DE102020215966A1 - Method for controlling an autonomous wheel loader - Google Patents

Abstract

The invention relates to a method for controlling an autonomous wheel loader for picking up bulk material from a pile using a shovel of the wheel loader. The wheel loader is driven into the heap (121) with the shovel lowered. A pressure (pA) is measured in a hydraulic drive system of the wheel loader or a force applied by the drive system is measured. If the pressure (pA) is above a pressure threshold (pAS) for the propulsion system or if the force is above a force threshold for the propulsion system, the bucket (2) is tilted up (130) and a boom of the bucket is raised (132). Then, when the blade angle (a) exceeds a first angle threshold (αS1) and the height (h) of the boom exceeds a height threshold (hs), or when a pressure (pZ) on an actuator of the blade exceeds a pressure threshold (pzs) for the actuator and the bucket angle (a) reaches a second angle threshold value (αS2), the raising of the boom is stopped (140) and the wheel loader is driven out of the heap (141).

Description

The present invention relates to a method for controlling an autonomous wheel loader for picking up bulk material from a pile. Furthermore, the invention relates to a computer program that executes each step of the method when it runs on a computing device, and a machine-readable storage medium that stores the computer program. Finally, the invention relates to an electronic control unit that is set up to carry out the method according to the invention.

State of the art

Wheel loaders come in a variety of configurations. What they all have in common is a forward-facing implement, specifically a shovel, which is connected to the vehicle via a boom (also known as a lift frame). P-kinematics (parallel kinematics) and Z-kinematics are common configurations for the boom and the working device. The boom and the working device are moved via a hydraulic system with actuating cylinders. Wheel loaders often take on the task of picking up bulk material from a heap with their shovel and transporting it to an unloading point. Wheel loaders with wheels, track loaders with a crawler track, skid steer loaders and the like are to be considered herein as configurations of the wheel loader.

Nowadays, systems and methods are known for autonomously controlling a wheel loader so that it carries out work orders. The control typically includes moving to/running into a pile of bulk goods to be picked up, picking up goods, moving to an unloading location and unloading. Path planning and obstacle detection are also known. Typically, the autonomous wheel loader has a large number of sensors: On the one hand, sensors are provided which record the surroundings of the wheel loader. On the other hand, sensors for the boom and/or the working device are provided. For this purpose, inertial measurement units (IMU) can be used, the inertial sensors such. B. have acceleration sensors and yaw rate sensors.

Disclosure of Invention

The method is intended for an autonomous wheel loader that has a front-facing bucket as a working implement. The bucket is connected to the vehicle via a boom (also known as a lift frame). The boom and the implement are moved via a hydraulic system with actuating cylinders. Crawler loaders, skid steer loaders and the like are also considered to be wheel loaders. An autonomous wheel loader can automatically carry out work tasks and/or work steps assigned to it without manual control. Nevertheless, the autonomous wheel loader can also be controlled manually by an operator or from a control station.

• Der Radlader fährt mit gesenkter Schaufel in den Haufen aus beispielsweise Schüttgut ein. Die Lage des Haufens kann beispielsweise von einem Leitstand vorgegeben (siehe unten) oder selbstständig durch Sensoren des Radladers, welche die Umgebung erfassen, ermittelt werden. Dabei fährt der Radlader mit einer vorgegebenen Geschwindigkeit auf den Haufen zu. Die Position und die Orientierung, mit denen der Radlader in den Haufen einfährt, können abhängig von der Position und/oder der Form des Haufens, vom Material des Schüttguts und/oder vom Radlader selbst bestimmt werden. Falls nötig, wird zuvor die Schaufel abgesenkt. Wenn die Schaufel den Haufen berührt, erfährt der Radlager einen Widerstand durch den Haufen. Dieser Widerstand nimmt weiter zu, umso mehr Schüttgut die Schaufel aufnimmt. Dadurch nimmt eine Last im hydraulischen Antriebssystem des Radladers beim Einfahren in den Haufen zu. Diese kann erfasst werden, indem ein Druck im hydraulischen Antriebssystem des Radladers und/oder ein Druck auf die Schaufel und/oder den Ausleger, beispielsweise mittels zumindest eines Drucksensors, gemessen wird. Alternativ oder zusätzlich wird eine Kraft, die vom Antriebssystem aufgebracht wird, oder eine Kraft auf die Schaufel und/oder auf den Ausleger gemessen. Es ist ersichtlich, dass die Messung des Drucks und die Messung der Kraft verschiedene Messgrößen für den gleichen Wirkzusammenhang sind.

The method of controlling the autonomous wheel loader to pick up bulk material from a pile using the bucket and boom carries out the following steps:

• The wheel loader drives into the heap of bulk material, for example, with the shovel lowered. The position of the heap can, for example, be specified by a control station (see below) or determined independently by sensors on the wheel loader that record the surroundings. The wheel loader drives towards the heap at a specified speed. The position and the orientation with which the wheel loader enters the heap can be determined depending on the position and/or the shape of the heap, the material of the bulk material and/or the wheel loader itself. If necessary, the shovel is lowered beforehand. When the blade touches the heap, the wheel bearing experiences resistance from the heap. This resistance increases as more bulk material is picked up by the shovel. As a result, a load in the hydraulic drive system of the wheel loader increases when entering the pile. This can be detected by measuring a pressure in the hydraulic drive system of the wheel loader and/or a pressure on the shovel and/or the boom, for example by means of at least one pressure sensor. Alternatively or additionally, a force applied by the drive system or a force on the bucket and/or on the boom is measured. It can be seen that the measurement of pressure and the measurement of force are different measurement variables for the same causal relationship.

The measured pressure is compared to a first pressure threshold. The first pressure threshold value is dependent on which pressure (pressure in the hydraulic drive system of the wheel loader and/or pressure on the bucket and/or boom) is measured, and how the first pressure threshold value can be determined is described below. If the measured pressure is above the first pressure threshold value, sufficient bulk material has been picked up or no more bulk material can be picked up by the present wheel loader because it has reached its performance limit. Heap breaking occurs by tipping up the bucket and the boom of the bucket is raised. The bulk material is thus lifted in the shovel (load lifting).

Alternatively or additionally, the measured force is compared to a force threshold value for the drive system. The force threshold depends on what force (force applied by the propulsion system or force on the bucket and/or on the boom) is measured. If the measured force is above the force threshold, sufficient bulk material has been picked up or no more bulk material can be picked up by the present wheel loader because it has reached its performance limit. Here again, the heap is broken by tipping the bucket up and raising the boom of the bucket. The bulk material is thus lifted in the shovel (load lifting).

In the following, the blade angle is monitored. The blade angle is the angle between the blade and the horizontal or vertical (relative to earth gravity). The blade position and thus the blade angle are preferably determined using at least one inertial measurement unit (IMU), preferably on a blade carrier between the blade and boom, and calculated using known kinematics of the boom and blade. In particular, the blade angle can be determined using an inertial measuring unit. If the blade angle exceeds a first angle threshold value, it is assumed that the bulk material has been optimally picked up. In addition, the height of the cantilever is measured using, for example, an inertial measuring unit or a potentiometer. When the height of the boom exceeds a height threshold, the bucket is sufficiently high above the pile that boom raising is stopped. Loose or excess bulk material may fall back onto the heap. Finally, the wheel loader is driven out of the heap.

It may happen that the boom cannot be raised far enough. For this purpose, alternatively or additionally, the pressure on the shovel and/or on the boom is monitored. In particular, a pressure on an actuating cylinder of the shovel, which causes the shovel to tilt, can be monitored for this purpose. If the pressure on the bucket and/or boom is above a second pressure threshold, an overload is detected. In this case, further lifting is not possible with certainty. The blade angle is now compared to a second angle threshold. The second angle threshold represents a minimum value for the blade angle at which the bulk material can still be removed from the heap and is therefore below the first angle threshold. If the bucket angle is above the second angle threshold, then it is assumed that the bucket can hold the bulk material and pull it out of the pile without losing too much bulk material. The raising of the boom is stopped and the wheel loader is finally driven out of the heap. If the second angle threshold value is not reached, provision can preferably be made for the shovel to be tilted downwards in order to empty part of the bulk material out of the shovel and thus to hold less.

The threshold values can be chosen depending on the material of the bulk material, so that the control runs according to the material of the bulk material. For this purpose, a material recognition to determine which material is involved, e.g. B. sand, gravel, etc., and / or what properties the material has, z. B. its grain size, and / or a material condition detection to determine the condition, z. B. its moisture, be carried out by sensors of the wheel loader or via the infrastructure. Alternatively, an operator or a control station can specify the parameters, i.e. specify the threshold values directly or select the material indirectly. In addition, the threshold values can preferably be set as a function of the operating parameters, such as e.g. B. the performance of the wheel loader can be selected. As an example, the pressure threshold value for the hydraulic drive system can be selected at a predetermined distance from the maximum available drive pressure. If the distance between the pressure threshold value and the maximum available drive pressure is not sufficient, the tool can be adjusted, for example, by e.g. B a blade with a smaller width is used. Accordingly, the shape and size of different blades can influence the threshold values. The threshold values can additionally or alternatively depend on other variables that are not specified here, but are preferably constant over time. Databases, characteristic curves, functional relationships or the like can be provided in order to provide the dependencies of the threshold values.

A time required for the raising of the boom can be detected. Advantageously, if the boom-raising time exceeds a time threshold, the bucket may be unloaded, for example by tilting it down, and the method repeated. This eliminates the possibility of the wheel loader getting stuck due to heavy material that it cannot lift. In addition, it is provided that after a specified number of repetitions of the method due to the exceeding of the time threshold values, the wheel loader and the shovel will be stopped and a message will be issued output to the operator and/or the control station.

It is preferred to check the acceptance of the bulk material for plausibility. For this purpose, a distance between the wheel loader and/or the shovel and the heap is recorded. The distance can be recorded using a camera or a comparable sensor (3D sensor) on the wheel loader. In this case, the localization can take place in particular by means of machine vision via the top, a base and/or an edge of the heap. In addition, the distance can be determined by measuring the route, in particular by means of an odometry sensor. The variants are preferably combined so that initially when approaching the heap, the distance is recorded by means of the camera or the comparable sensor and from a predeterminable distance at which the view of the sensor is obscured or at which the shovel is already immersed in the heap is, the remaining distance is determined by subtracting the travel distance measurement. Alternatively, a distance sensor can also be used. If the determination of the distance shows that the heap has been reached, the inclusion of bulk material can be checked for plausibility. The plausibility check ensures that the pressure threshold value or the force threshold value being exceeded is due to the interaction of the blade with the heap.

Additionally or alternatively, determining the distance can be used as a safety function. The distance to the heap is determined in the manner described above. If the distance falls below a distance threshold, the wheel loader is stopped. Advantageously, the distance threshold is negative, meaning that the wheel loader has driven too far into or through the pile. As a result, in situations in which the pile consists of loose or light bulk material or the pile is almost eroded and the pressure threshold value or the force threshold value for the drive system is therefore not reached, the wheel loader is stopped using an independent safety function. Preferably, the distance threshold is chosen depending only on the shape and size of the heap.

When driving into the pile, the wheels of the wheel loader may spin due to the resistance from the pile. Therefore, an anti-slip regulation (anti-slip control) is preferably provided in which spinning of the wheels is detected. When driving into the heap, the position of the wheel loader is recorded via a navigation system. A common global navigation satellite system (GNSS) such as GPS or Galileo can be used for this. On the other hand, the position is detected by means of an odometry sensor. If the wheels are spinning, the odometry sensor detects a movement that is misinterpreted as distance traveled, so that the position detected by the odometry sensor changes, while the actual position that can be detected by the GNSS does not change. The two positions determined in different ways are compared with one another and a deviation is determined. If the deviation of the positions is greater than a position threshold value, wheel spin is detected. The position threshold represents a measure of the wheel slip. Instead of the positions, the distances can also be used. In this case, the distance determined by the odometry sensor in the direction of travel is compared with a distance determined by means of the GNSS in a predefinable time interval. If the distance determined by the odometry sensor in the direction of travel is greater than the distance determined by the GNSS, wheel spin is detected. A tolerance range can also be provided here. If one of the variants detects that the wheels are spinning, the power of the drive system is reduced. The measurements of the odometry sensor are usually carried out with a higher frequency than the determination using the GNSS. Preferably, the odometry sensor can serve as an interpolar gate and the values are compared when the determination is made using the GNSS.

The wheel loader is advantageously connected to a control station. Basically, the wheel loader can receive its work tasks and/or its work steps, in particular for picking up bulk material from the heap, directly from the control station. In particular, the wheel loader can receive map data from its place of use. The location of the heap and additional loading areas, unloading areas and driving areas can be entered in the map data. In this regard, reference is also made to the description below regarding geofencing. Additionally or alternatively, the wheel loader can receive status sequences for loading, unloading and driving together with the associated statuses and the status change conditions with the parameters for the status change from the control station. The terms state sequences, state change and state change conditions and their use are known to a person skilled in the art and it is within his knowledge and ability to apply them accordingly.

• - die Position des Radladers im jeweiligen Bereich auf der Karte einsehen;
• - den Zustand des Radladers in der jeweiligen Zustandsfolge einsehen;
• - die Werte und Parameter, die für den Zustandswechsel mindestens notwendig sind, einsehen;
• - die Parameter ändern;
• - einen anderen Folgezustand vorgeben;
• - andere Zustandswechselbedingungen vorgeben;
• - per manueller Fernsteuerung in die Steuerung des Radladers eingreifen;
• - Bilder von Kameras an dem Radlader einsehen; und/oder
• - die autonome Steuerung für den Radlader wieder starten.

If a status change condition of the wheel loader is not met after a defined time or after a defined number of repetitions, this information can be transmitted to the control center. Examples of situations in which the state change condition is not met, are when the heap has already been removed or, as described above, when the power of the wheel loader is not sufficient to pick up the bulk material, or the wheel loader is defective. The wheel loader can then be operated remotely by an operator via the control station. The operator can view one or more of the following information and/or perform functions:

• - see the position of the wheel loader in the given area on the map;
• - view the status of the wheel loader in the respective status sequence;
• - view the minimum values and parameters required for the status change;
• - change the parameters;
• - specify a different subsequent state;
• - specify other state change conditions;
• - intervene in the control of the wheel loader by manual remote control;
• - View images from cameras on the wheel loader; and or
• - restart the autonomous control for the wheel loader.

Further functions of the control center have already been described above.

It is optionally provided that an operator carries out at least one cycle of the wheel loader manually. The operator can use the touchscreen, for example, to specify the current status of the wheel loader. If a subsequent state is reached, the operator confirms this with an input. The parameters recorded for the change of state, ie in particular the threshold values, are saved and learned during the manually performed cycle. This offers the advantage that the threshold values for different material properties or material types can be easily determined using an operator's controls. This means that automated material detection using sensors can be dispensed with. If optimal results are not achieved for certain status changes, the associated work steps can be carried out repeatedly and the parameters updated in the process.

Alternatively, it can be provided that the parameters are recorded during the cycle that is carried out manually and made available to an operator either on site or in the control station. The operator then selects the appropriate parameters after recording. As a result, the operator does not have to operate the wheel loader and enter the status change at the same time. The parameters can be available as a characteristic curve or as a table and can be viewed and changed by the operator.

According to a further aspect, the state change can be detected by the operator in the control center or by sensors in the infrastructure or by sensors on other machines instead of by the wheel loader itself. The change in status can then be transmitted to the wheel loader, for example by radio. In the event that only parts of the work task and/or work steps are automated and the other parts are carried out manually or by remote control (mixed operation), the operator can accept a status change from the wheel loader or hand it over to the wheel loader and thus execute the control functions in the next status or let it run.

Optionally, geographic areas can be defined in advance in which certain controls, movements and/or status changes for the wheel loader are permitted and prohibited. This is known as geofencing. This means that for each status and status change of the wheel loader, it is checked whether this also takes place in an approved geographical area. As an example, all loading states, such as e.g. B. raising the boom, take place only in the loading area. In addition, it is checked whether the wheel loader is allowed to enter the geographical area or whether it is allowed to move into this area with its boom and shovel. Similarly, it is checked whether the wheel loader is allowed to leave the geographical area again. If the status or the status change takes place in a geographical area that is not permitted for this, the wheel loader is safely stopped instead. This ensures that certain work tasks or work steps are only carried out in the areas provided for them.

The geographical areas can be stored on a map and the wheel loader locates itself on this map, for example via a navigation system, in particular GNSS and/or via the environment or environmental features using distance sensors (e.g. camera and/or LIDAR and/or radar - and/or ultrasonic sensors). The position and orientation of the bucket and boom can be determined using a kinematic model.

The specific controls, movements and/or state changes can be temporarily permitted or prohibited for the wheel loader in the geographic areas. For example, driving the wheel loader into the heap can be prohibited if another machine is entering the pile uses the same geographic area. The communication, in particular allowing and prohibiting or entering into the card, can take place between the working machines themselves or via the control station. This avoids collisions between the working machines and with the environment. In addition, the work flow of the work machines can be optimized by prioritizing the work steps.

The computer program is set up to carry out each step of the method, in particular when it is carried out on a computing device or control device. It enables the method to be implemented in a conventional electronic control unit without having to make structural changes to it. For this purpose, it is stored on the machine-readable storage medium.

By loading the computer program onto a conventional electronic control unit, the electronic control unit is obtained, which is set up to control an autonomous wheel loader for picking up bulk material from a pile.

character list

• 1 zeigt eine schematische Seitenansicht eines Radladers mit einer Schaufel und einem Ausleger.
• 2 zeigt eine schematische Darstellung eines Antriebssystems des Radladers aus 1.
• 3 zeigt eine schematische Darstellung eines Antriebssystems des Auslegers und der Schaufel.
• 4 zeigt ein Ablaufdiagramm eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens.
• 5a, b zeigen schematische Darstellungen eines Einsatzgebiets für den Radlader.

Embodiments of the invention are shown in the drawings and explained in more detail in the following description.

• 1 shows a schematic side view of a wheel loader with a bucket and a boom.
• 2 shows a schematic representation of a drive system of the wheel loader 1 .
• 3 Fig. 12 shows a schematic representation of a drive system of the boom and bucket.
• 4 shows a flow chart of an embodiment of the method according to the invention.
• 5a, b show schematic representations of an area of application for the wheel loader.

Embodiments of the invention

1 shows a schematic side view of a wheel loader 1. The wheel loader 1 has a shovel 2, which is connected to the vehicle (only partially shown) via a boom 3. Two actuating cylinders 4 (only one is visible in this representation) for the shovel 2 are arranged on the boom 3 . The actuating cylinders 4 are connected to the bucket 2 and can tilt it relative to the boom 3 . An angle between the tip of the blade 2 and the horizontal W (related to the earth's gravity) is referred to as the blade angle α. A pressure sensor 41 is provided, which measures the pressure p _Z on the actuating cylinder 4 for the shovel 2 . In addition, a position sensor in the form of a cable sensor 42 is provided on an actuating cylinder 4 for the shovel 2, which can measure the position and the inclination of the shovel 2 and thus the shovel angle α. On the vehicle side, two further actuating cylinders 5 (also only one visible) for the boom 3 are arranged on the boom 3 . Together with two stabilizing cylinders 50 (only one visible), the boom 3 can thus be raised. A pressure sensor 51 is provided, which measures the pressure on the actuating cylinder 5 for the boom 3 . In addition, a position sensor in the form of a cable sensor 52 is provided on an actuating cylinder 5 for the boom 3, which can measure the position and the inclination of the boom 3 and thus its height h.

Furthermore, inertial measurement units (IMU) 43, 53, 54 are provided along the kinematic chain from the vehicle via the boom 3 to the bucket 2. A first IMU 53 is arranged on the vehicle near the boom 3 , a second IMU 54 is arranged on the boom 3 , and a third IMU 43 is arranged on a bucket support for the bucket 2 . The attitude (position and inclination) of the blade and thus the blade angle α are calculated by means of the IMU 43, 53 and 54 along the known kinematic chain from the vehicle to the blade 2. The attitude (position and inclination) of the jib 3 and thus the height h of the jib 3 are calculated by the IMU 43 and 53 along the known kinematic chain from the vehicle to the jib 3 . The above-mentioned cable sensors 42, 52 can be used as an alternative or in addition to determining the position of the shovel 2 and/or the boom 3. In addition, for example, ultrasonic sensors, magnetic sensors, etc. can be provided in the cylinders 4, 5 in order to measure the cylinder path or its deflection and to determine the position of the bucket 2 and/or the boom 3 via the known kinematics. Furthermore, the wheel loader 1 has an electronic control unit S, which is connected to the sensors 41, 42, 43, 51, 52, 53, 54 and receives measurement data from them. The electronic control unit S is also set up to carry out the method according to the invention on the wheel loader 1 . It is with respect to the actuating cylinders 4, 5 and the sensors 41, 42, 43, 51, 52, 53, 54 also on the 3 referred. The same components are identified in the other figures with the same reference symbols.

2 shows a schematic representation of a drive system for driving the wheel loader. A motor 6 drives a hydraulic pump 61 which pumps hydraulic fluid to a hydraulic motor 62 through a forward passage FW or a reverse passage BW. Should the wheel loader 1 before driving downwards, the hydraulic fluid is pumped through the forward channel FW to the hydraulic motor 62, which then drives a drive train 63 of the wheel loader 1 accordingly. Reversing is also possible via the reverse channel BW. A pressure sensor 64 is arranged in the forward channel FW, which can measure the pressure p _A of the hydraulic fluid in the drive system of the wheel loader 1 . If the wheel loader 1 runs against a resistance, the load on the hydraulic motor 62 increases and the pressure in the forward channel FW increases. The electronic control unit controls the motor 6 and is also connected to the pressure sensor 64 and receives the measured values for the pressure p _A from this.

3 12 shows a schematic representation of a drive system for moving the boom 3 and the bucket 2 of the wheel loader 1. A motor 7 drives a hydraulic pump 71. FIG. The hydraulic pump 71 is connected via hydraulic channels to the actuating cylinders 4 for the shovel 2, the actuating cylinders 5 for the boom 3 and the stabilizing cylinders 50 and supplies them with hydraulic fluid. In addition, a valve 72 for controlling a tilting of the bucket 2 and a valve 73 for controlling a lifting of the boom 3 are provided in the hydraulic channels with which the jacks 4, jacks 5 and stabilizing jacks 50 are controlled. As in 1 already described, a position sensor in the form of a cable sensor 42 is arranged on an actuating cylinder 4 for the shovel 2 and another position sensor in the form of a cable sensor 52 on an actuating cylinder 5 for the boom 3 . In addition, a pressure sensor 41 is arranged between the valve 72 for controlling a tilting of the shovel 2 and the actuating cylinder 4 for the shovel 2, which measures a pressure of the hydraulic fluid in this hydraulic channel and thus the pressure p _Z on the actuating cylinder 4 for the shovel 2. Furthermore, a pressure sensor 51 is arranged between the valve 73 for controlling a lifting of the boom 3 and the actuating cylinder 5 for the boom 2, which measures a pressure of the hydraulic fluid in this hydraulic channel and thus the pressure on the actuating cylinder 5 for the boom 3. The electronic control unit S controls the motor 7 and the valves 72, 73 and is also connected to the sensors 41, 42, 43, 51, 52, 53, 54 and receives from them the measured values for the pressure p _Z and for the positions.

• - einen Arbeitsauftrag und/oder Arbeitsschritte;
• - Kartendaten vom Einsatzort;
• - Zustandsfolgen für das Laden, Abladen und Fahren zusammen mit den zugehörigen Zuständen; und/oder
• - Zustandswechselbedingungen mit den Parametern für die Zustandswechsel.

4 shows a flowchart of an embodiment of the method according to the invention for controlling the wheel loader 1 for picking up a pile of bulk material. The autonomous operation of the wheel loader 1 is started 100. This can be done, for example, by an operator in a control center L (see 5 ) take place. There is a transmission 101 from the control station L of one or more of the following items of information to the electronic control unit S of the wheel loader 1:

• - a work order and/or work steps;
• - Map data from the place of action;
• - State sequences for loading, unloading and driving together with the associated states; and or
• - State change conditions with the parameters for the state change.

The location of the heap is entered in the map data. In addition, loading areas, unloading areas and driving areas that are used for geofencing 110 are entered in this embodiment. Geofencing 110 is discussed below in connection with the 5a and 5b described in detail.

The wheel loader 1 detects 120 by means of sensors that are arranged on the wheel loader 1, such as. B. an optical camera (not shown), the heap. The shape and size of the heap is recognized using machine vision. Furthermore, a material detection is carried out and the material of the bulk material, such. B. sand, gravel, etc. and the properties of the material, z. B. its grain determined. In addition, a material condition detection is performed and the condition, z. B. its moisture determined. In further embodiments, this information can be recorded by sensors in the intrastructure and transmitted to the wheel loader 1 . In yet further embodiments, the parameters described below are specified by an operator at the control station L and transmitted from the control station L during transmission 101 .

If the recognition of the heap 120 has been carried out, the wheel loader 1 drives into the heap 121. Before that, the shovel 2 is lowered to ground level. During retraction 121, anti-slip regulation 122 (anti-slip control) is carried out. On the one hand, the position of the wheel loader 1 is determined via a global navigation satellite system (GNSS). On the other hand, the position is detected by means of an odometry sensor. The two positions determined in different ways are compared with one another and a deviation is determined. If the positions differ by more than a position threshold, wheel spin is detected. If wheel spin is detected, the output of motor 6 in the drive system is reduced.

In addition, the distance A of the shovel 2 to the tip, to a base point or to an edge of the heap is continuously measured 123 during retraction Distance used the above camera. When the wheel loader reaches a predefined distance that is so small that the camera has no line of sight to the measuring point of the heap, a route measurement is carried out using the above-mentioned odometry sensor to determine the distance A. The distance covered is subtracted from the predefined distance and distance A is obtained. In the following, the distance A is compared with two values 124. On the one hand, when the distance A to the heap reaches zero, it is verified that the wheel loader 1 has reached the heap. On the other hand, a negative distance threshold value A _S is defined in advance. If the wheel loader 1 drives over the heap, the distance A becomes negative. If the distance A reaches the negative distance threshold value A _S , the wheel loader 1 is already behind the heap and the wheel loader 1 is subsequently stopped 150. The information is transmitted to the control center L, so that the wheel loader 1 is now controlled by an operator in the control center L can be controlled remotely. Finally, the procedure ends 160.

Furthermore, during the retraction 121 of the wheel loader 1 into the heap, the pressure p _A in the drive system, as in connection with 2 described, measured 125. If the blade touches the heap and this has been checked for plausibility by the comparison 123 (distance A equal to 0), the wheel bearing 1 experiences resistance from the heap as a result. This resistance continues to increase, the more bulk material the shovel 2 picks up. As a result, the pressure p _A in the drive system increases. If the pressure p _A in the drive system in a comparison 126 exceeds a first pressure threshold value p _AS for the drive system, sufficient bulk material has been received in the shovel 2 and the heap is broken up. The first pressure threshold p _AS is dependent on the material of the bulk material and dependent on operating parameters such. B. the performance of the wheel loader 1 is selected. A definable distance between the first pressure threshold value p _AS and the maximum available drive pressure is selected. If the distance between the first pressure threshold p _AS and the maximum available drive pressure is not sufficient, another tool, e.g. B. selected a blade with a smaller width. Accordingly, the shape and size of different blades are included in the pressure threshold p _AS . Databases, characteristic curves, functional relationships or the like are used to provide the dependencies of the first pressure threshold value p _AS . In other embodiments, the pressure on the actuating cylinder 5 of the boom 3 by means of the pressure sensor 51, as in connection with 3 described, measured. In this case, the pressure on the actuating cylinder 5 is used below. In addition, the deflection of the actuating cylinder 5 is determined using the sensor 52 . Purely in principle, in other exemplary embodiments, the pressure p _Z on the actuating cylinder 4 of the blade 2 can also be measured by means of the pressure sensor 41 and this pressure can subsequently be used. Corresponding first pressure threshold values are then used. In still other embodiments, instead of the pressure p _A , a force applied by the propulsion system or a force acting on the blade 2 and/or the boom 3 is compared to a force threshold value for the propulsion system.

When the heap is broken up, the shovel 2 is tilted upwards 130. During the tipping 130, the shovel angle α is continuously measured 131. At the same time, the boom is raised 132. When the time t that the wheel loader 1 needs to raise 132 the boom 3, in a comparison 133 exceeds a time threshold value ts, it is determined that the wheel loader 1 cannot lift the bulk material in the shovel 2 . In this case the bucket 2 is tilted down 134 and emptied. The wheel loader 1 then drives back into the heap 121 and the process is repeated at this point. If the time threshold value ts is not fallen below in the comparison 133 even after a definable number of repetitions, the wheel loader 1 is stopped 150, the information is transmitted to a control station L and another working machine is requested there and the method is ended 160. The time threshold value t _S can be same dependency as the pressure threshold p _AS can be selected and provided in the same way.

The blade angle α, which is measured 131 when the blade 2 is tilted 130 and the boom 3 is raised 132, is compared 135 with two angle threshold values α _S1 and α _S2 . The first angle threshold value α _S1 represents an optimal pick-up of the bulk material. The second angle threshold α _S2 represents a minimum value at which the bulk material can be removed from the heap. The second angle threshold α _S2 is below the first angle threshold α _S1 . If the blade angle α does not reach the second angle threshold value α _S2 - and thus also not the first angle threshold value α _S1 - the blade 2 is tilted downward 136 so that the bulk material is emptied. The wheel loader 1 then drives back into the heap 121 and the process is repeated at this point.

If the blade angle α exceeds the first angle threshold value α _S1 , the height h of the boom 3 is compared 137 to a height threshold value hs. The height threshold value hs is chosen depending on the height of the heap and the configuration of the wheel loader 1 . When the height h of the boom 3 exceeds the height threshold hs the shovel 2 leave the heap upwards. The bucket 2 and the boom 3 are held in position 140. The wheel loader 1 moves out of the pile 141 and carries out another work task, such as e.g. B. moving to an unloading location and unloading the bulk material there. Finally, the procedure ends 160.

If the blade angle α is between the first angle threshold value α _S1 and the second angle threshold value α _S2 , i.e. it reaches the second angle threshold value α _S2 , but does not exceed the first angle threshold value α _S1 , then a pressure p _Z is applied to the actuating cylinder 4 of the blade 2, such as in connection with 3 described, measured 138. The pressure p _Z on the actuating cylinder 4 is compared 139 with a pressure threshold value pzs for the actuating cylinder 4. If the pressure p _Z on the actuating cylinder 4 is above the pressure threshold value pzs, an overload is detected. The shovel 2 and the boom 3 are also held in their position 140. The wheel loader 1 moves out of the pile 141 and carries out another work task. Finally, the procedure ends 160.

In the 5a and 5b In each case, a diagrammatically illustrated map of an application site is shown, in which a loading area B _L , an unloading area Bu, and a driving area B _D for the wheel loader 1 are entered. The pile of bulk material that is to be picked up by the wheel loader 1 is located in the loading area B _L . The unloading area B _U is located directly at an unloading point, in this example a truck. The driving area extends around the loading area B _L and the unloading area B _U . In addition, a trajectory T for the wheel loader 1 is entered in the map, which the wheel loader 1 follows in order to carry out a Y cycle. In the respective areas B _L , Bu, B _D and/or when crossing between the areas B _L , B _U , B _D , the wheel loader 1 is in a defined state and/or is executing a defined state change. Certain controls, movements and/or status changes for the wheel loader 1 are permitted or prohibited in the areas B _L , B _U , B _D . In the case of geofencing, a check is made for each state and state change of the wheel loader 1 to determine whether this takes place in an area B _L , B _U , B _D that is permitted for this purpose. As an example, all loading states, such as e.g. B. driving into the heap, only take place in the loading area B _L. In addition, it is checked whether the wheel loader 1 may enter the area B _L , B _U , B _D or whether it may move into this area B _L , B _U , B _D with its boom 3 and shovel 2 . Analogously, it is checked whether the wheel loader 1 is allowed to leave the area B _L , B _U , B _D again. If it is determined that the status or the status change is taking place in an area B _L , B _U , B _D that is not permitted for this, the wheel loader 1 is instead safely stopped 150. The information is transmitted to the control station L, so that the wheel loader 1 can now can be remotely controlled by an operator in the control station L. Finally, the procedure ends 160.

In 5a the areas B _L , B _U , B _D are permanently assigned to the wheel loader 1 and do not change. Also, the controls, movements, and state transitions that are allowed or forbidden in these areas remain constant over the time that the work order is being performed. In 5b another working machine M, here an excavator, is provided. The excavator M and the wheel loader 1 communicate with each other and with the control center L. For the excavator M, a loading area B _A and an unloading area B _B are also provided. The unloading area B _B of the excavator M overlaps with the loading area B _L . The driving area B _D is shared by the excavator M and the wheel loader 1. In this case, the controls, movements and state changes that are temporarily permitted or prohibited in these areas. If the excavator M swings into its unloading area _BB , it is checked whether the wheel loader 1 is in it or whether it is free. If the unloading area _BB is free, both the unloading area _BB of the excavator M and the loading area _BL of the wheel loader 1 are marked in the map of both working machines 1, M as "occupied by the first working machine (excavator)". Driving 121 into the heap is prohibited for the wheel loader 1 during this period. Only when the excavator M pivots back are the areas B _L , B _B released again. The wheel loader 1 can now continue the process by driving 121 into the heap. Both the unloading area B _B of the excavator M and the loading area B _L of the wheel loader 1 are marked in the map of both working machines 1, M as "occupied by the second working machine (wheel loader)". After the wheel loader 1 has moved into the loading area B _L , picked up the bulk material from the heap and driven out of the area B _L again, the areas _{B L} , BB are released again. The work machines 1, M themselves and/or the control station L can read and enter the card.

Claims (15)

Method for controlling an autonomous wheel loader (1) for picking up bulk material from a heap by means of a shovel (2) and a boom (3) of the wheel loader (1), characterized by the following steps: - retracting (121) the wheel loader (1) with lowered shovel (2) into the heap; - Measuring (125) a pressure (p _A ) in a hydraulic drive system of the wheel loader (1) and/or a pressure on the blade (2) and/or on the boom (3) or a force from the drive system tem is applied, and / or a force acting on the blade (2) and / or on the boom (3); - If the pressure (p _A ) is above a first pressure threshold (P _AS ) or if the force is above a force threshold, the bucket (2) is tilted up (130) and the boom (3) is raised (132); - When a blade angle (a) exceeds a first angle threshold (α _S1 ) and the height (h) of the boom (3) exceeds a height threshold (h _S ), or when a pressure (p _Z ) on the blade (2) and/ or on the boom (3) is above a second pressure threshold value (pzs) and the blade angle (a) reaches a second angle threshold value (α _S2 ), lifting of the boom is stopped (140) and the wheel loader is driven out of the heap (141). procedure after claim 1 , characterized in that when a time (t) for raising (132) the boom (3) exceeds a time threshold (ts), the bucket (2) is unloaded (134) again and the method is repeated. Procedure according to one of Claims 1 or 2 , characterized in that when entering (121) the distance (A) to the heap is detected (123) and that when the heap is reached the inclusion of bulk material is checked for plausibility. Method according to one of the preceding claims, characterized in that when entering (121) the distance (A) to the heap is detected (123) and that if the distance (A) falls below a distance threshold value (A _S ), the wheel loader (1) is stopped (150) will. Method according to one of the preceding claims, characterized in that when entering (121) on the one hand the position of the wheel loader is recorded via a navigation system and on the other hand the position is recorded by means of an odometry sensor and that if the positions deviate from one another by more than a position threshold value, spinning occurs of the wheels is detected and the power of the drive system is reduced (122). Method according to one of the preceding claims, characterized in that the wheel loader (1) is connected to a control station (L) and receives work tasks and/or work steps for picking up bulk material from the heap from the control station (L). procedure after claim 6 , characterized in that the wheel loader (1) receives map data and/or status sequences from the control station (L). Procedure according to one of Claims 6 or 7 , characterized in that if a state change condition of the wheel loader is not met, this information is transmitted to the control station (L). Procedure according to one of Claims 6 until 8th , characterized in that a state change is detected by an operator in the control station (L) or by sensors in the infrastructure or by sensors on other machines and is transmitted to the wheel loader. Method according to one of the preceding claims, characterized in that parameters for a state change are learned during a manually executed cycle. Method according to one of the preceding claims, characterized in that geographical areas (B _L , B _U , B _D ) are defined in advance in which specific controls, movements and/or status changes for the wheel loader (1) are permitted or prohibited. procedure after claim 11 , characterized in that the specific controls, movements and / or status changes for the wheel loader in the geographical areas (B _L , B _U , B _D ) can be temporarily allowed or prohibited. Computer program arranged, when executed on a computer or a control device, to carry out each step of the method according to any one of Claims 1 until 12 perform and/or control. Machine-readable storage medium on which a computer program Claim 13 is saved. Electronic control unit (S), which is set up to use a method according to one of Claims 1 until 12 to control an autonomous wheel loader (1).

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