In an embodiment of the invention, said virtual state signal is indicative of whether said robot arm is idle.

A virtual state signal is indicative of a status of the robot system. An operation cycle of a robot system may comprise various periods of the robot arm being moved, the robot tool being used, and the robot arm being idle. The robot arm may for example be idle in a period waiting for a new workpiece to be introduced. A virtual state signal may for example be indicative of whether the robot arm is idle or not. The term “virtual” relates to the virtual state signal not necessarily having a dedicated physical input/output on the robot controller which is easily accessible by the user. Instead, in typical embodiments of the invention, the virtual state signal is recorded within the robot controller. It may for example be recorded as a signal among internal processes within the robot controller.

Other examples of state signals may provide indication as to what part of an operation cycle which was being performed at a particular time, such as moving object, grabbing object, moving robot arm without object, interacting with an external device such as a peripheral device, etc.

A state signal may optionally be presented to a human operator in a manner where it is easily interpretable, such as via a Boolean signal indicative of a particular operation, in contrast to e.g. an analogue current of a robot joint which is difficult to interpret.

Recording a virtual state signal is advantageous, since it allows a comparison between a recorded peripheral signal and a recorded virtual state signal, which in combination provides improved tracking of robot system operations.

In an embodiment of the invention, said step of recording said virtual state signal further comprises obtaining an associated state time stamp, wherein said step of updating said operation signal history further comprises providing said state time stamp as an operation time stamp of one or more operation time stamps.

Including a state time stamp as an operation time stamp allows a user or an automated evaluation to perform a more detailed tracking of the state of the robot system, which is advantageous. It may for example allow tracking in combination with a recording of the peripheral signal, to provide a more detailed insight as to how the robot system was operated at a given time in the past.

In an embodiment of the invention, said method further comprises a step of truncating said operation signal history.

In an embodiment of the invention, said step of truncating said operation signal history comprises deleting a subset of said one or more operation time stamps which lies outside a running truncation time window and deleting an associated subset of said one or more operation representations.

Truncating the operation signal history may for example be understood as removing or deleting the oldest entries in the operation signal history. Doing so is advantageous, since it introduces a limitation to the storage space required to store the operation signal history on the digital storage. This is particularly relevant for size-limited digital storages, operation signal histories which has a high time resolution, or operation signal histories comprising data requiring large amounts of storage space such as images or detailed records of robot arm movement/positions.

Entries of the operation signal history or a subset of the operation signal history may for example be deleted based on a running truncation time window, such that entries lying outside that time window or a subset lying outside that time window is deleted. Alternatively, there may be an upper limit to the number of entries in the operation signal history, and entries are deleted such that this upper limit is not surpassed. Or alternatively, there is a maximum amount of storage which the operation signal history may use, and entries are deleted such that this maximum amount is not surpassed.

In an embodiment of the invention, said step of tracking operation of said robot system comprises providing a graphical representation of said operation signal history to a human operator of said robot system.

A graphical representation provides a human operator to gain a quick and/or detailed overview of at least part of the operation signal history. A graphical representation may for example be one or more graphs, or a table of data. It may for example be presented on paper, on a monitor, or via indicative lights, but note that the invention is not restricted to a particular type of medium of representation. A graphical representation may also be based on a data evaluation of the operation signal history. The operation signal history may for example be analyzed, for example automatically, to identify various time ranges of different types of operation. Such different types of operation may for example be indicative of whether the robot arm is idle. Such different types of operation may further be indicative of incorrect/erroneous operation of the robot system or robot arm.

Additionally, or alternatively, a graphical representation may be based on an analysis of the operation signal history. The graphical representation may thus be an analytical representation.

In an embodiment of the invention, said method comprises a step of executing one or more operation cycles, wherein each operation cycle of said one or more operation cycles comprises said step of executing said robot operation process.

In an embodiment of the invention, said step of executing said robot operation process of each of said one or more operation cycles is based on the same robot operation process.

An operation cycle may for example be understood as a task performed repetitively by the robot. Each performed operation cycle may typically be similar, or even identical, but the invention is not limited in this respect. An operation cycle may for example involve the robot arm applying its tool to a workpiece. Another operation cycle will then involve the robot arm applying its tool to another workpiece. Each operation cycle thus involves executing a robot operation process. And the robot operation process of each operation cycle may or may not be the same robot operation process.

Recording a peripheral signal during each operation cycle is advantageous, since this allows a comparison as to how each operation cycle was executed by the robot system.

In an embodiment of the invention, each operation cycle of said one or more operation cycles comprises said step of establishing said peripheral signal.

In an embodiment of the invention, each operation cycle of said one or more operation cycles comprises said step of recording said peripheral signal.

In an embodiment of the invention, each operation cycle of said one or more operation cycles comprises said step of updating said operation signal history.

In an embodiment of the invention, each operation cycle of said one or more operation cycles comprises said step of establishing said virtual state signal.

In an embodiment of the invention, each operation cycle of said one or more operation cycles comprises said step of recoding said virtual state signal.

Recording various data during each operation cycle is advantageous, since it allows an improved comparison between how the different operation cycles was carried out in practice by the robot system.

In an embodiment of the invention, said step of tracking operation of said robot system comprises performing an operation cycle comparison of one operation cycle of said one or more operation cycles with one other operation cycle of said one or more operation cycles.

In an embodiment of the invention, said operation cycle comparison is performed by a programming device identifying differences between:

- a subset of said operation signal history associated with one operation cycle of said one or more operation cycles; and
- a subset of said operation signal history associated with another operation cycle of said one or more operation cycles.

Comparing a subset of the operation signal history relating to one operation with a subset of the operation signal history relating to another operation cycle may improve the probability of identifying deviations in one of the subsets, which is advantageous for identifying errors.

In an embodiment of the invention, said step of tracking operation of said robot system is performed after said step of executing one or more operation cycles.

In an embodiment of the invention, said step of tracking operation of said robot system is performed at least 1 hour after an initial operation cycle of said one or more operation cycles, for example at least 2 hours, for example at least 5 hours, such as at least 10 hours, wherein said initial operation cycle is first in time of said one or more operation cycles.

Tracking the operation of the robot system subsequent to executing operation cycles typically allows a more detailed evaluation than, e.g., a live tracking of the operation, which is advantageous.

In particular, tracking operation of a robot system for several hours may permit identification of slow, gradual changes, which is advantageous.

Further, tracking operation of a robot system for several hours may permit a comparison of operation signal history from several operation cycles.

In an embodiment of the invention, said step of providing said communicative peripheral connection comprises providing a plurality of communicative peripheral connections between a plurality of peripheral devices and said robot controller, wherein said step of establishing said peripheral signal comprises establishing a plurality of peripheral signals respectively associated with said plurality of peripheral connections, wherein said step of recording said peripheral signal comprises recording a plurality of peripheral signals to obtain a plurality of peripheral signal representations respectively associated with said plurality of peripheral signals, wherein said step of updating said operation signal history comprises providing said plurality of peripheral signal representations as a subset of operation representations of said one or more operation representations.

Many modern robot systems involve multiple peripheral devices. Thus, recording the communication between the robot controller and a plurality of peripheral devices may often grant an improved depiction of how the operation of the robot system was carried out in practice, which is advantageous. In particular, having operation representations of several peripheral devices do not only permit tracking each individual peripheral device, but may also permit tracking interplay and interactions between peripheral devices, which is advantageous.

In an embodiment of the invention, said method further comprises a step of performing predictive maintenance of said robot system based on said step of tracking operation of said robot system.

Tracking operation of the robot system may enable a predictive maintenance. Predictive maintenance may for example be understood as monitoring the operation signal history to predict when maintenance may be necessary or advantageous. For example, through tracking changes in the operation signal history which may be indicative of degrading of the robot arm and/or peripheral devices. This may allow maintenance to be performed prior to any breakdown and planning the maintenance strategically to minimize interference with production, which is advantageous.

In an embodiment of the invention, at least one peripheral signal representation of said plurality of peripheral signal representations is a logic signal representation.

Logic signals are advantageous to use in many various contexts, including for control purposes, since they may be simple to interpret. A logic signal may also be understood as a digital signal or a binary signal.

In an embodiment of the invention, said robot controller is configured to control motion of said robot arm by controlling motor torque provided to joint motors of robot joints of said robot arm.

This may for example be as a part of executing the robot operation process. The robot controller may for example be configured to control motion of the robot arm based on a dynamic model of the robot arm, the direction of gravity acting on the robot arm, and/or one or more joint sensor signals.

That the robot controller controls motion of the robot arm may for example be combined with other functionalities relating to an aspect of the invention. For example, the robot controller may simultaneously perform the recording of the peripheral signal

In an embodiment of the invention, said method comprises a step of identifying an anomalous peripheral device based on said operation signal history.

The anomalous peripheral device may for example be identified based on identifying an anomalous part of the peripheral signal associated with the peripheral connection of the anomalous peripheral device. An anomalous peripheral device may for example be identified among several peripheral devices of a plurality of peripheral devices.

In an embodiment of the invention, said peripheral signal representation is indicative of a state of said peripheral device.

The peripheral signal representation may for example be a logical signal/Boolean signal. Such a signal is easy to interpret which is advantageous. Particularly given that robot systems may involve complex interactions between many different elements.

An aspect of the invention relates to a robot system comprising:

- a robot arm comprising a plurality of robot joints connecting a robot base to a robot tool flange,
- a robot controller configured to control operation of said robot arm,
- a peripheral device communicatively connected to said robot controller by a peripheral connection, and
- a digital storage comprising an operation signal history,
- wherein said operation signal history comprises one or more operation representations;
- wherein said robot controller is arranged to record a peripheral signal associated with said peripheral connection to obtain a peripheral signal representation;
- wherein said operation signal history is arranged to receive said peripheral signal representation as an operation representation of said one or more operation representations.

A robot system according to the invention may for example be used to facilitate a method of the invention and may thus have the same or similar advantages.

In an embodiment of the invention, said robot controller is a multi-core processor.

In an embodiment of the invention, said robot controller is communicatively connected to a plurality of peripheral devices by a plurality of respective peripheral connections, wherein said robot controller is arranged to record a plurality of peripheral signals respectively associated with said plurality of peripheral connections to obtain a plurality of peripheral signal representations respectively associated with said plurality of peripheral signals, wherein said operation signal history is arranged to receive said plurality of peripheral signal representations as a subset of operation representations of said one or more operation representations.

In an embodiment of the invention, said robot controller has at least two internal processes, wherein a first process of said at least two internal processes is configured to interact with said peripheral device, wherein a second process of said at least two internal processes is configured to control said robot arm.

In an embodiment of the invention, said robot controller is configured to execute said at least two internal processes.

In an embodiment of the invention, said first process is configured to control operation of said peripheral device.

In an embodiment of the invention, said first process of said robot controller is arranged to record said peripheral signal.

The first internal process may for example be performed on a first group of cores on said robot controller, and the second internal process may for example be performed on a second group of cores on said robot controller. The first and second groups of cores may be separate cores. The robot operation process may correspond to the second process of the at least two internal processes. The first process of the at least two internal processes may also be referred to as an auxiliary operation process or an auxiliary control process.

By performing multiple separate processes on the same robot controller, it is possible to simplify the setup of a robot system. Auxiliary circuitry for monitoring or controlling peripheral devices may be costly, may require expertise, may take up a substantial amount of physical volume, and it may be time-consuming to install. All of these disadvantages may advantageously be avoided by performing multiple separate processes on the robot controller as suggested by embodiments of the invention. Further, it may even speed up execution of operation cycles, since reduced intermediate signal processing is required.

In an embodiment of the invention, said peripheral device is communicatively connected directly to said robot controller by said peripheral connection.

In the context of the present invention, communicatively connected directly may be understood as the communication is directly between the peripheral device and the robot controller i.e. without communicating via an auxiliary circuitry such as a PLC. For example, if a peripheral device is communicatively connected directly to the robot controller, a communicative connection between the peripheral device and the robot controller does not involve auxiliary circuitry, e.g. a PLC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a robot arm according to the present invention;

FIG. 2 illustrates a simplified structural diagram of the robot arm and part of the robot controller;

FIG. 3 illustrates an embodiment of the invention;

FIG. 4 illustrates an embodiment of the invention arranged to store operation time stamps;

FIG. 5 illustrates an embodiment of the invention arranged to store state signal representations;

FIG. 6 illustrates an embodiment of the invention arranged to store a plurality of peripheral signal representations;

FIG. 7 illustrates an embodiment of the invention arranged to allow interaction with a human operator;

FIG. 8 illustrates a method of the invention having one or more operation cycles; and

FIG. 9 illustrates a method of the invention involving simulation of operation of the robot system.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described in view of exemplary embodiments only intended to illustrate the principles of the present invention. The skilled person will be able to provide several embodiments within the scope of the claims. Further it is to be understood that in the case that an embodiment comprises a plurality of the same features then only some of the features may be labeled by a reference number.

FIG. 1 illustrates a robot arm 101 comprising a plurality of robot joints 102a, 102b, 102c, 102d, 102e, 102f connecting a robot base 103 and a robot tool flange 104. A base joint 102a is configured to rotate the robot arm 101 around a base axis 105a (illustrated by a dashed dotted line) as illustrated by rotation arrow 106a; a shoulder joint 102b is configured to rotate the robot arm around a shoulder axis 105b (illustrated as a cross indicating the axis) as illustrated by rotation arrow 106b; an elbow joint 102c is configured to rotate the robot arm around an elbow axis 105c (illustrated as a cross indicating the axis) as illustrated by rotation arrow 106c, a first wrist joint 102d is configured to rotate the robot arm around a first wrist axis 105d (illustrated as a cross indicating the axis) as illustrated by rotation arrow 106d and a second wrist joint 102e is configured to rotate the robot arm around a second wrist axis 105e (illustrated by a dashed dotted line) as illustrated by rotation arrow 106e. Robot joint 102f is a tool joint comprising the robot tool flange 104, which is rotatable around a tool axis 105f (illustrated by a dashed dotted line) as illustrated by rotation arrow 106f. The illustrated robot arm is thus a six-axis robot arm with six degrees of freedom with six rotational robot joints, however it is noticed that the present invention can be provided in robot arms comprising less or more robot joints and also other types of robot joints such as prismatic robot joints providing a translation of parts of the robot arm for instance a linear translation.

A robot tool flange reference point 107 also known as a TCP is indicated at the robot tool flange and defines the origin of a tool flange coordinate system defining three coordinate axis x_flange, y_flange, z_flange. In the illustrated embodiment the origin of the robot tool flange coordinate system has been arrange on the tool flange axis 105f with one axis (z_flange) parallel with the tool flange axis and with another axis x_flange, y_flangeparallel with the outer surface of the robot tool flange 104. Further a base reference point 108 is coincident with the origin of a robot base coordinate system defining three coordinate axis x_base, y_base, z_base. In the illustrated embodiment the origin of the robot base coordinate system has been arrange on the base axis 105a with one axis (z_base) parallel with the base axis 105a axis and with another axis x_base, y_baseparallel with at the bottom surface of the robot base. The direction of gravity 109 in relation to the robot arm is also indicated by an arrow and it is to be understood the at robot arm can be arrange at any position and orientation in relation to gravity only limited by the freedom of operation of the robot joints.

The robot arm comprises at least one robot controller 110 configured to control robot arm 101 and can be provided as a computer comprising in interface device 111 enabling a user to control and program the robot arm. The controller 110 can be provided as an external device as illustrated in FIG. 1 or as a device integrated into the robot arm or as a combination thereof. The interface device can for instance be provided as a teach pendent as known from the field of industrial robots which can communicate with the controller 110 via wired or wireless communication protocols. The interface device can for instanced comprise a display 112 and a number of input devices 113 such as buttons, sliders, touchpads, joysticks, track balls, gesture recognition devices, keyboards etc. The display may be provided as a touch screen acting both as display and input device. The interface device can also be provided as an external device configured to communicate with the robot controller 110 for instance as smart phones, tablets, PCs, laptops, etc.

The robot tool flange 104 comprises a force-torque sensor 114 (sometimes referred to simply as fore sensor) integrated into the robot tool flange 104. The force-torque sensor 114 provides a tool flange force signal indicating a force-torque provided at the robot tool flange. In the illustrated embodiment the force-torque sensor is integrated into the robot tool flange and is configured to indicate the forces and torques applied to the robot tool flange in relation to the robot tool flange reference point 107. The force sensor 114 provides a force signal indicating a force provided at the tool flange. In the illustrated embodiment the force sensor is integrated into the robot tool flange and is configured to indicate the forces-torque applied to the robot tool flange in relation to the reference point 107 and in the tool flange coordinate system. However, the force-torque sensor can indicate the force-torque applied to the robot tool flange in relation to any point which can be linked to the robot tool flange coordinate system. In one embodiment the force-torque sensor is provided as a six-axis force-torque sensor configured to indicate the forces along and the torques around three perpendicular axes. The force-torque sensor can for instance be provided as any force-torque sensor capable of indicating the forces and torques in relation to a reference point for instance any of the force-torque sensors disclosed by WO2014/110682A1, U.S. Pat. No. 4,763,531, US2015204742. However, it is to be understood that the force sensor in relation to the present invention not necessarily need to be capable of sensing the torque applied to the tool sensor. It is noted that the force-torque sensor may be provided as an external device arranged at the robot tool flange or omitted.

An acceleration sensor 115 is arranged at the robot tool joint 102f and is configured to sense the acceleration of the robot tool joint 102f and/or the acceleration of the robot tool flange 104. The acceleration sensor 115 provides an acceleration signal indicating the acceleration of the robot tool joint 102f and/or the acceleration of the robot tool flange 104. In the illustrated embodiment the acceleration sensor is integrated into the robot tool joint and is configured to indicate accelerations of the robot tool joint in the robot tool coordinate system. However, the acceleration sensor can indicate the acceleration of the robot tool joint in relation to any point which can be linked to the robot tool flange coordinate system. The acceleration sensor can be provided as any accelerometer capable of indicating the accelerations of an object. The acceleration sensor can for instance be provided as an IMU (Inertial Measurement Unit) capable of indicating both linear acceleration and rotational accelerations of an object. It is noted that the acceleration sensor may be provided as an external device arranged at the robot tool flange or omitted.

Each of the robot joints comprises a robot joint body and an output flange rotatable or translatable in relation to the robot joint body and the output flange is connected to a neighbor robot joint either directly or via an arm section as known in the art. The robot joint comprises a joint motor configured to rotate or translate the output flange in relation to the robot joint body, for instance via a gearing or directly connected to the motor shaft. The robot joint body can for instance be formed as a joint housing and the joint motor can be arranged inside the joint housing and the output flange can extend out of the joint housing. Additionally, the robot joint comprises at least one joint sensor providing a sensor signal indicative of at least one of the following parameters: an angular and/or linear position of the output flange, an angular and/or linear position of the motor shaft of the joint motor, a motor current of the joint motor or an external force and/or torque trying to rotate the output flange or motor shaft. For instance, the angular position of the output flange can be indicated by an output encoder such as optical encoders, magnetic encoders which can indicate the angular position of the output flange in relation to the robot joint. Similarly, the angular position of the joint motor shaft can be provided by an input encoder such as optical encoders, magnetic encoders which can indicate the angular position of the motor shaft in relation to the robot joint. It is noted that both output encoders indicating the angular position of the output flange and input encoders indicating the angular position of the motor shaft can be provided, which in embodiments where a gearing have been provided makes it possible to determine a relationship between the input and output side of the gearing. The joint sensor can also be provided as a current sensor indicating the current through the joint motor and thus be used to obtain the torque provided by the motor. For instance, in connection with a multiphase motor, a plurality of current sensors can be provided in order to obtain the current through each of the phases of the multiphase motor. It is also noted that some of the robot joints may comprise a plurality of output flanges rotatable and/or translatable by joint actuators, for instance one of the robot joints may comprise a first output flange rotating/translating a first part of the robot arm in relation to the robot joint and a second output flange rotating/translating a second part of the robot arm in relation to the robot joint.

The robot controller 110 is configured to control the motions of the robot arm and the robot joints by controlling the motor torque provided to the joint motors based on a dynamic model of the robot arm, the direction of gravity acting 109 and the joint sensor signal.

FIG. 2 illustrates a simplified structural diagram of the robot arm 101 illustrated in FIG. 1. The robot joints 102a, 102b and 102f have been illustrated in structural form and the robot joints 102c, 102, 102e and the robot links connecting the robot joints have been omitted for the sake of simplicity of the drawing. Further the robot joints are illustrated as separate elements however it is to be understood that they are interconnected as illustrated in FIG. 1. The robot joints comprise an output flange 216a,216b,216f and a joint motor 217a, 217b, 217f or another kind of actuator, where the output flange 216a,216b,216f is rotatable in relation to the robot joint body. The joint motors 217a, 217b, 217f are respectively configured to rotate the output flanges 216a, 216b, 216f via an output axle 218a, 218b, 218f. It is to be understood that the joint motor or joint actuator may be configured to rotate the output flange via a transmission system such as a gear (not shown). In this embodiment the output flange 216f of the tool joint 123f constitutes the tool flange 104. At least one joint sensor 219a, 219b, 219f providing a sensor signal 220a, 220b, 220f indicative of at least one joint sensor parameter J_sensor,a, J_sensor,b, J_sensor,fof the respective joint. The joint sensor parameter can for instance indicate a pose parameter indicating the position and orientation of the output flange in relation to the robot joint body, an angular position of the output flange, an angular position of a shaft of the joint motor, a motor current of the joint motor. For instance, the angular position of the output flange can be indicated by an output encoder such as optical encoders, magnetic encoders which can indicate the angular position of the output flange in relation to the robot joint. Similar, the angular position of the joint motor shaft can be provided by an input encoder such as optical encoders, magnetic encoders which can indicate the angular position of the motor shaft in relation to the robot joint. The motor currents can be obtained and indicated by current sensors.

The robot controller 110 comprises a processer 220 and memory 221 and is configured to control the joint motors of the robot joints by providing motor control signals 223a, 223b, 223f to the joint motors. The motor control signals 223a, 223b, 223f are indicative of the motor torque T_motor,a, T_{motor, b}, and T_motor,fthat each joint motor shall provide to the output flanges and the robot controller 110 is configured to determine the motor torque based on a dynamic model of the robot arm as known in the prior art. The dynamic model makes it possible for the controller 110 to calculate which torque the joint motors shall provide to each of the joint motors to make the robot arm perform a desired movement. The dynamic model of the robot arm can be stored in the memory 221 and be adjusted based on the joint sensor parameters J_sensor,a, J_sensor,b, J_sensor,fFor instance, the joint motors can be provided as multiphase electromotors and the robot controller 110 can be configured to adjust the motor torque provided by the joint motors by regulating the current through the phases of the multiphase motors as known in the art of motor regulation.

Robot tool joint 102f comprises the force sensor 114 providing a tool flange force signal 224 indicating a force-torque FT_flangeprovided to the tool flange. For instance, the force signal-torque FT_flangecan be indicated as a force vector {right arrow over (F_sensor^flange)} and a torque vector {right arrow over (T_sensor^flange)} in the robot tool flange coordinate system:

F

sensor

flange

⟶

=

(

F

x
,
sensor

flange

F

y
,
sensor

flange

F

z
,
sensor

flange

)

eq
.

1

where F_x,sensor^flangeis the indicated force along the x_flangeaxis, F_y,sensor^flangeis the indicated force along the y_flangeaxis and F_z,sensor^flangeis the indicated force along the z_flangeaxis.

In an embodiment where the force sensor is provided as a combined force-torque sensor the force-torque sensor can additionally also provide a torque signal indicating the torque provide to the tool flange, for instance as a separate signal (not illustrated) or as a part of the force signal. The torque can be indicated as a torque vector in the robot tool flange coordinate system:

T

sensor

flange

⟶

=

(

T

x
,
sensor

flange

T

y
,
sensor

flange

T

z
,
sensor

flange

)

eq
.

2

where T_x,sensor^flangeis the indicated torque around the x_flangeaxis, F_y,sensor^flangeis the indicated torque around the y_flangeaxis and T_z,sensor^flangeis the indicated torque around the z_flangeaxis.

Robot tool joint 102f comprises the acceleration sensor 115 providing an acceleration signal 225 indicating the acceleration of the robot tool flange where the acceleration may be indicated in relation to the tool flange coordinate system

A

sensor

flange

⟶

=

(

A

x
,
sensor

flange

A

y
,
sensor

flange

A

z
,
sensor

flange

)

where A_x,sensor^flangeis the sensed acceleration along the x_flangeaxis, A_y,sensor^flangeis the sensed acceleration along the y_flangeaxis and A_z,sensor^flangeis the sensed acceleration along the z_flangeaxis.

In an embodiment where the acceleration sensor is provided as a combined accelerometer/gyrometer (e.g. an IMU) the acceleration sensor can additionally provide an angular acceleration signal indicating the angular acceleration of the output flange in relation to the robot tool flange coordinate system, for instance as a separate signal (not illustrated) or as a part of the acceleration signal. The angular acceleration signal can indicate an angular acceleration vector {right arrow over (α_sensor^flange)} in the robot tool flange coordinate system

α

sensor

flange

⟶

=

(

α

x
,
sensor

flange

α

y
,
sensor

flange

α

z
,
sensor

flange

)

eq
.

3

where α_x,sensor^flangeis the angular acceleration around the x_flangeaxis, α_y,sensor^flangeis the angular acceleration around the y_flangeaxis and α_z,sensor^flangeis the angular acceleration around the z_flangeaxis.

The force sensor and acceleration sensor of the illustrated embodiment are arranged at the robot tool joint 102f; however, it is to be understood that the force sensor and acceleration sensor can be arrange at any part of the robot arm.

The robot arm illustrated in FIGS. 1 and 2 can for instance be used in a robot system, for instance a robot system according to the present invention.

In an exemplary embodiment of the invention, the robot system comprises two peripheral devices: an object sensor and a conveyer belt. A robot tool is attached to the robot tool flange and is arranged to perform welding of an application object. The object sensor is arranged to detect the presence of an application object at a welding position. The auxiliary control process receives application input signals from the object sensor and the robot control process, upon which logic signals are established. Further, the auxiliary control process provides logic output signals to the conveyer belt and the robot control process based on the logic signals. When no application object is at the welding position, the auxiliary control process is arranged to activate the conveyer belt via a logic output signal. Then, when the object sensor detects an object at the welding position, the auxiliary control process stops the conveyer belt, and initiates movement of the robot arm and welding, via a logic output signal to the robot control process. When welding, as controlled by the robot control process, has completed, movement of the conveyer belt is initiated based on the application input signal from the robot control process. From here, the robot system is ready the receive a new application object via the conveyer belt to repeat the above explained welding process. In this embodiment, the robot controller records peripheral signals on communicative peripheral connections between the robot controller and each of the peripheral devices, and updates an operation signal history accordingly, thus permitting tracking of the robot system.

FIG. 3 illustrates an embodiment of the invention. The robot system 100 comprises a robot arm 101 controlled by a robot controller 110. In addition to the description of motion of the robot arm exemplified above, the robot controller is further communicatively connected to a peripheral device 336 through a peripheral connection 352. This connection may for example be used to perform control of the peripheral device 336 by the robot controller 110, or it may be used as input for the robot controller 110, such that the robot controller operates based on this input. In some embodiments of the invention, the peripheral connection 352 is a two-way communication connection, e.g. such that the peripheral device 336 is controlled based on input by the robot controller 110, and such that the robot controller 110 controls the robot arm 101 based on input by the peripheral device 110. Any communicative signal on the peripheral connection 352, e.g. a signal arranged to perform control, may be understood as a peripheral signal.

The robot system is further associated with a digital storage 354, e.g. a digital storage based on a hard disc or a cloud storage, the digital storage is communicatively connected to the robot controller 110. The digital storage 354 has an operation signal history 353 stored on it. The operation signal history is based on operation representations 355, i.e. it comprises a list of operation representations 355.

The robot system 100 is arranged to be operated based on executing a robot operation process on the robot controller. A robot operation process may for example be a program, software, or code, which the robot controller 110 is able to read/process, and upon this communicate with the robot arm and/or the peripheral device, e.g. to operate any of these.

Upon execution of the robot operation process on the robot controller 110, the robot system 100 is arranged to perform recording of a peripheral signal of the peripheral connection 352 to obtain a peripheral signal representation 357. This may for example be by simply measuring the voltage of the peripheral connection 352. It may also be facilitated by the robot controller 110, for example such that the robot controller provides the peripheral signal representation 357 as an output, e.g. as an output to a programming device or directly to the digital storage 354.

The peripheral signal representation 357 is added to the operation signal history 353 as an operation representation 355, e.g. to extend the number of existing operation representations 355.

Since the peripheral signal representation 357 has been added as an operation representation 355 to the operation signal history 353, it is possible for a user or an automated evaluation to monitor and assess the operation of the robot system 100, particularly the interaction with the peripheral device 336.

In typical embodiments of the invention, peripheral signal representations are continuously stored, e.g. with a certain frequency such as 1 Hz, 1 kHz, or a clock frequency of the robot system, or at key points during an operation cycle.

FIG. 4 illustrates an embodiment of the invention arranged to store operation time stamps 456.

The embodiment has a similar structure to the embodiment illustrated in FIG. 3. However, the embodiment illustrated in FIG. 4 is further arranged to store peripheral time stamps 458. The operation signal history 353 is further based on operation time stamps 456, besides being based on operation representations 355. The operation time stamps 456 may for example be associated with the operation representations 355. Thus, an operation time stamp 456 may for example be a data entity which enables pinpointing the time at which an associated operation representation 355 was recorded/stored.

When a peripheral signal is recorded to obtain a peripheral signal representation 357, the system is configured to establish a peripheral time stamp 458 which is associated with that peripheral signal representation 357. This value of the peripheral time stamp 458 may for example be provided by the robot controller 110, or from another time source such as an external time source.

The peripheral time stamp 458 is then added as an operation time stamp 456 to the operation signal history 353.

By storing peripheral signal representations 357 as operation representations 355 and peripheral time stamps 458 as operation time stamps 456, it is possible for a user or an automated evaluation to perform a more detailed assessment of the operation of the robot system. Particularly, it is possible to reconstruct a timeline of operation and possible events, such as an introduction of an error into the operation.

In some embodiments of the invention, each recorded value of a peripheral signal representation 357 has an associated peripheral time stamp 458, whereas in other embodiments, only a subset of recorded values of peripheral signal representations 357 has associated peripheral time stamps 458.

In some embodiments, a user and/or an automated evaluation system will be able to deduce timings of recorded peripheral signal representations/operation representations without operation time stamps. For example, if peripheral signal representations are recorded and stored with a certain frequency, knowledge of this frequency can be used to calculate how much time has passed since a given operation representation was stored.

FIG. 5 illustrates an embodiment of the invention arranged to store state signal representations 560.

The embodiment has a similar structure is the embodiment illustrated in FIG. 4. However, the embodiment illustrated in FIG. 5 is further arranged to store state signal representations 560 and state time stamps, originating from internal robot controller processes 564a, 564b of the robot controller 110.

In this embodiment, the robot controller 110 has at least two internal processes 564a, 564b which are communicatively connected within the robot controller 110. The robot controller 110 may for example be a multi-core processor, and the internal processes 564a, 564b may be processes respectively executed on separate cores or separate groups of cores of that multi-core processor. In the exemplary embodiment of FIG. 5, one group of cores facilitates an internal process 564a which controls the robot arm 101, and one other group of cores facilitates an internal process 564b which enables interaction with the peripheral device 336. Any such communication amongst such separate processes 564a, 564b is facilitated by signals which may be referred to as virtual state signals which may for example be indicative of a state of the robot arm 101, a peripheral device 336, a group of peripheral devices, and/or the robot system 100.

The robot controller 110 is arranged to record the virtual state signal to provide a state signal representation 560. It is further arranged to provide a state time stamp 561 associated with the state signal representation 560. The system is then arranged to provide the state signal representation 560 as an operation representation 355 of the operation signal history 353, and to provide the state time stamp 561 as an operation time stamp 456 of the operation signal history 353.

This allows improved monitoring of the robot system 100, since a recorded peripheral signal representation 357 can be analyzed together with state signal representation 560, as both are stored within the operation signal history 353. Such additional details allow an improved reconstruction of past operations of the robot system.

In some embodiments of the invention, state signal representations 560 and operation representations 355 are stored without storing operation time stamps 456 and state time stamps 561. In some other embodiments of the invention, state signal representations 560 and operation representations 355 are stored while storing one of either operation time stamps 456 or state time stamps 561. For example, the recording and storing of state signal representations 560 and operation representations 355 are at least partly synchronized, such that only storing one type of time stamp is sufficient to backtrack the timing of any of the state signal representations 560 and operation representations 355.

In some other embodiments of the invention, the robot system may be associated with a state machine or a state device, upon which different states of the robot system is associated. During operation of a robot, the robot may cycle through different states of the state machine. Similar operation cycles may typically cycle through similar states of a state machine. The states the robot system cycles through may be saved into the operation signal history as an operation representation.

FIG. 6 illustrates an embodiment of the invention arranged to store a plurality of peripheral signal representations 357a, 357b. The embodiment has a similar structure to the embodiment illustrated in FIG. 3. However, the embodiment illustrated in FIG. 6 features a plurality of peripheral devices, namely two peripheral devices 336a and 336b. Each of the peripheral devices 336a, 336b is connected to the robot controller 110 through a communicative peripheral connection 352a, 352b having a peripheral signal.

The two peripheral devices may for example be a sensor and a conveyer belt, respectively.

Other embodiments may have at least three peripheral devices, such as at least four peripheral devices, such as at least five peripheral devices, for example six or more peripheral devices.

The robot system 100 is arranged to perform recording of the peripheral signals of both of the peripheral connections 352a, 352b to obtain a peripheral signal representation 357a, 357b for each of the peripheral connections 352a, 352b. These separate peripheral signal representations 357a, 357b are then provided to the operation signal history 353 as operation representations 355.

The two peripheral signal representations 357a, 357b may be recorded and provided to the operation signal history in a synchronized process, or the recording and providing of the two representations 357a, 357b may be desynchronized.

Storing data from multiple communicative lines to peripheral devices 336a, 336b may give a user or an automated evaluation a more detailed insight into operation of the robot system. For example, into the complex interaction between a robot arm and multiple peripheral devices 336a,336b.

FIG. 7 illustrates an embodiment of the invention arranged to allow interaction with a human operator 763. The embodiment has a similar structure to the embodiment illustrated in FIG. 3. However, in the embodiment illustrated in FIG. 7, the robot controller 110 and the digital storage 354 are both communicatively connected to a programming device 762, which enables interaction with a human operator 763.

The programming device 762 has access to the operation signal history 353. The operation signal history 353, e.g. the operation representations 355 of the operation signal history 353, may thus be evaluated and/or displayed on the programming device 762. The programming device may for example be arranged to perform an automated evaluation of the operation signal history 753.

The operation signal history 353, a visual representation of the operation signal history, an evaluated version of the operation signal history, or an output of an evaluation of the operation signal history may be provided to the human operator 763 via the programming device 762. This allows the human operator 763 to assess the operation of the robot system 100. It further allows the human operator to interact with operation of the robot system via the communicative connection between the programming device 762 and the robot controller 110. This may for example allow the human operator to stop or pause operation. It may further allow the human operator to reconfigure the peripheral device 336 or its connection 352. It may even further allow the human operator to update the robot operation process, which the robot system is operated upon, e.g. to subsequently execute an updated robot operation process based on tracking operation of the robot system. It may additionally allow the human operator to identify whether any errors or inaccuracies has occurred during previous operation of the robot system

In some embodiments, the tracking of operation of the robot system 100 including interaction with a human operator 763 is performed while the robot system is being operated. The operation signal history may for example be continuously updated by providing peripheral signal representations. This allows the human operator to track the robot system during its operation. In other embodiments, the tracking of operation of the robot system 100 including interaction with a human operator 763 is performed to track previous operation, e.g. previous operation cycles, of the robot system 100. For example, to track whether an error has occurred within some past interval, for example within the past 8 hours.

FIG. 8 illustrates a method for tracking and operating a robot system according to an embodiment of the invention. The method has several steps and is based on one or more operation cycles 859. Other steps may be manual steps of handling the robot arm or peripheral device.

Robot systems and robot arms are sometimes employed to perform tasks/operations which are at least to some degree repetitive. Each repetition of a repetitive task may be referred to as an operation cycle 859. In the illustrated embodiment, four method steps M3-M6 are part of the operation cycle 859.

In a first step of the method M1, a communicative peripheral connection is provided between a peripheral device 336 and a robot controller 110. This connection may for example be provided/established upon installation of the robot system 100, or upon integration of a peripheral device 336 at a later stage.

In a next step of the method M2, an operation signal history 353 is established in a digital storage