SYSTEM OF MULTIPLE INERTIVE MEASURING UNITS

Description

[0001] The present invention relates to a system comprising several inertial measuring units (hereinafter referred to as IMU(s)) arranged on an excavator, which can measure rotation rates and / or accelerations. State of the art

[0002] An inertial measurement unit consists of several inertial sensors, specifically accelerometers, which measure acceleration in three dimensions, and gyroscopes, which measure the rotation rates—i.e., the angular velocity—in three dimensions. From this data, the position and (angular) velocity of an object to which the IMU is attached can be measured. Attitude is determined in a global coordinate system by measuring the Earth's gravity vector relative to the position of the IMU. If the object moves, errors in the accelerometer measurements can occur, which are compensated for by sensor fusion using the data from the gyroscopes.

[0003] IMU systems are now used for automated or semi-automated control of work machines. The IMUs are mounted, for example, on a tool arm of the work machine and measure acceleration and yaw rate. A specific application example is excavators, wheel loaders, and similar machines, where the IMUs are mounted on the excavator arm and, if necessary, on the superstructure.

[0004] Several approaches are known for controlling and evaluating IMUs. One approach is to use individual IMUs that use the inclination to determine the absolute position of the tool arm. The individual IMUs operate independently of the other IMUs on the working machine and do not receive any data from them. Consequently, the individual IMUs do not know their own position on the working machine, meaning they cannot optimally compensate for the accelerations that occur.

[0005] Secondly, combined systems consisting of IMUs and an additional central control unit are envisaged. The IMUs are connected to the central control unit and send the data measured by the individual IMUs to it. The data can be pre-processed by the IMUs or sent directly as raw data – i.e., the measured acceleration and the measured yaw rate – to the central control unit. The central control unit then uses the data to calculate the position, the (angular) velocity, the inclination, and / or the intermediate angles between the IMUs. The central control unit is either a control unit that must be specially installed in the working machine or a control unit already present in the working machine. Such combined systems with an additional central control unit are generally very expensive and cannot be easily retrofitted. One such solution is known, for example, from US Pat. No. 10,724,842 B2.

[0006] DE 10 2018 118147 A1 discloses a method for determining an angle of a working device of a machine, wherein the machine has an undercarriage and an upper carriage rotatable thereto, wherein the working device is fastened to the upper carriage via a rotary joint such that the axis of rotation of the rotary joint is orthogonal to the axis of rotation of the rotatable upper carriage, wherein the working device is provided with an IMU, i.e. an inertial measuring unit, which is designed to detect an angular velocity in three spatial directions, which are preferably perpendicular to one another, and a first of the three spatial directions, the angular velocity of which can be detected by the IMU, is parallel to the axis of rotation of the rotary joint.The method is characterized in that an angular velocity occurring during rotation of the superstructure is detected by the IMU, and an angle of the work implement relative to the rotation axis of the superstructure is determined on the basis of the detected superstructure angular velocity.

[0007] US 2018 / 373275 A1 discloses a method for using sensor feedback to control fluid pressures in a machine.This method includes receiving a time series of signals from each of a plurality of inertial measurement units (IMUs) attached to various components of the machine indicative of acceleration and angular velocity of motion measurements for each of the components of the machine to which one or more of the plurality of IMUs are attached, and receiving a signal from at least one non-IMU sensor indicative of at least one of the following: position, velocity, or acceleration of at least one of the machine components, position, velocity, or acceleration of possible obstacles or other features at a job site where the machine is operating, a fluid pressure, an engine speed, a fluid relief pressure, a maximum pump output pressure, or an operator input.The method further comprises solving a kinematic equation using best estimates of the current output joint angles for the components of the machine and structural design information characterizing the machine, determining whether a higher fluid pressure to a fluid actuation cylinder connected between two of the machine components is required to avoid stalling of one of the two machine components relative to the other of the two machine components under load after each successive time step of the series of time steps, or whether an adjustment to a pressure cutoff for a fluid pump on the machine is required for an operation.

[0008] A method for controlling the movement of a machine, as disclosed in DE 10 2021 100324 A1, may include receiving a plurality of signals from IMU modules mounted on a corresponding plurality of components of the machine, indicating alignment measurements and motion measurements for the components of the machine to which the plurality of IMU modules are mounted. The IMU modules contain a corresponding number of state estimators and form a mesh network communicatively coupled to a communication bus.The method may also include fusing the signals, determining estimates of output orientation data and output motion data for the components of the machine based on the fused signals, determining a real-time value for at least one of a position, a velocity, or an acceleration of the components of the machine based on a kinematic evaluation, and applying the determined real-time value in an implementation of a controlled operational motion of the components of the machine.

[0009] The task is to provide a system of IMUs that works in conjunction but does not require an additional central control unit and, in particular, enables improved preprocessing of the position data acquired by the IMU. Disclosure of the invention

[0010] A system comprising several IMUs mounted on an excavator is proposed, which includes at least one slave IMU and one master IMU. The IMUs are connected, in particular, via a CAN bus (Controller Area Network).

[0011] One of the system's IMUs is configured as a master IMU, which differs from the slave IMUs in that it has an evaluation processing unit. Like the slave IMUs, the master IMU is also configured to acquire data itself. The data also includes angular rates and / or accelerations of the objects on which the master IMU is located. Furthermore, the master IMU is configured to receive data from the at least one aforementioned slave IMU. The evaluation processing unit can be used for this purpose. Alternatively, the master IMU has an additional transmission unit to receive data from the at least one slave IMU. Using the evaluation processing unit, the master IMU is configured to jointly evaluate the data from the at least one slave IMU and the data acquired by itself in order to determine a kinematic chain.In particular, the positions and angles of the master IMU and / or the at least one slave IMU, as well as the object on which the at least one slave IMU or the master IMU is located, can be calculated. The evaluation unit of the master IMU is significantly more powerful than the transmission unit and preprocessing unit of the slave IMU. The master IMU then sends the evaluated data to a control unit of an excavator connected to the system.

[0012] The at least one slave IMU is configured to acquire data and transmit it within the system. The data are rotation rates and / or accelerations of the objects on which the at least one slave IMU is arranged. The data can be acquired and transmitted as raw data directly from the measurement. The at least one slave IMU has a processing unit configured to preprocess the acquired data. For example, a direction cosine matrix (DCM) can be calculated from the raw data and then transmitted. The preprocessing of the data, which can be carried out decentrally in the slave IMUs, simplifies the subsequent central evaluation. The slave IMU can have a transmission unit for transmission. The master IMU transmits the position data of the at least one slave IMU to it.

[0013] The master IMU may include a transmission unit for transmitting the calculated data to the excavator's control unit.

[0014] Just two IMUs, a slave IMU and a master IMU, are therefore sufficient to implement the system according to the invention. However, multiple slave IMUs can also be provided, which are connected to the same master IMU and transmit the data to it. In a preferred system, all IMUs except one are designed as slave IMUs. This reduces costs, since only the master IMU needs to have a computing unit that can perform an evaluation. In practice, up to four slave IMUs and one master IMU have proven particularly advantageous. Other configurations, for example more than four slave IMUs and one master IMU, are also possible.

[0015] It is also possible to create redundant systems, for example, where multiple slave IMUs are arranged at the same link in the kinematic chain. Partially redundant systems are also possible, where, for example, two IMU systems are mounted in a common housing, powered by a single supply, and communicate via the same CAN bus. Such redundant systems increase the functional safety of the overall system.

[0016] In this system, the multiple IMUs are interconnected, and the data is evaluated jointly. However, no additional control unit is required to connect the IMUs. The evaluation takes place within the system in the master IMU. This allows the system to be easily implemented on the work machine, such as the excavator, without installing an additional control unit, for example, inside the work machine, or modifying an existing electronic control unit of the work machine. The slave IMUs are preferably only connected to the master IMU for signaling purposes. The master IMU can also have a user interface or be connected to one.

[0017] Optionally, at least one angle sensor can be provided, which determines the angle of an object on which it is arranged, relative to a neighboring object in the kinematic chain. Different types of angle sensors can be provided. One angle sensor is preferably arranged in the respective center of rotation of the objects or at least mechanically connected to it. This angle sensor is arranged in particular at the beginning of the kinematic chain. Another angle sensor is preferably designed as a segment sensor. A segment sensor typically measures in an angular range of less than 180° and does not have to be arranged in the center of rotation. The segment sensor is arranged in particular at the end of the kinematic chain, since such a segment sensor is less sensitive, especially compared to an IMU, to strong vibrations and impacts that typically occur at the end of the kinematic chain.The data from at least one angle sensor is transmitted to the master IMU, where it is included in the evaluation. The angle sensor often allows for better determination of the angular position and angular velocity than the IMUs alone. For example, the angular position can be measured even in a horizontal orientation, which is not the case with IMUs. This allows for more precise compensation of centripetal acceleration.

[0018] If multiple slave IMUs are provided, the master IMU can calculate the intermediate angles between the individual slave IMUs and / or the master IMU from the jointly evaluated data. Alternatively, the master IMU can calculate the absolute angle of the individual IMUs relative to a reference from the jointly evaluated data. In particular, the vertical is used as a reference.

[0019] The inventive IMU system is used in an excavator. The IMUs are mounted on the excavator and its excavator arm. Generally, the master IMU can be mounted anywhere on the excavator. Preferably, the master IMU is mounted on the upper carriage of the excavator, and the slave IMUs are mounted on the excavator arm and, if applicable, on the tool. This allows the master IMU to detect the position and rotation rate of the upper carriage and thus the first link in the kinematic chain. Short description of the drawings

[0020] Figure 1 shows a schematic oblique view of an excavator having the inventive system of IMUs. Figure 2 shows a schematic plan view of an excavator from Figure 1 . Embodiments of the invention

[0021] In the Figures 1 and 2An excavator 10 is shown with an undercarriage 11 and a superstructure 12, which is rotatably mounted on the undercarriage 11. An excavator arm 13 is arranged on the superstructure 12, which here consists of four segments that can be tilted relative to each other and to the superstructure 12. An excavator bucket 14 is arranged as a tool on the last segment of the excavator arm 13.

[0022] According to the invention, several IMUs 1, 2, 3, 4, 5 are provided, which are implemented on the uppercarriage 12 and on the excavator arm 13. A slave IMU 1, 2, 3, 4 is arranged on each segment of the excavator arm, which detects an acceleration, in particular relative to the Earth's gravity in the X direction, and a rotation rate of the respective segment of the excavator arm 13. The slave IMUs 1, 2, 3, 4 do not have an evaluation unit configured to fully evaluate the data. However, they can have a less powerful processing unit with which raw data can be preprocessed. In addition, the slave IMUs can have a transmission unit with which data can be transmitted via a CAN bus. A master IMU 5 is arranged on the uppercarriage 12 and detects an acceleration and a rotation rate of the uppercarriage 12. The slave IMUs 1, 2, 3, 4 are connected to the master IMU 5 via the CAN bus and send the acquired data to the master IMU 5.The data can either be transmitted directly as acquired raw data or preprocessed and then transmitted to the master IMU 5 as preprocessed data, for example as DCM.

[0023] In addition, an angle sensor 6 is provided on the uppercarriage 12, which is arranged in the center of rotation or is otherwise mechanically connected to the center of rotation and which measures the angle relative to the undercarriage 11 in the YZ plane perpendicular to the Earth's gravity. The angle sensor 6 is also connected to the master IMU 5 and sends it the angle data. At the connection between the bucket 14 and the excavator arm 13, another angle sensor can be provided instead of the slave IMU 4 or in addition to it, which is preferably designed as a segment sensor 7. The segment sensor 7 measures the angle between the bucket 14 and the last section of the excavator arm 13 and is therefore arranged outside the center of rotation. The segment sensor 7 is also connected to the master IMU 5 and sends it the angle data. During operation, the excavator bucket 14 is subject to strong vibrations and impacts. The segment sensor 7 is less affected by these than the slave IMU 4.The master IMU 5 has a transmission unit with which the data from the slave IMUs 1, 2, 3, 4 and the angle sensors 6, 7 are received via the CAN bus. Furthermore, the master IMU 5 has an evaluation unit with which the data from the slave IMUs 1, 2, 3, 4, the acquired data from the master IMU 5, the data from the angle sensor 6, and, if applicable, the data from the segment sensor 7 are jointly evaluated. The evaluated data is transmitted via the transmission unit to a control unit (not shown) of the excavator 10.

[0024] In Figure 2An example of calculating the speed v 2 of the slave IMU 2 on the second segment of the excavator arm 13 (hereinafter referred to as the second IMU 2) and the speed v 5 of the master IMU 5 on the uppercarriage 12 is shown. The excavator arm 13 is rotated by the rotation of the uppercarriage 12 relative to the undercarriage 11. Thus, the speeds v 2 and v 5 are tangential to the circular path on which the uppercarriage 12 rotates and are therefore dependent on its angular velocity ω. The master IMU 5 uses the additional data from the angle sensor 6 to determine the angle of the uppercarriage 12 relative to the undercarriage 11. In addition, the absolute position P 5 of the master IMU 5 in the global coordinate system (in Figure 2only the YZ plane is shown). For this purpose, the master IMU 5 can determine its absolute angle in the global coordinate system. Additionally or alternatively, the angle sensor 6 can detect its angular position, from which the position P 5 can be determined. The movement of the undercarriage 11 during driving operation can also be recorded, and the different behavior of different drive types, such as crawler drive or wheel drive, can be taken into account.

[0025] In Figure 2only the simple case is considered in which the speed v 5 of the master IMU 5 is a pure tangential speed to the radius of the center of rotation of the excavator 10. To calculate the speed v 5 of the master IMU 5, the position P 5 of the master IMU 5 and the angular speed ω of the uppercarriage 12 are used in a conventional manner. The calculation is carried out directly in the evaluation unit of the master IMU 5. The speed v 2 of the second IMU 2 is calculated from the position P 2 of the second slave IMU 2 and the angular speed ω of the uppercarriage 12, also in a conventional manner. The position P 2 of the second slave IMU 2 is calculated from the recorded acceleration and yaw rate data of the second slave IMU 2 on the second segment, the slave IMU 1 on the first segment of the excavator arm 13 and the master IMU 5 on the uppercarriage 12.The data from slave IMUs 1, 2 are forwarded to the master IMU 5, and the calculation is also performed in the evaluation processing unit of the master IMU 5. To calculate the position P 2 of the second slave IMU 2, the master IMU 5 can calculate the absolute angle of the second slave IMU 2 to the X-axis of the global coordinate system. Especially for the position component in the X-direction, the master IMU 5 can alternatively determine the intermediate angle between the master IMU 5 and the slave IMU 1 at the first segment, and the intermediate angle between the slave IMU 1 at the first segment and the second slave IMU 2. The information about the position P 2 is finally transmitted from the master IMU 5 to the second slave IMU 2.

Claims

1. System consisting of multiple IMUs (1, 2, 3, 4, 5) arranged on an excavator (10), having at least one slave IMU (1, 2, 3, 4) which is set up to detect and transmit data, having a master-IMU (5) with an evaluation computing unit which is set up to detect data itself and to receive data from the at least one slave IMU (1, 2, 3, 4) and to jointly evaluate the data for calculating a kinematic chain and to send the evaluated data to an electronic control device of an excavator (10) connected to the system, characterised in that the at least one slave IMU (1, 2, 3, 4) has a processing unit, which is set up to carry out pre-processing of the detected data and that the master IMU (5) transmits the position data of the at least one slave IMU (1, 2, 3, 4) to this, where the transmitted position data feeds into the pre-processing.

2. System according to claim 1, characterised in that the master IMU has a transmission unit which is set up to receive the data from the at least one slave IMU and / or to send the evaluated data to the electronic control device of the excavator (10).

3. System according to one of the preceding claims, characterised by at least angle sensor (6, 7) which determines the angle between two links of the kinematic chain.

4. System according to claim 3, characterised in that an angle sensor is arranged on one end of the kinematic chain.

5. System according to one of the preceding claims, characterised in that multiple slave IMUs (1, 2, 3, 4) are provided and that the master IMU (5) is set up to calculate the intermediate angle between the individual slave IMUs (1, 2, 3, 4) and / or between the master IMU (5) and the individual slave IMUs (1, 2, 3, 4) or to calculate the absolute angle of the individual IMUs (1, 2, 3, 4, 5) to a reference from the jointly evaluated data.

6. System according to claim 1, characterised in that the master IMU (5) is arranged on the superstructure (12) of the excavator (10).