阅读说明：本技术 一种电动轮驱动车辆的制动效能试验装置及方法 (Braking efficiency test device and method for electric wheel driven vehicle ) 是由 许世维 张小鹏 许冀阳 杨乃兴 于 2021-09-08 设计创作，主要内容包括：本发明提供了一种电动轮驱动车辆的制动效能试验装置及方法,兼顾了电动轮驱动车辆在制动过程中轮毂电机和制动器温升变化,能够准确地反映其复合制动系统的温升变化规律,实现了电动轮驱动车辆复合制动控制的量化,以及从局部部件到整车制动效能的综合考量。该装置和方法既能够测量和评价制动器的机械摩擦生热与轮毂电机的损耗发热,又能够估算轮毂电机和制动器之间存在的热传导、热辐射等多种热耦合关系而对电动轮复合制动温升的影响,提高了电动轮复合制动系统制动效能评价的准确性。本发明不仅适用于小型四轮毂电机驱动车辆,对于大转矩、重载荷的电动大客车、多轴重型车辆等电动轮驱动重型车辆的复合制动效能试验同样能够实现较好的技术效果。(The invention provides a braking efficiency test device and method for an electric wheel driven vehicle, which give consideration to the temperature rise change of a hub motor and a brake of the electric wheel driven vehicle in the braking process, can accurately reflect the temperature rise change rule of a composite braking system of the electric wheel driven vehicle, and realizes the quantification of the composite braking control of the electric wheel driven vehicle and the comprehensive consideration of the braking efficiency of a local part to the whole vehicle. The device and the method can measure and evaluate the mechanical friction heat generation of the brake and the loss heat generation of the hub motor, can estimate the influence of various thermal coupling relations such as heat conduction, heat radiation and the like between the hub motor and the brake on the composite braking temperature rise of the electric wheel, and improve the accuracy of the composite braking system of the electric wheel. The invention is not only suitable for small four-hub motor-driven vehicles, but also can achieve better technical effects on the composite braking effectiveness test of electric motor-driven heavy vehicles such as large-torque heavy-load electric buses and multi-shaft heavy vehicles.)

1. The utility model provides a braking efficiency test device of electronic round of drive vehicle which characterized in that: the device consists of the following components:

the system comprises a dynamometer, a constant-temperature water cooling system, a vehicle control unit, a motor controller, a composite brake controller, a motor temperature measuring device, a brake temperature measuring device, an electric wheel test bed, an electric wheel test environment temperature cabin, a brake test bed and a brake test environment temperature cabin;

the vehicle control unit, the motor controller and the brake controller are used for being matched with each other in a test to provide corresponding control instructions for the hub motor and the brake;

the dynamometer is used for providing loads for the braking torques output by the hub motor under different temperature, different rotating speed and different braking torque instruction states;

the constant-temperature water cooling system is used for controlling the temperature of the hub motor and providing corresponding temperature conditions for measuring the braking torque of the hub motor at different temperatures;

the brake test bed is used for measuring the friction torque and the brake response rate of the brake under different temperature, different rotating speed and different brake pressure states; the brake test stand is provided with the brake test environment temperature cabin which is used for accommodating the hub motor, the brake and the speed reducer when testing the friction torque and the braking response of the brake and providing corresponding test temperature conditions;

the electric wheel test bed is used for measuring the braking torque of the electric wheel hub motor at different temperatures and different rotating speeds; the electric wheel test bed is provided with the electric wheel test environment temperature cabin which is used for accommodating the hub motor, the brake and the speed reducer when testing the braking torque of the hub motor and providing corresponding test temperature conditions;

the motor temperature measuring device and the brake temperature measuring device respectively comprise temperature sensors arranged at key positions on the electric wheel to be measured and the brake.

2. The apparatus of claim 1, wherein: the temperature sensor in the motor temperature measuring device specifically comprises: the brake comprises a contact temperature sensor arranged on a rim, a non-contact sensor arranged between a hub motor and a brake reducer in the rim and used for measuring air temperature, a contact temperature sensor arranged on a brake caliper, a temperature sensor arranged on the reducer, a temperature sensor arranged on a brake disc and a contact temperature sensor arranged on a shell of the hub motor;

the temperature sensor in the brake temperature measuring device specifically includes: a temperature sensor provided in the brake caliper, and a non-contact temperature sensor for the brake disk.

3. A braking effectiveness test method of an electric wheel drive vehicle using the apparatus according to any one of claims 1 or 2, characterized in that: the method specifically comprises the following steps:

(1) electric wheel test steps:

before the test is started, the electric wheel is arranged in an electric wheel test environment temperature cabin;

when the test is started, the vehicle control unit, the motor controller and the brake controller respectively provide corresponding control instructions, and the test temperature condition is provided by the electric wheel test environment temperature cabin;

under the condition of room temperature (20 ℃), the electric wheel test bed is utilized to calibrate the rotation speed of the hub motor from 0 to the maximum rotation speed n_maxRange of (1), torque command from 0 to maximum braking torque-T_maxThe braking torque which can be actually output by the motor in the range is obtained, so that an output braking torque matrix table of the hub motor under the room temperature condition is constructed; then, a constant temperature water cooling system is used for providing temperature conditions of 40 ℃, 60 ℃ and 80 ℃ for the hub motor and the controller thereof at intervals of 20 ℃, and a dynamometer is used for calibrating the rotation speed of the hub motor from 0 to the maximum rotation speed n_maxRange of (1), torque command from 0 to maximum braking torque-T_maxIn the range, the motors brake the brake torques which are actually output respectively, so that an output brake torque matrix table of the hub motor at the temperature of 40-80 ℃ is constructed; then sequentially providing temperature conditions of 90 ℃, 100 ℃ and 110 ℃ to the hub motor and the controller thereof at intervals of 10 ℃ by utilizing a constant-temperature water cooling system, thereby constructing an actual output braking torque matrix table of the hub motor under the temperature condition of 90-110 ℃; then, providing a motor maximum allowable temperature condition of 115 ℃ for the hub motor and a controller thereof by using a constant temperature water cooling system, thereby constructing an actual output braking torque matrix table of the hub motor under the motor maximum allowable temperature condition; obtaining the variation data of the braking torque-temperature of the hub motor through the braking torque matrix tables;

aiming at the change data of the braking torque-temperature of the hub motor, fitting a function relation of the braking torque of the motor and the temperature change by using an interpolation method to obtain a change rule of the output braking torque of the hub motor caused by the braking temperature rise; estimating a motor braking efficiency factor according to the change rule;

(2) a brake test step:

before the test is started, the electric wheel is arranged in a brake test environment temperature cabin;

when the test is started, the vehicle controller and the brake controller respectively provide corresponding control instructions, and the brake test environment temperature cabin provides test temperature conditions;

under the condition of room temperature of 20 ℃, testing pressing force on a brake lining and braking force generated by friction under the condition of different rotating speeds through a brake test bed, and further obtaining the friction factor of the brake disc under the room temperature state; adjusting the temperature of the brake test environment temperature cabin to 100 ℃, testing the pressing force on the brake lining and the braking force generated by friction under different rotating speeds through a brake test bench, and further obtaining the friction factor of the brake disc at the state of 100 ℃; then, according to the method, the temperature of the brake test environment temperature cabin is adjusted at intervals of 20 ℃ to obtain friction factors of brake discs at different rotating speeds and different temperatures, and a function of friction factor change of a brake friction plate caused by temperature rise is obtained through fitting;

obtaining the braking pressure of a friction pair by using a two-dimensional table look-up method according to the braking intensity, calculating the relative sliding speed of the friction pair by using the initial vehicle speed during braking, combining a friction factor change function of a friction plate of the brake caused by the temperature rise, and fitting a function of the dynamic friction factor of the brake related to the pressure and the temperature of a brake pipeline and the initial vehicle speed during braking by quadratic regression:

in the formula, mu_mb(t) represents a brake dynamic friction factor; p (t) is brake line pressure (Pa); t (t) is brake temperature (. degree. C.); v. of₀An initial vehicle speed (m/s) for braking; beta is a₀A constant term representing a coefficient of fit for the dynamic friction factor; beta is a₁₁、β₁₂Respectively representing the first and second fitting coefficients of the dynamic friction factor related to the pressure of the brake pipeline; beta is a₂₁、β₂₂Respectively representing the first and second fitting coefficients of the dynamic friction factor related to the temperature of the brake; beta is a₃₁、β₃₂Respectively representing the primary and secondary fitting coefficients of the dynamic friction factor related to the initial braking speed;

then, the mechanical braking efficiency factor is estimated by combining a brake efficiency factor and friction factor relation curve data table look-up provided by a brake supplier;

(3) calculating the equivalent braking efficiency of the composite braking system of the electric wheel driven vehicle:

calculating corresponding equivalent braking efficiency factors according to the ratio of the mechanical braking force to the motor braking force in the total required braking force and by combining the estimated motor equivalent braking efficiency factor and the mechanical braking efficiency factor at a certain temperature:

in the formula, K_{ef_veh}Representing an equivalent braking effectiveness factor; i represents the ith electric wheel; n represents the number of electric wheels; lambda [ alpha ]_{i_eB}Represents the proportion of the regenerative braking force of the motor in the ith electric wheel, lambda_{i_eM}Represents the proportion of the mechanical braking force of the brake in the ith electric wheel, lambda_{i_eB}+λ_{i_eM}＝1；K_{ef_eB_i}Expressing the equivalent braking efficiency factor, K, of the motor in the ith electric wheel_{ef_eM_i}Representing the mechanical braking efficiency factor in the ith electric wheel.

4. The method of claim 3, wherein: according to the temperature of a hub motor and a brake obtained by a real-time temperature rise prediction model of the electric wheel composite braking system, by combining the mapping relation between braking temperature rise, motor braking torque and brake friction factor, and utilizing the mapping relation between the braking temperature rise characteristic of an electric wheel and the braking efficiency of the whole vehicle, a characterization model of the comprehensive braking efficiency of the electric wheel composite braking system is obtained, a coupling model between the braking efficiency and the braking dynamics of the whole vehicle is established by calculating the braking efficiency factor of the whole vehicle, and an evaluation index of the whole vehicle braking efficiency of the electric wheel driven vehicle shown as the following formula is obtained by derivation and used for evaluating the whole vehicle braking efficiency of the electric wheel driven vehicle:

wherein the content of the first and second substances,is the predicted vehicle braking deceleration (m/s)²)；Is an estimated vehicle braking distance (m); n is the number of electric wheels or service brakes of the vehicle; p is a radical of_BIs the brake fluid pressure (Pa); d_wIs the brake wheel cylinder diameter (m); eta_BTo brake efficiency; mu.s_BIs the brake coefficient of friction; d₁And D₂Effective inner and outer diameters (m) of the friction lining respectively; k_{ef_veh}Is an equivalent braking effectiveness factor; m is vehicle mass (kg); r is the tire radius (m); v. of₀The initial braking speed (m/s) of the vehicle is obtained.

Technical Field

The invention belongs to the technical field of composite braking of electric wheel driven vehicles, and particularly relates to a braking efficiency test device and method of an electric wheel driven vehicle with an electromechanical-thermal coupling characteristic.

Background

The electric wheel is composed of a hub motor, a speed reducer, a brake, a rim and other parts, and the arrangement space of each part is limited, and the integration level is high. In the braking process of the electric wheel, the phenomena of mechanical friction heating of the brake and loss heating of the hub motor exist, and multiple thermal coupling relations of heat conduction, heat radiation and the like also exist between the hub motor and the brake, so that the heat of the electric wheel composite braking system can be continuously accumulated, and the braking temperature rise is intensified. However, in most electric vehicles at present, only the change of braking effectiveness caused by the braking temperature rise of the friction brake is taken into consideration, and the reduction of braking effectiveness of the composite braking system caused by the heating of the motor brake is not considered, so that the composite braking performance of the electric wheel driven vehicle under the heating condition of the electric wheels is difficult to be effectively mastered and evaluated, and further optimization of the composite braking performance is hindered.

Disclosure of Invention

In view of the above technical problems in the art, the present invention provides a braking effectiveness testing apparatus for an electric wheel-driven vehicle, comprising:

the system comprises a dynamometer, a constant-temperature water cooling system, a vehicle control unit, a motor controller, a composite brake controller, a motor temperature measuring device, a brake temperature measuring device, an electric wheel test bed, an electric wheel test environment temperature cabin, a brake test bed and a brake test environment temperature cabin;

the vehicle control unit, the motor controller and the brake controller are used for being matched with each other in a test to provide corresponding control instructions for the hub motor and the brake;

the dynamometer is used for controlling the braking torque output by the hub motor under different temperature, different rotating speed and different braking torque instruction states;

the constant-temperature water cooling system is used for controlling the temperature of the hub motor and providing corresponding temperature conditions for measuring the braking torque of the hub motor at different temperatures;

the brake test bed is used for measuring the friction torque, the brake response rate and the like of the brake under different temperatures, different rotating speeds and different brake pressure states; the brake test stand is provided with the brake test environment temperature cabin which is used for accommodating the hub motor, the brake and the speed reducer when testing the friction torque and the braking response of the brake and providing corresponding test temperature conditions;

the electric wheel test bed is used for measuring the braking torque of the electric wheel hub motor at different temperatures and different rotating speeds; the electric wheel test bed is provided with the electric wheel test environment temperature cabin which is used for accommodating the hub motor, the brake and the speed reducer when testing the braking torque of the hub motor and providing corresponding test temperature conditions;

the motor temperature measuring device and the brake temperature measuring device respectively comprise temperature sensors arranged at key positions on the electric wheel to be measured and the brake.

Further, a temperature sensor in the motor temperature measuring device specifically includes: the brake comprises a contact temperature sensor arranged on a rim, a non-contact sensor arranged between a hub motor and a brake reducer in the rim and used for measuring air temperature, a contact temperature sensor arranged on a brake caliper, a temperature sensor arranged on the reducer, a temperature sensor arranged on a brake disc and a contact temperature sensor arranged on a shell of the hub motor;

the temperature sensor in the brake temperature measuring device specifically includes: a temperature sensor provided in the brake caliper, and a non-contact temperature sensor for the brake disk.

Correspondingly, the invention also provides a method for testing the braking efficiency of the electric wheel driven vehicle by using the device, which comprises the following steps:

(1) electric wheel test steps:

before the test is started, the electric wheel is arranged in an electric wheel test environment temperature cabin;

when the test is started, the vehicle control unit, the motor controller and the brake controller respectively provide corresponding control instructions, and the test temperature condition is provided by the electric wheel test environment temperature cabin;

under the condition of room temperature (20 ℃), the electric wheel test bed is utilized to calibrate the rotation speed of the hub motor from 0 to the maximum rotation speed n_maxRange of (1), torque command from 0 to maximum braking torque-T_maxThe braking torque which can be actually output by the motor in the range is obtained, so that an output braking torque matrix table of the hub motor under the room temperature condition is constructed; then, a constant temperature water cooling system is used for providing temperature conditions of 40 ℃, 60 ℃ and 80 ℃ for the hub motor and the controller thereof at intervals of 20 ℃, and a dynamometer is used for calibrating the rotation speed of the hub motor from 0 to the maximum rotation speed n_maxRange of (1), torque command from 0 to maximum braking torque-T_maxIn the range, the motors brake the brake torques which are actually output respectively, so that an output brake torque matrix table of the hub motor at the temperature of 40-80 ℃ is constructed; then sequentially providing temperature conditions of 90 ℃, 100 ℃ and 110 ℃ to the hub motor and the controller thereof at intervals of 10 ℃ by utilizing a constant-temperature water cooling system, thereby constructing an actual output braking torque matrix table of the hub motor under the temperature condition of 90-110 ℃; then, providing a motor maximum allowable temperature condition of 115 ℃ for the hub motor and a controller thereof by using a constant temperature water cooling system, thereby constructing an actual output braking torque matrix table of the hub motor under the motor maximum allowable temperature condition; obtaining the variation data of the braking torque-temperature of the hub motor through the braking torque matrix tables;

aiming at the change data of the braking torque-temperature of the hub motor, fitting a function relation of the braking torque of the motor and the temperature change by using an interpolation method to obtain a change rule of the output braking torque of the hub motor caused by the braking temperature rise; and estimating the equivalent braking efficiency factor of the motor according to the change rule.

(2) A brake test step:

before the test is started, the electric wheel is arranged in a brake test environment temperature cabin;

when the test is started, the vehicle controller and the brake controller respectively provide corresponding control instructions, and the brake test environment temperature cabin provides test temperature conditions;

under the condition of room temperature (20 ℃), testing the pressing force on the brake lining and the braking force generated by friction under the condition of different rotating speeds by a brake test bed, and further obtaining the friction factor of the brake disc under the room temperature state; adjusting the temperature of the brake test environment temperature cabin to 100 ℃, testing the pressing force on the brake lining and the braking force generated by friction under different rotating speeds through a brake test bench, and further obtaining the friction factor of the brake disc at the state of 100 ℃; then, according to the method, the temperature of the brake test environment temperature cabin is adjusted at intervals of 20 ℃ to obtain friction factors of brake discs at different rotating speeds and different temperatures, and a function of friction factor change of a brake friction plate caused by temperature rise is obtained through fitting;

obtaining the braking pressure of a friction pair by using a two-dimensional table look-up method according to the braking intensity, calculating the relative sliding speed of the friction pair by using the initial speed during braking, combining a friction factor change function of a friction plate of the brake caused by the temperature rise, and fitting a function of the dynamic friction factor of the brake related to the pressure of a brake pipeline, the temperature of the brake and the initial speed of the brake by quadratic regression:

in the formula, mu_mb(t) represents a brake dynamic friction factor; p (t) is brake line pressure (Pa); t (t) is brake temperature (. degree. C.); v. of₀An initial vehicle speed (m/s) for braking; beta is a₀A constant term representing a coefficient of fit for the dynamic friction factor; beta is a₁₁、β₁₂Respectively representing the first and second fitting coefficients of the dynamic friction factor related to the pressure of the brake pipeline; beta is a₂₁、β₂₂Respectively representing the first and second fitting coefficients of the dynamic friction factor related to the temperature of the brake; beta is a₃₁、β₃₂The first and second fitting coefficients of the dynamic friction factor relating to the initial vehicle speed at braking are respectively expressed.

And estimating the mechanical braking efficiency factor by combining a brake efficiency factor and friction factor relation curve data lookup table provided by a brake supplier.

(3) Calculation of equivalent braking efficiency of composite braking system of electric wheel driven vehicle

Calculating corresponding equivalent braking efficiency factors according to the ratio of the mechanical braking force to the motor braking force in the total required braking force and by combining the estimated motor equivalent braking efficiency factor and the mechanical braking efficiency factor at a certain temperature:

in the formula, K_{ef_veh}Representing an equivalent braking effectiveness factor; i represents the ith electric wheel; n represents the number of electric wheels; lambda [ alpha ]_{i_eB}Represents the proportion of the regenerative braking force of the motor in the ith electric wheel, lambda_{i_eM}Represents the proportion of the mechanical braking force of the brake in the ith electric wheel, lambda_{i_eB}+λ_{i_eM}＝1；K_{ef_eB_i}Expressing the equivalent braking efficiency factor, K, of the motor in the ith electric wheel_{ef_eM_i}Representing the mechanical braking efficiency factor in the ith electric wheel.

Further, as shown in an implementation flow diagram of the method for evaluating the overall braking efficiency of the electric wheel driven vehicle shown in fig. 5, according to the temperatures of the hub motor and the brake obtained by the real-time temperature rise prediction model of the electric wheel composite braking system, by combining the mapping relationship between the braking temperature rise and the motor braking torque and the brake friction factor, the mapping relationship between the electric wheel braking temperature rise characteristic and the overall braking efficiency is utilized to obtain a characterization model of the comprehensive braking efficiency of the electric wheel composite braking system, and by calculating the overall braking efficiency factor, a coupling model between the braking efficiency and the overall braking dynamics of the vehicle is established, for example, a total braking efficiency evaluation index of the electric wheel driven vehicle shown in the following formula is obtained by derivation, so that the method for evaluating the overall braking efficiency of the electric wheel driven vehicle is formed.

Wherein the content of the first and second substances,is the predicted vehicle braking deceleration (m/s)²)；Is an estimated vehicle braking distance (m); n is the number of electric wheels or service brakes of the vehicle; p is a radical of_BIs the brake fluid pressure (Pa); d_wIs the brake wheel cylinder diameter (m); eta_BTo brake efficiency; mu.s_BIs the brake coefficient of friction; d₁And D₂Effective inner and outer diameters (m) of the friction lining respectively; k_{ef_veh}The equivalent braking efficiency factor is obtained by the above formula; m is vehicle mass (kg); r is the tire radius (m); v. of₀The initial braking speed (m/s) of the vehicle is obtained.

The device and the method provided by the invention have the advantages that the temperature rise changes of the hub motor and the brake in the braking process of the electric wheel driven vehicle are considered, the temperature rise change rule of the composite braking system of the electric wheel driven vehicle can be accurately reflected, the composite braking control of the electric wheel driven vehicle is quantized, and the comprehensive consideration from local parts to the braking efficiency of the whole vehicle is realized. The device and the method can measure and evaluate the mechanical friction heat generation of the brake and the loss heat generation of the hub motor, can estimate the influence of various thermal coupling relations such as heat conduction, heat radiation and the like between the hub motor and the brake on the composite braking temperature rise of the electric wheel, and improve the accuracy of the composite braking system of the electric wheel. The invention is not only suitable for small four-hub motor-driven vehicles, but also can achieve better technical effects on the composite braking effectiveness test of electric motor-driven heavy vehicles such as large-torque heavy-load electric buses and multi-shaft heavy vehicles.

Drawings

FIG. 1 is a schematic structural diagram of an apparatus according to the present invention;

FIG. 2 is a schematic layout of temperature sensors for electric wheel testing;

FIG. 3 is a schematic layout of temperature sensors for a brake test;

fig. 4 is a schematic flow chart of a method for calculating the composite braking effectiveness of the electric wheel according to the present invention.

Fig. 5 is a schematic flow chart of an implementation of the method for evaluating the braking effectiveness of the whole electric wheel-driven vehicle provided by the invention.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a braking effectiveness test device of an electric wheel drive vehicle, which comprises the following components as shown in figure 1:

the system comprises a dynamometer, a constant-temperature water cooling system, a vehicle control unit, a motor controller, a composite brake controller, a motor temperature measuring device, a brake temperature measuring device, an electric wheel test bed, an electric wheel test environment temperature cabin, a brake test bed and a brake test environment temperature cabin;

the vehicle control unit, the motor controller and the brake controller are used for being matched with each other in a test to provide corresponding control instructions for the hub motor and the brake;

the dynamometer is used for controlling the braking torque output by the hub motor under different temperature, different rotating speed and different braking torque instruction states;

the constant-temperature water cooling system is used for controlling the temperature of the hub motor and providing corresponding temperature conditions for measuring the braking torque of the hub motor at different temperatures;

the brake test bed is used for measuring the friction torque, the brake response rate and the like of the brake under different temperatures, different rotating speeds and different brake pressure states; the brake test stand is provided with the brake test environment temperature cabin which is used for accommodating the hub motor, the brake and the speed reducer when testing the friction torque and the braking response of the brake and providing corresponding test temperature conditions;

the electric wheel test bed is used for measuring the braking torque of the electric wheel hub motor at different temperatures and different rotating speeds; the electric wheel test bed is provided with the electric wheel test environment temperature cabin which is used for accommodating the hub motor, the brake and the speed reducer when testing the braking torque of the hub motor and providing corresponding test temperature conditions;

the motor temperature measuring device and the brake temperature measuring device respectively comprise temperature sensors arranged at key positions on the electric wheel to be measured and the brake.

In a preferred embodiment of the present invention, as shown in fig. 2, the temperature sensor in the motor temperature measuring device specifically includes: the temperature measurement device comprises a contact type temperature sensor 2 arranged on a rim of an electric wheel 1, a non-contact type sensor 4 arranged between a hub motor and a brake reducer in the rim and used for measuring air temperature, a contact type temperature sensor 3 arranged on a brake caliper, a temperature sensor 5 arranged on the reducer, a temperature sensor 6 arranged on a brake disc and a contact type temperature sensor 7 arranged on a shell of the hub motor;

as shown in fig. 3, the temperature sensor in the brake temperature measuring device specifically includes: a temperature sensor 8 provided in the brake caliper, and a noncontact temperature sensor 9 for the brake disk.

Correspondingly, the method for testing the braking effectiveness of the electric wheel driven vehicle by using the device provided by the invention, as shown in fig. 4, specifically comprises the following steps:

(1) electric wheel test steps:

before the test is started, the electric wheel is arranged in an electric wheel test environment temperature cabin;

when the test is started, the vehicle control unit, the motor controller and the brake controller respectively provide corresponding control instructions, and the test temperature condition is provided by the electric wheel test environment temperature cabin;

under the condition of room temperature (20 ℃), the electric wheel test bed is utilized to calibrate the rotation speed of the hub motor from 0 to the maximum rotation speed n_maxRange of (1), torque command from 0 to maximum braking torque-T_maxTime of flight electricityThe braking torque which can be actually output by the hub motor is calculated, and therefore an output braking torque matrix table of the hub motor under the room temperature condition is constructed; then, a constant temperature water cooling system is used for providing temperature conditions of 40 ℃, 60 ℃ and 80 ℃ for the hub motor and the controller thereof at intervals of 20 ℃, and a dynamometer is used for calibrating the rotation speed of the hub motor from 0 to the maximum rotation speed n_maxRange of (1), torque command from 0 to maximum braking torque-T_maxIn the range, the motors brake the brake torques which are actually output respectively, so that an output brake torque matrix table of the hub motor at the temperature of 40-80 ℃ is constructed; then sequentially providing temperature conditions of 90 ℃, 100 ℃ and 110 ℃ to the hub motor and the controller thereof at intervals of 10 ℃ by utilizing a constant-temperature water cooling system, thereby constructing an actual output braking torque matrix table of the hub motor under the temperature condition of 90-110 ℃; then, providing a motor maximum allowable temperature condition of 115 ℃ for the hub motor and a controller thereof by using a constant temperature water cooling system, thereby constructing an actual output braking torque matrix table of the hub motor under the motor maximum allowable temperature condition; obtaining the variation data of the braking torque-temperature of the hub motor through the braking torque matrix tables;

aiming at the change data of the braking torque-temperature of the hub motor, fitting a function relation of the braking torque of the motor and the temperature change by using an interpolation method to obtain a change rule of the output braking torque of the hub motor caused by the braking temperature rise; estimating a motor braking efficiency factor according to the change rule;

(2) a brake test step:

before the test is started, the electric wheel is arranged in a brake test environment temperature cabin;

when the test is started, the vehicle controller, the motor controller and the brake controller respectively provide corresponding control instructions, and the brake test environment temperature cabin provides test temperature conditions;

under the condition of room temperature (20 ℃), testing the pressing force on the brake lining and the braking force generated by friction under the condition of different rotating speeds by a brake test bed, and further obtaining the friction factor of the brake disc under the room temperature state; adjusting the temperature of the brake test environment temperature cabin to 100 ℃, testing the pressing force on the brake lining and the braking force generated by friction under different rotating speeds through a brake test bench, and further obtaining the friction factor of the brake disc at the state of 100 ℃; then, according to the method, the temperature of the brake test environment temperature cabin is adjusted at intervals of 20 ℃ to obtain friction factors of brake discs at different rotating speeds and different temperatures, and a function of friction factor change of a brake friction plate caused by temperature rise is obtained through fitting;

obtaining the braking pressure of a friction pair by using a two-dimensional table look-up method according to the braking intensity, calculating the relative sliding speed of the friction pair by using the initial vehicle speed during braking, combining a friction factor change function of a friction plate of the brake caused by the temperature rise, and fitting a function of the dynamic friction factor of the brake related to the pressure of a brake pipeline, the temperature of the brake and the initial vehicle speed during braking by quadratic regression:

in the formula, mu_mb(t) represents a brake dynamic friction factor; p (t) is brake line pressure (Pa); t (t) is brake temperature (. degree. C.); v. of₀An initial vehicle speed (m/s) for braking; beta is a₀A constant term representing a coefficient of fit for the dynamic friction factor; beta is a₁₁、β₁₂Respectively representing the first and second fitting coefficients of the dynamic friction factor related to the pressure of the brake pipeline; beta is a₂₁、β₂₂Respectively representing the first and second fitting coefficients of the dynamic friction factor related to the temperature of the brake; beta is a₃₁、β₃₂The first and second fitting coefficients of the dynamic friction factor relating to the initial vehicle speed at braking are respectively expressed.

And estimating the mechanical braking efficiency factor by combining a brake efficiency factor and friction factor relation curve data lookup table provided by a brake supplier.

(3) Calculation of equivalent braking efficiency of composite braking system of electric wheel driven vehicle

Calculating corresponding equivalent braking efficiency factors according to the ratio of the mechanical braking force to the motor braking force in the total required braking force and by combining the estimated motor equivalent braking efficiency factor and the mechanical braking efficiency factor at a certain temperature:

in the formula, K_{ef_veh}Representing an equivalent braking effectiveness factor; i represents the ith electric wheel; n represents the number of electric wheels; lambda [ alpha ]_{i_eB}Represents the proportion of the regenerative braking force of the motor in the ith electric wheel, lambda_{i_eM}Represents the proportion of the mechanical braking force of the brake in the ith electric wheel, lambda_{i_eB}+λ_{i_eM}＝1；K_{ef_eB_i}Expressing the equivalent braking efficiency factor, K, of the motor in the ith electric wheel_{ef_eM_i}Representing the mechanical braking efficiency factor in the ith electric wheel.

In a preferred embodiment of the present invention, as shown in fig. 5, an implementation flow diagram of a method for evaluating the overall braking efficiency of an electric wheel-driven vehicle is shown, wherein a characterization model of the comprehensive braking efficiency of the electric wheel-driven braking system is obtained according to the temperatures of a hub motor and a brake obtained by a real-time temperature rise prediction model of the electric wheel-driven composite braking system, by combining a mapping relationship between the braking temperature rise and a motor braking torque and a brake friction factor, and using a mapping relationship between the braking temperature rise characteristic and the overall braking efficiency of the electric wheel-driven composite braking system, and a coupling model between the braking efficiency and the overall braking dynamics of the overall vehicle is established by calculating the overall braking efficiency factor, for example, a total braking efficiency evaluation index of the electric wheel-driven vehicle shown in the following formula is obtained by derivation, so as to form the method for evaluating the overall braking efficiency of the electric wheel-driven vehicle.

Wherein the content of the first and second substances,is the predicted vehicle braking deceleration (m/s)²)；Is an estimated vehicle braking distance (m); n is the number of electric wheels or service brakes of the vehicle; p is a radical of_BIs the brake fluid pressure (Pa); d_wIs the brake wheel cylinder diameter (m); eta_BTo brake efficiency; mu.s_BIs the brake coefficient of friction; d₁And D₂Effective inner and outer diameters (m) of the friction lining respectively; k_{ef_veh}The equivalent braking efficiency factor is obtained by the above formula; m is vehicle mass (kg); r is the tire radius (m); v. of₀The initial braking speed (m/s) of the vehicle is obtained.

It should be understood that, the sequence numbers of the steps in the embodiments of the present invention do not mean the execution sequence, and the execution sequence of each process should be determined by the function and the inherent logic of the process, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.