Motor torque control method and system of electric tractor

Abstract

The invention discloses a motor torque control method and system of an electric tractor. When the first manual gear is adopted, all energy recovery can be achieved under the long-distance heavy-load downhill working condition. And when the manual second gear is adopted, the long-distance downhill working condition with medium and lower loads and higher speed can be met. A driver can control the running speed of the vehicle at will within a controllable range under the two downhill working conditions. The system has strong load adaptability, and the energy-saving effect is better than that of a common vehicle. Correspondingly, the abrasion of a brake friction plate of the axle is relatively small, and the service life of the axle is correspondingly prolonged.

Description

Technical Field

[0001] The present invention belongs to the field of electric tractor control, and in particular relates to a motor torque control method and system for an electric tractor. Background Art

[0002] The current application of electric tractors in industrial scenarios such as ports and docks generally faces the following technical bottlenecks:

[0003] 1. When decelerating while coasting on flat roads, the negative torque provided by the motor of existing electric tractors is typically only sufficient for normal operating conditions. However, when driving downhill with a heavy load and a steep gradient, the motor cannot output sufficient sustained braking torque to maintain a constant speed. The driver must frequently engage the mechanical braking system, such as the air brake, for auxiliary deceleration. This approach not only increases brake component wear but also poses the risk of brake thermal decay, compromising driving safety.

[0004] 2. Traditional tractors mostly use direct motor drive, but their torque output is limited by the motor's inherent characteristics and heat dissipation requirements. This is especially true during heavy-load starting or steep slope towing, where existing systems struggle to meet the instantaneous peak torque required by heavy loads, resulting in insufficient vehicle towing capacity.

[0005] 3. Current downhill control systems often use a fixed speed maintenance mode, lacking the ability to dynamically respond to changes in slope, load variations, and road conditions. This rigid control strategy prevents the system from adjusting torque distribution based on real-time operating conditions, reducing energy recovery efficiency and impacting driving flexibility, making it difficult to adapt to the refined control requirements of complex driving conditions. Summary of the Invention

[0006] In view of the technical problems pointed out in the above background technology, the purpose of the present invention is to provide a motor torque control method and system for an electric tractor.

[0007] To achieve the purpose of the present invention, the technical solution provided by the present invention is as follows:

[0008] First aspect

[0009] The present application provides a method for controlling the motor torque of an electric tractor, comprising the following steps:

[0010] Determine the transmission control mode and gear position;

[0011] If the transmission is in manual transmission control mode, in 1st or 2nd gear, the motor set speed is determined according to the brake pedal depth or the accelerator pedal depth, and the motor feedback speed is obtained. The motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value;

[0012] If the transmission is in automatic control mode, the transmission gear is switched between 2nd and 3rd gear according to the motor speed; the motor set speed is determined according to the brake pedal depth, and the motor feedback speed is obtained, and the motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value; alternatively, the transmission set output speed is determined according to the accelerator pedal depth, and the transmission feedback output speed is obtained, and the transmission set output speed and the transmission feedback output speed are input into the PID control algorithm to output the motor torque value;

[0013] According to the output motor torque value, the motor is controlled to output the corresponding torque.

[0014] Furthermore, the method for switching the gear of the transmission between the 2nd gear and the 3rd gear according to the motor speed is:

[0015] When the vehicle speed is greater than 8km / h, 2nd gear is shifted to 3rd gear;

[0016] When the vehicle speed is lower than 5km / h, 3rd gear will be changed to 2nd gear.

[0017] Furthermore, the method further includes the step of determining whether the electric tractor meets the driving conditions. If the driving conditions are not met, the torque output by the motor is zero. The details are as follows:

[0018] If at least one of the information given by the driver and the information fed back by the device is valid, the electric tractor does not meet the driving conditions;

[0019] The driver-given information includes:

[0020] The driver selects cab flip, emergency stop, parking and N gear;

[0021] The device feedback information includes:

[0022] The vehicle cannot be powered by high voltage, the vehicle has a level 3 fault, the vehicle's steering gear has a fault, the vehicle's air compressor has a fault, the pressure of the vehicle's service brake air reservoir is lower than the threshold, and the vehicle has a gun connection signal.

[0023] Furthermore, if the driving conditions are met, it is further determined whether the electric tractor meets the energy recovery conditions; if the energy recovery conditions are met, the torque corresponding to the motor output is determined according to the brake pedal depth, the accelerator pedal depth and the current vehicle speed signal; otherwise, the braking torque output by the motor is zero, and no braking electric braking torque is provided, and the braking torque is only provided by the air brake.

[0024] Furthermore, if the energy recovery conditions are met, the specific operations are as follows:

[0025] When the brake pedal depth is greater than 2000mV:

[0026] The actual vehicle speed is greater than the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold. The corresponding motor braking torque is output according to the corresponding speed difference, and the air brake and electric brake are effective simultaneously;

[0027] If the actual vehicle speed is less than or equal to the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold, only the air brake is in effect;

[0028] When the brake pedal depth is between 750-2000mV:

[0029] Determining the torque corresponding to the motor output according to the brake pedal depth, the accelerator pedal depth, and the current vehicle speed signal, further comprising: in creep mode, the motor output torque ranges from a negative maximum torque to a positive maximum torque, and adjusting the motor output torque through a PID control algorithm according to a given motor speed and a feedback motor speed;

[0030] When the brake pedal depth is between 420-750mV;

[0031] It is believed that the brake pedal is not depressed.

[0032] Furthermore, if any one or more of the following information exists, the energy recovery condition is not met: the power level of the power battery pack is higher than 95%, the energy recovery mode is canceled, or the motor has a level 1 or level 2 fault.

[0033] Furthermore, the PID control algorithm is:

[0034] e=n giv -n act ;

[0035]

[0036] Tmin <Tout<Tmax;

[0037] Where: e is the calculated deviation of the motor speed or the gearbox output speed; n giv It is the motor speed value determined by the brake pedal depth, the accelerator pedal depth, or the gearbox output speed determined by the accelerator pedal depth; n actIt is the motor feedback speed value or the gearbox feedback speed value; Tout represents the motor output torque calculated by PID; Tmax is the motor peak torque with the maximum torque output value set to positive, indicating the maximum driving torque output in the forward direction; Tmin is the maximum motor peak torque with a negative minimum value, indicating the negative torque in the forward direction, which is used to control vehicle deceleration or reverse drive; I(e) represents the integral processing result of the speed deviation; D(e) represents the differential processing result of the speed deviation; Kp is the proportional coefficient, which is set by parameters; TN is the integral coefficient, which can be set by parameters; Kd is the differential coefficient.

[0038] Second aspect

[0039] The present application provides a motor torque control system for an electric tractor, comprising: a vehicle controller and a gear mode selection handle connected to the vehicle controller, a brake pedal sensor, an accelerator pedal sensor, a motor controller, a gearbox controller, a motor, and a power battery pack;

[0040] The gear mode selection handle is used to shift the gears of the gearbox through the gearbox controller. The gear modes include manual gear control mode and automatic gear control mode. The manual gear control mode includes 1st gear and 2nd gear. 1st gear is used for driving control of the vehicle uphill or downhill with maximum load, and 2nd gear is used for driving control of the vehicle uphill or downhill with heavy load. The automatic gear control mode is used for driving control of the vehicle on a flat slope with light or heavy load.

[0041] The brake pedal sensor is used to obtain a brake pedal depth signal;

[0042] The accelerator pedal sensor is used to obtain an accelerator pedal depth signal;

[0043] The motor controller is used to determine the motor's given speed according to the brake pedal depth or the accelerator pedal depth, and obtain the motor's feedback speed;

[0044] The transmission controller is further configured to determine a given output speed of the transmission according to the accelerator pedal depth, and obtain an output speed fed back by the transmission;

[0045] The vehicle controller is used to determine the transmission control mode and gear position;

[0046] If the transmission is in manual transmission control mode, in 1st or 2nd gear, the motor set speed is determined according to the brake pedal depth or the accelerator pedal depth, and the motor feedback speed is obtained. The motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value;

[0047] If the transmission is in automatic control mode, the transmission gear is switched between 2nd and 3rd gear according to the motor speed; the motor set speed is determined according to the brake pedal depth, and the motor feedback speed is obtained, and the motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value; alternatively, the transmission set output speed is determined according to the accelerator pedal depth, and the transmission feedback output speed is obtained, and the transmission set output speed and the transmission feedback output speed are input into the PID control algorithm to output the motor torque value;

[0048] According to the output motor torque value, the motor is controlled to output the corresponding torque.

[0049] Furthermore, it also includes an energy recovery determination module, which is used to determine whether the electric tractor meets the energy recovery conditions.

[0050] Furthermore, an energy recovery control module is included, which is used to perform corresponding braking control on the electric tractor when the energy recovery determination module determines that the electric tractor meets the energy recovery conditions:

[0051] When the brake pedal depth is greater than 2000mV:

[0052] The actual vehicle speed is greater than the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold. The corresponding motor braking torque is output according to the corresponding speed difference, and the air brake and electric brake are effective simultaneously;

[0053] If the actual vehicle speed is less than or equal to the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold, only the air brake is in effect;

[0054] When the brake pedal depth is between 750-2000mV:

[0055] Determining the torque corresponding to the motor output according to the brake pedal depth, the accelerator pedal depth, and the current vehicle speed signal, further comprising: in creep mode, the motor output torque ranges from a negative maximum torque to a positive maximum torque, and adjusting the motor output torque through a PID control algorithm according to a given motor speed and a feedback motor speed;

[0056] When the brake pedal depth is between 420-750mV;

[0057] It is believed that the brake pedal is not depressed.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The present invention adopts a manual transmission control mode and an automatic transmission control mode. The manual transmission control mode includes 1st gear and 2nd gear. 1st gear is used for driving control of uphill or downhill with maximum load, and 2nd gear is used for driving control of uphill or downhill with heavy load. The automatic transmission control mode is used for driving control of light load or heavy load on flat slope. When manual 1st gear is used, full energy recovery can be achieved under long-distance heavy load downhill conditions. When manual 2nd gear is used, long-distance downhill conditions with fast speeds and medium or lower loads can be met. In both downhill conditions, the driver can freely control the vehicle's driving speed within a controllable range. It has strong load adaptability and better energy-saving effect than ordinary vehicles. The wear of the corresponding axle brake friction pads is also relatively small, which correspondingly increases the service life of the axle. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A schematic flow chart of a control method provided by an embodiment of the present invention;

[0061] Figure 2 A schematic diagram of a control system provided by an embodiment of the present invention;

[0062] Figure 3 Schematic diagram of energy flow direction in an embodiment of the present invention;

[0063] Figure 4 Schematic diagram of the PID control algorithm flow in an embodiment of the present invention. DETAILED DESCRIPTION

[0064] The following is a clear and complete description of the technical solutions in the embodiments of the present invention, in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0065] Example 1

[0066] like Figure 1 As shown, the present application provides a motor torque control method for an electric tractor, comprising the following steps:

[0067] Determine the transmission control mode and gear position;

[0068] If the transmission is in manual transmission control mode, in 1st or 2nd gear, the motor set speed is determined according to the brake pedal depth or the accelerator pedal depth, and the motor feedback speed is obtained. The motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value;

[0069] If the transmission is in automatic control mode, the transmission gear is switched between 2nd and 3rd gear according to the motor speed; the motor set speed is determined according to the brake pedal depth, and the motor feedback speed is obtained, and the motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value; alternatively, the transmission set output speed is determined according to the accelerator pedal depth, and the transmission feedback output speed is obtained, and the transmission set output speed and the transmission feedback output speed are input into the PID control algorithm to output the motor torque value;

[0070] According to the output motor torque value, the motor is controlled to output the corresponding torque.

[0071] It should be noted that the current gear is used to determine whether it is manual gear (1st or 2nd gear climbing a slope) or automatic gear (2nd gear light load or heavy load flat slope). If it is manual gear, the gearbox gear is fixed at the selected gear and there is no gear shifting. If it is automatic gear, the gearbox automatically switches between 2nd and 3rd gear according to the actual speed to complete the automatic up and down gear operation.

[0072] In manual 1st gear low-speed and heavy-load conditions, the motor speed operates below the rated speed and can output the maximum peak torque.

[0073] It should be noted that the pedal depth in this embodiment is actually the analog input voltage signal of the pedal collected by the controller, with a voltage range of 0-5V, and the corresponding depth signal is 0-5000mV.

[0074] In manual transmission 1st gear, the maximum torque output by the motor is limited according to the maximum allowable input torque of the transmission 1st gear. (1st gear has the highest speed ratio, and the transmission has a maximum output torque limit for the motor in 1st gear).

[0075] The speed setting value of the motor speed closed loop PID is determined according to the setting of the brake pedal and the accelerator pedal. Under the action of the brake pedal (750-2000mV), the corresponding motor speed setting value is from 0-500rpm.

[0076] When the accelerator pedal is pressed from 0 to the middle value, the motor speed increases from 500 rpm to the rated speed (1400 rpm).

[0077] When the accelerator pedal is in the middle position and upward, the motor speed remains unchanged at the rated speed (1400 rpm).

[0078] The accelerator pedal input signal is converted into a motor speed reference through ramp processing, which is used to control the vehicle's maximum acceleration. The ramp reference during acceleration is greater than that during deceleration. This ensures that the torque increase rate during acceleration does not exceed the maximum axle torque variation. This also prevents large speed differences during deceleration, which could cause significant shock and affect driver comfort.

[0079] In the case of manual transmission 2nd gear, the transmission switches to 2nd gear without shifting. 2nd gear has a smaller ratio and output torque, making it suitable for medium-load flat and climbing conditions, and the speed is faster than 1st gear.

[0080] The control method is similar to manual 1st gear. However, due to the different gearbox ratio, when the brake pedal is set, the motor speed remains unchanged. The brake pedal depth of 750-2000mV corresponds to the motor speed of 0-500rpm.

[0081] When the accelerator pedal is applied, the motor speed changes from 500 to nearly 2500 rpm corresponding to the accelerator pedal changing from 0-100%.

[0082] While satisfying the torque output requirement, try to maintain a faster speed. This is suitable for general cargo, which accounts for a large proportion, and the efficiency of the entire vehicle is relatively high.

[0083] The motor's output torque also enables both uphill and downhill driving, ensuring complete energy recovery during downhill driving. Using a closed-loop speed control system, the output torque limit automatically adjusts between the negative and positive maximum motor torques. This allows the system to adapt to varying operating conditions while maintaining a constant given speed.

[0084] Limiting the slope of the given speed change controls the maximum acceleration and deceleration during acceleration and deceleration. The slopes of the brake and accelerator pedal ramps, as well as the proportional and integral coefficients of the speed loop, differ from those in manual first gear. Regarding ramps, the acceleration ramp is greater than the deceleration ramp.

[0085] With automatic transmission control, the driver can automatically shift between 2nd and 3rd gears based on the motor speed, depending on whether the load is lightly loaded and on a slope, or heavily loaded and on a flat slope. This allows for higher vehicle speeds. 3rd gear has the smallest ratio, allowing for a higher output speed than 2nd gear at the same motor speed.

[0086] Due to the change in gear position of the transmission, the automatic transmission control adopts the creep mode speed loop setting when the brake pedal is given (similarly 750-2000mV corresponds to the motor speed of 0-500rpm), and the speed control is achieved by using the motor speed as the setting and feedback of the speed loop.

[0087] During the accelerator pedal setting process, the accelerator pedal setting corresponds to the transmission output speed, and the transmission output speed and vehicle speed feedback are used as the speed PID control. The PID output is still the motor torque.

[0088] Among them, the automatic shifting process in automatic mode is as follows:

[0089] At speeds above 8 km / h, the transmission intervenes in the shift control, shifting from 2nd gear to 3rd gear while ensuring that torque does not change suddenly during the shift, preventing any shock. At speeds below 5 km / h, 3rd gear automatically shifts to 2nd gear. Again, the transmission intervenes to ensure smooth shifting.

[0090] The shifting strategy during the shifting process controls the motor controller to output different torques by exchanging control rights between the gearbox and the vehicle controller, ultimately achieving smooth shifting.

[0091] When switching from the brake pedal to the accelerator pedal, or from the accelerator pedal to the brake pedal, two PIDs are called to ensure that the torque does not change suddenly during the switching process and to ensure smooth switching.

[0092] Furthermore, this embodiment also includes an energy recovery control method for braking an electric tractor. First, it is determined whether the electric tractor meets the driving conditions. If the driving conditions are not met, the torque output by the motor is zero. The details are as follows:

[0093] If at least one of the information given by the driver and the information fed back by the device is valid, the electric tractor does not meet the driving conditions;

[0094] The driver-given information includes:

[0095] The driver selects cab flip, emergency stop, parking and N gear;

[0096] The device feedback information includes:

[0097] The vehicle cannot be powered by high voltage, the vehicle has a level 3 fault, the vehicle's steering gear has a fault, the vehicle's air compressor has a fault, the pressure of the vehicle's service brake air reservoir is lower than the threshold, and the vehicle has a gun connection signal.

[0098] Furthermore, if the driving conditions are met, it is further determined whether the electric tractor meets the energy recovery conditions; if the energy recovery conditions are met, the torque corresponding to the motor output is determined according to the brake pedal depth, the accelerator pedal depth and the current vehicle speed signal; otherwise, the braking torque output by the motor is zero, and no braking electric braking torque is provided, and the braking torque is only provided by the air brake.

[0099] Furthermore, if the energy recovery conditions are met, the specific operations are as follows:

[0100] When the brake pedal depth is greater than 2000mV:

[0101] The actual vehicle speed is greater than the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold. The corresponding motor braking torque is output according to the corresponding speed difference, and the air brake and electric brake are effective simultaneously;

[0102] If the actual vehicle speed is less than or equal to the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold, only the air brake is in effect;

[0103] When the brake pedal depth is between 750-2000mV:

[0104] Determining the torque corresponding to the motor output according to the brake pedal depth, the accelerator pedal depth, and the current vehicle speed signal, further comprising: in creep mode, the motor output torque ranges from a negative maximum torque to a positive maximum torque, and adjusting the motor output torque through a PID control algorithm according to a given motor speed and a feedback motor speed;

[0105] When the brake pedal depth is between 420-750mV;

[0106] It is assumed that the brake pedal is not depressed. At this time, the speed is adjusted according to the setting of the accelerator pedal and the relevant PID control selected according to the gear status.

[0107] Furthermore, if any one or more of the following information exists, the energy recovery condition is not met: the power level of the power battery pack is higher than 95%, the energy recovery mode is canceled, or the motor has a level 1 or level 2 fault.

[0108] It should be noted that when descending in 2nd gear, if the previous solution is used and the air brake is not used, the speed will increase gradually, or it will only be able to maintain a fixed speed when descending. With this vehicle's control strategy, the driver can control the speed of the descent, and the braking torque for the descent is completely achieved by the motor output. This allows flexible speed control without the need for air brakes, which will not wear the friction plates, and can also achieve energy recovery.

[0109] like Figure 4 As shown, the PID control algorithm used in this embodiment is:

[0110] e=n giv -n act ;

[0111]

[0112] Tmin <Tout<Tmax;

[0113] Where: e is the calculated deviation of the motor speed or the gearbox output speed; n giv It is the motor speed value determined by the brake pedal depth, the accelerator pedal depth, or the gearbox output speed determined by the accelerator pedal depth; n actIt is the motor feedback speed value or the gearbox feedback speed value; Tout represents the motor output torque calculated by PID; Tmax is the motor peak torque with the maximum torque output value set to positive, indicating the maximum driving torque output in the forward direction; Tmin is the maximum motor peak torque with a negative minimum value, indicating the negative torque in the forward direction, which is used to control vehicle deceleration or reverse drive; I(e) represents the integral processing result of the speed deviation; D(e) represents the differential processing result of the speed deviation; Kp is the proportional coefficient, which is set by parameters; TN is the integral coefficient, which can be set by parameters; Kd is the differential coefficient.

[0114] The algorithm ensures that vehicle control meets basic handling and usage performance by adjusting appropriate proportional coefficients and integral coefficients.

[0115] Example 2

[0116] like Figure 2 As shown, this embodiment provides a motor torque control system for an electric tractor, comprising: a vehicle controller and a gear mode selection handle connected to the vehicle controller, a brake pedal sensor, an accelerator pedal sensor, a motor controller, a gearbox controller, a motor, and a power battery pack;

[0117] The gear mode selection handle is used to shift the gears of the gearbox through the gearbox controller. The gear modes include manual gear control mode and automatic gear control mode. The manual gear control mode includes 1st gear and 2nd gear. 1st gear is used for driving control of the vehicle uphill or downhill with maximum load, and 2nd gear is used for driving control of the vehicle uphill or downhill with heavy load. The automatic gear control mode is used for driving control of the vehicle on a flat slope with light or heavy load.

[0118] It should be noted that the signal of the gear mode selection handle is a switch signal, which is ultimately output to the vehicle controller.

[0119] The brake pedal sensor is used to obtain a brake pedal depth signal;

[0120] The accelerator pedal sensor is used to obtain an accelerator pedal depth signal;

[0121] The motor controller is used to determine the motor's given speed according to the brake pedal depth or the accelerator pedal depth, and obtain the motor's feedback speed;

[0122] The transmission controller is further configured to determine a given output speed of the transmission according to the accelerator pedal depth, and obtain an output speed fed back by the transmission;

[0123] The vehicle controller is used to determine the transmission control mode and gear position. It communicates with the transmission and motor controller based on the gear position requirements, brake pedal depth, accelerator pedal depth, transmission gear position information, and current vehicle speed signal, and ultimately completes gear control and motor torque control under different working conditions, ultimately ensuring that the vehicle outputs optimal torque and speed while meeting the driver's intentions.

[0124] If the transmission is in manual transmission control mode, in 1st or 2nd gear, the motor set speed is determined according to the brake pedal depth or the accelerator pedal depth, and the motor feedback speed is obtained. The motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value;

[0125] If the transmission is in automatic control mode, the transmission gear is switched between 2nd and 3rd gear according to the motor speed; the motor set speed is determined according to the brake pedal depth, and the motor feedback speed is obtained, and the motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value; alternatively, the transmission set output speed is determined according to the accelerator pedal depth, and the transmission feedback output speed is obtained, and the transmission set output speed and the transmission feedback output speed are input into the PID control algorithm to output the motor torque value;

[0126] According to the output motor torque value, the motor is controlled to output the corresponding torque.

[0127] Furthermore, it also includes an energy recovery determination module, which is used to determine whether the electric tractor meets the energy recovery conditions.

[0128] Furthermore, an energy recovery control module is included, which is used to perform corresponding braking control on the electric tractor when the energy recovery determination module determines that the electric tractor meets the energy recovery conditions:

[0129] When the brake pedal depth is greater than 2000mV:

[0130] The actual vehicle speed is greater than the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold. The corresponding motor braking torque is output according to the corresponding speed difference, and the air brake and electric brake are effective simultaneously;

[0131] If the actual vehicle speed is less than or equal to the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold, only the air brake is in effect;

[0132] When the brake pedal depth is between 750-2000mV:

[0133] Determining the torque corresponding to the motor output according to the brake pedal depth, the accelerator pedal depth, and the current vehicle speed signal, further comprising: in creep mode, the motor output torque ranges from a negative maximum torque to a positive maximum torque, and adjusting the motor output torque through a PID control algorithm according to a given motor speed and a feedback motor speed;

[0134] When the brake pedal depth is between 420-750mV;

[0135] It is believed that the brake pedal is not depressed.

[0136] like Figure 3 As shown, in the motor torque control system of the electric tractor of this embodiment, the energy outputted circulates among the power battery, the motor controller, the motor, the gearbox and the axle.

[0137] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

[0138] Finally, it should be noted that the above embodiments are merely examples and illustrations of the present invention and are not intended to limit the present invention to the described embodiments. Furthermore, those skilled in the art will appreciate that the present invention is not limited to the above embodiments and that various variations and modifications may be made based on the teachings of the present invention, all of which fall within the scope of the present invention.

Claims

1. A method for controlling the motor torque of an electric tractor, characterized in that: The steps include: Determine the transmission control mode and gear position; If the transmission is in manual transmission control mode, in 1st or 2nd gear, the motor set speed is determined according to the brake pedal depth or the accelerator pedal depth, and the motor feedback speed is obtained. The motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value; If the transmission is in automatic control mode, the transmission gear is switched between 2nd and 3rd gear according to the motor speed; the motor set speed is determined according to the brake pedal depth, and the motor feedback speed is obtained, and the motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value; alternatively, the transmission set output speed is determined according to the accelerator pedal depth, and the transmission feedback output speed is obtained, and the transmission set output speed and the transmission feedback output speed are input into the PID control algorithm to output the motor torque value; According to the output motor torque value, the motor is controlled to output the corresponding torque.

2. The motor torque control method of an electric tractor according to claim 1, characterized in that: The method for switching the gear of the transmission between the 2nd gear and the 3rd gear according to the motor speed is as follows: When the vehicle speed is greater than 8km / h, 2nd gear is shifted to 3rd gear; When the vehicle speed is lower than 5km / h, 3rd gear will be changed to 2nd gear.

3. The motor torque control method for an electric tractor according to claim 1, characterized in that: The method further includes the step of determining whether the electric tractor meets the driving conditions. If the driving conditions are not met, the torque output by the motor is zero. The details are as follows: If at least one of the information given by the driver and the information fed back by the device is valid, the electric tractor does not meet the driving conditions; The driver-given information includes: The driver selects cab flip, emergency stop, parking and N gear; The device feedback information includes: The vehicle cannot be powered by high voltage, the vehicle has a level 3 fault, the vehicle's steering gear has a fault, the vehicle's air compressor has a fault, the pressure of the vehicle's service brake air reservoir is lower than the threshold, and the vehicle has a gun connection signal.

4. The motor torque control method for an electric tractor according to claim 3, characterized in that: If the driving conditions are met, the system will continue to determine whether the electric tractor meets the energy recovery conditions; if the energy recovery conditions are met, the torque corresponding to the motor output will be determined based on the brake pedal depth, accelerator pedal depth and current vehicle speed signal; otherwise, the braking torque output by the motor is zero, and no electric braking torque is provided, and only the air brake provides braking torque.

5. The motor torque control method for an electric tractor according to claim 4, characterized in that: If the energy recovery conditions are met, the specific operations are as follows; When the brake pedal depth is greater than 2000mV: The actual vehicle speed is greater than the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold. The corresponding motor braking torque is output according to the corresponding speed difference, and the air brake and electric brake are effective simultaneously; If the actual vehicle speed is less than or equal to the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold, only the air brake is in effect; When the brake pedal depth is between 750-2000mV: Determining the torque corresponding to the motor output according to the brake pedal depth, the accelerator pedal depth, and the current vehicle speed signal, further comprising: in creep mode, the motor output torque ranges from a negative maximum torque to a positive maximum torque, and adjusting the motor output torque through a PID control algorithm according to a given motor speed and a feedback motor speed; When the brake pedal depth is between 420-750mV; It is believed that the brake pedal is not depressed.

6. The motor torque control method for an electric tractor according to claim 4, characterized in that: If any one or more of the following information exists, the energy recovery conditions are not met: the power level of the power battery pack is higher than 95%, the energy recovery mode is canceled, or the motor has a level 1 or level 2 fault.

7. A motor torque control method for an electric tractor according to any one of claims 1 to 6, characterized in that: The PID control algorithm is: e=n giv -n act ; Tmin <Tout<Tmax; Where: e is the calculated deviation of the motor speed or the gearbox output speed; n giv It is the motor speed value determined by the brake pedal depth, the accelerator pedal depth, or the gearbox output speed determined by the accelerator pedal depth; n act It is the motor feedback speed value or the gearbox feedback speed value; Tout represents the motor output torque calculated by PID; Tmax is the motor peak torque with the maximum torque output value set to positive, indicating the maximum driving torque output in the forward direction; Tmin is the maximum motor peak torque with a negative minimum value, indicating the negative torque in the forward direction, which is used to control vehicle deceleration or reverse drive; I(e) represents the integral processing result of the speed deviation; D(e) represents the differential processing result of the speed deviation; Kp is the proportional coefficient, which is set by parameters; TN is the integral coefficient, which can be set by parameters; Kd is the differential coefficient.

8. A motor torque control system for an electric tractor, characterized in that: include: A vehicle controller and a gear mode selection handle, a brake pedal sensor, an accelerator pedal sensor, a motor controller, a transmission controller, a motor, and a power battery pack connected to the vehicle controller; The gear mode selection handle is used to shift the gears of the gearbox through the gearbox controller. The gear modes include manual gear control mode and automatic gear control mode. The manual gear control mode includes 1st gear and 2nd gear. 1st gear is used for driving control of the vehicle uphill or downhill with maximum load, and 2nd gear is used for driving control of the vehicle uphill or downhill with heavy load. The automatic gear control mode is used for driving control of the vehicle on a flat slope with light or heavy load. The brake pedal sensor is used to obtain a brake pedal depth signal; The accelerator pedal sensor is used to obtain an accelerator pedal depth signal; The motor controller is used to determine the motor's given speed according to the brake pedal depth or the accelerator pedal depth, and obtain the motor's feedback speed; The transmission controller is further configured to determine a given output speed of the transmission according to the accelerator pedal depth, and obtain an output speed fed back by the transmission; The vehicle controller is used to determine the transmission control mode and gear position; If the transmission is in manual transmission control mode, in 1st or 2nd gear, the motor set speed is determined according to the brake pedal depth or the accelerator pedal depth, and the motor feedback speed is obtained. The motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value; If the transmission is in automatic control mode, the transmission gear is switched between 2nd and 3rd gear according to the motor speed; the motor set speed is determined according to the brake pedal depth, and the motor feedback speed is obtained, and the motor set speed and the motor feedback speed are input into the PID control algorithm to output the motor torque value; alternatively, the transmission set output speed is determined according to the accelerator pedal depth, and the transmission feedback output speed is obtained, and the transmission set output speed and the transmission feedback output speed are input into the PID control algorithm to output the motor torque value; According to the output motor torque value, the motor is controlled to output the corresponding torque.

9. The motor torque control system of an electric tractor according to claim 8, characterized in that: It also includes an energy recovery determination module, which is used to determine whether the electric tractor meets the energy recovery conditions.

10. The motor torque control system of an electric tractor according to claim 8, characterized in that: The system further includes an energy recovery control module, which is used to perform corresponding braking control on the electric tractor when the energy recovery determination module determines that the electric tractor meets the energy recovery conditions: When the brake pedal depth is greater than 2000mV: The actual vehicle speed is greater than the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold. The corresponding motor braking torque is output according to the corresponding speed difference, and the air brake and electric brake are effective simultaneously; If the actual vehicle speed is less than or equal to the preset speed threshold, the accelerator pedal depth is zero, and the brake pedal depth is greater than the preset first braking threshold, only the air brake is in effect; When the brake pedal depth is between 750-2000mV: Determining the torque corresponding to the motor output according to the brake pedal depth, the accelerator pedal depth, and the current vehicle speed signal, further comprising: in creep mode, the motor output torque ranges from a negative maximum torque to a positive maximum torque, and adjusting the motor output torque through a PID control algorithm according to a given motor speed and a feedback motor speed; When the brake pedal depth is between 420-750mV; It is believed that the brake pedal is not depressed.

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