CN101833334A - Tractor automatic navigation control system and method thereof - Google Patents

Abstract

The present invention provides a tractor automatic navigation control system, comprising: a navigation control device, which receives GPS positioning data in real time and calculates the lateral deviation between the current position of the tractor and the operation navigation target, according to the lateral deviation and the tractor running speed measured in real time Calculate the target angle of the steering wheel in the current control cycle and convert it into a steering control command and send it to the steering control device; the steering control device judges whether the measured value of the steering wheel angle of the tractor is less than the preset limit value, and if so, it will The target rotation angle value is compared with the measured value, and the PWM duty cycle is calculated according to the rotation angle difference and the control signal for driving the electro-hydraulic proportional steering actuator is output; the electro-hydraulic proportional steering actuator responds to the PWM control signal through the electro-hydraulic proportional direction The opening of the spool of the valve is used to control the oil flow direction and flow rate of the steering system of the tractor, so that the steering hydraulic cylinder piston is extended or retracted to deflect the steering wheel to the target steering angle.

Description

Tractor automatic navigation control system and its method

technical field

The invention relates to the technical field of control, in particular to an automatic navigation control system and method suitable for hydraulic steering tractors.

Background technique

During the field operation of tractors, due to the poor maneuverability of the operation unit, it is easy to affect the productivity due to heavy plowing, missed plowing or extra distance. In order to reduce the occurrence of rework and missed work between adjacent working ridges, the existing technology mostly uses the method of marking with a marker or spraying foam to mark in the field as the basis for the driver's work navigation. With the development of domestic precision agricultural technology research in recent years, researchers have developed an agricultural machinery navigation system, which uses GPS, PC104 computers and navigation light sticks to provide navigation instructions for agricultural machinery field operations. However, there are certain defects in the above two navigation instruction methods for agricultural machinery operations.

The traditional method of marking with a liner and spraying foam is basically infeasible or the navigation indication effect is poor when the visibility of the farmland operation environment is low, there is no obvious reference on the farmland surface, and the ground surface is undulating. The purpose of improving the quality of work.

Most of the existing navigation indication systems use RS232/RS485 bus, which leads to complicated system wiring and poor reliability, and the versatility and compatibility of each module of the system are not strong. At the same time, this type of navigation indication system is greatly affected by human operation factors, and the navigation accuracy of the operation is poor, which cannot meet the application requirements of farmland operations with high precision requirements, such as sowing. In addition, the operation and control of the existing navigation indication system still needs to be completed by the driver. In fact, it is an auxiliary operation navigation system, and the labor intensity of the driver is still relatively high.

Contents of the invention

The technical problem to be solved by the present invention is to overcome at least one of the above-mentioned defects of the prior art, and realize the automatic navigation control of the hydraulic steering tractor.

In order to solve the above technical problems, the technical solution of the present invention discloses a tractor automatic navigation control system on the one hand, including:

The navigation control device receives GPS positioning data in real time and calculates the lateral deviation between the current position of the tractor and the operation navigation target, calculates the target rotation angle of the steering wheel in the current control cycle according to the lateral deviation and the real-time measured tractor driving speed value and calculates it Convert it into a steering control command and send it to the steering control device, and send a detection error command or stop automatic steering command to it when receiving the steering command error information from the steering control device;

The steering control device judges whether the measured value of the steering wheel angle of the tractor is less than the preset limit value, and if so, compares the target angle value with the measured value, calculates the PWM duty cycle according to the angle difference and outputs the driving electro-hydraulic proportional steering The PWM control signal of the device; otherwise, send a steering instruction error message to the navigation control device;

The electro-hydraulic proportional steering actuator controls the oil flow direction and flow rate of the tractor steering system through the spool opening of the electro-hydraulic proportional directional valve in response to the PWM control signal, so that the steering hydraulic cylinder piston extends or retracts to turn the steering wheel deflecting to the target steering angle; or, de-energizing the solenoid switching valve in response to the stop autosteering command.

Wherein, the transmission of information and instructions is realized between the navigation control device and the steering control device through CAN bus.

Wherein, the navigation control device acquires the latitude and longitude coordinates of the current position of the tractor through RTK-GPS; and measures the current driving speed of the tractor through the ground speed radar.

Wherein, the steering control device measures the current steering wheel angle value of the tractor through the steering wheel angle sensor.

Another aspect of the present invention also discloses a tractor automatic navigation control method, comprising the following steps:

S101: The navigation control device receives GPS positioning data in real time and calculates the lateral deviation between the current position of the tractor and the operation navigation target, and calculates the steering wheel in the current control cycle according to the PID control algorithm according to the lateral deviation and the real-time measured driving speed value of the tractor. and convert it into a steering control command and send it to the steering control device;

S102: The steering control device judges whether the measured value of the steering wheel angle of the tractor is less than the preset limit value, if so, reads the level signal sent by the pressure switch to judge whether it is currently in the automatic steering state, and if so, enters the next step;

S103: the steering control device compares the target rotation angle value with the measured value, calculates the PWM duty cycle according to the PID control algorithm according to the rotation angle difference, and outputs a PWM control signal for driving the electro-hydraulic proportional steering device;

S104: The electro-hydraulic proportional steering actuator responds to the PWM control signal to control the oil flow direction and flow rate of the tractor steering system through the spool opening of the electro-hydraulic proportional directional valve, so that the steering hydraulic cylinder piston extends or retracts to turn the steering The wheels are deflected to the desired steering angle.

Further, in step 102, if the steering control device determines that the measured value of the steering wheel angle of the tractor is greater than the preset limit value, it sends a steering command error message to the navigation control device, and the navigation control device returns to stop after receiving the error message. Autopilot instructions.

Further, in step 102, if the level signal sent by the pressure switch indicates that the current state is in the manual steering state, the steering control device sends stop steering information to the navigation control device, and the navigation control device returns an instruction to stop automatic navigation after receiving the information.

Among them, through the priority valve, the electro-hydraulic proportional directional valve or the tractor's hydraulic steering gear is connected with the oil circuit of the steering cylinder to realize the switching between the tractor's automatic steering and manual steering.

Compared with the prior art, the advantages of the technical solution of the present invention are:

1. Based on the full hydraulic steering tractor, a mechanical-electrical-hydraulic integrated tractor automatic navigation system is constructed; from the system structure and design method, the tractor navigation control device and steering controller integrated with software and hardware are realized, and the suitable A fieldbus method for farm work machinery enables real-time communication between navigation controls and steering controllers.

2. Using the electro-hydraulic proportional control technology, a method of connecting the electro-hydraulic proportional steering control system on the basis of the full hydraulic steering tractor steering system is proposed, and the hydraulic mechanism and device of the electro-hydraulic proportional steering are designed and realized, so that the digital control of tractor steering becomes possible.

3. Propose and implement the tractor automatic steering PID control method based on real-time detection of tractor steering wheel angle as feedback, and support manual steering operation shielding automatic steering control and synchronous operation function of navigation control device and steering controller based on steering system pressure detection.

4. Propose and implement a software-based navigation control device design method, design a navigation PID control method based on lateral deviation, and realize the precise operation of the tractor according to the preset path. At the same time, the navigation control device supports the status self-inspection and status monitoring functions of key components of the tractor automatic navigation system, and can smoothly switch between manual and automatic steering operations of the tractor according to the system status.

Description of drawings

Fig. 1 is the structural diagram of an embodiment of the automatic navigation control system applicable to the full hydraulic steering tractor of the present invention;

Fig. 2 is the structural diagram of the automatic hydraulic steering part of the tractor automatic navigation control system of the present invention;

Fig. 3 is the flow chart of the steering control device of the tractor automatic navigation control system of the present invention executing the steering command;

Fig. 4 is a flow chart of the navigation control performed by the navigation control device of the tractor automatic navigation control system of the present invention.

1. Digital radio antenna 2. RTK-GPS antenna 3. On-board control computer 4. Junction box 5. Steering controller 6. Steering gear 7. Pressure switch 8. Priority valve 9. Steering oil source system 10. Steering cylinder 11 , battery 12, angle sensor 13, electronic pressure sensor 14, electromagnetic switch valve 15, electro-hydraulic proportional directional valve 16, valve block assembly 17, ground speed radar 18, RTK-GPS receiver 19, digital radio

Detailed ways

The system and method of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. The following examples are for the purpose of illustrating the present invention, but are not intended to limit the scope of the present invention.

Figure 1 is a structural diagram of an embodiment of an automatic navigation control system suitable for fully hydraulic steering tractors of the present invention, which consists of three parts: a navigation control device, a steering control device and an electro-hydraulic proportional steering actuator.

The navigation control device mainly includes: vehicle control computer 3 , RTK-GPS receiver 18 , RTK-GPS receiver antenna 2 , digital radio station 19 , digital radio station antenna 1 , ground speed radar 17 . The vehicle-mounted control computer 3 stores the tractor navigation operation base map and runs the navigation control program, and the navigation control program can automatically generate a map covering the entire operation plot according to the operation plot on the operation base map, the set operation direction and the operation width. The job guidance line can also import the vector data of the job guidance line planned or created in other software into the software as the job guidance line. The navigation control program calculates the deviation distance (referred to as lateral deviation) between the RTK-GPS positioning data received in real time and the stored or generated operation navigation line (operation navigation target), and the ground speed radar 17 measures and obtains the real-time driving speed value of the tractor , take the lateral deviation calculated in the current control cycle as the input of the navigation control program, calculate the steering angle of the steering wheel of the tractor in real time according to the PID control algorithm, and use it as the control target in the current control cycle, and according to the customized communication protocol, The control target is converted into a control instruction and sent to the steering controller to complete a control cycle navigation control process.

The steering control device mainly includes: a microprocessor-based steering controller 5 (with a steering PID control program running therein), a tractor steering wheel angle sensor 12, and an on-board control computer 3, an electro-hydraulic proportional directional valve 15 and other components. . After the steering controller 5 receives the steering control command sent by the on-board control computer 3, it runs the steering angle PID control program in the steering control program, and compares the target steering angle of the steering wheel with the actual steering angle of the front wheels detected by the steering angle sensor 12 in real time. , and according to the PID control algorithm, output a PWM control signal that can directly drive the electro-hydraulic proportional valve 15, control the flow and direction of the electro-hydraulic proportional directional valve 15, and then drive the hydraulic steering mechanism to rotate in a predetermined direction.

The electro-hydraulic proportional steering actuator mainly includes: tractor steering gear oil source system 9, electro-hydraulic proportional directional valve 15, electromagnetic switch valve 14, priority valve 8, pressure switch 7, closed hydraulic steering gear 6 and steering cylinder 10. Among them, hydraulic components such as electro-hydraulic proportional directional valve 15, electromagnetic switch valve 14, and pressure switch 7 are connected through valve blocks, and are connected in parallel with the oil circuit of tractor hydraulic steering gear 6 through hydraulic pipelines. The electro-hydraulic proportional steering actuator responds to the PWM control signal, controls the oil flow direction and flow rate of the steering system of the tractor through the spool opening of the electro-hydraulic proportional directional valve 15, and makes the steering hydraulic cylinder piston extend or retract to The steering wheel is deflected to the target steering angle, thereby realizing the automatic steering function of the tractor. In addition, the electro-hydraulic proportional directional valve 15 or the hydraulic steering gear 6 communicates with the oil circuit of the steering cylinder 10 through the priority valve 8 and the electromagnetic switch valve 14 to realize free switching between automatic steering and manual steering, and ensure any Priority for manual steering functions at all times. At the same time, when the automatic steering control function of the tractor fails, it supports manual steering to realize manual driving.

Fig. 2 shows that by above-mentioned on-board computer 3, steering controller 5, priority valve 8, electro-hydraulic proportional directional valve 15, electromagnetic switch valve 14, hydraulic steering gear 6, steering oil cylinder 10, steering angle sensor 12, steering oil source The structural diagram of the automatic hydraulic steering part of the system composed of the system 9 and the pressure switch 7. In the present invention, an electro-hydraulic proportional directional valve system is connected to the steering system of a fully hydraulic steering tractor. When the hydraulic oil of the steering system is controlled by the priority valve 8 and enters the steering cylinder 10 through the electro-hydraulic proportional directional valve 15, it can pass through the steering controller. 5 Realize the digital control of the steering system of the tractor and the expected turning angle of the steering wheel.

Specifically, as shown in Figure 2, the pressure sensing port LS of the priority valve 8 is connected to the control port of the tractor steering gear 6, the CF port is connected to the oil inlet port of the steering gear and the pressure switch 7, and the EF port is connected to the electro-hydraulic proportional directional valve 15 to the oil inlet connection. When the system pressure is established and the steering gear 6 is not working, the CF port of the priority valve 8 is in a closed state, and the pressure at the LS port is zero at this time, and oil enters the right end of the spool, and the hydraulic pressure acts on the right end of the spool to overcome the spring of the spool At this time, the P port is connected to the EF port, and the pressure oil pumped out of the tractor steering gear oil source system 9 flows to the electro-hydraulic proportional directional valve 15, so that the electro-hydraulic proportional directional valve 15 and the steering cylinder The oil circuit of 10 is communicated, and tractor auto-steering function is effective now, can realize the real-time control to the direction of rotation and angle of steering wheel by energizing electromagnetic switch valve 14 and digital control to electro-hydraulic proportional directional valve 15. When the steering gear 6 is working, that is, in the manual operation state, the pressure sensing port LS of the priority valve 8 makes the P port communicate with the CF port under the action of pressure oil. At this time, the oil circuit between the steering gear 6 and the steering cylinder 10 Connected, the pressure oil pumped by the steering system oil pump 9 enters the steering cylinder 10 through the priority valve 8 and the steering gear 6 to make the tractor turn.

Fig. 3 shows that steering controller 5 executes the flow chart of the steering control instruction of vehicle-mounted computer 3, as shown in the figure, at first to the CAN bus of steering controller 5, each state parameter and steering control PID parameter relevant to steering control Initialize; then detect the state of the steering angle sensor 12 in the steering closed-loop control system, read its current measured value, and judge whether the value exceeds the limit value set by the system (the limit value is from the straight position to the left-turn dead point and right-turn dead point, depending on the maximum deflection angle), if the limit value is exceeded, a steering command error message will be sent to the CAN bus, and the navigation control device will immediately stop sending the steering control message after receiving and parsing the error message , and display the error message of the angle sensor detection value through the human-computer interaction interface, reminding the user to detect the state of the rotation angle sensor 12; if the current detection value of the steering angle sensor 12 is within the normal range (less than the limit value), then the detection value according The ISO11783 protocol is converted into a message and sent to the CAN bus, and the navigation control device displays the value through the man-machine interface after receiving the message; at the same time, the steering controller 5 receives the steering control message sent to the bus by the navigation control device in real time, and reads Get the state information of the pressure switch 7 indicating the driver’s manual steering operation. If the pressure switch 7 indicates that the current system is in the automatic steering control state, the steering controller 5 will power up the electromagnetic switch valve 14 to make it in the closed state, and the electro-hydraulic proportional steering will be executed. The device starts to build pressure; at the same time, the steering controller 5 calls the steering PID control program, and the PID control program performs PID linear adjustment on the rotation angle difference after comparing the currently detected rotation angle value with the expected rotation angle value in the steering control message to calculate the PWM Duty ratio, control the opening of the spool of the electro-hydraulic proportional directional valve 15 to control the flow direction and velocity of the oil in the system, and make the piston of the steering hydraulic cylinder 10 stretch out or retract to control the deflection of the steering wheel to the desired position to realize automatic steering of the tractor. Thereby completing a cycle of control action; when the steering controller 5 receives the stop steering message sent by the navigation control device, it controls the electromagnetic switch valve 14 to turn off the power to make it conduct, the electro-hydraulic proportional automatic steering system is unloaded, and the electro-hydraulic proportional automatic steering system is controlled at the same time. The proportional directional valve 15 is powered off to stop the automatic steering; if the steering wheel needs to be turned manually when the steering controller 5 is in the automatic steering state, the pressure oil circuit is switched to the steering gear 6 by the priority valve 8, and the oil of the electro-hydraulic proportional directional valve 15 At the same time, the pressure switch 7 generates a low level, and the steering controller 5 turns off the electromagnetic switch valve 14 after receiving the level signal of the pressure switch 7. power, so that the electromagnetic switch valve is in the conduction state, and control the electro-hydraulic proportional directional valve 15 to cut off the power, and at the same time send a stop automatic steering control message to the navigation control device.

Figure 4 shows the flow chart of navigation control performed by the navigation control device. As shown in the figure, after the navigation control device is started, it first performs the initialization process, which mainly completes the initialization of the CAN bus and the establishment of CAN communication connections, the establishment of RTK-GPS communication connections, Initialize the control cycle of the navigation control device, PID parameters and other related state parameters; after the initialization process is completed, the navigation control device begins to detect the key sensors of the entire automatic navigation control system (including the angle sensor 12 and RTK-GPS18) and the steering controller 5 If any part fails to work normally, the navigation control device will record its state parameters, and reflect the relevant information on the vehicle control computer 3 in the form of text and sound alarms according to different parts and abnormal state categories. In the interactive interface of the tractor, the navigation control device will not perform automatic navigation operation until the relevant abnormal state is processed and works normally; if the system self-test passes, the user can start the automatic navigation operation of the tractor through interactive operation. A valid navigation target on the job base map or a job navigation target generated by defining the job direction, etc., and then the navigation control device runs the automatic navigation process according to the control period set by initialization and the corresponding PID parameters: read the current position of the GPS The longitude and latitude coordinates of the longitude and latitude are converted into plane coordinates, and the distance between the current position expressed in plane coordinates and the navigation target is calculated, that is, the lateral deviation value; the lateral deviation PID control program is started, and the steering angle control amount of the tractor steering wheel is calculated within the current control cycle , and convert the steering angle control amount into a steering control message, which is sent to the steering controller 5, and the steering controller 5 executes the steering control process as shown in the flow chart in Figure 3, thereby completing a navigation control process, and simultaneously recording the steering control process in the control cycle GPS longitude, latitude, UTC time, heading, rotation angle, control amount and other related data. After the system self-checks and the state is normal, the navigation control device will simultaneously start a state monitoring process of the steering controller 5, which is used to monitor the state of the manual steering sensor (pressure switch 7) and the working state of the angle sensor 12 in real time. The signal state of the pressure switch 7 is monitored at all times, that is, when the driver manually operates the steering wheel, the navigation control device immediately stops the automatic navigation process, stops sending steering control messages to the steering controller, and the steering controller controls the electromagnetic switch valve to power off. The electromagnetic switch valve is in the conduction state, the automatic steering system is in the unloading state, and at the same time, the steering controller controls the electro-hydraulic proportional directional valve to cut off the power, the hydraulic control automatic steering system stops working, and the tractor is in the manual steering operation state. When the steering controller monitoring process detects that the rotation angle value measured by the rotation angle sensor is abnormal, it also stops sending steering control messages to the steering controller, so that the hydraulically controlled automatic steering system of the tractor stops working and is in the manual steering operation state.

The invention combines the tractor operation navigation control and automatic steering control into a complete system, realizes the precise operation of the tractor according to the set operation route, and shields the automatic steering control function under the condition of manual steering operation intervention, so as to ensure the safe operation of the system. The full-hydraulic steering tractor automatic navigation system of the present invention can ensure that the tractor operates accurately and stably according to the preset path, effectively reduces the overlap and omission between the working ridges during the reciprocating straight-line operation of the farmland, significantly improves the quality and efficiency of the work, and can reduce the burden on the operator. labor intensity. The tractor automatic navigation system relies on the GPS that can work around the clock as the main positioning and navigation sensor, so it can also effectively extend the working time of the tractor operating group.

The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Those of ordinary skill in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all Equivalent technical solutions also belong to the category of the present invention, and the scope of patent protection of the present invention should be defined by the claims.

Claims (7)

1. A tractor automatic navigation control system, characterized in that, comprising: The navigation control device receives GPS positioning data in real time and calculates the lateral deviation between the current position of the tractor and the operation navigation target, calculates the target rotation angle of the steering wheel in the current control cycle according to the lateral deviation and the real-time measured tractor driving speed value and calculates it Convert it into a steering control command and send it to the steering control device, and send a detection error command or stop automatic steering command to it when receiving the steering command error information from the steering control device; The steering control device judges whether the measured value of the rotation angle of the steering wheel of the tractor is less than a preset limit value, and if so, compares the target rotation angle value with the measured value, calculates the PWM duty ratio according to the rotation angle difference, and calculates the PWM duty ratio according to the duty ratio than outputting a PWM control signal for driving the electro-hydraulic proportional steering actuator; otherwise, sending a steering command error message to the navigation control device; The electro-hydraulic proportional steering actuator, in response to the PWM control signal, controls the oil flow direction and flow rate of the tractor steering system through the spool opening of the electro-hydraulic proportional directional valve, so that the steering hydraulic cylinder piston extends or retracts to turn the steering turning the wheels to the target steering angle; or, de-energizing the electromagnetic switch valve in response to the stop automatic steering command. 2. The tractor automatic navigation control system according to claim 1, wherein the transmission of information and instructions is realized between the navigation control device and the steering control device through CAN bus. 3. tractor automatic navigation control system as claimed in claim 1, is characterized in that, described navigation control device comprises: RTK-GPS, used to obtain the latitude and longitude coordinates of the current location of the tractor, The ground speed radar is used to measure the current driving speed value of the tractor. 4. The tractor automatic navigation control system according to claim 1, wherein the steering control device comprises a steering wheel angle sensor for measuring the current steering wheel angle value of the tractor. 5. A method for performing automatic navigation control utilizing any one of the automatic navigation control systems of claims 1 to 4, characterized in that it comprises the following steps: S101: The navigation control device receives GPS positioning data in real time and calculates the lateral deviation between the current position of the tractor and the operation navigation target, and calculates the steering wheel speed in the current control cycle according to the PID control algorithm according to the lateral deviation and the tractor driving speed value measured in real time. The target corner is converted into a steering control command and sent to the steering control device; S102: The steering control device judges whether the measured value of the steering wheel angle of the tractor is less than the preset limit value, if so, reads the level signal sent by the pressure switch to judge whether it is currently in the automatic steering state, and if so, enters the next step; S103: the steering control device compares the target rotation angle value with the measured value, calculates the PWM duty cycle according to the PID control algorithm according to the rotation angle difference, and outputs a PWM control signal for driving the electro-hydraulic proportional steering device; S104: The electro-hydraulic proportional steering actuator responds to the PWM control signal to control the oil flow direction and flow rate of the tractor steering system through the spool opening of the electro-hydraulic proportional directional valve, so that the steering hydraulic cylinder piston extends or retracts to turn the steering The wheels are deflected to the desired steering angle. 6. The tractor automatic navigation control method according to claim 5, wherein in step 102, if the steering control device judges that the measured value of the steering wheel angle of the tractor is greater than the preset limit value, then the steering control device is sent to the navigation control device. Instruction error information, the navigation control device returns an instruction to stop automatic navigation after receiving the error information. 7. The tractor automatic navigation control method according to claim 6, wherein in step 102, if the level signal sent by the pressure switch shows that it is currently in a manual steering state, the steering control device sends stop steering information to the navigation control device, After receiving the information, the navigation control device returns an instruction to stop the automatic navigation.

Images