CN111605610B - Dual-motor coupling drive-by-wire steering system and energy optimization method thereof - Google Patents
Dual-motor coupling drive-by-wire steering system and energy optimization method thereof Download PDFInfo
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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
- B62D5/0403—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 constructional features, e.g. common housing for motor and gear box
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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
- B62D5/0421—Electric motor acting on or near steering gear
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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
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Abstract
The invention discloses a dual-motor coupling drive-by-wire steering system which is characterized by comprising a steering wheel module, a steering execution module, a signal acquisition module, a variable transmission ratio module, a vehicle ideal state calculation module, a required motor rotating speed and torque calculation module, a torque distribution coefficient optimization module and an ECU module; in addition, the invention also provides an energy optimization method for the double-motor coupling drive steer-by-wire system, which enables the motors to work in a high-efficiency area by reasonably and optimally distributing the torques of the two motors, thereby not only realizing the safety and the reliability of the steer-by-wire system, but also achieving the purpose of reducing the steering energy consumption.
Description
Technical Field
The invention relates to the field of vehicle steer-by-wire, in particular to a dual-motor steer-by-wire system and an energy optimization method thereof.
Background
In recent years, automobiles are gradually developed towards electromotion, intellectualization, networking and sharing, unmanned technology is gradually matured, and the steer-by-wire technology is increasingly emphasized due to the easy realization of integrated control. In contrast to conventional mechanical steering, steer-by-wire systems eliminate some of the mechanical linkage between the steering wheel and the steered wheels. The steering motor directly drives the wheels to complete the steering function of the automobile, so that the decoupling of the force transmission characteristic and the angle transmission characteristic of the steering system is realized, a larger space is provided for the arrangement of a power integration system, a suspension system and the like, and the steering characteristic, the operation stability, the active safety and the comfort of the automobile are effectively improved.
Although the steer-by-wire system gets rid of the inherent limitations of the traditional steering system, the steering performance is effectively improved. However, most of the existing steer-by-wire systems only have one set of steering execution motors, and the steer-by-wire systems mainly rely on electrical connection to control the steering motors to complete steering functions, once an electrical system or the motor fails, the automobile loses the steering capability, which leads to serious traffic accidents.
In order to improve the fault-tolerant capability and the running safety performance of the steer-by-wire system, the invention provides a dual-motor coupling drive steer-by-wire system. Compared with the existing steer-by-wire system of the automobile, the double-motor coupling drive steer-by-wire system is additionally provided with a set of steering motor on the basis of a single steering motor, so that the reliability and the safety of the steer-by-wire system are greatly improved.
However, the dual-motor coupling driving steer-by-wire system can effectively improve the fault-tolerant capability of the steer-by-wire system on one hand, and on the other hand, the introduction of the dual motors can change the energy consumption of the steer-by-wire system. Compared with the traditional single-motor steer-by-wire system, because the double-motor coupling driving steer-by-wire system has two sets of steering motors, if the steering energy consumption is not optimally managed, the energy consumption of the steering system is increased. Therefore, the energy of the dual-motor coupling drive-by-wire steering system needs to be optimized, so that the energy-saving purpose is achieved.
Disclosure of Invention
The invention aims to solve the technical problem of providing a dual-motor steer-by-wire system and an energy optimization method thereof aiming at the defects involved in the background technology.
The invention adopts the following technical scheme for solving the technical problems:
a dual-motor coupling drive-by-wire steering system comprises a steering wheel module, a steering execution module, a signal acquisition module, a variable transmission ratio module, a vehicle ideal state calculation module, a required motor rotating speed and torque calculation module, a torque distribution coefficient optimization module and an ECU module;
the steering wheel module comprises a steering wheel, a steering column, a road sensing motor reducer and a corner sensor;
the upper end of the steering column is fixedly connected with a steering wheel;
the output shaft of the road sensing motor is connected with the lower end of the steering column through a road sensing motor reducer and used for transmitting road sensing to a steering wheel through the steering column;
the steering angle sensor is arranged on the steering column and used for collecting a steering wheel steering angle signal and transmitting the steering wheel steering angle signal to the information collection module;
the steering execution module comprises a first steering motor, a first steering motor reducer, a first gear, a second steering motor reducer, a second gear, a rack, a steering tie rod, wheels and a vehicle speed sensor;
the first steering motor is connected with a rotating shaft of the first gear through a first steering motor reducer, the second steering motor is connected with a rotating shaft of the second gear through a second steering motor reducer, and the models of the first steering motor and the second steering motor are the same;
the first gear and the second gear are meshed with the rack; the rack is connected with the steering tie rod; two ends of the tie rod are correspondingly connected with two steering wheels of the vehicle respectively;
the vehicle speed sensor is arranged in a wheel and used for acquiring the vehicle speed of the vehicle and transmitting the vehicle speed to the information acquisition module;
the signal acquisition module carries out filtering and noise reduction on the steering wheel corner signal, the steering wheel corner differential signal and the vehicle speed signal which are obtained, and transmits the signals to the variable transmission ratio module and the vehicle ideal state calculation module;
the variable transmission ratio module calculates a variable transmission ratio signal of the vehicle according to the signal transmitted by the signal acquisition module and transmits the variable transmission ratio signal to the required motor rotating speed and torque calculation module;
the vehicle ideal state calculation module calculates the ideal yaw rate and the ideal centroid side slip angle of the vehicle according to the signals transmitted by the signal acquisition module and transmits the ideal yaw rate and the ideal centroid side slip angle to the required motor rotating speed and torque calculation module;
the required motor rotating speed and torque calculating module calculates the required rotating speeds of the first steering motor and the second steering motor and the required total torque of the first steering motor and the second steering motor according to the variable transmission ratio signal, the ideal yaw rate and the ideal mass center slip angle transmitted by the variable transmission ratio module and the vehicle ideal state calculating module, and transmits the required rotating speeds and the required total torque of the first steering motor and the second steering motor to the torque distribution coefficient optimizing module;
the torque distribution coefficient optimization module optimizes the torque distribution coefficient by adopting a self-adaptive particle swarm algorithm according to the required rotating speed and the required total torque signals of the first steering motor and the second steering motor, which are transmitted by the required motor rotating speed and torque calculation module, and transmits the obtained optimal torque distribution coefficient to the ECU control module;
the ECU control module is electrically connected with the first steering motor and the second steering motor respectively, and controls the first steering motor and the second steering motor to output torques with corresponding magnitudes according to the optimal torque distribution coefficient signals transmitted by the torque distribution coefficient optimization module, so that the output torques drive wheels through the rack and the steering tie rod together to complete vehicle steering.
The invention also discloses an energy optimization method of the double-motor coupling drive steer-by-wire system, which comprises the following steps:
step 1.1), steering wheel corner signals and vehicle speed signals are collected through a steering wheel corner sensor and a vehicle speed sensor, and the collected corner signals are subjected to differential processing to obtain steering wheel rotating speed signals;
step 1.2), establishing a two-degree-of-freedom model of the whole vehicle:
wherein a is the distance from the center of mass of the automobile to the front axle, b is the distance from the center of mass of the automobile to the rear axle, u is the longitudinal speed of the automobile, and deltafIs the angle of rotation of the front wheel, kfFor front wheel cornering stiffness, krThe lateral deflection rigidity of the rear wheel, m is the whole vehicle mass, beta is the barycenter lateral deflection angle of the vehicle body, wrAs yaw rate, IzThe moment of inertia of the automobile around the z axis;
step 1.3), calculating an ideal yaw rate and a centroid side slip angle when the vehicle enters a steady state according to a two-degree-of-freedom model of the whole vehicle:
in the formula (I), the compound is shown in the specification,
step 1.4), establishing a steer-by-wire variable transmission ratio model:
in the formula (I), the compound is shown in the specification,
as yaw-rate gain, thetaswThe rotational angle of the steering wheel, the gear ratio i,
a steady state yaw rate gain;
step 1.5), a vehicle steering resistance model is deduced according to the ideal yaw velocity, the mass center slip angle and the variable transmission ratio model:
in the formula, d is the tire drag distance;
step 1.6), calculating the total torque T required by the first steering motor and the second steering motor according to the steering resistance model:
in the formula eta1The transmission efficiency of the first steering motor reducer and the second steering motor reducer is obtained; eta2The transmission efficiency of the first steering motor, the second steering motor and the rack is obtained; n is a radical of1For reducing the first and second steering motor speed reducersA speed ratio; n is a radical of2The transmission ratio of the first steering motor, the second steering motor and the rack is obtained;
step 1.7), calculating the required rotating speeds of the first steering motor and the second steering motor according to the rotating speed signal of the steering wheel:
n＝nswN1
where n is a required rotation speed of the first steering motor and the second steering motor, and n is a required rotation speed of the first steering motor and the second steering motorswIs the steering wheel speed;
step 1.8), the energy optimization module optimizes an optimal torque distribution coefficient by adopting a self-adaptive particle swarm optimization according to the required rotating speeds of the first steering motor and the second steering motor and the required total torque signals of the first steering motor and the second steering motor, so that the total power of the motors is the lowest.
As a further optimization scheme of the energy optimization method of the double-motor coupling drive steer-by-wire system, the specific process of the energy optimization module in the step 1.8) comprises the following steps:
step 2.1), defining a torque distribution coefficient x as the ratio of the torque of the first steering motor to the total torque required by the first steering motor and the second steering motor, wherein the expression is as follows:
in the formula, T1For outputting torque, T, to the first steering motor2Outputting torque for the second steering motor, wherein T is the total torque required by the first steering motor and the second steering motor, and x is a torque distribution coefficient;
step 2.2), establishing a total power consumption model of the dual-motor coupling drive steer-by-wire system:
in the formula, P1Consuming power for the first steering motor, P2For the second steering motor, P is the total power consumed by the steering system, n1Is the rotational speed of the first steering motor, n2Is the rotational speed, η, of the second steering motor1(T1,n1) For the first steering motor at the operating point (T)1,n1) Efficiency of time, η2(T2,n2) For the second steering motor at the operating point (T)2,n2) Efficiency of the time;
step 2.3), establishing a constraint model of the dual-motor coupling drive steer-by-wire system:
in the formula, n1maxIs the maximum rotational speed of the first steering motor, n2maxAt the maximum speed of the second steering motor, T1maxIs the maximum torque of the first steering motor, T2maxIs the maximum torque of the second steering motor;
step 2.4), establishing a mathematical model for optimizing the steer-by-wire system driven by the double-motor coupling:
and 2.5) optimizing the optimized mathematical model by adopting a self-adaptive particle swarm algorithm, and searching an optimal torque distribution coefficient.
As a further optimization scheme of the energy optimization method of the double-motor coupling drive steer-by-wire system, the adaptive particle swarm algorithm in the step 2.5) comprises the following steps:
step 3.1), initializing a particle swarm, namely setting the population number N, the dimension D, the iteration times M and the minimum inertia weight w of the adaptive particle swarm algorithmminMaximum inertial weight wmaxIndividual optimal learning factor c1Global optimal learning factor c2；
Step 3.2), randomly setting the initial position of each particle in the defined field
And initial velocity
Wherein i is the particle number;
step 3.3), calculating a fitness function value of the initial population, and selecting a global optimal particle gbest of the initial population:
in the formula, Fi 1An initial fitness function for the ith particle;
step 3.4), calculating the average fitness function value of the population:
in the formula, N is the population number,
the value of the average fitness function of the population during the t iteration;
step 3.5), adjusting the inertia weight of the particles according to the individual fitness function value:
in the formula (I), the compound is shown in the specification,
the inertia weight value of the ith particle at the t iteration is obtained; w is amin,wmaxThe minimum value and the maximum value of the inertia weight are respectively;
the value of the minimum fitness function of the population during the t iteration;
step 3.6), updating the speed of the particles:
in the formula (I), the compound is shown in the specification,
position of ith particle at the t-th iteration, pbestiIs the optimum position of the ith particle, r1、r2Is distributed in [0,1 ]]Random number in between, c1Optimum learning factor for the individual, c2The gbest is a global optimal learning factor, and the gbest is a global optimal particle;
step 3.7), updating the positions of the particles:
in the formula (I), the compound is shown in the specification,
the position of the ith particle in the t iteration;
step 3.8), calculating the fitness function value of the particle:
in the formula, Fi tIs to beThe fitness function value of the ith particle in the t iteration;
step 3.9), comparison Fi t、F(pbesti) F, (gbest) and reselecting the individual optimum particle pbestiGlobal optimal particle gbest;
step 3.10), updating iteration times:
t＝t+ 1
in the formula, t is iteration times;
step 3.11), judging whether the maximum iteration number is reached, namely whether t > M is true, if yes, outputting the optimal torque distribution coefficient x as gbest, and if not, returning to the step 3.3).
Compared with the prior art, the invention adopting the technical scheme has the following technical effects:
(1) compared with a single-motor steer-by-wire system, the double-motor coupling drive steer-by-wire system is additionally provided with a set of steering motor on the basis of a single steering motor, so that the fault tolerance of the steer-by-wire system is greatly improved.
(2) According to the efficiency map of the motor, the energy utilization efficiency difference of the motor is large when the motor has different torques and rotating speeds, and each motor has a high efficiency area. The conventional single-motor steer-by-wire system has only one high efficiency region, while the dual-motor coupling driving steer-by-wire system has two high efficiency regions because of having two motors. The increase of the high-efficiency area leads the probability that the motor works in the high-efficiency area to be high, thereby achieving the purpose of reducing the steering energy consumption.
(3) The total torque of the required motors is optimally distributed, so that each optimized motor works in a high-efficiency area, and the aim of reducing steering energy consumption is fulfilled.
Drawings
Fig. 1 is a schematic diagram of a dual-motor coupling drive-by-wire steering system according to an embodiment of the present invention;
fig. 2 is a flow chart of energy optimization for steer-by-wire with dual-motor coupling driving according to an embodiment of the present invention;
FIG. 3 is a flow chart of an adaptive particle swarm algorithm provided by an embodiment of the present invention;
in the figure, 1-steering wheel, 2-steering column, 3-road sensing motor reducer, 4-steering wheel angle sensor, 5-first steering motor, 6-first steering motor reducer, 7-wheel, 8-first gear, 9-rack, 10-second gear, 11-second steering motor reducer, 12-second steering motor, 13-ECU, 14-road sensing motor.
Detailed Description
The technical scheme of the invention is further explained in detail by combining the attached drawings:
the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, components are exaggerated for clarity.
As shown in FIG. 1, the invention discloses a dual-motor coupling drive-by-wire steering system, which comprises a steering wheel module, a steering execution module, a signal acquisition module, a variable transmission ratio module, a vehicle ideal state calculation module, a required motor rotating speed and torque calculation module, a torque distribution coefficient optimization module and an ECU module, wherein the steering wheel module is used for driving the steering execution module to rotate;
the steering wheel module comprises a steering wheel, a steering column, a road sensing motor reducer and a corner sensor;
the upper end of the steering column is fixedly connected with a steering wheel;
the output shaft of the road sensing motor is connected with the lower end of the steering column through a road sensing motor reducer and used for transmitting road sensing to a steering wheel through the steering column;
the steering angle sensor is arranged on the steering column and used for collecting a steering wheel steering angle signal and transmitting the steering wheel steering angle signal to the information collection module;
the steering execution module comprises a first steering motor, a first steering motor reducer, a first gear, a second steering motor reducer, a second gear, a rack, a steering tie rod, wheels and a vehicle speed sensor;
the first steering motor is connected with a rotating shaft of the first gear through a first steering motor reducer, the second steering motor is connected with a rotating shaft of the second gear through a second steering motor reducer, and the models of the first steering motor and the second steering motor are the same;
the first gear and the second gear are meshed with the rack; the rack is connected with the steering tie rod; two ends of the tie rod are correspondingly connected with two steering wheels of the vehicle respectively;
the vehicle speed sensor is arranged in a wheel and used for acquiring the vehicle speed of the vehicle and transmitting the vehicle speed to the information acquisition module;
the signal acquisition module carries out filtering and noise reduction on the steering wheel corner signal, the steering wheel corner differential signal and the vehicle speed signal which are obtained, and transmits the signals to the variable transmission ratio module and the vehicle ideal state calculation module;
the variable transmission ratio module calculates a variable transmission ratio signal of the vehicle according to the signal transmitted by the signal acquisition module and transmits the variable transmission ratio signal to the required motor rotating speed and torque calculation module;
the vehicle ideal state calculation module calculates the ideal yaw rate and the ideal centroid side slip angle of the vehicle according to the signals transmitted by the signal acquisition module and transmits the ideal yaw rate and the ideal centroid side slip angle to the required motor rotating speed and torque calculation module;
the required motor rotating speed and torque calculating module calculates the required rotating speeds of the first steering motor and the second steering motor and the required total torque of the first steering motor and the second steering motor according to the variable transmission ratio signal, the ideal yaw rate and the ideal mass center slip angle transmitted by the variable transmission ratio module and the vehicle ideal state calculating module, and transmits the required rotating speeds and the required total torque of the first steering motor and the second steering motor to the torque distribution coefficient optimizing module;
the torque distribution coefficient optimization module optimizes the torque distribution coefficient by adopting a self-adaptive particle swarm algorithm according to the required rotating speed and the required total torque signals of the first steering motor and the second steering motor, which are transmitted by the required motor rotating speed and torque calculation module, and transmits the obtained optimal torque distribution coefficient to the ECU control module;
the ECU control module is electrically connected with the first steering motor and the second steering motor respectively, and controls the first steering motor and the second steering motor to output torques with corresponding magnitudes according to the optimal torque distribution coefficient signals transmitted by the torque distribution coefficient optimization module, so that the output torques drive wheels through the rack and the steering tie rod together to complete vehicle steering.
As shown in fig. 2, the invention also discloses an energy optimization method of the dual-motor coupling drive steer-by-wire system, which comprises the following steps:
step 1.1), steering wheel corner signals and vehicle speed signals are collected through a steering wheel corner sensor and a vehicle speed sensor, and the collected corner signals are subjected to differential processing to obtain steering wheel rotating speed signals;
step 1.2), establishing a two-degree-of-freedom model of the whole vehicle:
wherein a is the distance from the center of mass of the automobile to the front axle, b is the distance from the center of mass of the automobile to the rear axle, u is the longitudinal speed of the automobile, and deltafIs the angle of rotation of the front wheel, kfFor front wheel cornering stiffness, krThe lateral deflection rigidity of the rear wheel, m is the whole vehicle mass, beta is the barycenter lateral deflection angle of the vehicle body, wrAs yaw rate, IzThe moment of inertia of the automobile around the z axis;
step 1.3), calculating an ideal yaw rate and a centroid side slip angle when the vehicle enters a steady state according to a two-degree-of-freedom model of the whole vehicle:
in the formula (I), the compound is shown in the specification,
step 1.4), establishing a steer-by-wire variable transmission ratio model:
in the formula (I), the compound is shown in the specification,
as yaw-rate gain, thetaswThe rotational angle of the steering wheel, the gear ratio i,
a steady state yaw rate gain;
step 1.5), a vehicle steering resistance model is deduced according to the ideal yaw velocity, the mass center slip angle and the variable transmission ratio model:
in the formula, d is the tire drag distance;
step 1.6), calculating the total torque T required by the first steering motor and the second steering motor according to the steering resistance model:
in the formula eta1For the transmission of a first steering motor reducer and a second steering motor reducerEfficiency; eta2The transmission efficiency of the first steering motor, the second steering motor and the rack is obtained; n is a radical of1The speed reduction ratio of the first steering motor speed reducer and the second steering motor speed reducer is obtained; n is a radical of2The transmission ratio of the first steering motor, the second steering motor and the rack is obtained;
step 1.7), calculating the required rotating speeds of the first steering motor and the second steering motor according to the rotating speed signal of the steering wheel:
n＝nswN1
where n is a required rotation speed of the first steering motor and the second steering motor, and n is a required rotation speed of the first steering motor and the second steering motorswIs the steering wheel speed;
step 1.8), the energy optimization module optimizes an optimal torque distribution coefficient by adopting a self-adaptive particle swarm optimization according to the required rotating speeds of the first steering motor and the second steering motor and the required total torque signals of the first steering motor and the second steering motor, so that the total power of the motors is the lowest.
Step 1.7) the specific process of the energy optimization module comprises the following steps:
step 2.1), defining a torque distribution coefficient x as the ratio of the torque of the first steering motor to the total torque required by the first steering motor and the second steering motor, wherein the expression is as follows:
in the formula, T1For outputting torque, T, to the first steering motor2Outputting torque for the second steering motor, wherein T is the total torque required by the first steering motor and the second steering motor, and x is a torque distribution coefficient;
step 2.2), establishing a total power consumption model of the dual-motor coupling drive steer-by-wire system:
in the formula, P1Consuming power for the first steering motor, P2For the second steering motor, P is the total power consumed by the steering system, n1Is the rotational speed of the first steering motor, n2Is the rotational speed, η, of the second steering motor1(T1,n1) For the first steering motor at the operating point (T)1,n1) Efficiency of time, η2(T2,n2) For the second steering motor at the operating point (T)2,n2) Efficiency of the time;
step 2.3), establishing a constraint model of the dual-motor coupling drive steer-by-wire system:
in the formula, n1maxIs the maximum rotational speed of the first steering motor, n2maxAt the maximum speed of the second steering motor, T1maxIs the maximum torque of the first steering motor, T2maxIs the maximum torque of the second steering motor;
step 2.4), establishing a mathematical model for optimizing the steer-by-wire system driven by the double-motor coupling:
and 2.5) optimizing the optimized mathematical model by adopting a self-adaptive particle swarm algorithm, and searching an optimal torque distribution coefficient.
As shown in fig. 3, the adaptive particle swarm algorithm in step 2.5) comprises the following steps:
step 3.1), initializing a particle swarm, namely setting the population number N, the dimension D, the iteration times M and the minimum inertia weight w of the adaptive particle swarm algorithmminMaximum inertial weight wmaxIndividual optimal learning factor c1Global optimal learning factor c2；
Step 3.2), randomly setting the initial position of each particle in the defined field
And initial velocity
Wherein i is the particle number;
step 3.3), calculating a fitness function value of the initial population, and selecting a global optimal particle gbest of the initial population:
in the formula, Fi 1An initial fitness function for the ith particle;
step 3.4), calculating the average fitness function value of the population:
in the formula, N is the population number,
the value of the average fitness function of the population during the t iteration;
step 3.5), adjusting the inertia weight of the particles according to the individual fitness function value:
in the formula (I), the compound is shown in the specification,
the inertia weight value of the ith particle at the t iteration is obtained; w is amin,wmaxThe minimum value and the maximum value of the inertia weight are respectively;
the value of the minimum fitness function of the population during the t iteration;
step 3.6), updating the speed of the particles:
in the formula (I), the compound is shown in the specification,
position of ith particle at the t-th iteration, pbestiIs the optimum position of the ith particle, r1、r2Is distributed in [0,1 ]]Random number in between, c1Optimum learning factor for the individual, c2The gbest is a global optimal learning factor, and the gbest is a global optimal particle;
step 3.7), updating the positions of the particles:
in the formula (I), the compound is shown in the specification,
the position of the ith particle in the t iteration;
step 3.8), calculating the fitness function value of the particle:
in the formula, Fi tFor the ith particle in the t th iterationA fitness function value of time;
step 3.9), comparison Fi t、F(pbesti) F, (gbest) and reselecting the individual optimum particle pbestiGlobal optimal particle gbest;
step 3.10), updating iteration times:
t＝t+ 1
in the formula, t is iteration times;
step 3.11), judging whether the maximum iteration number is reached, namely whether t > M is true, if yes, outputting the optimal torque distribution coefficient x as gbest, and if not, returning to the step 3.3).
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only illustrative of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. An energy optimization method of a dual-motor coupling drive steer-by-wire system comprises a steering wheel module, a steering execution module, a signal acquisition module, a variable transmission ratio module, a vehicle ideal state calculation module, a required motor rotating speed and torque calculation module, a torque distribution coefficient optimization module and an ECU control module;
the steering wheel module comprises a steering wheel, a steering column, a road sensing motor reducer and a corner sensor;
the upper end of the steering column is fixedly connected with a steering wheel;
the output shaft of the road sensing motor is connected with the lower end of the steering column through a road sensing motor reducer and used for transmitting road sensing to a steering wheel through the steering column;
the steering angle sensor is arranged on the steering column and used for collecting a steering wheel steering angle signal and transmitting the steering wheel steering angle signal to the signal collection module;
the steering execution module comprises a first steering motor, a first steering motor reducer, a first gear, a second steering motor reducer, a second gear, a rack, a steering tie rod, wheels and a vehicle speed sensor;
the first steering motor is connected with a rotating shaft of the first gear through a first steering motor reducer, the second steering motor is connected with a rotating shaft of the second gear through a second steering motor reducer, and the models of the first steering motor and the second steering motor are the same;
the first gear and the second gear are meshed with the rack; the rack is connected with the steering tie rod; two ends of the tie rod are correspondingly connected with two steering wheels of the vehicle respectively;
the vehicle speed sensor is arranged in a wheel and used for acquiring the vehicle speed of the vehicle and transmitting the vehicle speed to the signal acquisition module;
the signal acquisition module carries out filtering and noise reduction on the steering wheel corner signal, the steering wheel corner differential signal and the vehicle speed signal which are obtained, and transmits the signals to the variable transmission ratio module and the vehicle ideal state calculation module;
the variable transmission ratio module calculates a variable transmission ratio signal of the vehicle according to the signal transmitted by the signal acquisition module and transmits the variable transmission ratio signal to the required motor rotating speed and torque calculation module;
the vehicle ideal state calculation module calculates the ideal yaw rate and the ideal centroid side slip angle of the vehicle according to the signals transmitted by the signal acquisition module and transmits the ideal yaw rate and the ideal centroid side slip angle to the required motor rotating speed and torque calculation module;
the required motor rotating speed and torque calculating module calculates the required rotating speeds of the first steering motor and the second steering motor and the required total torque of the first steering motor and the second steering motor according to the variable transmission ratio signal, the ideal yaw rate and the ideal mass center slip angle transmitted by the variable transmission ratio module and the vehicle ideal state calculating module, and transmits the required rotating speeds and the required total torque of the first steering motor and the second steering motor to the torque distribution coefficient optimizing module;
the torque distribution coefficient optimization module optimizes the torque distribution coefficient by adopting a self-adaptive particle swarm algorithm according to the required rotating speed and the required total torque signals of the first steering motor and the second steering motor, which are transmitted by the required motor rotating speed and torque calculation module, and transmits the obtained optimal torque distribution coefficient to the ECU control module;
the ECU control module is respectively electrically connected with the first steering motor and the second steering motor, and controls the first steering motor and the second steering motor to output torques with corresponding magnitudes according to the optimal torque distribution coefficient signal transmitted by the torque distribution coefficient optimization module, so that the output torques drive wheels through the rack and the steering tie rod to complete vehicle steering;
the energy optimization method of the dual-motor coupling drive steer-by-wire system is characterized by comprising the following steps of:
step 1.1), steering wheel corner signals and vehicle speed signals are collected through a steering wheel corner sensor and a vehicle speed sensor, and the collected corner signals are subjected to differential processing to obtain steering wheel rotating speed signals;
step 1.2), establishing a two-degree-of-freedom model of the whole vehicle:
wherein a is the distance from the center of mass of the automobile to the front axle, b is the distance from the center of mass of the automobile to the rear axle, u is the longitudinal speed of the automobile, and deltafIs the angle of rotation of the front wheel, kfFor front wheel cornering stiffness, krThe lateral deflection rigidity of the rear wheel, m is the whole vehicle mass, beta is the barycenter lateral deflection angle of the vehicle body, wrAs yaw rate, IzThe moment of inertia of the automobile around the z axis;
step 1.3), calculating an ideal yaw rate and a centroid side slip angle when the vehicle enters a steady state according to a two-degree-of-freedom model of the whole vehicle:
in the formula (I), the compound is shown in the specification,
step 1.4), establishing a steer-by-wire variable transmission ratio model:
in the formula (I), the compound is shown in the specification,
as yaw-rate gain, thetaswThe rotational angle of the steering wheel, the gear ratio i,
for steady yaw rateDegree gain;
step 1.5), a vehicle steering resistance model is deduced according to the ideal yaw velocity, the mass center slip angle and the variable transmission ratio model:
in the formula, d is the tire drag distance;
step 1.6), calculating the total torque T required by the first steering motor and the second steering motor according to the steering resistance model:
in the formula eta1The transmission efficiency of the first steering motor reducer and the second steering motor reducer is obtained; eta2The transmission efficiency of the first steering motor, the second steering motor and the rack is improved; n is a radical of1The speed reduction ratio of the first steering motor speed reducer and the second steering motor speed reducer is obtained; n is a radical of2The transmission ratio of the first steering motor, the second steering motor and the rack is set;
step 1.7), calculating the required rotating speeds of the first steering motor and the second steering motor according to the rotating speed signal of the steering wheel:
n＝nswN1
where n is a required rotation speed of the first steering motor and the second steering motor, and n is a required rotation speed of the first steering motor and the second steering motorswIs the steering wheel speed;
step 1.8), the energy optimization module optimizes an optimal torque distribution coefficient by adopting a self-adaptive particle swarm optimization according to the required rotating speeds of the first steering motor and the second steering motor and the required total torque signals of the first steering motor and the second steering motor, so that the total power of the motors is the lowest.
2. The energy optimization method of the dual-motor coupling drive-by-wire steering system according to claim 1, wherein the specific process of the step 1.8) energy optimization module comprises the following steps:
step 2.1), defining a torque distribution coefficient x as the ratio of the torque of the first steering motor to the total torque required by the first steering motor and the second steering motor, wherein the expression is as follows:
in the formula, T1For outputting torque, T, to the first steering motor2Outputting torque for the second steering motor, wherein T is the total torque required by the first steering motor and the second steering motor, and x is a torque distribution coefficient;
step 2.2), establishing a total power consumption model of the dual-motor coupling drive steer-by-wire system:
in the formula, P1Consuming power for the first steering motor, P2For the second steering motor, P is the total power consumed by the steering system, n1Is the rotational speed of the first steering motor, n2Is the rotational speed, η, of the second steering motor1(T1,n1) For the first steering motor at the operating point (T)1,n1) Efficiency of time, η2(T2,n2) For the second steering motor at the operating point (T)2,n2) Efficiency of the time;
step 2.3), establishing a constraint model of the dual-motor coupling drive steer-by-wire system:
in the formula, n1maxIs the maximum rotational speed of the first steering motor, n2maxAt the maximum speed of the second steering motor, T1maxIs the maximum torque of the first steering motor, T2maxIs the maximum torque of the second steering motor;
step 2.4), establishing a mathematical model for optimizing the steer-by-wire system driven by the double-motor coupling:
and 2.5) optimizing the optimized mathematical model by adopting a self-adaptive particle swarm algorithm, and searching an optimal torque distribution coefficient.
3. The energy optimization method of the dual-motor coupled drive steer-by-wire system according to claim 2, wherein the adaptive particle swarm algorithm in step 2.5) comprises the following steps:
step 3.1), initializing a particle swarm, namely setting the population number N, the dimension D, the iteration times M and the minimum inertia weight w of the adaptive particle swarm algorithmminMaximum inertial weight wmaxIndividual optimal learning factor c1Global optimal learning factor c2；
Step 3.2), randomly setting the initial position of each particle in the defined field
And initial velocity
Wherein i is a granuleSub-numbering;
step 3.3), calculating a fitness function value of the initial population, and selecting a global optimal particle gbest of the initial population:
in the formula, Fi 1An initial fitness function for the ith particle;
step 3.4), calculating the average fitness function value of the population:
in the formula, N is the population number,
the value of the average fitness function of the population during the t iteration;
step 3.5), adjusting the inertia weight of the particles according to the individual fitness function value:
in the formula (I), the compound is shown in the specification,
the inertia weight value of the ith particle at the t iteration is obtained; w is amin,wmaxThe minimum value and the maximum value of the inertia weight are respectively;
the value of the minimum fitness function of the population during the t iteration;
step 3.6), updating the speed of the particles:
in the formula (I), the compound is shown in the specification,
position of ith particle at the t-th iteration, pbestiIs the optimum position of the ith particle, r1、r2Is distributed in [0,1 ]]Random number in between, c1Optimum learning factor for the individual, c2The gbest is a global optimal learning factor, and the gbest is a global optimal particle;
step 3.7), updating the positions of the particles:
in the formula (I), the compound is shown in the specification,
the position of the ith particle in the t iteration;
step 3.8), calculating the fitness function value of the particle:
in the formula, Fi tThe fitness function value of the ith particle in the t iteration is obtained;
step 3.9), comparison Fi t、F(pbesti) F, (gbest) and reselecting the individual optimum particle pbestiGlobal optimal particle gbest;
step 3.10), updating iteration times:
t＝t+1
in the formula, t is iteration times;
step 3.11), judging whether the maximum iteration number is reached, namely whether t > M is true, if yes, outputting the optimal torque distribution coefficient x as gbest, and if not, returning to the step 3.3).
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