Fusion control method for power and heat dissipation system of four-axle hub electrically-driven vehicle

Abstract

The invention discloses a power and heat dissipation system fusion control method of a four-axle hub electric drive vehicle, linkage control of a drive system and a heat dissipation system can be achieved according to cross-country working conditions and heat dissipation system signals, the precision and accuracy of vehicle control can be greatly improved through the method, scientific operation of the system is guaranteed, and the power and heat dissipation system fusion control method of the four-axle hub electric drive vehicle is suitable for large-scale popularization and application. And important significance is achieved for improving the maneuvering characteristics of the whole vehicle.

Description

Technical Field

[0001] The present invention relates to the field of control strategies for multi-wheel electric hub vehicles, and in particular to a method for integrating power and heat dissipation system control of a four-axle hub electric drive vehicle. Background Art

[0002] The torque distribution of four-axle hub electric drive vehicles is closely related to the heat dissipation system of each electric drive system. When the vehicle is operating in high-mobility off-road conditions, the operating status and temperature rise of each electric drive unit are inconsistent. If each unit adopts the same control method, the torque distribution between the electric drive units will always be inconsistent, which will lead to a larger temperature rise difference between the wheel drive units and a certain impact on the vehicle's maneuverability. Therefore, finding a method to independently monitor the temperature of each drive system of the vehicle, so as to balance the torque distribution of different axles by controlling the temperature of each unit, is of great significance to the capacity allocation of multi-wheel distributed electric drive vehicles.

[0003] Therefore, according to the temperature rise law of the vehicle's electric drive system, there must be differences in the temperature of the electric drive units of the wheel hubs at different axle positions. Taking the real-time temperature of the wheel drive unit, radiator water flow, fan switch and other monitoring quantities as variables, it is very important to quantitatively study the method of coordinated distribution of torque ratio and heat dissipation of each electric drive unit under working conditions and design a fusion control method of the power and cooling system of a four-axis wheel hub electric drive vehicle. Summary of the invention

[0004] In view of this, the present invention provides a method for integrating power and cooling system control of a four-axle hub electric drive vehicle, which can realize control of the drive system and the cooling system according to off-road conditions and cooling system signals.

[0005] A method for integrating power and cooling system control of a four-axle wheel hub electric drive vehicle comprises the following steps:

[0006] Step 1. The vehicle control system obtains off-road conditions and cooling system signals of the vehicle;

[0007] Step 2: The vehicle control system obtains the torque distribution ratio coefficient of the rear two axles according to the off-road working condition, and sets the actual distribution wheelbase of the rear two axles according to the torque distribution ratio coefficient of the rear two axles;

[0008] Step 3. The vehicle control system sets the cooling system control signal according to the cooling system signal and the torque distribution ratio coefficient of the rear two axles and sends it to the cooling control system.

[0009] Furthermore, the step 2 specifically includes the following contents:

[0010] The vehicle control system obtains the road surface gradient, acceleration, and vehicle mass through off-road conditions and calculates the theoretical axle loads of each axle of the vehicle. According to the theoretical axle loads of the rear two axles and the total axle load of the four axles, the torque distribution ratio coefficient of the rear two axles is calculated. The specific calculation formula is as follows:

[0011]

[0012] F total = mg

[0013] Among them, α is the torque distribution ratio coefficient of the rear two axles, F rear is the sum of the theoretical axle loads of the rear two axles, F total is the total theoretical axle load of the four axles, and m is the vehicle mass.

[0014] Furthermore, step 3 specifically includes the following content:

[0015] The vehicle control system sets the following control strategies according to the torque distribution ratio coefficient of the rear two axles and the heat dissipation system signal:

[0016] (1) If α ≤ 0.5 and the radiator startup time t < x min, set the radiator water tank flow rates of the four axles to be L at the same time, as shown in the following formula:

[0017] q1 = q2 = q3 = q4 = L, when α < 0.5;

[0018] Among them, q1 and q2 are the radiator water tank flow rates of the front two axles, q3 and q4 are the radiator water tank flow rates of the rear two axles, and x is the set value;

[0019] (2) If 0.5 < α < 0.7 and the radiator startup time t < x min, set the radiator water tank flow rates of the rear two axles to be L at the same time, as shown in the following formula:

[0020] q3 = q4 = aL, when 0.5 ≤ α < 0.7;

[0021] Among them, a is the set value;

[0022] (3) If 0.7 ≤ α and the radiator startup time t < x min, set the radiator water tank flow rates of the rear two axles to be L at the same time, as shown in the following formula:

[0023] q3 = q4 = bL, when 0.7 ≤ α;

[0024] Among them, b is the set value;

[0025] (4) When the radiator startup time t ≥ x min, if 0.65 ≤ α, the radiator water tank flow rates of the rear two axles are set to bL. If 0.45 ≤ α < 0.65, the radiator water tank flow rates of the rear two axles are set to aL. If α < 0.45, the radiator water tank flow rates of the four axles are set to L at the same time;

[0026] (5) If the radiator water tank temperature t in the cooling system signal box >t out When the vehicle control system turns on the radiator fan, if t box <t out -t diff When the vehicle control system controls to shut down the water tank fan;

[0027] Among them, t out The temperature threshold for the water tank fan to start, t diff is the water tank fan closing threshold, and both are set values.

[0028] Furthermore, the off-road operating conditions include: road slope, acceleration, starting speed, driving time, current mileage, steady speed and terminal speed.

[0029] Furthermore, the heat dissipation system signal includes the following contents: radiator water tank flow, radiator water tank temperature and radiator fan on / off status.

[0030] Furthermore, a and b respectively satisfy the following conditions:

[0031] 1<a<1.5;

[0032] 1.5≤b<2.

[0033] Beneficial effects:

[0034] 1. The present invention proposes a fusion control method for the power and cooling systems of a four-axle wheel hub electric drive vehicle, which controls the cooling system and the drive system of the vehicle system in a linked manner. Compared with the existing conventional control logic, the dual states of the power and cooling systems are comprehensively considered, making the control mode of the method more intelligent and closer to the actual operation of the vehicle, which is of great significance to improving the mobility of the whole vehicle;

[0035] 2. This method sets the specific value of the torque distribution ratio coefficient of the rear two axles according to the off-road working conditions of the vehicle. This method can ensure the accuracy and precision of the system's value and ensure the scientific operation of the system;

[0036] 3. The cooling system control method of the present invention designs a specific cooling scheme according to different rear two-axle torque distribution ratio coefficients, and balances the cooling system schemes of different axles by controlling different cooling schemes. Compared with the conventional cooling system control scheme, the scheme of designing the control logic according to the rear two-axle torque distribution ratio coefficient can effectively narrow the temperature control gap of each axle and ensure the stability of the vehicle's maneuverability.

[0037] 4. This method does not require the installation of too much hardware equipment. It mainly operates through the vehicle's existing system to perform the corresponding control method. It is simple to operate, easy to replicate and promote, with low economic cost and good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of dynamic distribution of driving torque and heat dissipation of a four-axle hub electric drive vehicle according to an embodiment of the present invention.

[0039] Figure 2 1 is a graph showing the corresponding relationship between vehicle speed and time in a high-mobility off-road condition in an embodiment of the present invention.

[0040] Figure 3 This is a flow chart of water flow control of two axes in the embodiment of the present invention.

[0041] Figure 4 This is a fan switch control flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0043] The embodiment of the present invention provides a method for integrating power and cooling system control of a four-axle wheel hub electric drive vehicle, comprising the following steps:

[0044] Step 1. The vehicle control system obtains off-road conditions and cooling system signals of the vehicle;

[0045] The vehicle's system generator and radiator control distribution circuit for the vehicle's four axes is shown in the attached Figure 1 As shown, based on the working characteristics of special vehicles, the off-road working conditions include: road slope, acceleration, starting speed, driving time, current mileage, steady speed and terminal speed; the cooling system signal includes the following: radiator water tank flow, radiator water tank temperature and radiator fan on and off status.

[0046] The off-road working condition is relatively complex, and a single cycle loading test condition is formulated. Some of the conditions are shown in the following table. The curve of vehicle speed changing with time is as follows: Figure 2 As shown;

[0047] Table 1 Composition of some off-road conditions

[0048]

[0049] In this embodiment, the cooling system mainly collects signals such as the flow rate of the cooling system water outlet, the temperature of the cooling system water tank, the temperature of each axis electric drive system unit, and the switch status of the cooling fan.

[0050] Step 2: The vehicle control system obtains the torque distribution ratio coefficient of the rear two axles according to the off-road working condition, and sets the actual distribution wheelbase of the rear two axles according to the torque distribution ratio coefficient of the rear two axles;

[0051] Torque distribution of electric drive systems on each axle: Torque distribution of each drive axle is carried out according to off-road conditions and driver needs. Based on the working characteristics of four-axle vehicles, the torque of the vehicle is divided according to the axle load of each axle;

[0052] The vehicle control system obtains the road slope, acceleration and vehicle mass through off-road conditions and calculates the theoretical axle load of each axle of the vehicle. The torque distribution ratio coefficient of the rear two axles is calculated based on the theoretical axle load of the rear two axles and the total axle load of the four axles. The specific calculation formula is as follows:

[0053]

[0054] F total =mg

[0055] Among them, α is the torque distribution ratio coefficient of the rear two axles, F rear is the sum of the theoretical axle loads of the rear two axles, F total is the theoretical total axle load of the four axles, and m is the mass of the vehicle;

[0056] According to the calculated total torque, each axis is allocated, and the four axes are divided into the front two axes and the rear two axes. Taking the calculation of the torque of the rear two axes as an example, the total torque value of the rear two axes is:

[0057] T Rear =α·T Total

[0058] Among them, T Rear is the actual distributed torque of the rear two axles, Nm; T Total is the vehicle required torque, Nm.

[0059] Step 3. The vehicle control system designs a cooling system control signal according to the cooling system signal and the torque distribution ratio coefficient of the rear two axles and sends it to the cooling control system;

[0060] The temperature of each axle's electric drive system is collected in real time. The initial state is that the four axles have the same cooling water flow. When the vehicle starts running, the cooling water flow is increased or decreased according to the torque distribution characteristics of the four axles to ensure that the temperature of the vehicle's electric drive system will not be too high, thereby ensuring the best driving performance of the vehicle. At the same time, the temperature of the water tank is monitored in real time. When the temperature exceeds the threshold, the cooling fan is turned on to reduce the temperature of the cooling water tank.

[0061] The vehicle control system sets the following control strategy based on the torque distribution ratio coefficient of the rear two axles and the cooling system signal. The corresponding flow chart is shown in the attached figure. Figure 3 As shown:

[0062] (1) If α ≤ 0.5 and the radiator start-up time t < xmin, set the flow rates of the radiator water tanks of the four axes to be L simultaneously, as shown in the following formula:

[0063] q1 = q1 = q3 = q4 = L, when α < 0.5;

[0064] Wherein, q1 and q2 are the flow rates of the radiator water tanks of the first two axes, q3 and q4 are the flow rates of the radiator water tanks of the last two axes, and x is a set value;

[0065] (2) If 0.5 < α < 0.7 and the radiator start-up time t < xmin, set the flow rates of the radiator water tanks of the last two axes to be L simultaneously, as shown in the following formula:

[0066] q3 = q4 = aL, when 0.5 ≤ α < 0.7;

[0067] Wherein, a is a set value;

[0068] (3) If 0.7 ≤ α and the radiator start-up time t < xmin, set the flow rates of the radiator water tanks of the last two axes to be L simultaneously, as shown in the following formula:

[0069] q3 = q4 = bL, when 0.7 ≤ α;

[0070] Wherein, b is a set value;

[0071] (4) After the above process continues for a period of time, when the radiator start-up time t ≥ xmin, if 0.65 ≤ α, the flow rates of the radiator water tanks of the last two axes are set to bL, if 0.45 ≤ α < 0.65, the flow rates of the radiator water tanks of the last two axes are set to aL, and if α < 0.45, the flow rates of the radiator water tanks of the four axes are set to L simultaneously;

[0072] (5) The control process for the fan is as Figure 4 shown. The specific control logic is that when the radiator water tank temperature t in the heat dissipation system signal > t out , the vehicle control system controls to turn on the water tank fan for temperature reduction. If t < t out - t diff , the vehicle control system controls to turn off the water tank fan. Introducing t diff is to prevent the fan from turning on and off frequently;

[0073] Wherein, t out is the temperature threshold for turning on the water tank fan, and t diff is the temperature threshold for turning off the water tank fan, and both are set values.

[0074] To better control the operating state of the corresponding system, a and b respectively satisfy the following conditions:

[0075] 1 < a < 1.5;

[0076] 1.5≤b<2.

[0077] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for integrating power and cooling systems of a four-axle wheel hub electric drive vehicle, characterized in that: It includes the following steps: Step 1. The vehicle control system obtains the off-road working conditions of the vehicle and the heat dissipation system signals. Step 2. The vehicle control system obtains the torque distribution ratio coefficient of the rear two axles according to the off-road working conditions, and sets the actual distribution wheelbase of the rear two axles according to the torque distribution ratio coefficient of the rear two axles. Step 3. The vehicle control system sets the heat dissipation system control signal according to the heat dissipation system signal and the torque distribution ratio coefficient of the rear two axles, and sends it to the heat dissipation control system.

2. The method according to claim 1, characterized in that The specific content of step 2 is as follows: The vehicle control system obtains the road surface slope, acceleration and vehicle mass through the off-road working conditions, calculates and obtains the theoretical axle loads of each axle of the vehicle, and calculates the torque distribution ratio coefficient of the rear two axles according to the theoretical axle loads of the rear two axles and the total axle load of the four axles. The specific calculation formula is as follows: F total =mg Among them, α is the torque distribution ratio coefficient of the rear two axles, F rear is the sum of the theoretical axle loads of the rear two axles, F total is the theoretical total axle load of the four axles, and m is the mass of the vehicle.

3. The method according to claim 1 or 2, characterized in that The specific content of step 3 is as follows: The vehicle control system sets the following control strategies according to the torque distribution ratio coefficient of the rear two axles and the heat dissipation system signal: (1) If α ≤ 0.5 and the radiator start-up time t < xmin, set the radiator water tank flow rates of the four axles to be L at the same time, as shown in the following formula: q1 = q2 = q3 = q4 = L, when α < 0.5; Where, q1 and q2 are the radiator water tank flow rates of the front two axles, q3 and q4 are the radiator water tank flow rates of the rear two axles, and x is the set value. (2) If 0.5 < α < 0.7 and the radiator start-up time t < xmin, set the radiator water tank flow rates of the rear two axles to be L at the same time, as shown in the following formula: q3 = q4 = aL, when 0.5 ≤ α < 0.7; Where, a is the set value. (3) If 0.7 ≤ α and the radiator start-up time t < xmin, set the radiator water tank flow rates of the rear two axles to be L at the same time, as shown in the following formula: q3 = q4 = bL, when 0.7 ≤ α; Where, b is the set value. (4) When the radiator start-up time t ≥ xmin, if 0.65 ≤ α, the radiator water tank flow rates of the rear two axles are set to bL, if 0.45 ≤ α < 0.65, the radiator water tank flow rates of the rear two axles are set to aL, and if α < 0.45, the radiator water tank flow rates of the four axles are set to L at the same time. (5) If the radiator water tank temperature t in the cooling system signal box >t out When the vehicle control system turns on the radiator fan, if t box <t out -t diff When the vehicle control system controls the radiator fan to be turned off.

4. The method according to claim 3, characterized in that t out The temperature threshold for the water tank fan to start, t diff is the water tank fan closing threshold, and both are set values. Furthermore, the off-road working conditions include: road surface slope, acceleration, starting speed, driving time, current mileage, steady speed and end speed.

5. The method according to claim 4, characterized in that The heat dissipation system signals include the following content: radiator water tank flow rate, radiator water tank temperature and radiator fan on / off state.

6. The method according to claim 5, characterized in that The a and b respectively satisfy the following conditions: 1<a<1.5； 1.5≤b<2。

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