CN113044110B - Electric power steering temperature control method and device, electric power steering system with device and automobile - Google Patents
Electric power steering temperature control method and device, electric power steering system with device and automobile Download PDFInfo
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- 238000004804 winding Methods 0.000 claims description 9
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- 230000001629 suppression Effects 0.000 abstract description 8
- 238000004422 calculation algorithm Methods 0.000 description 5
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- 238000013021 overheating Methods 0.000 description 3
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- 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
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- 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
- B62D5/0481—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 monitoring the steering system, e.g. failures
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- 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
- B62D5/0481—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 monitoring the steering system, e.g. failures
- B62D5/0496—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 monitoring the steering system, e.g. failures by using a temperature sensor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
- B62D—MOTOR VEHICLES; TRAILERS
- B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
- B62D6/001—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits the torque NOT being among the input parameters
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- Power Steering Mechanism (AREA)
- Steering Control In Accordance With Driving Conditions (AREA)
Abstract
The invention discloses an electric power steering temperature control method, which comprises the following steps: s1, estimating the current steering system temperature; s2, identifying the current driving condition; and S3, calculating a current reduction rate based on the basic current limiting rate and the working condition current limiting coefficient, and restraining the boosting current according to the calculated current reduction rate. The invention then provides an electric power steering temperature control device having a temperature estimation module, a condition identification module and a current suppression module corresponding to the aforementioned method in that order. The invention further provides an electric power steering system comprising the device and an automobile comprising the system. According to the invention, by setting the current suppression strategy corresponding to each driving working condition, the heating of the steering motor is effectively controlled, and the influence of current suppression on the steering hand feeling is reduced.
Description
Technical Field
The invention relates to an electric power steering system of a vehicle, in particular to an electric power steering temperature control method and device, an electric power steering system with the device and an automobile.
Background
Currently, in the steering technology of a vehicle, an electric power steering system (abbreviated as "EPS") is generally used to assist a driver in steering by controlling an output current of a motor to generate a power assist.
The main power element in the EPS system is a motor (if the motor in the invention is not particularly indicated to be a power steering motor), no matter the type of the motor is brushless or brushed, a large amount of heat energy is generated in the working and rotating operation, so that the temperature of the system is increased, however, the high temperature has great influence on the service life and the function of various electronic components on a controller chip, and even more, the overheating and overcurrent damage of the electronic components can be caused, so that the loss of power assistance in the driving process is caused, and potential safety hazards are generated. In the existing EPS system, the cost for installing the temperature sensor on the motor and the selection of the installation position have some problems, so that the temperature of the motor cannot be accurately detected, and the temperature sensor arranged on the main controller chip can only be used for detecting the temperature around the installation position.
Therefore, researchers estimate the temperature of the motor and limit the power-assisted current based on the estimated temperature so as to prevent the motor from being failed due to overhigh temperature rise. However, the method does not consider the vehicle state, and a single linear proportional reduction strategy is adopted for limiting the power-assisted current, so that the temperature fluctuation is large, and a complex engineering control system cannot be met; on the other hand, sudden rising and falling of the power-assisted current are easy to occur, so that the steering hand feeling is suddenly changed, and the user experience is seriously influenced.
Disclosure of Invention
The invention aims to provide an electric power steering temperature control method and device capable of effectively controlling the heating of a steering motor, an electric power steering system with the device and an automobile.
In order to achieve the above object, the present invention provides a temperature control method for electric power steering, comprising the steps of:
s1, estimating the current steering system temperature tSystem；
S2, identifying the current driving condition;
s3, calculating a current reduction rate based on the basic current limiting rate and the working condition current limiting coefficient, and restraining the power-assisted current according to the calculated current reduction rate; wherein the basic current limiting rate is the current t estimated in step S1SystemThe boost current reduction rate corresponding to the value, and the condition current limiting coefficient is a boost current reduction proportionality coefficient (also called driving condition coefficient or condition coefficient) corresponding to the current driving condition determined in step S2.
In the invention, the S1, S2, S1.1 and the like are only named for steps, the sequence of the steps is not implied, and the sequence of the steps is not limited.
Preferably, the step S1 specifically includes the following steps:
s1.1, estimating the temperature of the motor to obtain the estimated temperature t of the motormotor；
S1.2, estimating temperature t based on motormotorAnd the measured controller temperature tECUCalculating the system estimated temperature tSystem。
Preferably, in the step S1.1, the estimated motor temperature t is calculated according to the following formulamotor，tmotor＝tL*KL+tR*KR+ C; wherein, KLIs the proportionality coefficient of winding temperature rise to total motor temperature rise, KRThe proportional coefficient of the resistance temperature rise to the total temperature rise of the motor (the two temperature rise coefficients can be determined according to parameters provided by a motor manufacturer or an experimental method), KL+KR＝1；tLIs the temperature rise, t, calculated based on the change in winding resistanceRIs the temperature rise calculated based on the estimated motor heat; c is normal temperature.
In step S1.2, the system estimated temperature is calculated according to the following formula: t is tSystem＝tmotor*Kmotor+tECU*KECUWherein, K ismotorAnd KECUAre respectively tmotorAnd tECUCoefficient of extent of influence on the overall temperature, Kmotor+KECU＝1。
Preferably, in step S2, the driving conditions include a locked-rotor condition, a limit position driving condition and a normal driving condition, and when the conditions are identified, it is determined whether the conditions are the locked-rotor condition first, and then other conditions are determined. Preferably, the three working conditions are sequentially identified.
Preferably, in step S2, the steering wheel torque T is determined according to the steering wheel angle θSWAnd identifying the driving condition by the motor current I and the abnormal current duration time t.
Preferably, in step S2, the specific identification conditions of the three driving conditions are as follows:
s2.1, when the motor current I is more than or equal to IMax90%, the steering wheel rotating speed is more than 0 and not more than omega and not more than 50deg/S, the duration time t of the abnormal current is not less than 500ms, the driving working condition is identified as a locked-rotor working condition, and the current limiting coefficient is set to be 1 corresponding to the working condition in the step S3; wherein, IMaxThe maximum current allowed for the steering motor;
s2.2, when the steering wheel rotation angle theta meets the condition that theta-beta is less than or equal to 20deg, the steering wheel rotation speed omega is more than or equal to 300deg/S, and the motor current I is (50A, I |)Max90%) and the duration time t of the abnormal current is more than or equal to 1000ms, the driving condition is identified as the driving condition at the limit position, and the current limiting coefficient is set to be 0.7 corresponding to the working condition in the step S3; wherein beta is the steering wheel limit position angle, IMaxThe maximum current allowed for the steering motor;
s2.3 when the steering wheel rotation angle theta satisfies | theta-beta ¬ ventilation>20deg, steering wheel torque TSWIn [ -3Nm,3Nm]Within the range, the rotating speed of the steering wheel meets 50deg/s<ω<300deg/S, the motor current I is less than or equal to 50A, and the abnormal current duration t is greater than or equal to 5000ms, the driving condition is identified as a conventional driving condition, and the current limiting coefficient is set to be 0.5 corresponding to the condition in the step S3; wherein beta is the steering wheel limit position angle.
Preferably, in the step S3, the steering system temperature t is adjustedSystemThe method includes dividing the temperature range into a plurality of temperature ranges, and determining a basic current limiting rate corresponding to each temperature range.
Preferably, in step S3: the current reduction rate is in direct proportion to the basic current limiting rate and the working condition current limiting coefficient; will turn to the system temperature tSystemDividing the temperature range into a plurality of temperature ranges, and determining a basic current limiting rate corresponding to each temperature range; for each temperature interval, only when tSystemWhen the time length of the value in the temperature interval exceeds a set time threshold value, changing the basic current limiting rate to be a value corresponding to the interval; the time threshold values are respectively set according to different temperature intervals, and the time threshold value is set to be smaller in the interval with higher temperature. This scheme divides into a plurality of cascaded falling current protection with the electric current, effectively prevents the sudden change of driving feel that the reduction helping hand electric current that is too fast brought.
The present invention then provides an electric power steering temperature control apparatus, comprising:
a temperature estimation module configured to perform the step S1;
a condition identification module configured to execute the step S2;
a current suppressing module configured to perform the step S3.
The invention further provides an electric power steering system, which comprises a steering motor and an EPS controller (also called ECU), wherein the EPS controller is provided with the steering temperature control device.
The invention also provides an automobile comprising the electric power steering system.
Compared with the prior art, the invention has the beneficial effects that: according to the invention, on one hand, reasonable current is set according to the current temperature rise condition to reduce the basic current limiting rate, on the other hand, corresponding working condition current limiting coefficients are set according to different driving working conditions, so that a current suppression strategy corresponding to each driving working condition is realized, the heating of the steering motor is effectively controlled, the influence of current suppression on steering hand feeling is reduced, and the user experience is improved.
Drawings
Fig. 1 is a flowchart illustrating identification of three driving conditions according to embodiment 1 of the present invention.
Fig. 2 is a flowchart of a current suppressing method according to embodiment 1 of the present invention.
Fig. 3 is a schematic block diagram of a steering temperature control device according to embodiment 2 of the present invention.
Fig. 4 is a schematic structural diagram of an electric power steering system according to embodiment 3 of the present invention.
Wherein:
the device comprises an EPS controller 1, a storage battery 2, a motor 3, a CAN bus 4, a steering wheel torque sensor 5, a steering wheel rotating speed sensor 6, a steering wheel rotating angle sensor 7, a signal receiving module 11, a motor temperature estimation module 12, a system temperature estimation module 13, a current suppression module 14, a working condition recognition module 15 and an ECU temperature sensor 16.
Detailed Description
The invention is described in further detail below with reference to the figures and the specific embodiments.
Example 1
The embodiment provides an electric power steering temperature control method, which comprises the following steps:
s0, receiving signal
As a preceding step, the received signal comprises:
1) the steering wheel state signals comprise steering wheel angle signals, steering wheel moment signals and steering wheel rotating speed signals;
2) and ECU temperature signals, motor current signals and motor rotating speed signals transmitted from the inside of the EPS controller.
S1, estimating the current steering system temperature tSystem
The heating of the steering system comprises the heating of a motor and the heating of a controller circuit board, the temperature of the controller circuit board is directly measured by an ECU temperature sensor, and the temperature of the motor needs to be estimated. By tSystemInstead of tmotorThe current limiting circuit can play a role in protecting electronic components of the controller as one of the references of subsequent current limiting.
Specifically, the following steps can be adopted for estimation:
s1.1, estimating the temperature of the motor to obtain the estimated temperature t of the motormotor。
Estimated temperature t of the electric machinemotorThe known estimation methods can be used, but in order to obtain more accurate results, the following methods are preferably used:
firstly, the heat productivity of the motor is estimated according to the following motor heat estimation model:
in the above formula, the meaning of each parameter is:
q: heat generated by the motor during the delta t time;
t: a start time;
i: the effective value of the motor current in delta t time;
r (T): according to the temperature of the motorThe equivalent resistance value of the motor with variable degree can be determined by motor voltage U, current I and power factor
Is obtained by calculation
C: the cooling coefficient is obtained according to motor parameters provided by a motor manufacturer and is obtained by a simulation cooling test of the motor manufacturer;
because the equivalent resistance of the motor changes along with the change of the temperature of the motor, negative feedback based on the temperature of the motor can be further added, and the temperature estimation value of the motor is input into the calculation loop again, so that the heat estimation value of the motor is more accurate.
After the motor heat estimated value is obtained through calculation, a motor temperature estimation model is used for:
tmotor＝tL*KL+tR*KR+C；
calculating to obtain the estimated temperature t of the motormotor；
In the above formula:
tLthe temperature rise calculated based on the change relation of the winding resistance with the temperature is ((R2-R1) (235+ T1))/R1;
tRq/(cm), which is the temperature rise calculated based on the correspondence of resistance heating to temperature;
KLweighting the influence factor of the heating of the winding corresponding to the temperature rise of the motor;
KRthe weight of an influence factor of the temperature rise of the motor caused by the heating of the equivalent resistance corresponding to the current flowing through the motor;
KLand KRThe two proportionality coefficients are calibrated and adjusted according to actual conditions according to the ratio of the two temperature rises to the influence of the temperature rise of the whole system, and the preset values are 0.3 and 0.7 respectively; kL+KR＝1；
C is normal temperature and is consistent with the reference temperature in temperature rise calculation.
The overall calculation formula is therefore:
in the above formula, the meaning of each parameter is:
r2: a motor winding thermal state resistance;
r1: a motor winding cold resistance;
t1: the cold temperature of the motor winding is in K;
c: equivalent specific heat capacity of the motor;
m: motor equivalent mass.
S1.2, estimating temperature t based on motormotorAnd the controller temperature tECUThe system estimated temperature is calculated as follows:
tSystem＝tmotor*Kmotor+tECU*KECU
in the above formula:
tECUthe controller temperature detected by a temperature sensor in the EPS controller is used as feedforward compensation;
Kmotorand KECUAre respectively tmotorAnd tECUDetermining a specific numerical value according to an actual vehicle experiment on the degree coefficient of the overall temperature influence;
Kmotor+KECU＝1。
s2, identifying the current driving condition
In the embodiment, the driving conditions comprise a locked-rotor condition, a limit position driving condition and a conventional driving condition, and the three conditions are sequentially identified; other driving conditions may actually be set to meet the differential requirements for the rate of current reduction.
Fig. 1 shows a specific working condition identification method, which includes the following steps:
s2.0, obtaining the current steering wheel rotation angle theta and the steering wheel torque TSWSteering wheel speed ω, motor current I;
s2.1, firstly, judging whether the blockage is caused by the rotation blockageThe judgment condition can be set reasonably according to the actual vehicle condition, for example: motor current | I | ≧ IMax90%, the rotating speed of the steering wheel is more than 0 and less than or equal to 50deg/s, and the duration time t of the abnormal current is more than or equal to 500 ms; setting the current limiting coefficient to be 1 corresponding to the working condition in the step S3;
s2.2, if not the locked-rotor condition, then continue to judge whether for extreme position driving condition, judge that the condition can be according to for the reasonable setting of real car condition, for example: the rotation angle theta of the steering wheel meets the condition that theta-beta is less than or equal to 20deg, the rotating speed omega of the steering wheel is more than or equal to 300deg/s, and the motor current I is (50A, I)Max90%) and the duration time t of abnormal current is more than or equal to 1000 ms; setting the current limiting coefficient to 0.7 corresponding to the working condition in the step S3;
s2.3, if also not the extreme position driving condition, then continue to judge whether for the conventional driving condition, the judgement condition can be according to for the reasonable setting of real vehicle condition, for example: the steering wheel angle theta satisfies | theta-beta->20deg, steering wheel torque TSWIn [ -3Nm,3Nm]Within the range, the rotating speed of the steering wheel meets 50deg/s<ω<300deg/s, the motor current I is less than or equal to 50A, and the duration time t of the abnormal current is more than or equal to 5000 ms; setting the current limiting coefficient to be 0.5 corresponding to the working condition in the step S3;
s2.4, if the driving condition is not the normal driving condition, identifying the driving condition as a default condition, and setting the condition current limiting coefficient in the step S3 as a default value of 0.25;
in the above steps, beta is the steering wheel limit position angle, IMaxSteering wheel angle theta and steering wheel torque T set for maximum current allowed by steering motor and various working conditionsSWThe motor current I and the abnormal current duration time t range are only examples and can be reasonably set or calibrated according to the actual vehicle condition.
S3, suppressing current to realize overheat protection
As shown in fig. 2, step S3 is to perform degradation processing on the boost current to realize overheating protection according to the current reduction rate determined by the following formula:
the current reduction rate is the basic current limiting rate and the working condition current limiting coefficient;
wherein:
s3.1 setting of basic current limiting rate
The basic current limiting rate is compared with the current t estimated in step S1SystemThe value corresponds to the rate of decrease of the boost current. In the present embodiment, the steering system temperature t is setSystemThe method is divided into three temperature intervals, and corresponding basic current limiting rates are set in the temperature intervals respectively. The current can be divided into three stepped down current protection by the arrangement, and sudden change of driving hand feeling caused by excessively fast reduction of the boosting current is effectively prevented.
When the temperature t of the systemSystemIn the vicinity of the boundary value, it may frequently change between the two temperature ranges. To avoid frequent switching of the current reduction rate, only when t is present for each temperature intervalSystemWhen the time length of the temperature interval exceeds the set time threshold value, the basic current limiting rate is changed into the value corresponding to the interval. The values of the time thresholds can be respectively set according to different temperature intervals, and preferably, a smaller time threshold is set in an interval with higher temperature, so that the rapid control heating at high temperature is ensured; and a larger time threshold is set in a lower temperature interval so as to reduce the adverse effect on the operation hand feeling.
The following is further illustrated by a sample.
Defining three critical temperature values according to the heat-resisting grade of each electronic component of the EPS controller and the guaranteed temperature of the performance of the controller, wherein the t is the sequence from high to low1＝85℃，t2＝75℃，t365 ℃, from which 3 temperature intervals were determined: not less than t1，[t2，t1)，[t3，t2)。
When t isSystem≥t1And when the time lasts 500ms, the basic current limiting rate is set as the basic current limiting rate 1, the current reduction rate 1 is obtained by combining the working condition coefficient, and the boosting current is limited by the current reduction rate 1 until the temperature is reduced to a second step ([ t)2，t1))。
When t is2≤tSystem<t1The time and the duration are 1000ms, the basic current limiting rate is set as the basic current limiting rate 2, the current reduction rate 2 is obtained by combining the working condition coefficient, the power-assisted current is limited by the current reduction rate 2 until the temperature is reduced to a third step ([ t ] t)3，t2))。
When t is3≤tSystem<t2The time is 5000ms and the duration is 5000ms, the basic current limiting rate is set as the basic current limiting rate 3, the current reduction rate 3 is obtained by combining the working condition coefficient, the boosting current is limited by the current reduction rate 3 until tSystem<t3(corresponding time thresholds may be set) and the over-temperature protection function is turned off.
The specific values of the basic limiting rates 1,2 and 3 are calibrated according to the actual vehicle.
S3.2, setting of working condition current limiting coefficient
The condition current limiting coefficient is an assist current reduction proportional coefficient (also referred to as a driving condition coefficient or a condition coefficient) corresponding to the current driving condition determined in step S2.
Corresponding to the three conditions in the step S2, the condition current limiting coefficients are respectively set as follows:
when the vehicle is in a normal driving condition, the condition current limiting coefficient is set to be 0.5. At the moment, the rate of the reduction of the power-assisted current of the EPS system after the overheat protection function is activated is properly slowed compared with other two working conditions, most of the heat dissipation of the EPS system can be naturally cooled by the system, and the intervention proportion of the current suppression module is low, so that the condition of hand feeling change caused by the excessive intervention of the power-assisted current by the overcurrent suppression module can be improved;
when the vehicle is in the limit position driving condition, the condition current limiting coefficient is set to be 0.7. Compared with the conventional driving working condition, the working condition has the advantages that the probability of triggering the system overheat protection is increased, and once the overheat protection is activated, the boosting current can be limited within a safety range within a short time, so that the influence on electronic components due to the fact that the high current with overhigh temperature and lasting for a long time passes is prevented.
When the vehicle is in a locked-rotor working condition, the working condition current limiting coefficient is set to be 1, under the condition, the EPS system is in the worst thermal management condition, and the ESP controller is easy to burn due to overheating and overcurrent. After the overheat protection function is activated, the controller reduces the boosting current at the fastest limiting rate so as to prevent the components of the controller from being damaged due to overhigh temperature.
When the vehicle is not in any of the working conditions, namely in a default working condition, the working condition current limiting coefficient is set to be 0.25 of a default value.
Example 2
The embodiment provides an electric power steering temperature control device which is realized on the basis of hardware of an existing vehicle and mainly based on a software mode.
As shown in fig. 3, the temperature control device includes the following software modules:
a signal receiving module 11 configured to perform step S0 in embodiment 1;
a temperature estimation module configured to execute step S1 in embodiment 1; the temperature estimation module further includes a motor temperature estimation module 12 and a system temperature estimation module 13 configured to perform steps S1.1 and S1.2 in embodiment 1, respectively.
An operation condition recognition module 15 configured to execute step S2 in embodiment 1;
a current suppressing module 14 configured to perform step S3 in embodiment 1.
Each software module corresponds to each main step in embodiment 1, and a specific algorithm is as shown in embodiment 1.
Example 3
As shown in fig. 4, the present embodiment provides an electric power steering system, which adopts an existing configuration in hardware, and mainly includes: EPS controller 1, battery 2, motor 3, CAN bus 4, steering wheel moment sensor 5, steering wheel rotational speed sensor 6, steering wheel corner sensor 7. The storage battery 2 supplies power to the EPS controller 1, and the EPS controller 1 is respectively connected with the motor 3 and the CAN bus 4.
Except that the system further has the electric power steering temperature control device provided in embodiment 2. This temperature control device is installed in the form of software in the memory of the EPS controller 1, and can be executed by the EPS controller 1 to implement the electric power steering temperature control method provided in embodiment 1.
The control process of the electric power steering system to the EPS system temperature is briefly described as follows:
the steering wheel angle sensor 7, the steering wheel speed sensor 6 and the steering wheel moment sensor 5 respectively transmit the current steering wheel angle, steering wheel speed and steering wheel moment signals (corresponding to each other) which are respectively acquired to the CAN bus 4, and the EPS controller 1 receives the signals and transmits the signals to the signal receiving module 11.
Controller temperature signal (t) measured by ECU temperature sensor 16 inside EPS controllerECU) And motor current signals and motor speed signals fed back by the motor 3 are also transmitted to the signal receiving module 11 through the EPS controller 1.
After receiving the signal, the signal receiving module 11 transmits the signal to a corresponding software module.
The motor temperature estimation module 12 estimates the motor temperature t according to the given algorithm in the embodiment 1 according to the input informationmotor。
The system temperature estimation module 13 estimates the system temperature according to the motor temperature tmotorAnd the controller temperature tECUThe estimated system temperature t is calculated according to the algorithm given in example 1System。
The working condition recognition module 15 judges the current driving working condition according to the given algorithm in embodiment 1 according to the input information.
A current suppressing module 14 for estimating the temperature t according to the systemSystemAnd the current driving condition, the power-assisted current reduction rate is calculated according to the given algorithm in the embodiment 1.
And finally, controlling the motor current by the EPS controller to adjust the motor current according to the calculated power-assisted current reduction rate.
Example 4
This embodiment provides an automobile equipped with the electric power steering system described in embodiment 3. The rest of the vehicle is of the prior art.
Abbreviations and Key term definitions
EPS: electronic Power Steering system
Controller area network of Controller Area Network (CAN)
An ECU; the Electronic Control Unit is also a controller of the EPS system, and is the same component with the EPS controller in the invention.
Claims (7)
1. An electric power steering temperature control method is characterized in that:
the method comprises the following steps:
s1, estimating the current steering system temperature tSystem；
S2, identifying the current driving condition;
s3, calculating a current reduction rate based on the basic current limiting rate and the working condition current limiting coefficient, and restraining the power-assisted current according to the calculated current reduction rate; wherein the basic current limiting rate is the current t estimated in step S1SystemA boost current reduction rate corresponding to the value, the condition current limit coefficient being a boost current reduction scale coefficient corresponding to the current driving condition determined at step S2;
in step S2, the driving conditions include a locked-rotor condition, a limit position driving condition, and a normal driving condition, and when the conditions are identified, it is determined whether the locked-rotor condition is present, and then other conditions are determined;
in step S2, the steering wheel angle θ and the steering wheel torque T are usedSWIdentifying the driving condition by the motor current I and the abnormal current duration time t; the specific recognition conditions for the three driving conditions are as follows:
s2.1, when the motor current I is more than or equal to IMax90%, the steering wheel rotating speed is more than 0 and not more than omega and not more than 50deg/S, the duration time t of the abnormal current is not less than 500ms, the driving working condition is identified as a locked-rotor working condition, and the current limiting coefficient is set to be 1 corresponding to the working condition in the step S3; wherein, IMaxThe maximum current allowed for the steering motor;
s2.2, when the steering wheel rotation angle theta meets the condition that theta-beta is less than or equal to 20deg, the steering wheel rotation speed omega is more than or equal to 300deg/S, and the motor current I is (50A, I |)Max90%) and the duration time t of the abnormal current is more than or equal to 1000ms, the driving condition is identified as the driving condition at the limit position, and the current limiting coefficient is set to be 0.7 corresponding to the working condition in the step S3; wherein beta is the steering wheel limit position angle, IMaxThe maximum current allowed for the steering motor;
s2.3 when the steering wheel rotation angle theta satisfies | theta-beta ¬ ventilation>20deg, directionDisk torque TSWIn [ -3Nm,3Nm]Within the range, the rotating speed of the steering wheel meets 50deg/s<ω<300deg/S, the motor current I is less than or equal to 50A, and the abnormal current duration t is greater than or equal to 5000ms, the driving condition is identified as a conventional driving condition, and the current limiting coefficient is set to be 0.5 corresponding to the condition in the step S3; wherein beta is the steering wheel limit position angle.
2. The electric power steering temperature control method according to claim 1, characterized in that: the step S1 specifically includes the following steps:
s1.1, estimating the temperature of the motor to obtain the estimated temperature t of the motormotor；
S1.2, estimating temperature t based on motormotorAnd the measured controller temperature tECUCalculating the system estimated temperature tSystem。
3. The electric power steering temperature control method according to claim 2, characterized in that:
in the step S1.1, the estimated motor temperature t is obtained by calculation according to the following formulamotor，tmotor＝tL*KL+tR*KR+ C; wherein, KLIs the proportionality coefficient of winding temperature rise to total motor temperature rise, KRIs the proportional coefficient of resistance temperature rise to total motor temperature rise, KL+KR＝1；tLCalculating to obtain the temperature rise t based on the resistance change of the windingRCalculating to obtain temperature rise based on the estimated motor heat; c is normal temperature;
in step S1.2, the system estimated temperature is calculated according to the following formula: t is tSystem＝tmotor*Kmotor+tECU*KECUWherein, K ismotorAnd KECUAre respectively tmotorAnd tECUCoefficient of extent of influence on the overall temperature, Kmotor+KECU＝1。
4. The electric power steering temperature control method according to any one of claims 1 to 3, characterized in that: in the step S3, electricity is suppliedThe flow reduction rate is proportional to the base current limiting rate and the operating condition current limiting coefficient; will turn to the system temperature tSystemDividing the temperature range into a plurality of temperature ranges, and determining a basic current limiting rate corresponding to each temperature range; for each temperature interval, only when tSystemWhen the time length of the value in the temperature interval exceeds a set time threshold value, changing the basic current limiting rate to be a value corresponding to the interval; the time threshold values are respectively set according to different temperature intervals, and the time threshold value is set to be smaller in the interval with higher temperature.
5. An electric power steering temperature control device designed to implement the steering temperature control method according to any one of claims 1 to 4, characterized in that: the method comprises the following steps:
a temperature estimation module configured to perform the step S1;
a condition identification module configured to execute the step S2;
a current suppressing module configured to perform the step S3.
6. An electric power steering system, includes steering motor and EPS controller, its characterized in that: the EPS controller is provided with the electric power steering temperature control device according to claim 5.
7. An automobile, characterized in that: comprising an electric power steering system according to claim 6.
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