A method for improving the levelling angle control of a working machine

Abstract

The invention relates to a method for controlling a working machine (1) comprising a main body (2) and a motion device (3) connected to the main body (2) of the working machine (1) and configured to receive loads and move them relative to the main body (2), wherein the motion device has a boom with one or more boom elements (4, 5) and a holding element (6) arranged at an end section of the boom for receiving loads, wherein the boom elements (4, 5) and the holding element (6) are movable by one or more independently acting actuators (7, 8, 9), wherein sensors are provided which are configured to detect state data of the motion device (3), wherein the method comprises the following steps: a. detecting a movement of at least one boom element (4, 5); b.a. Receiving a command to maintain a target inclination (ϕ) of the holding element (6) during the movement of the at least one boom element (4, 5), wherein the target inclination (ϕ) describes a target angle of the holding element (6) relative to the main body (2) of the working machine (1); c. Calculating the weight of a load held by the holding element (6); d. Calculating a target movement of one of the actuators (9) responsible for the movement of the holding element (6) such that the target inclination (ϕ) of the holding element (6) remains constant during the movement of the at least one boom element (4, 5), the calculation taking into account the weight calculated in step c. and the detected movement of the at least one boom element (4, 5); e. Controlling the actuator (9) responsible for the movement of the holding element based on the target movement calculated in step d.

Description

TECHNICAL AREA

[0001] The invention relates to a method for controlling a work machine which makes it possible to keep an inclination of a holding element constant while at least one boom element is moved. STATE OF THE ART

[0002] Mobile work machines with the "Bucket Retain" assistance function are used worldwide. One such function is disclosed in patent application DE 11 2017 000 130 T5. The "Bucket Retain" assistance function is designed to regulate a set grading angle of a work machine. The grading angle describes the angle of the bucket in relation to the external, higher-level coordinate system and depends on the boom, stick, and bucket angles in their respective coordinate systems. The "Bucket Retain" function adjusts the bucket angle in a controlled manner to maintain a desired grading angle. The boom and stick can still be adjusted by the vehicle operator. Other work machines with assistance functions are known, for example, from JP 7 009600 B1 and JP H10 259619 A.

[0003] Such a function can be applied to various types of machines. Indeed, excavators (standard, mini, midi, mining, mobile), wheel loaders, telehandlers, and forestry machines with corresponding functionality can be found on the market. Therefore, in the present invention, the term "work machine" refers to any of these or other machines known from the prior art.

[0004] However, the control accuracy and speed of this function are not particularly high due to the varying weight of the attached holding element (e.g., the load in a bucket) and the associated dynamics. For this reason, the purpose of the invention is to improve the existing function. SUMMARY

[0005] According to one embodiment of the present invention, a method is provided for controlling a work machine comprising a main body and a movement device connected to the main body of the work machine and configured to receive loads and move them relative to the main body, wherein the movement device has a boom with one or more boom elements and a holding element arranged at an end section of the boom for receiving loads, wherein the boom elements and the holding element are movable by one or more independently acting actuators, wherein sensors are provided which are configured to detect status data of the movement device, the method comprising the following steps: a. Detecting a movement of at least one boom element; b. Detecting a command to keep a target inclination of the holding element constant during the movement of the at least one boom element, wherein the target inclination describes a target angle of the holding element in a coordinate system that is independent of the at least one boom element; c. Calculating a weight of a load carried by the holding element; d. Calculating a target movement of one of the actuators responsible for the movement of the holding element such that the target inclination of the holding element remains constant during the movement of the at least one boom element, wherein the calculation is carried out taking into account the weight calculated in step c. and the detected movement of the at least one boom element; e. Controlling the actuator responsible for the movement of the holding element based on the target movement calculated in step d.

[0006] The present invention is particularly advantageous because this function significantly increases the accuracy of the "bucket retain" function. In particular, functional testing and measurements on the excavator have shown that control improvements are enormous when the load is taken into account. In the current implementation, a linear controller is used for all operating points, regardless of the load. However, the inventor has observed that the system dynamics are highly dependent on the orientation and load of the bucket. In particular, the inventor has observed that optimal control parameters with a full bucket differ significantly from those with an empty bucket. If the current load is not taken into account, only one set of control parameters (as a compromise between the various operating points) can be used.However, such a solution causes enormous inaccuracies, such as oscillations and long-term control deviations, when compared to the accuracy enabled by a method according to the present invention. SHORT DESCRIPTION OF THE CHARACTERS

[0007] The present invention is described with reference to the accompanying figures, wherein like reference numerals refer to like parts and / or similar parts and / or corresponding parts of the system. Regarding the figures: Figure 1 shows schematically a working machine with moving elements; Figure 2 shows schematically a method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0008] The present invention will now be described with reference to specific embodiments as shown in the accompanying figures. Nevertheless, the present invention is not limited to the specific embodiments described in the following detailed description and shown in the figures; rather, the described embodiments merely illustrate some aspects of the present invention, the scope of which is defined by the claims.

[0009] Further modifications and variations of the present invention will be apparent to those skilled in the art. The present description thus encompasses all modifications and / or variations of the present invention, the scope of which is defined by the claims.

[0010] Figure 1shows an excavator 1 as an example of a work machine. The excavator 1 has a main body 2 and a movement device 3 connected to the main body 2 of the work machine 1. The movement device is configured to pick up loads and move them relative to the main body 2. The movement device 1 has a boom, which in turn has several boom elements for moving a support element 6. The boom elements are, for example, a lifting arm 4 (or simply known as "boom") and an arm 5 (or also known as "stick"), which are rotatably or pivotably connected to each other or to the main body 2 of the excavator 1. In addition, the Figure 1 The excavator shown has a bucket 6 arranged at an end portion of the arm 5. The boom elements 4, 5 and the bucket are movable by means of actuators 7, 8, 9, ie the rotational or pivoting movement about the axes is effected by a movement of the actuators.

[0011] A first actuator 7 is provided for the lifting arm 4, which causes the movement or rotation of the lifting arm 4 relative to the main body 2. Likewise, a second actuator 8 is provided for the arm 5, which causes the movement or rotation of the arm 4 relative to the lifting arm 4. Likewise, a third actuator 9 is provided for the bucket, which moves or rotates (tilts) the bucket (also called the "shovel").

[0012] The actuators 7, 8, 9 can be controlled by a controller, whereby in the case of hydraulic cylinders, directional control valves are provided which control the flow of hydraulic fluid to the hydraulic cylinders.

[0013] Sensors are provided (in Figure 1not shown) which record force data and position data. Force data is data or measurement data that characterizes or displays the forces applied by the actuators. In particular, pressure sensors can be used for this purpose, e.g. the pressure on both sides of the piston is measured on the hydraulic cylinders, whereby the force applied by the hydraulic cylinder is then characterized by the pressure difference. Position data is data or measurement data that characterizes or displays the position (e.g. angle) of the boom elements, in particular their relative position or their position relative to the boom support (in particular also relative angles). In particular, angle sensors or sensors that determine the deflection of the hydraulic cylinders can be provided for this purpose.

[0014] Particular attention will be paid to force data and position data and corresponding sensors. These are preferred examples of state data or sensors; in general, state data from other sensors can also be acquired additionally or alternatively, for example, to acquire pressure data, moment data, torque data, speed data, acceleration data, and / or stress data (which, as noted, can in principle also be understood as force and / or position data).

[0015] Since the geometric relationships of the boom elements and their weights or masses are known, the weight or mass of a supported load can be calculated or estimated from the force and position data. For this purpose, a so-called weighing function is used, the implementation of which is well known to those skilled in the art. The time or period at which the force and position data are recorded, based on which the supported load is calculated, is referred to as the weighing time or weighing period.

[0016] An example of a weighing function is disclosed in patent application DE 102021205407.2, which was not yet published on the filing date of this patent application.

[0017] As in Figure 1As shown, the angle θa corresponds to the inclination of the lifting arm 4 with respect to a horizontal plane, the angle θb to the inclination of the arm 5 with respect to the axis of the lifting arm 4, the angle θc 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 a horizontal plane. The angle ϕ is represented in a coordinate system that is independent of the other boom elements 4, 5.

[0018] The objective of the present invention is therefore to automatically maintain the angle ϕ constant while changing the other angles θa and θb. Therefore, the grading angle ϕ is automatically maintained constant by the third actuator 9 (when the "Bucket Retain" function is active).

[0019] Figure 2 schematically shows a method for the "Bucket Retain" function according to an embodiment of the present invention.

[0020] In a first step, information about a target grading angle ϕ is obtained using an input device (e.g., a joystick or a button). This information 108 can be either a value of the target grading angle ϕ or the command to keep the current grading angle ϕ constant. In addition, sensor data 109 is acquired to record the position of the boom 4, 5 and the bucket 6. In the first step, the weight 110 calculated during the weighing time is also recorded. A bus system 107 records all the information 108, 109, and 110 and transmits it to a control unit 103, which is responsible for controlling the third actuator 9. The control unit 103 can control the position 106 of the third actuator by means of a pump 104 and a main control valve 105.

[0021] The control takes place in the loop 100, 101, 102, 103. In a first step, the desired inclination ϕ of the holding element 6 is detected 100 during the movement of the at least one boom element 4, 5 and compared with the actual inclination ϕ of the holding element 6 and the difference 101 is communicated to the control unit 103.

[0022] The control unit 103 will then use the information 101 and the information acquired from the bus system 107 to generate a control signal for the main control valve 105.

[0023] The signal is therefore calculated taking into account the weight of the load supported by the holding element 6. The weight information can be used, for example, as a control parameter in gain scheduling or in model-based control.

[0024] Control parameters can also be selected depending on the positioning (e.g., the angle) of the boom 4, 5. This means different control parameters when moving the bucket close to the main body 2 than when moving further away from the main body 2.

[0025] The estimated load mass can also be used in other functions where variable dynamics play a role. For example, in the workspace limitation assistance function.

[0026] The core of the present invention therefore lies in the use of an additional assistance function for estimating the current load mass, in order to incorporate this information into the control of the grading angle. This can be implemented in the form of operating point-dependent control methods, such as gain scheduling, or a general, model-based approach. By combining the two functions, improved and operating point-independent control behavior is expected.

Claims

1. Method for controlling a mobile machine (1) comprising a main body (2) and a movement device (3) which is connected to the main body (2) of the mobile machine (1) and which is configured to accept loads and to move with respect to the main body (2), wherein the movement device comprises a boom having one or more boom elements (4, 5) and a holding element (6) arranged on an end portion of the boom for receiving load, wherein the boom elements (4, 5) and the holding element (6) are movable by one or more independently acting actuators (7, 8, 9), wherein sensors are provided which are configured to detect state data of the movement device (3), wherein the method involves the following steps: a. detecting a movement of at least one boom element (4, 5); b. detecting a command to keep a setpoint inclination (ϕ) of the holding element (6) constant during the movement of at least one boom element (4, 5), wherein the setpoint inclination (ϕ) describes a setpoint angle of the holding element (6) in a coordinate system which is independent of the at least one boom element (4, 5); c. calculating a weight of a load received by the holding element (6); d. calculating a setpoint movement of one of the actuators (9) responsible for the movement of the holding element (6), with the result that the setpoint inclination (ϕ) of the holding element (6) remains constant during the movement of the at least one boom element (4, 5), wherein the calculation is made taking into account the weight calculated in step c. and the detected movement of the at least one boom element (4, 5); e. regulating the actuator (9) which is responsible for the movement of the holding element, based on the setpoint movement calculated in step d.

2. Method according to Claim 1, wherein the holding element (6) is a bucket, and wherein the setpoint inclination (ϕ) is a setpoint levelling angle of the bucket (6).

3. Method according to either of Claims 1 or 2, wherein the boom exclusively comprises a first (4) and a second (5) boom element.

4. Method according to one of Claims 1 to 3, wherein, in step d., the calculation continues taking into account the position of the holding element (6) with respect to the main body (2).

5. Method according to one of Claims 1 to 4, wherein at least one regulating parameter is used in step d. for taking into account the weight calculated in step c., wherein the regulating parameter is dependent on the position of the holding element (6).

6. Computing unit which is configured to carry out a method according to one of the preceding claims.

7. Mobile machine (1) comprising a main body (2) and a movement device (3) which is connected to the main body (2) of the mobile machine (1) and which is configured to accept loads and to move with respect to the main body (2), wherein the movement device comprises a boom having one or more boom elements (4, 5) and a holding element (6) arranged on an end portion of the boom for receiving load, wherein the boom elements (4, 5) and the holding element (6) are movable by one or more independently acting actuators (7, 8, 9), wherein sensors are provided which are configured to detect state data of the movement device, wherein a controller is provided, which implements a weighing function, which is designed to evaluate acquired state data in order to determine a weight of a load received by the movement device (3); comprising a computing unit according to Claim 6.

8. Computer program which causes a computing unit to carry out a method according to one of Claims 1 to 6 when it is executed on the computing unit.

9. Machine-readable storage medium with a computer program according to Claim 8 stored thereon.

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