CN108001293B - Pivot steering control system and method for electric vehicle - Google Patents

Pivot steering control system and method for electric vehicle Download PDF

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Publication number
CN108001293B
CN108001293B CN201610927714.6A CN201610927714A CN108001293B CN 108001293 B CN108001293 B CN 108001293B CN 201610927714 A CN201610927714 A CN 201610927714A CN 108001293 B CN108001293 B CN 108001293B
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steering
vehicle
wheel
controller
motor
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CN108001293A (en
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凌和平
孟繁亮
石明川
王文静
陈伟强
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BYD Co Ltd
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BYD Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
    • B60L15/20—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D7/00—Steering linkage; Stub axles or their mountings
    • B62D7/06—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins
    • B62D7/14—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering
    • B62D7/15—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering characterised by means varying the ratio between the steering angles of the steered wheels
    • B62D7/1581—Steering linkage; Stub axles or their mountings for individually-pivoted wheels, e.g. on king-pins the pivotal axes being situated in more than one plane transverse to the longitudinal centre line of the vehicle, e.g. all-wheel steering characterised by means varying the ratio between the steering angles of the steered wheels characterised by comprising an electrical interconnecting system between the steering control means of the different axles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2220/00—Electrical machine types; Structures or applications thereof
    • B60L2220/40—Electrical machine applications
    • B60L2220/42—Electrical machine applications with use of more than one motor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2220/00—Electrical machine types; Structures or applications thereof
    • B60L2220/40—Electrical machine applications
    • B60L2220/46—Wheel motors, i.e. motor connected to only one wheel
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/10—Vehicle control parameters
    • B60L2240/14—Acceleration
    • B60L2240/16—Acceleration longitudinal
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/10—Vehicle control parameters
    • B60L2240/14—Acceleration
    • B60L2240/18—Acceleration lateral
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/40—Drive Train control parameters
    • B60L2240/42—Drive Train control parameters related to electric machines
    • B60L2240/423—Torque
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/72—Electric energy management in electromobility

Abstract

The invention is applicable to the technical field of automobiles, and provides a pivot steering control system and a pivot steering control method for an electric vehicle. The in-situ steering control system of the electric vehicle comprises a left steering motor controller, a right steering motor controller, a left steering motor and a right steering motor, wherein the left front wheel and the right front wheel rotate and form an 'inner splayed' shape with a preset angle, and the steering motor controller sends a steering completion instruction to the vehicle controller. The system utilizes a vehicle controller to control a left steering motor controller and a right steering motor controller according to a received pivot steering command, the left steering motor controller controls the left front wheel to steer according to the received pivot steering command, the right steering motor controller controls the right front wheel to steer according to the received pivot steering control command, the rotating directions of the left front wheel and the right front wheel are opposite, an 'inner eight-character' of a preset angle is formed between the left front wheel and the right front wheel, and a steering completion command is sent to the vehicle controller by the control of a steering motor.

Description

Pivot steering control system and method for electric vehicle
Technical Field
The invention belongs to the technical field of automobiles, and particularly relates to an electric vehicle and a pivot steering control method of the electric vehicle.
Background
The automobile is an indispensable vehicle for modern people's life, brings very big facility for people's trip, and the car can touch in situ steering (especially turn around) operation in narrow and small space in the line of moving unavoidably, especially in the great muse of traffic flow or residential area, not only turns around inconveniently, also can cause certain vehicle to block up the problem.
To solve the above problems, the pivot steering technology should be developed. The existing pivot steering mode comprises the following steps: one is to lift the vehicle by a certain height from the ground by using a jack and rotate the vehicle by manpower, so as to complete the in-situ turning of the vehicle, such as the chinese patent (application No. CN 201310202609.2); the other is to adopt a tie rod and a steering gear to realize the pivot steering of the vehicle, such as the Chinese patent application (with the application number of CN 201510550082.1). However, the existing pivot steering method does not consider the influence of the yaw moment of the vehicle during steering on the stability of the vehicle body.
Disclosure of Invention
The invention aims to provide an electric vehicle, and aims to solve the technical problem that the influence on the stability of a vehicle body caused by the yaw moment of the vehicle in the steering process is not considered in the pivot steering mode in the prior art.
The present invention is achieved in that a pivot steering control system of an electric vehicle, which is used in the electric vehicle including a vehicle controller, includes:
the left steering motor controller and the right steering motor controller are used for receiving an external pivot steering command, the left steering motor controller is used for controlling steering of the left front wheel, and the right steering motor controller is used for controlling steering of the right front wheel;
the left steering motor receives an in-situ steering command of the left steering motor controller and drives the left front wheel to rotate;
the right steering motor receives an in-situ steering instruction of the right steering motor controller and drives the right front wheel to rotate;
the yaw rate sensor is used for detecting the yaw information of the whole vehicle and sending the yaw information of the whole vehicle to the vehicle controller in real time;
the method comprises the following steps that a driver sends an in-situ steering command to a steering motor controller, and the steering motor controller receives the in-situ steering command and starts a steering motor; stopping pivot steering when the yaw information of the whole vehicle exceeds the range of a preset value; when the yaw information of the whole vehicle is in a preset value, the left front wheel and the right front wheel rotate and form an inner splayed shape with a preset angle, and the steering motor controller sends a steering completion instruction to the vehicle controller.
Further, the left steering motor controller is connected between the vehicle controller and the left front wheel, and the right steering motor controller is connected between the vehicle controller and the right front wheel.
Further, the left steering motor is arranged between the left steering motor controller and the left front wheel, and the right steering motor is arranged between the right steering motor controller and the right front wheel.
Further, the pivot steering control system of the electric vehicle further includes driving motors respectively corresponding to the left front wheel and the right front wheel, a motor controller electrically connected between each of the driving motors and the vehicle controller, a wheel speed sensor for detecting wheel speeds of the left front wheel and the right front wheel to generate wheel speed signals, a steering wheel angle sensor for detecting steering wheel direction information, and an electronic parking brake device for maintaining a vehicle body stable.
Further, the vehicle controller sends a driving instruction to the motor controllers of the left front wheel and the right front wheel after receiving a steering wheel lock instruction fed back by the steering wheel angle sensor and a locking rear wheel instruction fed back by the electronic parking brake device, and the left steering motor outputs a forward torque and the right steering motor outputs a reverse torque, or the left front wheel driving motor outputs a reverse torque and the right front wheel driving motor outputs a forward torque.
The invention also provides a pivot steering control method of the electric vehicle, which comprises the following steps:
a driver sends an in-situ steering instruction to a steering motor controller, the steering motor controller receives the in-situ steering instruction and starts a steering motor, the steering motor drives two front wheels to rotate, the two front wheels form an inward splayed shape with a preset angle, and the steering motor sends a steering completion instruction to a vehicle controller;
the steering wheel angle sensor detects that a steering wheel is in a locked state and sends a steering wheel locking instruction to the vehicle controller;
the vehicle controller sends a locking instruction for locking the right rear wheel or the left rear wheel to the electronic parking braking device, and the electronic parking braking device feeds the locking instruction back to the vehicle controller after completing locking of the right rear wheel or the left rear wheel;
and the vehicle controller sends a driving instruction to the motor controller according to the received steering finishing instruction, the steering wheel locking instruction and the locking instruction, and the motor controller controls the torque of each driving motor.
Further, in the step of controlling the torque of each driving motor by the motor controller, the method further includes:
each driving motor is driven by torque T1, and wheel speed sensors corresponding to the two front wheels detect whether the wheel speeds of the two front wheels are larger than zero;
if the detected wheel speed is larger than zero, the vehicle is in a moving state, and the driving motor is driven by a torque T2 at the next control time T;
if the detected wheel speed is equal to zero, the vehicle is in a static state, the driving motor is driven by torque T3 at the next control time T, the torque of the driving motor is increased in each control time T until the wheel speed is greater than zero, and the control time for increasing the torque is not more than Tmax；
Wherein T1 is more than T3 is more than T2, and T is less than or equal to Tmax。
Further, the pivot steering control method of the electric vehicle further includes the steps of:
sending the yaw information of the whole vehicle to the vehicle controller in real time by using a yaw rate sensor;
if the yaw information of the whole vehicle is in a preset value, performing pivot steering; otherwise, the pivot steering is stopped.
Further, in the step of sending the yaw information of the whole vehicle to the vehicle controller in real time by using the yaw rate sensor, the method further comprises the following steps:
detecting a yaw rate using a yaw rate sensor and determining whether the detected yaw rate exceeds a yaw rate threshold value gammalimitWhen the detected yaw rate exceeds the yaw rate threshold value gammalimitWhen the vehicle is in motion, performing active whole vehicle yaw control; and/or
Using longitudinal and lateral acceleration sensorsMeasuring the finished automobile mass center slip angle, and judging whether the detected finished automobile mass center slip angle exceeds a mass center slip angle threshold value betalimitWhen the detected vehicle mass center slip angle exceeds the mass center slip angle threshold betalimitAnd in time, performing active whole vehicle yaw control.
Further, the step of actively controlling the yaw of the whole vehicle comprises the following steps:
the whole vehicle is simplified into a linear two-degree-of-freedom vehicle model, the rotation angle of a front wheel is directly used as input, a vehicle compartment only carries out plane motion parallel to the ground, the lateral deviation characteristic of a tire and the action of air power are zero, and the longitudinal speed of the vehicle along an x axis is regarded as unchanged;
controlling a yaw moment generated by the longitudinal driving force of each wheel around the z-axis of the mass center of the vehicle, namely:
Figure GDA0002522553980000041
wherein, FX1Longitudinal force of the left front wheel, FX2Longitudinal force of the right front wheel, FX3Longitudinal force of the left rear wheel, FX4Is the longitudinal force of the right rear wheel; d is the wheel track;
controlling the mass center slip angle of the whole vehicle to be equal to the mass center slip angle threshold betalimitAnd controlling the yaw rate to be equal to the desired yaw rate.
Further, the step of actively controlling the yaw of the whole vehicle comprises the following steps:
will control the yaw moment MZLeft and right wheel distribution is carried out, and the driving torque directions of the left and right wheels are opposite.
Compared with the prior art, the invention has the technical effects that: the pivot steering control system of the electric vehicle utilizes the vehicle controller to control the left steering motor controller and the right steering motor controller according to a received pivot steering command, the left steering motor controller controls the left front wheel to steer according to the received pivot steering command, the right steering motor controller controls the right front wheel to steer according to the received pivot steering control command, the rotating directions of the left front wheel and the right front wheel are opposite, an 'inner eight-letter' with a preset angle is formed between the left front wheel and the right front wheel, and the rotating motor controls the vehicle controller to send a steering completion command.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention or in the description of the prior art will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an electric vehicle according to an embodiment of the present invention;
FIG. 2 is a schematic wheel speed diagram of the electric vehicle of FIG. 1 in pivot steering;
FIG. 3 is a diagram of a dynamic model of in-situ steering of the electric vehicle of FIG. 1;
fig. 4 is a flowchart of an electric vehicle pivot steering control method of fig. 1.
Description of reference numerals:
10 steering wheel 62 Wheel speed sensor
20 Wheel of vehicle 64 Rotary transformer sensor
21 Left front wheel 66 Steering wheel angle sensor
22 Right front wheel 68 Yaw rate sensor
23 Left rear wheel 70 Power battery
24 Right rear wheel 80 Electronic parking brake device
30 Vehicle controller 90 Pivot steering control device
40 Speed variator 92 Left steering motor controller
50 Driving motor 94 Right steering motor controller
60 Motor controller 96 Left steering motor
98 Right steering motor
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In the description of the present invention, it is to be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships illustrated in the drawings, and are used merely for convenience in describing the present invention and for simplicity in description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments.
Referring to fig. 1 to 3, an electric vehicle according to an embodiment of the present invention includes a steering wheel 10 for controlling a driving direction, a plurality of wheels 20, a vehicle controller 30, a plurality of transmissions 40 respectively connected to the wheels 20, a plurality of driving motors respectively connected to the transmissions 40 and respectively corresponding to the wheels 20, and a motor controller electrically connected between each of the driving motors and the vehicle controller 30, a wheel speed sensor 62 for detecting a wheel speed of each of the wheels 20 to generate a wheel speed signal, a steering wheel angle sensor 66 for detecting direction information of the steering wheel 10, a yaw rate sensor 68 for detecting yaw information of the entire vehicle, a power battery 70 for supplying power, an electronic Parking Brake device 80 (EPB) for maintaining stability of the vehicle body, and a steering control device 90 for steering the vehicle in place by controlling torque and rotational speed of the two front wheels corresponding to the driving motors; each of the motor controllers, each of the wheel speed sensors 62, the steering wheel angle sensor 66, the electronic parking brake device 80, the yaw rate sensor 68, and the power battery 70 is electrically connected to the vehicle controller 30, and the pivot steering control device 90 corresponds to two front wheels and controls rotation directions of the two front wheels, respectively, and output torques of the two front wheels are opposite in direction.
The electric vehicle provided by the embodiment of the invention is provided with the original steering control device 90 for controlling the torque and the rotating speed of the driving motor 50 of the two front wheels to steer the vehicle in situ, and utilizes the yaw rate sensor 68 to detect the yaw information of the whole vehicle and transmit the detected yaw information of the whole vehicle to the vehicle controller 30 in real time so as to detect the yaw condition of the whole vehicle, namely detect the yaw moment of the vehicle, and judge whether the vehicle body is stable or not according to the yaw information, so as to control the original steering control device 90 to steer the vehicle in situ, thereby enabling the electric vehicle to be smoothly steered in situ.
In this embodiment, the plurality of wheels 20 includes a left front wheel 21, a right front wheel 22, a left rear wheel 23, and a right rear wheel 24, the left front wheel 21, the right front wheel 22, the left rear wheel 23, and the right rear wheel 24 are respectively provided with a transmission 40, a drive motor 50, and a motor controller 60, and the left front wheel 21, the right front wheel 22, the left rear wheel 23, and the right rear wheel 24 are respectively provided with a wheel speed sensor 62. The wheel speed sensor 62 is configured to detect a wheel speed of the electric vehicle to generate a wheel speed signal, and a rotation sensor 64 is correspondingly disposed on each of the driving motors 50, and the detection of the wheel speed of each of the wheels 20 is achieved through the wheel speed sensor 62 and the rotation sensor 64.
In this embodiment, a pivot steering control device 90 is correspondingly disposed on the left front wheel 21, a pivot steering control device 90 is correspondingly disposed on the right front wheel 22, and both the pivot steering control devices 90 are electrically connected to the power battery 70 through a high voltage cable and are in signal connection with the vehicle controller 30.
When the device is installed, each transmission 40 is connected with each wheel 20 through a transmission shaft, each driving motor 50 is connected with each transmission 40, and each transmission 40 is positioned between the corresponding wheel 20 and the corresponding driving motor 50; each of the motor controllers 60 is electrically connected between the power battery 70 and the corresponding driving motor 50 through a high-voltage line; each of the motor controllers 60, each of the wheel speed sensors 62, each of the rotation change sensors 64, the steering wheel angle sensor 66, the yaw rate sensor 68, the electronic parking brake device 80, and the two pivot steering control devices 90 are communicatively connected to the vehicle controller 30, and the vehicle controller 30 generates control commands to control the four drive motors 50 and controls the two pivot steering control devices 90 according to the state signals of the electric vehicle, the wheel speed signals, the state information of the power battery 70, and the state information of the four drive motors 50, which are transmitted from the steering wheel angle sensor 66, the yaw rate sensor 68, and the electronic parking brake device 80.
Specifically, the steering wheel angle sensor 66, the yaw rate sensor 68 and the electronic parking brake device 80 transmit a state signal sensed to the electric vehicle to the vehicle controller 30 through the CAN network. The four rotation sensors 64 and the four wheel speed sensors 62 are connected to the vehicle controller 30 through a hard wire or a CAN network, both of which CAN provide a function of measuring wheel speed, and any one set of wheel speed measuring system CAN be selected, or two sets of wheel speed measuring systems CAN be used at the same time to check each other, so that if one set of wheel speed sensor 62 fails, the other set of measured wheel speed is used as a judgment basis. The electric vehicle of the embodiment of the invention adopts two sets of wheel speed measuring systems respectively composed of four rotation sensors 64 and four wheel speed sensors 62, namely the four rotation sensors 64 are used for measuring the wheel speed, or the four wheel speed sensors 62 are used for measuring the wheel speed, or the four rotation sensors 64 and the four wheel speed sensors 62 are combined for measuring the wheel speed. The four driving motors 50 are independently controlled and do not influence each other, each driving motor 50 is fixedly connected with each speed changer 40, and each speed changer 40 is connected with each wheel 20 through a transmission shaft.
Therefore, in the embodiment of the present invention, the vehicle controller 30 receives the state signals of the steering wheel angle sensor 66, the yaw rate sensor 68, the four rotation sensors 64, the four wheel speed sensors 62, the power battery 70, the four driving motors 50, the electronic parking brake device 80, and the like, and then determines the entire vehicle state of the electric vehicle. When the state of the electric vehicle needs to be adjusted, the vehicle controller 30 obtains corresponding control information through calculation according to data detected by the steering wheel angle sensor 66, the yaw rate sensor 68, the rotation sensor 64, the wheel speed sensor 62 and the electronic parking brake device 80, and simultaneously sends out control commands according to the state of the power battery 70 and the capabilities of the four driving motors 50 to enable the four driving motors 50 to send out driving torque or braking torque, so as to change the torque at the wheel 20 end, achieve target data set by the vehicle controller 30, and enable the electric vehicle to reach a stable state. In the execution process, the vehicle controller 30 monitors the states of the steering wheel angle sensor 66, the yaw rate sensor 68, the rotation sensor 64, the wheel speed sensor 62, the power battery 70, the four driving motors 50, the electronic parking brake device 80 and other components in real time, judges through the received parameters, adjusts target parameters in real time, and sends control instructions to the four driving motors 50.
Referring to fig. 1, a pivot steering control system of an electric vehicle according to an embodiment of the present invention is used in the electric vehicle, and the pivot steering control system 90 includes:
a left steering motor controller 92 and a right steering motor controller 94 for receiving external pivot steering commands, the left steering motor controller 92 for controlling steering of the left front wheel 21, the right steering motor controller 94 for controlling steering of the right front wheel 22;
a left steering motor 96, wherein the left steering motor 96 receives the pivot steering command of the left steering motor controller 92 of the left steering motor 96 and drives the left front wheel 21 to rotate;
a right steering motor 98, wherein the right steering motor 98 receives the pivot steering command from the right steering motor controller 94 and drives the right front wheel 22 to rotate;
wherein, the left front wheel 21 and the right front wheel 22 rotate and form a shape of a 'inner eight' with a preset angle, and the steering motor controller sends a steering completion instruction to the vehicle controller 30.
In the pivot steering control system of the electric vehicle according to the embodiment of the present invention, the vehicle controller 30 is used to control the left steering motor controller 92 and the right steering motor controller 94 according to the received pivot steering command, the left steering motor controller 92 controls the left front wheel 21 to steer according to the received pivot steering command, the right steering motor controller 94 controls the right front wheel 22 to steer according to the received pivot steering control command, the left front wheel 21 and the right front wheel 22 rotate in opposite directions, a preset angle is formed between the left front wheel 21 and the right front wheel 22, and the steering motor controller sends a steering completion command to the vehicle controller 30.
In this embodiment, during the pivot steering, the steering wheel 10 is in the locked state, that is, the steering operating mechanism is in the locked state, the left steering motor controller 92 and the right steering motor controller 94 are controlled by the automobile controller 30, and the left steering motor 96 is controlled to output power to the left front wheel 21 through the steering transmission mechanism (not shown) and the right steering motor 98 is controlled to output power to the right front wheel 22 through the steering transmission mechanism, so as to realize the steering control of the left front wheel 21 and the right front wheel 22. The left steering motor 96 and the right steering motor 98 can convert the rotational motion of the motor rotors into the linear motion of the steering transmission mechanism by using a transmission conversion structure (not shown) of the lead screw principle to realize the steering control of the left front wheel 21 and the right front wheel 22.
In this embodiment, the left steering motor controller 92 is connected between the vehicle controller 30 and the left front wheel 21, and the right steering motor controller 94 is connected between the vehicle controller 30 and the right front wheel 22.
In this embodiment, the left steering motor 96 is disposed between the left steering motor controller 92 and the left front wheel 21 of the left steering motor 96, and the right steering motor 98 is disposed between the right steering motor controller 94 and the right front wheel 22.
It will be appreciated that the left steering motor 96 is connected to the left front wheel 21 via a rotating shaft, and the right steering motor 98 is connected to the right front wheel 22 via a rotating shaft; the left steering motor 96 and the left steering motor controller 92 are electrically connected between the left steering motor 96 and the power battery 70 through high-voltage wires or hard wires, and the right steering motor controller 94 is electrically connected between the right steering motor 98 and the power battery 70 through high-voltage wires or hard wires; the left steering motor 96, the left steering motor controller 92 and the right steering motor controller 94 are communicatively coupled to the vehicle controller 30 via a CAN network.
Referring to fig. 1 to 3, in this embodiment, the yaw rate sensor 68 includes a yaw rate sensor, a longitudinal acceleration sensor, and a lateral acceleration sensor. During the running of the electric vehicle, the vehicle controller 30 calculates a target yaw rate of the electric vehicle in real time based on the steering wheel 10 angle signal and the wheel speed signal detected by the steering wheel angle sensor 66, and compares the target yaw rate with an actual yaw rate of the electric vehicle detected by the yaw rate sensor to obtain a yaw rate difference; meanwhile, the vehicle controller 30 calculates a rear axle yaw angle of the electric vehicle according to the wheel speed signal, the steering wheel 10 rotation angle signal, the actual yaw rate of the electric vehicle, and the lateral acceleration of the electric vehicle detected by the lateral acceleration sensor, and the vehicle controller 30 calculates a yaw moment difference between the target yaw moment and the actual yaw moment of the electric vehicle in real time by using the entire vehicle moment of inertia of the electric vehicle according to the target yaw rate and the actual yaw rate of the electric vehicle.
It should be noted that, in the embodiment of the present invention, if the yaw rate difference is smaller than the first preset angular velocity or the rear axle slip angle is smaller than the first preset angle, it indicates that the electric vehicle does not slip, the entire vehicle is very stable, and active yaw control is not required; if the yaw angular velocity difference value is larger than a first preset angular velocity and smaller than or equal to a second preset angular velocity or the rear axle sideslip angle is larger than a first preset angle and smaller than or equal to a second preset angle, the situation that the electric vehicle sideslips and is in a sideslip limit interval before is indicated, active yaw control needs to be carried out, and the electric vehicle enters a driving force yaw control mode; and if the yaw rate difference value is greater than a second preset angular speed or the rear axle side slip angle is greater than a second preset angle, the situation that the electric vehicle is in a side slip limit interval is shown, active yaw control needs to be carried out, and a driving force yaw control mode and a braking force yaw control mode need to be simultaneously entered.
Referring to fig. 1 to 3, further, the vehicle controller 30 sends a driving command to the motor controllers 60 of the two front wheels after receiving a steering wheel 10 locking command fed back by the steering wheel angle sensor 66 and a locking rear wheel command fed back by the electronic parking brake device 80, and the left steering motor 96 outputs a forward torque and the right steering motor 98 outputs a reverse torque, or the left front wheel 21 driving motor 50 outputs a reverse torque and the right front wheel 22 driving motor 50 outputs a forward torque.
In use, a driver uses a remote control device to send pivot steering commands (for example, to steer to the right, the same applies below) to the left steering motor 96, the left steering motor controller 92 and the right steering motor controller 94, the left steering motor 96, the left steering motor controller 92 and the right steering motor controller 94 send steering signals to the left steering motor 96 and the right steering motor 98, and the left steering motor 96 and the right steering motor 98 start to rotate until the left front wheel 21 and the right front wheel 22 form an "inner eight character" shape with a preset angle (as shown in fig. 1). After completing the "inside toed" steering of the left and right front wheels 21 and 22, the left steering motor 96, the left steering motor controller 92, and the right steering motor controller 94 send a complete command to the vehicle controller 30; the steering wheel angle sensor 66 detects that the steering wheel 10 has been locked, i.e., the steering wheel 10 is in a locked state and cannot be rotated, and sends a steering wheel 10 lock instruction to the vehicle controller 30; the vehicle controller 30 sends a command of locking the right rear wheel 24 to the EPB, and feeds back information to the vehicle controller 30 after locking is completed; the vehicle controller 30 sends a drive command to the motor controller 60, and the left front wheel 21 drive motor 50 outputs a forward torque and the right front wheel 22 drive motor 50 outputs a reverse torque. During the pivot steering event, the yaw rate sensor 68 sends a signal to the vehicle controller 30 in real time to monitor the overall vehicle yaw. And if the unstable condition occurs, carrying out the yaw control or stopping of the whole vehicle.
After the pivot steering is completed, the driver uses the remote control device to turn off the pivot steering button, that is, sends a pivot steering completion command, so that the steering wheel 10 is unlocked, and the steering wheel angle sensor 66 is used to detect that the steering wheel 10 is in a rotatable state.
In this embodiment, when the pivot steering button is pressed, that is, the pivot steering function is activated, the steering wheel 10 is in a locked state, that is, in a non-rotatable state, and a lock command generated by detecting the locked state of the steering wheel 10 is transmitted to the vehicle controller 30 by using the steering wheel angle sensor 66, at this time, the steering wheel 10 is locked by the assist motor being driven and the assist motor being in a non-operation state, and the vehicle controller 30 performs a control process according to the received lock command. When the pivot steering button is pressed again, that is, the pivot steering function is turned off, the steering wheel 10 is automatically unlocked and is in a rotatable state.
When the left pivot steering is performed, the vehicle controller 30 sends a drive command to the motor controller 60, the left front wheel 21 drive motor 50 outputs a reverse torque, and the right front wheel 22 drive motor 50 outputs a forward torque.
Referring to fig. 1 to 4, a pivot steering control method for an electric vehicle according to an embodiment of the present invention includes the following steps:
a driver sends an in-situ steering instruction to a steering motor controller, the steering motor controller receives the in-situ steering instruction and starts a steering motor, the steering motor drives two front wheels to rotate, the two front wheels form an inward splayed shape with a preset angle, and the steering motor sends a steering completion instruction to a vehicle controller 30;
the steering wheel angle sensor 66 detects that the steering wheel 10 is in the locked state and sends a steering wheel 10 lock instruction to the vehicle controller 30;
the vehicle controller 30 sends a locking instruction for locking the right rear wheel 24 or the left rear wheel 23 to the electronic parking brake device 80, and the electronic parking brake device 80 feeds the locking instruction back to the vehicle controller 30 after the right rear wheel 24 or the left rear wheel 23 is locked;
the vehicle controller 30 sends a driving instruction to the motor controller 60 according to the received steering completion instruction, steering wheel 10 locking instruction and locking instruction, and the motor controller 60 controls the torque of each driving motor 50;
sending full vehicle yaw information to the vehicle controller 30 in real time using the yaw rate sensor 68;
if the yaw information of the whole vehicle is in a threshold value, performing pivot steering; otherwise, the pivot steering is stopped.
The pivot steering control method for the electric vehicle provided by the embodiment of the invention uses the steering motor controller to start the steering motor, drives the two front wheels to rotate by the steering motor to form an inward splayed shape with a preset angle, uses the yaw rate sensor 68 to detect the yaw information of the whole vehicle in real time and transmits the detected yaw information of the whole vehicle to the vehicle controller 30 in real time so as to detect the yaw condition of the whole vehicle, namely detect the yaw moment of the vehicle, and accordingly judges whether the vehicle body is stable or not so as to control the pivot steering control device 90 to perform pivot steering action on the vehicle or not, so that the electric vehicle can be smoothly performed in the pivot steering process.
In this embodiment, the steering motor controllers include a left steering motor controller 92 and a right steering motor controller 94 for receiving external pivot steering commands, the left steering motor controller 92 for controlling steering of the left front wheel 21, the right steering motor controller 94 for controlling steering of the right front wheel 22;
the steering motors comprise a left steering motor 96 and a right steering motor 98, the left steering motor 96 is arranged between the left steering motor controller 92 of the left steering motor 96 and the left front wheel 21, and the left steering motor 96 receives a pivot steering instruction of the left steering motor controller 92 of the left steering motor 96 and drives the left front wheel 21 to rotate; the right steering motor 98 is disposed between the right steering motor controller 94 and the right front wheel 22, and the right steering motor 98 receives the pivot steering command from the right steering motor controller 94 and drives the right front wheel 22 to rotate; wherein, the left front wheel 21 and the right front wheel 22 rotate and form a shape of a 'inner eight' with a preset angle, and the steering motor controller sends a steering completion instruction to the vehicle controller 30.
In this embodiment, the electric vehicle includes: a steering wheel 10 for controlling a driving direction, a plurality of wheels 20, a vehicle controller 30, a plurality of transmissions 40 respectively connected to the wheels 20, a plurality of driving motors 50 respectively connected to the transmissions 40 and respectively corresponding to the wheels 20, a motor controller 60 electrically connected between the driving motors 50 and the vehicle controller 30, a wheel speed sensor 62 for detecting a wheel speed of each of the wheels 20 to generate a wheel speed signal, a steering wheel angle sensor 66 for detecting direction information of the steering wheel 10, a yaw rate sensor 68 for detecting yaw information of the entire vehicle, a power battery 70 for supplying power, an electronic Parking Brake device 80 (EPB) for maintaining stability of the vehicle body, and a steering control device 90 for steering the vehicle in place by controlling torque and rotational speed of the two front wheels corresponding to the driving motor 50; each of the motor controller 60, each of the wheel speed sensors 62, the steering wheel angle sensor 66, the electronic parking brake device 80, the yaw rate sensor 68, and the power battery 70 is electrically connected to the vehicle controller 30, and the pivot steering control device 90 corresponds to two front wheels and controls rotation directions of the two front wheels, respectively, and output torques of the two front wheels are opposite in direction.
Referring to fig. 1, in the embodiment, the plurality of wheels 20 includes a left front wheel 21, a right front wheel 22, a left rear wheel 23, and a right rear wheel 24, the left front wheel 21, the right front wheel 22, the left rear wheel 23, and the right rear wheel 24 are respectively provided with a transmission 40, a driving motor 50, and a motor controller 60, and the left front wheel 21, the right front wheel 22, the left rear wheel 23, and the right rear wheel 24 are respectively provided with a wheel speed sensor 62. The wheel speed sensor 62 is configured to detect a wheel speed of the electric vehicle to generate a wheel speed signal, and a rotation sensor 64 is correspondingly disposed on each of the driving motors 50, and the detection of the wheel speed of each of the wheels 20 is achieved through the wheel speed sensor 62 and the rotation sensor 64.
In this embodiment, a pivot steering control device 90 is correspondingly disposed on the left front wheel 21, a pivot steering control device 90 is correspondingly disposed on the right front wheel 22, and both the pivot steering control devices 90 are electrically connected to the power battery 70 through a high voltage cable and are in signal connection with the vehicle controller 30.
Referring to fig. 1, when installed, each transmission 40 is connected to each wheel 20 through a transmission shaft, each driving motor 50 is connected to each transmission 40, and each transmission 40 is located between a corresponding wheel 20 and a corresponding driving motor 50; each of the motor controllers 60 is electrically connected between the power battery 70 and the corresponding driving motor 50 through a high-voltage line; each of the motor controllers 60, each of the wheel speed sensors 62, each of the rotation change sensors 64, the steering wheel angle sensor 66, the yaw rate sensor 68, the electronic parking brake device 80, and the two pivot steering control devices 90 are communicatively connected to the vehicle controller 30, and the vehicle controller 30 generates control commands to control the four drive motors 50 and controls the two pivot steering control devices 90 according to the state signals of the electric vehicle, the wheel speed signals, the state information of the power battery 70, and the state information of the four drive motors 50, which are transmitted from the steering wheel angle sensor 66, the yaw rate sensor 68, and the electronic parking brake device 80.
Referring to fig. 1, in particular, the steering wheel angle sensor 66, the yaw rate sensor 68 and the electronic parking brake device 80 transmit a state signal sensed to the electric vehicle to the vehicle controller 30 through the CAN network. The four rotation sensors 64 and the four wheel speed sensors 62 are connected to the vehicle controller 30 through a hard wire or a CAN network, both of which CAN provide a function of measuring wheel speed, and any one set of wheel speed measuring system CAN be selected, or two sets of wheel speed measuring systems CAN be used at the same time to check each other, so that if one set of wheel speed sensor 62 fails, the other set of measured wheel speed is used as a judgment basis. The electric vehicle of the embodiment of the invention adopts two sets of wheel speed measuring systems respectively composed of four rotation sensors 64 and four wheel speed sensors 62, namely the four rotation sensors 64 are used for measuring the wheel speed, or the four wheel speed sensors 62 are used for measuring the wheel speed, or the four rotation sensors 64 and the four wheel speed sensors 62 are combined for measuring the wheel speed. The four driving motors 50 are independently controlled and do not influence each other, each driving motor 50 is fixedly connected with each speed changer 40, and each speed changer 40 is connected with each wheel 20 through a transmission shaft.
Referring to fig. 1, in the embodiment of the present invention, the vehicle controller 30 receives status signals of various components, such as the steering wheel angle sensor 66, the yaw rate sensor 68, the four rotation sensors 64, the four wheel speed sensors 62, the power battery 70, the four driving motors 50, and the electronic parking brake device 80, and then determines the overall vehicle status of the electric vehicle. When the state of the electric vehicle needs to be adjusted, the vehicle controller 30 obtains corresponding control information through calculation according to data detected by the steering wheel angle sensor 66, the yaw rate sensor 68, the rotation sensor 64, the wheel speed sensor 62 and the electronic parking brake device 80, and simultaneously sends out control commands according to the state of the power battery 70 and the capabilities of the four driving motors 50 to enable the four driving motors 50 to send out driving torque or braking torque, so as to change the torque at the wheel 20 end, achieve target data set by the vehicle controller 30, and enable the electric vehicle to reach a stable state. In the execution process, the vehicle controller 30 monitors the states of the steering wheel angle sensor 66, the yaw rate sensor 68, the rotation sensor 64, the wheel speed sensor 62, the power battery 70, the four driving motors 50, the electronic parking brake device 80 and other components in real time, judges through the received parameters, adjusts target parameters in real time, and sends control instructions to the four driving motors 50.
Referring to fig. 1 to 3, the step of controlling the torque of each driving motor 50 by the motor controller 60 further includes:
the motor controller 60 calculates the driving torque T required by each of the driving motors 50 according to a preset pivot steering vehicle speed and according to the following formula:
T＝F(M,g,f,r,i,η)
in the formula: m is the vehicle mass; g is the acceleration of gravity;
Figure GDA0002522553980000161
is the rolling resistance coefficient; r is the wheel 20 rolling radius; i is the variator 40 speed ratio; η is a constant.
After each of the motor controllers 60 receives a driving instruction sent by the vehicle controller 30, each of the motor controllers 60 calculates a driving torque required by each of the driving motors 50 according to a preset pivot steering vehicle speed, and controls the torque required by each of the driving motors 50 so that the motor controllers 60 control the rotation speeds of the driving motors 50 corresponding to the left and right front wheels 21 and 22.
Referring to fig. 1 to 3, the step of controlling the torque of each driving motor 50 by the motor controller 60 further includes:
each of the driving motors 50 is driven with a torque T1, and the wheel speed sensors 62 corresponding to the two front wheels detect whether the wheel speeds of the two front wheels are greater than zero;
if the detected wheel speed is greater than zero, the vehicle is in motion, and at the next control time T, the driving motor 50 is driven with a torque T2;
if the detected wheel speed is equal to zero, the vehicle is in a stationary state, the driving motor 50 is driven at a torque T3 at the next control time T, the torque of the driving motor 50 is increased within each control time T until the wheel speed is greater than zero, and the control time for increasing the torque does not exceed Tmax；
Wherein T1 is more than T3 is more than T2, and T is less than or equal to Tmax。
The output torque of the driving motor 50 is calculated by detecting whether the wheel speed is greater than zero. In the case where the wheel speed is zero, the output torque of the drive motor 50 must be increased at each control time until the wheel speed is greater than zero.
Through the starting control of the steps, the vehicle is already moved. And then entering a vehicle speed control link. Since the right front wheel 22 is pushed away (for example, right pivot steering, the same applies hereinafter), the tire of each of the wheels 20 is worn to a great extent, and the wheel speed thereof is precisely controlled to reduce the tire wear. As shown in FIG. 2, the velocity at the center of the right front wheel 22 has components V in the X-axis and Y-axis directionsXAnd VYAnd assumes that the right front wheel 22 is centered at ΔtThe displacements in the X-axis direction and the Y-axis direction are respectively Delta S in timeX、ΔSY. Then there are:
angular velocity ω at the center of mass O of the vehicleo:
ωo＝F(ΔSX，ΔSYΔt，a)
The vehicle speed of the left front wheel 21 is:
VL＝bωo＝F(ΔSX，ΔSY，Δt，a，b)
where a is a track width between the left front wheel 21 and the left rear wheel 23 or a track width between the right front wheel 22 and the right rear wheel 24; b is a track width between the left front wheel 21 and the right front wheel 22 or a track width between the left rear wheel 23 and the right rear wheel 24.
The motor controller 60 should control the rotation speed n of the driving motor 50 for the left and right front wheels 21 and 221、n2Respectively as follows:
Figure GDA0002522553980000171
wherein i is a transmission ratio; r is the rolling radius of the wheel 20.
Further, the pivot steering control method of the electric vehicle further includes the steps of:
sending full vehicle yaw information to the vehicle controller 30 in real time using the yaw rate sensor 68;
if the yaw information of the whole vehicle is in a preset value, performing pivot steering; otherwise, the pivot steering is stopped.
The pivot steering control method detects the yaw information of the whole vehicle in real time through the yaw rate sensor 68 and sends the yaw information of the whole vehicle to the vehicle controller 30, the vehicle controller 30 compares the yaw information of the whole vehicle with the preset value of the yaw of the whole vehicle to judge whether pivot steering is carried out, specifically, the pivot steering is carried out when the yaw information of the whole vehicle reaches the preset value, and the pivot steering is stopped if the yaw information of the whole vehicle does not reach the preset value.
Referring to fig. 1 to 3, further, in the step of sending the yaw information of the entire vehicle to the vehicle controller 30 in real time by using the yaw rate sensor 68, the method further includes:
detecting yaw rate using a yaw rate sensor and determining whether the detected yaw rate exceeds a yaw rate threshold value gammalimitWhen the detected yaw rate exceeds the yaw rate threshold value gammalimitWhen the vehicle is in motion, performing active whole vehicle yaw control; or
Detecting the mass center slip angle of the whole vehicle by utilizing a longitudinal acceleration sensor and a lateral acceleration sensor, and judging whether the detected mass center slip angle of the whole vehicle exceeds a mass center slip angle threshold value betalimitWhen the detected barycenter slip angle of the whole vehicle exceeds a barycenter slip angle threshold betalimitAnd in time, performing active whole vehicle yaw control.
The yaw rate sensor 68 is utilized to send a signal to the vehicle controller 30 in real time to monitor the yaw of the entire vehicle. If the pivot steering is normally performed, the torque and rotation speed control is performed in the above manner. If the unstable condition occurs, the mass center side slip angle or the yaw velocity of the whole vehicle exceeds a threshold value betaHmitOr gammaHmitNamely, the yaw control of the whole vehicle is carried out, and the pivot steering is stopped when the yaw control cannot be acted.
As can be appreciated, the whole vehicle yaw information comprises a yaw rate and a whole vehicle mass center side slip angle, and the preset value of the whole vehicle yaw comprises a yaw rate threshold value gammalimitAnd centroid slip angle threshold βlimit。
In this embodiment, the yaw rate sensor 68 includes a yaw rate sensor, a longitudinal acceleration sensor, and a lateral acceleration sensor.
During the running of the electric vehicle, the vehicle controller 30 calculates a target yaw rate of the electric vehicle in real time based on the steering wheel 10 angle signal and the wheel speed signal detected by the steering wheel angle sensor 66, and compares the target yaw rate with an actual yaw rate of the electric vehicle detected by the yaw rate sensor to obtain a yaw rate difference; meanwhile, the vehicle controller 30 calculates a rear axle yaw angle of the electric vehicle according to the wheel speed signal, the steering wheel 10 rotation angle signal, the actual yaw rate of the electric vehicle, and the lateral acceleration of the electric vehicle detected by the lateral acceleration sensor, and the vehicle controller 30 calculates a yaw moment difference between the target yaw moment and the actual yaw moment of the electric vehicle in real time by using the entire vehicle moment of inertia of the electric vehicle according to the target yaw rate and the actual yaw rate of the electric vehicle.
It should be noted that, in the embodiment of the present invention, if the yaw rate difference is smaller than the first preset angular velocity or the rear axle slip angle is smaller than the first preset angle, it indicates that the electric vehicle does not slip, the entire vehicle is very stable, and active yaw control is not required; if the yaw angular velocity difference value is larger than a first preset angular velocity and smaller than or equal to a second preset angular velocity or the rear axle sideslip angle is larger than a first preset angle and smaller than or equal to a second preset angle, the situation that the electric vehicle sideslips and is in a sideslip limit interval before is indicated, active yaw control needs to be carried out, and the electric vehicle enters a driving force yaw control mode; and if the yaw rate difference value is greater than a second preset angular speed or the rear axle side slip angle is greater than a second preset angle, the situation that the electric vehicle is in a side slip limit interval is shown, active yaw control needs to be carried out, and a driving force yaw control mode and a braking force yaw control mode need to be simultaneously entered.
Referring to fig. 1 to 3, further, the step of actively controlling the yaw of the entire vehicle includes:
the whole vehicle is simplified into a linear two-degree-of-freedom vehicle model, as shown in fig. 3, the corner of a front wheel is directly used as input, a vehicle compartment only carries out plane motion parallel to the ground, the lateral deviation characteristic of a tire and the action of air power are zero, and the longitudinal speed of the vehicle along an x axis is regarded as constant;
the yaw moment around the z-axis of the vehicle's center of mass generated by the longitudinal driving force of each wheel 20 is controlled, that is:
Figure GDA0002522553980000191
wherein, FX1Is a longitudinal force of the left front wheel 21, FX2Is the longitudinal force of the right front wheel 22, FX3Is a longitudinal force of the left rear wheel 23, FX4Is the longitudinal force of the right rear wheel 24; d is the wheel track;
controlling the mass center slip angle of the whole vehicle to be equal to the mass center slip angle threshold betalimitAnd controlling the yaw rate to be equal to the desired yaw rate.
It should be noted that: when yaw control is carried out, corresponding preconditions need to be set, namely, the whole vehicle is simplified into a linear two-degree-of-freedom vehicle model (as shown in fig. 3); the influence of a steering system is ignored in the analysis, and the front wheel steering angle is directly used as input; neglecting the effect of the suspension, the carriage of the vehicle is considered to only do plane motion parallel to the ground, namely the displacement of the vehicle along the z axis, and the pitch angle around the y axis and the roll angle around the x axis are both zero; the cornering property and the action of aerodynamic force of the tire are not considered; and the longitudinal speed of the vehicle along the x-axis is considered constant.
In the yaw control process, O is an automobile center of mass point; beta is the centroid slip angle; gamma is a yaw angular velocity;iis a front wheel corner; fX1Is a longitudinal force of the left front wheel 21, FX2Is the longitudinal force of the right front wheel 22, FX3Is a longitudinal force of the left rear wheel 23, FX4Is the longitudinal force of the right rear wheel 24; (ii) a FY1Is a lateral force of the left front wheel 21, FY2Is the lateral force of the right front wheel 22, FY3Is a lateral force of the left rear wheel 23, FY4Is the lateral force of the right rear wheel 24; fY1Is a lateral force of the left front wheel 21, FY2Is the lateral force of the right front wheel 22, FY3Is a lateral force of the left rear wheel 23, FY4Is the lateral force of the right rear wheel 24; d is the wheel track; laAnd lbThe distances from the centroid to the front and rear axes, respectively; vZ、VYThe longitudinal and lateral speeds of the vehicle body under a fixed coordinate system are shown.
The kinetic equation is expressed as follows:
Figure GDA0002522553980000201
Figure GDA0002522553980000202
Figure GDA0002522553980000203
in the formula, m is the mass of the whole vehicle; i iszThe moment of inertia of the vehicle about the z-axis; mzFor the yaw moment about the z-axis of the center of mass of the vehicle generated by the longitudinal driving force of each wheel 20,namely:
Figure GDA0002522553980000204
the goal of yaw control is to try to keep the centroid slip angle β to a minimum (i.e., equal to β)Hmit) While causing the yaw rate γ to track the desired angular velocity to achieve the intention of the driver.
According to the two-degree-of-freedom vehicle steady-state steering theory, the desired yaw rate can be expressed as:
Figure GDA0002522553980000205
in the formula, gammaeA desired yaw rate; k is the stability factor.
The yaw moment calculation method will be described with reference to sliding mode control as an example. The combined control of the mass center side slip angle beta and the yaw angular velocity gamma is adopted, and the sliding mode surface is defined as
Figure GDA0002522553980000211
Wherein c is a joint control parameter. As shown in the formula (2),
Figure GDA0002522553980000212
as a function of γ, equation (6) is referred to as the joint control of β and γ. According to arrival conditions
Figure GDA0002522553980000213
Obtaining:
Figure GDA0002522553980000214
substituting the formulas (1) and (7) into the formula (2) to obtain
Figure GDA0002522553980000215
Therefore, an expression of the additional yaw moment using beta and gamma as control variables is obtained as
Figure GDA0002522553980000216
The calculation method of the yaw moment in the embodiment of the invention is not limited to sliding mode control, and other control methods can be adopted, and the calculation idea is to generate the yaw moment to stabilize the vehicle body.
Referring to fig. 1 to 3, further, the step of actively controlling the yaw of the entire vehicle includes:
will control the yaw moment MZLeft and right wheel distribution is performed, and the driving torque directions of the left and right wheels 20 are opposite.
The yaw control process is to calculate an additional yaw moment and to allocate the moment to the left and right wheels, and to achieve the purpose of yaw control by making the driving forces of the left and right wheels 20 opposite in direction. Motor output torque F of each wheelM：
FM＝F(MZ,i,r,d)
In the formula, MZA yaw moment, d a track width, i a corresponding wheel 20, i 1, 2, 3 and 4, 1 a left front wheel 21, 2 a right front wheel 22, 3 a left rear wheel 23, 4 a right rear wheel 24; r is the rolling radius of the wheel 20.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (9)

1. An in-place steering control system for an electric vehicle, the electric vehicle including a vehicle controller, the in-place steering control system comprising:
the left steering motor controller is used for controlling the steering of the left front wheel, and the right steering motor controller is used for controlling the steering of the right front wheel;
the left steering motor receives an in-situ steering command of the left steering motor controller and drives the left front wheel to rotate;
the right steering motor receives an in-situ steering instruction of the right steering motor controller and drives the right front wheel to rotate;
the yaw rate sensor is used for detecting the yaw information of the whole vehicle and sending the yaw information of the whole vehicle to the vehicle controller in real time;
the in-situ steering control system of the electric vehicle further comprises driving motors respectively corresponding to the left front wheel and the right front wheel, a motor controller electrically connected between each driving motor and the vehicle controller, a wheel speed sensor for detecting the wheel speeds of the left front wheel and the right front wheel to generate wheel speed signals, a steering wheel angle sensor for detecting steering wheel direction information, and an electronic parking brake device for keeping a vehicle body stable;
the method comprises the following steps that a driver sends an in-situ steering command to a steering motor controller, and the steering motor controller receives the in-situ steering command and starts a steering motor; stopping pivot steering when the yaw information of the whole vehicle exceeds the range of a preset value; when the yaw information of the whole vehicle is in a preset value, the left front wheel and the right front wheel rotate and form an inner splayed shape with a preset angle, and the steering motor controller sends a steering completion instruction to the vehicle controller;
the steering wheel angle sensor detects that a steering wheel is in a locked state and sends a steering wheel locking instruction to the vehicle controller;
the vehicle controller sends a locking instruction for locking the right rear wheel or the left rear wheel to the electronic parking braking device, and the electronic parking braking device feeds the locking instruction back to the vehicle controller after completing locking of the right rear wheel or the left rear wheel;
the vehicle controller sends a driving instruction to a motor controller according to the received steering finishing instruction, the steering wheel locking instruction and the locking instruction, and the motor controller controls the torque of each driving motor;
in the step of controlling the torque of each driving motor by the motor controller, the method further includes:
each driving motor is driven by torque T1, and wheel speed sensors corresponding to the two front wheels detect whether the wheel speeds of the two front wheels are larger than zero;
if the detected wheel speed is larger than zero, the vehicle is in a moving state, and at the next control time T, the driving motor is driven by a torque T2;
if the detected wheel speed is equal to zero, the vehicle is in a static state, the driving motor is driven by torque T3 at the next control time T, the torque of the driving motor is increased in each control time T until the wheel speed is greater than zero, and the control time for increasing the torque is not more than Tmax；
Wherein T1 is more than T3 is more than T2, and T is less than or equal to Tmax。
2. The pivot steering control system of an electric vehicle as claimed in claim 1, wherein the left steering motor controller is connected between the vehicle controller and a left front wheel, and the right steering motor controller is connected between the vehicle controller and a right front wheel.
3. The pivot steering control system of an electric vehicle according to claim 1, wherein the left steering motor is disposed between the left steering motor controller and the left front wheel, and the right steering motor is disposed between the right steering motor controller and the right front wheel.
4. The pivot steering control system of an electric vehicle according to claim 1, wherein the vehicle controller sends a drive command to the motor controllers of the left and right front wheels after receiving a steering wheel lock command fed back from the steering wheel angle sensor and a lock rear wheel command fed back from the electronic parking brake device, the left steering motor outputs a forward torque and the right steering motor outputs a reverse torque, or the left front wheel drive motor outputs a reverse torque and the right front wheel drive motor outputs a forward torque.
5. A pivot steering control method of an electric vehicle, characterized by comprising the steps of:
a driver sends a pivot steering instruction to a steering motor controller, the steering motor controller receives the pivot steering instruction and starts a steering motor, and the pivot steering is stopped when the yaw information of the whole vehicle exceeds the range of a preset value; when the yaw information of the whole vehicle is in a preset value, the steering motor drives the two front wheels to rotate, the two front wheels form an inner splayed shape with a preset angle, and the steering motor sends a steering completion instruction to the vehicle controller;
the steering wheel angle sensor detects that a steering wheel is in a locked state and sends a steering wheel locking instruction to the vehicle controller;
the vehicle controller sends a locking instruction for locking the right rear wheel or the left rear wheel to the electronic parking braking device, and the electronic parking braking device feeds the locking instruction back to the vehicle controller after completing locking of the right rear wheel or the left rear wheel;
the vehicle controller sends a driving instruction to a motor controller according to the received steering finishing instruction, the steering wheel locking instruction and the locking instruction, and the motor controller controls the torque of each driving motor;
in the step of controlling the torque of each driving motor by the motor controller, the method further includes:
each driving motor is driven by torque T1, and wheel speed sensors corresponding to the two front wheels detect whether the wheel speeds of the two front wheels are larger than zero;
if the detected wheel speed is larger than zero, the vehicle is in a moving state, and at the next control time T, the driving motor is driven by a torque T2;
if the detected wheel speed is equal to zero, the vehicle is in a static state, the driving motor is driven by torque T3 at the next control time T, the torque of the driving motor is increased in each control time T until the wheel speed is greater than zero, and the control time for increasing the torque is not more than Tmax；
Wherein T1 is more than T3 is more than T2, and T is less than or equal to Tmax。
6. The pivot steering control method of an electric vehicle according to claim 5, characterized by further comprising the steps of:
sending the yaw information of the whole vehicle to the vehicle controller in real time by using a yaw rate sensor;
if the yaw information of the whole vehicle is in a preset value, performing pivot steering; otherwise, the pivot steering is stopped.
7. The pivot steering control method of an electric vehicle according to claim 6, wherein in the step of transmitting the yaw information of the entire vehicle to the vehicle controller in real time using a yaw rate sensor, further comprising:
detecting a yaw rate using a yaw rate sensor and determining whether the detected yaw rate exceeds a yaw rate threshold value gammalimitWhen the detected yaw rate exceeds the yaw rate threshold value gammalimitWhen the vehicle is in motion, performing active whole vehicle yaw control; or
Detecting the mass center slip angle of the whole vehicle by utilizing a longitudinal acceleration sensor and a lateral acceleration sensor, and judging whether the detected mass center slip angle of the whole vehicle exceeds a mass center slip angle threshold value betalimitWhen the detected vehicle mass center slip angle exceeds the mass center slip angle threshold betalimitAnd in time, performing active whole vehicle yaw control.
8. The pivot steering control method of an electric vehicle according to claim 7, wherein in the step of actively controlling the yaw of the entire vehicle, it comprises:
the whole vehicle is simplified into a linear two-degree-of-freedom vehicle model, the rotation angle of a front wheel is directly used as input, a vehicle compartment only carries out plane motion parallel to the ground, the lateral deviation characteristic of a tire and the action of air power are zero, and the longitudinal speed of the vehicle along an x axis is regarded as unchanged;
controlling a yaw moment generated by the longitudinal driving force of each wheel around the z-axis of the mass center of the vehicle, namely:
Figure FDA0002522553970000041
wherein, FX1Longitudinal force of the left front wheel, FX2Longitudinal force of the right front wheel, FX3Longitudinal force of the left rear wheel, FX4Is the longitudinal force of the right rear wheel; d is the wheel track;
controlling the mass center slip angle of the whole vehicle to be equal to the mass center slip angle threshold betalimitAnd controlling the yaw rate to be equal to the desired yaw rate.
9. The pivot steering control method of an electric vehicle according to claim 8, wherein in the step of actively controlling the yaw of the entire vehicle, it comprises:
will control the yaw moment MZLeft and right wheel distribution is carried out, and the driving torque directions of the left and right wheels are opposite.
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