U.S. patent application number 17/595355 was filed with the patent office on 2022-06-23 for method for putting down a tool of a construction machine.
The applicant listed for this patent is Robert Bosch GmbH. Invention is credited to Christian Krause, Kai Liu, Bilge Manga, Horst Wagner.
Application Number | 20220195705 17/595355 |
Document ID | / |
Family ID | 1000006254336 |
Filed Date | 2022-06-23 |
United States Patent
Application |
20220195705 |
Kind Code |
A1 |
Krause; Christian ; et
al. |
June 23, 2022 |
METHOD FOR PUTTING DOWN A TOOL OF A CONSTRUCTION MACHINE
Abstract
A method is for putting down a tool of a construction machine. A
position and an orientation of the tool relative to the
construction machine or to a direction of Earth's gravity is
determined by one or more of the following sensors including: an
inertial measuring unit, an angle sensor, a linear sensor, and/or
by an algorithm for determining a kinematic chain of the
construction machine. Moreover, an orientation of at least one part
of the construction machine, which part touches the ground, and
which orientation characterizes an orientation of the construction
machine relative to the ground, is determined relative to Earth's
gravity. Based on this determination, movement of the tool is
controlled, in order to bring a lower face of the tool to the same
level and in the same orientation as the at least one part touching
the ground, for putting down the tool.
Inventors: |
Krause; Christian;
(Stuttgart, DE) ; Liu; Kai; (Asperg, DE) ;
Wagner; Horst; (Niederstotzingen, DE) ; Manga;
Bilge; (Leonberg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Robert Bosch GmbH |
Stuttgart |
|
DE |
|
|
Family ID: |
1000006254336 |
Appl. No.: |
17/595355 |
Filed: |
May 7, 2020 |
PCT Filed: |
May 7, 2020 |
PCT NO: |
PCT/EP2020/062643 |
371 Date: |
November 15, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F 9/265 20130101;
E02F 9/2041 20130101 |
International
Class: |
E02F 9/26 20060101
E02F009/26; E02F 9/20 20060101 E02F009/20 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2019 |
DE |
10 2019 207 164.3 |
Claims
1. A method for depositing a tool of a construction machine on the
ground, comprising: determining a position and an orientation of
the tool relative to the construction machine or to a direction of
Earth's gravity using one or more of an inertial measurement unit,
an angle sensor, a linear sensor, and/or by use of an algorithm for
determining a kinematic chain of the construction machine;
determining, relative to Earth's gravity, an orientation of at
least one part of the construction machine contacting the ground
that characterizes an orientation of the construction machine
relative to the ground; and controlling a movement of the tool by
closed-loop control in order to bring an underside of the tool to a
same level and to the same orientation as the at least one part of
the construction machine contacting the ground, for depositing the
tool on the ground.
2. The method as claimed in claim 1, wherein: the orientation of
the at least one part of the construction machine contacting the
ground is determined with the inertial measurement unit, and a
sensor signal of an inertial sensor of the inertial measurement
unit located on the construction machine is used to determine the
orientation of the at least one part of the construction machine
contacting the ground.
3. The method as claimed in claim 1, wherein: determining the
orientation of the tool includes determining an inclination of the
tool, and determining the orientation of the at least one part of
the construction machine contacting the ground includes determining
an inclination of the at least one part of the construction machine
contracting ground.
4. The method as claimed in claim 3, wherein, in controlling the
movement of the tool by closed-loop control, at least one joint
angle of at least one joint between the tool and the construction
machine is controlled by closed loop control, such that the
underside of the tool is deposited horizontally and/or parallel to
the ground.
5. The method as claimed in claim 1, wherein the at least one part
of the construction machine contacting the ground includes one or
more wheels and/or a drive chain.
6. The method as claimed in claim 1, wherein a computer program is
configured to perform the method.
7. The method as claimed in claim 6, wherein the computer program
is stored on a non-transitory machine-readable storage medium.
8. The method as claimed in claim 1, wherein an electronic control
device is configured to deposit the tool using the method.
Description
[0001] The present invention relates to a method for depositing a
tool of a construction machine on the ground with the aid of tool
center point estimation. Further, the invention relates to a
computer program, which performs each step of the method when
executed on a computing device, and to a machine-readable storage
medium that stores the computer program. Finally, the invention
relates to an electronic control device that is configured to
execute the method according to the invention.
PRIOR ART
[0002] One of the basic maneuvers of many construction machines
such as, for example, excavators, wheel loaders, bulldozers and the
like, is to deposit the tool of the construction machine on the
ground. The tool in this case must be placed on the ground safely,
i.e. without tipping or slipping (off), and with as little impact
force as possible. This maneuver is often difficult, especially for
inexperienced operators, in particular if the view of the tool
and/or of the ground is obstructed.
[0003] Algorithms for determining the kinematic chain are known.
For this purpose, one or more of the following sensors are arranged
on each link of the tool arm, inertial measurement unit (IMU),
angle sensors, linear sensors, which send sensor data to a
computing device. The sensor data thus ascertained are filtered
individually for each sensor and are fused for the purpose of
estimating the state of the orientation of the respective sensor
relative to a stationary inertial coordinate system. Such an
algorithm is used, for example, in tool center point estimation.
Tool center point estimation is an algorithm for estimating the
state of orientation and position of an end effector. In
particular, the end effector is a tool or a part of a tool that has
a tool arm having a plurality of links connected by joints.
[0004] Typically used methods are described in the paper by Nikolas
Trawny and Stergios I. Roumeliotis, "Indirect Kalman filter for 3D
attitude estimation", University of Minnesota, Dept. of Comp. Sei.
& Eng, Tech. Rep 2 (2005), in the paper by Robert Mahony, Tarek
Hamei, and Jean-Michel Pflimlin, "Nonlinear complementary filters
on the special orthogonal group", IEEE Transactions on automatic
control 53.5 (2008): 1203-1218, and in the paper by Sebastian
Madgwick, "An efficient Orientation filter for inertial and
inertial/magnetic sensor arrays", Report x-io and University of
Bristol (UK) 25 (2010), to which reference is made in this
respect.
[0005] From the orientation of the sensor estimated in this way,
the orientation of the link on which the sensor is located is first
determined. This is done for all links of the tool arm. From the
relative orientation of two successive links, the joint angle of
the joint connecting the two links can be calculated if the
kinematics are known (for example, if the Denavit-Hartenberg
parameters are known). Finally, if all joint angles and the
dimensions of the links are known, the entire configuration of the
tool arm follows directly from the forward kinematics, and hence
the orientation and position of the end effector.
[0006] For a detailed description, reference is made to the paper
by Mark W. Spong, Seth Hutchinson and Mathukumalli Vidyasagar,
"Robot modeling and control", Vol. 3. New York: Wiley, 2006.
DISCLOSURE OF THE INVENTION
[0007] A method for depositing a tool of a construction machine on
the ground is proposed. "Depositing" is understood here as the
process of guiding the tool to the ground until the underside of
the tool rests securely on the ground.
[0008] Throughout the method, the position and orientation of the
links of the kinematic chain, including the tool, relative to the
construction machine or to the earth's gravity are determined by
means of one or more of the following sensors, inertial measurement
unit, angle sensor, linear sensor, by use of an algorithm for
determining the kinematic chain. The algorithm for determining the
kinematic chain is based on sensor signals from the sensors
arranged on at least the at least one part of the tool, and
preferably arranged on each link of the kinematic chain between the
construction machine and the tool. Inertial measurement units can
be easily and inexpensively retrofitted and can be used for other
methods.
[0009] In addition, the orientation of at least one part of the
construction machine contacting the ground, that characterizes the
orientation of the construction machine relative to the ground, is
determined relative to the earth's gravity. The orientation between
the at least one part of the construction machine contacting the
ground and a part of the construction machine indicating the
orientation of the construction machine is known, or can at least
be ascertained. Due to the direct contact between the at least one
part contacting the ground and the surface of the ground, the two
orientations correspond, at least at the point of contact. Since
the orientation of the surface typically changes only slightly over
a distance corresponding to the distance between the at least one
part contacting the ground and the tool--provided the construction
machine is not directly on a ledge--the orientation of the surface
of the ground at the place where the tool is deposited can be
estimated from the orientation of the surface of the ground at the
point of contact, and thus substantially corresponds to the
orientation of the at least one part of the construction machine
contacting the ground.
[0010] Preferably, the orientation of the at least one part of the
construction machine contacting the ground is determined via the
inertial measurement unit, and particularly preferably by the
previously mentioned algorithm for determining the kinematic chain.
For this purpose, a sensor signal of an inertial sensor of the
inertial measurement unit on the construction machine is used. In
this case, the inertial sensor is arranged on the construction
machine in such a manner that the orientation between this inertial
sensor and the at least one part of the construction machine
contacting the ground is known from the design of the construction
machine, or can at least be ascertained. Optionally, the
orientation of the vertical axis of the construction machine
relative to the earth's gravity can be determined in order to
determine the orientation of the at least one part of the
construction machine contacting the ground.
[0011] In particular, the at least one part of the construction
machine contacting the ground is realized by wheels or a track
chain, i.e. elements that contact the ground to move the
construction machine. Generally, the construction machine may also
stand on the ground with the at least one part contacting the
ground; examples of this are a support or a foot.
[0012] If the tool is now to be deposited on the basis of a command
from an operator or on the basis of automatic control of the
construction machine, the movement of the tool is controlled by
closed-loop control, taking into account the position and
orientation of the tool and the orientation of the at least one
part of the construction machine contacting the ground. The
closed-loop control of the movement of the tool as the tool is
being deposited is executed in such a manner that the underside of
the tool, which is to rest on the ground after being deposited, is
brought to the same level, hence in particular to the same height,
and to the same orientation as the at least one part contacting the
ground. As already described, the orientation of the at least one
part of the construction machine contacting the ground corresponds
substantially to the orientation of the surface of the ground at
the place of deposit.
[0013] Advantageously, in the determination of the orientation of
the tool, the inclination of the tool is determined and, in the
determination of the orientation of the at least one part of the
construction machine contacting the ground, the inclination of this
part is determined. In this case, in the closed-loop control, at
least one joint angle of a joint between the tool and the
construction machine may be controlled by closed-loop control such
that the underside of the tool is deposited horizontally
and/or--even if the ground is not horizontal--parallel to the
ground. In other words, the joint angle is controlled by
closed-loop control such that the inclination of the underside of
the tool corresponds to the inclination of the at least one part of
the construction machine contacting the ground, which also
corresponds substantially to the inclination of the surface of the
ground at the place of deposit.
[0014] Depositing the tool is a basic maneuver in the case of many
construction machines. As a result of the closed-loop control
according to the method according to the invention, the depositing
of the tool is at least partially automated. For example,
depositing of the tool may be triggered by the operator, by the
pressing of a button. The automation of this particular maneuver
may be performed independently of an autonomous control. However,
an autonomous control of the construction machine may make use of
this automated depositing of the tool according to the method.
[0015] For the operator, the automated depositing of the tool
offers, inter alia, the following advantages: if an operator's view
of the tool is obstructed, for example by the construction machine
itself, manual control for depositing the tool is often difficult
and can only be executed by skilled operators. The automated
depositing of the tool according to the method therefore
facilitates operation, especially for inexperienced operators. If a
work sequence in which the tool is deposited is repeated
continuously, which is the case, for example, with a so-called
Y-cycle for loading and unloading, e.g. in the case of a wheel
loader, the automation simplifies the operation. When the operator
parks and leaves the vehicle, the tool can be deposited
automatically in order to increase safety. In this case, however,
it must be ensured that the tool can actually be put down safely at
this place and time without causing damage.
[0016] An ambient sensor system may be provided on the construction
machine to sense the surroundings of the construction machine. This
is often able to sense the orientation and level of the ground in
the surroundings. Consequently, with the aid of the ambient sensor
system, it is possible to detect ledges. The data from the ambient
sensor system may be taken into account in the closed-loop control
of the movement of the tool. In general, however, this method also
makes it possible to dispense with the ambient sensor system.
[0017] A further advantage is that the depositing of the tool can
be controlled, by closed-loop control, more precisely by this
method than by a method based only on the ambient sensor system or
by a method in which a change in the hydraulic pressure is
evaluated.
[0018] The computer program is configured to perform each step of
the method, in particular when executed on a computing device or
control device. It enables the method to be implemented in a
conventional electronic control device without the necessity of
making structural changes to it. For this purpose, it is stored on
the machine-readable storage medium.
[0019] As a result of the computer program being uploaded to a
conventional electronic control device, the electronic control
device obtained is a device configured to control the depositing of
the tool by closed-loop control.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Exemplary embodiments of the invention are represented in
the drawings and explained in more detail in the description that
follows.
[0021] FIG. 1 shows a schematic representation of a construction
machine in which, by means of the method according to the
invention, a tool, from an initial state (a), is deposited on the
ground (b).
[0022] FIG. 2 shows a flow diagram of the method according to the
invention.
EXEMPLARY EMBODIMENTS OF THE INVENTION
[0023] FIG. 1 shows a schematic representation of a construction
machine 1 in the form of a wheel loader, having a tool 2 realized
as a shovel. The tool 2 is connected to the construction machine 1
via a working arm 3, there being a respective joint 4 arranged
between the construction machine 1 and the working arm 3, and
between the tool 2 and the working arm 3, which movably connects
the respective components. In further exemplary embodiments that
are not shown, the working arm may also be of a multi-link design,
in which case there is also a joint arranged between each of the
individual links. The construction machine 1, the working arm 3 and
the tool 2 form a kinematic chain. There is a respective inertial
sensor 5, 5' of an inertial measurement unit arranged on each link
of the kinematic chain, i.e. on the construction machine 1, the
working arm 3 and the tool 2. The inertial sensor 5' arranged on
the construction machine 1 has a special significance in this case
(see below) and is therefore denoted by a dash ('). The inertial
sensors 5, 5' are connected to an electronic control device 6 of
the construction machine 1. The construction machine 1 in the form
of the wheel loader has wheels 7 that are connected to the
construction machine 1 via axles (not shown) and contact the ground
8.
[0024] In further embodiments, not shown here, the construction
machine 1 is realized, for example, in the form of a bulldozer, in
which, instead of the wheels, a track chain contacts the ground. In
still further embodiments, the construction machine 1 may contact
the ground with a support or a foot, for example when the
construction machine 1 is a stationary construction machine 1 or is
supported in a working mode.
[0025] Represented in FIG. 1 are two states a) and b), which were
recorded at different times. In the initial state a), the tool 2 is
still raised. In the final state b), the tool 2 is at the same
level as the underside of the wheels 7, and the orientation of the
tool 2 corresponds to the orientation of the ground 8, such that
the tool 2 is deposited on the ground 8. The joints 4 are oriented
differently in the two states.
[0026] Represented in FIG. 2 is a flow diagram of an exemplary
embodiment of the method according to the invention. At the
beginning and throughout the method, the orientation, in particular
the inclination, and the position of the tool 2 and of the working
arm 3 relative to the construction machine 1 or to the earth's
gravity are determined, by means of the inertial sensors 5, 5' on
the construction machine 1, the working arm 3 and the tool 5, by
use of an algorithm for determining the kinematic chain 10. For
this purpose, the sensor data from the inertial sensors 5, 5' along
the kinematic chain are used. From the orientation, or inclination,
and the position of the tool 2 and of the working arm 3, current
actual joint angles .theta..sub.actual for the joints 4 are then
determined 11 by means of so-called Denavit-Hartenberg parameters
(see, for example, Spong et al. "Robot modeling and control", Vol.
3. New York: Wiley, 2006). Also determined 20 at the beginning are
the contact points of the wheels 7 relative to the earth's gravity,
which substantially represent the orientation of the surface of the
ground 8. Preferably, the orientation of the inertial sensor 5'
arranged on the construction machine 1 may be determined by means
of a part of the same algorithm for determining the kinematic
chain, using only the sensor data of this inertial sensor 5'. In
the case of the wheel loader shown here, there is a fixed
relationship between the contact points of the wheels 7 and the
orientation of this inertial sensor 5', such that the contact
points of the wheels 7, and thus the orientation of the ground 8,
can be inferred from the orientation of the inertial sensor 5'.
[0027] If the depositing of the tool 2 is activated by an operator
30, for example by pressing a button provided for this purpose, the
orientation of the tool 2 in the inertial system, i.e. the
inclination with respect to the earth's gravity, is ascertained 40.
Then target joint angles .theta..sub.target are ascertained 41 from
the orientation of the tool 2 in the inertial system and the
contact points of the wheels 7.
[0028] In a further exemplary embodiment, not shown, when the
depositing of the tool 2 is activated by an operator 30,
trajectories of movement for the tool 2 are ascertained. In the
trajectories of movement, trajectories are described in the
coordinates of a solid coordinate system. For this purpose, the
position of the tool 2 is specified in the coordinates of the
construction machine 1. Target joint angles .theta..sub.target are
then ascertained from these trajectories of movement.
[0029] Finally, a closed-loop control 50 is provided for depositing
the tool 2 on the ground 8, in which the actual joint angles
.theta..sub.actual are controlled to the target joint angles
.theta..sub.target, such that the underside of the tool 2 is
brought to the same level, i.e. the same height, as the plane of
the contact points of the wheels 7, parallel to the plane of the
contact points of the wheels 7 and thus parallel to the ground 8,
therefore horizontal in this exemplary embodiment.
* * * * *