Electric loader full-hydrostatic driving and braking system based on gravity center estimation

Abstract

The invention discloses an electric loader full-hydrostatic driving and braking system based on gravity center estimation. Comprising a pressure sensor, a bucket oil cylinder displacement sensor, a large arm oil cylinder displacement sensor, a first motor controller, a second motor controller, a first walking motor, a second walking motor, a first variable pump, a second variable pump, a first four-quadrant pump, a second four-quadrant pump, a first electromagnetic valve switch, a third electromagnetic valve switch and a first clutch. The complete machine controller receives feedback signals of the pressure sensor, the bucket oil cylinder displacement sensor and the large arm oil cylinder displacement sensor and obtains the gravity center position after calculation through a control algorithm; when the gravity center deviates from the front wheel, an independent front hydrostatic transmission strategy is selected, and when the gravity center deviates from the rear wheel, an independent rear hydrostatic transmission strategy is selected.

Description

Technical Field

[0001] The invention relates to the technical field of engineering machinery, and in particular to a fully hydrostatic drive and brake system of an electric loader based on gravity center estimation. Background Art

[0002] Traditional loaders are usually fixed to four-wheel drive, or can only drive the front axle or the rear axle. In some working conditions, this causes a lot of performance waste, low efficiency, poor economy and other problems. At the same time, traditional loaders use a combination of diesel engines and torque converters, which have problems such as high fuel consumption, poor emissions and low efficiency. Pure electric loaders use direct motor drive, which has the advantages of zero emissions, low noise and high efficiency, but the installation space is difficult to arrange. At the same time, the load of the loader fluctuates violently. Usually, a high-power motor that meets the maximum load is selected during installation, resulting in excess performance most of the time during the operation. The problem of unstable performance of the motor near zero speed seriously affects the operation of loaders with frequent start-stop conditions, and the instantaneous large current discharge easily causes a decrease in battery life, which affects its application. Summary of the invention

[0003] In view of this, the present invention aims at the deficiencies of the existing technology in the background technology, and its main purpose is to provide a fully hydrostatic drive and braking system for an electric loader based on center of gravity estimation, which can effectively solve the deficiencies of the existing technology in the background technology.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a fully hydrostatic drive and brake 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 whole machine controller, wherein the whole machine controller receives feedback signals of the pressure sensor, the bucket cylinder displacement sensor and the boom cylinder displacement sensor and obtains the center of gravity position after calculation by a control algorithm;

[0005] When the center of gravity is biased toward the front wheel, a separate front hydrostatic transmission strategy is selected, wherein the separate front hydrostatic transmission strategy is as follows: the whole machine controller calculates the current required torque of the whole machine through the organizational layer, and as a feedforward control, sends a control instruction to the first motor controller, and the first motor controller controls the torque of 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 the separate front hydrostatic transmission is performed;

[0006] When the center of gravity is biased towards the rear wheel, a separate rear hydrostatic transmission strategy is selected. The separate rear hydrostatic transmission strategy is: the whole machine controller calculates the current required vehicle speed of the whole machine through the organizational layer, and uses the difference between the current vehicle speed and the required vehicle speed as the PID algorithm input. The whole machine controller sends a control instruction to the second motor controller, and the second motor controller controls the speed of the second travel motor. At the same time, the displacement of the second variable pump and the second four-quadrant pump is controlled through the fuzzy control algorithm. The third solenoid switch valve is in the working position, and the second clutch is closed to perform a separate rear hydrostatic transmission.

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

[0008] Preferably, a third pressure sensor and a fourth pressure sensor are also included, 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 chamber of the first boom cylinder and the second boom cylinder, and the fourth pressure sensor is used to collect the pressure of the rodless chamber of the first boom cylinder and the second boom cylinder.

[0009] Preferably, the whole machine controller of the system is capable of receiving signals from the bucket cylinder displacement sensor and the boom cylinder displacement sensor, and estimating 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 displacement of the piston rods of the first boom cylinder and the second boom cylinder.

[0011] Preferably, the whole machine controller can control the displacement of the first variable pump and the second variable pump, and can also control the operating mode switching and displacement of the pumps and motors of the first four-quadrant pump and the second four-quadrant pump.

[0012] Preferably, the first four-quadrant pump and the second four-quadrant pump can be used as pumps and can also be used as motors in a switched working state.

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

[0014] The present invention has the following beneficial effects: the present invention has three modes: separate front hydrostatic transmission, separate rear hydrostatic transmission, and simultaneous transmission of front and rear hydrostatic devices. It can estimate the center of gravity position and select the transmission mode with the best power and economy. The high power density of the hydraulic accumulator can quickly respond to the requirements of braking energy conversion and storage, effectively absorb load impact, reduce the peak power demand of the motor, and switch dual-path braking energy recovery to provide a wide range of braking torque. The front and rear hydrostatic devices can be driven simultaneously to meet the demand for sudden large torque during excavation. During high-speed transportation, the displacement of the four-quadrant pump can be reduced to meet the maximum vehicle speed requirement. A control strategy for the full hydrostatic drive and braking system of an electric loader based on center of gravity estimation is proposed. Through the hierarchical control method of the organization layer, coordination layer, and execution layer, the complex calculation time of the whole machine controller is reduced, the frequency response of the electric loader is improved, and the working reliability is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For a technician in this field, other related drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 The figure is a schematic diagram of the structure of the electric loader's fully hydrostatic drive and braking system based on center of gravity estimation of the present invention.

[0017] Figure 2 This is a control strategy diagram of the electric loader's fully hydrostatic drive and braking system based on center of gravity estimation of the present invention.

[0018] In the figure: 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 overflow valve, 8-first electromagnetic switch valve, 9-first four-quadrant pump, 10-first clutch, 11-first reducer, 12-first tire, 13-second tire, 14-second electromagnetic switch valve, 15-hydraulic accumulator, 16-second overflow valve, 17-second motor controller, 18-second travel motor, 19-second variable pump, 20-third overflow valve, 21-third electromagnetic switch valve, 22-fourth electromagnetic switch 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 overflow 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 DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by the first technician in the field without making creative work belong to the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by the first technician in the field without making creative work belong to the scope of protection of the present invention.

[0020] Example

[0021] The following are only preferred implementations of the present invention. The protection scope of the present invention is not limited to the following embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention.

[0022] As 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 relief 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 relief valve 16, a second motor controller 17, a second travel motor 18, a second variable pump 19, a third relief valve 20, a third electromagnetic switch valve 21, and a fourth electromagnetic switch valve 22. 2. The second four-quadrant pump 23, the second clutch 24, the second reducer 25, the third tire 26, the fourth tire 27, the third motor controller 28, the working motor 29, the third variable pump 30, the fourth overflow valve 31, the first three-position four-way solenoid valve 32, the first pressure sensor 33, the second pressure sensor 34, the bucket cylinder 35, the bucket cylinder displacement sensor 36, the second three-position four-way solenoid valve 37, the third pressure sensor 38, the fourth pressure sensor 39, the first boom cylinder 40, the second boom cylinder 41, and the boom cylinder displacement sensor 42.

[0023] Its mechanical connection relationship is 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; the boom cylinder displacement sensor 42 is mechanically connected to the first boom cylinder 40.

[0024] The high-voltage connection relationship is as follows: the power battery 2 is electrically connected to the high-voltage management unit 3 at high voltage; 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 at high voltage; the first motor controller 4 is electrically connected to the first travel motor 5 at high voltage; the second motor controller 17 is electrically connected to the second travel motor 18 at high voltage; the third motor controller 28 is electrically connected to the working motor 29 at high voltage;

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

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

[0027] The working principle of the system is as follows: the loader driver drives the loader to operate according to the real-time working condition requirements. When driving, 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 arm cylinder displacement sensor 42 send feedback signals to the whole machine controller 1 in real time. The whole machine controller 1 uses the received feedback signals to calculate the center of gravity position through the control algorithm. When the center of gravity is biased towards the front wheel, the single front hydrostatic transmission strategy is selected. When the center of gravity is biased towards the rear wheel, the single rear hydrostatic transmission strategy is selected. When the driving and braking torques are large or the wheels slip severely, the front and rear walking devices are selected. Simultaneous transmission strategy. In high-speed transportation conditions, the whole machine controller 1 controls the four-quadrant pump to reduce the displacement to reach the maximum vehicle speed.

[0028] Example A

[0029] When in no-load or light-load condition, the details are as follows:

[0030] The loader driver drives the loader to operate according to the real-time working condition requirements. 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 arm cylinder displacement sensor 42 send feedback signals to the whole machine controller 1 in real time. The whole machine controller 1 uses the received feedback signals to calculate the center of gravity position through the control algorithm. At this time, the center of gravity is biased towards the rear wheel, and the single rear hydrostatic transmission strategy is selected. The whole machine controller 1 sends a control instruction to the second motor controller 17, and the second motor controller 17 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 at the same time. The third electromagnetic switch valve 21 is in the working position, and the second clutch 24 is closed to perform a single rear hydrostatic transmission, which not only meets the power requirements but also improves the economy.

[0031] Example B

[0032] When in heavy-load transportation conditions, the details are as follows:

[0033] The loader driver drives the loader to operate according to the real-time working condition requirements. 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 arm cylinder displacement sensor 42 send feedback signals to the whole machine controller 1 in real time. The whole machine controller 1 uses the received feedback signals to calculate the center of gravity position through the control algorithm. At this time, the center of gravity is biased towards the front wheel, and the single front hydrostatic transmission strategy is selected. The whole machine controller 1 sends a control instruction to the first motor controller 4, and the first motor controller 4 controls the speed and torque of the first travel motor 5, and controls the displacement of the first variable pump 6 and the first four-quadrant pump 9 at the same time. The first electromagnetic switch valve 8 is in the working position, and the first clutch 10 is closed to perform a single front hydrostatic transmission, which not only meets the power requirements but also improves the economy.

[0034] Example C

[0035] When the wheels are in severe slippage or digging conditions, the details are as follows:

[0036] The loader driver drives the loader to operate according to the real-time working condition requirements. The whole machine controller 1 receives the driver's feedback signal and selects the simultaneous transmission strategy of the front and rear travel devices after calculation by the control algorithm. The whole machine controller 1 sends a control instruction to the first motor controller 4, and the first motor controller 4 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, and the first electromagnetic switch valve 8 is in the working position, and the first clutch 10 is closed. At the same time, a control instruction is sent to the second motor controller 17, and the second motor controller 17 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 electromagnetic switch valve 21 is in the working position, and the second clutch 24 is closed, and the front and rear travel devices are simultaneously transmitted, further improving the operating performance and power of the loader.

[0037] Example D

[0038] When braking, the details 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 whole machine controller 1 in real time. The whole machine controller 1 uses the received feedback signals to calculate the center of gravity position through the control algorithm. When the braking torque demand is small and the center of gravity is biased to the rear wheel, the single rear hydrostatic transmission strategy is selected to recover and reuse the braking energy. When the braking torque demand is small and the center of gravity is biased to the front wheel, the single front hydrostatic transmission strategy is selected to recover and reuse the braking energy. When the braking torque demand is large, the front and rear walking device simultaneous transmission strategy is selected to recover and reuse the braking energy.

[0040] The fully hydrostatic drive and brake system of an electric loader based on center of gravity estimation of the present invention can be applied to various working conditions of engineering machinery to realize drive and braking functions, and is particularly suitable for loaders with severe load fluctuations, frequent starts and stops, and large center of gravity changes.

[0041] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A fully hydrostatic drive and brake 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 whole machine controller. The whole machine controller receives feedback signals from the pressure sensor, the bucket cylinder displacement sensor and the boom cylinder displacement sensor and obtains the center of gravity position after calculation by a control algorithm. When the center of gravity is biased toward the front wheel, a separate front hydrostatic transmission strategy is selected, wherein the separate front hydrostatic transmission strategy is as follows: the whole machine controller calculates the current required torque of the whole machine through the organizational layer, and as a feedforward control, sends a control instruction to the first motor controller, and the first motor controller controls the torque of 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 the separate front hydrostatic transmission is performed; When the center of gravity is biased towards the rear wheel, a separate rear hydrostatic transmission strategy is selected. The separate rear hydrostatic transmission strategy is: the whole machine controller calculates the current required vehicle speed of the whole machine through the organizational layer, and uses the difference between the current vehicle speed and the required vehicle speed as the PID algorithm input. The whole machine controller sends a control instruction to the second motor controller, and the second motor controller controls the speed of the second travel motor. At the same time, the displacement of the second variable pump and the second four-quadrant pump is controlled through the fuzzy control algorithm. The third solenoid switch valve is in the working position, and the second clutch is closed to perform a separate rear hydrostatic transmission.

2. The electric loader fully hydrostatic drive and brake system based on center of gravity estimation according to claim 1 is characterized in that: When the required driving and braking torque is large or the wheel slip is serious, the simultaneous transmission strategy of the front and rear travel devices is selected: the whole machine controller sends a control instruction 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 solenoid switch valve is in the working position, closes the first clutch, and sends a control instruction to the second motor controller at the same time, the second motor controller controls the speed and torque of the second travel motor, and controls the displacement of the second variable pump and the second four-quadrant pump, the third solenoid switch valve is in the working position, closes the second clutch, and drives the front and rear travel devices simultaneously.

3. The fully hydrostatic drive and brake system for an electric loader 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 chamber of the first boom cylinder and the second boom cylinder, and the fourth pressure sensor is used to collect the pressure of the rodless chamber of the first boom cylinder and the second boom cylinder.

4. The electric loader fully hydrostatic drive and brake system based on center of gravity estimation according to claim 1, characterized in that: The system's whole machine 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 fully hydrostatic drive and brake system for an electric loader based on center of gravity estimation according to claim 4, characterized in that: The bucket cylinder displacement sensor can collect the displacement of the bucket cylinder piston rod, 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 electric loader fully hydrostatic drive and brake system based on center of gravity estimation according to claim 1, characterized in that: The whole machine controller can control the displacement of the first variable pump and the second variable pump, and can also control the working state switching and displacement of the pumps and motors of the first four-quadrant pump and the second four-quadrant pump.

7. The electric loader fully hydrostatic drive and brake system based on center of gravity estimation according to claim 1, characterized in that: The first four-quadrant pump and the second four-quadrant pump can be used as pumps and can also be used as motors in a switched working state.

8. The electric loader fully hydrostatic drive and brake system based on center of gravity estimation according to claim 1, characterized in that: The motor of the system is a permanent magnet synchronous motor, a switched reluctance motor, a DC motor or an AC induction motor.

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