Brake force compensation method for dynamic control of vehicle based on brake disc temperature

Abstract

The invention discloses a brake force compensation method for dynamic control of a vehicle based on brake disc temperature, which comprises the following steps: acquiring brake disc temperature and original brake force, the brake disc temperature being calculated by a brake-by-wire product according to an original signal of the vehicle; determining a basic compensation coefficient corresponding to the temperature of the brake disc from a compensation coefficient curve, wherein the compensation coefficient curve is constructed according to a corresponding relation between the temperature of the brake disc and the compensation coefficient; according to the basic compensation coefficient and the original braking force, target braking force is calculated, and temperature gradient correction is conducted on the target braking force; and carrying out filtering processing and limit value control on the corrected target braking force, and outputting the final target braking force. According to the method, through dynamic correlation of the temperature of the brake disc and brake force compensation, accurate correction of the brake force in the full-temperature section ranging from-50 DEG C to 600 DEG C is achieved; and meanwhile, temperature gradient correction is combined, so that the deviation of braking force output is greatly reduced, and the control precision is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of brake-by-wire, in particular to a brake force compensation method for vehicle dynamic control based on brake disc temperature. BACKGROUND

[0002] With the emergence of brake-by-wire, the traditional mechanical hydraulic brake mode is gradually replaced by brake-by-wire. Electronic hydraulic brake (EHB) retains part of the hydraulic brake foundation and has high control accuracy, and has gradually replaced the traditional hydraulic brake system. At present, the one-box EHB brake-by-wire product is widely used. Electronic mechanical brake (EMB) refers to a brake-by-wire system that completely cancels the hydraulic pipeline, has a more flexible layout, and is faster and more accurate than hydraulic transmission. At present, the brake-by-wire product of EMB has taken shape. Since the conditions for mass production of EMB are not met at present, EMB has not been widely used in vehicle design. However, in the future, the brake-by-wire product of EMB will gradually replace one-box and become the mainstream brake-by-wire scheme.

[0003] During the driving of the vehicle, due to the change of the external temperature, the performance of the vehicle parts will also change, which affects the overall safety of the vehicle, especially the dynamic performance of the vehicle. The dynamic control performance of the vehicle refers to: when the vehicle has understeering or oversteering, the brake-by-wire product actively builds pressure to apply brake force to a single or multiple wheels, adjusts the yaw angular velocity of the vehicle body, and makes the vehicle return to the stable driving track.

[0004] In the prior art, the brake force output of the vehicle dynamic control condition is not corrected or compensated during brake control. Specifically, when the brake-by-wire system intervenes in the braking of the vehicle, the influence of the brake disc temperature change on the braking efficiency is not considered, but the brake force command is directly output according to the fixed logic. Therefore, when in different temperatures, the actual brake force of the brake-by-wire product and the control demand will have a significant deviation; especially in extreme temperature conditions, the dynamic control accuracy of the vehicle will be greatly reduced.

[0005] For example: at low temperature, the control deviation caused by the change of the viscosity of the hydraulic oil (for EHB) and the response delay of the motor (for EMB). At high temperature (300℃-500℃), the brake friction plate is heat-degraded, and the braking efficiency is significantly degraded, but the prior art does not compensate for it, resulting in a serious shortage of brake force output for vehicle dynamic control and a large control deviation. At extremely high temperature (> 500℃), because the braking efficiency of some vehicle models is severely degraded, the vehicle dynamic control function is difficult to effectively execute, and even "control failure" occurs, which cannot inhibit the instability of the vehicle. SUMMARY

[0006] The application aims to provide a brake force compensation method based on brake disc temperature for vehicle dynamic control, so as to solve the problems of control deviation in low-temperature working conditions and significant control deviation in high-temperature working conditions.

[0007] To achieve the above-mentioned purpose, the application provides the following technical scheme: a brake force compensation method based on brake disc temperature for vehicle dynamic control, comprising:

[0008] obtaining a brake disc temperature and an original brake force, wherein the brake disc temperature is calculated by a line control brake product according to vehicle original signals; determining a basic compensation coefficient corresponding to the brake disc temperature from a compensation coefficient curve, wherein the compensation coefficient curve is constructed according to the corresponding relationship between brake disc temperature and compensation coefficient;

[0009] calculating a target brake force according to the basic compensation coefficient and the original brake force, and performing temperature gradient correction on the target brake force; performing filtering processing and limit control on the corrected target brake force, and outputting a final target brake force.

[0010] Preferably, the compensation coefficient curve divides-50℃-600℃ into multiple temperature sections, and the basic compensation coefficient linearly changes with temperature in each temperature section.

[0011] Preferably, the temperature gradient correction on the target brake force comprises:

[0012] obtaining a brake disc temperature change rate, determining a dynamic correction coefficient corresponding to the brake disc temperature change rate from a correction coefficient curve, wherein the correction coefficient curve is constructed according to the corresponding relationship between brake disc temperature change rate and correction coefficient;

[0013] correcting the target brake force according to the dynamic correction coefficient.

[0014] Preferably, the dynamic correction coefficient is dynamically and positively correlated with the brake disc temperature change rate in a threshold-dependent manner.

[0015] Preferably, the formula for calculating the target brake force is:

[0016] F base = F linear ×(1+K comp0 )

[0017] wherein F comp1 is the original brake force output by a vehicle dynamic control function, and the unit is N; K base is a basic compensation coefficient corresponding to the current brake disc temperature, which is used to offset the brake efficiency loss under the corresponding brake disc temperature; and F linear is the target brake force obtained only after the basic compensation.

[0018] Preferably, the formula for correcting the target braking force is:

[0019] F comp1 = F base × (1 + K linear × (1 + K grad ))

[0020] Wherein, K grad is a dynamic correction coefficient corresponding to the current brake disc temperature change rate, F comp1 is the target braking force obtained after the basic compensation and temperature gradient dynamic correction, and when the brake disc temperature change rate does not exceed the threshold, K grad = 0, F comp1 = F comp0 .

[0021] Preferably, the filter processing adopts a first-order low-pass filter, and the formula is:

[0022] F comp = alpha * F comp_filtered_last + (1-alpha) * F comp1

[0023] Wherein, alpha is a filter coefficient determined according to the smoothing control requirement; F comp_filtered_last is the braking force instruction filtered in the last period.

[0024] Preferably, the limit control sets upper and lower limits according to the original braking force, the upper limit is 1.5 times the original braking force, and the lower limit is the original braking force.

[0025] Compared with the prior art, the present application has the beneficial effects of:

[0026] 1. Precise correction in the whole temperature range, improving control accuracy

[0027] Through the dynamic correlation of brake disc temperature and braking force compensation, precise correction of braking force in the whole temperature range of-50℃-600℃ is realized. Combined with basic compensation (matching the continuous attenuation law of braking efficiency with temperature) and temperature gradient correction (adaptation to rapid temperature change scene), the deviation of braking force output of vehicle dynamic control from the control target is greatly reduced, the control accuracy is significantly improved, and precise control of the vehicle can be ensured in different temperature conditions when the vehicle dynamic control function is activated.

[0028] 2. Solve the problem of control failure at extremely high temperature

[0029] In view of the characteristics of the severe attenuation of braking efficiency in the extremely high temperature range, the activation of the vehicle dynamic control function at high brake disc temperature is avoided by compensating the braking force, which can cope with the emergency instability scene at high brake disc temperature and reduce the risk of accidents. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a system architecture diagram of the system based on which the present application is made;

[0031] Figure 2 is a compensation coefficient curve example diagram of the present application;

[0032] Figure 3 is a logic flow diagram of the present application. DETAILED DESCRIPTION

[0033] The present application discloses a brake force compensation method based on brake disc temperature when controlling vehicle dynamics, comprising: acquiring brake disc temperature and original brake force, wherein the brake disc temperature is calculated by a line control brake product according to vehicle original signals; determining a basic compensation coefficient corresponding to the brake disc temperature from a compensation coefficient curve, wherein the compensation coefficient curve is constructed according to the corresponding relationship between brake disc temperature and compensation coefficient; calculating a target brake force according to the basic compensation coefficient and the original brake force, and performing temperature gradient correction on the target brake force; performing filtering processing and limit control on the corrected target brake force, and outputting a final target brake force.

[0034] The above method is applicable to EHB systems or EMB systems, and relies on the cooperative work of two core modules of an electronic control unit and an actuator of a line control brake product, and specific reference can be made to Table 1 and Figure 1 .

[0035]

[0036]

[0037] Table 1

[0038] The basic compensation coefficient corresponding to the brake disc temperature is determined from the compensation coefficient curve, and the compensation coefficient curve is constructed according to the corresponding relationship between the brake disc temperature and the compensation coefficient, and specifically comprises:

[0039] The compensation coefficient curve is determined based on the change rule of the braking efficiency of the line control brake product with temperature (the characteristic difference between the EHB system and the EMB system is distinguished in the low-temperature section, and the high-temperature section is universal), and the temperature range of-50 DEG C to 600 DEG C is divided into multiple temperature sections, and the basic compensation coefficient K changes linearly with temperature in each temperature section (K is an adjustable parameter, which is set according to the type of the line control brake product, the braking efficiency characteristics of the vehicle brake, and other factors).

[0040] A temperature section division case is proposed in the present application, and specific reference can be made to Table 2.

[0041]

[0042] Table 2

[0043] It should be noted that the temperature section in Table 2 is presented with specific temperature values for ease of understanding, and the division values of each section of the temperature section are also adjustable parameters in actual operation. Based on the temperature section division of Table 2, a compensation coefficient curve graph is provided as shown in the figure, and the parameters in the figure are for illustration only. The specific parameter adjustment needs to be determined according to the braking efficiency and temperature relationship of different vehicle brake models and through real vehicle debugging. Figure 2

[0044] The target braking force is calculated according to the basic compensation coefficient and the original braking force, and the target braking force is temperature gradient corrected, including a two-level calculation logic of "basic compensation + temperature gradient dynamic correction", which is specifically as follows:

[0045] ① Basic compensation calculation

[0046] Based on the attenuation law of braking efficiency with temperature, the basic compensation coefficient K linear is used to offset the loss of braking efficiency at the corresponding temperature, and the calculation formula is:

[0047] F comp0 =F base ×(1+K linear )

[0048] Where F base is the original braking force output by the vehicle dynamic control function (unit: N); K linear is the linear basic compensation coefficient K corresponding to the current temperature T, which is an adjustable parameter; F comp0 is the target braking force obtained after only basic compensation calculation.

[0049] ② Temperature gradient dynamic correction

[0050] When the temperature change gradient is large (i.e. the brake disc is rapidly heated or cooled), the braking efficiency change rate is accelerated, and the dynamic correction coefficient K grad needs to be increased. The value of the dynamic correction coefficient K grad is obtained from: obtaining the brake disc temperature change rate, determining the dynamic correction coefficient corresponding to the brake disc temperature change rate from the correction coefficient curve, and the correction coefficient curve is constructed according to the corresponding relationship between the brake disc temperature change rate and the correction coefficient. The correction coefficient curve is set based on the temperature change rate and the change characteristics of the braking efficiency with temperature. The dynamic correction coefficient is dynamically and positively correlated with the brake disc temperature change rate ΔT / Δt in a threshold-dependent manner, and the threshold value can be adjusted, for example, set to 5℃ / s:

[0051] When ΔT / Δt exceeds the given threshold value, the dynamic correction coefficient K grad is positively correlated with the temperature change rate ΔT / Δt, and K grad ​Linearly increases with the increasing of temperature change rate;

[0052] When ΔT / Δt does not exceed a given threshold, K grad = 0.

[0053] According to the dynamic correction coefficient, the target braking force is corrected, and the correction formula is:

[0054] F comp1 = F base × (1 + K linear × (1 + K grad ))

[0055] Wherein, K grad is a linear basic compensation coefficient corresponding to the current temperature change rate, and is an adjustable parameter; F comp1 is the target braking force obtained after "linear basic compensation + temperature gradient dynamic correction". Based on the formula, when K grad = 0, F comp1 = F comp0 .

[0056] The corrected target braking force is filtered and limited, and the final target braking force is output, including the combined control method of "first-order low-pass filter + upper and lower limit value limitation":

[0057] ① First-order low-pass filter

[0058] The target braking force corrected by the temperature gradient is filtered by the first-order low-pass filter, and the filtering formula is:

[0059] F comp = α × F comp_filtered_last + (1-α) × F comp1

[0060] Wherein: α is a filter coefficient, which is an adjustable parameter and is set according to the smoothing control requirement; F comp_filtered_last is the braking force instruction filtered in the last period.

[0061] ② Upper and lower limit value limitation

[0062] The limit value control sets the upper and lower limits according to the original braking force F base , the upper limit is 1.5 times the original braking force F base , and the lower limit is the original braking force F base . The compensated braking force needs to meet F base ≤ F comp ≤ F base · 1.5, to avoid the situation that the compensated F comp is too large to exceed the load limit of the actuator or too small to cause no braking force output due to parameter setting error or calculation error.

[0063] Based on the above technical solution, the following specific execution steps are provided, and the logic flow chart is referred to Figure 3 :

[0064] Step 1: Basic parameter adjustment

[0065] The following adjustable parameters are calibrated by vehicle brake characteristics or real vehicle test, etc.:

[0066] Temperature segment-linear compensation coefficient K;

[0067] Temperature gradient correction threshold and K grad Adjustable parameters;

[0068] Smooth control parameter (filter coefficient a);

[0069] Step 2: System initialization

[0070] After the vehicle dynamic controller is powered on, the initialization is completed, and the preset parameter value has been calibrated.

[0071] Step 3: System signal collection

[0072] According to the original logic of the brake-by-wire product, the brake disc temperature T is calculated, and the vehicle dynamic control original braking force F base is controlled and calculated together.

[0073] Step 4: Basic compensation coefficient K value calculation

[0074] The control module determines the temperature segment according to the temperature T, and calculates the current K linear according to the calibrated linear rule (linear derivation based on the preset adjustable parameters).

[0075] Step 5: Basic compensation and temperature gradient correction calculation

[0076] First, substitute the formula F comp0 = F base × (1+K linear ) to get the initial target braking force;

[0077] Then calculate the temperature change rate AT / At, if it exceeds the threshold, substitute F comp1 = F base × (1+K linear × (1+K grad )), otherwise F comp1 = F comp0 , get the corrected target braking force

[0078] Step 6: Filter processing and limit control on the corrected target braking force

[0079] Fcomp1 First-order low-pass filtering is performed to obtain F comp :

[0080] If F comp > F base ·1.5, the F comp is forcibly adjusted to F base ·1.5;

[0081] If F comp < F base , the F comp is forcibly adjusted to F base ;

[0082] Step 7: instruction output

[0083] The final F comp is sent to the execution module of the line control braking product to execute the brake force instruction of the vehicle dynamic control.

[0084] In summary, the original brake disc model temperature signal of the line control braking product is used, combined with the original brake force instruction of each wheel during vehicle dynamic control (since the same control is used for the brake force on each wheel, the control of each wheel is not described separately), -50℃-600℃ is divided into multiple temperature segments, the basic compensation coefficient (adjustable parameter) is designed based on the change rule of brake efficiency with temperature, dynamic correction (adjustable parameter) is added for the scene with large temperature change gradient, and the final target brake force is output after filtering and limit control, to realize precise and smooth compensation of the vehicle dynamic control brake force in the full temperature range.

[0085] Finally, it should be noted that: the above only describes the preferred embodiments of the present application and is not used to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A brake force compensation method for use in dynamic control of a vehicle based on brake disc temperature, characterized by, The application relates to a brake force compensation method and device. The application comprises: acquiring a brake disc temperature and an original brake force, wherein the brake disc temperature is calculated by a line control brake product according to a vehicle original signal; determining a basic compensation coefficient corresponding to the brake disc temperature from a compensation coefficient curve, wherein the compensation coefficient curve is constructed according to a corresponding relationship between a brake disc temperature and a compensation coefficient; calculating a target brake force according to the basic compensation coefficient and the original brake force, and performing temperature gradient correction on the target brake force; 2. The brake force compensation method according to claim 1, characterized by, performing filtering processing and limit control on the corrected target brake force, and outputting a final target brake force.

3. The brake force compensation method according to claim 1, characterized by, The compensation coefficient curve divides -50 DEG C to 600 DEG C into multiple temperature sections, and the basic compensation coefficient linearly changes with temperature in each temperature section. The temperature gradient correction on the target brake force comprises: acquiring a brake disc temperature change rate, determining a dynamic correction coefficient corresponding to the brake disc temperature change rate from a correction coefficient curve, wherein the correction coefficient curve is constructed according to a corresponding relationship between a brake disc temperature change rate and a correction coefficient; 4. The brake force compensation method according to claim 3, characterized by, correcting the target brake force according to the dynamic correction coefficient.

5. The brake force compensation method according to claim 3, characterized by, The dynamic correction coefficient is dynamically and positively correlated with the brake disc temperature change rate in a threshold-dependent manner. F comp0 = F base × (1 + K linear ) Wherein, F base is the original braking force output by the vehicle dynamic control function, in units of N; K linear is the basic compensation coefficient corresponding to the current brake disc temperature, used to offset the loss of braking efficiency at the corresponding brake disc temperature; F comp0 is the target braking force obtained only after basic compensation.

6. The brake force compensation method according to claim 5, characterized by, The formula for calculating the target brake force is: F comp1 = F base × (1 + K linear × (1 + K grad )) Wherein, K grad is a dynamic correction coefficient corresponding to the current brake disc temperature change rate, F comp1 is the target braking force obtained after the basic compensation and temperature gradient dynamic correction, and when the brake disc temperature change rate does not exceed the threshold, K grad = 0, F comp1 = F comp0 .

7. The brake force compensation method according to claim 6, characterized by, The formula for correcting the target brake force is: F comp = a x F comp_filtered_last + (1 - a) x F comp1 Wherein, a is filter coefficient, determined according to smoothing control demand;F comp_filtered_last is the braking force command filtered in the last cycle.

8. The brake force compensation method according to claim 1, characterized by, The filtering processing adopts first-order low-pass filtering, and the formula is: The limit control sets upper and lower limits according to the original brake force, wherein the upper limit value is 1.5 times of the original brake force, and the lower limit value is the original brake force.

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