Eps system short-time overcurrent protection method, device, apparatus and storage medium

Abstract

The application provides an EPS system short-time overcurrent protection method, device, equipment and storage medium, and belongs to the technical field of EPS system control, wherein the method comprises the following steps: S1, when the real-time current is greater than a preset current threshold, executing steps S2-S5; S2, calculating a current change rate; S3, generating a Vds voltage inference threshold; S4, acquiring a working condition parameter, determining a working condition correction factor, and correcting the Vds voltage inference threshold; S5, comparing the Vds voltage with the Vds voltage inference threshold; and S6, repeatedly executing steps S2-S5, and cutting off the driving circuit when the fault frequency is greater than a first preset frequency threshold. The EPS system short-time overcurrent protection method, device, equipment and storage medium provided by the application can effectively prevent the impedance characteristic change of the power loop and the influence of the parasitic inductance on the judgment result, so as to reduce the false alarm probability.

Description

Technical Field

[0001] This invention belongs to the field of EPS system control technology, and in particular relates to a method, device, equipment and storage medium for short-time overcurrent protection of EPS systems. Background Technology

[0002] EPS, or Electric Power Steering, is a power steering system that relies on an electric motor to provide auxiliary torque. Its working principle is that the torque sensor transmits the signal of the steering wheel rotation to the controller. After the controller processes the signal, it drives the motor to rotate. The motor is then amplified by the reduction mechanism and pushes the steering column or rack, thereby providing power steering assistance.

[0003] In existing brushless motor EPS systems, the three-phase bridge composed of MOSFETs is the core of its power. Overcurrent protection is typically achieved by detecting the drain-source voltage (Vds) of the MOSFETs. However, in actual three-phase bridge power circuits, Vds is a dynamic variable affected by drive conditions and temperature. Furthermore, the source and drain voltages of the three-phase bridge circuit inevitably include the impedance and parasitic inductance of the power loop. Therefore, when the current change rate is high, the induced voltage generated by the parasitic inductance will significantly superimpose on Vds. This leads to a risk of false alarms in Vds-based overcurrent detection, especially under complex conditions such as bumpy driving or continuous cornering. False alarms from overcurrent detection can easily trigger malfunctions in the protection circuit, causing abnormal failure of the EPS system and ultimately affecting driving safety. Summary of the Invention

[0004] In view of this, the present invention aims to provide a method, apparatus, device and storage medium for short-time overcurrent protection of EPS systems to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0006] In a first aspect, embodiments of the present invention provide a short-time overcurrent protection method for an EPS system, comprising:

[0007] S1. Collect the real-time current of the EPS system, compare the real-time current with the preset current threshold, and execute steps S2-S5 when the real-time current is greater than the preset current threshold.

[0008] S2. Collect the system temperature and Vds voltage for the current sampling period, and calculate the current change rate for the current sampling period;

[0009] S3. Perform fuzzy inference based on the system temperature and the rate of change of current in the current sampling period to generate the Vds voltage inference threshold for the current sampling period.

[0010] S4. Obtain the operating parameters of the current sampling period, determine the operating status of the current sampling period based on the operating parameters of the current sampling period, and determine the operating correction factor of the current sampling period based on the operating status of the current sampling period; correct the Vds voltage inference threshold of the current sampling period using the operating correction factor of the current sampling period.

[0011] S5. Compare the Vds voltage of the current sampling period with the Vds voltage inference threshold of the current sampling period, accumulate and record the number of comparisons, and accumulate and record the number of faults when the Vds voltage of the current sampling period is greater than the Vds voltage inference threshold of the current sampling period.

[0012] S6. Repeat steps S2-S5 according to the preset time interval. When the number of faults is greater than the first preset threshold, disconnect the drive circuit of the EPS system. When the number of faults is less than the first preset threshold and the comparison number is greater than the second preset threshold, return to step S1.

[0013] Furthermore, the calculation of the current change rate in the current sampling period includes:

[0014] Obtain the real-time current of the previous sampling period and the real-time current of the current sampling period;

[0015] Calculate the current difference between the real-time current of the current sampling period and the real-time current of the previous sampling period, and calculate the time difference between the current sampling period and the previous sampling period.

[0016] Calculate the ratio between the current difference and the time difference, and determine the ratio as the rate of change of current in the current sampling period.

[0017] Furthermore, the step of generating the Vds voltage inference threshold for the current sampling period by performing fuzzy inference based on the system temperature and the current change rate of the current sampling period includes:

[0018] The system temperature and the rate of change of current in the current sampling period are fuzzified respectively to generate fuzzified results for temperature and fuzzified results for rate of change of current.

[0019] Based on the preset fuzzy inference rules, fuzzy inference is performed on the fuzzification results of temperature and the fuzzification results of current change rate to determine the fuzzy set of Vds voltage inference threshold.

[0020] The fuzzy set of Vds voltage inference thresholds is defuzzified to generate the Vds voltage inference threshold for the current sampling period.

[0021] Furthermore, the fuzzification process employs a Gaussian membership function, the expression of which is:

[0022] ;

[0023] In the above formula, This represents the membership degree value. For input quantity, Center parameter, This is the diffusivity parameter;

[0024] The defuzzing process employs the centroid method, whose expression is:

[0025] ;

[0026] In the above formula, The Vds voltage inference threshold for the current sampling period. To output discrete points in the universe of discourse, for membership degree Let be the number of fuzzy sets, and .

[0027] Furthermore, the operating parameters for the current sampling period include: the torque for the current sampling period, the motor speed for the current sampling period, and the motor current for the current sampling period.

[0028] Determining the operating condition status of the current sampling period based on the operating condition parameters of the current sampling period includes:

[0029] Obtain the torque of the previous sampling period, and calculate the torque fluctuation rate based on the torque of the current sampling period and the torque of the previous sampling period. When the torque fluctuation rate is greater than or equal to the preset fluctuation rate threshold, the operating condition of the current sampling period is determined to be the torque impact state. When the torque fluctuation rate is less than the preset fluctuation rate threshold, the operating condition of the current sampling period is determined to be the torque stable state.

[0030] Obtain the rated current value of the motor in the EPS system. When the motor current in the current sampling period is greater than 80% of the rated current value, calculate the cumulative duration for which the motor current is greater than 80% of the rated current value. When the motor speed in the current sampling period is less than or equal to a preset speed threshold and the cumulative duration is greater than a preset duration threshold, determine the operating condition of the current sampling period as a stalled state. When the motor speed in the current sampling period is greater than a preset speed threshold or the cumulative duration is less than a preset duration threshold, determine the operating condition of the current sampling period as a non-stalled state.

[0031] Furthermore, determining the operating condition correction factor for the current sampling period based on the operating condition status of the current sampling period includes:

[0032] When the operating condition in the current sampling period is a torque stable state and a non-stalled state, the operating condition correction factor for the current sampling period is 1;

[0033] When the operating condition in the current sampling period is a torque impact state and a non-stalled state, the operating condition correction factor for the current sampling period is 1.05;

[0034] When the operating conditions in the current sampling period are torque stable state and stalled state, the operating condition correction factor for the current sampling period is 1.1;

[0035] When the operating conditions in the current sampling period are torque impact and stall conditions, the operating condition correction factor for the current sampling period is 1.2.

[0036] Secondly, embodiments of the present invention also provide a short-time overcurrent protection device for an EPS system, comprising:

[0037] The trigger module is used to collect the real-time current of the EPS system, compare the real-time current with a preset current threshold, and execute steps S2-S5 when the real-time current is greater than the preset current threshold.

[0038] The acquisition module is used to acquire the system temperature and Vds voltage in the current sampling period and calculate the current change rate in the current sampling period.

[0039] The inference module is used to perform fuzzy inference based on the system temperature and the rate of change of current in the current sampling period to generate the Vds voltage inference threshold for the current sampling period.

[0040] The operating condition correction module is used to obtain the operating condition parameters of the current sampling period, determine the operating condition status of the current sampling period based on the operating condition parameters of the current sampling period, and determine the operating condition correction factor of the current sampling period based on the operating condition status of the current sampling period; and correct the Vds voltage inference threshold of the current sampling period using the operating condition correction factor of the current sampling period.

[0041] The comparison module is used to compare the Vds voltage of the current sampling period with the Vds voltage inference threshold of the current sampling period, accumulate and record the number of comparisons, and accumulate and record the number of faults when the Vds voltage of the current sampling period is greater than the Vds voltage inference threshold of the current sampling period.

[0042] The determination module is used to cut off the drive circuit of the EPS system when the number of faults exceeds the first preset threshold number, and to return to the execution step S1 when the number of faults is less than the first preset threshold number and the comparison number is greater than the second preset threshold number.

[0043] Thirdly, embodiments of the present invention also provide an apparatus, comprising:

[0044] One or more processors;

[0045] Storage device for storing one or more programs;

[0046] When the one or more programs are executed by the one or more processors, the one or more processors implement the short-time overcurrent protection method for EPS systems as provided in the above embodiments.

[0047] Fourthly, embodiments of the present invention also provide a storage medium containing computer-executable instructions, which, when executed by a computer processor, are used to perform the short-time overcurrent protection method for EPS systems provided in the above embodiments.

[0048] Compared with existing technologies, the short-time overcurrent protection method, device, equipment, and storage medium of the present invention for EPS systems have the following advantages:

[0049] This invention provides a short-time overcurrent protection method, device, equipment, and storage medium for EPS systems. When the real-time current of the EPS system exceeds a preset current threshold, it infers the Vds voltage inference threshold based on the system temperature and current change rate during the current sampling period. The Vds voltage is then compared with the Vds voltage inference threshold to achieve overcurrent detection in the EPS system. Compared to existing technologies, using the Vds voltage inference threshold as the comparison benchmark for Vds detection effectively prevents changes in the impedance characteristics of the power circuit and parasitic inductance from affecting the actual judgment result, thereby reducing the probability of false alarms and improving overall stability. Attached Figure Description

[0050] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0051] Figure 1 A flowchart of the short-time overcurrent protection method for the EPS system described in Embodiment 1 of this invention is provided;

[0052] Figure 2 This is a schematic diagram of the short-time overcurrent protection device for the EPS system described in Embodiment 2 of the present invention;

[0053] Figure 3 A schematic diagram of the structure of the device described in Embodiment 3 of the present invention. Detailed Implementation

[0054] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0055] Example 1

[0056] Figure 1 The flowchart of the short-time overcurrent protection method for an EPS system provided in Embodiment 1 of the present invention is shown in the figure. In this embodiment, the short-time overcurrent protection method for an EPS system specifically includes the following steps:

[0057] Step S1: Collect the real-time current of the EPS system, compare the real-time current with the preset current threshold, and execute steps S2-S5 when the real-time current is greater than the preset current threshold.

[0058] EPS (Electric Power Steering) is a power steering system that relies on an electric motor to provide auxiliary torque. During operation, the real-time current of the EPS system changes dynamically in real time depending on factors such as the driver's steering intention, vehicle speed, and road resistance. However, when the EPS system malfunctions or encounters adverse operating conditions, the real-time current can abnormally increase. Since abnormally high real-time current can damage power devices (such as MOSFETs) in the motor drive circuit and even threaten driving safety, it is necessary to detect and protect against overcurrent phenomena in the EPS system.

[0059] To achieve this objective, this embodiment will collect the real-time current of the EPS system to determine whether there is an overcurrent risk by comparing the real-time current with a preset current threshold. Specifically, the preset current threshold provided in this embodiment should be set in conjunction with the EPS system safety specifications, the actual performance of hardware such as power devices (e.g., the rated current value of MOSFETs), and the work experience of those skilled in the art, so as to avoid abnormal judgments by this method when the EPS system is operating under normal low-current conditions.

[0060] When the real-time current is less than or equal to the preset current threshold, the EPS system is considered to be within its normal operating current range. In this case, there is no risk of overcurrent requiring immediate intervention, and continuous monitoring of the real-time current is sufficient. When the real-time current exceeds the preset current threshold, it indicates that the current level in the EPS system has crossed the safety baseline, posing an overcurrent risk. In this case, steps S2-S5 should be executed to effectively prevent changes in the impedance characteristics of the power circuit and parasitic inductance from affecting the subsequent Vds detection results. This reduces the probability of false alarms, improves adaptability to different operating states, and enhances overall system stability.

[0061] It should be noted that the real-time current of the EPS system described in this embodiment can be the phase current of the motor in the EPS system or the drain current of the MOSFET. The specific method for acquiring the real-time current is a mature existing technology, and the relevant hardware equipment for performing the acquisition is also well known to the public, so it will not be described in this application.

[0062] Step S2: Collect the system temperature and Vds voltage for the current sampling period, and calculate the current change rate for the current sampling period.

[0063] Since system temperature and current change rate are key indicators for evaluating changes in power loop impedance characteristics and the impact of parasitic inductance, this embodiment will collect the system temperature and calculate the current change rate for the current sampling period when the real-time current exceeds a preset current threshold (i.e., the EPS system is at risk of overcurrent). This will facilitate accurate determination of the Vds voltage inference threshold for the current sampling period in subsequent processing. Correspondingly, the Vds voltage (i.e., the drain-source voltage of the MOSFET) for the current sampling period should also be collected and compared with the Vds voltage inference threshold in subsequent processing to determine whether an overcurrent phenomenon has occurred in the EPS system.

[0064] It should be noted that, since sensors that collect different parameters have different sampling frequencies, when collecting parameters in step S2, those skilled in the art should set an appropriate sampling period based on the sampling frequency of various sensors so that different parameters can be collected within the same sampling period.

[0065] Optionally, in this embodiment, the calculation of the current change rate in the current sampling period can be optimized as follows:

[0066] Obtain the real-time current of the previous sampling period and the real-time current of the current sampling period;

[0067] Calculate the current difference between the real-time current of the current sampling period and the real-time current of the previous sampling period, and calculate the time difference between the current sampling period and the previous sampling period.

[0068] Calculate the ratio between the current difference and the time difference, and determine the ratio as the rate of change of current in the current sampling period.

[0069] Step S3: Perform fuzzy inference based on the system temperature and current change rate of the current sampling period to generate the Vds voltage inference threshold for the current sampling period.

[0070] After determining the system temperature and current change rates for the current control cycle, this embodiment uses fuzzy inference to convert these rates into a dynamic and accurate Vds voltage inference threshold. Compared to the fixed threshold in traditional Vds detection methods, the Vds voltage inference threshold provided in this embodiment can match the actual state of the EPS system, thereby reducing the false alarm probability of Vds detection and adapting to different actual operating conditions.

[0071] Specifically, in this embodiment, fuzzy inference is performed based on the system temperature and the rate of change of current in the current sampling period to generate the Vds voltage inference threshold for the current sampling period. This can be optimized as follows:

[0072] The system temperature and the rate of change of current in the current sampling period are fuzzified respectively to generate fuzzified results for temperature and fuzzified results for rate of change of current.

[0073] Based on the preset fuzzy inference rules, fuzzy inference is performed on the fuzzification results of temperature and the fuzzification results of current change rate to determine the fuzzy set of Vds voltage inference threshold.

[0074] The fuzzy set of Vds voltage inference thresholds is defuzzified to generate the Vds voltage inference threshold for the current sampling period.

[0075] Fuzzification is applied to the system temperature and current change rate to transform these two precise input quantities into fuzzy linguistic descriptive variables. During fuzzification, the fundamental domain of discourse for system temperature is [-30, 110]℃, described using six fuzzy subsets: {low, low-medium, zero, medium-high, high, very high}. The fundamental domain of discourse for current change rate is [3, 20] A / s, described using three fuzzy subsets: {small, medium, large}. Furthermore, as the output of fuzzy inference, the fundamental domain of discourse for the voltage inference threshold Vds is [0.3, 0.8]V, with fuzzy subsets of {minimal, small, medium, large, maximum}.

[0076] To calculate the membership value during fuzzy inference, this embodiment can use a Gaussian membership function, the expression of which is:

[0077] ;

[0078] In the above formula, This represents the membership degree value. For input quantity, Let be the central parameter, i.e., the representative point of the fuzzy set, and when The membership value is set to the maximum value of 1. The diffusivity parameter is 0.85 in this embodiment.

[0079] After the fuzzification process is completed, the temperature fuzzification result and the current change rate fuzzification result should both be matrices composed of membership values, so as to be used as input in the subsequent fuzzy inference process, so as to obtain the fuzzy set of output (i.e. the fuzzy set of Vds voltage inference threshold).

[0080] It should be noted that the preset fuzzy inference rule in this embodiment is used to define a fuzzy set of Vds voltage inference thresholds that should be output under different system temperature and current change rate conditions (i.e., when the system temperature is low and the current change rate is small, the Vds voltage inference threshold is small, and vice versa). Its fuzzy rule statement can be expressed as:

[0081] ;

[0082] in, The input temperature is the fuzzy result. The result of fuzzifying the input current rate of change. This is a fuzzy set of inference thresholds for the output Vds voltage.

[0083] Since the fuzzy set output by fuzzy inference is in matrix form with membership values ​​as elements, this embodiment can use the centroid method for defuzzification in order to convert it into an accurate Vds voltage inference threshold for the current sampling period. This results in a smoother final fuzzy inference result, expressed as follows:

[0084] ;

[0085] In the above formula, The Vds voltage inference threshold for the current sampling period. To output discrete points in the universe of discourse, for membership degree Let be the number of fuzzy sets, and .

[0086] Step S4: Obtain the operating parameters of the current sampling period, determine the operating status of the current sampling period based on the operating parameters of the current sampling period, and determine the operating correction factor of the current sampling period based on the operating status of the current sampling period; correct the Vds voltage inference threshold of the current sampling period using the operating correction factor of the current sampling period.

[0087] Since the EPS system is affected not only by the system temperature and current change rate during operation, but also by the operating conditions, this embodiment introduces an operating condition correction factor to avoid distortion of the Vds voltage inference threshold in the current sampling period due to the influence of operating conditions. This factor can adjust the Vds voltage inference threshold according to the actual operating conditions, thereby further reducing the risk of false alarms and improving the matching degree between this embodiment and actual application scenarios.

[0088] Specifically, in this embodiment, the operating parameters for the current sampling period may include: the torque for the current sampling period, the motor speed for the current sampling period, and the motor current for the current sampling period. Correspondingly, determining the operating state for the current sampling period based on the operating parameters includes:

[0089] Obtain the torque of the previous sampling period, and calculate the torque fluctuation rate based on the torque of the current sampling period and the torque of the previous sampling period. When the torque fluctuation rate is greater than or equal to the preset fluctuation rate threshold, the operating condition of the current sampling period is determined to be the torque impact state. When the torque fluctuation rate is less than the preset fluctuation rate threshold, the operating condition of the current sampling period is determined to be the torque stable state.

[0090] Obtain the rated current value of the motor in the EPS system. When the motor current in the current sampling period is greater than 80% of the rated current value, calculate the cumulative duration for which the motor current is greater than 80% of the rated current value. When the motor speed in the current sampling period is less than or equal to a preset speed threshold and the cumulative duration is greater than a preset duration threshold, determine the operating condition of the current sampling period as a stalled state. When the motor speed in the current sampling period is greater than a preset speed threshold or the cumulative duration is less than a preset duration threshold, determine the operating condition of the current sampling period as a non-stalled state.

[0091] It should be noted that the preset volatility threshold can be set to 10%, the preset rotation speed threshold can be set to 30 revolutions per minute, and the preset duration threshold can be set to 60 seconds.

[0092] In practical applications, since the torque in the EPS system can characterize the steering wheel rotation, comparing the torque volatility with a preset volatility threshold can determine whether the vehicle is in a sharp turn or lane change during the current sampling period. When calculating the torque volatility, the torque for the current sampling period can be set to... And set the torque of the previous sampling period to ,at this time This refers to the torque volatility. When the torque volatility is greater than or equal to a preset volatility threshold, the operating condition of the current sampling period is determined to be a torque impact state; when the torque volatility is less than the preset volatility threshold, the operating condition of the current sampling period is determined to be a torque stable state.

[0093] Furthermore, during the actual operation of the EPS system, the motor may stall due to excessive resistance. When stalling occurs, the motor speed is low, and a large current input is maintained for an extended period. Therefore, when the motor current in the current sampling period is greater than 80% of the motor's rated current, this embodiment calculates the cumulative duration for which the motor current is greater than 80% of the rated current. If the cumulative duration is greater than a preset duration threshold and the motor speed is less than or equal to a preset speed threshold, it can be determined that the motor is currently in a stalled state. If the motor speed is greater than the preset speed threshold or the cumulative duration is less than the preset duration threshold, it can be determined that the motor is currently in a non-stalled state.

[0094] When the operating conditions in the current sampling period are stable torque and non-stalled, it can be determined that the vehicle is currently in a constant speed steering state and can obtain steady-state assistance. At this time, the probability of false Vds detection is extremely low. Therefore, the operating condition correction factor for the current sampling period can be set to 1, that is, the Vds voltage inference threshold is directly used as the comparison benchmark with the Vds voltage.

[0095] When the operating conditions in the current sampling period are torque impact and non-stalled, it can be determined that the vehicle is currently in a state of sudden load change such as sharp turn or lane change. At this time, there is a certain probability of false alarm in Vds detection. Therefore, the operating condition correction factor for the current sampling period can be set to 1.05, so as to appropriately increase the Vds voltage inference threshold obtained by fuzzy inference and reduce the probability of false alarm by means of the operating condition correction factor.

[0096] When the current sampling period is in a stable torque state or a stalled state, it can be determined that the vehicle is in a high-steering-resistance application scenario, such as turning the wheel while stationary or the tires getting stuck on a stone. In this case, there is a high probability of false alarms in Vds detection. Therefore, the operating condition correction factor for the current sampling period can be set to 1.1, thereby significantly improving the Vds voltage inference threshold obtained by fuzzy inference and reducing the probability of false alarms.

[0097] When the current sampling period is in a torque impact state or a stalled state, it can be determined that the vehicle is in a special condition with high steering resistance and sharp steering. At this time, there is a very high probability of false alarm in Vds detection. Therefore, the operating condition correction factor for the current sampling period can be set to 1.2. This will help to significantly improve the Vds voltage inference threshold obtained by fuzzy inference and prevent false alarms under special operating conditions.

[0098] For example, when correcting the Vds voltage inference threshold of the current sampling period using the operating condition correction factor of the current sampling period, the following formula can be used:

[0099] ;

[0100] in, Vds is the voltage inference threshold. For operating condition correction factors, To correct the result, when performing step S4, the corrected result should be used as the comparison benchmark for the current sampling period Vds voltage for subsequent comparison work.

[0101] Step S5: Compare the Vds voltage of the current sampling period with the Vds voltage inference threshold of the current sampling period, accumulate and record the number of comparisons, and accumulate and record the number of faults when the Vds voltage of the current sampling period is greater than the Vds voltage inference threshold of the current sampling period.

[0102] Once the Vds voltage inference threshold for the current sampling period is determined, a comparison can be made between the Vds voltage for the current sampling period and the Vds voltage inference threshold. If the Vds voltage is greater than the Vds voltage inference threshold, it can be determined that there is an overcurrent problem in the current sampling period; if the Vds voltage is less than or equal to the Vds voltage inference threshold, it can be determined that there is no overcurrent problem in the current sampling period.

[0103] However, due to the short duration of a single sampling period, directly determining the presence of overcurrent in the EPS system based solely on the comparison results of a single sampling period can easily lead to misjudgment in practical applications. Therefore, this embodiment should accumulate and record the number of comparisons when comparing the Vds voltage with the Vds voltage inference threshold for the current sampling period, and should also accumulate and record the number of faults when the Vds voltage exceeds the Vds voltage inference threshold. This allows for further improvement in the accuracy of the final judgment by utilizing the number of comparisons and faults.

[0104] Step S6: Repeat steps S2-S5 according to the preset time interval. When the number of faults is greater than the first preset threshold, disconnect the drive circuit of the EPS system. When the number of faults is less than the first preset threshold and the number of comparisons is greater than the second preset threshold, return to step S1.

[0105] To differentiate between multiple sampling periods and avoid misjudgments caused by continuous sampling, this embodiment repeats steps S2-S5 multiple times according to a preset time interval (e.g., 40μs) to accumulate the number of comparisons and faults. When the number of faults accumulates to a value greater than a first preset threshold, it indicates that the current EPS system does indeed have an overcurrent problem. In this case, the drive circuit of the EPS system should be disconnected to protect the EPS system. When the number of faults is less than the first preset threshold and the number of comparisons is greater than a second preset threshold, it indicates that the current EPS system does not have an overcurrent problem. In this case, the execution should return to step S1 to continuously monitor the real-time current and avoid continuously consuming computing power for calculating the Vds voltage inference threshold.

[0106] It should be noted that in this embodiment, the first preset number of times threshold should be less than the second preset number of times threshold, wherein the first preset number of times threshold can be set to 9 times and the second preset number of times threshold can be set to 15 times.

[0107] For example, in practical applications, the above tasks can be performed using a fault detection state machine. Specifically, the fault detection state machine can include four states: IDLE, START, RUN, and WAIT. IDLE indicates that detection is idle, START indicates that detection is started, RUN indicates that detection is in progress, and WAIT indicates that detection is waiting. The fault detection state machine should also contain a fault counter for accumulating and recording the number of faults, and a detection count counter for accumulating and recording the number of comparisons.

[0108] When the real-time current acquired in step S1 exceeds the preset current threshold, the fault detection state machine switches from the IDLE state to the START state to begin Vds detection. After completing the acquisition of various parameters in step S2, the fault detection state machine enters the RUN state to begin fuzzy inference of the Vds voltage inference threshold and comparison of the Vds voltage. At this time, the detection count counter increments the comparison count. If the Vds voltage is greater than the Vds voltage inference threshold, the fault counter increments the fault count; if the Vds voltage is less than or equal to the Vds voltage inference threshold, the fault counter does not increment the fault count. After completing the comparison of the Vds voltage with the Vds voltage inference threshold for one sampling cycle, the fault detection state machine enters the WAIT state, waits for a preset time interval, and then switches back to the START state, thus repeating steps S2-S5 in subsequent sampling cycles. When the number of faults accumulated by the fault counter exceeds the first preset threshold, it is determined that an overcurrent problem has occurred in the EPS system. At this time, the drive circuit is cut off, and the fault detection state machine switches to the IDLE state. When the number of faults accumulated by the fault counter is less than the first preset threshold, and the number of comparisons accumulated by the detection counter is greater than the second preset threshold, it is determined that the EPS system has not experienced an overcurrent problem. At this time, the fault detection state machine switches to the IDLE state and returns to continuously monitoring the real-time current of the EPS system.

[0109] This embodiment provides a short-time overcurrent protection method for an EPS system. When the real-time current of the EPS system exceeds a preset current threshold, it infers the Vds voltage inference threshold based on the system temperature and current change rate during the current sampling period. The Vds voltage is then compared with the Vds voltage inference threshold to achieve overcurrent detection in the EPS system. This effectively prevents changes in the impedance characteristics of the power circuit and parasitic inductance from affecting the actual judgment result, reducing the probability of false alarms and improving overall stability. Furthermore, this embodiment can determine the operating condition based on operating parameters, determine an operating condition correction factor based on the operating condition, and correct the Vds voltage inference threshold based on the operating condition correction factor, thereby improving the accuracy of subsequent comparisons in conjunction with the actual operating condition.

[0110] Example 2

[0111] Figure 2 This is a schematic diagram of the short-time overcurrent protection device for the EPS system provided in Embodiment 2 of the present invention, as shown below. Figure 2 As shown, the short-time overcurrent protection device of the EPS system includes:

[0112] Trigger module 210 is used to collect the real-time current of the EPS system, compare the real-time current with a preset current threshold, and execute steps S2-S5 when the real-time current is greater than the preset current threshold.

[0113] The acquisition module 220 is used to acquire the system temperature and Vds voltage in the current sampling period and calculate the current change rate in the current sampling period.

[0114] The inference module 230 is used to perform fuzzy inference based on the system temperature and the rate of change of current in the current sampling period to generate the Vds voltage inference threshold for the current sampling period.

[0115] The operating condition correction module 240 is used to obtain the operating condition parameters of the current sampling period, determine the operating condition status of the current sampling period based on the operating condition parameters of the current sampling period, and determine the operating condition correction factor of the current sampling period based on the operating condition status of the current sampling period; and correct the Vds voltage inference threshold of the current sampling period using the operating condition correction factor of the current sampling period.

[0116] The comparison module 250 is used to compare the Vds voltage of the current sampling period with the Vds voltage inference threshold of the current sampling period, accumulate and record the number of comparisons, and accumulate and record the number of faults when the Vds voltage of the current sampling period is greater than the Vds voltage inference threshold of the current sampling period.

[0117] The determination module 260 is used to cut off the drive circuit of the EPS system when the number of faults is greater than the first preset number threshold, and to return to the execution step S1 when the number of faults is less than the first preset number threshold and the comparison number is greater than the second preset number threshold.

[0118] Based on the above embodiments, the acquisition module includes:

[0119] The acquisition unit is used to obtain the real-time current of the previous sampling period and the real-time current of the current sampling period.

[0120] The first calculation unit is used to calculate the current difference between the real-time current of the current sampling period and the real-time current of the previous sampling period, and to calculate the time difference between the current sampling period and the previous sampling period.

[0121] The second calculation unit is used to calculate the ratio between the current difference and the time difference, and to determine the ratio as the current change rate of the current sampling period.

[0122] Based on the above embodiments, the inference module includes:

[0123] The fuzzification unit is used to fuzzify the system temperature and the rate of change of current in the current sampling period, respectively, to generate fuzzified results for temperature and fuzzified results for rate of change of current.

[0124] The inference unit is used to perform fuzzy inference on the temperature fuzzification result and the current change rate fuzzification result according to the preset fuzzy inference rules, and determine the fuzzy set of the Vds voltage inference threshold.

[0125] The defuzzing unit is used to defuzzify the fuzzy set of the Vds voltage inference threshold and generate the Vds voltage inference threshold for the current sampling period.

[0126] Based on the above embodiments,

[0127] The operating condition correction module also includes:

[0128] The torque state judgment unit is used to obtain the torque of the previous sampling period, calculate the torque fluctuation rate based on the torque of the current sampling period and the torque of the previous sampling period; when the torque fluctuation rate is greater than or equal to the preset fluctuation rate threshold, the operating condition of the current sampling period is determined to be the torque impact state; when the torque fluctuation rate is less than the preset fluctuation rate threshold, the operating condition of the current sampling period is determined to be the torque stable state.

[0129] The stall state determination unit is used to obtain the rated current value of the motor in the EPS system. When the motor current in the current sampling period is greater than 80% of the rated current value, it calculates the cumulative duration for which the motor current is greater than 80% of the rated current value. When the motor speed in the current sampling period is less than or equal to a preset speed threshold and the cumulative duration is greater than a preset duration threshold, the operating condition of the current sampling period is determined to be stall state. When the motor speed in the current sampling period is greater than the preset speed threshold or the cumulative duration is less than the preset duration threshold, the operating condition of the current sampling period is determined to be non-stall state.

[0130] The EPS system short-time overcurrent protection device provided in this embodiment of the invention can execute the EPS system short-time overcurrent protection method provided in this embodiment of the invention, and has the corresponding functional modules and beneficial effects of the method.

[0131] Example 3

[0132] Figure 3 This is a schematic diagram of the structure of a terminal provided in Embodiment 3 of the present invention. Figure 3 A block diagram of an exemplary device 12 suitable for implementing embodiments of the present invention is shown. Figure 3 The device 12 shown is merely an example and should not impose any limitations on the functionality and scope of use of the embodiments of the present invention.

[0133] like Figure 3 As shown, device 12 is represented as a general-purpose computing device. Components of device 12 may include, but are not limited to: one or more processors or processing units 16, system memory 28, and a bus 18 connecting different system components (including system memory 28 and processing unit 16).

[0134] Bus 18 represents one or more of several bus architectures, including a memory bus or memory controller, a peripheral bus, a graphics acceleration port, a processor, or a local bus using any of the various bus architectures. For example, these architectures include, but are not limited to, the Industry Standard Architecture (ISA) bus, the Micro Channel Architecture (MAC) bus, the Enhanced ISA bus, the Video Electronics Standards Association (VESA) local bus, and the Peripheral Component Interconnect (PCI) bus.

[0135] Device 12 typically includes a variety of computer system readable media. These media can be any available media that can be accessed by device 12, including volatile and non-volatile media, removable and non-removable media.

[0136] System memory 28 may include computer system readable media in the form of volatile memory, such as random access memory 30 and / or cache memory 32. Device 12 may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, storage system 34 may be used to read and write non-removable, non-volatile magnetic media ( Figure 3 Not shown; usually referred to as a "hard drive"). Although Figure 3 Not shown, a disk drive for reading and writing to a removable non-volatile disk (e.g., a "floppy disk") and an optical disk drive for reading and writing to a removable non-volatile optical disk (e.g., a CD-ROM, DVD-ROM, or other optical media) may be provided. In these cases, each drive may be connected to bus 18 via one or more data media interfaces. System memory 28 may include at least one program product having a set (e.g., at least one) of program modules configured to perform the functions of the embodiments of the present invention.

[0137] A program / utility 40 having a set (at least one) of program modules 42 may be stored, for example, in system memory 28. Such program modules 42 include, but are not limited to, an operating system, one or more application programs, other program modules, and program data. Each or some combination of these examples may include an implementation of a network environment. Program modules 42 typically perform the functions and / or methods described in the embodiments of the present invention.

[0138] Device 12 can also communicate with one or more external devices 14 (e.g., keyboard, pointing device, display 24, etc.), and with one or more devices that enable a user to interact with device 12, and / or with any device that enables device 12 to communicate with one or more other computing devices (e.g., network card, modem, etc.). This communication can be performed via input / output interface 22. Furthermore, device 12 can also communicate with one or more networks (e.g., local area network (LAN), wide area network (WAN), and / or public networks, such as the Internet) via network adapter 20. As shown, network adapter 20 communicates with other modules of device 12 via bus 18. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with device 12, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0139] The processing unit 16 executes various functional applications and data processing by running programs stored in the system memory 28, such as implementing the short-time overcurrent protection method for EPS systems provided in the embodiments of the present invention.

[0140] Example 4

[0141] Embodiment 4 of the present invention also provides a storage medium containing computer-executable instructions, which, when executed by a computer processor, are used to perform the short-time overcurrent protection method for EPS systems as described in any of the above embodiments.

[0142] The computer storage medium of this invention can be any combination of one or more computer-readable media. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: an electrical connection having one or more wires, a portable computer disk, a hard disk, a random access memory, 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 this document, a computer-readable storage medium can be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0143] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media may also be any computer-readable medium other than computer-readable storage media, capable of sending, propagating, or transmitting programs for use by or in connection with an instruction execution system, apparatus, or device.

[0144] Program code contained on a computer-readable medium may be transmitted using any suitable medium, including—but not limited to—wireless, wire, optical fiber, RF, etc., or any suitable combination thereof.

[0145] Computer program code for performing the operations of this invention can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, as well as 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 standalone 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 remote computers, the remote computer can be connected to the user's computer via 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).

[0146] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A short-time overcurrent protection method for an EPS system, characterized in that, Includes the following steps: S1. Collect the real-time current of the EPS system, compare the real-time current with the preset current threshold, and execute steps S2-S5 when the real-time current is greater than the preset current threshold. S2. Collect the system temperature and Vds voltage for the current sampling period, and calculate the current change rate for the current sampling period; S3. Perform fuzzy inference based on the system temperature and the rate of change of current in the current sampling period to generate the Vds voltage inference threshold for the current sampling period. S4. Obtain the operating parameters of the current sampling period, determine the operating status of the current sampling period based on the operating parameters of the current sampling period, and determine the operating correction factor of the current sampling period based on the operating status of the current sampling period. The Vds voltage inference threshold for the current sampling period is corrected by the operating condition correction factor for the current sampling period. S5. Compare the Vds voltage of the current sampling period with the Vds voltage inference threshold of the current sampling period, accumulate and record the number of comparisons, and accumulate and record the number of faults when the Vds voltage of the current sampling period is greater than the Vds voltage inference threshold of the current sampling period. S6. Repeat steps S2-S5 according to the preset time interval. When the number of faults is greater than the first preset threshold, disconnect the drive circuit of the EPS system. When the number of faults is less than the first preset threshold and the comparison number is greater than the second preset threshold, return to step S1.

2. The short-time overcurrent protection method for an EPS system according to claim 1, characterized in that: The calculation of the current change rate in the current sampling period includes: Obtain the real-time current of the previous sampling period and the real-time current of the current sampling period; Calculate the current difference between the real-time current of the current sampling period and the real-time current of the previous sampling period, and calculate the time difference between the current sampling period and the previous sampling period. Calculate the ratio between the current difference and the time difference, and determine the ratio as the rate of change of current in the current sampling period.

3. The short-time overcurrent protection method for an EPS system according to claim 1, characterized in that: The step of generating the Vds voltage inference threshold for the current sampling period by performing fuzzy inference based on the system temperature and the current change rate of the current sampling period includes: The system temperature and the rate of change of current in the current sampling period are fuzzified respectively to generate fuzzified results for temperature and fuzzified results for rate of change of current. Based on the preset fuzzy inference rules, fuzzy inference is performed on the fuzzification results of temperature and the fuzzification results of current change rate to determine the fuzzy set of Vds voltage inference threshold. The fuzzy set of Vds voltage inference thresholds is defuzzified to generate the Vds voltage inference threshold for the current sampling period.

4. The short-time overcurrent protection method for an EPS system according to claim 3, characterized in that: The fuzzification process uses a Gaussian membership function, the expression of which is: ； In the above formula, This represents the membership degree value. For input quantity, Center parameter, This is the diffusivity parameter; The defuzzing process employs the centroid method, whose expression is: ； In the above formula, The Vds voltage inference threshold for the current sampling period. To output discrete points in the universe of discourse, for membership degree Let be the number of fuzzy sets, and .

5. The short-time overcurrent protection method for an EPS system according to claim 1, characterized in that: The operating parameters for the current sampling period include: the torque, the motor speed, and the motor current for the current sampling period. Determining the operating condition status of the current sampling period based on the operating condition parameters of the current sampling period includes: Obtain the torque of the previous sampling period, and calculate the torque fluctuation rate based on the torque of the current sampling period and the torque of the previous sampling period. When the torque fluctuation rate is greater than or equal to the preset fluctuation rate threshold, the operating condition of the current sampling period is determined to be the torque impact state. When the torque fluctuation rate is less than the preset fluctuation rate threshold, the operating condition of the current sampling period is determined to be the torque stable state. Obtain the rated current value of the motor in the EPS system. When the motor current in the current sampling period is greater than 80% of the rated current value, calculate the cumulative duration for which the motor current is greater than 80% of the rated current value. When the motor speed in the current sampling period is less than or equal to a preset speed threshold and the cumulative duration is greater than a preset duration threshold, determine the operating condition of the current sampling period as a stalled state. When the motor speed in the current sampling period is greater than a preset speed threshold or the cumulative duration is less than a preset duration threshold, determine the operating condition of the current sampling period as a non-stalled state.

6. The short-time overcurrent protection method for an EPS system according to claim 5, characterized in that: The step of determining the operating condition correction factor for the current sampling period based on the operating condition status of the current sampling period includes: When the operating condition in the current sampling period is a torque stable state and a non-stalled state, the operating condition correction factor for the current sampling period is 1; When the operating condition in the current sampling period is a torque impact state and a non-stalled state, the operating condition correction factor for the current sampling period is 1.05; When the operating conditions in the current sampling period are torque stable state and stalled state, the operating condition correction factor for the current sampling period is 1.1; When the operating conditions in the current sampling period are torque impact and stall conditions, the operating condition correction factor for the current sampling period is 1.

2.

7. A short-time overcurrent protection device for an EPS system, characterized in that, include: The trigger module is used to collect the real-time current of the EPS system, compare the real-time current with a preset current threshold, and execute steps S2-S5 when the real-time current is greater than the preset current threshold. The acquisition module is used to acquire the system temperature and Vds voltage in the current sampling period and calculate the current change rate in the current sampling period. The inference module is used to perform fuzzy inference based on the system temperature and the rate of change of current in the current sampling period to generate the Vds voltage inference threshold for the current sampling period. The operating condition correction module is used to obtain the operating condition parameters of the current sampling period, determine the operating condition status of the current sampling period based on the operating condition parameters of the current sampling period, and determine the operating condition correction factor of the current sampling period based on the operating condition status of the current sampling period. The Vds voltage inference threshold for the current sampling period is corrected by the operating condition correction factor for the current sampling period. The comparison module is used to compare the Vds voltage of the current sampling period with the Vds voltage inference threshold of the current sampling period, accumulate and record the number of comparisons, and accumulate and record the number of faults when the Vds voltage of the current sampling period is greater than the Vds voltage inference threshold of the current sampling period. The determination module is used to cut off the drive circuit of the EPS system when the number of faults exceeds the first preset threshold number, and to return to the execution step S1 when the number of faults is less than the first preset threshold number and the comparison number is greater than the second preset threshold number.

8. A device, characterized in that, The device includes: One or more processors; Storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the short-time overcurrent protection method for EPS systems as described in any one of claims 1-6.

9. A storage medium containing computer-executable instructions, characterized in that: The computer-executable instructions, when executed by a computer processor, are used to perform the short-time overcurrent protection method for an EPS system as described in any one of claims 1-6.

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