A motor controller test system for distributed electric drive vehicles

Abstract

The present application provides a motor controller test system for a distributed electric drive vehicle, including multiple motor controller modules and multiple motor simulator modules connected to the motor controller modules; it also includes a multi-degree-of-freedom model unit for the distributed electric drive vehicle, the multi-degree-of-freedom model unit includes a driving action model, a vehicle dynamics model, a wheel force model, and a target current model; the driving action model is used to determine the turning angle of each wheel and the torque command of each motor, the vehicle dynamics model and the wheel force model are coupled to each other, and the rotation speed of each wheel is determined based on the turning angle and the torque command; the target current model determines the target current of the motor simulator module corresponding to each motor controller module based on the rotation speed of each wheel. The test system provided by the present application effectively improves the credibility of the towing test of the motor controller of the distributed electric drive vehicle by establishing a multi-degree-of-freedom model of the distributed electric drive vehicle that is more in line with the actual working conditions.

Description

Technical Field

[0001] The present application belongs to the technical field of new energy vehicles and relates to vehicle motor testing technology. Specifically, a motor controller testing system for a distributed electric drive vehicle is provided. Background Art

[0002] Distributed electric drive vehicles are driven by two or more motors, each of which drives the wheels by controlling torque or speed. Compared with traditional centralized drive systems, distributed drive can not only achieve more flexible vehicle chassis layout and integrated vehicle control, but also facilitate accurate vehicle safety control and optimal driving force / braking force distribution, especially ensuring safety in the event of partial drive motor failure. With the above advantages, distributed drive has become the mainstream trend of new energy vehicle chassis configuration.

[0003] The testing of vehicle motor controllers is generally carried out by establishing a towing test platform through a motor controller (MCU) and a motor simulator (EME). In the existing vehicle motor towing test platform, the motor simulator used to simulate the output characteristics of the vehicle motor, its motor speed, current and other state parameters are generally set manually or determined by a relatively simple motor model in the form of a transfer function. However, the state characteristics of each motor of a distributed electric drive vehicle are simultaneously affected by the combined influence of the steering angle, torque and tire stress conditions of each wheel, and its motor speed and corresponding real-time current and other parameters all show complex changes. Therefore, if they are not accurately characterized, the output of the motor simulator will not be able to reflect the operating conditions of the motor under actual working conditions, thereby greatly reducing the credibility of the towing test results of the vehicle motor controller.

[0004] To this end, it is necessary to improve the existing automotive motor controller test system by establishing a multi-degree-of-freedom model of a distributed electric drive vehicle that is more in line with actual working conditions, so as to accurately simulate the state characteristics and speed and torque of each motor of the distributed electric drive vehicle under real working conditions, thereby providing the motor simulator with input quantities that are more in line with actual working conditions in the motor controller drag test. Summary of the invention

[0005] The present application provides a motor controller test system for a distributed electric drive vehicle through an embodiment, the test system comprising a plurality of motor controller modules and a plurality of motor simulator modules connected to the motor controller modules, wherein each motor controller module is used to control a motor driving a wheel;

[0006] The test system also includes a multi-degree-of-freedom model unit for distributed electric drive vehicles;

[0007] The multi-degree-of-freedom model unit includes a driving action model, a vehicle dynamics model, a wheel force model and a target current model;

[0008] The driving action model determines the steering angle of each wheel of the distributed electric drive vehicle and the torque command of each motor based on a preset driving action, wherein the driving action includes a steering wheel action, an accelerator pedal action and a brake pedal action, and the torque command includes a driving torque command and a braking torque command;

[0009] The vehicle dynamics model and the wheel force model are coupled to each other, and the rotation speed of each wheel is determined based on the rotation angle and the torque command;

[0010] The target current model determines the target current of the motor simulator module corresponding to each motor controller module based on the rotation speed of each wheel.

[0011] Preferably, the degrees of freedom of the multi-degree-of-freedom model unit include the longitudinal and lateral translational motions of the vehicle body, the yaw motion of the vehicle body, and the rotational motion of each wheel of the distributed electric drive vehicle.

[0012] Furthermore, the whole vehicle dynamics model and the wheel force model are coupled to each other through the longitudinal force and lateral force received by each wheel.

[0013] Furthermore, the vehicle dynamics model determines the longitudinal movement, lateral movement and yaw movement of the distributed electric drive vehicle based on the turning angle of each wheel and the longitudinal force and lateral force exerted on each wheel; the wheel force model determines the longitudinal force and lateral force exerted on each wheel based on the tire sideslip angle, tire slip rate and vertical load fitting of each wheel.

[0014] Specifically, the longitudinal motion of the distributed electric drive vehicle is determined by the following formula:

[0015]

[0016] Where m, a x 、V x are the vehicle mass, vehicle longitudinal acceleration, and vehicle longitudinal velocity, respectively. xfl 、F xfr 、F xrl 、F xrr are the longitudinal forces on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, F yfl 、F yfr 、F yrl 、F yrr are the lateral forces on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, δ fl , δ fr , δ rl , δ rr are the turning angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, C Dis the air resistance coefficient, A is the frontal area, ρ is the air density, and f is the rolling resistance coefficient;

[0017] The lateral motion of the distributed electric drive vehicle is determined by the following formula:

[0018]

[0019] Among them, a y is the vehicle lateral acceleration;

[0020] The yaw motion of the distributed electric drive vehicle is determined by the following formula:

[0021]

[0022] Among them, I z is the vertical moment of inertia of the vehicle around the z-axis, r is the yaw angular velocity of the vehicle, a is the distance from the front axle to the center of mass of the vehicle, b is the distance from the rear axle to the center of mass of the vehicle, and w is the wheelbase of the front and rear axles.

[0023] Specifically, the wheel force model determines the longitudinal force and lateral force of each wheel based on the following fitting expression:

[0024]

[0025] Among them, D is the peak factor, B is the stiffness factor, C is the curve shape factor, E is the curve curvature factor, and F is the peak factor. z is the vertical load, A 1 , A 2 F z The quadratic and linear coefficients of the tire are: when x is the tire slip angle, Y is the lateral force; when x is the tire slip rate, Y is the longitudinal force.

[0026] Specifically, the tire slip angle of each wheel is determined by the following formula:

[0027]

[0028] Among them, α fl , α fr , α rl , α rr are the tire slip angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. y is the lateral speed of the vehicle;

[0029] The tire slip ratio of each wheel is determined by the following formula:

[0030]

[0031] Among them, λ fl , fr ,rl , rr are the tire slip rates of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, ω fl ,ω fr ,ω rl ,ω rr are the speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, R wfl , R wfr , R wrl , R wrr are the rolling radii of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, V t_fl 、V t_fr 、V t_rl 、V t_rr They are the center speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively;

[0032] The vertical load of each wheel is determined by the following formula:

[0033]

[0034] Among them, F z_fl 、F z_fr 、F z_rl 、F z_rr are the vertical loads on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, m t is the sprung mass, l is the vehicle wheelbase, h g is the height of the vehicle's center of mass, m wfl 、m wfr 、m wrl 、m wrr They are the unsprung masses of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively.

[0035] Specifically, the rotation speed of each wheel is determined by the following formula:

[0036]

[0037] Among them, T bfl , T bfr , T brl , T brr are the braking torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, T dfl , T dfr , T drl , T drr are the driving torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, M yfl 、M yfr 、M yrl 、M yrr are the resistance torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively;

[0038] The center speed of each wheel is determined by the following formula:

[0039]

[0040] Furthermore, for any motor controller module, the target current model determines the target current of the corresponding motor simulator module based on the following formula:

[0041]

[0042] Among them, i d 、i q are the d-axis and q-axis target currents, u d 、u q The d and q axis voltages are collected respectively, L d , L q are the d-axis and q-axis inductances, R s is the stator resistance, ψ f is the rotor flux, ω l is the speed of the wheel driven by the motor controller module, k l is the proportional coefficient between the wheel speed and the motor mechanical speed, and n is the number of pole pairs of the permanent magnet synchronous motor.

[0043] The motor controller testing system for distributed electric drive vehicles provided in the present application optimizes the relatively simple motor model in the existing single motor controller towing test platform, and establishes a multi-degree-of-freedom model based on the forces on the whole vehicle and multiple wheels of the distributed electric drive vehicle. The model can determine the steering angle and motor torque command of each wheel according to the actual working conditions, and obtain the precise rotation speed of each wheel by jointly solving the above-mentioned whole vehicle dynamics model and wheel force model. Then, the target current of each motor is obtained as the input parameter of the motor simulator through the wheel speed that matches the actual working conditions, so that the control quantity of the motor simulator can be determined based on the actual working conditions of the vehicle, thereby greatly improving the fit between the state of the motor simulator and the actual state of the motor, and effectively improving the credibility of testing the motor controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of the architecture of an existing motor controller towing test platform;

[0045] Figure 2 A schematic diagram of the architecture of a motor controller test system for a distributed electric drive vehicle provided according to an embodiment of the present application;

[0046] Figure 3 It is a schematic diagram of the forces acting on a distributed electric drive vehicle;

[0047] Figure 4A schematic diagram of tire longitudinal force fitting according to an embodiment of the present application;

[0048] Figure 5 A schematic diagram of tire lateral force fitting according to an embodiment of the present application;

[0049] Figure 6 A schematic diagram of the longitudinal acceleration change of a vehicle model provided according to an embodiment of the present application;

[0050] Figure 7 A schematic diagram of the change in yaw rate of a vehicle model provided according to an embodiment of the present application;

[0051] Figure 8 A schematic diagram of the change in lateral acceleration of a vehicle model provided according to an embodiment of the present application;

[0052] Fig. 9 A schematic diagram of longitudinal speed change of a vehicle model provided according to an embodiment of the present application;

[0053] Fig.10 A schematic diagram of a yaw angle change of a vehicle model provided according to an embodiment of the present application;

[0054] Fig.11 A schematic diagram of the lateral speed change of the vehicle model provided according to an embodiment of the present application;

[0055] Fig.12 A schematic diagram of the change in the rotation speed of the left front wheel of a vehicle according to an embodiment of the present application;

[0056] Fig.13 A schematic diagram of the change in the speed of the right front wheel of a vehicle provided according to an embodiment of the present application;

[0057] Fig.14 A schematic diagram of the change in the d-axis current of the motor driving the left front wheel of the vehicle according to an embodiment of the present application;

[0058] Fig.15 A schematic diagram of the change in the q-axis current of the motor driving the left front wheel of the vehicle according to an embodiment of the present application;

[0059] Fig.16 A schematic diagram of the change in the d-axis current of the motor driving the right front wheel of the vehicle according to an embodiment of the present application;

[0060] Fig.17 This is a schematic diagram of the change in the q-axis current of the motor driving the right front wheel of a vehicle according to an embodiment of the present application. DETAILED DESCRIPTION

[0061] Hereinafter, the present application will be further described based on preferred embodiments with reference to the accompanying drawings.

[0062] In the description of the embodiments of the present application, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the products of the embodiments of the present application are usually placed when in use, it is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, in the description of the present application, in order to distinguish different units, the words first, second, etc. are used in this specification, but these are not limited by the order of manufacture, nor can they be understood as indicating or implying relative importance, and their names may be different in the detailed description and claims of the present application.

[0063] The vocabulary in this specification is used to illustrate the embodiments of the present application, but is not intended to limit the present application. It should also be noted that, unless otherwise clearly specified and limited, the terms "disposed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, an indirect connection through an intermediate medium, or a connection between the two elements. For those skilled in the art, the specific meanings of the above terms in this application can be specifically understood.

[0064] Figure 1 A schematic diagram of the architecture of an existing vehicle motor controller towing test platform is shown in FIG. Figure 1 As shown, the hardware part of the towing test platform includes a motor controller part on the left (its core hardware is the drive inverter on the left side of the figure) and a motor simulator on the right (its core hardware is the inverter on the right) and a filter coupling network connecting the two, wherein the motor controller compares the real-time position information corresponding to the torque command and the feedback signal on the motor simulator side, and uses a preset drive control algorithm to control the switch of its power device to switch the current and voltage in each phase topology. The continuously switched current and voltage are collected by the sensor and input into the preset motor model, and the target current is generated by the preset current control algorithm to control the switch of the power device on the motor simulator side, so that the motor simulator can simulate the response of the real motor to the control command.

[0065] As analyzed in the background technology, in the existing motor controller towing test platform, the parameters such as the motor speed or current for controlling the motor simulator are generally determined by a simple motor model, for example, by manual setting or by a relatively simple motor model in the form of a transfer function. However, the state characteristics of each motor of the distributed electric drive vehicle are simultaneously affected by the comprehensive influence of the rotation angle, torque and tire stress of each wheel, and the motor speed and corresponding real-time current both show complex changes. Therefore, when it is necessary to test multiple motor controllers of a distributed electric drive vehicle, it is necessary to establish a test system that is more in line with actual working conditions, and to more accurately characterize the state of each motor under the actual control instructions and the interaction of the vehicle body, tires, and road conditions, so as to ensure that the output of the motor simulator can accurately reflect the operating status of the motor under actual working conditions, thereby effectively improving the credibility of the towing test results of the vehicle motor controller.

[0066] Figure 2 The schematic diagram of the framework of the motor control test system of the distributed electric drive vehicle provided according to some embodiments of the present application is as follows: Figure 2 As shown, the test system includes N motor controllers and N motor simulator modules connected to each other, wherein each motor controller module is used to control a motor that drives a wheel.

[0067] As mentioned above, the core hardware of each motor controller module and motor simulator is its own inverter. In addition, each motor controller module and motor simulator module also includes a processing module that runs the control algorithm, which is not shown in the figure, and sensors for collecting current and voltage. Their functions and settings can be referred to in Figure 1 , I will not go into details here.

[0068] The number N can be determined according to the number of motors that actually drive the wheels of the distributed electric drive vehicle. For example, N can be 2, indicating that there are two motors (one for driving the two front wheels, or one for driving the two rear wheels). In another example, N can be 4, indicating that the left front wheel, right front wheel, left rear wheel, and right rear wheel of the distributed electric drive vehicle are all driven by motors.

[0069] In addition to the above parts that are similar to the existing towing test platform, such as Figure 2 As shown, the test system also includes a multi-degree-of-freedom model unit of a distributed electric drive vehicle. In the embodiment of the present application, the multi-degree-of-freedom model unit is used to replace the simpler motor model in the prior art, and accurately characterizes the motor state based on actual driving actions, overall vehicle force and tire force conditions, so that the state of the motor simulator is more consistent with actual driving conditions, so as to improve the credibility of the motor controller test results.

[0070] like Figure 2As shown, the multi-degree-of-freedom model unit includes a driving action model, a vehicle dynamics model, a wheel force model and a target current model.

[0071] Specifically, the driving action model determines the steering angle of each wheel of the distributed electric drive vehicle and the torque command of each motor based on the preset driving action, wherein the driving action includes steering wheel action, accelerator pedal action and brake pedal action, and the torque command includes driving torque command and braking torque command; the vehicle dynamics model and the wheel force model are coupled with each other, and the rotation speed of each wheel is determined based on the steering angle and torque command; the target current model determines the target current of the motor simulator corresponding to each motor controller based on the rotation speed of each wheel.

[0072] The above-mentioned multi-degree-of-freedom model unit is arranged between the motor controller module and the motor simulator module. According to the preset working conditions, such as double lane change conditions under high-speed driving conditions, or emergency acceleration conditions, emergency braking conditions, etc., it determines the steering angle and motor torque command of each wheel in turn through the driving action model, and the torque command of each motor is input into the corresponding motor controller module. At the same time, the wheel angle information and the motor torque command are used as input quantities to enter the mutually coupled vehicle dynamics model and wheel force model. By jointly solving the above-mentioned vehicle dynamics model and wheel force model, the precise rotation speed of each wheel is obtained. The above-mentioned wheel rotation speed is further solved by the target current model to obtain the target current input of each motor to the motor simulator corresponding to the actual vehicle working condition, so that the control quantity of the motor simulator is determined based on the actual vehicle working condition, thereby greatly improving the fit between the state of the motor simulator and the actual state of the motor, and effectively improving the credibility of the motor controller test.

[0073] The following is combined with the accompanying drawings. Figure 2 The specific implementation methods of each functional module of the multi-degree-of-freedom model unit are described in detail.

[0074] 1. Driving action model:

[0075] The driving action model determines the steering angle of each wheel and the torque of each motor according to the preset driving conditions. In some optional embodiments, the preset driving conditions can be determined according to driving scenarios such as double lane changes, acceleration, and braking. For example, the steering wheel angle is determined according to the route of the double lane change, or the position of the accelerator pedal and the brake pedal is determined according to the time and distance of acceleration and braking.

[0076] After the above driving conditions are determined, they can be further converted into the steering angle corresponding to each wheel, as well as the acceleration torque and braking torque (or acceleration torque and braking torque) applied to each motor through a driving action model.

[0077] In some specific embodiments, the driving action model can be implemented using existing commercial software for simulating vehicle dynamics characteristics. For example, CarSim software familiar to those skilled in the art can be used, with steering wheel angle, accelerator and brake pedal as input quantities, and the angle of each wheel and the torque of each motor selected as output quantities. In other specific embodiments, the driving action model can also be a pre-established empirical model that reflects the correspondence between driving conditions and wheel angles and motor torques. For example, the correspondence between the steering wheel angle and the angle of each wheel at each vehicle speed, the correspondence between the accelerator, brake pedal and motor drive torque and braking torque are obtained through preliminary experiments, and a corresponding comparison table is established. Then, the actual driving condition to be tested is converted into the angle of each wheel and the torque of each motor by looking up the table.

[0078] 2. Vehicle dynamics model:

[0079] Figure 3 The force diagram of the distributed electric drive vehicle is shown in FIG. Figure 3 As shown, the four wheels of the vehicle are respectively subjected to longitudinal force and lateral force, and the four wheels have their own wheel angles.

[0080] The vehicle dynamics model is used to describe the motion characteristics of the distributed electric drive vehicle under the influence of the forces of each tire and other factors (such as air resistance and rolling resistance). In the process of modeling the vehicle dynamics model, it is assumed that the vehicle body only moves in a plane parallel to the ground (refer to Figure 3 , that is, the linear velocity along the z-axis, the pitch angular velocity around the y-axis, and the roll angular velocity around the x-axis are all 0), and the road condition is assumed to be a dry and flat horizontal road surface.

[0081] 2.1) Analysis of vehicle longitudinal motion state:

[0082] The longitudinal force of the distributed electric drive vehicle is analyzed. The vehicle is subject to the longitudinal force and lateral force of the ground on the four wheels, which are projected to the longitudinal direction of the vehicle. In addition, the vehicle is also affected by air resistance and rolling resistance in the longitudinal direction. Considering the above factors, the expression of the longitudinal motion of the distributed electric drive vehicle can be obtained as shown in formula (1):

[0083]

[0084] Where m, a x 、V x are the vehicle mass, vehicle longitudinal acceleration, and vehicle longitudinal velocity, respectively. xfl 、F xfr 、F xrl 、F xrrare the longitudinal forces on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, F yfl 、F yfr 、F yrl 、F yrr are the lateral forces on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, δ fl , δ fr , δ rl , δ rr are the turning angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, C D is the air resistance coefficient, A is the frontal area, ρ is the air density, and f is the rolling resistance coefficient.

[0085] 2.2) Analysis of vehicle lateral motion state:

[0086] The lateral force of the distributed electric drive vehicle is analyzed. The vehicle is subjected to the longitudinal force and lateral force of the ground on the four wheels. Projecting them to the lateral direction of the vehicle, the expression of the lateral motion of the distributed electric drive vehicle can be obtained as shown in formula (2):

[0087]

[0088] Among them, a y is the lateral acceleration of the vehicle.

[0089] 2.3) Analysis of vehicle yaw motion state:

[0090] During the driving process, the vehicle may also experience yaw motion around the z-axis. By taking the moment of the vehicle center of mass, the yaw motion expression of the distributed electric drive vehicle can be obtained as shown in formula (3):

[0091]

[0092] Among them, I z is the vertical moment of inertia of the vehicle around the z-axis, r is the yaw angular velocity of the vehicle, a is the distance from the front axle to the center of mass of the vehicle, b is the distance from the rear axle to the center of mass of the vehicle, and w is the wheelbase of the front and rear axles.

[0093] 3. Wheel force model:

[0094] 3.1) Fitting expression of tire force:

[0095] The vehicle dynamics model reflects the influence of tire force on the vehicle's motion state. Furthermore, during the driving process, the force of the wheel is affected by the combined influence of slip rate, sideslip angle and vertical load, and has a nonlinear relationship with the above factors. Therefore, the tire force is generally determined by fitting based on experimental data, and its expression is shown in formula (4):

[0096]

[0097] (4) where D is the peak factor, B is the stiffness factor, C is the curve shape factor, E is the curve curvature factor, and F z is the vertical load, A 1 , A 2 F z The quadratic and linear coefficients of the tire are: when x is the tire slip angle, Y is the lateral force; when x is the tire slip rate, Y is the longitudinal force.

[0098] Specifically, in some embodiments, experiments may be conducted on the stress conditions of the wheels under different slip rates, sideslip angles, and vertical loads, and the coefficients in formula (4) may be determined by fitting the experimental data.

[0099] Figure 4 and Figure 5 The figures show the wheel longitudinal force and lateral force curves obtained by fitting in a specific embodiment.

[0100] For any driving condition, once the slip rate, sideslip angle and vertical load are determined, the longitudinal force and lateral force of each wheel can be obtained by using formula (4).

[0101] 3.2) Tire slip angle of each wheel:

[0102] When the wheel rolls, the center line of the contact patch with the ground is offset from the wheel plane by a certain distance and is no longer parallel to the wheel plane. The angle between the center line of the contact patch and the wheel plane is the tire slip angle, which is expressed as shown in formula (5):

[0103]

[0104] Among them, α fl , α fr , α rl , α rr are the tire slip angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. y is the lateral velocity of the vehicle.

[0105] 3.3) Tire slip rate of each wheel:

[0106] When a tire is subjected to traction or braking force, relative movement occurs between the tire and the ground. The slip rate is the proportion of the sliding component in the wheel motion. To calculate the slip rate of the wheel, the wheel rotation speed (angular velocity) and the center speed of the wheel must be obtained first.

[0107] Specifically, the rotation speeds of the four wheels can be expressed as (6):

[0108]

[0109] Among them, ω fl ,ω fr ,ω rl ,ω rr are the speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, R wfl , R wfr , R wrl , R wrr are the rolling radii of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, T bfl , T bfr , T brl , T brr are the braking torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, T dfl , T dfr , T drl , T drr are the driving torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, M yfl 、M yfr 、M yrl 、M yrr They are the resistance torque of the left front wheel, right front wheel, left rear wheel and right rear wheel respectively.

[0110] As analyzed above, T bfl , T bfr , T brl , T brr and T dfl , T dfr , T drl , T drr It can be determined according to the preset working condition by the driving action model. In addition, M yfl 、M yfr 、M yrl 、M yrr It is also determined by comparing the preset operating conditions with the actual measured data obtained in advance.

[0111] During the vehicle's driving, in addition to the longitudinal and lateral translational motions, there is also yaw motion around the z-axis, which can give the center velocities of the four wheels as shown in equation (7):

[0112]

[0113] Among them, V t_fl 、V t_fr 、V t_rl 、V t_rr They are the center speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively;

[0114] Furthermore, the tire slip rate of each wheel can be expressed by the wheel speed and the center speed, and its specific expression is shown in formula (8):

[0115]

[0116] Among them, λ fl , fr , rl , rr They are the tire slip rates of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively.

[0117] 3.4) Vertical load of each wheel:

[0118] When the vehicle is stationary, the four wheels are subject to static loads. When the vehicle has longitudinal and lateral accelerations, load transfer occurs. By equating the entire vehicle to a sprung mass part and unsprung mass parts corresponding to the four wheels, the vertical loads on the four wheels can be expressed as formula (9):

[0119]

[0120] Among them, F z_fl 、F z_fr 、F z_rl 、F z_rr are the vertical loads on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, m t is the sprung mass, l is the vehicle wheelbase, h g is the height of the vehicle's center of mass, m wfl 、m wfr 、m wrl 、m wrr They are the unsprung masses of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively.

[0121] 4. Mutual coupling between vehicle dynamics model and wheel force model:

[0122] The vehicle dynamics model and the wheel force model can be used to output the rotational speed of each wheel under preset working conditions. By observing the vehicle dynamics model and the wheel force model, it can be found that they contain multiple degrees of freedom, namely the longitudinal and lateral translational motion of the distributed electric drive vehicle, the yaw motion of the vehicle body rotating around the z-axis, and the rotational motion of each wheel. Since the dynamic state of the whole vehicle (i.e., the vehicle's speed, acceleration, and wheel speed, etc.) is determined by the wheel force and the angle of rotation, and the wheel force is determined by parameters such as the driving torque, braking torque, and wheel speed, it is obvious that the two models are coupled through the longitudinal force and lateral force exerted on each wheel. Therefore, in some specific embodiments, the expressions of the two models can be jointly solved to obtain the real-time rotational speed of each wheel, or through PI control and other methods known to those skilled in the art, the rotational speed output by the model can track the actual rotational speed in real time.

[0123] 5. Determine the target current of each motor simulator:

[0124] In an embodiment of the present application, after acquiring the real-time rotation speed information of each wheel, the target current model can determine the target current input to the motor simulator based on the wheel rotation speed.

[0125] The modeling process of the target current model is described in detail below. The inverter topology of the motor controller and simulator can be found in Figure 1 , where the bus voltage of the inverter on the motor controller side is U dc_mcu , the voltage zero potential reference point is point O, and the bus voltage of the inverter on the motor simulator side is U dc_eme The voltage zero potential reference point is point N, and the inverter upper bridge arm conduction is defined as S x =1, the lower bridge arm conduction is defined as S x = 0, x∈{A,B,C,a,b,c}, ignoring the non-ideal characteristics of the inverter such as dead zone and switch conduction voltage drop, the actual three-phase current of the motor simulator is defined as i a 、i b 、i c .

[0126] Taking phase A as an example, the following expression can be listed based on the voltage vector relationship:

[0127] U AO =U Aa +U aN +U NO (11)

[0128] Where U AO =S A ·U dc_mcu , U aN =Sa ·U dc_eme , substituting into (11) we can get:

[0129]

[0130] Similarly, the equations for phases B and C can be obtained:

[0131]

[0132]

[0133] In the above formula, L is the EME filter inductor, R L is the equivalent resistance of the EME filter inductor.

[0134] Assume that each motor is a three-phase star-connected permanent magnet synchronous motor, so the three-phase current satisfies equation (15):

[0135] i a +i b +i c =0(15),

[0136] Adding equations (12) to (14) yields:

[0137]

[0138] Substituting equation (16) into equations (12) to (14), we can obtain the mathematical model of the motor simulator in the three-phase coordinate system:

[0139]

[0140]

[0141]

[0142] The mathematical model of the motor simulator in the dq two-phase rotating coordinate system can be obtained through Clark transformation and Park transformation:

[0143]

[0144]

[0145] In the above formula, U d_mcu and U q_mcu is the d and q axis voltage output by the motor controller, U d_eme and U q_eme is the d and q axis voltage output by the motor simulator, ω e This is the angular velocity of the motor rotor used by the motor simulator.

[0146] Angular velocity of permanent magnet synchronous motor rotor ωe (Electrical speed) is equal to its mechanical speed ω m The product of the number of motor pole pairs n and the motor mechanical speed ω m The speed of the wheel it drives is l is linearly related, so the angular velocity ω of the motor rotor can be e The speed of the wheel driven by it ω l To express:

[0147] ω e =n·ω m =n·k l ·ω l (twenty two),

[0148] Among them, k l is the proportional coefficient between the wheel speed and the motor mechanical speed. According to the permanent magnet synchronous motor voltage equation, the relationship between the wheel speed and the target current input by the motor simulator can be obtained:

[0149]

[0150] In the above formula, i d 、i q are the d-axis and q-axis target currents, u d 、u q The d and q axis voltages are collected respectively, L d , L q are the d-axis and q-axis inductances, R s is the stator resistance, ψ f is the rotor flux.

[0151] Obviously, for a distributed electric drive vehicle, the speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel can be respectively fl ,ω fr ,ω rl ,ω rr Substitute ω into (23) l , the target current corresponding to each motor can be obtained. Specific embodiments

[0153] This embodiment is a simulation example, in which each motor of the distributed electric drive vehicle is tested by building the motor controller test system of the distributed electric drive vehicle.

[0154] Table 1 lists the vehicle parameters used in this embodiment:

[0155] Table 1 Distributed electric drive vehicle parameters

[0156]

[0157]

[0158] The double lane change test was carried out at a speed of 50km / h. Figures 6 to 11 The vehicle longitudinal acceleration, yaw angular velocity, lateral acceleration, longitudinal velocity, yaw angle and lateral velocity calculated by the multi-degree-of-freedom model unit are shown respectively.

[0159] Fig.12 , Fig.13 The figures show the right and left front wheel speeds of the vehicle obtained from the double lane change test at a speed of 50 km / h (due to the complexity of the model and the long running time, the wheel speed time coordinates are compressed 100 times and then input into the motor simulator). Fig.14 , Fig.15 The d-axis and q-axis target currents and actual current changes of the motor driving the left front wheel of the vehicle are shown respectively. Fig.16 , Fig.17 The d-axis and q-axis target currents and actual current changes of the motor driving the right front wheel of the vehicle are shown respectively. Figures 12 to 17 It can be seen that under the double lane-changing condition, the wheel speeds of the right front wheel and the left front wheel of the vehicle are different, and at the same time, the target currents of the corresponding motors are also different. It can be seen that the motor controller test system provided in the present application can input state parameters that are more in line with the actual operating conditions of the motor to the towing test platform based on actual driving conditions, thereby effectively improving the credibility of the test results.

[0160] The above is a detailed introduction to the specific implementation methods of the present application. For those skilled in the art, several improvements and modifications may be made to the present application without departing from the principles of the present application. These improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A motor controller test system for a distributed electric drive vehicle, comprising a plurality of motor controller modules and a plurality of motor simulator modules connected to the motor controller modules, wherein: Each motor controller module is used to control a motor that drives a wheel, and is characterized in that: It also includes a multi-degree-of-freedom model unit for distributed electric drive vehicles; The multi-degree-of-freedom model unit includes a driving action model, a vehicle dynamics model, a wheel force model and a target current model; The driving action model determines the steering angle of each wheel of the distributed electric drive vehicle and the torque command of each motor based on a preset driving action, wherein the driving action includes a steering wheel action, an accelerator pedal action and a brake pedal action, and the torque command includes a driving torque command and a braking torque command; The vehicle dynamics model and the wheel force model are coupled to each other, and the rotation speed of each wheel is determined based on the rotation angle and the torque command; The target current model determines the target current of the motor simulator module corresponding to each motor controller module based on the rotation speed of each wheel.

2. The motor controller test system for a distributed electric drive vehicle according to claim 1, characterized in that: The degrees of freedom of the multi-degree-of-freedom model unit include the longitudinal and lateral translational motions of the vehicle body, the yaw motion of the vehicle body, and the rotational motion of each wheel of the distributed electric drive vehicle.

3. The motor controller test system for a distributed electric drive vehicle according to claim 1, characterized in that: The whole vehicle dynamics model and the wheel force model are coupled to each other through the longitudinal force and lateral force received by each wheel.

4. The motor controller test system for a distributed electric drive vehicle according to claim 3, characterized in that: The vehicle dynamics model determines the longitudinal motion, lateral motion and yaw motion of the distributed electric drive vehicle based on the turning angle of each wheel, the longitudinal force and lateral force received by each wheel; The wheel force model determines the longitudinal force and lateral force on each wheel based on the tire slip angle, tire slip rate and vertical load of each wheel.

5. The motor controller test system for a distributed electric drive vehicle according to claim 4, characterized in that: The longitudinal motion of the distributed electric drive vehicle is determined by the following formula: Where m, a x 、V x are the vehicle mass, vehicle longitudinal acceleration, and vehicle longitudinal velocity, respectively. xfl 、F xfr 、F xrl 、F xrr are the longitudinal forces on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, F yfl 、F yfr 、F yrl 、F yrr are the lateral forces on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, δ fl , δ fr , δ rl , δ rr are the turning angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, C D is the air resistance coefficient, A is the frontal area, ρ is the air density, and f is the rolling resistance coefficient; The lateral motion of the distributed electric drive vehicle is determined by the following formula: Among them, a y is the lateral acceleration of the vehicle; The yaw motion of the distributed electric drive vehicle is determined by the following formula: Among them, I z is the vertical moment of inertia of the vehicle around the z-axis, r is the yaw angular velocity of the vehicle, a is the distance from the front axle to the center of mass of the vehicle, b is the distance from the rear axle to the center of mass of the vehicle, and w is the wheelbase of the front and rear axles.

6. The motor controller test system for a distributed electric drive vehicle according to claim 5, characterized in that: The wheel force model determines the longitudinal force and lateral force of each wheel based on the following fitting expression: Among them, D is the peak factor, B is the stiffness factor, C is the curve shape factor, E is the curve curvature factor, and F is the peak factor. z is the vertical load, A1 and A2 are F z The quadratic and linear coefficients of the tire are: when x is the tire slip angle, Y is the lateral force; when x is the tire slip rate, Y is the longitudinal force.

7. The motor controller test system for a distributed electric drive vehicle according to claim 6, characterized in that: The tire slip angle of each wheel is determined by the following formula: Among them, α fl , α fr , α rl , α rr are the tire slip angles of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. y is the lateral speed of the vehicle; The tire slip ratio of each wheel is determined by the following formula: Among them, λ fl , fr , rl , rr are the tire slip rates of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, ω fl ,ω fr ,ω rl ,ω rr are the speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, R wfl , R wfr , R wrl , R wrr are the rolling radii of the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, V t_fl 、V t_fr 、V t_rl 、V t_rr They are the center speeds of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; The vertical load of each wheel is determined by the following formula: Among them, F z_fl 、F z_fr 、F z_rl 、F z_rr are the vertical loads on the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively, m t is the sprung mass, l is the vehicle wheelbase, h g is the height of the vehicle's center of mass, m wfl 、m wfr 、m wrl 、m wrr They are the unsprung masses of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively.

8. The motor controller test system for a distributed electric drive vehicle according to claim 7, characterized in that: The speed of each wheel is determined by the following formula: Among them, T bfl , T bfr , T brl , T brr are the braking torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, T dfl , T dfr , T drl , T drr are the driving torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively, M yfl 、M yfr 、M yrl 、M yrr are the resistance torques of the left front wheel, right front wheel, left rear wheel, and right rear wheel respectively; The center speed of each wheel is determined by the following formula:

9. The motor controller test system for a distributed electric drive vehicle according to claim 1, characterized in that: For any motor controller module, the target current model determines the target current of its corresponding motor simulator module based on the following formula: Among them, i d 、i q are the d-axis and q-axis target currents, u d 、u q The d and q axis voltages are collected respectively, L d , L q are the d-axis and q-axis inductances, R s is the stator resistance, ψ f is the rotor flux, ω l is the speed of the wheel driven by the motor controller module, k l is the proportional coefficient between the wheel speed and the motor mechanical speed, and n is the number of pole pairs of the permanent magnet synchronous motor.

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