A method for integrated control of the power and cooling systems of a four-axle hub-driven electric vehicle

Abstract

This invention discloses a fusion control method for the power and cooling systems of a four-axle hub electric drive vehicle. It can realize the linkage control of the drive system and the cooling system based on off-road conditions and cooling system signals. This method can significantly improve the precision and accuracy of vehicle control, ensure the scientific operation of the system, and is of great significance for improving the overall vehicle's mobility performance.

Description

Technical Field

[0001] This invention relates to the field of control strategies for multi-wheel electric hub vehicles, and more specifically to a method for integrated control of the power and cooling systems of a four-axle hub electric drive vehicle. Background Technology

[0002] The torque distribution and cooling systems of each electric drive system in a four-axle hub electric drive vehicle are inextricably linked. Under high-mobility off-road conditions, the operating states and temperature rises of each electric drive unit are inconsistent. If the same control method is adopted for each unit, the torque distribution between the electric drive units will always be inconsistent, which will lead to a greater temperature rise difference between the drive units of each wheel and affect the vehicle's mobility. Therefore, finding a method to independently monitor the temperature of each drive system of the vehicle, thereby controlling the temperature of each unit to balance the torque distribution of different axles, is of great significance for the capacity allocation of multi-wheel distributed electric drive vehicles.

[0003] Therefore, based on the temperature rise pattern of the vehicle's electric drive system, the temperature of the wheel hub electric drive units at different axles must differ. It is very important to quantitatively study the method of coordinating the torque ratio and heat dissipation of each electric drive unit under working conditions, using the real-time temperature of the wheel drive unit, radiator water flow, fan switch and other monitored quantities as variables, and to design a fusion control method for the power and heat dissipation system of a four-axle wheel hub electric drive vehicle. Summary of the Invention

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

[0005] A method for integrated control of the power and cooling systems of a four-axle hub-driven electric vehicle includes the following steps:

[0006] Step 1. The vehicle control system acquires signals from the vehicle's off-road operating conditions and cooling system;

[0007] Step 2. The vehicle control system obtains the torque distribution ratio coefficient of the rear two axles based on the off-road conditions, and sets the actual wheelbase of the rear two axles based on the torque distribution ratio coefficient of the rear two axles.

[0008] Step 3. The vehicle control system sets the cooling system control signal based on 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, step 2 specifically includes the following:

[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

[0022] ,

[0021] ,

[0025] ,

[0020] ,

[0024] ,

[0023] , , , , , =mg

[0013] Where, 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 simultaneously, as shown in the following formula:

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

[0018] 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 a 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 simultaneously, as shown in the following formula:

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

[0021] Where, a is a set value;

[0022] ​​​​​​​​​​

[0026] (5) If the radiator water tank temperature t in the heat dissipation system signal box >t out At that time, the vehicle control system controls the water tank fan to turn on. If t box <t out -t diff At that time, the vehicle control system shuts off the water tank fan;

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

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

[0029] Furthermore, the heat dissipation system signals include the following: radiator water tank flow rate, 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. This invention proposes a fusion control method for the power and cooling systems of a four-axle hub electric drive vehicle. It links the vehicle system's cooling system and drive system for control. Compared with existing conventional control logic, this method comprehensively considers the dual states of the power and cooling systems, making the control mode more intelligent and closer to the actual operating conditions of the vehicle. This is of great significance for improving the overall vehicle's maneuverability.

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

[0036] 3. The cooling system control method of this method designs specific cooling schemes based on different torque distribution ratios of the rear two axles. By controlling different cooling schemes, the cooling system schemes of different axles are balanced. Compared with conventional cooling system control schemes, this scheme, which designs control logic based on the torque distribution ratios of the rear two axles, can effectively reduce the temperature control gap of each axle and ensure the stability of vehicle maneuverability.

[0037] 4. This method does not require the installation of excessive hardware equipment. It mainly operates through the vehicle's existing system, making it simple to run, easy to replicate and promote, with low economic cost and good economic benefits. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the 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 This is a diagram showing the relationship between vehicle speed and time under high-mobility off-road conditions in an embodiment of the present invention.

[0040] Figure 3 This is a flowchart of the water flow control process for the latter two axes in an embodiment of the present invention.

[0041] Figure 4 This is a flowchart of the fan switch control according to an embodiment of the present invention. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] This invention provides a method for the integrated control of the power and cooling systems of a four-axle hub-driven electric vehicle, comprising the following steps:

[0044] Step 1. The vehicle control system acquires signals from the vehicle's off-road operating conditions and cooling system;

[0045] The control wiring for the vehicle's system generator and radiator for the four axles is attached. Figure 1 As shown, based on the working characteristics of special vehicles, the off-road conditions include: road slope, acceleration, starting speed, travel time, current mileage, steady speed, and final speed; the cooling system signals include the following: radiator water tank flow rate, radiator water tank temperature, and radiator fan on / off status.

[0046] Its off-road conditions are quite complex. A single-cycle loading test condition was established, and some of the conditions are shown in the table below. The curve of vehicle speed changing over time is shown in the figure. Figure 2 As shown;

[0047] Table 1. Composition of Some Off-Road Operating Conditions

[0048]

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

[0050] Step 2. The vehicle control system obtains the torque distribution ratio coefficient of the rear two axles based on the off-road conditions, and sets the actual wheelbase of the rear two axles based on the torque distribution ratio coefficient of the rear two axles.

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

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

[0053]

[0054] F total =mg

[0055] Where α is the torque distribution ratio coefficient between the two rear axles, and F rear F is the sum of the theoretical shaft loads of the latter two axles. total denoted as the theoretical total axle load for four axles, and m as the vehicle mass.

[0056] The torque is distributed to each shaft based on the calculated total torque, dividing the four shafts into two parts: the front two shafts and the rear two shafts. Taking the torque calculation of the rear two shafts as an example, the total torque value of the rear two shafts is:

[0057] T Rear =α·T Total

[0058] Among them, T Rear The actual torque distributed between the two rear axles, in Nm; T Total The torque required for the entire vehicle is expressed in Nm.

[0059] Step 3. The vehicle control system designs the cooling system control signal based on 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 system collects the temperature of each axle's electric drive system in real time. Initially, all four axles have the same coolant flow rate. When the vehicle starts running, the coolant flow rate is increased or decreased based on the torque distribution characteristics of the four axles to ensure that the temperature of the entire vehicle's electric drive system does not become too high, thereby guaranteeing the vehicle's optimal driving performance. Simultaneously, the system monitors the radiator temperature in real time. When the temperature exceeds a threshold, the cooling fan is activated to lower the radiator temperature.

[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 flowchart is attached. Figure 3 As shown:

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

[0063] q1 = q2 = q3 = q4 = L, when α < 0.5;

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

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

[0069] q3 = q4 = bL, when 0.7 ≤ α;

[0070] Where, b is a set value;

[0071] (4) After the above process continues for a period of time and the radiator start-up time t ≥ xmin, if 0.65 ≤ α, then set the radiator water tank flow rates of the last two axes to be bL, if 0.45 ≤ α < 0.6, then set the radiator water tank flow rates of the last two axes to be aL, if α < 0.45, then set the radiator water tank flow rates of all four axes to be L simultaneously;

[0072] (5) The control process for the fan is as Figure 4 shown. The specific control logic is that if 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. Introduce t diff to prevent the fan from turning on and off frequently;

[0073] Where, t out is the water tank fan turn-on temperature threshold, t diff is the water tank fan turn-off threshold, 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 merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for integrated control of the power and cooling systems of a four-axle hub-driven electric vehicle, characterized in that, It includes the following steps: Step 1. The vehicle control system obtains the off-road working condition of the vehicle and the heat dissipation system signal; 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; 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; 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 startup time t < xmin, set the radiator water tank flow rates of the four axles to be L simultaneously, as shown in the following formula: q1 = q2 = q3 = q4 = L, when α < 0.5; 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 a set value; (2) If 0.5 < α < 0.7 and the radiator startup time t < xmin, set the radiator water tank flow rates of the rear two axles to be L simultaneously, as shown in the following formula: q3 = q4 = aL, when 0.5 ≤ α < 0.7; Among them, a is a set value; (3) If 0.7 ≤ α and the radiator startup time t < xmin, set the radiator water tank flow rates of the rear two axles to be L simultaneously, as shown in the following formula: q3 = q4 = bL, when 0.7 ≤ α; Among them, b is a set value; (4) When the radiator startup 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 simultaneously; (5) If the radiator water tank temperature t in the heat dissipation system signal box >t out At that time, the vehicle control system controls the water tank fan to turn on. If t box <t out -t fiff At that time, the vehicle control system shuts off the water tank fan.

2. The method as described in claim 1, characterized in that, The specific content of the said Step 2 includes the following: The vehicle control system obtains the road surface slope, acceleration and vehicle mass through the off-road working condition, and calculates and obtains 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: F total =mg Where α is the torque distribution ratio coefficient between the two rear axles, and F rear F is the sum of the theoretical shaft loads of the latter two axles. total denoted as the theoretical total axle load for the four axles, and m as the total vehicle mass.

3. The method as described in claim 1, characterized in that, t out The temperature threshold for the water tank fan to start, t diff Both are set values ​​and represent the threshold for shutting off the water tank fan. Furthermore, the off-road working condition includes: road surface slope, acceleration, starting speed, driving time, current mileage, steady speed and end speed.

4. The method as described in claim 3, characterized in that, The heat dissipation system signal includes the following content: radiator water tank flow rate, radiator water tank temperature and radiator fan on / off state.

5. The method as described in claim 4, characterized in that, The a and b respectively satisfy the following conditions: 1<a<1.5； 1.5≤b<2。

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