CN111497628B - Vehicle pedal force compensation system based on magnetorheological fluid and control method - Google Patents

Vehicle pedal force compensation system based on magnetorheological fluid and control method Download PDF

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Publication number
CN111497628B
CN111497628B CN202010241889.8A CN202010241889A CN111497628B CN 111497628 B CN111497628 B CN 111497628B CN 202010241889 A CN202010241889 A CN 202010241889A CN 111497628 B CN111497628 B CN 111497628B
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pedal
current
magnetorheological
connecting shaft
force compensation
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CN111497628A (en
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王春燕
施帅朋
张自宇
何鹏
吴子涵
赵万忠
颜伸翔
冯建
匡登明
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L7/00—Electrodynamic brake systems for vehicles in general
    • B60L7/10—Dynamic electric regenerative braking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L7/00—Electrodynamic brake systems for vehicles in general
    • B60L7/10—Dynamic electric regenerative braking
    • B60L7/18—Controlling the braking effect
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T7/00—Brake-action initiating means
    • B60T7/02—Brake-action initiating means for personal initiation
    • B60T7/04—Brake-action initiating means for personal initiation foot actuated
    • B60T7/042—Brake-action initiating means for personal initiation foot actuated by electrical means, e.g. using travel or force sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units
    • B60W30/18—Propelling the vehicle
    • B60W30/18009—Propelling the vehicle related to particular drive situations
    • B60W30/18109—Braking
    • B60W30/18127—Regenerative braking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
    • B60W2050/0001—Details of the control system
    • B60W2050/0019—Control system elements or transfer functions
    • B60W2050/0028—Mathematical models, e.g. for simulation
    • B60W2050/0037—Mathematical models of vehicle sub-units

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  • Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Power Engineering (AREA)
  • Automation & Control Theory (AREA)
  • Human Computer Interaction (AREA)
  • Regulating Braking Force (AREA)

Abstract

The invention discloses a vehicle pedal force compensation system based on magnetorheological fluid and a control method. The invention provides a multi-objective optimization method based on magnetorheological fluid, which compensates the force of a brake pedal when a regenerative braking system works and meets the basic function. Compared with the existing pedal force compensation system, the magnetorheological hydraulic compensation mode is adopted, the system structure is greatly simplified, the design of a complex controller is avoided, the adverse effect on driving experience due to intervention of regenerative braking is avoided, meanwhile, the magnetorheological fluid can change the yield strength per se within millisecond time, and the characteristic of quick response of the system is ensured.

Description

Vehicle pedal force compensation system based on magnetorheological fluid and control method
Technical Field
The invention relates to the field of automobile braking, in particular to a vehicle pedal force compensation system based on magnetorheological fluid and a control method.
Background
Due to the short endurance mileage of electric vehicles, most electric vehicles are equipped with a regenerative braking system. The regenerative braking system switches the motor into the generator to run under the working condition of automobile braking, drives the rotor of the motor to rotate by utilizing the inertia of the automobile to generate reaction torque, converts part of kinetic energy or potential energy into electric energy and stores or utilizes the electric energy, thereby improving the endurance mileage of the automobile.
However, since the regenerative braking system operates to generate a portion of the braking torque applied to the wheels that offsets a portion of the total braking torque required by the driver, the amount of brake pedal effort required by the driver is correspondingly reduced. During braking, the braking torque generated by the regenerative braking system is limited by various factors and is a time-varying parameter, so that the feedback force felt by a driver when the driver presses a brake pedal changes along with the change of external conditions, which seriously deteriorates the driving experience of the driver. Currently, the following solutions to this problem are generally available:
1. the influence of the regenerative braking on the pedal force is limited within a certain range by setting the upper limit of the torque generated by the regenerative braking.
2. A road sensing motor is additionally arranged in a brake pedal force transmission path to compensate the influence generated by regenerative braking. 3. With brake-by-wire technology, brake pedal force is generated entirely by the pedal simulator.
The above mode has the defects of complex structure, complex controller design and the like.
Disclosure of Invention
The invention aims to solve the technical problem of providing a vehicle pedal force compensation system and a control method based on magnetorheological fluid aiming at the defects related in the background art.
The invention adopts the following technical scheme for solving the technical problems:
a vehicle pedal force compensation system based on magnetorheological fluid is characterized in that a vehicle is driven and braked by a regenerative brake motor, the regenerative brake motor rotates forwards when the vehicle is driven and rotates backwards when the vehicle is braked to generate brake torque and convert automobile kinetic energy into electric energy for recovery, and the vehicle pedal force compensation system comprises a storage battery, a rotating speed sensor, a current sensor, a voltage sensor, a brake pedal, a connecting block, a connecting shaft, a pedal push rod, a pedal force compensation module and a magnetorheological controller;
the storage battery is used for providing a power supply for the regenerative braking motor and storing electric energy recovered by the regenerative braking motor when the vehicle brakes;
the rotating speed sensor adopts a photoelectric rotating speed sensor, is fixed on an end cover on the output shaft side of the regenerative braking motor through a bolt, and is used for detecting the rotating speed of the regenerative braking motor and transmitting a rotating speed signal to the magnetorheological controller;
the current sensor and the voltage sensor are respectively used for detecting the current and the voltage of the recovered electric energy in the braking process and transmitting signals to the magnetorheological controller;
the pedal force compensation module comprises a shell, a first end cover, a second end cover, a magnetic core, magnetorheological fluid and a magnetic flux coil set;
the shell is a hollow cylinder with openings at two ends and is fixed on a frame of a vehicle; the first end cover and the second end cover are respectively connected with two ends of the shell in a sealing manner, a through hole for the connecting shaft to pass through is formed in the center of the first end cover, and a through hole for the connecting shaft to pass through is formed in the center of the second end cover;
the magnetic core is arranged in a cylinder in the shell, and a through hole for the connecting shaft to pass through is formed in the magnetic core along the axis; the magnetic flux coil group comprises a plurality of groups of magnetic flux coils which are uniformly wound on the magnetic core and used for generating a magnetic field; the magnetic core is used for increasing the magnetic induction intensity of the magnetic flux coil group;
one end of the connecting shaft is connected with the brake pedal through a connecting block, and the other end of the connecting shaft is coaxially and fixedly connected with one end of the pedal push rod after sequentially passing through the through hole in the first end cover, the through hole in the magnetic core and the through hole in the second end cover; the connecting shaft is in clearance fit with the first end cover and the second end cover and can freely slide relative to the shell, and sealing rings are arranged between the connecting shaft and the first end cover and between the connecting shaft and the second end cover, so that a closed cavity is formed between the shell and the connecting shaft; the connecting shaft is fixedly connected with the magnetic core; the magnetorheological fluid is filled in a closed cavity between the shell and the connecting shaft and is used for adjusting the yield strength of the magnetorheological fluid according to the size of the magnetic field of the magnetic flux coil group so as to adjust the force for blocking the movement of the magnetic core;
the other end of the pedal push rod is connected with an input shaft of a vehicle brake master cylinder;
the connecting shaft is used for transmitting the pedal stroke of the brake pedal to a brake master cylinder of a vehicle and transmitting feedback force to the brake pedal;
the magneto-rheological controller is respectively and electrically connected with the rotating speed sensor, the current sensor, the voltage sensor and the magnetic flux coil set and is used for controlling the output current of the magnetic flux coil set according to the sensing signals of the rotating speed sensor, the current sensor and the voltage sensor so as to adjust the pedal force of the vehicle.
The invention also discloses a control method of the vehicle pedal force compensation system based on the magnetorheological fluid, which comprises the following steps:
step 1), establishing a pedal force compensation system model, which comprises a motor torque model, a brake pedal force model and a magnetorheological fluid current-force model;
step 2), selecting performance evaluation indexes of the pedal force compensation system as the total mass of the system, the maximum output force and the energy consumption of the system;
step 3), selecting design variables as the diameter d of the connecting shaft1Diameter d of magnetic core2Diameter d of the housing3Length of housing a, number of flux coil sets N1And the number of turns N of each group of magnetic flux coils2(ii) a Determining an optimization target as the maximum output force of the system and the energy consumption of the system; setting a constraint condition as the total mass of the system, and establishing a multi-objective optimization model of the pedal force compensation system;
and 4) optimizing the design variables of the pedal force compensation system by adopting a multi-objective optimization algorithm, obtaining an optimal solution according to the optimization algorithm, and further controlling the output current of the magnetic flux coil set according to the optimal solution.
As a further optimization scheme of the control method of the magnetorheological fluid-based vehicle pedal force compensation system, in the step 1), a motor torque model is as follows:
Figure BDA0002432830250000031
in the formula, T is the torque of the regenerative braking motor, P is the power of the regenerative braking motor, n is the rotation speed of the regenerative braking motor, U is the battery voltage, and I is the battery current.
As a further optimization scheme of the control method of the magnetorheological fluid-based vehicle pedal force compensation system, in the step 1), a brake pedal model is as follows:
Figure BDA0002432830250000032
wherein F is the force on the brake pedal, k is the brake pedal lever ratio, i is the assist ratio of the brake booster, SmIs the main cylinder cross-sectional area, SwThe sectional area of the wheel cylinder is mu, the friction coefficient of the brake disc is mu, R is the acting radius of the friction block, M is the mass of the pedal, C is the equivalent damping coefficient of the pedal, K is the rigidity of the pedal return spring, and X is the displacement input by the pedal.
As a further optimization scheme of the control method of the magnetorheological fluid-based vehicle pedal force compensation system, in the step 1), a current-force model of the magnetorheological fluid is as follows:
Figure BDA0002432830250000033
in the formula,. DELTA.FCThe compensation moment of the magnetorheological fluid to the pedal is shown, eta is the dynamic viscosity coefficient of the magnetorheological fluid, L is the total width of the magnetic flux coil, ApIs the effective area of the magnetic core piston, D is the inner diameter of the shell, DhThe diameter of a flowing pore channel of the magnetorheological fluid, v is the moving speed of the magnetic core relative to the shell, tau is shear yield stress and is related to current, sgn is a sign function, A1、A2、A3Are respectively a predetermined constant coefficient, wherein A1Is a negative exponential coefficient of current, A2Is a logarithmic coefficient of current, A3I is the current of the flux coil, which is the current proportionality coefficient.
As a further optimization scheme of the control method of the magnetorheological fluid-based vehicle pedal force compensation system, the multi-objective optimization model of the pedal force compensation system in the step 3) is as follows:
Figure BDA0002432830250000034
in the formula (f)1(x) For maximum output force of the system, f2(x) For system energy consumption, M (x) is the total mass of the system.
As a further optimization scheme of the control method of the magnetorheological-fluid-based vehicle pedal force compensation system, in the step 4), the adopted multi-objective optimization algorithm is a multi-objective particle swarm optimization algorithm based on Pareto entropy, and the specific steps are as follows:
step 4.1), initializing a particle population m and randomly generating an initial position X0And an initial velocity V0Initial individual optimal position of particle Pbest ═ X0Approximating a Pareto optimal solution set gArchive, wherein the iteration time t is 0;
step 4.2), calculating objective function values of all particles, and initializing an individual external file pArchive for each particlei；
Step 4.3), mapping gArchive into a parallel grid coordinate system according to the following formula:
Figure BDA0002432830250000041
in the formula (I), the compound is shown in the specification,
Figure BDA0002432830250000042
is an upward rounding function, returns the minimum integer no less than x; k is 1, 2, …, and K is the number of members of the external file in the current iteration; m is 1, 2, …, M isThe target number of the problem to be optimized;
Figure BDA0002432830250000043
and
Figure BDA0002432830250000044
respectively is the maximum value and the minimum value of the mth target on the front end of the current Pareto; l isk,mE {1, 2, …, K } is fk.mAn integer index mapped into the parallel grid coordinate system, representing the mth grid coordinate component of the kth non-dominant solution;
step 4.4), computing Pareto entropy Encopy (t) and difference entropy Δ Encopy (t) of gArchive according to the following formula:
Figure BDA0002432830250000045
ΔEntropy(t)＝Entropy(t)-Entropy(t-1)
in the formula, Cellk,m(t) represents the number of lattice coordinate components falling in the lattice of the kth row and the mth column after the approximate Pareto front end is mapped to the PCCS;
step 4.5), judging the evolution state of Pareto entropy, and respectively calculating the individual Density Density (P) of each Pareto optimal solution in gArchive according to the following formulai) And the occupation intensity of individual case;
Figure BDA0002432830250000046
in the formula, PjIs different from P in the external fileiOther non-dominant solutions of (a); PCD (P)i，Pj) Represents PiAnd PjThe parallel grid distance between;
Sc(x)＝|{y|y∈A∧x＞y}|
in the formula, Sc(x) The lattice dominant intensity of x is shown, x is more than y and means that y is dominated by x lattices;
step 4.6), based on the evolution state of Pareto entropy, respectively calculating the current particle motion parameters including particle motion according to the following formulaKinetic inertia coefficient w (t), acceleration coefficient c of individual optimal solution on particles1(t) and the acceleration coefficient c of the population-optimal solution on the particle2(t)；
Figure BDA0002432830250000051
Wherein d (t) { w (t), c1(t)，c2(t), step is the step length of adjustment;
step 4.7), finding out the global optimal gBestiFrom pArchiveiSelect one of them and gBestiThe member with the closest spatial distance is taken as the individual optimal solution pBest of the particle ii；
Step 4.8), the speed and the position of the particle i are updated according to the particle motion equation, and an individual external file pArchive is updatediAnd a global external archive gArchive;
Figure BDA0002432830250000052
in the formula, t represents the number of iterations; c. C1、c2The acceleration coefficients are respectively greater than or equal to 0 and respectively represent the acceleration coefficients of the individual optimal solution and the group optimal solution on the current particle; rand (-) is a random number; pBestiRepresenting an individual optimal solution for the ith particle; gBest represents the global optimal solution for the entire population;
step 4.9), updating the counter t to t +1, if t is greater than Tmax, outputting gArchive, and selecting an optimal solution; otherwise, jump to step 4.3).
Compared with the prior art, the invention adopting the technical scheme has the following technical effects:
the invention provides a multi-objective optimization method based on magnetorheological fluid, which compensates the force of a brake pedal when a regenerative braking system works and meets the basic function. Compared with the existing pedal force compensation system, the magnetorheological hydraulic compensation mode is adopted, the system structure is greatly simplified, the design of a complex controller is avoided, the adverse effect on driving experience due to intervention of regenerative braking is avoided, meanwhile, the magnetorheological fluid can change the yield strength per se within millisecond time, and the characteristic of quick response of the system is ensured.
The invention utilizes the combination of the magnetorheological fluid, the magnetic flux coil and the magnetic core to replace a complex motor or hydraulic mechanism, generates similar compensation effect and simultaneously improves the reliability and controllability of the system.
The control method considers the multi-target coupling of the pedal force compensation system, adopts a multi-target particle swarm optimization algorithm based on Pareto entropy, optimizes the total mass, the maximum output force and the system energy consumption of the pedal force compensation system, and can obtain an optimization result with better comprehensive performance.
Drawings
FIG. 1 is a schematic layout of a pedal force compensation system according to the present invention;
FIG. 2 is a schematic diagram of the pedal force compensation of the present invention;
FIG. 3 is a flow chart of the multi-objective optimization of the present invention.
In the figure, 1-a brake pedal, 2-a connecting block, 3-a shell, 4-a first end cover, 5-a second end cover, 6-a connecting shaft, 7-a pedal push rod, 8-a magnetic core, 9-a magnetic flux coil, 10-magnetorheological fluid, 11-a sealing ring, 12-a storage battery and 13-a regenerative brake 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 vehicle pedal force compensation system based on magnetorheological fluid, wherein a vehicle is driven and braked by a regenerative brake motor, the regenerative brake motor rotates forwards when the vehicle is driven and rotates backwards when the vehicle is braked to generate brake torque and convert the kinetic energy of the vehicle into electric energy for recycling, and the vehicle pedal force compensation system comprises a storage battery, a rotating speed sensor, a current sensor, a voltage sensor, a brake pedal, a connecting block, a connecting shaft, a pedal push rod, a pedal force compensation module and a magnetorheological controller;
the storage battery is used for providing a power supply for the regenerative braking motor and storing electric energy recovered by the regenerative braking motor when the vehicle brakes;
the rotating speed sensor adopts a photoelectric rotating speed sensor, is fixed on an end cover on the output shaft side of the regenerative braking motor through a bolt, and is used for detecting the rotating speed of the regenerative braking motor and transmitting a rotating speed signal to the magnetorheological controller;
the current sensor and the voltage sensor are respectively used for detecting the current and the voltage of the recovered electric energy in the braking process and transmitting signals to the magnetorheological controller;
the pedal force compensation module comprises a shell, a first end cover, a second end cover, a magnetic core, magnetorheological fluid and a magnetic flux coil set;
the shell is a hollow cylinder with openings at two ends and is fixed on a frame of a vehicle; the first end cover and the second end cover are respectively connected with two ends of the shell in a sealing manner, a through hole for the connecting shaft to pass through is formed in the center of the first end cover, and a through hole for the connecting shaft to pass through is formed in the center of the second end cover;
the magnetic core is arranged in a cylinder in the shell, and a through hole for the connecting shaft to pass through is formed in the magnetic core along the axis; the magnetic flux coil group comprises a plurality of groups of magnetic flux coils which are uniformly wound on the magnetic core and used for generating a magnetic field; the magnetic core is used for increasing the magnetic induction intensity of the magnetic flux coil group;
one end of the connecting shaft is connected with the brake pedal through a connecting block, and the other end of the connecting shaft is coaxially and fixedly connected with one end of the pedal push rod after sequentially passing through the through hole in the first end cover, the through hole in the magnetic core and the through hole in the second end cover; the connecting shaft is in clearance fit with the first end cover and the second end cover and can freely slide relative to the shell, and sealing rings are arranged between the connecting shaft and the first end cover and between the connecting shaft and the second end cover, so that a closed cavity is formed between the shell and the connecting shaft; the connecting shaft is fixedly connected with the magnetic core; the magnetorheological fluid is filled in a closed cavity between the shell and the connecting shaft and is used for adjusting the yield strength of the magnetorheological fluid according to the size of the magnetic field of the magnetic flux coil group so as to adjust the force for blocking the movement of the magnetic core;
the other end of the pedal push rod is connected with an input shaft of a vehicle brake master cylinder;
the connecting shaft is used for transmitting the pedal stroke of the brake pedal to a brake master cylinder of a vehicle and transmitting feedback force to the brake pedal;
the magneto-rheological controller is respectively and electrically connected with the rotating speed sensor, the current sensor, the voltage sensor and the magnetic flux coil set and is used for controlling the output current of the magnetic flux coil set according to the sensing signals of the rotating speed sensor, the current sensor and the voltage sensor so as to adjust the pedal force of the vehicle.
As shown in FIG. 2, the invention also discloses a control method of the vehicle pedal force compensation system based on the magnetorheological fluid, which comprises the following steps:
step 1), establishing a pedal force compensation system model, which comprises a motor torque model, a brake pedal force model and a magnetorheological fluid current-force model;
step 2), selecting performance evaluation indexes of the pedal force compensation system as the total mass of the system, the maximum output force and the energy consumption of the system;
step 3), selecting design variables as the diameter d of the connecting shaft1Diameter d of magnetic core2Diameter d of the housing3Length of housing a, number of flux coil sets N1And the number of turns N of each group of magnetic flux coils2(ii) a Determining an optimization target as the maximum output force of the system and the energy consumption of the system; setting a constraint condition as the total mass of the system, and establishing a multi-objective optimization model of the pedal force compensation system;
and 4) optimizing the design variables of the pedal force compensation system by adopting a multi-objective optimization algorithm, obtaining an optimal solution according to the optimization algorithm, and further controlling the output current of the magnetic flux coil set according to the optimal solution.
The motor torque model in the step 1) is as follows:
Figure BDA0002432830250000071
in the formula, T is the torque of the regenerative braking motor, P is the power of the regenerative braking motor, n is the rotation speed of the regenerative braking motor, U is the battery voltage, and I is the battery current.
The brake pedal model in the step 1) is as follows:
Figure BDA0002432830250000072
wherein F is the force on the brake pedal, k is the brake pedal lever ratio, i is the assist ratio of the brake booster, SmIs the main cylinder cross-sectional area, SwThe sectional area of the wheel cylinder is mu, the friction coefficient of the brake disc is mu, R is the acting radius of the friction block, M is the mass of the pedal, C is the equivalent damping coefficient of the pedal, K is the rigidity of the pedal return spring, and X is the displacement input by the pedal.
The current-force model of the magnetorheological fluid in the step 1) is as follows:
Figure BDA0002432830250000081
in the formula,. DELTA.FCThe compensation moment of the magnetorheological fluid to the pedal is shown, eta is the dynamic viscosity coefficient of the magnetorheological fluid, L is the total width of the magnetic flux coil, ApIs the effective area of the magnetic core piston, D is the inner diameter of the shell, DhThe diameter of a flowing pore channel of the magnetorheological fluid, v is the moving speed of the magnetic core relative to the shell, tau is shear yield stress and is related to current, sgn is a sign function, A1、A2、A3The current is a preset negative exponential coefficient, a preset logarithmic coefficient and a preset proportional coefficient, and I is the current of the magnetic flux coil.
The multi-objective optimization model of the pedal force compensation system in the step 3) is as follows:
Figure BDA0002432830250000082
in the formula (f)1(x) For maximum output force of the system, f2(x) For system energy consumption, M (x) is the total mass of the system.
As shown in fig. 3, the multi-objective optimization algorithm adopted in step 4) is a multi-objective particle swarm optimization algorithm based on Pareto entropy, and specifically includes the following steps:
step 4.1), initializing a particle population m and randomly generating an initial position X0And an initial velocity V0Initial individual optimal position of particle Pbest ═ X0Approximating a Pareto optimal solution set gArchive, wherein the iteration time t is 0;
step 4.2), calculating objective function values of all particles, and initializing an individual external file pArchive for each particlei；
Step 4.3), mapping gArchive into a parallel grid coordinate system according to the following formula:
Figure BDA0002432830250000083
in the formula (I), the compound is shown in the specification,
Figure BDA0002432830250000084
is an upward rounding function, returns the minimum integer no less than x; k is 1, 2, …, and K is the number of members of the external file in the current iteration; m is 1, 2, …, and M is the target number of the problem to be optimized;
Figure BDA0002432830250000085
and
Figure BDA0002432830250000086
respectively is the maximum value and the minimum value of the mth target on the front end of the current Pareto; l isk,mE {1, 2, …, K } is fk.mAn integer index mapped into the parallel grid coordinate system, representing the mth grid coordinate component of the kth non-dominant solution;
step 4.4), computing Pareto entropy Encopy (t) and difference entropy Δ Encopy (t) of gArchive according to the following formula:
Figure BDA0002432830250000087
ΔEntropy(t)＝Entropy(t)-Entropy(t-1)
in the formula, Cellk,m(t) represents the number of lattice coordinate components falling in the lattice of the kth row and the mth column after the approximate Pareto front end is mapped to the PCCS;
step 4.5), judging the evolution state of Pareto entropy, and respectively calculating the individual Density Density (P) of each Pareto optimal solution in gArchive according to the following formulai) And the occupation intensity of individual case;
Figure BDA0002432830250000091
in the formula, PjIs different from P in the external fileiOther non-dominant solutions of (a); PCD (P)i，Pj) Represents PiAnd PjThe parallel grid distance between;
Sc(x)＝|{y|y∈A∧x＞y}|
in the formula, Sc(x) The lattice dominant intensity of x is shown, x is more than y and means that y is dominated by x lattices;
step 4.6), based on the evolution state of Pareto entropy, respectively calculating the current particle motion parameters including the particle motion inertia coefficient w (t) and the acceleration coefficient c of the individual optimal solution on the particle according to the following formula1(t) and the acceleration coefficient c of the population-optimal solution on the particle2(t)；
Figure BDA0002432830250000092
Wherein d (t) { w (t), c1(t)，c2(t), step is the step length of adjustment;
step 4.7), finding out the global optimal gBestiFrom pArchiveiSelect one of them and gBestiThe member with the closest spatial distance is taken as the individual optimal solution pB of the particle iesti；
Step 4.8), the speed and the position of the particle i are updated according to the particle motion equation, and an individual external file pArchive is updatediAnd a global external archive gArchive;
Figure BDA0002432830250000093
in the formula, t represents the number of iterations; c. C1、c2The acceleration coefficients are respectively greater than or equal to 0 and respectively represent the acceleration coefficients of the individual optimal solution and the group optimal solution on the current particle; rand (-) is a random number; pBestiRepresenting an individual optimal solution for the ith particle; gBest represents the global optimal solution for the entire population;
step 4.9), updating the counter t to t +1, if t is greater than Tmax, outputting gArchive, and selecting an optimal solution; otherwise, jump to step 4.3).
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 (7)

1. A vehicle pedal force compensation system based on magnetorheological fluid is characterized in that the vehicle pedal force compensation system comprises a storage battery, a rotating speed sensor, a current sensor, a voltage sensor, a brake pedal, a connecting block, a connecting shaft, a pedal push rod, a pedal force compensation module and a magnetorheological controller;
the storage battery is used for providing a power supply for the regenerative braking motor and storing electric energy recovered by the regenerative braking motor when the vehicle brakes;
the rotating speed sensor adopts a photoelectric rotating speed sensor, is fixed on an end cover on the output shaft side of the regenerative braking motor through a bolt, and is used for detecting the rotating speed of the regenerative braking motor and transmitting a rotating speed signal to the magnetorheological controller;
the current sensor and the voltage sensor are respectively used for detecting the current and the voltage of the recovered electric energy in the braking process and transmitting signals to the magnetorheological controller;
the pedal force compensation module comprises a shell, a first end cover, a second end cover, a magnetic core, magnetorheological fluid and a magnetic flux coil set;
the shell is a hollow cylinder with openings at two ends and is fixed on a frame of a vehicle; the first end cover and the second end cover are respectively connected with two ends of the shell in a sealing manner, a through hole for the connecting shaft to pass through is formed in the center of the first end cover, and a through hole for the connecting shaft to pass through is formed in the center of the second end cover;
the magnetic core is a cylinder arranged in the shell, and a through hole for the connecting shaft to pass through is formed in the magnetic core along the axis; the magnetic flux coil group comprises a plurality of groups of magnetic flux coils which are uniformly wound on the magnetic core and used for generating a magnetic field; the magnetic core is used for increasing the magnetic induction intensity of the magnetic flux coil group;
one end of the connecting shaft is connected with the brake pedal through a connecting block, and the other end of the connecting shaft is coaxially and fixedly connected with one end of the pedal push rod after sequentially passing through the through hole in the first end cover, the through hole in the magnetic core and the through hole in the second end cover; the connecting shaft is in clearance fit with the first end cover and the second end cover and can freely slide relative to the shell, and sealing rings are arranged between the connecting shaft and the first end cover and between the connecting shaft and the second end cover, so that a closed cavity is formed between the shell and the connecting shaft; the connecting shaft is fixedly connected with the magnetic core; the magnetorheological fluid is filled in a closed cavity between the shell and the connecting shaft and is used for adjusting the yield strength of the magnetorheological fluid according to the size of the magnetic field of the magnetic flux coil group so as to adjust the force for blocking the movement of the magnetic core;
the other end of the pedal push rod is connected with an input shaft of a vehicle brake master cylinder;
the connecting shaft is used for transmitting the pedal stroke of the brake pedal to a brake master cylinder of a vehicle and transmitting feedback force to the brake pedal;
the magneto-rheological controller is respectively and electrically connected with the rotating speed sensor, the current sensor, the voltage sensor and the magnetic flux coil set and is used for controlling the current of the magnetic flux coil set according to the sensing signals of the rotating speed sensor, the current sensor and the voltage sensor so as to adjust the pedal force of the vehicle.
2. The method for controlling a magnetorheological-fluid-based vehicle pedal force compensation system according to claim 1, comprising the steps of:
step 1), establishing a pedal force compensation system model, which comprises a motor torque model, a brake pedal force model and a magnetorheological fluid current-force model;
step 2), selecting performance evaluation indexes of the pedal force compensation system as the total mass of the system, the maximum output force and the energy consumption of the system;
step 3), selecting the design variable as the diameter d of the connecting shaft1Diameter d of magnetic core2Diameter d of the housing3Length of housing a, number of flux coil sets N1And the number of turns N of each group of magnetic flux coils2(ii) a Determining an optimization target as the maximum output force of the system and the energy consumption of the system; setting a constraint condition as the total mass of the system, and establishing a multi-objective optimization model of the pedal force compensation system;
and 4) optimizing the design variables of the pedal force compensation system by adopting a multi-objective optimization algorithm, obtaining an optimal solution according to the optimization algorithm, and controlling the current of the magnetic flux coil set according to the optimal solution.
3. The control method of a magnetorheological-fluid-based vehicle pedal force compensation system according to claim 2, wherein in the step 1), the motor torque model is:
Figure FDA0003013319100000021
in the formula, T is the torque of the regenerative braking motor, P is the power of the regenerative braking motor, n is the rotation speed of the regenerative braking motor, U is the battery voltage, and I is the battery current.
4. The control method of a magnetorheological-fluid-based vehicle pedal force compensation system according to claim 3, wherein in the step 1), the brake pedal model is:
Figure FDA0003013319100000022
wherein F is the force on the brake pedal, k is the brake pedal lever ratio, i is the assist ratio of the brake booster, SmIs the main cylinder cross-sectional area, SwThe sectional area of the wheel cylinder is mu, the friction coefficient of the brake disc is mu, R is the acting radius of the friction block, M is the mass of the pedal, C is the equivalent damping coefficient of the pedal, K is the rigidity of the pedal return spring, and X is the displacement input by the pedal.
5. The method for controlling a magnetorheological-fluid-based vehicle pedal-force compensation system according to claim 4, wherein in the step 1), the magnetorheological-fluid current-force model is as follows:
Figure FDA0003013319100000023
in the formula,. DELTA.FCThe compensation moment of the magnetorheological fluid to the pedal is shown, eta is the dynamic viscosity coefficient of the magnetorheological fluid, L is the total width of the magnetic flux coil, ApBeing effective surfaces of magnetic core pistonsVolume D is the inner diameter of the shell DhThe diameter of a flowing pore channel of the magnetorheological fluid, v is the moving speed of the magnetic core relative to the shell, tau is shear yield stress and is related to current, sgn is a sign function, A1、A2、A3The current is a preset negative exponential coefficient, a preset logarithmic coefficient and a preset proportional coefficient, and I is the current of the magnetic flux coil.
6. The method for controlling the pedal force compensation system of the magnetorheological fluid-based vehicle according to claim 5, wherein the multi-objective optimization model of the pedal force compensation system in the step 3) is as follows:
Figure 1
in the formula (f)1(x) For maximum output force of the system, f2(x) For system energy consumption, M (x) is the total mass of the system.
7. The method for controlling the magnetorheological-fluid-based vehicle pedal force compensation system according to claim 2, wherein the step 4) adopts a multi-objective optimization algorithm which is a multi-objective particle swarm optimization algorithm based on Pareto entropy, and comprises the following specific steps:
step 4.1), initializing a particle population m and randomly generating an initial position X0And an initial velocity V0Initial individual optimal position of particle Pbest ═ X0Approximating a Pareto optimal solution set gArchive, wherein the iteration time t is 0;
step 4.2), calculating objective function values of all particles, and initializing an individual external file pArchive for each particlei；
Step 4.3), mapping gArchive into a parallel grid coordinate system according to the following formula:
Figure FDA0003013319100000032
wherein a gamma-is a rounded-up componentCounting, returning the minimum integer not less than x; k is 1, 2, …, and K is the number of members of the external file in the current iteration; m is 1, 2, …, and M is the target number of the problem to be optimized;
Figure FDA0003013319100000033
and
Figure FDA0003013319100000034
respectively is the maximum value and the minimum value of the mth target on the front end of the current Pareto; l isk,mE {1, 2, …, K } is fk.mAn integer index mapped into the parallel grid coordinate system, representing the mth grid coordinate component of the kth non-dominant solution;
step 4.4), computing Pareto entropy Encopy (t) and difference entropy Δ Encopy (t) of gArchive according to the following formula:
Figure FDA0003013319100000035
ΔEntropy(t)＝Entropy(t)-Entropy(t-1)
in the formula, Cellk,m(t) represents the number of lattice coordinate components falling in the lattice of the kth row and the mth column after the approximate Pareto front end is mapped to the PCCS;
step 4.5), judging the evolution state of Pareto entropy, and respectively calculating the individual Density Density (P) of each Pareto optimal solution in gArchive according to the following formulai) And the occupation intensity of individual case;
Figure FDA0003013319100000041
in the formula, PjIs different from P in the external fileiOther non-dominant solutions of (a); PCD (P)i，Pj) Represents PiAnd PjThe parallel grid distance between;
Sc(x)＝|{y|y∈A∧x＞y}|
in the formula, Sc(x) Lattice occupations of xThe strength is excellent, x is more than y, and y is dominated by x;
step 4.6), based on the evolution state of Pareto entropy, respectively calculating the current particle motion parameters including the particle motion inertia coefficient w (t) and the acceleration coefficient c of the individual optimal solution on the particle according to the following formula1(t) and c for population-optimal solution on particles2(t)；
Figure FDA0003013319100000042
Wherein d (t) { w (t), c1(t)，c2(t), step is the step length of adjustment;
step 4.7), finding out the global optimal gBestiFrom pArchiveiSelect one of them and gBestiThe member with the closest spatial distance is taken as the individual optimal solution pBest of the particle ii；
Step 4.8), the speed and the position of the particle i are updated according to the particle motion equation, and an individual external file pArchive is updatediAnd a global external archive gArchive;
Figure FDA0003013319100000043
in the formula, t represents the number of iterations; c. C1、c2The acceleration coefficients are respectively greater than or equal to 0 and respectively represent the acceleration coefficients of the individual optimal solution and the group optimal solution on the current particle; rand (-) is a random number; pBestiRepresenting an individual optimal solution for the ith particle; gBest represents the global optimal solution for the entire population;
step 4.9), updating the counter t to t +1, if t is greater than Tmax, outputting gArchive, and selecting an optimal solution; otherwise, jump to step 4.3).
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