CN110962626A - Self-adaptive electronic differential control method for multi-shaft hub motor driven vehicle - Google Patents
Self-adaptive electronic differential control method for multi-shaft hub motor driven vehicle Download PDFInfo
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- B60—VEHICLES IN GENERAL
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- 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
- B60L15/2036—Electric differentials, e.g. for supporting steering vehicles
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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
- B60L15/32—Control or regulation of multiple-unit electrically-propelled vehicles
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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
- 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
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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
- B60L2220/00—Electrical machine types; Structures or applications thereof
- B60L2220/40—Electrical machine applications
- B60L2220/44—Wheel Hub motors, i.e. integrated in the wheel hub
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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
- B60L2240/00—Control parameters of input or output; Target parameters
- B60L2240/10—Vehicle control parameters
- B60L2240/12—Speed
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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
- B60L2240/00—Control parameters of input or output; Target parameters
- B60L2240/10—Vehicle control parameters
- B60L2240/24—Steering angle
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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
- 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
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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
- B60L2250/00—Driver interactions
- B60L2250/26—Driver interactions by pedal actuation
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- 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
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- 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 provides a self-adaptive electronic differential control method for a multi-shaft hub motor driven vehicle, aims to solve the problems that the electronic differential control of the existing electric wheel driven vehicle cannot adapt to various running conditions, the motor performance requirement is high and the like, and belongs to an automobile control system. The control method comprises the following steps: s1, establishing an 8 x 8 in-wheel motor independent drive vehicle body motion equation; s2, establishing a wheel vertical jumping model; s3, establishing a wheel rotation dynamic equation; and S4, making a control strategy, and selecting the driving torque as a control parameter to control the motor. The invention has the advantages that the power distribution characteristic of the traditional automobile power transmission is simulated in a mode of motor torque instruction control and rotating speed follow-up, so that the multi-shaft hub motor driven vehicle has better differential performance under three working conditions of steering, uneven road surface and different wheel rolling radii, and the accuracy of electronic differential control and the self-adaptive capacity of the system under various working conditions are improved.
Description
Technical Field
The invention belongs to an automobile control system, and particularly relates to a self-adaptive electronic differential control method for a multi-shaft hub motor driven vehicle.
Background
The hub motor independently drives the vehicle, and a transmission system of the traditional vehicle is omitted, and meanwhile, the driving torque of each wheel is independently controllable, and information such as torque, rotating speed and the like can be accurately fed back in real time, so that the transmission efficiency of the whole vehicle is greatly improved, and the arrangement design is more flexible. The electronic differential mainly replaces a mechanical differential of a traditional vehicle, and the control stability of the vehicle during running is ensured by coordinating all driving motors. Because the dead weight and the load of the multi-shaft heavy vehicle are large, the running working condition is complex and changeable, and the differential problem is relatively more prominent and serious, the self-adaptive capacity of the hub motor electronic differential controller is also required to be higher. A balance equation is established according to the actual stress state of each wheel of the multi-axis in-wheel motor driven vehicle, and meanwhile, the requirements of the differential performance of the whole vehicle under various running working conditions are considered, so that the self-adaptive electronic differential control method of the multi-axis in-wheel motor driven vehicle is provided, the accuracy of the electronic differential control of the in-wheel motor and the self-adaptive capacity of system control are further improved, the electronic differential control strategy is guaranteed to be capable of adapting to various differential working conditions, and the differential performance is better.
Some vehicle enterprises in japan, europe, america, etc. such as honda, audi, general, etc. have successively applied the electronic differential system to the in-wheel motor driven vehicle. In recent years, domestic researchers have also conducted relevant research on electronic differential control systems in order to fully utilize the outstanding advantages of electronic differential systems to meet actual driving needs. For example, Chinese patent publication No. CN110116635A, publication No. 2019-08-13, discloses an electronic differential control method for a two-wheel independent drive vehicle. The control method is based on a double-wheel independent driving system, the driving wheels on two sides output basically the same driving torque by adjusting the rotating speed difference of two motors, and good turning differential speed can be realized. Chinese patent publication No. CN108177693A, publication No. 2018-06-19, discloses an electronic differential control system of a hub-driven electric automobile. The system calculates the target rotating speeds of the inner and outer driving wheels through the measured wheel steering angle and the target driving speed, and completes closed-loop control on the rotating speed of the driving wheels through the deviation calculation with the actual rotating speed, so that the actual speed of the driving wheels follows the target speed, and differential control is realized. According to the invention, aiming at the requirements of the differential performance of the whole vehicle under various running conditions, the motor torque control is realized by carrying out closed-loop feedback on the rotating speed signal of the hub motor, and the power distribution characteristic from a power system to a differential of the traditional vehicle is simulated, so that the multi-shaft hub motor driven vehicle realizes better differential performance under various running conditions, and has stronger robustness and adaptability.
Disclosure of Invention
The invention aims to solve the technical problems that an electronic differential control system of the existing multi-axis in-wheel motor driven vehicle cannot realize differential coordination of all wheels under various working conditions, cannot ensure that the system can realize self-adaptive control and the like, and provides a self-adaptive electronic differential control method of the multi-axis in-wheel motor driven vehicle.
In order to solve the technical problems, the invention is realized by adopting the following technical scheme: comprises the following steps:
1. a self-adaptive electronic differential control method of a multi-shaft hub motor driven vehicle is characterized by comprising the following steps:
firstly, establishing an 8 multiplied by 8 wheel hub motor independent driving vehicle motion equation;
establishing a coordinate system according to 6 degrees of freedom of longitudinal, lateral, vertical, yaw, pitch and roll motions of the vehicle body, wherein the positive direction of the x axis is positive along the longitudinal symmetric line of the vehicle body; the y-axis is positive to the right along the transverse position of the automobile through the mass center; the z axis is vertically downward positive according to the right hand rule; establishing a vehicle body motion equation;
the method comprises the following steps of considering the interaction force of a suspension and a wheel on the basis of the stress of the wheel of a traditional vehicle, and establishing a wheel rotation kinetic equation as shown in a formula (1):
in the formula: i isw-moment of inertia of the wheel
Tq-wheel drive torque
FdLongitudinal forces between the tyre and the ground
TbBraking torque
Mω-wheel mass
ξ -coefficient of action
In the formula (1), the last term on the right side of the equation is the counterforce formed on the ground by the action of the wheel shaft on the wheel center of the driven wheel, the driving wheel and the driven wheel dynamics problem can be simultaneously expressed by the supplementary term (1), and the ξ value is determined by the formula (2):
secondly, calculating the actual movement speed of the wheel center of the wheel;
calculating the horizontal movement speed of the wheel center by using the formula (3):
in the formula: v. ofhiHorizontal movement velocity of the wheel center of each wheel
u-longitudinal speed of vehicle body
v-lateral velocity of vehicle body
r-vehicle body yaw rate
LiDistances of the axes to the centre of mass in the plane
δi-deflection angle of each wheel
Calculating the vertical movement speed w of the wheel center by using the formula (4)ui：
In the formula: muiUnsprung masses at each wheel
wui-wheel wheelsVelocity of vertical movement of heart
KuiVertical stiffness of the tire
ZriUnevenness of the road surface on which the wheels are located
ZuiHeight of wheel center of mass
CuiVertical damping of the tyre
wri-rate of change of road surface unevenness at wheels
Fvi-forces acting on the suspension in the direction of the z-axis from the wheels
Bi-structural parameters of the suspension
Calculating the actual movement velocity v at the wheel center of the wheel by using the formula (5)wi：
Thirdly, calculating the comprehensive vehicle speed;
obtaining the expected speed value V of the driver according to the accelerator-vehicle speed table look-upR(ii) a Calculating to obtain the actual speed V of the vehicle by using the rotating speed of the wheelsZ(ii) a Carrying out weighted calculation according to the obtained driver expected vehicle speed value and the vehicle actual vehicle speed value to obtain a comprehensive vehicle speed value, as shown in formula (6):
VT＝AVR+BVZ(6)
in the formula: vT-integrated vehicle speed
A. B is a weighting coefficient, and is calibrated through experiments;
fourthly, calculating target torque of each driving motor;
taking the opening degree of an accelerator pedal and the current steering wheel angle as control inputs, and obtaining the expected speed of each wheel center by utilizing the geometrical relationship of the structure of the vehicle according to the comprehensive vehicle speed value calculated by the formula (6); inputting the calculated actual speed at the wheel center and the expected speed at each wheel center into a PID controller, and calculating the target torque of each driving motor by using an equation (7):
TTi＝KP(vTi-vwi)+KI(vTi-vwi)+KD(vTi-vwi) (7)
in the formula: t isTi-target torques of the drive motors
vTi-desired speed at the wheel center of each wheel
KP、KI、KD-PID controller parameters, calibrated by experiment;
the actual rotating speed of the wheels is determined by the balance point of the driving torque of the motor and the stress of the actual wheels, and is fed back to the whole vehicle controller to realize closed loop, the self-adaptive differential speed of each wheel is realized according to the strategy of torque instruction control and rotating speed follow-up, and the whole vehicle control system outputs a driving motor torque instruction signal according to the motion state of the vehicle, so that the accelerator pedal controls the vehicle speed and the motor torque at the same time; the motor torque can be controlled by open loop or closed loop feedback.
2. The adaptive electronic differential control method for a multi-axle in-wheel motor-driven vehicle according to claim 1, wherein the wheel differential operation comprises: A. when the vehicle is steered to run, the vehicle generates yaw motion, so that the acceleration at the wheel center of each wheel generates difference, and the wheel speed of each wheel is different; B. when the vehicle runs on an uneven road surface, the lengths of tracks passed by the wheel centers of the wheels are different, so that the rotating speeds of the wheels are different; C. when the rolling radius of each wheel is different, the rotating speed of each wheel is different because each wheel core passes through the same track length.
3. The adaptive electronic differential control method for a multi-axle in-wheel motor-driven vehicle according to claim 1, wherein the electronic differential control system comprises: the system comprises a main controller, hub motors, a controller system and a CAN bus communication network.
Compared with the prior art, the invention has the beneficial effects that:
1. the self-adaptive electronic differential control method of the multi-shaft hub motor driven vehicle can adapt to various running working conditions by adopting the torque instruction control and the rotating speed follow-up mode of the hub motor, so that the wheels freely rotate according to the self stress state, and the self-adaptive electronic differential control method has better differential performance and strong robustness;
2. according to the self-adaptive electronic differential control method for the multi-shaft hub motor driven vehicle, disclosed by the invention, the motor torque control is realized by carrying out closed-loop feedback on the rotating speed signal of the hub motor, the power distribution characteristic from a power system to a differential mechanism of a traditional vehicle can be simulated, the control mode of the electronic differential system is more reasonable, and the characteristic of independent driving of the hub motor is fully exerted;
3. according to the self-adaptive electronic differential control method for the multi-shaft in-wheel motor driven vehicle, the interaction force of the suspension and the wheel and the problems of the driving wheel and the driven wheel are considered on the basis of the stress of the wheel of the traditional vehicle, a wheel rotation dynamic equation which can reflect the influence of the driving, braking and road surface effects of the driving wheel and the interaction of the vehicle body and the wheel on the motion of the driven wheel is established, and the rotation dynamic analysis requirement of the wheel independently driven by the in-wheel motor is fully met.
Drawings
The invention is further described with reference to the accompanying drawings in which:
FIG. 1 is a flow chart of a method for adaptive electronic differential control of a multi-axle in-wheel motor driven vehicle according to the present invention;
FIG. 2 is a schematic view of a full rotational dynamics model of a wheel of a multi-axle in-wheel motor-driven vehicle according to the present invention;
fig. 3 is a schematic diagram of a suspension model of a multi-shaft in-wheel motor driven vehicle according to the invention.
Detailed Description
The invention is described in detail below with reference to the attached drawing figures:
the invention discloses a self-adaptive electronic differential control method of a multi-shaft in-wheel motor driven vehicle, which utilizes deviation values of expected vehicle speed and wheel speed signals of a driver to obtain target torque of a driving motor, carries out torque control on each wheel and feeds back actual rotating speed of the wheel to a vehicle controller to form closed-loop control, thereby realizing torque instruction control and rotating speed follow-up control mode of the in-wheel motor, simulating power distribution characteristics from a power system to a differential mechanism of a traditional vehicle, effectively avoiding the slip phenomenon of each wheel due to the differential mechanism, and ensuring that the multi-shaft in-wheel motor driven vehicle has better differential performance under three running conditions of different steering, uneven road surfaces and wheel rolling radiuses.
Referring to fig. 1, the adaptive electronic differential control method for a multi-axle in-wheel motor driven vehicle according to the present invention mainly includes: establishing an 8 x 8 wheel hub motor independent drive vehicle body motion equation; calculating the actual movement speed of the wheel center of the wheel; calculating a comprehensive vehicle speed; and calculating the target torque of each driving motor. The following step specifically describes an adaptive electronic differential control method of a multi-shaft hub motor driven vehicle.
Comprises the following steps:
firstly, establishing an 8 multiplied by 8 wheel hub motor independent drive vehicle body motion equation;
establishing a coordinate system according to 6 degrees of freedom of longitudinal, lateral, vertical, yaw, pitch and roll motions of the vehicle body, wherein the x axis is positive forwards along a longitudinal symmetric line of the vehicle body; the y-axis is positive to the right along the transverse position of the automobile through the mass center; the z-axis is positive vertically downward according to the right hand rule. According to the stress condition of the vehicle, the influence between the motions in all directions is comprehensively considered, and the motion equation of the vehicle body is calculated by the following equations (1), (2), (3), (4), (5) and (6):
longitudinal movement
Lateral movement
Vertical movement
In the formula: mt-total mass of the vehicle
u-longitudinal speed of vehicle body
v-lateral velocity of vehicle body
w-vehicle body vertical velocity
r-vehicle body yaw rate
p-vehicle body roll velocity
q-vehicle body pitch angle velocity
MsSprung mass
h' -distance from sprung mass center of mass to side-tipping axle
FfTotal running resistance
FxiThe forces acting on the suspension by the wheels in the direction of the x-axis
FyiForces acting on the suspension by the wheels in the direction of the y-axis
Fvi-forces acting on the suspension in the direction of the z-axis from the wheels
Bi-structural parameters of the suspension
Pitching movement
Yaw motion
Roll motion
In the formula: i isxxsMoment of inertia of sprung mass about the x-axis
IyysMoment of inertia of sprung mass about y-axis
IzzsMoment of inertia of sprung mass about z-axis
IxxMoment of inertia of the entire vehicle about the x-axis
IyyMoment of inertia of the entire vehicle about the y-axis
IzzMoment of inertia of the vehicle about the z-axis
Ai-structural parameters of the suspension
T-track
LiDistances of the axes to the centre of mass in the plane
Phi-vehicle body side inclination angle
Referring to fig. 2, the dynamic model of the complete rotation of the vehicle wheel driven by the multi-shaft in-wheel motor is shown schematically. Using equation (7), the angular acceleration of the driven wheel at the wheel center contact point p during non-braking is calculated:
in the formula: omegapAngular velocity of the wheel centre about the contact point p
rωWheel rolling radius
vω-wheel center velocity
The wheel rotation angular acceleration and the angular acceleration at the wheel center around the ground point are equal, and equation (7) can be expressed as equation (8):
in the formula: omegao-angular velocity of wheel rotation
The method comprises the following steps of establishing a wheel rotation dynamic equation according to the formula (9) by considering the interaction force of a suspension and a wheel on the basis of the stress of the wheel of a traditional vehicle:
in the formula: i isw-moment of inertia of the wheel
Tq-wheel drive torque
FdLongitudinal forces between the tyre and the ground
TbBraking torque
Mω-wheel mass
ξ -coefficient of action
In the formula (9), the last term on the right side of the equation is the counterforce formed on the ground by the action of the wheel shaft on the wheel center of the driven wheel, the driving wheel and the driven wheel dynamics problem can be simultaneously expressed by the formula (9) through the supplementary term, and the ξ value is determined by the formula (10)
Secondly, calculating the actual movement speed of the wheel center of the wheel;
calculating the horizontal movement speed of the wheel center by using the formula (11):
in the formula: v. ofhiHorizontal movement velocity of the wheel center of each wheel
δi-deflection angle of each wheel
Referring to fig. 3, the multi-shaft in-wheel motor driven vehicle adopts a Macpherson independent suspension, wherein C' is a sprung mass center of mass; kui、KsiVertical stiffness of each tire and suspension is respectively; cui、CsiRespectively corresponding damping; zriUnevenness of a road surface on which the wheels are located; zuiIs the height of the mass center of each wheel; zsIs the sprung mass centre of mass height; a isi、bi、diIs a suspension geometry parameter. The vertical wheel runout is calculated according to the formula (12):
in the formula: muiUnsprung masses at each wheel
wui-vertical movement speed of wheel
wri-rate of change of road surface unevenness at wheels
Suspension structural parameter A in equations (3), (4), (6), (12)i、BiCalculated by the following formulas (13), (14), respectively:
calculating the actual velocity v at the wheel center of the wheel using equation (15)wi：
Thirdly, calculating the comprehensive vehicle speed;
obtaining the expected speed value V of the driver according to the accelerator-vehicle speed table look-upR(ii) a Calculating to obtain the actual speed V of the vehicle by using the rotating speed of the wheelsZ(ii) a And performing weighted calculation according to the obtained driver expected vehicle speed value and the vehicle actual vehicle speed value to obtain a comprehensive vehicle speed value, as shown in formula (16):
VT＝AVR+BVZ(16)
in the formula: vT-integrated vehicle speed
A. B is a weighting coefficient, and is calibrated through experiments;
fourthly, calculating target torque of each driving motor;
taking the opening degree of an accelerator pedal and the current steering wheel angle as control inputs, and obtaining the expected speed of each wheel center by utilizing the geometrical relationship of the structure of the vehicle according to the comprehensive vehicle speed value calculated by the formula (16); inputting the calculated actual speed at the wheel center and the expected speed at each wheel center into a PID controller, and calculating each driving motor target torque by using an equation (17):
TTi＝KP(vTi-vwi)+KI(vTi-vwi)+KD(vTi-vwi) (17)
in the formula: t isTi-target torques of the drive motors
vTi-desired speed at the wheel center of each wheel
KP、KI、KD-PID controller parameters, calibrated by experiment;
the actual rotating speed of the wheels is determined by the balance point of the driving torque of the motor and the stress of the actual wheels, and is fed back to the whole vehicle controller to realize closed loop, the self-adaptive differential speed of each wheel is realized according to the strategy of torque instruction control and rotating speed follow-up, and the whole vehicle control system outputs a driving motor torque instruction signal according to the motion state of the vehicle, so that the accelerator pedal controls the vehicle speed and the motor torque at the same time; the motor torque can be controlled by open loop or closed loop feedback.
The invention discloses a self-adaptive electronic differential control method of a multi-axis hub motor driven vehicle, which is characterized in that the wheel differential working condition comprises the following steps: A. when the vehicle is steered to run, the vehicle generates yaw motion, so that the acceleration at the wheel center of each wheel generates difference, and the wheel speed of each wheel is different; B. when the vehicle runs on an uneven road surface, the lengths of tracks passed by the wheel centers of the wheels are different, so that the rotating speeds of the wheels are different; C. when the rolling radius of each wheel is different, the rotating speed of each wheel is different because each wheel core passes through the same track length.
The invention discloses a self-adaptive electronic differential control method of a multi-shaft hub motor driven vehicle, which is characterized in that an electronic differential control system comprises: the system comprises a main controller, hub motors, a controller system and a CAN bus communication network.
Claims (3)
1. A self-adaptive electronic differential control method of a multi-shaft hub motor driven vehicle is characterized by comprising the following steps:
firstly, establishing an 8 multiplied by 8 wheel hub motor independent driving vehicle motion equation;
establishing a coordinate system according to 6 degrees of freedom of longitudinal, lateral, vertical, yaw, pitch and roll motions of the vehicle body, wherein the positive direction of the x axis is positive along the longitudinal symmetric line of the vehicle body; the y-axis is positive to the right along the transverse position of the automobile through the mass center; the z axis is vertically downward positive according to the right hand rule; establishing a vehicle body motion equation;
the method comprises the following steps of considering the interaction force of a suspension and a wheel on the basis of the stress of the wheel of a traditional vehicle, and establishing a wheel rotation kinetic equation as shown in a formula (1):
in the formula: i isw-moment of inertia of the wheel
Tq-wheel drive torque
FdLongitudinal forces between the tyre and the ground
TbBraking torque
Mω-wheel mass
ξ -coefficient of action
In the formula (1), the last term on the right side of the equation is the counterforce formed on the ground by the action of the wheel shaft on the wheel center of the driven wheel, the driving wheel and the driven wheel dynamics problem can be simultaneously expressed by the supplementary term (1), and the ξ value is determined by the formula (2):
secondly, calculating the actual movement speed of the wheel center of the wheel;
calculating the horizontal movement speed of the wheel center by using the formula (3):
in the formula: v. ofhiHorizontal movement velocity of the wheel center of each wheel
u-longitudinal speed of vehicle body
v-lateral velocity of vehicle body
r-vehicle body yaw rate
LiDistances of the axes to the centre of mass in the plane
δi-deflection angle of each wheel
Calculating the vertical movement speed w of the wheel center by using the formula (4)ui：
In the formula: muiUnsprung masses at each wheel
wui-vertical movement speed of wheel center
KuiVertical stiffness of the tire
ZriUnevenness of the road surface on which the wheels are located
ZuiHeight of wheel center of mass
CuiVertical damping of the tyre
wri-rate of change of road surface unevenness at wheels
Fvi-forces acting on the suspension in the direction of the z-axis from the wheels
Bi-structural parameters of the suspension
Calculating the actual movement velocity v at the wheel center of the wheel by using the formula (5)wi：
Thirdly, calculating the comprehensive vehicle speed;
obtaining the expected speed value V of the driver according to the accelerator-vehicle speed table look-upR(ii) a Calculating to obtain the actual speed V of the vehicle by using the rotating speed of the wheelsZ(ii) a Carrying out weighted calculation according to the obtained driver expected vehicle speed value and the vehicle actual vehicle speed value to obtain a comprehensive vehicle speed value, as shown in formula (6):
VT＝AVR+BVZ(6)
in the formula: vT-integrated vehicle speed
A. B is a weighting coefficient, and is calibrated through experiments;
fourthly, calculating target torque of each driving motor;
taking the opening degree of an accelerator pedal and the current steering wheel angle as control inputs, and obtaining the expected speed of each wheel center by utilizing the geometrical relationship of the structure of the vehicle according to the comprehensive vehicle speed value calculated by the formula (6); inputting the calculated actual speed at the wheel center and the expected speed at each wheel center into a PID controller, and calculating the target torque of each driving motor by using an equation (7):
TTi＝KP(vTi-vwi)+KI(vTi-vwi)+KD(vTi-vwi) (7)
in the formula: t isTi-target torques of the drive motors
vTi-desired speed at the wheel center of each wheel
KP、KI、KD-PID controller parameters, calibrated by experiment;
the actual rotating speed of the wheels is determined by the balance point of the driving torque of the motor and the stress of the actual wheels, and is fed back to the whole vehicle controller to realize closed loop, the self-adaptive differential speed of each wheel is realized according to the strategy of torque instruction control and rotating speed follow-up, and the whole vehicle control system outputs a driving motor torque instruction signal according to the motion state of the vehicle, so that the accelerator pedal controls the vehicle speed and the motor torque at the same time; the motor torque can be controlled by open loop or closed loop feedback.
2. The adaptive electronic differential control method for a multi-axle in-wheel motor-driven vehicle according to claim 1, wherein the wheel differential operation comprises: A. when the vehicle is steered to run, the vehicle generates yaw motion, so that the acceleration at the wheel center of each wheel generates difference, and the wheel speed of each wheel is different; B. when the vehicle runs on an uneven road surface, the lengths of tracks passed by the wheel centers of the wheels are different, so that the rotating speeds of the wheels are different; C. when the rolling radius of each wheel is different, the rotating speed of each wheel is different because each wheel core passes through the same track length.
3. The adaptive electronic differential control method for a multi-axle in-wheel motor-driven vehicle according to claim 1, wherein the electronic differential control system comprises: the system comprises a main controller, hub motors, a controller system and a CAN bus communication network.
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