A tractor PTO control system and control method

Abstract

A tractor PTO control system and control method, the control system includes a PTO operating system, a vehicle control system, a signal detection system, a PTO execution system, a signal transmission system and a display system. Based on the control system, the control method ensures that the PTO control system can work normally, including manual mode and automatic mode. The manual mode directly controls the PTO clutch, and the automatic mode automatically engages or opens the clutch according to the change of the lifting height, which is convenient for field operations. During the clutch engagement process, the PID algorithm is used to calculate the requested torque according to the target torque, the actual speed and the actual torque, and then the torque is converted into pressure, and then the pressure is converted into current to drive the solenoid valve to perform the clutch operation. The control method makes the requested torque equal to the target torque through iteration. The entire engagement process is a slow change process, which can ensure that the agricultural implement works slowly and improve the driving comfort. Through the PTO brake switch, the PTO can stop rotating immediately to ensure the safety of the operation.

Description

Technical Field

[0001] The invention relates to the technical field of tractors, and in particular to a tractor PTO control system and a control method. Background Art

[0002] With the improvement of agricultural mechanization, the use scope of the power output shaft of the tractor in the operation process is getting wider and wider. PTO is not limited to providing power for traditional agricultural machinery such as rotary tillers, but also new agricultural tools such as seeders, fertilizer sprayers, intertillage soil machines, etc. also need PTO to provide power to meet work requirements. Because agricultural tools have different requirements for PTO speed, it is necessary to select the appropriate engine speed according to different agricultural tools to meet the PTO speed requirements, which is very necessary to improve the quality of operation.

[0003] During the operation, when the tractor turns, the farm implement needs to be lifted. At this time, the driver often needs to manually cut off the PTO clutch to stop the power output of the PTO; after the tractor's driving route is adjusted, the driver manually engages the PTO clutch again, and the PTO outputs power again. The operation of this process is relatively complicated and requires a high level of operation from the driver, which greatly increases the driver's labor intensity and reduces production efficiency. Therefore, it is also very valuable to design a reasonable PTO control system to improve the current working conditions. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a tractor PTO control system and control method, which can not only make the agricultural implement better match the engine speed, but also better cope with various complex working environments of the tractor, reduce the labor intensity of the driver, and improve the working efficiency and the service life of the agricultural implement.

[0005] In order to achieve the above technical purpose, the technical solution adopted is: a tractor PTO control system, including a PTO operating system, a vehicle control system, a signal detection system, a PTO execution system, a signal transmission system and a display system;

[0006] The vehicle control system includes a PTO controller, a vehicle controller, an engine controller and a lifting controller. The PTO controller is connected to a PTO operating system, a signal detection system and a PTO execution system. The PTO controller is respectively connected to the vehicle controller, the engine controller, the lifting controller and the display system through a signal transmission system.

[0007] The PTO execution system is mainly composed of PTO clutch, PTO brake and corresponding solenoid valves.

[0008] The PTO control system consists of a cab PTO switch, an automatic PTO switch, an external PTO switch, a 540 gear switch, a 1000 gear switch, a PTO brake switch and an automatic calibration switch. The automatic calibration switch is a resettable switch that pops up automatically after being pressed.

[0009] The signal transmission system is a CAN communication module.

[0010] The display system is used to display PTO speed, PTO gear status, PTO power, PTO engagement status, and mode status.

[0011] A control method for a tractor PTO control system comprises the following steps:

[0012] Step 1: After the tractor is powered on, the engine is started, and the engine controller sends a speed signal to the PTO controller. The PTO controller checks the engine speed. When the engine speed is higher than the set threshold, the next step is executed;

[0013] Step 2: The PTO controller detects the PTO brake switch. If the PTO brake switch is in the off state, the next step is executed;

[0014] Step 3: The PTO controller detects whether the PTO gear is engaged. When either the 540 gear switch or the 1000 gear switch is engaged, the next step is executed;

[0015] Step 4, the PTO controller detects whether the automatic PTO switch is engaged. If the automatic PTO switch is engaged, it is determined that the control system enters the automatic mode. If the automatic PTO switch is not engaged, the external PTO switch is in a normally closed state, and it is determined that the control system enters the manual mode.

[0016] Step 5: In the automatic mode, the PTO controller receives the lifting height signal from the lifting controller. When the lifting height exceeds 30%, the control system executes the automatic mode opening condition. When it is less than 30%, the control system executes the automatic mode combined condition.

[0017] Step 6: In manual mode, when the PTO controller detects that the cab PTO switch or the PTO brake switch is engaged, the control system executes the manual mode engagement condition; when it is not engaged, the control system executes the manual mode opening condition;

[0018] Step 7: The control system executes one of the opening working conditions or combined working conditions set in the PTO controller according to the specific instructions, and each working condition corresponds to setting the PTO target torque, target speed and target pressure;

[0019] Step 8, the PTO controller detects the speed signal through the signal detection system. If the target speed is reached and the clutch is fully engaged, the target torque corresponding to the target speed is set as the current request torque, and step 10 is executed; if the target speed is not reached, step 9 is executed; the initial request torque is used as the iterative request torque for the first time, and then the current request torque value of the previous cycle is used as the iterative request torque, and the next operation is executed;

[0020] Step 9, the PTO controller detects the actual torque through the signal detection system, and determines whether the iterative request torque reaches the target torque. If the target torque is reached, a fault is output and corresponding fault processing is performed. If the target torque is not reached, the PID control algorithm is used to calculate the torque increase value based on the actual torque detected by the PTO controller and the speed difference at both ends of the clutch, and then the iterative torque is accumulated. Finally, the current request torque value is output in combination with the PTO gear and the torque limit.

[0021] Step 10: Convert the current requested torque value into a corresponding pressure value. During the clutch engagement process, there will be an oil filling process. After the oil filling is completed, the requested pressure value after the torque conversion is output;

[0022] Step 11: convert the requested pressure value into a corresponding current value, drive the clutch solenoid valve, and the clutch performs engagement and opening actions;

[0023] Step 12: The PTO controller detects the actual clutch pressure. If the target pressure is reached, the clutch operation is completed. If the pressure is not satisfied, step 8 is executed.

[0024] A control method for a tractor PTO control system, in the above step 10, the oil filling process of the clutch needs to calibrate the oil filling time and the contact point pressure, and the steps are as follows:

[0025] Step 10.1, after the tractor is powered on, the engine is started, and the PTO controller receives the speed signal of the engine controller, the parking, oil temperature and seat switch signals of the vehicle controller, the speed, torque and pressure signals detected by the signal detection system, and various switch signals in the PTO control system, and processes the signals;

[0026] Step 10.2, determine that the clutch meets the calibration conditions, the calibration conditions include that the engine speed is higher than the speed when the external characteristic maximum torque is 80%, one of the 540 gear switch or the 1000 gear switch is engaged, the oil temperature is higher than 20°C, the parking switch is engaged, and then proceed to the next step;

[0027] Step 10.3, calibrate the corresponding relationship between the clutch pressure and the solenoid valve current, record the actual pressure value of the PTO clutch by giving the clutch solenoid valve current, and finally calculate the corresponding relationship between the pressure and the current;

[0028] Step 10.4, the PTO controller detects whether the automatic calibration switch is engaged, and if so, sets the oil filling pressure and the number of oil filling times;

[0029] Step 10.5, convert the oil filling pressure into current, start driving the solenoid valve, and the clutch starts filling with oil;

[0030] Step 10.6, the PTO controller detects whether the PTO speed increases. Before the clutch is engaged, the PTO speed will be very small or zero. When the clutch speed starts to rise, it is determined that the calibration is completed, and the oil filling time and oil filling pressure are recorded. Then the oil filling pressure is set to zero, and the oil filling times are increased by one. If the PTO speed does not increase, return to step 10.5 and continue to fill the oil.

[0031] Step 10.7, determine whether the number of oil filling times meets the target number of oil filling times, if not, perform the next calibration; if satisfied, complete the automatic calibration, calculate the average of the clutch oil filling time and the clutch contact point pressure value and save it as the calibration value.

[0032] 7. A control method for a tractor PTO control system as claimed in claim 1, characterized in that: the threshold value set in step 1 is a low speed value when the torque on the engine external characteristic curve reaches 80% of the maximum torque.

[0033] The beneficial effects of the present invention are:

[0034] During PTO operation, selecting the automatic mode can automatically open or engage the PTO clutch according to the lifting height, so that the driver can focus on other operations and improve work efficiency.

[0035] After the operation stops, the PTO brake can be performed as needed to stop the PTO speed immediately and improve the safety of the entire vehicle.

[0036] During the clutch execution process, the clutch is controlled and adjusted according to variables such as speed, torque and pressure to make the clutch engagement process smooth and gentle, so as to protect the agricultural machinery and improve driving comfort.

[0037] Before using the PTO clutch, calibrate the corresponding relationship between the solenoid valve current and the clutch pressure, and then automatically calibrate the clutch oil filling time and the contact point pressure, which can improve the response speed when the clutch is engaged and make the engagement process smoother. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of PTO control system;

[0039] Figure 2 It is a flow chart of the PTO clutch control method;

[0040] Figure 3 Flow chart for automatic calibration of PTO clutch. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below with reference to the accompanying drawings and specific implementation examples.

[0042] like Figure 1 As shown, the present invention discloses a tractor PTO control system. The control system can be divided into five parts, including a PTO operating system, a vehicle control system, a signal detection system, a PTO execution system, a signal transmission system and a display system.

[0043] The vehicle control system includes the PTO controller, vehicle controller, engine controller and lifting controller. The PTO controller is directly connected to the PTO control system, signal detection system and PTO execution system. The PTO controller is connected to the vehicle controller, engine controller, lifting controller and display system through the signal transmission system. The PTO execution system is mainly composed of the PTO clutch, PTO brake and the corresponding solenoid valve. The signal transmission system can use the CAN communication module.

[0044] The driver control system is composed of a cab PTO switch, an automatic PTO switch, an external PTO switch, a 540 gear switch, a 1000 gear switch, a PTO brake switch and an automatic calibration switch. It should be noted that at a certain engine speed, the 540 gear switch and the 1000 gear switch can ensure that the PTO output shaft speed is stabilized at 540rpm and 1000rpm respectively. The two switches correspond to two different transmission ratios. Select one of them to adjust the engine speed so that the PTO output shaft speed meets the requirements of the agricultural implement.

[0045] The vehicle control system mainly includes PTO controller, vehicle controller, engine controller, and lifting controller, which are connected through CAN communication module. In the vehicle control system, data can be transmitted between controllers through CAN communication module; the engine speed signal is sent from the engine controller to the PTO controller, and the display system can also obtain signals from the PTO controller through the CAN communication module to display the actual PTO speed, PTO gear status, PTO power, PTO engagement status, mode status and other related information.

[0046] like Figure 1 As shown, the signal detection system consists of a PTO speed sensor, a torque sensor and a pressure sensor.

[0047] The lifting height signal is sent from the lifting controller to the PTO controller. The vehicle parking switch, oil temperature and seat switch signals are sent from the vehicle controller to the PTO controller. The PTO controller sends information such as PTO speed, PTO power, PTO gear information, automatic PTO, and PTO engagement status to the display through the CAN communication module to facilitate the driver to operate the vehicle and improve work efficiency.

[0048] A control method for a tractor PTO control system comprises the following steps:

[0049] Step 1: After the tractor is powered on, the engine is started, and the engine controller sends a speed signal to the PTO controller. The PTO controller checks the engine speed. Only when the engine speed is higher than the set threshold (the low speed value when the engine torque reaches 80% of the maximum torque) will the next step be executed to ensure that the engine has a strong power output and avoid engine stalling when engaging PTO.

[0050] Step 2: The PTO controller detects the PTO brake switch. Only when the PTO brake switch is in the closed state can the next operation be performed to avoid the vehicle being stuck. If the PTO brake switch is in the activated state, the brake solenoid valve is in the on state, enabling the brake.

[0051] Step 3: The PTO controller detects whether the PTO gear is engaged. Only one of the 540 gear switch and the 1000 gear switch needs to be engaged to ensure that the rest of the PTO power transmission chain except the clutch is in an engaged state.

[0052] Step 4: The PTO controller detects whether the automatic PTO switch is engaged. If the automatic PTO switch is engaged, the control system is determined to enter the automatic mode. Whether the internal or external switch of the PTO is engaged does not affect the determination of the automatic mode. If the automatic mode switch is not engaged, the external PTO switch is in a normally closed state, and the control system is determined to enter the manual mode, that is, the default is the manual mode.

[0053] Step 5. In automatic mode, the PTO controller receives the lifting height signal from the lifting controller. When the lifting height exceeds 30%, the control system executes the automatic mode opening condition. When it is lower than 30%, it executes the automatic mode combined condition.

[0054] Step 6: In manual mode, when the PTO controller detects that the internal PTO switch or the external PTO switch is engaged, the control system executes the manual mode engagement condition; when it is not engaged, the control system executes the manual mode opening condition.

[0055] Step 7: The control system executes one of the opening conditions or the automatic combination conditions according to the specific instructions. Each condition corresponds to setting the PTO target torque, target speed and target pressure, and sets the initial requested torque.

[0056] Step 8, the PTO controller detects the speed signal through the signal detection system. If the target speed is reached and the clutch is fully engaged, the target torque corresponding to the target speed is set as the current request torque, and step 10 is executed; if the target speed is not reached, step 9 is executed; the initial request torque is used as the iterative request torque for the first time, and then the current request torque value of the previous cycle is used as the iterative request torque, and the next operation is executed;

[0057] Step 9, the PTO controller detects the actual torque through the signal detection system, and determines whether the iterative request torque reaches the target torque. If the target torque is reached, a fault is output and corresponding fault processing is performed. If the target torque is not reached, the PID control algorithm is used to calculate the torque increase value based on the actual torque detected by the PTO controller and the speed difference at both ends of the clutch, and then the iterative torque is accumulated. Finally, the current request torque value is output in combination with the PTO gear and the torque limit.

[0058] Step 10: Convert the current requested torque value into a corresponding pressure value. During the clutch engagement process, there will be an oil filling process. After the oil filling is completed, the requested pressure value after the torque conversion is output;

[0059] Step 11: Convert the pressure value into a corresponding current value to drive the clutch solenoid valve, and the clutch performs engagement and opening actions.

[0060] Step 12: The PTO controller detects the actual clutch pressure. If the target pressure is reached, the clutch operation is completed. If the pressure is not met, go to step 8.

[0061] Furthermore, in the above step 10, the oil filling process of the clutch needs to calibrate the oil filling time and the contact point pressure, and the steps are as follows:

[0062] Step 10.1: After the tractor is powered on, the engine is started, and the PTO controller receives the speed signal from the engine controller, the parking, oil temperature and seat switch signals from the vehicle controller, and the sensors and various switch signals connected to the PTO controller, and processes the signals.

[0063] Step 10.2: When the engine speed is higher than the speed at which the external characteristic maximum torque is 80%, and at the same time one of the PTO gear switches is engaged, the oil temperature is higher than 20°C, and the parking brake is engaged, it is determined that the clutch meets the calibration conditions.

[0064] Step 10.3, calibrate the corresponding relationship between clutch pressure and solenoid valve current, record the actual pressure value of the PTO clutch by giving the clutch solenoid valve current, and finally calculate the corresponding relationship between pressure and current, which is not limited to the form of calculation formula and table lookup.

[0065] Step 10.4, the PTO controller detects whether the automatic calibration switch is engaged. If so, it sets the oil filling pressure and the number of oil filling times.

[0066] Step 10.5: Convert the oil filling pressure into current, start driving the solenoid valve, and start filling the clutch with oil.

[0067] Step 10.6, check the PTO controller to see if the PTO speed increases. The PTO speed will be very small or non-existent before the clutch is engaged. When the clutch speed starts to rise, the calibration is considered complete. Record the oil filling time and oil filling pressure, then set the oil filling pressure to zero and increase the oil filling times by one. If the PTO speed does not increase, continue filling.

[0068] Step 10.7, determine whether the number of oil filling times meets the target number of oil filling times, if not, perform the next calibration; if satisfied, complete the automatic calibration, calculate and save the average of the clutch oil filling time and the clutch contact point pressure as the calibration value of the automatic calibration.

[0069] In actual operation, after the driver starts the tractor, the PTO controller first checks the engine speed signal. If the engine speed is lower than 1100rpm, the PTO controller will not perform related actions. When it is higher than 1100rpm, the PTO brake switch will be detected. If the PTO brake switch is in the engaged state, the PTO clutch cannot be engaged. When the PTO brake switch is not closed, after selecting the 540 gear or 1000 gear, the corresponding switch will be engaged, and then the PTO working mode will be determined based on whether the automatic PTO switch is engaged. If it is engaged, it is automatic mode, and if it is not engaged, it is manual mode. In the control system, the default is manual mode. After selecting the automatic mode, the PTO can be engaged and opened according to the lifting height. When the lifting height is less than 30%, the PTO working condition can be judged as the automatic mode engagement state. Each working condition will output the corresponding target speed, target torque and target pressure; when the lifting height is greater than 30%, the PTO working condition is judged as the automatic mode opening working condition; when the automatic PTO is not engaged, but the cab PTO switch or the external PTO switch is engaged, it enters the manual mode engagement working condition. If neither is engaged, it enters the manual mode opening working condition. Select a working condition according to the operating instruction, and its corresponding target speed, target torque and target pressure are used as the target value of the control system. The control method first determines whether the PTO speed reaches the target speed. If the target speed is reached, the target torque speed is set to the requested torque, so that the maximum allowable current can be obtained to ensure that the clutch is fully engaged. If the target speed is not reached, it is determined whether the actual torque reaches the maximum torque. If it is the maximum torque, a fault will be reported at this time, indicating that the clutch is slipping and fault handling is required. If the maximum torque is not reached, PID control is performed according to the target torque, target speed, actual torque and actual speed to calculate the requested torque and limit the torque change rate to make the entire engagement process smoother. Finally, whether the adjustment process is completed is determined based on whether the clutch pressure reaches the target pressure. If the target pressure is not reached, it is necessary to re-judge whether the PTO speed reaches the target speed and adjust again according to the smooth judgment.

[0070] Before the PTO clutch works, it needs to be calibrated, mainly to calibrate the PTO clutch filling time and the contact point pressure, where the contact point pressure is the pressure when the clutch friction plate is in contact but does not transmit torque but the speed has slightly increased, and the filling time is the time from the start of calibration to the contact point pressure. For automatic clutch calibration, the calibration conditions must be met first, such as engine speed exceeding 1100rpm, PTO gear engaged, parking switch engaged, seat switch engaged, oil temperature greater than 20 degrees, etc. After the conditions are met, the corresponding relationship between current and pressure is calibrated first, and the corresponding clutch pressure is recorded by adjusting the current value to complete the preliminary calibration. Then check whether the automatic calibration switch is engaged. Since it is a resettable switch, the control method uses the rising edge signal of the switch. When the signal is detected, the calibration will start, and the filling pressure is set to 1.1MPa, the number of fillings is 3, and the pressure is converted into current to drive the solenoid valve to work. When the PTO speed is detected to increase, it means that one oil filling has been completed. After completing three calibrations, calculate the average of the oil filling time and the pressure at the fitting point, and then save it in the controller. If it is less than three times, perform the next calibration iteration.

Claims

1. A control method for a tractor PTO control system, wherein the tractor PTO control system comprises a PTO operating system, a vehicle control system, a signal detection system, a PTO execution system, a signal transmission system and a display system; The vehicle control system includes a PTO controller, a vehicle controller, an engine controller and a lifting controller. The PTO controller is connected to a PTO operating system, a signal detection system and a PTO execution system. The PTO controller is respectively connected to the vehicle controller, the engine controller, the lifting controller and the display system through a signal transmission system. The PTO execution system is mainly composed of PTO clutch, PTO brake and corresponding solenoid valve; The PTO control system is composed of a cab PTO switch, an automatic PTO switch, an external PTO switch, a 540 gear switch, a 1000 gear switch, a PTO brake switch and an automatic calibration switch. in, The automatic calibration switch is a resettable switch that pops up automatically after being pressed; Features: The following steps are involved: Step 1: After the tractor is powered on, the engine is started, and the engine controller sends a speed signal to the PTO controller. The PTO controller checks the engine speed. When the engine speed is higher than the set threshold, the next step is executed; Step 2: The PTO controller detects the PTO brake switch. If the PTO brake switch is in the off state, the next step is executed; Step 3: The PTO controller detects whether the PTO gear is engaged. When either the 540 gear switch or the 1000 gear switch is engaged, the next step is executed; Step 4, the PTO controller detects whether the automatic PTO switch is engaged. If the automatic PTO switch is engaged, it is determined that the control system enters the automatic mode. If the automatic PTO switch is not engaged, the external PTO switch is in a normally closed state, and it is determined that the control system enters the manual mode. Step 5: In the automatic mode, the PTO controller receives the lifting height signal from the lifting controller. When the lifting height exceeds 30%, the control system executes the automatic mode opening condition. When it is less than 30%, the control system executes the automatic mode combined condition. Step 6: In manual mode, when the PTO controller detects that the cab PTO switch or the PTO brake switch is engaged, the control system executes the manual mode engagement condition; when it is not engaged, the control system executes the manual mode opening condition; Step 7: The control system executes one of the opening conditions or combined conditions set in the PTO controller according to the specific instructions, and each condition corresponds to setting the PTO target torque, target speed and target pressure, and sets the initial request torque; Step 8, the PTO controller detects the speed signal through the signal detection system. If the target speed is reached and the clutch is fully engaged, the target torque corresponding to the target speed is set as the current request torque, and step 10 is executed; if the target speed is not reached, step 9 is executed; the initial request torque is used as the iterative request torque for the first time, and then the current request torque value of the previous cycle is used as the iterative request torque, and the next operation is executed; Step 9, the PTO controller detects the actual torque through the signal detection system, and determines whether the iterative request torque reaches the target torque. If the target torque is reached, a fault is output and corresponding fault processing is performed. If the target torque is not reached, the PID control algorithm is used to calculate the torque increase value based on the actual torque detected by the PTO controller and the speed difference at both ends of the clutch, and then the iterative torque is accumulated. Finally, the current request torque value is output in combination with the PTO gear and the torque limit. Step 10: Convert the current requested torque value into a corresponding pressure value. During the clutch engagement process, there will be an oil filling process. After the oil filling is completed, the requested pressure value after the torque conversion is output; Step 11: convert the requested pressure value into a corresponding current value, drive the clutch solenoid valve, and the clutch performs engagement and opening actions; Step 12: The PTO controller detects the actual clutch pressure. If the target pressure is reached, the clutch operation is completed. If the pressure is not satisfied, step 8 is executed.

2. A control method for a tractor PTO control system as claimed in claim 1, Features: The signal transmission system is a CAN communication module.

3. A control method for a tractor PTO control system as claimed in claim 1, Features: The display system is used to display PTO speed, PTO gear status, PTO power, PTO engagement status, and mode status.

4. A control method for a tractor PTO control system as claimed in claim 1, Features: In the above step 10, the clutch oil filling process needs to calibrate the oil filling time and the contact point pressure, and the steps are as follows: Step 10.1, after the tractor is powered on, the engine is started, and the PTO controller receives the speed signal of the engine controller, the parking, oil temperature and seat switch signals of the vehicle controller, the speed, torque and pressure signals detected by the signal detection system, and various switch signals in the PTO control system, and processes the signals; Step 10.2: Determine that the clutch meets the calibration conditions, which include that the engine speed is higher than the speed at which the external characteristic maximum torque is 80%, one of the 540 gear switch or the 1000 gear switch is engaged, the oil temperature is higher than 20°C, and the parking switch is engaged, and then proceed to the next step; Step 10.3, calibrate the corresponding relationship between the clutch pressure and the solenoid valve current, record the actual pressure value of the PTO clutch by giving the clutch solenoid valve current, and finally calculate the corresponding relationship between the pressure and the current; Step 10.4, the PTO controller detects whether the automatic calibration switch is engaged, and if so, sets the oil filling pressure and the number of oil filling times; Step 10.5, convert the oil filling pressure into current, start driving the solenoid valve, and the clutch starts filling with oil; Step 10.6, the PTO controller detects whether the PTO speed increases. Before the clutch is engaged, the PTO speed will be very small or zero. When the clutch speed starts to rise, it is determined that the calibration is completed, and the oil filling time and oil filling pressure are recorded. Then the oil filling pressure is set to zero, and the oil filling times are increased by one. If the PTO speed does not increase, return to step 10.5 and continue to fill the oil. Step 10.7, determine whether the number of oil filling times meets the target number of oil filling times, if not, perform the next calibration; if satisfied, complete the automatic calibration, calculate the average of the clutch oil filling time and the clutch contact point pressure value and save it as the calibration value.

5. A control method for a tractor PTO control system as claimed in claim 1, Features: In step 1, the threshold is set to a low speed value when the torque on the engine external characteristic curve reaches 80% of the maximum torque.

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