CN108909828A - A kind of steering-by-wire and braking system and its control method - Google Patents

A kind of steering-by-wire and braking system and its control method Download PDF

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Publication number
CN108909828A
CN108909828A CN201810537315.8A CN201810537315A CN108909828A CN 108909828 A CN108909828 A CN 108909828A CN 201810537315 A CN201810537315 A CN 201810537315A CN 108909828 A CN108909828 A CN 108909828A
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China
Prior art keywords
steering
wheel
front wheel
brake cylinder
sensor
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CN201810537315.8A
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Chinese (zh)
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CN108909828B (en
Inventor
王衍圣
王春燕
赵万忠
鲁广超
钱兴国
吴刚
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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Priority to CN201810537315.8A priority Critical patent/CN108909828B/en
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
    • B62D5/046—Controlling the motor
    • B62D5/0463—Controlling the motor calculating assisting torque from the motor based on driver input
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
    • B62D5/0475—Controlling other elements
    • B62D5/0478—Clutches
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear
    • B62D5/0457—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such
    • B62D5/0481—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such monitoring the steering system, e.g. failures
    • B62D5/0487—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear characterised by control features of the drive means as such monitoring the steering system, e.g. failures detecting motor faults
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D6/00—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits
    • B62D6/001—Arrangements for automatically controlling steering depending on driving conditions sensed and responded to, e.g. control circuits the torque NOT being among the input parameters
    • 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

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Steering Control In Accordance With Driving Conditions (AREA)
  • Regulating Braking Force (AREA)

Abstract

The invention discloses a kind of steering-by-wire and braking system and its control method, which includes wire-controlled steering system, line control brake system and electronic control unit.Steering wheel angle sensor, front wheel angle sensor, vehicle speed sensor, wheel speed sensors, yaw-rate sensor, the DATA REASONING automotive service state of brake pedal sensor are acquired in the process of moving, change control model by its information to meet the control of motor turning motor, four-wheel braking wheel cylinder under different operating conditions, it ensure that automobile turns to light and flexible when driving in normal operating conditions low speed, high speed steering is reliable and stable when driving, the control method of automobile in emergency situations is provided again, and line traffic control automobile is made to play the advantage of vehicle integrated control.

Description

Wire-controlled steering and braking system and control method thereof
Technical Field
The invention relates to the technical field of steering systems and braking systems, in particular to a line-controlled steering and braking system and a control method thereof.
Background
In recent years, with the continuous development of electronics and control technology, chassis electric control systems such as an anti-lock brake system, a traction control system, an electronic stability control system, an active suspension system and the like have been widely applied to automobiles, and the application of the electric control systems greatly improves the performances of the automobiles such as the steering stability, the active safety, the driving comfort and the like.
However, at present, no matter steering or braking is still in a mechanical connection stage, and the mechanical connection of a steering system causes the steering characteristic of an automobile to be in a strong nonlinear time-varying characteristic along with the change of the speed, the steering wheel angle and the road adhesion condition. In order to control the driving of the car along the path desired by the driver, the driver must adjust his own characteristics from time to time, which increases the mental and physical burden on the driver, which is often difficult for non-professional drivers to adapt. When complex working conditions (such as split road surfaces, side wind, low adhesion road surfaces and the like) are met, a driver can hardly control the automobile, and traffic accidents are easy to happen. Therefore, researchers in various countries are continuously researching new steering technologies to solve the above problems, and steer-by-wire systems have been developed. The brake-by-wire system changes the traditional hydraulic or pneumatic brake executing element into an electric driving element, has the characteristics of good controllability and high response speed, and has good development prospect.
At present, a method which is strong in universality, simple and easy to implement is lacked for the integrated control of a drive-by-wire system.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a steer-by-wire and brake system and a control method thereof, aiming at the problems involved in the background art.
The invention adopts the following technical scheme for solving the technical problems:
a steer-by-wire and brake system comprising a steer-by-wire system, a steer-by-wire system and an electronic control unit:
the steer-by-wire system comprises a steering wheel, a steering wheel corner sensor, an upper steering column, a lower steering column, a road feel motor, a first speed reducing mechanism, an electromagnetic clutch, a steering motor, a second speed reducing mechanism, a front shaft, a front wheel corner sensor, a vehicle speed sensor, a wheel speed sensor and a yaw angle speed sensor;
the upper end of the upper steering column is fixedly connected with the steering wheel, the lower end of the upper steering column is connected with the upper end of the lower steering column through the electromagnetic clutch, and the electromagnetic clutch is in a disconnected state;
the steering wheel angle sensor is arranged on the upper steering column and used for acquiring a steering wheel angle and transmitting the steering wheel angle to the electronic control unit;
an output shaft of the road feel motor is connected with the upper steering column through the first speed reducing mechanism and used for transmitting road feel feedback to a steering wheel through the upper steering column;
the lower end of the lower steering column is connected with the front shaft through the gear rack steering gear;
two ends of the front shaft are respectively connected with a left front wheel and a right front wheel of the automobile;
an output shaft of the steering motor is connected with the lower steering column through the second speed reducing mechanism and is used for transmitting steering torque to the lower steering column so as to drive two front wheels of the automobile to steer through a gear rack steering gear;
the front wheel rotation angle sensor and the wheel speed sensor are arranged on a front wheel of the automobile, are respectively used for obtaining the front wheel rotation angle and the front wheel speed of the automobile and transmitting the front wheel rotation angle and the front wheel speed to the electronic control unit;
the vehicle speed sensor and the yaw rate sensor are arranged on the automobile and are respectively used for obtaining the vehicle speed and the yaw rate of the automobile and transmitting the vehicle speed and the yaw rate to the electronic control unit;
the brake-by-wire system comprises a brake pedal sensor, a left front wheel brake cylinder, a right front wheel brake cylinder, a left rear wheel brake cylinder and a right rear wheel brake cylinder;
the brake pedal sensor is arranged at the tail end of an automobile brake pedal and used for collecting pedal signals when a driver brakes and transmitting the pedal signals to the electronic control unit;
the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder are respectively used for controlling the braking of the left front wheel, the right front wheel, the left rear wheel and the right rear wheel;
the electronic control unit is electrically connected with the steering wheel angle sensor, the front wheel rotation angle sensor, the vehicle speed sensor, the wheel speed sensor, the yaw rate sensor, the brake pedal sensor, the road sense motor, the steering motor, the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder respectively, and is used for controlling the road sense motor, the steering motor, the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to work according to data measured by the steering wheel angle sensor, the front wheel rotation angle sensor, the vehicle speed sensor, the wheel speed sensor, the yaw rate sensor and the brake pedal sensor.
The invention also discloses a control method based on the steer-by-wire and brake system, which comprises the following steps:
step 1) of performing a step of,steering wheel angular velocity omega measured by steering wheel angular sensorrSteering wheel angle thetar(ii) a Brake pedal opening delta measured by brake pedal sensorrBrake pedal rate of change αrA front wheel rotation angle η measured by the front wheel rotation angle sensor and the wheel speed sensor respectivelyrAnd front wheel speed; the vehicle speed sensor, the yaw rate sensor and the slip rate sensor respectively measure the vehicle speed V of the current vehiclerAnd yaw rate βr；
Step 2), the electronic control unit converts the steering wheel angular speed omegarAnd a preset steering wheel angular velocity threshold omegamComparing, and comparing thetarAnd a preset steering wheel angle threshold thetamComparing and comparing the automobile speed VrAnd a preset vehicle speed threshold value VmComparing the opening delta of the brake pedalrAnd a brake pedal opening degree threshold value deltamBy comparison, the brake pedal rate of change αrAnd a brake pedal rate of change threshold αmAnd (3) comparison:
step 2.1), when thetarGreater than thetamAnd V isrGreater than VmWhen, or when thetarLess than thetam、ωrGreater than omegamAnd V isrGreater than VmWhen the steering characteristic parameter is A, the steering characteristic parameter is set as A; otherwise, making the steering characteristic parameter be B;
step 2.2) when drGreater than deltam、αrGreater than αmAnd V isrGreater than VmWhen the braking characteristic parameter is A; otherwise, making the braking characteristic parameter be B;
and step 3), when the steering characteristic parameter is B and the braking characteristic parameter is B, the system works in an online control normal working mode:
step 3.1), the electronic control unit according to thetarControlling the steering motor to work to make the front wheel of the automobile rotate at an angle of i thetar, wherein ：Cafthe tire sidewall deflection stiffness of the front wheel tire; carIs the tire sidewall deflection stiffness of the rear wheel; a is the distance from the center of mass to the front axle; b is the distance from the center of mass to the rear axle; l ═ a + b; m is the mass of the automobile;
step 3.2), the electronic control unit responds to deltarAnd a preset brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to respectively generate K deltarBraking force;
and 4), when the steering characteristic parameter is A and the brake characteristic parameter is B, the steer-by-wire emergency steering mode comprises the following steps:
step 4.1), the electronic control unit is in accordance with βrAnd ideal yaw rate βwCalculating the additional rotation angle q required by the front wheelθThe calculation formula is as follows:
wherein ,
step 4.2), the electronic sub-control unit according to thetarControlling the steering motor to work to make the front wheel of the automobile rotate at an angle of i thetar+qθ；
Step 4.3), the electronic control unit responds to deltarAnd a preset first brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to respectively generate K deltarBraking force;
and 5), when the steering characteristic parameter is B and the braking characteristic parameter is A, the system works in an emergency braking mode:
step 5.1), the electronic control unit according to thetarControlling the steering motor to work to make the front wheel of the automobile rotate at an angle of i thetar；
Step 5.2), the electronic control unit η according to the front wheel steering anglerCalculating the slip ratio of the automobile according to the wheel speed of the front wheel;
step 5.3), the electronic control unit responds to deltarAnd a preset brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to respectively generate K deltarBraking force;
and 5.4), adjusting the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder according to the automobile slip ratio:
step 5.4.1), when the slip ratio is less than 15%, simultaneously increasing the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder according to a preset braking force step length until the slip ratio is equal to 15%;
step 5.4.2), when the slip ratio is larger than 15%, reducing the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder simultaneously according to a preset braking force step length until the slip ratio is equal to 15%;
step 6), when the steering characteristic parameter is A and the braking characteristic parameter is A, the steer-by-wire emergency collision avoidance mode:
step 6.1), the electronic control unit is in accordance with βrAnd ideal yaw rate βwCalculating the additional rotation angle q required by the front wheelθThe calculation formula is as follows:
step 6.2), the electronic control unit η according to the front wheel steering anglerCalculating the slip ratio of the automobile according to the wheel speed of the front wheel;
step 6.3), the electronic control unit according to the steering angle η of the front wheels in the vehicle curverAnd yawAngular velocity βrAnd velocity VrSolving a current stability index Q:
the current stability index Q is used for representing understeer, neutral steering and oversteer, when Q is 0, the current stability index Q is neutral steering, when Q is more than 0, the current stability index Q is understeer, and when Q is less than 0, the current stability index Q is oversteer;
step 6.4), the electronic control unit responds to deltarAnd a preset brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to respectively generate K deltarBraking force;
step 6.5), adjusting the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder according to the current stability index Q:
step 6.5.1), when turning left and turning over, the electronic control unit applies extra K to the right front brake wheel cylinder1Delta braking force, the braking force of the right front brake wheel cylinder is K delta + K1δ, wherein ,K1The braking coefficient is a preset second braking coefficient;
step 6.5.2), when turning left and turning understeer, the electronic control unit applies an extra K to the left rear brake wheel cylinder2Delta braking force, the braking force of the left rear brake wheel cylinder is K delta + K2δ, wherein ,K2The braking coefficient is a preset second braking coefficient;
step 6.5.3), when the vehicle turns to the right and turns over, the electronic control unit applies extra K to the front left brake wheel cylinder1Delta braking force, the braking force of the left front brake wheel cylinder is K delta + K1δ；
Step 6.5.4), when the vehicle turns to the right and the steering is insufficient, the electronic control unit applies extra K to the right rear brake wheel cylinder2Delta braking force, making the braking force of the right rear brake wheel cylinder K delta + K2δ。
Compared with the prior art, the invention adopting the technical scheme has the following technical effects:
1. the invention provides a mode conversion and control method, which can solve the problem of joint control in a steering-by-wire and braking system;
2. different steering and braking working modes can be switched according to different automobile running conditions and driver operation, and an automobile body control method under an emergency condition is provided.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic diagram of a steering control flow according to the present invention.
In the figure, 1-a steering wheel, 2-a steering wheel angle sensor, 3-a road sensing motor and a first speed reducing mechanism, 4-an electronic control unit, 5-an electromagnetic clutch, 6-a steering motor and a second speed reducing mechanism, 7-a gear rack sensor, 8-a left front brake wheel cylinder and 9-a brake pedal sensor.
Detailed Description
The technical scheme of the invention is further explained in detail by combining the attached drawings:
the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, components are exaggerated for clarity.
As shown in fig. 1, the present invention discloses a steer-by-wire and brake system, comprising a steer-by-wire system, a steer-by-wire system and an electronic control unit:
the steer-by-wire system comprises a steering wheel, a steering wheel corner sensor, an upper steering column, a lower steering column, a road feel motor, a first speed reducing mechanism, an electromagnetic clutch, a steering motor, a second speed reducing mechanism, a front shaft, a front wheel corner sensor, a vehicle speed sensor, a wheel speed sensor and a yaw angle speed sensor;
the upper end of the upper steering column is fixedly connected with the steering wheel, the lower end of the upper steering column is connected with the upper end of the lower steering column through the electromagnetic clutch, and the electromagnetic clutch is in a disconnected state;
the steering wheel angle sensor is arranged on the upper steering column and used for acquiring a steering wheel angle and transmitting the steering wheel angle to the electronic control unit;
an output shaft of the road feel motor is connected with the upper steering column through the first speed reducing mechanism and used for transmitting road feel feedback to a steering wheel through the upper steering column;
the lower end of the lower steering column is connected with the front shaft through the gear rack steering gear;
two ends of the front shaft are respectively connected with a left front wheel and a right front wheel of the automobile;
an output shaft of the steering motor is connected with the lower steering column through the second speed reducing mechanism and is used for transmitting steering torque to the lower steering column so as to drive two front wheels of the automobile to steer through a gear rack steering gear;
the front wheel rotation angle sensor and the wheel speed sensor are arranged on a front wheel of the automobile, are respectively used for obtaining the front wheel rotation angle and the front wheel speed of the automobile and transmitting the front wheel rotation angle and the front wheel speed to the electronic control unit;
the vehicle speed sensor and the yaw rate sensor are arranged on the automobile and are respectively used for obtaining the vehicle speed and the yaw rate of the automobile and transmitting the vehicle speed and the yaw rate to the electronic control unit;
the brake-by-wire system comprises a brake pedal sensor, a left front wheel brake cylinder, a right front wheel brake cylinder, a left rear wheel brake cylinder and a right rear wheel brake cylinder;
the brake pedal sensor is arranged at the tail end of an automobile brake pedal and used for collecting pedal signals when a driver brakes and transmitting the pedal signals to the electronic control unit;
the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder are respectively used for controlling the braking of the left front wheel, the right front wheel, the left rear wheel and the right rear wheel;
the electronic control unit is electrically connected with the steering wheel angle sensor, the front wheel rotation angle sensor, the vehicle speed sensor, the wheel speed sensor, the yaw rate sensor, the brake pedal sensor, the road sense motor, the steering motor, the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder respectively, and is used for controlling the road sense motor, the steering motor, the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to work according to data measured by the steering wheel angle sensor, the front wheel rotation angle sensor, the vehicle speed sensor, the wheel speed sensor, the yaw rate sensor and the brake pedal sensor.
As shown in fig. 2, the invention also discloses a control method based on the steer-by-wire and brake system, comprising the following steps:
step 1), steering wheel angular velocity omega measured by steering wheel angular sensorrSteering wheel angle thetar(ii) a Brake pedal opening delta measured by brake pedal sensorrBrake pedal rate of change αrA front wheel rotation angle η measured by the front wheel rotation angle sensor and the wheel speed sensor respectivelyrAnd front wheel speed; the vehicle speed sensor, the yaw rate sensor and the slip rate sensor respectively measure the vehicle speed V of the current vehiclerAnd yaw rate βr；
Step 2), the electronic control unit converts the steering wheel angular speed omegarAnd a preset steering wheel angular velocity threshold omegamComparing, and comparing thetarAnd presetSteering wheel angle threshold thetamComparing and comparing the automobile speed VrAnd a preset vehicle speed threshold value VmComparing the opening delta of the brake pedalrAnd a brake pedal opening degree threshold value deltamBy comparison, the brake pedal rate of change αrAnd a brake pedal rate of change threshold αmAnd (3) comparison:
step 2.1), when thetarGreater than thetamAnd V isrGreater than VmWhen, or when thetarLess than thetam、ωrGreater than omegamAnd V isrGreater than VmWhen the steering characteristic parameter is A, the steering characteristic parameter is set as A; otherwise, making the steering characteristic parameter be B;
step 2.2) when drGreater than deltam、αrGreater than αmAnd V isrGreater than VmWhen the braking characteristic parameter is A; otherwise, making the braking characteristic parameter be B;
and step 3), when the steering characteristic parameter is B and the braking characteristic parameter is B, the system works in an online control normal working mode:
step 3.1), the electronic control unit according to thetarControlling the steering motor to work to make the front wheel of the automobile rotate at an angle of i thetar, wherein ：Cafthe tire sidewall deflection stiffness of the front wheel tire; carIs the tire sidewall deflection stiffness of the rear wheel; a is the distance from the center of mass to the front axle; b is the distance from the center of mass to the rear axle; l ═ a + b; m is the mass of the automobile;
step 3.2), the electronic control unit responds to deltarAnd a preset brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to respectively generate K deltarBraking force;
and 4), when the steering characteristic parameter is A and the brake characteristic parameter is B, the steer-by-wire emergency steering mode comprises the following steps:
step 4.1)Electronic control unit according to βrAnd ideal yaw rate βwCalculating the additional rotation angle q required by the front wheelθThe calculation formula is as follows:
wherein ,
step 4.2), the electronic sub-control unit according to thetarControlling the steering motor to work to make the front wheel of the automobile rotate at an angle of i thetar+qθ；
Step 4.3), the electronic control unit responds to deltarAnd a preset first brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to respectively generate K deltarBraking force;
and 5), when the steering characteristic parameter is B and the braking characteristic parameter is A, the system works in an emergency braking mode:
step 5.1), the electronic control unit according to thetarControlling the steering motor to work to make the front wheel of the automobile rotate at an angle of i thetar；
Step 5.2), the electronic control unit η according to the front wheel steering anglerCalculating the slip ratio of the automobile according to the wheel speed of the front wheel;
step 5.3), the electronic control unit responds to deltarAnd a preset brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to respectively generate K deltarBraking force;
and 5.4), adjusting the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder according to the automobile slip ratio:
step 5.4.1), when the slip ratio is less than 15%, simultaneously increasing the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder according to a preset braking force step length until the slip ratio is equal to 15%;
step 5.4.2), when the slip ratio is larger than 15%, reducing the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder simultaneously according to a preset braking force step length until the slip ratio is equal to 15%;
step 6), when the steering characteristic parameter is A and the braking characteristic parameter is A, the steer-by-wire emergency collision avoidance mode:
step 6.1), the electronic control unit is in accordance with βrAnd ideal yaw rate βwCalculating the additional rotation angle q required by the front wheelθThe calculation formula is as follows:
step 6.2), the electronic control unit η according to the front wheel steering anglerCalculating the slip ratio of the automobile according to the wheel speed of the front wheel;
step 6.3), the electronic control unit according to the steering angle η of the front wheels in the vehicle curverYaw rate βrAnd velocity VrSolving a current stability index Q:
the current stability index Q is used for representing understeer, neutral steering and oversteer, when Q is 0, the current stability index Q is neutral steering, when Q is more than 0, the current stability index Q is understeer, and when Q is less than 0, the current stability index Q is oversteer;
step 6.4), the electronic control unit responds to deltarAnd a preset brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder,K delta is generated by the left rear wheel brake cylinder and the right rear wheel brake cylinder respectivelyrBraking force;
step 6.5), adjusting the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder according to the current stability index Q:
step 6.5.1), when turning left and turning over, the electronic control unit applies extra K to the right front brake wheel cylinder1Delta braking force, the braking force of the right front brake wheel cylinder is K delta + K1δ, wherein ,K1The braking coefficient is a preset second braking coefficient;
step 6.5.2), when turning left and turning understeer, the electronic control unit applies an extra K to the left rear brake wheel cylinder2Delta braking force, the braking force of the left rear brake wheel cylinder is K delta + K2δ, wherein ,K2The braking coefficient is a preset second braking coefficient;
step 6.5.3), when the vehicle turns to the right and turns over, the electronic control unit applies extra K to the front left brake wheel cylinder1Delta braking force, the braking force of the left front brake wheel cylinder is K delta + K1δ；
Step 6.5.4), when the vehicle turns to the right and the steering is insufficient, the electronic control unit applies extra K to the right rear brake wheel cylinder2Delta braking force, making the braking force of the right rear brake wheel cylinder K delta + K2δ。
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only illustrative of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (2)

1. A steer-by-wire and brake system, comprising a steer-by-wire system, a steer-by-wire system and an electronic control unit:
the steer-by-wire system comprises a steering wheel, a steering wheel corner sensor, an upper steering column, a lower steering column, a road feel motor, a first speed reducing mechanism, an electromagnetic clutch, a steering motor, a second speed reducing mechanism, a front shaft, a front wheel corner sensor, a vehicle speed sensor, a wheel speed sensor and a yaw angle speed sensor;
the upper end of the upper steering column is fixedly connected with the steering wheel, the lower end of the upper steering column is connected with the upper end of the lower steering column through the electromagnetic clutch, and the electromagnetic clutch is in a disconnected state;
the steering wheel angle sensor is arranged on the upper steering column and used for acquiring a steering wheel angle and transmitting the steering wheel angle to the electronic control unit;
an output shaft of the road feel motor is connected with the upper steering column through the first speed reducing mechanism and used for transmitting road feel feedback to a steering wheel through the upper steering column;
the lower end of the lower steering column is connected with the front shaft through the gear rack steering gear;
two ends of the front shaft are respectively connected with a left front wheel and a right front wheel of the automobile;
an output shaft of the steering motor is connected with the lower steering column through the second speed reducing mechanism and is used for transmitting steering torque to the lower steering column so as to drive two front wheels of the automobile to steer through a gear rack steering gear;
the front wheel rotation angle sensor and the wheel speed sensor are arranged on a front wheel of the automobile, are respectively used for obtaining the front wheel rotation angle and the front wheel speed of the automobile and transmitting the front wheel rotation angle and the front wheel speed to the electronic control unit;
the vehicle speed sensor and the yaw rate sensor are arranged on the automobile and are respectively used for obtaining the vehicle speed and the yaw rate of the automobile and transmitting the vehicle speed and the yaw rate to the electronic control unit;
the brake-by-wire system comprises a brake pedal sensor, a left front wheel brake cylinder, a right front wheel brake cylinder, a left rear wheel brake cylinder and a right rear wheel brake cylinder;
the brake pedal sensor is arranged at the tail end of an automobile brake pedal and used for collecting pedal signals when a driver brakes and transmitting the pedal signals to the electronic control unit;
the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder are respectively used for controlling the braking of the left front wheel, the right front wheel, the left rear wheel and the right rear wheel;
the electronic control unit is electrically connected with the steering wheel angle sensor, the front wheel rotation angle sensor, the vehicle speed sensor, the wheel speed sensor, the yaw rate sensor, the brake pedal sensor, the road sense motor, the steering motor, the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder respectively, and is used for controlling the road sense motor, the steering motor, the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to work according to data measured by the steering wheel angle sensor, the front wheel rotation angle sensor, the vehicle speed sensor, the wheel speed sensor, the yaw rate sensor and the brake pedal sensor.
2. The control method of a steer-by-wire and brake system according to claim 1, comprising the steps of:
step 1), steering wheel angular velocity omega measured by steering wheel angular sensorrSteering wheel angle thetar(ii) a Brake pedal opening delta measured by brake pedal sensorrBrake pedal rate of change αrA front wheel rotation angle η measured by the front wheel rotation angle sensor and the wheel speed sensor respectivelyrAnd front wheel speed; the vehicle speed sensor, the yaw rate sensor and the slip rate sensor respectively measure the vehicle speed V of the current vehiclerAnd yaw rate βr；
Step 2), the electronic control unit converts the steering wheel angular speed omegarAnd a preset steering wheel angular velocity threshold omegamComparing, and comparing thetarAnd a preset steering wheel angle threshold thetamComparing and comparing the automobile speed VrAnd a preset vehicle speed threshold value VmComparing the opening delta of the brake pedalrAnd a brake pedal opening degree threshold value deltamBy comparison, the brake pedal rate of change αrAnd a brake pedal rate of change threshold αmAnd (3) comparison:
step 2.1), when thetarGreater than thetamAnd V isrGreater than VmWhen, or when thetarLess than thetam、ωrGreater than omegamAnd V isrGreater than VmWhen the steering characteristic parameter is A, the steering characteristic parameter is set as A; otherwise, making the steering characteristic parameter be B;
step 2.2) of the method,when deltarGreater than deltam、αrGreater than αmAnd V isrGreater than VmWhen the braking characteristic parameter is A; otherwise, making the braking characteristic parameter be B;
and step 3), when the steering characteristic parameter is B and the braking characteristic parameter is B, the system works in an online control normal working mode:
step 3.1), the electronic control unit according to thetarControlling the steering motor to work to make the front wheel of the automobile rotate at an angle of i thetar, wherein ：Cafthe tire sidewall deflection stiffness of the front wheel tire; carIs the tire sidewall deflection stiffness of the rear wheel; a is the distance from the center of mass to the front axle; b is the distance from the center of mass to the rear axle; l ═ a + b; m is the mass of the automobile;
step 3.2), the electronic control unit responds to deltarAnd a preset brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to respectively generate K deltarBraking force;
and 4), when the steering characteristic parameter is A and the brake characteristic parameter is B, the steer-by-wire emergency steering mode comprises the following steps:
step 4.1), the electronic control unit is in accordance with βrAnd ideal yaw rate βwCalculating the additional rotation angle q required by the front wheelθThe calculation formula is as follows:
wherein ,
step 4.2), the electronic sub-control unit according to thetarControlling the steering motor to work to make the front wheel of the automobile rotate at an angle of i thetar+qθ；
Step 4.3), the electronic control unit responds to deltarAnd a preset first braking coefficient K controls the left front wheelThe brake wheel cylinder, the right front wheel brake wheel cylinder, the left rear wheel brake wheel cylinder and the right rear wheel brake wheel cylinder respectively generate K deltarBraking force;
and 5), when the steering characteristic parameter is B and the braking characteristic parameter is A, the system works in an emergency braking mode:
step 5.1), the electronic control unit according to thetarControlling the steering motor to work to make the front wheel of the automobile rotate at an angle of i thetar；
Step 5.2), the electronic control unit η according to the front wheel steering anglerCalculating the slip ratio of the automobile according to the wheel speed of the front wheel;
step 5.3), the electronic control unit responds to deltarAnd a preset brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to respectively generate K deltarBraking force;
and 5.4), adjusting the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder according to the automobile slip ratio:
step 5.4.1), when the slip ratio is less than 15%, simultaneously increasing the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder according to a preset braking force step length until the slip ratio is equal to 15%;
step 5.4.2), when the slip ratio is larger than 15%, reducing the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder simultaneously according to a preset braking force step length until the slip ratio is equal to 15%;
step 6), when the steering characteristic parameter is A and the braking characteristic parameter is A, the steer-by-wire emergency collision avoidance mode:
step 6.1), the electronic control unit is in accordance with βrAnd ideal yaw rate βwCalculating the additional rotation angle q required by the front wheelθThe calculation formula is as follows:
step 6.2), the electronic control unitAccording to front wheel steering angle ηrCalculating the slip ratio of the automobile according to the wheel speed of the front wheel;
step 6.3), the electronic control unit according to the steering angle η of the front wheels in the vehicle curverYaw rate βrAnd velocity VrSolving a current stability index Q:
the current stability index Q is used for representing understeer, neutral steering and oversteer, when Q is 0, the current stability index Q is neutral steering, when Q is more than 0, the current stability index Q is understeer, and when Q is less than 0, the current stability index Q is oversteer;
step 6.4), the electronic control unit responds to deltarAnd a preset brake coefficient K controls the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder to respectively generate K deltarBraking force;
step 6.5), adjusting the braking force of the left front wheel brake cylinder, the right front wheel brake cylinder, the left rear wheel brake cylinder and the right rear wheel brake cylinder according to the current stability index Q:
step 6.5.1), when turning left and turning over, the electronic control unit applies extra K to the right front brake wheel cylinder1Delta braking force, the braking force of the right front brake wheel cylinder is K delta + K1δ, wherein ,K1The braking coefficient is a preset second braking coefficient;
step 6.5.2), when turning left and turning understeer, the electronic control unit applies an extra K to the left rear brake wheel cylinder2Delta braking force, the braking force of the left rear brake wheel cylinder is K delta + K2δ, wherein ,K2The braking coefficient is a preset second braking coefficient;
step 6.5.3), when the vehicle turns to the right and turns over, the electronic control unit applies extra K to the front left brake wheel cylinder1Delta braking force, the braking force of the left front brake wheel cylinder is K delta + K1δ；
Step 6.5.4), when the vehicle turns to the right and the steering is insufficient, the electronic control unit applies extra K to the right rear brake wheel cylinder2Delta braking force, making the braking force of the right rear brake wheel cylinder K delta + K2δ。
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