A control system and method for leveling excavators

Abstract

This invention discloses a leveling control system and method for an excavator. The control system includes a signal input system, a leveling calculation control system, and a leveling execution system. The control method is as follows: The main controller acquires real-time angle data of the working device, calculates the real-time stroke and real-time extension / retraction speed of the hydraulic cylinder; calculates the position of the shovel tip, and the real-time target angle and target angular acceleration of the boom, stick, and bucket; calculates the target stroke and target extension / retraction speed of the corresponding hydraulic cylinder; obtains the base current of the pilot solenoid valve corresponding to the target extension / retraction speed of the hydraulic cylinder; calculates the moment of inertia of the working device around the hinge point of the boom and turntable at any given time and the frictional resistance of the hinge point through upper computer simulation, and calculates the secondary current from the base current; performs PID compensation on the stroke deviation of the hydraulic cylinder to obtain the output current of the pilot solenoid valve, and simultaneously calculates the required flow rate and current of the main pump; the pilot solenoid valve controls the flow rate according to the current magnitude, thereby controlling the extension / retraction speed of the hydraulic cylinder to complete the leveling action.

Description

Technical Field

[0001] This invention relates to excavators in the field of engineering machinery technology, and more particularly to an excavator leveling control system. This invention also relates to an excavator leveling control method. Background Technology

[0002] When using excavators for leveling, the key to accuracy lies in controlling the position of the shovel tip. Currently, the mainstream method in the industry is to calculate the real-time position of the shovel tip using DH coordinate transformation, calculate the real-time target angular velocity and angle of each working device during the leveling process, initialize the current based on the target angular velocity of the working device, and use PID control to adjust the angle, thereby controlling the leveling trajectory. However, since the angular velocity of the working device and the current are not directly correlated, this method of leveling calculation introduces errors. Furthermore, current methods do not control the main pump current during leveling, failing to consider the main pump's influence. Additionally, the excavator's actuators have different moments of inertia around the hinge point in different positions, and these moments of inertia affect the change in rotational speed, significantly impacting the boom's starting, stopping, and direction switching.

[0003] The existing technology has the following shortcomings:

[0004] (1) During the leveling process, the initial current is applied according to the target angular velocity of the working device, and the real-time PID calculation is performed based on the deviation between the target angle and the actual angle. The current error of the solenoid valve obtained by this method is large.

[0005] (2) Only the current of the solenoid valve of the working device is calculated and assigned, and the current of the main pump is not controlled.

[0006] (3) During the leveling process, the moment of inertia around the boom and turntable hinge point differs depending on the working device's position: when the bucket and stick are far from the cab, the moment of inertia around the boom and turntable hinge point is large; when the bucket and stick are close to the cab, the moment of inertia around the boom and turntable hinge point is small. Under different moments of inertia, achieving the same angular velocity for the boom, especially during startup and reversing phases, presents varying difficulties, requiring different main valve openings and correspondingly different currents for the pilot solenoid valves. Current technology assigns a base current to one pilot solenoid valve for each cylinder speed, without considering the impact of different positions and moments of inertia. Therefore, changes in moment of inertia affect the accuracy of leveling or slope repair. Summary of the Invention

[0007] Purpose of the invention: To address the shortcomings of existing technologies, this invention provides a leveling control system and method for excavators. During the leveling process, it not only calculates and assigns values ​​to the current of the solenoid valve in the working device, but also calculates the flow rate required by the main pump, thereby obtaining the corresponding current of the main pump and improving the leveling accuracy. It also solves the problem of inaccurate solenoid valve current corresponding to the angle of the working device, and avoids the influence of changes in rotational inertia on the motion control of the working device.

[0008] Technical solution: The excavator leveling control system of the present invention includes a signal input system, a leveling calculation control system, and a leveling execution system; the signal input system includes an angle sensor and an automatic leveling host computer; the leveling execution system includes a main controller, a hydraulic cylinder, a hydraulic main valve, a pilot solenoid valve, a working device, and a main pump;

[0009] The main controller is connected to the angle sensor and the automatic leveling host computer; the pilot solenoid valve is connected to the control end of the valve core of the hydraulic main valve, and the hydraulic main valve is connected to the working device.

[0010] Pilot solenoid valves include boom raising pilot solenoid valve, boom lowering pilot solenoid valve, stick retraction pilot solenoid valve, stick swing pilot solenoid valve, bucket retraction pilot solenoid valve, and bucket swing pilot solenoid valve.

[0011] Angle sensors include boom angle sensors, stick angle sensors, and rocker angle sensors.

[0012] The working device includes a boom, stick, bucket, and hydraulic cylinders.

[0013] The excavator leveling control method of the present invention includes the following steps:

[0014] (1) Enter automatic leveling mode via automatic leveling host computer;

[0015] (2) Select the leveling mode through the automatic leveling host computer, determine the leveling mode of inward leveling, outward leveling, two-compound leveling or three-compound leveling, as well as the leveling speed, and send the instruction to the main controller;

[0016] (3) Automatic leveling action is performed by the automatic leveling host computer;

[0017] (4) The real-time angle data of the working device is obtained through the main controller, and the real-time stroke and real-time extension speed of the oil cylinder are calculated by analyzing the dynamic triangle formed by the oil cylinder and the working device.

[0018] (5) Calculate the position of the shovel tip based on the DH coordinate transformation, and calculate the real-time target angle and target angular acceleration of the boom, stick and bucket based on the flat ground trajectory, speed and working device size; calculate the target stroke and target extension speed of the corresponding hydraulic cylinder based on the dynamic triangle formed by the working device and the hydraulic cylinder.

[0019] (6) According to the cylinder speed-base current diagram, the base current of the pilot solenoid valve corresponding to the target extension speed of the cylinder is obtained; the moment of inertia around the hinge point of the boom and the turntable at any time is calculated by simulation, and the frictional resistance of the hinge point is calculated at the same time. The host computer sends the calculation results to the main controller, and calculates the base current according to the results to obtain the secondary current.

[0020] (7) Based on the secondary current, perform PID compensation on the stroke deviation of the oil cylinder to obtain the output current of the pilot solenoid valve, and at the same time calculate the flow rate and current required by the main pump.

[0021] (8) The pilot solenoid valve controls the flow rate according to the current, and then controls the extension and retraction speed of the oil cylinder to complete the leveling action.

[0022] In step (4), the real-time stroke and real-time extension speed of each cylinder are calculated based on the dynamic triangle formed by each cylinder and the actuator.

[0023] In step (6), the speed and base current of the hydraulic cylinder are calibrated first to obtain the hydraulic cylinder speed-base current calibration diagram.

[0024] In step (6), the mass, center of gravity, and density parameters of the working device are set in the simulation software of the automatic leveling host computer. The angle data of the working device is transmitted to the simulation software of the host computer in real time. The moment of inertia of the working device around the hinge point of the boom and the turntable at any time is calculated through simulation. At the same time, the frictional resistance of the hinge point is calculated. The host computer sends the calculation results to the main controller and calculates the foundation current based on the results to obtain the secondary current.

[0025] In step (7), the target flow rate of all cylinders is calculated based on the cylinder diameter and rod diameter; then, the required flow rate of each main pump is calculated based on the main pump flow rate distribution.

[0026] In step (8), the current of the pilot solenoid valve corresponds to the speed of the oil cylinder.

[0027] Working Principle: This invention calculates the target stroke and target extension / retraction speed of the hydraulic cylinder based on the trajectory coordinates of the shovel tip, the target angle data of the working device, and the relative position dimensions of the working device and the hydraulic cylinder during the leveling process. A base current is assigned to the solenoid valve of the working device based on the target speed of the hydraulic cylinder, and PID control is performed based on the cylinder stroke deviation. Changes in rotational inertia affect the hydraulic cylinder speed-current relationship. Therefore, based on the mass and center of gravity position of the working devices such as the bucket, boom, arm, rocker arm, connecting rod, and hydraulic cylinder, as well as the pose calculated by the angle sensor, the rotational inertia of the working device around the hinge point between the boom and the turntable at any given moment is calculated using automatic leveling computer simulation software. A secondary current is calculated based on the magnitude of the rotational inertia. Specifically, during the acceleration, deceleration, and reversing phases of the working device boom, the base current is increased or decreased accordingly based on the magnitude of the rotational inertia to reduce the impact of changes in rotational inertia on the hydraulic cylinder speed-current relationship.

[0028] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0029] (1) The present invention calculates the base current from the target speed of the hydraulic cylinder. Without considering the moment of inertia, the hydraulic cylinder speed and the current correspond one-to-one. By calibrating the hydraulic cylinder speed and base current of the whole vehicle, a hydraulic cylinder speed-base current calibration chart is obtained. The base current is calculated based on the chart, making the calculation results more accurate and improving the leveling accuracy.

[0030] (2) The present invention uses automatic leveling computer simulation software to calculate the rotational variables of the working device in real time, and calculates the secondary current based on the real-time changing moment of inertia, so as to reduce the influence of the change of moment of inertia on the calibration relationship of cylinder speed-base current and improve the accuracy of the output current of the solenoid valve.

[0031] (3) The leveling process of the present invention calculates the flow rate required by the main pump based on the leveling speed and flow rate requirements, thereby controlling the main pump current and improving the accuracy of the excavator's automatic leveling. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the excavator leveling control system of the present invention;

[0033] Figure 2 This is a flowchart of the excavator leveling control method of the present invention. Detailed Implementation

[0034] like Figure 1As shown, the excavator leveling control system of the present invention includes a signal input system, a leveling calculation control system, and a leveling execution system; the signal input system includes an angle sensor 3 and an automatic leveling host computer 1; the leveling execution system includes a main controller 2, a hydraulic cylinder, a hydraulic main valve 6, a pilot solenoid valve 4, a working device 7, and a main pump 5.

[0035] The main controller 2 is connected to the angle sensor 3 and the automatic leveling host computer 1; the pilot solenoid valve 4 is connected to the control end of the valve core of the hydraulic main valve 6, and the hydraulic main valve 6 is connected to the working device 7.

[0036] The pilot solenoid valve 4 includes a boom raising pilot solenoid valve, a boom lowering pilot solenoid valve, a stick retraction pilot solenoid valve, a stick swing pilot solenoid valve, a bucket retraction pilot solenoid valve, and a bucket swing pilot solenoid valve.

[0037] Angle sensor 3 includes a boom angle sensor, a stick angle sensor, and a rocker arm angle sensor. Working device 7 includes a boom, a stick, a bucket, and corresponding hydraulic cylinders.

[0038] The automatic leveling host computer 1 is equipped with commands for entering automatic leveling mode, one-click leveling, leveling mode selection, and leveling speed selection. The 3D model, mass, density, and center of gravity data of the excavator's working device are input into the host computer to build a simulation model. The angle sensor 3 is connected to the host computer via a CAN bus to acquire the attitude of the working device 7 in real time and perform simulation calculations.

[0039] Angle sensor 3 is connected to main controller 2 via a CAN bus. Main controller 2 reads data from the CAN bus to obtain the real-time angle values ​​of each sensor. Main controller 2 is connected to automatic leveling host computer 1 via a CAN bus and receives commands from automatic leveling host computer 1, including commands to enter automatic leveling mode, one-click leveling, leveling mode selection, and leveling speed selection. At the same time, it receives simulation calculation results from automatic leveling host computer 1, including the rotational inertia and frictional resistance of the working device around the hinge point of the boom and turntable.

[0040] The main controller 2 is connected to each pilot solenoid valve 4 via signal lines, and each pilot solenoid valve 4 is connected to the valve core control end of the corresponding hydraulic main valve 6 via hydraulic pipes; the hydraulic main valve 6 is connected to the working device cylinder via hydraulic pipes.

[0041] Automatic leveling host computer 1 transmits the automatic leveling selection mode command and simulation calculation results to main controller 2; boom angle sensor transmits the absolute angle data of boom to main controller 2; stick angle sensor transmits the absolute angle data of stick to main controller 2; rocker angle sensor transmits the absolute angle data of rocker to main controller 2.

[0042] The main controller 2 calculates the actual stroke and displacement speed of each cylinder based on the data received from the angle sensor 3; simultaneously, it calculates the position of the shovel tip based on DH coordinate transformation, and calculates the real-time target angle and target angular acceleration of the boom, stick, and bucket based on the flat ground trajectory, speed, and structural component dimensions. Then, based on the relative position dimensions of the structural components and cylinders, it calculates the real-time target stroke and real-time extension / retraction speed of the corresponding cylinder. Next, based on the cylinder speed-current meter, it looks up the base current of the pilot solenoid valve 4 corresponding to the cylinder's target speed. Based on the moment of inertia and frictional resistance sent from the host computer to the main controller, it calculates the base current to obtain the secondary current. Based on the secondary current, it performs PID calculations on the actual and target strokes of the cylinders to calculate the compensation current. The secondary current and the compensation current are added together to obtain the final output current of the pilot solenoid valve. The pilot solenoid valve controls the flow rate through the hydraulic main valve 6 according to the current magnitude.

[0043] The formula for calculating the secondary current is:

[0044] I2=C1×C2×C0×|a|+I1

[0045] —a is the target angular acceleration of the working device of the hydraulic cylinder;

[0046] —C0 is the calculation coefficient between the angular acceleration and current of the working device;

[0047] —C1 is the calculation coefficient between the moment of inertia of the working device and the current;

[0048] —C2 is the calculation coefficient between the frictional resistance of the working device and the current;

[0049] —I1 is the base current;

[0050] —I2 is the secondary current.

[0051] like Figure 2 As shown, the excavator leveling control method of the present invention includes the following steps:

[0052] (1) Enter the automatic leveling mode through the automatic leveling host computer 1 to put the excavator in the automatic leveling preparation state;

[0053] (2) Select the leveling mode through the automatic leveling host computer 1, determine the inward leveling or outward leveling, the two-compound action leveling or the three-compound action leveling and the leveling speed, and send the instruction to the main controller 2 through the CAN line;

[0054] (3) Automatic leveling action is performed by automatic leveling host computer 1;

[0055] (4) The main controller 2 reads the real-time angle data of the boom, stick, and rocker arm from the angle sensor 3, and calculates the real-time stroke and real-time extension speed of the boom, stick, and bucket cylinders based on the dynamic triangle formed by the working device and the cylinders, using the angle sensor data and corresponding dimensions of the working device. Specifically, the main controller 2 acquires the real-time angle data of the working device 7, reads the angle sensor data, and calculates the real-time stroke and extension speed of the corresponding cylinders. That is, based on the dynamic triangle formed by each cylinder and the actuator, the real-time stroke and real-time extension speed of each cylinder are calculated using the triangle cosine theorem.

[0056] (5) Calculate the position of the shovel tip based on the DH coordinate transformation, and calculate the real-time target angle and target angular acceleration of the boom, stick and bucket based on the flat ground trajectory, speed and working device size; the specific process is as follows: based on the dynamic triangle formed by each cylinder and the actuator, calculate one angle of the dynamic triangle through the target angle of the actuator, and since the lengths of the two sides of the dynamic triangle are known, calculate the target stroke and target extension speed of each cylinder through the triangle cosine theorem.

[0057] (6) The cylinder speed and current are in one-to-one correspondence. First, the cylinder speed and basic current of the whole vehicle are calibrated to obtain the cylinder speed-basic current calibration diagram. According to the cylinder speed-basic current calibration diagram, the basic current of the pilot solenoid valve 4 corresponding to the target speed of the cylinder is obtained by looking up the table. According to the mass, center of gravity position and posture of the working device such as bucket, stick, boom, rocker arm, connecting rod, and cylinder, the moment of inertia of the working device around the hinge point of the boom and turntable at any time is calculated by the automatic leveling computer simulation software. At the same time, the frictional resistance of the hinge point is calculated. The host computer sends the calculation results to the main controller 2. The basic current is calculated according to the results to obtain the secondary current.

[0058] (7) Based on the secondary current, perform PID calculation on the actual stroke and target stroke of the cylinder, calculate the compensation current, add the secondary current and the compensation current to obtain the output current of each pilot solenoid valve.

[0059] Given the target speed of the hydraulic cylinder, the target flow rate of all hydraulic cylinders is calculated based on the cylinder diameter and rod diameter. Then, based on the main pump flow distribution, the target flow rate of each main pump is calculated. Finally, based on the main pump flow-current correspondence table, the current required by main pump 5 is calculated.

[0060] (8) The pilot solenoid valve controls the flow rate through the hydraulic main valve 6 according to the current magnitude. At the same time, it calculates the flow rate required by the main pump 5 according to the target cylinder speed and cylinder size, and obtains the current of the main pump 5 accordingly, thereby controlling the extension and retraction speed of the cylinder so that the working device 7 reaches the target position and completes the leveling action.

Claims

1. A method for controlling the leveling of ground by an excavator, characterized in that: The excavator leveling control system is adopted, which includes a signal input system, a leveling calculation control system, and a leveling execution system. The signal input system includes an angle sensor (3) and an automatic leveling host computer (1). The leveling execution system includes a main controller (2), a hydraulic cylinder, a hydraulic main valve (6), a pilot solenoid valve (4), a working device (7), and a main pump (5). The main controller (2) is connected to the angle sensor (3) and the automatic leveling host computer (1); the pilot solenoid valve (4) is connected to the control end of the valve core of the hydraulic main valve (6), and the hydraulic main valve (6) is connected to the working device (7); The control method includes the following steps: (1) Enter the automatic leveling mode through the automatic leveling host computer (1); (2) Select the leveling mode through the automatic leveling host computer (1), determine the leveling mode of inward leveling, outward leveling, two-compound action leveling or three-compound action leveling, as well as the leveling speed, and send the instruction to the main controller (2); (3) The automatic leveling action is executed by the automatic leveling host computer (1); (4) The real-time angle data of the working device (7) is obtained through the main controller (2), and the real-time stroke and real-time extension speed of the oil cylinder are calculated by analyzing the dynamic triangle formed by the oil cylinder and the working device. (5) Calculate the position of the shovel tip based on the DH coordinate transformation, and calculate the real-time target angle and target angular acceleration of the boom, stick and bucket based on the flat ground trajectory, speed and working device size; calculate the target stroke and target extension speed of the corresponding hydraulic cylinder based on the dynamic triangle formed by the working device and the hydraulic cylinder. (6) According to the cylinder speed-base current diagram, the base current of the pilot solenoid valve (4) corresponding to the target extension speed of the cylinder is obtained; the moment of inertia around the hinge point of the boom and the turntable at any time is calculated by simulation, and the frictional resistance of the hinge point is calculated at the same time. The host computer sends the calculation results to the main controller (2), and calculates the base current according to the results to obtain the secondary current. (7) Based on the secondary current, PID compensation is performed on the stroke deviation of the oil cylinder to obtain the output current of the pilot solenoid valve (4), and the required flow rate and current of the main pump (5) are calculated at the same time. (8) The pilot solenoid valve controls the flow rate according to the current, and then controls the extension and retraction speed of the oil cylinder to complete the leveling action.

2. The excavator leveling control method according to claim 1, characterized in that: In step (4), the real-time stroke and real-time extension speed of each cylinder are calculated based on the dynamic triangle formed by each cylinder and the actuator.

3. The excavator leveling control method according to claim 1, characterized in that: In step (6), the speed and base current of the hydraulic cylinder are calibrated first to obtain the hydraulic cylinder speed-base current calibration diagram.

4. The excavator leveling control method according to claim 1, characterized in that: In step (6), the mass, center of gravity and density parameters of the working device are set in the simulation software of the automatic leveling host computer (1). The angle data of the working device is transmitted to the simulation software of the host computer in real time. The moment of inertia of the working device around the hinge point of the boom and the turntable at any time is calculated by simulation. At the same time, the frictional resistance of the hinge point is calculated. The host computer sends the calculation results to the main controller (2). The basic current is calculated according to the results to obtain the secondary current.

5. The excavator leveling control method according to claim 1, characterized in that: In step (7), the target flow rate of all cylinders is calculated based on the cylinder diameter and rod diameter; Then, based on the main pump flow distribution, calculate the required flow rate for each main pump.

6. The excavator leveling control method according to claim 1, characterized in that: In step (8), the current of the pilot solenoid valve corresponds to the speed of the oil cylinder.

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