CN104129305B - A kind of electric automobile method for controlling driving speed - Google Patents

Abstract

The invention relates to a vehicle speed control method for an electric vehicle, which comprises the following steps: 1) the actual vehicle speed signal measured by a Hall-type wheel speed signal sensor is input into a vehicle controller, and a control chip judges whether to start the vehicle speed closed-loop control; 2) driving The driver selects the driving mode on the driving mode selection module according to the current road conditions, and at the same time depresses the electronic accelerator pedal to a certain position; 3) The driving mode signal, accelerator pedal position signal, and actual vehicle speed signal are input to the vehicle controller through corresponding channels ; 4) The low-pass filter module filters the input accelerator pedal position signal; 5) The PID controller calculates the processed accelerator pedal position signal and the actual vehicle speed signal to obtain the drive motor torque command, and transmits it through the CAN communication channel Input to the drive motor controller; 6) The drive motor controller controls the action of the drive motor according to the command of the drive motor. The invention can be widely used in the speed control of various electric vehicles.

Description

A method for controlling the speed of an electric vehicle

technical field

The invention relates to a vehicle speed control method, in particular to a vehicle speed control method of an electric vehicle in which the position of the accelerator pedal corresponds to the vehicle speed of the electric vehicle.

Background technique

As of the end of 2013, the number of automobiles in China has exceeded 130 million, and there are 31 cities in the country with more than 1 million automobiles, including Beijing, Tianjin, Chengdu, Shenzhen, Shanghai, Guangzhou, Suzhou, and Hangzhou. The inventory exceeds 2 million vehicles. At present, the vast majority of cars in the Chinese market and on the market still use traditional internal combustion engines as power, which brings huge pressure on energy conservation and environmental protection. Compared with internal combustion engine vehicles, electric vehicles have many advantages, such as high energy conversion efficiency and large torque at low speeds. With the continuous tightening of fuel consumption and emission regulations, it is reasonable to believe that the market share of electric vehicles (such as hybrid vehicles and pure electric vehicles) will gradually increase, and then occupy a part of the market of traditional internal combustion engine vehicles, and even eventually make internal combustion engine vehicles out of history stage.

On the other hand, in a traditional internal combustion engine vehicle, the driver needs to participate in the negative feedback closed-loop control of the vehicle speed. The control process is as follows: 1. The driver generates a desired speed in his heart, which is related to many factors, such as the road speed limit, Distance to the vehicle ahead or overtaking intention, etc. 2. The instrument panel gives the actual vehicle speed visual feedback to the driver, and the driver judges the relationship between the actual vehicle speed and the expected vehicle speed, that is, whether the actual vehicle speed is greater than, less than or equal to the expected vehicle speed. 3. When the actual speed is lower than the expected speed, the driver's brain outputs an acceleration signal to control the right foot to step on the accelerator pedal to increase the opening of the accelerator; when the actual speed is equal to the expected speed, the driver's brain outputs a signal to maintain the status quo, and the right foot does not Make an action; when the actual speed is greater than the expected speed, the driver's brain outputs a deceleration signal, controls the right foot to lift up, reduces the opening of the accelerator, and even moves the right foot from the accelerator pedal to the brake pedal, and depresses the brake pedal. 4. The dashboard will give the actual vehicle speed visual feedback to the driver again, and then repeat steps 2 and 3 to finally realize the closed-loop control of the vehicle speed.

In the traditional negative feedback closed-loop control of internal combustion engine, the driver's eyes are responsible for feedback signal input, the brain is responsible for closed-loop control, hands and feet are responsible for executing the output signal of the brain, and the driver undertakes the main control task. When the vehicle speed is low, especially in the congested road conditions of big cities, two problems appear: first, under the stop-and-go working condition, the driver's work intensity is greatly increased, and the driver needs to constantly switch between the accelerator and the brake Pedal, if it is in a manual transmission model, the driver also needs to operate the clutch pedal and the transmission joystick, which is very easy to cause driving fatigue, which is not conducive to driving comfort and safety; secondly, each driver is an independent individual , the control period, response speed, overshoot and dynamic error of the above control method cannot be exactly the same for every driver. In layman's terms, it is driving habits. Some people like to drive softly, and the response speed and overshoot are relatively small, which is not conducive to the speed of traffic flow; while others like aggressive driving, and the response speed and overshoot are relatively large, which is not conducive to energy saving and emission reduction.

The transformation of the power system creates the possibility of changing the vehicle speed control method, and the configuration of the electric vehicle provides the possibility to solve the above two problems. The electric motor of an electric vehicle can generate driving torque and braking torque, and has a high response speed, and the speed and torque can be precisely controlled. However, under the traditional vehicle speed control method, the electric vehicle may produce excessive acceleration and deceleration, which will cause the motor to not work in the optimal efficiency zone, and also lose part of the braking energy.

Contents of the invention

In view of the above problems, the object of the present invention is to provide a vehicle speed control method for an electric vehicle that uses the position of the accelerator pedal to correspond to the vehicle speed of the electric vehicle when the electric vehicle is running at a low speed.

In order to achieve the above object, the present invention adopts the following technical solutions: a method for controlling the speed of an electric vehicle, which includes the following steps: 1) setting an analog input channel, a frequency quantity acquisition channel, a CAN communication channel and a control chip in the vehicle controller ;A low-pass filter module and a PID controller are set in the control chip; 2) the actual vehicle speed signal measured by the Hall-type wheel speed sensor is input to the vehicle controller through the frequency quantity acquisition channel, and the control chip judges whether to start the vehicle speed Closed-loop control; when the actual vehicle speed is less than the critical vehicle speed, the vehicle speed closed-loop control is started; when the actual vehicle speed is greater than or equal to the critical vehicle speed, the vehicle speed closed-loop control is not activated; 3) The driver selects Comfortable, A driving mode in normal or sports, while stepping on the electronic accelerator pedal to a certain position; 4) The driving mode signal of the driving mode selection module and the accelerator pedal position signal of the electronic accelerator pedal are input through the analog input channel Vehicle controller; the actual vehicle speed signal of the Hall-type wheel speed sensor is input to the vehicle controller through the frequency acquisition channel; 5) The low-pass filter module filters the input accelerator pedal position signal, and filters out the accelerator pedal position signal 6) The PID controller calculates the processed accelerator pedal position signal and the actual vehicle speed signal to obtain the drive motor torque command, and input it to the drive motor controller through the CAN communication channel; 7) drive The motor controller increases or decreases the required torque of the drive motor according to the command of the drive motor, so that the whole vehicle accelerates or decelerates according to the corresponding acceleration or deceleration speed response curve.

The present invention has the following advantages due to the adoption of the above technical solutions: 1. In the present invention, when the vehicle speed is low, the driver only needs to select the desired driving mode and step on the position of the accelerator pedal according to the desired vehicle speed, and the vehicle controller can control the vehicle according to the desired driving mode. The accelerator pedal position signal performs closed-loop control on the vehicle speed, which greatly reduces the driver's work intensity. 2. Since the present invention introduces the PID control law, the rapid and accurate response of the actual vehicle speed to the expected vehicle speed can be realized by rationally selecting the control parameters, and the vehicle speed can be precisely controlled. 3. Since the present invention optimizes the response curve according to the universal characteristic curve of the driving motor, the acceleration and deceleration of the whole vehicle are carried out according to the pre-designed acceleration speed response curve or deceleration speed response curve, and the driving efficiency and braking energy of the driving motor are optimized Recovery efficiency, able to recover as much energy as possible, effectively improving energy use efficiency. The present invention can be widely used in speed control of various electric vehicles such as pure electric passenger cars, plug-in hybrid electric passenger cars, pure electric cars, plug-in hybrid electric cars and the like.

Description of drawings

Fig. 1 is a block diagram of the control principle of the present invention

Fig. 2 is a control flow schematic diagram of the present invention

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

As shown in FIG. 1 , the vehicle controller of the present invention is provided with an analog quantity input channel 1 , a frequency quantity acquisition channel 2 , a CAN communication channel 3 and a control chip 4 . A low-pass filter module 41 and a PID controller 42 are provided in the control chip 4 . The electronic accelerator pedal 5 and the driving mode selection module 6 of the vehicle are connected to the vehicle controller through the analog input channel 1; the Hall wheel speed sensor 7 is connected to the vehicle controller through the frequency acquisition channel 2; the drive motor 8 is connected to the drive motor controller 9, and the drive motor controller 9 is connected to the vehicle controller through the CAN communication channel 3. The control chip 4 in the vehicle controller processes each signal, and outputs the obtained driving motor torque command to the driving motor controller 9 through the CAN communication channel 3 to control the driving motor 8 .

The P (proportional), I (integral) and D (differential) control parameters in the PID controller 42 can be artificially selected according to the specific vehicle type, and the PID control technology is an existing technology, so it will not be repeated here.

As shown in Figure 2, the electric vehicle speed control method of the present invention comprises the following steps:

1) The actual vehicle speed signal measured by the Hall-type wheel speed sensor 7 is input to the vehicle controller through the frequency quantity acquisition channel 2, and the control chip 4 judges whether to start the closed-loop control of the vehicle speed.

When the actual vehicle speed is less than the critical vehicle speed, the vehicle speed closed-loop control is started;

When the actual vehicle speed is greater than or equal to the critical vehicle speed, the vehicle speed closed-loop control is not started.

The specific value of the above-mentioned critical speed can be determined according to different application occasions. For example, the average speed of urban buses is generally low, and the critical speed of the closed-loop control of vehicle speed can be set lower, such as 10km/h; while the average speed of cars is generally higher. High, the critical speed of vehicle speed closed-loop control can be set a little higher, such as 20km/h.

2) The driver selects one of the three driving modes of comfort, normal or sports in the driving mode selection module 6 according to the current road conditions, such as traffic speed and vehicle density, and simultaneously depresses the electronic accelerator pedal 5 to a certain value. Location. The present invention defines the driving mode selected by the driver as the desired driving mode. Since the different positions of the electronic accelerator pedal 5 correspond to different speeds, the present invention defines the position of the electronic accelerator pedal 5 set by the driver. The corresponding vehicle speed is defined as the desired vehicle speed.

The driving mode corresponding to the driving mode selection module 6 determines the response speed of the vehicle speed closed-loop control, and the order of the response speed corresponding to the three driving modes from slow to fast is: comfortable<normal<sports. According to the three driving modes, the present invention designs the acceleration speed response curve and the deceleration speed response curve of the whole vehicle under the corresponding three driving modes based on the universal characteristic curve of the drive motor 8. When the driver selects the desired driving mode, , the whole vehicle is accelerated or decelerated according to the acceleration or deceleration speed response curve corresponding to the driving mode, so that the operating point (such as rotational speed and torque) of the drive motor 8 is in a region with high efficiency (for example, greater than 80%).

3) The driving mode signal of the driving mode selection module 6 and the accelerator pedal position signal of the electronic accelerator pedal 5 are input to the vehicle controller through the analog input channel 1; the Hall wheel speed sensor 7 collects the actual vehicle speed signal through the frequency quantity Channel 2 is input to the vehicle controller.

4) The low-pass filter module 41 filters the input accelerator pedal position signal to filter out high-frequency fluctuations and noise signals in the accelerator pedal position signal.

5) The PID controller 42 calculates the processed accelerator pedal position signal and the actual vehicle speed signal to obtain the drive motor torque command, and inputs it to the drive motor controller 9 through the CAN communication channel 3 .

6) The drive motor controller 9 increases or decreases the required torque of the drive motor 8 according to the command of the drive motor, so that the vehicle accelerates or decelerates according to the corresponding acceleration or deceleration speed response curve, and finally realizes the real vehicle speed and the expected speed of the vehicle. The vehicle speeds are equal within the allowable range of error.

The above-mentioned embodiments are only used to illustrate the present invention, wherein the structure, connection mode and manufacturing process of each component can be changed to some extent, and any equivalent transformation and improvement carried out on the basis of the technical solution of the present invention should not excluded from the protection scope of the present invention.

Claims (1)

1. an electric automobile method for controlling driving speed, it comprises the following steps:

1) entire car controller arranges analog input channel, frequency quantity acquisition channel, CAN communication passage and control chip; Described control chip arranges low pass filter blocks and PID controller;

2) the actual vehicle speed signal that Hall wheel speed sensor records, by frequency quantity acquisition channel input entire car controller, is judged whether to start speed closed loop control by control chip;

When actual vehicle speed is less than critical speed, start speed closed loop control;

When actual vehicle speed is more than or equal to critical speed, do not start speed closed loop control;

3) driver is according to present road situation, selects to select a kind of driving model in comfortable, normal or motion in module at driving model, steps on electronic type accelerating throttle pedal to a certain position simultaneously;

4) driving model selects the driving model signal of module and the acceleration pedal position signal of electronic type accelerating throttle pedal to input entire car controller by analog input channel; The actual vehicle speed signal of Hall wheel speed sensor is by frequency quantity acquisition channel input entire car controller;

5) acceleration pedal position signal of input is filtered by low pass filter blocks, filters the high-frequency fluctuation in acceleration pedal position signal and noise signal;

6) acceleration pedal position signal after processing and actual vehicle speed signal are calculated by PID controller, obtain drive motor torque command, and are input to drive motor controller by CAN communication passage;

7) drive motor controller increases according to drive motor order or reduces the demand torque of drive motor, car load is made to be accelerated according to corresponding acceleration or deceleration velocity-response curve or slow down, namely according to three kinds of driving models, based on the universal characteristic curve of drive motor, devise accelerating velocity response curve and the geard-down speed response curve of car load under corresponding 3 kinds of driving models, after driver selects expectation driving model, car load is accelerated according to the acceleration or deceleration velocity-response curve that this driving model is corresponding or slows down.