CN109291991B - Dual-motor drive-by-wire composite steering system and control method thereof - Google Patents
Dual-motor drive-by-wire composite steering system and control method thereof Download PDFInfo
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- CN109291991B CN109291991B CN201811460984.6A CN201811460984A CN109291991B CN 109291991 B CN109291991 B CN 109291991B CN 201811460984 A CN201811460984 A CN 201811460984A CN 109291991 B CN109291991 B CN 109291991B
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- 238000000034 method Methods 0.000 title claims abstract description 28
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- 238000006073 displacement reaction Methods 0.000 claims description 66
- 238000003745 diagnosis Methods 0.000 claims description 12
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- 239000003921 oil Substances 0.000 claims description 4
- 241000826860 Trapezium Species 0.000 claims description 3
- 230000002159 abnormal effect Effects 0.000 claims description 3
- 230000003044 adaptive effect Effects 0.000 claims description 3
- 238000012937 correction Methods 0.000 claims description 3
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Classifications
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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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
- B60Q9/00—Arrangement or adaptation of signal devices not provided for in one of main groups B60Q1/00 - B60Q7/00, e.g. haptic signalling
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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
- B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
- B62D5/09—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle characterised by means for actuating valves
- B62D5/091—Hydraulic steer-by-wire systems, e.g. the valve being actuated by an electric motor
Abstract
The invention provides a double-motor drive-by-wire composite steering system and a control method thereof, wherein the double-motor drive-by-wire composite steering system comprises a steering wheel, a steering column assembly, a road sensing assembly, a double-motor steering execution device and a steering control unit, and steering control of the system is completed through a self-adaptive control method. The system can realize the integration of steering performances such as larger steering moment, lower energy consumption, faster response speed and the like, and the control method automatically adjusts steering control parameters according to the actual driving situation, can better resist the uncertainty in the driving environment and ensures the steering precision and the vehicle safety.
Description
Technical Field
The invention belongs to the technical field of automobile steering systems, and particularly relates to a double-motor drive-by-wire composite steering system and a control method thereof.
Background
As the degree of automotive intellectualization becomes higher, the various execution modules of the automobile also tend to be wire-controlled. The drive-by-wire steering system can freely design the transmission ratio, improves the active safety performance, saves the arrangement space, is easier to cooperate with drive-by-wire brake and throttle, and the like, and is a hot spot of current research. The existing implementation modes of the steer-by-wire system mainly comprise the following types: single motor steer-by-wire, dual motor steer-by-wire, four wheel steering, etc. The single motor wire control steering structure is simple, but the adopted motor power is larger; the double-motor steering can be performed by using the other motor when one motor fails, so that the safety is higher; four wheels can be independently controlled by four-wheel steering, but the structure is complex, and the control difficulty is high.
Because of installation space and cost limitations, motors used in steer-by-wire systems tend to be less powerful and provide less steering torque, most of the existing steer-by-wire systems are designed for passenger vehicles with lighter forward axle mass. For commercial, mining, agricultural and other vehicles with heavy front axle mass, a hydraulic system is generally adopted to provide larger steering torque, but the hydraulic system has the defects of larger energy consumption, lower response speed than a motor and the like.
Disclosure of Invention
Aiming at the problems that the prior art is difficult to realize the fusion unification of the performances of larger steering torque, lower energy consumption, faster response speed and the like, the invention aims to provide a double-motor drive-by-wire composite steering system and a control method thereof so as to overcome the problems in the prior art.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention relates to a double-motor drive-by-wire compound steering system, which comprises: steering wheel, steering column assembly, road sensing assembly, double-motor steering executing device and steering control unit;
the steering wheel is connected with a steering column assembly, and the steering column assembly comprises: steering column, torsion bar, torque sensor, rotation angle sensor; the acting force input by the steering wheel acts on the torsion bar through the steering column, and a torque sensor and a rotation angle sensor are respectively and fixedly arranged on the steering column;
the road feel assembly includes: the road sensing motor, the third rotating speed sensor and the worm gear; the output end of the road sensing motor is connected with the turbine end of the turbine and the worm through a third rotating speed sensor, and the worm end of the turbine and the worm acts on the steering column; the acting force output by the road sensing motor is transmitted to a steering wheel through a worm gear and a steering column in sequence;
the dual motor steering performing device includes: the steering system comprises a first motor module, a second motor module, a steering tie rod, a steering trapezoid and steering wheels;
the first motor module includes: the device comprises a first power-assisted motor, a one-way clutch, a ball screw and a first rotation speed sensor;
the output end of the first power-assisted motor is connected with the nut end of the ball screw through a first rotation speed sensor and a one-way clutch in sequence; the two ends of the screw rod are axially fixedly connected with two ports of the broken steering tie rod; when the one-way clutch is engaged, the rotary motion output by the first power-assisted motor is converted into displacement motion of the steering tie rod through the ball screw;
the second motor module includes: the hydraulic pump, the second booster motor, the electromagnetic directional valve, the hydraulic cylinder, the piston rod, the displacement sensor and the second rotating speed sensor;
the piston rod is positioned in the hydraulic cylinder, a piston is fixedly arranged on the piston rod, the piston rod breaks the steering tie rod, and two ends of the piston rod are fixedly connected with two broken ends of the steering tie rod; the displacement sensor is arranged on the piston rod, and the second rotating speed sensor is arranged at the output end of the second power-assisted motor; under the action of a second power-assisted motor, hydraulic oil sequentially flows through two sides of a piston in a hydraulic cylinder from an oil tank, a hydraulic pump and an electromagnetic reversing valve, and pressure difference of two sides of the piston generates axial acting force, and the axial acting force is transmitted to a steering tie rod through the piston and a piston rod and is converted into displacement motion of the steering tie rod;
the steering control unit includes: a controller, a vehicle status unit; the controller is electrically connected with the sensors to acquire torque and rotation angle signals on the steering column, rotation speed signals of the road sensing motor, the first power-assisted motor and the second power-assisted motor and steering tie rod displacement signals; the vehicle state unit provides the controller with a vehicle speed signal, a yaw rate signal, and a lateral acceleration signal in the current state of the vehicle.
Further, the steering tie rod is fixedly connected with the piston rod and the ball screw to form a whole, displacement of the piston rod and the ball screw is overlapped on the steering tie rod, two ends of the steering tie rod are respectively connected with steering wheels through a steering trapezoid, displacement movement of the steering tie rod is converted into steering angles of the steering wheels, and steering action of the vehicle is completed.
Further, the controller comprises a signal processing unit, a steering decision unit, a steering database, a diagnosis unit, a fault alarm unit, a motor driving unit and an electromagnetic reversing valve driving unit; the signal processing unit is electrically connected with the sensors to acquire signals acquired by the sensors in real time, and is electrically connected with the vehicle state unit to acquire other state signals of the vehicle; the steering decision unit receives input signals of the signal processing unit, the steering database and the diagnosis unit through the vehicle-mounted communication line respectively, and outputs control signals of the road sensing motor, the first power-assisted motor, the second power-assisted motor and the electromagnetic reversing valve through the vehicle-mounted communication line through calculation to complete a steering control process.
The invention discloses a self-adaptive control method of a double-motor drive-by-wire composite steering system, which is based on the system and comprises the following steps of:
1) The vehicle is started, the diagnosis unit detects the initial state of each part of the system, and if the abnormal state exists, the fault alarm unit is triggered by the steering decision unit to remind the driver of fault information; if the states of all parts of the system are normal, no prompt is given;
2) The signal processing unit receives signals sent by the sensors and signals sent by other state units of the vehicle in real time, obtains a current vehicle state signal through calculation, and transmits the current vehicle state signal to the steering decision unit;
3) The steering decision unit carries out steering decision calculation on the current vehicle state signal according to the expected vehicle front wheel rotation angle and the expected driving road feel under each vehicle state stored in the steering database to obtain the expected vehicle front wheel rotation angle at the next moment, and calculates the steering tie rod displacement and the electromagnetic directional valve working position corresponding to the expected vehicle front wheel rotation angle at the next moment; the steering decision unit also obtains expected driving road feel at the next moment, and calculates steering column moment corresponding to the expected driving road feel at the next moment;
4) The electromagnetic reversing valve driving unit controls the working position of the electromagnetic reversing valve according to the output instruction of the steering decision unit; meanwhile, the motor driving unit calculates the current required by the road sensing motor, the first power-assisted motor and the second power-assisted motor respectively according to the output instruction of the steering decision unit and drives the three motors to work.
Further, the signals of the sensors in the step 2) include: torque signal, first rotation speed signal, second rotation speed signal, third rotation speed signal, displacement signal, rotation angle signal; signals of other state units of the vehicle include: vehicle speed signal, yaw rate signal, lateral acceleration signal.
Further, the step 4) specifically includes: the motor driving unit has three working modes according to the expected front wheel steering angle instruction of the vehicle at the next moment output by the steering decision unit: the first provides assistance for only the first assistance motor, the second provides assistance for only the second assistance motor, and the third provides assistance for both the first and second motors; the diagnosis unit detects whether the system works normally or not in the running process of the vehicle, and if the vehicle is judged to run normally, a third working mode is adopted; if the first motor module is judged to be faulty, triggering a fault alarm unit, and adopting a second working mode at the same time, wherein the one-way clutch of the first motor module is disconnected at the moment, and the displacement of the steering tie rod only depends on the second power-assisted motor; if the second motor module is judged to be faulty, the fault alarm unit is triggered, and meanwhile, a first working mode is adopted, the electromagnetic directional valve is in an unloading state, and the displacement of the steering tie rod only depends on the first power-assisted motor.
Further, the step 4) specifically further includes: the electromagnetic torque output by the road sensing motor acts on the steering column, and the formed steering column torque is transmitted to the steering wheel to provide driving road sensing for a driver; the electromagnetic torque output by the first power-assisted motor acts on the screw rod through the first clutch and is converted into displacement of the steering tie rod; the electromagnetic torque output by the second power-assisted motor drives the hydraulic pump to work, so that pressure difference is generated on two sides of a piston in the hydraulic cylinder to output axial acting force, and the axial acting force is transmitted to the steering tie rod through the piston and a piston rod and is converted into displacement of the axial tie rod; the first power-assisted motor and the second power-assisted motor superimpose the displacement acted by the steering tie rod, output the displacement to the steering trapezium and the steering wheels, and convert the displacement into the front wheel corner at the next moment.
Further, the step 4) specifically further includes: the generalized minimum variance self-correction control is adopted, so that the parameters of the controller can be corrected in real time, and the specific steps are as follows:
1) Initial data is input to the controller, and the actual output weighting polynomial P (z -1 ) It is desirable to output a weighted polynomial R (z -1 ) Control quantity weighting polynomial Q (z -1 )；
2) In the running process of the vehicle, d is a sampling period, and the displacement sensor samples the actual displacement y of the steering tie rod of the vehicle at the current moment r (k) And acquires the desired tie rod displacement y at the next time r (k+d)；
3) The controlled object steering tie rod displacement model satisfies the equation:
A(z -1 )y(k)＝z -d B(z -1 )u(k)+C(z -1 )ξ(k)
C(z -1 )＝A(z -1 )E(z -1 )+z -d G(z -1 )
F(z -1 )＝B(z -1 )E(z -1 )
wherein the method comprises the steps of
Where A, B, C, E, F, G is a polynomial, y (k) is the output control quantity at time k, and ζ (k) is the variance σ 2 U (k) is the input control quantity at time k, and the above equation is solved to obtain polynomial coefficients E (z) -1 )，G(z -1 )，F(z -1 )：
4) u (k) is a control amount at k time, and is controlled according to a generalized minimum variance control rate, wherein the control rate is as follows:
the performance index Jv is:
Jv＝Ev{[{P(z -1 )y(k+d)-R(z -1 )y r (k)] 2 +[Q(z -1 )u(k)] 2 }
in which y * (k+d|k) is the optimal predicted estimate of the desired vehicle tie rod displacement at time (k+d), ev is the error variance function;
5) Let k=k+1, return to step 2, continue the circulation control, finish the vehicle and turn to the action.
The invention designs a double-motor drive-by-wire composite steering system, wherein a first motor is used for electric power assistance, a second motor is used for driving a hydraulic pump to provide hydraulic power assistance, so that the composite steering and the safe backup of hardware can be realized through two sets of motors, the rapidity, the accuracy and the energy conservation of steering operation can be simultaneously considered, the double-motor drive-by-wire composite steering system can be used for passenger vehicles with lighter mass and heavy vehicles, and the double-motor drive-by-wire composite steering system has higher practicability.
The invention has the beneficial effects that:
compared with the existing double-motor steer-by-wire system, the hydraulic power steering system has the advantages that the hydraulic power steering function is integrated, larger steering torque can be output, and the defect that the existing double-motor steer-by-wire system is difficult to apply to a heavy vehicle is overcome; compared with the existing hydraulic line control steering, the electric power steering function is integrated, and steering is more accurate and energy-saving.
The invention has the hardware safety redundancy function, and under the condition that the first motor or the second motor fails to work, any motor can work independently, thereby ensuring the controllability of a driver on the steering function of the vehicle, completing the emergency steering operation and improving the safety of the vehicle.
The invention adopts the self-adaptive control method, can automatically adjust the steering control parameters according to the actual driving situation, can better resist the uncertainty in the driving environment, has better robustness, and ensures the steering execution precision and the vehicle safety.
Drawings
FIG. 1 is a schematic block diagram of a dual motor drive-by-wire compound steering system of the present invention;
FIG. 2 is a flow chart of a control method of the present invention;
FIG. 3 is a generalized minimum variance self-correcting control schematic block diagram of the present invention;
in the figure, a 1-steering wheel, a 2-rotation angle sensor, a 3-steering column, a 4-torque sensor, a 5-worm gear, a 6-torsion bar, a 7-controller, an 8-electromagnetic directional valve, a 9-hydraulic pump, a 10-second rotation speed sensor, an 11-second power motor, a 12-oil tank, a 13-displacement sensor, a 14-piston rod, a 15-piston, a 16-hydraulic cylinder, a 17-steering tie rod, an 18-nut, a 19-ball screw, a 20-steering trapezoid, 21-steering wheels, a 22-one-way clutch, a 23-first rotation speed sensor, a 24-first power motor, a 25-other state unit of the vehicle, a 26-road motor and a 27-third rotation speed sensor are shown;
n-torque signal, S-third rotating speed signal, T-first rotating speed signal, U-displacement signal, V-second rotating speed signal, W-rotating angle signal, X-vehicle speed signal, H-yaw rate signal, I-lateral acceleration signal, J-first power-assisted motor control signal, Y-second power-assisted motor control signal, L-road-sensing motor control signal and M-electromagnetic directional valve control signal.
Detailed Description
The invention will be further described with reference to examples and drawings, to which reference is made, but which are not intended to limit the scope of the invention.
Referring to fig. 1, a dual motor drive-by-wire compound steering system of the present invention includes: steering wheel, steering column assembly, road sensing assembly, double-motor steering executing device and steering control unit;
the steering wheel is connected with a steering column assembly, and the steering column assembly comprises: steering column 3, torsion bar 6, torque sensor 4, and rotation angle sensor 2; the acting force input by the steering wheel 1 acts on the torsion bar 6 through the steering column 3, and a torque sensor 4 and a rotation angle sensor 2 are respectively and fixedly arranged on the steering column 3;
the road feel assembly includes: a road-sensing motor 26, a third rotation speed sensor 27 and a worm gear 5; the output end of the road sensing motor 26 is connected with the turbine end of the turbine worm 5 through a third rotation speed sensor 27, and the worm end of the turbine worm 5 acts on the steering column 3; the acting force output by the road sensing motor 26 is transmitted to the steering wheel 1 through the worm gear 5 and the steering column 3 in sequence;
the dual motor steering performing device includes: a first motor module, a second motor module, a tie rod 17, a steering trapezoid 20, and steering wheels 21;
the first motor module includes: a first booster motor 24, a one-way clutch 22, a ball screw 19, a first rotational speed sensor 23;
the output end of the first power-assisted motor 24 is connected with the nut end of the ball screw 19 through the first rotational speed sensor 23 and the one-way clutch 22 in sequence; the wire rod end of the ball screw breaks the steering tie rod 17, and two ends of the screw are axially and fixedly connected with two broken ports of the steering tie rod 17; when the one-way clutch 22 is engaged, the rotational motion output by the first assist motor 24 is converted into displacement motion of the tie rod 17 via the ball screw 19;
the second motor module includes: the hydraulic pump 9, the second booster motor 11, the electromagnetic directional valve 8, the hydraulic cylinder 16, the piston 15, the piston rod 14, the displacement sensor 13 and the second rotation speed sensor 10;
the piston rod 14 is positioned in the hydraulic cylinder 16, a piston 15 is fixedly arranged on the piston rod 14, the piston rod 14 breaks a steering tie rod 17, and two ends of the piston rod 14 are fixedly connected with two broken ports of the steering tie rod 17; the displacement sensor 13 is arranged on the piston rod 14, and the second rotating speed sensor 10 is arranged at the output end of the second booster motor 11; under the action of a second power-assisted motor, hydraulic oil sequentially flows through two sides of a piston 15 in a hydraulic cylinder 16 from an oil tank 12, a hydraulic pump 9 and an electromagnetic reversing valve 8, the pressure difference of the two sides of the piston 15 generates axial acting force, and the axial acting force is transmitted to a steering tie rod 17 through the piston 15 and a piston rod 14 and is converted into displacement motion of the steering tie rod;
the steering control unit includes: a controller 7, other status unit 25 of the vehicle; the controller 7 is electrically connected with the sensors to acquire torque and rotation angle signals on the steering column 3, rotation speed signals of the road sensing motor, the first power-assisted motor and the second power-assisted motor and steering tie rod displacement signals; the other state unit 25 of the vehicle supplies the controller 7 with a vehicle speed signal, a yaw rate signal, and a lateral acceleration signal in the current state of the vehicle.
The steering tie rod 17 is fixedly connected with the piston rod 14 and the ball screw 19 into a whole, displacement of the piston rod 14 and the ball screw 19 is overlapped on the steering tie rod, two ends of the steering tie rod 17 are respectively connected with steering wheels 21 through a steering trapezoid 20, displacement movement of the steering tie rod is converted into steering angles of the steering wheels, and steering action of the vehicle is completed.
The controller 7 comprises a signal processing unit, a steering decision unit, a steering database, a diagnosis unit, a fault alarm unit, a motor driving unit and an electromagnetic reversing valve driving unit; the signal processing unit is electrically connected with the sensors to acquire signals acquired by the sensors in real time, and is electrically connected with the other state units 25 of the vehicle to acquire other state signals of the vehicle; the steering decision unit receives input signals of the signal processing unit, the steering database and the diagnosis unit through the vehicle-mounted communication line respectively, and transmits driving signals to the motor driving unit and the electromagnetic reversing valve driving unit through the vehicle-mounted communication line after calculation; the motor driving unit outputs a road sensing motor control signal L, a first power assisting motor control signal J and a second power assisting motor control signal Y respectively, so that the three motors respectively execute the output of electromagnetic torque; the electromagnetic reversing valve driving unit outputs an electromagnetic reversing valve control signal M to enable the electromagnetic reversing valve to execute conversion of the working position; the electromagnetic torque of the second power-assisted motor is converted into hydraulic cylinder output displacement at the working position of the corresponding electromagnetic reversing valve, and the hydraulic cylinder output displacement and the screw rod output displacement generated by the electromagnetic torque of the second power-assisted motor are transmitted to the steering tie rod together to complete the control process of steering actions.
Referring to fig. 2, the adaptive control method of the dual-motor drive-by-wire composite steering system of the present invention is based on the above system, and comprises the following steps:
1) The vehicle is started, the diagnosis unit detects the initial state of each part of the system, and if the abnormal state exists, the fault alarm unit is triggered by the steering decision unit to remind the driver of fault information; if the states of all parts of the system are normal, no prompt is given;
2) The signal processing unit receives signals sent by the sensors and signals sent by other state units of the vehicle in real time, obtains a current vehicle state signal through calculation, and transmits the current vehicle state signal to the steering decision unit;
3) The steering decision unit carries out steering decision calculation on the current vehicle state signal according to the expected vehicle front wheel rotation angle and the expected driving road feel under each vehicle state stored in the steering database to obtain the expected vehicle front wheel rotation angle at the next moment, and calculates the steering tie rod displacement and the electromagnetic directional valve working position corresponding to the expected vehicle front wheel rotation angle at the next moment; the steering decision unit also obtains expected driving road feel at the next moment, and calculates steering column moment corresponding to the expected driving road feel at the next moment;
4) The electromagnetic reversing valve driving unit controls the working position of the electromagnetic reversing valve according to the output instruction of the steering decision unit; meanwhile, the motor driving unit calculates the current required by the road sensing motor, the first power-assisted motor and the second power-assisted motor respectively according to the output instruction of the steering decision unit and drives the three motors to work.
Wherein, the signals of each sensor in the step 2) include: the signals of the torque signal N, the first rotating speed signal T, the second rotating speed signal V, the third rotating speed signal S, the displacement signal U and the rotating angle signal W and other state units of the vehicle comprise: a vehicle speed signal X, a yaw rate signal H, and a lateral acceleration signal I.
Wherein, the step 4) specifically includes: the motor driving unit has three working modes according to the expected front wheel steering angle instruction of the vehicle at the next moment output by the steering decision unit: the first provides assistance for only the first assistance motor, the second provides assistance for only the second assistance motor, and the third provides assistance for both the first and second motors; the diagnosis unit detects whether the system works normally or not in the running process of the vehicle, and if the vehicle is judged to run normally, a third working mode is adopted; if the first motor module is judged to be faulty, triggering a fault alarm unit, and adopting a second working mode at the same time, wherein the one-way clutch of the first motor module is disconnected at the moment, and the displacement of the steering tie rod only depends on the second power-assisted motor; if the second motor module is judged to be faulty, the fault alarm unit is triggered, and meanwhile, a first working mode is adopted, the electromagnetic directional valve is in an unloading state, and the displacement of the steering tie rod only depends on the first power-assisted motor.
Wherein, the step 4) specifically further includes: the electromagnetic torque output by the road sensing motor acts on the steering column, and the formed steering column torque is transmitted to the steering wheel to provide driving road sensing for a driver; the electromagnetic torque output by the first power-assisted motor acts on the screw rod through the first clutch and is converted into displacement of the steering tie rod; the electromagnetic torque output by the second power-assisted motor drives the hydraulic pump to work, so that pressure difference is generated on two sides of a piston in the hydraulic cylinder to output axial acting force, and the axial acting force is transmitted to the steering tie rod through the piston and a piston rod and is converted into displacement of the axial tie rod; the first power-assisted motor and the second power-assisted motor superimpose the displacement acted by the steering tie rod, output the displacement to the steering trapezium and the steering wheels, and convert the displacement into the front wheel corner at the next moment.
Wherein, the step 4) specifically further includes: the generalized minimum variance self-correction control is adopted, the parameters of the controller can be corrected in real time, and the method comprises the following specific steps of
1. Initial data is input to the controller, and the actual output weighting polynomial P (z -1 ) It is desirable to output a weighted polynomial R (z -1 ) Control quantity weighting polynomial Q (z -1 )；
2. In the running process of the vehicle, d is a sampling period, and the displacement sensor samples the actual displacement y of the steering tie rod of the vehicle at the current moment r (k) And acquires the desired tie rod displacement y at the next time r (k+d)；
3. The controlled object steering tie rod displacement model satisfies the equation:
A(z -1 )y(k)＝z -d B(z -1 )u(k)+C(z -1 )ξ(k)
C(z -1 )＝A(z -1 )E(z -1 )+z -d G(z -1 )
F(z -1 )＝B(z -1 )E(z -1 )
wherein the method comprises the steps of
Where A, B, C, E, F, G is a polynomial, y (k) is the output control quantity at time k, and ζ (k) is the variance σ 2 U (k) is the input control quantity at time k, and the above equation is solved to obtain polynomial coefficients E (z) -1 )，G(z -1 )，F(z -1 )：
4.u (k) is a control amount at time k, and is controlled according to a generalized minimum variance control rate, which is:
the performance index Jv is:
Jv＝Ev{[{P(z -1 )y(k+d)-R(z -1 )y r (k)] 2 +[Q(z -1 )u(k)] 2 }
in which y * (k+d|k) is the optimal predicted estimate of the desired vehicle tie rod displacement at time (k+d), ev is the error variance function;
5. let k=k+1, return to step 2, continue the circulation control, finish the vehicle and turn to the action.
The invention designs a double-motor drive-by-wire composite steering system, wherein a first motor is used for electric power assistance, a second motor is used for driving a hydraulic pump to provide hydraulic power assistance, so that the composite steering and the safe backup of hardware can be realized through two sets of motors, the rapidity, the accuracy and the energy conservation of steering operation can be simultaneously considered, the double-motor drive-by-wire composite steering system can be used for passenger vehicles with lighter mass and heavy vehicles, and the double-motor drive-by-wire composite steering system has higher practicability.
The present invention has been described in terms of the preferred embodiments thereof, and it should be understood by those skilled in the art that various modifications can be made without departing from the principles of the invention, and such modifications should also be considered as being within the scope of the invention.
Claims (4)
1. An adaptive control method of a double-motor drive-by-wire composite steering system is based on the double-motor drive-by-wire composite steering system, and the system comprises: steering wheel, steering column assembly, road sensing assembly, double-motor steering executing device and steering control unit;
the steering wheel is connected with a steering column assembly, and the steering column assembly comprises: steering column, torsion bar, torque sensor, rotation angle sensor; the acting force input by the steering wheel acts on the torsion bar through the steering column, and a torque sensor and a rotation angle sensor are respectively and fixedly arranged on the steering column;
the road feel assembly includes: the road sensing motor, the third rotating speed sensor and the worm gear; the output end of the road sensing motor is connected with the worm wheel end of the worm wheel and the worm through a third rotation speed sensor, and the worm end of the worm wheel and the worm acts on the steering column; the acting force output by the road sensing motor is transmitted to a steering wheel through a worm gear and a steering column in sequence;
the dual motor steering performing device includes: the steering system comprises a first motor module, a second motor module, a steering tie rod, a steering trapezoid and steering wheels;
the first motor module includes: the device comprises a first power-assisted motor, a one-way clutch, a ball screw and a first rotation speed sensor;
the output end of the first power-assisted motor is connected with the nut end of the ball screw through a first rotation speed sensor and a one-way clutch in sequence; the two ends of the screw rod are axially fixedly connected with two ports of the broken steering tie rod; when the one-way clutch is engaged, the rotary motion output by the first power-assisted motor is converted into displacement motion of the steering tie rod through the ball screw;
the second motor module includes: the hydraulic pump, the second booster motor, the electromagnetic directional valve, the hydraulic cylinder, the piston rod, the displacement sensor and the second rotating speed sensor;
the piston rod is positioned in the hydraulic cylinder, a piston is fixedly arranged on the piston rod, the piston rod breaks the steering tie rod, and two ends of the piston rod are fixedly connected with two broken ends of the steering tie rod; the displacement sensor is arranged on the piston rod, and the second rotating speed sensor is arranged at the output end of the second power-assisted motor; under the action of a second power-assisted motor, hydraulic oil sequentially flows through two sides of a piston in a hydraulic cylinder from an oil tank, a hydraulic pump and an electromagnetic reversing valve, and pressure difference of two sides of the piston generates axial acting force, and the axial acting force is transmitted to a steering tie rod through the piston and a piston rod and is converted into displacement motion of the steering tie rod;
the steering control unit includes: a controller, a vehicle status unit; the controller is electrically connected with the sensors to acquire torque and rotation angle signals on the steering column, rotation speed signals of the road sensing motor, the first power-assisted motor and the second power-assisted motor and steering tie rod displacement signals; the vehicle state unit provides a vehicle speed signal, a yaw rate signal and a lateral acceleration signal for the controller in the current state of the vehicle;
the controller comprises a signal processing unit, a steering decision unit, a steering database, a diagnosis unit, a fault alarm unit, a motor driving unit and an electromagnetic reversing valve driving unit; the signal processing unit is electrically connected with the sensors to acquire signals acquired by the sensors in real time, and is electrically connected with the vehicle state unit to acquire other state signals of the vehicle; the steering decision unit receives input signals of the signal processing unit, the steering database and the diagnosis unit through the vehicle-mounted communication line respectively, and outputs control signals of the road sensing motor, the first power-assisted motor, the second power-assisted motor and the electromagnetic reversing valve through the vehicle-mounted communication line through calculation to complete a control process of steering action;
the method is characterized by comprising the following steps of:
1) The vehicle is started, the diagnosis unit detects the initial state of each part of the system, and if the abnormal state exists, the fault alarm unit is triggered by the steering decision unit to remind the driver of fault information; if the states of all parts of the system are normal, no prompt is given;
2) The signal processing unit receives signals sent by the sensors and signals sent by other state units of the vehicle in real time, obtains a current vehicle state signal through calculation, and transmits the current vehicle state signal to the steering decision unit;
3) The steering decision unit carries out steering decision calculation on the current vehicle state signal according to the expected vehicle front wheel rotation angle and the expected driving road feel under each vehicle state stored in the steering database to obtain the expected vehicle front wheel rotation angle at the next moment, and calculates the steering tie rod displacement and the electromagnetic directional valve working position corresponding to the expected vehicle front wheel rotation angle at the next moment; the steering decision unit also obtains expected driving road feel at the next moment, and calculates steering column moment corresponding to the expected driving road feel at the next moment;
4) The electromagnetic reversing valve driving unit controls the working position of the electromagnetic reversing valve according to the output instruction of the steering decision unit; meanwhile, the motor driving unit calculates the current required by the road sensing motor, the first power-assisted motor and the second power-assisted motor respectively according to the output instruction of the steering decision unit and drives the three motors to work;
the step 4) specifically further includes: the generalized minimum variance self-correction control is adopted, so that the parameters of the controller can be corrected in real time, and the specific steps are as follows:
41 Inputting initial data to the controller, setting the actual output weighting polynomial P (z) -1 ) It is desirable to output a weighted polynomial R (z -1 ) Control quantity weighting polynomial Q (z -1 )；
42 During the running of the vehicle, d is the sampling period, and the displacement sensor samples the actual displacement y of the steering tie rod of the vehicle at the current moment r (k) And acquires the desired tie rod displacement y at the next time r (k+d)；
43 A controlled object tie rod displacement model satisfies the equation:
A(z -1 )y(k)＝z -d B(z -1 )u(k)+C(z -1 )ξ(k)
C(z -1 )＝A(z -1 )E(z -1 )+z -d G(z -1 )
F(z -1 )＝B(z -1 )E(z -1 )
wherein the method comprises the steps of
Where A, B, C, E, F, G is a polynomial, y (k) is the output control quantity at time k, and ζ (k) is the variance σ 2 U (k) is the input control quantity at time k, and the above equation is solved to obtain polynomial coefficients E (z) -1 )，G(z -1 )，F(z -1 )：
44 U (k) is a control amount at time k, and is controlled according to a generalized minimum variance control rate, wherein the control rate is:
the performance index Jv is:
wherein y is * (k+d|k) is the optimal predicted estimate of the desired vehicle tie rod displacement at time (k+d), ev is the error variance function;
45 Let k=k+1, return to step 2, continue the circulation control, finish the vehicle steering action.
2. The adaptive control method of a dual-motor drive-by-wire compound steering system as set forth in claim 1, wherein the signals of each sensor in said step 2) include: torque signal, first rotation speed signal, second rotation speed signal, third rotation speed signal, displacement signal, rotation angle signal; signals of other state units of the vehicle include: vehicle speed signal, yaw rate signal, lateral acceleration signal.
3. The method for adaptively controlling a dual-motor drive-by-wire compound steering system as set forth in claim 1, wherein said step 4) specifically includes: the motor driving unit has three working modes according to the expected front wheel steering angle instruction of the vehicle at the next moment output by the steering decision unit: the first provides assistance for only the first assistance motor, the second provides assistance for only the second assistance motor, and the third provides assistance for both the first and second motors; the diagnosis unit detects whether the system works normally or not in the running process of the vehicle, and if the vehicle is judged to run normally, a third working mode is adopted; if the first motor module is judged to be faulty, triggering a fault alarm unit, and adopting a second working mode at the same time, wherein the one-way clutch of the first motor module is disconnected at the moment, and the displacement of the steering tie rod only depends on the second power-assisted motor; if the second motor module is judged to be faulty, the fault alarm unit is triggered, and meanwhile, a first working mode is adopted, the electromagnetic directional valve is in an unloading state, and the displacement of the steering tie rod only depends on the first power-assisted motor.
4. The method for adaptively controlling a dual-motor drive-by-wire compound steering system as set forth in claim 1, wherein said step 4) specifically further includes: the electromagnetic torque output by the road sensing motor acts on the steering column, and the formed steering column torque is transmitted to the steering wheel to provide driving road sensing for a driver; the electromagnetic torque output by the first power-assisted motor acts on the screw rod through the first clutch and is converted into displacement of the steering tie rod; the electromagnetic torque output by the second power-assisted motor drives the hydraulic pump to work, so that pressure difference is generated on two sides of a piston in the hydraulic cylinder to output axial acting force, and the axial acting force is transmitted to the steering tie rod through the piston and a piston rod and is converted into displacement of the axial tie rod; the first power-assisted motor and the second power-assisted motor superimpose the displacement acted by the steering tie rod, output the displacement to the steering trapezium and the steering wheels, and convert the displacement into the front wheel corner at the next moment.
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| PCT/CN2019/116092 WO2020108260A1 (en) | 2018-12-01 | 2019-11-06 | Dual-motor wire-controlled composite steering system and control method therefor |
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