WO2001041976A1

WO2001041976A1 - Mobile robots travelling on powered floor

Info

Publication number: WO2001041976A1
Application number: PCT/GB2000/004717
Authority: WO
Inventors: Alan Frank Thomas Winfield; Robert Derek Channon
Original assignee: University Of The West Of England, Bristol
Priority date: 1999-12-09
Filing date: 2000-12-08
Publication date: 2001-06-14
Also published as: GB2358003A; AU2193001A; GB9929094D0

Abstract

A miniature robot (1) comprises a chassis (3), which houses a vertically mounted control box (5). The control box (5) contains the control electronics required for controlling the operation of the robot (1). The underside of the chassis (3) houses two drive wheels (7), each drive wheel capable of being independently driven by an associated motor/gearbox assembly (shown as item 9 in Figure 2). The chassis (3) also houses a set of brushes (11), which act to stabilise the robot, and maintain it in its upright position. The robot (1) can be powered from a powered floor via the brushes (11). The robot (1) may also include a battery, which can be charged by the powered floor. The construction of the robot allows it to be miniaturised, making it suited for applications such as cooperative robotics, vacuuming, inspection work or use with industrial machinery, for example cleaning up.

Description

MOBILE ROBOTS TRAVELLING ON POWERED FLOOR

Field of the Invention The invention relates to robotics, and m particular, to miniature robots for use m applications such as conducting experiments relating to distributed mobile robotics, cooperative robotics, and industrial applications such as cleaning or inspecting machinery, including m locations such as spacecraft, environmental applications such as monitoring gases, military applications sucn as mine clearance, commercial applications such as vacuuming, or communication applications such as mocile weo-sites or telecommunication applications.

Background of the Invention

It is known for robots to be controlled by wireless communication means. It is also known for multiple robots to operate m distributed wireless systems, in which a plurality of robots interact with one another. Such a system is sometimes referred to as a distributed moh le rooctics system.

When developing a distributed mobile robotics system, for example m a laboratory, it is desirable to conduct large scale experiments m collective robotics, so tnat features such as swarming and self-organisation can be investigated. Ideally, such experiments should be conducted using about fifty robots, or more.

However, laboratory experiments are limited by the physical size of the robots themselves. Existing robots which are capable of operating m a wireless local area network (LAN) are approximately 30cm (twelve incnes) m diameter. This means that laboratory experiments are constrained to a relatively small population of rocots, oemg typically between twelve to fifteen for even a large sized laboratory. Carrying out experiments with greater numcers of rooots, for example fifty, v/culd require extremely large laccratoπes , which would therefore be impractical.

To allow experiments to be carried out with large populations of rooots, each robot must be made as small as possible. Altnough miniature robots themselves are known, the phys_cal constraints placed on available processing space -leans that known miniature robots αo not nave wireless networking capabilities, and are generally not intelligent enough to take part m experiments relating to distributed mobile roootics.

The miniaturisation of a robot is constrained by a numcer of factors. For example, a robot requires a plurality of wneels to enable it to move from one location to anotπer. Some form of steering mechanism is also needed to enable the direction of the robot to be controlled. A rcoot also requires some form of power source, sucn as a battery, for supplying power to tne drive mechanism of the robot. All these elements act against the miniaturisation process.

For example, ideally the size of the battery should be as small as possible. However, reducing the size of the battery also reduces its capacity, whicn means that it must be replaced, or recharged more often.

The aim of tne present invention is to provide a miniature rooot which is physically small enough to allow large scale distributed mobile robotic experiments to be conducted in a laboratory environment, yet having the processing capabilities which allow it to function in a wireless distributed mobile robctics system, and without having the disadvantages mentioned above.

The robot of the present invention is also suited for many ether applications which require miniature robots. As indicated above, these include cooperative robotics, or industrial applications such as cleaning or inspecting machinery, environmental applications sucr. as monitoring cases, military applications such as mine clearance, commercial applications such as vacuuming, or communication applications such as mobile web-sites or telecommunication applications.

Summary of the Invention

According to a first aspect of the invention, there is provided a robot as defined in the claims hereof .

According to another aspect of the invention, there is provided a development system for conducting distributed mobile robotic experiments. According to yet another aspect of the invention, there is provided a method of conducting distributed mobile robotic experiments.

3rief Description of the drawings For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will new be made, by way of example, to the accompanying drawings, in which: -

Figure 1 shows a robot according to a preferred embodiment of the present invention; Figure 2 shows a underside view of the robot of

Figure 1.

Detailed description of a preferred embodiment of the present invention.

Figure 1 shows a miniature robot 1 according to a preferred embodiment of the present invention. The robot 1 comprises a chassis 3 , which houses a vertically mounted control box 5. The control box 5 contains the control electronics required for controlling the operation of the robot 1.

The underside cf the chassis 3 houses two drive wheels 7, each drive wheel having an associated motor/gearbox assembly 9, as shown in Figure 2. The chassis 3 also houses a set of brushes 11, which act to stabilise the robot, and maintain it in its upright position.

Figure 2 shows an underside view of the robot of

Figure 1. Each wheel 7 is driven by a respective motcr/gearbox assembly 9. The provision of an independent motcr/gearbox assembly 9 for each wheel 7 enables the direction of the robot 1 to be controlled.

A plurality of batteries 13 are provided for powering the motors 9, and are preferably evenly distributed in the chassis 3 so that the robot 1 is evenly balanced.

The brushes 11 mounted in chassis 3 are sufficiently stiff so as to maintain the robct 1 in its upright position, yet sufficiently flexible horizontally to allow the robot 1 to turn under the power of the wheels 7, with negligible resistance from the brushes 11. In this way, the need for castors or trailing wheels associated with conventional robots is avoided. The horizontal flexibility of the brushes also allows acceleration and braking of the robot.

In Figure 2, the robot is shown having two pairs of brushes 11, each pair being located on opposite sides of the axis of the wheels, and also being equally spaced from the axis .

However, the arrangement cf the brushes 11, or other supports, can be chosen to suit any particular application. For example, the front of the robot may have a different arrangement to that of the back of the robot. A number of different variables may be considered when choosing the arrangement of the supports. These include the actual number of supports, the horizontal and vertical stiffness of the individual supports and the position of the supports in location to the axis of the wheels.

For example, a plurality of supports, each having a relatively low stiffness, may be chosen as an alternative to a smaller number of supports, each having a higher stiffness.

Also, the choice of stiffness can vary depending on distance between the support and the axis of the wheels. The further the support is located away from the axis, the greater the vertical stiffness needed to support the robot, but the lower the horizontal stiffness needed to produce the required turning moment .

All these factors enable the arrangement of supports to be chosen to suit the particular application, or accεleraticn/crakmg requirements, turning requirements, and so on. Examples include a robot having two supports on one side, and a single support on the other. In such an embodiment, the stiffness of each support can vary, such that the single support may have a stiffness wnich is equivalent to the combined stiffness of the pair of supports located on the opposite side.

Moreover, m Figure 2, the brushes 11 are mace from an electrically conductive material, whicn allows the orusneε 11 to ccl.ec: EC power from a powered floor, as will be described below. For example, the brushes can advantageously ce formed from individual bristles made of a copper alloy or copper coated steel. The number of pπstles must be chosen to give the vertical stiffness required to support the weight of the robot, while allowing sufficient horizontal flexibility as descπoed aoove .

The powered floor can advantageously consist of conducting strips, alternately connected to positive and negative voltage sides of a DC power supply 3y cncosmg strip widths which are suitable for the dimensions of the robot, and by providing a diode bridge in the robot, power can be collected by the conducting brusnes 11, regardless of the orientation of the robot .

To prevent the brushes from electrically shorting, the cnassis 3 is made from an insulating material, for example Delrm™, whicn is a machinable, nylon-like insulating material. This aspect of the invention avoids the need for tne batteries 13 to be replaced, or removed for recharging, which is a major advantage in a highly populated distributed mobile robotics system.

The control electronics within the control box Ξ contains a complete PC compatible micro controller, sufficiently powered to run an operating system such as Linux. The control electronics controls the power management, motor drive electronics and wireless communications. The Linux operating system includes full TCP/IP networking, including Telnet, FTP and Web servers, which enable the robot 1 to operate as a node en a wireless IP network. It is therefore possible for the robot 1 to be controlled remotely frc any PC cr workstation with Internet connectivity.

The robot 1 may have a miniature magnet mounted within the inside walls of each drive wheel 7, having a corresponding Hall-effect sensor set into the chassis 3, close to the drive wheels 7, thereby enabling the control electronics to count drive wheel revolutions for closed loop or speed control. Alternatively, each motor 9 may be a stepped motor, the robot being controlled by stepping each motcr through a predetermined number of revolutions.

The chassis 3 is preferably made as a single-piece machined chassis, with insets for the motor/gearbox assemblies 9, brushes 11 and batteries 13. The chassis 3 is preferably circular, and the miniaturisation techniques described above enable the diameter to be made less than 6cm.

The miniature robot described above allows large scale experiments to be conducted in collective robctics to enable, for example, swarming or self- organisation to be studied.

Although the preferred embodiment has been shown to have a plurality of batteries 13, it will be readily understood by a person skilled in the art that the invention may equally be used with just one battery 13.

Further, although the preferred embodiment has been shown to have four brushes 11, it will be readily understood by a person skilled in the art that the invention may equally be used with just one pair of conductive brushes. Indeed, if the robot is to be supplied with electrical power only from its battery or batteries, and is net pick up power from a powered floor, the wheels 7 can be mounted on an offset axle, and only one brush or other supporting member need be used.

Furthermore although the robots have been described mainly for use in conducting experiments in distributed mobile robotics, the robots may also used be used in other applications. For example, the brushes 11 may have inbuilt strain gauges to allow the robot to sense surface textures, cracks or flaws, allowing the robot 1 to be used in applications such as surface inspection, particularly in situations where larger robots are unable to access.

In addition, the robots described above are suited to ether applications, such as cooperative robotics, or industrial applications such as cleaning or inspecting machinery, environmental applications such as monitoring gases, military applications such as mine clearance, commercial applications such as vacuuming, or communication applications such as mobile web-sites or telecommunication applications.

Claims

1. A robot comprising; a chassis; a pair of wheels, each wheel being independently driven; first and second motors for independently driving the respective wheels; control means for controlling the operation of the robot ; and at least one support member for supporting the robot m its upright position.

2. A robot as claimed m claim 1, wherein the support member is sufficiently rigid so as to maintain the robot m its upright position, yet sufficiently flexible to allow the robot to be driven .

3. A robot as claimed in any one of the preceding claims, wherein the chassis is made from an insulating material .

4. A robot as claimed in claim 3, comprising a plurality of electrically conductive support members, the support members being in contact, when in use, with a powered floor.

5. A robot as claimed in any one of the preceding claims, having a plurality of support members .

6. A robot as claimed m claim 5, wnerein the plurality of support members are evenly distributed around a circular path on the chassis.

7. A robot as claimed in claim 5, wherein the stiffness of each support member is related to the number of support members provided.

8. A robot as claimed in claim 5 or , wherein the stiffness of each support member is related to the position of the support member with respect to an axis of the wheels.

9. A robot as claimed in any one of claims 4-S, wherein the robot is powered by the powered floor via the conductive support member or members.

10. A robot as claimed in any one of claims 4-8, wherein the robot is powered by at least one battery, the battery being charged by the powered floor via the conductive support member or members .

11. A robot as claimed in any preceding claim, wherein the chassis is a single piece machined chassis .

12. A. robot as claimed in claim 11, wherein the chassis body is circular, having a diameter less than 6cm.

13 A robot as claimed in any one of the preceding claims, wherein the chassis is made from a machinable insulating material, for example Delrm .

14. A rcbct as claimed in anv one of the precedmg claims, wherein the pair of wheels are mounted along the same axis.

15. A robot as claimed m claim 14, wherein the axis of the wheels is centrally located m the chassis, and at least one support member is provided en either side of said axis for supporting the robot m the upright position.

16. A robot as claimed m claim 14, having two support memoers positioned either side of the central axis.

17. A robot as claimed m claim 14, having two support members positioned on one side of the central axis and one support member positioned en the other side of the central axis, the stiffness of the one support member being equal to the combined stiffness of the other two support members.

18. A robot as claimed m claim 14, wherein the axis of the wneeis is located m tne cnassis away from the centre of gravity, and at least cne support member is provided on the opposite side of the centre of gravity, for supporting the robot m the upright position.

19. A robot as claimed m any preceding claim, further comprising a magnet provided m each wneel , and a corresponding Hall effect sensor provided in tne chassis .

20. A robot as claimed m any one of tne preceding claims, wnerεm eacn support memher nas a sensor .

21. A robot as claimed in ciaim 20, wherein the sensor is a strain gauge for sensing surface texture .

22. A robot, comprising; a chassis; a pair of wheels, for contact with a support surface; first and second motors, for independently driving the respective wheels; control means for controlling the operation of the robo ,- and a plurality of electrically conductive support members, mounted on the chassis for contact with said support surface to support the robot in an upright position.

23. A development system for conducting experiments in distributed mobile robotics, the system comprising a plurality of robots as defined in claim 22, and further comprising a powered floor for powering the plurality of robots.

24. A development system as claimed in claim 23 , having in excess of fifty robots.

25. A robot, comprising; a single pair of wheels; at least one support member, the support member and the wheels together supporting the robot on a support surface; first and second motors for independently driving the respective wheels; control means fcr controlling the operation of the rocot; and a wireless transceiver, for communicating <vιth a remote control device.

26. A method of conducting an experiment m distributed mobile robotics, the method comprising providing a plurality of robots as defined m claim 25, wherein eacn robot forms a node m a wireless network.

27. A method as claimed m claim 26, the method further comprising the step of powering eacn robot from a powered floor.

28. A method of conducting an experiment m distributed mobile robotics, the method comprising providing a plurality of robots as claimed m claim 1, wherein each robot forms a node m a wireless network, and wherein each robot is powered by a powered floor.

29. A metnod as claimed m any one of claims 26- 28, wnerem eacn rocot is controlled using TCP/IP communications protocol.

30. A method as claimed m claim 29, wnerem eacn robot may be controlled from any workstation or PC with Internet connectivity.

31. A roDot comprising; a chassis machined as a single piece; a pair of wheels housed m said chassis along the same general axis, each wneei being independently driven; first and second motors for independently driving the respective wheels; control means for controlling the operation of the first and second motors; and at least one support member extending downward from said chassis, for supporting the robot in its upright position.