WO1994023351A1 - Systeme de localisation - Google Patents

Systeme de localisation Download PDF

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Publication number
WO1994023351A1
WO1994023351A1 PCT/GB1994/000710 GB9400710W WO9423351A1 WO 1994023351 A1 WO1994023351 A1 WO 1994023351A1 GB 9400710 W GB9400710 W GB 9400710W WO 9423351 A1 WO9423351 A1 WO 9423351A1
Authority
WO
WIPO (PCT)
Prior art keywords
εtation
mobile work
εtationε
εpaced
εyεtem
Prior art date
Application number
PCT/GB1994/000710
Other languages
English (en)
Inventor
Gareth Anthony Edwards
Original Assignee
Cat Systems Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB939307084A external-priority patent/GB9307084D0/en
Application filed by Cat Systems Limited filed Critical Cat Systems Limited
Priority to AU63834/94A priority Critical patent/AU6383494A/en
Publication of WO1994023351A1 publication Critical patent/WO1994023351A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/87—Combinations of sonar systems
    • G01S15/876—Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/87—Combinations of radar systems, e.g. primary radar and secondary radar
    • G01S13/878—Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
    • G05D1/02—Control of position or course in two dimensions
    • G05D1/021—Control of position or course in two dimensions specially adapted to land vehicles
    • G05D1/0212—Control of position or course in two dimensions specially adapted to land vehicles with means for defining a desired trajectory
    • G05D1/0221—Control of position or course in two dimensions specially adapted to land vehicles with means for defining a desired trajectory involving a learning process
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
    • G05D1/02—Control of position or course in two dimensions
    • G05D1/021—Control of position or course in two dimensions specially adapted to land vehicles
    • G05D1/0255—Control of position or course in two dimensions specially adapted to land vehicles using acoustic signals, e.g. ultra-sonic singals
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D1/00—Control of position, course, altitude or attitude of land, water, air or space vehicles, e.g. using automatic pilots
    • G05D1/02—Control of position or course in two dimensions
    • G05D1/021—Control of position or course in two dimensions specially adapted to land vehicles
    • G05D1/0268—Control of position or course in two dimensions specially adapted to land vehicles using internal positioning means
    • G05D1/0274—Control of position or course in two dimensions specially adapted to land vehicles using internal positioning means using mapping information stored in a memory device

Definitions

  • This invention relates to a system for and a method of enabling a mobile work station to localise itself, namely, to determine its distance and bearing, with respect to a plurality of fixed reference stations associated with an area to be worked by the mobile station.
  • the inventive system and method have numerous applications and are especially, but not exclusively, related to a mobile robotic unit which is required to carry out a task over a working area.
  • One particular application of the invention is relevant to a robotic lawn mower which needs no operator intervention beyond being shown the boundary of a lawn to be mowed, whereafter the mower is able to mow the lawn automatically at predetermined intervals on demand, whilst optionally dumping mowed grass cuttings at given locations and/or returning to a home base, to recharge or refuel, as necessary.
  • the mower can be rendered sensitive to foreign objects, such as people, in its mowing area, such that it will not overrun such objects.
  • the mower may be programmed to mow the lawn in any desired pattern, for instance, spirally or striped.
  • Such a robotic lawn mower may also be arranged to perform other tasks, such as, distributing fertiliser, weed killer or the like, sweeping and/or collecting fallen leaves.
  • Another application of the invention is as a robotic floor cleaner, such as, a vacuum cleaner, floor polisher or the like, for domestic and/or industrial use.
  • mobile work station is used to denote such devices, and any other devices which are capable of carrying out a task or tasks over a working area in robotic manner.
  • one aspect of the present invention provides a localising system comprising a plurality of spaced reference stations associated or associable with a working area in given positions with respect thereto, and a mobile work station arranged to communicate with the or two or more of the spaced reference stations to determine its distance from and bearing with respect thereto, thereby localising the position of the mobile work station relative to the working area, such determinations being used to enable the mobile work station to carry out a task over at least part of the working area in a controlled manner.
  • Another aspect of the invention resides in a method of localising a mobile work station with respect to an area to be worked thereby, wherein a plurality of spaced reference stations are associated with the area to be worked in given positions in relation thereto and wherein the mobile work station communicates with the or two or more of the spaced reference stations to determine its distance from and bearing with respect thereto, thereby localising the position of the mobile work station relative to the working area, such determinations being used to enable the mobile work station to carry out a task over at least part of the working area in a controlled manner.
  • the or at least some of the spaced reference stations may be capable of communicating with each other or others of the reference stations, to determine their relative spacings and bearings, which determination may then be transmitted to the mobile work station.
  • the mobile work station may be arranged to determine its distance from and bearing with respect to the or at least two of the spaced reference stations whilst it is stationary, either before or during its carrying out a task over at least part of the working area. Alternatively or additionally, such determinations may be carried out whilst the mobile work station is moving, preferably, over the working area, again before or during its carrying out a task over at least part thereof.
  • Communication between the spaced reference stations and/or between the mobile working station and the or at least two of the spaced reference stations may be effected by using ultrasonic radiation, although other forms of radiation, such as, electromagnetic radiation, may be employed.
  • the reference stations may be linked together, for example, by cabling or wiring, to effect communication therebetween.
  • the mobile work station may be so-linked to one or more of the spaced reference stations.
  • the spaced reference stations maybe "passive”, in that they can only reflect radiation transmitted from the mobile work station back thereto, to enable the mobile work station to determine its distance from and bearing with respect to the or two or more of the reference stations, in which case the reference stations are likely not to be able to communicate with each other.
  • the spaced reference stations may be "active" in that they can be activated and/or interrogated by the mobile work station to enable them to communicate therewith, so that the mobile work station can determine its distance from and bearing with respect to the or two or more of the reference stations.
  • the spaced reference stations may be arranged to communicate with the mobile work station by means of a continuous transmission of radiation or pulsed radiation without having to be activated thereby or they may be ⁇ o- activated and/or interrogated on demand by the mobile station to communicate therewith after a given time interval or on receiving a further transmission activating and/or interrogating therefrom.
  • This arrangement allows the mobile work station to "orchestrate" all transmissions from the mobile station to the or two or more of the reference stations, between the or two or more of the reference stations and from the or two or more of the reference stations to the mobile station.
  • only the mobile work station need to be used to determine where the reference stations are located and where it is itself relative to the working area.
  • the localising system of the preferred embodiment is based upon the use of an intelligent, microprocessor-controlled mobile work station capable of activating and interrogating the spaced reference stations which may also be intelligent and microprocessor-controlled.
  • the ultrasonic or other radiation can be encoded to communicate information between the spaced reference and/or mobile work stations by, say, pulse modulation, with the stations measuring transmit/receive times to determine the respective distances between them.
  • the stations may use a stereophonic technique, namely, the time difference between receiving the same pulse at two stations, to determine the bearing of a transmitting reference station and/or the mobile work station.
  • the accuracy of an ultrasonic localising system is largely independent on the speed of sound in air, which can vary considerably due to temperature and/or humidity, and wind speed, and all distance measurements can be calibrated relative to transmission times between the spaced reference stations and, thus, the wind speed deduced.
  • the reference stations may be arranged to compensate also for isotropic changes in speed of the ultrasonic radiation in air due to temperature changes, as well as being able to take into account constant wind speed.
  • the system can be calibrated and controlled by the mobile work station which detects a reference station, determines its position relative to others already encountered, and gives it an identifying code, if necessary.
  • the mobile station can then wander at will, activating or interrogating specific reference stations, usually, the nearest one, to respond, measuring transmit/receive times to determine a radial distance fix, and measuring ⁇ tereophonically to determine a bearing.
  • Exact positional fixes are obtained by geometry, namely, by obtaining three radial distances from different fixed stations and high positional accuracy can be obtained by trilineation.
  • This method of specific interrogation means that a reference station only needs to be “woken up” from a low-power “sleep” state when the mobile station is in the area and only needs to transmit at sufficiently a high energy pulse when specifically asked to do so by the mobile station.
  • the ⁇ tation ⁇ be ⁇ elf-contained battery driven units, perhaps operated by the power generated from a solar cell, and hence low power consumption could be important.
  • a further advantage is that multiple stations do not interfere with each other.
  • a further advantage of the inventive system and method of localisation is that the mobile work station can listen for any natural reflection of its transmitted ultrasonic radiation and detect the range and direction of an object in its vicinity. This information can be used to enable the mobile station to avoid unknown obstacles or take any other action, for example, stopping until the object is removed.
  • the mobile station may be arranged to programme and/or interrogate the reference stations and cause them to transmit radiation, such as an ultrasonic pulse, of given duration at predetermined time intervals.
  • radiation such as an ultrasonic pulse
  • the mobile station can avoid any delay in re- interrogating the reference stations, but retains the ability to synchronise such stations, whilst minimising the possibility of two or more ultrasonic pulses clashing with each other.
  • the mobile station is able to maximise the accuracy of its localisation with respect to the closest reference station( ⁇ ), preferably employing very short pulses, whilst boosting signal to noise ratio from more distant reference stations using longer duration pulses.
  • Programmability of the spaced reference stations permits the mobile station to optimise its pulse strategy as it moves over the working area.
  • the inventive localising system has particular application in association with a robotic lawn mower arranged to mow a working area, namely, a lawn, with the reference stations preferably being spaced around the boundary of the lawn, although such positioning may be otherwise.
  • the reference stations may be positioned on the area of the lawn, with, say, one such station positioned at the centre of the lawn.
  • the mower, or other mobile work station is subjected to a calibration phase in which it interrogates the reference stations to determine its spacing therefrom and bearing with respect thereto, possibly after the reference stations have carried out the same exercise with respect to each other.
  • This localising information is stored in the microprocessor control unit of the mower or other mobile station.
  • a so-called “learning phase” may be carried out, whereby the mobile work station is moved by a user around the boundary of the working area, to establish an internal model or map thereof which is also stored in the control unit of the mobile station.
  • This learning phase also takes into account areas within the working area upon which tasks are not required to be carried out by the mobile station.
  • the wires can be used for several purposes, for example:
  • any mobile station within the area can detect the strength of the magnetic field created by a wire loop, which can be modulated to carry information.
  • a specific reference station can be employed as a charging point for the mobile station which can "home in” on to it and connect up to recharge its power source, such as a battery, when required.
  • the power source for that charging point might be a large solar panel, although any other suitable source may be used.
  • the mobile station may be fitted with a solar panel used to recharge its batteries directly.
  • the station itself detects a low- charge situation and goes into a stationary "basking" mode, where the solar panel is actively maintained in the optimum position relative to the sun by the whole mower rotating as necessary.
  • a 270mm x 270mm solar panel may be used, giving approximately lAh at 12 volts per day during the summer.
  • a lawn mower would have a characteristic basking time of, say, two to three days and a mowing time of up to, say, three hours.
  • inventive system and method can be used to determine the orientation of the mobile station in space, as will be described in more detail hereinbelow with reference to a preferred embodiment.
  • Figure 1 is a plan view of the system in association with a garden lawn to be mowed by the mower;
  • Figure 2 is a diagrammatic plan view of the mower in association with three spaced reference stations of the system;
  • Figure 3 is a diagrammatic view of one of the reference stations shown in Figure 2;
  • FIGS 4A and 4B are respective diagrammatic side and bottom plan views of the mower of Figure 2;
  • Figure 5 shows respective flowcharts for typical ultrasonic sequences of the mower or other mobile work unit and a reference station.
  • a robotic lawn mower 1 is of largely the same size and construction as a conventional lawn mower except that it incorporates a microprocessor control unit (not shown) accommodated in a housing 2 on the body 3 of the mower 1, and a steering assembly (also not shown) for at least one pair of its wheels 4 upon which the body 3 is mounted.
  • the mower 1 may be provided with a detachable handle for manual use, whilst the microprocessor control unit controls the manoeuvrability of the mower and the associated grass cutting device (not shown).
  • Optional sensing wheels (also not shown) and/or other suitable sensors, such as the wheels 4, may be used in the mower 1, to ensure that the latter is moving correctly over the desired distances.
  • a fail-safe electro-mechanical arrangement such as, micro ⁇ witches, may be used to ensure that the power to the grass cutting device of the mower 1 is cut-off when the mower is tilted significantly from the horizontal.
  • the location system comprises also three spaced, reference stations 5, 6 and 7 which are separate and self-contained with respect to each other and which are spaced around the boundary 10 of a lawn L of a garden G, whilst the mower 1 constitutes a mobile work station.
  • the three reference stations 5 to 7 are located at convenient positions on the lawn boundary 10 and may be mounted on posts, although this is not absolutely necessary.
  • the reference stations 5 to 7 are provided with rechargeable batteries, using solar power for recharging and/or operating.
  • the precise positions of the fixed reference stations 5 to 7 are not critical, provided that they are reasonably spread out and fixed in position once installed.
  • the system is subjected to a calibration phase wherein the mower 1 is placed randomly between the three fixed reference stations 5 to 7 on the lawn, as shown in the drawing.
  • the microprocessor unit of the mower 1 activates and interrogates each station 5 to 7, such that the mower can determine its distance from and bearing with respect to each of the reference stations.
  • the mower 1 localises itself with respect to the fixed reference stations 5 to 7 and, to a certain extent, with respect to the shape of the lawn L to be mowed.
  • the reference stations 5 to 7 can communicate ultrasonically with each other, to determine their relative spacings and bearings with respect to each other, with the relevant information being transmitted to the mower 1, to assist in determining or confirm determination of its di ⁇ tancings and bearings from the reference stations.
  • each fixed reference station 5 to 7 may require only to measure its distance from the other fixed stations and, thus, has only one ultrasonic receiving transducer (monaural), the mower 1 (mobile station) ha ⁇ two ⁇ uch transducers 21 (multiaural).
  • the mower 1 to determine not only its di ⁇ tance from and bearing with respect to each of the fixed stations 5 to 7 but also it ⁇ body orientation in ⁇ pace.
  • At least one of the reference stations 5 to 7 and/or the mobile work station, in this case, the mower 1, may be provided with a single transducer arranged to transmit and/or receive radiation in an omnidirectional manner using a suitable "horn" arrangement, preferably of cylindrical construction.
  • a so-called “learning phase” is carried out, whereby the mower 1 is ⁇ teered manually around the boundary 10 of the lawn L, commencing with the largest enclosed area, namely, the lawn itself in this particular case. This may or may not be carried out during an initial mowing operation.
  • Internal boundaries, ⁇ uch as island beds or trees T, within the boundary 10 of the lawn L are also included in thi ⁇ learning pha ⁇ e, ⁇ o that the microproce ⁇ or control unit of the mower 1 monitors continuou ⁇ ly it ⁇ position during thi ⁇ pha ⁇ e and, on completion, is able to define for it ⁇ elf a working area within ⁇ pecified boundarie ⁇ .
  • control unit of the mower 1 is able to steer the latter, ⁇ uch that it mow ⁇ only the lawn defined by that model or map.
  • the control unit may al ⁇ o be programmed to cau ⁇ e the mower 1 to mow the lawn L in any desired pattern, for instance, spirally or striped.
  • Thi ⁇ learning pha ⁇ e can be extended by the user moving the mower 1 manually over the entirety of the lawn L in a mowing pattern which is monitored by and stored in the mower's control unit, to provide an internal model or map thereof. Subsequently, the mower 1 can then move itself to the start of or an intermediate point on the pattern using the stored information determined by previous communication with the reference stations 5 to 7, for example, in the calibration phase, ⁇ o that it can then replicate the mowing pattern from the start or intermediate point thereof.
  • the mower 1 could use this internal model or map to determine its body orientation and, also, use the stereophonic principle to determine its position with respect to a ⁇ ingle fixed reference ⁇ tation 5 to 7 which i ⁇ still operational.
  • FIG 3 there i ⁇ ⁇ hown diagrammatically one of the fixed reference ⁇ tations 5 to 7 which comprise ⁇ an ultra ⁇ onic tran ⁇ ducer 31 which i ⁇ used for both the reception and tran ⁇ mi ⁇ ion of ultrasonic radiation from and to and the mower 1 and, optionally, the fixed stations.
  • An omnidirectional resonant cavity or horn 32 allows omnidirection receipt and transmission of ultra ⁇ onic radiation without ⁇ ignificant lo ⁇ se ⁇ .
  • a microprocessor 33 drives ultrasonic tran ⁇ mi ⁇ ion pul ⁇ e ⁇ directly off "TTL" and ⁇ en ⁇ es "TTL" logic level ⁇ on an amplified input signal from the transducer 31 via a tuned analogue amplifier 34.
  • the microproce ⁇ or 33 i ⁇ al ⁇ o able to ⁇ witch off power to at lea ⁇ t the amplifier E, thereby ⁇ aving power.
  • a solar cell 35 and rechargeable battery 36 enable maintenance-free operation of the station which i ⁇ ⁇ upported, in use, upon a fixing post 37.
  • a rotary cutting device 44 i ⁇ provided at the front of the mower 1 adjacent a pair of wheels 45 having wheel movement ⁇ en ⁇ or ⁇ (not ⁇ hown).
  • An auxiliary motor 47 for driving the rotary cutting device 44 i ⁇ provided, along with a rechargeable battery 48, a microproce ⁇ or 49, an analogue motor control 50 and a ⁇ olar panel 52.
  • Two ultrasonic transducer arrangements 51 each similar to the corresponding arrangement for each fixed ⁇ tation 5 to 7, a ⁇ described above in relation to Figure 3, receive and transmit ultrasonic radiation from and to the fixed reference ⁇ tation ⁇ 5 to 7.
  • the main drive motor ⁇ 42 are controllable independently of each other and rotation thereof i ⁇ ⁇ en ⁇ ed, ⁇ o a ⁇ to allow the microprocessor 49 to maintain a dynamic model of the movement of the mower 1. Rotation of the front wheels 45 i ⁇ al ⁇ o monitored to determine di ⁇ tance ⁇ moved by the mower 1.
  • the moving mower 1 i ⁇ communicating ultra ⁇ onically with the fixed reference ⁇ tations 5 to 7 by actuating and interrogating them to maintain it ⁇ locali ⁇ ing function with re ⁇ pect thereto.
  • the calibration pha ⁇ e only require ⁇ repeating if a fixed ⁇ tation 5 to 7 i ⁇ moved, whil ⁇ t the learning pha ⁇ e need ⁇ to be repeated if the working area of the lawn L i ⁇ changed.
  • the mower 1 As the mower 1 moves over the lawn L, it tran ⁇ mit ⁇ a master pulse and al ⁇ o "listens" stereophonically for any reflected pul ⁇ e ⁇ , thereby detecting the pre ⁇ ence and po ⁇ ition of any ob ⁇ tacle in it ⁇ path of movement.
  • the fixed reference stations 5 to 7 are interrogated by the mower 1, they are "silent" for long enough for all ultrasonic echoes to decay to insignificant level ⁇ .
  • the preprogrammed timing of the fixed reference ⁇ tation ⁇ 5 to 7 then cau ⁇ e ⁇ one of them to transmit a pulse which i ⁇ detected and proce ⁇ sed by the mower 1. Then, the other reference ⁇ tation ⁇ take their turn to tran ⁇ mit ⁇ uccessive ultra ⁇ onic pul ⁇ e ⁇ to the mower 1, so that the latter i ⁇ able to determine an accurate di ⁇ tance and bearing with re ⁇ pect to tho ⁇ e ⁇ tations. The mower 1 then retran ⁇ it ⁇ the master pulse and the cycle is repeated, thereby locali ⁇ ing the po ⁇ ition of the mower with re ⁇ pect to the fixed reference ⁇ tations 5 to 7 and, hence, the lawn L.
  • the orientation in ⁇ pace of the body 3, 43 of the mower 1 i ⁇ determined stereophonically using the pair of ultrasonic transducer arrangements.
  • the master pulse transmitted by the mower 1 can be encoded with instructions to adju ⁇ t the waiting times of the respective reference ⁇ tation ⁇ 5 to 7, to e ⁇ tablish an optimum pulse cycle repeat rate as the mower moves across the lawn L.
  • the mower 1 can use it ⁇ internal dynamic model to compen ⁇ ate any errors in the locali ⁇ ing ⁇ y ⁇ tem. Any ⁇ uch errors can be detected and used to stop the mower 1 ⁇ o that it can then obtain a corrected "fix" with respect to the reference stations 5 to 7. Typically, two ⁇ uch error ⁇ are required before the mower 1 ⁇ top ⁇ and obtain ⁇ a corrected "fix" with reque ⁇ t to the reference ⁇ tations 5 to 7.
  • Absolute fixes may also be made conveniently at the end of each "run” of the mower when mowing in striped patterns.
  • the mower 1 doe ⁇ not nece ⁇ arily have to ⁇ top to obtain a corrected "fix".
  • it under ⁇ tand ⁇ it ⁇ wheel movement ⁇ to be correct during each ultra ⁇ onic cycle and can ⁇ olve for it ⁇ late ⁇ t ab ⁇ olute po ⁇ ition whil ⁇ t moving.
  • the main reason for this process to fail would be slippage of a wheel 4 during a ⁇ onic cycle.
  • two ⁇ uch corrective failure ⁇ are required before the mower 1 ⁇ top ⁇ and obtain ⁇ a corrected ⁇ tationary "fix".
  • the mower 1 may be ⁇ tored in, say, a shed S, when not in use, and then brought out on to the lawn L via a path P, when required to mow the lawn.
  • control unit of the mower 1 can be programmed to operate the latter at periodic time interval ⁇ , with due regard to the weather, to mow the working area of the lawn L, return to the ⁇ hed S (home base) after the mowing operation and then recharge its power ⁇ ource.
  • the mower' ⁇ control unit may be programmed during the learning pha ⁇ e, to differentiate path ⁇ from lawn working area ⁇ , to that it ⁇ gra ⁇ s cutting device i ⁇ not operational whil ⁇ t the mower 1 i ⁇ on a path.
  • an optional dump mode allows the mower's control unit to be programmed to recognise the location of a dump where gras ⁇ cuttings can be dumped. Such a location, as well a ⁇ tho ⁇ e of any connecting path( ⁇ ) and the configuration thereof, i ⁇ included in the model or map generated during the learning pha ⁇ e, a ⁇ di ⁇ cu ⁇ ed above.
  • Specific in ⁇ truction ⁇ may be given to the mower' ⁇ control unit by an operator using either a control panel on the mower or a hand-held, remote programmer or personal computer, instructing the mower to, say, mow or not mow particular portion ⁇ of the working area of the lawn or to mow to a particular pattern.
  • the accuracy of the ⁇ yste is substantially independent of the speed of the ultrasonic radiation in air, which can vary considerably due to temperature, humidity and/or wind direction changes, because all the di ⁇ tance measurement ⁇ carried out by the mobile station (mower).
  • the mower 1 i ⁇ al ⁇ o able to detect ultra ⁇ onically any foreign body in it ⁇ path on the lawn L, whereby it can be stopped quickly.
  • a mechanical fail-safe arrangement such as a ⁇ , micro ⁇ witche ⁇ , may be employed.
  • inventive locali ⁇ ing system described above in relation to the drawing u ⁇ e ⁇ ultra ⁇ onic radiation for communication between the mower 1 and/or the fixed reference station ⁇ 5 to 7, other form ⁇ of radiation, ⁇ uch a ⁇ , electromagnetic radiation, may be employed.
  • a po ⁇ ible modification of the ultrasonic arrangement described above would be to add electromagnetic radiation to allow a faster fix at an ab ⁇ olute position.
  • the mobile ⁇ tation emit ⁇ an ultra ⁇ onic pul ⁇ e whilst at a position A, possibly whil ⁇ t in motion.
  • Each fixed reference station receive the pul ⁇ e, wait ⁇ a period of time ⁇ pecific to it ⁇ elf to avoid cla ⁇ he ⁇ and then emit ⁇ an electromagnetic pulse.
  • the mobile ⁇ tation receives the electromagnetic pul ⁇ e and, as the transmission time is negligible compared with the ultra ⁇ onic pul ⁇ e ⁇ , can determine the time taken for the pulse emitted at position A to reach each fixed ⁇ tation. From thi ⁇ , po ⁇ ition A can be determined by trilineation.
  • a pa ⁇ ive light beam arrangement for the fixed reference ⁇ tation ⁇ 5 to 7 could be used analogous to the intelligent ultrasonic arrangement discus ⁇ ed above, in that the ⁇ tation po ⁇ ition ⁇ are "learnt" by the mobile ⁇ tation but where the fixed stations are merely light beam reflectors, namely, reflective cams or tri-cornered reflector ⁇ designed to return a beam in the reverse direction irre ⁇ pective of it ⁇ incidence angle, ⁇ uch a beam may be in the invi ⁇ ible infra-red range.
  • the mobile ⁇ tation senses the angular direction of ⁇ uch "pa ⁇ ive" ⁇ tation ⁇ and, optionally, the time-of-flight of a light pul ⁇ e in order to determine a range.
  • an infra-red light- emitting diode and a matching photoelectric ⁇ en ⁇ or diode are mounted pointing vertically at a rotating pri ⁇ m or mirror rotating at a comparatively ⁇ low rate of, ⁇ ay, 1-lOHz and it ⁇ angular po ⁇ ition ⁇ en ⁇ ed to the required accuracy.
  • the pri ⁇ m angle needs to be ⁇ en ⁇ ed to 1/20th of a degree (3 inute ⁇ ), that is to say, 10,000 angular positions per revolution would be adequate.
  • the background light level i ⁇ ea ⁇ ured at the ⁇ en ⁇ or diode, a pul ⁇ e of light i ⁇ emitted and a timer ⁇ tarted At each graticule po ⁇ ition, the background light level i ⁇ ea ⁇ ured at the ⁇ en ⁇ or diode, a pul ⁇ e of light i ⁇ emitted and a timer ⁇ tarted.
  • the return pul ⁇ e By monitoring the ⁇ ensor diode output during the maximum expected two-way flight time of the pulse, namely, the next 70ns for a 10m range, the return pul ⁇ e will be detected again ⁇ t the background, ⁇ hould the fixed ⁇ tation be at thi ⁇ angular po ⁇ ition.
  • the time of flight of the pul ⁇ e give ⁇ an approximate range for the reflection and thi ⁇ , plu ⁇ the knowledge of the expected approximate angular po ⁇ ition, will aid po ⁇ itive identification of a true fixed station reflection.
  • the light pul ⁇ e i ⁇ directed horizontally in all direction ⁇ by a conical mirror and the returning light directed down by the ⁇ ame mirror on to an annulus of charge- coupled ⁇ en ⁇ itive element ⁇ , similar to tho ⁇ e u ⁇ ed in cameras.
  • the annular array of element ⁇ is exposed and the background inten ⁇ ities noted.
  • the annular array is then cleared and the light pul ⁇ e emitted.
  • the content ⁇ of the array are again noted.
  • the fir ⁇ t ⁇ et of calibration data i ⁇ then subtracted, giving the return intensities due to the light pulse.
  • Fixed ⁇ tation ⁇ are identified by intensity level and approximate annular po ⁇ ition and an accurate fixed obtained, again, by triangulation.
  • An active light beam arrangement for the fixed ⁇ tation ⁇ similar to the passive arrangement can be employed although the mobile station simply senses the light pulse ⁇ and has no tran ⁇ mi ⁇ ion capability.
  • the light pulse ⁇ are emitted periodically by active fixed reference stations equipped with light-emitting diodes and, perhaps, powered by solar energy.
  • Each ⁇ tation has a different periodicity, enabling it to be easily identified from background light sources. In thi ⁇ case an exact po ⁇ ition i ⁇ calculated by triangulation once again.
  • the ⁇ ame "learnt" reference arrangement can be implemented u ⁇ ing active radio frequency fixed station ⁇ transmitting at different known frequencies.
  • the mobile ⁇ tation i ⁇ By ⁇ ensing the phase difference of the incident wave on a pair of aerials, the mobile ⁇ tation i ⁇ able to deduce the angular po ⁇ ition of a particular fixed station and by using three or more ⁇ uch ⁇ tation ⁇ , the mobile ⁇ tation i ⁇ able to calculate an exact po ⁇ ition by trilineation.
  • FIG. 5 shows respective flowcharts for typical command sequences of the control unit of the mower 1 or other mobile work station and a reference ⁇ tation 5 to 7, wherein the mower is referred to a ⁇ the "mobile unit” and the reference ⁇ tation a ⁇ a "beacon".

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Automation & Control Theory (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Acoustics & Sound (AREA)
  • Control Of Position, Course, Altitude, Or Attitude Of Moving Bodies (AREA)

Abstract

Système de localisation et procédé adaptés pour être utilisés avec une tondeuse robotisée (1), dans lequel une pluralité de postes de référence espacés (5 à 7) sont associés à une zone (L) sur laquelle travaille un poste de travail mobile (tondeuse 1) selon des positions données par rapport à celle-ci, et dans lequel le poste de travail mobile (1) communique avec un, deux ou plusieurs postes de référence espacés (5 à 7) et ceci afin de calculer sa distance et son orientation par rapport à ceux-ci. Ceci permet de localiser la position du poste de travail mobile (1) par rapport à la zone de travail (pelouse L). Ce calcul permet au poste de travail mobile (1) d'accomplir une tâche sur au moins une partie de la zone de travail (L) de manière dirigée.
PCT/GB1994/000710 1993-04-03 1994-03-31 Systeme de localisation WO1994023351A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU63834/94A AU6383494A (en) 1993-04-03 1994-03-31 Localising system

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB9307084.5 1993-04-03
GB939307084A GB9307084D0 (en) 1993-04-03 1993-04-03 Localising system
GB939313295A GB9313295D0 (en) 1993-04-03 1993-06-28 Localising system
GB9313295.9 1993-06-28

Publications (1)

Publication Number Publication Date
WO1994023351A1 true WO1994023351A1 (fr) 1994-10-13

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Application Number Title Priority Date Filing Date
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Country Status (3)

Country Link
AU (1) AU6383494A (fr)
GB (1) GB2277152A (fr)
WO (1) WO1994023351A1 (fr)

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CN109005867A (zh) * 2018-08-02 2018-12-18 苏州科瓴精密机械科技有限公司 充电站及具有该充电站的智能机器人***
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Publication number Priority date Publication date Assignee Title
DE102007000280A1 (de) 2007-05-21 2008-11-27 Hilti Aktiengesellschaft Selbstfahrende Beton-Schleifmaschine
DE102008009208A1 (de) * 2008-02-15 2009-08-20 Gunter Arnold Navigationssystem für einen autonomen mobilen Roboter, insbesondere Rasenmähroboter
US11252863B2 (en) 2015-12-06 2022-02-22 Robotic Lawn Care Sweden Ab System for mowing lawns with robotic lawn mowers and a charging mobile carrier
EP4270140A2 (fr) 2015-12-06 2023-11-01 Robotic Lawn Care Sweden AB Procédé et dispositif pour tondre des gazons
CN109005867A (zh) * 2018-08-02 2018-12-18 苏州科瓴精密机械科技有限公司 充电站及具有该充电站的智能机器人***
CN109005867B (zh) * 2018-08-02 2024-01-12 苏州科瓴精密机械科技有限公司 充电站及具有该充电站的智能机器人***

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Publication number Publication date
AU6383494A (en) 1994-10-24
GB9406452D0 (en) 1994-05-25
GB2277152A (en) 1994-10-19

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