System and method for sanding floors

Abstract

The present disclosure relates to a system for sanding a floor, the system comprising: a driving unit comprising wheels for moving the driving unit; a floor sanding machine connected to the driving unit such that the driving unit can move the floor sanding machine; and a controller configured to control the driving unit to sand a floor via the floor sanding machine. The disclosure further relates to a method for sanding floors.

Description

[0001] SYSTEM AND METHOD FOR SANDING FLOORS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to systems and methods for sanding floors.

[0004] BACKGROUND OF THE INVENTION

[0005] Sanding of floors is an essential step in many renovation and construction projects, aimed at creating smooth, even surfaces for subsequent treatments such as staining, varnishing, or painting. Conventionally, this task is carried out through manual labour using handheld sanding tools or floor sanding machines. These machines typically require the operator to guide the tool over the surface manually, ensuring that each area is properly sanded. While this method has been widely adopted, it remains heavily dependent on the skill and endurance of the worker, often requiring significant time and effort to achieve satisfactory results.

[0006] However, conventional methods for floor sanding come with notable drawbacks. Firstly, the process is physically demanding, requiring operators to perform repetitive movements over extended periods. This can lead to fatigue, decreased efficiency, and an increased risk of errors in achieving a uniform surface finish. Moreover, the sanding process generates substantial amounts of fine dust particles, which are typically dispersed into the surrounding environment. Despite the availability of dust collection systems in some sanding tools, many operators are still exposed to these particles, raising concerns about occupational health risks such as respiratory issues and long-term exposure to harmful substances.

[0007] Another disadvantage lies in the inefficiency of current sanding techniques. Achieving a consistent surface finish often requires multiple passes, with the operator needing to adjust their technique to account for variations in floor material, uneven surfaces, or corners and edges that are difficult to access. This increases the time required for sanding, particularly for larger areas, and adds to the physical strain on the operator. Furthermore, the reliance on manual effort makes it challenging to maintain consistent results across different projects or among operators with varying levels of experience.

[0008] It is therefore an objective of the present invention to provide methods and systems for sanding floors that are efficient, enable faster completion of tasks, and reduce or eliminate the worker's exposure to dust and repetitive manual labour. SUMMARY OF THE INVENTION

[0009] On the above background, it is an object of preferred embodiments of the present disclosure to provide efficient sanding of floors. It is further an object of preferred embodiments of the present disclosure to reduce or eliminate the worker's exposure to dust and repetitive manual labour.

[0010] A first aspect of the present disclosure relates to a system for sanding a floor, the system comprising : a driving unit comprising wheels for moving the driving unit; a floor sanding machine connected to the driving unit such that the driving unit can move the floor sanding machine; and a controller configured to control the driving unit to sand a floor via the floor sanding machine.

[0011] Systems and methods according to the present disclosure may provide efficient sanding of floors facilitated by an automated driving unit which move a floor sanding machine, such as a conventional floor sanding machine, to thereby sand a floor. In turn, a human worker does not need to be present in the vicinity of the floor sanding machine, thereby reducing exposure of the worker to dust.

[0012] Utilization of a conventional floor sanding machine, for example via a coupling arrangement through which such a floor sanding machine can be coupled, ensures that any desired floor sanding machine can be attached to the driving unit depending on needs and preferences. In turn, this reduces the burden of actually realizing an automated floor sanding machine.

[0013] The controller may be integrated into the driving unit.

[0014] The floor sanding machine preferably comprises a sanding element which is configured to engage with a floor to sand said floor. A sanding element may for example be sandpaper. The sanding element may be rotated by the floor sanding machine to perform sanding.

[0015] Often, the floor will be made of wood or other biological material, such as bamboo. Floors made of synthetic materials such as rubber, polymer or the like may also require sanding to regain its original look or at least a more appealable look. According to examples of the present disclosure, the system further comprises a coupling arrangement for detachably connecting the floor sanding machine to the driving unit, wherein the floor sanding machine is connected to the driving unit via the coupling arrangement. The coupling arrangement preferably fixes the driving unit and the floor sanding machine at least in a horizontal plane. Thus, rotation of the driving unit also causes a rotation of the floor sanding machine.

[0016] The provision of a coupling arrangement for detachably connecting a floor sanding machine to the driving unit further facilitates that any compatible desired floor sanding machine can be attached to the driving unit depending on needs and preferences, and reduces the burden of actually realizing an automated floor sanding machine.

[0017] The coupling arrangement can be operated by a mechanical and / or an electromechanical activation, for example such that no manual operation is required to couple / decouple the driving unit and the floor sanding machine, for example such that the driving unit can autonomously switch to sanding operation, for example coming from a recharging operation.

[0018] According to examples of the present disclosure, the floor sanding machine is configured to be manually operated when it is not connected to the driving unit. Thus, the floor sanding machine may comprise a manual user interface, such as one or more handles, in order for a human operator to operate the sanding machine during manual operation.

[0019] In other words, the floor sanding machine can, at least in some examples, be a conventional floor sanding machine, with no particular adaptations performed to adapt it to connecting it to the driving unit. In some examples, a floor sanding machine may be adapted, for example by attachment of a first coupling arrangement member configured to mate with a second coupling arrangement member of the driving unit, the coupling arrangement comprising the first coupling arrangement member and the second coupling arrangement member. The floor sanding machine may also be adapted by attachment of means of conveying machine-specific information, for example an RFID.

[0020] According to examples of the present disclosure, the controller is configured to control the driving unit to sand a floor via the floor sanding machine based on machine-specific information of the sanding machine.

[0021] According to examples of the present disclosure, the controller is configured to receive the machine-specific information upon detachably connecting the floor sanding machine to the driving unit, for example manually or automatically, for example via near-field communication with a communication unit on the floor sanding machine. This communication unit may comprise the information required for the driving unit so move the sanding machine to obtain the desired sanding.

[0022] Machine-specific information is information which varies between different sanding machines, for example the specific position of the sanding element vis-a-vis the driving unit. Using such information may enable improved accuracy when performing a sanding operation. Also, a size, such as a width of the sanding element of the particular sanding machine may be desired fed to the controller.

[0023] Then, knowing the position and stance of the driving unit enables the controller to determine the position of the sanding machine and the sanding element. In this manner, the sanding may be controlled by the controller.

[0024] According to examples of the present disclosure, the driving unit has a flat top.

[0025] A flat top can, for example, be used to facilitate transportation of the driving unit on, e.g., a sack truck. Further, a flat top can be used to accommodate a (detachable) waste container.

[0026] According to examples of the present disclosure, one or both of the driving unit and the floor sanding unit receives power from a cable. Then, the system may further comprise a roll-up mechanism for rolling up said cable while the controller controls the driving unit to sand the floor via the floor sanding machine.

[0027] According to examples of the present disclosure, the controller is configured to control the driving unit such that the sanding machine is primarily positioned relative to the driving unit in a driving direction of the driving unit while the floor machine sands the floor. Such control contrasts control in which the floor sanding machine is behind the driving unit, for example where the floor sanding machine is towed. By instead having the floor sanding machine in front of the driving unit, the driving unit can generally control sanding operation more accurately. Further, in this manner, the sanding machine may move closer to an obstacle than if the driving unit was provided between the obstacle and the sanding machine.

[0028] According to examples of the present disclosure, at least some of the wheels of the driving unit are rotatable at least 180 degrees around a vertical axis. This allows the driving unit to move the sanding machine in any desired manner over the floor irrespective of where the driving unit is positioned vis-a-vis the sanding machine. According to examples of the present disclosure, the system comprises one or more sensor units positioned on the driving unit, wherein the controller is configured to control the driving unit based on sensor data from the one or more sensor units.

[0029] The sensor unit may ensure that the system can be operated by performing simultaneous mapping and localization (SLAM).

[0030] According to examples of the present disclosure, the one or more sensor units comprises a first sensor unit and a second sensor unit, wherein the first sensor unit and the second sensor unit are displaced in opposite directions relative to a central horizontal axis defined by the driving unit and the floor sanding machine such that the first sensor unit and / or the second sensor unit receives sensor data from behind the floor sanding machine relative to the central horizontal axis.

[0031] Hence, even though a floor sanding machine may obstruct vision from the point of view of the driving unit, the provision of two sensor units displaced in opposite directions may ensure that a significant portion of vision being the floor sanding machine is provided, which in turn can be used for accurate navigation and safety.

[0032] According to examples of the present disclosure, the system further comprises a waste container and a suction unit, wherein the suction unit is configured to displace material removed from the floor by the floor sanding machine into the waste container.

[0033] The suction unit may be a cyclone suction unit which ensures a separation of larger and smaller particles, which in turn can reduce the need to replacing filters.

[0034] According to examples of the present disclosure, the waste container is positioned on top of the driving unit.

[0035] According to examples of the present disclosure, the waste container is positioned so as to not obstruct a sensor range of the one or more sensor units.

[0036] According to examples of the present disclosure, the controller is configured to control the driving unit based on a smoothness of the floor. In one situation, the smoothness is determined via vacuum power of the suction unit, via a laser unit configured to measure a surface roughness of the floor, and / or via operation of a sanding element of the sanding machine. The controlling may be performed based on a predetermined smoothness or on a smoothness determined in real time. For example, an upwardly extending floor portion will exert an increased force on the sanding machine, requiring a larger torque to rotate the sanding element, whereby a measure of the smoothness is obtained by a measure of the variation of the torque required to sand the floor.

[0037] According to examples of the present disclosure, the controller is configured to determine when a sanding element of the floor sanding machine is worn and / or needs replacing based on operation of the sanding element of the sanding machine.

[0038] A second aspect of the present disclosure relates to a method for sanding floors, the method comprising : providing a system according to the first aspect of the invention; sanding a floor via the floor sanding machine by using the controller to control the driving unit.

[0039] According to examples of the present disclosure, the floor sanding machine is a first floor sanding machine, wherein the method comprises the steps of: detaching the first floor sanding machine; and attaching a second floor sanding machine.

[0040] According to examples of the present disclosure, the method comprises a step of sanding the same or another floor via the second floor sanding machine by using the controller to control the driving unit.

[0041] According to examples of the present disclosure, the method comprises a step of displacing wheels of the floor sanding machine from the floor, wherein the step of displacing the wheels is performed prior to the step of sanding the floor via the floor sanding machine. This displacing may be obtained in a number of manners. In one situation, the sanding machine allows displacing of the wheels vis-a-vis the sanding element. In another situation, the driving unit comprises a carrying element on which the wheels are provided so that the wheels do not contact the floor during operation.

[0042] According to examples of the present disclosure, the controller is provided with information particular to a pertaining sanding machine prior to operation so that the driving of the driving unit takes such information into account when driving the driving unit. Such information is described further below and above. According to examples of the present disclosure the information may be received from an external user interface. According to other examples, the driving unit comprises a reader configured to read the information from an information element of the sanding machine. Embodiments of such reader and element are provided above and below.

[0043] According to examples of the present disclosure, the robot may be rechargeable or may be replenished with fuel. Then, the coupling arrangement may be operable by the driving unit so that the sanding machine may be left at a position while the driving moves to a charging or replenishment station.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Embodiments of the invention will now be further described by reference to the accompanying drawings, in which:

[0046] Figure 1 illustrates a preferred embodiment of an assembly according to the invention,

[0047] Figure 2 illustrates relevant portions of the assembly of figure 1 seen from above,

[0048] Figure 3 illustrates the embodiment of figure 1 with a sanding machine with an elevatable wheel,

[0049] Figure 4 illustrates the embodiment of figure 1 with a sanding machine with an elevated wheel, and

[0050] Figure 5 illustrates an embodiment of the assembly of the invention within a room with navigation elements.

[0051] DETAILED DESCRIPTION

[0052] Figure 1 illustrates an embodiment 10 of the assembly of the invention. The assembly 10 or system comprises a driving unit or robot 20 and a floor sanding machine 30 connected to each other via a coupling or coupling arrangement 38.

[0053] The floor sanding machine 30 may be of any common type. In the present embodiment, the floor sanding machine (or sander) of the type having a sanding element in the form of a sanding disc 33 for sanding the floor 11 by rotating around a vertical axis (the floor being horizontal). Other types of sanding elements may be rotatable cylinders or drums rotating around an axis perpendicular to a plane of the floor.

[0054] The sanding disc is provided in a sanding unit 32 of the sanding machine 30. The sanding machine 30 also has a motor unit 34 comprising a motor for driving the sanding element, such as in relation to a frame 35 of the sanding machine.

[0055] The sanding machine is of a type which may be manually operated and thus preferably has a handle 36 for an operator to use for moving the sanding element over the floor 11 while the disc or drum rotates. The sanding machine is powered via a cable 381. During manual operation, the cable 381 may be connected to mains outlet of a building in which the floor 11 is provided.

[0056] Preferably, the sanding machine is rather simple and is not able to move itself in relation to the floor 11. Naturally, the sanding unit will engage the floor and thus potentially move the sanding machine (if not attended to) over the floor, but any other engagement of the sanding machine and the floor is preferably inactive in the sense that it will not act to attempt to move the sanding machine over the floor. In particular, if the sanding machine has wheels, these wheels may be retractable from the floor during operation or are preferably not driven by a separate drive of the sanding machine.

[0057] If the sanding machine comprises one or more wheels, 33, (see figures 3 and 4), such as for transporting the sanding machine to the floor 11, these may be elevatable (figure 3) so as to not interfere with the movement of the sanding unit over the floor during operation.

[0058] Alternatively, the robot may comprise elements 331 configured to lift the wheels 33 from the floor to disengage the wheels 33 from the floor during elevation. Such elements 331 may be simple trays on to which the wheels 33 are positioned while the robot and sanding machine are attached to each other.

[0059] The robot 20 comprises a number of wheels 25 for moving the robot over the floor 11. The robot 20 is connected, such as fixedly connected, to the sanding machine 30 via the coupling 38.

[0060] The coupling 38 may be a fixed coupling not allowing the sanding machine, such as the frame 35, to move in relation to a frame 21 of the robot 20. The sanding machine may allow a slight rotation of the rotation axis of the sanding element vis-a-vis horizontal, vertical and / or the frame 35 in order to allow for non-planar portions of the floor 11. It is desired that the robot may both push and pull the sanding machine in order to allow the sanding unit to cover portions of the floor 11 where the robot has not yet been or will not even have to be at any point in time.

[0061] The coupling may be manually engageable and disengageable, or it may be electronically controlled, such as when it is based on one or more electromagnetic actuators. In this manner, the robot may identify the sanding machine, move to the sanding machine and engage it itself. Also, the robot may disengage the sanding machine if (see below), the sanding unit needs a new sanding surface, if the robot needs to go to a charging station, a replenishment station or an emptying station. The sanding machine may be left in the latest sanded portion of the floor, where the robot may then re-engage and commence the sanding operation once ready to do so.

[0062] During operation of the assembly 10, the sanding unit is operated so that the disc 33 is rotated, while the robot 20 controls the position of the sanding machine 20 over the floor 11.

[0063] The robot has wheels 25 which are controlled by a wheel controller 24 which may be configured to both drive the wheels 25 as well as provide information as to how much each wheel is rotated. Also, in addition to rotating each wheel around a horizontal axis to have the wheel and thus the robot move over the floor, one or more wheels, and preferably all wheels, is / are rotatable around a vertical axis 251 (see figure 2). In this manner, the robot may move more or less sideways in relation to an axis, A, through a centre of the robot and a centre of the sanding machine. In this manner, the position and movement of the sanding unit 32 may be controlled in a suitable manner to obtain the desired sanding of the floor 11.

[0064] The robot 20 further comprises one or more sensor units 26 for determining a position of the robot and / or sanding machine over the floor 11. A controller 22 may receive information from the sensor unit(s) 26

[0065] During operation, the robot 20, based on information from the sensor unit(s) 26, drives the wheels 25 to move the sanding unit 32 over the floor 11 while the sanding unit 32 operates to rotate the disc 33 to sand the floor 11.

[0066] The robot may be powered by a power cable 26 connected to e.g. a mains plug. The sanding machine 30 may be powered by the robot 20, such as if the cable 381 is connected to the robot 20. In this situation, the robot 20 may control the supply of power to the sanding machine and thus, e.g. control a rotation or rotational frequency of the sanding unit, such as the disc 33. Alternatively, the sanding machine and robot may be individually powered, or the robot may be powered via the sanding machine, such as if the cable 381 was for powering the robot (then not needing the cable 26). Further alternatively, any or both of the sanding machine and the robot may be powered by a battery and / or a fuel cell 28 carried by the robot and / or the sanding machine.

[0067] When a cable 26 is provided for powering the robot and / or sanding machine, it may be desired to not allow the cable 26 to touch the floor 11 to avoid the risk of the cable being run over by the sanding unit and thus destroyed. The cable may be suspended from a ceiling and / or walls of a building having the floor 11. Alternatively, a cable tightening system may be employed, such as one attached to the robot, which keeps the cable 26 tightened and straight between the robot or sanding machine and a wall plug. If such an element is used, the robot may control the assembly so that the sanding unit does not cover any stretch covered by the straight cable during operation.

[0068] In general, the robot 20 may, in a storage of the controller 22, hold a map or information describing a shape of the floor 11 to be sanded. The robot 20 may determine a position of the robot and / or the sanding unit in the room, based on information from the sensor unit 26. The controller 22 may also determine a position of the cable 26 in relation to the map, so that the cable 26 is not run over by the sanding unit. The robot may continuously determine the position thereof or of the sanding unit as well as a position of the cable if desired.

[0069] The controller 22 may, in order to determine a position of the sanding unit 32 over the floor, comprise information as to a position of the sanding unit 32 in relation to the robot 20. This information may comprise, for a sanding disc, a diameter / radius thereof, as well as a position of a rotational axis 341 vis-a-vis the robot, such as a particular portion of the robot, such as a sensor unit or a centre of the robot. If the sanding unit comprises a rotating drum, a distance from the drum axis to the portion of the robot may be known as well as a length of the drum. From this information, the controller 22 may, from a position of the robot or the portion thereof, as determined based on the sensor unit(s), determine a position of the sanding unit and thus of the portion of the floor 11 presently being sanded.

[0070] In general, any type of sensor unit 26 may be used for determining a position thereof, or of the robot itself, in relation to the floor 11. A wide array of sensors for such use are known, such as RADAR, LIDAR, vision systems, such as stereo vision, ultrasound and the like.

[0071] The sensor unit 26 may determine its position in a wireless manner, such as from a determination of distances to known elements, such as walls, furniture, pillars or the like, of a room in which the floor 11 is present. The distances may be determined by a scanning sensor unit or multiple units viewing different directions from the robot to its surroundings.

[0072] Not only the position of the robot but also its stance (direction in relation to the floor) may be determined, as may its movement over the floor 11.

[0073] Navigation using such sensor elements is known and need not be described in further detail.

[0074] In this situation, the robot may use this information to determine the position and movement over the floor of the sanding unit. It is desired that neither the robot nor the sanding unit collides with predetermined elements, such as walls, furniture and the like, in the room in which the floor 11 is provided, so the robot should be navigated accordingly.

[0075] As mentioned, some types of sensor units 26 may perform such detection by themselves. A LIDAR will determine a distance to an obstacle along the direction of the radiation without requiring additional elements, but it may be desired to provided further navigation elements within the room in which the floor 11 is provided or generally at predetermined positions in relation to the floor. Such navigation elements may be transmitters of wireless signals from which the robot may determine its position such as based on triangulation. Other types of navigation elements are reflectors which optical sensing may use for determining a relative position and distance to such elements. From knowledge of a position of such navigation elements, the relative position and stance of the robot, and thus of the sanding unit, may be determined. Knowing the position of such elements vis-a-vis the floor, the position of the robot / sanding unit vis-a-vis the floor may be determined.

[0076] As mentioned, the sensor unit(s) may be used for determining a position of the robot / sanding unit in relation to the floor. In addition, or alternatively, the sensor unit(s) may be used for preventing collisions between the assembly and obstacles or other elements in a room in which the floor 11 is provided. Such obstacles may be fixed in relation to the floor so that these may be pre-determined or even provided in a map held in the controller 22 so that the navigation takes this into account. For such obstacles, any positioning determination method may be used for the robot.

[0077] However, it may also be desired to prevent collision with unknown or un-determined obstacles such as persons, pets or the like, which may move around on the floor. The assembly may be operating in an environment which is not entirely constant, so that collision avoidance may be desired also vis-a-vis unknown or unexpected obstacles. Then, it would be desirable that the sensor unit(s) 26 view the surroundings at least in a preferred direction of movement of the assembly - the direction A of figure 2. This has the challenge that this is the direction from the robot toward the sanding machine, whereby sensor units provided on the robot may have a field of view blocked by the sanding machine.

[0078] In figure 1, the sensor unit 26 sits at a height where its field of view is blocked by the motor unit 34 of the sanding machine. The motor unit has a (see figure 2) width which is smaller than that of the sanding unit (dashed-line circle). The robot comprises two sensor units, 261 and 262, positioned with a distance, B, exceeding that of the width of the motor unit 34 partly blocking their views, so that the fields of view 201 of these two sensor units (dashed lines) converge in front of the sanding machine. In this case, the sensor units 26 may not be able to see an area immediately in front of the sanding unit, but the difference in distance B and size of the motor unit as well as the distance to the motor unit will determine the size of this area.

[0079] Then, even though it would be possible to provide a sensor unit, 27, on the sanding machine (see figure 1), this is not required. During operation the sanding machine vibrates considerably, so that a sensor unit 27 provided thereon may be desired vibration damped or vibration compensated in order to provide dependable information. When damped or compensated, this unit 27 may provide information which the controller 22 may use in its operation of the assembly. The unit 27, if provided, may be in communication with the controller, wired or wirelessly, and may be detachably attachable to the sanding machine.

[0080] Naturally, the fields of view of the sensor units 26 may extend more than 180 degrees and may extend 360 degrees or at least along the direction A toward the back of the robot. Then, output from such sensor units may also be used for determining a velocity with which the robot moves in direction A. An odometer may be provided with one of or each wheel, optionally combined with information as to an angle of the wheel vis-a-vis the direction A. This information may be used for determining the position, direction, stance and / or velocity of the assembly. This odometer information may be combined, as is known, with information from the sensor units in order to provide more reliable position / stance / velocity data.

[0081] In figure 4, another sensor unit 263 (for example, a third sensor unit) is illustrated, which may add information relating to obstacles behind the robot during operation. The sensor unit 263 may be especially desired when the suction unit 50 is provided (see below).

[0082] During operation, the sanding machine 30 may operate as during manual operation - such as with a constant rotation of the sanding unit. It may, however, be desired for the robot to control the operation of the sanding unit. This may be obtained by controlling the power delivered to the sanding machine. When only the power delivered is controlled, the sanding machine need not be adapted compared to today's manually operated sanding machines.

[0083] Thus, by varying the power supplied to the sanding machine, the rotational velocity of the sanding unit may be controlled. This has the advantage that the starting of the sanding unit may be controlled so that the rotational velocity or frequency is slowly increased, for example corresponding to an increase in velocity of the assembly over the floor 11. The same may be the situation when shutting down the assembly. The power to the sanding unit may be controlled to reduce the rotation frequency at a pace corresponding to a reduction in velocity of the assembly.

[0084] This also has the advantage that the rotational frequency of the sanding unit may be controlled if the robot wants to move in relation to the floor in a manner where the sanding unit does not move in relation to the floor or moves to a lesser degree over the floor. In this situation, the rotation frequency of the sanding unit may be reduced to not excessively sand the floor at that location during the movement of the robot. Also, the robot may control the operation of the sanding unit, such as if battery powered and running low on power, so that the sanding unit does not rotate or rotates to a lesser degree when the robot e.g. moves to a charging station or sits in a charging station.

[0085] Naturally, the sanding unit may be controlled in other manners, such as when the sanding machine comprises a controller for controlling the operation of the sanding unit, such as a rotation frequency thereof, based on an input which the sanding machine controller may receive from the robot controller.

[0086] During operation, the controller 22 may perform additional operations, such as determine, receive or log a rotational frequency of the sanding unit. Combining this information with information as to a position, stance, and / or velocity of the sanding unit during operation will enable the controller 22 to provide information as to a degree of sanding of different portions of the floor 11.

[0087] Preferably, the coupling 38 allows detachment of the sanding machine and the robot, so that the sanding machine may be used in manual operation where the operator engages the handle 36 to move the sanding machine over the floor during operation.

[0088] The coupling 38 may be configured to attach to multiple different sanding machines, such as sanding machines of different types, makes, or brands. Different types of coupling may have to be devised for different sizes and shapes of sanding machines. Also, for different types, sizes and the like of sanding machines, the controller 22 may be provided with suitable data, such as a type (rotating disc, rotating drum), dimensions such as diameter / radius of rotating disc, length of rotating drum and distance to centre of rotating disc or engagement line between rotating drum and the floor. From this information the position and stance of the robot may be used for determining the position of the sanding unit and particularly of the rotating disc and the portion of a rotating disc engaging the floor. Based on this, the controller may determine the sanded area of the floor from the position of the robot.

[0089] Naturally, information relating to the particular type of sanding machine may be entered into the controller via a connection to an external user interface, such as a mobile phone, pad, PC or the like. Alternatively, the sanding machine may comprise a remotely readable element 31, such as a bar code, visible code or element, RFID tag or the like which may be read by A reader 23 of the robot, where the reader may be a camera, Radio transceiver or the like. Naturally, identification may also take place via the cable 381 if coupled to the robot.

[0090] As indicated on figure 4, the assembly may further comprise a vacuuming or suction unit and a waste container, collectively illustrated by reference numeral "50", for sucking and receiving, dust from the sanding machine. The suction unit comprises a suction element, such as a motor with a fan, and a suction tube 52 for engagement with the sanding machine to retrieve the dust from the sanding operation and feed this to the container.

[0091] The suction unit and container 50 may be carried by the robot so as to be moved with the assembly, and the suction unit may be powered by the robot in the same manner as the sanding machine. A docking station may be provided for emptying the suction unit in the same manner as is known from robotic vacuum cleaners. Such a docking station may also be used for charging / replenishing the robot if it is battery operated or powered by a fuel cell.

[0092] In one embodiment, a roughness of the floor 11 may be determined. In one situation, the robot comprises a surface roughness sensor, such as a laser scanning a horizontal plane and thus intersecting upwardly directed portions of the floor. The robot may alternatively sense floor unevenness when moving over the floor. Deviations of the plane of the robot, such as the directions A and B, from horizontal may be determined, as may lower or higher weight on the wheels 25 caused by uneven floor surface. Knowing the floor unevenness on beforehand may allow the deriving of a path of the sanding unit with e.g. a lower velocity at the portions of the floor requiring more sanding. In this manner, the unevenness may be reduced by a suitable definition of the path and velocity of the sanding unit.

[0093] Unevenness may also be determined during or after the sanding operation, as an upwardly pointing floor portion will cause more of the floor removed by the sanding operation. This will cause an increase in sanding debris (dust), and this amount may be determined in one of many manners, such as from an analysis of the material removed by the suction unit 50. Also, an upwardly pointing floor portion will increase the work of the sanding unit, increasing the torque required to rotate the sanding disc at the desired rotation frequency. In the same manner, a downwardly directed portion will generate less dust and demand a lower torque.

[0094] The robot may deliver a report on the floor unevenness either before or after the sanding.

[0095] Also, the amount of time of operation using a particular sanding disc or sanding paper of a sanding drum may be logged, optionally together with information on the unevenness of the floor and / or the torque applied by the motor unit. A higher torque will increase the wear of the sanding surface of the disc / paper. In this manner, the wear status of the sanding surface may be determined.

[0096] A sanding surface with a high degree of wear requires more time than a fresh surface for removing a certain area of the floor surface. Thus, the velocity of the robot and sanding machine may be adapted to the actual wear status of the sanding surface.

[0097] Then, replacement of the sanding surface may be fed to the processor so that the amended wear status is taken into account once the operation starts or commences.

[0098] Naturally, the robot and sanding machine may be detachable, such as for replacement of the sanding surface. Often, the sanding surface is replaced by tilting the sanding machine, which would otherwise require the tilting of also the robot, which could be rather cumbersome for an operator.

[0099] In one embodiment, the robot may have a major surface which is flat and without sensitive elements, so that the robot may be tilted on to that side and provided on a transportable element such as a bag truck or dolly or a transport helper.

[0100] It is noted that the above description provides a large number of alternative solutions based on alternative manners of operating and embodying the robot and sanding machine. Such alternatives may be selected from in any combination. Thus, the manner of powering the robot and / or sanding machine may be combined with any type of sensor unit set-up which again may be combined with any manner of operating the assembly. Different manners of powering are described, as are different types of sanding machines, different manners of operating and driving the robot and different information may be derived therefrom during or after operation.

Claims

CLAIMS1. A system for sanding a floor, the system comprising : a driving unit comprising wheels for moving the driving unit; a floor sanding machine connected to the driving unit such that the driving unit can move the floor sanding machine; and a controller configured to control the driving unit to sand a floor via the floor sanding machine.

2. A system according to claim 1, wherein the system further comprises a coupling arrangement for detachably connecting the floor sanding machine to the driving unit, wherein the floor sanding machine is connected to the driving unit via the coupling arrangement.

3. A system according to any of the preceding claims, wherein the floor sanding machine is configured to be manually operated when it is not connected to the driving unit.

4. A system according to any of the preceding claims, wherein the controller is configured to control the driving unit to sand a floor via the floor sanding machine based on machinespecific information of the sanding machine.

5. A system according to any of the preceding claims, wherein the controller is configured to control the driving unit such that the sanding machine is primarily positioned relative to the driving unit in a driving direction of the driving unit while the floor machine sands the floor.

6. A system according to any of the preceding claims, wherein the system comprises one or more sensor units positioned on the driving unit, wherein the controller is configured to control the driving unit based on sensor data from the one or more sensor units.

7. A system according to claim 6, wherein the one or more sensor units comprises a first sensor unit and a second sensor unit, wherein the first sensor unit and the second sensor unit are displaced in opposite directions relative to a central horizontal axis defined by the driving unit and the floor sanding machine such that the first sensor unit and / or the second sensor unit receives sensor data from behind the floor sanding machine relative to the central horizontal axis.

8. A system according to any of the preceding claims, wherein the system further comprises a waste container and a suction unit, wherein the suction unit is configured to displace material removed from the floor by the floor sanding machine into the waste container.

9. A system according to any of the preceding claims, wherein the waste container is positioned on top of the driving unit and / or wherein the waste container is positioned so as to not obstruct a sensor range of the one or more sensor units.

10. A system according to any of the preceding claims, wherein the controller is configured to control the driving unit based on a smoothness of the floor, wherein the smoothness is determined via vacuum power of the suction unit, via a laser unit configured to measure a surface roughness of the floor, and / or via operation of a sanding element of the sanding machine.

11. A system according to any of the preceding claims, wherein the controller is configured to determine when a sanding element of the floor sanding machine based on operation of the sanding element of the sanding machine.

12. A method for sanding floors, the method comprising : providing a system according to any of the previous claims; sanding a floor via the floor sanding machine by using the controller to control the driving unit.

13. A method according to claim 12, wherein the floor sanding machine is a first floor sanding machine, wherein the method comprises the steps of: detaching the first floor sanding machine; and attaching a second floor sanding machine.

14. A method according to claim 13, wherein the method comprises a step of sanding the same or another floor via the second floor sanding machine by using the controller to control the driving unit.1815. A method according to any of claims 12-14, wherein the method comprises a step of displacing wheels of the floor sanding machine from the floor, wherein the step of displacing the wheels is performed prior to the step of sanding the floor via the floor sanding machine.

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