English:
[0002] Various types of electrical motors may need to transition between operational modes. For example, block-commutating permanent magnet synchronous motors (PMSMs) may begin operation in a first mode (e.g., an open-loop initialization mode) where forced commutation is used and a stator generates a rotating magnetic field that begins to rotate a rotor at low speeds. Once the rotor achieves a sufficient speed, a controller and/or switch may have the PMSM switched from the first-mode (initialization mode) to a second-mode that may be referred to as closed-loop or sensorless operating mode.
[0004] Another example is a method. The method includes measuring back electromotive force (BEMF) signals of a motor during each of a plurality of commutation states of the motor. The method also includes detecting one-or-more periodic characteristics associated with a back- electromotive force signal (BEMF signal) during each of the plurality of commutation states of the motor. The motor also includes switching the motor from a first control mode to a second control mode in response to detecting that the predetermined pattern occurs in a plurality of consecutive commutation states.
[0005] An example system includes sensor circuitry to provide a measure of the back electromotive force (BEMF) for a floating phase of a multi-phase electric motor. A controller has outputs to provide control signals to control operation of the multi-phase electric motor. The controller is configured to utilize a non-BEMF based first mode of control to initially control the multi-phase electric motor. The controller is also configured to detect each occurrence of a pattern in the sensor signal that includes crossing a predetermined signal value during a selected commutation state of the multi-phase electric motor. The controller is further configured switch from the first mode of control to a BEMF -based mode of control in response to detecting occurrences of the pattern over a plurality of consecutive commutation states.
[0006] FIG. 1 illustrates an example system to control switching between different control modes of an electric motor.
[0007] FIG. 2 illustrates an example of a motor circuit.
[0008] FIG. 3 is a graph showing an example of back-electromotive-force (BEMF) voltage waveforms over a plurality of commutation states.
[0009] FIG. 4 is a graph illustrating an example BEMF waveform for a given phase over multiple commutation states.
[0010] FIG. 5 is a graph of example BEMF waveforms for multiple phases over a plurality of commutation states.
[0011] FIG. 6 is a graph illustrating an example BEMF waveform for a given phase over multiple commutation states lacking stability to change the control mode for a motor.
[0012] FIG. 7 illustrates an example of a motor system.
[0013] FIG. 8 illustrates an example flow diagram of a method to control switching between control modes of a motor.
[0014] FIG. 9 illustrates another example flow diagram of a method to control switching between control modes of a motor.
[0015] This disclosure provides systems and methods to switch an electric motor from an initialization mode to a closed-loop (e.g., sensorless) mode.
[0016] By way of example, a system may measure the back-electromotive-force (BEMF) (e.g., BEMF voltage) of one or more phases of an electric motor (e.g., a three-phase permanent magnet synchronous motor (PMSM)). In response to recognizing a predetermined signal pattern in the BEMF voltage, the motor may be switched from an initial, low speed control mode to a closed- loop control mode. For example, during low-speed, open-loop control, a motor controller or other circuitry may monitor and evaluate the BEMF signals for a given current speed and/or reference current for the motor. If the predetermined pattern is not detected at the given speed and/or reference current, the speed and/or reference current signals may be increased (e.g., incrementally) during the initial open-loop control mode for additional evaluation of the BEMF. The BEMF thus may be monitored to detect the pattern in each commutation state while changing the speed and/or current parameters of the motor during the open-loop control mode until the predetermined BEMF pattern is detected over a plurality of commutation states. For example, the predetermined pattern may correspond to the BEMF signal crossing a predetermined voltage (e.g., a midpoint or zero crossing) during a selected commutation state for a given phase (e.g., while the phase is floating). Once the pattern of crossings is detected over a number of commutation states, which itself may constitute the predetermined pattern, the motor controller or other circuitry may automatically transition operational control from the initial (e.g., open-loop) control to closed-loop control (e.g., BEMF-based, sensorless control).
[0017] FIG. 1 illustrates an example of a motor control system 100 configured to control a motor 101. The system 100 includes logic (e.g., implemented in a motor controller) that is configured to switch between operational modes of an electric motor. For example, during start up of the motor, the system 100 enables automatic transition between low-speed, open-loop control and BEMF-based, sensorless control at higher speeds of operation. The example system 100 includes measurement logic 104, pattern detection logic 106, mode logic 108, and control logic 112. The control logic 112 is coupled to a driver 116 that is configured to supply electric current to phase windings of the motor 101 in response to control signals provided by the control logic 112.
[0018] In some examples, some or all of the logic may be fabricated as part of a motor controller implemented on a common substrate (e.g., integrated in a common chip or die). For example, the control system 100 and its logic blocks may be implemented as hardware on a silicon chip, in an integrated circuit, in a field-programmable gate-array (FPGA), with discreet logic devices. In other examples, the logic may be implemented in an arithmetic logic unit (ALU), which may be a standalone ALU or within a processor core. Thus, the functionality implemented by the logic in the motor control system 100 may be implemented in a variety of ways.
[0019] In one example, the measurement logic 104 includes voltage measurement circuitry configured to measure the BEMF for each phase of the motor 101 such as via one or more connections 102. While in the example of FIG. 1, the measured signals are shown received via line(s) 102 from the motor, such signals alternatively may be measured by sensing voltages from the driver 116 via corresponding sensing circuitry. The measurement logic 104 is configured to measure BEMF signal voltages provided by each phase of the motor 101 and provide the measurements to the pattern detection logic 106 for subsequent processing. In some examples, the measurement logic 104 may implement digital processing of measured signals for further evaluation by the pattern detection logic 106.
[0020] As a further example, the measurement logic 104 periodically samples the BEMF signals at a sample rate, such as with an analog-to-digital converter (A/D converter) that converts the BEMF signals into digital data for further analysis by the pattern detection logic 106. Signals converted from analog to digital data can include BEMF voltage signals generated by each floating phase of the motor 101. In an example three-phase PMSM, only two phases conduct current at any time, leaving the third phase floating, which depends on the current commutation state. The measurement logic 104 thus may take several (e.g., periodic) measurements of the BEMF signal of a respective floating phase as that signal travels through one or more commutation periods of the motor 101. The measurements of the BEMF signal from each floating phase thus is measured and provided to the pattern detection logic 106.
[0021] The pattern detection logic 106 receives, as inputs, measurements of the BEMF signals provided by the measurement logic 104 over time. The pattern detection logic 106 is configured to detect instances of the monitored BEMF signal exhibiting a predetermined pattern. In response to detecting the predetermined pattern, the pattern detection logic 106 may enable (or instruct) the mode logic 108 to switch from an initial (e.g., open-loop) mode of control to a different (e.g., closed-loop) mode of control.
[0022] For example, the pattern detection logic 106 is configured to identify each instance of the predetermined pattern based on the measured BEMF signal (e.g., from measurement logic 104) crossing a predetermined signal value during a selected commutation state of the electric motor 101. An example predetermined voltage is zero volts (e.g., a zero crossing) for a floating phase of the motor, although other voltage levels may be used. In some examples, the pattern detection logic 106 may detect that the predetermined pattern (e.g., zero crossing) occurs in each a plurality of consecutive commutation states. For instance, the pattern detection logic 106 may count a number of consecutive valid crossings that occur and store the count value in memory. The pattern detection logic 106 may reset the count value in response to detecting that the BEMF signal does not exhibit the predetermined pattern during any of the plurality of commutation states. The mode logic 108 thus may monitor or receive the count value to control whether or not to switch to the next control mode, as disclosed herein. In other examples, the pattern detection logic 106 may utilize additional or different patterns based on various signals or other characteristics that are useful for determining when it is desirable to switch the mode of the motor 101. As yet another example, the measurement logic 104 and pattern detection logic 106 may be implemented as hardware, such as a comparator to compare the measured BEMF voltage for each phase relative to a voltage threshold (e.g., a mid-point of the BEMF voltage).
[0023] The mode logic 108 is configured to control an operating mode of the electric motor 101 according to one of a plurality of modes of control. For example, the control modes can include a non-BEMF based control mode during low speeds and a closed-loop (e.g., sensorless) control mode at higher speeds. For example, the control mode for low speeds may utilize open- loop or closed-loop control and a BEMF -based control may be used for higher speeds. The mode logic 108 thus may switch between its control modes based on pattern detection information determined by the pattern detection logic 106. For example, the mode logic 108 is configured to initially (e.g., during start up) employ open-loop control and switch from such open-loop control to a closed-loop control in response to the pattern detection logic 106 detecting that BEMF signals exhibit the predetermined pattern over a plurality of commutation states, such as disclosed herein. As an example, the mode logic implements a state machine that transitions between control modes based on detecting (or not detecting) a pattern in the BEMF signals.
[0024] Control logic 112 is configured to set speed and/or current applied to the electric motor 101. For example, the control logic 112 is coupled to inputs of the driver 116, such as to supply PWM signals to switch devices (e.g., transistors) that are activated and deactivated to supply electric current to phase windings of the motor 101 according to a commutation state of the motor. The control logic 112 thus implements a mode of control (e.g., low-speed or closed-loop control) based on instructions from the mode logic 108. The control logic 112 may implement a cascaded control using speed and current or use only speed or only current during low speed control of the motor 101.
[0025] As an example, during the first mode of control (e.g., during start up at low speeds), in response to detecting that the BEMF signal fails to exhibit the predetermined pattern during at least one of the plurality of commutation states, the control logic 114 adjusts speed and/or current applied to the electric motor. For example, the control logic 114 incrementally adjusts (e.g., increases) speed and/or current applied to the electric motor 101 over consecutive time intervals during the first operating mode until the pattern detection logic 106 detects the predetermined pattern in a series of consecutive commutation states. As mentioned, the mode logic 108 switches from the first (e.g., non-BEMF) mode of control to the second (closed-loop) mode of control based on the predetermined pattern being detected in a series of consecutive commutation states of the motor. The control logic 112 uses the mode of control (e.g., established by mode logic 108) as well as the speed and/or reference current setting to implement corresponding control of associated drive circuitry.
[0026] The control logic 112 provides control signals to the drive circuitry 116 for controlling the motor 101 based on the control mode determined by the mode logic 108. The drive circuitry 116 thus supplies current for exciting windings of the motor 101 based on control signals from the control logic 112. For example, as shown in FIG. 2, the drive circuitry 116 may include an H-bridge or other drive arrangement of switch (e.g., transistor) devices configured to supply current to respective pairs of windings based on control signals from a motor controller that includes the control logic 112.
[0027] ETnlike other approaches for transitioning from open to closed-loop control, the systems and methods disclosed herein do not require a pre-defmed motor speed or a motor current threshold. Rather, the operating mode transition occurs according to the BEMF voltages of the motor 101 as well as other useful/desirable operating conditions and/or system parameters. For example, at low motor speeds, the BEMF’s signal to noise ratio (SNR) is too low to be used for BEMF sensor-less closed-loop motor control and this causes the rotor position detection to be unreliable. Thus, at low speeds, operation of the motor is generally limited to non-BEMF speed control (e.g., open-loop or forced commutation) that exhibits degraded performance compared to closed-loop speed control at higher speeds. However, as disclosed herein, the system 100 of FIG. 1 determines when the BEMF signal is sufficiently stable, by detecting a predetermined pattern in the BEMF signals, to switch to a closed-loop mode of control, such as a BEMF -based sensorless, closed-loop mode of control. In other examples, the control may transition from closed-loop (e.g., low speed, non-BEMF-based control, which may be sensorless or employ sensors) to another closed-loop mode of control (e.g., BEMF-based sensorless control). The type of non-BEMF based control implemented at lower speeds can vary depending on application requirements.
[0028] FIG. 2 illustrates an example of a motor system 200. The motor system 200 includes a driver 202 that is coupled to motor 204, demonstrated as a three phase motor having phase windings A, B and C. In the example of FIG. 2, the phase windings A, B and C each has an inductance shown as Ll, L2 and L3, respectively. As one example, the motor may be a PMSM that includes three non-permanent electromagnetically activated magnets (electromagnets) mounted in its stator/housing and may have four permanent magnets mounted to its central rotator. However, other example motors may be employed in the examples herein with these other example motors having different numbers of permanent magnets and electromagnets. For example, the three electromagnets of the stator may be activated with six commutation states that work in pairs to generate the phase voltages (three-phased power supply) to rotate the motor.
[0029] The driver 202 includes an arrangement (e.g., H-bridge) of switch devices Sl, S2, S3, S4, S5 and S6 (e.g., transistors, such as field-effect transistors or bipolar junction transistors). A motor controller 206 (e.g., corresponding to control system of FIG. 1) is coupled to control the switches of the driver 202 to generate output phase voltages VA, VB, and Vc which are generally out-of-phase from each other (e.g., by 120 degrees). In this example, there are three upper switches Sl, S3, and S5 connected to a high voltage supply V+ and three lower switches S2, S4, and S6 connected to a low (e.g., ground) voltage. The upper switches Sl, S3, and S5 and the lower switches S2, S4, and S6 work in conjunction to supply current to the phase windings, which generate corresponding phase voltages VA, VB, and Vc. As disclosed herein, the motor controller 206 is configured to automatically switch the PMSM from an initialization mode (e.g., implementing open-loop or forced commutation control) to a run mode (e.g., closed-loop control) based on BEMF signals exhibiting a prescribed pattern. If appropriate, other signals and operating parameters associated with the motor operation may be utilized as part of the determination to change modes of control. The motor controller 206 may utilize the same BEMF signals, which are monitored to control transition between control modes, to sustain the motor 101 in the run mode during normal (high-speed, BEMF-based sensorless) operation. In at least some examples, the motor controller 206 supplies control signals to switches S1-S6 in a prescribed order in order to generate the three phase voltages (VA, VB, and Vc) to power the electromagnets in the stator that effect desired movement of the rotor.
[0030] FIG. 3 is a graph 300 illustrating various example ideal waveforms of a multi-phase motor, such as motor 101 or 204. FIG. 3 illustrates phase voltages for phases A, B and C at different rotor electrical positions and associated commutation states (e.g., six commutations states of 60 electrical degrees each). In some examples of motor control, PWM signals may drive switches S1-S6 (FIG. 2) on and off to generate the respective phase voltages VA, VB, and Vc. In this example, each of the phase voltages exhibits a crossing of a predetermined voltage (e.g., midpoint or zero crossing) centered near a selected commutation state, as respective floating phases ramp up or down.
[0031] FIG. 4 is a graph 400 illustrating an example phase voltage 404 for a given phase of a motor (e.g., motor 204) superimposed over motor commutation states 402. Additional phase and BEMF signals for different phases could have been graphed in FIG. 4 with other signals (see, e.g., FIG. 5); however, for the sake of clarity a single phase voltage waveform 404 is shown in the example of FIG. 4. As shown, during its floating phase, the phase voltage 404 decreases from its energized, high-voltage state (e.g., near about 2 V) to its low voltage state (e.g., about 0 V). The decreasing portion of the phase voltage corresponds to a BEMF generated for the given phase (during floating). In this example, the BEMF voltage crosses a predetermined voltage (e.g., a midpoint of about 1 V) that meets stability criteria. For example, the stability criteria includes the BEMF voltage having a zero or other predetermined crossing during a selected commutation state, which may be detected (e.g., by pattern detection logic) during the floating phase of the selected commutation state.
[0032] As disclosed herein, the measurement logic 104 (FIG. 1) measures the BEMF voltage waveform 404 during commutation states. When the measurement logic 104 measures the BEMF voltage of the phase voltage 404, the phase winding is floating (e.g., non-energized), such that the BEMF voltage waveform 404 decreases from its high to its low voltage amplitude. In the example of FIG. 4, the crossing is demonstrated to occur at point 412 (e.g., about IV), which is valid crossing for the floating phase since it occurs during the selected commutation state (state 1 in this six commutation state example), indicated at 402’. The measurement of BEMF voltage for each phase (e.g., by measurement logic) may be triggered by commutation states when each respective phase is determined to be floating. As illustrated in FIG. 4, this may occur during a time interval of a respective commutation state 402’. In particular, the midpoint (e.g., zero) crossing of the BEMF voltage for the given phase, demonstrated at 412, may occur at an intermediate portion of the floating phase during commutation state 402’. The pattern detection logic is configured to detect each occurrence of the BEMF voltage crossing the predetermined voltage (e.g., valid crossings) for each phase of the motor.
[0033] As shown in FIG. 4, the crossing point 412 may further be determined (by pattern detection logic) to be a valid crossing if it occurs within a range of the midpoint or at a midpoint value. In some examples, the crossing point 412 may be also determined to be a valid crossing if it occurs at any time within the commutation period or within a prescribed time interval at or near a center of such commutation period. In this way, the pattern detection logic can condition the validity of a BEMF crossing as having both a component of voltage (e.g,. crossing a predetermined voltage, such as zero) and a component of time (e.g., synchronized with a prescribed commutation state), which conditions are represented within a box 413 in FIG. 4. As discussed below, each of the other phase BEMF signals may be evaluated (by pattern detection logic) in combination with those of example FIG. 5 to determine that the existence of a pattern, including valid crossings, occurs over a plurality of consecutive commutation states for the motor.
[0034] FIG. 5 illustrates an example graph 500 of each of a plurality of phase voltages 504, 505 and 506 superimposed on commutation state signal 502. In the example of FIG. 5, the phase voltages 504, 505, 506 provide BEMF signals that cross predetermined voltage values (e.g., zero crossings), shown at 510, 512 and 514 during the corresponding commutation state for each respective floating phase. Accordingly, by detecting such pattern in the BEMF voltages signals over a series of commutation states, a motor controller can determine the operation of the motor system is sufficiently stable and switch from its closed-loop control to its open-loop control.
[0035] FIG. 6 illustrates an example graph 600 that depicts a commutation state signal 602 and a given phase voltage signal 604, similar to FIG. 4. In this example, the BEMF voltage transitions from a high voltage level to a low voltage value. However, in this example, the crossing of the predetermined voltage (e.g., zero crossing) does not occur during an expected commutation state for the floating phase. Instead, the crossing occurs in a subsequent commutation state of the motor, such that the crossing is not a valid crossing for purposes of pattern detection to enable switching the motor from the first-mode (e.g., open loop Low speed) to the second-mode (e.g., closed loop BEMF Sensorless). For example, arrows 608 generally indicate areas where the phase voltage signal 604 continues to increase during its expected floating phase period such that the threshold crossing occurs during a wrong commutation state. The example motor represented by the signals of FIG. 6 can be similar a motor discussed above that implements six commutation states for a block-commutated motor. The magnitude (or predetermined magnitudes) of BEMF voltage signal is dependent on motor frequency/speed and a supply voltage.
[0036] FIG. 7 illustrates an example of a motor system 700 that includes a motor controller 710 configured to implement logic that controls an electric motor 701. For example, the motor 701 may be a multi-phase (e.g., three-phase) PMSM, such as a brushless DC motor exhibiting trapezoidal or sinusoidal BEMF signals. In the example of FIG. 7, the motor controller 710 includes measurement logic 704, pattern detection logic 706, mode logic 708 and control logic 714. In other examples, the measurement logic 704 and associated phase sensing circuitry (not shown) could be implemented external or internal of the motor controller 710.
[0037] As disclosed herein, the measurement logic 704 receives BEMF signals for each phase of the motor 701 via one or more input connections 703. The measurement logic 704 may include voltage measurement circuitry that supplies the measured BEMF voltage signals to pattern detection logic 706, such as disclosed herein. In this example, the pattern detection logic 706 includes crossing detection logic 716 and a counter 718. The crossing detection logic 716 can detect each occurrence of the measured BEMF signal for a floating phase crossing a predetermined value (e.g., 0 V) during a corresponding commutation state of the motor, such as discussed above. For example, crossing detection logic 716 detects a zero or midpoint crossing of the BEMF signal for a given phase decrease from its positive to a negative voltage values during a commutation state while the given phase is floating.
[0038] The pattern detection logic 706 may also control the counter 718 to count each consecutive occurrence that the measured BEMF signal crosses the predetermined value (e.g., zero crossing). For example the counter 718 includes a counter value 719 tracking the number of times that the prescribed pattern of the BEMF occurs during consecutive commutation states. The counter 718 can store the counter value 719 in a register, a memory location, or similar location that is accessible by the pattern detection logic 706. The counter 718 further may be configured to reset the counter value in response to the crossing detection logic 716 detecting that the BEMF signal does not cross the predetermined value during one or more of the commutation states.
[0039] The mode logic 708 may be configured to operate similar to the mode logic 108 of FIG. 1. For example, the mode logic 708 is configured to switch between two or more control modes for the motor 701 based on the counter value 719, which can be accessed by or provided to the mode logic 708 by the pattern detection logic 706. For example, the mode logic 708 (and/or pattern detection logic 706) may compare the counter value 719 to predetermined threshold that establishes the number of consecutive zero crossings needed to switch from open-loop control to closed-loop control. The threshold may be a default value or be user-defined (e.g., programmable). As one example, the counter threshold may be set based on (or at) the number of commutation states that occur over 360 electrical degrees of the motor. In response to determining to switch between modes of operation, the mode logic 708 can provide a mode change command to the control logic 714.
[0040] The control logic 714 provides control signals to a driver 724 to apply corresponding current to phases of the motor 701. The control signals depend on speed and/or current values that the control logic sets for motor control. The control logic 714 may be implement open-loop control 720 or closed-loop control 722 depending on the mode of control established by the mode logic 708. During start up, while the motor is operating in its open-loop control operating mode, the control logic 714 incrementally adjusts the speed and/or current applied to the motor 701 over time. The incremental increase in speed and/or current may continue over time during the closed-loop control mode until the pattern detection logic 706 detects the predetermined pattern in a series of consecutive commutation states. For example, if the pattern is not detected during the series of consecutive commutation states or a predetermined time interval elapses, the control logic 714 increments the speed and/or current applied to the motor. Once the predetermined pattern is detected a threshold number of times in a series of consecutive commutation states, the mode logic 708 commands the control logic 714 to switch from the open-loop control 720 to the closed-loop control 722. The control logic 714 can further adjust at least one of the speed and/or current applied to the electric motor 701 in response to detecting that the BEMF signal fails to exhibit the predetermined pattern during at least one of the plurality of commutation states. In some examples, however, the pattern detection logic 706 may continue to look for the predetermined pattern in a series of consecutive commutation states and thereby control switching between the respective modes of control 720 and 722 being implemented by the control logic 714.
[0041] In view of the foregoing structural and functional features described above, example methods will be better appreciated with reference to FIGS. 8 and 9. It is appreciated that the methods are not limited by the illustrated order. Some actions could occur, in other examples, in different orders and/or concurrently from that shown and described herein. Moreover, not all illustrated features may be needed to implement a method. For example, each of the methods of FIGS. 8 and 9 may, in some examples, be implemented in a motor controller to control a motor similar to as described above with reference to FIGS. 1 - 7.
[0042] FIG. 8 illustrates an example method 800 of controlling run modes for operating an electric motor 101. At 802, back electromotive force (BEMF) signal(s) of a motor are measured. For example, the BEMF signal(s) may be periodically measured during each of a plurality of commutation states of the motor. These measurements may be performed by measurement logic 104 or 704. Additionally, the first control mode may be maintained until the method 800 determines (as discussed below) that the predetermined pattern occurs in each of a plurality of consecutive commutation states.
[0043] The method 800 detects, at 804, occurrences of a predetermined pattern in the BEMF signal during each of the plurality of commutation states of the motor. In some examples, the detections may include periodic detections of one-or-more characteristics associated with the BEMF signal during each of the plurality of commutation states of the motor. For example, the detection may be performed by pattern detection logic 106 or 706.
[0044] At 806, the motor 101 is switched from a first control mode to a second control mode in response to detecting that the predetermined pattern occurs in a plurality of consecutive commutation states. This switching of the control modes thus is performed by control logic based on a mode determined by the mode logic, such as disclosed herein. In some examples, the method 800 includes counting a number of times the BEMF signal crosses a predetermined value during each of the respective commutation states. A counter may be reset in response to detecting that the BEMF signal for a floating phase does not cross the predetermined value during one of the commutation states. The motor may be switched from the first control mode to the second control mode if the counter is determined (e.g., by comparator) to have a count value that satisfies a predetermined threshold value.
[0045] For example, the electric motor may be operated in the second control mode (e.g., closed-loop operating mode) using a trapezoidal BEMF technique. Thus, the method 800 may automatically switch from the first operating mode to the second operating mode without interaction from an external actor, and without requiring a pre-defmed motor speed or a motor current threshold. The approach disclosed herein is applicable to different types of motors and control schemes.
[0046] In some further examples, the method 800 may control at least one of speed or current applied to the motor. This can be performed by adjusting at least one of speed or current applied to the motor during a first mode of control in response to detecting that the BEMF signal fails to exhibit the predetermined pattern during at least one of the plurality of commutation states. The detecting and the switching may be repeated based on speed and/or current being applied to the motor, which speed and/or current may be adjusted over time.
[0047] FIG. 9 illustrates another example of a method 900 of controlling an electric motor 101, including switching between modes of control (e.g., between low-speed open-loop control and BEMF-based sensorless control). The method 900 begins, at 902, by initializing a motor. In some examples, the required motor initialization may be performed by a motor control logic similar to the control logic 112 of FIG. 1. This initialization may include starting the motor in a forced commutation mode, ramping up its commutation frequency until a minimum motor rotational speed is reached, and increasing the motor speed so as to begin generating BEMF signals. Once such speed is reached, the method 900 may proceed to 904.
[0048] At 904, a one or more one or more signals are evaluated for a predetermined signal pattern. For example, the signals being evaluated include BEMF waveforms for the respective phase windings in each commutation state. This checking may be performed by pattern detection logic (e.g., logic 106 or 706). For example, logic monitors and determines if a BEMF signal characteristic occurs, such as whether a zero crossing of one or more BEMF signals is present during a respective commutation period. In some examples, after or concurrently with 904, at 906, a determination is performed to determine if an overcurrent condition has occurred regarding the motor. If so, the motor 101 is placed into a fault condition (e.g., safe state), at 908, and, after a predetermined time the motor is switched, at 910, to its initial forced commutation frequency and the method returns to 902. A motor control logic (e.g., logic 112 or 714) may place the motor 101 into this fault condition.
[0049] If an over current condition was not detected at 906, then a determination is made as to if a pattern was recognized, at 912. Logic such as the pattern detection logic 106 or 706 discussed above with reference to FIG. 1 may perform the determination at 912 and may contribute to determining if a predetermined pattern was recognized (detected). As disclosed herein, the pattern may correspond to a predetermined BEMF signal pattern in which one or more BEMF voltage signals cross a predetermined voltage (e.g., zero crossings) during one or more commutation states. In some examples, the predetermined BEMF signal pattern corresponds to detecting each of the BEMF voltage signals crossing a predetermined voltage (e.g., zero crossings) during a plurality of consecutive commutation states. For each detection of the predetermined pattern, a count value is incremented to track each valid crossing. If the pattern is not recognized during a commutation state, then the count value is reset, at 914, and a current driven to the motor is adjusted. For example, the current may be adjusted by using an incremental up or down current amperage. Thus, while the signal doesn’t match the expected pattern, the reference current and/or speed values in the open-loop control are changed after a certain number of commutations. From 914, the method returns to block 904.
[0050] If there is a recognized pattern at 912, then a determination is made, at 916 as to if the pattern was recognized“N” (a threshold) number of times. For example, a counter (e.g., counter 718) may provide a corresponding counter value to represent the number of valid crossings detected over a series of commutation states. If the pattern is not recognized at 916, then the method returns to block 904. In response to detecting the predetermined pattern, at 916,“N” number of times, the method proceeds to 920 where a control mode of the motor may be changed. For example, the mode change at 920 can correspond to switching from an open-loop (e.g., forced commutation) control mode to a closed-loop (e.g., BEMF-based sensorless) control mode. As mentioned, the mode logic 108, 808 discussed above may be provided information as to whether the pattern was recognized“N” times to enable switching between respective modes as disclosed herein. In one example,“N” may be set to N>6, which would reflect two detections per phase in a three-phase motor. In other examples, different values of“N” may be used. Additionally, or alternatively, the value of“N” may be set to a default value (e.g., N=6) or be user programmable (e.g., a register entry set in response to a user input).
[0051] In view of the foregoing, employing the above description and figures explained example systems and methods that may eliminate a lengthy manual tuning to find a minimum speed and current needed to generate run time signal(s) from the a motor that can include the BEMF signal(s). Eliminating manual tuning enables faster time to market and applicability to a variety of different motor configurations and operating conditions. ETnlike implementations that may use previously chosen speed and current values that were fixed and specific to the motor and load conditions, the approach herein affords automatic mode changes that increase system robustness and flexibility.

中文:
[0002]各种类型的电动马达可能需要在操作模式之间转换。例如,块换向式永磁体同步马达(PMSM)可以在第一模式(例如,开环初始化模式)下开始运行,在该模式下使用强制换向,并且定子产生旋转磁场,该旋转磁场开始使转子以低速旋转。一旦转子达到足够的速度,控制器和/或开关就可以使PMSM从第一模式(初始化模式)切换到第二模式,该第二模式可以称为闭环或无传感器运行模式。
[0004]另一个示例是一种方法。该方法包括在马达的多个换向状态中的每个期间测量马达的反电动势(BEMF)信号。该方法还包括在马达的多个换向状态中的每个期间检测与反电动势信号(BEMF信号)相关联的一或多个周期性特征。马达还包括响应于检测到预定模式在多个连续换向状态中发生而将马达从第一控制模式切换到第二控制模式。
[0005]一种示例性系统包括传感器电路,以提供针对多相电动马达的浮置相的反电动势(BEMF)的量度。控制器具有输出以提供用来控制多相电动马达的操作的控制信号。控制器被配置为利用非基于BEMF的第一控制模式来初始地控制多相电动马达。控制器还被配置为检测传感器信号中模式的每次发生,该模式包括在多相电动马达的选定换向状态期间越过预定信号值。控制器被进一步配置为响应于在多个连续换向状态上检测到该模式的发生而从第一控制模式切换到基于BEMF的控制模式。
[0006]图1示出了用于控制在电动马达的不同控制模式之间进行切换的示例性系统。
[0007]图2示出了马达电路的示例。
[0008]图3是示出在多个换向状态上的反电动势(BEMF)电压波形的示例的曲线图。
[0009]图4是示出在多个换向状态上针对给定相的示例性BEMF波形的曲线图。
[0010]图5是在多个换向状态上针对多个相的示例性BEMF波形的曲线图。
[0011]图6是示出在缺乏改变马达的控制模式的稳定性情况下在多个换向状态上针对给定相的示例性BEMF波形的曲线图。
[0012]图7示出了马达系统的示例。
[0013]图8示出了用于控制在马达的控制模式之间进行切换的方法的示例性流程图。
[0014]图9示出了用于控制在马达的控制模式之间进行切换的方法的另一示例性流程图。
[0015]本公开提供了使电动马达从初始化模式切换到闭环(例如,无传感器)模式的系统和方法。
[0016]举例来说,系统可以测量电动马达(例如,三相永磁体同步马达(PMSM))的一或多个相的反电动势(BEMF)(例如,BEMF电压)。响应于识别出BEMF电压中的预定信号模式,可以使马达从初始的低速控制模式切换到闭环控制模式。例如,在低速开环控制期间,马达控制器或其他电路可以针对马达的给定电流速度和/或参考电流来监测和评估BEMF信号。如果在给定的速度和/或参考电流下未检测到预定模式,则可以在初始开环控制模式期间(例如,递增地)增加速度和/或参考电流信号以用于BEMF的附加评估。因此,在开环控制模式期间,在改变马达的速度和/或电流参数的同时,可以监测BEMF以检测每个换向状态中的模式,直到在多个换向状态上检测到预定的BEMF模式为止。例如,预定模式可以对应于在针对给定相的选定换向状态期间(例如,当相浮置时)越过预定电压(例如,中点或零交叉)的BEMF信号。一旦在多个换向状态上检测到交叉的模式,其本身可以构成预定模式,则马达控制器或其他电路可以自动地将操作控制从初始(例如,开环)控制转换为闭环控制(例如基于BEMF的无传感器控制)。
[0017]图1示出了被配置为控制马达101的马达控制系统100的示例。系统100包括被配置为在电动马达的操作模式之间切换的逻辑(例如,在马达控制器中实现的逻辑)。例如,在马达的启动期间,系统100使得能够以较高的操作速度在低速开环控制与基于BEMF的无传感器控制之间进行自动转换。示例性系统100包括测量逻辑104、模式检测逻辑106、模式逻辑108和控制逻辑112。控制逻辑112耦合到驱动器116,该驱动器被配置为响应于由控制逻辑112提供的控制信号向马达101的相绕组供应电流。
[0018]在一些示例中,一些或全部逻辑可以被制造为在公共基板上实现的马达控制器的一部分(例如,集成在公共芯片或管芯中)。例如,控制系统100及其逻辑块可以实现为具有分立逻辑器件的硅芯片上的、集成电路中的、现场可编程门阵列(FPGA)中的硬件。在其他示例中,该逻辑可以在算术逻辑单元(ALU)中实现,该算术逻辑单元可以是独立的ALU或在处理器内核内。因此,可以以各种方式来实现由马达控制系统100中的逻辑实现的功能。
[0019]在一个示例中,测量逻辑104包括电压测量电路,该电压测量电路被配置为例如经由一或多个连接102来测量马达101的每个相的BEMF。尽管在图1的示例中,所测量的信号被显示为经由线路102从马达接收,但是另选地,此类信号可以通过经由对应的感测电路从驱动器116感测电压来测量。测量逻辑104被配置为测量由马达101的每个相提供的BEMF信号电压,并将测量结果提供给模式检测逻辑106以进行后续处理。在一些示例中,测量逻辑104可以实现对所测量的信号的数字处理,以由模式检测逻辑106进一步评估。
[0020]作为另一示例,测量逻辑104以一定采样率周期性地采样BEMF信号,例如利用将BEMF信号转换为数字数据以通过模式检测逻辑106进一步分析的模数转换器(A/D转换器)。从模拟数据转换为数字数据的信号可以包括由马达101的每个浮置相生成的BEMF电压信号。在示例性三相PMSM中,在任何时间只有两相传导电流,而使第三相浮置,这取决于电流换向状态。因此,测量逻辑104可以在针对相应浮置相的BEMF信号经历马达101的一或多个换向周期时,对该信号进行若干次(例如,周期性的)测量。因此,对来自每个浮置相的BEMF信号的量度进行测量并将其提供给模式检测逻辑106。
[0021]模式检测逻辑106随时间推移接收由测量逻辑104提供的BEMF信号的量度作为输入。模式检测逻辑106被配置为检测所监测的BEMF信号表现出预定模式的实例。响应于检测到该预定模式,模式检测逻辑106可以使(或指示)模式逻辑108从初始(例如,开环)控制模式切换到不同(例如,闭环)的控制模式。
[0022]例如,模式检测逻辑106被配置为基于在电动马达101的选定换向状态期间所测量的BEMF信号(例如,来自测量逻辑104)越过预定信号值来识别预定模式的每个实例。尽管可以使用其他电压电平,但是示例性的预定电压针对马达的浮置相为零伏(例如,零交叉)。在一些示例中,模式检测逻辑106可以检测到预定模式(例如,零交叉)在多个连续换向状态中的每一个中发生。例如,模式检测逻辑106可以对发生的连续有效交叉的数量进行计数,并将计数值存储在存储器中。模式检测逻辑106可以响应于在多个换向状态中的任何一个期间检测到BEMF信号未表现出该预定模式而重置计数值。模式逻辑108因此可以监测或接收该计数值,以控制是否要切换到下一控制模式,如本文所公开的。在其他示例中,模式检测逻辑106可以基于可用于确定何时需要切换马达101的模式的各种信号或其他特征来利用其他模式或不同的模式。作为又另一个示例,测量逻辑104和模式检测逻辑106可以被实现为硬件,例如比较器,以相对于电压阈值(例如,BEMF电压的中点)比较针对每个相所测量的BEMF电压。
[0023]模式逻辑108被配置为根据多种控制模式中的一种来控制电动马达101的操作模式。例如,控制模式可以包括在低速期间的非基于BEMF的控制模式和在较高速度下的闭环(例如,无传感器)控制模式。例如,针对低速的控制模式可以利用开环或闭环控制,而基于BEMF的控制可以用于更高的速度。因此,模式逻辑108可以基于由模式检测逻辑106确定的模式检测信息在其控制模式之间切换。例如,模式逻辑108被配置为初始地(例如,在启动期间)采用开环控制并且响应于模式检测逻辑106检测到BEMF信号在多个换向状态上表现出预定模式而从此类开环控制切换到闭环控制,如本文所公开的。作为示例,模式逻辑实现状态机,该状态机基于检测(或未检测)到BEMF信号中的模式在控制模式之间转换。
[0024]控制逻辑112被配置为设置施加给电动马达101的速度和/或电流。例如,控制逻辑112耦合到驱动器116的输入,以向开关装置(例如,晶体管)提供PWM信号,该开关装置被启用和停用以根据马达的换向状态向马达101的相绕组供应电流。因此,控制逻辑112基于来自模式逻辑108的指令来实现控制模式(例如,低速或闭环控制)。控制逻辑112可以在马达101的低速控制期间使用速度和电流,或者仅使用速度或仅使用电流来实现级联控制。
[0025]作为示例,在第一控制模式期间(例如,在低速启动期间),响应于在多个换向状态中的至少一个期间检测到BEMF信号未能表现出预定模式,控制逻辑114调整施加给电动马达的速度和/或电流。例如,控制逻辑114在第一操作模式期间的连续时间间隔内增量地调整(例如,增加)施加给电动马达101的速度和/或电流,直到模式检测逻辑106在一系列连续换向状态中检测到预定模式为止。如所提及的,模式逻辑108基于在马达的一系列连续换向状态中检测到预定模式,从第一(例如,非BEMF)控制模式切换到第二(闭环)控制模式。控制逻辑112使用控制模式(例如,由模式逻辑108建立的)以及速度和/或参考电流设置来实现对相关驱动电路的对应控制。
[0026]控制逻辑112基于由模式逻辑108确定的控制模式,向驱动电路116提供控制信号以控制马达101。因此,驱动电路116基于来自控制逻辑112的控制信号来提供电流以用于激励马达101的绕组。例如,如图2所示,驱动电路116可以包括开关(例如,晶体管)装置的H桥或其他驱动布置,其被配置为基于来自包括控制逻辑112的马达控制器的控制信号向相应的绕组对供应电流。
[0027]与用于从开环控制过渡到闭环控制的其他方法不同,本文公开的系统和方法不需要预先定义的马达速度或马达电流阈值。而是,根据马达101的BEMF电压以及其他有用/期望的工作条件和/或系统参数而发生操作模式转换。例如,在低马达速度下,BEMF的信噪比(SNR)太低而无法用于无BEMF传感器的闭环马达控制,这会导致转子位置检测不可靠。因此,在低速下,对马达的操作通常限于非BEMF速度控制(例如,开环或强制换向),与在较高速度下的闭环速度控制相比,其表现出性能降低。然而,如本文所公开的,图1的系统100通过检测BEMF信号中的预定模式来确定BEMF信号何时足够稳定从而切换到闭环控制模式,例如基于BEMF的无传感器、闭环控制模式。在其他示例中,控制可以从闭环(例如,低速、非基于BEMF的控制,可以是无传感器的或采用传感器)转换到另一种闭环控制模式(例如,基于BEMF的无传感器控制)。以较低速度实施的非基于BEMF的控制类型可能会根据应用要求而有所不同。
[0028]图2示出了马达系统200的示例。马达系统200包括耦合到马达204的驱动器202,该马达被示为具有相绕组A、B和C的三相马达。在图2的示例中,相绕组A、B和C各自具有分别显示为L1、L2和L3的电感。作为一个示例,马达可以是PMSM,其包括安装在其定子/壳体中的三个非永久性电磁激活磁体(电磁体),并且可以具有安装至其中央转子的四个永磁体。然而,在本文的示例中也可以采用其他示例性马达,这些其他示例性马达具有不同数量的永磁体和电磁体。例如,定子的三个电磁体可以通过成对工作的六个换向状态来激活,以产生相电压(三相电源)来旋转马达。
[0029]驱动器202包括开关装置S1、S2、S3、S4、S5和S6(例如,诸如场效应晶体管或双极结型晶体管的晶体管)的布置(例如,H桥)。马达控制器206(例如,对应于图1的控制系统)被耦合以控制驱动器202的开关以产生通常彼此异相(例如,以120度)的输出相电压VA、VB和VC。在该示例中,存在连接到高电压电源V+的三个上部开关S1、S3和S5,以及连接到低(例如,接地)电压的三个下部开关S2、S4和S6。上部开关S1、S3和S5以及下部开关S2、S4和S6共同工作,以向相绕组提供电流,相绕组产生对应的相电压VA、VB和VC。如本文所公开的,马达控制器206被配置为基于表现出规定模式的BEMF信号自动地将PMSM从初始化模式(例如,实现开环或强制换向控制)切换到运行模式(例如,闭环控制)。如果合适,可以将与马达运行相关联的其他信号和运行参数用作改变控制模式的确定的一部分。马达控制器206可以利用相同的BEMF信号,其被监测以控制控制模式之间的转换,以在正常(高速、基于BEMF的无传感器)操作期间将马达101维持在运行模式。在至少一些示例中,马达控制器206以规定的顺序向开关S1-S6提供控制信号,以便产生三相电压(VA、VB和VC),以向定子中的电磁体供电,从而实现转子所需的运动。
[0030]图3是示出多相马达(诸如马达101或204)的各种示例理想波形的曲线图300。图3示出了在不同转子电位置和相关的换向状态(例如,每个60电度的六个换向状态)下的相A、B和C的相电压。在马达控制的一些示例中,PWM信号可以驱动开关S1-S6(图2)接通和断开以生成相应的相电压VA、VB和VC。在该示例中,随着各个浮置相斜升或斜降,每个相电压都表现出以选定的换向状态为中心的预定电压的交叉(例如,中点或零交叉)。
[0031]图4是示出了叠加在马达换向状态402上的马达(例如马达204)的给定相的示例性相电压404的曲线图400。对于不同相的附加相和BEMF信号可能已经在图4中与其他信号一起绘制(例如,参见图5);然而,为了清楚起见,在图4的示例中示出了单相电压波形404。如图所示,在其浮置相期间,相电压404从其被激励的高压状态(例如,大约2V附近)降低到其低压状态(例如,大约0V)。相电压的下降部分对应于给定相(浮置期间)产生的BEMF。在该示例中,BEMF电压越过满足稳定性标准的预定电压(例如,约1V的中点)。例如,稳定性标准包括在所选换向状态期间具有零或其他预定交叉的BEMF电压,其可以在所选换向状态的浮置相期间被检测到(例如,通过模式检测逻辑)。
[0032]如本文所公开的,测量逻辑104(图1)在换向状态期间测量BEMF电压波形404。当测量逻辑104测量相电压404的BEMF电压时,相绕组是浮置的(例如,未通电),从而使得BEMF电压波形404从其高电压幅度减小到其低电压幅度。在图4的示例中,示出了交叉发生在点412(例如,约1V)处,这对浮置相是有效交叉,因为其发生在选定的换向状态(该六个换向状态示例中的状态1)期间,在402'处指示。当每个相应的相被确定为浮置时,可以通过换向状态来触发针对每个相的BEMF电压的测量(例如,通过测量逻辑)。如图4所示,这可能在各个换向状态402'的时间间隔期间发生。特别地,在412处示出的给定相的BEMF电压的中点(例如,零)交叉可发生在换向状态402'期间的浮置相的中间部分。模式检测逻辑被配置为针对马达的每个相检测BEMF电压越过预定电压的每次发生(例如,有效交叉)。
[0033]如图4所示,如果交叉点412出现在中点范围内或中点值处,则可以进一步确定该交叉点(通过模式检测逻辑)为有效交叉。在一些示例中,如果交叉点412在换向周期内或在该换向周期的中心处或附近的规定时间间隔内的任何时间出现,则也可以确定该交叉点为有效交叉。以此方式,模式检测逻辑可以将BEMF交叉的有效性确定为具有电压分量(例如,越过预定电压,例如零)和时间分量(例如,与规定的换向状态同步)两者,这些条件表示在图4的方框413中。如以下所讨论的,可以结合示例图5评估每个其他相BEMF信号(通过模式检测逻辑),以确定在马达多个连续换向状态上是否存在包括有效交叉的模式。
[0034]图5示出了叠加在换向状态信号502上的多个相电压504、505和506中的每一个的示例曲线图500。在图5的示例中,相电压504、505、506提供了在每个相应的浮置相的对应换向状态期间与预定电压值交叉(例如,零交叉)的BEMF信号,其在510、512和514处示出。因此,通过在一系列换向状态上在BEMF电压信号中检测到此类模式,马达控制器可以确定马达系统的运行足够稳定,并从其闭环控制切换到其开环控制。
[0035]图6示出了示例曲线图600,其描绘了与图4类似的换向状态信号602和给定相电压信号604。在该示例中,BEMF电压从高电压电平过渡到低电压值。然而,在该示例中,在针对浮置相的预期换向状态期间,未发生预定电压的交叉(例如,零交叉)。取而代之的是,交叉会在马达的随后的换向状态下发生,因此该交叉不是用于模式检测目的以使马达能够从第一模式(例如,开环低速)切换到第二模式(例如,闭环BEMF无传感器)的有效交叉。例如,箭头608通常指示相电压信号604在其预期的浮置相阶段期间继续增加的区域,使得阈值交叉在错误的换向状态期间发生。由图6的信号表示的示例性马达可以类似于上面讨论的为块换向马达实现六个换向状态的马达。BEMF电压信号的幅度(或预定幅度)取决于马达频率/速度和电源电压。
[0036]图7示出了马达系统700的示例,该马达系统包括马达控制器710,该马达控制器被配置为实现控制电动马达701的逻辑。例如,马达701可以是多相(例如,三相)PMSM,例如表现出梯形或正弦BEMF信号的无刷DC马达。在图7的示例中,马达控制器710包括测量逻辑704、模式检测逻辑706、模式逻辑708和控制逻辑714。在其他示例中,测量逻辑704和相关联的相感测电路(未示出)可以在马达控制器710的外部或内部实现。
[0037]如本文所公开的,测量逻辑704经由一或多个输入连接703接收针对马达701的每个相的BEMF信号。测量逻辑704可以包括电压测量电路,该电压测量电路将所测量的BEMF电压信号提供给模式检测逻辑706,例如本文所公开的。在该示例中,模式检测逻辑706包括交叉检测逻辑716和计数器718。交叉检测逻辑716可以针对在马达的对应换向状态期间越过预定值(例如,0V)的浮置相检测所测量的BEMF信号的每次发生,如上所述。例如,在给定相处于浮置状态时,在换向状态期间,交叉检测逻辑716针对给定相从其正电压值到负电压值的减小来检测BEMF信号的零或中点交叉。
[0038]模式检测逻辑706还可控制计数器718以对所测量的BEMF信号越过预定值(例如,零交叉)的每次连续发生进行计数。例如,计数器718包括计数器值719,该计数器值跟踪在连续换向状态期间BEMF的规定模式发生的次数。计数器718可以将计数器值719存储在模式检测逻辑706可访问的寄存器、存储器位置或类似位置中。计数器718可被进一步配置为响应于交叉检测逻辑716在一或多个换向状态期间检测到BEMF信号未与预定值交叉而重置计数器值。
[0039]模式逻辑708可以被配置为类似于图1的模式逻辑108进行操作。例如,模式逻辑708被配置为基于计数器值719来在马达701的两或更多种控制模式之间切换,该计数器值可以由模式逻辑708访问或由模式检测逻辑706提供给模式逻辑。例如,模式逻辑708(和/或模式检测逻辑706)可以将计数器值719与预定阈值进行比较,该预定阈值确立从开环控制切换到闭环控制所需的连续零交叉的数量。阈值可以是默认值或是用户定义的(例如,可编程的)。作为一个示例,可以基于(或处于)马达的360度电度上发生的换向状态的数量来设置计数器阈值。响应于确定在操作模式之间切换,模式逻辑708可以将模式改变命令提供给控制逻辑714。
[0040]控制逻辑714将控制信号提供给驱动器724,以向马达701的各相施加对应的电流。控制信号取决于控制逻辑为马达控制设置的速度和/或电流值。取决于由模式逻辑708确立的控制模式,控制逻辑714可以实现开环控制720或闭环控制722。在启动期间,当马达以其开环控制操作模式进行操作时,控制逻辑714随时间增量地调整施加给马达701的速度和/或电流。在闭环控制模式期间,速度和/或电流的增量增加可以随时间持续,直到模式检测逻辑706在一系列连续的换向状态中检测到预定模式。例如,如果在一系列连续的换向状态期间或者在经过预定的时间间隔没有检测到该模式,则控制逻辑714增加施加给马达的速度和/或电流。一旦在一系列连续的换向状态中检测到预定模式阈值次数,则模式逻辑708命令控制逻辑714从开环控制720切换到闭环控制722。控制逻辑714可以进一步响应于在多个换向状态中的至少一个期间检测到BEMF信号未能表现出预定模式来调整施加给马达701的速度和/或电流中的至少一者。然而,在一些示例中,模式检测逻辑706可以继续在一系列连续换向状态中寻找预定模式,并由此控制由控制逻辑714实现的相应控制模式720和722的之间的切换。
[0041]考虑到上述的前述结构和功能特征,参考图8和9可以更好地理解示例性方法。应当理解,该方法并不局限于所示顺序。在其他示例中,某些动作可能以与本文所示和所述不同的顺序和/或同时发生。此外,可能不需要所有示出的特征来实现方法。例如,在一些示例中,图8和9的每种方法可以在马达控制器中实现以类似于以上参考图1至7所描述的那样控制马达。
[0042]图8示出了控制用于操作电动马达101的运行模式的示例性方法800。在802处,测量马达的反电动势(BEMF)信号。例如,可以在马达的多个换向状态的每个期间周期性地测量BEMF信号。这些测量可以由测量逻辑104或704执行。另外,可以保持第一控制模式,直到方法800确定(如下所述)预定模式在多个连续换向状态中的每一个中发生为止。
[0043]在804处,方法800在马达的多个换向状态中的每个期间,检测BEMF信号中预定模式的发生。在一些示例中,检测可以包括在马达的多个换向状态中的每个期间周期性地检测与BEMF信号相关联的一或多个特征。例如,该检测可以由模式检测逻辑106或706执行。
[0044]在806处,马达101响应于检测到预定模式在多个连续换向状态中发生而从第一控制模式切换到第二控制模式。因此,控制模式的该切换由控制逻辑基于由模式逻辑确定的模式来执行,例如本文所公开的。在一些示例中,方法800包括:在各个换向状态中的每个换向状态期间,对BEMF信号越过预定值的次数进行计数。计数器可以响应于在换向状态中的一个期间检测到针对浮置相的BEMF信号未超过预定值而进行重置。如果计数器(例如,通过比较器)被确定为具有满足预定阈值的计数值,则马达可以从第一控制模式切换到第二控制模式。
[0045]例如,可以使用梯形BEMF技术以第二控制模式(例如,闭环操作模式)操作马达。因此,方法800可以自动地从第一操作模式切换到第二操作模式,而无需来自外部参与者的相互作用,并且不需要预定的马达速度或马达电流阈值。本文公开的方法适用于不同类型的马达和控制方案。
[0046]在一些其他示例中,方法800可以控制施加给马达的速度或电流中的至少一者。这可以通过响应于在多个换向状态中的至少一个期间检测到BEMF信号未能表现出预定模式而调整在第一控制模式期间施加给马达的速度或电流中的至少一者来执行。可以基于施加给马达的速度和/或电流来重复检测和切换,该速度和/或电流可以随时间调整。
[0047]图9示出了控制电动马达101的方法900的另一示例,包括在控制模式之间进行切换(例如,在低速开环控制与基于BEMF的无传感器控制之间)。方法900在902处通过初始化马达开始。在一些示例中,所需的马达初始化可以由类似于图1的控制逻辑112的马达控制逻辑来执行。该初始化可以包括以强制换向模式启动马达,逐渐提升其换向频率直至达到最小马达旋转速度,以及增加马达速度以开始生成BEMF信号。一旦达到这样的速度,方法900就可以前进到904。
[0048]在904处,针对预定信号模式评估一或多个信号。例如,被评估的信号包括在每个换向状态中用于各个相绕组的BEMF波形。该检查可以由模式检测逻辑(例如,逻辑106或706)执行。例如,逻辑监测并确定BEMF信号特征是否发生,例如在相应的换向周期期间是否存在一或多个BEMF信号的零交叉。在一些示例中,在904之后或与之同时,在906处,执行确定以确定关于马达是否已经发生过电流状况。如果发生了,则在908处将马达101置于故障状况(例如,安全状态),并且在预定时间之后,在910处将马达切换到其初始强制换向频率,然后该方法返回到902。马达控制逻辑(例如,逻辑112或714)可将马达101置于该故障状况。
[0049]如果在906处未检测到过电流状况,则在912处确定是否识别出模式。诸如以上参考图1讨论的模式检测逻辑106或706之类的逻辑可以在912处执行确定,并且可以有助于确定是否识别出(检测到)预定模式。如本文所公开的,该模式可以对应于预定的BEMF信号模式,其中一或多个BEMF电压信号在一或多个换向状态期间与预定电压交叉(例如,零交叉)。在一些示例中,预定BEMF信号模式对应于在多个连续换向状态期间检测到BEMF电压信号中的每个越过预定电压(例如,零交叉)。对于每次检测到预定模式,递增计数值以跟踪每次有效交叉。如果在换向状态期间未识别出该模式,则在914处重置计数值,并且调整驱动至马达的电流。例如,可以通过使用递增的向上或向下电流强度来调整电流。因此,尽管信号与预期模式并不匹配,但是在一定数量的换向之后,开环控制中的参考电流和/或速度值会改变。该方法从914返回到框904。
[0050]如果在912处识别出模式,则在916处确定该模式是否被识别“N”(阈值)次。例如,计数器(例如,计数器718)可以提供对应的计数器值,以表示在一系列换向状态上检测到的有效交叉的数量。如果在916处未识别出该模式,则该方法返回至框904。响应于在916处检测到预定模式“N”次,该方法前进到920,此时可以改变马达的控制模式。例如,在920处的模式改变可以对应于从开环(例如,强制换向)控制模式切换到闭环(例如,基于BEMF的无传感器)控制模式。如所提及的,可以向上述模式逻辑108、808提供关于是否识别出模式“N”次的信息,以使得能够在本文公开的各种模式之间进行切换。在一个示例中,可以将“N”设置为N≥6,这将反映三相马达中每相两次检测。在其他示例中,可以使用不同的“N”值。除此之外或可替代地,“N”的值可以被设置为默认值(例如,N=6)或者可以是用户可编程的(例如,响应于用户输入而设置的寄存器条目)。
[0051]鉴于前述内容,通过采用以上描述和附图说明了示例性系统和方法,这些示例性系统和方法可以省去冗长的手动调整,以找到生成马达的可包括BEMF信号的运行时间信号所需的最小速度和电流。通过消除手动调整,可以加快上市时间,并适用于各种不同的马达配置和工作条件。与可以使用先前选择的固定和特定于马达和负载条件的速度和电流值的实施方式不同,本文中的方法提供了自动模式改变,从而增加了系统的鲁棒性和灵活性。