Robot system, and method of handling robot system

Abstract

A robot system (10) comprising a mobile robot (12); an elongated line (14) connected to the mobile robot (12) and for connection to a source (22); a line feeding device (16) configured to feed out the line (14) and to feed in the line (14); and a control system (24) configured to provide a path length value (84) indicative of a path length (76) of a path (86) for the mobile robot (12) from a current position (80) to the line feeding device (16), and to control the line feeding device (16) based on the path length value (84). A method of handling a robot system (10) is also provided.

Description

[0001] ROBOT SYSTEM, AND METHOD OF HANDLING ROBOT SYSTEM

[0002] Technical Field

[0003] The present disclosure generally relates to robot systems comprising a mobile robot. In particular, a robot system comprising a mobile robot and a line feeding device, and a method of handling a robot system, are provided.

[0004] Background

[0005] In the food and beverage industry, cleanliness is a key concern. Any sanitary problem in a plant where foods or beverages are handled might result in severe consequences. For this reason, comprehensive cleaning measures are often taken in such plants. The cleaning is often performed manually where trained personnel apply different washdown chemicals. The manual cleaning instructions are typically extremely comprehensive, resulting in long cleaning times, high costs and a high environmental impact. The personnel performing the cleaning and validation of the cleaning is often difficult to recruit due to the difficulty of the tasks and the conditions of the work environment. Although mobile robots may be used to automize various cleaning operations, most prior art mobile cleaning robots provide an unsatisfactory cleaning, have a limited cleaning medium supply or have a complex and bulky design resulting in limited navigation performance.

[0006] CN 102091706 B discloses a winding system for a cleaning robot. The winding system winds a hose and a cable. Two reels are driven to rotate by a motor. The document teaches that the hose and cable are always in tension.

[0007] Summary

[0008] One object of the invention is to provide an improved robot system.

[0009] A further object of the invention is to provide an improved method of handling a robot system. These objects are achieved by the robot system according to appended claim 1 and the method according to appended claim 13.

[0010] The invention is based on the realization that by providing a robot system comprising an elongated line interconnecting a source and a mobile robot, where a line feeding device is controlled to handle the line based on a path length of a path for the mobile robot from a current position to the line feeding device, the line can be positioned on a ground surface with an appropriate line length for a wide range of positions of the mobile robot which in turn enables improved navigation of the mobile robot and use of a line of high capacity.

[0011] According to a first aspect, there is provided a robot system comprising a mobile robot; an elongated line connected to the mobile robot and for connection to a source; a line feeding device configured to feed out the line and to feed in the line; and a control system configured to provide a path length value indicative of a path length of a path for the mobile robot from a current position to the line feeding device, and to control the line feeding device based on the path length value.

[0012] By controlling the line feeding device based on the path length value, the navigation performance of the mobile robot is improved. This control for example enables the mobile robot to navigate in tight and complex environments, enables the mobile robot to move away from the line feeding device without necessarily having to provide a force to pull the line out from the line feeding device or a force to tension the line adjacent to the line feeding device, and enables the mobile robot to reverse its way without getting trapped in the line. For example, the concept enables a line length of the line fed out by the line feeding device to always be appropriate with respect to a current position of the mobile robot. A line length may be defined as a length of the line between the line feeding device and the mobile robot. According to some examples, the control system is further configured to provide a line length value indicative of the line length, e.g., continuously or repeatedly. In these cases, the control system may be configured to control the line feeding device based on both the path length value and the line length value.

[0013] The line feeding device controls the line length of the line between the line feeding device and the mobile robot. By feeding out and feeding in the line, the line length is increased and decreased, respectively. The line feeding device may be stationary in space. The robot system may be configured to feed out the line from the line feeding device to a line length of at least 3 m, such as at least 10 m. Thus, also the line may be at least 3 m. The control system may be configured to control the line feeding device to increase and decrease the line length when the path length increases and decreases, respectively. The control system may thus be configured to continuously or repeatedly determine the path length value indicative of the current path length in view of the current position of the mobile robot. The line length may substantially correspond to, or correspond to, the path length.

[0014] The control system is configured to provide one or more paths for the mobile robot. Each path may be two-dimensional, e.g., defined on a ground surface. Moreover, each path may be straight or non-straight. A non-straight path may for example comprise one or more non-parallel straight path sections and one or more curved path sections.

[0015] In some examples, a single path can be used both as an outbound path from the line feeding device to the current position of the mobile robot, and as a return path from the current position of the mobile robot back to the line feeding device. In some alternative examples, the return path differs from the outbound path. In these cases, the return path may be shorter than the outbound path. The return path may for example be constituted by a shortest path for the mobile robot from the current position to the line feeding device. In any case, the path from the current position of the mobile robot to the line feeding device may be constituted by the return path. Furthermore, the return path may substantially correspond to, or correspond to, the outbound path. Moreover, the outbound path and the return path may be positioned on a same side of any obstacle in the environment such that the mobile robot does not encircle the obstacle and trapping the line.

[0016] If a too large line length with respect to the path length is fed out, there may be a risk that the mobile robot gets entangled in the line. On the other hand, if a too small line length with respect to the path length is fed out, there may be a risk that tension in the line deteriorates or even prevents movements of the mobile robot. By providing an appropriate line length for each position of the mobile robot, a smooth navigation of the mobile robot can be ensured at all times. With smooth navigation may be meant that forces from the line acting on the mobile robot, and a risk that the mobile robot gets trapped in the line, are reduced.

[0017] Furthermore, the control of the line feeding device based on the path length value enables a line of high capacity to be used. The line may for example be used to supply both a cleaning medium and electric power to the mobile robot in a robotic cleaning application. The principles of the robot system are however also applicable for other types of lines and other types of applications.

[0018] In case the mobile robot travels on a flat ground surface, the control system may be configured to control the line feeding device based on the path length value such that the line is always in contact with the ground surface. In these cases, the mobile robot may pull the line over the ground surface and the line feeding device may feed out the line when the path length increases, and the line feeding device may feed in the line and thereby pull the line over the ground surface when the path length decreases. In these ways, an appropriate line length can be provided by the line feeding device to thereby enable the mobile robot to move freely. With appropriate line length may be meant an amount sufficiently large to enable the line to be positioned on the ground surface and sufficiently small to reduce a risk of the mobile robot getting entangled in the line. When the line is positioned on the ground surface, there may be some tension in the line due to gravity in a section between the line feeding device and the ground surface where the line hangs from the line feeding device, and some tension in the line due to gravity in a section between the mobile robot and the ground surface where the line hangs from the mobile robot. However, since the line is positioned on the ground surface, such tensions are not indicative of the line length. Instead, such tensions may be the same, or substantially the same, for different line lengths. Moreover, in a section of the line on the ground surface, there may be no tension when the mobile robot is at standstill, and even when mobile robot moves slightly. By controlling the line feeding device based on the path length value, an appropriate line length can be provided to improve navigation performance of the mobile robot. Forces from a line positioned entirely above the ground surface between a line feeding device and a mobile robot will be high. In contrast, forces from a line positioned on the ground surface and acting on the mobile robot may be very small, e.g., only caused by tension in the line due to gravity in a section between the mobile robot and the ground surface where the line hangs from the mobile robot. This further improves navigation performance of the mobile robot. In addition, a rating of the mobile robot, such as of a traction arrangement thereof, can be relatively small.

[0019] The path length value may be determined based on a position of the mobile robot in various ways known as such. The path length value may be determined based on the current position of the mobile robot in relation to the line feeding device and based on a return path for the mobile robot to the line feeding device. The path length value may for example be determined by using an odometer in the mobile robot. Alternatively, or in addition, the path length value may be determined based on an absolute position of the mobile robot with respect to a known absolute position of the line feeding device. Such absolute positions of the mobile robot may for example be determined by triangulation and / or by using one or more lidar (light detection and ranging) sensors on the mobile robot. Optionally, environmental data, e.g., containing one or more obstacles, may be considered to provide a return path and / or to determine the path length value.

[0020] The control system may comprise at least one data processing device and at least one memory having at least one computer program stored therein, the at least one computer program comprising program code which, when executed by the at least one data processing device, causes the at least one data processing device to perform, or command performance of, various operations according to the present disclosure. The control system may comprise a robot controller onboard the mobile robot. The robot controller may be configured to provide the path length value and to control the line feeding device, e.g., through wireless communication or through the line. Alternatively, or in addition, the control system may comprise a stationary controller, e.g., fixed with respect to the source. For example, the line feeding device may be controlled by the stationary controller instead of by the robot controller.

[0021] The robot system may optionally also comprise the source. The source may be stationary in space.

[0022] The control system may be configured to control the line feeding device based on the path length value such that a slack is provided in the line between the line feeding device and the mobile robot. To this end, the control system may be configured to control the line feeding device such that the line length is always larger than the path length. The slack may be determined as the difference between the line length and the path length, i.e., as a length of the line overshooting the path length. Optionally, the difference may be corrected based on any offset between a point on the mobile robot serving as the basis of the position of the mobile robot and hence of the path length, and a connection point on the mobile robot where the line is connected to the mobile robot. The control system may be configured to control the line feeding device based on a target slack in the line. The slack may be at least 0.3 m. Alternatively, or in addition, the slack may be less than 4 m. A slack of at least 0.3 m and / or less than 4 m constitutes one example of an appropriate amount of line between the line feeding device and the mobile robot.

[0023] The control system may be configured to provide a model of the line. In these cases, the control system may be configured to control the line feeding device based on the model. The model may include one or more of a line length and a mass of the line between the line feeding device and the mobile robot, a feed height from the line feeding device above the ground surface, a connection height to the mobile robot above the ground surface, a static friction coefficient between the line and the ground surface, a dynamic friction coefficient between the line and the ground surface, a bending stiffness of the line, the path, and obstacles on the ground surface. The model may be a two- or three-dimensional model. The control system may be configured to estimate a shape of the line adopted by the line between the line feeding device and the mobile robot based on the model. The control system may further be configured to control the line feeding device based on the shape, in addition to the path length.

[0024] The control system may further be configured to determine the slack of the line based on the model, e.g., based on the shape of the line. The control system may further be configured to control the line feeding device based on the model and based on a target slack in the line.

[0025] The line may be configured to convey a cleaning medium and electric power. In these cases, the source may comprise a cleaning medium supply, such as one or more tanks, and an electric power supply, such as a mains supply. The mobile robot can thereby be supplied with high amounts of cleaning medium and electric power in comparison with a mobile robot comprising a tank as the sole cleaning medium supply and a battery as the sole electric power supply. Moreover, if the mobile robot does not include such tank and battery, the mobile robot can be made smaller which further improves navigation performance of the mobile robot, e.g., in a narrow environment. Moreover, in these cases, there will be no need to replace or recharge a battery of the mobile robot.

[0026] In cases where the mobile robot is supplied with a cleaning medium from the source, the mobile robot constitutes a cleaning robot. The robot system may however comprise a mobile robot that is not necessarily a cleaning robot.

[0027] The line may comprise a sheath between the line feeding device and the mobile robot, e.g., at least along a line length of at least 3 m. The line may further comprise one or more hoses for the cleaning medium and one or more cables for the electric power. In these cases, the one or more hoses and the one or more cables may be housed inside of the common sheath.

[0028] The cleaning medium may for example comprise water and / or chemicals. For example, a first hose may supply a cleaning medium comprising hot water and a second hose may supply a cleaning medium comprising cold water.

[0029] The line may have a mass of at least 250 g / m, such as at least 500 g / m.

[0030] The robot system may comprise a base and a traction arrangement arranged to move the base on a ground surface. In these cases, a clearance between the base and the ground surface may be smaller than a width of the line between the line feeding device and the mobile robot.

[0031] A feed height from the line feeding device above a ground surface may be less than 1.2 m.

[0032] The line may be connected to the mobile robot at a connection height above the ground surface of less than 0.3 m.

[0033] According to a second aspect, there is provided a method of handling a robot system according to the first aspect, the method comprising providing, in the control system, a path length value indicative of a path length of a path for the mobile robot from a current position to the line feeding device; and controlling, by the control system, the line feeding device based on the path length value. The robot system in the second aspect may be of any type described in connection with the first aspect, and vice versa.

[0034] The method may further comprise controlling, by the control system, the mobile robot to be positioned on a ground surface at a primary position and the line feeding device to feed the line such that the line is positioned on the ground surface; and controlling, by the control system, the mobile robot to move on the ground surface from the primary position to a secondary position while controlling, by the control system, the line feeding device to feed the line such that the line is maintained on the ground surface.

[0035] Brief Description of the Drawings

[0036] Further details, advantages and aspects of the present disclosure will become apparent from the following description taken in conjunction with the drawings, wherein:

[0037] Fig. 1: schematically represents a robot system comprising a mobile robot and an elongated line;

[0038] Fig. 2: schematically represents a block diagram of components of the robot system;

[0039] Fig. 3: schematically represents a top view of the robot system when the mobile robot is at a first position and travels along a path;

[0040] Fig. 4: schematically represents a top view of the robot system when the mobile robot is at a second position on the path;

[0041] Fig. 5: schematically represents a top view of the robot system when the mobile robot is at a third position on the path;

[0042] Fig. 6: schematically represents a top view of the robot system when the mobile robot is at a fourth position on the path;

[0043] Fig. 7: schematically represents a top view of the robot system when the mobile robot is at the fourth position on the path;

[0044] Fig. 8: schematically represents a top view of the robot system when the mobile robot has travelled along a path according to a further example; Fig. 9: schematically represents a top view of the robot system when the mobile robot travels along the path in Fig. 8;

[0045] Fig. 10: schematically represents a top view of the robot system when the mobile robot has travelled along an outbound path according to one example; and

[0046] Fig. 11: schematically represents a top view of the robot system and a return path corresponding to the position of the mobile robot in Fig. 10.

[0047] Detailed Description

[0048] In the following, a robot system comprising a mobile robot and a line feeding device, and a method of handling a robot system, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

[0049] Fig. 1 schematically represents a robot system 10. The robot system 10 comprises a mobile robot 12, an elongated line 14 and a line feeding device 16. The mobile robot 12 of this illustrative example is a cleaning robot configured to clean an environment, such as a plant. The mobile robot 12 is arranged to travel on a ground surface 18, here exemplified as a floor. As shown in Fig. 1, a ground portion 20 of the line 14 lies on the ground surface 18.

[0050] The robot system 10 of this example further comprises a source 22. The line 14 is connected to the source 22 and to the mobile robot 12.

[0051] The robot system 10 of this example further comprises a controller 24 onboard the mobile robot 12. The controller 24 is one example of a control system according to the present disclosure. The controller 24 comprises a data processing device 26 and a memory 28. The memory 28 has a computer program stored therein. The computer program comprises program code which, when executed by the data processing device 26, causes the data processing device 26 to perform, or command performance of, various operations as described herein. The line feeding device 16 is stationary and configured to feed out the line 14 and to feed in the line 14. The line feeding device 16 is thus configured to handle the line 14 to provide a certain line length of the line 14 between the line feeding device 16 and the mobile robot 12. The line feeding device 16 of this specific example comprises a rotatable reel 30 around which the line 14 is wound, and an actuator 32 for driving the reel 30 to rotate. The line feeding device 16 of this example further comprises a guide element 34 for guiding the line 14 out from, and in to, the reel 30. The guide element 34 provides a first connection point 36 via which the line 14 enters and leaves the line feeding device 16.

[0052] The controller 24 is in signal communication with the line feeding device 16, e.g., wirelessly or through the line 14, and is configured to control the actuator 32. When the reel 30 is controlled by the actuator 32 to rotate in a first direction, the line 14 is fed out. When the reel 30 is controlled by the actuator 32 to rotate in a second direction, opposite to the first direction, the line 14 is fed in. The line 14 does however not necessarily have to be wound around a reel. Alternative types of line feeding devices are conceivable.

[0053] Fig. 1 further shows a feed height 38 above the ground surface 18. The feed height 38 is here defined as a height of the first connection point 36 above the ground surface 18. The feed height 38 may for example be 0.5 m to 1 m. In Fig. 1, the line feeding device 16 is attached to a wall 40. The line 14 here passes through the wall 40 to the source 22 on an opposite side of the wall 40. The line feeding device 16 may however alternatively be provided on the ground surface 18.

[0054] The source 22 of this example comprises an electric power supply 42 and a cleaning medium supply 44. In this example, the line feeding device 16 and the mobile robot 12 are electrically powered by the electric power supply 42 via the line 14, and the mobile robot 12 is provided with a cleaning medium 46 from the cleaning medium supply 44 via the line 14. The electric power supply 42 may for example be a mains supply. The cleaning medium supply 44 may for example be a tank containing a cleaning medium 46 comprising water and chemicals.

[0055] The line 14 of this example comprises a sheath 48, a cable 50 connected to the electric power supply 42, and a hose 52 connected to the cleaning medium supply 44. Between the line feeding device 16 and the mobile robot 12, here between the wall 40 and the mobile robot 12, the cable 50 and the hose 52 are positioned inside of the sheath 48. Between the line feeding device 16 and the mobile robot 12, the line 14 of this example has a uniform character and a mass of at least 250 g / m. This mass includes the sheath 48, the cable 50 and the hose 52, but not any cleaning medium 46 therein.

[0056] In addition to the controller 24, the mobile robot 12 of this specific and nonlimiting example comprises a base 54, a traction arrangement 56 arranged to move the base 54 on the ground surface 18, a manipulator 58 connected to the base 54, and a nozzle 60. The traction arrangement 56 of this example comprises a plurality of wheels 62, such as steerable drive wheels. The manipulator 58 of this example is a serial manipulator programmable in three or more axes, such as in six or seven axes. The nozzle 60 is carried by the manipulator 58. The nozzle 60 is configured to spray the cleaning medium 46 from the cleaning medium supply 44 onto an object (not shown) for cleaning the object.

[0057] The controller 24 is here housed inside of the base 54. The controller 24 is configured to control the traction arrangement 56, the manipulator 58 and the nozzle 60.

[0058] Fig. 1 further shows a width 64 of the line 14 and a vertical clearance 66 between the base 54 and the ground surface 18. The clearance 66 is here made smaller than the width 64 such that it is prevented that the line 14 comes under the base 54. Should the base 54 come into contact with the line 14 on the ground surface 18, e.g., when feeding in the line 14 or when the mobile robot 12 moves, the small clearance 66 prevents the line 14 from obstructing the wheels 62. The mobile robot 12 of this example further comprises a support element 68 for supporting the line 14, here fixed to the base 54. The support element 68 provides a second connection point 70 where the line 14 is connected to the mobile robot 12. Fig. 1 further shows a connection height 72 above the ground surface 18. The connection height 72 is here defined as a height of the second connection point 70 above the ground surface 18. The connection height 72 may for example be 0.1 m to 0.3 m.

[0059] Since the line 14 is positioned on the ground surface 18 and since the line 14 is raised above the ground surface 18 by the feed height 38 adjacent to the line feeding device 16, and by the connection height 72 adjacent to the mobile robot 12, there is a slack in the line 14. Fig. 1 illustrates the slack by a first slack portion 74a of the line 14 adjacent to the line feeding device 16, and a second slack portion 74b of the line 14 adjacent to the mobile robot 12. One or both of the first and second slack portions 74a, 74b, and any slack in the line 14, may also be referred to with reference numeral "74". Should there be no slack 74 in the line 14, the line 14 would extend straight between the first and second connection points 36, 70 and thereby not touch the ground surface 18.

[0060] Fig. 1 further shows a path length 76 of a path for the mobile robot 12 from a current position 80 of the mobile robot 12 to the line feeding device 16. The path is a straight path in this example. The path length 76 here corresponds to a distance between the line feeding device 16 and the current position 80 of the mobile robot 12. The path length 76 may for example be defined as a length of the path between the first connection point 36 of the line feeding device 16 and a geometric center point 78 of the mobile robot 12 at the current position 80 thereof, even though in some examples it may not be possible to completely align the geometric center point 78 with the first connection point 36.

[0061] Fig. 1 further shows an offset 82 between the geometric center point 78 of the mobile robot 12, here corresponding to the position 80 of the mobile robot 12, and a point of the mobile robot 12 where the line 14 is connected, here the second connection point 70. In the orientation adopted by the mobile robot 12 in Fig. 1, and assuming or estimating that the ground portion 20 of the line 14 is straight, the slack 74 can be determined as the difference between the line length from the first connection point 36 to the second connection point 70 on the one hand, and the difference between the path length 76 and the offset 82 on the other hand. Thus, in Fig. 1, the slack 74 can be determined by subtracting the distance between the first and second connection points 36, 70 from the line length. The position 80 of the mobile robot 12 can be determined in various ways using a positioning system previously known as such, for example including an odometer or one or more lidar sensors in the mobile robot 12.

[0062] Fig. 2 schematically represents a block diagram of components of the robot system 10. As shown in Fig. 2, the cable 50 provides electric power to each of the actuator 32, the traction arrangement 56, the manipulator 58 and the nozzle 60, and the hose 52 provides the cleaning medium 46 to the nozzle 60.

[0063] Fig. 2 further shows that the controller 24 is configured to provide a path length value 84, e.g., continuously or repeatedly during operation of the robot system 10. The path length value 84 is indicative of the path length 76 of the path for the mobile robot 12 from a current position 80 of the mobile robot 12 to a position of the line feeding device 16. The path length value 84 may for example be expressed in meters. For example, in case the path is straight, the controller 24 may determine the path length value 84 as a distance between the current position 80 of the mobile robot 12 and a position of the line feeding device 16. The controller 24 is further configured to control the line feeding device 16 based on the path length value 84. For example, the controller 24 may control the line feeding device 16 such that the line length increases when the path length value 84 increases, and vice versa.

[0064] Fig. 2 further shows that the controller 24 is configured to provide a line length value 85, e.g., continuously or repeatedly during operation of the robot system 10. The line length value 85 is indicative of the line length of the line 14 between the line feeding device 16 and the mobile robot 12, such as between the first connection point 36 and the second connection point 70. The line length value 85 may for example be expressed in meters. The controller 24 may be configured to control the line feeding device 16 based on both the path length value 84 and the line length value 85, e.g., such that the line length value 85 is always larger than the path length value 84. In some examples, each rotational position of the actuator 32 corresponds to a unique line length. The rotational position may for example be determined by a sensor (not shown), such as a rotary encoder. Data indicative of the rotational position or of the line length may be communicated from the line feeding device 16 to the controller 24 to provide the line length value 85 in the controller 24. As one alternative option, a history of commands from the controller 24 to the line feeding device 16 may be used to determine the line length value 85 in the controller 24. In the above example when the controller 24 controls the line feeding device 16 such that the line length increases when the path length value 84 increases, and vice versa, the controller 24 may or may not employ the line length value 85. In case the line length value 85 is employed, the slack 74 in the line 14 can be controlled more accurately.

[0065] In the robot system 10 of this example, the controller 24 is configured to control the mobile robot 12 to move over the ground surface 18 while controlling the line feeding device 16 such that the line length is always sufficient to maintain the line 14 on the ground surface 18. For example, the controller 24 may control the line feeding device 16 based on the path length value 84, and optionally also based on the offset 82 and the line length value 85, to maintain a target slack 74 in the line 14, such as from 0.3 m to 4 m, while the mobile robot 12 moves over the ground surface 18. An appropriate line length is thereby provided. Such control provides several advantages. The line 14 can be of high capacity since the line 14 is permanently connected to the source 22. The connection of the line 14 to the source 22 also enables elimination of any tank or power source onboard the mobile robot 12, which in turn enables a small size of the mobile robot 12. Forces from the line 14 acting on the mobile robot 12 are kept low. Furthermore, since the slack 74 is not too large, the line feeding device 16 can feed in and remove some portion of the line 14 from the path when the mobile robot 12 travels towards the line feeding device 16. The mobile robot 12 can also push some portion of the line 14 due to the small clearance 66, if needed. The mobile robot 12 therefore has improved navigation and cleaning performances.

[0066] Fig. 2 further shows that the controller 24 is configured to provide one or more paths 86 for the mobile robot 12. The controller 24 is configured to control the traction arrangement 56 such that the mobile robot 12 moves along each path 86.

[0067] Fig. 2 further shows that the controller 24 is configured to provide a model 88 of the line 14. The controller 24 is here configured to control the line feeding device 16 based on the model 88. The the model 88 of the line 14 may be defined in various ways known to the skilled person. One example of such model 88 is described in the following publication, the content of which is incorporated herein in its entirety:

[0068] Fritzkowski et al. DYNAMICS OF A ROPE AS A RIGID MULTIBODY SYSTEM. In: Journal of Mechanics of Materials and Structures, Volume 3, No 6, June 2008.

[0069] Based on the model 88, the controller 24 can estimate a shape of the line 14 between the line feeding device 16 and the mobile robot 12. This estimation enables a further improved control of the line feeding device 16. For example, in case the estimated shape of the line 14 indicates that the line 14 contains a slack 74 in the form of one or more serpentine-shaped portions on the ground surface 18, the controller 24 may determine that there is currently no need, or a reduced need, for the line feeding device 16 to feed out the line 14 when the mobile robot 12 moves away from the line feeding device 16, and vice versa. The model 88 may be said to serve as a complement to the path length value 84 to enable an even better control of the line feeding device 16. For example, some behavior of the line 14 that is not deducible from the path length value 84 alone can be detected based on the model 88. The model 88 may for example be based on one or more parameters among the line length and the mass of the line 14 between the line feeding device 16 and the mobile robot 12, the feed height 38, the connection height 72, a static friction coefficient between the line 14 and the ground surface 18, a dynamic friction coefficient between the line 14 and the ground surface 18, a bending stiffness of the line 14, and the path 86.

[0070] Fig. 3 schematically represents a top view of the robot system 10 when the mobile robot 12 is at a first position 80a. Fig. 3 also shows a first path 86a for the mobile robot 12. In the first position 80a, there is a first path length 76a of the first path 86a from the first position 80a to the line feeding device 16. The first path 86a is here straight and two-dimensional. Thus, the first path length 76a corresponds to a distance between the mobile robot 12 and the line feeding device 16.

[0071] Fig. 3 illustrates the ground portion 20 of the line 14 with a dashed line and the first and second slack portions 74a, 74b of the line 14 with solid lines. Fig. 3 further illustrates a first line length 90a of the line 14 between the line feeding device 16 and the mobile robot 12. In the situation in Fig. 3, the line length value 85 is indicative of the first line length 90a. Note that the line 14 here extends in two dimensions in a vertical plane. Thus, the line 14 does not extend along a straight line between the line feeding device 16 and the mobile robot 12.

[0072] Fig. 4 schematically represents a top view of the robot system 10 when the mobile robot 12 has travelled along the first path 86a from the first position 80a to a second position 80b in a forward direction 92. In the second position 80b, the mobile robot 12 is at a second path length 76b from the line feeding device 16 along the first path 86a. The path length value 84 indicative of the second path length 76b is larger than the path length value 84 indicative of the first path length 76a. In association with the movement of the mobile robot 12 from the first position 80a to the second position 80b, such as before and / or during the movement, the controller 24 controls the line feeding device 16 to feed out the line 14 from the first line length 90a to a second line length 90b based on the path length value 84 indicative of the second path length 76b. Although the mobile robot 12 pulls the line 14 on the ground surface 18 when travelling in the forward direction 92, the mobile robot 12 does not have to provide any force to pull the line 14 out from the line feeding device 16. A third slack portion 74c may be formed in the line 14 on the ground surface 18 adjacent to the line feeding device 16 due to the feeding of the line 14 therefrom. In the third slack portion 74c, the line 14 may adopt a serpentine shape.

[0073] Fig. 5 schematically represents a top view of the robot system 10 when the mobile robot 12 has travelled along the first path 86a from the second position 80b to a third position 80c in the forward direction 92. The first path 86a of this example is both an outbound path for the mobile robot 12 from the line feeding device 16 to the third position 80c, and a return path for the mobile robot 12 from the third position 80c back to the line feeding device 16.

[0074] In the third position 80c, the mobile robot 12 is at a third path length 76c from the line feeding device 16 along the first path 86a. The third path length 76c may for example be 10 m. In association with the movement of the mobile robot 12 from the second position 80b to the third position 80c, the controller 24 controls the line feeding device 16 to feed out the line 14 from the second line length 90b to a third line length 90c based on the path length value 84 indicative of the third path length 76c. During the movement of the mobile robot 12 from the second position 80b to the third position 80c, the third slack portion 74c is straightened out in this example. Thus, the feeding of the line 14 by the line feeding device 16 does not necessarily have to be linearly proportional to the current path length value for the mobile robot 12. For example, the controller 24 may control the line feeding device 16 such that the third slack portion 74c is formed when the mobile robot 12 is in the second position 80b (like in Fig. 4) to anticipate a movement of the mobile robot 12 from the second position 80b to the third position 80c that is faster than a feeding out speed of the line feeding device 16. The first and third positions 80a, 80c constitute one example of primary and secondary positions, respectively, between which the mobile robot 12 can move while the line feeding device 16 feeds the line 14 such that the line 14 is maintained on the ground surface 18.

[0075] Fig. 6 schematically represents a top view of the robot system 10 when the mobile robot 12 has travelled along the first path 86a from the third position 80c to a fourth position 8od in a rearward direction 94. In the fourth position 8od, the mobile robot 12 is at a fourth path length y6d from the line feeding device 16 along the first path 86a. In Fig. 6, the controller 24 is currently controlling the line feeding device 16 to feed in the line 14 from the third line length 90c based on the path length value 84 indicative of the fourth path length y6d. The controller 24 controls the line feeding device 16 to feed in the line 14 simultaneously with movement of the mobile robot 12 in the rearward direction 94. In case the mobile robot 12 travels faster than a feeding in speed of the line feeding device 16, the third slack portion 74c may form adjacent to the mobile robot 12. Due to the clearance 66 being smaller than the width 64, the base 54 prevents the wheels 62 from becoming entangled in the line 14, and may instead push the line 14 on the ground surface 18, while enabling a fast movement of the mobile robot 12.

[0076] Fig. 7 schematically represents a top view of the robot system 10 when the mobile robot 12 is still at the fourth position 8od. The controller 24 has now controlled the line feeding device 16 to feed in the line 14 to a fourth line length 9od substantially corresponding to the fourth path length y6d. The third and fourth positions 80c, 8od constitute a further example of primary and secondary positions, respectively, between which the mobile robot 12 can move while the line feeding device 16 feeds the line 14 such that the line 14 is maintained on the ground surface 18.

[0077] Fig. 8 schematically represents a top view of the robot system 10 when the mobile robot 12 has travelled along a second path 86b according one example. In Fig. 8, the line 14 is omitted. In the illustrative example in Fig. 8, a first obstacle 96a and a second obstacle 96b are positioned on the ground surface 18. The first and second obstacles 96a, 96b may for example be tables or machines. In Fig. 8, the mobile robot 12 is at a fifth position 8oe at an end of the second path 86b. The second path 86b of this example is both an outbound path for the mobile robot 12 from the line feeding device 16 to the fifth position 8oe, and a return path for the mobile robot 12 from the fifth position 8oe back to the line feeding device 16.

[0078] As shown in Fig. 8, the second path 86b is non-straight and comprises a plurality of non-parallel straight path sections, here exemplified as a first path section 98a, a second path section 98b and a third path section 98c. The first path section 98a extends between the line feeding device 16 and the second path section 98b, the second path section 98b extends between the first path section 98a and the third path section 98c, and the third path section 98c extends between the second path section 98b and the fifth position 8oe of the mobile robot 12. By following the second path 86b, the mobile robot 12 can travel from the line feeding device 16 to the fifth position 8oe, and back from the fifth position 8oe to the line feeding device 16, while avoiding collision with the first and second obstacles 96a, 96b.

[0079] The first path section 98a has a first path section length 100a, the second path section 98b has a second path section length 100b, and the third path section 98c has a third path section length 100c. When the mobile robot 12 is at the fifth position 8oe, a path length 76 of the second path 86b from the fifth position 8oe to the line feeding device 16 may be defined as a sum of the first to third path section lengths tooa-iooc.

[0080] Fig. 9 schematically represents a top view of the robot system 10 when the mobile robot 12 travels along the second path 86b. In Fig. 9, the mobile robot 12 is at a sixth position 8of and travels towards the fifth position 8oe in the forward direction 92. As shown in Fig. 9, the ground portion 20 of the line 14 cannot extend straight on the ground surface 18 between the line feeding device 16 and the mobile robot 12 due to being obstructed by the first and second obstacles 96a, 96b. By taking environmental data, here the first and second obstacles 96a, 96b, into consideration, e.g., by the model 88, the controller 24 can control the line feeding device 16 to provide an appropriate slack 74 in the line 14 also in more complex environments to enable the mobile robot 12 to move freely. Regarding the line length in Fig. 9, on the one hand, there is the third slack portion 74c formed in the line 14 adjacent to the line feeding device 16, and on the other hand, the line 14 has been slightly straightened out adjacent to the first and second obstacles 96a, 96b in comparison with the second path 86b. The line length thereby substantially corresponds to the path length 76 from the sixth position 8of to the line feeding device 16.

[0081] Fig. 10 schematically represents a top view of the robot system 10 when the mobile robot 12 has travelled along a third path 86c according to one example. In Fig. 10, the mobile robot 12 is at a seventh position 80g at an end of the third path 86c. The third path 86c is here an outbound path for the mobile robot 12 from the line feeding device 16 to the seventh position 80g.

[0082] The third path 86c of this example comprises the first path section 98a between the line feeding device 16 and a first point 102a, the second path section 98b between the first point 102a and a second point 102b, and the third path section 98c between the second point 102b and a third point 102c. Thus, the third path 86c of this example comprises the second path 86b. The third path 86c of this example further comprises a straight fourth path section 98d between the third point 102c and a fourth point iO2d corresponding to the seventh position 80g.

[0083] Fig. 11 schematically represents a top view of the robot system 10 and a fourth path 86d according to one example. Also in Fig. 11, the mobile robot 12 is at the seventh position 80g at the end of the third path 86c. The fourth path 86d is here a shortest suitable return path for the mobile robot 12 from the seventh position 80g back to the line feeding device 16. A path on an opposite side of the second obstacle 96b with respect to the third path 86c (above the second obstacle 96b in Fig. 11) would not be suitable for the mobile robot 12 since the line 14 would then be wound around the second obstacle 96b. The fourth path 86d of this example comprises a straight fifth path section 98e between the fourth point iO2d and a fifth point iO2e on the fourth path section 98d, here substantially centered between the third and fourth points 102c, iO2d The fourth path 86d of this example further comprises a straight sixth path section 98f between the fifth point iO2e and a sixth point iO2f on the third path section 98c, here substantially centered between the second and third points 102b, 102c. The fourth path 86d of this example further comprises a straight seventh path section 98g between the fifth point iO2e and the second point 102b. The fourth path 86d of this example further comprises the first and second path sections 98a, 98b.

[0084] As can be seen in Figs. 10 and 11, the fourth path 86d is shorter than the third path 86c. When the mobile robot 12 is in the seventh position 80g, a path length of the fourth path 86d for the mobile robot 12 from the seventh position 80g to the line feeding device 16 is constituted by a sum of each length of the first, second, fifth, sixth and seventh path sections 98a, 98b, 98e, 98f, 98g. Although the mobile robot 12 does not necessarily have to follow the fourth path 86d if returning to the line feeding device 16, the line feeding device 16 is controlled based on the path length of the fourth path 86d when the mobile robot 12 is in the seventh position 80g on the third path 86c. This implies that when the mobile robot 12 travels from the third point 102c to the fourth point iO2d along the third path 86c, the line length is first decreased and then increased.

[0085] One, several or all of the first to fourth line lengths 9oa-9od, one, several or all of the first to fourth path lengths 76a-y6d, one, several or all of the first to seventh positions 8oa-8og, and one, several or all of the first to fourth paths 86a, 86d may also be referred to with reference numerals "90", "76", "80" and "86", respectively.

[0086] While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts may be varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.

Claims

CLAIMS1. A robot system (io) comprising:- a mobile robot (12);- an elongated line (14) connected to the mobile robot (12) and for connection to a source (22);- a line feeding device (16) configured to feed out the line (14) and to feed in the line (14); and- a control system (24) configured to provide a path length value (84) indicative of a path length (76) of a path (86) for the mobile robot (12) from a current position (80) to the line feeding device (16), and to control the line feeding device (16) based on the path length value (84).

2. The robot system (10) according to claim 1, wherein the control system (24) is configured to provide a line length value (85) indicative of a line length (90) between the line feeding device (16) and the mobile robot (12), and to control the line feeding device (16) based on the line length value (85).

3. The robot system (10) according to any of the preceding claims, wherein the path (86) is a shortest path for the mobile robot (12) from the current position (80) to the line feeding device (16).

4. The robot system (10) according to any of the preceding claims, wherein the control system (24) is configured to control the line feeding device (16) based on the path length value (84) such that a slack (74) is provided in the line (14) between the line feeding device (16) and the mobile robot (12).

5. The robot system (10) according to claim 4, wherein the slack (74) is at least 0.3 m.

6. The robot system (10) according to claim 4 or 5, wherein the slack (74) is less than 4 m.

7. The robot system (io) according to any of the preceding claims, wherein the control system (24) is configured to provide a model (88) of the line (14), and to control the line feeding device (16) based on the model (88).

8. The robot system (10) according to any of the preceding claims, wherein the line (14) is configured to convey a cleaning medium (46) and electric power.

9. The robot system (10) according to any of the preceding claims, wherein the line (14) has a mass of at least 250 g / m.

10. The robot system (10) according to any of the preceding claims, wherein the robot system (10) comprises a base (54) and a traction arrangement (56) arranged to move the base (54) on a ground surface (18), and wherein a clearance (66) between the base (54) and the ground surface (18) is smaller than a width (64) of the line (14) between the line feeding device (16) and the mobile robot (12).

11. The robot system (10) according to any of the preceding claims, wherein a feed height (38) from the line feeding device (16) above a ground surface (18) is less than 1.2 m.

12. The robot system (10) according to any of the preceding claims, wherein the line (14) is connected to the mobile robot (12) at a connection height (72) above the ground surface (18) of less than 0.3 m.

13. A method of handling a robot system (10) according to any of the preceding claims, the method comprising:- providing, in the control system (24), a path length value (84) indicative of a path length (76) of a path (86) for the mobile robot (12) from a current position (80) to the line feeding device (16); and- controlling, by the control system (24), the line feeding device (16) based on the path length value (84).

14. The method according to claim 13, further comprising:- controlling, by the control system (24), the mobile robot (12) to bepositioned on a ground surface (18) at a primary position (80) and the line feeding device (16) to feed the line (14) such that the line (14) is positioned on the ground surface (18); and- controlling, by the control system (24), the mobile robot (12) to move on the ground surface (18) from the primary position (80) to a secondary position (80) while controlling, by the control system (24), the line feeding device (16) to feed the line (14) such that the line (14) is maintained on the ground surface (18).

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