Motor operation mode control

Abstract

One example is a system (100) for controlling a motor during startup. The system (100) includes measurement logic (104), mode detection logic (106), and mode logic (108). The measurement logic (104) monitors a BEMF signal representing a back electromotive force (BEMF) of an electric motor, and the mode detection logic (106) monitors the signal to detect instances where the monitored BEMF signal exhibits a predetermined pattern. The mode logic (108) enables the electric motor to be controlled according to multiple control modes. In some examples, the mode logic (108) initially employs a first control mode and switches from the first control mode to a second control mode in response to the mode detection logic (106) detecting that the BEMF signal exhibits the predetermined pattern over multiple commutation states.

Description

[0001] The present application relates generally to controlling operating modes of motors. Background Art

[0002] Various types of electric motors may need to switch between operating modes. For example, a block-commutated permanent magnet synchronous motor (PMSM) may begin operating in a first mode (e.g., an open-loop initialization mode) in which forced commutation is used and the stator generates a rotating magnetic field that begins to rotate the rotor at a low speed. Once the rotor reaches sufficient speed, a controller and / or switch may cause the PMSM to switch from the first mode (initialization mode) to a second mode, which may be referred to as a closed-loop or sensorless operating mode. Summary of the invention

[0003] One example is a system including measurement logic, pattern detection logic, and mode logic. The measurement logic measures a BEMF signal representing a back electromotive force (BEMF) of an electric motor. The pattern detection logic detects instances where the monitored BEMF signal exhibits a predetermined pattern. The mode logic enables control of the electric motor according to a plurality of control modes. The mode logic initially employs a first control mode and switches from the first control mode to a second control mode in response to the pattern detection logic detecting that the BEMF signal exhibits a predetermined pattern over a plurality of commutation states.

[0004] Another example is a method. The method includes measuring a back electromotive force (BEMF) signal of a motor during each of a plurality of commutation states of the motor. The method also includes detecting one or more periodic features associated with the 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 a predetermined pattern occurs in a plurality of consecutive commutation states.

[0005] An exemplary system includes a sensor circuit to provide a measure of a back electromotive force (BEMF) for a floating phase of a multiphase electric motor. A controller has an output to provide a control signal for controlling the operation of the multiphase electric motor. The controller is configured to initially control the multiphase electric motor using a first control mode that is not BEMF-based. The controller is also configured to detect each occurrence of a pattern in the sensor signal, the pattern comprising crossing a predetermined signal value during a selected commutation state of the multiphase electric motor. The controller is further configured to switch from the first control mode to a BEMF-based control mode in response to detecting the occurrence of the pattern over a plurality of consecutive commutation states. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 An exemplary system for controlling switching between different control modes of an electric motor is shown.

[0007] Figure 2 An example of a motor circuit is shown.

[0008] Figure 3 is a graph showing examples of back electromotive force (BEMF) voltage waveforms over multiple commutation states.

[0009] Figure 4 is a graph showing exemplary BEMF waveforms for a given phase over multiple commutation states.

[0010] Figure 5 is a graph of exemplary BEMF waveforms for multiple phases over multiple commutation states.

[0011] Figure 6 is a graph showing exemplary BEMF waveforms for a given phase over multiple commutation states in the absence of stability to change the control mode of the motor.

[0012] Figure 7 An example of a motor system is shown.

[0013] Figure 8 An exemplary flow chart of a method for controlling switching between control modes of a motor is shown.

[0014] Fig. 9 Another exemplary flow chart of a method for controlling switching between control modes of a motor is shown. DETAILED DESCRIPTION

[0015] The present disclosure provides systems and methods for switching an electric motor from an initialization mode to a closed-loop (eg, sensorless) mode.

[0016] For 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 identifying 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 signal for a given current speed and / or reference current of the motor. If the predetermined pattern is not detected at a given speed and / or reference current, the speed and / or reference current signal may be increased (e.g., incrementally) during the initial open-loop control mode for additional evaluation of the BEMF. Thus, during the open-loop control mode, while varying the speed and / or current parameters of the motor, the BEMF may be monitored to detect a pattern in each commutation state until a predetermined BEMF pattern is detected over a plurality of commutation states. For example, the predetermined pattern may correspond to a BEMF signal crossing a predetermined voltage (e.g., a midpoint or zero crossing) during a selected commutation state for a given phase (e.g., when the phase is floating). Once a pattern of crossings is detected across multiple commutation states, which may themselves constitute a predetermined pattern, a motor controller or other circuit may automatically transition operational control from initial (e.g., open loop) control to closed loop control (e.g., BEMF-based sensorless control).

[0017] Figure 1 An example of a motor control system 100 configured to control a motor 101 is shown. The system 100 includes logic (e.g., logic implemented in a motor controller) configured to switch between operating modes of an electric motor. For example, during startup of the motor, the system 100 enables automatic transition between low-speed open-loop control and BEMF-based sensorless control at higher operating speeds. The exemplary system 100 includes measurement logic 104, mode 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 current to a phase winding of the motor 101 in response to a control signal 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 into a common chip or die). For example, the control system 100 and its logic blocks may be implemented as hardware on a silicon chip with discrete logic devices, in an integrated circuit, or in a field programmable gate array (FPGA). In other examples, the logic may be implemented in an arithmetic logic unit (ALU), which may be a stand-alone ALU or within a processor core. Thus, the functions 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 a voltage measurement circuit configured to measure the BEMF of each phase of the motor 101, for example, via one or more connections 102. Figure 1 In the example of , the measured signal is shown as being received from the motor via line 102, but alternatively, such a signal can be measured by sensing a voltage from the driver 116 via a corresponding sensing circuit. The measurement logic 104 is configured to measure the BEMF signal voltage provided by each phase of the motor 101 and provide the measurement results to the mode detection logic 106 for subsequent processing. In some examples, the measurement logic 104 can implement digital processing of the measured signal for further evaluation by the mode detection logic 106.

[0020] As another example, the measurement logic 104 periodically samples the BEMF signal at a sampling rate, such as using an analog-to-digital converter (A / D converter) that converts the BEMF signal into digital data for further analysis by the mode detection logic 106. The signal converted from the analog data to digital data may include a BEMF voltage signal generated by each floating phase of the motor 101. In an exemplary three-phase PMSM, only two phases conduct current at any time, leaving the third phase floating, depending on the current commutation state. Therefore, the measurement logic 104 may make several (e.g., periodic) measurements of the BEMF signal for the corresponding floating phase as the signal undergoes one or more commutation cycles of the motor 101. Therefore, a measure of the BEMF signal from each floating phase is measured and provided to the mode detection logic 106.

[0021] The mode detection logic 106 receives as input the measurements of the BEMF signal provided by the measurement logic 104 over time. The mode detection logic 106 is configured to detect instances where the monitored BEMF signal exhibits a predetermined pattern. In response to detecting the predetermined pattern, the mode detection logic 106 may cause (or instruct) the mode logic 108 to switch from an initial (e.g., open-loop) control mode to a different (e.g., closed-loop) control mode.

[0022] For example, the mode detection logic 106 is configured to identify each instance of a predetermined pattern based on a BEMF signal (e.g., from the measurement logic 104) measured during a selected commutation state of the electric motor 101 crossing a predetermined signal value. Although other voltage levels may be used, an exemplary predetermined voltage is zero volts (e.g., zero crossings) for the floating phase of the motor. In some examples, the mode detection logic 106 may detect that a predetermined pattern (e.g., zero crossings) occurs in each of a plurality of consecutive commutation states. For example, the mode detection logic 106 may count the number of consecutive valid crossings that occur and store the count value in a memory. The mode 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 may therefore monitor or receive the count value to control whether to switch to the next control mode, as disclosed herein. In other examples, the mode detection logic 106 may utilize other or different modes based on various signals or other features that may be used to determine when it is necessary to switch the mode of the motor 101. As yet another example, the measurement logic 104 and the mode detection logic 106 may be implemented as hardware, such as comparators, to compare the measured BEMF voltage for each phase relative to a voltage threshold (eg, a midpoint of the BEMF voltage).

[0023] The mode logic 108 is configured to control the operating mode of the electric motor 101 according to one of a plurality of control modes. For example, the control modes may 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, while BEMF-based control may be used for higher speeds. Thus, the mode logic 108 may switch between its control modes based on mode detection information determined by the mode detection logic 106. For example, the mode logic 108 is configured to initially (e.g., during startup) employ open-loop control and switch from such open-loop control to closed-loop control in response to the mode detection logic 106 detecting that the BEMF signal exhibits a predetermined pattern over a plurality of commutation states, as disclosed herein. As an example, the mode logic implements a state machine that switches between control modes based on detecting (or not detecting) a pattern in the BEMF signal.

[0024] The control logic 112 is configured to set the speed and / or current applied to the electric motor 101. For example, the control logic 112 is coupled to the input of the driver 116 to provide a PWM signal to a switching device (e.g., a transistor) that is enabled and disabled to supply current to the phase windings of the motor 101 according to the commutation state of the motor. Thus, the control logic 112 implements a control mode (e.g., low speed or closed loop control) based on instructions from the mode logic 108. The control logic 112 can use both speed and current during low speed control of the motor 101, or use only speed or only current to implement cascade control.

[0025] As an example, during a first control mode (e.g., during a low speed start-up), in response to detecting that the BEMF signal fails to exhibit a predetermined pattern during at least one of the plurality of commutation states, the control logic 114 adjusts the speed and / or current applied to the electric motor. For example, the control logic 114 incrementally adjusts (e.g., increases) the speed and / or current applied to the electric motor 101 at successive time intervals during the first operating mode until the mode 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) control mode to the second (closed-loop) control mode based on detecting the predetermined pattern in a series of consecutive commutation states of the motor. The control logic 112 uses the control mode (e.g., established by the mode logic 108) and the speed and / or reference current settings to implement corresponding control of the associated drive circuit.

[0026] The control logic 112 provides a control signal to the drive circuit 116 to control the motor 101 based on the control mode determined by the mode logic 108. Therefore, the drive circuit 116 provides a current for exciting the winding of the motor 101 based on the control signal from the control logic 112. For example, Figure 2 As shown, the drive circuit 116 may include an H-bridge or other drive arrangement of switching (eg, transistor) devices configured to supply current to respective winding pairs based on control signals from a motor controller including the control logic 112 .

[0027] Unlike other methods for transitioning from open-loop control to closed-loop control, the systems and methods disclosed herein do not require predefined motor speed or motor current thresholds. Instead, the operating mode transition occurs based on the BEMF voltage of the motor 101 and other useful / desired operating conditions and / or system parameters. For example, at low motor speeds, the signal-to-noise ratio (SNR) of the BEMF is too low to be used for closed-loop motor control without a BEMF sensor, which can result in unreliable rotor position detection. Therefore, at low speeds, operation of the motor is typically limited to non-BEMF speed control (e.g., open-loop or forced commutation), which exhibits reduced performance compared to closed-loop speed control at higher speeds. However, as disclosed herein, Figure 1 The system 100 determines when the BEMF signal is stable enough to switch to a closed-loop control mode, such as a BEMF-based sensorless, closed-loop control mode, by detecting a predetermined pattern in the BEMF signal. In other examples, control can be switched from closed-loop (e.g., low-speed, non-BEMF-based control, which can be sensorless or employing sensors) to another closed-loop control mode (e.g., BEMF-based sensorless control). The type of non-BEMF-based control implemented at lower speeds may vary depending on the application requirements.

[0028] Figure 2 An example of a motor system 200 is shown. The motor system 200 includes a drive 202 coupled to a motor 204, which is shown as a three-phase motor having phase windings A, B, and C. Figure 2 In the example of , phase windings A, B, and C each have an inductance shown as L1, L2, and L3, respectively. As an example, the motor can be a PMSM, which includes three non-permanent electromagnetically activated magnets (electromagnets) mounted in its stator / housing, and can have four permanent magnets mounted to its central rotor. However, other exemplary motors having different numbers of permanent magnets and electromagnets can also be used in the examples herein. For example, the three electromagnets of the stator can be activated by six commutation states working in pairs to produce phase voltages (three-phase power) to rotate the motor.

[0029] The driver 202 includes an arrangement (eg, an H-bridge) of switching devices S1, S2, S3, S4, S5, and S6 (eg, transistors such as field effect transistors or bipolar junction transistors). The motor controller 206 (eg, corresponding to Figure 1 A control system ) is coupled to control the switches of driver 202 to generate output phase voltages V that are generally out of phase with each other (e.g., by 120 degrees) A 、V B and V CIn this example, there are three upper switches S1, 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 S1, S3, and S5 and the lower switches S2, S4, and S6 work together to provide current to the phase winding, which generates a corresponding phase voltage V A 、V B and V C 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 an operating mode (e.g., closed-loop control) based on a BEMF signal that exhibits a prescribed pattern. If appropriate, other signals and operating parameters associated with motor operation may be used as part of the determination to change the control mode. The motor controller 206 can utilize the same BEMF signal that is monitored to control transitions between control modes to maintain the motor 101 in the operating mode during normal (high-speed, BEMF-based sensorless) operation. In at least some examples, the motor controller 206 provides control signals to the switches S1-S6 in a prescribed sequence to generate a three-phase voltage (V A 、V B and V C ) to power the electromagnets in the stator, thereby achieving the desired movement of the rotor.

[0030] Figure 3 is a graph 300 illustrating various example ideal waveforms for a multi-phase motor, such as motor 101 or 204 . Figure 3 The phase voltages of phases A, B, and C are shown at different rotor electrical positions and associated commutation states (e.g., six commutation states of 60 electrical degrees each). In some examples of motor control, the PWM signal can drive switches S1-S6 ( Figure 2 ) is turned on and off to generate the corresponding phase voltage V A 、V B and V C In this example, as the respective floating phases ramp up or down, each phase voltage exhibits a crossing of a predetermined voltage (eg, a midpoint or zero crossing) centered about a selected commutation state.

[0031] Figure 4 is a graph 400 showing an exemplary phase voltage 404 of a given phase of a motor (e.g., motor 204) superimposed on a motor commutation state 402. Additional phase and BEMF signals for different phases may have been Figure 4 d together with other signals (see, for example, Figure 5 ); however, for clarity, Figure 4A single-phase voltage waveform 404 is shown in the example of . As shown, during its floating phase, the phase voltage 404 decreases from its energized high voltage state (e.g., in the vicinity of approximately 2V) to its low voltage state (e.g., approximately 0V). The decreasing portion of the phase voltage corresponds to the BEMF generated by a given phase (during floating). In this example, the BEMF voltage crosses a predetermined voltage (e.g., a midpoint of approximately 1V) that meets stability criteria. For example, the stability criteria include a BEMF voltage having zero or other predetermined crossings during a selected commutation state, which can be detected during the floating phase of the selected commutation state (e.g., by mode detection logic).

[0032] As disclosed herein, the measurement logic 104 ( Figure 1 ) BEMF voltage waveform 404 is measured during the commutation state. When the measurement logic 104 measures the BEMF voltage of the phase voltage 404, the phase winding is floating (e.g., not energized), causing the BEMF voltage waveform 404 to decrease from its high voltage amplitude to its low voltage amplitude. Figure 4 In the example of FIG. 4 , it is shown that the crossing occurs at point 412 (e.g., approximately 1V), which is a valid crossing for the floating phase because it occurs during the selected commutation state (state 1 in the example of six commutation states), indicated at 402 ′. When each corresponding phase is determined to be floating, the measurement of the BEMF voltage for each phase can be triggered by the commutation state (e.g., by measurement logic). Figure 4 As shown, this may occur during time intervals of various commutation states 402'. In particular, a midpoint (e.g., zero) crossing of the BEMF voltage of a given phase shown at 412 may occur in the middle portion of the floating phase during the commutation state 402'. The pattern detection logic is configured to detect each occurrence (e.g., a valid crossing) of the BEMF voltage crossing a predetermined voltage for each phase of the motor.

[0033] like Figure 4 As shown, if the crossing point 412 occurs within the midpoint range or at the midpoint value, the crossing point can be further determined (by the pattern detection logic) to be a valid crossing. In some examples, the crossing point 412 can also be determined to be a valid crossing if it occurs at any time within the commutation period or within a specified time interval at or near the center of the commutation period. In this way, the pattern detection logic can determine the validity of the BEMF crossing as having both a voltage component (e.g., crossing a predetermined voltage, such as zero) and a time component (e.g., synchronization with a specified commutation state), these conditions representing the validity of the BEMF crossing. Figure 4 As discussed below, the example Figure 5 Each of the other phase BEMF signals is evaluated (via pattern detection logic) to determine if a pattern exists that includes a valid crossover over a plurality of consecutive commutation states of the motor.

[0034] Figure 5 An example graph 500 of each of a plurality of phase voltages 504, 505, and 506 superimposed on a commutation state signal 502 is shown. Figure 5 , the phase voltages 504, 505, 506 provide BEMF signals that cross predetermined voltage values ​​(e.g., zero crossings) during corresponding commutation states of each respective floating phase, which are shown at 510, 512, and 514. Thus, by detecting such patterns in the BEMF voltage signal over a range of commutation states, the motor controller can determine that the operation of the motor system is sufficiently stable and switch from its closed-loop control to its open-loop control.

[0035] Figure 6 An example graph 600 is shown that depicts Figure 4 A similar commutation state signal 602 and a given phase voltage signal 604. In this example, the BEMF voltage transitions from a high voltage level to a low voltage value. However, in this example, a crossing of a predetermined voltage (e.g., a zero crossing) does not occur during the expected commutation state for the floating phase. Instead, the crossing would occur at a subsequent commutation state of the motor, and thus the crossing is not a valid crossing for mode detection purposes to enable the motor to switch from a first mode (e.g., open loop low speed) to a second mode (e.g., closed loop BEMF sensorless). For example, arrow 608 generally indicates a region where the phase voltage signal 604 continues to increase during its expected floating phase phase, such that the threshold crossing occurs during an erroneous commutation state. By Figure 6 The exemplary motor represented by the signal of can be similar to the motor discussed above to implement six commutation states for a block commutated motor. The amplitude (or predetermined amplitude) of the BEMF voltage signal depends on the motor frequency / speed and the supply voltage.

[0036] Figure 7 An example of a motor system 700 is shown that includes a motor controller 710 configured to implement logic for controlling 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 a trapezoidal or sinusoidal BEMF signal. Figure 7 In the example of FIG. 7 , the motor controller 710 includes measurement logic 704, mode detection logic 706, mode logic 708, and control logic 714. In other examples, the measurement logic 704 and associated phase sensing circuitry (not shown) can be implemented externally or internally to the motor controller 710.

[0037] As disclosed herein, the measurement logic 704 receives a BEMF signal for each phase of the motor 701 via one or more input connections 703. The measurement logic 704 may include a voltage measurement circuit that provides the measured BEMF voltage signal to the mode detection logic 706, such as disclosed herein. In this example, the mode detection logic 706 includes a crossing detection logic 716 and a counter 718. The crossing detection logic 716 may detect each occurrence of the measured BEMF signal for a floating phase crossing a predetermined value (e.g., 0V) during a corresponding commutation state of the motor, as described above. For example, when a given phase is in a floating state, during a commutation state, the crossing detection logic 716 detects a zero or midpoint crossing of the BEMF signal for a decrease in a given phase from its positive voltage value to a negative voltage value.

[0038] The pattern detection logic 706 may also control the counter 718 to count each consecutive occurrence of the measured BEMF signal crossing a predetermined value (e.g., a zero crossing). For example, the counter 718 includes a counter value 719 that tracks the number of times a specified pattern of the BEMF occurs during consecutive commutation states. The counter 718 may store the counter value 719 in a register, memory location, or the like accessible to the pattern detection logic 706. The counter 718 may be further 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 commutation states.

[0039] Mode logic 708 may be configured similar to Figure 1 708 is configured to switch between two or more control modes of the motor 701 based on a counter value 719, which can be accessed by the mode logic 708 or provided to the mode logic by the mode detection logic 706. For example, the mode logic 708 (and / or the mode detection logic 706) can compare the counter value 719 to a predetermined threshold that establishes the number of consecutive zero crossings required to switch from open-loop control to closed-loop control. The threshold can be a default value or user-defined (e.g., programmable). As an example, the counter threshold can be set based on the number of commutation states that occur (or are in) 360 electrical degrees of the motor. In response to determining to switch between operating modes, the mode logic 708 can provide a mode change command to the control logic 714.

[0040] The control logic 714 provides a control signal to the driver 724 to apply a corresponding current to each phase of the motor 701. The control signal depends on the speed and / or current value set by the control logic for the motor control. Depending on the control mode established by the mode logic 708, the control logic 714 can implement open-loop control 720 or closed-loop control 722. During startup, when 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. During the closed-loop control mode, the incremental increase in speed and / or current can continue over time until the mode detection logic 706 detects a predetermined pattern in a series of consecutive commutation states. For example, if the pattern is not detected during a series of consecutive commutation states or after a predetermined time interval, the control logic 714 increases the speed and / or current applied to the motor. Once the predetermined pattern threshold number of times is detected in a series of consecutive commutation states, the mode logic 708 commands the control logic 714 to switch from open-loop control 720 to closed-loop control 722. The control logic 714 may further adjust at least one of the speed and / or current applied to the motor 701 in response to detecting that the BEMF signal fails to exhibit a predetermined pattern during at least one of the plurality of commutation states. However, in some examples, 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 corresponding control modes 720 and 722 implemented by the control logic 714.

[0041] Considering the aforementioned structural and functional characteristics, reference Figure 8 and 9 The exemplary method may be better understood. It should be understood that the method is not limited to the order shown. In other examples, certain actions may occur in a different order and / or at the same time than shown and described herein. In addition, not all of the features shown may be required to implement the method. For example, in some examples, Figure 8 and 9 Each method can be implemented in the motor controller similar to the above reference Figures 1 to 7 The motor is controlled as described.

[0042] Figure 8 An exemplary method 800 of controlling an operating mode for operating an electric motor 101 is shown. At 802, a back electromotive force (BEMF) signal of the motor is measured. For example, the BEMF signal 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, a first control mode may be maintained until the method 800 determines (as described below) that a predetermined pattern occurs in each of a plurality of consecutive commutation states.

[0043] At 804, method 800 detects an occurrence of a predetermined pattern in the BEMF signal during each of a plurality of commutation states of the motor. In some examples, the detection may include periodically detecting one or more features associated with the BEMF signal during each of a 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 switches from the first control mode to the second control mode in response to detecting that a predetermined pattern occurs in a plurality of consecutive commutation states. Thus, this switching of the control mode is performed by control logic based on a pattern determined by mode logic, such as disclosed herein. In some examples, the method 800 includes counting the number of times the BEMF signal crosses a predetermined value during each of the respective commutation states. The counter may be reset in response to detecting that the BEMF signal for the floating phase does not exceed the predetermined value during one of the commutation states. If the counter is determined (e.g., by a comparator) to have a count value that satisfies a predetermined threshold, the motor may switch from the first control mode to the second control mode.

[0045] For example, the motor can be operated in a second control mode (e.g., a closed-loop operating mode) using a trapezoidal BEMF technique. Thus, the method 800 can automatically switch from the first operating mode to the second operating mode without interaction from external parties and without requiring predetermined motor speed or motor current thresholds. The methods disclosed herein are applicable to different types of motors and control schemes.

[0046] In some other examples, method 800 can control at least one of a speed or a current applied to the motor. This can be performed by adjusting at least one of a speed or a current applied to the motor during the first control mode in response to detecting that the BEMF signal fails to exhibit a predetermined pattern during at least one of the plurality of commutation states. The detection and switching can be repeated based on the speed and / or current applied to the motor, which speed and / or current can be adjusted over time.

[0047] Fig. 9 Another example of a method 900 for controlling an electric motor 101 is shown, including switching between control modes (e.g., between low speed open loop control and BEMF based sensorless control). The method 900 begins at 902 by initializing the motor. In some examples, the required motor initialization may be performed by a command similar to Figure 1 The initialization may be performed by the motor control logic of the control logic 112 of the control logic 112. The initialization may include starting the motor in a forced commutation mode, gradually increasing its commutation frequency until a minimum motor rotation speed is reached, and increasing the motor speed to begin generating a BEMF signal. Once such a speed is reached, the method 900 may proceed to 904.

[0048] At 904, one or more signals are evaluated for a predetermined signal pattern. For example, the signals evaluated include BEMF waveforms for each phase winding in each commutation state. This check can be performed by pattern detection logic (e.g., logic 106 or 706). For example, the logic monitors and determines whether a BEMF signal feature occurs, such as whether there are one or more zero crossings of the BEMF signal during a corresponding commutation cycle. In some examples, after or simultaneously with 904, at 906, a determination is performed to determine whether an overcurrent condition has occurred with respect to the motor. If it has occurred, the motor 101 is placed in a fault condition (e.g., a safe state) at 908, and after a predetermined time, the motor is switched to its initial forced commutation frequency at 910, and then the method returns to 902. The motor control logic (e.g., logic 112 or 714) may place the motor 101 in the fault condition.

[0049] If an overcurrent condition is not detected at 906, then at 912 it is determined whether a mode is recognized. Figure 1 Logic such as the discussed pattern detection logic 106 or 706 can perform a determination at 912 and can help determine whether a predetermined pattern is identified (detected). As disclosed herein, the pattern can correspond to a predetermined BEMF signal pattern in which one or more BEMF voltage signals cross a predetermined voltage (e.g., zero crossing) 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 crossing) during multiple 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 identified during the commutation state, the count value is reset at 914 and the current driven to the motor is adjusted. For example, the current can be adjusted by using an increasing upward or downward current intensity. Therefore, although the signal does not match the expected pattern, after a certain number of commutations, the reference current and / or speed value in the open-loop control will change. The method returns from 914 to box 904.

[0050] If a pattern is identified at 912, it is determined at 916 whether the pattern is identified "N" (threshold) times. For example, a counter (e.g., counter 718) can provide a corresponding counter value to represent the number of valid crossings detected over a series of commutation states. If the pattern is not identified at 916, the method returns to box 904. In response to detecting the predetermined pattern "N" times at 916, the method proceeds to 920, at which time the control mode of the motor can 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, information about whether the pattern is identified "N" times can be provided to the above-mentioned mode logic 108, 808 to enable switching between various modes disclosed herein. In one example, "N" can be set to N≥6, which will reflect two detections per phase in a three-phase motor. In other examples, different "N" values ​​can be used. Additionally or alternatively, the value of "N" may be set to a default value (eg, N=6) or may be user programmable (eg, a register entry set in response to user input).

[0051] In view of the foregoing, exemplary systems and methods are described using the above description and accompanying drawings, which can eliminate the need for tedious manual adjustments to find the minimum speed and current required to generate a motor's run-time signal that can include a BEMF signal. By eliminating manual adjustments, time to market can be accelerated and applicable to a variety of different motor configurations and operating conditions. Unlike implementations that can use previously selected fixed and motor- and load-condition-specific speed and current values, the methods herein provide automatic mode changes, thereby increasing the robustness and flexibility of the system.

[0052] What has been described above are examples of the present disclosure. This disclosure is intended to embrace all changes, modifications and variations that fall within the scope of this application, including the appended claims.

Claims

1. A system for controlling switching between different control modes of an electric motor, comprising: a measurement logic for measuring a BEMF signal representing a back electromotive force BEMF of the electric motor; pattern detection logic for detecting instances where the measured BEMF signal exhibits a predetermined pattern; and mode logic for implementing control of the electric motor according to a plurality of control modes, the mode logic initially adopting a first control mode and switching from the first control mode to a second control mode in response to the mode detection logic detecting that the measured BEMF signal exhibits the predetermined pattern over a plurality of commutation states, wherein the mode detection logic further comprises: crossover detection logic for identifying each instance of the predetermined pattern based on the BEMF signal crossing a predetermined signal value during a commutation state of the electric motor, wherein the mode logic maintains the first control mode until the predetermined pattern is detected to occur in a plurality of consecutive commutation states, and In response to detecting that the predetermined pattern occurs in the plurality of consecutive commutation states, the mode logic of the system switches from the first control mode to the second control mode. 2 . The system of claim 1 , wherein the crossing detection logic finds a crossing based on the BEMF signal measured during each commutation state.

3. The system of claim 1 , wherein the mode logic maintains the first control mode until the predetermined mode is detected to occur in each of the plurality of commutation states of the electric motor, and in response to detecting that the predetermined mode occurs in each of the plurality of commutation states, the mode logic switches from the first control mode to the second control mode.

4. The system of claim 1, further comprising a counter that counts a number of consecutive valid crossings that occur, the mode logic switching from the first control mode to the second control mode based on the count value exceeding a count threshold. 5 . The system of claim 4 , wherein the counter is reset in response to detecting that the BEMF signal does not exhibit the predetermined pattern during at least one of the plurality of commutation states. 6 . The system of claim 1 , wherein the first control mode is a low speed, non-BEMF based control mode and the second control mode is a closed loop control mode.

7. The system of claim 1, wherein: The BEMF signal is associated with a phase of the electric motor; During the commutation state, the phase of the electric motor includes a floating phase; and The crossing detection logic is for identifying the instance of the predetermined pattern based on a portion of the BEMF signal associated with the floating phase crossing the predetermined signal value during the commutation state.

8. The system of claim 7, wherein: The floating phase is a first phase; and The predetermined signal value corresponds to a midpoint between a voltage of the first phase during a first state immediately before the commutation state and a voltage of the first phase during a second state immediately after the commutation state.

9. The system of claim 1, wherein the predetermined signal value corresponds to zero volts.

10. A system for controlling switching between different control modes of an electric motor, comprising: a measurement logic for measuring a BEMF signal representing a back electromotive force BEMF of the electric motor; pattern detection logic for detecting instances where the measured BEMF signal exhibits a predetermined pattern; mode logic for implementing control of the electric motor according to a plurality of control modes, the mode logic initially employing a first control mode and switching from the first control mode to a second control mode in response to the mode detection logic detecting that the measured BEMF signal exhibits the predetermined pattern over a plurality of commutation states; as well as and control logic for setting at least one of a speed or a current applied to the electric motor, the control logic adjusting at least one of a speed or a current applied to the electric motor during the first control mode in response to detecting that the BEMF signal fails to exhibit the predetermined pattern during at least one of the plurality of commutation states.

11. The system of claim 10, wherein the control logic incrementally adjusts at least one of the speed or current applied to the electric motor over time during the first control mode until the mode detection logic detects the predetermined pattern in a series of consecutive commutation states and the mode logic causes the control logic to switch from the first control mode to the second control mode.

12. A method for controlling switching between control modes of a motor, comprising: measuring a back electromotive force (BEMF) signal of the motor during each of a plurality of commutation states of the motor; detecting each occurrence of a predetermined pattern in the BEMF signal during each of the plurality of commutation states of the motor; and The motor is switched from a first control mode to a second control mode in response to detecting that the predetermined pattern in the BEMF signal occurs in a plurality of consecutive commutation states, wherein the first control mode is a low speed, non-BEMF based control mode and the second control mode is a closed loop control mode of the motor.

13. The method according to claim 12, further comprising: controlling at least one of a speed or a current applied to the motor; responsive to detecting that the BEMF signal fails to exhibit the predetermined pattern during at least one of the plurality of commutation states, adjusting the at least one of speed or current applied to the motor during the first control mode; and The detecting and the switching are repeated based on at least one of an adjusted speed or an adjusted current applied to the motor.

14. The method of claim 12, wherein the predetermined pattern is detected by detecting during a corresponding commutation state that a floating phase for the motor crosses a predetermined value during the corresponding commutation state, and The first control mode is maintained until it is detected that the predetermined pattern occurs in each of a plurality of consecutive commutation states.

15. The method of claim 12, wherein detecting further comprises: counting the number of times the BEMF signal crosses a predetermined value during each successive commutation state; resetting a counter in response to detecting that the BEMF signal has not crossed the predetermined value during one of the commutation states; and If the count value of the counter exceeds a predetermined threshold, the motor is switched from the first control mode to the second control mode.

16. The method of claim 15, wherein the predetermined value is a midpoint voltage value of each BEMF signal.

17. The method of claim 12, wherein detecting each occurrence of the predetermined pattern further comprises: At least one data point within the predetermined pattern and at least one characteristic associated with the motor outside of the predetermined pattern are detected.

18. The method according to claim 12, further comprising: A rotational speed of a rotor of the motor is measured, and wherein the motor is switched to the second control mode in response to detecting that the predetermined pattern occurs in a plurality of consecutive commutation states if the rotational speed crosses a speed threshold.

19. A system for controlling switching between different control modes of an electric motor, comprising: a sensor providing a sensor signal representative of a back electromotive force, BEMF, measure for each floating phase of the multi-phase electric motor; a controller having an output for providing a control signal for controlling operation of the multi-phase electric motor, the controller being configured to: initially controlling the multi-phase electric motor using a first non-BEMF based control mode; detecting each occurrence of a pattern in the sensor signal during at least one commutation state of the multi-phase electric motor, the pattern in the sensor signal comprising a crossing of a predetermined signal value; switching from the first control mode to a second BEMF-based control mode in response to detecting an occurrence of the mode over a plurality of consecutive commutation states; counting the number of times the sensor signal crosses the predetermined signal value over the plurality of consecutive commutation states; resetting the count in response to detecting that the sensor signal has not crossed the predetermined signal value during at least one of the plurality of consecutive commutation states; as well as If the count exceeds a predetermined threshold, the multi-phase electric motor is switched from the first control mode to the second control mode.

20. The system of claim 19, wherein the controller provides the control signal to set at least one of a speed or a current applied to the polyphase electric motor, the controller adjusting at least one of a speed or a current applied to the polyphase electric motor during the first control mode in response to detecting that the sensor signal fails to exhibit the mode during at least one of the plurality of consecutive commutation states, and in, The controller incrementally adjusts at least one of speed or current applied to the multi-phase electric motor over time during a first control mode until the mode is detected over the plurality of consecutive commutation states and the controller switches from the first control mode to the second control mode.

Images