CN106004515A - Automobile speed control method and system used for automatic parking of electric automobile - Google Patents

Abstract

The invention discloses an automobile speed control method and system used for automatic parking of an electric automobile. The system comprises an automobile speed sensor module, an ultrasonic sensor, an automobile positioning module, a parking controller and an automobile speed controller. The automobile speed sensor module is used for detecting the running automobile speed of the electric automobile. The ultrasonic sensor is used for acquiring information of obstacles around the electric automobile. The automobile positioning module is used for acquiring current position information of the electric automobile. The parking controller is used for setting the ideal parking automobile speed according to the acquired information of the obstacles, the acquired current position information and a preset parking track. The automobile speed controller is used for adjusting the motor torque of the electric automobile according to the running automobile speed and the ideal parking automobile speed. By the adoption of the method and system, under the condition of the low speed, a parking speed control function can be better achieved, errors are small, a response is made rapidly, the process is smooth, and the method and system can be widely applied to the field of automatic parking.

Description

Vehicle speed control method and system for automatic parking of electric vehicle

Technical Field

The invention relates to the field of automatic parking of electric automobiles, in particular to a vehicle speed control method and a vehicle speed control system for automatic parking of electric automobiles.

Background

Name interpretation:

a PID controller: the proportional-integral-derivative controller is a common feedback loop component in industrial control application and consists of a proportional unit P, an integral unit I and a derivative unit D;

ESC: electronic Stability Control, vehicle body Electronic Stability Control system.

The automatic parking system requires stable vehicle longitudinal low-speed control so that the vehicle speed is generally stabilized within the range of 0.5-1.0 m/s. The conventional common method for the pure electric vehicle is to measure the speed of the vehicle firstly and then adopt a PID (proportion integration differentiation) controller to adjust the torque of the motor. To address the non-linear nature of vehicle dynamics, some designs employ gain scheduled PID controllers or fuzzy PID controllers. However, the design of the PID controller is mostly set by manual experience, which wastes time and labor, sometimes even causes unstable phenomena such as oscillation of the system under certain situations, and affects user experience and safety. The main disadvantages of the PID controller include slow vehicle start, low response speed, difficult setting of controller parameters, etc., so various improved PID controller forms are helpful to improve the nonlinearity of the control system, but the design setting method is more complicated and often needs more engineering experience. Therefore, the application range of the PID controller is often limited, different controller parameters are often required under different working conditions, or the performance and even the stability of the system are affected. Comprehensively, the existing method for realizing automatic parking through a PID controller has complex control process and is difficult to stably realize automatic control.

Disclosure of Invention

In order to solve the above technical problems, it is another object of the present invention to provide a vehicle speed control system for automatic parking of an electric vehicle, and it is an object of the present invention to provide a vehicle speed control method for automatic parking of an electric vehicle.

The technical scheme adopted by the invention for solving the technical problems is as follows:

the vehicle speed control system for automatic parking of the electric vehicle comprises a vehicle speed sensor module, an ultrasonic sensor, a vehicle positioning module, a parking controller and a vehicle speed controller, wherein the vehicle speed sensor module is used for detecting the movement vehicle speed of the electric vehicle, the ultrasonic sensor is used for acquiring the information of obstacles around the electric vehicle, the vehicle positioning module is used for acquiring the current position information of the electric vehicle, the parking controller is used for setting an ideal parking vehicle speed according to the acquired information of the obstacles, the current position information and a preset parking track, and the vehicle speed controller is used for adjusting the motor torque of the electric vehicle according to the movement vehicle speed and the ideal parking vehicle speed.

Further, the process of setting the ideal parking speed according to the acquired obstacle information, the current position information and the preset parking trajectory specifically includes:

and matching the current position information with a preset parking track, and judging that the electric automobile is in a parking process state, a parking completion state or a parking obstacle state by combining the collected obstacle information, so as to set a corresponding ideal parking speed.

Further, the process for adjusting the motor torque of the electric vehicle according to the movement vehicle speed and the ideal parking vehicle speed specifically includes:

and (3) correspondingly adjusting the output motor torque after the motor torque corresponding to the electric automobile at the moment is obtained according to the movement speed and the ideal parking speed by combining the following formula:

$T=b(F_R+F_L+{\stackrel{\‾}{F}}_S)+k(v_s-\stackrel{\‾}{v})$

in the above formula, b represents the coefficient of the motion model of the electric vehicle, T represents the motor torque, F_RDenotes rolling resistance, F_LRepresenting wind resistance, k representing gain of vehicle speed controller, v_sThe ideal parking vehicle speed is indicated,and sequentially representing the estimated value of the gravity component and the estimated value of the vehicle speed obtained by adopting a state observer according to the motion vehicle speed estimation.

Further, in the present invention,andis calculated by adopting a state observer according to the following formula:

$\left\{\begin{array}{c}\stackrel{\·}{\stackrel{\‾}{v}}=aT-b\left(F_R+F_L+{\stackrel{\‾}{F}}_S\right)+L_1\left(v-\stackrel{\‾}{v}\right)\\ {\stackrel{\·}{\stackrel{\‾}{F}}}_S=L_2\left(v-\stackrel{\‾}{v}\right)\end{array}\right.$

in the above formula, a and b represent the motion model coefficients of the electric vehicle respectively and a and b areKnown value, L₁、L₂V represents the moving vehicle speed of the electric vehicle, which is the gain of the state observer.

Further, F_LIs calculated by the following formula:

F_L＝0.5ρAC_xv²；

F_Ris calculated by the following formula:

$F_R=F_Z(f_{R0}+f_{R1}\frac{v}{30}+f_{R2}\frac{v^4}{{30}^4});$

wherein, F_ZRepresenting the gravity of the automobile, rho representing the air density, A representing the frontal area, C_xRepresenting the air resistance coefficient, v representing the moving speed of the electric vehicle, f_R0Representing rolling resistance coefficient of order 0, f_R1Representing a coefficient of order 1, f, of rolling resistance_R2Coefficient of 4 th order of rolling resistance, ρ, A, C_x、f_R0、f_R1And f_R2Are all known parameters.

The other technical scheme adopted by the invention for solving the technical problem is as follows:

the vehicle speed control method for automatic parking of the electric vehicle comprises the following steps:

s1, detecting the movement speed of the electric automobile by adopting a speed sensor module, acquiring obstacle information around the electric automobile by adopting an ultrasonic sensor, and acquiring current position information of the electric automobile by adopting a vehicle positioning module;

s2, setting an ideal parking speed according to the collected obstacle information, the current position information and a preset parking track;

s3, adjusting the motor torque of the electric automobile according to the movement speed and the ideal parking speed;

and S4, the motor adjusts the speed of the electric automobile in real time according to the motor torque output by the speed controller.

Further, in step S2, it specifically includes:

and matching the current position information with a preset parking track, and judging that the electric automobile is in a parking process state, a parking completion state or a parking obstacle state by combining the collected obstacle information, so as to set a corresponding ideal parking speed.

Further, in step S3, it specifically includes:

and (3) correspondingly adjusting the output motor torque after the motor torque corresponding to the electric automobile at the moment is obtained according to the movement speed and the ideal parking speed by combining the following formula:

$T=b(F_R+F_L+{\stackrel{\‾}{F}}_S)+k(v_s-\stackrel{\‾}{v})$

in the above formula, b represents the coefficient of the motion model of the electric vehicle, T represents the motor torque, F_RDenotes rolling resistance, F_LRepresenting wind resistance, k representing gain of vehicle speed controller, v_sThe ideal parking vehicle speed is indicated,and sequentially representing the estimated value of the gravity component and the estimated value of the vehicle speed obtained by adopting a state observer according to the motion vehicle speed estimation.

Further, theAndis calculated by adopting a state observer according to the following formula:

$\left\{\begin{array}{c}\stackrel{\·}{\stackrel{\‾}{v}}=aT-b\left(F_R+F_L+{\stackrel{\‾}{F}}_S\right)+L_1\left(v-\stackrel{\‾}{v}\right)\\ {\stackrel{\·}{\stackrel{\‾}{F}}}_S=L_2\left(v-\stackrel{\‾}{v}\right)\end{array}\right.$

in the above formula, a and b represent the motion model coefficients of the electric vehicle respectively and are known values, L₁、L₂V represents the moving vehicle speed of the electric vehicle, which is the gain of the state observer.

Further, said F_LIs calculated by the following formula:

F_L＝0.5ρAC_xv²；

F_Ris calculated by the following formula:

$F_R=F_Z(f_{R0}+f_{R1}\frac{v}{30}+f_{R2}\frac{v^4}{{30}^4});$

wherein, F_ZRepresenting the gravity of the automobile, rho representing the air density, A representing the frontal area, C_xRepresenting the air resistance coefficient, v representing the moving speed of the electric vehicle, f_R0Representing rolling resistance coefficient of order 0, f_R1Representing a coefficient of order 1, f, of rolling resistance_R2Coefficient of 4 th order of rolling resistance, ρ, A, C_x、f_R0、f_R1And f_R2Are all known parameters.

The invention has the beneficial effects that: the invention discloses a vehicle speed control system for automatic parking of an electric vehicle, which comprises a vehicle speed sensor module, an ultrasonic sensor, a vehicle positioning module, a parking controller and a vehicle speed controller, wherein the vehicle speed sensor module is used for detecting the movement vehicle speed of the electric vehicle, the ultrasonic sensor is used for acquiring the obstacle information around the electric vehicle, the vehicle positioning module is used for acquiring and obtaining the current position information of the electric vehicle, the parking controller is used for setting an ideal parking vehicle speed according to the acquired obstacle information, the current position information and a preset parking track, and the vehicle speed controller is used for adjusting the motor torque of the electric vehicle according to the movement vehicle speed and the ideal parking vehicle speed. The vehicle speed control system can better realize the parking speed control function under the condition of low speed, has small error, quick response and stable process.

The invention has the following beneficial effects: the invention discloses a vehicle speed control method for automatic parking of an electric vehicle, which comprises the following steps: s1, detecting the movement speed of the electric automobile by adopting a speed sensor module, acquiring obstacle information around the electric automobile by adopting an ultrasonic sensor, and acquiring current position information of the electric automobile by adopting a vehicle positioning module; s2, setting an ideal parking speed according to the collected obstacle information, the current position information and a preset parking track; s3, adjusting the motor torque of the electric automobile according to the movement speed and the ideal parking speed; and S4, the motor adjusts the speed of the electric automobile in real time according to the motor torque output by the speed controller. The vehicle speed control method can better realize parking speed control under the condition of low speed, has small error, quick response and stable process.

Drawings

The invention is further illustrated by the following figures and examples.

FIG. 1 is a block diagram of a vehicle speed control system for automatic parking of an electric vehicle according to the present invention;

FIG. 2 is a schematic diagram of a vehicle positioning module of the vehicle speed control system for automatic parking of an electric vehicle acquiring vehicle position information according to the invention;

FIG. 3 is a block diagram of an implementation manner of a vehicle speed control system for automatic parking of an electric vehicle according to a first embodiment of the invention;

FIG. 4 is a schematic diagram illustrating a parking test control result for a first operating condition in a third embodiment of the vehicle speed control system for automatic parking of an electric vehicle according to the present invention;

FIG. 5 is a schematic diagram illustrating a parking test result under a second operating condition in a third embodiment of the vehicle speed control system for automatic parking of an electric vehicle according to the present invention;

FIG. 6 is a schematic diagram illustrating a parking test result under a third operating condition in the third embodiment of the vehicle speed control system for automatic parking of an electric vehicle according to the present invention;

FIG. 7 is a schematic diagram illustrating the control result of the parking test performed on the working condition four in the third embodiment of the vehicle speed control system for automatic parking of the electric vehicle according to the present invention;

fig. 8 is a schematic diagram of a control result of a parking test performed on a working condition five in the third embodiment of the vehicle speed control system for automatic parking of an electric vehicle according to the present invention.

Detailed Description

Referring to fig. 1, the invention provides a vehicle speed control system for automatic parking of an electric vehicle, which includes a vehicle speed sensor module, an ultrasonic sensor, a vehicle positioning module, a parking controller and a vehicle speed controller, wherein the vehicle speed sensor module is used for detecting a moving vehicle speed of the electric vehicle, the ultrasonic sensor is used for acquiring obstacle information around the electric vehicle, the vehicle positioning module is used for acquiring current position information of the electric vehicle, the parking controller is used for setting an ideal parking vehicle speed according to the acquired obstacle information, the current position information and a preset parking track, and the vehicle speed controller is used for adjusting a motor torque of the electric vehicle according to the moving vehicle speed and the ideal parking vehicle speed.

Further, as a preferred embodiment, the process of setting the ideal parking speed according to the acquired obstacle information, the current position information, and the preset parking trajectory specifically includes:

and matching the current position information with a preset parking track, and judging that the electric automobile is in a parking process state, a parking completion state or a parking obstacle state by combining the collected obstacle information, so as to set a corresponding ideal parking speed.

Further, as a preferred embodiment, the process for adjusting the motor torque of the electric vehicle according to the moving vehicle speed and the ideal parking vehicle speed is specifically as follows:

and (3) correspondingly adjusting the output motor torque after the motor torque corresponding to the electric automobile at the moment is obtained according to the movement speed and the ideal parking speed by combining the following formula:

$T=b(F_R+F_L+{\stackrel{\‾}{F}}_S)+k(v_s-\stackrel{\‾}{v})$

in the above formula, b represents the coefficient of the motion model of the electric vehicle, T represents the motor torque, F_RDenotes rolling resistance, F_LRepresenting wind resistance, k representing gain of vehicle speed controller, v_sThe ideal parking vehicle speed is indicated,and sequentially representing the estimated value of the gravity component and the estimated value of the vehicle speed obtained by adopting a state observer according to the motion vehicle speed estimation.

Further as a preferred embodiment it is proposed that,andis calculated by adopting a state observer according to the following formula:

$\left\{\begin{array}{c}\stackrel{\·}{\stackrel{\‾}{v}}=aT-b\left(F_R+F_L+{\stackrel{\‾}{F}}_S\right)+L_1\left(v-\stackrel{\‾}{v}\right)\\ {\stackrel{\·}{\stackrel{\‾}{F}}}_S=L_2\left(v-\stackrel{\‾}{v}\right)\end{array}\right.$

in the above formula, a and b represent the motion model coefficients of the electric vehicle respectively and are known values, L₁、L₂V represents the moving vehicle speed of the electric vehicle, which is the gain of the state observer.

Further as a preferred embodiment, F_LIs calculated by the following formula:

F_L＝0.5ρAC_xv²；

F_Ris calculated by the following formula:

$F_R=F_Z(f_{R0}+f_{R1}\frac{v}{30}+f_{R2}\frac{v^4}{{30}^4});$

wherein, F_ZRepresenting the gravity of the automobile, rho representing the air density, A representing the frontal area, C_xRepresenting the air resistance coefficient, v representing the moving speed of the electric vehicle, f_R0Representing rolling resistance coefficient of order 0, f_R1Representing a coefficient of order 1, f, of rolling resistance_R2Coefficient of 4 th order of rolling resistance, ρ, A, C_x、f_R0、f_R1And f_R2Are all known parameters.

The invention also provides a vehicle speed control method for automatic parking of the electric vehicle, which comprises the following steps:

s1, detecting the movement speed of the electric automobile by adopting a speed sensor module, acquiring obstacle information around the electric automobile by adopting an ultrasonic sensor, and acquiring current position information of the electric automobile by adopting a vehicle positioning module;

s2, setting an ideal parking speed according to the collected obstacle information, the current position information and a preset parking track;

s3, adjusting the motor torque of the electric automobile according to the movement speed and the ideal parking speed;

and S4, the motor adjusts the speed of the electric automobile in real time according to the motor torque output by the speed controller.

Further, as a preferred embodiment, in step S2, it is specifically:

and matching the current position information with a preset parking track, and judging that the electric automobile is in a parking process state, a parking completion state or a parking obstacle state by combining the collected obstacle information, so as to set a corresponding ideal parking speed.

Further, as a preferred embodiment, in step S3, it is specifically:

and (3) correspondingly adjusting the output motor torque after the motor torque corresponding to the electric automobile at the moment is obtained according to the movement speed and the ideal parking speed by combining the following formula:

$T=b(F_R+F_L+{\stackrel{\‾}{F}}_S)+k(v_s-\stackrel{\‾}{v})$

in the above formula, b represents the coefficient of the motion model of the electric vehicle, T represents the motor torque, F_RDenotes rolling resistance, F_LRepresenting wind resistance, k representing gain of vehicle speed controller, v_sThe ideal parking vehicle speed is indicated,and sequentially representing the estimated value of the gravity component and the estimated value of the vehicle speed obtained by adopting a state observer according to the motion vehicle speed estimation.

Further, as a preferred embodiment, theAndis calculated by adopting a state observer according to the following formula:

$\left\{\begin{array}{c}\stackrel{\·}{\stackrel{\‾}{v}}=aT-b\left(F_R+F_L+{\stackrel{\‾}{F}}_S\right)+L_1\left(v-\stackrel{\‾}{v}\right)\\ {\stackrel{\·}{\stackrel{\‾}{F}}}_S=L_2\left(v-\stackrel{\‾}{v}\right)\end{array}\right.$

in the above formula, a and b represent the motion model coefficients of the electric vehicle respectively and are known values, L₁、L₂V represents the moving vehicle speed of the electric vehicle, which is the gain of the state observer.

Further preferably, F is_LIs calculated by the following formula:

F_L＝0.5ρAC_xv²；

F_Ris calculated by the following formula:

$F_R=F_Z(f_{R0}+f_{R1}\frac{v}{30}+f_{R2}\frac{v^4}{{30}^4});$

wherein, F_ZRepresenting the gravity of the automobile, rho representing the air density, A representing the frontal area, C_xRepresenting the air resistance coefficient, v representing the moving speed of the electric vehicle, f_R0Representing rolling resistance coefficient of order 0, f_R1Representing a coefficient of order 1, f, of rolling resistance_R2Coefficient of 4 th order of rolling resistance, ρ, A, C_x、f_R0、f_R1And f_R2Are all known parameters.

The present invention will be described in detail with reference to specific examples.

Example one

Referring to fig. 1, a vehicle speed control system for automatic parking of an electric vehicle includes a vehicle speed sensor module, an ultrasonic sensor, a vehicle positioning module, a parking controller and a vehicle speed controller, wherein the vehicle speed sensor module is configured to detect a moving vehicle speed of the electric vehicle, the ultrasonic sensor is configured to acquire obstacle information around the electric vehicle, the vehicle positioning module is configured to acquire current position information of the electric vehicle, the parking controller is configured to set an ideal parking vehicle speed according to the acquired obstacle information, the current position information and a preset parking track, and the vehicle speed controller is configured to adjust a motor torque of the electric vehicle according to the moving vehicle speed and the ideal parking vehicle speed. In this embodiment, the number of the ultrasonic sensors is 12, and the ultrasonic sensors are respectively installed around the electric vehicle, and can detect the obstacle information around the electric vehicle. The vehicle positioning module is configured to acquire and obtain current position information of an electric vehicle, specifically, as shown in fig. 2, a dashed box in fig. 2 represents a target parking space, an xy coordinate system in fig. 2 is that a rear axle center of the target parking space is 0 point, a solid box represents an electric vehicle to be parked, and a rear axle center coordinate (x) is obtained_c,y_c) Representing the position of the electric vehicle, the angle theta representing the orientation of the electric vehicle, and a vehicle positioning system for providing real-time (x) of the electric vehicle_c,y_cθ), which is also called current location information of the electric vehicle. How to acquire the current position information is a relatively mature content in the prior art, and can be obtained through image processing and other manners, which is not described in detail herein.

In addition, because various sensor signals have noise, the speed signal is firstly processed by a filtering signal, for example, a limiting filter or a linear filter, and then output to a corresponding controller. In this embodiment, the cut-off frequency of the selected filter may be selected to be between 2Hz and 5 Hz.

The method for setting the ideal parking speed by the parking controller according to the acquired obstacle information, the current position information and the preset parking track specifically comprises the following steps:

and matching the current position information with a preset parking track, and judging that the electric automobile is in a parking process state, a parking completion state or a parking obstacle state by combining the collected obstacle information, so as to set a corresponding ideal parking speed. For example, the ideal parking vehicle speed in the parking process state may be set to 0.5m/s or 1.0m/s, and in the parking completion state, the ideal parking vehicle speed is set to 0m/s, and the parking obstacle state may have a risk of collision, so that the ideal parking vehicle speed is set to 0m/s, and the opposite ideal parking vehicle speed may also be set to avoid collision. Matching the current position information with a preset parking track, and judging the state of the electric automobile by combining the acquired barrier information, for example, judging that the electric automobile is in a track tracking state after the current position information is matched with the preset parking track, and judging that the electric automobile is in a parking process state currently if the electric automobile is judged to have no barrier within a preset distance; when the matching judges that the electric automobile runs to the target parking stall, judging that the electric automobile is in a parking finishing state at present; and when the electric automobile is judged to have no barrier within the preset distance, the collision danger is indicated, and the electric automobile is judged to be in the parking barrier state at present.

The vehicle speed controller is used for adjusting the process of motor torque of the electric vehicle according to the movement vehicle speed and the ideal parking vehicle speed, and the process specifically comprises the following steps:

and (3) correspondingly adjusting the output motor torque after the motor torque corresponding to the electric automobile at the moment is obtained according to the movement speed and the ideal parking speed by combining the following formula:

$T=b(F_R+F_L+{\stackrel{\‾}{F}}_S)+k(v_s-\stackrel{\‾}{v})$

in the above formula, b represents the coefficient of the motion model of the electric vehicle, T represents the motor torque, F_RDenotes rolling resistance, F_LRepresenting wind resistance, k representing gain of vehicle speed controller, v_sThe ideal parking vehicle speed is indicated,and sequentially representing the estimated value of the gravity component and the estimated value of the vehicle speed obtained by adopting a state observer according to the motion vehicle speed estimation. The motor system receives a torque command sent by the vehicle speed controller and executes the torque command. Meanwhile, if braking is needed, the control system sends a braking pressure command, and the ESC system receives and executes the braking pressure command. For example, when the ideal parking speed is 0m/s, the output motor torque is 0Nm, the ESC system outputs a certain braking pressure, and if the speed of the electric automobile is not reduced to 0m/s after a period of time, the braking pressure is increased to assist in reducing the speed of the electric automobile to 0 m/s.

Wherein,andis calculated by adopting a state observer according to the following formula:

$\left\{\begin{array}{c}\stackrel{\·}{\stackrel{\‾}{v}}=aT-b\left(F_R+F_L+{\stackrel{\‾}{F}}_S\right)+L_1\left(v-\stackrel{\‾}{v}\right)\\ {\stackrel{\·}{\stackrel{\‾}{F}}}_S=L_2\left(v-\stackrel{\‾}{v}\right)\end{array}\right.$

in the above formula, a and b represent the motion model coefficients of the electric vehicle respectively and are known values, L₁、L₂V represents the moving vehicle speed of the electric vehicle, which is the gain of the state observer.

F_LAnd F_RRespectively calculated by the following formula:

F_L＝0.5ρAC_xv²；

$F_R=F_Z(f_{R0}+f_{R1}\frac{v}{30}+f_{R2}\frac{v^4}{{30}^4});$

wherein, F_ZRepresenting the gravity of the automobile, rho representing the air density, A representing the frontal area, C_xRepresenting the air resistance coefficient, v representing the moving speed of the electric vehicle, f_R0Representing rolling resistance coefficient of order 0, f_R1Representing a coefficient of order 1, f, of rolling resistance_R2Coefficient of 4 th order of rolling resistance, ρ, A, C_x、f_R0、f_R1And f_R2Are all known parameters.

The calculation model of the present embodiment is obtained by:

first, because the object of the present invention is to maintain the speed of the electric vehicle at a set speed during parking, while the parking process takes into account only low-speed movement of the vehicle, a simplified vehicle movement model is obtained as follows:

$\stackrel{\·}{v}=\mathrm{aT}-b(F_R+F_L+F_S)$

in the above formula, v represents the moving speed of the electric vehicle,expressing the differential of v, T expressing the motor torque, a and b expressing the motor motion model coefficients, respectively, the values of a and b are obtained by a model identification technology, F_RDenotes rolling resistance, F_LDenotes wind resistance, F_SRepresenting the component of gravity along the gradient of the road surface.

F_RAnd F_LThe estimation is carried out according to the following approximate formula in sequence:

F_L＝0.5ρAC_xv²；

$F_R=F_Z(f_{R0}+f_{R1}\frac{v}{30}+f_{R2}\frac{v^4}{{30}^4});$

wherein, F_ZRepresenting the gravity of the automobile, rho representing the air density, A representing the frontal area, C_xRepresenting the air resistance coefficient, v representing the moving speed of the electric vehicle, f_R0Representing rolling resistance coefficient of order 0, f_R1Representing a coefficient of order 1, f, of rolling resistance_R2Coefficient of 4 th order of rolling resistance, ρ, A, C_x、f_R0、f_R1And f_R2Are all known parameters.

F_SThis can be obtained by a gradient sensor (typically using inertial acceleration) where we estimate the influence of the gradient by means of a state observer. The dynamics of the moving speed of the electric vehicle can be represented by the following 2-step system:

$\left\{\begin{array}{c}\stackrel{\·}{v}=aT-b(F_R+F_L+F_S)\\ {\stackrel{\·}{F}}_S=0\end{array}\right.$

wherein,is represented by F_SDifferentiation of (2).

The state observer can be designed by adopting a design method of a Luenberger observer or a Kalman filter, and the dynamic state of the state observer is as follows:

$\left\{\begin{array}{c}\stackrel{\·}{\stackrel{\‾}{v}}=aT-b\left(F_R+F_L+{\stackrel{\‾}{F}}_S\right)+L_1\left(v-\stackrel{\‾}{v}\right)\\ {\stackrel{\·}{\stackrel{\‾}{F}}}_S=L_2\left(v-\stackrel{\‾}{v}\right)\end{array}\right.$

wherein,sequentially representing an estimated value of a gravity component and an estimated value of a vehicle speed obtained by a state observer according to the estimation of the moving vehicle speed,in turn representDifferential of (L)₁、L₂Is the gain of the state observer, L₁、L₂The selection of (2) needs to ensure the convergence of the state observer.

The vehicle speed controller is designed in the following form:

$T=b(F_R+F_L+{\stackrel{\‾}{F}}_S)+k(v_s-\stackrel{\‾}{v})$

wherein k is the gain of the controller, and the selection of k needs to ensure the stability of the closed-loop system. In the above-described vehicle speed control system, the state observer may be a part of the vehicle speed controller, or may be a separate component, and the vehicle speed controller is assisted by the state observer to realize control of the electric vehicle, in which case the block diagram of the vehicle speed control system is shown in fig. 3.

In the embodiment, the motor torque output by the vehicle speed controller in real time is calculated through the formula and then the motor is controlled, so that the parking speed can be simply and quickly controlled, the vehicle speed is controlled along with the movement of the electric vehicle, the parking speed can be stabilized near the set ideal parking speed, and the working stability is high. In addition, when the torque changes rapidly, the electric automobile may be impacted too much, so that automobile parts are damaged, and riding experience is affected.

Example two

The embodiment is a vehicle speed control method for automatic parking of an electric vehicle based on the first embodiment, and the method comprises the following steps:

s1, detecting the movement speed of the electric automobile by adopting a speed sensor module, acquiring obstacle information around the electric automobile by adopting an ultrasonic sensor, and acquiring current position information of the electric automobile by adopting a vehicle positioning module;

s2, setting an ideal parking speed according to the collected obstacle information, the current position information and a preset parking track;

s3, adjusting the motor torque of the electric automobile according to the movement speed and the ideal parking speed;

and S4, the motor adjusts the speed of the electric automobile in real time according to the motor torque output by the speed controller.

Wherein, step S2 specifically includes:

and matching the current position information with a preset parking track, and judging that the electric automobile is in a parking process state, a parking completion state or a parking obstacle state by combining the collected obstacle information, so as to set a corresponding ideal parking speed.

Step S3, which specifically includes:

and (3) correspondingly adjusting the output motor torque after the motor torque corresponding to the electric automobile at the moment is obtained according to the movement speed and the ideal parking speed by combining the following formula:

$T=b(F_R+F_L+{\stackrel{\‾}{F}}_S)+k(v_s-\stackrel{\‾}{v})$

in the above formula, b represents the coefficient of the motion model of the electric vehicle, T represents the motor torque, F_RDenotes rolling resistance, F_LRepresenting wind resistance, k representing gain of vehicle speed controller, v_sThe ideal parking vehicle speed is indicated,and sequentially representing the estimated value of the gravity component and the estimated value of the vehicle speed obtained by adopting a state observer according to the motion vehicle speed estimation.

Wherein,andis calculated by adopting a state observer according to the following formula:

$\left\{\begin{array}{c}\stackrel{\·}{\stackrel{\‾}{v}}=aT-b\left(F_R+F_L+{\stackrel{\‾}{F}}_s\right)+L_1\left(v-\stackrel{\‾}{v}\right)\\ \stackrel{\·}{\stackrel{\‾}{F}}=L_2\left(v-\stackrel{\‾}{v}\right)\end{array}\right.$

in the above formula, a and b represent the motion model coefficients of the electric vehicle respectively and are known values, L₁、L₂V represents the moving vehicle speed of the electric vehicle, which is the gain of the state observer.

F_LIs calculated by the following formula:

F_L＝0.5ρAC_xv²；

F_Ris calculated by the following formula:

$F_R=F_Z(f_{R0}+f_{R1}\frac{v}{30}+f_{R2}\frac{v^4}{{30}^4});$

wherein, F_ZRepresenting the gravity of the automobile, rho representing the air density, A representing the frontal area, C_xRepresenting the air resistance coefficient, v representing the moving speed of the electric vehicle, f_R0Representing rolling resistance coefficient of order 0, f_R1Representing a coefficient of order 1, f, of rolling resistance_R2Coefficient of 4 th order of rolling resistance, ρ, A, C_x、f_R0、f_R1And f_R2Are all known parameters.

EXAMPLE III

In the embodiment, the parking test under different working conditions is performed on a certain electric automobile by applying the vehicle speed control system of the first embodiment. The test is mainly carried out under the following five working conditions: under the working condition I, the asphalt road has no obvious gradient; under the working condition II, the sand and stone road has no obvious gradient; working condition three, asphalt road, the gradient is about 10 degrees; working condition four, cement road, have not slope, the artificial steering wheel corner of ceaselessly adjusting carries on the intervention test in the test procedure; and under the working condition of five, on a slightly muddy road with accumulated water after rain. The average vehicle speed control results obtained after the tests are carried out under different manned conditions (1-5 persons) under the five working conditions are sequentially shown in fig. 4, 5, 6, 7 and 8. In fig. 4, 5, 6, 7 and 8, the measured vehicle speed refers to the movement vehicle speed of the electric vehicle obtained by detection, the set speed refers to the set ideal parking vehicle speed, and the comprehensive result shows that the speed control system designed by the invention can better realize the speed control function under the condition of low speed, has small error, quick response, stable process and no uncomfortable feeling of passengers caused by impact shock and the like, and can be applied to an automatic parking system.

While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

1. The vehicle speed control system for automatic parking of the electric vehicle is characterized by comprising a vehicle speed sensor module, an ultrasonic sensor, a vehicle positioning module, a parking controller and a vehicle speed controller, wherein the vehicle speed sensor module is used for detecting the movement vehicle speed of the electric vehicle, the ultrasonic sensor is used for acquiring obstacle information around the electric vehicle, the vehicle positioning module is used for acquiring and obtaining the current position information of the electric vehicle, the parking controller is used for setting an ideal parking vehicle speed according to the acquired obstacle information, the current position information and a preset parking track, and the vehicle speed controller is used for adjusting the motor torque of the electric vehicle according to the movement vehicle speed and the ideal parking vehicle speed.

2. The vehicle speed control system for automatic parking of an electric vehicle according to claim 1, wherein the process of setting the ideal parking vehicle speed according to the collected obstacle information, the current position information, and the preset parking trajectory specifically comprises:

and matching the current position information with a preset parking track, and judging that the electric automobile is in a parking process state, a parking completion state or a parking obstacle state by combining the collected obstacle information, so as to set a corresponding ideal parking speed.

3. The vehicle speed control system for automatic parking of an electric vehicle according to claim 1, wherein the process for adjusting the motor torque of the electric vehicle according to the moving vehicle speed and the ideal parking vehicle speed is specifically:

and (3) correspondingly adjusting the output motor torque after the motor torque corresponding to the electric automobile at the moment is obtained according to the movement speed and the ideal parking speed by combining the following formula:

$T=b(F_R+F_L+{\stackrel{\‾}{F}}_S)+k(v_s-\stackrel{\‾}{v})$

in the above formula, b represents the coefficient of the motion model of the electric vehicleT represents the motor torque, F_RDenotes rolling resistance, F_LRepresenting wind resistance, k representing gain of vehicle speed controller, v_sThe ideal parking vehicle speed is indicated,and sequentially representing the estimated value of the gravity component and the estimated value of the vehicle speed obtained by adopting a state observer according to the motion vehicle speed estimation.

4. The vehicle speed control system for automatic parking of an electric vehicle according to claim 3,andis calculated by adopting a state observer according to the following formula:

$\left\{\begin{array}{c}\stackrel{\·}{\stackrel{\‾}{v}}=aT-b(F_R+F_L+{\stackrel{\‾}{F}}_S)+L_1(v-\stackrel{\‾}{v})\\ {\stackrel{\·}{\stackrel{\‾}{F}}}_S=L_2(v-\stackrel{\‾}{v})\end{array}\right.$

in the above formula, a and b represent the motion model coefficients of the electric vehicle respectively and are known values, L₁、L₂V represents the moving vehicle speed of the electric vehicle, which is the gain of the state observer.

5. The vehicle speed control system for automatic parking of an electric vehicle according to claim 3, wherein F_LIs calculated by the following formula:

F_L＝0.5ρAC_xv²；

F_Ris calculated by the following formula:

$F_R=F_Z(f_{R0}+f_{R1}\frac{v}{30}+f_{R2}\frac{v^4}{{30}^4});$

wherein, F_ZRepresenting the gravity of the automobile, rho representing the air density, A representing the frontal area, C_xRepresenting the air resistance coefficient, v representing the moving speed of the electric vehicle, f_R0Representing rolling resistance coefficient of order 0, f_R1Representing a coefficient of order 1, f, of rolling resistance_R2Coefficient of 4 th order of rolling resistance, ρ, A, C_x、f_R0、f_R1And f_R2Are all known parameters.

6. The vehicle speed control method for automatic parking of the electric vehicle is characterized by comprising the following steps of:

s1, detecting the movement speed of the electric automobile by adopting a speed sensor module, acquiring obstacle information around the electric automobile by adopting an ultrasonic sensor, and acquiring current position information of the electric automobile by adopting a vehicle positioning module;

s2, setting an ideal parking speed according to the collected obstacle information, the current position information and a preset parking track;

s3, adjusting the motor torque of the electric automobile according to the movement speed and the ideal parking speed;

and S4, the motor adjusts the speed of the electric automobile in real time according to the motor torque output by the speed controller.

7. The vehicle speed control method for automatic parking of an electric vehicle according to claim 6, wherein said step S2 is embodied as:

and matching the current position information with a preset parking track, and judging that the electric automobile is in a parking process state, a parking completion state or a parking obstacle state by combining the collected obstacle information, so as to set a corresponding ideal parking speed.

8. The vehicle speed control method for automatic parking of an electric vehicle according to claim 6, wherein said step S3 is embodied as:

and (3) correspondingly adjusting the output motor torque after the motor torque corresponding to the electric automobile at the moment is obtained according to the movement speed and the ideal parking speed by combining the following formula:

$T=b(F_R+F_L+{\stackrel{\‾}{F}}_S)+k(v_s-\stackrel{\‾}{v})$

in the above formula, b represents the coefficient of the motion model of the electric vehicle, T represents the motor torque, F_RDenotes rolling resistance, F_LRepresenting wind resistance, k representing gain of vehicle speed controller, v_sThe ideal parking vehicle speed is indicated,and sequentially representing the estimated value of the gravity component and the estimated value of the vehicle speed obtained by adopting a state observer according to the motion vehicle speed estimation.

9. The vehicle speed control method for automatic parking of an electric vehicle according to claim 8, wherein the vehicle speed control method is characterized in thatAndis calculated by adopting a state observer according to the following formula:

$\left\{\begin{array}{c}\stackrel{\·}{\stackrel{\‾}{v}}=aT-b(F_R+F_L+{\stackrel{\‾}{F}}_S)+L_1(v-\stackrel{\‾}{v})\\ {\stackrel{\·}{\stackrel{\‾}{F}}}_S=L_2(v-\stackrel{\‾}{v})\end{array}\right.$

in the above formula, a and b represent the motion model coefficients of the electric vehicle respectively and are known values, L₁、L₂V represents the moving speed of the electric vehicle, which is the gain of the state observer。

10. The vehicle speed control method for automatic parking of an electric vehicle according to claim 8, wherein F is_LIs calculated by the following formula:

F_L＝0.5ρAC_xv²；

F_Ris calculated by the following formula:

$F_R=F_Z(f_{R0}+f_{R1}\frac{v}{30}+f_{R2}\frac{v^4}{{30}^4});$

wherein, F_ZRepresenting the gravity of the automobile, rho representing the air density, A representing the frontal area, C_xRepresenting the air resistance coefficient, v representing the moving speed of the electric vehicle, f_R0Representing rolling resistance coefficient of order 0, f_R1Representing a coefficient of order 1, f, of rolling resistance_R2Coefficient of 4 th order of rolling resistance, ρ, A, C_x、f_R0、f_R1And f_R2Are all known parameters.