A fully hydrostatic drive and braking system for electric loader based on center of gravity estimation

Abstract

This invention discloses a fully hydrostatic drive and braking system for an electric loader based on center of gravity estimation, comprising a pressure sensor, a bucket cylinder displacement sensor, a boom cylinder displacement sensor, a first motor controller, a second motor controller, a first travel motor, a second travel motor, a first variable pump, a second variable pump, a first four-quadrant pump, a second four-quadrant pump, a first solenoid valve switch, a third solenoid valve switch, a first clutch, a second clutch, and a machine controller. The machine controller receives feedback signals from the pressure sensor, the bucket cylinder displacement sensor, and the boom cylinder displacement sensor, and calculates the center of gravity position using a control algorithm. When the center of gravity is biased towards the front wheels, a single front hydrostatic drive strategy is selected; when the center of gravity is biased towards the rear wheels, a single rear hydrostatic drive strategy is selected.

Description

Technical Field

[0001] This invention relates to the field of engineering machinery technology, specifically to a fully hydrostatic drive and braking system for an electric loader based on center of gravity estimation. Background Technology

[0002] Traditional loaders are typically fixed in four-wheel drive, or front-axle drive or rear-axle drive only. In some applications, this results in significant performance waste, low efficiency, and poor economy. Furthermore, traditional loaders use a combination of diesel engines and hydraulic torque converters, leading to high fuel consumption, poor emissions, and low efficiency. Pure electric loaders use a direct-drive motor, offering advantages such as zero emissions, low noise, and high efficiency. However, they face challenges in terms of installation space, and the load fluctuates dramatically. Typically, a high-power motor is selected to meet the maximum load, resulting in overkill performance for most of the operation. The unstable performance of the motor near zero speed severely impacts the operation of loaders with frequent start-stop conditions, and the instantaneous high-current discharge can reduce battery life, further affecting their application. Summary of the Invention

[0003] In view of this, the present invention addresses the shortcomings of the prior art in the background art, and its main objective is to provide an electric loader fully hydrostatic drive and braking system based on center of gravity estimation, which can effectively solve the shortcomings of the prior art in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a fully hydrostatic drive and braking system for an electric loader based on center of gravity estimation, comprising a pressure sensor, a bucket cylinder displacement sensor, a boom cylinder displacement sensor, a first motor controller, a second motor controller, a first travel motor, a second travel motor, a first variable pump, a second variable pump, a first four-quadrant pump, a second four-quadrant pump, a first solenoid valve switch, a third solenoid valve switch, a first clutch, a second clutch, and a machine controller. The machine controller receives feedback signals from the pressure sensor, the bucket cylinder displacement sensor, and the boom cylinder displacement sensor, and calculates the center of gravity position using a control algorithm.

[0005] When the center of gravity is biased towards the front wheel, a separate front hydrostatic transmission strategy is selected. The separate front hydrostatic transmission strategy is as follows: the whole machine controller calculates the current torque required by the whole machine through the organization layer, and sends a control command to the first motor controller as feedforward control. The first motor controller performs torque control on the first travel motor, and at the same time controls the displacement of the first variable pump and the first four-quadrant pump through the PID algorithm. The first electromagnetic switch valve is in the working position, the first clutch is closed, and separate front hydrostatic transmission is performed.

[0006] When the center of gravity is shifted to the rear wheel, a separate rear hydrostatic transmission strategy is selected. The separate rear hydrostatic transmission strategy is as follows: the whole machine controller calculates the current required speed of the whole machine through the organization layer, and uses the difference between the current speed and the required speed as the input of the PID algorithm. The whole machine controller sends a control command to the second motor controller. The second motor controller controls the speed of the second travel motor. At the same time, it controls the displacement of the second variable pump and the second fourth quadrant pump through a fuzzy control algorithm. The third electromagnetic switch valve is in the working position, the second clutch is closed, and separate rear hydrostatic transmission is performed.

[0007] Preferably, when the demand for driving and braking torque is large or the wheels slip severely, a simultaneous transmission strategy for the front and rear travel devices is selected: the whole machine controller sends a control command to the first motor controller, the first motor controller controls the speed and torque of the first travel motor, controls the displacement of the first variable pump and the first four-quadrant pump, the first electromagnetic switch valve is in the working position, the first clutch is closed, and at the same time, a control command is sent to the second motor controller, the second motor controller controls the speed and torque of the second travel motor, controls the displacement of the second variable pump and the second four-quadrant pump, the third electromagnetic switch valve is in the working position, the second clutch is closed, and the front and rear travel devices are simultaneously driven.

[0008] Preferably, the device also includes a third pressure sensor and a fourth pressure sensor, wherein the first pressure sensor is used to collect the pressure in the rod chamber of the bucket cylinder, the second pressure sensor is used to collect the pressure in the rodless chamber of the bucket cylinder, the third pressure sensor is used to collect the pressure in the rod chambers of the first boom cylinder and the second boom cylinder, and the fourth pressure sensor is used to collect the pressure in the rodless chambers of the first boom cylinder and the second boom cylinder.

[0009] Preferably, the system's overall controller is able to receive signals from the bucket cylinder displacement sensor and the boom cylinder displacement sensor, and estimate the bucket position through the controller's own algorithm.

[0010] Preferably, the bucket cylinder displacement sensor can collect the displacement of the bucket cylinder piston rod, and the boom cylinder displacement sensor can collect the piston rod displacement of the first boom cylinder and the second boom cylinder.

[0011] Preferably, the overall controller can control the displacement of the first variable pump and the second variable pump, and can also control the switching of pump and motor operating conditions and displacement of the first four-quadrant pump and the second four-quadrant pump.

[0012] Preferably, the first and second four-quadrant pumps can be used as pumps or switched to motors.

[0013] Preferably, the motor in this system is a permanent magnet synchronous motor, a switched reluctance motor, a DC motor, or an AC induction motor.

[0014] This invention offers the following advantages: It features three modes: separate front hydrostatic drive, separate rear hydrostatic drive, and simultaneous drive of both front and rear hydrostatic devices. It can estimate the center of gravity position and select the optimal power and economical transmission method. The high power density of the hydraulic accumulator enables rapid response to braking energy conversion and storage requirements, effectively absorbing load impacts, reducing peak motor power demands, and allowing for switching between dual-path braking energy recovery to provide a wide range of braking torque. Simultaneous drive of both front and rear hydrostatic devices meets the demands of sudden large torque changes during digging, and during high-speed transport, it reduces the displacement of the four-quadrant pump to meet maximum vehicle speed requirements. A control strategy for the all-hydrostatic drive and braking system of an electric loader based on center of gravity estimation is proposed. Through a hierarchical control method involving the organization, coordination, and execution layers, the complex calculation time of the overall controller is reduced, improving the frequency response and operational reliability of the electric loader. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the all-hydrostatic drive and braking system for an electric loader based on center of gravity estimation according to the present invention.

[0017] Figure 2 This is a diagram illustrating the control strategy of the all-hydrostatic drive and braking system for an electric loader based on center of gravity estimation, as described in this invention.

[0018] In the diagram: 1-Machine controller, 2-Power battery, 3-High voltage management unit, 4-First motor controller, 5-First travel motor, 6-First variable pump, 7-First relief valve, 8-First solenoid valve, 9-First four-quadrant pump, 10-First clutch, 11-First reducer, 12-First tire, 13-Second tire, 14-Second solenoid valve, 15-Hydraulic accumulator, 16-Second relief valve, 17-Second motor controller, 18-Second travel motor, 19-Second variable pump, 20-Third relief valve, 21-Third solenoid valve, 22-Fourth solenoid valve. 23-Second four-quadrant pump, 24-Second clutch, 25-Second reducer, 26-Third tire, 27-Fourth tire, 28-Third motor controller, 29-Working motor, 30-Third variable pump, 31-Fourth relief valve, 32-First three-position four-way solenoid valve, 33-First pressure sensor, 34-Second pressure sensor, 35-Bucket cylinder, 36-Bucket cylinder displacement sensor, 37-Second three-position four-way solenoid valve, 38-Third pressure sensor, 39-Fourth pressure sensor, 40-First boom cylinder, 41-Second boom cylinder, 42-Boom cylinder displacement sensor. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0020] Example

[0021] The following are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the following embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention.

[0022] As per the instruction manual Figure 1-2As shown, the present invention includes a whole machine controller 1, a power battery 2, a high-voltage management unit 3, a first motor controller 4, a first travel motor 5, a first variable pump 6, a first overflow valve 7, a first electromagnetic switch valve 8, a first four-quadrant pump 9, a first clutch 10, a first reducer 11, a first tire 12, a second tire 13, a second electromagnetic switch valve 14, a hydraulic accumulator 15, a second overflow valve 16, a second motor controller 17, a second travel motor 18, a second variable pump 19, a third overflow valve 20, a third electromagnetic switch valve 21, and a fourth electromagnetic switch valve 22. 2. Second four-quadrant pump 23. Second clutch 24. Second reducer 25. Third tire 26. Fourth tire 27. Third motor controller 28. Work motor 29. Third variable pump 30. Fourth overflow valve 31. First three-position four-way solenoid valve 32. First pressure sensor 33. Second pressure sensor 34. Bucket cylinder 35. Bucket cylinder displacement sensor 36. Second three-position four-way solenoid valve 37. Third pressure sensor 38. Fourth pressure sensor 39. First boom cylinder 40. Second boom cylinder 41. Boom cylinder displacement sensor 42.

[0023] The mechanical connections are as follows: the first travel motor 5 is mechanically connected to the first variable pump 6; the second travel motor 18 is mechanically connected to the second variable pump 19; the working motor 29 is mechanically connected to the third variable pump 30; the first four-quadrant pump 9 is mechanically connected to the first clutch 10; the first clutch 10 is mechanically connected to the first reducer 11; the first reducer 11 is mechanically connected to the first tire 12 and the second tire 13; the second four-quadrant pump 23 is mechanically connected to the second clutch 24; the second clutch 24 is mechanically connected to the second reducer 25; the second reducer 25 is mechanically connected to the third tire 26 and the fourth tire 27; the bucket cylinder displacement sensor 36 is mechanically connected to the bucket cylinder 35; and the boom cylinder displacement sensor 42 is mechanically connected to the first boom cylinder 40.

[0024] The high-voltage connections are as follows: the power battery 2 is electrically connected to the high-voltage management unit 3; the high-voltage management unit 3 is electrically connected to the first motor controller 4, the second motor controller 17, and the third motor controller 28; the first motor controller 4 is electrically connected to the first walking motor 5; the second motor controller 17 is electrically connected to the second walking motor 18; and the third motor controller 28 is electrically connected to the working motor 29.

[0025] The CAN connection relationships are as follows: High-voltage management unit 3, first motor controller 4, first variable pump 6, first solenoid valve 8, first four-quadrant pump 9, second solenoid valve 14, second motor controller 17, second variable pump 19, third solenoid valve 21, fourth solenoid valve 22, second four-quadrant pump 23, third motor controller 28, third variable pump 30, first three-position four-way solenoid valve 32, first pressure sensor 33, second pressure sensor 34, bucket cylinder displacement sensor 36, second three-position four-way solenoid valve 37, third pressure sensor 38, fourth pressure sensor 39, and boom cylinder displacement sensor 42 are respectively connected to the low-voltage electrical connection of the whole machine controller 1, and communicate and control through the CAN network.

[0026] The hydraulic pipeline connections are as follows: the first variable pump 6 is connected to the first relief valve 7 and the first solenoid valve 8 via hydraulic pipelines; the first solenoid valve 8 is connected to the first four-quadrant pump 9 and the second solenoid valve 14 via hydraulic pipelines; the second solenoid valve 14 is connected to the hydraulic accumulator 15, the second relief valve 16, and the fourth solenoid valve 22 via hydraulic pipelines; the second variable pump 19 is connected to the third relief valve 20 and the third solenoid valve 21 via hydraulic pipelines; the third solenoid valve 21 is connected to the fourth solenoid valve 22 and the second four-quadrant pump 23 via hydraulic pipelines; the third variable pump 30 is connected to the fourth relief valve 31, the first three-position four-way solenoid valve 32, and the second three-position four-way solenoid valve 37 via hydraulic pipelines; the first three-position four-way solenoid valve 32 is connected to the bucket cylinder 35 via hydraulic pipelines; and the second three-position four-way solenoid valve 37 is connected to the first boom cylinder 40 and the second boom cylinder 41 via hydraulic pipelines.

[0027] The system works as follows: The loader operator drives the loader according to real-time working conditions. During operation, the first pressure sensor 33, the second pressure sensor 34, the bucket cylinder displacement sensor 36, the third pressure sensor 38, the fourth pressure sensor 39, and the boom cylinder displacement sensor 42 send feedback signals to the machine controller 1 in real time. The machine controller 1 uses the received feedback signals to calculate the center of gravity position through a control algorithm. When the center of gravity is biased towards the front wheels, a separate front hydrostatic transmission strategy is selected; when the center of gravity is biased towards the rear wheels, a separate rear hydrostatic transmission strategy is selected; when the required driving and braking torque is large or wheel slippage is severe, a simultaneous transmission strategy for the front and rear travel devices is selected. During high-speed transport, the machine controller 1 controls the four-quadrant pump to reduce the displacement to achieve the maximum vehicle speed.

[0028] Example A

[0029] When under no-load or light-load conditions, the specifics are as follows:

[0030] The loader operator drives the loader according to real-time working conditions. The first pressure sensor 33, the second pressure sensor 34, the bucket cylinder displacement sensor 36, the third pressure sensor 38, the fourth pressure sensor 39, and the boom cylinder displacement sensor 42 send feedback signals to the machine controller 1 in real time. The machine controller 1 uses the received feedback signals and calculates the center of gravity position using a control algorithm. At this point, the center of gravity is biased towards the rear wheel, and a separate rear hydrostatic drive strategy is selected. The machine controller 1 sends control commands to the second motor controller 17, which controls the speed and torque of the second travel motor 18, while simultaneously controlling the displacement of the second variable pump 19 and the second fourth-quadrant pump 23. The third solenoid valve 21 is in the working position, closing the second clutch 24 to perform separate rear hydrostatic drive, satisfying both power requirements and improving economy.

[0031] Example B

[0032] When under heavy-load transportation conditions, the specifics are as follows:

[0033] The loader operator drives the loader according to real-time working conditions. The first pressure sensor 33, the second pressure sensor 34, the bucket cylinder displacement sensor 36, the third pressure sensor 38, the fourth pressure sensor 39, and the boom cylinder displacement sensor 42 send feedback signals to the machine controller 1 in real time. The machine controller 1 uses the received feedback signals and calculates the center of gravity position using a control algorithm. At this point, the center of gravity is biased towards the front wheels, and a separate front hydrostatic transmission strategy is selected. The machine controller 1 sends control commands to the first motor controller 4. The first motor controller 4 controls the speed and torque of the first travel motor 5, and simultaneously controls the displacement of the first variable pump 6 and the first four-quadrant pump 9. The first solenoid valve 8 is in the working position, and the first clutch 10 is closed, enabling separate front hydrostatic transmission, which satisfies both power requirements and improves economy.

[0034] Example C

[0035] When the wheels are slipping severely or during digging operations, the specific situation is as follows:

[0036] The loader operator drives the loader according to real-time working conditions. The machine controller 1 receives feedback signals from the operator, calculates the loaders using a control algorithm, and selects a simultaneous drive strategy for the front and rear travel devices. The machine controller 1 sends control commands to the first motor controller 4, which controls the speed and torque of the first travel motor 5, controls the displacement of the first variable pump 6 and the first four-quadrant pump 9, puts the first solenoid valve 8 in the working position, and closes the first clutch 10. Simultaneously, the machine controller 1 sends control commands to the second motor controller 17, which controls the speed and torque of the second travel motor 18, and controls the displacement of the second variable pump 19 and the second four-quadrant pump 23. The third solenoid valve 21 is in the working position, closes the second clutch 24, and performs simultaneous drive of the front and rear travel devices, further improving the loader's operational performance and power.

[0037] Example D

[0038] When braking, the specifics are as follows:

[0039] The first pressure sensor 33, the second pressure sensor 34, the bucket cylinder displacement sensor 36, the third pressure sensor 38, the fourth pressure sensor 39, and the boom cylinder displacement sensor 42 send feedback signals to the machine controller 1 in real time. The machine controller 1 uses the received feedback signals to calculate the center of gravity position through a control algorithm. When the braking torque demand is small and the center of gravity is shifted towards the rear wheels, a separate rear hydrostatic drive strategy is selected for brake energy recovery and reuse. When the braking torque demand is small and the center of gravity is shifted towards the front wheels, a separate front hydrostatic drive strategy is selected for brake energy recovery and reuse. When the braking torque demand is large, a simultaneous drive strategy for both the front and rear travel devices is selected for brake energy recovery and reuse.

[0040] The electric loader of the present invention is a fully hydrostatic drive and braking system based on center of gravity estimation, which can be applied to various working conditions of construction machinery to realize drive and braking functions, and is especially suitable for loaders with severe load fluctuations, frequent start and stop, and large center of gravity changes.

[0041] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A fully hydrostatic drive and braking system for an electric loader based on center of gravity estimation, characterized in that, It includes a pressure sensor, a bucket cylinder displacement sensor, a boom cylinder displacement sensor, a first motor controller, a second motor controller, a first travel motor, a second travel motor, a first variable pump, a second variable pump, a first four-quadrant pump, a second four-quadrant pump, a first solenoid valve switch, a third solenoid valve switch, a first clutch, a second clutch, and a machine controller. The machine controller receives feedback signals from the pressure sensor, the bucket cylinder displacement sensor, and the boom cylinder displacement sensor, and calculates the center of gravity position through a control algorithm. When the center of gravity is biased towards the front wheel, a separate front hydrostatic transmission strategy is selected. The separate front hydrostatic transmission strategy is as follows: the whole machine controller calculates the current torque required by the whole machine through the organization layer, and sends a control command to the first motor controller as feedforward control. The first motor controller performs torque control on the first travel motor, and at the same time controls the displacement of the first variable pump and the first four-quadrant pump through the PID algorithm. The first electromagnetic switch valve is in the working position, the first clutch is closed, and separate front hydrostatic transmission is performed. When the center of gravity is shifted to the rear wheel, a separate rear hydrostatic transmission strategy is selected. The separate rear hydrostatic transmission strategy is as follows: the whole machine controller calculates the current required speed of the whole machine through the organization layer, and uses the difference between the current speed and the required speed as the input of the PID algorithm. The whole machine controller sends a control command to the second motor controller. The second motor controller controls the speed of the second travel motor. At the same time, it controls the displacement of the second variable pump and the second fourth quadrant pump through a fuzzy control algorithm. The third electromagnetic switch valve is in the working position, the second clutch is closed, and separate rear hydrostatic transmission is performed.

2. The all-hydrostatic drive and braking system for electric loaders based on center of gravity estimation according to claim 1, characterized in that, When the demand-driven braking torque is large or the wheels slip severely, a simultaneous transmission strategy for the front and rear travel devices is selected: The main controller sends a control command to the first motor controller, which controls the speed and torque of the first travel motor, controls the displacement of the first variable pump and the first four-quadrant pump, the first solenoid valve is in the working position, the first clutch is closed, and at the same time, it sends a control command to the second motor controller, which controls the speed and torque of the second travel motor, controls the displacement of the second variable pump and the second four-quadrant pump, the third solenoid valve is in the working position, the second clutch is closed, and the front and rear travel devices are simultaneously driven.

3. The all-hydrostatic drive and braking system for electric loaders based on center of gravity estimation according to claim 1, characterized in that, It also includes a third pressure sensor and a fourth pressure sensor, wherein the first pressure sensor is used to collect the pressure of the rod chamber of the bucket cylinder, the second pressure sensor is used to collect the pressure of the rodless chamber of the bucket cylinder, the third pressure sensor is used to collect the pressure of the rod chambers of the first boom cylinder and the second boom cylinder, and the fourth pressure sensor is used to collect the pressure of the rodless chambers of the first boom cylinder and the second boom cylinder.

4. The all-hydrostatic drive and braking system for electric loaders based on center of gravity estimation according to claim 1, characterized in that, The system's overall controller can receive signals from the bucket cylinder displacement sensor and the boom cylinder displacement sensor, and estimate the bucket position through the controller's internal PID algorithm.

5. The all-hydrostatic drive and braking system for electric loaders based on center of gravity estimation according to claim 4, characterized in that, The bucket cylinder displacement sensor can collect the displacement of the piston rod of the bucket cylinder, and the boom cylinder displacement sensor can collect the displacement of the piston rods of the first boom cylinder and the second boom cylinder.

6. The all-hydrostatic drive and braking system for electric loaders based on center of gravity estimation according to claim 1, characterized in that, The overall controller can control the displacement of the first variable pump and the second variable pump, and can also control the switching of pump and motor operating conditions and displacement of the first four-quadrant pump and the second four-quadrant pump.

7. The all-hydrostatic drive and braking system for electric loaders based on center of gravity estimation according to claim 1, characterized in that, The first and second four-quadrant pumps can be used as pumps or switched to motors.

8. The all-hydrostatic drive and braking system for electric loaders based on center of gravity estimation according to claim 1, characterized in that, The motor in this system can be a permanent magnet synchronous motor, a switched reluctance motor, a DC motor, or an AC induction motor.

Images