.
37. The method of claim 32, further comprising energizing motor phases at a set of predetermined current combinations for a set of predetermined rotor positions using a controller and receiving a resultant static torque from the static load unit for each of the predetermined current combinations and corresponding rotor positions.
38. The method of claim 37, further comprising varying, using the controller, the additional motor phase currents for each of the predetermined rotor position and the predetermined first motor phase currents.
39. The method of claim 37 further comprising generating a torque value from the composite static torque using the controller and plotting the associated phase current combination and the torque value for each predetermined rotor position to form a set of motor operation data look-up tables.
40. A method for a brushless motor, the method comprising:
providing a passive rotor having at least one rotor pole;
providing a stator having at least one stator pole and a phase coil associated with each of the at least one stator pole;
establishing flux in a magnetic circuit between the rotor and a stator using the phase coils, wherein the rotor and stator define a predetermined motor form factor; and
controlling the current to each phase coil with a controller to generate a predetermined rotor torque, the controller programmed with at least a predetermined constant torque value and a phase current value for each phase coil corresponding to a predetermined constant torque value combination and a corresponding combination of adjacent phase coils, such that the controller determines the current for each phase coil generating the required rotor torque based on the predetermined constant torque value and the phase current value for each phase coil and the corresponding combination of adjacent phase coils.
41. The method of claim 40, wherein the predetermined constant torque value and associated phase current value are empirically generated values.
42. The method of claim 40, wherein the predetermined constant torque values and associated phase current values of the brushless motor are generated from a system modeling analysis including one of a numerical modeling analysis or a finite element analysis.
43. The method of claim 40, wherein the brushless electric machine comprises a rotary or linear configured variable reluctance motor.
44. The method of claim 40, wherein the brushless electric machine comprises a variable reluctance motor configured to operate in a vacuum environment.
45. The method of claim 40, wherein the passive rotor is a non-coil and non-magnet rotor.
46. The method of claim 40, wherein the associated phase current value is a batch of phase current values, such that each phase current vector produces a predetermined constant torque value that is common to the batch of phase current values.
47. The method of claim 40, wherein the controller is programmed with a minimum power value associated with each of the predetermined constant torque values.
48. The method of claim 47 wherein the predetermined constant torque value and associated power and phase current values are reversible for each motor having a form factor similar to the predetermined motor form factor.
49. The method of claim 40, wherein the correlated phase current values are pre-measured current values.
50. The method of claim 40, wherein the constant torque values and associated phase current values form one or more commutation tables relating phase current strengths to torque, rotor position, and motor phase.
51. A method for a brushless motor, the method comprising:
providing a passive rotor having at least one rotor pole;
providing a stator having at least one stator pole and a phase coil associated with each of the at least one stator pole;
establishing flux in a magnetic circuit between the rotor and a stator using phase coils, wherein the rotor and stator define a predetermined motor form factor; and
the current to each phase coil is controlled using a controller programmed to provide a non-zero phase current to each phase coil at the zero torque motor output in order to generate a predetermined rotor torque.
52. The method of claim 51, wherein the non-zero phase current provided to each phase coil achieves a net torque substantially equal to zero.
53. The method of claim 51, wherein the non-zero phase current effects a reduction in a dynamic response time of the brushless motor.
1. Field of the invention
Exemplary embodiments relate generally to electric machines, and more particularly to control of electric machines.
2. Brief introduction to related developments
In general, variable (or switched) reluctance motors (VRMs) are sought to be cost effective alternatives to brushless dc motors. Variable reluctance motors do not require magnets and are mechanically simple in construction, however, their use for precise control remains challenging due to highly non-linear relationships between, for example, phase current, rotor electrical position, torque, and geometry. One of the main challenges in the accurate control of variable reluctance machines is: smooth and ripple-free pre-specified torque is provided at any given position of the rotor. The torque ripple inherent in variable reluctance motors can be due to modeling uncertainty. Thus, the performance of a variable reluctance motor may depend on the existence of an accurate commutation model that relates the desired torque to the phase current and position. Furthermore, typical feedback loops (as in conventional off-the-shelf amplifiers) are usually designed for fixed inductance and are optimally tuned, and variable reluctance motors usually do not have fixed inductance. In a variable reluctance motor, variations in motor coil or winding inductance are desirable because this is the primary mechanism by which the variable reluctance motor generates mechanical torque.
For example, in robotic servo applications, servo performance may be affected by the dynamic response of the actuator or motor. Slow motor response may limit the response speed of the servo system. The use of motors as actuators in robotic servo applications typically assumes that the motor response is at least an order of magnitude faster than the servo loop and is typically ignored in system models, especially in brushless dc motors. However, variable reluctance motors have a rather slow response so that some adjustment of the commutation strategy can be guaranteed to compensate for the slow response. As such, substantially instantaneous torque control of a variable reluctance motor drive for positioning servo applications may be required. Transient torque control may be provided, for example, by a digital electronic controller that may control the current through each motor phase as a function of motor position and required transient torque. Determining the current required in each motor phase based on motor position and torque may be referred to as current commutation. In a three-phase permanent magnet brushless motor (where the three phase currents are 120 degrees apart), the current through each motor winding is sinusoidal and a uniquely defined function of rotor position and torque. On the other hand, the phase current in a variable reluctance motor is not sinusoidal, but has a shape derived from the motor torque curve. The motor torque curve of the motor is measured or determined from finite element analysis of a motor model. In general, for a switched reluctance motor, torque may be a function of motor position and current per phase. The purpose of current commutation is to determine the required current in each motor phase as a function of motor position and motor torque. Advantageously, the effect of torque ripple is minimized when controlling a variable reluctance motor. It would also be advantageous to provide an optimal commutation scheme that provides a method to calculate the current in each motor phase to accomplish one or more optimization criteria. It would further be advantageous to provide a control system that mitigates the dependence on the exact commutation pattern for a variable reluctance motor.
Background
Drawings
The foregoing aspects and other features of the disclosed embodiments are explained in the following description, taken in connection with the accompanying drawings, wherein:
1A-1D are schematic diagrams of a substrate processing tool in accordance with aspects of the disclosed embodiments;
FIGS. 1E and 1F are schematic diagrams of portions of a variable reluctance motor in accordance with aspects of the disclosed embodiments;
FIG. 2 illustrates an exemplary table in accordance with aspects of the disclosed embodiments;
FIG. 3 illustrates another exemplary table in accordance with aspects of the disclosed embodiments;
FIG. 4 is a schematic diagram of portions of the variable reluctance motor shown in FIGS. 1E and 1F in accordance with aspects of the disclosed embodiments;
FIG. 5 is a schematic illustration of an iso-torque generating station in accordance with aspects of the disclosed embodiments;
FIG. 5A illustrates a flow diagram in accordance with aspects of the disclosed embodiments;
FIG. 6 illustrates a portion of an iso-torque curve table in accordance with aspects of the disclosed embodiments;
FIG. 7 illustrates an exemplary look-up table in accordance with aspects of the disclosed embodiments;
8A and 8B illustrate an exemplary phase current meter with respect to rotor position in accordance with aspects of the disclosed embodiments;
FIGS. 9A and 9B illustrate an exemplary motor input power table with respect to rotor position in accordance with aspects of the disclosed embodiments;
10A and 10B illustrate portions of an iso-torque curve table in accordance with aspects of the disclosed embodiments;
11A and 11B are schematic diagrams of portions of a variable reluctance motor in accordance with aspects of the disclosed embodiments;
FIGS. 12 and 13 illustrate schematic diagrams of a transport device and its control system in accordance with aspects of the disclosed embodiments;
FIGS. 14 and 15 illustrate exemplary look-up tables in accordance with aspects of the disclosed embodiments;
FIG. 16 illustrates an exemplary look-up table in accordance with aspects of the disclosed embodiments; and
FIG. 17 illustrates a flow diagram in accordance with aspects of the disclosed embodiments.
Detailed Description
In accordance with aspects of the disclosed embodiments, there is thus provided a switched reluctance brushless motor or motor and an optimal commutation scheme or strategy therefor. The commutation scheme or strategy refers to determining the current in each motor phase based on the motor position and the desired torque. Although aspects of the disclosed embodiments will be described with reference to the accompanying drawings, it should be understood that aspects of the disclosed embodiments can be embodied in various forms. In addition, any suitable size, shape or type of elements or materials could be used.
Referring to fig. 1A-1D, schematic diagrams of substrate processing apparatuses or tools incorporating aspects of the disclosed embodiments further disclosed herein are shown.
Referring to fig. 1A and 1B, a processing apparatus, such as, for example, a
In one aspect, the
The
The vacuum
Referring now to fig. 1C, a schematic plan view of a linear
Referring to fig. 1D, a schematic front view of an
The preferred commutation scheme described herein is the following: the scheme provides a method to calculate the current in each phase of the brushless motor to accomplish one or more optimization criteria. In aspects of the disclosed embodiments, an optimal commutation scheme can substantially maximize torque subject to certain constraints, which will be described in more detail below. The commutation schemes described herein may be applicable to any motor type, but are shown herein with reference to, for example, a variable reluctance motor for exemplary purposes. Fig. 1E and 1F illustrate portions of a brushless motor with a passive rotor in accordance with aspects of the disclosed embodiments. The exemplary configuration of the direct drive brushless motor shown in fig. 1E and 1F is representative of such machines having a rotary configuration and is used to facilitate the description of aspects of the embodiments herein. It should be noted that aspects of the embodiments described further below apply in a similar manner to linear brushless motors. In one aspect, as mentioned above, the brushless electric machine with passive rotor may be a variable or switched
Here, the
As may be realized, each of the at least one
In general, several methods have been proposed to define the desired phase currents or the desired commutation strategy in order to achieve the desired amount of torque for any given time and rotor position. These methods attempt to minimize torque ripple by: it is assumed that each phase torque contribution can be quantified independently by measurements such as those shown in fig. 2. However, these approaches typically ignore the effect of the adjacent phases once they are energized. For example, as adjacent coils are energized, the inductance of one of the active coils changes. Thus, the shape of the torque curves shown, for example, in fig. 2 and 3 may vary depending on the current adjacent to the phase. This can result in torque ripple of the
In one aspect of the disclosed embodiments, a method is provided for obtaining a commutation strategy that can naturally capture the effects of mutual inductance (e.g., the effects of inductance on one coil when energizing an adjacent coil) and thus substantially minimize the effects of torque ripple in the commutation of a variable reluctance motor. Referring now to fig. 4 and 5, in one aspect, a commutation strategy comprises: an apparatus, such as the torque
In this aspect, the
It should be noted that the generation of the iso-torque table described above may be repeatedly used for any given motor or family of motors (e.g., two or more motors having substantially the same operating characteristics, such as number of stator poles, number of rotor poles, air gap between stator and rotor poles, etc.). As such, the iso-torque tables described above may be generated for any suitable motor having any suitable predetermined operating characteristics, and the commutation schemes described herein with respect to aspects of the disclosed embodiments may be applied to any such suitable motor.
Referring again to fig. 1E, the
In accordance with aspects of the disclosed embodiments, referring again to fig. 1E and 1F and as described herein, the torque of the
Still referring to fig. 4, 8A and 8B, as noted above, an example of the phase current change in phase a and phase B at constant torque is shown as the
In one aspect, the commutation schemes described herein may use one or more torque meters, such as the torque meter described above with reference to fig. 6, that produce motor torque as phase current i for any suitable motor interval (such as the about 0 degree to about 15 degree intervals mentioned above)AAnd iBAnd a function of motor position theta. In one aspect, the torque table may be analytically represented as:
wherein the torque T is position dependent. In other aspects, the torque table may be measured experimentally (e.g., as described above with reference to the torque curve generation station 510). In other aspects, the torque meter may be calculated by finite element analysis of a motor model, for example. In other aspects, the torque table may be generated in any suitable manner. It should be noted that although the commutation schemes described herein will be described with respect to the approximately 15 degree spacing mentioned above, in other aspects the commutation schemes described herein may be applied to any suitable spacing.
With reference to a periodicity of about 15 degrees (which may be any suitable interval in other aspects), the phase current iAAnd iBThe appropriate boundary conditions for (b) may be established as:
i A =0 inθ=15 deg. [ 2]]
And
i B =0 inθ=0 degree [3]
To solve for the two phase currents shown in, for example, fig. 3A and 3B, the approximately 15 degree interval may be divided generally into two halves or sub-intervals, one half being approximately 0 degrees to approximately 7.5 degrees and the other half being approximately 7.5 degrees to approximately 15 degrees. In each subinterval, one of the phase currents is defined by any suitable shape function, e.g. as described above, and the remaining phase currents may be determined from any suitable torque meter, e.g. such as shown in fig. 6.
Referring to fig. 9A and 9B, the total electrical power Pc consumed by energizing the phases (in this example, energizing phase a and phase B) is shown as a rotor rotating at any suitable number of revolutions (rpm), which in this example is about 60rpm for exemplary purposes. The power curve in fig. 9A corresponds to the phase current in fig. 8A, and the power curve in fig. 9B corresponds to the phase current in fig. 8B. Here, for exemplary purposes, a constraint may be placed on the available power of the motor such that the available power is about 540W. In other aspects, the power may be constrained to any suitable value, such as, for example, the rated power of the motor is commutated by the schemes described herein. The torque may be adjusted such that the peak power consumption falls below the approximately 540W power constraint. As can be seen in fig. 9A and 9B, at about 60rpm, the torque corresponding to a power constraint of about 540W is about 7.1 Nm for the linear shape function of fig. 8A and about 7.2 Nm for the quadratic shape function of fig. 8B in this example. It should be noted that in one aspect, the slope of the shape function may also be constrained, such as for the voltage of the bus supplying the phases as will be described below.
In one aspect of the disclosed embodiment, a method may be provided to detect a phase current that maximizes motor torque for a given limit of input power, where the shape function described above with reference to fig. 8A and 8B is replaced by a constraint on motor power consumption. In general, the voltage drop over a single phase of the motor can be written as:
wherein V is the voltage over the phase, i is the phase current, R is the phase resistance, and
is the flux linkage rate for the motor angular position theta and current i. Also, in the same manner as above,
where L (θ, i) is inductance. Thus, the voltage on the phase can be rewritten as:
and multiplying both sides of equation [6] by the current i yields the power equation:
thus, based on, for example, equation [7 ]]Can be directed to the phase current iAAnd iBPhase resistor R, and flux linkage
Andthe constraints on motor power consumption or total power are written as:
wherein "
"denotes the mechanical power output of the motor (T is the motor torque andis the angular velocity),andrepresents resistive power loss in the motor winding or coil, andandrepresenting the magnetic field energy stored in the motor. It should be noted that in one aspect, the torque may be specified by a motion analysis of the transport 111 (fig. 1), for example, as described in the following applications: international patent publication No. PCT/US2012/052977 entitled "Time-OptimalTracories for Robotic Transfer Devices" filed on 30/8/2012 and filed on 13/9/2012 (WO publication No. 2013/033289)U.S. patent application No. 13/614,007 entitled "Method for Transporting a subsystem with a subsystem Transport," the entire contents of which are incorporated herein by reference. In other aspects, torque (and/or angular velocity) may be obtained by motor sensors in real time, and power may be regulated by, for example,In another aspect of the disclosed embodiments, a method may be provided for determining a phase current that maximizes motor torque for a given limit of input power, wherein the shape function described above with reference to fig. 8A and 8B is represented by phase voltage VbusThe constraint above. For example, given equation [6] as above]The voltage on the phase described in (e.g., phase a and phase B in this example), then the constraint on the voltage in each phase can be written as:
and
wherein the content of the first and second substances,
andmay be determined empirically from, for example, an iso-torque meter, a motor model, from motor sensors, or in any other suitable manner. In one aspect, equation [8 ] is constrained]Can be matched with an equal torque table and an equation [ 2]]And [3]Together determine the phase current i in a rotor position (or any other suitable rotor position) of, for example, about 0 degrees to about 15 degreesAAnd iB(or any other suitable phase current of the above-mentioned phase current pairs). In one aspect, the equation [9 ] is constrained]And [10 ]]Can be matched with an equal torque table and an equation [ 2]]And [3]Together determine the phase current i in a rotor position (or any other suitable rotor position) of, for example, about 0 degrees to about 15 degreesAAnd iB(or any other suitable phase current of the above-mentioned phase current pairs).In one aspect of the disclosed embodiments, another commutation scheme can be provided in which a minimum power P is achievedminAs described below. Here, the desired torque is known from a position control loop of the transport device 111 (fig. 1), for example, as mentioned above. Referring to fig. 10A and 10B, an iso-torque meter (which is substantially similar to the iso-torque meter described above) may be used to determine phase currents, such as i, for a given torque and motor rotor position in any suitable mannerAAnd iB. For example, in one aspect, a unique set of phase currents i may be identified along a desired iso-torque lineAAnd iB(see also fig. 6) to achieve minimum dissipated power in phase a and phase B. In other aspects, the minimum power P may be determined empirically, through numerical analysis, or the likemin. Once the minimum power is achieved, the corresponding phase current i for a given desired torque and at the respective rotor position may beAAnd iBSuch as, for example, in a table. Equation [9 ] above]And [10 ]]Can be used to verify: p for given torque and torque positionminAssociated phase current iAAnd iBCan be matched with the bus voltage VbusIs applied aboutAnd (4) bundling.
In another aspect of the disclosed embodiment, a real-time comparator commutation scheme can be used to operate the
An inductance model module 1204 (where an inductance module may be represented as
) May be configured such that: resulting in a change in the inductance of theFlux-ramp rate (which can be written as
) The measurements may be made in any suitable manner, such as by using the sensor orEach motor phase may have its
It should be noted that the torque ripple compensation performed by the torque ripple estimator includes: the ability to indirectly measure the actual torque generated by the motor output. The indirect measurement of the actual torque is compared to the desired torque so that the torque ripple estimator can calculate a phase voltage correction that will bring the actual torque close to the desired torque. An indirect measurement of the actual torque can be derived from the following equation:
torque (b) = torquex [12]
By using equation [12] and the flux linkage (see equation [5] above), an indirect measure of actual torque can be calculated from the following equation:
torque =
[13]Wherein the flux linkage
Measured as described above (see equation [11 ]]) InductanceIs determined empirically through the use of look-up tables, models, or in any other suitable manner, and expressionsMay be calculated from, for example, current and speed feedback or in any other suitable manner.A synthetic phase current may be generated from the modified phase voltage (e.g., the modified phase voltage after the
In aspects of the disclosed embodiments described herein, the torque-current-position relationship reflects: for example, under steady state conditions where the desired torque and rotor position are fixed in time, the motor torque is a function of the motor position and phase current. If the torque or rotor position changes over time, as is the case in robotic applications, the effectiveness of using the static torque relationship can be determined by the speed of response of the motor dynamics. The measure of motor dynamics is the torque step response speed of the motor. Fig. 14 shows the torque output of a brushless DC motor that commands a torque of about 3 Nm. The motor torque step response (e.g., dynamic response time) may be measured in any suitable manner. Fig. 14 also shows the torque step response of a variable reluctance motor (which has a similar form factor as a brushless DC motor). As can be seen from fig. 14 and 15, the brushless DC motor has a faster response time than the variable reluctance motor. It should be noted that the torque curve in a variable reluctance motor may begin at a substantially zero slope, while the torque curve on a brushless DC motor may begin at a non-zero slope. This is because the torque-current relationship is a quadratic relationship in the switched reluctance motor, and the torque-current relationship is a linear relationship in the brushless DC motor. Accordingly, it is expected that conventional switched reluctance motors may have an inherently low response time near zero current and torque compared to brushless DC motors. In one aspect of the disclosed embodiments, a system and method (such as may be embodied in a suitable algorithm) allows a switched reluctance motor to respond faster in a near zero torque/current range, as described further below. In accordance with aspects of the disclosed embodiments, the dynamic response of a variable reluctance motor may be improved as indicated next. The following equation is given:
wherein, TVRMIs a variable (or, switched) reluctance motor torque, "i" is a phase current, "θ" is a rotor position, and "f (θ)" represents a dependence on the rotor position; then from equation [15 ]]It is appreciated that the dynamic response of a variable reluctance motor (such as motor 100) may be a function of phase current; variable reluctance motor (dT)VRMDt) increases with increasing phase current; and when no current is passed through the coil 104 (fig. 1E and 1F), the dynamic response is substantially zero.
In this aspect of the disclosed embodiment, referring again to fig. 1E and 1F, the commutation scheme is to have a non-zero phase current at zero torque. The non-zero phase current may generate "bias torque" in other phases of the motor such that the dynamic response time of the motor increases (e.g., faster) (e.g., the gradient is between T =0, and the required torque TdemandChange). In a four-phase motor, such as
As an example, if at a given motor position, phase a and phase B produce positive motor torque, and phase C and phase D produce negative motor torque, and the desired torque is T, and △ T is the selected offset torque compensation value, and the function f represents a torque-current-position relationship, the phase current may be defined as:
and
wherein iA、iB、iCAnd iDFIG. 16 illustrates a motor torque step response in response to a commanded torque of, for example, about 3 Nm for a brushless DC motor, a variable reluctance motor without phase current bias (basic VRM), a variable reluctance motor with constant phase current bias (e.g., when generating unbalanced torque (i.e., T T.sub.D.)demand) When the bias does not substantially change with actuation of the motor), and variable reluctance motors with variable phase current bias (e.g., when generating unbalanced torque (i.e., T;)demand) The bias changes with actuation of the motor). FIG. 16 shows response curves of desired torque for different motor configurations for comparison. The dashed portions in the figures represent an approximate representation of steady state operating conditions and are included for completeness and in other respects are not relevant to aspects of the features described herein. As can be seen in fig. 16, the response (rise) time of the variable reluctance motor with constant phase current bias is reduced more (i.e., faster response) than the basic VRM (without torque bias) and the response time of the variable reluctance motor with variable phase current bias is reduced more than the response time of the variable reluctance motor with constant phase current bias. To minimize the loss of motor power, the compensation torque may be set to a non-zero value as needed and determined by the application. In one aspect, a non-zero phase current may be applied so as toAt any appropriate time (e.g. within a predetermined time period or at a desired TdemandA predetermined time before the desired time of demand) generates a compensation torque (fig. 17, block 1700) (i.e., the compensation torque may be considered a pre-applied torque applied just before the demanded torque is demanded), rather than being applied in concert with the demanded torque. Also, as shown in fig. 16, a time-varying torque compensation curve may produce a faster dynamic response than a constant torque compensation. In one aspect, to make dynamic responses faster in, for example, robotic transport applications, a controller, such as
As described above, the controller 400 (fig. 1E) may have a distributed architecture that includes high-level and low-level controllers similar to the controllers described in U.S. patent No. 7,904,182, the entire contents of which were previously incorporated herein by reference. In one aspect, the constant torque meter may be located in one or more high level controllers, such that aspects of the commutation scheme (which may include any suitable calculations, comparisons, sending commands to the variable reluctance motor, monitoring operating characteristics of the variable reluctance motor, altering the torque output of the motor, etc.) may be performed by one or more low level controllers.
As may be realized, aspects of the disclosed embodiments may be used alone or in any suitable combination.
In accordance with one or more aspects of the disclosed embodiments, a variable reluctance motor load mapping apparatus is provided. The apparatus comprises: a frame; an interface disposed on a frame configured for mounting a variable reluctance motor; a static load unit mounted to the frame and coupled to the variable reluctance motor; and a controller communicatively coupled to the static load unit and the variable reluctance motor. The controller is configured to: the method includes selecting at least one motor phase of the variable reluctance motor, energizing the at least one motor phase, and receiving motor operation data from at least the static load unit for mapping and generating a set of look-up tables of motor operation data.
In accordance with one or more aspects of the disclosed embodiments, the controller is configured to receive motor operation data from the static load unit and the variable reluctance motor, wherein the motor operation data includes at least one of a static motor torque, a respective phase current for each of at least the respective motor phases, and a motor rotor position.
In accordance with one or more aspects of the disclosed embodiment, the controller is configured to generate a constant torque value from the motor operation data as a function of the rotor position and the phase current of the adjacent motor phase.
In accordance with one or more aspects of the disclosed embodiment, the controller is configured to generate a minimum power value associated with each constant torque value and provide the minimum power values in a look-up table.
In accordance with one or more aspects of the disclosed embodiment, the controller is configured to generate a look-up table of motor operation data, wherein each look-up table of motor operation data comprises a collection of constant torque values and corresponding phase currents for a given rotor position.
In accordance with one or more aspects of the disclosed embodiments, the controller is configured to, for a batch of predetermined rotor positions corresponding to each predetermined rotor position, energize adjacent motor phases at a batch of predetermined current combinations, and receive a resultant static torque for each predetermined current combination from the static load unit.
In accordance with one or more aspects of the disclosed embodiment, the controller is configured to vary the additional motor phase current or any suitable combination of the additional phase currents for each of the predetermined rotor positions and the predetermined first motor phase currents.
In accordance with one or more aspects of the disclosed embodiment, the controller is configured to generate a torque value from the resultant static torque, and map the torque value and associated phase current combination for each predetermined rotor position to form a set of motor operation data look-up tables.
In accordance with one or more aspects of the disclosed embodiments, a method is provided for characterizing a relationship between torque, current, and position of a motor load that determines a variable reluctance motor. The method comprises the following steps: providing a static load unit; coupling a variable reluctance motor to a static load unit; selecting at least one motor phase of the variable reluctance motor; energizing the at least one motor phase; receiving motor operation data from at least one static load unit by using a controller; and drawing and generating a plurality of look-up tables of motor operation data by using the controller.
In accordance with one or more aspects of the disclosed embodiment, the method further comprises: receiving, by using the controller, motor operation data from the static load unit and the variable reluctance motor, wherein the motor operation data includes at least one of a static motor torque, a respective phase current for each of at least the respective motor phases, and a motor rotor position.
In accordance with one or more aspects of the disclosed embodiments, the method comprises: a constant torque value is generated from the motor operation data as a function of the phase current and the rotor position by using a controller.
In accordance with one or more aspects of the disclosed embodiment, the controller is configured to generate a minimum power value associated with each constant torque value and provide the minimum power values in a look-up table.
In accordance with one or more aspects of the disclosed embodiment, each motor operation data look-up table comprises: a set of constant torque values and corresponding phase currents for a given rotor position.
In accordance with one or more aspects of the disclosed embodiments, the method comprises: the motor phases at a set of predetermined current combinations for a set of predetermined rotor positions are energized by using a controller, and a resultant static torque for each of the predetermined current combinations and corresponding rotor positions is received from a static load unit.
In accordance with one or more aspects of the disclosed embodiments, the method comprises: the additional motor phase currents are varied for each predetermined motor position and predetermined first motor phase current by using the controller.
In accordance with one or more aspects of the disclosed embodiments, the method comprises: a torque value is generated from the resultant static torque by using a controller, and the associated phase current combination for each predetermined rotor position and the torque value are plotted to form a set of motor operation data look-up tables.
In accordance with one or more aspects of the disclosed embodiments, a method comprises: coupling a load to an output shaft of the variable reluctance motor; generating a batch of static torque on an output shaft by using a variable reluctance motor; adjusting a rotor position of the variable reluctance motor; and recording motor data including static torque values, rotor positions, and phase currents of adjacent phases of the variable reluctance motor by using the controller.
In accordance with one or more aspects of the disclosed embodiments, a batch of phase current combinations is recorded for adjacent phases of each static torque value in a batch of static torques.
In accordance with one or more aspects of the disclosed embodiments, a batch of static torque is generated for each rotor position in a batch of rotor positions.
In accordance with one or more aspects of the disclosed embodiments, the method comprises: a data look-up table is formed by using the controller to plot a set of static torques and corresponding phase current combinations for each rotor position.
In accordance with one or more aspects of the disclosed embodiments, the method comprises: the motor phases at a set of predetermined current combinations for a set of predetermined rotor positions are energized using a controller, and the resultant static torque for each of the predetermined current combinations and corresponding rotor positions is recorded.
In accordance with one or more aspects of the disclosed embodiments, the method comprises: the additional motor phase currents are varied for each predetermined motor position and predetermined first motor phase current by using the controller.
In accordance with one or more aspects of the disclosed embodiments, an electric machine is provided. The brushless motor includes: a passive rotor having at least one rotor pole; a stator having at least one stator pole and a phase coil associated with each of the at least one stator pole, the phase coil configured to establish flux in a magnetic circuit located between the rotor and the stator, wherein the rotor and the stator define a predetermined motor form factor; and a controller configured to control the current to each phase coil to generate a predetermined rotor torque, the controller programmed with at least a predetermined constant torque value and an associated phase current value, such that the controller determines the current for each phase coil to generate the required rotor torque based on the predetermined constant torque value and the associated phase current value.
In accordance with one or more aspects of the disclosed embodiment, the predetermined constant torque value and the associated phase current value are empirically generated values.
In accordance with one or more aspects of the disclosed embodiment, the predetermined constant torque values and associated phase current values of the brushless motor are generated from a system modeling analysis including one of a numerical modeling analysis or a finite element analysis.
In accordance with one or more aspects of the disclosed embodiments, a brushless motor includes a variable reluctance motor in either a rotary configuration or a linear configuration.
In accordance with one or more aspects of the disclosed embodiments, a brushless electric machine includes a variable reluctance motor configured to operate in a vacuum environment.
In accordance with one or more aspects of the disclosed embodiment, the passive rotor is a coil-less and magnet-less rotor.
In accordance with one or more aspects of the disclosed embodiment, the associated phase current value is a batch of phase current values, such that each phase current vector produces a predetermined constant torque value that is common to the batch of phase current values.
In accordance with one or more aspects of the disclosed embodiment, the controller is programmed with a minimum power value associated with each predetermined constant torque value.
In accordance with one or more aspects of the disclosed embodiments, the predetermined constant torque value and associated power and phase current values are commutatable for each motor having a form factor similar to the predetermined motor form factor.
In accordance with one or more aspects of the disclosed embodiment, the correlated phase current values are pre-measured current values.
In accordance with one or more aspects of the disclosed embodiments, the constant torque values and associated phase current values form one or more commutation tables relating torque, rotor position, and phase current strength of the motor phases.
In accordance with one or more aspects of the disclosed embodiments, a variable reluctance motor controller is provided. The controller includes: one or more sensors configured to measure predetermined operating characteristics of the variable reluctance motor; a current loop module configured to provide a phase voltage to the variable reluctance motor; and a torque ripple estimator configured to generate a substantially real-time phase voltage correction signal based on predetermined operating characteristics and apply the real-time phase voltage correction signal to the phase voltage so as to attenuate a torque ripple effect of the variable reluctance motor.
In accordance with one or more aspects of the disclosed embodiment, the predetermined operational characteristics include: one or more of motor rotor position, motor rotor angular velocity, phase current per motor phase, flux linkage rate, and inductance per phase.
In accordance with one or more aspects of the disclosed embodiments, the flux turn-chain rate is determined from a measurement.
In accordance with one or more aspects of the disclosed embodiments, one or more sensors comprise: a coupling coil at or adjacent each motor phase coil configured to measure a flux linkage associated with the respective motor phase coil.
In accordance with one or more aspects of the disclosed embodiment, the inductance is an estimated inductance obtained by the controller from a look-up table or a motor model.
In accordance with one or more aspects of the disclosed embodiments, a variable reluctance motor controller includes an inductance module configured to determine a change in inductance of a motor relative to a motor rotor position and phase current.
In accordance with one or more aspects of the disclosed embodiments, the torque ripple estimator includes a real-time comparator between the desired motor torque and the actual motor torque such that the phase voltage correction signal causes the actual motor torque to approach the desired motor torque.
In accordance with one or more aspects of the disclosed embodiments, a brushless motor is provided. The brushless motor includes: a passive rotor having at least one rotor pole; a stator having at least one stator pole and a phase coil associated with each of the at least one stator pole, the phase coil configured to establish flux in a magnetic circuit located between the rotor and the stator, wherein the rotor and the stator define a predetermined motor form factor; and a controller configured to control the current to each phase coil so as to generate a predetermined rotor torque, the controller programmed to provide a non-zero phase current to each phase coil at a zero-torque motor output.
In accordance with one or more aspects of the disclosed embodiment, the non-zero phase current provided to each phase coil achieves a net torque substantially equal to zero.
In accordance with one or more aspects of the disclosed embodiments, the non-zero phase current enables a reduction in the dynamic response time (i.e., an increase in response speed) of the brushless motor.
It is to be understood that the above description is only illustrative of aspects of the disclosed embodiments. Various alternatives and modifications can be devised by those skilled in the art without departing from aspects of the disclosed embodiments. Accordingly, aspects of the disclosed embodiments are intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims. Further, the different features recited in mutually different dependent claims or in the independent claims do not indicate that a combination of these features, which is included in the scope of aspects of the invention, may not be used to advantage.