Patent Description:
Automated or robotic power tools such as robotic lawn mowers are becoming increasingly more popular. In a typical deployment a work area, such as a garden, the work area is enclosed by a boundary wire with the purpose of keeping the robotic lawn mower inside the work area. An electric control signal may be transmitted through the boundary wire thereby generating an (electro-) magnetic field emanating from the boundary wire. The robotic working tool is typically arranged with one or more sensors adapted to sense the control signal.

The robotic lawn mower can then cut grass on a user's lawn automatically and can be charged automatically without intervention of the user, and no longer needs to be manually managed after being set once. The robotic lawn mower needs to have a function of recognizing an obstacle to avoid colliding with the obstacle before encountering the obstacle, and to have a function of recognizing that a collision has occurred.

In the latter case, a collision sensor can be disposed on the body of the robotic lawn mower, and when the robotic lawn mower collides with an obstacle, the body moves in such a way that the collision sensor generates a collision signal. In the former case, different kinds of environment detection sensors are use such as ultrasonic sensors as disclosed in <CIT> and radar sensors as disclosed in <CIT>.

<CIT> discloses a robotic work tool in the form of a robotic vacuum cleaner which have second and third sensor units disposed on the left and right sides of a first sensor unit, respectively, where signal radiation ranges are arranged to overlap each other. A fourth and fifth sensor units are used for detecting obstacles on the side of a housing and arranged at predetermined inclination angles on the outer surface of the housing, directed to point away from a forward travelling direction.

<CIT> relates to a floor cleaning robot comprising an obstacle sensing module including at least one group of light transmitting and receiving components. Each group of the light transmitting and receiving components includes a light emitting unit, comprising a first light emitter with a first light source and a second light emitter with a second light source. The first light emitter and the second light emitter alternately emit corresponding light beams successively.

There is, however, a need to improve the coverage, reliably and efficiency of such environment detection sensors such that all obstacles are detected in time such that a collision can be avoided by stopping the robotic lawn mower and/or turning the robotic lawn mower away from the obstacle.

The object of the present disclosure is to provide a robotic work tool with environment detection system that has an improved coverage, reliably and efficiency compared to prior art.

This object is achieved by means of an outdoor robotic work tool adapted for a forward travelling direction and comprising an environmental detection system that comprises a set of outer detector transceivers and a set of inner detector transceivers, where the inner detector transceivers are positioned between the outer detector transceivers. Each detector transceiver is adapted to transmit signals and to receive reflected signals that have been reflected by an object. The outer detector transceivers are associated with outer coverage main directions that are directed at corresponding outer angles to the forward travelling direction, and the inner detector transceivers are associated with inner coverage main directions that are directed at corresponding inner angles to the forward travelling direction. The inner angles have magnitudes that exceed the magnitudes of the outer angles, and the inner coverage main directions intersect in front of the outdoor robotic work tool in the forward travelling direction.

This means that a robotic work tool with an increased sensor coverage is provided, increasing the robotic work tool's ability to avoid collisions with other objects.

Each coverage main direction is associated with a corresponding transceiver coverage, where a combined rectangular coverage having a certain width is formed in front of the outdoor robotic work tool in the forward travelling direction, where the combined coverage comprises at least two separate transceiver coverages.

Forming such a combined area increases the reliability of the detections.

According to some aspects, the outer angles are of the same magnitude and the inner angles are of the same magnitude.

According to some aspects, the outer coverage main directions do not intersect in front of the outdoor robotic work tool in the forward travelling direction.

In this way an increased coverage is enabled.

According to some aspects, the outer coverage main directions are mutually parallel.

In this way, a desirable combined area is formed.

According to some aspects, the detector transceivers are adapted to transmit signals at least partly at the same time.

In this way, objects in front of the robotic work tool are detected in a quicker and more efficient manner.

According to some aspects, the detector transceivers are any one of radar transceivers, ultrasonic transceivers or Lidar transceivers.

This means that the present disclosure is applicable for many types of detector transceivers.

According to some aspects, the robotic work tool is a robotic lawn mower.

According to some aspects, the robotic work tool comprises a first outer detector transceiver, a second outer detector transceiver, a first inner detector transceiver and a second inner detector transceiver.

According to some aspects, the robotic work tool comprises a propulsion motor arrangement, a power source adapted to provide power to the propulsion motor arrangement and a plurality of wheels, where at least two wheels are adapted to be propelled by the propulsion motor arrangement. The robotic work tool further comprises a control unit that is adapted to control the detector transceivers and to control the speed and direction of the robotic work tool in dependence of information acquired by means of the of the detector transceivers when the robotic work tool is moving.

In this manner, a safe and reliable control of the robotic work tool is provided.

It should be noted that even though the description given herein will be focused on robotic lawn mowers, the teachings herein may also be applied to any type of outdoor robotic work tool, such as for example robotic ball collectors, robotic mine sweepers and robotic farming equipment.

<FIG> shows a top view of a robotic working tool <NUM>, <FIG> shows a front view of the robotic working tool <NUM> and <FIG> shows a bottom view of the robotic working tool <NUM>, here exemplified by a robotic lawn mower <NUM>. The robotic lawn mower <NUM> comprises a body 20a, 20b, a propulsion motor arrangement <NUM>, a power source <NUM> such as a rechargeable battery adapted to provide power to the propulsion motor arrangement <NUM>, and a plurality of wheels 17a, 17b; 21a, 21b, where two or more of the wheels, according to some aspects two rear wheels 21a, 21b, are adapted to be propelled by the propulsion motor arrangement <NUM>, enabling the robotic working tool <NUM> to move with respect to a forward travelling direction D. It is of course possible that all four wheels 17a, 17b; 21a, 21b are adapted to be propelled by the propulsion motor arrangement <NUM>.

The robotic lawn mower <NUM> also comprises a grass cutting device <NUM>, in this example a plurality of cutting blade arrangements driven by a cutter motor arrangement <NUM> that also is powered by the power source <NUM> or, alternatively, by a separate power source. The grass cutting device is an example of a general work tool for a robotic work tool.

According to some aspects, the propulsion motor arrangement <NUM> comprises one separate propulsion motor for each wheel 17a, 17b; 21a, 21b to be driven, and according to some further aspects, the cutter motor arrangement <NUM> comprises one separate cutter motor for each cutting blade arrangement.

It should be noted that even if the description herein is focused on electric motors, combustion engines may alternatively be used, possibly in combination with an electric motor.

The robotic lawn mower <NUM> further comprises a control unit <NUM>. The robotic lawn mower <NUM> may be a multi-chassis type or a mono-chassis type. A multi-chassis type comprises more than one body parts that are movable with respect to one another. A mono-chassis type comprises only one main body part. In this example there is a front body part 20a and a rear body part 20b.

The robotic lawn mower <NUM> typically comprises charging skids <NUM> for contacting contact plates in a charging station when docking into the charging station for receiving a charging current through, and possibly also for transferring information by means of electrical communication between the charging station and the robotic lawn mower <NUM>. Other means of establishing a charging contact are possible and are incorporated herein.

In a previously well-known manner, the robotic lawn mower <NUM> is adapted to navigate with reference to a boundary wire emitting a magnetic field caused by a control signal transmitted through the boundary wire. The robotic lawn mower is further configured to detect the magnetic field and for detecting the boundary wire, for example by means of one or more magnetic field sensors. It is also conceivable that the robotic lawn mower <NUM> is adapted to navigate without a boundary wire, other navigation systems are conceivable, for example navigation systems based on GPS and/or one or more wireless communication systems.

The robotic lawn mower <NUM> further comprises an environmental detection system <NUM> that comprises a set of outer detector transceivers 2a, 2b and a set of inner detector transceivers 3a, 3b. The inner detector transceivers 3a, 3b are positioned between the outer detector transceivers 2a, 2b along an extension E that is perpendicular to the forward travelling direction D. According to some aspects, all detector transceivers 2a, 2b; 3a, 3b are positioned along the extension E, and one or more detector transceiver can according to some further aspects be mutually displaced along the forward travelling direction D. In this example the inner detector transceivers 3a, 3b are displaced along the forward travelling direction D with respect to the outer detector transceivers 2a, 2b as will be discussed more later.

It is also conceivable that the detector transceivers 2a, 2b; 3a, 3b are positioned along an extension that is inclined with respect to the forward travelling direction D, or that the detector transceivers 2a, 2b; 3a, 3b are positioned in an irregular manner. According to some aspects, the inner detector transceivers 3a, 3b are positioned between the outer detector transceivers 2a, 2b along an extension and one or more detector transceiver can according to some further aspects be mutually displaced in a direction perpendicular to that extension. That extension can be any suitable extension, not having to be the extension E that is perpendicular to the forward travelling direction D.

With reference also to <FIG>, Each detector transceiver 2a, 2b; 3a, 3b is adapted to transmit signals 4a, 4b; 5a, 5b and to receive reflected signals 6a, 6b, <NUM> that have been reflected by an object <NUM>, <NUM>. According to some aspects, the detector transceivers 2a, 2b; 3a, 3b are ultrasonic detector transceivers, being adapted to transmit and receive ultrasonic signals. This should not be regarded as limiting; the detector transceivers 2a, 2b; 3a, 3b can of any suitable kind such as for example radar transceivers or Lidar transceivers, applying a corresponding well-known technology for transmitting and receiving reflected signals. To enable this, according to some aspects, each detector transceiver 2a, 2b; 3a, 3b comprises a corresponding transmitter arrangement and receiver arrangement together with other necessary circuitry in a well-known manner.

The detector transceivers 2a, 2b; 3a, 3b can be arranged in many ways within the scope of the present disclosure, according to some aspects there is a first outer detector transceiver 2a, a second outer detector transceiver 2b, a first inner detector transceiver 3a and a second inner detector transceiver 3b. According to some aspects, all detector transceivers 2a, 2b; 3a, 3b are positioned at a common horizontal level L as indicated in <FIG>. Other position arrangements are of course conceivable.

With reference also to <FIG>, the outer detector transceivers 2a, 2b are associated with outer coverage main directions 7a, 7b that are directed at corresponding outer angles αa, αb to the forward travelling direction D, and the inner detector transceivers 3a, 3b are associated with inner coverage main directions 8a, 8b that are directed at corresponding inner angles βa, βb to the forward travelling direction D.

According to the present disclosure, the inner angles βa, βb have magnitudes that exceed the magnitudes of the outer angles αa, αb, and the inner coverage main directions 8a, 8b intersect in front of the outdoor robotic work tool <NUM> in the forward travelling direction D. According to some aspects, the outer angles αa, αb are of the same magnitude and the inner angles βa, βb are of the same magnitude.

In <FIG>, in accordance with some aspects, the outer angles αa, αb are zero degrees, the outer coverage main directions 7a, 7b being parallel and coinciding with the forward travelling direction D. In <FIG>, in accordance with some aspects, the outer angles αa, αb have a certain magnitude and are directed such that the outer coverage main directions 7a, 7b do not intersect in front of the outdoor robotic work tool <NUM> in the forward travelling direction D. It is also conceivable that the outer coverage main directions 7a, 7b do intersect in front of the outdoor robotic work tool <NUM>.

As only shown in <FIG> for reasons of clarity, according to some aspects, each coverage main direction 7a, 7b; 8a, 8b is associated with a corresponding transceiver coverage 12a, 12b; 13a, 13b, where the associated main direction 7a, 7b; 8a, 8b indicates a direction in which that transceiver coverage 12a, 12b; 13a, 13b has a maximum range. A combined rectangular coverage <NUM>, having a certain width w, is formed in front of the outdoor robotic work tool <NUM> in the forward travelling direction D, where the combined coverage <NUM> comprises at least two separate transceiver coverages 12a, 12b; 13a, 13b. According to the invention, the width w is equal to or exceeds to a maximum width of the robotic lawn mower <NUM>, where said width w extends in a direction orthogonal to the forward travelling direction D. In <FIG>, the width w is shown to exceed the maximum width of the robotic lawn mower <NUM>.

By means of the relation of the coverage main directions 7a, 7b; 8a, 8b, a larger combined rectangular coverage <NUM>, comprising at least two separate transceiver coverages 12a, 12b; 13a, 13b, is achieved than previously possible. This enables objects in the path of the robotic lawn mower <NUM> to be detected in an efficient and reliable manner, in particular earlier than previously possible, such that all obstacles are detected in time such that a collision can be avoided by stopping the robotic lawn mower <NUM> and/or turning the robotic lawn mower <NUM> away from the obstacle.

For this purpose, as shown in <FIG> and <FIG>, the robotic lawn mower <NUM> comprises a control unit <NUM> that is adapted to control the detector transceivers 2a, 2b; 3a, 3b and to control the speed and direction of the robotic work tool <NUM> in dependence of information acquired by means of the of the detector transceivers 2a, 2b; 3a, 3b when the robotic lawn mower <NUM> is moving. The control unit <NUM> can be constituted by several separate control sub-units or one single integrated control unit. The control unit <NUM> is adapted to perform all necessary signal processing necessary for controlling the detector transceivers 2a, 2b; 3a, 3b and to acquire the desired information from the detected measurement results.

Should a collision occur anyway, at least the front body part 20a is movable and in contact with a collision sensor <NUM> as illustrated in <FIG> and being adapted to detect that the front body part 20a has been displaced to such a degree that a collision most likely has occurred. One or more collision sensors can be used for each one body part, preferably all body parts 20a, 20b, here only one collision sensor <NUM> is shown as an example. The control unit <NUM> that is adapted to control the speed and direction of the robotic work tool <NUM> in dependence of information from said collision sensor <NUM> well, for example to reverse the movement direction when a possible collision has been detects.

As indicated in <FIG>, in accordance with some aspects, the robotic lawn mower <NUM> comprises a handle part <NUM> that is provided for lifting and handling the robotic lawn mower <NUM> when necessary, for example for service, inspection and/or cleaning. The handle part <NUM> is placed closer to the ground than the detector transceivers 2a, 2b; 3a, 3b when the robotic lawn mower <NUM> is operating, and is positioned in a front recess <NUM> such that it does not protrude as a frontmost part. This means that the first outer detector transceiver 2a and the second outer detector transceiver 2b are positioned closer to a front line F of the robotic lawn mower <NUM> than the first inner detector transceiver 3a and the second inner detector transceiver 3b, and in other words, the inner detector transceivers 3a, 3b are displaced along the forward travelling direction D with respect to the outer detector transceivers 2a, 2b.

As a consequence, the handle part <NUM> does not disturb the operation of the inner detector transceivers 3a, 3b, and the front recess <NUM> is formed such that the front body parts 20a does not disturb the operation of the inner detector transceivers 3a, 3b, mainly by causing unwanted reflections. By means of the present design, a front wheel pair 17a, 17b, the so-called caster wheels 17a, 17b, can be arranged as close to the front line F as possible and as spaced apart as possible for increased stability of the robotic lawn mower <NUM>.

In accordance with some further aspects of the present disclosure, with reference to in particular <FIG>, the detector transceivers 2a, 2b; 3a, 3b are adapted to transmit signals 4a, 4b; 5a, 5b at the same time. This means that in the illustrated example, where there is a first object <NUM> and a second object <NUM> in front of the robotic lawn mower <NUM>, the first object <NUM> will be detected by the first outer detector transceiver 2a by means of a first signal 4a transmitted by the first outer detector transceiver 2a that results in a second signal 6a, reflected from the first object <NUM>, that is received by the first outer detector transceiver 2a.

Furthermore, the second object <NUM> will be detected by the second outer detector transceiver 2b since a third signal 5a transmitted by the first inner detector transceiver 3a results in a fourth signal 6b, reflected from the second object <NUM>, that is received by the second outer detector transceiver 2b. The second object <NUM> will also be detected by the first inner detector transceiver 3a since a fifth signal 4b transmitted by the second outer detector transceiver 2b results in a sixth signal <NUM>, reflected from the second object <NUM>, that is received by the first inner detector transceiver 3a.

Since the detector transceivers 2a, 2b; 3a, 3b are adapted to transmit signals 4a, 4b; 5a, 5b at the same time, detection of reflected signals will indicate the presence of one or more objects ahead, but not more specific details such as for example azimuth heading and/or distance, since a signal received at one detector transceivers can result from a signal transmitted from any one of the detector transceivers 2a, 2b; 3a, 3b. Normally it is sufficient for a robotic lawn mower <NUM> to be informed about the fact that there is one or more objects ahead in order to avoid a collision. Should a more specific detection be desired and/or required, each detector transceivers 2a, 2b; 3a, 3b can be adapted to transmit specific signals, such that a received signal can be identified with respect to its transmitting detector transceivers 2a, 2b; 3a, 3b. Such an identification can for example be accomplished by means of utilizing different waveforms or embedded identifications codes for the transmitted signals 4a, 4b, 5a, 5b.

Generally, at least two detector transceivers 2a, 2b; 3a, 3b are adapted to transmit signals 4a, 4b; 5a, 5b and to receive reflected signals 6a, 6b, <NUM> that have been reflected by an object <NUM>, <NUM>, where the detector transceivers 2a, 2b; 3a, 3b are adapted to transmit signals 4a, 4b; 5a, 5b at least partly at the same time. This means that several alternatives are possible, separately or in combination. For example:.

This means that the simultaneous transmission can be adapted either for different need that arise in dependence of detection results and/or in dependence of a certain predetermined scheduling.

Having a signal transmitted by one detector transceiver 2a, 2b; 3a, 3b being detectable by any one of the detector transceivers 2a, 2b; 3a, 3b increases the possibility that an object <NUM>, <NUM> in front of the robotic lawn mower <NUM> is detected.

It should be noted that the second inner detector transceiver 3b transmits a signal 5b where the transceiver coverage 13b indicated in <FIG> implies that the signal 5b will be reflected by the first object <NUM>, but where a reflected signal will travel away from the robotic lawn mower <NUM> and not be detected by any detector transceiver.

<FIG> schematically illustrates, in terms of a number of functional units, the components of the control unit <NUM> according to embodiments of the discussions herein. Processing circuitry <NUM> is provided using any combination of one or more of a suitable central processing unit CPU, multiprocessor, microcontroller, digital signal processor DSP, etc., capable of executing software instructions stored in a computer program product, e.g. in the form of a storage medium <NUM>. The processing circuitry <NUM> may further be provided as at least one application specific integrated circuit ASIC, or field programmable gate array FPGA. The processing circuitry thus comprises a plurality of digital logic components.

Particularly, the processing circuitry <NUM> is configured to cause the control unit <NUM> to perform a set of operations, or steps to control the operation of the robotic lawn mower <NUM> including, but not being limited to, controlling the detector transceivers 2a, 2b; 3a, 3b, processing measurements results received via the detector transceivers 2a, 2b; 3a, 3b, and the propulsion of the robotic lawn mower1.

According to some aspects, the control unit <NUM> further comprises an interface <NUM> for communications with at least one external device such as a control panel <NUM> or an external device. As such the interface <NUM> may comprise one or more transmitters and receivers, comprising analogue and digital components and a suitable number of ports for wireline communication. The interface <NUM> can be adapted for communication with other devices <NUM>, such as a server, a personal computer or smartphone, the charging station, and/or other robotic working tools. Examples of such wireless communication devices are Bluetooth®, WiFi® (IEEE802.11b), Global System Mobile (GSM) and LTE (Long Term Evolution), to name a few.

<FIG> shows a computer program product <NUM> comprising computer executable instructions <NUM> stored on media <NUM> to execute any of the methods disclosed herein.

With reference to <FIG>, the present disclosure also relates to a method in an outdoor robotic work tool <NUM> adapted for a forward travelling direction D, where the method comprises transmitting and receiving S100 reflected signals 6a, 6b, <NUM> that have been reflected by an object <NUM>, <NUM> using at least two detector transceivers 2a, 2b; 3a, 3b, and transmitting S200 signals 4a, 4b; 5a, 5b at all detector transceivers 2a, 2b; 3a, 3b at least partly at the same time.

According to some aspects, the method further comprises transmitting S210 signals at the same time at all detector transceivers 2a, 2b; 3a, 3b.

According to some aspects, the method further comprises transmitting S220 signals at the same time at two or more detector transceivers, in the same or in different constellations at different times.

According to some aspects, the method further comprises transmitting S230 signals at only one detector transceiver 2a, 2b; 3a, 3b at a time at certain times.

According to some aspects, the method further comprises transmitting S240 a signal comprising a specific signal identification at each detector transceiver 2a, 2b; 3a, 3b, such that a received signal can be identified with respect to its transmitting detector transceiver 2a, 2b; 3a, 3b.

According to some aspects, the signal identification is accomplished by means of utilizing different waveforms or embedded identifications codes.

Generally, the present disclosure relates to an outdoor robotic work tool <NUM> adapted for a forward travelling direction D and comprising an environmental detection system <NUM> that comprises a set of outer detector transceivers 2a, 2b and a set of inner detector transceivers 3a, 3b, where the inner detector transceivers 3a, 3b are positioned between the outer detector transceivers 2a, 2b. Each detector transceiver 2a, 2b; 3a, 3b is adapted to transmit signals 4a, 4b; 5a, 5b and to receive reflected signals 6a, 6b, <NUM> that have been reflected by an object <NUM>, <NUM>. The outer detector transceivers 2a, 2b are associated with outer coverage main directions 7a, 7b that are directed at corresponding outer angles αa, αb to the forward travelling direction D, and the inner detector transceivers 3a, 3b are associated with inner coverage main directions 8a, 8b that are directed at corresponding inner angles βa, βb to the forward travelling direction D. The inner angles βa, βb have magnitudes that exceed the magnitudes of the outer angles αa, αb, and the inner coverage main directions 8a, 8b intersect in front of the outdoor robotic work tool <NUM> in the forward travelling direction D.

According to the invention, each coverage main direction 7a, 7b; 8a, 8b is associated with a corresponding transceiver coverage 12a, 12b; 13a, 13b, where a combined rectangular coverage <NUM> having a certain width w is formed in front of the outdoor robotic work tool <NUM> in the forward travelling direction D. The combined coverage <NUM> comprises at least two separate transceiver coverages 12a, 12b; 13a, 13b.

According to some aspects, the outer angles αa, αb are of the same magnitude and the inner angles βa, βb are of the same magnitude.

According to some aspects, the outer coverage main directions 7a, 7b do not intersect in front of the outdoor robotic work tool <NUM> in the forward travelling direction D.

According to some aspects, the outer coverage main directions 7a, 7b are mutually parallel.

According to some aspects, the detector transceivers 2a, 2b; 3a, 3b are adapted to transmit signals 4a, 4b; 5a, 5b at least partly at the same time.

According to some aspects, the detector transceivers 2a, 2b; 3a, 3b are any one of radar transceivers, ultrasonic transceivers or Lidar transceivers.

According to some aspects, the robotic work tool <NUM> is a robotic lawn mower.

According to some aspects, the robotic work tool <NUM> comprises a first outer detector transceiver 2a, a second outer detector transceiver 2b, a first inner detector transceiver 3a and a second inner detector transceiver 3b.

According to some aspects, the robotic work tool <NUM> comprises a propulsion motor arrangement <NUM>, a power source <NUM> adapted to provide power to the propulsion motor arrangement <NUM>, a plurality of wheels 17a, 17b; 21a, 21b where at least two wheels are adapted to be propelled by the propulsion motor arrangement <NUM>, and a control unit <NUM> that is adapted to control the detector transceivers 2a, 2b; 3a, 3b and to control the speed and direction of the robotic work tool <NUM> in dependence of information acquired by means of the of the detector transceivers 2a, 2b; 3a, 3b when the robotic work tool <NUM> is moving.

Generally, the present disclosure additionally presents a non claimed outdoor robotic work tool <NUM> adapted for a forward travelling direction D and comprising an environmental detection system that comprises at least two detector transceivers 2a, 2b; 3a, 3b that are adapted to transmit signals 4a, 4b; 5a, 5b and to receive reflected signals 6a, 6b, <NUM> that have been reflected by an object <NUM>, <NUM>. The detector transceivers 2a, 2b; 3a, 3b are adapted to transmit signals 4a, 4b; 5a, 5b at least partly at the same time.

The robotic work tool <NUM> comprises a set of outer detector transceivers 2a, 2b, a set of inner detector transceiver 3a, 3b, where the inner detector transceivers 3a, 3b are positioned between the outer detector transceivers 2a, 2b, where the outer detector transceivers 2a, 2b are associated with outer coverage main directions 7a, 7b that are directed at corresponding outer angles αa, αb to the forward travelling direction D, and the inner detector transceivers 3a, 3b are associated with inner coverage main directions 8a, 8b that are directed at corresponding inner angles βa, βb to the forward travelling direction D, wherein the inner angles βa, βb have magnitudes that exceed the magnitudes of the outer angles αa, αb, and where the inner coverage main directions 8a, 8b intersect in front of the outdoor robotic work tool <NUM> in the forward travelling direction D.

According to some aspects, the detector transceivers 2a, 2b; 3a, 3b are adapted to transmit signals at the same time at all detector transceivers 2a, 2b; 3a, 3b.

According to some aspects, the detector transceivers 2a, 2b; 3a, 3b are adapted to transmit signals at the same time at two or more detector transceivers, in the same or in different constellations at different times.

According to some aspects, the detector transceivers 2a, 2b; 3a, 3b are adapted to transmit signals at only one detector transceiver 2a, 2b; 3a, 3b at a time at certain times.

According to some aspects, each detector transceiver 2a, 2b; 3a, 3b is adapted to transmit a signal comprising a specific signal identification, such that a received signal can be identified with respect to its transmitting detector transceivers 2a, 2b; 3a, 3b.

Claim 1:
An outdoor robotic work tool (<NUM>) adapted for a forward travelling direction (D) and comprising an environmental detection system (<NUM>) that comprises a set of outer detector transceivers (2a, 2b) and a set of inner detector transceivers (3a, 3b), where the inner detector transceivers (3a, 3b) are positioned between the outer detector transceivers (2a, 2b), where each detector transceiver (2a, 2b; 3a, 3b) is adapted to transmit signals (4a, 4b; 5a, 5b) and to receive reflected signals (6a, 6b, <NUM>) that have been reflected by an object (<NUM>, <NUM>), wherein the outer detector transceivers (2a, 2b) are associated with outer coverage main directions (7a, 7b) that are directed at corresponding outer angles (αa, αb) to the forward travelling direction (D), and the inner detector transceivers (3a, 3b) are associated with inner coverage main directions (8a, 8b) that are directed at corresponding inner angles (βa, βb) to the forward travelling direction (D), wherein the inner angles (βa, βb) have magnitudes that exceed the magnitudes of the outer angles (αa, αb), and where the inner coverage main directions (8a, 8b) intersect in front of the outdoor robotic work tool (<NUM>) in the forward travelling direction (D), wherein each coverage main direction (7a, 7b; 8a, 8b) is associated with a corresponding transceiver coverage (12a, 12b; 13a, 13b), where a combined rectangular coverage (<NUM>) having a certain width (w) is formed in front of the outdoor robotic work tool (<NUM>) in the forward travelling direction (D), where the combined coverage (<NUM>) comprises at least two separate transceiver coverages (12a, 12b; 13a, 13b), where the width (w) is equal to or exceeds to a maximum width of the robotic work tool (<NUM>), where said width (w) extends in a direction orthogonal to the forward travelling direction (D).