A torque control method for a tractor engine

Abstract

This invention provides a torque control method for a tractor engine, which fully considers the coordination of the main gearbox, auxiliary gearbox, shift gears, and rear axle speed ratios. In particular, it ensures the safe updating of the shift gear ratio under specific conditions and the orderly switching of the speed ratios during main and auxiliary gearbox shifting, thus guaranteeing the continuity and efficiency of power transmission and adapting to the speed and torque requirements under different operating conditions. At the same time, it rationally sets starting conditions such as engine start, driver seating, and steering wheel neutral, as well as the updating strategy of the main and auxiliary gearbox speed ratios at different starting stages, avoiding abnormal fluctuations in engine speed during startup, ensuring smooth start-up, reducing the impact on the transmission system, and extending the service life of the equipment.

Description

Technical Field

[0001] This invention belongs to the field of power machinery, and specifically relates to a torque control method for a tractor engine. Background Technology

[0002] In agricultural production, tractors are crucial power machinery, and their performance directly impacts operational efficiency and quality. Traditional tractors suffer from several shortcomings in engine torque control. For example, during starting, gear shifting, and speed maintenance, they cannot precisely adjust engine torque according to working conditions, leading to unstable engine speed, uneven power transmission, and even engine overload or power waste. Furthermore, previous technologies failed to adequately consider the appropriate switching timing for different gear combinations and driving conditions in their speed ratio update control logic, thus affecting the overall performance of the tractor.

[0003] Some existing related technologies either focus on the control of a single gear, ignoring the complexity of the coordination of the main gearbox, auxiliary gearbox, shift gears, and multiple gears on the rear axle; or they are not precise enough in the matching and control of vehicle speed and engine speed, making it difficult to meet the needs of heavy tractors in complex operating scenarios. Summary of the Invention

[0004] The purpose of this invention is to provide a torque control method for tractor engines, so as to solve the problems of inaccurate torque control, unreasonable speed ratio updates, and poor matching between vehicle speed and engine speed in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A torque control method for a tractor engine, the tractor comprising a control system, an engine, and a gearbox, the gearbox comprising a main gearbox and an auxiliary gearbox, comprising the following steps:

[0007] Step 0: When the tractor is powered on but not started, the control system sets the speed ratio of the main gearbox and the auxiliary gearbox to 0.

[0008] Step 1: After the engine starts, the control system determines the engine speed:

[0009] When the engine speed exceeds the first threshold, the control system sets the auxiliary gearbox to gear 2 and sets the corresponding gear ratio; and sets the main gearbox to neutral.

[0010] When the engine speed exceeds the second threshold, the control system sets the main gearbox to gear 2 and sets the corresponding speed ratio before proceeding to step 2.

[0011] Step 2: After the control system detects that the tractor meets the starting conditions, it controls the tractor to start and resets the corresponding speed ratio according to the gear positions of the main gearbox and auxiliary gearbox after starting.

[0012] Step 3: During driving, when the driver shifts gears, the control system determines the gear that needs to be shifted:

[0013] If the driver selects to shift gears in the master gearbox, when the control system detects that the clutch engagement has reached the synchronization stage, the control system determines the gears and corresponding speed ratios of the master and auxiliary gearboxes respectively, and then determines the overall speed ratio of the transmission.

[0014] If the driver selects to shift gears in the auxiliary gearbox, the control system first switches the master gearbox to neutral. After the auxiliary gearbox shift is completed, the master gearbox is automatically selected according to the actual speed. When the input group clutch is filled with oil beyond the KP point, the control system determines the gears and corresponding speed ratios of the master and auxiliary gearboxes respectively, and then determines the overall speed ratio of the transmission.

[0015] Step 4: The control system takes the maximum value of the foot throttle percentage and the hand throttle percentage as the throttle control percentage, and then obtains the desired engine speed under the current throttle percentage. The actual engine speed is made to approach the desired engine speed under the current throttle percentage according to a fixed gradient until it reaches the closest point. Then, the current actual engine speed is taken as the engine speed limited by the rate.

[0016] Step 5: Convert the engine speed that is limited by the speed into the desired vehicle speed, and obtain the desired engine speed based on the desired vehicle speed;

[0017] Step 6: Determine the requested torque of the engine based on the difference between the desired engine speed and the actual engine speed, thus completing the torque control of the tractor engine.

[0018] The present invention also has the following features:

[0019] Furthermore, the starting conditions for the tractor in step 2 are: the engine is started, the driver is seated, and the tractor's steering lever is in neutral.

[0020] Furthermore, in step 2, when the control system controls the tractor to start, the control system causes the output clutch of the main gearbox to engage first, and then causes the input clutch of the main gearbox to engage; wherein, when the input clutch is more than half engaged, the control system adjusts the speed ratio according to the target gear of the main gearbox and the auxiliary gearbox.

[0021] Furthermore, the main gearbox of the tractor has 9 gears, and the auxiliary gearbox has 5 gears.

[0022] Furthermore, in step 3, the overall gear ratio of the transmission is determined using the following formula. :

[0023]

[0024] in, Indicates the main gearbox speed ratio

[0025] Indicates the speed ratio of the auxiliary gearbox;

[0026] This indicates the rear axle speed ratio, with a value of 39.36;

[0027] This indicates the creepage gear ratio, with a value of 14.023.

[0028] Furthermore, step 4 includes the following sub-steps:

[0029] Step 41: The control system takes the maximum value of the foot throttle percentage and the hand throttle percentage as the throttle control percentage, and then obtains the desired engine speed under the current throttle percentage;

[0030] Step 42: The control system determines the relationship between the desired engine speed and the actual engine speed.

[0031] If the desired engine speed is greater than the actual engine speed, the engine speed is increased multiple times in a fixed speed increase gradient until the actual engine speed after multiple speed increases is closest to the desired engine speed; the actual engine speed after multiple speed increases is taken as the engine speed limited by the rate.

[0032] If the desired engine speed is lower than the actual engine speed, the engine speed is reduced multiple times according to a fixed speed reduction gradient until the actual engine speed after multiple speed reductions is closest to the desired engine speed; the actual engine speed after multiple speed reductions is taken as the engine speed limited by the rate.

[0033] Furthermore, in step 5, when determining the desired vehicle speed, the engine speed limited by the speed is converted into the desired vehicle speed using the following formula:

[0034] Desired vehicle speed = Engine speed limited by speed × Tractor tire circumference / 60 / Total gear ratio of the gearbox × 3.6;

[0035] Specifically, when the speed enable / hold signal of the main container and the speed enable / hold signal of the auxiliary container are both 0, the actual speed is taken as the desired speed.

[0036] Furthermore, step 6 includes the following sub-steps:

[0037] Step 61: Using the PID control method, torque is calculated based on the speed difference between the desired engine speed and the actual engine speed, thereby obtaining... ;

[0038] Step 62, convert the coefficients Multiply by the speed difference to obtain the integral torque percentage of the control system in one operating cycle. Accumulate the integral torque percentage in each operating cycle to obtain the total integral torque percentage.

[0039] If the integral torque percentage value under one operating cycle is less than 0, then the value is 0;

[0040] Step 63: Take the absolute value of the speed difference to obtain the coefficient. The speed difference and the coefficient Multiply them to get the percentage of torque in the overall proportional component;

[0041] Step 64: Take the absolute value of the speed difference to obtain the coefficient. The difference between the speed difference in the current operating cycle and the speed difference in the previous operating cycle of the control system is multiplied and low-pass filtered to obtain the torque percentage of the differential element.

[0042] Step 65, calculate the engine's requested torque using the following formula:

[0043] The engine's requested torque = total integral torque percentage + total proportional torque percentage + derivative torque percentage.

[0044] Furthermore, steps 61, 63, and 64 all obtain the coefficients by looking up a table. , and ;

[0045] The table below shows the comparison between the speed difference and the coefficient:

[0046] Speed ​​Difference and Coefficient Comparison Table

[0047]

[0048] Compared with the prior art, the present invention has the following technical effects:

[0049] (I) The torque control method of the tractor engine of the present invention fully considers the coordination of the main gearbox, auxiliary gearbox, shift gear and rear axle speed ratio, especially the safe updating of the shift gear ratio under specific conditions and the orderly switching of the speed ratio when the main gearbox and auxiliary gearbox are shifted, which ensures the continuity and efficiency of power transmission, adapts to the speed and torque requirements under different working conditions, and reasonably sets the starting conditions such as engine start, driver seat, and steering wheel neutral, as well as the updating strategy of the main gearbox and auxiliary gearbox speed ratio at different starting stages, to avoid abnormal fluctuations in engine speed when starting, ensure smooth starting, reduce the impact on the transmission system and extend the service life of the equipment.

[0050] (II) The torque control method for the tractor engine of the present invention obtains the desired engine speed by looking up a table based on the throttle control percentage and the engine speed change rate. Through rate limiting and closed-loop adjustment, the engine speed can accurately track the desired speed. Simultaneously, combined with the vehicle speed holding enable signal, the vehicle speed is rationally regulated to maximize fuel economy while meeting operating speed requirements. Employing dynamic parameter PID control, the requested torque is accurately calculated based on the difference between the desired and actual speeds. This ensures sufficient engine power output while avoiding excessive torque that could lead to energy waste or equipment damage, thus improving the overall performance and operating quality of the tractor. It is suitable for large-scale industrial use and promotion. Detailed Implementation

[0051] It should be noted that, unless otherwise specified, all components in this invention are components known in the prior art.

[0052] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0053] A torque control method for a tractor engine, the tractor including a control system, an engine, and a gearbox, the gearbox including a main gearbox and an auxiliary gearbox, comprising the following steps:

[0054] Step 0: When the tractor is powered on but not started, the control system sets the speed ratio of the main gearbox and the auxiliary gearbox to 0.

[0055] The purpose of this step is to avoid the speed difference between the expected speed and the actual speed, which would cause the torque integral to accumulate and prevent the engine speed from soaring after starting the engine.

[0056] Step 1: After the engine starts, the control system determines the engine speed:

[0057] When the engine speed exceeds the first threshold, the control system sets the auxiliary gearbox to second gear and sets the corresponding speed ratio; and sets the main gearbox to neutral.

[0058] In practice, the first and second thresholds are automatically determined by the control system based on the specific specifications of the tractor, or they can be defined by those skilled in the art.

[0059] When the engine speed exceeds the second threshold, the control system sets the main gearbox to gear 2, activates the engine start enable signal E1, and sets the corresponding speed ratio before proceeding to step 2.

[0060] Step 2: After the control system detects that the tractor meets the starting conditions, it controls the tractor to start and resets the corresponding speed ratio according to the gear positions of the main gearbox and auxiliary gearbox after starting.

[0061] Specifically, the conditions for starting a tractor are: the engine is started, the driver is seated, and the tractor's steering lever is in neutral.

[0062] Specifically, when the control system starts the tractor, it first engages the output clutch of the main gearbox and then engages the input clutch of the main gearbox. When the input clutch is filled with oil past point KP, the control system sends a target gear ratio update enable signal L1 to the main gearbox. The speed ratio is adjusted according to the target gear of the main gearbox and the auxiliary gearbox (the driver may pre-select the target gear of the main gearbox instead of the second gear ratio of the main gearbox updated after the engine speed exceeds the threshold. If the target gear value remains unchanged, the updated value is the same as the previous one).

[0063] Step 3: During driving, when the driver shifts gears, the control system determines the gear that needs to be shifted:

[0064] During vehicle operation, when the main gearbox shifts gears and the closed clutch reaches the synchronization stage, it sends out the main gearbox gear ratio update enable signal M1 and the vehicle speed hold enable signal S1 to update the target gear ratio for engine speed regulation total ratio calculation.

[0065] Therefore, if the driver selects to shift gears in the master gearbox, when the control system detects that the clutch is closed and reaches the synchronization stage, the control system determines the gears and corresponding speed ratios of the master and auxiliary gearboxes respectively, and then determines the total speed ratio of the engine.

[0066] When the auxiliary gearbox shifts gears, after the target gear is updated, it is necessary to determine that the clutch state value of the main gearbox is greater than the synchronization state value (i.e., the vehicle is shifting gears while in motion). Before the auxiliary gearbox shifts gears, the main gearbox automatically returns to neutral. The gear ratio is not updated during the shift. After the shift is completed, the appropriate main gearbox gear is matched and engaged according to the actual vehicle speed. The output clutch engages first, followed by the input clutch. When the input clutch's lubrication state passes point KP, the auxiliary gearbox target gear ratio update enable signal M2 and the vehicle speed hold enable signal S2 are issued, and the target gear ratios of both the main and auxiliary gearboxes are updated simultaneously.

[0067] Therefore, if the driver chooses to shift gears in the auxiliary gearbox, the control system first switches the main gearbox to neutral; after the auxiliary gearbox shift is completed, the main gearbox is automatically selected according to the actual speed; when the input group clutch is filled with oil beyond the KP point, the control system determines the gears and corresponding speed ratios of the main and auxiliary gearboxes respectively, and then determines the overall speed ratio of the engine.

[0068] Step 4: The control system takes the maximum value of the foot throttle percentage and the hand throttle percentage as the throttle control percentage, and then obtains the desired engine speed under the current throttle percentage. The actual engine speed is made to approach the desired engine speed under the current throttle percentage according to a fixed gradient until it reaches the closest point. Then, the current actual engine speed is taken as the engine speed limited by the rate.

[0069] Step 5: Convert the engine speed that is limited by the speed into the desired vehicle speed, and obtain the desired engine speed based on the desired vehicle speed;

[0070] Step 6: Determine the requested torque of the engine based on the difference between the desired engine speed and the actual engine speed, thus completing the torque control of the tractor engine.

[0071] As one specific implementation method: the tractor's main gearbox has 9 gears, and the auxiliary gearbox has 5 gears;

[0072] This embodiment provides a specific correspondence between gear and speed ratio:

[0073] The main gearbox speed ratio and auxiliary gearbox speed ratio in step 3 are obtained by looking up the desired gear table;

[0074] The expected gear tables include the expected gear tables for the main gearbox, the expected gear tables for the auxiliary gearbox, and the expected gear tables for the creeper gearbox, as shown in Table 1 and Table 2 respectively:

[0075] Table 1 Expected Gear Position Table for Main Container

[0076]

[0077] Table 2 Expected Gear Position Table for Auxiliary Box

[0078]

[0079] Furthermore, in step 3, the overall gear ratio of the transmission is calculated using the following formula. :

[0080]

[0081] in, Indicates the main gearbox speed ratio

[0082] Indicates the speed ratio of the auxiliary gearbox;

[0083] This indicates the rear axle speed ratio, with a value of 39.36;

[0084] This indicates the creepage gear ratio, with a value of 14.023.

[0085] The conditions for updating the gear ratio are fixed. The vehicle defaults to the direct gear ratio. When the vehicle steering lever is in neutral and the clutch pedal and foot brake pedal are pressed, the gear ratio is updated directly after the gear is switched. The engine control is not affected because the power is interrupted.

[0086] Specifically, step 4 includes the following sub-steps:

[0087] Step 41: The control system takes the maximum value of the foot throttle percentage and the hand throttle percentage as the throttle control percentage, and then obtains the desired engine speed under the current throttle percentage;

[0088] Step 42: The control system determines the relationship between the desired engine speed and the actual engine speed.

[0089] If the desired engine speed is greater than the actual engine speed, the engine speed is increased multiple times according to a fixed speed increase gradient until the actual engine speed is closest to the desired engine speed; the current actual engine speed is taken as the engine speed limited by the rate.

[0090] If the desired engine speed is lower than the actual engine speed, the engine speed is reduced multiple times according to a fixed speed decrease gradient until the actual engine speed is closest to the desired engine speed; the current actual engine speed is then used as the engine speed limited by the rate.

[0091] Specifically, when the desired engine speed is greater than the actual engine speed, the actual engine speed plus the speed rise gradient T1 is used as the rate-limited engine speed. After each software operation cycle of the control system, the closed-loop cumulative gradient value of the rate-limited engine speed is close to the desired engine speed.

[0092] When the desired engine speed is less than the actual engine speed, the actual engine speed minus the speed descent gradient T2 is used as the rate-limited engine speed. After each software running cycle, the closed-loop cumulative gradient value of the rate-limited engine speed approaches the desired engine speed.

[0093] When the enable signal of the main vehicle speed holding signal S1 or the enable signal of the auxiliary vehicle speed holding signal S2 is 1, the engine speed limited by the rate is replaced by the actual engine speed.

[0094] When the enable signal S1 of the main gearbox or the enable signal S2 of the auxiliary gearbox is 0, the closed-loop accumulation or subtraction gradient value is made by adding the actual engine speed to the speed increase gradient T1 or subtracting the speed decrease gradient T2 to approach the desired engine speed.

[0095] This embodiment provides a specific implementation method:

[0096] By consulting the table comparing throttle control percentage and engine speed change rate, the expected engine speed at the current throttle percentage can be obtained.

[0097] The comparison table between throttle control percentage and engine speed change rate is shown in Table 3:

[0098] Table 3. Comparison of Throttle Control Percentage and Engine Speed ​​Change Rate.

[0099]

[0100] Specifically, in step 5, when determining the desired vehicle speed, the engine speed limited by the speed is converted into the desired vehicle speed using the following formula:

[0101] Desired vehicle speed = Engine speed limited by speed × Tractor tire circumference / 60 / Total gear ratio of the gearbox × 3.6;

[0102] Specifically, when the speed enable / hold signal of the main container and the speed enable / hold signal of the auxiliary container are both 0, the actual speed is taken as the desired speed.

[0103] Specifically, step 6 includes the following sub-steps:

[0104] It should be noted that the PID control method includes three coefficients. , and These correspond to the current error, historical cumulative error, and future error trends, respectively, all of which are well-known in this field.

[0105] Step 61: Using the PID control method, torque is calculated based on the speed difference between the desired engine speed and the actual engine speed, thereby obtaining... coefficient;

[0106] Step 62, will Multiply the coefficient by the speed difference to obtain the integral torque percentage of the control system in one operating cycle. Accumulate the integral torque percentage in each operating cycle to obtain the total integral torque percentage.

[0107] If the integral torque percentage value under one operating cycle is less than 0, then the value is 0;

[0108] Step 63: Take the absolute value of the speed difference to obtain... Coefficient, which combines the speed difference with Multiplying the coefficients gives the percentage of torque in the overall proportional component.

[0109] Step 64: Take the absolute value of the speed difference to obtain... The coefficient is obtained by multiplying the speed difference of the current operating cycle of the control system with the speed difference of the previous operating cycle, and then using low-pass filtering to obtain the torque percentage of the differential element.

[0110] Step 65, calculate the engine's requested torque using the following formula:

[0111] The engine's requested torque = total integral torque percentage + total proportional torque percentage + derivative torque percentage.

[0112] Steps 61, 63, and 64 are all obtained by looking up a table. , and coefficient;

[0113] Among them, the speed difference and Coefficient comparison table, speed difference and Coefficient comparison table and speed difference with The coefficient comparison tables are as follows:

[0114] Table 4 Speed ​​Difference and Coefficient Comparison Table

[0115]

[0116] Table 5 Speed ​​Difference and Coefficient Comparison Table

[0117]

[0118] Table 6 Speed ​​Difference and Coefficient Comparison Table

[0119]

Claims

1. A torque control method for a tractor engine, wherein the tractor includes a control system, an engine, and a gearbox, and the gearbox includes a main gearbox and an auxiliary gearbox, characterized in that, Includes the following steps: Step 0: When the tractor is powered on but not started, the control system sets the speed ratio of the main gearbox and the auxiliary gearbox to 0. Step 1: After the engine starts, the control system determines the engine speed: When the engine speed exceeds the first threshold, the control system sets the auxiliary gearbox to gear 2 and sets the corresponding gear ratio; and sets the main gearbox to neutral. When the engine speed exceeds the second threshold, the control system sets the main gearbox to gear 2 and sets the corresponding speed ratio before proceeding to step 2. Step 2: After the control system detects that the tractor meets the starting conditions, it controls the tractor to start and resets the corresponding speed ratio according to the gear positions of the main gearbox and auxiliary gearbox after starting. Step 3: During driving, when the driver shifts gears, the control system determines the gear that needs to be shifted: If the driver selects to shift gears in the master gearbox, when the control system detects that the clutch engagement has reached the synchronization stage, the control system determines the gears and corresponding speed ratios of the master and auxiliary gearboxes respectively, and then determines the overall speed ratio of the transmission. If the driver selects to shift gears in the auxiliary gearbox, the control system first switches the master gearbox to neutral. After the auxiliary gearbox shift is completed, the master gearbox is automatically selected according to the actual speed. When the input group clutch is filled with oil beyond the KP point, the control system determines the gears and corresponding speed ratios of the master and auxiliary gearboxes respectively, and then determines the overall speed ratio of the transmission. Step 4: The control system takes the maximum value of the foot throttle percentage and the hand throttle percentage as the throttle control percentage, and then obtains the desired engine speed under the current throttle percentage. The actual engine speed is made to approach the desired engine speed under the current throttle percentage according to a fixed gradient until it reaches the closest point. Then, the current actual engine speed is taken as the engine speed limited by the rate. Step 5: Convert the engine speed that is limited by the speed into the desired vehicle speed, and obtain the desired engine speed based on the desired vehicle speed; Step 6: Determine the requested torque of the engine based on the difference between the desired engine speed and the actual engine speed, thus completing the torque control of the tractor engine.

2. The torque control method for a tractor engine as described in claim 1, characterized in that, The starting conditions for the tractor in step 2 are: The engine is started, the driver is seated, and the tractor's steering lever is in neutral.

3. The torque control method for a tractor engine as described in claim 2, characterized in that, In step 2, when the control system starts the tractor, it first engages the output clutch of the main gearbox, and then engages the input clutch of the main gearbox. When the input clutch is half-engaged, the control system adjusts the speed ratio according to the target gear positions of the main gearbox and the auxiliary gearbox.

4. The torque control method for a tractor engine as described in claim 2, characterized in that, The tractor's main gearbox has 9 gears, and the auxiliary gearbox has 5 gears.

5. The torque control method for a tractor engine as described in claim 3, characterized in that, In step 3, the overall gear ratio of the transmission is determined using the following formula. : in, Indicates the main gearbox speed ratio Indicates the speed ratio of the auxiliary gearbox; Indicates the rear axle speed ratio; This indicates the gear ratio for climbing.

6. The torque control method for a tractor engine as described in claim 5, characterized in that, Step 4 includes the following sub-steps: Step 41: The control system takes the maximum value of the foot throttle percentage and the hand throttle percentage as the throttle control percentage, and then obtains the desired engine speed under the current throttle percentage; Step 42: The control system determines the relationship between the desired engine speed and the actual engine speed. If the desired engine speed is greater than the actual engine speed, the engine speed is increased multiple times in a fixed speed increase gradient until the actual engine speed after multiple speed increases is closest to the desired engine speed. The actual engine speed after multiple increases in speed is taken as the engine speed limited by the rate. If the desired engine speed is lower than the actual engine speed, the engine speed is reduced multiple times according to a fixed speed reduction gradient until the actual engine speed after multiple speed reductions is closest to the desired engine speed; the actual engine speed after multiple speed reductions is taken as the engine speed limited by the rate.

7. The torque control method for a tractor engine as described in claim 6, characterized in that, In step 5, when determining the desired vehicle speed, the engine speed limited by the speed is converted into the desired vehicle speed using the following formula: Desired vehicle speed = Engine speed limited by speed × Tractor tire circumference / 60 / Total gear ratio of the gearbox × 3.6; Specifically, when the speed enable / hold signal of the main container and the speed enable / hold signal of the auxiliary container are both 0, the actual speed is taken as the desired speed.

8. The torque control method for a tractor engine as described in claim 7, characterized in that, Step 6 includes the following sub-steps: Step 61: Use the PID control method to obtain... ; Step 62, convert the coefficients Multiplying this by the speed difference yields the percentage of integral torque of the control system over one operating cycle. Accumulate the integral torque percentage for each operating cycle to obtain the total integral torque percentage. If the integral torque percentage value under one operating cycle is less than 0, then the value is 0; Step 63: Take the absolute value of the speed difference to obtain the coefficient. The speed difference and the coefficient Multiply them to get the percentage of torque in the overall proportional component; Step 64: Take the absolute value of the speed difference to obtain the coefficient. ; Multiply the speed difference of the current operating cycle of the control system with the speed difference of the previous operating cycle, and then use low-pass filtering to obtain the torque percentage of the differential element. Step 65, calculate the engine's requested torque using the following formula: The engine's requested torque = total integral torque percentage + total proportional torque percentage + derivative torque percentage.

9. The torque control method for a tractor engine as described in claim 8, characterized in that, Steps 61, 63, and 64 all obtain the coefficients by looking up a table. , and ; The table below shows the comparison between the speed difference and the coefficient: Speed ​​Difference and Coefficient Comparison Table 。

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