CN117544066B - Half-locked-rotor protection method for steering motor in EPS system - Google Patents

Half-locked-rotor protection method for steering motor in EPS system Download PDF

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Publication number
CN117544066B
CN117544066B CN202410026384.8A CN202410026384A CN117544066B CN 117544066 B CN117544066 B CN 117544066B CN 202410026384 A CN202410026384 A CN 202410026384A CN 117544066 B CN117544066 B CN 117544066B
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value
interval
increment
mosfet
current
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CN117544066A (en
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平霞
沈敬祖
刘忆博
安海超
王豪
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Tianjin Dexing Intelligent Technology Co ltd
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Tianjin Dexing Intelligent Technology Co ltd
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
    • B62D5/046—Controlling the motor
    • B62D5/0463—Controlling the motor calculating assisting torque from the motor based on driver input
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
    • H02H7/0833—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors for electric motors with control arrangements
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
    • H02P29/02—Providing protection against overload without automatic interruption of supply
    • H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
    • H02P29/02—Providing protection against overload without automatic interruption of supply
    • H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
    • H02P29/027—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load the fault being an over-current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
    • H02P29/02—Providing protection against overload without automatic interruption of supply
    • H02P29/024—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
    • H02P29/028—Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load the motor continuing operation despite the fault condition, e.g. eliminating, compensating for or remedying the fault
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P29/00—Arrangements for regulating or controlling electric motors, appropriate for both AC and DC motors
    • H02P29/60—Controlling or determining the temperature of the motor or of the drive
    • H02P29/68—Controlling or determining the temperature of the motor or of the drive based on the temperature of a drive component or a semiconductor component

Abstract

The invention provides a half-locked-rotor protection method of a steering motor in an EPS system, which is characterized in that a safety state variable S is arranged for each MOSFET, the safety state variable S is mapped to each MOSFET through a certain rule according to the real-time current condition of each MOSFET and the environmental temperature value of the MOSFET, and whether protection is started or not and the protection degree is set are determined by judging the safety state variable S. The invention is based on the safety state variables of each MOSFETSWhether the system starts capacity reduction protection or not is judged by the change of the power steering system, the capacity reduction ratio is dynamically changed, and the real-time performance and the reliability of self-protection of the EPS steering system after half locked rotation are improved; the dynamic change of the capacity reduction ratio realizes smooth and fine steering hand feeling without fluctuation of hand feeling under the capacity reduction protection strategy, and ensures the maneuvering performance of the EPS under the half locked-rotor state.

Description

Half-locked-rotor protection method for steering motor in EPS system
Technical Field
The invention belongs to the technical field of motor vehicles, IPC classification belongs to the subclass B62D, and also belongs to the technical field of control or regulation of motors with the IPC classification number of H02P, and particularly relates to a semi-locked rotor protection method of a steering motor in an EPS system.
Background
In the prior art, anti-blocking protection of an EPS system (electric power steering, EPS, electric power steering system) is generally aimed at a condition that a steering motor is knocked to the end of a steering wheel (commonly referred to as steering wheel is knocked down) or is in a stuck condition, and the condition is referred to as a locked-up condition, and an anti-blocking strategy is started by the EPS system to prevent devices in the system from being burned down to cause paralysis of a steering gear. However, there is a working condition that the steering wheel is not stuck completely even though the steering wheel is not hit to the tail end when the vehicle is in a mud pit or a low-lying area, but the driver continuously rotates the steering wheel in a small angle range, and the working condition is called a half locked-rotor working condition.
Under the semi-locked-rotor working condition, the controller continuously outputs large torque, the current flowing through the MOSFET (Metal Oxide Semiconductor Field Effect Transistor, metal-oxide semiconductor field effect transistor) in the EPS system is increased rapidly in a very short time, the junction temperature of the MOSFET is increased rapidly, the temperature-current characteristic of the MOSFET is that the resistance of the MOSFET is increased along with the increase of the temperature of the MOSFET, and the overcurrent capacity of the MOSFET is reduced. Meanwhile, the environment temperature of the MOSFET can influence the heat dissipation power of the MOSFET, and the higher the environment temperature is, the slower the heat dissipation of the MOSFET is, so that the MOSFET is more easily burnt.
In EPS systems, 6 MOSFETs are typically provided on the circuit board of the EPS controller for current, power, fault tolerance, and heat dissipation and thermal management requirements, as shown in fig. 1. Since the 6 MOSFETs are operated cooperatively, each MOSFET cannot be burned out after half-stall occurs. However, the anti-rotation strategy in the prior art generally only monitors the temperature change of the temperature sensor and the three-phase current change of the motor, and the three-phase current of the motor is synthesized after 6 MOSFETs, so that the delay of the reaction time exists, and the hidden danger that the three-phase current of the motor meets the requirements, but the single MOSFET is in a dangerous state, namely the hidden danger that the anti-rotation strategy in the prior art is not timely and accurate exists.
Disclosure of Invention
In view of this, the present invention provides a half locked-rotor protection method for a steering motor in an EPS system, which specifically includes:
in order to monitor the safety state of 6 MOSFETs in an EPS system controller in real time, the invention sets a safety state variable S for each MOSFET, maps the safety state variable S of each MOSFET according to the real-time current condition of each MOSFET and the environmental temperature value of the MOSFET by a certain rule, and determines whether to start protection and set the protection degree by judging the safety state variable S.
The method of the invention comprises the following steps:
calculating to obtain effective currents and values i_add corresponding to 6 MOSFETs of the steering controller respectively and an environment temperature value T common to all MOSFETs;
the detection period t=δ×m, wherein δ is a control period of the steering controller, and m is a positive integer greater than 1;
the common ambient temperature value t of all MOSFETs is a temperature value measured by a temperature sensor which is positioned on the same control circuit board as the 6 MOSFETs of the steering controller;
the effective current and value i_add of a single MOSFET flowing through itself in a single detection period T are calculated according to equation 1:
formula 1;
wherein I is i Sampling the value of the current M for a single MOSFET in a control period delta i For the PWM duty cycle of the control period δ, i is a positive integer from 1 to m;
searching a pre-established effective current and value interval index table according to the effective current and value i_add flowing through a single MOSFET in the current detection period T, judging an interval to which the effective current and value i_add belong, and obtaining a current heat increment delta_i corresponding to the interval;
searching a pre-established index table of the environmental temperature value interval according to the environmental temperature value T of the current detection period T, and judging the environmental temperature valuetThe temperature heat increment delta_t corresponding to the interval is obtained;
the safe state variable S for each MOSFET is obtained by calculation according to equation 2:
formula 2;
in formula 2, S last The sum of the current heat increment delta_i and the temperature heat increment delta_t of all detection periods before the current detection period;
if the safety state variable S of any one of the 6 MOSFETs is greater than or equal to the preset pre-start threshold S on And then the capacitance reduction ratio k of the MOSFET in the detection period is obtained through calculation according to the formula 3:
formula 3;
the maximum value of the safety state variable S does not exceed the preset capacity reduction limit threshold S keep ；
The buck-to-capacitive ratio of each detection cycle to 6 MOSFETskComparing, selecting the minimum volume reduction ratiokTo reduce the given target current on the q-axis and ensure that each MOSFET is not burned out.
Further, the creating rule of the effective current and value interval index table is:
dividing the effective current sum value into at least 10 intervals, see equation 4:
formula 4;
in the method, in the process of the invention,is the interval limit value, and->Sequentially increasing (I) in (I)>For each interval, the converted current heat increment value is corresponding to the current heat increment value, and +.>Sequentially increasing the steps; of at least 10 intervals, including:
one interval (negative increment interval) in which the increment value is negative: i_add<i 1 The method comprises the steps of carrying out a first treatment on the surface of the Meaning of setting negative increment interval: i.e 1 To test the absolute safe current of the selected MOSFET, even if half-locked rotation occurs, only the i_add of the MOSFET<i 1 Even if the MOSFET is in a half locked-rotor working condition for a long time, the MOSFET cannot be burnt out, so that the current heat increment value of a negative value obtained by corresponding conversion in a negative increment interval cannot cause erroneous judgment due to infinite increase of a safety state variable S; the reason why the ambient temperature value interval index table sets the negative increment interval is similar.
A zero increment interval with an increment value equal to zero:the method comprises the steps of carrying out a first treatment on the surface of the This interval may be referred to as a buffer interval, and is set for the reason that the system makes the determination of the half-stall state more explicit. If this interval is not set, when iadd current at i 1 When the vicinity is slightly changed, the increment will jump back and forth between a negative value and a positive value, so this is set The buffer interval can be more clearly defined as i/uIncremental change is carried out after the change trend of add; the reason why the ambient temperature value interval index table sets this interval is similar.
A maximum delta interval with delta value greater than zero and being the maximum delta value: i_add>i n ；
The remaining number of intermediate intervals are sequentially distributed between the zero increment interval and the maximum increment interval.
Further, the method comprises the steps of,the setting rules of (1) are:
i 1 which is the absolute safe effective current value of the selected MOSFET; even if half-locked rotation occurs, only the i_add of the MOSFET is needed<i 1 Even if the MOSFET is in a half locked-rotor working condition for a long time, the MOSFET can not be burnt. i.e 1 Specific numerical values of the components are testedDuring the experiment, different current flows into the MOSFETs at room temperature (usually 25 ℃), the temperature of the measured MOSFETs is detected by using a temperature gun, and the effective current value of the corresponding MOSFETs is set to be i when the temperature of the temperature gun is not changed 1。
i 2 The setting rules are as follows: according to the experiment, it is matched withSatisfy->；
i n Which is the maximum effective current value that the selected MOSFET can withstand; i_add>i n In the interval, the heat dissipation efficiency of the MOSFET is extremely low, so that the MOSFET is burnt out in a short time without taking protective measures under the working condition. The MOSFET data reference manual used in the experiment is marked with the maximum effective current value which can be born by the MOSFET of the type, and according to practical use experience, 2/3 of the maximum effective current value marked by the general reference manual is the maximum effective current value which can be born by the MOSFET in the practical use process.
i 2 And i n The remaining interval limit value between the two intervals is satisfied that each remaining intermediate interval is uniformly distributed between a zero increment interval and a maximum increment interval; the more evenly and densely the intermediate intervals are divided through experiments, the better the half-locked rotor protection effect is.
Further, the current heat increment value converted correspondingly in each section in the effective current and value section index tableThe setting rules of (1) are:
the current heat increment value a corresponding to the conversion of the negative increment interval 1 Set to a negative value less than zero and greater than-5; the aim is to bring S slowly back to zero, the driver perceiving a sense of force build-up.
Converted current thermal increment value a corresponding to zero increment interval 2 Set to zero;
current heat increment value a converted corresponding to maximum increment interval n Is arranged between more than or equal to 20 and less than or equal to 25; this interval of values is determined experimentally ifExcessive values of (c) can lead to the immediate half-locked-rotor protection when the MOSFET is not damaged yet, and the target current of the q-axis is rapidly reduced.
The current heat increment value of each middle interval is a 2 And a n The values are uniformly taken.
Further, the creating rule of the index table of the environmental temperature value interval is as follows:
dividing the ambient temperature value into at least 5 intervals, see formula 5:
formula 5;
in the method, in the process of the invention,is the interval limit value, and->Sequentially increasing (I) in (I)>The temperature increment value converted for each interval is corresponding to the temperature increment value, and +.>Sequentially increasing the steps; of at least 5 intervals, including:
a negative increment interval in which the increment value is negative: t is t<t 1 The method comprises the steps of carrying out a first treatment on the surface of the Wherein t is 1 Set to 0, the interval corresponds to the converted temperature heat increment b 1 Set to between-5 and 0; in this interval, the ambient temperature is less than zero and the heat dissipation efficiency is high, so the increment is set to be negative to reduce S.
A zero increment interval with an increment value equal to zero:the method comprises the steps of carrying out a first treatment on the surface of the The temperature heat increment b corresponding to the conversion of the interval 2 Zero; wherein t is 2 The setting rules of (1) are: at ambient temperature t +.>When the temperature sensor is used, the heat generation and the heat dissipation of the MOSFET are balanced, and the temperature sensor can be obtained by detecting the ambient temperature of the MOSFET in real time by using a temperature gun or a thermocouple;
a maximum delta interval with delta value greater than zero and being the maximum delta value:the method comprises the steps of carrying out a first treatment on the surface of the T is t of n Reference is made to the data manual of the MOSFETs used, which provides an ambient temperature value corresponding to the time when the heat dissipation efficiency of the MOSFETs is the lowest, and the ambient temperature value is set as t n The interval corresponds to the converted temperature heat increment value b n Between 10 and 15; since S is determined by both the current and the ambient temperature, but the ambient temperature is less affected than the current, the temperature rise value b n Less than the current thermal increment value a n 。
The interval limit value of the rest number of intervals (intermediate intervals) is satisfied so that each intermediate interval is sequentially and uniformly distributed between the zero increment interval and the maximum increment interval, and the temperature heat increment value of each intermediate interval is b 2 And b n The rule of the uniform value is used as the corresponding temperature heat increment value of each middle interval. The more uniform and dense the intermediate intervals are divided, the better the semi-locked rotor protection effect is.
The invention can not only timely identify whether the motor enters a half locked-rotor state or not and judge whether the half locked-rotor capacity-reducing protection is started, but also enable the steering gear to transition to a safe state by reducing the given q-axis target current; based on the safety state variables of each MOSFETSWhether the system starts capacity reduction protection or not is judged by the change of the power steering system, the capacity reduction ratio is dynamically changed, and the real-time performance and the reliability of self-protection of the EPS steering system after half locked rotation are improved; the dynamic change of the volume reduction ratio realizes smooth and fine steering hand feeling without hand feeling under the volume reduction protection strategyFluctuation ensures the steering performance of the EPS in a half locked-rotor state.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention.
Fig. 1 is a schematic diagram of a setup circuit of 6 MOSFETs in an EPS controller circuit board.
Detailed Description
It should be noted that, without conflict, the embodiments of the present invention and features of the embodiments may be combined with each other.
The invention provides a method for reducing capacity to protect MOSFET from being burnt when half locked rotation occurs in EPS steering system and realization. After EPS is blocked, judging whether the steering system starts capacity-reducing protection or not by calculating the safety state variable S of each MOSFET, if the variable S reaches the pre-starting threshold value of capacity-reducing protectionI.e. +.>Then calculate the volume-decreasing ratiokSelecting all MOSFET decreasing capacity ratioskTo reduce the target given current of the q-axis.
The embodiment is realized based on an EPS controller taking R7F701382 of Renesas company as a main MCU, the steering motor adopts a three-pair-pole non-salient pole Permanent Magnet Synchronous Motor (PMSM), the torque is 5.0 N.m, and the rated rotation speed is 950R/min.
In this embodiment, the detection period is set to 10ms, and the control period of the EPS controller is 80So every detection period, the EPS controller passes 125 control periods. Dividing the effective current value of each MOSFET in one detection periodAnd add up to obtain iadd, index table pair i according to effective current and value intervalAnd carrying out interval judgment by_add to obtain the increment delta_i of the safety state variable S. The effective current and value interval index table of this embodiment has 9 intervals in total for i_add, as shown in the following equation 6:
formula 6;
the calculation of each interval value of i_add is as follows:
interval boundary value=mosfet effective current value 125 PWM duty cycle
For each MOSFET, the effective current values of the control periods in the detection period are different, the corresponding PWM duty ratios are also different, and the different voltage durations correspond to the different PWM duty ratios because the PWM duty ratios are the voltage acting durations applied to the corresponding MOSFETs, so that the different current effective values are obtained. Assuming that the effective current value of the MOSFET remains unchanged during one detection period, and that the effective current values of the MOSFETs are 150A, 140A, 130A, 120A, 110A, 100A, 90A, 80A, 70A, respectively, the boundary values of the intervals corresponding to i_add are 13000, 12000, 11000, 1000, 9000, 8000, 7000, 6000, 5000. For the model MOSFET used in this experiment, the decrease in effective current values of 150A, 140A, 130A, 120A, 110A, 100A, 90A, 80A, 70A also represents a decrease in the current hazard level of the MOSFET. 150A and above represent that the current condition of the MOSFET is very dangerous, and 70A and below represent that the current of the MOSFET enters a relatively safe zone, so that the value of the delta_i corresponding to the effective current zone of 150A and above is the largest, and the value of the delta_i corresponding to the zone of 70A and below is the smallest. A larger delta_i represents a more dangerous state of the MOSFET at this time, and the faster the safe state variable S reaches the pre-opening value of the buck-boost. The setting of the value of deltai is not unique and follows the principle that the larger the i_add is, the larger the deltai is in one detection period. In addition, the ideal interval limit value, interval step length and interval number which accord with the MOSFET model can be obtained through experiments by selecting the interval limit value, the interval number and the range size of each interval. Through experimental tests, the finer and uniform division of the intervals is, and the better the actual effect is.
The negative increment interval i_add <5000 is set, because when the effective current value of the MOSFET in one detection period is less than 70A, the MOSFET is in a relatively safe current state without opening capacity reduction protection, and if the safety state variable value S accumulated before is larger, the value of the safety state variable value S is gradually reduced by a negative increment value, so that the steering system gradually exits the capacity reduction protection, and the power assistance is recovered. If the effective current of the MOSFET is always below 70A, the value of the safety state variable S will not decrease infinitely, and setting the minimum value of the variable S to 0 in the program will avoid negative values of the safety state variable S due to negative delta_i obtained by consecutive detection periods.
The section of (1) is a buffer section, if the value of i_add falls in the section. If the next detection period's delta i is negative, it is indicated that the MOSFET is in a relatively safe section, and if the next detection period's delta i is positive, it is indicated that the MOSFET current is rising, and this buffer section is provided for the purpose of making the system more explicit in the determination of the half-stall condition.
The index table of the environmental temperature value interval in this embodiment is provided with 5 intervals in total, as shown in the following formula 7:
formula 7;
ambient temperature shared by MOSFETs of current detection periodtThe higher the corresponding converted temperature delta deltat is, the larger.
When the ambient temperature is greater than or equal to 105 ℃, the heat dissipation speed of the MOSFET is very slow at the temperature, and the overcurrent capacity of the MOSFET is also greatly reduced due to the high ambient temperature, so that the state of the MOSFET is very dangerous at the high ambient temperature, the corresponding converted temperature heat increment value is also maximum, and the larger temperature heat increment value can enable the safety state variable S to reach the pre-opening value S of capacity reduction protection more quickly on Protecting the MOSFET from being burned. The lower the temperature, the faster the heat dissipation of the MOSFET, so the smaller the corresponding temperature delta value. When the ambient temperature is below 0 ℃, the heat dissipation condition of the MOSFET is optimistic, so thatThe value of the setting deltat is negative. Setting an interval limit value, an interval number and a temperature heat increment value converted correspondingly in each interval of an environment temperature value interval index table according to the actual used MOSFET model; according to the principle that the higher the ambient temperature is, the more difficult the heat dissipation is, and the larger the temperature heat increment value of the corresponding conversion of the interval is, the setting is carried out. The proper interval limit value, interval number and temperature heat increment value corresponding to each interval can be measured through experiments. Through experiments, the finer and uniform division of the temperature interval can be obtained, and the better the actual effect can be.
And (3) calculating a reduction ratio k:
pre-opening threshold S on =1000 and capacitance-reduction limit threshold S keep =6000, the initial value of the decreasing capacitance ratio k is 1, and the minimum value in the decreasing capacitance ratio k is selected as the final decreasing capacitance ratio to reduce the given target current of the q axis for decreasing capacitance protection in each detection period.
According to the invention, through periodically detecting the current of the MOSFET and the environmental temperature of the MOSFET, each detection period is used for judging whether the steering system is in a semi-locked state and whether the pre-starting threshold of capacity reduction protection is reached, if the system reaches the pre-starting threshold of capacity reduction protection, the capacity reduction ratio k is calculated, and the final capacity reduction ratio is selected to reduce the target given current of the q-axis. The half locked-rotor protection strategy provided by the invention is tested, the working condition that the steering system generates half locked-rotor is simulated, namely, the fixed rotor angle is 270 degrees, the steering system enters a half locked-rotor state, and at the moment, only MOSFETs of an A phase high bridge and a B, C phase low bridge have current. Tests are carried out on the fixed rotor at different angles, so that the correctness and feasibility of the semi-locked rotor capacity reduction protection strategy provided by the invention are proved. And counting a plurality of tests, wherein after half locked-rotor occurs, the steering system starts capacity-reducing protection about 3 seconds, and the capacity-reducing protection is maximum at 9 seconds. After the system is separated from the half locked-rotor state, the target given current of the q-axis is gradually recovered. The capacity-reducing protection mechanism not only greatly reduces the danger of no power assistance of the steering system caused by burning the MOSFET when half locked-rotor occurs, but also enables the steering hand feeling to be transitionally smooth by dynamically changing the capacity-reducing ratio, and has flexible and reliable calibration parameters.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.

Claims (3)

  1. The semi-locked-rotor protection method for the steering motor in the EPS system is characterized by comprising the following steps of:
    calculating to obtain the effective current and the effective value corresponding to each detection period T of 6 MOSFETs of the steering controlleri_addAnd an ambient temperature value t common to all MOSFETs;
    the detection period t=δ×m, wherein δ is a control period of the steering controller, and m is a positive integer greater than 1;
    the common ambient temperature value t of all MOSFETs is a temperature value measured by a temperature sensor which is positioned on the same control circuit board as the 6 MOSFETs of the steering controller;
    the effective current and value of single MOSFET flowing through the MOSFET during single detection period Ti_addCalculated according to equation 1:
    formula 1;
    wherein I is i Sampling the value of the current M for a single MOSFET in a control period delta i For the PWM duty cycle of the control period δ, i is a positive integer from 1 to m;
    effective current sum value flowing through single MOSFET according to current detection period Ti_addSearching a pre-established effective current and value interval index table, and judging the effective current and valuei_addBelonging to the interval and obtaining the current heat increment corresponding to the intervaldeta_i；
    According to the ambient temperature value of the current detection period TtSearching a pre-established index table of the environmental temperature value interval, and judging the environmental temperature valuetThe corresponding interval is obtained, and the temperature heat increment corresponding to the interval is obtaineddeta_t；
    The safe state variable S for each MOSFET is obtained by calculation according to equation 2:
    formula 2;
    in formula 2, S last Current thermal delta for all sensing periods prior to the current sensing perioddelta_i and temperature delta deta_tAnd (3) summing;
    if the safety state variable S of any one of the 6 MOSFETs is greater than or equal to the preset pre-start threshold S on Then the capacitance-reducing ratio of the MOSFET in the detection period is obtained according to the calculation of the formula 3k：
    Formula 3;
    the maximum value of the safety state variable S does not exceed the preset capacity reduction limit threshold S keep ；
    The buck-to-capacitive ratio of each detection cycle to 6 MOSFETskComparing, selecting the minimum volume reduction ratiokTo reduce a given target current on the q-axis.
  2. 2. The method for protecting half stalling of a steering motor in an EPS system according to claim 1 wherein the creating rule of the effective current and value interval index table is:
    dividing the effective current sum value into at least 10 intervals, see equation 4:
    formula 4;
    in the method, in the process of the invention,is the interval limit value, and->Sequentially increasing (I) in (I)>For each interval, the converted current heat increment value is corresponding to the current heat increment value, and +.>Sequentially increasing the steps;
    of at least 10 intervals, including:
    a negative increment interval in which the increment value is negative: i_add<i 1 ;i 1 Absolute safe current for the MOSFET selected for the experiment;
    a zero increment interval with an increment value equal to zero:；
    a maximum delta interval with delta value greater than zero and being the maximum delta value:i_add>i n ；
    the rest intermediate intervals are sequentially distributed between the zero increment interval and the maximum increment interval;
    in 4The setting rules of (1) are:
    i 1 which is the absolute safe effective current value of the selected MOSFET;
    i 2 it is connected withSatisfy->；
    i n Which is the maximum effective current value that the selected MOSFET can withstand;
    i 2 and i n The remaining interval limit value between the two intervals is satisfied that each remaining intermediate interval is uniformly distributed between a zero increment interval and a maximum increment interval;
    in 4The setting rules of (1) are:
    the current heat increment value a corresponding to the conversion of the negative increment interval 1 Set to a negative value less than zero and greater than-5;
    converted current thermal increment value a corresponding to zero increment interval 2 Set to zero;
    current heat increment value a converted corresponding to maximum increment interval n Is arranged between more than or equal to 20 and less than or equal to 25;
    the current heat increment value of each middle interval is a 2 And a n The values are uniformly taken.
  3. 3. The method for protecting half locked rotor of steering motor in EPS system according to claim 1 wherein the creating rule of the ambient temperature value interval index table is:
    dividing the ambient temperature value into at least 5 intervals, see formula 5:
    formula 5;
    in the formula 5, the components are,is the interval limit value, and->Sequentially increasing (I) in (I)>The temperature increment value converted for each interval is corresponding to the temperature increment value, and +.>Sequentially increasing the steps;
    of at least 5 intervals, including:
    a negative increment interval in which the increment value is negative: t is t<t 1 The method comprises the steps of carrying out a first treatment on the surface of the Wherein t is 1 Set to 0, the interval corresponds to the converted temperature heat increment b 1 Set to between-5 and 0;
    a zero increment interval with an increment value equal to zero:the method comprises the steps of carrying out a first treatment on the surface of the The temperature heat increment of the corresponding conversion of the interval is zero; wherein t is 2 The setting rules of (1) are: at ambient temperature t +.>When the MOSFET is in the state of heat generation and heat dissipation, the MOSFET is balanced;
    a maximum delta interval with delta value greater than zero and being the maximum delta value:the method comprises the steps of carrying out a first treatment on the surface of the T is t of n According to the setting of the corresponding ambient temperature value when the heat dissipation efficiency of the MOSFET is lowest in the data manual of the selected MOSFET, and the interval corresponds to the converted temperature heat increment value b n Between 10 and 15;
    the remaining number of sections is taken as intermediate sections, the corresponding limit value of each intermediate section is satisfied so that each intermediate section is sequentially and uniformly distributed between a zero increment section and a maximum increment section, and the temperature heat increment value of each intermediate section is b 2 And b n Rules of uniformly taking values.
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