WO2020140603A1 - 一种基于磁流变液的齿轮齿条式电液转向系统及优化方法 - Google Patents

一种基于磁流变液的齿轮齿条式电液转向系统及优化方法 Download PDF

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Publication number
WO2020140603A1
WO2020140603A1 PCT/CN2019/116095 CN2019116095W WO2020140603A1 WO 2020140603 A1 WO2020140603 A1 WO 2020140603A1 CN 2019116095 W CN2019116095 W CN 2019116095W WO 2020140603 A1 WO2020140603 A1 WO 2020140603A1
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Prior art keywords
steering
rack
magnetorheological fluid
pinion
optimization
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English (en)
French (fr)
Inventor
周小川
赵万忠
王一松
张自宇
汪桉旭
王春燕
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Nanjing Tianhang Institute Of Intelligent Equipment Co Ltd
Nanjing University of Aeronautics and Astronautics
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Nanjing Tianhang Institute Of Intelligent Equipment Co Ltd
Nanjing University of Aeronautics and Astronautics
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Priority claimed from CN201920002471.4U external-priority patent/CN209739146U/zh
Priority claimed from CN201910002267.7A external-priority patent/CN109774785B/zh
Application filed by Nanjing Tianhang Institute Of Intelligent Equipment Co Ltd, Nanjing University of Aeronautics and Astronautics filed Critical Nanjing Tianhang Institute Of Intelligent Equipment Co Ltd
Publication of WO2020140603A1 publication Critical patent/WO2020140603A1/zh
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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
    • 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
    • B62D5/065—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 specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist

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  • the invention belongs to the technical field of automobile steering systems, and in particular relates to a rack-and-pinion electro-hydraulic steering system based on magnetorheological fluid and its multi-objective optimization method.
  • the most common power steering systems currently include hydraulic power steering systems and electric power steering systems.
  • the hydraulic power steering system has a large output torque and stable operation, but the energy consumption is large and the maintenance is inconvenient; the electric power steering system can adjust the auxiliary power according to the real-time working conditions, and the quality is small and the installation space is saved, but the output torque is relatively high Small, it is difficult to meet the needs of large vehicles.
  • Limited by the inherent characteristics of the hydraulic system and the electrical system it is difficult to optimize the steering performance independently of the hydraulic power steering system or the electric power steering system.
  • Using the electro-hydraulic power steering system can combine the advantages of the two.
  • magnetorheological fluid As a new material, magnetorheological fluid has been widely used in many fields. It exhibits the characteristics of Newtonian fluid with low viscosity under the condition of zero magnetic field, and the Bingham body with high viscosity and low fluidity under the action of strong magnetic field. Characteristics, and the change process is instantaneous, and at the same time has the characteristics of low energy consumption, has been used in automotive steering systems.
  • the Chinese patent application number is CN201410557874.7, the name “a rack and pinion type magnetic fluid electronically controlled hydraulic power steering device and control method” uses magnetorheological fluid as the hydraulic power, but because it relies solely on the Lorentz force as the power Source, the power assistance it can provide is limited and cannot achieve the desired effect, and it cannot completely replace the hydraulic power steering system;
  • the Chinese patent application number is CN201720488038.7, the name “Magnetorheological Damper for Vehicle Semi-active Control Steering System”, using magnetic The rheological characteristics improve the steering stability of the car, but its main use is its damping characteristics rather than providing assistance. Therefore, designing an automotive electro-hydraulic power steering system that uses magnetorheological fluid for power assist and combines with electric power assist can save energy consumed during the steering process, speed up the response speed, and obtain better steering characteristics, which has in-depth research value.
  • the electro-hydraulic steering system involves multiple modules cooperating with each other and having a complex structure, requiring the synergy of multiple disciplines such as machinery, fluids, and electronics. At the same time, it involves many performance parameter indexes, and reasonable and scientific parameter optimization design plays a key role in system performance. Therefore, accurately establishing an optimization model and using an appropriate optimization algorithm have a non-negligible role in obtaining good overall performance of the electro-hydraulic steering system.
  • the object of the present invention is to provide a rack-and-pinion electro-hydraulic steering system and an optimization method based on magnetorheological fluid to overcome the problems in the prior art.
  • the invention uses magnetorheological fluid to replace the original hydraulic oil to provide assistance, greatly simplifying the hydraulic structure of the rack and pinion steering gear, by controlling the cooperation of the electric assistance module and the magnetorheological fluid assistance module, and providing a multi-objective optimization method
  • the optimization of key parameters enables the car to obtain better steering feel while reducing system energy loss and obtain good overall steering performance.
  • a rack-and-pinion electro-hydraulic steering system based on magnetorheological fluid of the present invention includes: a mechanical transmission module, a magnetorheological fluid power assist module, an electric power assist module, and a power assist control module;
  • the mechanical transmission module includes a steering wheel, a rotation angle sensor, a torque sensor, a steering shaft, a rack and pinion steering gear, a tie rod, a left-hand steering trapezoid, a right-hand steering trapezium, a left-hand wheel, and a right-hand wheel;
  • the upper end is connected to the steering wheel, and a rotation angle sensor is installed on the steering wheel;
  • the lower end of the steering shaft is connected to the input end of the rack and pinion steering gear, and a torque sensor is installed on the lower end of the steering shaft;
  • the rack and pinion steering gear includes a steering gear and a radial ball bearing, Steering rack, spring, pressure block, adjusting nut, steering gear housing;
  • the steering gear is supported in the steering gear housing through a radial ball bearing, the upper end of the steering gear is connected to the steering shaft, and the lower end is meshed with the horizontally arranged steering rack , Forming a pair of transmission pairs;
  • the spring presses the steering rack
  • the magnetorheological fluid booster module includes a magnetorheological fluid shell, an upper metal plate, a lower metal plate, a left tapered roller bearing, a right tapered roller bearing, a left force plate, a right force plate, an input shaft, and an output Shaft, magnetorheological fluid material, excitation coil, power supply unit;
  • the tie rod is interrupted by the magnetorheological fluid booster module and is divided into left and right ends.
  • the left end of the tie rod is connected to the output shaft, and the right end of the tie rod is connected to the input shaft; the input shaft depends on the right
  • the tapered roller bearing is supported on the magnetorheological fluid shell, and is connected to the lower metal plate through the right force plate; the output shaft is supported on the magnetorheological fluid shell by the left tapered roller bearing, through the left force plate and the upper metal plate Connected; the magnetorheological fluid shell surrounds the upper and lower metal plates and the input shaft and output shaft staggered up and down; the magnetorheological fluid shell is filled with magnetorheological fluid material; the magnetorheological fluid shell is wound horizontally with an excitation coil to supply power The unit is electrically connected to the excitation coil.
  • the excitation coil When the power supply unit is energized, the excitation coil generates a variable magnetic field.
  • the magnetorheological fluid material changes under the action characteristics of the magnetic field, and generates a shearing force acting on the upper and lower metal plates, which is converted into left and right force.
  • the output force of the plate is transmitted through the output shaft and the input axial tie rod, and the steering power provided by the magnetorheological fluid power assist module is output;
  • the electric power assist module includes a motor, a clutch, and a speed reduction mechanism; the motor is fixed on the steering shaft side, and is connected to the steering shaft through the speed reduction mechanism, and a clutch is provided between the speed reduction mechanism and the motor;
  • the input end of the power assist control module is connected to the torque sensor, the rotation angle sensor and the vehicle speed sensor respectively, and receives the steering wheel angle signal, torque signal and vehicle speed signal input by the driver, and the output end thereof is connected to the motor, clutch and power supply unit through
  • the output of the magnetorheological fluid control signal changes the current provided by the power supply unit
  • the output of the motor control signal controls the electromagnetic torque provided by the motor
  • the output of the clutch control signal to adjust the working state of the clutch.
  • a multi-objective optimization method of a rack-and-pinion electro-hydraulic steering system based on magnetorheological fluid of the present invention is based on the above system and includes the following steps:
  • step (3) Based on the system optimization goal selected in step (2), perform performance analysis; based on the performance analysis results, select mechanical parameters and magnetorheological fluid parameters that have a large impact on steering performance as optimization variables;
  • a multi-objective evolution algorithm based on reference points is used to optimize the multi-objective parameters.
  • the rack and pinion electro-hydraulic steering system model includes: a steering wheel-steering shaft model, a rack and pinion steering model, a magnetorheological fluid power assist module model, and an electric power assist module model.
  • step (1) the model of the rack and pinion electro-hydraulic steering system in step (1) is:
  • J s is the steering wheel moment of inertia
  • ⁇ s is the driver input torque
  • B s is the steering shaft damping coefficient
  • k s is the steering sensor stiffness
  • ⁇ e is the steering gear angle
  • J ds Is the rotational inertia of the steering shaft and the reduction mechanism
  • B ds is the damping coefficient of the reduction mechanism
  • G is the reduction ratio of the reduction mechanism
  • T eps is the motor assist torque
  • T sen is the torque output by the torque sensor
  • T w is the rack and pinion force
  • J m1 is the motor inertia
  • ⁇ m1 is the motor rotation angle
  • B m1 is the motor damping coefficient
  • T em1 is the assisted motor electromagnetic torque
  • m r is the rack mass
  • x r is the steering rack displacement
  • B r is the steering gear Bar damping coefficient
  • r p is the radius of the steering gear
  • F hyd is
  • the vehicle model is:
  • the tire model is:
  • I z is the moment of inertia of the car mass on the z-axis
  • ⁇ r is the yaw rate
  • ⁇ is the body roll angle
  • N r , N ⁇ , N ⁇ , and N ⁇ are the unit yaw rate and the unit center of mass side deviation, respectively
  • Angle, unit roll angle speed, unit front wheel rotation angle to the z-axis, u is the longitudinal speed
  • m is the mass of the vehicle
  • I x is the moment of inertia of the suspension mass to the x-axis
  • ⁇ is the lateral angle of the center of mass
  • ⁇ is the front wheel slip angle
  • ⁇ is the front wheel steering angle
  • d is the tread
  • G P is a steering shaft to the front wheel transmission ratio
  • h is the centroid of the suspension to the roll axis
  • step (2) includes: steering feel, steering assist, and steering energy consumption; wherein, the steering feel formula is:
  • the steering assist formula is:
  • E m represents the energy consumption of the mechanical transmission module
  • E MRF represents the energy consumption of the magnetorheological fluid power module
  • E motor represents the energy consumption of the motor
  • E ecu represents the energy consumption of the ECU.
  • step (3) the optimized variables in step (3) include: motor inertia J m1 , torque sensor stiffness K S , metal plate gap L, magnetorheological fluid shear area A, excitation coil turns Z, deceleration mechanism Reduction ratio G.
  • step (4) the multi-objective optimization model of the rack-and-pinion electro-hydraulic steering system in step (4) is:
  • F energy (X) is the steering energy consumption function
  • F road (X) is the steering feel function
  • F force (X) is the steering assist function
  • g 1 (X) is the steering sensitivity.
  • f m (x) is the desired objective function value of the selected optimization variable for steering feel, steering assist, and steering energy consumption.
  • i d is the crowded distance between individuals; Is the value of i+1 individuals on the m-th optimization objective function; Is the value of i-1 individuals on the mth optimization objective function;
  • f m (x i ) is the value of the individual x i on the mth target;
  • the invention utilizes the combination of two assisting modes of the motor and the magnetorheological fluid, which not only accelerates the steering response speed, but also provides variable steering assist according to different working conditions, with less energy consumption.
  • the invention uses magneto-rheological fluid to replace the existing hydraulic power, does not need to install a hydraulic pump, hydraulic valve, hydraulic pipeline, liquid storage tank, the structure is simple and reduces the quality of the system, while providing additional steering assistance for electric steering.
  • the present invention utilizes a multi-objective evolution algorithm based on reference points to optimize the electro-hydraulic steering system, effectively solving the conflicting problems among multiple optimization goals of steering feel, steering energy consumption and steering assistance, and obtaining a better comprehensive steering performance.
  • Group solution set
  • FIG. 1 is a schematic structural diagram of a rack-and-pinion electro-hydraulic steering system based on magnetorheological fluid of the present invention
  • FIG. 2 is a structural diagram of a rack and pinion steering gear of the present invention
  • FIG. 3 is a structural diagram of a magnetorheological fluid boosting module of the present invention.
  • FIG. 5 is a flowchart of a multi-objective evolution algorithm based on reference points of the present invention.
  • a rack-and-pinion electro-hydraulic steering system based on magnetorheological fluid of the present invention includes: a mechanical transmission module, a magnetorheological fluid power assist module 11, an electric power assist module, and a power assist control module 14 (ECU);
  • the mechanical transmission module includes a steering wheel 1, a rotation angle sensor, a torque sensor 3, a steering shaft 2, a rack and pinion steering gear 8, a tie rod 7, a right-hand steering trapezoid 6, a left-hand steering trapezoid 12, and a right wheel 5 And the left wheel 13; the upper end of the steering shaft 2 is connected to the steering wheel 1, and a steering wheel sensor is installed on the steering wheel 1; the lower end of the steering shaft 2 is connected to the input end of the rack and pinion steering gear 8, and the torque sensor 3 is installed at the lower end of the steering shaft 2
  • the rack and pinion steering gear includes a steering gear 19, a radial ball bearing 18, a steering rack 20, a spring 22, a pressure block 21, an adjusting nut 23, and a steering gear housing 24; the steering gear 19 is supported by the radial ball bearing 18; In the steering gear housing 24, the upper end of the steering gear 19 is connected to the steering shaft 2, and the lower end is meshed with the horizontally arranged steering rack 20 to form a pair of transmission
  • the magnetorheological fluid assist module includes a magnetorheological fluid housing 28, an upper metal plate 29, a lower metal plate 31, a left tapered roller bearing 25, a right tapered roller bearing 35, a left force plate 27, a right force Plate 33, input shaft 34, output shaft 26, magnetorheological fluid material 30, excitation coil 32, power supply unit 36;
  • the tie rod 7 is interrupted by the magnetorheological fluid booster module and is divided into left and right ends.
  • the left end of the tie rod is connected to the output shaft, and the right end of the tie rod is connected to the input shaft;
  • the input shaft depends on
  • the right tapered roller bearing is supported on the magnetorheological fluid shell, and is connected to the lower metal plate through the right force plate;
  • the output shaft is supported on the magnetorheological fluid shell on the left tapered roller bearing, through the left force plate and the upper metal
  • the plate is connected; the magnetorheological fluid shell surrounds the upper and lower metal plates and the input shaft and output shaft staggered up and down;
  • the magnetorheological fluid shell is filled with magnetorheological fluid material;
  • the magnetorheological fluid shell is wound horizontally with an excitation coil,
  • the power supply unit is electrically connected to the excitation coil.
  • the excitation coil When the power supply unit is energized, the excitation coil generates a variable magnetic field.
  • the magnetorheological fluid material changes under the action characteristics of the magnetic field, and the shear force is generated on the upper and lower metal plates, which is converted into left and right.
  • the output force of the force plate is transmitted through the output shaft and the input axial tie rod, and the steering assist provided by the magnetorheological fluid assist module is output;
  • the electric power assist module includes a motor 10, a clutch 9, and a speed reduction mechanism 4; the motor 10 is fixed on the steering shaft 2 side and connected to the steering shaft 2 through the speed reduction mechanism 4; a clutch 9 is provided between the speed reduction mechanism 4 and the motor 10;
  • the input end of the power-assist control module is respectively connected with a torque sensor, a rotation angle sensor and a vehicle speed sensor, and receives the steering wheel angle signal, torque signal and vehicle speed signal input by the driver, and the output end thereof is connected with a motor, a clutch and a power supply unit;
  • the power control module calculates based on each sensor signal, it outputs a motor control signal 16, a clutch control signal 17, and a magnetorheological fluid control signal 15 to control the motor current, clutch switch status, and power supply unit current, respectively, to adjust the motor output
  • the magnitude of the electromagnetic torque, and the current input to the excitation coil through the power supply unit generates a corresponding magnetic field between the two metal plates, so that the magnetorheological fluid material outputs the corresponding steering assistance.
  • a multi-objective optimization method of a rack-and-pinion electro-hydraulic steering system based on magnetorheological fluid of the present invention includes the following steps:
  • the rack and pinion type electro-hydraulic steering system model includes: a steering wheel-steering shaft model, a rack and pinion steering model, a magnetorheological fluid power assist module model and an electric power assist module model.
  • the model of the rack and pinion electro-hydraulic steering system is:
  • J s is the steering wheel moment of inertia
  • ⁇ s is the driver input torque
  • B s is the steering shaft damping coefficient
  • k s is the steering sensor stiffness
  • ⁇ e is the steering gear angle
  • J ds Is the rotational inertia of the steering shaft and the reduction mechanism
  • B ds is the damping coefficient of the reduction mechanism
  • G is the reduction ratio of the reduction mechanism
  • T eps is the motor assist torque
  • T sen is the torque output by the torque sensor
  • T w is the rack and pinion force
  • J m1 is the motor inertia
  • ⁇ m1 is the motor rotation angle
  • B m1 is the motor damping coefficient
  • T em1 is the assisted motor electromagnetic torque
  • m r is the rack mass
  • x r is the steering rack displacement
  • B r is the steering gear Bar damping coefficient
  • r p is the radius of the steering gear
  • F hyd is
  • the vehicle model is:
  • the tire model is:
  • I z is the mass moment of inertia of the car on the z-axis
  • ⁇ r is the yaw rate
  • ⁇ is the body roll angle
  • N r , N ⁇ , N ⁇ , and N ⁇ are the unit yaw rate and the center of mass side deviation Angle
  • unit roll angle speed, unit front wheel rotation angle to the z-axis u is the longitudinal speed
  • m is the mass of the vehicle
  • I x is the moment of inertia of the suspension mass to the x-axis
  • ⁇ is the lateral angle of the center of mass
  • ⁇ is the front wheel slip angle
  • ⁇ is the front wheel steering angle
  • d is the tread
  • G P is a steering shaft to the front wheel transmission ratio
  • h is the centroid of the suspension to the roll axis
  • the distance, L p and L ⁇ are the
  • the optimization goals include: steering feel, steering assist, and steering energy consumption;
  • the steering assist formula is:
  • E m represents the energy consumption of the mechanical transmission module
  • E MRF represents the energy consumption of the magnetorheological fluid power module
  • E motor represents the energy consumption of the motor
  • E ecu represents the energy consumption of the ECU.
  • optimization variables include: motor rotation Inertia J m1 , torque sensor stiffness K S , metal plate gap L, magnetorheological fluid shear area A, excitation coil turns Z, reduction gear reduction ratio G.
  • the multi-objective optimization model of the rack and pinion electro-hydraulic steering system is:
  • F energy (X) is the steering energy consumption function
  • F road (X) is the steering feel function
  • F force (X) is the steering assist function
  • g 1 (X) is the steering sensitivity.
  • a multi-objective evolution algorithm based on reference points is used to optimize the multi-objective parameters.
  • f m (x) is the desired objective function value of the selected optimization variable for steering feel, steering assist, and steering energy consumption.
  • i d is the crowded distance between individuals; Is the value of i+1 individuals on the m-th optimization objective function; Is the value of i-1 individuals on the mth optimization objective function;
  • f m (x i ) is the value of the individual x i on the mth target;

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Abstract

一种基于磁流变液的齿轮齿条式电液转向系统及优化方法，系统包括：机械传动模块、磁流变液助力模块（11）、电动助力模块、助力控制模块（14）；该优化方法包括以下步骤：(1)建立齿轮齿条式电液转向系统模型、整车模型及轮胎模型，(2)选择系统优化目标，推导评价公式；(3)选择对转向性能影响大的参数为优化变量，(4)在转向灵敏度和优化变量取值范围的约束条件下，建立系统多目标优化模型；(5)采用基于参考点的多目标进化算法进行优化。利用电动机（10）与磁流变液两种助力方式，转向响应速度快，转向助力范围大，能量消耗少，并有效解决了转向路感、转向能耗和转向助力多个优化目标之间相互冲突的问题。

Description

一种基于磁流变液的齿轮齿条式电液转向系统及优化方法 技术领域
本发明属于汽车转向系统技术领域，具体涉及一种基于磁流变液的齿轮齿条式电液转向系统及其多目标优化方法。
背景技术
随着助力转向系统的发展，汽车转向系统的性能在轻便化、节能化、智能化等方面有了极大提高。目前最常见的助力转向系统主要包括液压助力转向系统和电动助力转向系统。其中，液压助力转向系统输出力矩大，操作稳定，但能耗较大，维修不方便；电动助力转向系统可根据实时工况调节辅助动力，且质量小、节省安装空间，但其输出力矩相对较小，很难满足大型车辆助力的需求。受限于液压系统和电气系统固有的特性，无论是液压助力转向系统还是电动助力转向系统，都难以单独实现转向性能的最优化，采用电液助力转向系统则可以将二者优点结合。
磁流变液作为一种新兴材料在许多领域得到了广泛应用，其在零磁场条件下呈现出低粘度的牛顿流体特性，而在强磁场作用下则呈现出高粘度、低流动性的Bingham体特性，且变化过程是瞬时的，并同时具有低能耗的特点，在汽车转向系统得到了一些应用。例如中国专利申请号为CN201410557874.7，名称“一种齿轮齿条式磁流体电控液压助力转向装置及控制方法”中将磁流变液作为液压助力，但由于单独依靠洛伦兹力为动力源，所能提供的助力受限而不能达到理想效果，无法完全替代液压助力转向系统；中国专利申请号为CN201720488038.7，名称“车辆半主动控制转向系统用磁流变阻尼器”，利用磁流变液特性提高汽车转向稳定性，但主要利用的是其阻尼特性而非提供助力。因此，设计一种利用磁流变液进行助力并与电动助力相结合的汽车电液助力转向系统，节约转向过程消耗的能量，加快响应速度，获得更好的转向特性，具有深入研究价值。
电液转向系统涉及多个模块相互配合，结构复杂，需要机械，流体，电子等多门学科协同作用。同时其中涉及众多的性能参数指标，合理科学的参数优化设计对系统性能起到关键性作用。因此，准确建立优化模型，采用合适优化算法对获得电液转向系统的良好综合性能有着不可忽视的作用。
发明内容
针对于上述现有技术的不足，本发明的目的在于提供一种基于磁流变液的齿轮齿条式电液转向系统及优化方法，以克服现有技术中存在的问题。本发明利用磁流变液替代原有液压油提供助力，大大简化了齿轮齿条转向器的液压结构，通过控制电动助力模块和磁流变液助力模块的配合，并提供一种多目标优化方法优化关键参数，使得汽车在获得较好的转向路感 的同时降低系统能量损耗，得到良好的综合转向性能。
为达到上述目的，本发明采用的技术方案如下：
本发明的一种基于磁流变液的齿轮齿条式电液转向系统，包括：机械传动模块、磁流变液助力模块、电动助力模块、助力控制模块；
所述的机械传动模块包括方向盘、转角传感器、转矩传感器、转向轴、齿轮齿条式转向器、横拉杆、左侧转向梯形、右侧转向梯形、左侧车轮及右侧车轮；转向轴的上端与方向盘相连，方向盘上安装转角传感器；转向轴的下端与齿轮齿条转向器的输入端连接，转向轴下端安装有转矩传感器；齿轮齿条式转向器包括转向齿轮，向心球轴承，转向齿条，弹簧，压块，调整螺母，转向器壳体；转向齿轮通过向心球轴承支承在转向器壳体内，转向齿轮的上端与转向轴连接，下端与水平布置的转向齿条相啮合，形成一对传动副；弹簧通过压块将转向齿条压靠在转向齿轮上，使转向齿条和转向齿轮无间隙啮合；调整螺母通过转向器壳体与弹簧相连，提供弹簧预紧力；转向齿条两端连接横拉杆，横拉杆右端通过右侧转向梯形与右侧车轮连接，横拉杆左端通过磁流变液助力模块连接左侧转向梯形及左侧车轮；
所述的磁流变液助力模块包括磁流变液外壳、上金属板、下金属板、左圆锥滚子轴承、右圆锥滚子轴承、左受力板、右受力板、输入轴、输出轴、磁流变液材料、励磁线圈、供电单元；
所述横拉杆被磁流变液助力模块打断分为左右两端打断处，横拉杆的左端打断处与输出轴连接，横拉杆的右端打断处与输入轴连接；输入轴依靠右圆锥滚子轴承支撑在磁流变液外壳上，通过右受力板与下金属板连接；输出轴依靠左圆锥滚子轴承支撑在磁流变液外壳上，通过左受力板与上金属板相连；磁流变液外壳包围了上下错开设置的上、下金属板及输入轴、输出轴；磁流变液外壳内部充满磁流变液材料；磁流变液外壳外部水平缠绕励磁线圈，供电单元与励磁线圈电气连接，供电单元通电时励磁线圈产生可变磁场，磁流变液材料在磁场的作用特性下发生变化，产生剪切力作用在上、下金属板上，转化为左右受力板的输出力，并通过输出轴和输入轴向横拉杆传递，输出磁流变液助力模块提供的转向助力；
所述的电动助力模块包括电动机，离合器，减速机构；电动机固定在转向轴一侧，并通过减速机构与转向轴连接，减速机构与电动机间设有离合器；
所述的助力控制模块输入端分别与转矩传感器，转角传感器及车速传感器相连，接收驾驶员输入的方向盘转角信号、转矩信号、车速信号，其输出端与电动机、离合器、供电单元相连，通过输出磁流变液控制信号改变供电单元提供的电流，输出电机控制信号控制电动机提供的电磁转矩，输出离合器控制信号调整离合器的工作状态。
本发明的一种基于磁流变液的齿轮齿条式电液转向系统的多目标优化方法，基于上述系统，包括步骤如下：
(1)建立齿轮齿条式电液转向系统模型、整车模型及轮胎模型；
(2)选择齿轮齿条式电液转向系统优化目标，并根据步骤(1)建立的模型，推导对应优化目标的评价公式；
(3)以步骤(2)选择的系统优化目标为基础，进行性能分析；根据性能分析结果，选择对转向性能影响大的机械参数和磁流变液参数为优化变量；
(4)在转向灵敏度和优化变量取值范围的约束条件下，建立齿轮齿条式电液转向系统多目标优化模型；
(5)根据齿轮齿条式电液转向系统多目标优化模型，采用基于参考点的多目标进化算法，进行多目标参数优化。
进一步地，所述齿轮齿条式电液转向系统模型包括：转向盘-转向轴模型、齿轮齿条转向器模型、磁流变液助力模块模型及电动助力模块模型。
进一步地，所述步骤(1)中的齿轮齿条式电液转向系统模型为：
Figure PCTCN2019116095-appb-000001
式中：J s为方向盘转动惯量，θ s为驾驶员输入转角；T dri为驾驶员输入力矩，B s为转向轴阻尼系数，k s为转向传感器刚度，θ e为转向齿轮转角，J ds为转向轴与减速机构的转动惯量，B ds为减速机构阻尼系数，G为减速机构减速比，T eps为电动机助力转矩，T sen为转矩传感器输出力矩，T w为齿轮齿条作用力，J m1为电动机转动惯量，θ m1为电动机转角，B m1为电动机阻尼系数，T em1为助力电机电磁转矩，m r为齿条质量，x r为转向齿条位移，B r为转向齿条阻尼系数，r p为转向齿轮半径，F hyd为磁流变液助力模块提供的助力，F z为转向齿条上的阻力；
整车模型为：
Figure PCTCN2019116095-appb-000002
轮胎模型为：
Figure PCTCN2019116095-appb-000003
式中，I z为汽车质量对z轴的转动惯量，ω r为横摆角速度，φ为车身侧倾角，N r、N β、N φ、N δ分别为单位横摆角速度、单位质心侧偏角、单位侧倾角速度、单位前轮转角对z轴 的力矩，u为纵向速度，m为整车质量，I x为悬挂质量对x轴的转动惯量，β为质心侧偏角，α为前轮侧偏角，δ为前轮转向角，I xz为悬挂质量对x、z轴的惯性积，d为轮距，G P为转向轴到前轮传动比，h为悬挂质心至侧倾轴线的距离，L p、L φ分别为单位侧倾角速度、单位侧倾角对x轴的外力矩，Y r、Y β、Y φ、Y δ分别为单位横摆角速度、单位整车侧偏角、单位侧倾角、单位前轮转角引起的地面侧向反作用力，k 1为前轮侧偏刚度，E 1为弧度因子。
进一步地，所述步骤(2)中的优化目标包括：转向路感、转向助力、转向能耗；其中，转向路感公式为：
Figure PCTCN2019116095-appb-000004
转向助力公式为：
F force＝T w/r p+F MRF
转向能耗公式为：
F energy＝E m+E MRF+E motor+E ecu
式中，E m表示机械传动模块能耗，E MRF表示磁流变液助力模块能耗，E motor表示电动机能耗，E ecu表示ECU能耗。
进一步地，所述步骤(3)中的优化变量包括：电动机转动惯量J m1，转矩传感器刚度K S，金属板间隙L，磁流变液剪切面积A，励磁线圈匝数Z，减速机构减速比G。
进一步地，所述步骤(4)中的齿轮齿条式电液转向系统多目标优化模型为：
Figure PCTCN2019116095-appb-000005
式中，F energy(X)为转向能耗函数，F road(X)为转向路感函数，F force(X)为转向助力函数，g 1(X)为转向灵敏度。
进一步地，所述步骤(5)中的基于参考点的多目标进化算法，具体步骤如下：
51)随机生成规模为N的初始父种群P t(J m1，K S，L,A,Z,G)，设置进化代数计数t＝1，根据电液转向系统优化变量的初值对种群进行初始化；
52)对父代种群P t进行交叉、变异、选择等操作，生成子代种群Q t；
53)将P t与子代种群Q t合并到一个集合中，对集合里的个体进行非支配排序，将所有非支配个体保存到集合U t中；
54)对集合U t进行非支配排序并保存所有非支配个体，根据公式(1)计算最优目标函数值，通过选择最优目标值生成候选参考点，保存到集合R m中；
Figure PCTCN2019116095-appb-000006
式中，f m(x)为所选优化变量对转向路感、转向助力、转向能耗的期望目标函数值，m＝1时目标函数为转向路感，m＝2时目标函数为转向助力，m＝3时目标函数为转向能耗，
Figure PCTCN2019116095-appb-000007
为最优目标函数值，ε m为零或任意小的正数；
55)根据公式(2)计算R m中候选参考点的拥挤距离，选取前N个拥挤距离较大的候选参考点，保存到最终参考点集合R中；
Figure PCTCN2019116095-appb-000008
式中，i d为个体间的拥挤距离；
Figure PCTCN2019116095-appb-000009
为i+1个个体在第m个优化目标函数上的值；
Figure PCTCN2019116095-appb-000010
为i-1个个体在第m个优化目标函数上的值；
56)对集合R中的每个参考点，根据公式(3)计算集合U t中所有个体的加权欧几里得距离
Figure PCTCN2019116095-appb-000011
Figure PCTCN2019116095-appb-000012
式中，x i为上述所选的非支配个体，i＝6；f m(x i)为个体x i在第m目标上的值；
57)找出最小的加权欧几里得距离值对应的集合U t中非支配个体和R m中的候选参考点，将所找出的非支配个体保存到下一代种群P t+1中，循环操作直到得到N个个体作为下一代父种群P t+1；
58)判断t是否等于设置的最大进化代数gen，若t＝gen，则算法结束退出优化，得到电液转向系统最优解；否则t＝t+1，转到步骤52)继续执行优化。
本发明的有益效果：
本发明利用电动机与磁流变液两种助力方式结合，既加快了转向响应速度，又可根据不同工况提供可变转向助力，能量消耗少。
本发明采用磁流变液代替现有液压助力，不需要安装液压泵，液压阀、液压管路、储液罐，结构简单且减轻了系统质量，同时为电动转向提供额外的转向助力。
本发明利用基于参考点的多目标进化算法对电液转向系统进行优化，有效解决转向路感、转向能耗和转向助力多个优化目标之间相互冲突的问题，得到综合转向性能较好的一组解集。
附图说明
图1为本发明基于磁流变液的齿轮齿条式电液转向系统的原理结构图；
图2为本发明齿轮齿条转向器结构图；
图3为本发明磁流变液助力模块结构图；
图4为本发明优化方法流程图；
图5为本发明的基于参考点的多目标进化算法流程图；
图中，1-方向盘；2-转向轴；3-转矩传感器；4-减速机构；5-右侧车轮；6-右侧转向梯形；7-横拉杆；8-齿轮齿条转向器；9-离合器；10-电动机；11-磁流变液助力模块；12-左侧转向梯形；13-左侧车轮；14-助力控制模块；15-磁流变液控制信号；16-电机控制信号；17-离合器控制信号；18-向心球轴承；19-转向齿轮；20-转向齿条；21-压块；22-弹簧；23-调整螺母；24-转向器壳体；25-左圆锥滚子轴承；26-输出轴；27-左受力板；28-磁流变液外壳；29-上金属板；30-磁流变液材料；31-下金属板；32-励磁线圈；33右受力板；34-输入轴；35-右圆锥滚子轴承；36-供电单元。
具体实施方式
为了便于本领域技术人员的理解，下面结合实施例与附图对本发明作进一步的说明，实施方式提及的内容并非对本发明的限定。
参照图1至图3所示，本发明的一种基于磁流变液的齿轮齿条式电液转向系统，包括：机械传动模块、磁流变液助力模块11、电动助力模块、助力控制模块14(ECU)；
所述的机械传动模块包括方向盘1、转角传感器、转矩传感器3、转向轴2、齿轮齿条式转向器8、横拉杆7、右侧转向梯形6、左侧转向梯形12、右侧车轮5及左侧车轮13；转向轴2的上端与方向盘1相连，方向盘1上安装转角传感器；转向轴2的下端与齿轮齿条转向器8的输入端连接，转向轴2下端安装有转矩传感器3；齿轮齿条式转向器包括转向齿轮19，向心球轴承18，转向齿条20，弹簧22，压块21，调整螺母23，转向器壳体24；转向齿轮19通过向心球轴承18支承在转向器壳体24内，转向齿轮19的上端与转向轴2连接，下端与水平布置的转向齿条20相啮合，形成一对传动副；弹簧22通过压块21将转向齿条20压靠在转向齿轮19上，使转向齿条20和转向齿轮19无间隙啮合；调整螺母23通过转向器壳体24与弹簧22相连，提供弹簧预紧力；转向齿条两端连接横拉杆7，横拉杆7右端通过右侧转向梯形6与右侧车轮5连接，横拉杆左端通过磁流变液助力模块连接左侧转向梯形12及左侧车轮13；
所述的磁流变液助力模块包括磁流变液外壳28、上金属板29、下金属板31、左圆锥滚子轴承25、右圆锥滚子轴承35、左受力板27、右受力板33、输入轴34、输出轴26、磁流变液材料30、励磁线圈32、供电单元36；
所述横拉杆7被磁流变液助力模块打断分为左右两端打断处，横拉杆的左端打断处与输出轴连接，横拉杆的右端打断处与输入轴连接；输入轴依靠右圆锥滚子轴承支撑在磁流变液外壳上，通过右受力板与下金属板连接；输出轴依靠左圆锥滚子轴承支撑在磁流变液外壳上，通过左受力板与上金属板相连；磁流变液外壳包围了上下错开设置的上、下金属板及输入轴、 输出轴；磁流变液外壳内部充满磁流变液材料；磁流变液外壳外部水平缠绕励磁线圈，供电单元与励磁线圈电气连接，供电单元通电时励磁线圈产生可变磁场，磁流变液材料在磁场的作用特性下发生变化，产生剪切力作用在上、下金属板上，转化为左右受力板的输出力，并通过输出轴和输入轴向横拉杆传递，输出磁流变液助力模块提供的转向助力；
所述的电动助力模块包括电动机10，离合器9，减速机构4；电动机10固定在转向轴2一侧，并通过减速机构4与转向轴2连接，减速机构4与电动机10间设有离合器9；
所述的助力控制模块输入端分别与转矩传感器，转角传感器及车速传感器相连，接收驾驶员输入的方向盘转角信号、转矩信号、车速信号，其输出端与电动机、离合器、供电单元相连；转向时，助力控制模块根据各传感器信号进行计算，输出电机控制信号16、离合器控制信号17、磁流变液控制信号15，分别控制电动机电流大小、离合器开关状态、供电单元电流大小，从而调整电动机输出的电磁转矩大小，并通过供电单元输入励磁线圈的电流在两金属板间产生相应磁场，使磁流变液材料输出相应的转向助力。
参照图4所示，本发明的一种基于磁流变液的齿轮齿条式电液转向系统的多目标优化方法，基于上述系统，包括步骤如下：
(1)建立齿轮齿条式电液转向系统模型、整车模型及轮胎模型；
其中，所述齿轮齿条式电液转向系统模型包括：转向盘-转向轴模型、齿轮齿条转向器模型、磁流变液助力模块模型及电动助力模块模型。
齿轮齿条式电液转向系统模型为：
Figure PCTCN2019116095-appb-000013
式中：J s为方向盘转动惯量，θ s为驾驶员输入转角；T dri为驾驶员输入力矩，B s为转向轴阻尼系数，k s为转向传感器刚度，θ e为转向齿轮转角，J ds为转向轴与减速机构的转动惯量，B ds为减速机构阻尼系数，G为减速机构减速比，T eps为电动机助力转矩，T sen为转矩传感器输出力矩，T w为齿轮齿条作用力，J m1为电动机转动惯量，θ m1为电动机转角，B m1为电动机阻尼系数，T em1为助力电机电磁转矩，m r为齿条质量，x r为转向齿条位移，B r为转向齿条阻尼系数，r p为转向齿轮半径，F hyd为磁流变液助力模块提供的助力，F z为转向齿条上的阻力；
整车模型为：
Figure PCTCN2019116095-appb-000014
轮胎模型为：
Figure PCTCN2019116095-appb-000015
式中，I z为汽车质量对z轴的转动惯量，ω r为横摆角速度，φ为车身侧倾角，N r、N β、N φ、N δ分别为单位横摆角速度、单位质心侧偏角、单位侧倾角速度、单位前轮转角对z轴的力矩，u为纵向速度，m为整车质量，I x为悬挂质量对x轴的转动惯量，β为质心侧偏角，α为前轮侧偏角，δ为前轮转向角，I xz为悬挂质量对x、z轴的惯性积，d为轮距，G P为转向轴到前轮传动比，h为悬挂质心至侧倾轴线的距离，L p、L φ分别为单位侧倾角速度、单位侧倾角对x轴的外力矩，Y r、Y β、Y φ、Y δ分别为单位横摆角速度、单位整车侧偏角、单位侧倾角、单位前轮转角引起的地面侧向反作用力，k 1为前轮侧偏刚度，E 1为弧度因子。
(2)选择齿轮齿条式电液转向系统优化目标，并根据步骤(1)建立的模型，推导对应优化目标的评价公式；其中，
所述的优化目标包括：转向路感、转向助力、转向能耗；
其中，转向路感公式为：
Figure PCTCN2019116095-appb-000016
转向助力公式为：
F force＝T w/r p+F MRF
转向能耗公式为：
F energy＝E m+E MRF+E motor+E ecu
式中，E m表示机械传动模块能耗，E MRF表示磁流变液助力模块能耗，E motor表示电动机能耗，E ecu表示ECU能耗。
(3)以步骤(2)选择的系统优化目标为基础，进行性能分析；根据性能分析结果，选择对转向性能影响大的机械参数和磁流变液参数为优化变量；优化变量包括：电动机转动惯量J m1，转矩传感器刚度K S，金属板间隙L，磁流变液剪切面积A，励磁线圈匝数Z，减速机构减速比G。
(4)在转向灵敏度和优化变量取值范围的约束条件下，建立齿轮齿条式电液转向系统多目标优化模型；
其中，齿轮齿条式电液转向系统多目标优化模型为：
Figure PCTCN2019116095-appb-000017
式中，F energy(X)为转向能耗函数，F road(X)为转向路感函数，F force(X)为转向助力函数，g 1(X)为转向灵敏度。
(5)根据齿轮齿条式电液转向系统多目标优化模型，采用基于参考点的多目标进化算法，进行多目标参数优化。
参照图5所示，所述的基于参考点的多目标进化算法，具体步骤如下：
51)随机生成规模为N的初始父种群P t(J m1，K S，L,A,Z,G)，设置进化代数计数t＝1，根据电液转向系统优化变量的初值对种群进行初始化；
52)对父代种群P t进行交叉、变异、选择等操作，生成子代种群Q t；
53)将P t与子代种群Q t合并到一个集合中，对集合里的个体进行非支配排序，将所有非支配个体保存到集合U t中；
54)对集合U t进行非支配排序并保存所有非支配个体，根据公式(1)计算最优目标函数值，通过选择最优目标值生成候选参考点，保存到集合R m中；
Figure PCTCN2019116095-appb-000018
式中，f m(x)为所选优化变量对转向路感、转向助力、转向能耗的期望目标函数值，m＝1时目标函数为转向路感，m＝2时目标函数为转向助力，m＝3时目标函数为转向能耗，
Figure PCTCN2019116095-appb-000019
为最优目标函数值，ε m为零或任意小的正数；
55)根据公式(2)计算R m中候选参考点的拥挤距离，选取前N个拥挤距离较大的候选参考点，保存到最终参考点集合R中；
Figure PCTCN2019116095-appb-000020
式中，i d为个体间的拥挤距离；
Figure PCTCN2019116095-appb-000021
为i+1个个体在第m个优化目标函数上的值；
Figure PCTCN2019116095-appb-000022
为i-1个个体在第m个优化目标函数上的值；
56)对集合R中的每个参考点，根据公式(3)计算集合U t中所有个体的加权欧几里得距离
Figure PCTCN2019116095-appb-000023
Figure PCTCN2019116095-appb-000024
式中，x i为上述所选的非支配个体，i＝6；f m(x i)为个体x i在第m目标上的值；
57)找出最小的加权欧几里得距离值对应的集合U t中非支配个体和R m中的候选参考点，将所找出的非支配个体保存到下一代种群P t+1中，循环操作直到得到N个个体作为下一代父种群P t+1；
58)判断t是否等于设置的最大进化代数gen，若t＝gen，则算法结束退出优化，得到电液转向系统最优解；否则t＝t+1，转到步骤52)继续执行优化。
本发明具体应用途径很多，以上所述仅是本发明的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以作出若干改进，这些改进也应视为本发明的保护范围。

Claims (8)

  1. 一种基于磁流变液的齿轮齿条式电液转向系统，其特征在于，包括：机械传动模块、磁流变液助力模块、电动助力模块、助力控制模块；
    所述的机械传动模块包括方向盘、转角传感器、转矩传感器、转向轴、齿轮齿条式转向器、横拉杆、左侧转向梯形、右侧转向梯形、左侧车轮及右侧车轮；转向轴的上端与方向盘相连，方向盘上安装转角传感器；转向轴的下端与齿轮齿条转向器的输入端连接，转向轴下端安装有转矩传感器；齿轮齿条式转向器包括转向齿轮，向心球轴承，转向齿条，弹簧，压块，调整螺母，转向器壳体；转向齿轮通过向心球轴承支承在转向器壳体内，转向齿轮的上端与转向轴连接，下端与水平布置的转向齿条相啮合，形成一对传动副；弹簧通过压块将转向齿条压靠在转向齿轮上，使转向齿条和转向齿轮无间隙啮合；调整螺母通过转向器壳体与弹簧相连，提供弹簧预紧力；转向齿条两端连接横拉杆，横拉杆右端通过右侧转向梯形与右侧车轮连接，横拉杆左端通过磁流变液助力模块连接左侧转向梯形及左侧车轮；
    所述的磁流变液助力模块包括磁流变液外壳、上金属板、下金属板、左圆锥滚子轴承、右圆锥滚子轴承、左受力板、右受力板、输入轴、输出轴、磁流变液材料、励磁线圈、供电单元；
    所述横拉杆被磁流变液助力模块打断分为左右两端打断处，横拉杆的左端打断处与输出轴连接，横拉杆的右端打断处与输入轴连接；输入轴依靠右圆锥滚子轴承支撑在磁流变液外壳上，通过右受力板与下金属板连接；输出轴依靠左圆锥滚子轴承支撑在磁流变液外壳上，通过左受力板与上金属板相连；磁流变液外壳包围了上下错开设置的上、下金属板及输入轴、输出轴；磁流变液外壳内部充满磁流变液材料；磁流变液外壳外部水平缠绕励磁线圈，供电单元与励磁线圈电气连接；
    所述的电动助力模块包括电动机，离合器，减速机构；电动机固定在转向轴一侧，并通过减速机构与转向轴连接，减速机构与电动机间设有离合器；
    所述的助力控制模块输入端分别与转矩传感器，转角传感器及车速传感器相连，其输出端与电动机、离合器、供电单元相连。
  2. 一种基于磁流变液的齿轮齿条式电液转向系统的多目标优化方法，基于上述权利要求1所述的系统，其特征在于，包括步骤如下：
    (1)建立齿轮齿条式电液转向系统模型、整车模型及轮胎模型；
    (2)选择齿轮齿条式电液转向系统优化目标，并根据步骤(1)建立的模型，推导对应优化目标的评价公式；
    (3)以步骤(2)选择的系统优化目标为基础，进行性能分析；根据性能分析结果，选择对转向性能影响大的机械参数和磁流变液参数为优化变量；
    (4)在转向灵敏度和优化变量取值范围的约束条件下，建立齿轮齿条式电液转向系统多目标优化模型；
    (5)根据齿轮齿条式电液转向系统多目标优化模型，采用基于参考点的多目标进化算法，进行多目标参数优化。
  3. 根据权利要求2所述的基于磁流变液的齿轮齿条式电液转向系统的多目标优化方法，其特征在于，所述齿轮齿条式电液转向系统模型包括：转向盘-转向轴模型、齿轮齿条转向器模型、磁流变液助力模块模型及电动助力模块模型。
  4. 根据权利要求3所述的基于磁流变液的齿轮齿条式电液转向系统的多目标优化方法，其特征在于，所述步骤(1)中的齿轮齿条式电液转向系统模型为：
    Figure PCTCN2019116095-appb-100001
    式中：J s为方向盘转动惯量，θ s为驾驶员输入转角；T dri为驾驶员输入力矩，B s为转向轴阻尼系数，k s为转向传感器刚度，θ e为转向齿轮转角，J ds为转向轴与减速机构的转动惯量，B ds为减速机构阻尼系数，G为减速机构减速比，T eps为电动机助力转矩，T sen为转矩传感器输出力矩，T w为齿轮齿条作用力，J m1为电动机转动惯量，θ m1为电动机转角，B m1为电动机阻尼系数，T em1为助力电机电磁转矩，m r为齿条质量，x r为转向齿条位移，B r为转向齿条阻尼系数，r p为转向齿轮半径，F hyd为磁流变液助力模块提供的助力，F z为转向齿条上的阻力；
    整车模型为：
    Figure PCTCN2019116095-appb-100002
    轮胎模型为：
    Figure PCTCN2019116095-appb-100003
    式中，I z为汽车质量对z轴的转动惯量，ω r为横摆角速度，φ为车身侧倾角，N r、N β、N φ、N δ分别为单位横摆角速度、单位质心侧偏角、单位侧倾角速度、单位前轮转角对z轴的力矩，u为纵向速度，m为整车质量，I x为悬挂质量对x轴的转动惯量，β为质心侧偏角，α为前轮侧偏角，δ为前轮转向角，I xz为悬挂质量对x、z轴的惯性积，d为轮距，G P为转向轴到前轮传动比，h为悬挂质心至侧倾轴线的距离，L p、L φ分别为单位侧倾角速度、单位侧倾角对x轴的外力矩，Y r、Y β、Y φ、Y δ分别为单位横摆角速度、单位整车侧偏角、单位侧倾 角、单位前轮转角引起的地面侧向反作用力，k 1为前轮侧偏刚度，E 1为弧度因子。
  5. 根据权利要求2所述的基于磁流变液的齿轮齿条式电液转向系统的多目标优化方法，其特征在于，所述步骤(2)中的优化目标包括：转向路感、转向助力、转向能耗；其中，转向路感公式为：
    Figure PCTCN2019116095-appb-100004
    转向助力公式为：
    F force＝T w/r p+F MRF
    转向能耗公式为：
    F energy＝E m+E MRF+E motor+E ecu
    式中，E m表示机械传动模块能耗，E MRF表示磁流变液助力模块能耗，E motor表示电动机能耗，E ecu表示ECU能耗。
  6. 根据权利要求2所述的基于磁流变液的齿轮齿条式电液转向系统的多目标优化方法，其特征在于，所述步骤(3)中的优化变量包括：电动机转动惯量J m1，转矩传感器刚度K S，金属板间隙L，磁流变液剪切面积A，励磁线圈匝数Z，减速机构减速比G。
  7. 根据权利要求2所述的基于磁流变液的齿轮齿条式电液转向系统的多目标优化方法，其特征在于，所述步骤(4)中的齿轮齿条式电液转向系统多目标优化模型为：
    Figure PCTCN2019116095-appb-100005
    式中，F energy(X)为转向能耗函数，F road(X)为转向路感函数，F force(X)为转向助力函数，g 1(X)为转向灵敏度。
  8. 根据权利要求2所述的基于磁流变液的齿轮齿条式电液转向系统的多目标优化方法，其特征在于，所述步骤(5)中的基于参考点的多目标进化算法，具体步骤如下：
    51)随机生成规模为N的初始父种群P t(J m1，K S，L,A,Z,G)，设置进化代数计数t＝1，根据电液转向系统优化变量的初值对种群进行初始化；
    52)对父代种群P t进行交叉、变异、选择等操作，生成子代种群Q t；
    53)将P t与子代种群Q t合并到一个集合中，对集合里的个体进行非支配排序，将所有非支配个体保存到集合U t中；
    54)对集合U t进行非支配排序并保存所有非支配个体，根据公式(1)计算最优目标函数值，通过选择最优目标值生成候选参考点，保存到集合R m中；
    Figure PCTCN2019116095-appb-100006
    式中，f m(x)为所选优化变量对转向路感、转向助力、转向能耗的期望目标函数值，m＝1时目标函数为转向路感，m＝2时目标函数为转向助力，m＝3时目标函数为转向能耗，
    Figure PCTCN2019116095-appb-100007
    为最优目标函数值，ε m为零或任意小的正数；
    55)根据公式(2)计算R m中候选参考点的拥挤距离，选取前N个拥挤距离较大的候选参考点，保存到最终参考点集合R中；
    Figure PCTCN2019116095-appb-100008
    式中，i d为个体间的拥挤距离；
    Figure PCTCN2019116095-appb-100009
    为i+1个个体在第m个优化目标函数上的值；
    Figure PCTCN2019116095-appb-100010
    为i-1个个体在第m个优化目标函数上的值；
    56)对集合R中的每个参考点，根据公式(3)计算集合U t中所有个体的加权欧几里得距离
    Figure PCTCN2019116095-appb-100011
    Figure PCTCN2019116095-appb-100012
    式中，x i为上述所选的非支配个体，i＝6；f m(x i)为个体x i在第m目标上的值；
    57)找出最小的加权欧几里得距离值对应的集合U t中非支配个体和R m中的候选参考点，将所找出的非支配个体保存到下一代种群P t+1中，循环操作直到得到N个个体作为下一代父种群P t+1；
    58)判断t是否等于设置的最大进化代数gen，若t＝gen，则算法结束退出优化，得到电液转向系统最优解；否则t＝t+1，转到步骤52)继续执行优化。
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