Vehicle acceleration-limiting torque control method and apparatus

Abstract

The present invention belongs to the technical field of vehicle torque control, and in particular to a vehicle acceleration-limiting torque control method and apparatus. The method comprises: first, determining an acceleration calculation formula, which reflects the relationship between a calculated acceleration value ajsN+1 of the next cycle and a torque command request TtqN of the current cycle, a slope value αN of the current cycle and a vehicle speed uN of the current cycle; then, using the acceleration calculation formula to determine ajsN+1, subtracting the current acceleration limit target value aNlimit from ajsN+1 to obtain the current acceleration difference value △aN, and when △aN>0, on the basis of △aN, uN and the relationship between △aN, uN and the current acceleration limiting feedforward torque TfN, obtaining TfN; and finally, subtracting TfN from a driver-demanded torque TdN of the current cycle, and on the basis of an obtained difference value, determining an electric motor torque command request TtqN of the current cycle for controlling an electric motor. The present invention realizes acceleration limitation for vehicle launch and acceleration limitation for re-acceleration, thereby avoiding safety risks brought about by excessive acceleration during vehicle launch, and improving the operational convenience for drivers.

Description

A vehicle acceleration limiting torque control method and device Technical Field

[0001] The present invention belongs to the technical field of vehicle torque control, and in particular relates to a method and device for controlling acceleration-limited torque of a whole vehicle. Background Art

[0002] During actual vehicle operation, vehicle load, weather, road conditions, and tire pressure can all change in real time. When the powertrain outputs a fixed torque, vehicle acceleration will vary with these changes. This is particularly true for commercial vehicles like buses and logistics vehicles, where acceleration can vary significantly. Drivers must constantly adjust their driving style to balance vehicle power and comfort.

[0003] Passenger vehicles currently offer multiple driving modes for drivers to choose from, each corresponding to a specific engine or drive motor output power setting that the driver can manually adjust based on actual needs. Some commercial vehicles, such as medium- and heavy-duty trucks, are equipped with a multi-state switch knob that sets three maximum power output modes for no-load, half-load, and full-load, allowing the driver to manually select the desired setting. However, frequent manual intervention can easily lead to driver fatigue, and the discrete, multi-speed adjustment mode cannot truly meet the requirements for linear power regulation across the entire load range, as well as changes in environmental and road conditions.

[0004] To solve this problem, a commonly used method in the prior art is to subtract the limited torque after PID adjustment based on the acceleration deviation from the driver's original required torque to obtain the final motor torque command request. However, the calculation of the limited torque after PID adjustment based on the acceleration deviation is a closed-loop control method, which is a result-based adjustment with a slow response speed and untimely adjustment. It cannot give a good balance between vehicle dynamics and comfort, and is prone to large acceleration control overshoot. Summary of the Invention

[0005] The purpose of the present invention is to provide a vehicle acceleration limiting torque control method and device to solve the problem that the existing method cannot give good balance between vehicle dynamics and comfort and has a large acceleration control overshoot.

[0006] To solve the above technical problems, the present invention provides a vehicle acceleration limiting torque control method, comprising the following steps:

[0007] 1) The driver's demand torque T in the current cycle dN As the motor torque command request T in the current cycle tqN , and according to the slope value α of the current cycle N and the vehicle speed u of the current cycleN , and the calculated acceleration value a of the next cycle obtained according to the car driving equation jsN+1 With three parameters T tqN , α N 、u N The fitting relationship between them is used to obtain the acceleration calculation value a of the next cycle. jsN+1 ;

[0008] 2) Use a jsN+1 Subtract the current acceleration limit target value a Nlimit Get the current acceleration difference △a N , in △a N >0, according to △a N and u N , and △a N 、u N The current acceleration limit feedforward torque T fN The relationship between the current acceleration limit feedforward torque T is obtained. fN ;

[0009] 3) Calculate T dN Subtract T fN The motor torque command request T of the current cycle is determined based on the obtained difference. tqN , according to T tqN Control the motor.

[0010] Furthermore, the acceleration calculation value a of the next cycle is obtained according to the vehicle driving equation jsN+1 With three parameters T tqN , α N 、u N The fitting relationship between them is:

[0011]

[0012] In the formula, K0, K1, K2 and K3 are fitting coefficients, i g is the transmission ratio of the transmission, i0 is the transmission ratio of the main reducer, η t is the mechanical efficiency of the transmission system, σ is the vehicle rotation mass conversion coefficient, m is the vehicle mass, r is the wheel rolling radius, g is the acceleration of gravity, f is the rolling resistance coefficient, c D is the vehicle's air resistance coefficient, and A is the vehicle's frontal area.

[0013] Furthermore, multiple sets of acceleration, motor torque command request, slope value and vehicle speed data during starting and accelerating are collected, and the fitting coefficients K0, K1, K2 and K3 are obtained by using the least squares fitting method.

[0014] Furthermore, when the vehicle accelerates for the first time, the vehicle mass is taken as the vehicle unloaded mass, the slope value is 0, and the mechanical efficiency η of the transmission system tested in the vehicle test laboratory is combined. t , vehicle air resistance coefficient c D , vehicle rotation mass conversion coefficient σ and wheel rolling radius r, and calculate the initial fitting coefficients K0, K1, K2 and K3.

[0015] Furthermore, the current acceleration limit target value a Nlimit is based on the vehicle speed u of the current cycle N and the accelerator pedal opening D of the current cycle N , and a Nlimit With two parameters u N 、D N The relationship between them is obtained.

[0016] Furthermore, in step 3), the motor torque command request T of the current cycle is determined based on the obtained difference. tqN The means is: the difference is subtracted from the limit torque obtained by adjusting the acceleration deviation of the current cycle, thereby obtaining the motor torque command request T of the current cycle. tqN .

[0017] Furthermore, a PID controller is used to perform the adjustment.

[0018] Furthermore, the driver demand torque T dN is based on the vehicle speed u of the current cycle N and the accelerator pedal opening D of the current cycle N , and T dN With two parameters u N 、D N The relationship between them is obtained.

[0019] Furthermore, the actual vehicle is calibrated by calibrating the vehicle with no load and full load to obtain △a N 、u N With T fN The relationship between them.

[0020] To solve the above technical problems, the present invention also provides a vehicle acceleration limiting torque control device, including a memory and a processor, wherein the processor is used to execute computer program instructions stored in the memory to implement the vehicle torque limiting control method introduced above.

[0021] The beneficial effects of the present invention are as follows: the present invention is an improved invention creation, the present invention adds a feedforward quantity based on open-loop control, the feedforward quantity is the current acceleration limit feedforward torque, the current acceleration limit feedforward torque is calculated based on the acceleration calculation value of the current cycle and the vehicle speed of the current cycle, wherein, according to the automobile driving equation taking the vehicle driving resistance into consideration, the fitting relationship between the acceleration calculation value of the next cycle, the motor torque command request of the current cycle, the slope value of the current cycle, and the vehicle speed of the current cycle is obtained, and the fitting relationship is used to obtain the acceleration calculation value of the next cycle, and the acceleration calculation value table of the next cycle is as follows: The meaning of the characteristic is the value that the acceleration of the next cycle can reach when the motor torque is not restricted, and then it is judged whether the calculated acceleration value of the next cycle is greater than the current acceleration limit target value. If it is greater than, it means that the acceleration of the next cycle will exceed the target, and it needs to be restricted at this time. The specific restriction method is to use the calculated acceleration value of the next cycle to obtain the current acceleration limit feedforward torque required for the acceleration limit control, and finally subtract the acceleration limit feedforward torque required for the acceleration limit control from the driver's demand torque of the current cycle, and obtain the motor torque command request for controlling the motor in the current cycle according to the acceleration limit feedforward torque. Subtracting the acceleration limit feedforward torque required for the acceleration limit control realizes the advance limitation of the driver's required torque, avoids the problem of large acceleration control overshoot caused by the lag in vehicle acceleration calculation under starting and re-acceleration conditions, realizes the acceleration limit of the vehicle at starting and the acceleration limit during re-acceleration without adding hardware, avoids the safety risks caused by excessive acceleration of the vehicle at starting and improves the driver's operating convenience, and achieves basically consistent power under any load, different slopes, and re-acceleration conditions after starting, without manual intervention, and can well take into account the vehicle's power and comfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a flow chart of a vehicle acceleration limiting torque control method in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The main idea of ​​the present invention is to add a feedforward based on open loop control, which is the current acceleration limit feedforward torque T fN , is the feedforward torque required to calculate acceleration limit control, T fN is based on △a N 、u N and T fN The relationship between the three is obtained, where u N Refers to the vehicle speed of the current cycle, △a N Refers to the calculated acceleration value a of the next cycle jsN+1 Subtract the current acceleration limit target value a Nlimit The current acceleration difference is obtained, and ajsN+1 It is a jsN+1 、T tqN , α N 、u N The fitting relationship between jsN+1 、T tqN , α N 、u N The fitting relationship between is obtained based on the automobile driving equation taking the vehicle driving resistance into account. N >0, use T fN The driver's required torque is limited to limit the driver's torque in advance, and the problem of large acceleration control overshoot caused by the lag in vehicle acceleration calculation during starting and re-acceleration is reduced. The vehicle's starting acceleration limit and acceleration limit during re-acceleration are achieved without adding hardware, and the vehicle's power is basically consistent under any load, different slopes, and re-acceleration conditions after starting, thereby improving the vehicle's comfort during acceleration and the driver's convenience of operation. Based on this concept, a vehicle acceleration limiting torque control method and a vehicle acceleration limiting torque control device of the present invention can be realized. In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. Method embodiment:

[0024] An embodiment of a vehicle acceleration limiting torque control method of the present invention has a process as shown in FIG1 and is described as follows:

[0025] Step 1: Get the acceleration calculation formula based on the car driving equation. The acceleration calculation formula reflects the acceleration calculation value a of the next cycle. jsN+1 The motor torque command request T of the current cycle tqN , the slope value α of the current cycle N , the vehicle speed u of the current cycle N The fitting relationship between . This fitting relationship (i.e., the acceleration calculation formula) is obtained using the following method:

[0026] The vehicle acceleration can be derived from the time derivative of the real-time vehicle speed signal. The calculation formula is as follows:

[0027]

[0028] Where a N is the acceleration of the current cycle, u N is the vehicle speed of the current cycle, u N-1 is the vehicle speed of the previous cycle, and ΔT1 is the size of the acceleration calculation sampling period.

[0029] Based on the vehicle driving equation, combined with the current calculated acceleration value, the previous slope value, and the motor torque command request output at the previous acceleration sampling moment, the least squares method is used to fit the corresponding acceleration calculation formula for the vehicle. The vehicle driving equation is as follows:

[0030]

[0031] Where, T tqN-1 is the motor torque command request finally output at the last acceleration sampling moment, i g is the transmission ratio of the transmission, i0 is the transmission ratio of the main reducer, η t is the mechanical efficiency of the transmission system, r is the wheel rolling radius, m is the vehicle mass, g is the acceleration of gravity, f is the rolling resistance coefficient, α N-1 is the slope angle measured in the previous cycle, c D is the vehicle's air resistance coefficient, A is the vehicle's frontal area, and σ is the vehicle's rotational mass conversion coefficient. Since the slope angle of a normal road is not large, cosα N-1 ≈1, so the car's driving equation can be simplified to:

[0032]

[0033] The above formula can be transformed into:

[0034] Where,

[0035] Then transform the above formula to get:

[0036]

[0037] Based on the above formula, in addition to the slope value α of the current cycle N and the vehicle speed u of the current cycle N In addition to substituting the above formula, the driver's demand torque T in the current cycle is also dN As the motor torque command request T in the current cycle tqN Substituting into the above formula, we can get the acceleration calculation value a of the next cycle jsN+1 , which indicates the value that the acceleration can reach in the next cycle without limiting the motor torque.

[0038] The vehicle load does not change after the vehicle starts, so K0, K1, K2, and K3 can be considered to be basically unchanged. Therefore, we can record multiple sets of motor torque command requests for the vehicle output when the accelerator is pressed and calculated after each vehicle door is closed, as well as the sampled vehicle speed and slope. Then, we can use the least squares method to perform multivariate nonlinear fitting to calculate K0, K1, K2, and K3. In particular, when the vehicle accelerates for the first time, based on the vehicle's unloaded mass, a slope of 0°, and the η value tested in the vehicle test laboratory, we can calculate the vehicle load. t 、c D , σ, r and other parameters are calculated to obtain the initial K0, K1, K2, K3. Among them, the transmission ratio i g , the transmission ratio i0 of the main reducer and the vehicle's frontal area A can be based on the theoretical design values; the slope angle α measured in the current cycle N Take 0° and select the rolling resistance coefficient f according to the empirical value.

[0039] Of course, if the controller has limited computing power, the collected data can be uploaded to the cloud for calculation, and then the cloud will send the calculation results to the vehicle for execution.

[0040] Step 2: According to the fitted acceleration calculation formula, use the current vehicle speed u N , slope α N and the driver's original demand torque T dN Calculate the acceleration value a of the next cycle jsN+1 Then use a jsN+1 Subtract the current acceleration limit target value a Nlimit Get the current acceleration difference △a N Among them, if the acceleration difference △a N is not greater than 0, then let T fN Is 0; if the acceleration difference △a N If it is greater than 0, then according to the vehicle speed u N , acceleration difference △a N Perform a two-dimensional table lookup to obtain the current acceleration limit feedforward torque T fN .

[0041] Among them, the values ​​in the feedforward torque table are obtained by actual vehicle calibration. The range of the values ​​in the table is determined according to the no-load calibration results and the full-load calibration results. The lower limit is the acceleration change △a corresponding to different vehicle speed points under no-load and flat road conditions. k The required torque value, the upper limit is the acceleration change △a corresponding to different vehicle speed points under full load and flat road conditions k Required torque value, where △a kCorresponding to a set of data, such as: [0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0]. When calibrating the vehicle, you can choose to be more inclined to the no-load feedforward torque table or the full-load feedforward torque table according to the actual vehicle performance. For example, if you pay more attention to the vehicle's dynamic response performance, you can choose to be more inclined to the no-load feedforward torque table; if you pay more attention to comfort, you can choose to be more inclined to the full-load feedforward torque table. In addition, according to the current vehicle speed and accelerator pedal opening D N Perform a two-dimensional table lookup to obtain the current target acceleration limit target value a Nlimit The values ​​in the table are calculated based on the vehicle's dynamic requirements and can be calibrated and corrected based on actual vehicle test results.

[0042] Step 3: Calculate the driver's required torque T for the current cycle dN Subtract the current acceleration limit feedforward torque T fN The difference is then subtracted from the limit torque obtained after adjusting and controlling the acceleration deviation of the current cycle to obtain the motor torque command request T for the current cycle. tqN , and according to T tqN Control the motor.

[0043] In this embodiment, a PID controller is used for regulation and control. That is, acceleration and acceleration change rate are used as feedback to compare with the acceleration limit target value to perform PID closed-loop control. The PID control output is the limited torque control value. The specific calculation formula is:

[0044] T tqN =T dN -T fN -K p *e N -K i *∑e N -K d [e N -e N-1 ]

[0045] Where, T tqN T is the motor torque command request of the current cycle; dN K is the driver's original demand torque calculated based on the accelerator pedal opening and vehicle speed (e.g., the MAP relationship table of accelerator, vehicle speed, and torque), that is, the driver's demand torque for the current cycle; p , K i , K d is the proportional coefficient, integral coefficient and differential coefficient of PID control; e N is the acceleration deviation of this cycle; e N-1 is the acceleration deviation of the previous cycle; ∑e Nis the cumulative sum of acceleration deviations. It should be noted that e here N 、e N-1 It is calculated based on the acceleration obtained by time-deriving the real-time vehicle speed signal. Moreover, the PID controller used here can also be used as other embodiments, such as a fuzzy PID controller.

[0046] In summary, the present invention has the following characteristics:

[0047] (1) The present invention realizes the acceleration limit of the whole vehicle at start and the acceleration limit during re-acceleration without adding hardware, thereby avoiding the safety risks caused by excessive acceleration of the vehicle at start and improving the driver's operating convenience. It realizes that the power of the vehicle is basically consistent under any load, different slopes, and re-acceleration conditions after start, thereby improving the comfort of the vehicle during acceleration and the driver's operating convenience.

[0048] (2) The present invention uses the least squares method to perform multivariate nonlinear fitting based on the acceleration value, the collected slope value, and the motor torque command request to obtain the acceleration calculation formula corresponding to the vehicle, and then calculate the feedforward torque required for acceleration limit control. This method limits the driver's torque in advance, avoiding the problem of large acceleration control overshoot due to the lag in vehicle acceleration calculation under starting and re-acceleration conditions. It is applicable to any load and slope and improves control accuracy. Moreover, compared with the closed-loop control method with only acceleration feedback, it can provide an initial feedforward torque, reduce acceleration control overshoot, and improve control accuracy.

[0049] (3) When the vehicle accelerates for the first time, the present invention obtains an acceleration calculation formula according to the vehicle's unloaded mass and parameters tested in the vehicle laboratory.

[0050] (4) According to the computing power of the controller, the present invention can choose to upload the collected data to the cloud for calculation, and then the cloud sends the calculation results to the vehicle for execution, avoiding the situation where the control algorithm cannot be implemented due to insufficient computing power of the controller, thus saving hardware resources.

[0051] An embodiment of a vehicle acceleration torque control device according to the present invention includes a memory, a processor, and an internal bus. The internal bus enables communication and data exchange between the processor and the memory. The memory includes at least one software functional module stored in the memory. The processor executes various functional applications and data processing by running the software programs and modules stored in the memory, thereby implementing a vehicle acceleration torque control method described in the method embodiment of the present invention. The processor can be a processing device such as a microprocessor (MCU) or a programmable logic device (FPGA). The memory can be any type of memory that uses electrical energy to store information, such as RAM or ROM, or other types of memory.

[0052] While specific embodiments have been described above, the present invention is not limited to the described embodiments. The fundamental concept of the present invention lies in the aforementioned basic scheme. Based on the teachings of the present invention, those skilled in the art can devise various variations of models, formulas, and parameters without inventive effort. Changes, modifications, substitutions, and variations to the embodiments without departing from the principles and spirit of the present invention remain within the scope of protection of the present invention.

Claims

1. A vehicle acceleration limiting torque control method, characterized in that: The steps include: 1) The driver's demand torque T in the current cycle dN As the motor torque command request T in the current cycle tqN , and according to the slope value α of the current cycle N and the vehicle speed u of the current cycle N , and the calculated acceleration value a of the next cycle obtained according to the car driving equation jsN+1 With three parameters T tqN , α N 、u N The fitting relationship between them is used to obtain the acceleration calculation value a of the next cycle. jsN+1 ; 2) Use a jsN+1 Subtract the current acceleration limit target value a Nlimit Get the current acceleration difference △a N , in △a N >0, according to △a N and u N , and △a N 、u N The current acceleration limit feedforward torque T fN The relationship between the current acceleration limit feedforward torque T is obtained. fN ; 3) Calculate T dN Subtract T fN The motor torque command request T of the current cycle is determined based on the obtained difference. tqN , according to T tqN Control the motor.

2. The vehicle acceleration limiting torque control method according to claim 1, characterized in that: The calculated acceleration value a of the next cycle is obtained based on the car's driving equation jsN+1 With three parameters T tqN , α N 、u N The fitting relationship between them is: In the formula, K0, K1, K2 and K3 are fitting coefficients, i g is the transmission ratio of the transmission, i0 is the transmission ratio of the main reducer, η t is the mechanical efficiency of the transmission system, σ is the vehicle rotation mass conversion coefficient, m is the vehicle mass, r is the wheel rolling radius, g is the acceleration of gravity, f is the rolling resistance coefficient, cDD is the vehicle air resistance coefficient, and A is the vehicle frontal area.

3. The vehicle acceleration limiting torque control method according to claim 2, characterized in that: Multiple sets of acceleration, motor torque command request, slope value and vehicle speed data during starting and accelerating are collected, and the fitting coefficients K0, K1, K2 and K3 are obtained by least square fitting.

4. The vehicle acceleration limiting torque control method according to claim 2, characterized in that: When the vehicle accelerates for the first time, the vehicle mass is taken as the vehicle unloaded mass, the slope value is 0, and the mechanical efficiency η of the transmission system tested in the vehicle test laboratory is combined. t , vehicle air resistance coefficient c D , vehicle rotation mass conversion coefficient σ and wheel rolling radius r, and calculate the initial fitting coefficients K0, K1, K2 and K3.

5. The vehicle acceleration limiting torque control method according to claim 1, characterized in that: Current acceleration limit target value a Nlimit is based on the vehicle speed u of the current cycle N and the accelerator pedal opening D of the current cycle N , and a Nlimit With two parameters u N 、D N The relationship between them is obtained.

6. The vehicle acceleration limiting torque control method according to claim 1, characterized in that: In step 3), the motor torque command request T of the current cycle is determined based on the obtained difference. tqN The means is: the difference is subtracted from the limit torque obtained by adjusting the acceleration deviation of the current cycle, thereby obtaining the motor torque command request T of the current cycle. tqN .

7. The vehicle acceleration limiting torque control method according to claim 6, characterized in that: The regulation is performed using a PID controller.

8. The vehicle acceleration limiting torque control method according to claim 1, characterized in that: The driver's demand torque T in the current cycle dN is based on the vehicle speed u of the current cycle N and the accelerator pedal opening D of the current cycle N , and T dN With two parameters u N 、D N The relationship between them is obtained.

9. The vehicle acceleration limiting torque control method according to claim 1, characterized in that: The actual vehicle is calibrated by emptying and fully loading the vehicle to obtain △a N 、u N With T fN The relationship between them.

10. A vehicle acceleration limiting torque control device, comprising a memory and a processor, characterized in that: The processor is used to execute computer program instructions stored in the memory to implement the vehicle acceleration limiting torque control method according to any one of claims 1 to 9.

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