CN108073554A - The assist characteristic curve design method of automobile electric booster steering system based on SOC - Google Patents
The assist characteristic curve design method of automobile electric booster steering system based on SOC Download PDFInfo
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Abstract
The invention discloses the assist characteristic curve design method of the automobile electric booster steering system based on SOC, estimation to battery SOC carries out classification smoothing processing according to the value of battery SOC, is changed processing using hand Calculating Torque during Rotary target current process comparative example relation ζ, the curve under full speed is handled.Wherein, the methods of the estimation comprehensive utilization Current integrating method of battery SOC, open circuit voltage method, internal resistance of cell method, the precision of the estimation of SOC is effectively ensured；Classification smoothing processing is carried out according to the value of battery SOC, considers SOC respectively<40% and SOC>40% situation is smoothed virgin curve type assist characteristic curve respectively.On the one hand the present invention is the smoothing processing carried out on the basis of shaped form power-assisted curve during power-assisted curve is designed, effect is more good；On the other hand, the present invention makes the design carried out on the basis of battery capacity is considered, can ensure the sustainable supply of battery current.
Description
Technical Field
The invention relates to an EPS (electric power steering) power-assisted characteristic curve, in particular to a method for designing an SOC (system on chip) -based power-assisted characteristic curve of an automobile electric power steering system.
Background
The power characteristic curve of the EPS is a relationship between a power current of a motor and parameters such as a steering wheel input torque, a vehicle running speed, a front wheel air pressure, a front axle weight and the like, and the control requirement can be satisfied by considering two main parameters of the steering wheel input torque and the vehicle running speed in general.
The power-assisted characteristic curve of the EPS is a key technology of an EPS software system. The boost characteristic curve determines the magnitude of the boost current to be controlled by a controller (ECU) according to what target to meet the requirements on the boost torque under different driving conditions. The basic power characteristic curve is roughly divided into: linear, broken line, curved.
The basic power assisting characteristic curve can basically meet the design requirement, but the actual effect of the power assisting is poor, so that the improved design of the power assisting characteristic curve appears, wherein the curve type power assisting characteristic curve design with adjustable parameters is adopted, the shape of the curve type power assisting characteristic curve is changed through the set parameters, and the curve can be changed at any time. The double-slope smooth power-assisted curve has a double-slope smooth power-assisted curve, can independently calibrate curve parameters according to different hand feeling requirements of a small power-assisted area and a large power-assisted area, has the advantages of smooth power assistance, independent parameter function and easiness in debugging, and can better meet the expectation of a driver in the aspect of steering hand feeling.
The above design only starts from the curve itself, does not consider the influence of battery power on the vehicle power assistance, and when the hand moment change is great and the hand moment is great, the battery is very likely to be unable to provide the EPS current that satisfies the requirement, and the EPS system can cut off the power supply suddenly, and the steering power assistance system can not function in the twinkling of an eye, seriously influences driving safety.
Chinese patent application No. 200810202069.7, which discloses an "electric power steering system with independently adjustable parameter curve type power assist characteristic"; the existing parameter adjustment enables the design period of the curve to be long, and meanwhile, the actual condition of the vehicle cannot be contacted, so that the curve adjustment is carried out according to the actual condition of the vehicle.
Chinese patent application No. 201010600546.2 discloses an electric power steering system having a dual-slope smooth assist curve, which cannot ensure the practical application effect of the assist curve, i.e., whether the continuous supply of the battery power can be ensured or not, in the process of performing dual-slope smoothing processing in a polygonal line segment.
Disclosure of Invention
The invention aims to solve the technical problem of providing a power-assisted characteristic curve design method of an automobile electric power-assisted steering system based on SOC, which considers the influence of battery electric quantity on vehicle power assistance, can provide EPS current meeting requirements when the hand moment is changed greatly and the hand moment is large, and can not be powered off suddenly, thereby ensuring the normal function of the power-assisted steering system and ensuring the driving safety.
In order to solve the technical problems, the invention adopts the following technical means:
a design method of an assistance characteristic curve of an automobile electric power steering system based on SOC is disclosed, the design of the assistance characteristic curve considers the condition of the SOC of a battery, smoothing processing is carried out on the basis of an original curve type assistance characteristic curve in the curve design process, meanwhile, current required by an EPS system is restrained to ensure that the battery can have stable and continuous current output even under the condition of low electric quantity, and the realization of the whole assistance process of the EPS is ensured, wherein the curve design comprises the following steps:
step 1) estimating the SOC of the battery;
step 2) carrying out smoothing treatment on the SOC (state of charge) of less than 40% by a weighted moving average method corresponding to the curve-shaped power-assisted characteristic curve, and improving the change rate of the curve-shaped power-assisted curve so as to stabilize the current output of the battery;
step 3) carrying out simple moving average smoothing processing on the curve type power-assisted characteristic curve under the condition that the SOC is more than 40%;
step 4) in the process of calculating the target current by using the hand moment:
Ia＝ζTd(1)
wherein, the proportional relation zeta is changed,lambda is a transformation coefficient, and a power-assisted curve under a certain vehicle speed is determined;
and 5) for different vehicle speeds in different stages, obtaining complete power-assisted characteristic curves under different vehicle speeds through related terms of the speed, namely:
I＝e-av·ζTd； (2)
where I is the target current for each vehicle speed, e-avThe correction factor is a factor that includes velocity.
Compared with the prior art, the invention adopting the technical scheme has the outstanding characteristics that:
when the power-assisted characteristic curve is designed, the SOC condition is considered, particularly under the conditions of large hand moment change and large hand moment, the change rate of the power-assisted curve is changed, and the current of the EPS is controlled to be within the battery power supply range. The SOC value can be observed by comprehensively utilizing a current integration method, an open-circuit voltage method, a battery internal resistance method and the like, the original curve type power-assisted characteristic curve is subjected to condition division processing according to the SOC value, the original curve type power-assisted characteristic curve is subjected to smoothing processing by a weighted moving average method when the SOC is less than 40%, and the original curve type power-assisted characteristic curve is subjected to smoothing processing by a simple moving average method when the SOC is more than 40%. And meanwhile, the required current of the EPS is restrained, and the continuous supply of the battery to the EPS current is ensured, so that the power-assisted steering system continuously plays a role.
The residual capacity of the battery is considered in curve design, meanwhile, on the basis of an original curve type power-assisted characteristic curve, calculation of target current can be better achieved under the condition of meeting practical application, and stable output of actual tracking current is guaranteed. In the process of designing the power-assisted curve, on one hand, the smoothing treatment is carried out on the basis of the curve-type power-assisted curve, so that the effect is better; on the other hand, the design of this patent is carried out on the basis of considering battery electric quantity, can guarantee the continuous supply of battery current, simultaneously, in the calculation process of carrying out the target current, has carried out certain optimization restriction to the target current that produces because of hand moment, can further guarantee the stability of the electric current of battery.
The further preferred technical scheme is as follows:
the method for designing the power-assisted characteristic curve of the automobile electric power-assisted steering system based on the SOC comprises the following steps of 1) estimating the SOC of a battery, namely estimating the state of charge of the battery by comprehensively utilizing a current integration method, an open-circuit voltage method and a battery internal resistance method; the actual capacity of the battery is integrated by current ampere-hour corrected in the complete charging process of the battery, and SOC estimation in the using process is divided into two parts, namely a discharging process SOC and a charging process SOC; in the discharging process, reading the charging internal resistance RC in the battery internal resistance curve according to the current charge state, and calculating the current battery inner core voltage VOC according to the charging current; from the charging relationship, one can obtain:
VOC＝VC-RC×IC(3)
calculating VOCThe corrected SOC-VOC curve is brought in, and an open-circuit SOC estimated value can be obtained and recorded as SOCOC(ii) a The SOC value calculated by the ampere-hour integration method at this time is as follows:
according to SOCOCAnd SOCATComprehensively estimating the battery load state by adopting the following equation:
SOCC＝η1×SOCOC+η2×SOCAT(5)
in the formula, η1And η2For correcting the coefficient, according to the characteristics of the lithium ion battery, the battery is in a 10% -90% capacity interval, the voltage change is small, the correction coefficient can be flexibly set according to the characteristics of different batteries, the battery capacity is set in a 10% -90% interval, the ampere-hour integral is set to be dominant, η1Is 0.2, η2Is 0.8; capacity of battery<10% and>at 90%, the open circuit voltage estimate dominates, setting η1Is 0.8, η2Is 0.2;
the discharge process calculates the state SOC of the open-circuit load according to the dataOCLoad state SOC calculated by ampere-hour integrationATThe corrected battery load state is as follows:
SOCD＝η3×SOCOC+η4×SOCAT(6)
in the method for designing the power-assisted characteristic curve of the SOC-based automobile electric power-assisted steering system, the function of the curve-shaped power-assisted characteristic curve in the step 2) is as follows:
wherein,f (v) is a power assisting curve system corresponding to different speeds, F (v) is a function of the vehicle speed v, the faster v is, the smaller F (v) is, an exponential decreasing function of v is taken, G (T)d) In different directionsThe curve of the assist force when inputting the steering wheel torque is an increasing function, i.e., the larger the input torque of the steering wheel, the larger the assist torque must be for the sake of steering ease.
In the method for designing the power-assisted characteristic curve of the SOC-based automobile electric power-assisted steering system, step 2) smooth processing is performed by a weighted moving average method corresponding to the curve-shaped power-assisted characteristic curve, and the calculation formula of the weighted moving average method is as follows:
Ft＝w1A1+w2A2+w3A3+…+wnAn(8)
in the formula, w1-the weight of the 1 st point actual value; w is a2-the weight of the actual value at point 2; w is an-the weight of the actual value at the nth point;
n- -number of predicted values; w is a1+w2+…+wn＝1。
The moving average method is a simple smooth prediction technology, and the basic idea is as follows: and calculating the time-sequence average value containing a certain number of terms in sequence according to the time-sequence data item by item in order to reflect the long-term trend. Therefore, when the time series numerical value is influenced by the periodic variation and the random fluctuation, the fluctuation is large, and the development trend is not easy to be displayed, the influence of the factors can be eliminated by using the moving average method, the development direction and the trend (namely, the trend line) of the event can be displayed, and then the long-term trend of the time series can be analyzed and predicted according to the trend line.
The design method of the power-assisted characteristic curve of the automobile electric power-assisted steering system based on the SOC comprises the following steps of 3) carrying out simple moving average smoothing treatment on a curve type power-assisted characteristic curve when the SOC is more than 40%; the weights of the elements of the simple moving average are all equal, and the calculation formula of the simple moving average is as follows:
Ft＝(A1+A2+A3+…+An)/n (9)
in the formula, Ft-a predicted value for the next point; n-number of moving average points; a. the1-the actual value of the previous point; a. the2，A3And AnRespectively representing the actual values of the first two points, the first three points and the point from the first n point.
Drawings
Figure 1 is a curved boost characteristic curve of the prior art.
Fig. 2 is a power assist characteristic curve for the case where the SOC of the present invention is < 40%.
FIG. 3 is a power assist characteristic curve for a SOC > 40% of the present invention.
FIG. 4 is a flow chart of an SOC based boost characteristic curve design of the present invention.
Detailed Description
The present invention will be further described with reference to the following examples.
Referring to fig. 1, the basic curve type boosting characteristic curve of the prior art can basically meet the design requirement, but the actual effect of boosting is poor, especially when the hand torque is rapidly increased. In view of the above, there has been proposed an improved design of a power assist characteristic curve, in which a curve type power assist characteristic curve having adjustable parameters is designed, and the curve can be changed at any time by changing the shape of the curve type power assist characteristic curve by using set parameters. The double-slope smooth power-assisted curve has a double-slope smooth power-assisted curve, can independently calibrate curve parameters according to different hand feeling requirements of a small power-assisted area and a large power-assisted area, has the advantages of smooth power assistance, independent parameter function and easiness in debugging, and can better meet the expectation of a driver in the aspect of steering hand feeling. The above design only starts from the curve itself, does not consider the influence of battery power on the vehicle power assistance, and when the hand moment change is great and the hand moment is great, the battery is very likely to be unable to provide the EPS current that satisfies the requirement, and the EPS system can cut off the power supply suddenly, and the steering power assistance system can not function in the twinkling of an eye, seriously influences driving safety.
Referring to fig. 2, 3 and 4, in the method for designing the power-assisted characteristic curve of the electric power-assisted steering system of the vehicle based on the SOC of the invention, the power-assisted characteristic curve is designed in consideration of the SOC of the battery, smoothing is performed on the basis of the original curve-type power-assisted characteristic curve in the curve design process, and the current required by the EPS system is restricted to ensure that the battery can output a stable and continuous current even under the condition of low electric quantity, so as to ensure the realization of the whole power-assisted process of the EPS, wherein the curve design comprises the following steps:
step 1) estimating the SOC of the battery;
step 2) carrying out smoothing treatment on the SOC (state of charge) of less than 40% by a weighted moving average method corresponding to the curve-shaped power-assisted characteristic curve, and improving the change rate of the curve-shaped power-assisted curve so as to stabilize the current output of the battery;
step 3) carrying out simple moving average smoothing processing on the curve type power-assisted characteristic curve under the condition that the SOC is more than 40%;
step 4) in the process of calculating the target current by using the hand moment:
Ia＝ζTd (10)
wherein, the proportional relation zeta is changed,lambda is a transformation coefficient, and a power-assisted curve under a certain vehicle speed is determined; when the hand torque measured by the torque sensor is converted into the target current, the power characteristic curve can be smoothed by changing the conversion coefficient, so that the target current value is always kept in the discharge current range of the battery, namelyThe curve can be made to have a laterally elongated effect.
Step 5) for different ordersAt different vehicle speeds, by means of a correlation term e with respect to speed-avObtaining complete power-assisted characteristic curves under different vehicle speeds, namely:
I＝e-av·ζTd； (11)
where I is a target current for each vehicle speed, and is a correction coefficient including a speed.
The method comprises the steps that 1) the SOC of a battery is estimated, namely the SOC of the battery is estimated by comprehensively utilizing a current integration method, an open-circuit voltage method and a battery internal resistance method; the actual capacity of the battery is integrated by current ampere-hour corrected in the complete charging process of the battery, and SOC estimation in the using process is divided into two parts, namely a discharging process SOC and a charging process SOC; during the discharging process, reading the charging internal resistance R in the battery internal resistance curve according to the current charge stateCCalculating the current voltage V of the battery core according to the charging currentOC(ii) a From the charging relationship, one can obtain:
VOC＝VC-RC×IC(12)
calculating VOCSOC-V with correctionOCThe curve can be used to obtain the estimated value of open-circuit SOC, and the estimated value is recorded as SOCOC(ii) a The SOC value calculated by the ampere-hour integration method at this time is as follows:
according to SOCOCAnd SOCATComprehensively estimating the battery load state by adopting the following equation:
SOCC＝η1×SOCOC+η2×SOCAT(14)
in the formula, η1And η2For correcting the coefficient, the battery is charged in the range of 10-90% of the capacity according to the characteristics of the lithium ion batteryThe voltage change is small, the correction coefficient can be flexibly set according to the characteristics of different batteries, the battery capacity is set in a range of 10% -90%, the ampere-hour integral is set to be dominant, η1Is 0.2, η2Is 0.8; capacity of battery<10% and>at 90%, the open circuit voltage estimate dominates, setting η1Is 0.8, η2Is 0.2;
the discharge process calculates the state SOC of the open-circuit load according to the dataOCLoad state SOC calculated by ampere-hour integrationATThe corrected battery load state is as follows:
SOCD＝η3×SOCOC+η4×SOCAT(15)
the method for designing the power-assisted characteristic curve of the automobile electric power-assisted steering system based on the SOC comprises the following steps of 2) enabling a function of a curve-shaped power-assisted characteristic curve to be:
wherein,f (v) is a power assisting curve system corresponding to different speeds, F (v) is a function of the vehicle speed v, the faster v is, the smaller F (v) is, an exponential decreasing function of v is taken, G (T)d) For the boost curves at different steering wheel torque inputs, the boost function is increased, i.e. the higher the steering wheel input torque, the higher the boost torque must be for ease of steering.
An assistance characteristic curve design method of an automobile electric power steering system based on SOC (system on chip), comprising the following steps of 2) carrying out smoothing treatment on a curve assistance characteristic curve corresponding to the condition that the SOC is less than 40%, wherein a calculation formula of a weighted moving average method is as follows:
Ft＝w1A1+w2A2+w3A3+…+wnAn(17)
in the formula, w1-the weight of the 1 st point actual value; w is a2-the weight of the actual value at point 2; w is an-the weight of the actual value at the nth point;
n- -number of predicted values; w is a1+w2+…+wn1. Selecting n points At-1，At-2，At-3… …, a series of points (x) are obtained1，y1)，(x2，y2)(x3，y3) … … taking the initial value as T1And substituting the taken points in sequence: ft＝w1A1+w2A2+w3A3+…+wnAn(ii) a To obtain In＝w1T1+w2T2+w3T3+…+wnTn。
The design method of the power-assisted characteristic curve of the automobile electric power-assisted steering system based on the SOC comprises the following steps of 3) carrying out simple moving average smoothing treatment on a curve type power-assisted characteristic curve under the condition that the SOC is more than 40%; the weights of the elements of the simple moving average are all equal, and the calculation formula of the simple moving average is as follows:
Ft＝(A1+A2+A3+…+An)/n (18)
in the formula, Ft-a predicted value for the next point; n-number of moving average points; a. the1-the actual value of the previous point; a. the2，A3And AnRespectively representing the actual values of the first two points, the first three points and the point from the first n point.
Taking n points a1, a2 and a3 … … to obtain a series of points (x1, y1), (x2, y2) (x3, y3) … …, taking an initial value as T1, and sequentially substituting the taken points into: ft＝(A1+A2+A3+…An) N; to obtain In＝(T1+T2+T3+…Tn)/n。
As can be seen from fig. 4, the present embodiment performs classification smoothing processing on the estimation of the battery SOC, the value of the battery SOC, the calculation of the target current by the hand moment, the change processing on the proportional relationship ζ, and the processing on the curve at the full vehicle speed. The estimation of the SOC of the battery comprehensively utilizes methods such as a current integration method, an open-circuit voltage method, a battery internal resistance method and the like, and the estimation precision of the SOC is effectively ensured; and carrying out classification smoothing processing according to the SOC value of the battery, and respectively smoothing the original curve type boosting characteristic curves by considering the conditions that the SOC is less than 40% and the SOC is more than 40%.
As can be seen from a comparison of fig. 1, 2, and 3, when designing the assist characteristic curve, the current of the EPS is controlled within the battery power supply range by changing the change rate of the assist curve in consideration of the SOC, particularly, when the hand torque changes greatly and is large. The SOC value can be observed by comprehensively utilizing a current integration method, an open-circuit voltage method, a battery internal resistance method and the like, the original curve type power-assisted characteristic curve is subjected to condition division processing according to the SOC value, the original curve type power-assisted characteristic curve is subjected to smoothing processing by a weighted moving average method when the SOC is less than 40%, and the original curve type power-assisted characteristic curve is subjected to smoothing processing by a simple moving average method when the SOC is more than 40%. And meanwhile, the required current of the EPS is restrained, and the continuous supply of the battery to the EPS current is ensured, so that the power-assisted steering system continuously plays a role.
The beneficial effect of this embodiment lies in: the residual capacity of the battery is considered during curve design, and meanwhile, the curve design is based on the original curve type power-assisted characteristic curve, calculation of the target current can be better achieved under the condition of meeting practical application, and stable output of the actual tracking current is guaranteed. In the process of designing the power-assisted curve, on one hand, the smoothing treatment is carried out on the basis of the curve-type power-assisted curve, so that the effect is better; on the other hand, the design of this patent on the basis of considering battery electric quantity can guarantee the continuous supply of battery current, simultaneously, in the calculation process of carrying out the target current, has carried out certain optimization restriction to the target current that produces because of hand moment, can further guarantee the stability of the electric current of battery.
Since the above description is only a specific embodiment of the present invention, but the protection of the present invention is not limited thereto, any equivalent changes or substitutions of the technical features of the present invention which can be conceived by those skilled in the art are included in the protection scope of the present invention.
Claims (5)
1. A method for designing a power-assisted characteristic curve of an automobile electric power-assisted steering system based on SOC is characterized by comprising the following steps: the design of the power-assisted characteristic curve considers the condition of the SOC of the battery, the smoothing processing is carried out on the basis of the original curve type power-assisted characteristic curve in the curve design process, the current required by the EPS system is restrained to ensure that the battery can have stable and continuous current output even under the condition of low electric quantity, the realization of the whole power-assisted process of the EPS is ensured, and the curve design comprises the following steps:
step 1) estimating the SOC of the battery;
step 2) carrying out smoothing treatment on the SOC (state of charge) of less than 40% by a weighted moving average method corresponding to the curve-shaped power-assisted characteristic curve, and improving the change rate of the curve-shaped power-assisted curve so as to stabilize the current output of the battery;
step 3) carrying out simple moving average smoothing processing on the curve type power-assisted characteristic curve under the condition that the SOC is more than 40%;
step 4) in the process of calculating the target current by using the hand moment:
Ia＝ζTd(1)
wherein, the proportional relation zeta is changed,lambda is a transformation coefficient, and a power-assisted curve under a certain vehicle speed is determined;
and 5) for different vehicle speeds in different stages, obtaining complete power-assisted characteristic curves under different vehicle speeds through related terms of the speed, namely:
I＝e-av·ζTd； (2)
where I is the target current for each vehicle speed, e-avThe correction factor is a factor that includes velocity.
2. The method of claim 1, wherein the step 1) of estimating the SOC of the battery is a method of estimating the state of charge of the battery by comprehensively using a current integration method, an open-circuit voltage method and a battery internal resistance method; the actual capacity of the battery is integrated by current ampere-hour corrected in the complete charging process of the battery, and SOC estimation in the using process is divided into two parts, namely a discharging process SOC and a charging process SOC; in the discharging process, reading the charging internal resistance RC in the battery internal resistance curve according to the current charge state, and calculating the current battery inner core voltage VOC according to the charging current; from the charging relationship, one can obtain:
VOC＝VC-RC×IC(3)
calculating VOCThe corrected SOC-VOC curve is brought in, and an open-circuit SOC estimated value can be obtained and recorded as SOCOC(ii) a And thisThe SOC value calculated by the time ampere-hour integration method is as follows:
according to SOCOCAnd SOCATComprehensively estimating the battery load state by adopting the following equation:
SOCC＝η1×SOCOC+η2×SOCAT(5)
in the formula, η1And η2For correcting the coefficient, according to the characteristics of the lithium ion battery, the battery is in a 10% -90% capacity interval, the voltage change is small, the correction coefficient can be flexibly set according to the characteristics of different batteries, the battery capacity is set in a 10% -90% interval, the ampere-hour integral is set to be dominant, η1Is 0.2, η2Is 0.8; capacity of battery<10% and>at 90%, the open circuit voltage estimate dominates, setting η1Is 0.8, η2Is 0.2;
the discharge process calculates the state SOC of the open-circuit load according to the dataOCLoad state SOC calculated by ampere-hour integrationATThe corrected battery load state is as follows:
SOCD＝η3×SOCOC+η4×SOCAT(6) 。
3. the method of designing a power assist characteristic curve of an electric power steering system for an automobile based on SOC according to claim 1, characterized in that: the function of the curve-shaped power assisting characteristic curve in the step 2) is as follows:
wherein,f (v) is a power assisting curve system corresponding to different speeds, F (v) is a function of the vehicle speed v, the faster v is, the smaller F (v) is, the smaller v isExponential decreasing function, G (T)d) For the boost curves at different steering wheel torque inputs, the boost function is increased, i.e. the higher the steering wheel input torque, the higher the boost torque must be for ease of steering.
4. The method of claim 3, wherein the method further comprises: step 2) carrying out smoothing treatment on the curve-shaped power assisting characteristic curve by a weighted moving average method, wherein the calculation formula of the weighted moving average method is as follows:
Ft＝w1A1+w2A2+w3A3+…+wnAn(8)
in the formula, w1-the weight of the 1 st point actual value; w is a2-the weight of the actual value at point 2; w is an-the weight of the actual value at the nth point;
n- -number of predicted values; w is a1+w2+…+wn＝1。
5. The method of designing a power assist characteristic curve of an electric power steering system for an automobile based on SOC according to claim 1, characterized in that: the step 3) carries out simple moving average smoothing processing on the curve type power-assisted characteristic curve when the SOC is more than 40%; the weights of the elements of the simple moving average are all equal, and the calculation formula of the simple moving average is as follows:
Ft＝(A1+A2+A3+…+An)/n (9)
in the formula, Ft-a predicted value for the next point; n-number of moving average points; a. the1-the actual value of the previous point; a. the2，A3And AnRespectively representing the actual values of the first two points, the first three points and the point from the first n point.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810010869.2A CN108073554B (en) | 2018-01-05 | 2018-01-05 | Power-assisted characteristic curve design method of automobile electric power-assisted steering system based on SOC |
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