A highly adaptable creep control method for pure electric heavy trucks

Abstract

The present invention relates to the field of electric vehicles and to a highly adaptable creep control method for pure electric heavy-duty trucks. After the pure electric heavy-duty truck enters creep mode, the method performs P-term dynamic proportional control to obtain P-term dynamic proportional control torque; performs I-term dynamic integral proportional closed-loop control to obtain I-term dynamic proportional integral closed-loop regulation control torque; performs slope feedforward torque compensation control to obtain slope compensation torque; and performs vehicle weight feedforward torque compensation control to obtain vehicle weight compensation torque. The P-term dynamic proportional control torque, I-term dynamic proportional integral closed-loop regulation control torque, slope compensation torque, and vehicle weight compensation torque are added together to obtain creep closed-loop regulation control torque. The creep closed-loop regulation control torque is then subjected to a fixed limit to prevent abnormal torque output caused by closed-loop regulation. Through the method of the present invention, stable creep speed control can be achieved for pure electric heavy-duty trucks operating with or without a trailer, unloaded, fully loaded, and under various slope conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicles, and in particular to a creep control method for a pure electric heavy truck with high adaptability. Background Art

[0002] Electric vehicles meet the development requirements of low-carbon energy. At the same time, as an important carrier for the development of vehicle intelligence, they have developed rapidly in the commercial vehicle field in recent years. As the large-scale application scenarios of pure electric heavy-duty trucks become more and more extensive, higher requirements are placed on the functions and performance of pure electric heavy-duty trucks.

[0003] At present, in the field of domestic commercial electric vehicles, many pure electric heavy-duty trucks do not have creeping functions. At the same time, due to the complex traffic and road environment, especially the creeping torque required by pure electric heavy-duty trucks under conditions such as without a trailer, with a trailer, empty, fully loaded, and on different slopes, it is very difficult to achieve stable control of the creeping speed. It is easy to feel a sense of frustration during the creeping control process, resulting in poor driving controllability and comfort of pure electric heavy-duty trucks. Summary of the Invention

[0004] In response to the defects in the prior art, the present invention provides a highly adaptable creep control method for pure electric heavy-duty trucks to solve the problem of unstable creep control of existing pure electric heavy-duty trucks when starting under conditions such as without a trailer, with a trailer, empty, fully loaded, and on different slopes.

[0005] The technical solutions adopted in the present invention are as follows:

[0006] The present invention provides a highly adaptable creep control method for a pure electric heavy-duty truck. The method performs, after the pure electric heavy-duty truck enters the creep function, P-item dynamic proportional control to obtain P-item dynamic proportional control torque; performs I-item dynamic integral proportional closed-loop control to obtain I-item dynamic proportional integral closed-loop regulation control torque; performs slope feedforward torque compensation control to obtain slope compensation torque; performs vehicle weight feedforward torque compensation control to obtain vehicle weight compensation torque; adds the P-item dynamic proportional control torque, I-item dynamic proportional integral closed-loop regulation control torque, slope compensation torque, and vehicle weight compensation torque obtained in the above steps to obtain creep closed-loop regulation control torque; and finally performs fixed limit processing on the creep closed-loop regulation control torque to prevent abnormal output torque caused by closed-loop regulation, thereby ensuring the comfort and safety of creep control.

[0007] Furthermore, the method for performing P-term dynamic proportional control further includes:

[0008] Step 1: Based on the error between the current vehicle speed and the target speed, obtain the P-term proportional coefficient according to the speed error-P-term dynamic proportional curve;

[0009] In the second step, the obtained P-term proportional coefficient is multiplied by the error between the current vehicle speed and the target speed to obtain the P-term dynamic proportional control torque.

[0010] Furthermore, the method of I-term dynamic integral proportional closed-loop control further includes:

[0011] Step 1: Based on the error between the current vehicle speed and the target speed, the I-term dynamic integral proportional coefficient is obtained according to the speed error-I-term dynamic integral proportional curve;

[0012] Step 2: Based on the error between the current vehicle speed and the target speed, the dead zone of the dynamic proportional-integral adjustment item I is determined, and the activation flag of the dynamic proportional-integral adjustment item I is obtained, which has two states: 0 and 1. If the activation flag of the dynamic proportional-integral adjustment item I is 1, the coefficient of the dynamic integral ratio of item I is output normally. If the activation flag of the dynamic proportional-integral adjustment item I is 0, the coefficient of the dynamic integral ratio of item I is processed to 0, which is used to stop the dynamic proportional-integral adjustment item I.

[0013] Step 3: Based on the obtained coefficient of the dynamic integral ratio and the error between the current vehicle speed and the target vehicle speed, an integral calculation is performed to obtain the dynamic proportional integral closed-loop control torque. Based on this, the dynamic proportional integral closed-loop control torque is cleared to zero.

[0014] Step 4: Limit the obtained I-term dynamic proportional integral regulation control torque.

[0015] Furthermore, the method for performing zero control on the I-term dynamic proportional integral closed-loop regulation control torque further includes:

[0016] Each time the creep function is triggered, the I item dynamic proportional integral closed-loop control torque is cleared to 0 within 2 seconds; after the P item adjustment takes effect, the I item takes control; when the vehicle speed overshoot is detected and exceeds a certain error value, the clearing control must be exited immediately to allow the I item to perform callback control.

[0017] Furthermore, the slope feedforward torque compensation control method further includes:

[0018] Step 1: Based on the current slope of the vehicle, the slope compensation torque is obtained according to the slope-slope torque compensation curve;

[0019] Step 2: Based on the error between the current vehicle speed and the target speed, the slope torque sensor error compensation coefficient is obtained according to the speed error-slope torque sensor error compensation coefficient curve;

[0020] Step 3: Multiply the slope torque sensor error compensation coefficient obtained by the slope compensation torque to obtain the final slope compensation torque.

[0021] Furthermore, the vehicle weight feedforward torque compensation control method further includes:

[0022] Step 1: Based on the current vehicle weight and the vehicle weight-vehicle weight compensation coefficient curve, the vehicle weight compensation torque is obtained;

[0023] Step 2: Based on the current slope of the vehicle, the vehicle weight sensor error compensation coefficient is obtained according to the vehicle current slope-vehicle weight sensor error compensation coefficient curve;

[0024] In step 3, the obtained slope torque sensor error compensation coefficient is multiplied by the vehicle weight compensation torque to obtain the final vehicle weight compensation torque.

[0025] Beneficial effects of the present invention:

[0026] By adopting the method of the present invention, a pure electric heavy-duty truck can achieve stable creeping speed control when it is equipped with or without a trailer, empty, fully loaded, or on different slopes. After a 10,000km reliability test on an actual vehicle, no problems were found, indicating extremely high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 : P-term dynamic proportional control;

[0028] Figure 2 : I-term dynamic proportional closed-loop control;

[0029] Figure 3 : Slope feedforward compensation control;

[0030] Figure 4 : Vehicle weight feedforward compensation control;

[0031] Figure 5 : Creep control torque calculation. DETAILED DESCRIPTION

[0032] The following is combined with Figure 1 To the attached Figure 5 The present invention is described in further detail.

[0033] The present invention provides a highly adaptable creep control method for a pure electric heavy truck, comprising:

[0034] 1. After entering the creep function, perform P-term dynamic proportional control; see Figure 1 The specific process is as follows:

[0035] In the first step, based on the error between the current vehicle speed and the target speed, the P-item dynamic proportional table lookup module is used to obtain the P-item proportional coefficient according to the speed error-P-item dynamic proportional curve. This coefficient is improved from the classic fixed P-item coefficient to a dynamic P-item coefficient. The changing trend is that the larger the error, the larger the coefficient, and the smaller the error, the smaller the coefficient. This not only improves the real-time performance of the P-item control, but also effectively reduces the probability of overshoot.

[0036] In this step, the vehicle speed error-P term dynamic proportional curve can be obtained in advance using the P term proportional control method in Chapter 1 Digital PID Control, "New PID Control and Its Application", Tao Yonghua, Machinery Industry Press, 1998. The specific curve parameter values ​​are obtained according to the closed-loop calibration results of the actual vehicle.

[0037] In the second step, the obtained P-term proportional coefficient is multiplied by the error between the current vehicle speed and the target speed to obtain the P-term dynamic proportional control torque.

[0038] 2: I dynamic integral proportional closed loop control, see Figure 2 The specific process is as follows:

[0039] Step 1: Based on the error between the current vehicle speed and the target speed, the I-term dynamic integral proportional coefficient is obtained according to the speed error-I-term dynamic integral proportional curve.

[0040] In this step, the vehicle speed error-I dynamic integral proportional curve can also be obtained in advance using the method in Digital PID Control in Chapter 1 of "New PID Control and Its Application", Tao Yonghua, Machinery Industry Press, 1998. The specific curve parameter values ​​are obtained based on the closed-loop calibration results of the actual vehicle.

[0041] Step 2: Based on the vehicle's current speed, different speed error-I dynamic integral proportional curves are selected to obtain a dynamic integral to address the large difference in required creep torque before and after a creep start, ensuring smooth creep start. Based on the error between the vehicle's current speed and the target speed, the I dynamic proportional integral adjustment deadband is determined to obtain an I dynamic proportional integral adjustment activation flag, which has two states: 0 and 1. The I dynamic proportional integral adjustment activation flag is responsible for correcting the obtained I dynamic integral proportional coefficient. If the I dynamic proportional integral adjustment activation flag is 1, the obtained I dynamic integral proportional coefficient is output normally. If the I dynamic proportional integral adjustment activation flag is 0, the obtained I dynamic integral proportional coefficient is set to 0, thereby disabling the I dynamic proportional integral adjustment.

[0042] Step 3: Based on the obtained coefficient of the dynamic integral ratio (I) and the error between the current vehicle speed and the target speed, an integral calculation is performed to obtain the dynamic proportional integral closed-loop control torque (I). This torque is then reset to zero. The specific reset control strategy is to reset the I dynamic proportional integral closed-loop control torque within 2 seconds of each triggering of the creep function to prevent excessive acceleration during startup and avoid integral saturation. After the P control takes effect, the I control takes over. However, if the vehicle speed overshoot is detected and exceeds a certain error value, the reset control is immediately terminated, allowing the I control to resume.

[0043] In the fourth step, the obtained I-term dynamic proportional-integral regulation control torque is limited, and the limited torque is designed as a dynamic limit, which changes dynamically with the current vehicle speed and slope, thereby improving the ability of the I-term dynamic proportional-integral closed-loop regulation control to adapt to different driving conditions, and preventing the I-term dynamic proportional-integral closed-loop regulation callback control torque from being too large in the case of creep overshoot, resulting in a rapid callback of the creep speed after overshoot, causing the vehicle to feel frustrated, thereby improving driving comfort.

[0044] 3: Slope feedforward torque compensation control, see Figure 3 The specific process is as follows:

[0045] Step 1: Based on the current slope of the vehicle, the slope compensation torque is obtained according to the slope-slope torque compensation curve.

[0046] In this step, the slope-slope torque compensation curve can be obtained in advance using the digital PID control and feedforward control method in Chapter 1 of "New PID Control and Its Application", Tao Yonghua, Machinery Industry Press, 1998. The specific curve parameter values ​​are obtained according to the closed-loop calibration results of the actual vehicle. The subsequent feedforward compensation curve acquisition is not repeated here.

[0047] Step 2: Based on the error between the current vehicle speed and the target speed, the slope torque sensor error compensation coefficient is obtained according to the speed error-slope torque sensor error compensation coefficient curve.

[0048] The vehicle speed error-slope torque sensor error compensation coefficient curve can also be obtained in advance using the feedforward control method in digital PID control in Chapter 1 of "New PID Control and Its Application", Tao Yonghua, Machinery Industry Press, 1998. The specific curve parameter values ​​are obtained based on the closed-loop calibration results of the actual vehicle.

[0049] In the third step, the obtained slope torque sensor error compensation coefficient is multiplied by the slope compensation torque to obtain the final slope compensation torque, thereby solving the problem of unstable creep control and poor vehicle driving comfort caused by the currently common problem of poor slope sensor accuracy.

[0050] 4: Vehicle weight feedforward torque compensation control, see Figure 4 The specific process is as follows:

[0051] Step 1: Based on the current vehicle weight and the vehicle weight-vehicle weight compensation coefficient curve, the vehicle weight compensation torque is obtained to compensate for the torque that needs to be increased when the vehicle is heavier.

[0052] In this step, the vehicle weight-vehicle weight compensation coefficient curve can also be obtained in advance using the feedforward control method in digital PID control in Chapter 1 of "New PID Control and Its Application", Tao Yonghua, Machinery Industry Press, 1998. The specific curve parameter values ​​are obtained according to the closed-loop calibration results of the actual vehicle, and the subsequent feedforward compensation curve acquisition is not repeated here.

[0053] Step 2: Based on the current slope of the vehicle, obtain the vehicle weight sensor error compensation coefficient according to the vehicle current slope-vehicle weight sensor error compensation coefficient curve.

[0054] In step 3, the slope torque sensor error compensation coefficient is multiplied by the vehicle weight compensation torque to obtain the final vehicle weight compensation torque. Using the slope and current vehicle speed errors to compensate for vehicle weight calculation accuracy addresses the widespread issue of unstable creep control and poor driving comfort caused by poor slope and vehicle weight acquisition accuracy.

[0055] 5. Creep control torque calculation, see Figure 5 The specific process is as follows:

[0056] In the first step, the P dynamic proportional control torque, the I dynamic proportional integral closed-loop adjustment control torque, the slope compensation torque, and the vehicle weight compensation torque obtained in the above steps are added together to obtain the creep closed-loop adjustment control torque.

[0057] Step 2: Finally, a fixed limit is applied to the creep closed-loop control torque to prevent abnormal output torque caused by closed-loop regulation, thus ensuring the comfort and safety of creep control.

[0058] The method of the present invention is implemented by developing model-based control software based on MATLAB / Simulink / Stateflow software, using automatic code generation technology to automatically generate C code from the application layer model, and then integrating the application layer code with the underlying code based on the HighTecIDE compiler.

Claims

1. A highly adaptable creep control method for a pure electric heavy truck, characterized in that: After the pure electric heavy-duty truck enters the creep function, P-term dynamic proportional control is performed to obtain P-term dynamic proportional control torque; I-term dynamic integral proportional closed-loop control is performed to obtain I-term dynamic proportional integral closed-loop regulation control torque; slope feedforward torque compensation control is performed to obtain slope compensation torque; vehicle weight feedforward torque compensation control is performed to obtain vehicle weight compensation torque; the P-term dynamic proportional control torque, I-term dynamic proportional integral closed-loop regulation control torque, slope compensation torque, and vehicle weight compensation torque obtained in the above steps are added together to obtain the creep closed-loop regulation control torque, and finally a fixed limit processing is performed on the creep closed-loop regulation control torque to prevent abnormal torque output due to closed-loop regulation, thereby ensuring the comfort and safety of creep control; Each time the creep function is triggered, the I item dynamic proportional integral closed-loop control torque is cleared to 0 within 2 seconds; after the P item adjustment takes effect, the I item takes control again; when it is detected that the vehicle speed overshoot exceeds a certain error value, the clearing control must be exited immediately to allow the I item to perform callback control.

2. The highly adaptable creep control method for a pure electric heavy truck according to claim 1, characterized in that: The method for performing P-term dynamic proportional control further includes: Step 1: Based on the error between the current vehicle speed and the target speed, obtain the P-term proportional coefficient according to the speed error-P-term dynamic proportional curve; In the second step, the obtained P-term proportional coefficient is multiplied by the error between the current vehicle speed and the target speed to obtain the P-term dynamic proportional control torque.

3. The highly adaptable creep control method for a pure electric heavy truck according to claim 1, characterized in that: The method of dynamic integral proportional closed-loop control further includes: Step 1: Based on the error between the current vehicle speed and the target speed, the I-term dynamic integral proportional coefficient is obtained according to the speed error-I-term dynamic integral proportional curve; Step 2: Based on the error between the current vehicle speed and the target speed, the dead zone of the dynamic proportional-integral adjustment item I is determined, and the activation flag of the dynamic proportional-integral adjustment item I is obtained, which has two states: 0 and 1. If the activation flag of the dynamic proportional-integral adjustment item I is 1, the coefficient of the dynamic integral ratio of the item I is output normally. If the activation flag of the dynamic proportional-integral adjustment item I is 0, the coefficient of the dynamic integral ratio of the item I is processed to 0, which is used to stop the dynamic proportional-integral adjustment item I. Step 3: Based on the obtained coefficient of the dynamic integral ratio and the error between the current vehicle speed and the target vehicle speed, an integral calculation is performed to obtain the dynamic proportional integral closed-loop control torque. Based on this, the dynamic proportional integral closed-loop control torque is cleared to zero. In step 4, the obtained I-term dynamic proportional-integral regulation control torque is limited; at the same time, the callback torque of the I-term closed-loop regulation is limited.

4. The highly adaptable creep control method for a pure electric heavy truck according to claim 3, characterized in that: The method of grade feed-forward torque compensation control further includes: Step 1: Based on the current slope of the vehicle, the slope compensation torque is obtained according to the slope-slope torque compensation curve; Step 2: Based on the error between the current vehicle speed and the target speed, the slope torque sensor error compensation coefficient is obtained according to the speed error-slope torque sensor error compensation coefficient curve; Step 3: Multiply the slope torque sensor error compensation coefficient obtained by the slope compensation torque to obtain the final slope compensation torque.

5. The highly adaptable creep control method for a pure electric heavy truck according to claim 4, characterized in that: The vehicle weight feedforward torque compensation control method further includes: Step 1: Based on the current vehicle weight and the vehicle weight-vehicle weight compensation coefficient curve, the vehicle weight compensation torque is obtained; Step 2: Based on the current slope of the vehicle, the vehicle weight sensor error compensation coefficient is obtained according to the vehicle current slope-vehicle weight sensor error compensation coefficient curve; In step 3, the obtained slope torque sensor error compensation coefficient is multiplied by the vehicle weight compensation torque to obtain the final vehicle weight compensation torque.

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