Method for improving closed-loop control of work machine grading angle

Abstract

To relate to a method for controlling a work machine.SOLUTION: A method comprises steps of a. detecting movement of at least one jib element, b. detecting a command for maintaining a constant target tilt of a holding element during the movement of the at least one jib element, c. calculating the weight of a conveyance scooped up by the holding element, d. calculating a target movement of an actuator responsible for the movement of the holding element among the plurality of actuators such that the desired inclination of the holding element during the movement of at least one jib element is maintained constantly.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for controlling a working machine that enables the inclination of a holding element to be kept constant while at least one jib element is being moved.

Background Art

[0002] Prior Art Mobile working machines with a support function called "Bucket Retain" are used worldwide. Such a function is disclosed in the German Patent Application No. 112017000130 (DE112017000130T5). The support function of "Bucket Retain" aims to perform closed-loop control of the leveling angle of the working machine. The leveling angle represents the angle of the bucket with respect to an external upper coordinate system and depends on the boom angle, arm angle, and bucket angle in the respective coordinate systems of the boom, arm, and bucket. The "Bucket Retain" function is closed-loop controlled to adjust the bucket angle in order to maintain the desired leveling angle. The boom and the arm can be further adjusted by the vehicle driver.

[0003] Such a function can be used in various types of machines. In fact, excavators (standard type, small type, medium type, mining type, mobile type), wheel loaders, telehandlers, and forestry machines with corresponding functions can be found in the market. Therefore, the term "working machine" in the present invention means any one of the above-mentioned machines or other machines known from the prior art.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] However, the closed-loop control accuracy and speed of this function are not very high due to the varying weights of the attached retaining elements (e.g., load capacity in the bucket) and the associated dynamics. For this reason, the object of the present invention is to improve upon existing functions. [Means for solving the problem]

[0006] overview According to one embodiment of the present invention, a method for controlling a work machine, wherein the work machine includes a main body and a moving device, the moving device being connected to the main body of the work machine and configured to scoop up a transported object and move it relative to the main body, the moving device having a jib with one or more jib elements and holding elements positioned at the end portions of the jib for scooping up a transported object, the jib elements and the holding elements being movable by one or more actuators acting independently of each other, and the method being provided with sensors configured to detect state data of the moving device, a. A step of detecting the motion of at least one jib element, b. A step of detecting a command to maintain a constant target tilt of a holding element during the motion of at least one jib element, wherein the target tilt represents a target angle of the holding element in a coordinate system independent of at least one jib element, c. A step of calculating the weight of the transported object scooped up by the holding element, d. A step of calculating the target motion of an actuator, among a plurality of actuators, that is responsible for the motion of the holding element, such that the target inclination of the holding element is kept constant during the motion of at least one jib element, wherein the calculation is performed taking into account the weight calculated in step c and the detected motion of at least one jib element. e. A step in which the actuator responsible for the motion of the holding element is controlled in a closed loop based on the target motion calculated in step d. A method including this is provided.

[0007] The present invention is particularly advantageous because this function significantly improves the accuracy of the "bucket holding" function. In particular, functional testing and measurements on an excavator have shown that the improvement in closed-loop control when considering the transported material is extremely significant. In current implementations, linear control devices are used for all operating points without considering the transported material. However, the inventors have observed that the system dynamics are strongly dependent on the orientation and load of the bucket. In particular, the inventors have observed that the optimal control parameters when the bucket is full differ significantly from the optimal control parameters when the bucket is empty. When the current load is not considered, only a set of control parameters (as a compromise for various different operating points) can be used. However, such solutions result in extremely large inaccuracies, such as fluctuations and long-term control deviations, compared to the accuracy achieved by the method according to the present invention.

[0008] The present invention will be described with reference to the accompanying drawings. Note that the same reference numerals refer to the same parts and / or similar parts and / or corresponding parts of the system. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a work machine equipped with movable elements. [Figure 2] This is a schematic diagram illustrating a method according to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] Detailed explanation In the following description, the present invention will be described with reference to specific embodiments as shown in the accompanying drawings. However, the present invention is not limited to the specific embodiments shown in the drawings as described in the following detailed description, and the embodiments described are merely examples of some aspects of the present invention, and the scope of protection of the present invention is defined by the claims.

[0011] Further modifications and variations of the present invention will be apparent to those skilled in the art. Accordingly, this specification includes all modifications and / or variations of the present invention whose scope of protection is defined by the claims.

[0012] Figure 1 shows an excavator 1 as an example of a working machine. The excavator 1 has a main body 2 and a moving device 3, which is connected to the main body 2 of the working machine 1. The moving device is configured to scoop up a material to be transported and move it relative to the main body 2. The moving device 3 has a jib, which itself has multiple jib elements to move a holding element 6. The jib elements are, here exemplary, a boom 4 (also known simply as the "jib") and an arm 5 (also known as the "forearm"), which are rotatably or pivotably connected to each other or to the main body 2 of the excavator 1. Furthermore, the excavator shown in Figure 1 includes a bucket 6 positioned at the end section of the arm 5. The jib elements 4, 5 and the bucket are movable using actuators 7, 8, 9, i.e., rotational or pivotal motion about an axis is brought about by the movement of these actuators.

[0013] A first actuator 7 is provided for the boom 4, which causes the boom 4 to move or rotate relative to the main body 2. Similarly, a second actuator 8 is provided for the arm 5, which causes the arm 5 to move or rotate relative to the boom 4. Similarly, a third actuator 9 is provided for the bucket, which causes the bucket (also referred to as the "shovel") to move or rotate (tilt).

[0014] Actuators 7, 8, and 9 are drivable by a control device, and in the case of a hydraulic cylinder, a directional control valve is provided to control the flow of hydraulic fluid to the hydraulic cylinder.

[0015] Sensors (not shown in Figure 1) are provided to detect force data and position data. Force data is data or measurement data indicating or representing the force applied by the actuator. For this purpose, a pressure sensor can be used in particular to measure the pressure on both sides of the piston in a hydraulic cylinder, in which case the force applied by the hydraulic cylinder is indicated by the pressure difference. Position data is data or measurement data indicating or representing the position (e.g., angle) of the jib element, in particular the relative position of the jib element, or the position of the jib element relative to the jib carrier (in particular, the relative angles of each). For this purpose, an angle sensor can be provided in particular, or a sensor can be provided to determine the displacement of the hydraulic cylinder.

[0016] In particular, force data and position data and their corresponding sensors will be described. These sensors are preferred examples of state data or sensors, and it is also possible to detect state data from other sensors in addition to or instead of these, for example, pressure data, moment data, torque data, velocity data, acceleration data, and / or voltage data (which, as mentioned above, can basically also be understood as force data and / or position data).

[0017] Since the geometric relationship between the boom elements and the weight or mass of the boom elements are known, the weight or mass of the lifted load can be calculated or estimated from the force data and the position data. For this purpose, a so-called weighing function is used, and its implementation itself is known to those skilled in the art. The time point or period at which the force data and the position data serving as a basis for calculating the lifted load are detected is referred to as the weighing time point or weighing period.

[0018] An example of the weighing function is disclosed in German Patent Application Publication No. 102021205407.2, which is a patent application not yet published as of the filing date of the present application.

[0019] As shown in FIG. 1, the angle φa corresponds to the inclination of the boom 4 with respect to the horizontal plane, the angle φb corresponds to the inclination of the arm 5 with respect to the axis of the boom 4, and the angle φc corresponds to the inclination of the bucket 6 with respect to the axis of the arm 5. The angle φ corresponds to the inclination of the bucket 6 with respect to the horizontal plane. The angle φ is shown in a coordinate system independent of the other boom elements 4, 5.

[0020] Therefore, an object of the present invention is to automatically maintain this angle φ constant while the other angles φa and φb are being changed. Therefore, the leveling angle φ is automatically held constant by a third actuator 9 (when the "bucket holding" function is active).

[0021] FIG. 2 schematically shows a method for the "bucket holding" function according to one embodiment of the present invention.

[0022] In the first step, information regarding the target ground leveling angle φ is acquired via an input device (e.g., a joystick or button). This information 108 may be the value of the target ground leveling angle φ, or it may be a command to maintain the current actual ground leveling angle φ constant. Furthermore, sensor data 109 is detected to detect the positions of the jibs 4, 5 and bucket 6. In the first step, the weight 110 calculated at the time of weighing is also detected. The bus system 107 detects all the information 108, 109, and 110 and transmits it to the control unit 103, which is responsible for closed-loop control of the third actuator 9. The control unit 103 can control the position 106 of the third actuator using the pump 104 and the main control valve 105.

[0023] Closed-loop control is performed in loops 100, 101, 102, and 103. In the first step, the target tilt φ of the holding element 6 during the motion of at least one jib element 4, 5 is detected 100 and compared with the actual tilt φ of the holding element 6, and the difference 101 is notified to the control unit 103.

[0024] The control unit 103 then uses the information 101 and the information detected by the bus system 107 to generate a control signal for the main control valve 105.

[0025] Therefore, the signal is calculated taking into account the weight of the transported object scooped up by the holding element 6. Information regarding the weight can be used, for example, as a control parameter in gain scheduling or in model-based closed-loop control.

[0026] The control parameters can be selected additionally depending on the position (e.g., angle) of jibs 4 and 5. That is, the control parameters for guiding the bucket toward the vicinity of the main body 2 are different from the control parameters for moving away from the main body 2.

[0027] The estimated load mass can also be used in other functions where variable dynamics play a crucial role, such as support functions that limit the workspace.

[0028] Therefore, the core of the present invention lies in considering this information in the closed-loop control of the leveling angle, using further support functions for estimating the current load mass. This can be implemented in the form of a closed-loop control method that depends on the operating point, such as gain scheduling or an approach based on a general model. Combining both functions is expected to result in better closed-loop control behavior that is independent of the operating point.

Claims

1. A method for controlling a work machine (1), wherein the work machine (1) includes a main body (2) and a moving device (3), the moving device (3) is connected to the main body (2) of the work machine (1) and is configured to scoop up a transported object and move it relative to the main body (2), the moving device has a jib with one or more jib elements (4, 5) and a holding element (6) positioned at the end portion of the jib for scooping up a transported object, the jib elements (4, 5) and the holding element (6) are movable by one or more actuators (7, 8, 9) that act independently of each other, and a sensor configured to detect state data of the moving device (3) is provided in the method, a. A step of detecting the motion of at least one jib element (4, 5), b. A step of detecting a command to maintain a constant target tilt (φ) of the holding element (6) during the motion of the at least one jib element (4, 5), wherein the target tilt (φ) represents a target angle of the holding element (6) in a coordinate system independent of the at least one jib element (4, 5), c. A step of calculating the weight of the transported object scooped up by the holding element (6), d. A step of calculating the target motion of the actuator (9) responsible for the motion of the retaining element (6) among the plurality of actuators, such that the target inclination (φ) of the retaining element (6) is kept constant during the motion of the at least one jib element (4, 5), wherein the calculation is performed taking into account the weight calculated in step c and the detected motion of the at least one jib element (4, 5). e. A step of closed-loop control of the actuator (9) responsible for the motion of the holding element based on the target motion calculated in step d., A method that includes this.

2. The holding element (6) is a bucket, and the target inclination (φ) is the target leveling angle of the bucket (6). The method according to claim 1.

3. The jib includes only a first jib element (4) and a second jib element (5). The method according to claim 1.

4. In step d, the calculation is performed taking into account the position of the retaining element (6) relative to the main body (2). The method according to claim 1.

5. In step d, at least one control parameter is used to take into account the weight calculated in step c, the control parameter depending on the position of the retaining element (6). The method according to claim 1.

6. A computing unit configured to carry out the method described in any one of claims 1 to 5.

7. A working machine (1) comprising a main body (2) and a moving device (3), wherein the moving device (3) is connected to the main body (2) of the working machine (1) and is configured to scoop up a transported object and move it relative to the main body (2), the moving device having a jib with one or more jib elements (4, 5) and a holding element (6) positioned at the end portion of the jib for scooping up a transported object, the jib elements (4, 5) and the holding element (6) being movable by one or more actuators (7, 8, 9) acting independently of each other, a sensor configured to detect state data of the moving device is provided, a control device is provided, the control device implements a weighing function configured to evaluate the detected state data in order to determine the weight of the transported object scooped up by the moving device (3), and the working machine (1) has the calculation unit described in claim 6. Working machine (1).

8. A computer program, when executed on a computing unit, that causes the computing unit to perform the method according to any one of claims 1 to 5.

9. A machine-readable storage medium storing the computer program described in claim 8.

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