CN112814069A - Wheel loader and control method - Google Patents

Wheel loader and control method Download PDF

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Publication number
CN112814069A
CN112814069A CN202011603255.9A CN202011603255A CN112814069A CN 112814069 A CN112814069 A CN 112814069A CN 202011603255 A CN202011603255 A CN 202011603255A CN 112814069 A CN112814069 A CN 112814069A
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engine
transmission
power
hydraulic
control unit
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Inventor
刘志明
张卫东
刘艳芳
李莺莺
郄松涛
贾启康
乔征
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Tianjin Research Institute Of Construction Machinery Co ltd
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Tianjin Research Institute Of Construction Machinery Co ltd
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/202—Mechanical transmission, e.g. clutches, gears
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/2058—Electric or electro-mechanical or mechanical control devices of vehicle sub-units
    • E02F9/2062—Control of propulsion units
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives

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  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Control Of Transmission Device (AREA)
  • Operation Control Of Excavators (AREA)

Abstract

The invention discloses a wheel loader and a control method, comprising an engine, a hydraulic mechanical stepless speed changer, a hydraulic pump, a transmission shaft and a power transmission system of a drive axle; the hydraulic mechanical stepless speed changer comprises a mechanical transmission pair, a hydrostatic stepless transmission pair consisting of a hydrostatic pump and a hydrostatic motor and a PTO power output device; the mechanical transmission pair and the hydrostatic stepless transmission pair are converged by a converging mechanism to output power; the control system comprises a complete machine control unit VCU, a hydraulic mechanical continuously variable transmission control unit TCU and an engine control unit ECU; the control unit carries out information interaction through the interface communication module. According to the invention, the automatic distribution of the power of the transmission system and the power of the hydraulic system can be realized through the control system, the total power requirement is not more than the maximum output power of the engine, and the engine is prevented from being flameout due to overload; meanwhile, the efficient power distribution system utilizes the power of the engine to the maximum extent, improves the working efficiency of the whole machine and reduces the working oil consumption.

Description

Wheel loader and control method
Technical Field
The invention belongs to the field of engineering machinery, and particularly relates to a wheel loader applying hydraulic machinery stepless transmission and a control method.
Background
The wheel loader is one of the most widely applied earth moving machines in engineering machinery products, and the performance of the whole machine cannot be fully exerted and the fuel economy is low due to the fact that the working condition is complex, the load change is severe, and the power of an engine cannot be effectively utilized.
The current conventional wheel loaders employ a torque converter based transmission system. Although the hydraulic torque converter has good self-adaptability and good starting performance, the hydraulic torque converter can carry out overload protection on the engine and has great effects on the operation of a driver and the improvement of productivity. However, the hydraulic torque converter has a narrow working high-efficiency region and low transmission efficiency, and under an operating environment with complex working conditions and severe load, the power of an engine cannot be effectively utilized, so that the performance of the whole machine cannot be fully exerted, the fuel economy is low, and the increasingly strict emission standard and the requirement of users on reducing the operating cost cannot be met.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a wheel loader and a control method thereof. Based on the characteristic, the loader completely decouples the rotating speed of the engine and the vehicle speed during the working cycle, fully utilizes the power of the engine, allows the engine to work near the optimal oil consumption point, and improves the efficiency of the whole machine and the fuel economy.
The present invention is achieved as such, a wheel loader comprising: the hydraulic control system comprises an engine, a continuously variable transmission, a hydraulic pump for providing hydraulic power for a loader hydraulic system, a power transmission system of a transmission shaft and a drive axle, a complete machine control unit VCU, a hydraulic mechanical continuously variable transmission control unit TCU and an engine control unit ECU; the method is characterized in that: the power transmission system is arranged at the rear part of the loader body; the continuously variable transmission is an integrated hydraulic mechanical continuously variable transmission and comprises a direction clutch assembly, and the direction clutch assembly realizes the forward and backward movement of the loader;
the hydrostatic stepless transmission device can realize low-speed forward and backward of the loader by changing a variable mechanism of a hydraulic pump, and can realize stepless speed change among multi-gear speed ratios by changing a displacement ratio; the hydraulic power transmission device is composed of a transfer gear, a hydrostatic pump, a hydrostatic motor and the like; the PTO power output device can absorb the power output by the engine and transmit the power to the hydraulic pump to drive the working device to act; the planetary confluence mechanism can couple the torque transmitted by the engine through the gear mechanical transmission pair and the torque output by the hydrostatic stepless transmission device, so that the power transmitted in various ways can be effectively output; the motor clutch assembly can realize the motor power separation and combination of the hydrostatic stepless transmission device; the high-low gear clutch assembly can realize low-speed work and high-speed walking of the loader; the gear mechanical transmission pair is used for realizing power transmission among the directional clutch assembly, the hydrostatic stepless transmission device, the PTO power output, the planetary confluence mechanism, the motor clutch assembly and the high-low gear clutch assembly; and the complete machine control unit VCU, the hydraulic mechanical continuously variable transmission control unit TCU and the engine control unit ECU control unit carry out information interaction through the interface communication module.
Preferably, in the above technical solution, the hydraulic pump is a variable displacement hydraulic pump with an electric proportional swash plate swing angle control function cut off by a controller.
According to the control method of the wheel loader, the complete machine control unit VCU is used for sending an engine rotating speed request instruction according to a pilot handle, an accelerator pedal, a driving mode parameter and a brake pedal parameter when a vehicle runs; similarly, the TCU transmission case controller collects the output torque and the rotating speed information of the transmission in real time, and calculates the expected torque value of the transmission by combining the operation of a pilot handle, an accelerator pedal, a driving mode, a brake pedal and other drivers; the method comprises the following steps that a hydraulic mechanical stepless transmission control unit TCU receives an engine rotating speed request instruction, performs engine target rotating speed control by combining a transmission expected torque, and can generate a hydraulic system maximum available torque percentage and a transmission system maximum available torque percentage in real time according to real-time maximum available torque information sent by an engine control unit ECU; when the expected torque value of the gearbox exceeds the torque value corresponding to the maximum available torque percentage of the hydraulic mechanical continuously variable transmission, the TCU gearbox controller controls the speed ratio of the transmission and reduces the absorption torque of the transmission; when the torque value does not exceed the torque value corresponding to the maximum available torque percentage of the hydraulic mechanical stepless transmission, the TCU gearbox controller sends engine target rotating speed information according to the expected torque value of the transmission, and the ECU engine controller controls the rotating speed of the engine according to the information.
The whole machine control system can realize power distribution of a hydraulic system and a power transmission system according to the state parameters of the whole vehicle and the operation of a driver, so as to control the total power of the loader and realize the overload protection of the engine; when the load is increased, the rotating speed of the engine is instantaneously reduced due to the limitation of a physical structure, and when the engine stall speed is within an allowable range, the VCU vehicle controller judges the engine stall speed to be normal; when the engine stall speed exceeds the allowable range, the VCU vehicle controller judges that the engine is not enough to bear the current load, and sends a target power limit information instruction to limit the maximum swing angle of the swash plate of the hydraulic pump, reduce the absorption torque of the hydraulic pump and perform feedback regulation through the equivalent torque of the hydraulic system.
The VCU vehicle control unit adjusts the opening of the pilot valve according to the current engine rotating speed and the position of the movable arm and the rocker arm and through a PI algorithm, and the calculation formula is as follows:
Figure BDA0002871985920000031
in the formula: u (t) is a certain pilot valve opening; k is a radical ofp、kiProportional coefficient and integral coefficient; alpha is alpha1、α2Is a weight systemCounting; n isengIs the engine speed; a istThe current position angle of the movable arm or the rocker arm; a is0Calibrating a position angle for a movable arm or a rocker arm;
the invention has the advantages and positive effects that: compared with the prior art, the power split transmission is carried out through the hydraulic mechanical stepless transmission, the hydraulic mechanical stepless speed regulation and mechanical transmission high-efficiency characteristics are achieved, meanwhile, complete decoupling of the speed and the rotating speed of the engine can be achieved, the engine can work in a high-efficiency area, and the fuel economy of loader operation is effectively improved. The control system can automatically distribute the walking power and the hydraulic system power in real time according to the working conditions, so that the power of the engine is effectively utilized, the total power requirement is not more than the maximum output power of the engine, the engine is prevented from being flamed out due to overload, and the working efficiency and the operation comfort are improved. Another significant benefit brought by the invention is that the engine power requirement can be reduced when the complete machine is matched with power, the cost of the complete machine is effectively reduced, and the competitive advantage of the product is improved. The whole machine control system can optimally control a hydraulic pilot system of a working device, the opening degree of the pilot valve is adjusted through a PI algorithm according to the current engine rotating speed and the position of a swing arm of a movable arm, auxiliary automatic operation such as automatic leveling, automatic returning, automatic lifting, automatic bucket collecting of shovel loading and the like is realized, the dependence on the operation proficiency of a driver is reduced, and the working efficiency is improved.
Drawings
Figure 1 is a schematic view of a wheel loader and a power transmission system;
FIG. 2 is a hydromechanical continuously variable transmission transfer diagram;
FIG. 3 is a block diagram of a wheel loader control system;
FIG. 4 is a schematic diagram of engine overload protection;
fig. 5 is a flow chart of the auxiliary automatic work.
In the figure: 1. a loader body; 2. an engine; 3. a hydro-mechanical continuously variable transmission; 3.1, a static pressure pump; 3.2, a static pressure motor; 3.3, PTO power output device; 3.4, a confluence mechanism; 3.5, front and back power output; 3.6, a high-low gear clutch assembly; 4. a hydraulic pump; 5. a drive shaft; 6. a drive axle.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1 and 3, a wheel loader includes: the system comprises an engine 2, a continuously variable transmission, a hydraulic pump 4 for providing hydraulic power for a loader hydraulic system, a power transmission system of a transmission shaft 5 and a drive axle 6, a complete machine control unit VCU, a hydraulic mechanical continuously variable transmission control unit TCU and an engine control unit ECU; the power transmission system is arranged at the rear part of the loader body 1; the continuously variable transmission is an integrated hydraulic mechanical continuously variable transmission 3 and comprises a direction clutch assembly 3.1, and the direction clutch assembly 3.1 realizes the forward and backward movement of the loader; the hydrostatic stepless transmission device 3.2 can realize low-speed forward and backward of the loader by changing a variable mechanism of a hydraulic pump, and can realize stepless speed change among multiple speed ratios by changing a displacement ratio; the hydraulic power transmission device is composed of a transfer gear, a hydrostatic pump, a hydrostatic motor and the like; the PTO power output device 3.3 can absorb the power output by the engine and transmit the power to the hydraulic pump to drive the working device to act; the planetary confluence mechanism 3.4 can couple the torque transmitted by the engine through the gear mechanical transmission pair and the torque output by the hydrostatic stepless transmission device 3.2, so that the power transmitted in various ways can be effectively output; the motor clutch assembly 3.5, the motor clutch assembly 3.5 can realize the motor power separation and combination to the hydrostatic stepless transmission device; the high-low gear clutch assembly 3.6 and the high-low gear clutch assembly 3.6 can realize low-speed work and high-speed walking of the loader; the gear mechanical transmission pair is used for realizing power transmission among the directional clutch assembly 3.1, the hydrostatic stepless transmission device 3.2, the PTO power output 3.3, the planetary confluence mechanism 3.4, the motor clutch assembly 3.5 and the high-low gear clutch assembly 3.6; the structures and the working principles of the directional clutch assembly 3.1, the hydrostatic stepless transmission device 3.2, the PTO power output 3.3, the planetary confluence mechanism 3.4, the motor clutch assembly 3.5 and the high-low gear clutch assembly 3.6 belong to the prior art, and are not described herein again.
According to the wheel loader control method, the complete machine control unit VCU is used for sending an engine rotating speed request instruction according to a pilot handle, an accelerator pedal, a driving mode parameter and a brake pedal parameter when a vehicle runs; similarly, the TCU transmission case controller collects the output torque and the rotating speed information of the transmission in real time, and calculates the expected torque value of the transmission by combining the operation of a pilot handle, an accelerator pedal, a driving mode, a brake pedal and other drivers; the method comprises the following steps that a hydraulic mechanical stepless transmission control unit TCU receives an engine rotating speed request instruction, performs engine target rotating speed control by combining a transmission expected torque, and can generate a hydraulic system maximum available torque percentage and a transmission system maximum available torque percentage in real time according to real-time maximum available torque information sent by an engine control unit ECU; when the expected torque value of the transmission exceeds the torque value corresponding to the maximum available torque percentage of the hydraulic mechanical continuously variable transmission, the TCU transmission controller controls the speed ratio of the transmission to reduce the absorption torque of the transmission; when the torque value does not exceed the torque value corresponding to the maximum available torque percentage of the hydraulic mechanical stepless transmission, the TCU gearbox controller sends engine target rotating speed information according to the expected torque value of the transmission, and the ECU engine controller controls the rotating speed of the engine according to the information.
The whole machine control system can realize power distribution of a hydraulic system and a power transmission system according to the state parameters of the whole vehicle and the operation of a driver, so as to control the total power of the loader and realize the overload protection of the engine; when the load is increased, the rotating speed of the engine is instantaneously reduced due to the limitation of a physical structure, and when the engine stall speed is within an allowable range, the VCU vehicle controller judges the engine stall speed to be normal; when the engine stall speed exceeds the allowable range, the VCU vehicle controller judges that the engine is not enough to bear the current load, and sends a target power limit information instruction to limit the maximum swing angle of a hydraulic pump swash plate, reduce the absorption torque of the hydraulic pump and perform feedback regulation through the equivalent torque of a hydraulic system;
the VCU vehicle control unit adjusts the opening of the pilot valve according to the current engine rotating speed and the position of the movable arm rocker arm and through a PI algorithm, and the calculation formula is as follows:
Figure BDA0002871985920000061
in the formula: u (t) is a certain pilot valve opening; k is a radical ofp、kiProportional coefficient and integral coefficient; alpha is alpha1、α2Is a weight coefficient; n isengIs the engine speed; a istThe current position angle of the movable arm or the rocker arm; a is0Calibrating a position angle for a movable arm or a rocker arm; the hydraulic pump is a variable hydraulic pump with an electric proportional swash plate swing angle control function and is cut off by a controller.
According to the technical scheme, information interaction is carried out among the complete machine control unit VCU, the hydraulic mechanical continuously variable transmission control unit TCU and the engine control unit ECU through the interface communication module. The shovel can not only output large torque at low speed to carry out shoveling operation, but also can efficiently utilize the power of the engine at high speed to drive the vehicle; the whole machine control system mainly comprises an ECU engine controller, a TCU gearbox controller and a VCU whole machine controller, and performs information interaction and control method through an interface communication module. The automatic distribution of the power of a transmission system and the power of a hydraulic system can be realized based on the vehicle type, the total power requirement is not more than the maximum output power of an engine, and the overload flameout of the engine is avoided; the power is efficiently distributed, the power of the engine is utilized to the maximum extent, powerful power is output, and the oil consumption of operation is reduced. Meanwhile, the control method can optimize and adjust the opening of the pilot valve according to vehicle information, realize auxiliary autonomous operations such as automatic leveling, automatic returning, automatic lifting, shovel loading and automatic bucket collecting, reduce the dependence on the operation proficiency of a driver and improve the operation efficiency.
In summary, the real-time torque of the hydraulic system and the real-time torque of the hydraulic mechanical continuously variable transmission are less than or equal to the maximum available torque of the engine, so that the control system realizes power distribution of the hydraulic system and the power transmission system and total power control of the loader, and overload protection of the engine is realized.
Fig. 4 is an example of the wheel loader control system of the present invention implementing an engine overload protection function. and a is a real-time maximum available torque curve of the engine, and b is a real-time expected torque curve (sum of equivalent torque of a hydraulic system and real-time expected torque of a hydraulic mechanical continuously variable transmission) of the whole machine. When the real-time expected torque value of the whole machine exceeds the maximum available torque curve a of the engine, such as the curve c section, the system judges that the engine is overloaded at the moment, and controls the speed ratio of the speed changer or the swing angle of the hydraulic pump in real time according to the curve section d. In the section, the control system ensures that the total torque of the whole machine does not exceed the maximum available torque of the engine by reducing the power of the hydraulic pump or the absorption torque of the transmission, thereby ensuring that the engine does not overload to cause flameout.
Fig. 5 is a flow chart of an auxiliary automatic operation. Firstly, a driver needs to finish the position calibration of the movable arm and the rocker arm in the flat position, the recovery position and the lifting position, and then the position information can be stored after the position calibration is finished so as to be convenient for subsequent reading. When a driver selects an auxiliary automatic operation mode, the VCU vehicle controller respectively adjusts the opening degrees of a plurality of pilot valves by integrating the rotating speed of the engine and the positions of the movable arm and the rocker arm through a PI algorithm to realize the lifting and the descending of the movable arm and the receiving and the discharging of the rocker arm, so that the movable arm and the rocker arm move to expected calibration positions to complete auxiliary operation.
Although preferred embodiments of this patent have been described above with reference to the accompanying drawings, the patent is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and those skilled in the art can make many modifications without departing from the spirit and scope of the patent as defined by the appended claims.

Claims (2)

1. A wheel loader and a control method, comprising: the hydraulic control system comprises an engine, a continuously variable transmission, a hydraulic pump for providing hydraulic power for a loader hydraulic system, a power transmission system of a transmission shaft and a drive axle, a complete machine control unit VCU, a hydraulic mechanical continuously variable transmission control unit TCU and an engine control unit ECU; the method is characterized in that: the power transmission system is arranged at the rear part of the loader body; the continuously variable transmission is an integrated hydraulic mechanical continuously variable transmission and comprises a direction clutch assembly, and the direction clutch assembly realizes the forward and backward movement of the loader; the hydrostatic stepless transmission device can realize low-speed forward and backward of the loader by changing a variable mechanism of a hydraulic pump, and can realize stepless speed change among multi-gear speed ratios by changing a displacement ratio; the transfer gear comprises a transfer gear, a hydrostatic pump and a hydrostatic motor; the PTO power output device can absorb the power output by the engine and transmit the power to the hydraulic pump to drive the working device to act; the planetary confluence mechanism can couple the torque transmitted by the engine through the gear mechanical transmission pair and the torque output by the hydrostatic stepless transmission device, so that the power transmitted in various ways can be effectively output; the motor clutch assembly can realize the motor power separation and combination of the hydrostatic stepless transmission device; the high-low gear clutch assembly can realize low-speed work and high-speed walking of the loader; the gear mechanical transmission pair is used for realizing power transmission among the directional clutch assembly, the hydrostatic stepless transmission device, the PTO power output, the planetary confluence mechanism, the motor clutch assembly and the high-low gear clutch assembly; and the complete machine control unit VCU, the hydraulic mechanical continuously variable transmission control unit TCU and the engine control unit ECU control unit carry out information interaction through the interface communication module.
According to the control method of the wheel loader, the complete machine control unit VCU is used for sending an engine rotating speed request instruction according to a pilot handle, an accelerator pedal, a driving mode parameter and a brake pedal parameter when a vehicle runs; similarly, the TCU transmission case controller collects the output torque and the rotating speed information of the transmission in real time, and calculates the expected torque value of the transmission by combining the operation of a pilot handle, an accelerator pedal, a driving mode, a brake pedal and other drivers; the method comprises the following steps that a hydraulic mechanical stepless transmission control unit TCU receives an engine rotating speed request instruction, performs engine target rotating speed control by combining a transmission expected torque, and can generate a hydraulic system maximum available torque percentage and a transmission system maximum available torque percentage in real time according to real-time maximum available torque information sent by an engine control unit ECU; when the expected torque value of the transmission exceeds the torque value corresponding to the maximum available torque percentage of the hydraulic mechanical continuously variable transmission, the TCU transmission controller controls the speed ratio of the transmission and reduces the absorption torque of the transmission; when the torque value does not exceed the torque value corresponding to the maximum available torque percentage of the hydraulic mechanical stepless transmission, the TCU gearbox controller sends engine target rotating speed information according to the expected torque value of the transmission, and the ECU engine controller controls the rotating speed of the engine according to the information.
The whole machine control system can realize power distribution of a hydraulic system and a power transmission system according to the state parameters of the whole vehicle and the operation of a driver, so as to control the total power of the loader and realize the overload protection of the engine; when the load is increased, the rotating speed of the engine is instantaneously reduced due to the limitation of a physical structure, and when the engine stall speed is within an allowable range, the VCU vehicle controller judges the engine stall speed to be normal; when the engine stall speed exceeds the allowable range, the VCU vehicle controller judges that the engine is not enough to bear the current load, and sends a target power limit information instruction to limit the maximum swing angle of the swash plate of the hydraulic pump, reduce the absorption torque of the hydraulic pump and perform feedback regulation through the equivalent torque of the hydraulic system.
The VCU vehicle control unit adjusts the opening of the pilot valve according to the current engine rotating speed and the position of the movable arm and the rocker arm and through a PI algorithm, and the calculation formula is as follows:
Figure FDA0002871985910000021
in the formula: u (t) is a certain pilot valve opening; k is a radical ofp、kiProportional coefficient and integral coefficient; alpha is alpha1、α2Is a weight coefficient; n isengIs the engine speed; a istThe current position angle of the movable arm or the rocker arm; a is0And calibrating the position angle for the movable arm or the rocker arm.
2. The wheel loader and the control method according to claim 1, characterized in that: the hydraulic pump is a variable hydraulic pump with an electric proportional swash plate swing angle control function and is cut off by a controller.
CN202011603255.9A 2020-12-30 2020-12-30 Wheel loader and control method Withdrawn CN112814069A (en)

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CN113338385A (en) * 2021-06-21 2021-09-03 上海宏英智能科技股份有限公司 Loader bucket leveling system
CN114430950A (en) * 2022-01-24 2022-05-06 潍柴雷沃重工股份有限公司 Tractor lifter control method and device, storage medium and tractor
CN115013525A (en) * 2022-05-31 2022-09-06 合肥工业大学 Control method for transmission mode switching of double-flow transmission speed change system

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113338385A (en) * 2021-06-21 2021-09-03 上海宏英智能科技股份有限公司 Loader bucket leveling system
CN113338385B (en) * 2021-06-21 2022-07-26 上海宏英智能科技股份有限公司 Loader bucket leveling system
CN114430950A (en) * 2022-01-24 2022-05-06 潍柴雷沃重工股份有限公司 Tractor lifter control method and device, storage medium and tractor
CN115013525A (en) * 2022-05-31 2022-09-06 合肥工业大学 Control method for transmission mode switching of double-flow transmission speed change system
CN115013525B (en) * 2022-05-31 2023-07-25 合肥工业大学 Control method for switching transmission modes of double-flow transmission speed change system

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