A shoveling control method for an energy-saving electric-driven wheeled unmanned loader

Abstract

The present invention discloses an energy-saving electric drive wheeled unmanned loader excavation control method for solving the bucket retraction problem and the optimal control problem of motor torque. By pre-calibrating some parameters, when the loader reaches the front of the material pile and receives the excavation command, the bucket is first made to drop straight down until the pressure of the bucket cylinder pressure chamber reaches just touching the ground without causing excessive pressure on the ground. Then the vehicle is made to approach the material pile at a certain speed and corresponding driving torque. When the pressure of the boom cylinder pressure chamber measured in real time is greater than the calibration value, it is determined that the bucket has contacted the material pile and excavation begins. At this time, the driving torque of the drive motor is changed to 120% of the motor and hydraulic calibration driving torque. During the excavation process, the forward stroke of the loader is recorded at the same time. According to the changes in stroke and vehicle speed, it is determined whether the excavation is completed and what measures to take.

Description

Technical Field

[0001] The present invention relates to a loader, in particular to an improved method for shoveling control of a pure electric drive wheeled unmanned loader, belonging to the field of unmanned driving of engineering machinery. Background Art

[0002] In recent years, the efficiency of loaders has been greatly improved by autonomous driving, especially with all-electric wheel loaders. These loaders can determine the digging position near the material and determine whether the bucket is full without relying on radar or sensors, significantly improving efficiency.

[0003] However, this technology has two defects, the specific problems are:

[0004] 1. To scoop up the material, the bucket of an unmanned, all-electric wheel loader approaches the pile and places it on the ground. However, due to uneven ground conditions, the bucket may touch the ground but not touch the ground, or the contact may be so severe that the wheels are lifted. Without the bucket on the ground, some material may not be scooped cleanly. However, after the bucket touches the ground, the front wheels are suspended in the air, and the contact between the bucket and the ground is sliding friction. This friction is much greater than the rolling friction during normal driving. Furthermore, the loader's driving force is provided only by the rear wheels, significantly reducing the digging force. This greatly reduces its efficiency and wastes energy.

[0005] 2. An existing excavation control method for a pure electric-driven wheeled unmanned loader determines whether to enter the excavation position based on whether the vehicle speed change and stroke change exceed a threshold, and determines the softness and hardness of the excavated material, and ensures that the MCU always outputs maximum torque during the excavation process.

[0006] However, (1) this method ignores the actual working environment of the loader. It is possible that the obstacles encountered are not materials, but barriers, rocks, sponges, etc. The loader controller will not recognize them and will only continue to dig, and the driving force cannot be effectively adjusted according to the actual situation. When the unmanned loader passes by, it will only identify it as material and dig it through the set travel threshold and speed threshold. During digging, because the hard objects are very solid on the ground and difficult to dig, the loader will continue to increase the digging force by increasing the output external torque at a fixed rate, and finally reach the peak to dig it up. Due to excessive force, after digging up the hard objects, the loader will lose control due to excessive speed without material obstruction. This process not only consumes a lot of energy for the loader, but also the excessive output torque will cause the loader to drive too fast, which is dangerous.

[0007] (2) In addition, due to the different shapes and properties of ground materials, the set vehicle speed threshold and travel threshold are not general in the actual working environment. This will result in the torque increasing at a fixed rate resulting in excessive digging force, excessive digging speed, and slow digging growth, and the vehicle will stop and go during the automatic digging process.

[0008] Given the above two issues, unmanned pure electric wheel loaders have many practical shortcomings: energy consumption during excavation and uncontrollable driving force. This significantly reduces work efficiency and results in increased economic losses, contradicting the high-efficiency, economical, and environmentally friendly principles of unmanned wheel loaders. Therefore, addressing these two shortcomings is essential to enable the better and more widespread application of unmanned wheel loaders in practical situations. Summary of the Invention

[0009] The present invention aims at the problems in the background and proposes relevant solutions, namely a control method for unmanned excavation of an energy-saving electric-driven wheel loader. By improving the judgment conditions, the method can avoid the problems of incomplete material shoveling due to the bucket leaving the ground or excessive friction loss (insufficient driving force) due to excessive ground pressure of the bucket, as well as the problems of speed setbacks in the shoveling process due to inaccurate driving force control and loader speed loss due to misjudgment. In an actual working environment, the excavation work can be completed more efficiently and economically.

[0010] The technical solutions of the present invention are as follows:

[0011] A method for controlling the excavation of an energy-saving electric-driven wheeled unmanned loader. 1) The following parameters are pre-calibrated on the vehicle:

[0012] When the loader bucket lifts the front wheel on a flat field, the pressure in the bucket cylinder pressure chamber is: P 14 ;

[0013] Under the condition of flat ground, the loader bucket is grounded, so that the pressure in the pressure chamber of the bucket cylinder reaches a* P 14 , a takes a value in the range [0,1]. The average pressure of the boom cylinder pressure chamber measured when the vehicle is running steadily at a speed of 5 km / h for 30 seconds is: P 13-b , the average driving torque of the wheel drive motor during this time is: T 5-b ;

[0014] The bucket is placed flat on the ground against the pile of materials, so that the drive motor cannot move forward under the maximum torque. The maximum torque is maintained unchanged for 30 seconds. During this time, the average pressure in the pressure chamber of the boom cylinder is: P 13-max , the maximum driving torque of the driving motor is:T 5-max ;

[0015] 2) Based on the calibration of the above parameters, when the loader is driving towards the material, when it reaches the front of the material pile and receives the digging command, the bucket is first lowered straight down until the pressure in the bucket cylinder pressure chamber reaches a* P 14 , and then adjust the pressure of the bucket cylinder pressure chamber before reaching the digging state, and adjust it to [(ab)* P 14 ,(a+b)* P 14 ], the value range of b is [0,a];

[0016] Then, let the vehicle have a certain speed Vi and the corresponding driving torque be T c When approaching the pile, the pressure of the boom cylinder pressure chamber is measured in real time. P 13-i Greater than P 13-b When the bucket is judged to have touched the pile, the speed is reduced and digging begins. At this time, the driving torque of the drive motor is set to T i Change to 120% of the motor and hydraulic calibrated drive torque, as shown in formula (1): (1).

[0017] During the excavation process, the loader's forward travel is recorded simultaneously;

[0018] 2.1) When the loader's forward travel is less than the set threshold value L0, the driving torque reaches T 5-max , and when the vehicle speed is less than the threshold V0 or the wheels slip during the forward movement, it is determined that the loader has touched a hard material.

[0019] At this time, the controller controls the bucket cylinder and / or boom cylinder to make the bucket flip upward or lift horizontally upward until the vehicle speed exceeds the threshold V0 and the angle between the bottom of the bucket and the frame plane does not exceed 30 degrees. Then, the bucket flipping stops and the vehicle continues to move forward.

[0020] During the process of continuing to move forward, if the loader's forward travel is less than the threshold value L0, and the vehicle speed is again less than the threshold value V0 or the wheels slip, the above action is repeated;

[0021] Until the loader's forward travel reaches a threshold value L0 or the angle between the bucket bottom and the frame plane exceeds 30 degrees, the loader retracts the bucket to the retracted position. At the same time, when the angle between the bucket bottom and the frame plane exceeds 45 degrees, the drive torque is reduced to 0 Nm.

[0022] 2.2) When the loader's forward travel distance is greater than threshold L0 and the vehicle speed never drops below threshold V0 during the forward movement, the loader is determined to have encountered loose material. At this point, the controller controls the bucket cylinder to tilt the bucket upward to the retracted position.

[0023] To implement the above method, the loader is equipped with: a human-machine interface, a bucket control valve, a two-position four-way solenoid valve, a boom cylinder pressure sensor, a bucket cylinder pressure sensor, a boom inclination sensor, a bucket inclination sensor, and a positioning device; road condition information is input through the human-machine interface; and a two-position four-way solenoid valve is installed in parallel next to the bucket control valve.

[0024] The beneficial effects of the present invention are:

[0025] 1. The bucket grounding control method can ensure that the bucket is in real contact with the ground and exerts little pressure on the ground, which can maximize material collection and minimize energy waste.

[0026] 2. The motor torque control method can ensure that the digging force of the vehicle during the digging process is always greater than the resistance of the entire vehicle, and the vehicle speed will not be stuck. When a misjudgment occurs or the resistance suddenly disappears, the entire vehicle will not stall. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural diagram of the excavation control system of the unmanned loader of the present invention. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the embodiments. Those skilled in the art should know that the following embodiments are not the only limitations on the technical solutions of the present invention, and any equivalent transformations or modifications made within the spirit of the technical solutions of the present invention should be deemed to fall within the scope of protection of the present invention.

[0029] First, install the following excavation control system on the unmanned loader: Figure 1 As shown, it includes a vehicle controller 1, an accelerator pedal 2, a motor controller 3, a human-machine interface 4, a drive motor 5, a front axle main reducer 6, a rear axle main reducer 7, a wheel-side reducer 8, a bucket control valve 9, a two-position four-way solenoid valve 10, a boom cylinder 11, a bucket cylinder 12, a boom cylinder pressure sensor 13, a bucket cylinder pressure sensor 14, a boom inclination angle sensor 15, and a bucket inclination angle sensor 16. In addition, the vehicle is also equipped with a positioning device (GPS or Beidou).

[0030] The present invention incorporates a final reducer on each front and rear axle, and a wheel-side reducer on each wheel for secondary reduction. Both the front and rear axle final reducers 6 and 7 are driven and connected by a drive motor 5, which is controlled by a motor controller 3. A vehicle controller 1 formulates a control strategy based on the degree of accelerator pedal 2 operation, outputs a torque command, and transmits this torque command to the drive motor 5 via the motor controller 3, achieving the driving force required for the loader's excavation.

[0031] A human-machine interface 4 is provided in the vehicle, and the vehicle controller 1 interacts with the human-machine interface 4. The driver inputs road condition information, such as asphalt, cement, sand and gravel, dry soil, mud, ice and snow, through the human-machine interface 4 according to the conditions of the road surface on which the loader is operating at the time. The vehicle controller 1 combines the road condition information input by the human-machine interface 4 and retrieves the corresponding road surface parameters stored in the controller. Based on the road condition information, the maximum driving force that the vehicle can exert can be accurately calculated.

[0032] The present invention installs a two-position, four-way solenoid valve 10 in parallel with the loader's existing bucket control valve 9. This valve 10 is calibrated experimentally to ensure that the bucket cylinder 12 rotates slightly when the valve 10 is switched on. The solenoid control terminal of the two-position, four-way solenoid valve 10 is connected to the vehicle controller 1 to connect or disconnect the oil circuit.

[0033] A pressure sensor and an inclination sensor are installed on the boom cylinder 11 and the bucket cylinder 12 to measure the pressure in the boom and bucket cylinders' pressure chambers and the inclination angle of the cylinders. Generally speaking, the pressure sensor is installed in the cylinder's pressure chamber (mostly a rodless chamber).

[0034] In addition, a digging control program is pre-implanted in the vehicle controller 1 , and the digging control program is started by determining whether the digging conditions are met.

[0035] The method adopted by the present invention to solve the bucket grounding problem is:

[0036] By installing a bucket cylinder pressure sensor 14 on the pipeline from the loader bucket cylinder pressure chamber (mostly a rodless chamber) to the multi-way valve, the cylinder pressure (i.e., the pressure between the bucket and the ground) is monitored in real time. When the bucket of a pure electric drive wheel loader raises the front wheel on a flat ground, the pressure in the bucket cylinder pressure chamber is P 14 When the loader receives the start digging command, the bucket is made to descend straight down (adjusted by the data obtained by the boom inclination sensor 15 and the bucket inclination sensor 16) until the pressure in the ground pressure chamber of the bucket cylinder reaches a* P 14 , where a is in the interval [0,1], preferably a=0.1, when the pressure reaches this point, stop and then adjust slowly. P14 The purpose is to keep the pressure small enough to make it touch the ground, but the force is not too great so as not to waste more friction.

[0037] Then, before reaching the digging state, the pressure of the bucket cylinder pressure chamber is copied to the logic threshold value b through the two-position four-way solenoid valve 10, where b is in the interval [0, a], preferably b=0.05, so that the bucket cylinder pressure is always maintained at [(ab)* P 14 ,(a+b)* P 14 ] to ensure that the bucket is always in contact with the ground but does not cause excessive pressure on the ground to cause energy loss.

[0038] The method adopted by the present invention to solve the problem of excavation driving force is:

[0039] By installing a boom cylinder pressure sensor 13 on the boom cylinder pressure chamber (mostly a rodless chamber) of the loader, the digging force of the loader bucket acting on the boom pressure chamber is monitored in real time, and the driving force of the drive motor 5 is controlled based on this pressure.

[0040] First, calibrate the corresponding relationship between the driving torque of the driving motor and the pressure of the boom cylinder pressure chamber:

[0041] Ground the loader bucket on a straight asphalt or cement road surface, adjust the two-position four-way solenoid valve 10, and make the pressure in the bucket cylinder pressure chamber between [(ab)* P 14 ,(a+b)* P 14 ] interval; let the drive motor 5 drive the vehicle at a target speed of 5 km / h, and measure the pressure value of the boom cylinder pressure sensor 13 within 30 seconds when the vehicle is at a stable speed, so that the average value during this period is P 13-b , and collect the driving torque value of the driving motor 5, and let its average value be T 5-b Place the bucket flat on the ground, against the pile so that the drive motor 5 cannot move forward at the maximum torque, maintain the maximum torque unchanged for 30 seconds, and record the pressure value of the boom cylinder pressure sensor 13 during this process, and let its average value be P 13-max , let the maximum driving torque of the driving motor 5 in this process be T 5-max .

[0042] In actual work, when the loader determines that the vehicle has reached the front of the pile based on the positioning device (GPS or Beidou) or sensor information collection, it first places the bucket on the ground according to the aforementioned method ("the aforementioned method" refers to the method taken to solve the bucket grounding problem) and maintains pressure between the bucket and the ground.

[0043] At this time, the vehicle is set to a fixed speed Vi (the speed can be calibrated on site according to the working conditions) according to the type of material, and the corresponding driving torque of the driving motor 5 is T c Approaching the pile, when the pressure value of the boom cylinder pressure sensor 13 P 13-i Greater than P 13-b When the bucket is judged to have touched the pile, the speed is reduced to start the excavation process. At this time, the driving torque of the drive motor 5 is set to T i Change to 120% of the motor and hydraulic calibrated drive torque (the motor and hydraulic calibrated torque is the corresponding relationship between the two calibrated by using the bucket to push against the pile and the corresponding pressure value of the boom cylinder when the motor has different torques), as shown in formula (1): (1)

[0044] Furthermore, during the excavation process, the controller simultaneously records the forward travel of the loader.

[0045] 1) When the loader's forward travel is less than the threshold value L0, the driving torque reaches T 5-max (maximum driving force) and when the vehicle speed is less than the threshold V0 or the wheels slip during forward movement, it is determined that the loader has touched hard material;

[0046] At this time, the controller controls the bucket cylinder and / or boom cylinder to make the bucket flip upward or lift horizontally upward until the vehicle speed exceeds the threshold V0 and the angle between the bottom of the bucket and the frame plane does not exceed 30 degrees. Then, the bucket flipping stops and the vehicle continues to move forward.

[0047] During the process of continuing to move forward, if the loader's forward travel is less than the threshold value L0, and the vehicle speed is again less than the threshold value V0 or the wheels slip, the above action is repeated;

[0048] Until the loader's forward travel reaches a threshold value L0 or the angle between the bucket bottom and the frame plane exceeds 30 degrees, the loader retracts the bucket to the retracted position. At the same time, when the angle between the bucket bottom and the frame plane exceeds 45 degrees, the drive torque is reduced to 0 Nm.

[0049] 2) When the loader's forward travel is greater than the threshold value L0 and the vehicle speed never drops below the threshold value V0 during the forward movement, it is determined that the loader has touched loose material. At this time, the controller controls the bucket cylinder to flip the bucket up to the retracted position.

[0050] Compared with the existing technology, the present invention is not afraid of obstruction by the bucket and the boom. It determines whether the loader is close to the material through changes in the motor torque or the vehicle speed, and controls the ground pressure of the bucket. Then, it determines whether the contact is hard material or loose material, and whether the excavation is completed through changes in speed during the forward stroke. In this way, the excavation state of the bucket is adjusted to complete the excavation work accurately, which can avoid misjudgment of the excavation action and achieve energy saving and efficiency maximization.

Claims

1. A method for controlling the excavation of an energy-saving electrically driven wheeled unmanned loader, characterized in that: 1) Pre-calibrate the following parameters on the vehicle: When the loader bucket lifts the front wheel on a flat field, the pressure in the bucket cylinder pressure chamber is: P 14 ; Under the condition of flat ground, the loader bucket is grounded, so that the pressure in the pressure chamber of the bucket cylinder reaches a* P 14 , a takes a value in the range [0,1]. The average pressure of the boom cylinder pressure chamber measured when the vehicle is running steadily at a speed of 5 km / h for 30 seconds is: P 13-b , the average driving torque of the wheel drive motor during this time is: T 5-b ; The bucket is placed flat on the ground against the pile of materials, so that the drive motor cannot move forward under the maximum torque. The maximum torque is maintained unchanged for 30 seconds. During this time, the average pressure in the pressure chamber of the boom cylinder is: P 13-max , the maximum driving torque of the driving motor is: T 5-max ; 2) Based on the calibration of the above parameters, when the loader is driving towards the material, when it reaches the front of the material pile and receives the digging command, the bucket is first lowered straight down until the pressure in the bucket cylinder pressure chamber reaches a* P 14 , and then adjust the pressure of the bucket cylinder pressure chamber before reaching the digging state, and adjust it to [(ab)* P 14 ,(a+b)* P 14 ], the value range of b is [0,a]; Then, let the vehicle have a certain speed Vi and the corresponding driving torque be T c When approaching the pile, the pressure of the boom cylinder pressure chamber is measured in real time. P 13-i Greater than P 13-b When the bucket is judged to have touched the pile, the speed is reduced and digging begins. At this time, the driving torque of the drive motor is set to T i Change to 120% of the motor and hydraulic calibrated drive torque, as shown in formula (1): （1）。 2. The excavation control method of an energy-saving electric-drive wheeled unmanned loader according to claim 1, characterized in that: During the excavation process, the loader's forward travel is recorded simultaneously. 2.1) When the loader's forward travel is less than the set threshold value L0, the driving torque reaches T 5-max , and when the vehicle speed is less than the threshold V0 or the wheels slip during the forward movement, it is determined that the loader has touched a hard material. At this time, the controller controls the bucket cylinder and / or boom cylinder to make the bucket flip upward or lift horizontally upward until the vehicle speed exceeds the threshold V0 and the angle between the bottom of the bucket and the frame plane does not exceed 30 degrees. Then, the bucket flipping stops and the vehicle continues to move forward. During the process of continuing to move forward, if the vehicle speed again drops below the threshold value V0 or the wheels slip before the loader's forward travel falls below the threshold value L0, the controller will again control the bucket cylinder and / or boom cylinder to flip the bucket upward or lift it horizontally upward until the vehicle speed exceeds the threshold value V0 and the angle between the bottom of the bucket and the frame plane does not exceed 30 degrees. Then, the bucket flipping stops and the vehicle continues to move forward. Until the loader's forward travel reaches a threshold value L0 or the angle between the bucket bottom and the frame plane exceeds 30 degrees, the loader retracts the bucket to the retracted position. At the same time, when the angle between the bucket bottom and the frame plane exceeds 45 degrees, the drive torque is reduced to 0 Nm. 2.2) When the loader's forward travel distance is greater than threshold L0 and the vehicle speed never drops below threshold V0 during the forward movement, the loader is determined to have encountered loose material. At this point, the controller controls the bucket cylinder to tilt the bucket upward to the retracted position.

3. The excavation control method of an energy-saving electrically driven wheeled unmanned loader according to claim 1 or 2, characterized in that: The loader is equipped with: a human-machine interface, a bucket control valve, a two-position four-way solenoid valve, a boom cylinder pressure sensor, a bucket cylinder pressure sensor, a boom inclination sensor, a bucket inclination sensor, and a positioning device; Input traffic information through the human-machine interface; The two-position four-way solenoid is installed in parallel next to the bucket control valve.

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