DE102012208095A1 - Method for operating mobile robot, involves determining positions of mobile carrier device in polar coordinates and position of mobile carrier device in coordinates of fixed global coordinate system and angular positions of robot arm axes - Google Patents

Abstract

The method involves determining a target position and target orientation in a space of an end effector fixed to the robot arm (7) or a tool center point (8) arranged at the robot arm, to which a reference coordinate system with polar coordinates is assigned. The positions of the mobile carrier device (2) in the polar coordinates of the reference coordinate system, including an orientation of the mobile carrier unit relative to the reference coordinate system are determined, such that the tool center point assumes the specified target position and target orientation. The position of the mobile carrier device in the coordinates of a fixed global coordinate system (K-global) and the angular positions of the axes (A1 to A6) of the robot arm are determined, such that the tool center point assumes the specified target position and target orientation. An independent claim is included for a mobile robot with a robot arm.

Description

The invention relates to a mobile robot and a method for operating a mobile robot.

The US 5,550,953 discloses a mobile robot and a method for operating the mobile robot. The mobile robot includes a robot arm having a plurality of relatively movable members and a host vehicle to which the robotic arm is attached.

The object of the invention is to control the position, i. to determine the position and orientation of the mobile robot improved in the room so that the robot arm or a tool center point associated with the robot arm or an end effector attached to the robot arm can assume or assume a predefined desired position and desired orientation.

• a) Festlegen einer Soll-Position und Soll-Orientierung im Raum eines dem Roboterarm oder eines am Roboterarm befestigten Endeffektors zugeordneten Tool Center Points, dem ein Referenzkoordinatensystem mit Polarkoordinaten zugeordnet ist,
• b) Festlegen der Lage oder möglicher Lagen der mobilen Trägervorrichtung in den Polarkoordinaten des Referenzkoordinatensystems inklusive einer Ausrichtung der mobilen Trägervorrichtung bezüglich des Referenzkoordinatensystems, sodass der Tool Center Point die festgelegte Soll-Position und Soll-Orientierung einnimmt oder einzunehmen vermag, und
• c) basierend auf den Polarkoordinaten des Referenzkoordinatensystems, Bestimmen der Lage der mobilen Trägervorrichtung in Koordinaten eines feststehenden Weltkoordinatensystems und von Winkelstellungen der Achsen des Roboterarms, sodass der Tool Center Point die festgelegte Soll-Position und Soll-Orientierung einnimmt oder einzunehmen vermag.

The object of the invention is achieved by a method for operating a mobile robot, comprising a mobile carrier device with drives for moving the carrier device, at least one robot arm with a plurality of successively arranged with respect to axes relatively movable members and with drives for moving the members, and a control device, which is set up to control the drives of the mobile carrier device and of the at least one robot arm, comprising the following method steps:

• a) specifying a desired position and desired orientation in the space of a tool center point assigned to the robot arm or an end effector attached to the robot arm, to which a reference coordinate system with polar coordinates is assigned,
• b) setting the position or possible positions of the mobile carrier device in the polar coordinates of the reference coordinate system including an orientation of the mobile carrier device with respect to the reference coordinate system, so that the tool center point is able to take or take the specified desired position and target orientation, and
• c) based on the polar coordinates of the reference coordinate system, determining the position of the mobile carrier device in coordinates of a fixed world coordinate system and angular positions of the axes of the robot arm, so that the tool center point is able to take or take the specified desired position and target orientation.

Another aspect of the invention relates to a mobile robot comprising a mobile carrier device having drives for moving the carrier device, at least one robotic arm having a plurality of members movable in relation to each other and movable relative to one another and drives for moving the members relative to the axes, and a control device , which is set up to control the drives of the mobile carrier device and the robot arm. The mobile robot according to the invention is set up to carry out the method according to the invention. For this purpose, e.g. the control device of the mobile robot according to the invention suitably configured, for example by means of a computer program executing the method according to the invention, with which the control device is configured and which in particular runs on its control device during the intended operation of the mobile robot according to the invention. The drives of the robot arm and / or the carrier device are preferably electric drives and / or regulated drives, in particular regulated electric drives.

The mobile carrier device may preferably be formed as a carrier vehicle with wheels, wherein the drives of the mobile carrier device are adapted to move the wheels. The mobile robot according to the invention can also be designed as a humanoid robot whose mobile carrier device is designed as a robot leg.

The degrees of freedom of a conventional mobile robot or its mobile platform or its carrier device are usually considered independently of the robotic arm attached thereto and indicated as a global Cartesian position in 2D space as a 3-tuple with coordinates of a fixed world coordinate system (x, y, θ) that is, more specifically, as position and rotation about the center of the host vehicle in the 2D plane.

A mobile platform or the carrier device extends the working range of the robotic arm or manipulator mounted thereon beyond its reach. This results in additional degrees of freedom for the mobile robot and, as a result, additional redundancies of the mobile robot, which can be identified and described mathematically, so that an unambiguous assignment of Cartesian coordinates with respect to the world coordinate system of the end effector (x, y, z, A , B, C) to angular positions of the robot arm and Cartesian position (x, y, θ) of the mobile platform or the mobile carrier device is possible.

According to the invention, first the desired position and the desired orientation, ie the desired position or target pose of the tool center point of the mobile robot or its robot arm or of the Fixed to the robot arm attached end effector. Preferably, the desired position and the desired orientation of the tool center point are defined in coordinates of the fixed world coordinate system. Subsequently, however, the corresponding position, ie position and orientation, of the mobile robot or its carrier device is not given in coordinates of the world coordinate system, but first in polar coordinates of the tool center point associated with the reference coordinate system. If the mobile robot according to the invention is a redundant robot, ie, as is provided according to a variant of the mobile robot according to the invention, its robot arm is designed such that the mobile robot according to the invention has redundant degrees of freedom, then preferably the possible positions of the carrier vehicle in the polar coordinates of the reference coordinate system including possible orientations with respect to the reference coordinate system. This results in conditions for easier calculation of the position and orientation or the positions and orientations of the host vehicle, as well as a more intuitive operation and handling of the mobile robot, for example when programming the task.

Subsequently, the position of the carrier device in coordinates of the fixed world coordinate system is determined based on the polar coordinates of the reference coordinate system. In addition, according to the invention, angular positions of the axes of the robot arm are determined in the same step and based on the polar coordinates of the reference coordinate system, so that the tool center point can assume or assume the specified desired position and desired orientation.

The location of the mobile carrier device may be e.g. manually set. According to a preferred variant of the method according to the invention, the position or the possible positions of the mobile carrier device in the polar coordinates of the reference coordinate system and the orientation or the possible orientations of the mobile carrier device with respect to the reference coordinate system automatically by means of a higher-level planning system, in particular by means of a path planning and / or a control strategy established. Thereby, e.g. Also, a collision of the mobile robot with an object can be avoided.

In order to determine a complete path for the mobile robot, the steps a) to c) are preferably repeated for a plurality of consecutively following desired positions and desired positions of the tool center point.

The carrier vehicle is preferably designed as an omnidirectionally movable carrier vehicle (holonomic platform). Preferably, therefore, the wheels of the carrier vehicle are designed as omnidirectional wheels. An example of an omnidirectional wheel is the Mecanum wheel known to those skilled in the art. Due to the omnidirectional wheels, it is possible for the mobile robot according to the invention or its carrier vehicle to move freely in space. Thus, the host vehicle can not only move forwards, backwards, or sideways, or make turns, but can also travel e.g. rotate around a vertical axis.

Optionally, the method of the present invention provides a well thought-out approach to the positioning of mobile robots, since an analytical backward calculation for the overall system, i. the mobile robot, if necessary, can be provided and used. With the help of analytical backward calculation, it is possible, if necessary, to decide on all solutions to the task, i. that the Tool Center Point assumes its desired position and target orientation, iterate. This may be useful for a graphical programming tool, as well as automatic planning software.

Optionally, additional kinematic redundancies for collision avoidance, energy optimization, avoids Achsendanschlägen, etc. can be used

Optionally, redundancy of the mobile robot for collision avoidance in the application process (e.g., welding, bonding, mobile robot painting) may be enabled within collision-free path planning.

Optionally, null space movement can be enabled using the mobile robot.

There may be a possibility for coordinated movement of the carrier vehicle and robot arm by using the common inverse kinematics.

An embodiment of the invention is illustrated by way of example in the accompanying schematic drawings. Show it:

1 a mobile robot comprising a host vehicle and a robotic arm attached to the host vehicle,

2 an omnidirectional wheel,

3 a diagram illustrating the determination of the attitude of the host vehicle and

4 a diagram describing an inverse kinematics of the mobile robot.

The 1 shows a mobile robot 1 which, in the case of the present embodiment, an omnidirectionally movable carrier vehicle 2 having. This includes, for example, a vehicle body 3 and several, on the vehicle body 3 rotatably arranged wheels 4 , which are designed in particular as omnidirectional wheels. In the case of the present embodiment, the carrier vehicle 2 four omnidirectional wheels 4 on. At least one of the wheels 4 , preferably all wheels 4 is or are driven by one or more drives. The drives, not shown, are preferably electric drives, in particular regulated electric drives and are provided with an example in or on the vehicle body 3 arranged control device 5 connected, which is set up, the host vehicle 2 by appropriate activation of the drives for the wheels 4 to move.

An example of an omnidirectional wheel is the so-called Mecanum wheel. A wheel designed as an omnidirectional wheel 4 of the mobile robot 1 or its carrier vehicle 2 is in the 2 shown as a front view.

The wheel designed as omnidirectional or Mecanum wheel 4 has in the case of the present embodiment, two rigidly interconnected wheel discs 21 on, between which several rolling bodies 22 with respect to their longitudinal axes 23 are rotatably mounted. The two wheel discs 21 can with respect to a rotation axis 24 be rotatably mounted and by means of one of the drives of the carrier vehicle 2 be driven so that the two wheel discs 21 with respect to the axis of rotation 24 rotate.

In the case of the present embodiment, the rolling bodies 22 evenly spaced and so on the wheel discs 21 stored that their rolling surfaces over the circumference of the wheel discs 21 protrude. Besides, the rolling bodies 22 like that on the wheel discs 21 stored that their longitudinal axes 23 with the rotation axis 24 an angle α of, for example, 45 °.

Due to the omnidirectional wheels 4 it is the mobile robot 1 or its carrier vehicle 2 allows you to move freely around the room. So can the carrier vehicle 2 not only moving forward, backward, or sideways, or turning, but also rotating about any vertically aligned axis, for example, about the axis A1 of the robotic arm.

The mobile robot 1 further comprises a robot arm 7 in particular on the carrier vehicle 2 or on the vehicle body 3 is attached. Due to the omnidirectional wheels 4 represents the carrier vehicle 2 Thus, in the case of the present embodiment, a holonomic platform for the robot arm 7 dar. The carrier vehicle 2 but can also act as a non-holonomic platform for the robotic arm 7 be executed. The carrier vehicle 2 thus represents a mobile carrier device to which the robot arm 7 is attached. For example, if the mobile robot is designed as a humanoid or insect-like robot, then this carrier device can also be designed as a plurality of robot legs, by means of which the robot can be moved.

The robot arm 7 comprises in the case of the present embodiment, a plurality of successively arranged and connected by joints members. The limbs are in particular a frame 9 , by means of which the robot arm 7 on the vehicle body 3 is attached.

The robot arm 7 has as a further link, for example, relative to the frame 9 in particular about the vertical axis A1 rotatably mounted carousel 10 on. Further links of the robot arm 7 are in the case of the present embodiment, a rocker 11 , a boom 12 and a preferably multi-axis robotic hand 13 with a fastening device designed as a flange, for example 6 for fastening an end effector or a tool. The swingarm 11 is at the lower end, for example, on a swing bearing head not shown on the carousel 10 pivotally mounted about a preferably horizontal axis A2. At the upper end of the swingarm 11 is again about a likewise preferably horizontal axis A3 of the boom 12 pivoted. This carries the end of the robot hand 13 with their example, three axes of rotation (axes A4-A6). The robot hand 13 but can also have only 2 axes of rotation.

The robot arm 7 further comprises the control device 5 connected drives. The drives are in the case of the present embodiment, electric drives, in particular regulated electrical drives. In the 1 These are just a few of the electric motors 14 shown these electrical drives.

In the operation of the mobile robot 1 it is envisaged that the control device 5 the drives of the robotic arm 7 and the wheels 4 so controls, so that the fastening device 6 or one of the fastening device 6 or on the fastening device 6 attached end effector associated with so-called Tool Center Point 8th a predetermined target position or target pose, that occupies a desired position and target orientation in space. This is the carrier vehicle 2 controlled by the control device 5 , placed in a position according to this target pose and in an orientation in the Space aligned and the axes A1-A6 of the robot arm 7 in corresponding axis positions or angular positions θ1-θ6 brought.

In the case of the present exemplary embodiment, the tool center is assigned a coordinate system, ie a reference coordinate system K _Ref , which is _stored in the 3 is shown. The origin of the reference _coordinate system K _Ref lies in particular in the Tool Center Point 8th ,

In the case of the present embodiment, the position of the carrier vehicle is now 2 , ie its position and orientation, the carrier vehicle 2 takes the tool center point 8th assumes its target pose, not determined _globally in coordinates of a fixed world coordinate system K, but first in polar coordinates ρ1, ρ2 of the reference coordinate system K _Ref including an orientation ρ3 of the mobile carrier device 3 with respect to the reference _coordinate system (K _Ref ).

In the case of the present embodiment, the carrier vehicle 2 that is to say the degrees of freedom assigned to the polar coordinates ρ1, ρ2 of the reference coordinate system K _Ref and the orientation ρ3. Are for a target pose of the Tool Center Points 6 several positions and orientations of the carrier vehicle 2 possible, then the polar coordinates ρ1, ρ2 and the orientation ρ3 can be regarded as redundancy parameters.

Instead of a 3-tuple, indicate the position and orientation of the host vehicle 2 in the space with respect to the global world coordinate system K _Ref with the coordinates x, y, θ describes, a 3-tuple is first determined, which determines the position of the host vehicle 2 by means of the polar coordinates ρ1, ρ2 and the orientation ρ3 in the local reference coordinate system K _Ref .

The polar coordinates ρ1, ρ2 describe the position with respect to the reference coordinate system K _Ref in two-dimensional polar coordinates and additionally the rotation of the carrier vehicle 2 by means of the orientation ρ3.

Thus, the polar coordinate ρ1 describes the distance of the host vehicle 2 from the origin of the reference coordinate system K _Ref , the polar coordinate ρ2 the approach direction of the host vehicle 2 on a distance circle K of radius ρ1, and the orientation ρ3 on the orientation of the host vehicle 2 with respect to the reference coordinate system K _Ref and possibly relative to a carrier vehicle coordinate system K _carrier , whose origin is preferably at the origin of the robot arm 7 assigned coordinate system, so preferably a rotation axis of the host vehicle 2 with the axis A1 of the robot arm 7 concerning which the carousel 10 relative to the frame 9 is rotatable, falls together.

A location of the carrier vehicle 2 in the coordinates x, y, θ of the world coordinate system K _global can thus always be unambiguously described in the polar coordinates ρ1, ρ2 with respect to the reference system K _Ref and the orientation ρ3.

To the location of the carrier vehicle 2 and the robot arm 7 to align that with the Tool Center Point 6 assumes its desired pose, calculated in the case of the present embodiment, the control device 5 the axes A1-A6 of the robot arm 2 associated angular positions θ1-θ6 and the position of the host vehicle 2 in coordinates x, y, θ of the world coordinate system K _global based on the polar coordinates ρ1, ρ2 and the orientation ρ3 and the coordinates of the target position of the tool center point 8th , This is in the 4 illustrated.

Due to the target pose of the Tool Center Point 6 , which is indicated in particular in Cartesian coordinates x, y, z, A, B, C with respect to the world coordinate system, and the polar coordinates ρ1, ρ2, and the orientation ρ3, possibly also in addition due to kinematic redundancy parameters of the robot arm 7 Thus, the control device calculates the position of the host vehicle 2 in coordinates x, y, θ of the world coordinate system K _global and the angular positions θ1-θ6 of the axes A1-A6 of the robot arm 7 ,

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5550953 [0002]

Claims (10)

Method for operating a mobile robot ( 1 ), which is a mobile carrier device ( 2 ) with drives for moving the carrier device ( 2 ), at least one robotic arm ( 7 ) with a plurality of successively arranged, with respect to axes (A1-A6) relative to each other movable members ( 9 - 13 ) and with drives for moving the links ( 9 - 13 ), and a control device ( 5 ), which is set up, the drives of the mobile carrier device ( 2 ) and the at least one robot arm ( 7 ), comprising the following method steps: a) Specification of a desired position and desired orientation in the space of a robot arm ( 7 ) or one on the robot arm ( 7 attached end effector associated with Tool Center Points ( 8th ), to which a reference coordinate system (K _Ref ) with polar coordinates (ρ1, ρ2) is assigned, b) determining the position or possible positions of the mobile carrier device ( 2 ) in the polar coordinates (ρ1, ρ2) of the reference coordinate system (K _Ref ) including an orientation (ρ3) of the mobile carrier device ( 2 ) with respect to the reference _coordinate system (K _ref ) so that the tool center point ( 8th ) assumes or is able to assume the specified desired position and desired orientation, and c) based on the polar coordinates (ρ1, ρ2) of the reference coordinate system (K _Ref ) and the orientation (ρ3) of the mobile carrier device ( 2 ) with respect to the reference coordinate system (K _Ref ), determining the position of the mobile carrier device ( 2 ) in coordinates of a fixed world coordinate system (K _global ) and angular positions (θ1-θ6) of the axes (A1-A6) of the robot arm ( 7 ), so the Tool Center Point ( 8th ) assumes or is able to assume the specified desired position and desired orientation. Method according to Claim 1, in which the mobile carrier device is used as a carrier vehicle ( 2 ) with wheels ( 4 ) and the drives of the mobile carrier device are set up, the wheels ( 4 ) to move. Method according to claim 1 or 2, additionally comprising determining the desired position and the desired orientation of the Tool Center Point ( 8th ) in coordinates of the fixed world coordinate system (K _global ). Method according to one of Claims 1 to 3, in which the position or the possible positions of the mobile carrier device ( 2 ) in the polar coordinates (ρ1, ρ2) of the reference coordinate system (K _Ref ) including the orientation (ρ3) of the mobile carrier device with respect to the reference coordinate system (K _Ref ) is automatically determined by means of a higher-level planning system, in particular by means of a path planning and / or a control strategy. Method according to one of claims 1 to 4, comprising repeating steps a) to c) for a plurality of consecutively following desired positions and desired positions of the Tool Center Points ( 8th ). Mobile robot, comprising - a mobile carrier device ( 2 ) with drives for moving the carrier device ( 2 ), - at least one robot arm ( 7 ) with a plurality of successively arranged, with respect to axes (A1-A6) relative to each other movable members ( 9 - 13 ) and drives for moving the links ( 9 - 13 ) relative to the axes (A1-A6), and - a control device ( 5 ), which is set up, the drives of the mobile carrier device ( 2 ) and the robot arm ( 7 ), whereby the mobile robot ( 1 ), in particular its control device ( 5 ) is arranged to carry out the method according to one of claims 1 to 5. Mobile robot according to claim 6, wherein the mobile carrier device as a carrier vehicle ( 2 ) with wheels ( 4 ) is formed and the drives are the mobile carrier device, the wheels ( 4 ) to move. Mobile robot according to claim 7, in which the carrier vehicle ( 2 ) a vehicle body ( 3 ), on which the wheels ( 4 ) are rotatably arranged and on which the robot arm ( 7 ) is attached. Mobile robot according to claim 8, in which the wheels ( 4 ) of the host vehicle ( 2 ) are designed as omnidirectional wheels. Mobile robot according to one of claims 6 to 9, whose robot arm ( 7 ) is designed such that the mobile robot ( 1 ) has redundant degrees of freedom.

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