(12)UK Patent Application (19)GB (11)2 344 888 (13)A
`
`(211 Application No 9827758.5
`
`(221 Date of Filing 18.12.1998
`
`(71) Applicant(sl
`Notetry Limited
`(Incorporated in the United Kingdom)
`Kingsmead Mill, LITTLE SOMERFORD, Wiltshire,
`SN15 5JN, United Kingdom
`
`(72)
`
`lnventor(s)
`David Lindsey Bisset
`
`(74) Agent and/or Address for Service
`Dyson Research Limited
`PO Box 2080, Malmesbury, WILTSHIRE, SN16 OSW,
`United Kingdom
`
`(43) Date of A Publication 21.06.2000
`
`(511
`
`INTCL7
`G01S 15/93 // G01S 17/93, GOSD 1/03
`
`(52) UK CL (Edition R l
`G1G GRE GSA G9X
`G1A AA3 AG17 AG6 AG9 AR6 AT27 AT3
`U1S S1233 S1881
`
`(56) Documents Cited
`EP 0649709 A2.
`WO 87 /07056 A 1
`US 5279672A
`US 4815008A
`
`EP 0453905 A2. WO 88/04060 A2.
`JP 050011839 A US 5652593 A
`US 5170352 A
`US 5165064 A
`US4658385A
`
`(58) Field of Search
`UK CL (Edition Q I G1A AEEX AENX AEXS, G1G GPE
`GRE
`INT CL6 G01S 3n82. 3n83 3n84 3/786 13/93 15/93
`17/0217/0617/0817/93, GOSD 1/021/03
`ONLINE: WPI, JAPIO, EPODOC
`
`(54) Abstract Title
`Obstacle detection system
`
`(57) The invention provides an autonomous vehicle (100) having a plurality of sensors for detecting obstacles
`in the path of the vehicle (100), characterised in theat at least one forward looking sensor (250) is located at or
`near an uppermost extremity of the vehicle (100). It is disclosed that some infra-red emitters (220) are
`characterised in that the infra-red emitters (220) are arranged in groups of three or more (220a, 220b, 220c,
`220d) and are capable of emitting a signal over 160°. It is also disclosed that the infra-red emitters (220) and
`receivers (230) on the forward surface of the vehicle may be arranged such that at least two emitters are
`capable of sending a signal to a given point. Furthermore, ultra-sonic sensors (202, 204, 206) facing forward,
`left, right and rear directions are characterised in that a further ultra-sonic sensor (210) is located so as to face
`in a direction between forward and left or right. In a further disclosure, there are at least two infra-red sensors
`are arranged to face outwardly in substantially parallel directions on one side of the vehicle. A body carrying a
`plurality of sensors for detecting obstacles in the path of the vehicle (100) is also disclosed, where at least
`some of the sensors consist of infra-red sensors, and the vehicle (100) comprises a vacuum cleaner with a
`cleaner head housing a brush bar, characterised in thatthe cleaner head protrudes beyond the periphery of the
`body and at least one infra-red sensor is located so as to look along the cleaner head and beyond the
`protruding end thereof.
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`2344888
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`I
`
`Sensors
`
`The invention rela: !S to an arrangement of sensors for an autonomous vehicle,
`
`particularly but not exclusively for an autonomous vacuum cleaner.
`
`It is an object of the present invention to provide an autonomous vehicle having a
`
`plurality of sensors for detecting obstacles in the path of the vehicle in which the
`
`arrangement and nature of the sensors is selected so as to give improved performance of
`
`the vehicle during operation. It is a further object of the invention to provide an
`
`autonomous vehicle whose sensor arrangement is capable of detecting obstacles in its
`
`path with a high degree of accuracy. It is a still further object of the invention to
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`provide an autonomous vehicle which is capable of autonomous operation with a high
`
`degree of safety.
`
`According to a first aspect of the invention, there is provided an autonomous vehicle
`
`having a plurality of sensors for detecting obstacles in the path of the vehicle,
`
`characterised in that at least one forw~d-looking sensor is located at or near an
`
`uppermost extremity of the vehicle.
`
`According to a second aspect of the invention, there is provided an autonomous vehicle
`
`having a plurality of sensors for detecting obstacles in the path of the vehicle, at least
`
`some of the sensors consisting of infra-red emitters and receivers, characterised in that
`
`the infra-red emitters are arranged in groups of three or more so that each group of
`
`emitters is capable of emitting a signal over an angle of greater than 160°.
`
`According to a third aspect of the invention, there is provided an autonomous vehicle
`
`having a plurality of sensors for detecting obstacles in the path of the vehicle, the
`
`vehicle having a forward surf ace in which an array of sensors is located, some of the
`
`sensors consisting of infra-red emitters and receivers, characterised in that the emitters
`
`and receivers are located and arranged in the forward surface such that, at any point in
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`2
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`the path of the vehicle, at least two infra-red emitters are capable of sending a signal to
`
`that point.
`
`According to a fourth aspect of the invention, there is provided an autonomous vehicle
`
`having a plurality of sensors for detecting obstacles in the path of the vehicle, at least
`
`some of the sensors consisting of ultra-sonic sensors facing in forward, rearward, left
`
`and right directions, characterised in that a further ultra-sonic sensor is located so as to
`
`face in a direction which is between the forward direction and either the right direction
`
`or the left direction.
`
`According to a fifth aspect of the invention, there is provided an autonomous vehicle
`
`having a plurality of sensors for detecting obstacles in the path of the vehicle, at least
`
`some of the sensors consisting of infra-red sensors, characterised in that at least two
`
`infra-red sensors are arranged to face outwardly in substantially parallel directions on
`
`one side of the vehicle.
`
`According to a sixth aspect of the invention, there is provided an autonomous vehicle
`
`having a body carrying a plurality of sensors for detecting obstacles in the path of the
`
`vehicle, at least some of the sensors consisting of infra-red sensors, and the vehicle
`
`comprising a vacuum cleaner having a cleaner head housing a brush bar, characterised
`
`in that the cleaner head protrudes beyond the periphery of the body and at least a first of
`
`the infra-red sensors is located so as to look along the cleaner head and beyond the
`
`protruding end thereof.
`
`Advantageous and preferred features of the invention are set out in the subsidiary
`
`claims.
`
`An embodiment of the present invention will now be described, by way of example
`
`only, with reference to the accompanying drawings, wherein:
`
`Figure 1 is a perspective view of an autonomous vehicle, specifically a vacuum cleaner,
`
`according to the invention;
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`3
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`Figure 2 is a front view of the autonomous vehicle of Figure 1;
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`Figure 3 is a rear view of the autonomous vehicle of Figure 1;
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`Figures 4a and 4b are side views, taken from the right and left sides respectively, of the
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`autonomous vehicle of Figure 1;
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`Figures 5a and 5b are underneath and plan views respectively of the autonomous
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`vehicle of Figure 1;
`
`Figure 6 is a schematic view illustrating the positioning of infra-red sensors on the
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`autonomous vehicle of Figure 1;
`
`Figure 7 is a schematic view illustrating the grouping of infra-red sensors on the
`
`autonomous vehicle of Figure 1;
`
`Figure 8 is a schematic view illustrating the positioning of ultra-sonic sensors on the
`
`autonomous vehicle of Figure 1; and
`
`Figure 9 is a schematic view illustrating the positioning of further infra-red sensors on
`
`the autonomous vehicle of Figure 1.
`
`The embodiment illustrated talces the form of an autonomous vacuum cleaner. The
`
`vacuum cleaner 100 shown in the said drawings has a supporting chassis 102 which is
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`generally circular in shape and is supported on two driven wheels 104 and a castor
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`wheel 106. The chassis 102 is preferably manufactured from high-strength moulded
`
`plastics material, such as ABS, but can equally be made from metal such as aluminium
`
`or steel. The chassis 102 provides support for the components of the cleaner 100 which
`
`will be described below. The driven wheels 104 are arranged at either end of a diameter
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`of the chassis 102, the diameter lying perpendicular to the longitudinal axis of the
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`cleaner 100. Each driven wheel 104 is moulded from a high-strength plastics material
`
`and carries a comparatively soft, ridged band around its circumference to enhance the
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`grip of the wheel 104 when the cleaner 100 is traversing a smooth floor. The soft,
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`ridged band also enhances the ability of the wheels 104 to mount and climb over small
`
`obstacles. The driven wheels 104 are mounted independently of one another via support
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`bearings (not shown) and each driven wheel 104 is connected directly to a motor 105
`
`which is capable of driving the respective wheel 104 in either a forward direction or a
`
`reverse direction. By driving both wheels 104 forward at the same speed, the cleaner
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`4
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`100 can be driven in a forward direction. By driving both wheels 104 in a reverse
`
`direction at the same speed, the cleaner 100 can be driven in a backward direction. By
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`driving the wheels 104 in opposite directions, the cleaner 100 can be made to rotate
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`about its own central axis so as to effect a turning manoeuvre. The aforementioned
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`method of driving a vehicle is well known and will not therefore be described any
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`further here.
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`The castor wheel 106 is significantly smaller in diameter than the driven wheels 104 as
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`can be seen from, for example, Figures 4a and 4b. The castor wheel 106 is not driven
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`and merely serves to support the chassis 102 at the rear of the cleaner 100. The location
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`of the castor wheel 106 at the trailing edge of the chassis 102, and the fact that the
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`castor wheel 106 is swivellingly mounted on the chassis by means of a swivel joint 110,
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`allows the castor wheel 106 to trail behind the cleaner 100 in a manner which does not
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`hinder the manoeuvrability of the cleaner 100 whilst it is being driven by way of the
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`driven wheels 104. The castor wheel 106 can be made from a moulded plastics material
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`or can be formed from another synthetic material such as Nylon.
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`Mounted on the underside of the chassis 102 is a cleaner head 122 which includes a
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`suction opening 124 facing the surface on which the cleaner 100 is supported. The
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`suction opening 124 is essentially rectangular and extends across the majority of the
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`width of the cleaner head 122. A brush bar 125 is rotatably mounted in the suction
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`opening 124 and a motor (not shown) is mounted on the upper surface of the cleaner
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`head 122 for driving the brush bar 125 by way of a drive belt (not shown) extending
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`between a shaft of the motor and the brush bar 125. The cleaner head 122 is mounted
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`on the chassis 102 in such a way that the cleaner head 122 is able to float on the surface
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`to be cleaned. This is achieved in this embodiment in that the cleaner head 122 is
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`pivotally connected to an arm (not shown) which in tum is pivotally connected to the
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`underside of the chassis 102. The double articulation of the connection between the
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`cleaner head 122 and the chassis 102 allows the cleaner head to move freely in a vertical
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`direction with respect to the chassis 102. This enables the cleaner head to climb over
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`small obstacles such as books, magazines, rug edges, etc. Obstacles of up to
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`5
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`approximately 25mm in height can be traversed in this way. A flexible or telescopic
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`conduit is located between a rear portion of the cleaner head 122 and an inlet port
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`located in the chassis 102.
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`As can be seen from Figures 5a and 5b, the cleaner head 122 is asymmetrically
`
`mounted on the chassis 102 so that one side of the cleaner head 122 protrudes beyond
`
`the general circumference of the chassis 102. This allows the cleaner 100 to clean up to
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`the edge of a room on the side of the cleaner 100 on which the cleaner head 122
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`protrudes.
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`The chassis 102 carries a plurality of sensors which are designed and arranged to detect
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`obstacles in the path of the cleaner 100 and its proximity to, for example, a wall or other
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`boundary such as a piece of furniture. The sensors comprise several ultra-sonic sensors
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`and several infra-red sensors. The array of sensors will be described in more detail
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`below. Control software, comprising navigation controls and steering devices for
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`navigating and manoeuvring the cleaner 100 around a defined area in order to clean the
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`carpet or other surface within the area, is housed within a housing 142 located beneath a
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`control panel 144 or elsewhere within the cleaner 100. The specific design of the
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`control software does not form part of the present invention. In the manner of known
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`autonomous vehicles, the control software is able to receive the outputs of the sensors
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`and to drive the motors 105 so that obstacles are avoided whilst following a path
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`specified by algorithms appropriate to the nature of the vehicle. Any appropriate
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`software can be used in this way to navigate the cleaner 100 around a room to be
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`cleaned.
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`The vacuum cleaner 100 also includes a motor and fan unit 150 supported on the chassis
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`102 for drawing dirty air into the vacuum cleaner 100 via the suction opening 124 in the
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`cleaner head 122. The chassis 102 also carries a cyclonic separator 152 for separating
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`dirt and dust from the air drawn into the cleaner 100. The inlet port which
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`communicates with the rear portion of the cleaner head 122 via the conduit mentioned
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`above forms the inlet to the cyclonic separator 152. The cyclonic separator, which
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`preferably comprises two cyclones in series, need not be described any further here,
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`being known technology and described adequately elsewhere.
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`The cyclonic separator 152 is releasable from the chassis 102 in order to allow emptying
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`of the cyclonic separator 152. A hooked catch (not shown) is provided by means of
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`which the cyclonic separator 152 is held in position when the cleaner 100 is in use.
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`When the hooked catch is released (by manual pressing of a button 134 located in the
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`control panel 144), the cyclonic separator 152 can be lifted away from the chassis 102
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`by means of gripper portions 170. The cyclonic separator 152 can then be emptied.
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`Two battery packs 160 are located on the chassis 102 on either side of the cyclonic
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`separator 152. The battery packs 160 are identical and are spaced from the central axis
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`of the vacuum cleaner 100 by a significant distance, say between 50 and 150 mm.
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`The vacuum cleaner 100 described above operates in the following manner. In order for
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`the cleaner 100 to traverse the area to be cleaned, the wheels 104 are driven by the
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`motors 105 which, in turn, are powered by the batteries 160. The direction of
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`movement of the cleaner 100 is determined by the control software which
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`communicates with the sensors which are designed to detect any obstacles in the path of
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`the cleaner 100 so as to navigate the cleaner 100 around the area to be cleaned. The
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`normal forward direction of the cleaner 100 is such that the cleaner head 122 trails
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`behind the driven wheels 104. The battery packs 160 also power the motor and fan unit
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`150 which draws air into the cleaner 100 via the cleaner head 122 and passes it to the
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`cyclonic separator 152 where the dirt and dust is separated from the airflow. The
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`battery packs 160 are also used to power the motor which drives the brush bar 125
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`which, in turn assists with pick-up, particularly on carpets. The air which exits the
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`cyclonic separator 152 is passed across the motor and fan unit 150 by appropriate
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`ducting, as is common in many appliances, including vacuum cleaners.
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`The sensor array forming part of the vacuum cleaner 100 will now be described in more
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`detail. The array comprises a plurality of ultra-sonic sensors and a plurality of infra-red
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`sensors. The majority of the sensors are located in a forward surface 180 of the vacuum
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`cleaner 100. The forward surface 180 is substantially semi-circular in plan view, as can
`
`be seen from Figures 5a and 5b. However, further sensors are located at the uppermost
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`extremity of the cleaner 100, at the rear of the cleaner 100, immediately over the brush
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`bar 122, and on the underside of the cleaner 100. Details are given below.
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`Three ultra-sonic sensors 202, 204 and 206, each consisting of an ultra-sonic emitter
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`and an ultra-sonic receiver, are positioned in the forward surface 180. A first of the said
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`ultra-sonic sensors 202, comprising an emitter 202a and a receiver 202b, is directed in a
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`forward direction so that the emitted signals are transmitted in the normal forward
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`direction of travel of the cleaner 100. A second ultra-sonic sensor 204, comprising an
`
`emitter 204a and a receiver 204b, is directed such that the emitted signals are
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`transmitted outwardly to the left of the cleaner 100 in a direction which is perpendicular
`
`to the direction of transmission by the ultra-sonic sensor 202. A third ultra-sonic sensor
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`206, comprising an emitter 206a and a receiver 206b, is directed such that the emitted
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`signals are transmitted outwardly to the right of the cleaner 100 in a direction which is
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`perpendicular to the direction of transmission by the ultra-sonic sensor 202 and opposite
`
`to the direction of transmission by the ultra-sonic sensor 204. A fourth ultra-sonic
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`sensor 208, comprising an emitter 208a and a receiver 208b, is located in the rear of the
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`cleaner 100 (see Figure 3) and is directed rearwardly so that the emitted signals are
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`transmitted parallel to the normal forward direction of travel of the cleaner 100 but in
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`the opposite direction. These four sensors 202, 204, 206, 208 detect the presence of
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`walls and obstacles to the front, left, right and rear of the cleaner 100.
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`A fifth ultra-sonic sensor 210 is located in the forward surface 180. The fifth ultra-sonic
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`sensor 210 comprises an emitter 210a and a receiver 210b. The fifth ultra-sonic sensor
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`210 is positioned so that the emitter 210a transmits at an angle which is substantially
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`midway between the directions in which the forward- and left-looking sensors 202, 204
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`transmit. In the embodiment, the sensor 210 transmits in a direction of 45° to the
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`normal forward direction of travel of the vacuum cleaner 100. As can be seen from
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`Figure 1, the sensor 210 transmits to the side of the cleaner 100 on which the cleaner
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`head 122 protrudes.
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`Figure 8 shows schematically the arrangement of ultra-sonic sensors 202, 204, 206, 208
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`and 210 on the vacuum cleaner 100 if the normal direction of forward travel is along the
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`arrow F. In the arrangement shown, the angle a is 45°, although variations to this
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`arrangement are possible.
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`The inclusion of the sensor 210 provides the vehicle 100 with greater angular control as
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`it moves along a wall or other obstacle with the cleaner head 122 thereagainst or parallel
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`thereto. The sensor 210 is able to detect the presence of a wall or similar large obstacle
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`and, if the wall or other obstacle alongside which the vehicle is moving disappears (for
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`example, when a corner is encountered), then the vehicle 100 is made aware of the
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`change earlier than it would have been if the sensor 210 had not been present. This
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`allows the vehicle to take account of corners and other changes in its environment with
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`greater accuracy and manoeuvrablity.
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`A plurality of infra-red sensors are also included in the forward surface 180. The infra(cid:173)
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`red sensors comprise emitters 220 and receivers 230. Most of the emitters 220 are
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`arranged in four groups of three which are spaced substantially evenly around the
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`forward surface 180. A first emitter group 220a comprises a central emitter 222a and
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`two side emitters 224a. A second emitter group 220b comprises a central emitter 222b
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`and two side emitters 224b. A third emitter group 220c comprises a central emitter
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`222c and two side emitters 224c and a fourth emitter group 220d comprises a central
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`emitter 222d and two side emitters 224d. One of the emitter groups 220b is illustrated
`
`in Figure 7. Each side emitter 224b is arranged at an angle b of approximately 60° to
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`the central emitter 222b. Each emitter 222b, 224b has a beam angle c of approximately
`
`50°. This arrangement creates a field of relatively even emitted signals covering an
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`angle of substantially 170° to 180°. It will be appreciated that a similar field can be
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`created by providing a larger number of emitters, each having a smaller beam angle than
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`the arrangement illustrated in Figure 7.
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`Figure 6 illustrates the arrangement of the emitter groups 220a, 220b, 220c, 220d on the
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`cleaner 100. As will be seen from the figure, the first emitter group 220a is lo:ated at
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`the end of a radial line extending at an angled of 3D°to the transverse axis 190 of the
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`cleaner 100 on the left side thereof. The fourth emitter group 220d is located at the end
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`of a radial line also extending at an angled of 30° to the transverse axis 190 but on the
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`right side of the cleaner 100. The second and third emitter groups 220b, 220c are
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`located at the ends of radial lines extending at an angle e of 60° to the transverse axis
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`190 on the left and right sides of the cleaner 100 respectively. The third emitter group
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`220c is identical to the second emitter group 220b as illustrated in Figure 7. However,
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`the first and fourth emitter groups 220a, 220d each have one side emitter 224a', 224d'
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`which is specifically directioned so that the signal emitted is parallel to the transverse
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`axis 190. This is achieved, in this specific case, by varying the angle b between the
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`relevant central emitter 222a, 222d and the respective side emitter 224a', 224d' from
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`60° to 30°. It will be appreciated that, if either of the angles b and d differ from the
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`values given above, then the extent of the variation in angle b between the relevant
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`central emitter 222a, 222d and the respective side emitter 224a, 224d will need to be
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`adjusted so that the side emitter 224a', 224d' remains directed outwardly in a direction
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`parallel to the transverse axis 190. Two additional emitters 226 are positioned close to
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`the central axis of the cleaner 100 and are directioned so that they emit signals in a
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`substantially forward direction with respect to the normal direction of travel.
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`The first and fourth emitter groups 220a, 220d are located in a horizontal plane which is
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`vertically spaced from the horizontal plane in which the second and third emitter groups
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`220b, 220c are located. The first and fourth emitter groups 220a, 220d are located at a
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`higher level than the second and third emitter groups 220b, 220c. The additional
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`emitters 226 are also spaced vertically from the two aforementioned horizontal planes.
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`The arrangement is symmetrical about the longitudinal axis of the cleaner 100. The
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`whole of the array of emitters is designed so that at least two of the emitters will send
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`signals directly to any point in the path of the cleaner (in the forward direction). (This
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`will not apply, of course, to points which are extremely close to the cleaner itself.)
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`10
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`The receivers 230 are spaced substantially evenly around the forward surface 180. A
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`first receiver 230a is located adjacent each of the emitters 224a, 224d which are
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`directioned parallel to the transverse axis 190 so as to receive signals therefrom. These
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`receivers 230a are specifically paired with the emitters 224a, 224d. The remaining
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`receivers 230b are spaced substantially evenly around the forward surface 180 and are
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`not paired with any of the emitters at all. The receivers 230b are all located in a single
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`horizontal plane with the exception of two central receivers 230b which are located
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`adjacent the forward-looking emitters 226. The lack of pairing of the receivers with the
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`emitters gives the cleaner 100 an enhanced ability to detect its position within an
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`environment and with respect to objects and obstacles.
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`A passive infra-red detector 240, comprising an emitter 240a and a receiver 240b, is
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`located in the forward surface 180 for the purpose of detecting heat sources such as
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`humans, animals and fires. The passive infra-red detector 240 is directioned so that it
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`looks in a forward direction to detect heat sources in its path.
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`Two forward-looking ultra-sonic sensors 250, each comprising an emitter 250a and a
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`receiver 250b, are positioned at an uppermost extremity of the cleaner 100 so that they
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`are able to sense obstacles immediately in front of the cleaner and at or near an
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`uppermost extremity thereof. In this case, the sensors 250 are positioned in the casing
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`of the fan and motor unit 150 so that they both look along the uppermost edge of the
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`cyclonic separator 152. The direction of each sensor 250 is parallel to the direction of
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`the other sensor 250. The sensors 250 are able to detect any obstacles which are at a
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`sufficiently high level not to be detected by the sensors arranged in the forward surface
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`180 but which would constitute an obstruction to the forward movement of the cleaner
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`100. Rearward-looking sensors could also be provided at a high level if required, but
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`none is shown in the embodiment illustrated in the drawings. It will be appreciated that
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`a similar effect can be achieved using sensors (preferably ultra-sonic sensors) positioned
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`lower on the cleaner than the uppermost extremity but directioned so as to look towards
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`the appropriate area adjacent the uppermost extremity in front of the cleaner 100.
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`Further infra-red sensors 260, 262 are positioned on the chassis 102 immediately above
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`the protruding end of the cleaner head 122. Each sensor 260, 262 comprises an emitter
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`?.60a, 262a and a receiver 260b, 262b. The first of these sensors 260 is directioned so
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`that the emitter 260a emits a signal in a direction parallel to the iongitudinal axis of the
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`cleaner head 122 or of the brush bar 125. The direction of the signal from the sensor
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`260 is therefore perpendicular to the forward direction of travel and parallel to the
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`direction of the signal emitted by emitter 224a'. The sensor 260 is thus able to detect
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`the distance of a wall or other obstacle along which the cleaner 100 is intended to travel.
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`In combination with the emitter 224a' and the receiver 230a, the sensor 260 is also able
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`to maintain the direction of travel of the cleaner 100 parallel with the wall or other
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`obstacle along which the cleaner 100 is intended to travel. This is achieved by way of
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`the parallel signals being maintained essentially identical. Any variation between the
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`two signals can be easily recognised and the path of the cleaner 100 can then be
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`adjusted to compensate for the discrepancy. The arrangement is illustrated in Figure 9.
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`As will be seen from the figure, the distance between the directions of the two signals is
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`approximately one half of the length of the cleaner 100, although this can be varied to a
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`considerable extent. Preferably, the distance will not be less than a quarter of the length
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`of the vehicle nor more than three quarters thereof.
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`The second of the further infra-red sensors 262 is directioned so that the emitter 262a
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`sends a signal rearwardly in a direction parallel to the direction of travel of the cleaner
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`100. The sensor 262 is able to detect the presence of an obstacle on which the cleaner
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`head 122 may become lodged if the cleaner 100 were traveling in a rearward direction
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`or turning or rotating about a vertical axis.
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`Infra-red sensors 270, 272 are provided on the underside of the cleaner 100. Each
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`sensor 270, 272 is directioned so that it looks downwardly towards the surface across
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`which the cleaner 100 travels and which the cleaner 100 is intended to clean. Two
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`downward-looking sensors 270 are provided in the chassis 102 immediately in front of
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`each of the driven wheels 104. A further downward-looking sensor 272 is provided at
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`12
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`the front edge of the chassis 102 and on or close to the longitudinal axis of the cleaner
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`100. Each sensor 270, 272 comprises an emitter and a receiver. In the embodiment
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`illustrated, the outermost component of each sensor 270 is a receiver and the innermost
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`component is an emitter. Each of the sensors 270, 272 is capable of detecting the
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`presence or absence of the surface across which the cleaner 100 travels. A signal is sent
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`to the control software to bring the cleaner 100 to a halt, or to tum, immediately one of
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`the sensors 270, 272 detects that the surface is absent. This is likely to be due to the
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`presence of a stairway or other edge of the surface. The cleaner 100 is thus prevented
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`from falling from a height in the event that a stairway or other edge is encountered. For
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`safety reasons, each of the sensors located in front of each wheel is connected to the
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`control software via different circuits so that, should one circuit fail, the other sensor
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`will still be functional in order to avoid an accident occurring.
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`The invention is not limited to the precise details of the embodiment illustrated and
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`described above. Although the vehicle described is a vacuum cleaner, it will be
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`appreciated that the sensor arrangement can be applied to any other type of autonomous
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`vehicle which is required to propel itself across a surface without human intervention
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`and without colliding with obstacles or objects in its path. Domestic appliances are
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`becoming increasingly sophisticated and it is envisaged that domestic appliances other
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`than vacuum cleaners will become autonomous over the years. The sensor arrangement
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`described above will be equally applicable thereto.
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`Claims:
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`13
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`I. An auton( mous vehicle having a plurality of sensors for detecting obstacles in the
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`path of the vehicle, characterised in that at least one forward-looking sensor is located
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`on the vehicle and directioned so as to detect the presence of an obstacle located at or
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`near an uppermost extremity of the vehicle.
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`2. An autonomous vehicle as claimed in claim 1, wherein the or each forward-looking
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`sensor is located at or near an uppermost extremity of the vehicle.
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`3. An autonomous vehicle as claimed in claim 1 or 2, wherein two fo1 Y¥'ard-looking
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`sensors are provided.
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`4. An autonomous vehicle as claimed in claim 3, wherein the two forward-looking
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`sensors are arranged parallel to one another.
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`5. An autonomous vehicle as claimed in any one of the preceding claims, wherein at
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`least one rearward-looking sensor is also provided at or near the uppermost extremity of
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`the vehicle.
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`6. An autonomous vehicle as claimed in any one of the preceding claims, wherein the
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`two forward-looking sensors are ultra-sonic sensors.
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`7. An autonomous vehicle having a plurality of sensors for detecting obstacles in the
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`path of the vehicle, at least some of the sensors consisting of infra-red emitters and
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`receivers, characterised in that the infra-red emitters are arranged in groups of three or
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`more so that each group of emitters is capable of emitting a signal over an angle of
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`greater than 160°.
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`8. An autonomous vehicle as claimed in claim 7, wherein each group of emitters is
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`capable of emitting a signal over an angle of substantially 170°.
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`14
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`9. An autonomous vehicle as claimed in claim 7 or 8, wherein each group of emitters
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`comprises a central emitter and two side emitters.
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`10. An autonomous vehicle as claimed in claim 9, wherein the side emitters of at least
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`one of the groups of emitters are arranged at an angle of substantially 60° to the central
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`emitter.
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`11. An autonomous vehicle as claimed in any one of claims 7 to 10, wherein each
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`emitter has a beam angle of approximately 50°.
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`12. An autonomous vehicle as claimed in any one of claims 7 to 11, wherein each
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`group of emitters lies in a substantially horizontal plane.
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`13. An autonomous vehicle as claimed in any one of claims 7 to 12, wherein each
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`group of emitters is vertically spaced with respect to an ad