阅读说明：本技术 一种飞机牵引车用四轮转向系统和转向控制方法 (Four-wheel steering system for aircraft tractor and steering control method ) 是由 帖剑 黄小凡 李洁 于 2019-12-17 设计创作，主要内容包括：本发明公开了一种飞机牵引车用四轮转向系统和转向控制方法,系统包括前后轮转向油缸、电磁阀、全液压转向器和控制器,前后轮转向油缸均具有两个油腔；转向器的两个分配端口由车辆方向盘控制以使两个分配端口交替供油和回油；电磁阀为三位四通阀,其进油口与全液压转向器的一个分配口连接,第一端口和第二端口分别与前或后轮转向油缸中一个的两个油腔连接,另一油缸的两个油腔分别与转向器的另一个分配口,以及电磁阀回油口连接。控制方法基于前述系统实施。本发明的有益效果是,系统结构简单,故障率低,具有三种转向模式；控制方法通过PLC实现自动控制,并对车轮对中状态进行检测和纠偏,以确保前后轮偏转能够精确同步,消除车辆跑偏安全隐患。(The invention discloses a four-wheel steering system for an aircraft tractor and a steering control method, wherein the system comprises a front wheel steering oil cylinder, a rear wheel steering oil cylinder, an electromagnetic valve, a full hydraulic steering gear and a controller, wherein the front wheel steering oil cylinder and the rear wheel steering oil cylinder are respectively provided with two oil cavities; the two distribution ports of the steering gear are controlled by a vehicle steering wheel so that the two distribution ports alternately supply and return oil; the electromagnetic valve is a three-position four-way valve, an oil inlet of the electromagnetic valve is connected with a distribution port of the full hydraulic steering gear, a first port and a second port of the electromagnetic valve are respectively connected with two oil cavities of one of the front or rear wheel steering oil cylinders, and two oil cavities of the other oil cylinder are respectively connected with the other distribution port of the steering gear and an oil return port of the electromagnetic valve. The control method is implemented based on the system. The invention has the advantages that the system has simple structure, low failure rate and three steering modes; the control method realizes automatic control through a PLC, and detects and corrects the centering state of the wheels so as to ensure that the deflection of the front wheels and the rear wheels can be accurately synchronized and eliminate the potential safety hazard of vehicle deviation.)

1. A four-wheel steering system for an aircraft tractor comprises a front wheel steering oil cylinder, a rear wheel steering oil cylinder, an electromagnetic valve (5), a full hydraulic steering gear (6) and a controller (7); the full hydraulic steering gear (6) is provided with two distribution ports, the two distribution ports of the full hydraulic steering gear (6) correspondingly form the state alternate change of oil supply and oil return along with the change of the steering direction of the vehicle, so that the hydraulic steering of the vehicle is realized by respectively supplying oil to two oil cavities of the steering oil cylinder; the electromagnetic valve is characterized in that the electromagnetic valve (5) is a three-position four-way valve and comprises an electromagnetic valve oil inlet (5P), an electromagnetic valve oil return port (5T), an electromagnetic valve first port (5A) and an electromagnetic valve second port (5B); an oil inlet (5P) of the electromagnetic valve is connected with a distribution port of the full hydraulic steering gear (6), a first port (5A) and a second port (5B) of the electromagnetic valve are respectively connected with two oil cavities of the front wheel steering oil cylinder or the rear wheel steering oil cylinder, and two oil cavities of the other steering oil cylinder are respectively connected with the other distribution port of the full hydraulic steering gear (6) and an oil return port (5T) of the electromagnetic valve.

2. The four-wheel steering system for an aircraft tractor according to claim 1, characterized in that the front-wheel steering cylinder is constituted by a front steering cylinder (3) of a double-acting cylinder structure; or, the steering mechanism consists of a left front steering oil cylinder (31) and a right front steering oil cylinder (32) which are connected in parallel by oil ways, and piston rods of the left front steering oil cylinder and the right front steering oil cylinder form complementary synchronous extension; the rear wheel steering oil cylinder is composed of a rear steering oil cylinder (4) with a double-acting oil cylinder structure; or the steering mechanism is composed of a left rear steering oil cylinder (41) and a right rear steering oil cylinder (42) which are connected in parallel in oil way, and piston rods of the left rear steering oil cylinder and the right rear steering oil cylinder form complementary synchronous extension.

3. Four-wheel steering system for aircraft tractors according to claim 1 or 2, characterized in that the two distribution ports of the full hydraulic steering gear (6) are constituted by a first steering gear port (L) and a second steering gear port (R), respectively, and that the first steering gear port (L) is supplied with oil when the steering wheel is turned to the right and the second steering gear port (R) is supplied with oil when the steering wheel is turned to the left; when oil is fed into the first oil cavity of any oil cylinder, the wheels turn right, and when oil is fed into the second oil cavity, the wheels turn left; a first oil cavity of the front wheel steering oil cylinder is connected with a first port (L) of the steering gear, and a second oil cavity of the front wheel steering oil cylinder is connected with an oil return port (5T) of the electromagnetic valve; the electromagnetic valve first port (5A) and the electromagnetic valve second port (5B) are respectively connected with a first oil chamber and a second oil chamber of the rear wheel steering oil cylinder; the electromagnetic valve oil inlet (5P) is connected with the second port (R) of the steering gear.

4. The four-wheel steering system for aircraft tractors according to claim 1, further comprising a neutral sensor for providing a wheel return positive signal, the neutral sensor being connected to a detection signal input of the controller (7).

5. The four-wheel steering system for an aircraft tractor according to claim 4, wherein the neutral sensor is constituted by two position sensors; the position sensor is formed by one of a travel switch, a proximity switch or an optoelectronic switch.

6. Four-wheel steering system for aircraft tractors according to claim 1, characterized in that the controller (7) is also connected to an operating mode selection switch via an input.

7. A four-wheel steering control method for an aircraft tractor, which is implemented based on the control system of claims 1 to 6, wherein the controller (7) sends a command corresponding to the working state to the electromagnetic valve (5) according to a steering working mode command.

8. The control method according to claim 7, further comprising performing wheel deviation correction in a front wheel steering mode and a four wheel steering mode, wherein the deviation correction is performed by switching the operating modes, and after the deviation correction is completed, the controller (7) sends a command corresponding to the operating state to the solenoid valve (5) according to the steering operating mode command.

9. The control method according to claim 8, wherein the correction of the front wheel steering mode comprises the steps of:

the method comprises the steps of firstly, detecting whether a rear wheel is in a middle position or not; if the rear wheel is not in the middle position, executing the second step; if the rear wheel is in the middle position, executing the sixth step;

detecting a direction signal of vehicle steering, and executing a third step if the direction of the vehicle steering is the same as the deflection direction of the rear wheels; if the steering direction of the vehicle is opposite to the deflection direction of the rear wheels, executing a fourth step; if the vehicle has no steering direction signal, executing the fifth step;

thirdly, correcting the deviation according to a four-wheel steering mode, detecting the aligning condition of the rear wheel in the deviation correcting process, and if the rear wheel is not aligned, continuing to execute the step; if the rear wheel is back to the right position, executing the sixth step;

fourthly, correcting the deviation according to the crab steering mode, detecting the aligning condition of the rear wheel in the deviation correcting process, and if the rear wheel is not aligned, continuing to execute the step; if the rear wheel is back to the right position, executing the sixth step;

fifthly, correcting the deviation, preparing, including sending a deviation-correcting steering indicating signal, when the direction of the deviation-correcting steering indicating signal is the same as the deflection direction of the rear wheel, driving a steering wheel according to the deviation-correcting steering indicating direction, and returning to the third step; when the indication direction of the deviation-rectifying steering is opposite to the deflection direction of the rear wheel, the steering wheel is steered according to the deviation-rectifying steering indication direction, and the fourth step is returned;

sixthly; returning to the front wheel steering mode.

10. The control method according to claim 8, wherein the correction of the four-wheel steering mode includes the steps of;

s1, detecting whether the rear wheel is in the middle position, and executing S2 when the rear wheel is in the middle position; when the rear wheel is not in the neutral position, S4 is performed;

s2, detecting whether the front wheel is in the middle position, and executing S3 when the front wheel is not in the middle position; when the front wheel is in the middle position, executing S7;

s3, correcting the deviation according to the front wheel steering mode, detecting the front wheel aligning condition in the deviation correcting process, and executing S7 after the front wheel aligning; if the front wheel is not aligned, the step is continuously executed;

s4, detecting a steering direction signal of the vehicle, and executing S5 when the steering direction of the vehicle is the same as the deflection direction of the rear wheels; when the steering direction of the vehicle is opposite to the rear wheel yaw direction, S6 is executed;

s5, correcting the rear wheel according to the four-wheel steering mode, and returning to S1;

s6, correcting the rear wheel according to the crab steering mode, and returning to S1;

and S7, returning to the four-wheel steering mode.

Technical Field

The invention relates to a vehicle running control technology, in particular to a four-wheel steering system for an aircraft tractor for full hydraulic steering and a steering control method.

Background

The aircraft tractor is a special vehicle for dragging aircraft in an airport, and the steering control of the aircraft tractor usually adopts hydraulic steering because of large tonnage and large traction power of the aircraft, and the direction is controlled by a steering wheel and a hydraulic oil way is converted by a full hydraulic steering gear in the steering process, so that the steering is realized. In different stages of airplane traction, a plurality of steering modes such as front wheel steering, four-wheel steering and crab steering are needed. The steering control of the existing tractor generally adopts a plurality of electromagnetic valves to control and realize the on-off switching of oil paths, so as to achieve the steering mode. The arrangement of a plurality of electromagnetic valves inevitably causes the defects of complex system structure, high manufacturing cost and many fault points. In addition, because the steering oil cylinder, the electromagnetic valve and the steering gear leak internally, the problem that the deflection angles of the front wheel and the rear wheel cannot be accurately synchronized can be caused after a period of work, at the moment, when the front wheel is in the middle position, the rear wheel can be in a left or right position, and the vehicle can be deviated seriously to influence the driving safety. For this reason, improvements are required.

Disclosure of Invention

The invention aims to overcome the defects of complex structure, high manufacturing cost and more fault points of the existing aircraft tractor, and provides a four-wheel steering system for the aircraft tractor, which utilizes the characteristic that a three-position four-way valve has multiple switchable working states, reduces the number of electromagnetic valves, reduces the manufacturing cost and effectively reduces the fault points. The invention also aims to provide a steering control method based on the system, so as to realize multiple steering modes of the airport tractor, ensure that the deflection of the front wheels and the rear wheels can be accurately synchronized through deviation rectification and eliminate the potential safety hazard of vehicle deviation.

In order to achieve the first object, the invention adopts the following technical scheme.

A four-wheel steering system for an aircraft tractor comprises a front wheel steering oil cylinder, a rear wheel steering oil cylinder, an electromagnetic valve, a full hydraulic steering gear and a controller; the full hydraulic steering gear is provided with two distribution ports, the two distribution ports of the full hydraulic steering gear correspondingly form the state of oil supply and oil return to be changed alternately along with the change of the steering direction of the vehicle, so that the hydraulic steering of the vehicle is realized by respectively supplying oil to two oil cavities of the steering oil cylinder; the electromagnetic valve is a three-position four-way valve and comprises an electromagnetic valve oil inlet, an electromagnetic valve oil return port, an electromagnetic valve first port and an electromagnetic valve second port; an oil inlet of the electromagnetic valve is connected with a distribution port of the full hydraulic steering gear, a first port of the electromagnetic valve and a second port of the electromagnetic valve are respectively connected with two oil cavities of the front wheel steering oil cylinder or the rear wheel steering oil cylinder, and two oil cavities of the other steering oil cylinder are respectively connected with the other distribution port of the full hydraulic steering gear and an oil return port of the electromagnetic valve.

According to the invention adopting the technical scheme, the electromagnetic valve is arranged on the steering hydraulic circuit, three steering modes are obtained by utilizing three working states of the electromagnetic valve, for example, the oil inlet of the electromagnetic valve is communicated with the oil return port of the electromagnetic valve, and the two-wheel steering is realized under the working state that the first port of the electromagnetic valve and the second port of the electromagnetic valve are cut off, and when the cut-off oil cylinder is a rear wheel steering oil cylinder, the front wheel steering is realized; when the cut-off oil cylinder is a front wheel steering oil cylinder, the rear wheel steering is realized; under the working state that the first port of the electromagnetic valve is communicated with the oil return port of the electromagnetic valve and the second port of the electromagnetic valve is communicated with the oil inlet of the electromagnetic valve; when the oil cavities on the opposite sides of the front wheel steering oil cylinder and the rear wheel steering oil cylinder are communicated through electromagnetic valves, four-wheel same-direction steering, namely crab steering, is realized; when the oil chambers on the same side of the front wheel steering oil cylinder and the rear wheel steering oil cylinder are communicated through the electromagnetic valve, four-wheel reverse steering, namely four-wheel steering, is realized. Under the working state that a first port of the electromagnetic valve is communicated with an oil inlet of the electromagnetic valve and a second port of the electromagnetic valve is communicated with an oil return port of the electromagnetic valve, when an oil cavity on the same side of a front wheel steering oil cylinder and a rear wheel steering oil cylinder is communicated through the electromagnetic valve, four-wheel reverse steering, namely four-wheel steering, is realized; when the oil chambers on the opposite sides of the front wheel steering oil cylinder and the rear wheel steering oil cylinder are communicated through electromagnetic valves, four-wheel same-direction steering, namely crab steering, is realized. Under the latter two working states, under the condition that the connection states of the first port and the second port of the electromagnetic valve and the left oil chamber and the right oil chamber of the corresponding steering oil cylinder are not changed, the working states can be switched through the electromagnetic valve, and the switching from four-wheel steering to crab steering or from crab steering to four-wheel steering is realized. Therefore, the characteristic that three working states of the three-position four-way valve can be switched is fully utilized, the number of the electromagnetic valves is reduced, the manufacturing cost is reduced, and fault points are effectively reduced. The controller can be a PC microprocessor, a PLC controller or other electronic or analog controllers.

Preferably, the front wheel steering cylinder is formed by a front steering cylinder of a double-acting cylinder structure; or the steering mechanism consists of a left front steering oil cylinder and a right front steering oil cylinder which are connected in parallel by oil passages, and piston rods of the left front steering oil cylinder and the right front steering oil cylinder form complementary synchronous extension; the rear wheel steering oil cylinder is composed of a rear steering oil cylinder with a double-acting oil cylinder structure; or the oil path is formed by a left rear steering oil cylinder and a right rear steering oil cylinder which are connected in parallel, and piston rods of the left rear steering oil cylinder and the right rear steering oil cylinder form complementary synchronous extension; when the first oil cavity of any oil cylinder is fed with oil, the wheels turn right, and when the second oil cavity is fed with oil, the wheels turn left. When the steering oil cylinder adopts a double-acting oil cylinder, the double-acting oil cylinder is used as a part of a rod section of a steering tie rod; when the steering oil cylinder adopts a scheme that a left oil cylinder and a right oil cylinder are connected in parallel, and piston rods of the left oil cylinder and the right oil cylinder form complementary synchronous extension, the two oil cylinders can respectively form a corresponding part of rod sections of a steering tie rod, and can also be independently connected with a corresponding steering arm to form various selectable structural forms. In the scheme that two oil cylinders are connected in parallel, the complementary synchronous extension and retraction of the two piston rods means that when one piston rod extends, the other piston rod retracts, and the retraction speed is the same as the extension speed of the other piston rod, and vice versa.

Preferably, the two distribution ports of the full hydraulic steering gear are respectively composed of a first port of the steering gear and a second port of the steering gear, the first port of the steering gear supplies oil when the steering wheel is turned to the right, and the second port of the steering gear supplies oil when the steering wheel is turned to the left; when oil is fed into the first oil cavity of any oil cylinder, the wheels turn right, and when oil is fed into the second oil cavity, the wheels turn left; a first oil cavity of the front wheel steering oil cylinder is connected with a first port of the steering gear, and a second oil cavity of the front wheel steering oil cylinder is connected with an oil return port of the electromagnetic valve; the first port and the second port of the electromagnetic valve are respectively connected with the first oil chamber and the second oil chamber of the rear wheel steering oil cylinder; and the oil inlet of the electromagnetic valve is connected with the second port of the steering gear. The front wheel steering is realized in a working state that an oil inlet of the electromagnetic valve is communicated with an oil return port of the electromagnetic valve and a first port of the electromagnetic valve and a second port of the electromagnetic valve are cut off by fixing in a connection mode; under the working state that the first port of the electromagnetic valve is communicated with the oil return port of the electromagnetic valve and the second port of the electromagnetic valve is communicated with the oil inlet of the electromagnetic valve; four-wheel steering is realized; under the working state that the first port of the electromagnetic valve is communicated with the oil inlet of the electromagnetic valve and the second port of the electromagnetic valve is communicated with the oil return port of the electromagnetic valve, crab steering is realized.

Preferably, the vehicle wheel turning device further comprises a neutral position sensor for providing a wheel turning positive signal, wherein the neutral position sensor is connected with a detection signal input end of the controller. The steering mode is determined to steer according to the steering signal obtained by the middle position sensor, and misoperation is avoided.

Further preferably, the neutral position sensor is composed of two position sensors; the position sensor is formed by one of a travel switch, a proximity switch or an optoelectronic switch. When the wheel is just in the middle position, the two sensors both have signals, when the wheel deflects, the sensor close to the wheel has a signal, and the other sensor far away from the wheel has no signal; therefore, the detection element with simple structure, low manufacturing cost and stable performance can realize the purpose of middle position detection, and the manufacturing cost and the failure rate are reduced. The mounting position of the position sensor can be determined according to a detection object, the position sensor can be used for detecting through a steel ring or other additional components on a wheel, and can also be used for detecting through components related to the steering direction and the steering angle, such as a steering arm, the mounting position precision can be adjusted according to the detected object as long as the aligning state of the wheel can be accurately reflected, and a signal that the wheel is not aligned can be obtained when the wheel deflects at a small angle.

Preferably, the controller is further connected with a working mode selection switch through an input end. So as to determine a steering strategy according to the field requirement and ensure the safety and high efficiency of the traction work.

In order to achieve the second object, the present invention adopts the following technical solutions.

A four-wheel steering control method of an aircraft tractor is implemented on the basis of a control system for achieving the first purpose, wherein a controller sends a command corresponding to a working state to an electromagnetic valve according to a steering working mode command.

By adopting the method of the scheme, the controller sends the instruction corresponding to the working state to the electromagnetic valve according to the instruction of the steering working mode, thereby realizing the steering purpose of two-wheel steering, four-wheel steering or crab steering, and ensuring the running safety of the vehicle by utilizing the characteristics of simple structure and high reliability of the system.

Preferably, the method further comprises the step of performing wheel deviation correction in a front wheel steering mode and a four-wheel steering mode, wherein the deviation correction is performed by switching the working modes, and after the deviation correction is completed, the controller sends a command corresponding to the working state to the electromagnetic valve according to the steering working mode command. The purpose of the front wheel steering mode deviation correction is to enable the rear wheels to be aligned before the front wheel steering mode is executed, and the purpose of the four-wheel steering mode deviation correction is to enable the front wheels and the rear wheels to be aligned before the four-wheel steering mode is executed, so that accurate control of steering can be achieved under two steering modes through deviation correction, and potential safety hazards of vehicle deviation are eliminated.

Further preferably, the rectification of the front wheel steering mode comprises the following steps:

the method comprises the steps of firstly, detecting whether a rear wheel is in a middle position or not; if the rear wheel is not in the middle position, executing the second step; if the rear wheel is in the middle position, executing the sixth step;

detecting a direction signal of vehicle steering, and executing a third step if the direction of the vehicle steering is the same as the deflection direction of the rear wheels; if the steering direction of the vehicle is opposite to the deflection direction of the rear wheels, executing a fourth step; if the vehicle has no steering direction signal, executing the fifth step;

thirdly, correcting the deviation according to a four-wheel steering mode, detecting the aligning condition of the rear wheel in the deviation correcting process, and if the rear wheel is not aligned, continuing to execute the step; if the rear wheel is back to the right position, executing the sixth step;

fourthly, correcting the deviation according to the crab steering mode, detecting the aligning condition of the rear wheel in the deviation correcting process, and if the rear wheel is not aligned, continuing to execute the step; if the rear wheel is back to the right position, executing the sixth step;

fifthly, correcting the deviation, preparing, including sending a deviation-correcting steering indicating signal, when the direction of the deviation-correcting steering indicating signal is the same as the deflection direction of the rear wheel, driving a steering wheel according to the deviation-correcting steering indicating direction, and returning to the third step; when the indication direction of the deviation-rectifying steering is opposite to the deflection direction of the rear wheel, the steering wheel is steered according to the deviation-rectifying steering indication direction, and the fourth step is returned;

sixthly; returning to the front wheel steering mode.

The reliability, the steering accuracy and the vehicle running safety of the front wheel steering mode are ensured. The deviation-rectifying steering indicating signal is an indicating signal special for deviation-rectifying steering. When the vehicle is a vehicle driven by a person, the deviation rectifying indication signal only needs to meet the requirement recognizable by the driver, and the driver operates the steering wheel; when the vehicle is an automatic driving vehicle, the deviation rectifying indication signal must meet the recognizable requirement of the automatic driving system, and the steering wheel driving is automatically executed by the automatic driving system.

Further preferably, the correction of the four-wheel steering mode includes the following steps;

s1, detecting whether the rear wheel is in the middle position, and executing S2 when the rear wheel is in the middle position; when the rear wheel is not in the neutral position, S4 is performed;

s2, detecting whether the front wheel is in the middle position, and executing S3 when the front wheel is not in the middle position; when the front wheel is in the middle position, executing S7;

s3, correcting the deviation according to the front wheel steering mode, detecting the front wheel aligning condition in the deviation correcting process, and executing S7 after the front wheel aligning; if the front wheel is not aligned, the step is continuously executed;

s4, detecting a steering direction signal of the vehicle, and executing S5 when the steering direction of the vehicle is the same as the deflection direction of the rear wheels; when the steering direction of the vehicle is opposite to the rear wheel yaw direction, S6 is executed;

s5, correcting the rear wheel according to the four-wheel steering mode, and returning to S1;

s6, correcting the rear wheel according to the crab steering mode, and returning to S1;

and S7, returning to the four-wheel steering mode.

The reliability, the steering accuracy and the vehicle running safety of the four-wheel steering operation mode are ensured.

The steering system has the advantages of simple structure, reliable operation and low failure rate, and can realize steering in three modes; the control method realizes automatic control through the controller, and detects and corrects the centering state of the wheels before the steering mode is set to work so as to ensure the steering to be reliable and eliminate the potential safety hazard of vehicle deviation.

Drawings

Fig. 1 is a schematic structural view of embodiment 1 of the present invention.

Fig. 2 is a schematic structural diagram of embodiment 2 of the present invention.

Fig. 3 is a schematic structural diagram of embodiment 3 of the present invention.

Fig. 4 is a schematic structural diagram of embodiment 4 of the present invention.

Detailed Description

The present invention is further described with reference to the accompanying drawings, but the invention is not limited thereby within the scope of the described embodiments.