A power matching method and system for a hydraulic mechanical continuously variable transmission tractor

Abstract

A power matching method and system of a hydraulic mechanical continuously variable transmission tractor, relating to the field of continuously variable transmission tractors, wherein the power matching method comprises the following steps: obtaining a request speed of the tractor by the driver, calculating the required torque of the engine at the request speed; calculating the actual minimum speed of the engine at the request speed and the theoretical minimum engine speed, taking the larger value of the actual minimum speed and the theoretical minimum engine speed as the required speed of the engine; taking the required speed as the initial request speed of the engine, calculating the maximum driving torque of the engine at the initial request speed. The power matching method and system can avoid the situation of engine speed reduction or even engine stall and parking when the continuously variable transmission tractor is under heavy load and the driver quickly increases or decreases the speed of the tractor or the load suddenly changes, while ensuring the comfort of the driver.

Description

Technical Field

[0001] This invention relates to the field of continuously variable transmission (CVT) tractors, specifically to a power matching method and system for a hydraulic mechanical CVT tractor. Background Technology

[0002] In continuous high-production and high-efficiency operations, implement protection has become a basic requirement for modern intelligent tractors. At the same time, drivers' demands for agricultural machinery comfort are constantly increasing, which places higher demands on the level of intelligence in agricultural machinery. Improving the intelligence level of agricultural machinery and reducing the labor intensity of agricultural machinery drivers is one of the important trends in agricultural machinery development. Tractors operate under complex and diverse conditions, and their power source is generally a diesel engine. Due to the limitations of diesel engines' inherent external characteristics (the engine external characteristic curve is the curve showing the engine output power (torque) changing with speed when the engine throttle opening is 100%), when its load torque exceeds its maximum torque at that speed, the engine will slow down or even stall, causing the tractor to experience a shock-induced deceleration or even stop. This situation not only affects the driving experience but also causes considerable damage to the entire transmission system.

[0003] Hydraulic mechanical continuously variable transmission (CVT) tractors can achieve stepless speed regulation. While maintaining a constant engine speed, the tractor's speed can be increased or decreased by adjusting the gearbox ratio, resulting in high driving comfort. However, they are typically powered by diesel engines, and there is a possibility that the load may exceed the engine's maximum torque at that speed, causing the entire machine to stall. Since hydraulic mechanical CVT tractors have continuously adjustable gear ratios and employ an electronic control system, it is necessary to develop a power matching method and system that can prevent the tractor from stalling while simultaneously improving driver comfort. Summary of the Invention

[0004] The purpose of this invention is to propose a power matching method and system for a hydraulic continuously variable transmission (CVT) tractor. When the CVT tractor is working under heavy load, and the driver rapidly increases or decreases the speed of the machine or the load changes suddenly, a reasonable power matching method can be used to avoid the engine speed from dropping or even stalling, while ensuring the driver's comfort.

[0005] The technical solution adopted in this invention is: a power matching method for a hydraulic mechanical continuously variable transmission tractor, comprising the following steps:

[0006] Obtain the driver's requested vehicle speed and calculate the engine's required torque at that speed;

[0007] Calculate the actual minimum engine speed and the theoretical minimum engine speed at the requested vehicle speed, and take the larger value between the actual minimum engine speed and the theoretical minimum engine speed as the required engine speed.

[0008] The required speed is used as the initial requested speed of the engine, and the maximum driving torque of the engine at the initial requested speed is calculated.

[0009] If the maximum drive torque at the initial requested speed is greater than or equal to the engine's required torque, then the engine is controlled according to the initial requested speed.

[0010] If the maximum driving torque at the initial requested speed is less than the engine's required torque, then the engine's required speed is compensated step by step within the engine's maximum speed range, and the compensated required speed is used as the requested speed to control the engine, and the gear ratio is reduced in coordination until the whole machine is maintained at the requested vehicle speed. At this time, the engine's maximum driving torque at the requested vehicle speed is greater than or equal to the required torque.

[0011] As a preferred option, the calculation of the engine torque required at the requested vehicle speed includes:

[0012] Obtain the load torque when the overall machine acceleration is zero;

[0013] Get the requested vehicle speed input by the driver and the current vehicle speed of the whole machine, and calculate the requested acceleration based on the requested vehicle speed and the current vehicle speed;

[0014] Calculate the engine's required torque at the requested vehicle speed based on the requested acceleration, total load, and load torque.

[0015] As a preferred option, the calculation of the engine's actual minimum speed at the requested vehicle speed includes:

[0016] Calculate the required power based on the requested vehicle speed, and then query the engine external characteristic table of the whole machine to obtain the actual minimum speed of the engine under the required power.

[0017] As a preferred option, the theoretical minimum engine speed is calculated based on the requested vehicle speed and the maximum gear ratio of the whole machine, where the maximum gear ratio of the whole machine is the product of the central transmission ratio and the maximum gear ratio of the gearbox.

[0018] As a preferred embodiment, the calculation of the engine's maximum drive torque at the requested speed includes:

[0019] Query the engine external characteristics table of the whole machine to obtain the maximum torque of the engine at the requested speed, and obtain the requested gear ratio by using the requested vehicle speed and the requested speed;

[0020] The maximum drive torque at the requested speed is obtained by using the maximum torque at the requested speed and the requested gear ratio.

[0021] As a preferred approach, the actual torque T at the current vehicle speed is periodically acquired and compared. ac The maximum torque T at the requested speed re If T ac ≥t*Tre Where t is the engine torque safety factor, 0 < t < 1, then the engine speed compensation is performed step by step within the range of the engine's maximum speed; if T ac <t*T re Then no speed compensation is needed.

[0022] As a preferred option, before controlling the engine with the compensated required speed, if the compensated required speed exceeds the engine's maximum speed, the lifting arm is raised step by step within the working stroke range of the lifting arm to reduce the load until the whole machine maintains the requested speed and the engine's maximum driving torque is greater than or equal to the required torque; if the compensated required speed does not exceed the engine's maximum speed, there is no need to change the lifting arm height.

[0023] As a preferred solution, the gear ratio is reduced in a coordinated manner until the entire machine maintains the requested speed, including:

[0024] Obtain the actual acceleration and requested acceleration of the entire machine;

[0025] The requested gear ratio is adjusted step by step according to the requested acceleration of the whole machine and the actual rate of change of engine speed until the actual acceleration of the whole machine equals the requested acceleration.

[0026] A power matching system for a hydraulic mechanical continuously variable transmission tractor includes:

[0027] Driver control module: used to acquire the driver's requested vehicle speed and transmit the acquired signal data to the TCU control module;

[0028] Sensing module: Used to acquire the load, speed and torque of the whole machine, and transmit the acquired signal data to the TCU control module;

[0029] Execution module: Used to receive and execute the gear ratio sent by the TCU control module, so that the whole machine maintains the requested speed;

[0030] Engine control module: Used to receive and execute the requested speed sent by the TCU control module, and at the same time feed back the current engine speed and torque to the TCU control module;

[0031] TCU control module: It is used to receive signal data from the driver control module, the sensing module and the engine control module, and send the gear ratio determined by the power matching method and the requested engine speed to the execution module and the engine control module respectively.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] The power matching method for a hydraulic mechanical continuously variable transmission tractor proposed in this invention, and the system applying this power matching method, can control the engine speed and the gear ratio of the whole machine through control logic to meet the control needs of the driver's control system, while ensuring that the engine does not stall or stop, thus avoiding the whole machine stalling or stopping due to operational errors and sudden load changes. It also avoids damage to the transmission system caused by such abnormal stopping, thereby improving driving comfort. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the power distribution system control principle of the present invention;

[0036] Figure 2 This is a schematic diagram illustrating the working principle of the hydraulic mechanical continuously variable transmission tractor of the present invention.

[0037] Figure 3 This is a schematic diagram of the transmission circuit of a hydraulic continuously variable transmission (CVT) tractor.

[0038] Figure 4 This is a schematic diagram of the working state of a single planetary set in a composite planetary set;

[0039] Figure 5 A schematic diagram of the dynamics model of a tractor in operation;

[0040] Figure 6 This is a diagram illustrating the driver's intention transformation.

[0041] Figure 7 This is a schematic diagram of the power matching method of the present invention. Detailed Implementation

[0042] The present invention will now be described in detail through exemplary embodiments. However, it should be understood that, without further description, elements, structures, and features in one embodiment may be advantageously incorporated into other embodiments.

[0043] It should be noted that, unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "a," "an," or "the," etc., used in the specification and claims of this patent application do not express a limitation on quantity, but rather indicate the presence of at least one; the terms "first," "second," and "third," as used herein, should not be considered as a limitation on the order of components, but are merely for distinguishing different components; the terms "comprising," "including," etc., indicate that the elements or objects preceding "comprising" or "including" encompass the elements or objects listed following "comprising" or "including" and their equivalents, but do not exclude other elements or objects having the same function.

[0044] To more clearly describe the power matching method and specific components of this hydraulic mechanical continuously variable transmission tractor, in conjunction with the attached... Figure 1-7 This embodiment is described as follows:

[0045] The principle of the power matching method in this hydraulic mechanical continuously variable transmission tractor is as follows:

[0046] The working principle of a continuously variable transmission (CVT) tractor is as follows: Figure 2 As shown, the engine power is first split into two paths: one via hydraulic transmission through the pump motor, and the other via mechanical transmission through gears. The two power sources are then combined and output through a compound planetary gearbox to drive the entire machine.

[0047] To avoid the engine stalling, the maximum torque should not be exceeded at the engine's operating speed. Therefore, the speed and torque characteristics of the transmission system must be calculated first.

[0048] Taking the power transmission system of a certain type of hydraulic continuously variable transmission tractor as an example, this paper analyzes the power distribution during the operation of the entire machine. The power transmission system route is as follows: Figure 3 As shown. Ne and Te are the engine's input speed and torque, respectively; e is the pump-motor system's displacement ratio (e is defined as the ratio of the fixed displacement motor's output speed to the variable displacement pump's input speed); K1 and K2 are clutches;

[0049] S1, S2, S3, and S4 are synchronizers; i1, i2, i3, i4, i5, i6, i7, i8, i9, and i 10 i 11 i 12 Let i be the speed ratio of each pair of gears (speed ratio is defined as the ratio of the output speed of the gear pair to the input speed of the gear pair). c For the central transmission ratio (defined as the ratio of the drive shaft output speed to the transmission output speed), R w The radius of the drive wheel.

[0050] The hydraulic-mechanical continuously variable transmission (CVT) achieves continuous transmission changes by adjusting the displacement ratio of the pump-motor system and switching the compound planetary gear set. The working state diagram of a single planetary gear set is shown below. Figure 4 As shown, s1, r1, and c1 are the sun gear, ring gear, and planet carrier of planetary gear set P1, respectively; s2, r2, and c2 are the sun gear, ring gear, and planet carrier of planetary gear set P2, respectively. Figure 4 The red components are those that transmit power when the planetary setter is in operation.

[0051] When planetary gear set P1 operates alone, the rotational speeds of the sun gear s1, ring gear r1, and planet carrier c1 of planetary gear set P1 are as follows: [5] As in Formula 1:

[0052] n s1 +p1*n r1 = (1+p1)*n c1 (1)

[0053] In the formula n s1 n r1 n c1 Let be the rotational speed of the sun gear s1, ring gear r1, and planet carrier c1, in r / min; p1 is a constant of the planetary set P1, the size of which is the product of the ratio of the number of teeth of the ring gear r1 to the number of teeth of its meshing gear and the ratio of the number of teeth of the gear meshing with the sun gear s1 to the number of teeth of the sun gear.

[0054] When the sun gear of planetary gear set P2 is the sole output, the rotational speeds of the sun gear s2, ring gear r2, and planet carrier c2 of planetary gear set P2 are as shown in Formula 2:

[0055] n s2 +p2*n r2 = (1+p2)*n c2 (2)

[0056] n s2 n r2 n c2 is the rotational speed (r / min) of the sun gear s2, ring gear r2, and planet carrier c2; p2 is the constant of the planetary set P2; and its magnitude is the ratio of the number of teeth on the ring gear r2 to the number of teeth on the sun gear s2.

[0057] When the sun gear of planetary gear set P2 is the sole output, the rotational speeds on its planet carrier and ring gear are in the same direction as the rotational speeds on planetary gear set P1, i.e., n c2＝ n c1 n r2＝ n r1 The rotational speeds of the sun gear and ring gear of planetary gear set P2 and the sun gear of planetary gear set P1 are related as shown in Formula 3:

[0058]

[0059] Table 1 shows the working states of the four stages of the transmission system and the speed ratio of each stage. In the table, S... r1 S r2 S r3 S r4 The speed ratio for each gear segment (the ratio of the output speed to the input speed of the transmission, n) out / n e ), where i n = i1*i2*i3*i4*i5.

[0060] Table 1. Transmission System Speed ​​Ratio Table

[0061]

[0062] Transmission system gear ratio S r＝ f r (d,e), where d is the transmission system segment.

[0063] Ignoring transmission friction and pump motor system power loss, the working states of the four stages of the transmission system and the output torque of each working stage are shown in Table 2. In the table, T... out1 T out2 T out3 T out4 This represents the output torque for each segment.

[0064] Table 2 HMCVT Torque Characteristics

[0065]

[0066]

[0067] Transmission system gear ratio T out＝ f t (d,e,T e ), where d represents the transmission system segment.

[0068] Overall vehicle speed v t and engine speed n e The relationship between them is shown in Formula 4:

[0069]

[0070] Then the vehicle speed v t =f v( d,e,n e ).

[0071] Overall drive torque T t and the output torque T of the transmission system out The relationship between them is shown in Formula 5:

[0072]

[0073] Overall drive torque T t =f t (d,e,T e ).

[0074] When the tractor is working normally, the dynamic model is as follows: Figure 5 As shown. The tractor's driving torque T t Tractor load torque T f Tractor mass m, overall acceleration a = dv t The relationship between / dt is shown in the figure.

[0075] ma+T f =T t (6)

[0076] Based on the working principle and transmission characteristics of a hydraulic continuously variable transmission (CVT) tractor, a power distribution scheme for the entire tractor was designed, consisting of two main parts: driver intent conversion and power distribution. The first part, driver intent conversion, is as follows: Figure 6 As shown, the steps are a, b, c, and d:

[0077] When operating under heavy load, the machine can accelerate by increasing engine speed and gear ratio when the operator pushes the gear lever. At a constant engine speed, increasing the gear ratio allows for faster speed increase, provided the machine's performance permits.

[0078] like Figure 1-7 As shown, a power matching method for a hydraulic mechanical continuously variable transmission tractor includes the following steps:

[0079] S1. Obtain the driver's requested vehicle speed v. r Calculate the required engine torque T at the requested vehicle speed. tr ;

[0080] Specifically, this includes: after the tractor is powered on, obtaining the current load torque T of the tractor when the overall acceleration is zero through the sensing system. f When the driver accelerates the machine using the driver control system (multi-function armrest or accelerator pedal), the requested speed v of the machine is obtained. r Based on the current requested vehicle speed v r And the current speed v of the whole machine t Calculate the requested acceleration a r ;

[0081] Based on the requested acceleration a r Total load m (tractor mass) and load torque T f Calculate the requested vehicle speed v r The required torque T of the engine tr Ttr =k(ma r+ T f In considering the overall dynamics model, wind resistance, rolling resistance, and frictional resistance are ignored. k is the compensation coefficient for calculating the required driving torque of the whole machine. f The value of T is obtained by combining the engine torque and the actual gear ratio when the machine is moving at a constant speed. f =T ef *(i c *S rac ), S rac T represents the actual gear ratio of the transmission; ef The engine torque represents the engine torque when the entire machine was in a stable state during the previous cycle.

[0082] S2, Calculate the engine speed at the requested vehicle speed v. r The actual minimum rotational speed n pmix and the theoretical minimum engine speed n rmix Take the actual minimum speed n pmix and the theoretical minimum engine speed n rmix The larger value in n is used as the required engine speed n d ;

[0083] Among them, based on the requested vehicle speed v r Calculate the required power P r By consulting the engine external characteristics table for the entire machine, the required power P can be obtained. r The actual minimum speed n of the engine pmix n pmix =f mix (P r );

[0084] Theoretical minimum engine speed n rmix Based on the requested vehicle speed v r And the maximum gear ratio of the whole machine i c *S rmax Calculate the maximum gear ratio i of the entire machine. c *S rmax For the central transmission ratio i c and the maximum gear ratio S of the transmission rmax The product;

[0085] S3, the required rotational speed n d The initial requested engine speed n r Calculate the engine's initial requested speed n. r Maximum driving torque T rmax ;

[0086] The engine's external characteristics table is consulted to obtain the engine's speed at the requested speed n. r Maximum torque Tre By requesting vehicle speed v r and requested rotational speed n r Get the requested gear ratio S rn According to the requested rotational speed n r Maximum torque T re And the requested gear ratio S rn Obtain the maximum driving torque T at the requested speed. rmax =T re / (S rn *i c ).

[0087] S4. If the initial requested rotational speed n r Maximum driving torque T rmax Greater than or equal to the engine's required torque T tr This indicates that the engine is in the requested gear ratio S rn If the maximum driving torque can meet the speed regulation requirements of the entire machine under this operating condition, then no speed compensation is needed. Based on the initial requested speed n... r (at this time n) r =n d Simply control the engine;

[0088] If the initial requested rotational speed n r Maximum driving torque T rmax Less than the engine's required torque T tr This indicates that the engine is requesting gear ratio S. rn The maximum driving torque cannot meet the speed regulation requirements of the entire machine under this operating condition, so speed compensation is required. If compensation is not performed, the engine will slow down or even stall, and the entire machine will stop. This sudden stop will damage the engine and transmission system. To avoid this phenomenon, the required engine speed n is adjusted step by step (for example, every 1% is a step) within the range of the engine's maximum speed (the engine has a speed limit). d Perform speed compensation; after each compensation stage, reduce the requested gear ratio S. rn Make the overall speed of the machine close to the requested speed n. r Continue until the overall speed of the vehicle equals the requested speed n. r Then, the corresponding compensated required rotational speed n d As the requested rotational speed n r Control the engine and coordinate the reduction of the gear ratio until the entire machine maintains the requested vehicle speed n. r superior;

[0089] Based on engine characteristics, the maximum power of an engine increases with its speed. To determine the maximum driving torque T of the engine after reducing the gear ratio and increasing the engine speed while maintaining a constant vehicle speed,... rmaxThe torque will increase when the engine's maximum drive torque at the requested vehicle speed is greater than or equal to the required torque, thus preventing torque build-up due to T. rmax <T tr The engine stalled and the car stopped.

[0090] Reduce the gear ratio until the entire machine maintains the requested speed n. r The method is as follows: obtain the actual acceleration and requested acceleration of the entire machine; adjust the requested gear ratio step by step according to the requested acceleration of the entire machine and the actual rate of change of engine speed until the actual acceleration of the entire machine equals the requested acceleration; specifically, it includes the following steps:

[0091] Overall acceleration control is achieved by controlling the engine's actual speed n. ac The change yields the engine speed change rate a n =dn ac / dt, through the actual gear ratio S of the whole machine rac The change yields the actual speed ratio change rate a s =dS rac / dt, the actual acceleration S of the whole machine rac =n ac *a s +a n *S rac The entire machine requests acceleration a. r and actual acceleration a ac Feedback adjustment request speed ratio change rate a rs a rs =dS rn / dt is a method used to ensure consistency between the requested acceleration and the actual acceleration of the entire machine. Adjustment stops when the requested acceleration and the actual acceleration are consistent.

[0092] The requested gear ratio is achieved by the corresponding requested gear position and the requested displacement ratio of the pump motor (the requested displacement ratio of the pump motor is the ratio of the motor speed to the pump speed).

[0093] To cope with sudden changes and temporary increases in load, the actual torque T at the current vehicle speed is periodically acquired and compared. ac The maximum torque T at the requested speed re If T ac ≥t*T re Where t is the engine torque safety factor, 0 < t < 1, indicating that the load exceeds the control limit, then the engine speed is compensated step by step within the maximum engine speed range; if T ac <t*T re Then no speed compensation is needed.

[0094] Before controlling the engine with the compensated required speed as the requested speed, if the compensated required speed exceeds the engine's maximum speed, the lifting arm is raised step by step within the working stroke range of the lifting arm (for example, every 10% from low to high within the stroke range is one level) to reduce the load until the whole machine maintains the requested speed and the engine's maximum drive torque is greater than or equal to the required torque; if the compensated required speed does not exceed the engine's maximum speed, there is no need to change the lifting arm height.

[0095] A power matching system for a hydraulic mechanical continuously variable transmission tractor includes:

[0096] Driver control module: mainly includes a multi-functional control armrest and accelerator pedal, used to obtain the driver's requested vehicle speed and transmit the obtained signal data to the TCU control module;

[0097] Sensing module: This module consists of sensors used to acquire the load, speed, and torque of the entire machine, and transmit the acquired signal data to the TCU control module.

[0098] The execution module mainly consists of solenoid valves for the clutch, synchronizer, and variable pump. It receives and executes the gear ratio sent by the TCU control module to maintain the machine at the requested speed.

[0099] Engine control module: Used to receive and execute the requested speed sent by the TCU control module, and at the same time feed back the current engine speed and torque to the TCU control module;

[0100] TCU control module: It is used to receive signal data from the driver control module, the sensing module and the engine control module, and send the gear ratio determined by any power matching method and the requested engine speed to the execution module and the engine control module respectively.

[0101] The parts not described in detail in the above embodiments are existing technologies.

[0102] It should be noted that although the present invention has been described through the above embodiments, the present invention may have many other embodiments. Without departing from the spirit and scope of the present invention, those skilled in the art can obviously make various corresponding changes and modifications to the present invention, but all such changes and modifications should fall within the scope of protection of the appended claims and their equivalents.

Claims

1. A power matching method for a hydraulic mechanical continuously variable transmission tractor, characterized in that: Obtain the driver's requested vehicle speed and calculate the engine's required torque at that speed; Calculate the actual minimum engine speed and the theoretical minimum engine speed at the requested vehicle speed, and take the larger value between the actual minimum engine speed and the theoretical minimum engine speed as the required engine speed. The required speed is used as the initial requested speed of the engine, and the maximum driving torque of the engine at the initial requested speed is calculated. If the maximum drive torque at the initial requested speed is greater than or equal to the engine's required torque, then the engine is controlled according to the initial requested speed. If the maximum driving torque at the initial requested speed is less than the engine's required torque, then the engine's required speed is compensated step by step within the engine's maximum speed range, and the compensated required speed is used as the requested speed to control the engine, and the gear ratio is reduced in coordination until the whole machine is maintained at the requested vehicle speed. At this time, the engine's maximum driving torque at the requested vehicle speed is greater than or equal to the required torque. The calculation of the engine's actual minimum speed at the requested vehicle speed includes: calculating the required power based on the requested vehicle speed, querying the engine's external characteristic table for the whole machine, and obtaining the engine's actual minimum speed at the required power. The theoretical minimum engine speed is calculated based on the requested vehicle speed and the maximum gear ratio of the whole machine, where the maximum gear ratio of the whole machine is the product of the central transmission ratio and the maximum gear ratio of the gearbox.

2. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 1, characterized in that, The calculation of the engine torque required at the requested vehicle speed includes: Obtain the load torque when the overall machine acceleration is zero; Get the requested vehicle speed input by the driver and the current vehicle speed of the whole machine, and calculate the requested acceleration based on the requested vehicle speed and the current vehicle speed; Calculate the engine's required torque at the requested vehicle speed based on the requested acceleration, total load, and load torque.

3. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 1, characterized in that, The calculation of the engine's maximum drive torque at the requested speed includes: Query the engine external characteristics table of the whole machine to obtain the maximum torque of the engine at the requested speed, and obtain the requested gear ratio by using the requested vehicle speed and the requested speed; The maximum drive torque at the requested speed is obtained by using the maximum torque at the requested speed and the requested gear ratio.

4. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 3, characterized in that: Periodically acquire and compare the actual torque at the current vehicle speed T ac Maximum torque at the requested speed T re ,like T ac ≥ t T re ,in t For the engine torque safety factor, 0 < t If <1, then speed compensation is performed step by step within the range of the engine's maximum speed to meet the engine's required speed. like T ac < t T re Then no speed compensation is needed.

5. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 1, characterized in that: Before controlling the engine with the compensated required speed as the requested speed, if the compensated required speed exceeds the engine's maximum speed, the lifting arm is raised step by step within the working stroke range of the lifting arm to reduce the load until the whole machine maintains the requested speed and the engine's maximum drive torque is greater than or equal to the required torque; if the compensated required speed does not exceed the engine's maximum speed, there is no need to change the lifting arm height.

6. The power matching method for a hydraulic mechanical continuously variable transmission tractor according to claim 3, characterized in that, Collaboratively reduce the gear ratio until the entire machine maintains the requested speed, including: Obtain the actual acceleration and requested acceleration of the entire machine; The requested gear ratio is adjusted step by step according to the requested acceleration of the whole machine and the actual rate of change of engine speed, until the actual acceleration of the whole machine equals the requested acceleration.

7. A power matching system for a hydraulic mechanical continuously variable transmission tractor, characterized in that, include: Driver control module: used to acquire the driver's requested vehicle speed and transmit the acquired signal data to the TCU control module; Sensing module: Used to acquire the load, speed and torque of the whole machine, and transmit the acquired signal data to the TCU control module; Execution module: Used to receive and execute the gear ratio sent by the TCU control module, so that the whole machine maintains the requested speed; Engine control module: Used to receive and execute the requested speed sent by the TCU control module, and at the same time feed back the current engine speed and torque to the TCU control module; TCU control module: used to receive signal data from the driver control module, the sensing module and the engine control module, and send the gear ratio determined by the power matching method as described in any one of claims 1-6 and the requested engine speed to the execution module and the engine control module respectively.

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