WO2019206924A1

WO2019206924A1 - Method for inserting objects into a common object receptacle

Info

Publication number: WO2019206924A1
Application number: PCT/EP2019/060402
Authority: WO
Inventors: Saskia Golz; Tobias Ende; Simon Gabl; Florian Walch
Original assignee: Franka Emika Gmbh
Priority date: 2018-04-23
Filing date: 2019-04-23
Publication date: 2019-10-31
Also published as: DE102018003271A1; TW202003175A

Abstract

The present invention concerns a method for inserting objects (5) into a common object holder (4) by means of a robot manipulator (1) and a robot manipulator (1) for carrying out such a method.

Description

Method for inserting objects into a common object receptacle

This invention concerns a method of inserting at least two objects into a common object holder using a robot manipulator. Furthermore, the invention concerns a robot manipulator for carrying out such a method.

Various products are combined and packaged in larger units for delivery. For example, smaller packaging units are

accommodated in a larger packaging unit, e.g. a cardboard box.

Depending on the weight, dimensions and properties of the products or units to be packaged, this packaging can still be carried out almost completely by hand.

Such manual processes have the disadvantage that the speed of loading is generally limited in relation to the packaging and depends on the skill of the packer.

Furthermore, there are automated processes, e.g. using pick & place robots, which, however, require a very high and

therefore economically undesirable programming effort, which only works with exactly defined positions in space.

Against this background, it is an objective of the present invention to provide a simple, robust and more cost-effective method for inserting several objects into an object holder common to these objects by means of a robot manipulator.

Furthermore, it is an objective to provide a robot manipulator that is trained to perform such a method. This objective is solved by a method of inserting objects into a common object receptacle using a robot manipulator according to claim 1 and a robot manipulator according to claim 10.

In a first aspect, therefore, the invention concerns a method for inserting objects into a common object receptacle by means of an actuator-driven robot manipulator of a robot and for controlling the robot manipulator, the robot manipulator having at its distal end an effector designed to receive and/or grip the objects,

with the following method steps:

a) picking up a first object from a storage device by the effector;

b) transferring the first object by means of the robot

manipulator to a position relative to the object receptacle which allows the first object to be inserted into the object receptacle by means of the robot manipulator;

c) inserting the first object into the object receptacle along a first insertion trajectory using the robot manipulator;

d) releasing of the first object by the effector;

e) picking up a second object from a storage device by the effector;

f) transferring the second object by means of the robot manipulator to a position relative to the object receptacle which allows the second object to be inserted into the object receptacle by means of the robot manipulator;

g) inserting the second object into the object receptacle along a second insertion trajectory using the robot

manipulator; and

h) releasing of the second object by the effector;

the second insertion trajectory being determined during insertion by

- a contact of the second object with the first object already present in the object receptacle; and/or - a contact of the second object with an inner boundary of the object receptacle; and/or

- a shifting mobility of the first object relative to the second object inside the object receptacle.

A package or cardboard box for accommodating smaller objects is preferably designed in such a way that it can accommodate n objects which are also dimensioned in such a way that, when the package is fully loaded, the objects generally completely fill the receiving space of the package. In a further

embodiment of the invention, the method is therefore designed in such a way that the above steps e) to h) are repeated for each further object (n-2) times until the object receptacle is fully loaded, the insertion trajectory of each further object being determined by

- contact of the further object with at least one of the objects already present in the object receptacle; and/or

- a contact of the further object with an inner boundary of the object receptacle; and/or

- a shifting movability of the objects already present in the object receptacle relative to each other and/or relative to the other object inside the object receptacle.

In an advantageous variant of the method, the insertion trajectory is defined or determined for each object by

recognizing the state of how far the insertion of the

respective object has progressed and/or whether the insertion of the respective object has been successfully completed, the state being defined by reaching or exceeding at least one predetermined limit value condition for a torque acting on the effector and/or a force acting on the effector, and/or a provided force/torque signature and/or a position/speed signature on the effector being reached or exceeded. The robot manipulator is preferably designed to follow the respective insertion trajectories for each object individually by force-controlled and/or impedance-controlled rotary/tilting movements and/or translatory movements of the robot

manipulator .

In a further advantageous embodiment of the method, if an error occurs when inserting the objects along the respective insertion trajectories into the object receptacle by means of the robot manipulator, the insertion of the corresponding object into the object receptacle can be repeated with a modified insertion trajectory and/or with modified parameters for the force-controlled and/or impedance-controlled

translatory and/or rotary/tilting movements of the object by means of the robot manipulator.

The core of the invention, in other words, lies in the fact that the robot manipulator can essentially "freely", i.e. in any order with regard to the arrangement of the individual objects, load the object receptacle while using during further course of loading the contact forces detectable by the robot sensors as an orientation aid within the framework of the control, which contact forces arise on the one hand when contacts occur between the object to be inserted and one or more objects already inserted and on the other hand when contacts occur between the object to be inserted and the internal boundaries, such as side walls and floor.

Since the robot also knows the dimensions and position of the object receptacle as well as the dimensions of the objects to be inserted, which are stored in a memory of the control unit of the robot, a program realizing the method according to the invention knows where approximately objects have already been deposited in the object receptacle by the robot manipulator, and thus where within the object receptacle there are approximately the free spaces still available for inserting the further objects, and can then align its further insertion or packaging strategy accordingly, taking into account

predefined tolerances.

Both the inner boundaries of the object receptacle and the outer boundaries of the objects (packagings) can be

advantageously used by the robot manipulator as guide surfaces for insertion, which it uses in the context of its compliance behaviour, as explained below.

Both the lateral translation and the rotational/tilting movements during the insertion of an object can be used on the one hand to move objects already inserted in the object receptacle, taking into account the remaining free spaces, and on the other hand to counter tolerance deviations between the objects and the object receptacle to ensure that the objects can be inserted more easily. In addition, they can be used during the insertion process to overcome frictional

resistances that occur between two surfaces when guided strictly linearly.

In order that the above-mentioned individual method steps can be carried out automatically in the course of equipping a packaging with objects in the manner described, it is

advantageous that these steps are preferably carried out by means of a robot which is compliantly and/or sensitively designed .

Robots with position-controlled axes are generally not

suitable for such steps in the method, since the forces acting on the robot from outside must be measured for position control. These forces form the basis for the desired dynamic behavior, which is then transmitted to the robot via inverse kinematics, also known as admittance control. A strictly position-controlled robot could not be programmed at all in this case, since the "free" placement of objects cannot be mapped at all with a "free" movement of the objects in the object receptacle due to the lack of exact coordinates in space.

Due to the control principle used, such position-controlled robots would also not be able to detect errors or deviations, for example if for any reason the actual position of the object to be inserted deviates slightly from the set position provided for this purpose when it is picked up by the effector from a storage device in order to react accordingly. A perfect insertion of the objects into the available space within the object receptacle would only be possible if these freely available spaces are provided exactly in relation to the working range of the robot, namely in relation to the object receptacle, within the framework of the programming.

For carrying out the method it is a core of the invention that the robot used, at least one robot, has such an integrated compliance control or is equipped with an intrinsic compliance or with a combination of active and passive compliance, the method also preferably being carried out by such programmable, multi-axis robot manipulators of robots of the lightweight design .

In this context, it should be mentioned that the compliance control is based, for example, on the so-called impedance control, which, in contrast to the admittance control already mentioned, is based on torque control at joint level.

Depending on a desired dynamic behavior and taking into account the deviations of an actual position from a defined target position and/or an actual velocity from a target velocity and/or an actual acceleration from a target acceleration, forces or torques are determined, which are then mapped via the known kinematics of the robot, which results from the number and arrangement of the joints and axes of the manipulator and thus degrees of freedom, to corresponding joint torques, which are set via the torque control. The torque sensor elements integrated in the joints record the one-dimensional torque prevailing at the output of the gear of the drive unit located in the joint, which can take into account the elasticity of the joint within the scope of control as a measured variable. In particular, the use of a corresponding torque sensor device, in contrast to the use of only one force moment sensor on the effector, as in admittance control, also allows the measurement of forces which are not exerted on the effector but on the links of the robot and on an object held by or to be processed by the robot when it is inserted into an object receptacle. The torques can also be measured via force sensors in the structure and/or base of the robot system. In particular, joint mechanisms between the individual axes of the manipulator can also be used, which allow multi-axis torque detection. Also conceivable are translatory joints equipped with corresponding force sensors.

The compliance control and sensitivity achieved in this way proves to be advantageous for this invention in many respects.

In principle, such a compliance control allows the robot used for the intended method or for individual method steps thereof to be able to carry out controlled internal movements, whereby these internal movements then correspond to individual steps of the method. In this context, such a robot would also be able to, if necessary, independently "search" and non- destructively "feel" the different positions of the objects and the storage devices as well as the receptacles or freely available spaces within the object receptacle. Such internal movements occur, for example, in connection with guiding the object to be inserted along surfaces of the internal boundaries of the object receptacle and the surfaces of the external boundaries of the objects already inserted.

A further advantage of the compliance control is that it allows the objects to be inserted to be placed more

inaccurately or not exactly positioned, which means that both the depositing devices and the object receptacle can be manufactured with higher tolerances. It is also possible that the object receptacle as such is easily deformable on contact, as is the case with cardboard packaging. Inaccuracies caused by this can be compensated for in a corresponding manner by means of a correspondingly compliant regulation by reducing the associated contact forces when taking up and inserting the obj ects .

The robot manipulator is advantageously designed and set up to move a determined point of the effector, for example the so- called "Tool Center Point" (TCP) or a determined point of the object (for example its center of gravity or geometric center) along the given insertion trajectory, whereby the center of gravity is determined individually by the respective object.

The insertion trajectory is therefore advantageously

determined depending on the relative starting position of the object arranged at the effector to its intended receiving space in the object receptacle, on the geometry of the object and on the geometry of the object receptacle.

When inserting objects, the insertion trajectory is preferably a straight line directed at the intended receiving space.

However, three-dimensional, single or multiple inclined curves are also conceivable until the object can be inserted into the receiving space. The effector can move along the respective insertion trajectories at a relatively high speed until shortly before reaching the receiving space. The effector then moves towards the receiving space at a much slower speed.

In principle, the robot manipulator must recognize what the actual state of the insertion process is, which, according to the invention, is realized by the aforementioned limit value conditions and/or individual signatures. These signatures are in principle concrete characteristic properties of forces and/or torques and/or positions and/or speeds recorded on the robot manipulator that exceed a simple threshold value. These may include, for example, a certain time behavior of the measured forces, torques, positions and/or speeds, as well as characteristic properties that depend on these parameters.

The aforementioned measures can significantly increase the success rate of the insertion process. As mentioned, it is therefore not necessary for the objects to be inserted to be positioned exactly inside the storage device, and furthermore, it is not necessary for the effector to pick up the objects exactly. The compliantly controlled robot manipulator is able to apply the above-mentioned compensatory measures during the insertion process into the object receptacle.

As a result, the method according to the invention proves to be much more economical than a well-known pick & place process with position-controlled robots.

Another aspect of the invention concerns a computer system with a data processing device, wherein the data processing device is designed such that a method as described above is performed on the data processing device. Another aspect of the invention concerns a digital storage medium with electronically readable control signals, whereby the control signals can interact with a programmable computer system in such a way that a method as described above is carried out.

Furthermore, the invention concerns a computer program product with a program code stored on a machine-readable medium for carrying out the method as described above when the program code is executed on a data processing device, and a computer program with program codes for carrying out this method when the program is executed on a data processing device.

A further aspect of the invention concerns a robot with an actuator-driven robot manipulator, the robot manipulator having at its distal end an effector designed to receive an object, comprising a control unit which is designed and arranged such that a method as described above is executable.

According to the invention, the robot is preferably an

articulated arm robot of lightweight construction with a robot manipulator with at least 6, preferably 7 degrees of freedom.

According to the invention, the robot is to be used in

connection with the loading of a packaging with products which have essentially the same weight and dimensions, which

simplifies teaching.

Further advantages and features of the invention result from the description of the embodiment shown in the enclosed drawings, in which

Fig. 1 schematically shows a configuration of a robot station for carrying out the method according to the invention; Fig. 2 is an enlarged representation of the object receptacle; Fig. 3a - 3b show the pick up and transfer of a first object of the method according to the invention;

Fig. 4a - 4c show the insertion of the first object into the object receptacle of the method according to the invention; Fig. 5 is another enlarged view of the object receptacle;

Fig. 6 show the pick up of a second object of the method according to the invention; and

Fig. 7a - 7i show the insertion of the second object into the object receptacle of the method according to the invention.

Fig. 1 shows a schematic structure of a robot station for carrying out the method according to the invention using the example of packaging smaller units in a single cardboard box.

The proposed method of inserting several objects into a common object receptacle is implemented by means of an actuator- driven robot manipulator 1 of a robot which has at its distal end an effector 2 with gripping fingers 3 which are designed for holding and/or gripping the objects.

In front of the stationary robot are arranged in defined stationary positions an object receptacle 4, a cardboard box, for holding or packaging smaller objects 5, e.g. boxes, and storage devices 6 for these objects 5. It is not necessary that the storage device is stationary; the objects 5 can also be fed continuously to the robot station or removed from a chute .

As can be seen in the enlarged illustration of Fig. 2, if the object receptacle 4 is only partially equipped, a free space 7 is created for accommodating further objects. The robot manipulator 1 grips a first object 5.1 (Fig. 3a) with its effector 2, lifts it (Fig. 3b) and transfers it into a starting position for insertion into free space 7 (Fig. 4a) .

Along a first trajectory T, as shown in Fig. 4a, the robot manipulator 1 then places the object 5.1 in free space 7 (Fig. 4b) and then retracts (Fig. 4c), leaving sufficient space on both sides of the object 5.1, as can be seen in Fig. 5.

The robot manipulator 1 then grips a second object 5.2 (Fig.

6) and transfers it into a starting position for insertion into the object receptacle 4 (Fig. 7a) .

Figures 7a to 7i show in detail the insertion of the second object 5.2.

The robot manipulator 1 lowers the object 5.2 (Fig. 7a) and simultaneously leads it to the right wall or inner boundary of box 4 (Fig. 7b) until it comes to rest on an object 5 already in the object receptacle 4 (Fig. 7c).

Then the robot manipulator 1, using the wall of box 4 on the one hand and the surface of the object 5 located there on the other hand, pushes object 5.2 towards object 5.1 (Fig. 7c), whereby on contact with object 5.1 it slightly tilts object 5.2, which is indicated by corresponding arrows (Fig. 7d) so that the object 5.2 can engage in the free space in front of it in order to move the object 5.1 as part of a further translatory movement up to the front wall of box 4, and then finally move the object 5.2 downwards into the resulting free space by a translatory movement (Fig. 7e) . Here the robot manipulator 1 can perform slight tilting movements.

Finally the robot manipulator 1 inserts the object 5.2 (Fig. 7f,7g), releases it and lets it slide down the last distance (Fig. 7h) before the robot manipulator (Fig. 7i) withdraws to get another object 5.

It becomes clear that during the insertion process with respect to the object 5.2 a three-dimensional trajectory is traversed, which consists of several lateral and vertical translational as well as tilting and/or rotating movements.

In this context, all movements of robot manipulator 1 are force-controlled and/or impedance-controlled. The outer surfaces of the already inserted objects 5 and the inner walls of the packaging 4 serve as guide surfaces for the robot manipulator 1, which acts with them within the scope of its compliance control.

All the above-mentioned insertion and displacement movements have in common that the robot manipulator 1 is designed with its control unit, based on at least one predetermined ideal limit value condition G_±, e.g. a counterforce resulting from a completely inserted object 5, or based on an ideal

force/torque signature and/or position/speed signature Si, to recognize how far the insertion process has progressed or whether the respective object 5 is completely inserted into the spaces provided for this purpose.

If the robot's sensors detect, e.g. by means of the torque and, if necessary, force sensors arranged in the joints of the robot manipulator 1, that an insertion of the respective object 5 into its receptacle was not easily possible, because the object 5 could not exactly intervene in the receptacle during the preferably translatory insertion movement along the respective insertion trajectory, which can also be defined by corresponding predetermined limit value conditions Gi and/or signatures Si, the robot manipulator 1 together with its effector 2 can perform force- and/or impedance-controlled rotary/tilting movements and/or lateral translational movements (not shown in the figures) until object 5 engages precisely in the receptacle and before the robot manipulator 1 performs the final translational insertion movement.

The robot manipulator 1 is therefore designed in such a way that during the insertion process it "feels" or "senses" the respective free spaces 7 or their boundaries or edges as well as the objects 5 already inserted.

All movements of the above mentioned method steps can be repeated until box 4 is completely filled, so that the

packaging of such objects can be carried out automatically and reliably. The assembly cycle times can be reduced, making the automated process more economical.

The movements of robot manipulator 1 in all the method steps described above are force and/or impedance controlled and can be taught or programmed to the robot by a user, preferably by means of a predefined App control system which maps individual process steps within the entire method according to the invention .

Claims

1. Method for inserting objects (5) into a common object

receptacle (4) by means of an actuator-driven robot

manipulator (1) of a robot and for controlling the robot manipulator (1), the robot manipulator (1) having at its distal end an effector (2) which is designed for receiving and/or gripping the objects (5),

with the following method steps:

a) picking up a first object (5.1) from a storage device (6) by the effector (2);

b) transferring the first object (5.1) by means of the robot manipulator (1) into a position relative to the object receptacle (4), which allows the first object (5.1) to be inserted into the object receptacle (4) by means of the robot manipulator (1);

c) inserting the first object (5.1) by means of the robot manipulator (1) into the object receptacle (4) along a first insertion trajectory (T_5.i) ;

d) releasing the first object (5.1) by the effector (2);

e) picking up a second object (5.2) from a storage device (6) by the effector (2);

f) transferring the second object (5.2) by means of the robot manipulator (1) into a position relative to the object receptacle (4), which allows the second object (5.2) to be inserted into the object receptacle (4) by means of the robot manipulator (1);

g) inserting the second object (5.2) by means of the robot manipulator (1) into the object receptacle (4) along a second insertion trajectory (T_5.2) ; and

h) releasing the second object (5.2) by the effector (2);

1 where the second insertion trajectory (T_5.2) is determined during insertion by

- a contact of the second object (5.2) with the first object (5.1) already present in the object receptacle (4); and/or

- a contact of the second object (5.2) with an inner boundary of the object receptacle (4); and/or

- a displaceability of the first object (5.1) relative to the second object (5.2) inside the object receptacle (4).

2. The method according to claim 1, in which the object

receptacle (4) is designed to receive n objects (5) and steps e) to h) are repeated for each further object (5) (n-2) times until the object receptacle (4) is completely filled, wherein the insertion trajectory (T_n) of each further object (5) is determined by

- a contact of the further object (5) with at least one of the objects (5) already present in the object receptacle (4); and/or

- a contact of the further object (5) with an inner boundary of the object receptacle (4); and/or

- a displaceability of the objects (5) already present in the object receptacle (4) relative to each other and/or relative to the other object (5) inside the object receptacle (4) .

3. The method according to claim 1 or 2 in which the insertion trajectory (T_n) for each object (5) is determined by

recognizing the state of how far the insertion of the

respective object (5) has progressed and/or recognizing whether the insertion of the respective object (5) has been successfully completed, the state being defined thereby, in that at least one predetermined limit value condition (Gi) for a torque acting on the effector (2) and/or a force acting on the effector (2) is reached or exceeded, and/or a provided force/torque signature (Si) and/or a position/speed signature

2 (Si) on the effector (2) is reached or exceeded.

4. The method according to claim 1, 2 or 3, in which the

insertion trajectory (T_n) for each object (5) is followed by means of the robot manipulator (1) by force-controlled and/or impedance-controlled rotary/tilting movements and/or

translatory movements of the robot manipulator (1) .

5. The method according to claim 4, in which, if an error occurs when inserting the objects (5) along the respective insertion trajectory (T_n) into the object receptacle (4) by means of the robot manipulator (1), the insertion of the corresponding object (5) is repeated by means of the robot manipulator (1) into the object receptacle (4) with an altered insertion trajectory (T_n*) and/or with modified parameters for the force-controlled and/or impedance-controlled translatory and/or rotary/tilting movements of the object (5) .

6. Computer system having a data processing device, the data

processing device being configured so that a method according to any of the preceding claims 1 to 5 is performed on the data processing device.

7. Digital storage medium having electronically readable control signals, the control signals interacting with a programmable computer system such that a method according to any of the preceding claims 1 to 5 is performed.

8. Computer program product having a program code stored on a machine-readable medium for performing the method according to any of the preceding claims 1 to 5 when the program code is executed on a data processing device.

9. Computer program with program codes for carrying out the

method according to any of the preceding claims 1 to 5 when

3 the program is running on a data processing device.

10. Robot comprising an actuator-driven robot manipulator (1), the robot manipulator (1) having at its distal end an

effector (2) adapted to receive an object (5), comprising a control unit adapted to perform a method according to one of the preceding claims 1 to 5.

11. Use of a robot according to claim 10 for loading a package (4) with individual articles (5) having substantially the same weight and dimensions.

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