Railway vehicle electromechanical brake motor controller overcurrent protection method and system

Abstract

The present application relates to a kind of rail vehicle electronic mechanical brake motor controller overcurrent protection method and system.Overcurrent protection system includes motor, three-phase full bridge circuit, switch tube, driver chip and MCU, the conduction control signal of switch tube is exported according to the drive signal output of driver chip;Overcurrent protection method adopts the protection method of combination of hardware and software, software protection is completed by MCU, and software protection method is compared by real-time calculation digital current cumulative value and current density value with cumulative current protection value and current density protection value respectively, control motor works in power-saving braking mode or protection braking mode.The present application calculates the total amount of sampling current in a certain time and the current density of long duration single braking process according to the actual working condition of controller, effectively protects current on the basis of guaranteeing system function and performance, improves the safety of system.

Description

Technical Field

[0001] This invention relates to the field of braking system control technology, and in particular to an overcurrent protection method and system for an electromechanical brake motor controller for rail vehicles. Background Technology

[0002] The commonly used friction braking methods for rail vehicles are air braking and hydraulic braking. By controlling the pressure of compressed air or hydraulic oil, the calipers are pushed to apply different pressures to the brake disc in order to achieve different braking forces.

[0003] In recent years, a new type of friction braking method has emerged: electromechanical braking. A schematic diagram of an electromechanical braking system is attached. Figure 1 As shown, electromechanical braking uses an electric motor as a power source, which drives the calipers to apply different pressures to the brake disc through the transmission of mechanical transmission mechanisms (reducers, lead screws, etc.).

[0004] When a motor controller drives a motor, current protection is involved. On the one hand, it prevents the motor from overheating or even burning out due to excessive current. On the other hand, it protects the circuits and components of the motor controller from damage.

[0005] There are two common methods for overcurrent protection: Hardware method: This method uses a voltage comparison circuit, employing a current transformer / sensor or current-sensing resistor to detect the current and convert it into a voltage. This voltage value is compared with a pre-set protection threshold voltage. When the voltage corresponding to the actual current exceeds the threshold voltage, protection is triggered, blocking the drive circuit to stop the motor drive. Software method: The acquired current signal (usually converted into an analog voltage signal) is sent to the MCU, where it is converted into a digital current value by software. This digital current value is compared with a pre-set protection value. If it exceeds the protection threshold, the software program stops outputting drive signals to the motor, thus providing software protection.

[0006] When an electromechanical braking system is operating, the motor operates in various modes: during the elimination of idle travel or backlash, it rotates at high speed under light load; during the clamping force control phase, the motor frequently reverses direction and stalls. Under these operating modes, the motor current is highly unstable, exhibiting large starting currents and chaotic pulse currents. Traditional methods using fixed threshold protection are insufficient to effectively protect the current while ensuring system functionality and performance. If the threshold is set too low, false protection is easily triggered, affecting system function; if the threshold is set too high, it is difficult to effectively protect the motor and controller, leading to damage to electromechanical braking system components and a shortened lifespan.

[0007] For example, the controller controls a maximum current spike of approximately 15A when starting the motor, while the current during motor operation generally does not exceed 8A; the selected switching transistor has a maximum current withstand capability of 47A. During frequent forward and reverse rotation of the motor, a large current pulse of 35A occurs, but its duration is only 1ms. Although this value is less than the maximum current withstand capability of the drive circuit's switching transistor, it is significantly greater than the normal starting and operating current of the motor. If the current protection threshold is set according to the actual operating current of the controller, such as 28A, this pulse current will trigger the overcurrent protection, causing the controller to temporarily lose its function. If the current threshold is set higher, such as 40A, and a large number of large current pulses occur frequently (such as between 25 and 39A), the overcurrent protection will not be triggered, but the system will clearly have an abnormal problem. Summary of the Invention

[0008] To address the shortcomings of related technologies, this invention provides an overcurrent protection method for an electromechanical brake motor controller for rail vehicles, which provides effective current protection while ensuring system functionality and performance, based on the actual operating conditions of the controller.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for overcurrent protection of an electromechanical brake motor controller for rail vehicles, wherein the motor input terminal is connected to the output terminal of a three-phase full-bridge circuit, the three-phase full-bridge circuit includes a switching transistor, the switching transistor is connected to a driver chip, and the driver chip outputs a conduction control signal for the switching transistor according to a drive signal;

[0011] The overcurrent protection method includes the following steps:

[0012] Detecting the output voltage V at the negative terminal of a three-phase full-bridge circuit i ;

[0013] The negative terminal output voltage V i Convert to digital current;

[0014] Calculate the cumulative value of digital current and the current density value;

[0015] Set the cumulative current protection value and the current density protection value;

[0016] The motor is protected by a control strategy, including a power-saving braking mode and a protective braking mode. The protective braking mode is set such that if the accumulated current value is greater than the accumulated current protection value, or the current density value is greater than the current density protection value, the motor is stopped after a delay.

[0017] In some embodiments of the present invention, calculating the cumulative value of digital current includes the following steps:

[0018] Every interval ts The digital current value is acquired once per time interval, and the cumulative value of the digital current value within the time interval is calculated: I t1 =I d1 +I d2 +…+I di +…+i dn ;

[0019] Where t1 is the real-time time window, i.e., the time period from the current moment forward, I di Let t be the current value collected in the i-th time interval, and n be the number of times the digital current value is collected within the time interval t1, where n = t1 / t s ;

[0020] The step of setting the accumulated current protection value further includes: determining the first accumulated current protection value I. P1-1 Second cumulative current protection value I P1-2 , and I P1-1 <I P1-2 ;

[0021] The steps for implementing a protective control strategy for the motor further include: if I P1-1 <i t1 ≤I P1-2 If this happens, an overcurrent warning will be triggered, and the motor will be controlled to operate in energy-saving braking mode.

[0022] If I t1 >I P1-2 If this occurs, the overcurrent protection will be triggered, the drive motor will be stopped after a delay, and the motor will be controlled to operate in the protective braking mode.

[0023] In some embodiments of the present invention, calculating the current density value includes the following steps:

[0024] Record the duration t2 of each braking process;

[0025] Set braking time threshold t L ;

[0026] If the duration t2 of the braking process exceeds the braking time threshold t L Then every interval t s The digital current value is acquired once per second and the current density is calculated in real time: I ds =(I d1 +I d2 +…+I di +…+I dm ) / m; where m is the number of times the digital current value is collected within the time period t2, m=t2 / t s ;

[0027] The step of setting the current density protection value further includes: determining the first current density protection value I.P2-1 Second current density protection value I P2-2 , and I P2-1 <I P2-2 ;

[0028] The steps for implementing a protective control strategy for the motor further include: if I P2-1 <i ds ≤I P2-2 If this happens, an overcurrent warning will be triggered, and the motor will be controlled to operate in energy-saving braking mode.

[0029] If I ds >I P2-2 If this occurs, the overcurrent protection will be triggered, the drive motor will be stopped after a delay, and the motor will be controlled to operate in the protective braking mode.

[0030] In some embodiments of the present invention

[0031] The first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are set according to the temperature of the switching transistor; when the temperature of the switching transistor rises, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are decreased; when the temperature of the switching transistor falls, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are increased.

[0032] And / or,

[0033] The first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are set according to the motor temperature; when the motor temperature rises, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are decreased; when the motor temperature falls, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are increased.

[0034] And / or,

[0035] The first current density protection value and the second current density protection value are set according to the duration of the braking process; when the duration of the braking process is extended, the first current density protection value and the second current density protection value are decreased; when the duration of the braking process is shortened, the first current density protection value and the second current density protection value are increased.

[0036] In some embodiments of the present invention, the following steps are further included:

[0037] The negative terminal output voltage V iIf the output voltage at the negative terminal is greater than the first protection threshold voltage V1, the output of the turn-on control signal to the switching transistor is stopped.

[0038] The value of the first protection threshold voltage V1 is determined based on the current withstand capability of the switching transistor.

[0039] In some embodiments of the present invention, the following steps are further included:

[0040] The negative terminal output voltage V i If the output voltage at the negative terminal is greater than the second protection threshold voltage V2, the output of the turn-on control signal to the switching transistor is stopped.

[0041] The value of the second protection threshold voltage V2 is determined based on the current withstand capability of the switching transistor and the temperature of the switching transistor. When the temperature of the switching transistor increases, the second protection threshold voltage decreases, and when the temperature of the switching transistor decreases, the second protection threshold voltage increases. The value of the second protection threshold voltage V2 is less than the first protection threshold voltage.

[0042] In some embodiments of the present invention

[0043] The negative terminal output voltage V i Before comparing with the first protection threshold voltage V1, do not output voltage V at the negative terminal. i Perform filtering processing;

[0044] The negative terminal output voltage V i Before comparing with the second protection threshold voltage V2, the output voltage V at the negative terminal is... i Perform filtering processing;

[0045] or;

[0046] The negative terminal output voltage V i Before comparing with the first protection threshold voltage V1, the output voltage V at the negative terminal is... i Perform the first filtering process;

[0047] The negative terminal output voltage V i Before comparing with the second protection threshold voltage V2, the output voltage V at the negative terminal is... i Perform a second filtering process;

[0048] The negative terminal output voltage V i The filtering time constant for the first filtering process is less than that for the negative terminal output voltage V. i The filtering time constant for the second filtering process.

[0049] In addition, the present invention also provides an overcurrent protection system for an electromechanical brake motor controller of a rail vehicle, used to implement the overcurrent protection method described in the present invention, the protection system comprising:

[0050] Three-phase full-bridge circuit: The output terminal of the three-phase full-bridge circuit is connected to the input terminal of the motor; the three-phase full-bridge circuit includes a switching transistor, which is connected to a driver chip. The driver chip outputs a conduction control signal to the switching transistor according to a drive signal. A current-sensing resistor is provided at the negative terminal of the three-phase full-bridge circuit to generate the negative terminal output voltage V. i ;

[0051] MCU: The input terminal of the MCU is connected to the negative terminal of the three-phase full-bridge circuit, and the output voltage V is connected to the negative terminal. i The current is converted into a digital current value; it is configured to calculate the current accumulation value and current density value based on the digital current value, and output a motor control strategy based on the current accumulation value and current density value and to output a drive signal.

[0052] Voltage Comparison Circuit: The voltage comparison circuit includes a reference power supply and a resistor path connected in series with the reference power supply. A thermistor is installed in the resistor path. The thermistor senses the temperature of the switching transistor and adjusts its resistance value based on the switching transistor temperature. The voltage comparison circuit outputs a second protection threshold voltage V2 signal at any position in the resistor path. The input terminal of the voltage comparison circuit is connected to the negative terminal of the three-phase full-bridge circuit, and the output voltage V is connected to the negative terminal. i The output terminal outputs the negative terminal voltage V. i Compare the signal with the second protection threshold voltage V2;

[0053] Drive signal circuit: Its input terminal is connected to the output terminal of the MCU to receive the drive signal; its input terminal is connected to the output terminal of the voltage comparator circuit, and is connected to the negative terminal of the output voltage V. i The signal is compared with the second protection threshold voltage V2, and based on the comparison signal, the output of a drive signal is controlled.

[0054] Driver chip: Its input terminal is connected to the output terminal of the drive signal circuit, and it outputs a switch control signal according to the drive signal.

[0055] In some embodiments of the present invention, the input terminal of the driver chip is connected to the negative terminal of a three-phase full-bridge circuit, and the negative terminal output voltage V is applied. i The signal is compared with the first protection threshold voltage V1 to generate a comparison signal. The driver chip outputs a control signal for turning on the switching transistor based on the comparison signal.

[0056] In some embodiments of the present invention, it further includes:

[0057] Signal conditioning circuit: Its input terminal is connected to the negative terminal of the three-phase full-bridge circuit, and the output voltage V is connected to the negative terminal. i , for V i Amplification is performed and a conditioning voltage V is output. ii ;

[0058] The input terminal of the voltage comparator circuit is connected to the output terminal of the signal conditioning circuit, and the conditioning voltage Vi is applied. i The output terminal outputs a conditioning voltage V. ii Compare the signal with the second protection threshold voltage V2;

[0059] The MCU input terminal is connected to the output terminal of the signal conditioning circuit and is supplied with the conditioning voltage V. ii The current is converted into a digital current value; the current accumulation value and current density value are calculated based on the digital current value, and the motor control strategy and drive signal are output.

[0060] Drive signal circuit: Its input terminal is connected to the MCU output terminal to receive the drive signal; its input terminal is connected to the output terminal of the voltage comparator circuit to receive the output conditioning voltage V. ii The signal is compared with the second protection threshold voltage V2, and based on the comparison signal, the output of a drive signal is controlled.

[0061] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0062] 1. Given the highly unstable current during motor operation, including large starting currents and chaotic pulse currents, the software program does not use methods such as fixed threshold single-time overcurrent protection or fixed threshold multiple-confirmation. Instead, it calculates the cumulative current value and current density value, and adjusts the corresponding current protection value according to the actual operating conditions of the controller. This provides effective current protection while ensuring system functionality and performance, resolving the contradiction between traditional protection methods and the inability to effectively balance current protection and normal system function.

[0063] 2. When a system experiences frequent bursts of large current pulses or prolonged periods of high current, the switching transistors and motor coils may overheat, damaging the components. This invention addresses this by calculating the total sampled current over a given time period and the current density during a single, prolonged braking process, based on the actual operating conditions of the controller. This provides effective current protection while maintaining system functionality and performance, thereby improving system safety.

[0064] 3. This invention provides a multi-protection method combining hardware and software. By utilizing the current characteristics of the motor driven by the electromechanical braking system, it provides graded protection for the switching transistors and the motor, effectively addressing various operating conditions such as circuit short circuits, motor coil short circuits, and component temperature changes. On the hardware side, there are dual protections with different protection thresholds. If one protection fails, the other can still protect the hardware. This ensures the overcurrent protection response speed while preventing false protection that could affect system functionality, thus improving the system's practicality and safety. Attached Figure Description

[0065] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0066] Figure 1 A schematic diagram of the components of an electromechanical braking system;

[0067] Figure 2 This is a schematic diagram of the current accumulation value calculation and control process of the present invention;

[0068] Figure 3 This is a schematic diagram of the current density value calculation and control process of the present invention;

[0069] Figure 4 This is a circuit block diagram of the overcurrent protection system of the present invention;

[0070] Figure 5a This is a typical circuit diagram of the protection threshold V2 in some embodiments of the present invention;

[0071] Figure 5b This is a typical circuit diagram of the protection threshold V2 in some embodiments of the present invention;

[0072] Figure 5c This is a typical circuit diagram of the protection threshold V2 in some embodiments of the present invention;

[0073] Figure 5d This is a typical circuit diagram of the protection threshold V2 in some embodiments of the present invention. Detailed Implementation

[0074] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0075] The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature.

[0076] As attached Figure 1 Appendix Figure 2 Appendix Figure 3 , Figure 4 As shown in an illustrative embodiment of the overcurrent protection method for an electromechanical brake motor controller of a rail vehicle according to the present invention, the motor input terminal is connected to the output terminal of a three-phase full-bridge circuit. The three-phase full-bridge circuit includes a switching transistor, which is connected to a driver chip. The driver chip outputs a conduction control signal for the switching transistor according to a drive signal.

[0077] Overcurrent protection methods include the following steps:

[0078] Detecting the output voltage V at the negative terminal of a three-phase full-bridge circuit i ;

[0079] The negative terminal output voltage V i Convert to digital current;

[0080] Calculate the cumulative value of digital current and the current density value;

[0081] Set the cumulative current protection value and the current density protection value;

[0082] The motor is protected by a control strategy, including a power-saving braking mode and a protective braking mode. The protective braking mode is set to delay stopping the motor drive if the accumulated current value is greater than the accumulated current protection value or the current density value is greater than the current density protection value.

[0083] The electromechanical brake motor controller using this method includes three control modes: normal mode, power-saving braking mode, and protective braking mode. In normal mode, the system operates normally with no large current generation, prioritizing braking performance; that is, the digital current value does not reach any current protection value. In power-saving braking mode, within the allowable / acceptable range of braking performance degradation, current reduction is prioritized. In protective braking mode, the drive motor stops after a certain delay.

[0084] The delay time for stopping the drive motor is Δt. d This allows time for the braking system to replenish braking force. For example, if the communication cycle between the motor controller and the brake control unit is 5ms, then after the controller uploads overcurrent protection information to the brake control unit, it takes another 5ms for the brake control unit to distribute and transmit the required additional braking force to other motor controllers; therefore, Δt dThe timing should begin from the first communication after the overcurrent protection occurs, and should be no less than 5ms.

[0085] Furthermore, the method for calculating the cumulative value of digital current includes the following steps:

[0086] Every interval t s The digital current value is collected once per time interval, and the cumulative value of the digital current value within the time interval is calculated: i t1 =I d1 +I d2 +…+I di +…+I dn ;

[0087] Where t1 is the real-time time window, i.e., the time period from the current moment forward. The t1 time period is longer than the current sampling time and can contain multiple sampling periods; I di Let t be the current value collected in the i-th time interval, and n be the number of times the digital current value is collected within the time interval t1, where n = t1 / t s ;

[0088] The step of setting the accumulated current protection value further includes: determining the first accumulated current protection value I. P1-1 Second cumulative current protection value I P1-2 , and I P1-1 <I P1-2 ;

[0089] The steps for implementing a protective control strategy for the motor further include: if I P1-1 <I t1 ≤I P1-2 If this happens, an overcurrent warning will be triggered, and the motor will be controlled to operate in energy-saving braking mode.

[0090] If i t1 >I P1-2 If this occurs, the overcurrent protection will be triggered, the drive motor will be stopped after a delay, and the motor will be controlled to operate in the protective braking mode.

[0091] For example: the maximum current spike when the controller starts the motor is about 15A, and the current when the motor is running under braking conditions generally does not exceed 8A; the maximum current withstand capability of the selected switching transistor is 47A.

[0092] The sampling period t of the current s =50us, time period t1=10ms, then the number of calculations n=200 times; cumulative current protection value I P1-1 =3400A, I P1-2 =3800A.

[0093] If several samples with a current of 30A or more appear in 200 samples, or even one sample with a current of 40A or more, but the other samples are relatively small, and the cumulative current value of 200 samples is 2750A, then the control mode will not be switched or the overcurrent protection will not be triggered.

[0094] If several samples with current exceeding 30A appear in 200 samples, while the other samples are smaller, and the cumulative current value of 200 samples is 3480A, then the control mode will be switched to power saving braking mode, but overcurrent protection will not be triggered.

[0095] If the cumulative current value after 200 samplings is 3890A, the overcurrent protection will be triggered, and the drive motor will be stopped after a delay.

[0096] Furthermore, the method for calculating the digital current density value includes the following steps:

[0097] Record the duration t2 of each braking process;

[0098] Set braking time threshold t L ;

[0099] If the duration t2 of the braking process exceeds the braking time threshold t L Then every interval t s The digital current value is acquired once per second and the current density is calculated in real time: I ds =(I d1 +I d2 +…+I di +…+I dm ) / m; where m is the number of times the digital current value is collected within the time period t2, m=t2 / t s ;

[0100] The step of setting the current density protection value further includes: determining the first current density protection value I. P2-1 Second current density protection value I P2-2 , and I P2-1 <I P2-2 ;

[0101] The steps for implementing a protective control strategy for the motor further include: if I P2-1 <I ds ≤I P2-2 If this happens, an overcurrent warning will be triggered, and the motor will be controlled to operate in energy-saving braking mode.

[0102] If I ds >I P2-2 If this occurs, the overcurrent protection will be triggered, the drive motor will be stopped after a delay, and the motor will be controlled to operate in the protective braking mode.

[0103] For example: the maximum current spike when the controller starts the motor is about 15A, and the current when the motor is running under braking conditions generally does not exceed 8A; the maximum current withstand capability of the selected switching transistor is 47A.

[0104] Braking time threshold t L =10s, current density protection value I P2-1 =10A, I P2-2 =11A.

[0105] If a braking time is long, exceeding 10 seconds, and the current density value calculated at 11 seconds is I... ds =8.7A, then no protection will be triggered; if the braking process lasts for 15 seconds, the calculated current density reaches I ds If the current is 10.1A, an overcurrent warning will be triggered, and the control algorithm will be switched to power-saving braking mode.

[0106] If the braking time exceeds 10 seconds, the current density value calculated at (10 seconds + 50 seconds) within the 10.05-second time interval is I. ds If the current is 11.3A, the overcurrent protection will be triggered, and the drive motor will be stopped after a delay.

[0107] In some embodiments, the values ​​of the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are determined with a certain margin based on the actual motor current when the system is operating normally.

[0108] In some embodiments, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are set according to the temperature of the switching transistor; when the temperature of the switching transistor rises, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are decreased; when the temperature of the switching transistor falls, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are increased.

[0109] In the above embodiment, the switching transistor is equipped with a heat sink, and the temperature of the switching transistor is fed back from the heat sink, with a first accumulated current protection value I. P1-1 For example, after adjusting according to the temperature of the switching transistor, it becomes I. PP1-1 ,

[0110] I PP1-1 =I P1-1 ×[1-c×(T r -T rb ) / T rb ], I PP1-1 ≮d×I P1-1 T r T represents the temperature of the heatsink for the switching transistor.rb denoted as the radiator temperature threshold, c as the temperature adjustment coefficient, and d as the adjustment coefficient for the lower limit of the first cumulative current protection value.

[0111] For example: First accumulated current protection value I P1-1 =3400A, radiator temperature threshold T rb =70℃, coefficient c=0.2, d=0.85.

[0112] When T r =65℃, I PP1-1 =I P1-1 =3400A remains unchanged;

[0113] When T r =75℃, I PP1-1 =3400×[1-0.5×(75-70) / 70]≈3279A;

[0114] When T r At 100℃, calculate I according to the above formula. PP1-1 ≈2671A, but at this time I PP1-1 <0.85×I P1-1 =2890A, then take I PP1-1 =2890A.

[0115] The second accumulated current protection value, the first current density protection value, and the second current density protection value, adjusted according to the switching transistor temperature, are determined in a similar manner to the first accumulated current protection value, and will not be elaborated upon here.

[0116] In some embodiments, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are set according to the motor temperature; when the motor temperature rises, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are decreased; when the motor temperature falls, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are increased.

[0117] In the above embodiment, the motor is equipped with a temperature sensor, and the motor temperature is fed back by the temperature sensor. The first accumulated current protection value, the second accumulated current protection value, the first current density protection value and the second current density protection value are adjusted according to the motor temperature. The method of obtaining the values ​​is similar to the method of adjusting the values ​​according to the temperature of the switching transistor, and will not be described in detail here.

[0118] In some embodiments, the first current density protection value and the second current density protection value are set according to the duration of the braking process; when the duration of the braking process is extended, the first current density protection value and the second current density protection value are reduced; when the duration of the braking process is shortened, the first current density protection value and the second current density protection value are increased.

[0119] In the above embodiment, the first current density protection value I is used. P2-1 For example, the first current density protection value after adjustment based on the duration of the braking process is I. PP2-1 ;

[0120] I PP2-1 =I P2-1 ×[1-a×(t2-t L ) / t L ], I PP2 -1≮b×I P2-1 Where t2 is the duration of the braking process, t L Here, 'a' is the braking time threshold, 'b' is the braking time adjustment coefficient, and 'b' is the adjustment coefficient for the lower limit of the first current density protection value.

[0121] For I P2-1 and I P2-2 The relationship with t2, with I P2-1 For example, coefficients a = 0.05 and b = 0.9.

[0122] For example: braking time threshold t L =10s, current density protection value I P2-1 =10A,

[0123] When t2 = 20s, I PP2-1 =10×[1-0.05×(20-10) / 10]=9.5A;

[0124] When t2 = 40s, I PP2-1 =8.5A, but at this time I PP2-1 <0.9×I P2-1 =9A, then take I PP2-1 =9A.

[0125] The second current density protection value is determined based on the braking process duration and the method of obtaining I. PP2-1 Similarly, this will not be elaborated upon here.

[0126] In some embodiments, the present invention further includes the following steps:

[0127] The negative terminal output voltage V iIf the output voltage at the negative terminal is greater than the first protection threshold voltage V1, the output of the turn-on control signal to the switching transistor is stopped.

[0128] The value of the first protection threshold voltage V1 is determined based on the current withstand capability of the switching transistor.

[0129] First protection threshold voltage V i The value is a pre-set protection threshold. When the negative terminal output voltage V corresponds to the actual current... i When the current exceeds V1, overcurrent protection is triggered, blocking the drive circuit to stop motor drive. The value of the first protection threshold voltage V1 is determined based on the overcurrent protection current value I1. i1 is determined based on the maximum withstand current capability of the switching transistor. i1 is the largest among all overcurrent protection current values ​​and can be close to the maximum withstand current of the switching transistor, for example, set to 85% of the maximum withstand current of the switching transistor. This protection provides the largest protection value for the switching transistor and the fastest protection speed, preventing damage to the switching transistor and burning of electrical components when faults such as circuit short circuits or motor coil short circuits occur, thus improving system safety.

[0130] Furthermore, the present invention also includes the following steps:

[0131] The negative terminal output voltage V i If the output voltage at the negative terminal is greater than the second protection threshold voltage V2, the output control signal to the switching transistor is stopped.

[0132] The value of the second protection threshold voltage V2 is determined based on the current withstand capability and temperature of the switching transistor. When the temperature of the switching transistor increases, the second protection threshold voltage decreases, and when the temperature of the switching transistor decreases, the second protection threshold voltage increases. The value of the second protection threshold voltage V2 is less than the first protection threshold voltage.

[0133] The value of the second protection threshold voltage V2 is a variable protection threshold, determined based on the overcurrent protection current value I2 and the temperature of the switching transistor. The switching transistor is equipped with a heat sink to provide feedback on the switching transistor temperature.

[0134] The overcurrent protection current value I2 is less than the overcurrent protection current value I1. For example, the overcurrent protection current value I2 is set to 60% of the maximum withstand current of the switching transistor, forming dual hardware protection with different protection thresholds to improve the system's safety performance. Since the withstand current capability of the switching transistor is related to its temperature, the withstand current capability is lower when the temperature is high and higher when the temperature is low. Therefore, when the temperature of the switching transistor is high, the overcurrent protection current value I2 is automatically reduced through temperature sampling, thereby protecting the controller hardware. Conversely, when the temperature of the switching transistor is low, the overcurrent protection current value I2 is automatically increased, allowing the controller to output a larger current. This allows the system to adapt to complex operating conditions while ensuring system performance, thus improving the system's durability and practicality.

[0135] In some embodiments, when the negative terminal output voltage V i Before comparing with the first protection threshold voltage V1, do not output voltage V to the negative terminal. i Perform filtering processing;

[0136] The negative terminal output voltage V i Before comparing with the second protection threshold voltage V2, the output voltage V at the negative terminal is... i Perform filtering processing;

[0137] or:

[0138] In some embodiments, when the negative terminal output voltage V i Before comparing with the first protection threshold voltage V1, the output voltage V at the negative terminal is... i Perform the first filtering process;

[0139] The negative terminal output voltage V i Before comparing with the second protection threshold voltage V2, the output voltage V at the negative terminal is... i Perform a second filtering process;

[0140] Output voltage V at the negative terminal i The filtering time constant for the first filtering process is less than the output voltage V at the negative terminal. i The filtering time constant for the second filtering process.

[0141] In the above embodiment, the negative terminal output voltage V i Before comparing with the first protection threshold voltage V1, the output voltage V at the negative terminal is... i The system can either not perform filtering or perform a first filtering process, wherein the first filtering process is a filtering measure with a filtering time constant. The filtering time constant is within the time that the switching transistor can withstand, so as to ensure that the system performs overcurrent protection in a very short time and improves the response speed.

[0142] Because the motor generates large starting currents and chaotic pulse currents when its operating mode changes, the duration of these large currents needs to be considered for V. i A second filtering process is performed to prevent false protection and affect system functionality. The filtering time constant of the first filtering process is smaller than that of the second filtering process, resulting in a time difference between the two overcurrent protections in the hardware. This enables dual hardware protection for the system, so that if one protection fails, the other can still protect the hardware, thus improving the overall security of the system.

[0143] As attached Figure 4As shown, the present invention also provides an overcurrent protection system for an electromechanical brake motor controller of a rail vehicle, used to implement the overcurrent protection method provided by the present invention. The overcurrent protection system includes:

[0144] Three-phase full-bridge circuit: The output terminal of the three-phase full-bridge circuit is connected to the input terminal of the motor; the three-phase full-bridge circuit includes a switching transistor, which is connected to a driver chip. The driver chip outputs a control signal to turn on the switching transistor according to the drive signal. A current-sensing resistor is set at the negative terminal of the three-phase full-bridge circuit to generate the negative terminal output voltage V. i ;

[0145] MCU: The MCU input is connected to the negative terminal of the three-phase full-bridge circuit, and the output voltage V is connected to the negative terminal. i The current is converted into a digital current value; it is configured to calculate the current accumulation value and current density value based on the digital current value, and output the motor control strategy based on the current accumulation value and current density value and use it to output the drive signal.

[0146] Voltage Comparison Circuit: The voltage comparison circuit includes a reference power supply and a resistor path connected in series with the reference power supply. A thermistor is installed in the resistor path to sense the temperature of the switching transistor and adjust its resistance value based on the switching transistor temperature. The voltage comparison circuit outputs a second protection threshold voltage V2 signal at any position in the resistor path. The input terminal of the voltage comparison circuit is connected to the negative terminal of the three-phase full-bridge circuit, and the output voltage V is connected to the negative terminal. i The output terminal outputs the negative terminal voltage V. i Compare the signal with the second protection threshold voltage V2;

[0147] Drive signal circuit: Its input terminal is connected to the MCU output terminal to receive the drive signal; its input terminal is connected to the output terminal of the voltage comparator circuit, and the negative terminal of the output voltage V is connected to it. i The signal is compared with the second protection threshold voltage V2, and based on the comparison signal, the output of the drive signal is controlled.

[0148] Driver chip: Its input terminal is connected to the output terminal of the drive signal circuit, and it outputs the switching control signal according to the drive signal.

[0149] The above embodiments include both hardware and software overcurrent protection methods. Hardware overcurrent protection: The switching transistor is equipped with a heatsink, and the transistor temperature is fed back from the heatsink. The second protection threshold voltage V2 is variable, caused by the resistance change of a thermistor (temperature sensor) connected in the circuit that senses the temperature of the switching transistor's heatsink. The voltage V2 is output through the negative terminal. i The comparison signal with the second protection threshold voltage V2 controls whether to output a drive signal to the driver, thereby controlling the conduction of the switching transistor and realizing overcurrent protection of the circuit hardware.

[0150] Software overcurrent protection: negative terminal output voltage V i Connect to the ADC pin of the MCU chip, and sample at a fixed time interval / sampling period (t). s V i The current signal is converted into a digital current value. The MCU is configured to calculate the cumulative current value and current density value based on the current signal, and output the motor control strategy (protective braking mode / energy-saving braking mode / normal mode) based on the cumulative current value and current density value. The software calculates the total sampled current over a certain period of time and the current density of a single braking process with a longer duration, and provides effective current protection based on the actual working conditions of the controller while ensuring the system's functionality and performance.

[0151] A typical circuit for generating the second protection threshold voltage V2 is shown in the attached figure. Figure 5a Appendix Figure 5b Appendix Figure 5c Appendix Figure 5d As shown, only four typical circuits are described here, and should not be construed as limiting the present invention.

[0152] In some embodiments, the drive signal is a PWM pulse signal, which eliminates the need for digital-to-analog conversion, saves space, and provides strong noise immunity. This description only illustrates one implementation of the drive signal and should not be construed as limiting the invention.

[0153] In some embodiments, the input terminal of the driver chip is connected to the negative terminal of the three-phase full-bridge circuit, and the negative terminal output voltage V is applied. i The signal is compared with the first protection threshold voltage V1 to generate a comparison signal. Based on this comparison signal, the driver chip outputs a control signal to turn on the switching transistor. The driver chip has an overcurrent protection pin for connecting the negative terminal output voltage V. i .

[0154] For example: the maximum current spike when the controller starts the motor is about 15A, and the current when the motor is running generally does not exceed 8A. The maximum current withstand capability of the switching transistor is 47A, the current sensing resistor is 10mΩ, the voltage signal connected to the driver chip has no filtering measures, the overcurrent protection pin action voltage of the driver chip is 0.4V, and the internal filtering time constant of the chip is 4us. Then, when the current exceeds 0.4V / 10mΩ≈40A and continues to exceed 4us, the driver chip will trigger the overcurrent protection and stop outputting the conduction control signal to the switching transistor.

[0155] In some embodiments, the overcurrent protection system further includes:

[0156] Signal conditioning circuit: Its input terminal is connected to the negative terminal of the three-phase full-bridge circuit, and the output voltage V is connected to the negative terminal. i , for V i Amplification is performed and a conditioning voltage V is output.ii ;

[0157] The input terminal of the voltage comparator circuit is connected to the output terminal of the signal conditioning circuit, and the conditioning voltage V is applied. ii The output terminal outputs a conditioning voltage V. ii Compare the signal with the second protection threshold voltage V2;

[0158] The MCU input is connected to the output of the signal conditioning circuit, and the conditioning voltage V is applied. ii The current is converted into a digital current value; the current accumulation value and current density value are calculated based on the digital current value, and the motor control strategy and drive signal are output.

[0159] Drive signal circuit: Its input terminal is connected to the MCU output terminal to receive the drive signal; its input terminal is connected to the output terminal of the voltage comparator circuit to receive the output conditioning voltage V. ii The signal is compared with the second protection threshold voltage V2, and based on the comparison signal, the output of the drive signal is controlled.

[0160] V i V is generated after processing by the signal conditioning circuit. ii This is to reduce noise and improve measurement accuracy and sensitivity. Figure 5a The protection threshold V2 shown is a typical circuit example:

[0161] The current sensing resistor is 10mΩ, the signal conditioning circuit has an amplification factor of 10, and the filter time constant is 1ms. The voltage comparator circuit has a reference voltage of 5V, resistor R1 = 2.4kΩ, and resistor R2 = 1kΩ. The temperature sensor resistor is an NTC type, with a resistance value of R at 80℃. T =1.8kΩ, the resistance at 40℃ is 2.3kΩ. Therefore, when the heatsink is at 80℃, the second protection threshold voltage V2 = 5 × (1 + 1.8) / (1 + 1.8 + 2.4) = 2.7V, and the corresponding current is (2.7V / 10) / 0.01Ω = 27A. When the current exceeds 27A and lasts for more than 1ms, current protection will be triggered, the voltage comparator circuit will output a comparison signal, and the PWM drive signal transmission of the drive signal circuit will be cut off. When the heatsink is at 40℃, the corresponding current is 29A; when the current exceeds 29A and lasts for more than 1ms, current protection will be triggered.

[0162] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0163] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for overcurrent protection of an electromechanical brake motor controller for rail vehicles, characterized in that, The motor input terminal is connected to the output terminal of a three-phase full-bridge circuit. The three-phase full-bridge circuit includes a switching transistor, which is connected to a driver chip. The driver chip outputs a conduction control signal for the switching transistor according to a drive signal. The overcurrent protection method includes the following steps: Detecting the output voltage at the negative terminal of a three-phase full-bridge circuit ; The negative terminal output voltage Convert to digital current; Calculate the cumulative value of digital current and the current density value; Set the cumulative current protection value and the current density protection value; The motor is protected by a control strategy, including a power-saving braking mode and a protective braking mode. The power-saving braking mode is configured to prioritize reducing current within an acceptable range of braking performance degradation. The protective braking mode is set to delay stopping the motor drive if the accumulated current value is greater than the accumulated current protection value or the current density value is greater than the current density protection value. Calculating the cumulative value of digital current includes the following steps: Each interval The digital current value is collected once every certain period of time, and the cumulative value of the digital current value within that period is calculated. ; in A real-time time window is a period of time moving backward from the current moment. For the first The current value collected this time. for The number of times the digital current value is collected within a time period. ; The step of setting the accumulated current protection value further includes: determining the first accumulated current protection value. Second cumulative current protection value ,and ; The steps for implementing a protective control strategy for the motor further include: if If this happens, an overcurrent warning will be triggered, and the motor will be controlled to operate in energy-saving braking mode. Calculating the current density value includes the following steps: Record the duration of each braking process. ; Set the threshold for each braking time. ; If the duration of the braking process Exceeding the braking time threshold Then each interval The digital current value is acquired once every few seconds and the current density is calculated in real time. ;in for The number of times the digital current is sampled within a time period. ; The step of setting the current density protection value further includes: determining the first current density protection value. Second current density protection value ,and ; The steps for implementing a protective control strategy for the motor further include: if If this occurs, an overcurrent warning will be triggered, and the motor will be controlled to operate in energy-saving braking mode.

2. The overcurrent protection method for the electromechanical brake motor controller of a rail vehicle as described in claim 1, characterized in that, like If this occurs, the overcurrent protection will be triggered, the drive motor will be stopped after a delay, and the motor will be controlled to operate in the protective braking mode.

3. The overcurrent protection method for the electromechanical brake motor controller of a rail vehicle as described in claim 1, characterized in that, like If this occurs, the overcurrent protection will be triggered, the drive motor will be stopped after a delay, and the motor will be controlled to operate in the protective braking mode.

4. The overcurrent protection method for the electromechanical brake motor controller of a rail vehicle as described in claim 2 or 3, characterized in that, The first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are set according to the temperature of the switching transistor; when the temperature of the switching transistor rises, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are decreased; when the temperature of the switching transistor falls, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are increased. And / or, The first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are set according to the temperature of the motor; when the motor temperature rises, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are decreased; when the motor temperature falls, the first accumulated current protection value, the second accumulated current protection value, the first current density protection value, and the second current density protection value are increased. And / or, The first current density protection value and the second current density protection value are set according to the duration of the braking process; when the duration of the braking process is extended, the first current density protection value and the second current density protection value are decreased; when the duration of the braking process is shortened, the first current density protection value and the second current density protection value are increased.

5. The overcurrent protection method for the electromechanical brake motor controller of a rail vehicle as described in claim 1, characterized in that, Further steps include: The negative terminal output voltage With the first protection threshold voltage Comparison: If the output voltage at the negative terminal is greater than the first protection threshold voltage... Then stop outputting the turn-on control signal to the switching transistor; First protection threshold voltage The value is determined based on the current withstand capability of the switching transistor.

6. The overcurrent protection method for the electromechanical brake motor controller of a rail vehicle as described in claim 5, characterized in that, Further steps include: The negative terminal output voltage With the second protection threshold voltage If the output voltage at the negative terminal is greater than the second protection threshold voltage, then... Then stop outputting the turn-on control signal to the switching transistor; Second protection threshold voltage The value is determined based on the current withstand capability of the switching transistor and the temperature of the switching transistor. When the temperature of the switching transistor increases, the second protection threshold voltage is decreased; when the temperature of the switching transistor decreases, the second protection threshold voltage is increased. Second protection threshold voltage The value is less than the first protection threshold voltage.

7. The overcurrent protection method for the electromechanical brake motor controller of a rail vehicle as described in claim 6, characterized in that, The negative terminal output voltage With the first protection threshold voltage Before comparison, do not output voltage at the negative terminal. Perform filtering processing; The negative terminal output voltage With the second protection threshold voltage Before comparison, the output voltage of the negative terminal is... Perform filtering processing; or; The negative terminal output voltage With the first protection threshold voltage Before comparison, the output voltage of the negative terminal is... Perform the first filtering process; The negative terminal output voltage With the second protection threshold voltage Before comparison, the output voltage of the negative terminal is... Perform a second filtering process; Output voltage at the negative terminal The filtering time constant for the first filtering process is less than that for the output voltage at the negative terminal. The filtering time constant for the second filtering process.

8. An overcurrent protection system for an electromechanical brake motor controller of a rail vehicle, used to implement the overcurrent protection method according to any one of claims 1-7, characterized in that, The protection system includes: Three-phase full-bridge circuit: The output terminal of the three-phase full-bridge circuit is connected to the input terminal of the motor; the three-phase full-bridge circuit includes a switching transistor, which is connected to a driver chip. The driver chip outputs a conduction control signal to the switching transistor according to a drive signal. A current-sensing resistor is provided at the negative terminal of the three-phase full-bridge circuit to generate the negative terminal output voltage. ; MCU: The input terminal of the MCU is connected to the negative terminal of the three-phase full-bridge circuit, and the output voltage is connected to the negative terminal. The current is converted into a digital current value; it is configured to calculate the current accumulation value and current density value based on the digital current value, and output a motor control strategy based on the current accumulation value and current density value and to output a drive signal. Voltage Comparison Circuit: The voltage comparison circuit includes a reference power supply and a resistor path connected in series with the reference power supply. A thermistor is provided in the resistor path. The thermistor senses the temperature of the switching transistor and adjusts its resistance value based on the switching transistor temperature. The voltage comparison circuit outputs a second protection threshold voltage at any position in the resistor path. The signal; the input terminal of the voltage comparator circuit is connected to the negative terminal of the three-phase full-bridge circuit, and the output voltage is connected to the negative terminal. The output terminal outputs the negative terminal voltage. With the second protection threshold voltage Compare signals; Drive signal circuit: Its input terminal is connected to the output terminal of the MCU to receive the drive signal; its input terminal is connected to the output terminal of the voltage comparator circuit, and the negative terminal of the output voltage is connected to it. With the second protection threshold voltage Compare the signal, and based on the comparison signal, control whether to output a drive signal; Driver chip: Its input terminal is connected to the output terminal of the drive signal circuit, and it outputs a switch control signal according to the drive signal.

9. The overcurrent protection system for the electromechanical brake motor controller of a rail vehicle as described in claim 8, characterized in that, The input terminal of the driver chip is connected to the negative terminal of the three-phase full-bridge circuit, and the output voltage is connected to the negative terminal. and with the first protection threshold voltage The comparison generates a comparison signal, and the driver chip outputs a control signal for turning on the switching transistor based on the comparison signal.

10. The overcurrent protection system for the electromechanical brake motor controller of a rail vehicle as described in claim 9, characterized in that, Also includes: Signal conditioning circuit: Its input terminal is connected to the negative terminal of the three-phase full-bridge circuit, and the output voltage is connected to the negative terminal. ,right Amplification and conditioning voltage output ; The input terminal of the voltage comparator circuit is connected to the output terminal of the signal conditioning circuit, and a conditioning voltage is applied. Output signal conditioning voltage With the second protection threshold voltage Compare signals; The MCU input terminal is connected to the output terminal of the signal conditioning circuit and supplied with the conditioning voltage. The current is converted into a digital current value; the current accumulation value and current density value are calculated based on the digital current value, and the motor control strategy and drive signal are output. Drive signal circuit: Its input terminal is connected to the MCU output terminal to receive the drive signal; its input terminal is connected to the output terminal of the voltage comparator circuit to receive the output conditioning voltage. With the second protection threshold voltage The comparison signal is used to control whether to output a drive signal based on the comparison signal.

Images