Motor overcurrent protection method and system

Abstract

The invention discloses a motor overcurrent protection method and system, belongs to the technical field of motor overcurrent protection, and can improve the motor overcurrent protection effect. Acquiring a three-phase current signal of the motor; performing filtering and analog-to-digital conversion on the three-phase current signal to generate digital current amplitude data; comparing the digital current amplitude data with an over-current threshold value, and counting continuous threshold value exceeding duration; when the continuous threshold exceeding duration reaches a first preset duration, external power supply is cut off, and operation is maintained through the energy storage capacitor; a motor winding is connected to a dynamic braking circuit, and the dynamic braking circuit comprises braking resistors connected in parallel; after the dynamic braking circuit is activated, real-time current data are filtered, and the attenuation rate is calculated; when the attenuation rate is lower than a preset rate threshold value, the dynamic braking circuit is disconnected, and power supply is restored; and if it is detected that the continuous threshold exceeding duration reaches a second preset duration again after power supply is recovered, the power supply cut-off state is locked, and a locking signal is sent.

Description

Technical Field

[0001] The present invention relates to the field of motor control technology, and more particularly to an overcurrent protection method and system suitable for an integrated servo of an unmanned aerial vehicle (UAV), especially for rapid power-off, residual energy dissipation, and adaptive protection logic when the motor is stalled. Background Art

[0002] As the core actuator of a drone's flight control system, the integrated servo utilizes a highly integrated design. It uses an internal control driver to drive the motor to precisely deflect the rudder, thereby adjusting the flight attitude. Under normal flight conditions, the integrated servo load typically ranges from no-load to rated load, and the motor operates stably. However, when a drone encounters sudden airflow disturbances, mechanical obstruction, or abnormal force on the rudder, the motor may become stalled and overloaded. At this point, the motor's back EMF decreases significantly, even approaching zero, causing the stator winding impedance to drop sharply and the current to surge to several times the rated value. This high current in a short period of time can cause the winding to overheat or even burn out, potentially damaging surrounding circuit components and, in severe cases, threatening the drone's flight safety.

[0003] Related overcurrent protection schemes usually use fuses or current relays to cut off the power supply, but they have the following limitations: 1) The fuse needs to be manually replaced after it is activated, which cannot meet the needs of autonomous operation of drones; 2) After the power is directly cut off, the residual energy in the motor winding cannot be released quickly, and there is still a risk of local overheating; 3) The protection threshold is fixed, and the response time cannot be dynamically adjusted according to the severity of the overcurrent, which can easily lead to protection delays or false triggering.

[0004] Therefore, there is an urgent need for an overcurrent protection method with fast current cutoff, efficient dissipation of residual energy and adaptive protection logic to improve the safety and recoverability of the integrated servo under complex working conditions.

[0005] Existing motor overcurrent protection schemes (such as reference document CN112736848A) rely on predictive algorithms to trigger protection in advance, but they cannot address the problem of local overheating caused by residual energy in the winding after power failure. Another scheme (CN109017738B) uses fuses and circuit breakers to achieve multi-level protection, but lacks an adaptive adjustment mechanism. The present invention solves this problem by combining a dynamic braking circuit with an energy storage capacitor to maintain control and dynamically shortening the secondary protection response time based on the severity of the overcurrent. Summary of the Invention

[0006] The present invention provides a method and system for motor overcurrent protection, which can improve the motor overcurrent protection effect.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A method for overcurrent protection of a motor comprises the following steps:

[0009] (1) Obtain the three-phase current signal of the motor;

[0010] (2) filtering and performing analog-to-digital conversion on the three-phase current signal to generate digital current amplitude data;

[0011] (3) comparing the digital current amplitude data with the overcurrent threshold, and counting the duration of continuous over-threshold value;

[0012] (4) When the duration of continuous exceeding the threshold reaches a first preset duration, the external power supply is cut off and the operation is maintained by the energy storage capacitor; the motor winding is connected to a dynamic braking circuit, wherein the dynamic braking circuit includes a parallel braking resistor, the resistance of which is adapted to the motor impedance;

[0013] (5) After the dynamic braking circuit is activated, the real-time current data is filtered and the decay rate is calculated; when the decay rate is lower than the preset rate threshold, the dynamic braking circuit is disconnected and power is restored;

[0014] (6) If the duration of continuous over-threshold value exceeding the second preset duration is detected again after the power supply is restored, the power supply cut-off state is locked and a locking signal is sent. The second preset duration is shortened as the ratio of the over-current to the rated current increases; wherein, the locked power supply cut-off state is released only after receiving an external reset command.

[0015] Furthermore, the statistical method of the continuous exceeding threshold duration includes:

[0016] (1) establishing a ring buffer to store an over-threshold flag, wherein the capacity of the ring buffer is equal to an integer multiple of the motor fundamental frequency period;

[0017] (2) When N consecutive sampling points are detected to exceed the threshold, the timer is started, where N is calculated by the following formula:

[0018]

[0019] Among them, f base is the motor fundamental frequency, T sample is the current sampling period;

[0020] (3) Continuously verify the validity of the over-threshold state during the timer operation, and reset the timer when an invalid sampling point is detected; the accumulated value of the timer is used as the continuous over-threshold duration.

[0021] Furthermore, the dynamic braking circuit parameters are determined by the following method:

[0022] (1) According to the rated voltage V of the motor bus bus Calculate the total resistance R of the parallel brake resistors based on the allowable temperature rise ΔT b, the specific formula is as follows:

[0023]

[0024] Among them, ΔT is the difference between the maximum allowable temperature of the motor winding and the ambient temperature, R th is the thermal resistance coefficient of the motor measured by the steady-state method; γ is the proportional coefficient;

[0025] (2) According to the power supply switching time t hold And the servo maintains power P min Calculate the total capacity C of the energy storage capacitor. The specific formula is as follows:

[0026]

[0027] Where β is the voltage fluctuation coefficient.

[0028] Furthermore, the decay rate is calculated by the following steps:

[0029] (1) The window length of the filtered current data is R b Sliding difference operation of integer multiples of C to generate a difference sequence;

[0030] (2) Performing normalized exponentially weighted moving average processing on the differential sequence to obtain the decay rate, and the weight coefficient satisfies:

[0031]

[0032] Where t is the sampling time series starting from the moment the dynamic brake is activated, and n is the window length.

[0033] Furthermore, the second preset duration is determined by the following steps:

[0034] (1) Obtain the maximum current value I within the sliding window peak ;

[0035] (2) According to the maximum current value I peak The second preset time length T2 is calculated using the following formula:

[0036]

[0037] Where: T0 is the reference response time, I rated is the rated current of the motor, λ is the attenuation coefficient, T base is the benchmark time threshold, T0≥T base .

[0038] Furthermore, the three-phase current signal is filtered using a Butterworth bandpass filter, with a cutoff frequency set to 0.8-1.2 times the motor operating frequency. Common-mode noise elimination is required before filtering the three-phase current signal.

[0039] A motor overcurrent protection system, used in the above method, comprising:

[0040] A first acquisition module is used to acquire the three-phase current signal of the motor;

[0041] A first generating module is used to filter and perform analog-to-digital conversion on the three-phase current signal to generate digital current amplitude data;

[0042] A first comparison module is used to compare the digital current amplitude data with the overcurrent threshold and calculate the duration of continuous over-threshold value;

[0043] A first execution module is configured to, when the duration of continuous exceeding of the threshold reaches a first preset duration, cut off the external power supply and maintain operation through the energy storage capacitor; connect the motor winding to a dynamic braking circuit, wherein the dynamic braking circuit includes a parallel braking resistor with a resistance value adapted to the motor impedance;

[0044] The second execution module is configured to filter the real-time current data and calculate the decay rate after the dynamic braking circuit is activated; when the decay rate is lower than a preset rate threshold, disconnect the dynamic braking circuit and restore power supply;

[0045] The first locking module is used to lock the power supply cut-off state and send a locking signal if it is detected that the continuous exceeding of the threshold value reaches a second preset time after the power supply is restored. The second preset time is shortened as the ratio of the overcurrent to the rated current increases; wherein, the locked power supply cut-off state is only released after receiving an external reset command.

[0046] An electronic device, comprising:

[0047] one or more processors;

[0048] a storage device having one or more programs stored thereon;

[0049] When the one or more programs are executed by the one or more processors, the one or more processors implement the above-described method.

[0050] A computer-readable storage medium stores a computer program, which implements the above method when executed by a processing device.

[0051] A computer program product includes a computer program, which implements the above method when executed by a processing device.

[0052] The beneficial effects of the present invention are:

[0053] In the first aspect, the present invention provides a method for motor overcurrent protection. In the present invention, the three-phase current signal is first subjected to anti-interference processing, high-frequency noise and low-frequency bias are removed by bandpass filtering, and then accurate current quantization data is generated through analog-to-digital conversion, which effectively eliminates the common pulse interference in the complex electromagnetic environment of drones and provides a reliable data basis for subsequent judgment.

[0054] During the overcurrent detection phase, the system doesn't simply rely on momentary current exceeding the specified limit. Instead, it employs a continuous monitoring window designed based on the motor's fundamental frequency characteristics. Protection is triggered only when the current continuously exceeds the threshold for a preset duration, forming a cumulative judgment mechanism over a time dimension. This approach avoids instantaneous current spikes during normal servo commutation while capturing true stalled-rotor overcurrent conditions, significantly reducing the risk of false tripping caused by interference in traditional solutions.

[0055] When an overcurrent condition is confirmed, the system does not completely cut off power. Instead, it adopts a graded response strategy: first, it cuts off the external power supply to prevent the current from continuing to rise. At the same time, it maintains the lowest power consumption of the control system through pre-configured energy storage capacitors, ensuring the complete execution of safety processes such as fault logging and status feedback.

[0056] At the same time, by connecting the motor winding to the dynamic braking circuit and using parallel braking resistors to form a closed discharge loop, the magnetic field energy stored in the winding is quickly converted into heat energy and dissipated, effectively solving the hidden danger of local overheating caused by residual current after power failure in traditional fuse solutions, and controlling the winding temperature rise within the material tolerance range.

[0057] During this process, the system continuously monitors the current decay dynamics, and only when the current naturally drops to the safe recovery threshold will the power supply be reconnected to avoid the risk of secondary overcurrent caused by blind restart. For extreme working conditions with repeated overcurrent, when overcurrent is detected again after power is restored, the system will dynamically compress the secondary protection response time according to the real-time overcurrent multiple. Specifically, the greater the ratio of the overcurrent current to the rated current, the higher the severity of the fault determined by the system, and the corresponding protection action time limit is shortened exponentially. In this way, the opportunity for self-recovery is retained in the face of minor overcurrent, and in critical situations such as severe short circuits, the permanent protection state is quickly entered, achieving an optimal balance between protection timeliness and system availability. In summary, the effect of motor overcurrent protection can be effectively improved.

[0058] In a further technical solution of the first aspect, a statistical method for continuously exceeding the threshold value duration is as follows:

[0059] The validity of the over-threshold state is continuously verified during the timer's operation, and the timer is reset when an invalid sampling point is detected. The accumulated value of the timer is used as the duration of the continuous over-threshold state. In this way, the ring buffer is designed with integer multiples of the fundamental frequency period to ensure the integrity of the current fluctuation characteristics in the time domain; the dynamically calculated sampling point threshold converts the frequency domain characteristics into time domain criteria to accurately capture the overcurrent state; and the continuous verification mechanism dynamically filters interference signals during the timing process to form a closed-loop verification. The three form a self-consistent system through timing correlation and data iteration, which not only retains the periodic characteristics of the current signal but also has noise immunity, ultimately achieving dual optimization of the false alarm rate and missed alarm rate of overcurrent judgment.

[0060] In a further technical solution of the first aspect, the dynamic braking circuit parameters are determined as follows: bus Calculate the total resistance R of the parallel brake resistors based on the allowable temperature rise ΔT b , according to the power supply switching time t hold And the servo maintains power P min Calculate the total capacity of the energy storage capacitor C. In this way, in the design of the dynamic braking circuit, the resistance value The calculation is not to pursue the energy dissipation rate in isolation, but to conduct a multi-physics coupling analysis of bus voltage, motor thermal resistance characteristics and allowable temperature rise. When the motor is overcurrent, the higher bus voltage V bus Will drive a larger braking current, then the ΔT / R in the formula th The term is used as a thermal constraint condition, through the thermal resistance coefficient R th Dynamically matching the resistor power consumption with the motor's heat dissipation capacity ensures that while the braking resistor quickly releases energy, its heat generation is always controlled within the tolerance range of the winding material, avoiding the risk of local ablation caused by simply pursuing rapid braking in traditional solutions.

[0061] Energy storage capacitor parameters that form a time-space coordination Its design dimension extends to the level of system functional integrity. At the moment of external power supply cutoff, the inverse square relationship between the capacitor capacity and the bus voltage ensures that even under high voltage fluctuations (represented by the β coefficient), the capacitor can still provide continuous t hold This energy supply is not a simple "backup power" function, but enables the control system to continuously monitor key parameters such as winding temperature and current decay curve while the brake resistor is working, dynamically adjust the braking intensity, and form a closed-loop protection.

[0062] In a further technical solution of the first aspect, the decay rate is calculated by: performing a window length R on the filtered current data. bPerform sliding difference operations on integer multiples of C to generate a difference sequence; perform normalized exponentially weighted moving average processing on the difference sequence to obtain the decay rate.

[0063] In a further technical solution of the first aspect, the second preset time duration is determined by the following steps: obtaining the maximum current value I in the sliding window peak ;According to the maximum current value I peak Calculate the second preset time duration T2.

[0064] In a further technical solution of the first aspect, the three-phase current signal is filtered using a Butterworth bandpass filter, and the cutoff frequency is set to 0.8-1.2 times the motor operating frequency. Before filtering the three-phase current signal, the current signal needs to be subjected to common-mode noise elimination.

[0065] In a second aspect, the present invention provides a motor overcurrent protection system, comprising: a first acquisition module, a first generation module, a first comparison module, a first execution module, a second execution module, and a first locking module. The first execution module is further configured to: establish a ring buffer to store an over-threshold flag, wherein the capacity of the ring buffer is equal to an integer multiple of the motor fundamental frequency period; continuously verify the validity of the over-threshold state while a timer is running, resetting the timer when an invalid sampling point is detected; and using the accumulated value of the timer as the duration of the continuous over-threshold state.

[0066] In a further technical solution of the second aspect, the dynamic braking circuit parameters are determined by: bus Calculate the total resistance R of the parallel brake resistors based on the allowable temperature rise ΔT b ; According to the power supply switching time t hold And the servo maintains power P min Calculate the total capacity C of the energy storage capacitor.

[0067] In a further technical solution of the second aspect, the second execution module is further configured to: execute a window length R on the filtered current data. b Perform sliding difference operations on integer multiples of C to generate a difference sequence; perform normalized exponentially weighted moving average processing on the difference sequence to obtain the decay rate.

[0068] In a further technical solution of the second aspect, the second preset time duration is determined by the following steps: obtaining the maximum current value I in the sliding window peak ;According to the maximum current value I peak Calculate the second preset time duration T2.

[0069] In a further technical solution of the second aspect, the three-phase current signal is filtered using a Butterworth bandpass filter, and the cutoff frequency is set to 0.8-1.2 times the motor operating frequency. Before filtering the three-phase current signal, the current signal needs to be subjected to common-mode noise elimination.

[0070] In a third aspect, the present invention provides an electronic device comprising one or more processors; a storage device on which one or more programs are stored; when the one or more programs are executed by the one or more processors, the one or more processors implement the method described in any technical solution of the first aspect.

[0071] In a fourth aspect, the present invention provides a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the method described in any one of the technical solutions of the first aspect is implemented.

[0072] In a fifth aspect, the present invention provides a computer program product, comprising a computer program, which, when executed by a processor, implements the method described in any one of the technical solutions of the first aspect.

[0073] Among them, the technical effects brought about by any design method in the second to fifth aspects can refer to the technical effects brought about by different design methods in the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 A flow chart of a method for motor overcurrent protection provided by an embodiment of the present invention;

[0075] Figure 2 A schematic structural diagram of a motor overcurrent protection system provided by an embodiment of the present invention;

[0076] Figure 3 It is a schematic structural diagram of an electronic device suitable for implementing some embodiments of the present application. DETAILED DESCRIPTION

[0077] Specific embodiments of the present invention will now be mentioned in detail. Although the present invention is described in conjunction with these specific embodiments, it should be appreciated that the present invention is not intended to be limited to these specific embodiments. On the contrary, these embodiments are intended to cover substitutions, changes, or equivalent embodiments that may be included within the spirit and scope of the invention defined by the claims. In the following description, a large number of specific details are set forth in order to provide a comprehensive understanding of the present invention. The present invention may be implemented without some or all of these specific details.

[0078] Application Overview: The integrated servo, as the core actuator of the UAV flight control system, adopts a highly integrated design. It drives the motor through the internal control driver to achieve precise deflection of the rudder, thereby completing the flight attitude adjustment. Under normal flight conditions, the load of the integrated servo is usually in the range of no-load to rated load, and the motor can operate stably. However, when the UAV encounters sudden airflow disturbances, mechanical obstruction or abnormal force on the rudder, the motor may be in an overload state due to stalling. At this time, the back electromotive force of the motor is significantly reduced or even approaches zero, causing the stator winding impedance to drop sharply, causing the current to surge to several times the rated value. High current in a short period of time can cause the winding to overheat or even burn, and may also damage surrounding circuit components. In severe cases, it will threaten the flight safety of the UAV.

[0079] Related overcurrent protection schemes usually use fuses or current relays to cut off the power supply, but they have the following limitations: 1) The fuse needs to be manually replaced after it is activated, which cannot meet the needs of autonomous operation of drones; 2) After the power is directly cut off, the residual energy in the motor winding cannot be released quickly, and there is still a risk of local overheating; 3) The protection threshold is fixed, and the response time cannot be dynamically adjusted according to the severity of the overcurrent, which can easily lead to protection delays or false triggering.

[0080] Therefore, there is an urgent need for an overcurrent protection method with fast current cutoff, efficient dissipation of residual energy and adaptive protection logic to improve the safety and recoverability of the integrated servo under complex working conditions.

[0081] In response to the above technical problems, the overall idea of the technical solution provided by this application is as follows: a method for motor overcurrent protection is provided, comprising the following steps: obtaining the three-phase current signal of the motor; filtering and analog-to-digital conversion of the three-phase current signal to generate digital current amplitude data; comparing the digital current amplitude data with the overcurrent threshold and counting the continuous exceeding threshold time; when the continuous exceeding threshold time reaches a first preset time, cutting off the external power supply and maintaining operation through the energy storage capacitor; connecting the motor winding to the dynamic braking circuit, the dynamic braking circuit includes a parallel braking resistor, and the resistance value is adapted to the motor impedance; after the dynamic braking circuit is activated, the real-time current data is filtered and the decay rate is calculated; when the decay rate is lower than the preset rate threshold, the dynamic braking circuit is disconnected and the power supply is restored; if the continuous exceeding threshold time is detected again after the power supply is restored to reach the second preset time, the power supply cut-off state is locked and a locking signal is sent, and the second preset time is shortened as the ratio of the overcurrent current to the rated current increases; wherein, the locked power supply cut-off state is only released after receiving an external reset command.

[0082] This method first performs anti-interference processing on the three-phase current signal, removes high-frequency noise and low-frequency bias through bandpass filtering, and then generates accurate current quantization data through analog-to-digital conversion, effectively eliminating the common pulse interference in the complex electromagnetic environment of drones, and providing a reliable data basis for subsequent judgment.

[0083] During the overcurrent detection phase, the system doesn't simply rely on momentary current exceeding the specified limit. Instead, it employs a continuous monitoring window designed based on the motor's fundamental frequency characteristics. Protection is triggered only when the current continuously exceeds the threshold for a preset duration, forming a cumulative judgment mechanism over a time dimension. This approach avoids instantaneous current spikes during normal servo commutation while capturing true stalled-rotor overcurrent conditions, significantly reducing the risk of false tripping caused by interference in traditional solutions.

[0084] When an overcurrent condition is confirmed, the system does not completely cut off power. Instead, it adopts a graded response strategy: first, it cuts off the external power supply to prevent the current from continuing to rise. At the same time, it maintains the lowest power consumption of the control system through pre-configured energy storage capacitors, ensuring the complete execution of safety processes such as fault logging and status feedback.

[0085] At the same time, by connecting the motor winding to the dynamic braking circuit and using parallel braking resistors to form a closed discharge loop, the magnetic field energy stored in the winding is quickly converted into heat energy and dissipated, effectively solving the hidden danger of local overheating caused by residual current after power failure in traditional fuse solutions, and controlling the winding temperature rise within the material tolerance range.

[0086] During this process, the system continuously monitors the current decay dynamics and only reconnects the power supply when the current naturally drops to the safe recovery threshold, avoiding the risk of secondary overcurrent caused by blind restart. In extreme operating conditions with repeated overcurrent, when overcurrent is detected again after power is restored, the system dynamically compresses the secondary protection response time based on the real-time overcurrent multiple. Specifically, the greater the ratio of the overcurrent current to the rated current, the higher the severity of the fault determined by the system, and the corresponding protection action time limit is shortened exponentially. In this way, the opportunity for self-recovery is retained in the face of minor overcurrent, and the permanent protection state is quickly entered in critical situations such as severe short circuits, achieving an optimal balance between protection timeliness and system availability. In summary, the effect of motor overcurrent protection can be effectively improved.

[0087] After introducing the basic principles of this application, various non-limiting implementation methods of this application will be specifically introduced in conjunction with the accompanying drawings. Figure 1 The present invention provides a method for overcurrent protection of a motor, wherein the control driver inside the integrated servo performs the following steps:

[0088] S101: Acquire the three-phase current signal of the motor;

[0089] S102: Filtering and analog-to-digital conversion of the three-phase current signal to generate digital current amplitude data;

[0090] Specifically, in some embodiments, the three-phase current signal is filtered using a Butterworth bandpass filter, with the cutoff frequency set to 0.8-1.2 times the motor operating frequency. Common-mode noise elimination is required before filtering the three-phase current signal.

[0091] S103: Compare the digital current amplitude data with the overcurrent threshold, and count the duration of continuous over-threshold value;

[0092] Specifically, in some embodiments, the execution entity may count the duration of continuous exceeding the threshold value through the following steps:

[0093] The first step is to establish a ring buffer to store the over-threshold flag bit. The capacity of the ring buffer is equal to an integer multiple of the motor fundamental frequency period.

[0094] In the second step, a timer is started when N consecutive sampling points are detected to exceed the threshold, where N is calculated using the following formula:

[0095]

[0096] Among them, f base is the motor fundamental frequency, T sample is the current sampling period;

[0097] The third step is to continuously verify the validity of the over-threshold state while the timer is running. When an invalid sampling point is detected, the timer is reset; the accumulated value of the timer is used as the duration of continuous over-threshold. In this way, the ring buffer is designed with integer multiples of the fundamental frequency period to ensure the integrity of the current fluctuation characteristics in the time domain; the dynamically calculated sampling point threshold converts the frequency domain characteristics into time domain criteria to achieve accurate capture of the overcurrent state; the continuous verification mechanism dynamically filters the interference signal during the timing process to form a closed-loop verification. The three form a self-consistent system through timing correlation and data iteration, which not only retains the periodic characteristics of the current signal but also has noise immunity, ultimately achieving dual optimization of the false alarm rate and missed alarm rate of overcurrent judgment.

[0098] S104: When the duration of continuous exceeding the threshold reaches a first preset duration, cutting off the external power supply and maintaining operation through the energy storage capacitor; connecting the motor winding to a dynamic braking circuit, the dynamic braking circuit including a parallel braking resistor, the resistance of which is adapted to the motor impedance;

[0099] Specifically, in some embodiments, the dynamic braking circuit parameters are determined by:

[0100] The first step is to calculate the rated voltage of the motor busbar V bus Calculate the total resistance R of the parallel brake resistors based on the allowable temperature rise ΔT b , the specific formula is as follows:

[0101]

[0102] Among them, ΔT is the difference between the maximum allowable temperature of the motor winding and the ambient temperature, R th is the thermal resistance coefficient of the motor measured by the steady-state method; γ is the proportionality coefficient; illustratively, 0.8≤γ≤1.2.

[0103] The second step is to switch the power supply according to the time t hold And the servo maintains power P min Calculate the total capacity C of the energy storage capacitor. The specific formula is as follows:

[0104]

[0105] Where β is the voltage fluctuation coefficient. For example, β = 0.05. Thus, in the design of the dynamic braking circuit, the resistance value The calculation is not to pursue the energy dissipation rate in isolation, but to conduct a multi-physics coupling analysis of bus voltage, motor thermal resistance characteristics and allowable temperature rise. When the motor is overcurrent, the higher bus voltage V bus Will drive a larger braking current, then the ΔT / R in the formula th The term is used as a thermal constraint condition, through the thermal resistance coefficient R th Dynamically matching the resistor power consumption with the motor's heat dissipation capacity ensures that while the braking resistor quickly releases energy, its heat generation is always controlled within the tolerance range of the winding material, avoiding the risk of local ablation caused by simply pursuing rapid braking in traditional solutions.

[0106] Energy storage capacitor parameters that form a time-space coordination Its design dimension extends to the level of system functional integrity. At the moment of external power supply cutoff, the inverse square relationship between the capacitor capacity and the bus voltage ensures that even under high voltage fluctuations (represented by the β coefficient), the capacitor can still provide continuous t hold This energy supply is not a simple "backup power" function, but enables the control system to continuously monitor key parameters such as winding temperature and current decay curve while the brake resistor is working, dynamically adjust the braking intensity, and form a closed-loop protection.

[0107] S105: After the dynamic braking circuit is activated, the real-time current data is filtered and the decay rate is calculated; when the decay rate is lower than a preset rate threshold, the dynamic braking circuit is disconnected and power is restored;

[0108] Specifically, in some embodiments, the decay rate is calculated by the following steps:

[0109] The first step is to perform a window length R on the filtered current data. b Sliding difference operation of integer multiples of C to generate a difference sequence;

[0110] In the second step, the normalized exponentially weighted moving average is performed on the difference sequence to obtain the decay rate, and the weight coefficient satisfies:

[0111]

[0112] Where t is the sampling time series starting from the moment the dynamic brake is activated, and n is the window length.

[0113] S106: If the continuous exceeding of the threshold value for a second preset time is detected again after the power supply is restored, the power supply cut-off state is locked and a locking signal is sent. The second preset time is shortened as the ratio of the overcurrent to the rated current increases; wherein, the locked power supply cut-off state is released only after receiving an external reset command.

[0114] Specifically, in some embodiments, the second preset duration is determined by the following steps:

[0115] The first step is to obtain the maximum current value I in the sliding window peak ;

[0116] The second step is to calculate the maximum current value I peak The second preset time length T2 is calculated using the following formula:

[0117]

[0118] Where: T0 is the reference response time; I rated is the rated current of the motor, λ is the attenuation coefficient, for example, 0.5≤λ≤0.7; T base is the benchmark time threshold, T0≥T base . For example, T base =10ms;

[0119] See also Figure 2 Based on the same inventive concept as the motor overcurrent protection method in the aforementioned embodiment, the present embodiment provides a motor overcurrent protection system, including:

[0120] A first acquisition module 201 is used to acquire a three-phase current signal of the motor;

[0121] The first generating module 202 is used to filter and perform analog-to-digital conversion on the three-phase current signal to generate digital current amplitude data;

[0122] The first comparison module 203 is used to compare the digital current amplitude data with the overcurrent threshold and calculate the duration of continuous over-threshold value;

[0123] The first execution module 204 is configured to, when the duration of continuous exceeding of the threshold reaches a first preset duration, cut off the external power supply and maintain operation through the energy storage capacitor; connect the motor winding to a dynamic braking circuit, the dynamic braking circuit including a parallel braking resistor, the resistance of which is adapted to the motor impedance;

[0124] The second execution module 205 is configured to filter the real-time current data and calculate the decay rate after the dynamic braking circuit is activated; when the decay rate is lower than a preset rate threshold, disconnect the dynamic braking circuit and restore power supply;

[0125] The first locking module 206 is used to lock the power supply cut-off state and send a locking signal if it is detected that the continuous exceeding of the threshold value reaches a second preset time after the power supply is restored. The second preset time is shortened as the ratio of the overcurrent current to the rated current increases; wherein, the locked power supply cut-off state is released only after receiving an external reset command.

[0126] In some embodiments, the first execution module 204 is further configured to:

[0127] Establish a ring buffer to store the over-threshold flag bit, and the capacity of the ring buffer is equal to an integer multiple of the motor fundamental frequency period;

[0128] When N consecutive sampling points exceed the threshold, the timer is started, where N is calculated using the following formula:

[0129]

[0130] Among them, f base is the motor fundamental frequency, T sample is the current sampling period;

[0131] The validity of the over-threshold state is continuously verified during the operation of the timer, and the timer is reset when an invalid sampling point is detected; the accumulated value of the timer is used as the continuous over-threshold duration.

[0132] In some embodiments, dynamic braking circuit parameters are determined by:

[0133] According to the rated voltage of the motor bus V bus Calculate the total resistance R of the parallel brake resistors based on the allowable temperature rise ΔT b , the specific formula is as follows:

[0134]

[0135] Among them, ΔT is the difference between the maximum allowable temperature of the motor winding and the ambient temperature, R th is the thermal resistance coefficient of the motor measured by the steady-state method; γ is the proportional coefficient;

[0136] According to the power supply switching time t holdAnd the servo maintains power P min Calculate the total capacity C of the energy storage capacitor. The specific formula is as follows:

[0137]

[0138] Where β is the voltage fluctuation coefficient.

[0139] In some embodiments, the second execution module 205 is further configured to:

[0140] The filtered current data is processed with a window length of R b Sliding difference operation of integer multiples of C to generate a difference sequence;

[0141] Perform normalized exponentially weighted moving average processing on the difference sequence to obtain the decay rate, and the weight coefficient satisfies:

[0142]

[0143] Where t is the sampling time series starting from the moment the dynamic brake is activated, and n is the window length.

[0144] In some embodiments, the second preset time duration is determined by the following steps: obtaining the maximum current value I in the sliding window peak ;According to the maximum current value I peak The second preset time length T2 is calculated using the following formula:

[0145]

[0146] Where: T0 is the reference response time, I rated is the rated current of the motor, λ is the attenuation coefficient, T base is the benchmark time threshold, T0≥T base .

[0147] In some embodiments, the three-phase current signal is filtered using a Butterworth bandpass filter, with the cutoff frequency set to 0.8-1.2 times the motor operating frequency. Common-mode noise elimination is required before filtering the three-phase current signal.

[0148] It is understandable that the modules recorded in the motor overcurrent protection system are consistent with the reference Figure 1 Therefore, the operations, features and beneficial effects described above for the method are also applicable to the motor overcurrent protection system and the modules included therein, and will not be repeated here.

[0149] See also Figure 3Based on the inventive concept of a method for motor overcurrent protection in the aforementioned embodiment, an embodiment of the present application provides an electronic device. The electronic device may include but is not limited to mobile terminals such as mobile phones, laptops, digital broadcast receivers, PDAs (personal digital assistants), PADs (tablet computers), PMPs (portable multimedia players), etc., and fixed terminals such as digital TVs, desktop computers, etc. The electronic device includes a processing device 301 (such as a central processing unit, a graphics processing unit, etc.), which can perform various appropriate actions and processes according to the program stored in ROM 302 (read-only memory) or the program loaded from the storage device 308 into RAM 303 (random access memory). Various programs and data required for the operation of the electronic device are also stored in RAM 303. The processing device 301, ROM 302 and RAM 303 are connected to each other via a bus 304. The input / output interface (i.e., I / O interface 305) is also connected to the bus 304.

[0150] Typically, the following devices may be connected to the I / O interface 305: an input device 306 including, for example, a touch screen, a touchpad, a keyboard, a mouse, a camera, a microphone, an accelerometer, a gyroscope, etc.; an output device 307 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; a storage device 308 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 309. The communication device 309 may allow the electronic device to communicate with other devices wirelessly or by wire to exchange data.

[0151] In particular, according to some embodiments of the present invention, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, some embodiments of the present invention include a computer program product comprising a computer program carried on a computer-readable medium, the computer program comprising program code for executing the method shown in the flowchart. In some such embodiments, the computer program can be downloaded and installed from a network via the communication device 309, or installed from the storage device 308, or installed from the ROM 302. When the computer program is executed by the processing device 301, the above-mentioned functions defined in the method of some embodiments of the present application are performed.

[0152] It should be noted that the computer-readable medium described in some embodiments of the present invention may be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. The computer-readable storage medium may be an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device, or component, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to, an electrical connection having one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In some embodiments of the present application, the computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, device, or component. In some embodiments of the present application, the computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, which carries computer-readable program code. This propagated data signal may take a variety of forms, including, but not limited to, an electromagnetic signal, an optical signal, or any suitable combination thereof. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium that can transmit, propagate, or transport a program for use by or in conjunction with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium may be transmitted using any suitable medium, including but not limited to wires, optical cables, RF (radio frequency), etc., or any suitable combination thereof.

[0153] In some embodiments, the client and server can communicate using any currently known or future developed network protocol, such as HTTP (HyperText Transfer Protocol), and can be interconnected with any form or medium of digital data communication (e.g., a communication network). Examples of communication networks include a local area network ("LAN"), a wide area network ("WAN"), an internet (e.g., the Internet), and a peer-to-peer network (e.g., an adhoc peer-to-peer network), as well as any currently known or future developed network.

[0154] The computer-readable medium may be included in the electronic device, or may exist independently without being incorporated into the electronic device. The computer-readable medium carries one or more programs. When the one or more programs are executed by the electronic device, the electronic device can implement the method steps of any of the above technical solutions.

[0155] Computer program code for performing the operations of some embodiments of the present application can be written in one or more programming languages, or a combination thereof, including object-oriented programming languages such as Java, Smalltalk, C++, and conventional procedural programming languages such as "C" or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a separate software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0156] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of the systems, methods, and computer program products according to various embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, program segment, or portion of code, which contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the boxes can also occur in an order different from that marked in the accompanying drawings. For example, two boxes shown in succession can actually be executed substantially in parallel, or they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, as well as the combination of boxes in the block diagram and / or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or operation, or can be implemented using a combination of dedicated hardware and computer instructions. The modules described in some embodiments of the present application can be implemented using software or hardware. The modules described can also be provided in a processor. The names of these modules do not constitute a limitation on the modules themselves.

[0157] The functions described above herein may be performed, at least in part, by one or more hardware logic components. For example, and without limitation, exemplary types of hardware logic components that may be used include: field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chip (SOCs), complex programmable logic devices (CPLDs), and the like.

[0158] Some embodiments of the present invention further provide a computer program product, comprising a computer program, which implements any of the above-mentioned motor overcurrent protection methods when executed by a processor.

[0159] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made thereto. Therefore, such modifications and improvements, without departing from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A method for overcurrent protection of a motor, characterized in that: The following steps are involved: (1) Obtain the three-phase current signal of the motor; (2) filtering and performing analog-to-digital conversion on the three-phase current signal to generate digital current amplitude data; (3) comparing the digital current amplitude data with the overcurrent threshold, and counting the duration of continuous over-threshold value; (4) When the duration of continuous exceeding the threshold reaches a first preset duration, the external power supply is cut off and the operation is maintained by the energy storage capacitor; the motor winding is connected to a dynamic braking circuit, wherein the dynamic braking circuit includes a parallel braking resistor, the resistance of which is adapted to the motor impedance; (5) After the dynamic braking circuit is activated, the real-time current data is filtered and the decay rate is calculated; when the decay rate is lower than the preset rate threshold, the dynamic braking circuit is disconnected and power is restored; (6) If the duration of continuous over-threshold value exceeding the second preset duration is detected again after the power supply is restored, the power supply cut-off state is locked and a locking signal is sent. The second preset duration is shortened as the ratio of the over-current to the rated current increases; wherein, the locked power supply cut-off state is released only after receiving an external reset command.

2. The method for motor overcurrent protection according to claim 1, characterized in that: The statistical method of the continuous exceeding threshold duration includes: (1) establishing a ring buffer to store an over-threshold flag, wherein the capacity of the ring buffer is equal to an integer multiple of the motor fundamental frequency period; (2) When N consecutive sampling points are detected to exceed the threshold, the timer is started, where N is calculated by the following formula: Among them, f base is the motor fundamental frequency, T sample is the current sampling period; (3) Continuously verify the validity of the over-threshold state during the timer operation, and reset the timer when an invalid sampling point is detected; the accumulated value of the timer is used as the continuous over-threshold duration.

3. The method for motor overcurrent protection according to claim 1, characterized in that: The dynamic braking circuit parameters are determined by the following method: (1) According to the rated voltage V of the motor bus bus Calculate the total resistance R of the parallel brake resistors based on the allowable temperature rise ΔT b , the specific formula is as follows: Among them, ΔT is the difference between the maximum allowable temperature of the motor winding and the ambient temperature, R th is the thermal resistance coefficient of the motor measured by the steady-state method; γ is the proportional coefficient; (2) According to the power supply switching time t hold And the servo maintains power P min Calculate the total capacity C of the energy storage capacitor. The specific formula is as follows: Where β is the voltage fluctuation coefficient.

4. The method for motor overcurrent protection according to claim 1, characterized in that: The decay rate is calculated by the following steps: (1) The window length of the filtered current data is R b Sliding difference operation of integer multiples of C to generate a difference sequence; (2) Performing normalized exponentially weighted moving average processing on the differential sequence to obtain the decay rate, and the weight coefficient satisfies: Where t is the sampling time series starting from the moment the dynamic brake is activated, and n is the window length.

5. The method for motor overcurrent protection according to claim 1, characterized in that: The second preset duration is determined by the following steps: (1) Obtain the maximum current value I within the sliding window peak ; (2) According to the maximum current value I peak The second preset time length T2 is calculated using the following formula: Where: T0 is the reference response time, I rated is the rated current of the motor, λ is the attenuation coefficient, T base is the benchmark time threshold, T0≥T base .

6. The motor overcurrent protection method according to claim 1, characterized in that: The three-phase current signal is filtered using a Butterworth bandpass filter, with a cutoff frequency set to 0.8-1.2 times the motor operating frequency. Common-mode noise elimination is required before filtering the three-phase current signal.

7. A motor overcurrent protection system, used in the method according to any one of claims 1 to 6, characterized in that: include: A first acquisition module is used to acquire the three-phase current signal of the motor; A first generating module is used to filter and perform analog-to-digital conversion on the three-phase current signal to generate digital current amplitude data; A first comparison module is used to compare the digital current amplitude data with the overcurrent threshold and calculate the duration of continuous over-threshold value; A first execution module is configured to, when the duration of continuous exceeding of the threshold reaches a first preset duration, cut off the external power supply and maintain operation through the energy storage capacitor; connect the motor winding to a dynamic braking circuit, wherein the dynamic braking circuit includes a parallel braking resistor with a resistance value adapted to the motor impedance; The second execution module is configured to filter the real-time current data and calculate the decay rate after the dynamic braking circuit is activated; when the decay rate is lower than a preset rate threshold, disconnect the dynamic braking circuit and restore power supply; The first locking module is used to lock the power supply cut-off state and send a locking signal if it is detected that the continuous exceeding of the threshold value reaches a second preset time after the power supply is restored. The second preset time is shortened as the ratio of the overcurrent to the rated current increases; wherein, the locked power supply cut-off state is only released after receiving an external reset command.

8. An electronic device, characterized in that: include: one or more processors; a storage device having one or more programs stored thereon; When the one or more programs are executed by the one or more processors, the one or more processors implement the method according to any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, which implements the method according to any one of claims 1 to 6 when executed by a processing device.

10. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processing device, the method according to any one of claims 1 to 6 is implemented.

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