CN107600175B - Active steering system of passenger car based on energy accumulator and steering control method thereof - Google Patents
Active steering system of passenger car based on energy accumulator and steering control method thereof Download PDFInfo
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- CN107600175B CN107600175B CN201710927905.7A CN201710927905A CN107600175B CN 107600175 B CN107600175 B CN 107600175B CN 201710927905 A CN201710927905 A CN 201710927905A CN 107600175 B CN107600175 B CN 107600175B
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Abstract
The invention discloses an active steering system of a passenger car based on an energy accumulator and a steering control method thereof, comprising the following steps: the device comprises a mechanical module, a hydraulic module and an electric control module; the hydraulic module adopts a motor and a hydraulic pump to supply oil to two hydraulic circuits, the first hydraulic circuit adopts a direct oil supply mode to realize steering torque adjustment, the second hydraulic circuit adopts an energy accumulator oil supply mode to realize corner adjustment, and the two hydraulic circuits are coordinated and matched to complete the active steering function. The system of the invention reduces the system quality and simultaneously avoids the energy waste caused by adopting a plurality of hydraulic pumps by taking the energy accumulator as an auxiliary power source of the second hydraulic circuit.
Description
Technical Field
The invention belongs to the technical field of control of automobile power steering systems, and particularly relates to an active steering system of a passenger car based on an energy accumulator and a steering control method thereof.
Background
With the increasing requirements of automobiles on safety and energy conservation, automobile steering systems are also in continuous revolution. Conventional mechanical steering systems and hydraulic power assisted systems have failed to meet the current social demands, and electronically controlled hydraulic power assisted steering systems, electric power assisted steering systems, active steering systems and steer-by-wire systems have been developed and applied. The driving steering system and the drive-by-wire steering system can freely change the angular transmission ratio so as to overcome the contradiction between light and flexible steering systems, have optimal steering feel and safety performance, and are the development directions in the future.
Steer-by-wire eliminates the mechanical connection of the steering system, saves space and has good steering characteristics, but is limited by current regulations and is not applied due to electronic reliability problems. The foreign research on the active steering system starts earlier, the VGRS system of Toyota in Japan controls the wheel rotation angle through an actuator in a steering gear assembly, the German Benz company adopts a variable transmission ratio rack on an E-class vehicle, and the German BMW company changes the transmission ratio of the steering system through the combination of two groups of input shafts of a planetary gear mechanism and an electric control system. The defect of pure mechanical variable transmission ratio is small adjustable range and inflexible change; the electric control mechanical variable transmission ratio output torque is smaller, and the electric control mechanical variable transmission ratio output torque is not suitable for being applied to heavy vehicles.
The hybrid transmission unit provided by the Chinese patent application No. CN201610989595.7 and named as a hybrid front wheel active steering system can control the torque and the rotation angle, but the structure adopts a motor power assisting mode, has smaller power and cannot be used on a passenger car at present.
Therefore, the active steering system of the passenger car with simple structure, practical function, energy conservation and emission reduction is designed, the active safety performance of the passenger car is improved, and the active steering system has great significance and value.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide an active steering system of a passenger car based on an energy accumulator and a steering control method thereof, so as to overcome the technical defects of the steering control system in the prior art. The energy accumulator is used as an auxiliary power source of the second hydraulic circuit, so that the system quality is reduced, and meanwhile, the energy waste caused by adopting a plurality of hydraulic pumps is avoided.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention relates to an active steering system of a passenger car based on an energy accumulator, which comprises the following components: the device comprises a mechanical module, a hydraulic module and an electric control module;
the mechanical module comprises a steering wheel, a steering shaft, a recirculating ball steering gear, a steering rocker arm, a steering straight pull rod, a steering trapezoid and wheels which are connected in sequence;
the recirculating ball steering gear comprises a recirculating ball steering gear shell, a steering nut, a steering screw rod and a gear sector; the steering nut is used as a piston and forms a hydraulic cylinder-piston structure with the recirculating ball steering gear shell; the front end of the steering screw is connected with a steering shaft, the rear end of the steering screw is connected with a steering nut, and the rotary motion transmitted by the steering shaft is converted into the axial motion of the steering nut relative to the housing of the recirculating ball steering gear; one end of the gear sector is meshed with the steering nut, and the other end of the gear sector is connected with the steering rocker arm as the output end of the recirculating ball steering gear;
the steering straight pull rod comprises a steering straight pull rod piston, a steering straight pull rod hydraulic cylinder, a steering straight pull rod piston rod and a pull rod; the shell of the steering straight pull rod hydraulic cylinder is connected with the output end of the recirculating ball steering gear through a steering rocker arm, and an oil inlet and an oil outlet are formed in the shell; the steering straight pull rod piston is assembled in the steering straight pull rod hydraulic cylinder, and a steering straight pull rod piston rod is fixedly arranged at one end of the steering straight pull rod piston; the front end of the pull rod is connected with the steering straight pull rod piston rod, and the rear end of the pull rod is connected with a steering trapezoid and wheels;
the hydraulic module comprises an oil storage tank, an oil filter, a brushless direct current motor, a hydraulic pump, a first one-way valve, a first hydraulic circuit and a second hydraulic circuit;
the first hydraulic circuit comprises a first electromagnetic valve, a rotary valve, a first oil inlet pipeline and a first oil return pipeline;
the inlet of the first electromagnetic valve is connected with the outlet of the first one-way valve, and the outlet of the first electromagnetic valve is connected with the inlet of the rotary valve;
the rotary valve is arranged on a steering shaft of the mechanical steering module, two ends of a valve core of the rotary valve are respectively connected with the steering shaft and a steering screw of the recirculating ball steering gear, high-pressure oil input by the first electromagnetic valve is distributed when the position of the valve core is changed, and the valve core is connected with an oil inlet and an oil outlet of the recirculating ball steering gear through a first oil inlet pipeline and a first oil return pipeline;
the second hydraulic circuit comprises a second one-way valve, a second electromagnetic valve, an energy accumulator, an electrohydraulic proportional reversing valve, a second oil inlet pipeline, a second oil return pipeline and an overflow valve;
the inlet of the second electromagnetic valve is connected with the first one-way valve and is connected with the first electromagnetic valve in parallel; the outlet of the valve is connected with an oil inlet of the energy accumulator through a second one-way valve;
an oil outlet of the energy accumulator outputs hydraulic oil to the electro-hydraulic proportional reversing valve, and a pressure sensor is arranged at the oil outlet;
the electro-hydraulic proportional reversing valve is communicated with an oil inlet and an oil outlet of a steering straight pull rod hydraulic cylinder of the steering straight pull rod through a second oil inlet pipeline and a second oil return pipeline;
an oil inlet of the overflow valve is connected with the second electromagnetic valve in parallel, and an oil return port is communicated with the oil storage tank;
the hydraulic pump is driven by a brushless direct current motor, low-pressure oil in an oil storage tank is converted into high-pressure oil after being filtered by an oil filter, and the high-pressure oil is respectively output to a first hydraulic circuit and a second hydraulic circuit through a first one-way valve;
the electronic control module comprises a main controller, a rotation angle sensor, a torque sensor, a pressure sensor, a displacement sensor and a wheel speed sensor;
the main controller comprises an ECU, an ideal front wheel corner module, an ideal power-assisted torque module, a pressure control module and a displacement control module;
the steering angle sensor is arranged on the steering wheel and is used for providing a steering wheel steering angle signal b input by a driver to the ideal front-wheel steering angle module;
the torque sensor is arranged on the steering shaft and is used for providing a torque signal a input by a driver to the ideal power-assisted torque module and the ECU;
the pressure sensor is arranged at the outlet position of the energy accumulator in the second hydraulic circuit and is used for providing an oil pressure signal e at the outlet of the energy accumulator for the pressure control module;
the displacement sensor is arranged on the pull rod and used for providing a pull rod displacement signal d for the displacement control module;
the wheel speed sensor is mounted on the wheel and is used for providing a wheel speed signal c to the ideal power-assisted torque module and the ideal front wheel turning angle module.
Preferably, the first electromagnetic valve adopts a two-position two-way normally open mode.
Preferably, the second electromagnetic valve adopts a two-position two-way normally closed mode.
Preferably, the electro-hydraulic proportional reversing valve adopts a three-position four-way mode.
Preferably, the control method for changing the transmission ratio of the steering system by the second hydraulic circuit comprises the following steps:
11 Pressurized process: preset accumulator minimum operating pressure P 0 Filling pressure P 1 When the oil pressure at the outlet of the accumulator is smaller than the preset minimum working pressure P 0 When the pressure signal e is transmitted to the ECU, the ECU controls the first electromagnetic valve working position to be closed, and controls the second electromagnetic valve working position to be opened; the pressure control module adopts PID control, controls the second hydraulic circuit to enter a pressurizing working mode according to a brushless direct current motor control signal f and a pressure signal e, drives the hydraulic pump to work, converts the output flow of the hydraulic pump into the output flow of the second electromagnetic valve through the second electromagnetic valve, and pressurizes the energy accumulator;
12 Pressure maintaining process: when the oil pressure at the outlet of the accumulator reaches the preset full pressure P 1 When the ECU receives the pressure signal e, the first electromagnetic valve working position is controlled to be opened, the second electromagnetic valve working position is controlled to be closed, and the accumulator pressure is kept at P 0 To P 1 The pressure control module controls the second hydraulic circuit to enter a pressure maintaining working mode;
13 A) working process: when the passenger car turns, the ideal front wheel steering module calculates the ideal front wheel steering angle according to the wheel speed signal c and the steering wheel angle signal b input by a driver, converts the ideal front wheel steering angle into the ideal output displacement of the corresponding steering tie rod, and the displacement control module receives an electrohydraulic proportional reversing valve control signal i and a displacement signal d fed back by a displacement sensor, controls the electrohydraulic proportional reversing valve to move to a corresponding working position, and the output flow of the accumulator flows into the electrohydraulic proportional reversing valve, and the output flow of the electrohydraulic proportional reversing valve flows into the steering tie rod hydraulic cylinder to push the steering tie rod piston to move relative to the steering tie rod hydraulic cylinder and drive the tie rod to move so as to change the output displacement of the steering tie rod and the corresponding front wheel angle;
assuming that the ideal output displacement of the steering tie rod is x 0 The output displacement of the steering tie rod detected by the displacement sensor is x 1 The displacement control module continuously changes the flow according to the electro-hydraulic proportional reversing valve in proportionThe characteristic of the output displacement of the steering tie rod is changed, and a sliding mode control method is adopted according to the output displacement x 1 And ideal output displacement x 0 And calculating corresponding sliding mode control parameters.
Preferably, assuming that the transmission ratio of the steering system is i and the front wheel rotation angle is delta f When the steering wheel turns to delta
Ideal transmission ratio
Wherein V is wheel speed, K u For understeer coefficient, K S Parameters are set for an ideal front wheel steering module, and the range is 0.12-0.41;
according to the ideal transmission ratio i 0 The ideal front wheel steering angle characteristics under different vehicle speeds are obtained, the ideal front wheel steering angle module calculates the ideal front wheel steering angle according to the steering angle signals obtained by the steering angle sensor, and then the ideal steering straight pull rod output displacement is calculated according to the motion relation of the steering straight pull rod, the steering trapezium and the wheels.
Preferably, the sliding mode control method specifically comprises the following steps:
131 Defining a switching function of the sliding mode controller as: s=c (x 1 -x 0 ) Wherein c is a constant;
132 From the switching function, we get:
133 Selecting an exponential approach law
ε > 0, k > 0, where ∈0>
Is an exponential approach term, which solves for s=s (0) e -kt The constant epsilon is the rate at which the system motion point approaches the switching plane s=0;
134 Making:
wherein V is the wheel speed, delta is the steering wheel angle;
135 To sum up the above results:
the invention relates to a steering control method of an active steering system of a passenger car based on an energy accumulator, which is based on the system and comprises the following steps:
21 The ideal front wheel turning module receives a wheel speed signal sent by a wheel speed sensor and a steering wheel turning signal input by a driver and sent by a turning angle sensor, calculates the size of the ideal front wheel turning angle according to the characteristics of the ideal front wheel turning angle, converts the size of the ideal front wheel turning angle into the ideal output displacement of a corresponding steering straight pull rod, and outputs the ideal front wheel turning angle signal to the ECU; the ideal power-assisted torque module receives a wheel speed signal sent by a wheel speed sensor and a driver input torque signal sent by a torque sensor, calculates the size of ideal power-assisted torque according to the characteristic of the ideal power-assisted torque, and outputs the ideal power-assisted torque signal to the ECU; the ECU calculates the ideal transmission ratio and the working strategies of the first hydraulic circuit and the second hydraulic circuit according to the ideal front wheel steering angle signal and the ideal power-assisted torque signal;
22 The ECU determines a first hydraulic circuit working strategy according to the difference value between the torque input by the driver and the ideal power-assisted torque transmitted by the torque sensor, obtains the power-assisted torque required to be provided, calculates the corresponding hydraulic oil flow, controls the brushless direct current motor to enter a first hydraulic circuit working mode, and carries out power input on the recirculating ball steering gear; meanwhile, the ECU determines a working strategy of a second hydraulic circuit according to a steering straight pull rod feedback signal and an ideal front wheel steering angle signal output by the steering straight pull rod, calculates the flow required by the second hydraulic circuit, and controls the electro-hydraulic proportional reversing valve to move to a corresponding position;
hydraulic oil output by the energy accumulator is input to the steering straight pull rod hydraulic cylinder through the electro-hydraulic proportional reversing valve, so that the steering straight pull rod piston rod moves relative to the steering straight pull rod hydraulic cylinder, and the steering straight pull rod piston rod drives the pull rod, the steering trapezium and the wheels, so that the rotation angle of the front wheels is changed;
23 The torque and the rotation angle input by a driver are sequentially transmitted through a steering wheel, a steering shaft, a recirculating ball steering gear and a steering straight pull rod and are converted into the output displacement of the steering straight pull rod, and in the process, the ECU coordinately controls two hydraulic circuits to enable the first hydraulic circuit to assist the recirculating ball steering gear and the second hydraulic circuit to control the displacement of the steering straight pull rod so as to finish active steering.
Preferably, assuming that the transmission ratio of the steering system is i and the front wheel rotation angle is delta f When the steering wheel turns to delta
Ideal transmission ratio
Wherein V is wheel speed, K u For understeer coefficient, K S Parameters are set for an ideal front wheel steering module, and the range is 0.12-0.41;
according to the ideal transmission ratio i 0 The method comprises the steps of obtaining ideal front wheel steering angle characteristics under different vehicle speeds, calculating an ideal front wheel steering angle by an ideal front wheel steering angle module according to a steering angle signal obtained by a steering angle sensor, and calculating an ideal steering tie rod output displacement according to the motion relation of the steering tie rod, a steering trapezoid and wheels;
the ideal boosting characteristics are:
wherein: t (T) m To be ideal torque, T d For driver input torque, T 0 To start providing the torque at the time of assistance, T max For maximum power input torque, T f And k is the slope of the power assisting characteristic curve calculated by the ideal power assisting torque module.
The invention has the beneficial effects that:
the system and the control method can complete the active steering function through the coordination and the matching of the two hydraulic circuits, so that a driver has good driving feel and steering portability, the stability and the safety of a passenger car during high-speed running are enhanced, and the occurrence of accidents is reduced. The two hydraulic loops share one motor and one hydraulic pump, so that energy loss caused by low efficiency is reduced, and meanwhile, the quality and occupied space of the system are reduced.
Drawings
FIG. 1 is a block diagram of an active steering system of the present invention;
FIG. 2 is a schematic block diagram of the active steering system architecture of the present invention;
FIG. 3 is a schematic block diagram of a steering control method of the system of the present invention;
in the figure: 1-steering wheel, 2-rotation angle sensor, 3-torque sensor, 4-steering shaft, 5-rotary valve, 6-first oil inlet pipeline, 7-first oil return pipeline, 8-steering screw, 9-steering nut, 10-recirculating ball steering gear shell, 11-sector, 12-steering rocker arm, 13-steering straight-pull rod piston, 14-steering straight-pull rod hydraulic cylinder, 15-steering straight-pull rod piston rod, 16-displacement sensor, 17-second oil inlet pipeline, 18-pull rod, 19-second oil return pipeline, 20-steering trapezoid, 21-wheel, 22-wheel speed sensor, 23-electrohydraulic proportional reversing valve, 24-relief valve, 25-second electromagnetic valve, 26-pressure sensor, 27-accumulator, 28-second one-way valve, 29-main controller, 30-oil storage tank, 31-hydraulic pump, 32-brushless DC motor, 33-first one-way valve, 34-first electromagnetic valve, 35-first electromagnetic valve, 36-pressure control module, 37-displacement control module, 38-ideal front wheel angle module, 39-ideal front wheel angle module, 40-steering ball steering module, 40-ideal ball steering signal, 40-signal electronic control circuit, 24-torque signal electronic control circuit, 14-torque signal electronic control signal electronic circuit, i-electrohydraulic proportional reversing valve control signal.
Detailed Description
The invention will be further described with reference to examples and drawings, to which reference is made, but which are not intended to limit the scope of the invention.
Referring to fig. 1 and 2, an active steering system for a passenger car based on an energy accumulator according to the present invention includes: the device comprises a mechanical module, a hydraulic module and an electric control module;
the mechanical module comprises a steering wheel 1, a steering shaft 4, a recirculating ball steering gear 40, a steering rocker 12, a steering straight pull rod 41, a steering trapezoid 20 and wheels 21 which are connected in sequence;
the recirculating ball steering gear 40 comprises a recirculating ball steering gear housing 10, a steering nut 9, a steering screw 8 and a gear sector 11; the steering nut 9 is assembled in the recirculating ball steering gear shell 10 and moves axially, and the steering nut 9 serves as a piston and forms a hydraulic cylinder-piston structure with the recirculating ball steering gear shell 10; the front end of the steering screw rod 8 is connected with the steering shaft 4, the rear end of the steering screw rod 8 is connected with the steering nut 9, and the rotary motion transmitted by the steering shaft 4 is converted into the axial motion of the steering nut 9 relative to the circulating ball steering gear housing 10; one end of the gear sector 11 is meshed with the steering nut 9, and the other end of the gear sector is connected with the steering rocker arm 12 as the output end of the recirculating ball steering gear;
the steering straight pull rod 41 comprises a steering straight pull rod piston 13, a steering straight pull rod hydraulic cylinder 14, a steering straight pull rod piston rod 15 and a pull rod 18; the shell of the steering straight pull rod hydraulic cylinder 14 is connected with the output end of the recirculating ball steering gear through a steering rocker arm 12, and an oil inlet and an oil outlet are formed in the shell; the steering straight pull rod piston 13 is assembled in the steering straight pull rod hydraulic cylinder 14, and one end of the steering straight pull rod piston is fixedly provided with a steering straight pull rod piston rod 15; the front end of the pull rod 18 is connected with the steering straight pull rod piston rod 15, and the rear end is connected with a steering trapezoid 20 and wheels 21;
the hydraulic module includes an oil tank 30, an oil filter 35, a brushless DC motor 32, a hydraulic pump 31, a first check valve 33, a first hydraulic circuit 42, and a second hydraulic circuit 43;
the first hydraulic circuit 42 comprises a first electromagnetic valve 34, a rotary valve 5, a first oil inlet pipeline 6 and a first oil return pipeline 7;
the first electromagnetic valve 34 adopts a two-position two-way normally open mode, an inlet of the first electromagnetic valve is connected with an outlet of the first one-way valve 33, and an outlet of the first electromagnetic valve is connected with an inlet of the rotary valve 5;
the rotary valve 5 is arranged on the steering shaft 4 of the mechanical steering module, two ends of a valve core of the rotary valve 5 are respectively connected with the steering shaft 4 and the steering screw rod 8 of the recirculating ball steering gear, high-pressure oil input by the first electromagnetic valve 34 is distributed when the position of the valve core is changed, and the high-pressure oil is connected with an oil inlet and an oil outlet of the recirculating ball steering gear through the first oil inlet pipeline 6 and the first oil return pipeline 7;
the second hydraulic circuit 43 comprises a second one-way valve 28, a second electromagnetic valve 25, an accumulator 27, an electro-hydraulic proportional reversing valve 23, a second oil inlet pipeline 17, a second oil return pipeline 19 and an overflow valve 24;
the second electromagnetic valve 25 adopts a two-position two-way normally closed mode, and an inlet of the second electromagnetic valve is connected with the first one-way valve 33 and is connected with the first electromagnetic valve 34 in parallel; the outlet of the valve is connected with an oil inlet of an energy accumulator 27 through a second one-way valve 28;
the oil outlet of the accumulator 27 outputs hydraulic oil to the electro-hydraulic proportional reversing valve 23, and the pressure sensor 26 is arranged at the oil outlet;
the electro-hydraulic proportional reversing valve 23 is in a three-position four-way form and is communicated with an oil inlet and an oil outlet of the steering straight pull rod hydraulic cylinder 14 of the steering straight pull rod 41 through a second oil inlet pipeline 17 and a second oil return pipeline 19;
an oil inlet of the overflow valve 24 is connected with the second electromagnetic valve 25 in parallel, and an oil return port is communicated with the oil storage tank 30;
the hydraulic pump 31 is driven by the brushless direct current motor 32, low-pressure oil in the oil storage tank 30 is filtered by the oil filter 35 and is converted into high-pressure oil, and the high-pressure oil is respectively output to the first hydraulic circuit 42 and the second hydraulic circuit 43 through the first one-way valve 33;
the electronic control module comprises a main controller 29, a rotation angle sensor 2, a torque sensor 3, a pressure sensor 26, a displacement sensor 16 and a wheel speed sensor 22;
the main controller 29 comprises an ECU44, an ideal front wheel rotation angle module 38, an ideal power-assisted torque module 39, a pressure control module 36 and a displacement control module 37;
the steering angle sensor 2 is mounted on the steering wheel 1 for providing a driver-input steering wheel angle signal b to an ideal front wheel corner module 38;
the torque sensor 3 is mounted on the steering shaft 4 for providing a driver-input torque signal a to the ideal assist torque module 39 and the ECU 44;
the pressure sensor 26 is mounted in the second hydraulic circuit at the outlet of the accumulator 27 for providing an accumulator outlet oil pressure signal e to the pressure control module 36;
the displacement sensor 16 is mounted on the pull rod 18 for providing a pull rod displacement signal d to the displacement control module 37;
the wheel speed sensor 22 is mounted on the wheel 21 for providing a wheel speed signal c to the ideal assist torque module 39 and the ideal front wheel angle module 38.
The control method for changing the transmission ratio of the steering system by the second hydraulic circuit comprises the following steps:
11 Pressurized process: preset accumulator minimum operating pressure P 0 Filling pressure P 1 When the oil pressure at the outlet of the accumulator is smaller than the preset minimum working pressure P 0 When the pressure signal e is transmitted to the ECU, the ECU controls the first electromagnetic valve working position to be closed, and controls the second electromagnetic valve working position to be opened; the pressure control module adopts PID control, controls the second hydraulic circuit to enter a pressurizing working mode according to a brushless direct current motor control signal f and a pressure signal e, drives the hydraulic pump to work, converts the output flow of the hydraulic pump into the output flow of the second electromagnetic valve through the second electromagnetic valve, and pressurizes the energy accumulator;
12 Pressure maintaining process: when the oil pressure at the outlet of the accumulator reaches the preset full pressure P 1 When the ECU receives the pressure signal e, the first electromagnetic valve working position is controlled to be opened, the second electromagnetic valve working position is controlled to be closed, and the accumulator pressure is kept at P 0 To P 1 The pressure control module controls the second hydraulic circuit to enter a pressure maintaining working mode;
13 A) working process: when the passenger car turns, the ideal front wheel steering module calculates the ideal front wheel steering angle according to the wheel speed signal c and the steering wheel angle signal b input by a driver, converts the ideal front wheel steering angle into the ideal output displacement of the corresponding steering tie rod, and the displacement control module receives an electrohydraulic proportional reversing valve control signal i and a displacement signal d fed back by a displacement sensor, controls the electrohydraulic proportional reversing valve to move to a corresponding working position, and the output flow of the accumulator flows into the electrohydraulic proportional reversing valve, and the output flow of the electrohydraulic proportional reversing valve flows into the steering tie rod hydraulic cylinder to push the steering tie rod piston to move relative to the steering tie rod hydraulic cylinder and drive the tie rod to move so as to change the output displacement of the steering tie rod and the corresponding front wheel angle;
assuming that the ideal output displacement of the steering tie rod is x 0 The output displacement of the steering tie rod detected by the displacement sensor is x 1 The displacement control module changes the characteristic of the output displacement of the steering straight pull rod by continuously changing the flow according to the electro-hydraulic proportional reversing valve in proportion, adopts a sliding mode control method and is based on the output displacement x 1 And ideal output displacement x 0 And calculating corresponding sliding mode control parameters.
Wherein, the transmission ratio of the steering system is i, and the front wheel rotation angle is delta f When the steering wheel turns to delta
Ideal transmission ratio
Wherein V is wheel speed, K u For understeer coefficient, K S Parameters are set for an ideal front wheel steering module, and the range is 0.12-0.41 (1/s);
according to the ideal transmission ratio i 0 The ideal front wheel steering angle characteristics under different vehicle speeds are obtained, the ideal front wheel steering angle module calculates the ideal front wheel steering angle according to the steering angle signals obtained by the steering angle sensor, and then the ideal steering straight pull rod output displacement is calculated according to the motion relation of the steering straight pull rod, the steering trapezium and the wheels.
The sliding mode control method specifically comprises the following steps:
131 Defining a switching function of the sliding mode controller as: s=c (x 1 -x 0 ) Wherein c is a constant;
132 From the switching function, we get:
133 Selecting an exponential approach law
ε > 0, k > 0, where ∈0>
Is an exponential approach term, which solves for s=s (0) e -kt The constant epsilon is the rate at which the system motion point approaches the switching plane s=0;
134 Making:
wherein V is the wheel speed, delta is the steering wheel angle;
135 To sum up the above results:
referring to fig. 3, the steering control method of the active steering system of the passenger car based on the energy accumulator of the invention is based on the system and comprises the following steps:
21 The ideal front wheel turning module receives a wheel speed signal sent by a wheel speed sensor and a steering wheel turning signal input by a driver and sent by a turning angle sensor, calculates the size of the ideal front wheel turning angle according to the characteristics of the ideal front wheel turning angle, converts the size of the ideal front wheel turning angle into the ideal output displacement of a corresponding steering straight pull rod, and outputs the ideal front wheel turning angle signal to the ECU; the ideal power-assisted torque module receives a wheel speed signal sent by a wheel speed sensor and a driver input torque signal sent by a torque sensor, calculates the size of ideal power-assisted torque according to the characteristic of the ideal power-assisted torque, and outputs the ideal power-assisted torque signal to the ECU; the ECU calculates the ideal transmission ratio and the working strategies of the first hydraulic circuit and the second hydraulic circuit according to the ideal front wheel steering angle signal and the ideal power-assisted torque signal;
22 The ECU determines a first hydraulic circuit working strategy according to the difference value between the torque input by the driver and the ideal power-assisted torque transmitted by the torque sensor, obtains the power-assisted torque required to be provided, calculates the corresponding hydraulic oil flow, controls the brushless direct current motor to enter a first hydraulic circuit working mode, and carries out power input on the recirculating ball steering gear; meanwhile, the ECU determines a working strategy of a second hydraulic circuit according to a steering straight pull rod feedback signal and an ideal front wheel steering angle signal output by the steering straight pull rod, calculates the flow required by the second hydraulic circuit, and controls the electro-hydraulic proportional reversing valve to move to a corresponding position;
hydraulic oil output by the energy accumulator is input to the steering straight pull rod hydraulic cylinder through the electro-hydraulic proportional reversing valve, so that the steering straight pull rod piston rod moves relative to the steering straight pull rod hydraulic cylinder, and the steering straight pull rod piston rod drives the pull rod, the steering trapezium and the wheels, so that the rotation angle of the front wheels is changed;
23 The torque and the rotation angle input by a driver sequentially pass through a steering wheel, a steering shaft, a recirculating ball steering gear and a steering straight pull rod and are finally converted into the output displacement of the steering straight pull rod, and in the process, the ECU coordinately controls two hydraulic circuits to enable the first hydraulic circuit to assist the recirculating ball steering gear and the second hydraulic circuit to control the displacement of the steering straight pull rod so as to finish active steering.
Wherein, the transmission ratio of the steering system is i, and the front wheel rotation angle is delta f When the steering wheel turns to delta
Ideal transmission ratio
Wherein V is wheel speed, K u For understeer coefficient, K S Parameters are set for an ideal front wheel steering module, and the range is 0.12-0.41 (1/s);
according to the ideal transmission ratio i 0 Obtaining ideal front wheel steering angle characteristics under different vehicle speeds, and obtaining an ideal front wheel steering angle module meter according to the steering angle signals obtained by the steering angle sensorCalculating an ideal front wheel corner, and then calculating an ideal steering straight pull rod output displacement according to the motion relation of the steering straight pull rod, the steering trapezium and the wheels;
the ideal boosting characteristics are:
wherein: t (T) m To be ideal torque, T d For driver input torque, T 0 To start providing the torque at the time of assistance, T max For maximum power input torque, T f And k is the slope of the power assisting characteristic curve calculated by the ideal power assisting torque module.
The present invention has been described in terms of the preferred embodiments thereof, and it should be understood by those skilled in the art that various modifications can be made without departing from the principles of the invention, and such modifications should also be considered as being within the scope of the invention.
Claims (9)
1. An energy storage-based active steering system for a passenger vehicle, comprising: the device comprises a mechanical module, a hydraulic module and an electric control module;
the mechanical module comprises a steering wheel, a steering shaft, a recirculating ball steering gear, a steering rocker arm, a steering straight pull rod, a steering trapezoid and wheels which are connected in sequence;
the recirculating ball steering gear comprises a recirculating ball steering gear shell, a steering nut, a steering screw rod and a gear sector; the steering nut is used as a piston and forms a hydraulic cylinder-piston structure with the recirculating ball steering gear shell; the front end of the steering screw is connected with a steering shaft, the rear end of the steering screw is connected with a steering nut, and the rotary motion transmitted by the steering shaft is converted into the axial motion of the steering nut relative to the housing of the recirculating ball steering gear; one end of the gear sector is meshed with the steering nut, and the other end of the gear sector is connected with the steering rocker arm as the output end of the recirculating ball steering gear;
the steering straight pull rod comprises a steering straight pull rod piston, a steering straight pull rod hydraulic cylinder, a steering straight pull rod piston rod and a pull rod; the shell of the steering straight pull rod hydraulic cylinder is connected with the output end of the recirculating ball steering gear through a steering rocker arm, and an oil inlet and an oil outlet are formed in the shell; the steering straight pull rod piston is assembled in the steering straight pull rod hydraulic cylinder, and a steering straight pull rod piston rod is fixedly arranged at one end of the steering straight pull rod piston; the front end of the pull rod is connected with the steering straight pull rod piston rod, and the rear end of the pull rod is connected with a steering trapezoid and wheels;
the hydraulic module comprises an oil storage tank, an oil filter, a brushless direct current motor, a hydraulic pump, a first one-way valve, a first hydraulic circuit and a second hydraulic circuit;
the first hydraulic circuit comprises a first electromagnetic valve, a rotary valve, a first oil inlet pipeline and a first oil return pipeline;
the inlet of the first electromagnetic valve is connected with the outlet of the first one-way valve, and the outlet of the first electromagnetic valve is connected with the inlet of the rotary valve;
the rotary valve is arranged on a steering shaft of the mechanical steering module, two ends of a valve core of the rotary valve are respectively connected with the steering shaft and a steering screw of the recirculating ball steering gear, high-pressure oil input by the first electromagnetic valve is distributed when the position of the valve core is changed, and the valve core is connected with an oil inlet and an oil outlet of the recirculating ball steering gear through a first oil inlet pipeline and a first oil return pipeline;
the second hydraulic circuit comprises a second one-way valve, a second electromagnetic valve, an energy accumulator, an electrohydraulic proportional reversing valve, a second oil inlet pipeline, a second oil return pipeline and an overflow valve;
the inlet of the second electromagnetic valve is connected with the first one-way valve and is connected with the first electromagnetic valve in parallel; the outlet of the valve is connected with an oil inlet of the energy accumulator through a second one-way valve;
an oil outlet of the energy accumulator outputs hydraulic oil to the electro-hydraulic proportional reversing valve, and a pressure sensor is arranged at the oil outlet;
the electro-hydraulic proportional reversing valve is communicated with an oil inlet and an oil outlet of a steering straight pull rod hydraulic cylinder of the steering straight pull rod through a second oil inlet pipeline and a second oil return pipeline;
an oil inlet of the overflow valve is connected with the second electromagnetic valve in parallel, and an oil return port is communicated with the oil storage tank;
the hydraulic pump is driven by a brushless direct current motor, low-pressure oil in an oil storage tank is converted into high-pressure oil after being filtered by an oil filter, and the high-pressure oil is respectively output to a first hydraulic circuit and a second hydraulic circuit through a first one-way valve;
the electronic control module comprises a main controller, a rotation angle sensor, a torque sensor, a pressure sensor, a displacement sensor and a wheel speed sensor;
the main controller comprises an ECU, an ideal front wheel corner module, an ideal power-assisted torque module, a pressure control module and a displacement control module;
the steering angle sensor is arranged on the steering wheel and is used for providing a steering wheel steering angle signal b input by a driver to the ideal front-wheel steering angle module;
the torque sensor is arranged on the steering shaft and is used for providing a torque signal a input by a driver to the ideal power-assisted torque module and the ECU;
the pressure sensor is arranged at the outlet position of the energy accumulator in the second hydraulic circuit and is used for providing an oil pressure signal e at the outlet of the energy accumulator for the pressure control module;
the displacement sensor is arranged on the pull rod and used for providing a pull rod displacement signal d for the displacement control module;
the wheel speed sensor is mounted on the wheel and is used for providing a wheel speed signal c to the ideal power-assisted torque module and the ideal front wheel turning angle module.
2. The active steering system of claim 1, wherein the first solenoid valve is in a two-position, two-way, normally open configuration.
3. The active steering system of claim 1, wherein the second solenoid valve is in the form of a two-position, two-way, normally closed system.
4. The active steering system of an energy accumulator based passenger car of claim 1, wherein the electro-hydraulic proportional reversing valve is in the form of a three-position four-way valve.
5. The active steering system of an accumulator-based passenger vehicle of any one of claims 1 to 4, wherein the control method for changing the steering system transmission ratio by the second hydraulic circuit comprises the steps of:
11 Pressurized process: preset accumulator minimum operating pressure P 0 Filling pressure P 1 When the oil pressure at the outlet of the accumulator is smaller than the preset minimum working pressure P 0 When the pressure signal e is transmitted to the ECU, the ECU controls the first electromagnetic valve working position to be closed, and controls the second electromagnetic valve working position to be opened; the pressure control module adopts PID control, controls the second hydraulic circuit to enter a pressurizing working mode according to a brushless direct current motor control signal f and a pressure signal e, drives the hydraulic pump to work, converts the output flow of the hydraulic pump into the output flow of the second electromagnetic valve through the second electromagnetic valve, and pressurizes the energy accumulator;
12 Pressure maintaining process: when the oil pressure at the outlet of the accumulator reaches the preset full pressure P 1 When the ECU receives the pressure signal e, the first electromagnetic valve working position is controlled to be opened, the second electromagnetic valve working position is controlled to be closed, and the accumulator pressure is kept at P 0 To P 1 The pressure control module controls the second hydraulic circuit to enter a pressure maintaining working mode;
13 A) working process: when the passenger car turns, the ideal front wheel steering module calculates the ideal front wheel steering angle according to the wheel speed signal c and the steering wheel angle signal b input by a driver, converts the ideal front wheel steering angle into the ideal output displacement of the corresponding steering tie rod, and the displacement control module receives an electrohydraulic proportional reversing valve control signal i and a displacement signal d fed back by a displacement sensor, controls the electrohydraulic proportional reversing valve to move to a corresponding working position, and the output flow of the accumulator flows into the electrohydraulic proportional reversing valve, and the output flow of the electrohydraulic proportional reversing valve flows into the steering tie rod hydraulic cylinder to push the steering tie rod piston to move relative to the steering tie rod hydraulic cylinder and drive the tie rod to move so as to change the output displacement of the steering tie rod and the corresponding front wheel angle;
assuming that the ideal output displacement of the steering tie rod is x 0 Steering detected by displacement sensorThe output displacement of the straight pull rod is x 1 The displacement control module changes the characteristic of the output displacement of the steering straight pull rod by continuously changing the flow according to the electro-hydraulic proportional reversing valve in proportion, adopts a sliding mode control method and is based on the output displacement x 1 And ideal output displacement x 0 And calculating corresponding sliding mode control parameters.
6. The accumulator-based active steering system of claim 5, wherein assuming a ratio of i for the steering system, the front wheel angle is δ f When the steering wheel turns to delta
Ideal transmission ratio
Wherein V is wheel speed, K u For understeer coefficient, K S Parameters are set for an ideal front wheel steering module, and the range is 0.12-0.41;
according to the ideal transmission ratio i 0 The ideal front wheel steering angle characteristics under different vehicle speeds are obtained, the ideal front wheel steering angle module calculates the ideal front wheel steering angle according to the steering angle signals obtained by the steering angle sensor, and then the ideal steering straight pull rod output displacement is calculated according to the motion relation of the steering straight pull rod, the steering trapezium and the wheels.
7. The active steering system of an energy storage-based passenger car of claim 5, wherein the slip-form control method comprises the following steps:
131 Defining a switching function of the sliding mode controller as: s=c (x 1 -x 0 ) Wherein c is a constant;
132 From the switching function, we get:
133 Selecting an exponential approach law
Wherein->
Is an exponential approach term, which solves for s=s (0) e -kt The constant epsilon is the rate at which the system motion point approaches the switching plane s=0;
134 Making:
wherein V is the wheel speed, delta is the steering wheel angle;
135 To sum up the above results:
8. a steering control method of an active steering system of a passenger car based on an accumulator, characterized by the following steps based on the system according to any one of claims 1-7:
21 The ideal front wheel turning module receives a wheel speed signal sent by a wheel speed sensor and a steering wheel turning signal input by a driver and sent by a turning angle sensor, calculates the size of the ideal front wheel turning angle according to the characteristics of the ideal front wheel turning angle, converts the size of the ideal front wheel turning angle into the ideal output displacement of a corresponding steering straight pull rod, and outputs the ideal front wheel turning angle signal to the ECU; the ideal power-assisted torque module receives a wheel speed signal sent by a wheel speed sensor and a driver input torque signal sent by a torque sensor, calculates the size of ideal power-assisted torque according to the characteristic of the ideal power-assisted torque, and outputs the ideal power-assisted torque signal to the ECU; the ECU calculates the ideal transmission ratio and the working strategies of the first hydraulic circuit and the second hydraulic circuit according to the ideal front wheel steering angle signal and the ideal power-assisted torque signal;
22 The ECU determines a first hydraulic circuit working strategy according to the difference value between the torque input by the driver and the ideal power-assisted torque transmitted by the torque sensor, obtains the power-assisted torque required to be provided, calculates the corresponding hydraulic oil flow, controls the brushless direct current motor to enter a first hydraulic circuit working mode, and carries out power input on the recirculating ball steering gear; meanwhile, the ECU determines a working strategy of a second hydraulic circuit according to a steering straight pull rod feedback signal and an ideal front wheel steering angle signal output by the steering straight pull rod, calculates the flow required by the second hydraulic circuit, and controls the electro-hydraulic proportional reversing valve to move to a corresponding position;
hydraulic oil output by the energy accumulator is input to the steering straight pull rod hydraulic cylinder through the electro-hydraulic proportional reversing valve, so that the steering straight pull rod piston rod moves relative to the steering straight pull rod hydraulic cylinder, and the steering straight pull rod piston rod drives the pull rod, the steering trapezium and the wheels, so that the rotation angle of the front wheels is changed;
23 The torque and the rotation angle input by a driver are sequentially transmitted through a steering wheel, a steering shaft, a recirculating ball steering gear and a steering straight pull rod and are converted into the output displacement of the steering straight pull rod, and in the process, the ECU coordinately controls two hydraulic circuits to enable the first hydraulic circuit to assist the recirculating ball steering gear and the second hydraulic circuit to control the displacement of the steering straight pull rod so as to finish active steering.
9. The method for steering control of an active steering system of an accumulator-based passenger vehicle of claim 8, wherein assuming a transmission ratio of the steering system of i, a front wheel rotation angle is δ f When the steering wheel turns to delta
Ideal transmission ratio
Wherein V is wheel speed, K u For understeer coefficient, K S Parameters are set for an ideal front wheel steering module, and the range is 0.12-0.41;
according to the ideal transmission ratio i 0 Obtaining ideal front wheel steering angle characteristics under different vehicle speeds, calculating an ideal front wheel steering angle by an ideal front wheel steering angle module according to the steering angle signals obtained by the steering angle sensor, and then according to the steering tie rod, the steering trapezium and the steering trapeziumCalculating the motion relation of the wheels to obtain the ideal steering tie rod output displacement;
the ideal boosting characteristics are:
wherein: t (T) m To be ideal torque, T d For driver input torque, T 0 To start providing the torque at the time of assistance, T max For maximum power input torque, T f And k is the slope of the power assisting characteristic curve calculated by the ideal power assisting torque module.
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| CN110422229B (en) * | 2019-08-12 | 2021-08-24 | 三一汽车起重机械有限公司 | Pressure feedback control method and controller for vehicle auxiliary steering |
| CN111559424B (en) * | 2020-05-15 | 2022-05-27 | 山推工程机械股份有限公司 | Digital line control steering system and control method and device thereof |
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| KR101349464B1 (en) * | 2012-07-05 | 2014-01-09 | 현대자동차주식회사 | Commercial vehicle's hybrid power steering system and performance and fuel ratio improving method thereof |
| CN102897211B (en) * | 2012-10-11 | 2015-04-15 | 中联重科股份有限公司 | Hydraulic power-assisted steering system and chassis of engineering vehicle |
| CN204383559U (en) * | 2015-01-19 | 2015-06-10 | 吉林大学 | New forms of energy motorcoach electric hydraulic power-assisted steering system |
| CN105383553B (en) * | 2015-11-11 | 2018-03-23 | 江苏大学 | A kind of pure electric coach electric hydraulic power-assisted steering system |
| CN105752152A (en) * | 2016-05-17 | 2016-07-13 | 山东汇川汽车部件有限公司 | Electric hydraulic power steering system for automobile |
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