WO2022171417A1

WO2022171417A1 - Mobile robot with displaceable spray tool

Info

Publication number: WO2022171417A1
Application number: PCT/EP2022/051428
Authority: WO
Inventors: Palle FLYDTKJÆR; Lasse Thorfinn JAGD; Jens Peder Kvols KRISTENSEN; Rudi HANSEN; Christoffer MOSE; Peter Jensen; Kristian KORSGAARD
Original assignee: Tinymobilerobots Aps
Priority date: 2021-02-12
Filing date: 2022-01-24
Publication date: 2022-08-18

Abstract

The present invention relates to a mobile robot adapted for driving/maneuvering in a workspace limited by a known geometry, and with a mounted spray meansable to be actuated in a two-dimensional workspace relative to the mobile robot.

Description

Mobile robot with displaceable spray tool

Technical field of the invention

The present invention relates to mobile robots adapted for marking or painting a surface.

Background of the invention

Mobile robots are becoming a tool for marking surfaces. The mobile robot replaces tedious and hard manual marking operations done today e.g., at construction sites, using strings and measurement tapes combined with aerosol cans and handheld markers.

The marking operation, and hence the formed mark(s), is used in construction for many purposes. It is used to mark the position and/or circumferences of geometrical figures, such as lines or symbols. It is also used for marking construction work to be done like paving, mounting of pillars and walls, and for installations for sewers, water, and electricity.

Especially in difficult environments, the marking operation is today done by humans that can maneuver in spaces with cables hanging from the ceiling, garbage and spare parts scattered around on the floor, pipes sticking out of walls and ceiling, holes in the floor, and the like. For a mobile robot to be used in such an environment, workflows may have to be changed in the construction project as the robot needs space to work and will not be able to adapt to the difficult environment as easy as the human. Furthermore, as mobile robots are machines with a certain weight, they typically have issues with navigating very precisely. Even worse is the issue of trying to mark small geometric figures with millimeter precision, as the mobile robot has trouble following very small curves or navigating around or along constructions/objects.

It is an objective of the present invention to provide a mobile marking robot that solves or at least minimizes the above-mentioned problems.

Summary of the invention

One aspect relates to a mobile robot comprising:

- a chassis with a differential drive including at least a first and a second differentially driven wheel;

- a spray means comprising a spray nozzle; and

- a positioning system configured for continuously receiving a positioning signal; wherein said spray means further comprises a drive mechanism comprising a selectively compliant articulated robot arm (SCARA) fastened to said chassis, and is operably connected to said spray nozzle; said robot arm preferably having parallel pivot axes, and wherein said mobile robot further comprises:

- a control unit operably connected to said differential drive, said drive mechanism, and said spray nozzle; wherein said positioning system is configured for continuously or periodically determining the position of said spray nozzle based on said received positioning signal and to send this information to said control unit; wherein said control unit, in response to instructions about a given geometric figure to be marked on a surface at a specific geographic location, and in response to continuously or periodically received spray nozzle position data, is configured to:

- move or position said mobile robot by activating or deactivating said differential drive; and

- move, or position said spray nozzle by activating or deactivating said drive mechanism; and

- activate or deactivate said spray nozzle, thereby marking said geometric figure on a surface at a specific geographic location. This configuration result in a mobile robot with a spray nozzle that is suitable for use both when the robot is moving and when the robot is stationary as the spray nozzle can be moved in two dimensions by the drive mechanism. The robot, via the differential drive, may function as a second drive mechanism to be used in collaboration with the drive mechanism. The robot, via the control unit, controls the spray nozzle, via the drive mechanism, by moving it in two dimensions (in an X-Y grid), and by turning activating or deactivating it in a pattern of time. As the SCARA is more agile and precise in its movements, compared to the movements of the robot itself, the marking operation may be performed faster and more reliable compared to a mobile robot with a fixed spray nozzle. In combination with the movement of the robot, this operation results in marking of the intended text and logos. If the intended text or logos is wider than the spray nozzle’s spray width, the robot will have to do the marking in several steps.

The term “chassis” is used herein to refer to at least a part of the main framework of the mobile robot.

The term “spray nozzle” is defined to be a nozzle, an orifice, a spray valve, a pressure reducing tubing section, and any combination thereof.

SCARA is an acronym for Selective Compliance Articulated Robot Arm, meaning it is compliant in the X-Y axis, and rigid in the Z-axis. The SCARA’s structure may preferably comprise two arms (a first and a second) joined at a base, via the first arm, and the intersection of first and second arms. Two independent motors may use inverse kinematics and interpolation at the two joints (J1 and J2) to control the SCARA’s X-Y motion. The final X-Y location at the end of the second arm, where the spray nozzle is mounted, is a factor of the J1 angle, J2 angle, length of the first arm, and length of the second arm.

In one or more embodiments, the selectively compliant articulated robot arm is adapted to operate solely across the surface on which the mobile robot is operating. As the SCARA arm is more agile and precise in its movements, compared to the movements of the robot itself, the marking operation may be performed faster and more reliable compared to a mobile robot with a fixed spray nozzle or with spray nozzle mounted on comparable Cartesian robot systems. In combination with the movement of the robot, this operation results in marking of the intended text and logos. If the intended text or logos is wider than the spray nozzle’s spray width, the robot will have to do the marking in several steps.

In one or more embodiments, the selectively compliant articulated robot arm is a single-link type, i.e., with a single arm joined to a base.

In one or more embodiments, the selectively compliant articulated robot arm is a dual-link type, i.e., with two arms as explained above.

In one or more embodiments, the robot arm has parallel pivot axes.

In one or more embodiments, the selectively compliant articulated robot arm comprises a first arm and a second arm, and wherein said first and second arms have parallel pivot axes.

In one or more embodiments, the spray means comprises a tool comprising an array of spray nozzles, preferably arranged either in a direction along the length of said chassis, or in a direction along the width of said chassis. Advantageously, this tool may be adapted for rotating said array of spray nozzles around a common pivot axis, preferably parallel to one or more pivot axes of said robot arm.

In one or more embodiments, the spray means comprises a mechanism, such as a telescopic arm or the like, adapted for lowering and raising said spray nozzle(s) relative to the surface on which the mobile robot is moving. In one or more embodiments, the mobile robot further comprises a sensor configured for continuously determining the distance between said spray nozzle(s) and said surface, and wherein said control unit is configured to receive data about said distance from said sensor and in response thereto, changing or maintaining said distance by activating said mechanism to move said spray nozzle(s) relative to said surface. This configuration avoids collisions of the spray nozzle(s) with the (ground) surface and may also secure a more controlled marking of the geometric figure on the surface.

In one or more embodiments, the control unit, in response to line width information about said geometric figure to be marked, is configured to continuously or periodically alter or maintain said line width by activating said mechanism to lower or raise said spray nozzle(s) relative to said surface.

For the mobile robot to be able to mark the data in an area it will need to have a localization system telling the robot where it is, and how it is orientated. Furthermore, the data needs to be aligned to the locations system used by the robot. Most common used technologies for positioning are total stations and GNSS, but some solutions use advanced localization technologies together with cameras or lidars.

The orientation of the mobile robot can be determined by having two independent location systems placed apart with enough distance to allow the robot to calculate its orientation. Another method of orientation is to let the robot drive a certain distance with one location system and by driving it can calculate its orientation. Aligning the robot’s localization with the digital data provided require a shared coordinate system.

If the location system is global, like the GNSS, the global coordinates are sufficient for aligning the data and letting the robot start working. In one or more embodiments, the positioning system is configured for continuously receiving a positioning signal from a Global Navigation Satellite System (GNSS). Global Navigation Satellite Systems (GNSS) is a collective term for a variety of satellite navigation systems, which use orbiting satellites as navigation reference points to determine position fixes on the ground. GNSS includes the Global Positioning System (GPS), the Global Navigation Satellite System (GLONASS), the Compass system, Galileo, and several Satellite based augmentation systems (SBAS). In typical civilian applications, a single GNSS receiver can measure a ground position with a precision of about ten meters.

This is, in part, due to various error contributions, which often reduce the precision of determining a position fix. For example, as the GNSS signals pass through the ionosphere and troposphere, propagation delays may occur. Other factors, which may reduce the precision of determining a position fix, may include satellite clock errors, GNSS receiver clock errors, and satellite position errors. One method for improving the precision for determining a position fix is Real- Time Kinematic (RTK) GNSS. Real Time Kinematic (RTK) satellite navigation is a technique using the phase of the signal's carrier wave, rather than the information content of the signal, and relies on a single reference station or interpolated virtual station to provide real-time corrections.

In one or more embodiments, the positioning system is configured for continuously receiving a positioning signal from a total station. The total station needs to use fix points to calculate its own position as well as the position of the mobile robot. The fix points can be reflectors placed beforehand at known coordinates or it can be fixed points in the construction like corners of walls or windows, that has known coordinates and can be used to localize the total station. The mobile robot may comprise a retroreflector. Any retroreflector with retroreflectors, generally known within the art of land surveying, may be used. In one or more embodiments, the retroreflector is a 360-degree all-around retroreflector. In one or more embodiments, the positioning system is positioned on an elongate member extending upward from the chassis. In one or more embodiments, the elongate member is height adjustable, e.g., comprising telescoping elongate members.

If the localization system is cameras or lidars, several methods can be used. A common method is to let the robot move around and generate a map of the area. This map can then be used for positioning the robot.

In one or more embodiments, the spray means comprises an airbrush-based spray tool.

In one or more embodiments, the spray means comprises an inkjet-based spray tool, preferably based on a drop-on-demand technology.

In one or more embodiments, the spray means comprises a tool comprising an array of spray nozzles, such as 2-100 spray nozzles, preferably arranged either in a direction along the length of said chassis, or in a direction along the width of said chassis.

In one or more embodiments, the chassis comprises two differentially driven wheels in a fixed orientation and arranged on the same first axis line in parallel; and one off-centered orientable wheel arranged along a second axis line perpendicular to the first axis line, and in front or behind the first axis line.

The term “off-centered wheel” (castor wheel) is defined to be a wheel, where the vertical axis does not pass through the center of the wheel but is slightly off- centered. Some designs include a swivel joint (orientable) between the wheel and the fork so that it can rotate freely with 360° of freedom. The advantage with an off-centered orientable wheel compared to a centered orientable wheel is that the centered orientable wheel tends to lock in specific positions. In one or more embodiments, the mobile robot further comprises a paint reservoir. The paint reservoir may be configured as a bag-in-box type reservoir, or simply as a replaceable bag reservoir, or a replaceable box reservoir.

In one or more embodiments, the differentially driven wheels are positioned near the rear end of the chassis, and wherein the off-centered orientable wheel is positioned near the front end of the chassis. Preferably, the off-centered orientable wheel is positioned equally distanced from each of the drive wheels.

In one or more embodiments, the spray means further comprises a return line through which paint can recirculate from a position upstream to the spray nozzle outlet and back to the paint reservoir. This configuration removes air from the paint and tubing, such that the spray nozzle will not splutter when painting a line.

In one or more embodiments, the spray means comprises means adapted for adjusting the drive mechanism and/or spray nozzle position in the vertical direction relative to the ground surface on which the mobile robot moving.

In one or more embodiments, the spray means comprises a mechanism, such as a telescopic arm or the like, adapted for lowering and raising said spray nozzle(s) relative to the surface on which the mobile robot is moving. In one or more embodiments, the mobile robot further comprises a sensor configured for continuously determining the distance between said spray nozzle(s) and said surface, and wherein said control unit is configured to receive data about said distance from said sensor and in response thereto, change said distance by activating said mechanism to move said spray nozzle(s) relative to said surface. Distance sensors are well-known within the art and will thus not receive further attention.

In one or more embodiments, the control unit, in response to line width information about said geometric figure to be marked, is configured to continuously or periodically alter said line width by activating said mechanism to lower or raise said spray nozzle(s) relative to said surface. As the distance is increase between the spray nozzle and the surface, the paint, or the like, will spread more relative to a distance closer to the surface.

It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.

Brief description of the figures

Figure 1 shows a flow chart depicting a methodology in accordance with various embodiments of the invention.

Figure 2 shows a top view of a three-wheeled line marking mobile robot in accordance with various embodiments of the invention.

Figure 3 shows a top view of a three-wheeled line marking mobile robot in accordance with various embodiments of the invention.

Figure 4 shows a top view of a three-wheeled line marking mobile robot in accordance with various embodiments of the invention.

Detailed description of the invention

The present invention relates to a mobile robot with a displaceable spray tool, that can work next to the mobile robot and preferably also in front of and/or behind the chassis. When the mobile robot has received the digital data about a figure (including text) to mark, and localized itself, it can start marking.

As marking can be lines and symbols of varying length, the mobile robot needs to be able to handle such tasks. Furthermore, the figure may need to be marked close to walls or other physical objects that hinder the movement of the robot. Therefore, the mobile robot needs to able to mark close to walls and physical objects. Some lines can be rather short, down to 1-2 cm being part of symbols or text. The robot needs to be able to mark these short lines at a reasonable accuracy and speed.

To allow the robot to mark lines close to walls, and to mark symbols and text with short lines, this invention includes a SCARA that can compensate especially for the robot’s lack of ability to move sideways and for the robot’s lack of sideway accuracy, when marking lines and points.

The SCARA is mounted so that the spray nozzles can print at one side of the robot and in some preferred embodiments also at the other side of the robot.

This operation is performed by the aid of controlling the SCARA. This configuration allows the robot to mark to dimensional figures in a simple working process. If the spray tool is an airbrush-based marker, preferably with multiple spray nozzles, the sideway tool can mark any vector-based format of data. If the spray tool is an inkjet-based marker, preferably with multiple spay nozzles, the spray tool may also mark bitmap-based data, or it can convert smaller vector- based data sets to bitmap-based data for faster marking.

Having transferred data to the mobile robot, which has localized and orientated itself, the mobile robot transforms the data to movements that match the mobile robot’s spray and driving capabilities. If the robot is using an airbrush-based spray tool, it will mark all parts as lines of different lengths and curvatures. If the robot uses an inkjet-based spray tool, it will mark most parts as lines of different lengths but convert smaller components to be marked as dots from the inkjet- based spray tool.

Hence, the present invention discloses a mobile robot, preferably non-holonomic, configured for driving in a workspace limited by a known geometry, with a mounted spray means able to be actuated in a limited two-dimensional workspace relative to the mobile robot. Both the mobile robot and the spray means have a known collision geometry. The goal is to be able to paint or mark one or more curve geometries within the boundaries of the workspace, thereby avoiding collisions. Planning a valid robot and spray means movement that can produce a desired curve within the given bound can e.g., be done by the following non-limiting process, but many other solutions are available.

The paint geometry is sampled into poses (points with heading). A quantization of the possible spray means positions in the relative workspace is selected. For each pose on the paint geometry, each spray means configuration is tested for boundary collision in the two possible robot driving directions, as well as in the tool-elbow configurations. All valid configurations are added to a graph using selected configuration transition filter criteria. It could be considered giving bad scores to configurations near a collision state. Using a graph searching algorithm and a cost function, each separated graph component is traversed for a possible path. As it might not be possible to find a valid path that fulfils the entire goal using a single component of the graph, a collision aware robot planner is used to find valid transitions between separated graph components, e.g., near boundaries, where a driving direction change is needed. As two graph components may partly overlap, a cost function can be used to determine the transition point. The output is a list of graph nodes, where each node contains a reference to the geometry position and a tool position.

Each transition may be further sampled before sending to a local planner for robot execution.

Referring to Figure 1 , the general scheme of the invention is shown as a flow chart depicting a methodology in accordance with various embodiments of the invention in relation to a marking task at a construction site. The main steps of the methodology 200 is:

- Accessing relevant data, such as maps of the construction site, and figures to be marked at the floor of the construction site, from a given construction project (Step 210);

- Extracting relevant data, such as maps of the construction site, and figures to be marked at the floor of the construction site, for marking (Step 220);

- Transferring said extracted data to the robot (Step 230);

- Align position system to data from construction project (Step 240);

- Localizing the mobile robot using the position system (Step 250);

- Orientating the mobile robot using said position system (Step 260);

- Calculating the optimal position of said mobile robot and SCARA (arm) for marking a specific component present in said extracted data (Step 270);

- Marking said component (Step 280); and

- Determining if more components are to be marked (Step 290), and if yes, repeating Steps 270-290.

An exemplary mobile robot is depicted in Figure 2. Figure 2 shows a three wheeled line marking mobile robot comprising a chassis 100 and a spray means. The chassis 100 comprises two drive wheels 110, 111 in a fixed orientation and arranged on the same first axis line (not shown) in parallel. The chassis 100 also comprises one off-centered orientable wheel 102 arranged along a second axis line (not shown) perpendicular to the first axis line and in front of said first axis line. The drive wheels 110, 111 are positioned near the rear end 101 of the chassis 100, and wherein the off-centered orientable wheel 102 is positioned near the front end 104 of the chassis 100.

The spray means 200 comprises a drive mechanism 120 adapted for two- dimensional displacement of said spray nozzle 121, e.g., on both sides 103, 105 of said chassis 100. The drive mechanism 120 is fastened to the rear end 101 of said chassis 100 is here exemplified as a two joint SCARA 120A, 120B holding a single airbrush-based spray tool 121 at its free end.

Figure 3 shows a mobile robot according to various embodiments of the present invention, where the spray means comprises an inkjet-based spray tool with multiple, i.e. , eight, spray nozzles. The spray means may be configured for rotating said array of spray nozzles 121 around a common pivot axis 120C, here shown parallel to the two pivot axes 120A, 120B, as also shown in Figure 3. The array of spray nozzles 121 may be connected to the distal arm of the SCARA at different positions, such as at the middle of the array, as shown in Figure 3, or at one of the ends of the array, as shown in Figure 4.

As an example, an in order for the mobile robot to operate, the control unit may comprise a computing system including a processor, a memory, a communication unit, an output device, an input device, and a data store, which may be communicatively coupled by a communication bus. The mentioned computing system should be understood as an example and that it may take other forms and include additional or fewer components without departing from the scope of the present disclosure. For instance, various components of the computing device may be coupled for communication using a variety of communication protocols and/or technologies including, for instance, communication buses, software communication mechanisms, computer networks, etc. The computing system may include various operating systems, sensors, additional processors, and other physical configurations. The processor, memory, communication unit, etc., are representative of one or more of these components. The processor may execute software instructions by performing various input, logical, and/or mathematical operations. The processor may have various computing architectures to method data signals (e.g., CISC, RISC, etc.). The processor may be physical and/or virtual and may include a single core or plurality of processing units and/or cores. The processor may be coupled to the memory via the bus to access data and instructions therefrom and store data therein. The bus may couple the processor to the other components of the computing system including, for example, the memory, the communication unit, the input device, the output device, and the data store. The memory may store and provide data access to the other components of the computing system. The memory may be included in a single computing device or a plurality of computing devices. The memory may store instructions and/or data that may be executed by the processor. For example, the memory may store instructions and data, including, for example, an operating system, hardware drivers, other software applications, databases, etc., which may implement the techniques described herein. The memory may be coupled to the bus for communication with the processor and the other components of computing system. The memory may include a non-transitory computer-usable (e.g., readable, writeable, etc.) medium, which can be any non-transitory apparatus or device that can contain, store, communicate, propagate, or transport instructions, data, computer programs, software, code, routines, etc., for processing by or in connection with the processor. In some implementations, the memory may include one or more of volatile memory and non-volatile memory (e.g., RAM, ROM, hard disk, optical disk, etc.). It should be understood that the memory may be a single device or may include multiple types of devices and configurations. The input device may include any device for inputting information into the computing system. In some implementations, the input device may include one or more peripheral devices. For example, the input device may include the display unit comprising a touchscreen integrated with the output device, etc. The output device may be any device capable of outputting information from the computing system. The output device may be the display unit, which display electronic images and data output by a processor of the computing system for presentation to a user, such as the processor or another dedicated processor. The data store may include information sources for storing and providing access to data. In some implementations, the data store may store data associated with a database management system (DBMS) operable on the computing system. For example, the DBMS could include a structured query language (SQL) DBMS, a NoSQL DMBS, various combinations thereof, etc. In some instances, the DBMS may store data in multi-dimensional tables comprised of rows and columns, and manipulate, e.g., insert, query, update and/or delete, rows of data using programmatic operations. The data stored by the data store may be organized and queried using various criteria including any type of data stored by them. The data store may include data tables, databases, or other organized collections of data. The data store may be included in the computing system or in another computing system and/or storage system distinct from but coupled to or accessible by the computing system. The data stores can include one or more non-transitory computer-readable mediums for storing the data. In some implementations, the data stores may be incorporated with the memory or may be distinct therefrom. The components may be communicatively coupled by the bus and/or the processor to one another and/or the other components of the computing system. In some implementations, the components may include computer logic (e.g., software logic, hardware logic, etc.) executable by the processor to provide their acts and/or functionality. These components may be adapted for cooperation and communication with the processor and the other components of the computing system.

References

100 Chassis

101 Rear end

102 Wheel

103 Side

104 Front end

105 Side

106 Control unit

110 First drive wheel

111 Second drive wheel

120 Drive mechanism

121 Spray nozzle

200 Flow chart

210 Methodology step

220 Methodology step

230 Methodology step

240 Methodology step

250 Methodology step

260 Methodology step

270 Methodology step

280 Methodology step

290 Methodology step

Claims

1. A mobile robot comprising:

- a chassis (100) with a differential drive including at least a first (110) and a second (111) differentially driven wheel;

- a spray means comprising a spray nozzle (121); and

- a positioning system configured for continuously receiving a positioning signal; characterized in that said spray means further comprises a drive mechanism (120) comprising a selectively compliant articulated robot arm fastened to said chassis (100), and operably connected to said spray nozzle (121); and wherein said mobile robot further comprises:

- a control unit (106) operably connected to said differential drive, said drive mechanism (120), and said spray nozzle (121); wherein said positioning system is configured for continuously or periodically determining the position of said spray nozzle (121) based on said received positioning signal and to send this information to said control unit (106); wherein said control unit (106), in response to instructions about a given geometric figure to be marked on a surface at a specific geographic location, and in response to continuously or periodically received spray nozzle (121) position data, is configured to:

- move, or position said spray nozzle (121) by activating or deactivating said drive mechanism (120); and

- activate or deactivate said spray nozzle (121 ), thereby marking said geometric figure on a surface at a specific geographic location.

2. The mobile robot according to claim 1 , wherein said selectively compliant articulated robot arm is adapted to operate solely across the surface on which the mobile robot is operating.

3. The mobile robot according to any one of the claims 1-2, wherein said selectively compliant articulated robot arm comprises a first arm and a second arm, and wherein said first and second arms have parallel pivot axes.

4. The mobile robot according to any one of the claims 1-3, wherein said spray means comprises an inkjet-based spray tool, or an airbrush-based spray tool.

5. The mobile robot according to any one of the claims 1-3, wherein said spray means comprises an inkjet-based spray tool based on a drop-on-demand technology.

6. The mobile robot according to any one of the claims 1-5, wherein said spray means comprises a tool comprising an array of spray nozzles (121), preferably arranged either in a direction along the length of said chassis (100), or in a direction along the width of said chassis (100).

7. The mobile robot according to claim 6, wherein said tool is adapted for rotating said array of spray nozzles (121) around a common pivot axis, and parallel to one or more pivot axes of said robot arm.

8. The mobile robot according to any one of the claims 1-7, wherein said spray means comprises a mechanism, such as a telescopic arm or the like, adapted for lowering and raising said spray nozzle(s) (121) relative to the surface on which the mobile robot is moving.

9. The mobile robot according to claim 8, further comprising a sensor configured for continuously determining the distance between said spray nozzle(s) (121) and said surface, and wherein said control unit (106) is configured to receive data about said distance from said sensor and in response thereto, changing or maintaining said distance by activating said mechanism to move said spray nozzle(s) (121) relative to said surface.

10. The mobile robot according to claim 8, wherein said control unit (106), in response to line width information about said geometric figure to be marked, is configured to continuously or periodically alter or maintain said line width by activating said mechanism to lower or raise said spray nozzle(s) (121) relative to said surface.

11. The mobile robot according to any one of the claims 1 -10, wherein said positioning system is configured for continuously receiving a positioning signal from a total station.

12. The mobile robot according to any one of the claims 1-10, wherein said positioning system is configured for continuously receiving a positioning signal from a Global Navigation Satellite System (GNSS).