CN113815718A - Wire control automobile steering control method based on three-motor control - Google Patents
Wire control automobile steering control method based on three-motor control Download PDFInfo
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- CN113815718A CN113815718A CN202111091314.3A CN202111091314A CN113815718A CN 113815718 A CN113815718 A CN 113815718A CN 202111091314 A CN202111091314 A CN 202111091314A CN 113815718 A CN113815718 A CN 113815718A
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- 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
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- 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
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Abstract
The invention relates to a steer-by-wire control method of an automobile based on three-motor control, which overcomes the defect that a steering structure is difficult to realize intelligent active control compared with the prior art. The invention comprises the following steps: acquiring drive-by-wire automobile data; calculating the torque of the force sensing motor; establishing a steering module model; establishing a relation equation between the steering wheel angle and the front wheel angle; and the three motors are controlled by wire to perform intelligent active control. According to the invention, the real-time turning angle of the front wheel corresponding to the steering wheel when the driver operates the steering wheel is obtained by simplifying the modeling and the model of the steering system, the force sensing motor and the steering executing motor, so that a correct steering instruction is given to the steering executing motor, and the vehicle steering is realized.
Description
Technical Field
The invention relates to the technical field of steer-by-wire, in particular to a steer-by-wire control method of an automobile based on three-motor control.
Background
In a traditional mechanical steering system, a driver transmits a target steering angle to steering wheels by operating a steering gear and other steering system transmission components, the angle and force transmission characteristics of the steering system are fixed, and under the conditions of different vehicle speeds, lateral accelerations and yaw rates, an automobile can present nonlinear steering characteristics, so that the driver needs to concentrate on operating the steering gear and make adjustments all the time, the physical and mental consumption of the driver is greatly increased, the operating stability of the driver is influenced, and potential safety hazards are brought to driving safety. In addition, in extreme conditions (such as sideslip and steering instability), the possibility that a driver loses control over the driving stability of the automobile is greatly increased, or misoperation occurs under emergency conditions, and finally traffic accidents occur.
With the progress of automobile technology, in the fortieth past, designers have developed a hydraulic power steering system (HPS) which helps drivers to steer vehicles by means of the hydraulic pressure generated by an automobile engine oil pump, so as to relieve the burden of the drivers. When the hydraulic power steering technology is gradually mature and the system safety is increasingly reliable, the hydraulic power steering is widely applied to various large automobile companies. With the development of the technology, automobile designers develop an electric control hydraulic power steering system (EHPS) and an electric power steering system (EPS), and help drivers to obtain the power-assisted characteristics required by steering operation under various working conditions through software aided design and calculation, so that the physical consumption of the drivers during steering is further effectively reduced, and the driving safety is improved.
Although the EPS applies a plurality of modern new technologies, new devices and new theories, compared with the traditional steering system, the EPS system has great progress in the aspects of optimizing the steering performance of the vehicle, improving the electronic integration level of the vehicle and saving energy and protecting environment, but still has certain limitations. Because the steering mechanism still belongs to the mechanical steering system in the aspect of composition, when a driver realizes the steering intention, the driver mainly controls the steering wheel through hand force to obtain the steering corner to realize the steering of the vehicle, and the intelligent active control of the vehicle still can not be realized under the limit working condition or the emergency state.
The Steer-By-Wire System (SBW) cancels the mechanical connection between the steering wheel and the steered wheels, and transmits the control command of the driver in the form of an electric signal. In the application of the automobile steering system, the steer-by-wire system can be used as an intelligent electric control system, so that the traditional mechanical or hydraulic steering system is replaced, the degree of freedom of the design of the vehicle angle transmission characteristic and the force transmission characteristic is improved, the vehicle is more efficiently controlled, and the driving safety is greatly improved.
Disclosure of Invention
The invention aims to solve the defect that the steering structure in the prior art is difficult to realize intelligent active control, and provides a steer-by-wire automobile steering control method based on three-motor control to solve the problems.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a steer-by-wire control method of an automobile based on three-motor control comprises the following steps:
acquiring drive-by-wire automobile data: acquiring dynamic data and structural data of a steering system; acquiring finished automobile real-time parameters and finished automobile structure parameters of the three-motor steer-by-wire automobile;
calculating the torque of the force sensing motor: simplifying a force sensing motor module to a steering column by establishing a steering wheel and the force sensing motor module model to obtain a force sensing motor torque;
establishing a steering module model: establishing a steering module model consisting of a steering execution motor and speed reducing mechanisms of the two motors;
establishing a relation equation between the steering wheel angle and the front wheel steering angle: establishing a transmission ratio characteristic based on that the lateral acceleration gain and the yaw rate gain are not influenced by the vehicle speed or the input of a steering wheel, setting the transmission ratio characteristic as an ideal transmission ratio characteristic, and establishing a relation equation between the steering wheel angle and the front wheel steering angle;
three-motor steer-by-wire intelligent active control: the vehicle control unit obtains torque and corner information of a steering wheel, an internal control strategy calculates and obtains the corners of the two steering motors and torque of the force sensing motor according to the current working condition, steering is achieved, and the hand force of a driver is relieved through the force sensing motor.
The acquisition of the drive-by-wire automobile data comprises the following steps:
acquisition of dynamic data and structural data of the steering system: obtaining real-time steering wheel torque M in steering process through sensorsSteering wheel angle theta, real-time torque data and steering correcting moment M in the steering processzFriction moment M acting on steering wheel on road surfaceFObtaining the parameters of the steer-by-wire structure of the automobile, including the moment of inertia J of the steer-by-wire assemblyswDamping coefficient B of steering system assemblyswSteering wheel assembly friction MfA total steering gear ratio i;
acquiring finished automobile real-time parameters and finished automobile structure parameters of the three-motor steer-by-wire automobile: obtaining real-time front wheel average turning angle delta in running of three-motor steer-by-wire automobilefLongitudinal vehicle speed v, lateral acceleration ay(ii) a Acquiring the whole structure parameters of the three-motor steer-by-wire automobile: wheelbase l, distance l from automobile mass center to front axlefDistance l from the center of mass of the automobile to the rear axlerFront wheel side cornering stiffness CfRear wheel side cornering stiffness Cr。
The calculation of the force sensing motor torque comprises the following steps:
establishing a steering wheel and force sensing motor module model, wherein the steering wheel and force sensing motor module model comprises a steering system mechanical part, performing mechanical analysis on the steering wheel and force sensing motor module and simplifying a steering column, and obtaining the model according to a Newton second law:
Ms＝Jswθ”+Bswθ'+(MZ+MF)/i+Mf，
wherein M issFor steering wheel real-time torque, JswIs the moment of inertia of the steering system assembly, theta is the steering wheel angle, BswAs damping coefficient of steering system assembly, MzFor steering return torque, MFThe friction torque acting on the steering wheel for the road surface, i is the longitudinal transmission ratio of the steering system, MfFriction for a steering wheel assembly;
simplify the power-sensing motor module to the steering column, obtain power-sensing motor torque:
Ma3＝Ja3δ″a3+Ba3δ'a3+(MZ+MF)/(i*ia3)+Mf，
in the formula, Ma3For force-sensing motor output torque, Ja3For the moment of inertia of the force-sensitive motor structure, deltaa3Electromagnetic angle of force-sensitive motor, Ba3For outputting torque to a force-sensitive motor, ia3For the transmission ratio of the force-sensitive motor reduction mechanism, MzFor steering return torque, MFThe friction torque acting on the steering wheel for the road surface, i is the longitudinal transmission ratio of the steering system, MfFriction for a steering wheel assembly;
the total resisting moment of the three-motor steer-by-wire system is expressed as follows:
(MZ+MF)/i＝(Ma1*ia1+Ma2*ia2)，
in the formula, Ma1Output torque for a left-hand steering actuator motor, Ma2Output torque of the electric motor for right-hand steeringa1For left-hand steering actuator motor reduction gear ratio, ia2For left-hand steering, the transmission ratio of the reduction gear of the electric motor, MzFor steering return torque, MFThe friction torque acted on a steering wheel by a road surface is represented by i, and the longitudinal transmission ratio of a steering system is represented by i;
then, the following steps are obtained:
Ma3＝Ja3δ″a3+Ba3δ'a3+(Ma1*ia1+Ma2*ia2)/ia3+Mf，
Mf＝CF*sgnδ'，
in the formula, Ma3For force-sensing motor output torque, Ja3For the moment of inertia of the force-sensitive motor structure, deltaa3Electromagnetic angle of force-sensitive motor, Ba3For force-sensing motor output torque, Ma1Output torque for a left-hand steering actuator motor, Ma2Output torque of the electric motor for right-hand steeringa1For left-hand steering actuator motor reduction gear ratio, ia2For left-hand steering actuator motor reduction gear ratio, ia3For the transmission ratio of the force-sensitive motor reduction mechanism, MfFor steering wheel assembly friction, CFIs a constant determined by the system moment of inertia and the axle load;
control and turn to the permanent-magnet machine that motor and power of feeling all adopted same model, its reduction ratio of reduction gears equals then:
ia1＝ia2＝ia3，
the torque expression of the force-sensing motor is obtained as follows:
Ma3＝Ja3δ″a3+Ba3δ'a3+(Ma1+Ma2)+CF*sgnδ'。
the establishment of the steering module model comprises the following steps:
if the force sensing motor and the steering actuating motor both adopt the same permanent magnet motor, then a modeling equation of a steering module consisting of the steering actuating motor and the speed reducing mechanisms of the two motors is obtained as follows:
Ja1δ″a1+Ba1δ'a1＝Tem1-TL，
δ″a1＝(Tem1-TL-Ba1δ'a1)/Ja1，
in the formula, Ja1Is the rotational inertia of the steering actuator motor, Ba1For motor damping, deltaa1Is the angle of rotation of the motor, Tem1Output torque for steering actuator motor, and output torque M for left steering actuator motora1Equivalence, TLIs the motor load;
analyzing a steering execution motor, wherein the electromagnetic torque of the motor is as follows:
Tem1＝kbIa1
the motor armature voltage is then:
Ua1＝La1I'a1+Kbδ'a1+Rf1Ia1，
in the formula, kbIs the motor back electromotive force constant, Ia1For motor armature current, Ua1For steering the actuator voltage, La1Is the motor armature inductance, Rf1Is the sum of armature resistances of a steering execution motor;
the mathematical expression for sorting and simplifying the steering actuating motor to obtain the steering module model is as follows:
δ″a1＝(Tem1-TL-Ba1δ'a1)/Ja1，
in the formula, deltaa1Is the angle of rotation of the motor, Tem1Output torque for steering actuator motor, and output torque M for left steering actuator motora1Equivalence, TLIs the motor load, Ba1For motor damping, Ja1Is a steering actuating motorThe moment of inertia of the machine.
The method for establishing the relation equation between the steering wheel angle and the front wheel steering angle comprises the following steps:
setting the lateral acceleration gain constant, deriving the ideal gear ratio from the formula to be set depending on the lateral acceleration gain KyThe numerical value of (A):
δf＝θsw*[l2+mv2(lf/Cr-lr/Cf)]/(Ky*v2l)，
Ky＝θsw/ay；
in the formula, deltafIs the mean angle of rotation, theta, of the front wheelswIs the steering wheel angle, l is the wheel base, v is the longitudinal speed, m is the vehicle mass, lfIs the distance from the center of mass to the front axle,/, of the automobilerIs the distance from the center of mass to the rear axle, CfFor front wheel cornering stiffness, CrFor rear wheel cornering stiffness, KyAs a gain of lateral acceleration, ayIs the lateral acceleration;
setting yaw angular velocity gain constant, KwIs the steering wheel angle value and the vehicle yaw rate gain value wsBy the ratio of (A) to (B)wThe adjustment of the value to control the desired gear ratio of the vehicle is expressed as follows:
δf＝θsw*[l2+mv2(lf/Cr-lr/Cf)]/(Kw*v2l)
Kw＝θsw/ws；
an ideal transmission ratio formula determined by considering the lateral acceleration gain and the yaw rate gain is obtained by combining the relation equation of the steering wheel angle and the front wheel steering angle into
The intelligent active control of three-motor steer-by-wire comprises the following steps:
acquiring a target current steering wheel turning angle and steering wheel torque generated when a driver operates a steering wheel through a sensor on a steering column;
the sensor inputs the acquired data into the processor, the processor outputs the front wheel target rotation angle under the current real-time working condition through the steering module model, the voltages of the force sensing motor and the steering executing motor are obtained through calculation, and meanwhile, electric signals are formed and transmitted to the left and right steering executing motors;
the left and right steering executing motor receives the expected electric signal to form the motor rotation angle deltaa1Respectively driving the front wheel hub to form a front wheel corner delta around the suspensionfThe intelligent active control is realized, and meanwhile, the force sensing motor forms a reverse torque M with the hand force of a drivera3And the hand strength of the driver is reduced.
Advantageous effects
Compared with the prior art, the steering control method of the wire-controlled automobile based on three-motor control obtains the real-time turning angle of the front wheel when the driver operates the steering wheel by simplifying the modeling and the model of the steering system, the force sensing motor and the steering executing motor, thereby issuing a correct steering instruction to the steering executing motor and realizing the steering of the automobile.
The invention can further cancel mechanical parts between the steering wheel and the steering wheels, improve the initiative and the intellectualization of the steering system, improve the steering control strategy in real time in the optimization in the future, add algorithms of steering power-assisted active centering, steering operation anti-interference and the like, and improve the safety and the stability of the automobile steering without changing automobile hardware. Meanwhile, mechanical parts are replaced by a control algorithm strategy, so that the structure of the automobile chassis is simplified, and the dead weight of the automobile body is reduced.
Drawings
FIG. 1 is a sequence diagram of the method of the present invention;
FIG. 2 is a block diagram of a steer-by-wire system of the prior art;
FIG. 3 is a block diagram of a steer-by-wire system in which the present invention is employed;
wherein, the steering system comprises a 1-steering system pull rod, a 2-force sensing motor module and a 3-steering executing motor.
Detailed Description
So that the manner in which the above recited features of the present invention can be understood and readily understood, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings, wherein:
as shown in fig. 2, the conventional steer-by-wire automobile only cancels a mechanical connection part between a steering wheel and a steering system tie rod 1, adopts a force sensing motor to connect the steering wheel, obtains a steering wheel angle and a steering column torque when a driver operates, drives the steering system tie rod 1 to drive wheels to complete steering movement, and adds a power steering motor to assist steering. However, as can be seen from the figure, the conventional steer-by-wire system does not completely eliminate the tie rod 1 between the steering wheel and the steering wheel, which results in that the driver still needs to rely on his own driving technique and the like to directly operate the automobile to achieve steering when operating the steering system, and such a steering system is a great waste of physical power and energy for the driver. Therefore, the invention focuses on a method for replacing a mechanical steering system with a control strategy to realize the steer-by-wire of an automobile, when a driver operates a steering wheel, a control unit obtains a target front wheel turning angle by reading sensor data on a steering column and then sends related electric signals to a left executing motor and a right executing motor to complete the steering.
The method for completing the steering by adopting the control strategy reduces the burden of a driver, improves the driving safety of the automobile to a certain extent, and simultaneously, the control algorithm for assisting the automatic steering aligning and the steering anti-interference which are not completed temporarily can realize the upgrading and the perfection of the system only by operating the related electric control unit when the control algorithm is perfected in the future, and the method for changing the chassis structure and adding the related mechanical control as shown in figure 2 is not needed. As shown in fig. 3, the steer-by-wire vehicle applied in the present invention does not need the tie rod 1 in fig. 2, and only needs the force sensing motor module 2 directly connected to the steering wheel and the steering executing motor 3 connected to the wheel hub to complete the design of the steering strategy.
As shown in FIG. 1, the steering control method of the wire-controlled automobile based on the three-motor control comprises the following steps:
the method comprises the following steps of firstly, obtaining drive-by-wire automobile data. Acquiring dynamic data and structural data of a steering system; and acquiring the whole vehicle real-time parameters and the whole vehicle structure parameters of the three-motor steer-by-wire vehicle.
(1) Acquisition of dynamic data and structural data of the steering system: obtaining real-time steering wheel torque M in steering process through sensorsSteering wheel angle theta, real-time torque data and steering correcting moment M in the steering processzFriction moment M acting on steering wheel on road surfaceFObtaining the parameters of the steer-by-wire structure of the automobile, including the moment of inertia J of the steer-by-wire assemblyswDamping coefficient B of steering system assemblyswSteering wheel assembly friction MfA total steering gear ratio i;
(2) acquiring finished automobile real-time parameters and finished automobile structure parameters of the three-motor steer-by-wire automobile: obtaining real-time front wheel average turning angle delta in running of three-motor steer-by-wire automobilefLongitudinal vehicle speed v, lateral acceleration ay(ii) a Acquiring the whole structure parameters of the three-motor steer-by-wire automobile: wheelbase l, distance l from automobile mass center to front axlefDistance l from the center of mass of the automobile to the rear axlerFront wheel side cornering stiffness CfRear wheel side cornering stiffness Cr。
And secondly, calculating the torque of the force sensing motor: and simplifying the force sensing motor module to the steering column by establishing the force sensing motor module model to obtain the torque of the force sensing motor. After a mechanical connecting part between a steering column and a steering system pull rod 1 is cancelled, the reaction force of wheels acting on a steering wheel through the mechanical connecting part cannot be transmitted to the hands of a driver, the obtained force sensing motor can replace the original mechanical part to act, the torque is directly acted on the steering column, the road condition information is fed back to the driver, and meanwhile, the hand force of the driver is reduced;
the method comprises the following specific steps:
(1) establishing a force-sensitive motor module model, carrying out mechanical analysis on the force-sensitive motor module model, simplifying a steering column, and obtaining the force-sensitive motor module model according to a Newton second law:
Ms＝Jswθ”+Bswθ'+(MZ+MF)/i+Mf，
wherein M issIs a steering wheelTime torque, JswIs the moment of inertia of the steering system assembly, theta is the steering wheel angle, BswAs damping coefficient of steering system assembly, MzFor steering return torque, MFThe friction torque acting on the steering wheel for the road surface, i is the longitudinal transmission ratio of the steering system, MfIs the steering wheel assembly friction.
(2) Simplify the power-sensing motor module to the steering column, obtain power-sensing motor torque:
Ma3＝Ja3δ″a3+Ba3δ'a3+(MZ+MF)/(i*ia3)+Mf，
in the formula, Ma3For force-sensing motor output torque, Ja3For the moment of inertia of the force-sensitive motor structure, deltaa3Electromagnetic angle of force-sensitive motor, Ba3For outputting torque to a force-sensitive motor, ia3For the transmission ratio of the force-sensitive motor reduction mechanism, MzFor steering return torque, MFThe friction torque acting on the steering wheel for the road surface, i is the longitudinal transmission ratio of the steering system, MfFriction for a steering wheel assembly;
the total resisting moment of the three-motor steer-by-wire system is expressed as follows:
(MZ+MF)/i＝(Ma1*ia1+Ma2*ia2)，
in the formula, Ma1Output torque for a left-hand steering actuator motor, Ma2Output torque of the electric motor for right-hand steeringa1For left-hand steering actuator motor reduction gear ratio, ia2For left-hand steering, the transmission ratio of the reduction gear of the electric motor, MzFor steering return torque, MFThe friction torque acted on a steering wheel by a road surface is represented by i, and the longitudinal transmission ratio of a steering system is represented by i;
then, the following steps are obtained:
Ma3＝Ja3δ″a3+Ba3δ'a3+(Ma1*ia1+Ma2*ia2)/ia3+Mf，
Mf＝CF*sgnδ'，
in the formula, Ma3For force-sensing motor output torque, Ja3For the moment of inertia of the force-sensitive motor structure, deltaa3Electromagnetic angle of force-sensitive motor, Ba3For force-sensing motor output torque, Ma1Output torque for a left-hand steering actuator motor, Ma2Output torque of the electric motor for right-hand steeringa1For left-hand steering actuator motor reduction gear ratio, ia2For left-hand steering actuator motor reduction gear ratio, ia3For the transmission ratio of the force-sensitive motor reduction mechanism, MfFor steering wheel assembly friction, CFIs a constant determined by the system moment of inertia and the axle load;
set for about turn to the permanent-magnet machine that motor and force feel the motor and all adopt same model, its reduction ratio of reduction gears equals, then:
ia1＝ia2＝ia3，
the torque expression of the force-sensing motor is obtained as follows:
Ma3＝Ja3δ″a3+Ba3δ'a3+(Ma1+Ma2)+CF*sgnδ'。
thirdly, establishing a steering module model: and establishing a steering module model consisting of a steering execution motor and speed reducing mechanisms of the two motors. In the application of the invention, a steering system pull rod and other connecting pieces between the steering column and the front steering wheel are eliminated, and the steering is formed only through the action of the steering motor connected with the frame. The invention can further optimize the structure of the traditional wire-controlled steering automobile, lighten the mass of the whole automobile, and can not directly form a steering angle through the operation of the steering wheel under the condition that no mechanical part forms constraint on wheels and the steering wheel, so a steering module model between the steering wheel and a steering executing motor and between the steering executing motor and a speed reducing mechanism of the two motors needs to be established.
The method comprises the following specific steps:
(1) if the force sensing motor and the steering actuating motor both adopt the same permanent magnet motor, then a modeling equation of a steering module consisting of the steering actuating motor and the speed reducing mechanisms of the two motors is obtained as follows:
Ja1δ″a1+Ba1δ'a1＝Tem1-TL，
δ″a1＝(Tem1-TL-Ba1δ'a1)/Ja1，
in the formula, Ja1Is the rotational inertia of the steering actuator motor, Ba1For motor damping, deltaa1Is the angle of rotation of the motor, Tem1Output torque for steering actuator motor, and output torque M for left steering actuator motora1Equivalence, TLIs the motor load;
analyzing a steering execution motor, wherein the electromagnetic torque of the motor is as follows:
Tem1＝kbIa1
the motor armature voltage is then:
Ua1＝La1I'a1+Kbδ'a1+Rf1Ia1，
in the formula, kbIs the motor back electromotive force constant, Ia1For motor armature current, Ua1For steering the actuator voltage, La1Is the motor armature inductance, Rf1Is the sum of armature resistances of the steering actuator motor.
(2) The mathematical expression for sorting and simplifying the steering actuating motor to obtain the steering module model is as follows:
δ″a1＝(Tem1-TL-Ba1δ'a1)/Ja1，
in the formula, deltaa1Is the angle of rotation of the motor, Tem1Output torque for steering actuator motor, and output torque M for left steering actuator motora1Equivalence, TLIs the motor load, Ba1For motor damping, Ja1Is the rotational inertia of the steering actuator motor.
Fourthly, establishing a relation equation between the steering wheel angle and the front wheel steering angle: and establishing a gear ratio characteristic based on that the lateral acceleration gain and the yaw rate gain are not influenced by the vehicle speed or the input of a steering wheel, setting the gear ratio characteristic as an ideal gear ratio characteristic, and establishing a relation equation of the steering wheel angle and the front wheel steering angle. According to the invention, a mechanical connecting part between a steering wheel and front wheels of a drive-by-wire automobile is replaced by a relation equation of the steering wheel angle and the front wheels and an ideal transmission ratio, compared with the traditional steer-by-wire automobile, the mechanical part of a tie rod of a steering system cannot be changed after being manufactured, the formed steer-by-wire automobile transmission ratio and the like can only be changed within a certain range, and the steering requirements can not be met under specific working conditions; the difficulty is that the automobile is influenced by various parameters when steering, and the ideal transmission ratio and the relationship between the steering wheel angle and the front wheel steering angle are difficult to determine;
the method for establishing the relation equation between the steering wheel angle and the front wheel steering angle comprises the following steps:
(1) setting the lateral acceleration gain constant, deriving the ideal gear ratio from the formula to be set depending on the lateral acceleration gain KyThe numerical value of (A):
δf＝θsw*[l2+mv2(lf/Cr-lr/Cf)]/(Ky*v2l)，
Ky＝θsw/ay；
in the formula, deltafIs the mean angle of rotation, theta, of the front wheelswIs the steering wheel angle, l is the wheel base, v is the longitudinal speed, m is the vehicle mass, lfIs the distance from the center of mass to the front axle,/, of the automobilerIs the distance from the center of mass to the rear axle, CfFor front wheel cornering stiffness, CrFor rear wheel cornering stiffness, KyAs a gain of lateral acceleration, ayIs the lateral acceleration;
(2) setting yaw angular velocity gain constant, KwIs the steering wheel angle value and the vehicle yaw rate gain value wsBy the ratio of (A) to (B)wThe adjustment of the value to control the desired gear ratio of the vehicle is expressed as follows:
δf＝θsw*[l2+mv2(lf/Cr-lr/Cf)]/(Kw*v2l)
Kw＝θsw/ws；
(3) an ideal transmission ratio formula determined by considering the lateral acceleration gain and the yaw rate gain is obtained by combining the relation equation of the steering wheel angle and the front wheel steering angle into
And fifthly, controlling the steering by wire by the three motors intelligently and actively. The vehicle control unit obtains torque and corner information of a steering wheel, an internal control strategy calculates and obtains the corners of the two steering motors and torque of the force sensing motor according to the current working condition, steering is achieved, and the hand force of a driver is relieved through the force sensing motor.
(1) A sensor on a steering column acquires a target current steering wheel turning angle and steering wheel torque generated when a driver operates a steering wheel;
(2) the sensor inputs the acquired data into the processor, the processor outputs the real-time target turning angle of the front wheel under the current working condition through the established turning module model and the relation between the steering wheel and the front wheel turning angle, and simultaneously calculates the voltage of the force sensing motor and the turning executing motor under the current working condition to form an electric signal which is transmitted to the left and right turning executing motors.
(3) The left and right steering executing motor receives the expected corner electric signal to form the motor corner deltaa1Respectively driving the front wheel hub to form a front wheel corner delta around the suspensionfThe intelligent active control is realized, the force sensing motor receives an expected torque electric signal, and the 'road feel' information is fed back to the driver, so that the hand strength of the driver is reduced.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (6)
1. A steer-by-wire control method of an automobile based on three-motor control is characterized by comprising the following steps:
11) acquiring drive-by-wire automobile data: acquiring dynamic data and structural data of a steering system; acquiring finished automobile real-time parameters and finished automobile structure parameters of the three-motor steer-by-wire automobile;
12) calculating the torque of the force sensing motor: simplifying a force sensing motor module to a steering column by establishing a steering wheel and the force sensing motor module model to obtain a force sensing motor torque;
13) establishing a steering module model: establishing a steering module model consisting of a steering execution motor and speed reducing mechanisms of the two motors;
14) establishing a relation equation between the steering wheel angle and the front wheel steering angle: establishing a transmission ratio characteristic based on that the lateral acceleration gain and the yaw rate gain are not influenced by the vehicle speed or the input of a steering wheel, setting the transmission ratio characteristic as an ideal transmission ratio characteristic, and establishing a relation equation between the steering wheel angle and the front wheel steering angle;
15) three-motor steer-by-wire intelligent active control: the vehicle control unit obtains torque and corner information of a steering wheel, an internal control strategy calculates and obtains the corners of the two steering motors and torque of the force sensing motor according to the current working condition, steering is achieved, and the hand force of a driver is relieved through the force sensing motor.
2. The method for controlling the steering of the vehicle by wire based on the three-motor control according to claim 1, wherein the obtaining of the data of the vehicle by wire comprises the following steps:
21) acquisition of dynamic data and structural data of the steering system: obtaining real-time steering wheel torque M in steering process through sensorsSteering wheel angle theta, real-time torque data and steering correcting moment M in the steering processzFriction moment M acting on steering wheel on road surfaceFObtaining structural parameters of a steer-by-wire vehicle including rotation of a steer-by-wire assemblyInertia JswDamping coefficient B of steering system assemblyswSteering wheel assembly friction MfA total steering gear ratio i;
22) acquiring finished automobile real-time parameters and finished automobile structure parameters of the three-motor steer-by-wire automobile: obtaining real-time front wheel average turning angle delta in running of three-motor steer-by-wire automobilefLongitudinal vehicle speed v, lateral acceleration ay(ii) a Acquiring the whole structure parameters of the three-motor steer-by-wire automobile: wheelbase l, distance l from automobile mass center to front axlefDistance l from the center of mass of the automobile to the rear axlerFront wheel side cornering stiffness CfRear wheel side cornering stiffness Cr。
3. The steer-by-wire control method based on three-motor control of the claim 1, wherein the calculation of the force sensing motor torque comprises the following steps:
31) establishing a steering wheel and force sensing motor module model, wherein the steering wheel and force sensing motor module model comprises a steering system mechanical part, performing mechanical analysis on the steering wheel and force sensing motor module and simplifying a steering column, and obtaining the model according to a Newton second law:
Ms＝Jswθ”+Bswθ'+(MZ+MF)/i+Mf，
wherein M issFor steering wheel real-time torque, JswIs the moment of inertia of the steering system assembly, theta is the steering wheel angle, BswAs damping coefficient of steering system assembly, MzFor steering return torque, MFThe friction torque acting on the steering wheel for the road surface, i is the longitudinal transmission ratio of the steering system, MfFriction for a steering wheel assembly;
32) simplify the power-sensing motor module to the steering column, obtain power-sensing motor torque:
Ma3＝Ja3δ″a3+Ba3δ'a3+(MZ+MF)/(i*ia3)+Mf，
in the formula, Ma3For force-sensing motor output torque, Ja3For the moment of inertia of the force-sensitive motor structure, deltaa3Electromagnetic angle of force-sensitive motor, Ba3For outputting torque to a force-sensitive motor, ia3For the transmission ratio of the force-sensitive motor reduction mechanism, MzFor steering return torque, MFThe friction torque acting on the steering wheel for the road surface, i is the longitudinal transmission ratio of the steering system, MfFriction for a steering wheel assembly;
the total resisting moment of the three-motor steer-by-wire system is expressed as follows:
(MZ+MF)/i＝(Ma1*ia1+Ma2*ia2)，
in the formula, Ma1Output torque for a left-hand steering actuator motor, Ma2Output torque of the electric motor for right-hand steeringa1For left-hand steering actuator motor reduction gear ratio, ia2For left-hand steering, the transmission ratio of the reduction gear of the electric motor, MzFor steering return torque, MFThe friction torque acted on a steering wheel by a road surface is represented by i, and the longitudinal transmission ratio of a steering system is represented by i;
then, the following steps are obtained:
Ma3＝Ja3δ″a3+Ba3δ'a3+(Ma1*ia1+Ma2*ia2)/ia3+Mf，
Mf＝CF*sgnδ'，
in the formula, Ma3For force-sensing motor output torque, Ja3For the moment of inertia of the force-sensitive motor structure, deltaa3Electromagnetic angle of force-sensitive motor, Ba3For force-sensing motor output torque, Ma1Output torque for a left-hand steering actuator motor, Ma2Output torque of the electric motor for right-hand steeringa1For left-hand steering actuator motor reduction gear ratio, ia2For left-hand steering actuator motor reduction gear ratio, ia3For the transmission ratio of the force-sensitive motor reduction mechanism, MfFor steering wheel assembly friction, CFIs a constant determined by the system moment of inertia and the axle load;
control and turn to the permanent-magnet machine that motor and power of feeling all adopted same model, its reduction ratio of reduction gears equals then:
ia1＝ia2＝ia3，
the torque expression of the force-sensing motor is obtained as follows:
Ma3＝Ja3δ″a3+Ba3δ'a3+(Ma1+Ma2)+CF*sgnδ'。
4. the steering control method of the steer-by-wire automobile based on the three-motor control as claimed in claim 1, wherein the establishment of the steering module model comprises the following steps:
41) if the force sensing motor and the steering actuating motor both adopt the same permanent magnet motor, then a modeling equation of a steering module consisting of the steering actuating motor and the speed reducing mechanisms of the two motors is obtained as follows:
Ja1δ″a1+Ba1δ'a1＝Tem1-TL，
δ″a1＝(Tem1-TL-Ba1δ'a1)/Ja1，
in the formula, Ja1Is the rotational inertia of the steering actuator motor, Ba1For motor damping, deltaa1Is the angle of rotation of the motor, Tem1Output torque for steering actuator motor, and output torque M for left steering actuator motora1Equivalence, TLIs the motor load;
analyzing a steering execution motor, wherein the electromagnetic torque of the motor is as follows:
Tem1＝kbIa1
the motor armature voltage is then:
Ua1＝La1I'a1+Kbδ'a1+Rf1Ia1，
in the formula, kbIs the motor back electromotive force constant, Ia1For motor armature current, Ua1For steering the actuator voltage, La1Is the motor armature inductance, Rf1Is the sum of armature resistances of a steering execution motor;
42) the mathematical expression for sorting and simplifying the steering actuating motor to obtain the steering module model is as follows:
δ″a1＝(Tem1-TL-Ba1δ'a1)/Ja1，
in the formula, deltaa1Is the angle of rotation of the motor, Tem1Output torque for steering actuator motor, and output torque M for left steering actuator motora1Equivalence, TLIs the motor load, Ba1For motor damping, Ja1Is the rotational inertia of the steering actuator motor.
5. The method for controlling the steering of the steer-by-wire automobile based on the three-motor control of claim 1, wherein the step of establishing the relation between the steering wheel angle and the front wheel steering angle comprises the following steps:
51) setting the lateral acceleration gain constant, deriving the ideal gear ratio from the formula to be set depending on the lateral acceleration gain KyThe numerical value of (A):
δf＝θsw*[l2+mv2(lf/Cr-lr/Cf)]/(Ky*v2l)，
Ky＝θsw/ay；
in the formula, deltafIs the mean angle of rotation, theta, of the front wheelswIs the steering wheel angle, l is the wheel base, v is the longitudinal speed, m is the vehicle mass, lfIs the distance from the center of mass to the front axle,/, of the automobilerIs the distance from the center of mass to the rear axle, CfFor front wheel cornering stiffness, CrFor rear wheel cornering stiffness, KyAs a gain of lateral acceleration, ayIs the lateral acceleration;
52) setting yaw angular velocity gain constant, KwIs the steering wheel angle value and the vehicle yaw rate gain value wsBy the ratio of (A) to (B)wThe adjustment of the value to control the desired gear ratio of the vehicle is expressed as follows:
δf＝θsw*[l2+mv2(lf/Cr-lr/Cf)]/(Kw*v2l)
Kw＝θsw/ws；
53) an ideal transmission ratio formula determined by considering the lateral acceleration gain and the yaw rate gain is obtained by combining the relation equation of the steering wheel angle and the front wheel steering angle into
6. The method for controlling the steering of the three-motor-controlled-wire-controlled automobile according to claim 1, wherein the intelligent active control of the three-motor-controlled-wire steering comprises the following steps:
61) a sensor on a steering column acquires a target current steering wheel turning angle and steering wheel torque generated when a driver operates a steering wheel;
62) the sensor inputs the acquired data into the processor, the processor outputs the front wheel target rotation angle under the current real-time working condition through the steering module model, the voltages of the force sensing motor and the steering executing motor are obtained through calculation, and meanwhile, electric signals are formed and transmitted to the left and right steering executing motors;
63) the left and right steering executing motor receives the expected electric signal to form the motor rotation angle deltaa1Respectively driving the front wheel hub to form a front wheel corner delta around the suspensionfThe intelligent active control is realized, and meanwhile, the force sensing motor forms a reverse torque M with the hand force of a drivera3And the hand strength of the driver is reduced.
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