Control unit and method for detecting stall or step loss in a stepper motor

Abstract

A control unit and method for detecting stall or step loss in a stepper motor. The control unit 102 is adapted to determine a first parameter from a back EMF signal, determine at least one second parameter corresponding to the first parameter from the back EMF signal. The control unit 102 further verifies at least one condition comprising the at least one second parameter based on the first parameter, and detects stall or step loss in the stepper motor 110 based on the verification. The invention uses pattern detection by identifying characteristic features of peaks of the back EMF signal, the characteristic features being order (n), amplitude and polarity. These characteristic features are independent of RPM, cogging, load, and do not require any complex calculations, and are very robust even at lower RPMs.

Description

Technical Field

[0001] The present invention relates to a control unit and method for detecting stall or step loss when driving a stepper motor. Background Technology

[0002] There is a demand for sensorless stall and step-out detection in various stepper-based systems. These systems require motor operation at low revolutions per minute (RPM) under varying loads and backlash, where existing solutions cannot detect stall or step-out. Stall detection is needed for reference positioning, and the lack of detection leads to actuator overdrive, resulting in reduced operating time or gradual driver failure. Stall detection is also used to detect damage that may occur in the field, such as drive mechanical failure or even motor failure. Existing solutions extract back electromotive force (EMF) from the unexcited coil and use threshold-based comparisons to detect stall or step-out. The threshold is either dynamically derived based on RPM or statically fixed or calibrated for a given system.

[0003] Stall detection is a concept used in many systems. In most systems, stepper motors operate at high RPMs, or in systems with small backlash or no dynamic loads (where stall detection is stable). The concept used in existing solutions is to monitor the anti-EMF. Stall is detected when the anti-EMF drops below a given threshold or becomes close to zero in the event of a stall. Stall detection tends to be unrobust in drives with varying loads and backlash at low RPMs (ideally chosen for torque requirements or to avoid resonance). Generally, several products using stepper motors are available on the market. Stall detection is primarily used to detect damage in mechanical drives or to achieve reference positioning, while step loss detection is used for coarse correction.

[0004] Patent document US20110181229 discloses an apparatus, system, and method for stepper motor stall detection. The apparatus, system, and method for stepper motor stall detection include: a conversion module receiving a back electromotive force (“EMF”) waveform generated in the non-drive coils of the stepper motor by the magnetic field of the stepper motor rotor during full-step operation, and sampling the waveform at intervals starting at predetermined times within a predetermined time period during full-step operation to produce multiple sampled data points; a rectification module rectifying the waveform with respect to a predetermined static level; and a comparison module accumulating the rectified sampled data points into statistically representative sample values, comparing the representative sample values ​​with a predetermined threshold level, and indicating rotor stall if any representative sample value is less than the predetermined threshold level. Summary of the Invention

[0005] According to a first aspect of this disclosure, a control unit for detecting stall or step loss in a stepper motor is provided. The control unit is adapted to drive at least two excitation coils of the stepper motor and read a back electromotive force (EMF) signal, the back EMF signal being measurable in a first phase and a second phase. The control unit is further adapted to determine a first parameter based on the back EMF signal, determine at least one second parameter corresponding to the first parameter based on the back EMF signal, verify at least one condition including the at least one second parameter based on the first parameter, and detect stall or step loss in the stepper motor based on the verification. The first parameter is the order (n) of a peak in the back EMF signal corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n The group of ), wherein when the order (n) is equal to one, the at least one condition to be verified includes that the polarity of the peak is from any of the following list, the list including a) negative in the first phase of the inverse EMF signal and b) positive in the second phase of the inverse EMF signal.

[0006] According to a second aspect of this disclosure, a control unit for detecting stall or step loss in a stepper motor is provided. The control unit is adapted to drive at least two excitation coils of the stepper motor and read a back electromotive force (EMF) signal, the back EMF signal being measurable in a first phase and a second phase. The control unit is further adapted to determine a first parameter based on the back EMF signal, determine at least one second parameter corresponding to the first parameter based on the back EMF signal, verify at least one condition including the at least one second parameter based on the first parameter, and detect stall or step loss in the stepper motor based on the verification. The first parameter is the order (n) of a peak in the back EMF signal corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n The group of ), wherein when the order (n) is equal to two, the at least one condition to be verified includes that the polarity of the first peak and the second peak is selected from any one of the following list, the list including a) negative and positive in the first phase of the inverse EMF signal, and b) positive and negative in the second phase of the inverse EMF signal.

[0007] According to a third aspect of this disclosure, a control unit for detecting stall or step loss in a stepper motor is provided. The control unit is adapted to drive at least two excitation coils of the stepper motor and read a back electromotive force (EMF) signal, the back EMF signal being measurable in a first phase and a second phase. The control unit is further adapted to determine a first parameter based on the back EMF signal, determine at least one second parameter corresponding to the first parameter based on the back EMF signal, verify at least one condition including the at least one second parameter based on the first parameter, and detect stall or step loss in the stepper motor based on the verification. The first parameter is the order (n) of a peak in the back EMF signal corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n The group of ), wherein when the order (n) is equal to three, the at least one condition to be verified includes that the polarity of the first peak, the second peak and the third peak is selected from any one of the following list, the list including a) negative, positive and negative respectively in the first phase of the inverse EMF signal, and b) positive, negative and positive respectively in the second phase of the inverse EMF signal.

[0008] According to a fourth aspect of this disclosure, a method for detecting stall or step loss in a stepper motor is provided, the method comprising the steps of: monitoring a back electromotive force (EMF) signal from the stepper motor, the back EMF signal being measurable in a first phase and a second phase, characterized in that a control unit determines a first parameter of the back EMF signal; the control unit determines at least one second parameter of the back EMF signal corresponding to the first parameter; the control unit verifies at least one condition including the at least one second parameter based on the first parameter; and the control unit detects stall or step loss in the stepper motor based on the verification, wherein the first parameter is the order (n) of a peak in the back EMF signal corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n The group of ), wherein when the order (n) is equal to one, the at least one condition to be verified includes that the polarity of the peak is from any of the following list, the list including a) negative in the first phase of the inverse EMF signal and b) positive in the second phase of the inverse EMF signal.

[0009] According to a fifth aspect of this disclosure, a method for detecting stall or step loss in a stepper motor is provided, the method comprising the steps of: monitoring a back electromotive force (EMF) signal from the stepper motor, the back EMF signal being measurable in a first phase and a second phase, characterized in that a control unit determines a first parameter of the back EMF signal; the control unit determines at least one second parameter of the back EMF signal corresponding to the first parameter; the control unit verifies at least one condition including the at least one second parameter based on the first parameter; and the control unit detects stall or step loss in the stepper motor based on the verification, wherein the first parameter is the order (n) of a peak in the back EMF signal corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n The group of ), wherein when the order (n) is equal to two, the at least one condition to be verified includes that the polarity of the first peak and the second peak is selected from any one of the following list, the list including a) negative and positive in the first phase of the inverse EMF signal, and b) positive and negative in the second phase of the inverse EMF signal.

[0010] According to a sixth aspect of this disclosure, a method for detecting stall or step loss in a stepper motor is provided, the method comprising the steps of: monitoring a back electromotive force (EMF) signal from the stepper motor, the back EMF signal being measurable in a first phase and a second phase, characterized in that a control unit determines a first parameter of the back EMF signal; the control unit determines at least one second parameter of the back EMF signal corresponding to the first parameter; the control unit verifies at least one condition including the at least one second parameter based on the first parameter; and the control unit detects stall or step loss in the stepper motor based on the verification, wherein the first parameter is the order (n) of a peak in the back EMF signal corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n The group of ), wherein when the order (n) is equal to three, the at least one condition to be verified includes that the polarity of the first peak, the second peak and the third peak is selected from any one of the following list, the list including a) negative, positive and negative respectively in the first phase of the inverse EMF signal, and b) positive, negative and positive respectively in the second phase of the inverse EMF signal. Attached Figure Description

[0011] Embodiments of this disclosure are described below with reference to the accompanying drawings.

[0012] Figure 1 A block diagram of a control unit for a stepper motor according to an embodiment of the present invention is shown;

[0013] Figure 2 The figure illustrates a graph related to the inverse EMF signal according to an embodiment of the present invention;

[0014] Figure 3 The illustrations depict various scenarios of stall or step loss detection according to embodiments of the present invention; and

[0015] Figure 4 The illustration shows a method for detecting stall or step loss in a stepper motor according to the present invention. Detailed Implementation

[0016] Figure 1 A block diagram of a control unit for a stepper motor according to an embodiment of the present invention is illustrated. A system 100 including a control unit 102 is provided to detect stall or step loss in a stepper motor 110. Stall in a stepper motor may be caused by mechanical drive. The stepper motor 110 includes a rotor 112 (such as a magnet) and a stator (such as excitation coils or magnetic poles). The described stepper motor 110 has two excitation coils, namely a first coil 106 and a second coil 108. The present invention is not limited to a stepper motor 110 based on two excitation coils, but is instead applicable to a stepper motor 110 having multiple magnetic poles. The control unit 102 is adapted to drive at least two excitation coils (first coil 106 and second coil 108) of the stepper motor 110 via a driver circuit 104 and to detect / read electrical signals including back electromotive force (EMF), such as... Figure 2 As shown in the diagram. Detection is performed via detector circuit 114 and amplifier 116. Any other detector circuit 114 is suitable for use without departing from the scope of the invention. Detector circuit 114 is shown connected across first coil 106. Detector circuit 114 may also be connected across second coil 108. Further, detector circuit 114 may be connected across both first coil 106 and second coil 108. Detector circuit 114 extracts / reads an inverse EMF signal with a mid-level bias from stepper motor 110.

[0017] This invention is independent of the method of reading or measuring the reverse EMF signal. The reverse EMF signal in this invention is detected from the non-drive coil of the stepper motor 110 and is used throughout this disclosure. However, this is merely an example and should not be construed as limiting. The control unit 102 is configured to detect stall or loss of synchronization of the reverse EMF signal detected / read by circuits or methods known in the prior art.

[0018] Figure 2The diagram illustrates a graph relating to an inverse EMF signal according to an embodiment of the present invention. The first graph 200 includes a Y-axis 202, representing the current in amperes as shown in the first waveform 208 and the voltage in volts as shown in the second waveform 210 (i.e., the inverse EMF signal). The X-axis 204 for the first waveform 208 and the second waveform 210 is time expressed in appropriate units. Both waveforms are shown after some time has elapsed, indicated by the dashed line at the beginning of each waveform. The inverse EMF signal can be measured in both positive and negative phases. (Continued) Figure 1 The control unit 102 is further adapted to determine a first parameter based on the inverse EMF signal, and to determine at least one second parameter corresponding to the first parameter based on the inverse EMF signal. The control unit 102 further verifies at least one condition including the at least one second parameter based on the first parameter, and detects stall or step loss in the stepper motor 110 based on the verification.

[0019] The first parameter determined by the control unit 102 is the order (n) of the peaks in the inverse EMF signal. The order (n) corresponds to the number of peaks in the inverse EMF signal. The at least one second parameter is selected from a set including the polarity (P) of each peak. n ) and amplitude / amplitude of each peak (M) n The detector circuit 114 is used to extract / capture the order (n) and polarity (P) of the peaks in the inverse EMF signal. n ) and amplitude (M) n During capture, the inverse EMF signal induced in the first coil 106 is sampled at a high frequency, causing the peak to be captured. The captured signal is then amplified to perform analysis to detect stall or loss of synchronization.

[0020] The first waveform 208 corresponds to the actuation signal for at least two coils. In the case of the two-pole stepper motor 110, a pulse in the first waveform 208 indicates actuation of the first coil 106, and the absence of a pulse indicates that the first coil 106 is not driven. However, when the first coil 106 is not driven, the second coil 108 may or may not be driven, but to avoid complexity... Figure 2 It is not shown in the figure. Further, the positive phase / period corresponds to the waveform portion above the X-axis (204, 206), and the negative phase / period corresponds to the waveform portion below the X-axis (204, 206). Figure 2 The inverse EMF signal shown includes three peaks and has no stall or step loss. Specifically, first example 230 shows an inverse EMF signal in the positive phase, second example 232 shows an inverse EMF signal in the negative phase, and third example 234 shows an inverse EMF signal in the positive phase, and so on.

[0021] The amplification section 250 of the inverse EMF signal is illustrated. The amplification section 250 is shown to indicate the peak amplitudes. The first amplitude 224 of the first peak 212, the second amplitude 224 of the second peak 214, and the third amplitude 224 of the third peak 216 are illustrated. Furthermore, the time slot between time t1218 and time t2220 is considered a dead zone. To overcome erroneous detection due to sensor discharge, the control unit 102 processes the inverse EMF signal after the dead zone / window / time has elapsed. Therefore, the dead zone is discarded for stall or out-of-step detection in the inverse EMF signal. The time slot between time t2220 and time t3222 is the operating zone, where stall or out-of-step detection is performed by the control unit 102. Moreover, in both positive and negative phases, peaks are considered only if their amplitudes are above a threshold level.

[0022] Figure 3 The illustrations depict various scenarios of stall or step loss detection according to embodiments of the present invention. Figure 3 A second graph 300 with multiple waveforms is illustrated. It should be noted that this graph is not to scale but is intended to explain the invention and therefore should not be interpreted in a limiting manner. The first waveform 208 represents, as... Figure 2 The current is shown in the figure. Similarly, the second waveform 210 represents the inverse EMF signal in volts. Another example of the inverse EMF signal is shown by the third waveform 302, where there is only one peak after the dead zone, whereas in the second waveform 210 there are two peaks, one above the axis and the other below the axis. The second waveform 210 and the third waveform 302 are shown for clarity, and there is no stall or loss of synchronization in the second waveform 210 and the third waveform 302.

[0023] Control unit 102 detects stall or step loss in stepper motor 110 when the order is zero, as illustrated in the fourth waveform 304. If no peak is present in the inverse EMF signal, control unit 102 detects this condition as a stall or step loss condition and records it in a memory element. The first window (depicted with a dashed boundary) 318 shows the absence of a peak. This also applies to the phase / cycle of the inverse EMF signal.

[0024] According to an embodiment of the invention, the control unit 102 is adapted to detect stall or step loss in the stepper motor 110 when the order is equal to one. When the order (n) is equal to one, at least one condition to be verified by the control unit 102 includes: the polarity of the first peak 212 is from any one of the following groups: the group includes being negative in the positive phase of the inverse EMF signal and positive in the negative phase of the inverse EMF signal. The fifth waveform 306 represents an inverse EMF signal with only the first peak 212, wherein stall or step loss is detected in the negative phase. The second window 320 shows the stall or step loss in the fifth waveform 306. The peak above the axis (shown in dashed lines) inside the second window 320 is considered the first peak 212. Since it is above the axis, the polarity of the first peak 212 is positive. The two peaks below the axis are discarded because they are below a threshold limit. Because the polarity of the first peak 212 is positive in the negative phase, the control unit 102 detects it as stall or step loss and records / stores it in a memory element. Similarly, the sixth waveform 308 represents a stall or step loss detection for a single peak but in the positive phase. The third window 322 shows that the polarity of the first peak 212 is negative in the positive phase. The control unit 102 detects this condition as a stall or step loss and stores it in a memory element.

[0025] According to another embodiment of the invention, the control unit 102 is adapted to detect stall or loss of synchronism when the order (n) is equal to two. When the order is two, at least one condition to be verified by the control unit 102 includes that the polarities of the first peak 212 and the second peak 214 are selected from any one of the following lists: this list includes negative and positive respectively in the positive phase of the inverse EMF signal; and positive and negative respectively in the negative phase of the inverse EMF signal. To avoid Figure 3 The excessive crowding did not result in a waveform being shown for that condition.

[0026] According to another embodiment of the invention, the control unit 102 is adapted to detect stall or loss of synchronization when the order is equal to two and when a condition involving the amplitude of a peak is met. At least one condition to be verified by the control unit 102 includes that the amplitude 224 of the first peak 212 is less than the amplitude 224 of the second peak 214. The amplitude of the peaks is considered to have a predetermined tolerance. The seventh waveform 310 represents the inverse EMF signal for an order equal to two. The fourth window 324 shows the presence of two peaks. The polarity of the first peak 212 is negative, and the polarity of the second peak 214 is positive. No stall or loss of synchronization is indicated regarding the polarity condition. However, the amplitude 224 of the first peak 212 is less than the amplitude 224 of the second peak 214. If a match is found, the condition is detected as stall or loss of synchronization, and the control unit 102 stores the detection in a memory element. Thus, the amplitude-based condition is an alternative to the polarity-based condition. Furthermore, it allows the amplitude condition to be verified before verifying the polarity-based condition. Similarly, the eighth waveform 312 illustrates a stall or loss of synchronization in the positive phase of an inverse EMF signal with two peaks. The polarity of the first peak 212 is positive, and the polarity of the second peak 214 is negative, thus no stall or loss of synchronization is detected. However, the amplitude 224 of the first peak 212 is smaller than the amplitude 224 of the second peak 214. This condition is detected as a stall or loss of synchronization by the control unit 102, and therefore, the control unit 102 stores this data in a memory element.

[0027] According to another embodiment of the invention, the control unit 102 is adapted to detect stall or step loss when the order (n) is equal to three. When the order is three, at least one condition to be verified by the control unit 102 includes that the polarities of the first peak 212, the second peak 214, and the third peak 216 are selected from any one of the following groups: the group includes the three peaks being negative, positive, and negative respectively in the positive phase of the inverse EMF signal; and positive, negative, and positive respectively in the negative phase of the inverse EMF signal. Similarly, to avoid Figure 3 The excessive congestion did not result in a waveform being shown for that condition. Before checking at least one condition related to the third order, the control unit 102 checks for at least one condition applicable to the first and second orders against one and two available peaks. If at least one condition applicable to the first and second orders matches, the control unit 102 detects a stall or loss-of-step condition even without verifying at least one condition applicable to the third order.

[0028] According to another embodiment of the invention, the control unit 102 is adapted to detect stall or loss of synchronization when the order is equal to three and a condition containing the amplitude of a peak is met. When the order (n) is equal to three, at least one condition to be verified by the control unit 102 includes that the amplitude 224 of the first peak 212 is less than the amplitude 224 of the second peak 214 and the amplitude 224 of the third peak 216. To illustrate this condition, a ninth waveform 314 shows an inverse EMF signal with a fifth window 328. In the fifth window 328, three peaks are depicted. In the negative phase, the polarity of the first peak 212 is negative, the polarity of the second peak 214 is positive, and the polarity of the third peak 216 is negative. This indicates that there is no stall or loss of synchronization condition. However, when comparing the amplitudes, the control unit 102 detects that the amplitude 224 of the first peak 212 is less than the amplitude 224 of the second peak 214, but not less than the amplitude of the third peak 216. Therefore, the control unit 102 detects this condition as a stall or loss of synchronization and stores it in a memory element. Similarly, the tenth waveform 316 illustrates a stall or loss of synchronization in an inverse EMF signal with three peaks in the positive phase. The sixth window 330 shows the first peak 212 as positive, the second peak 214 as negative, and the third peak 216 as positive, indicating no stall or loss of synchronization. However, the amplitude 224 of the first peak 212 is smaller than the amplitude 224 of the second peak 214, but not smaller than the amplitude of the third peak 216. This is detected as a stall or loss of synchronization by the control unit 102 and recorded in the memory element.

[0029] According to an embodiment of the invention, once the order is greater than zero, the control unit 102 is adapted to verify the polarity-based condition as a first step, followed by the amplitude-based condition. Alternatively, the control unit 102 may also be configured to first verify the amplitude-based condition, followed by the polarity-based condition.

[0030] According to another embodiment of the invention, the control unit 102 extracts anti-EMF signals from at least two coils, based on which coil is inactive or not driven. Example: In the case of a two-coil-based stepper motor 110, when the first coil 106 is active / driven and the second coil 108 is inactive, the control unit 102 captures the anti-EMF signal from the second coil 108. Next, when the second coil 108 is active and the first coil 106 is inactive, the control unit 102 captures the anti-EMF signal from the first coil 106. Therefore, compared to the case where only the first coil 106 is used to capture the anti-EMF signal, the control unit 102 is provided with more data samples to detect stall or step loss in a shorter time. Before capturing the anti-EMF signal of the next phase, the control unit 102 processes the captured anti-EMF signal and verifies at least one condition.

[0031] In this embodiment, the stall or step loss detection increments / decrements to a threshold number. Once the number of detected stalls or step losses exceeds the threshold number, a stall or step loss is confirmed. The threshold number can be configured as required. Once a stall or step loss is detected, the control unit 102 triggers an alarm to the user or operator of the control unit 102 via at least one signal, including but not limited to audio, display, light, haptic means, etc.

[0032] Figure 4 The illustration depicts a method for detecting stall or step loss in a stepper motor according to the present invention. The method includes the following steps: Step 402, which includes monitoring a back electromotive force (EMF) signal from a stepper motor 110. The back EMF signal is detected, measured, or extracted in a manner known in the art and is not limited to any particular method. The back EMF signal can be measured in both positive and negative phases. The method is characterized by step 404, which includes determining a first parameter of the back EMF signal by a control unit 102. A next step 406 includes determining at least one second parameter of the back EMF signal corresponding to the first parameter by the control unit 102. Step 408 includes verifying at least one condition containing the at least one second parameter based on the first parameter. Step 410 includes detecting a stall or step loss in the stepper motor 110 by the control unit 102 based on the verification.

[0033] The first parameter is the order (n) of the peaks in the inverse EMF signal. The at least one second parameter is selected from a set including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n ) group.

[0034] After determining the order of the inverse EMF signal, the conditions to be verified are as follows: Figure 3 The conditions explained and covered in the description are the same. To avoid repetition, the same description will not be given here. However, before starting to actuate the stepper motor 110, the current electrical phase is read from the driver circuit 104 to synchronize with the phase of the inverse EMF signal. The phase is further used to detect polarity and amplitude as required.

[0035] The control unit 102 is also adapted to identify stall conditions and step loss conditions. When the lead screw mechanism is operated by the stepper motor 110, stall is identified if the lead screw reaches end positioning. If a peak is observed before reaching end positioning, the condition is identified as step loss. The method for identifying between stall and step loss follows the corresponding steps as described for the control unit 102.

[0036] According to the present invention, existing solutions require tuning, and the threshold for the anti-EMF signal is proportional to the revolutions per minute (RPM). However, the present invention is independent of RPM and does not require tuning or simulation to establish the elements. One application area of ​​the present invention is, but is not limited to, semi-active damping control (SDC) systems in vehicles, throttle control, dashboards, and many linear positioning systems (e.g., head-up displays). The present invention uses pattern detection by identifying the characteristic features of the peaks of the anti-EMF signal, namely, order (n), amplitude, and polarity. These characteristics are independent of RPM, backlash, and load, do not require any complex calculations, and are very robust even at low RPMs.

[0037] It should be understood that the embodiments described above are merely illustrative and do not limit the scope of the invention. Many such embodiments, as well as other modifications and variations to the embodiments described in the description, are contemplated. The scope of the invention is limited only by the scope of the claims.

Claims

1. A control unit (102) for detecting stall or step loss in a stepper motor (110), the control unit (102) being adapted to drive at least two excitation coils (106, 108) of the stepper motor (110) and read back electromotive force (EMF) signals, the back EMF signals being measurable in a first phase and a second phase, the control unit (102) being further adapted to The first parameter is determined based on the inverse EMF signal. At least one second parameter corresponding to the first parameter is determined based on the inverse EMF signal. Based on the first parameter, verify at least one condition that includes at least one second parameter, and Based on the verification, stalling or step loss in the stepper motor (110) can be detected. The first parameter is the order (n) of the peaks in the inverse EMF signal, corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n ) group, When the order (n) is equal to one, the at least one condition to be verified includes that the polarity of the peak is from any of the following list, which includes: a) is negative in the first phase of the inverse EMF signal, and b) is positive in the second phase of the inverse EMF signal.

2. A control unit (102) for detecting stall or step loss in a stepper motor (110), the control unit (102) being adapted to drive at least two excitation coils (106, 108) of the stepper motor (110) and read back electromotive force (EMF) signals, the back EMF signals being measurable in a first phase and a second phase, the control unit (102) being further adapted to The first parameter is determined based on the inverse EMF signal. At least one second parameter corresponding to the first parameter is determined based on the inverse EMF signal. Based on the first parameter, verify at least one condition that includes at least one second parameter, and Based on the verification, stalling or step loss in the stepper motor (110) can be detected. The first parameter is the order (n) of the peaks in the inverse EMF signal, corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n ) group, When the order (n) is equal to two, the at least one condition to be verified includes that the polarity of the first peak (212) and the second peak (214) is selected from any one of the following list, which includes: a) In the first phase of the inverse EMF signal, the signals are negative and positive, respectively, and b) The second phase of the inverse EMF signal is positive and negative, respectively.

3. The control unit (102) of claim 2, wherein when the order (n) is equal to two, the at least one condition to be verified includes that the amplitude of the first peak (212) is less than the amplitude of the second peak (214).

4. A control unit (102) for detecting stall or step loss in a stepper motor (110), the control unit (102) being adapted to drive at least two excitation coils (106, 108) of the stepper motor (110) and read back electromotive force (EMF) signals, the back EMF signals being measurable in a first phase and a second phase, the control unit (102) being further adapted to The first parameter is determined based on the inverse EMF signal. At least one second parameter corresponding to the first parameter is determined based on the inverse EMF signal. Based on the first parameter, verify at least one condition that includes at least one second parameter, and Based on the verification, stalling or step loss in the stepper motor (110) can be detected. The first parameter is the order (n) of the peaks in the inverse EMF signal, corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n ) group, When the order (n) is equal to three, the at least one condition to be verified includes that the polarities of the first peak (212), the second peak (214), and the third peak (216) are selected from any one of the following list, which includes a) In the first phase of the inverse EMF signal, the values ​​are negative, positive, and negative, respectively, and b) In the second phase of the inverse EMF signal, the values ​​are positive, negative, and positive, respectively.

5. The control unit (102) of claim 4, wherein when the order (n) is equal to three, the at least one condition to be verified includes that the amplitude of the first peak (212) is less than the amplitude of the second peak (214) and the amplitude of the third peak (216).

6. The control unit (102) of claim 4 or claim 5, wherein before verifying the at least one condition applicable to an order (n) equal to three, the control unit (102) is adapted to verify at least one corresponding condition applicable to an order (n) equal to two.

7. A method for detecting stall or step loss in a stepper motor (110), the method comprising the following steps: The method involves monitoring the back electromotive force (EMF) signal from the stepper motor (110), which can be measured in both the first and second phases. The first parameter of the inverse EMF signal is determined by the control unit (102); The control unit (102) determines at least one second parameter of the inverse EMF signal corresponding to the first parameter; The control unit (102) verifies at least one condition containing at least one second parameter based on the first parameter, and The control unit (102) detects stalling or step loss in the stepper motor (110) based on the verification. The first parameter is the order (n) of the peaks in the inverse EMF signal, corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n ) group, When the order (n) is equal to one, the at least one condition to be verified includes that the polarity of the peak is from any of the following list, which includes: a) is negative in the first phase of the inverse EMF signal, and b) is positive in the second phase of the inverse EMF signal.

8. A method for detecting stall or step loss in a stepper motor (110), the method comprising the following steps: The method involves monitoring the back electromotive force (EMF) signal from the stepper motor (110), which can be measured in both the first and second phases. The first parameter of the inverse EMF signal is determined by the control unit (102); The control unit (102) determines at least one second parameter of the inverse EMF signal corresponding to the first parameter; The control unit (102) verifies at least one condition containing at least one second parameter based on the first parameter, and The control unit (102) detects stalling or step loss in the stepper motor (110) based on the verification. The first parameter is the order (n) of the peaks in the inverse EMF signal, corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n ) group, When the order (n) is equal to two, the at least one condition to be verified includes that the polarity of the first peak (212) and the second peak (214) is selected from any one of the following list, which includes: a) In the first phase of the inverse EMF signal, the signals are negative and positive, respectively, and b) The second phase of the inverse EMF signal is positive and negative, respectively.

9. A method for detecting stall or step loss in a stepper motor (110), the method comprising the following steps: The method involves monitoring the back electromotive force (EMF) signal from the stepper motor (110), which can be measured in both the first and second phases. The first parameter of the inverse EMF signal is determined by the control unit (102); The control unit (102) determines at least one second parameter of the inverse EMF signal corresponding to the first parameter; The control unit (102) verifies at least one condition containing at least one second parameter based on the first parameter, and The control unit (102) detects stalling or step loss in the stepper motor (110) based on the verification. The first parameter is the order (n) of the peaks in the inverse EMF signal, corresponding to the number of peaks, and the at least one second parameter is selected from a subset including the polarity (P) of each peak. n ) and the amplitude of each peak (M) n ) group, When the order (n) is equal to three, the at least one condition to be verified includes that the polarities of the first peak (212), the second peak (214), and the third peak (216) are selected from any one of the following list, which includes a) In the first phase of the inverse EMF signal, the values ​​are negative, positive, and negative, respectively, and b) In the second phase of the inverse EMF signal, the values ​​are positive, negative, and positive, respectively.

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