Patent Description:
Many agricultural tasks to improve yield and quality of crops, or to harvest crops, (particularly soft fruit crops) require time consuming manual labour. However, many of the tasks required are repetitive and may therefore be suitable for help by autonomous machinery. Such autonomous machinery would typically be required to autonomously move around and between crops, and therefore presents a safety risk to people working in or around the crops or other users of the machinery.

<CIT> discloses a work vehicle including an electronic control system for automated driving that automatically drives the vehicle body. The electronic control system includes an obstacle detection module configured to detect presence or absence of an obstacle, and a contact avoidance control unit configured to perform, upon the obstacle detection module detecting an obstacle, contact avoidance control to keep the vehicle body from coming into contact with the obstacle. The obstacle detection module includes a plurality of obstacle searchers that are distributed on the front end portion and the right and left end portions of the vehicle body such that the front side and the right and left lateral sides of the vehicle body are search-target areas.

According to a first aspect, there is provided a mobile autonomous agricultural system comprising: a powered mobile unit for carrying agricultural equipment, and configured to move along rows of crops; at least one laser curtain sensor configured to project a laser curtain away from the mobile unit; a location module configured to monitor a location of the mobile unit relative to a row; a controller configured to control the travel of the mobile unit; a safety module configured to: receive a location signal from the location module related to the location of the mobile unit relative to a row, select a mode of operation to process the laser curtain in a predefined laser curtain pattern, based on the received location signal, each mode of operation corresponding to a different predefined laser curtain pattern, and to generate a safety output in response to determining that the laser curtain is interrupted within the laser curtain pattern.

The safety output may be a signal to control the mobile unit to slow or to stop. The mobile unit may comprise an arch profile extending along an axial direction.

The mobile autonomous agricultural system may comprise a plurality of laser curtain sensors distributed around the mobile unit configured together to form the laser curtain. Each laser curtain sensor may be configured to project a respective laser plane which overlaps with at least one other laser plane to form the laser curtain.

The safety module may be configured to select a default mode of operation unless any deviating criteria are met. The default mode may comprise processing the laser curtain in a laser curtain pattern which extends from the mobile unit in an axial direction up to a maximum axial distance from the mobile unit, and in a width direction, perpendicular to the axial direction, up to a maximum width distance from the mobile unit.

The deviating criteria may comprise a first deviating criterion comprising the mobile unit being controlled to move from one row to another row, wherein when the first deviating criterion is met, the safety mode is configured to select a crabbing mode. The crabbing mode may comprise processing the laser curtain in a laser curtain pattern which extends from the mobile unit along the axial direction up to a minimum axial distance, and in a width direction, perpendicular to the axial direction, up to a maximum width distance.

The deviating criteria may comprise a second deviating criterion comprising the mobile unit being controlled to approach a row, and the determining that the mobile unit is within a first threshold distance from an end of the row, such that when the mobile unit is determined to be within the first threshold distance from an end of a row, the safety module is configured to select an entry mode. The entry mode may comprise processing the laser curtain to the same extent as the default mode or a crabbing mode, but excluding from processing a channel in the laser curtain corresponding to the position of the row.

The deviating criteria may comprise a third deviating criterion comprising the mobile unit being within a second threshold distance from an end of a row or within the row, such that when the third deviating criterion is met, the safety module is configured to select a row mode. The row mode may comprise processing the laser curtain to form a laser curtain pattern which extends from the mobile unit along the axial direction up to a maximum axial distance, and in a width direction, perpendicular to the axial direction, up to a minimum width distance.

The mobile autonomous agricultural system may comprise at least one robot arm configured to perform agricultural tasks, and the safety output may be a signal to control the robot arms to stop.

For each mode of operation, each predefined laser curtain pattern, which the safety module is configured to process, may extend downwards from the laser curtain sensors, up to a threshold ground distance from the ground. The threshold distance may be <NUM>-<NUM> from the ground.

The laser curtain sensor may be configured to monitor and map the ground surface.

The safety module may be configured to dynamically alter the predefined laser curtain pattern for each mode of operation based on the mapped ground surface.

When the laser curtain sensor determines that there is an inclination in the local ground surface around the mobile unit beyond a threshold inclination, the safety module may be configured to dynamically alter the laser curtain pattern which is processed, by making an axial extent of the laser curtain pattern or a width extent, perpendicular to the axial direction, shorter.

According to a second aspect, there is provided a method of controlling a powered mobile unit of a mobile autonomous agricultural system according to any preceding claim, the mobile unit configured to carry agricultural equipment and configured to move along rows of crops, the method comprising: projecting a laser curtain away from the mobile unit; determining a location of the mobile unit relative to a row; selecting a mode of operation, to process the laser curtain in a predefined laser curtain pattern, based on the determined location of the mobile unit relative to the row, wherein each mode of operation comprises processing a different predefined laser curtain pattern; generating a safety output in response to determining that the laser curtain is interrupted within the laser curtain pattern.

The safety output may be a signal to control the mobile unit to slow or stop. The mobile unit may comprise an arch profile extending along an axial direction.

The laser curtain may be projected to surround the mobile unit.

The method may comprise selecting a default mode unless any deviating criteria is met. The default mode may comprise processing the laser curtain in a laser curtain pattern which extends from the mobile unit in an axial direction up to a maximum axial distance from the mobile unit, and in a width direction, perpendicular to the axial direction, up to a maximum width distance from the mobile unit.

The deviating criteria may comprise a first deviating criterion comprising the mobile unit being controlled to move from one row to another row, and determining that the mobile unit is within a first threshold distance from an end of a row, wherein when the first deviating criterion is met the method comprises selecting a crabbing mode. The crabbing mode may comprise processing the laser curtain in a laser curtain pattern which extends from the mobile unit along the axial direction up to a minimum axial distance, and in a width direction, perpendicular to the axial direction, up to a maximum width distance.

The deviating criteria may comprise a second deviating criterion comprising the mobile unit being controlled to approach a row, and determining that the mobile unit is within a first threshold distance from an end of a row, such that when the second deviating criterion is met, the method comprises selecting an entry mode. The entry mode may comprise processing the laser curtain to the same extent as a default mode or a crabbing mode, but excluding from processing a channel in the laser curtain corresponding to the location of the row.

The deviating criteria may comprise a third deviating criterion comprising the mobile unit being within a second threshold distance from an end of a row, such that when the third deviating criterion is met, the method comprises selecting a row mode. The row mode may comprise processing the laser curtain to form a laser curtain pattern which extends from the mobile unit along the axial direction up to a maximum axial distance, and in a width direction, perpendicular to the axial direction, up to a minimum width distance.

The safety output may be a signal to control robot arms on the mobile unit to stop.

For each mode of operation, each predefined laser curtain pattern, which the safety module is configured to process, may extend up to a threshold ground distance off the ground. The threshold ground distance may be <NUM>-<NUM> from the ground.

The method may comprise monitoring and mapping the ground surface and dynamically altering the predefined laser curtain pattern for each mode of operation based on the monitored ground surface.

The method may comprise determining that there is an inclination in the ground surface above an inclination threshold, based on the mapped ground surface, and dynamically altering the laser curtain pattern by making an axial extent of the laser curtain pattern or a width extent, perpendicular to the axial direction, shorter.

According to a third aspect, there is provided a computer program comprising computer-readable instructions that, when read by the controller of the above defined mobile autonomous agricultural system, causes the performance of the above defined method.

According to a fourth aspect, there is provided a non-transitory computer-readable storage medium comprising the above defined computer program.

Embodiments will now be described, by way of example only, with reference to the accompanying Figures, in which:.

<FIG> and <FIG> show a mobile autonomous agricultural system <NUM> comprising a powered mobile unit <NUM>. The mobile autonomous agricultural system <NUM> is configured to operate along rows <NUM> of crops (best shown in <FIG>, with each row <NUM> shown extending into the page) to perform agricultural tasks, such as harvesting, husbandry, or monitoring the crops.

In this example, the mobile unit <NUM> comprises an arch profile extending along an axial direction <NUM>. In other words, at any point in the axial direction, a cross section of the mobile unit <NUM> comprises an arch profile. In this example, distal ends of arms of the arch are fixed to powered wheels <NUM> (which are pivotable with respect to the mobile unit <NUM> for steering) and extend away from the wheels <NUM> to an apex of the arch. In this example, each distal end of the arch is attached to two wheels <NUM>, such that the whole arch is supported on the ground by a total of four wheels <NUM>. It will be appreciated that in other examples, any suitable number of wheels may be used, or any other suitable device for propelling the mobile unit <NUM> may be used.

The arch profile of the mobile unit <NUM> defines an inner zone <NUM>, in the form of a tunnel extending along the axial direction <NUM>, within which agricultural equipment <NUM> is disposed such that it is protected from damage. The agricultural equipment <NUM> in this example comprises robot arms. In other examples, it may include UV tubes or any other suitable equipment for carrying out agricultural tasks. The arch profile further allows the mobile unit <NUM> to traverse along rows <NUM> of crops, which are raised above the ground on posts (for ease of accessibility), with a single row <NUM> of crops extending through the inner zone <NUM> along the axial direction <NUM>, and simultaneously accessible by the agricultural equipment from two sides of the row <NUM>. In some examples, the crops may be disposed on the ground, and the mobile unit may comprise any suitable profile to access the crops on the ground.

The mobile autonomous agricultural system <NUM> comprises a controller <NUM> which is configured to control the travel of the mobile unit <NUM>. In this example, in an autonomous mode, the controller <NUM> is configured to autonomously move the mobile unit <NUM> along the rows <NUM> of crops, and between the rows <NUM>, where the rows may comprise a straight line of crops, or any other line of crops with a non-linear profile. In other words, the controller <NUM> is configured to align the axial direction <NUM> of the inner zone <NUM> of the mobile unit <NUM> with a first row <NUM> of crops such that the arch profile is centred and aligned with the row <NUM> of crops, and to move the mobile unit <NUM> to approach the first row <NUM>, and continue to move the mobile unit <NUM> along the row <NUM>, with the first row <NUM> received in the inner zone <NUM> until it reaches an end of the row <NUM>. At the end of the row <NUM>, the controller <NUM> is configured to control the mobile unit <NUM> to exit the row <NUM>, travel a predetermined distance away from the row <NUM>, and traverse towards an adjacent row <NUM> to begin the process again with the adjacent row <NUM>. In this example, the mobile autonomous agricultural system <NUM> may also be operated in a manual mode, in which a user can manually control the movement of the mobile unit <NUM>, for example up to a first row <NUM>, at which point the user may activate the autonomous mode.

In this example, the autonomous mode of the mobile autonomous agricultural system <NUM> provides for autonomous movement between adjacent rows <NUM> of crops, in a single polytunnel of plants, and also from one polytunnel to another.

During this autonomous movement, it is important that people around the mobile autonomous agricultural system <NUM> are kept safe. For example, during the approach of the mobile unit <NUM> towards a row <NUM>, there is a risk of crushing a person between the mobile unit <NUM> and the row <NUM>. Further, there are also risks during movement of the mobile unit <NUM> along the row <NUM>, and outside the row <NUM> which must be mitigated to ensure the safety of people around the mobile unit <NUM>.

To this end, the agricultural system <NUM> comprises a plurality of laser curtain sensors <NUM> distributed around the mobile unit <NUM>. In this example, there are six laser curtain sensors <NUM>, with one corner laser curtain sensor 18a disposed at each of four corners of the mobile unit <NUM>, which in this example is by each wheel <NUM>, and one side laser curtain sensor 18b disposed on each side of the mobile unit <NUM> between two wheels <NUM> in the axial direction <NUM>.

The laser curtain sensors <NUM> are each configured to project a respective laser plane towards the ground, and each laser plane overlaps with at least one other laser plane, so as together to form a laser curtain surrounding the mobile unit <NUM>. Each laser curtain sensor <NUM> can detect when its respective laser plane is interrupted by sensing reflected waves of emitted laser beam light. Specifically, the two side laser curtain sensors 18b project a laser plane close to vertically downwards such that the respective laser planes are not interrupted by the wheels <NUM> if the wheels are rotated by <NUM> degrees, and so that the respective laser planes are not interrupted by adjacent rows <NUM> when the mobile unit <NUM> is moving along a row <NUM>. As is explained in more detail below, this helps to reduce the risk of erroneous generation of a safety output. When the distance between rows is larger, the side laser curtains may be angled away from the mobile unit, or when the distance between the rows is narrow and constraining, and the wheels are smaller or do not rotate, then the side laser curtains may be angled towards the mobile unit.

Each corner laser curtain sensor 18a is configured to project a laser plane angled downwards with respect to the horizontal to project away from the mobile unit <NUM>, such that each laser plane from the corner laser curtain sensors 18a overlaps with the laser plane from an adjacent corner laser curtain sensor 18a, and so that the laser plane from each side laser curtain sensor 18b overlaps (or meets) with the laser planes from the adjacent corner laser curtain sensors 18a.

This particular configuration of laser curtain sensors <NUM> ensures that the mobile unit <NUM> is wholly surrounded by the laser curtain such that the presence of an object such as a person can be detected anywhere around the mobile unit <NUM>. It will be appreciated that there may be any suitable number of laser sensors for the particular application of the mobile autonomous agricultural system, such as one laser curtain sensor, or more than one laser curtain sensor.

The mobile autonomous agricultural system <NUM> further comprises a location module <NUM> which is configured to monitor a location of the mobile unit <NUM> relative to a row <NUM>. The location module <NUM> may comprise GPS or any other suitable sensor which can be used to identify the location of the mobile unit relative to a row.

The mobile autonomous agricultural system <NUM> further comprises a safety module <NUM> which is configured to receive a location signal from the location module <NUM>, related to the location of the mobile unit <NUM> relative to a row <NUM>, and to select a mode of operation based on the received location signal. Each mode of operation comprises processing the laser curtain in a different predefined laser curtain pattern to monitor interruptions to the laser curtain within the laser curtain pattern, as explained below with reference to <FIG>.

For each mode of operation, the safety module <NUM> is configured to generate a safety output in response to determining that the laser curtain is interrupted within the laser curtain pattern of the respective mode of operation. Therefore, any interruptions of the laser curtain outside the laser curtain pattern are ignored by the safety module.

In this example, the safety output includes sending a signal to the controller to control the mobile unit <NUM> to stop, and to control the robot arms <NUM> to stop. The safety output bringing the mobile unit to instant halt when the laser curtain pattern is interrupted, and the laser curtain patterns changing between modes, provides the compliance to regulation legislated for use of an autonomous system where there are likely to be people in the vicinity, whilst improving operation capability for the mobile unit not to be erroneously halted by anything not related to people straying too close to the mobile unit. Such solutions are currently unavailable for use in the agricultural environment where a crop is planted in rows. In some examples, the safety output signal may be to slow the mobile unit or to slow the robot arms. In other examples, the safety output may alternatively or additionally comprise producing an alarm, such as actuating an audible alarm on the mobile unit, or an alarm remote from the mobile unit to an operator, to alert the operator to the potential threat to safety of a person, or to alert the operator to the immobilising of the mobile unit or robot arms, such that they can restart the mobile unit or robot arms when it is determined to be safe again.

Although the location module, the safety module and the controller have been described as separate components, it will be appreciated that they can be incorporated into a single unit.

Further, although it has been described that the profile of the mobile unit defines an arch with distal ends of the arch fixed to wheels, in other examples, the mobile unit may have any suitable profile, or the arch profile may be inverted so that a portion of the arch at the apex is fixed to wheels and the distal ends extend upwards, away from the wheels and the ground. This can be used in situations where the crops are suspended from above, such that an inner zone between arms of the arch receives the suspended crop, and the crop is accessible to agricultural equipment in the arch from two sides simultaneously. For these examples, and the specific example described above, the axial direction may be the direction on the mobile unit which is configured to be parallel to a row while the controller controls the mobile unit to move along the row.

<FIG> and <FIG> show the mobile autonomous agricultural system <NUM> with a laser curtain pattern <NUM> in a default mode. The default mode is selected by the safety module <NUM> unless any deviating criteria are met. For example, the default mode in this example is selected when the mobile unit <NUM> is outside the rows <NUM> of crops and is moving from a location at which it has been switched from the manual mode to the autonomous mode, and when the mobile unit <NUM> is moving from one polytunnel comprising rows <NUM> of crops to another polytunnel comprising rows <NUM> of crops. During these periods, no deviating criteria are met.

In this example, the laser curtain pattern <NUM> in the default mode extends from each of the wheels <NUM>, away from the mobile unit <NUM>, in the axial direction <NUM> up to a maximum axial distance <NUM>, which in this example is <NUM>. The laser curtain pattern <NUM> in the default mode also extends from each of the wheels <NUM>, away from the mobile unit <NUM>, in a width direction <NUM>, which is perpendicular to the axial direction <NUM>, up to a maximum width distance <NUM>, which in this example is <NUM>.

Therefore, when a person or other unexpected object strays within <NUM> of the wheels <NUM> of the mobile unit <NUM> when in the default mode, the safety module <NUM> determines that the laser curtain is interrupted within the laser curtain pattern <NUM> for the default mode, and generates the safety output.

In other examples, the maximum axial distance and the maximum width distance may be any suitable distance, such as between <NUM>-<NUM>.

<FIG> shows the mobile autonomous agricultural system <NUM> with a laser curtain pattern <NUM> in a crabbing mode. The crabbing mode is selected by the safety module <NUM> when a first deviating criterion is met. In this example, the first deviating criterion comprises the mobile unit <NUM> being controlled to move, outside the rows <NUM> of crops, from one row <NUM> to align with another row <NUM>.

In this example, the laser curtain pattern <NUM> in the crabbing mode extends from the wheels <NUM> of the mobile unit <NUM>, along the axial direction <NUM> up to a minimum axial distance <NUM>, and in the width direction <NUM> up to the maximum width distance <NUM>. In this example, the minimum axial distance <NUM> is <NUM>. , and the maximum width distance <NUM> is the same as for the default mode. Therefore, the laser curtain pattern <NUM> for the crabbing mode in this example is similar to the default mode except that the axial distance is shorter. This is because, in the crabbing mode, the mobile unit <NUM> would only be moving in the width direction <NUM> (as shown in <FIG>) such that this direction is more critical, and requires a larger distance for the laser curtain pattern <NUM>, whereas, there is no movement in the axial direction <NUM> (as shown in <FIG>) in the crabbing mode, such that the important safety feature is merely preventing entry to the inner zone <NUM> of the mobile unit <NUM> while it is operating. It will be appreciated that the axial and width extents may be different to suit other agricultural applications.

<FIG> shows the mobile autonomous agricultural system <NUM> with a laser curtain pattern <NUM> in an entry mode. The entry mode is selected by the safety module <NUM> when a second deviating criterion is met. In this example, the second deviating criterion comprising the mobile unit <NUM> being controlled to approach the rows <NUM>, from outside the rows <NUM>, and the signal from the location module <NUM> indicating that the mobile unit <NUM> is within a first threshold distance from an end of a row <NUM>. In this example, the first threshold distance is the same as the maximum axial distance <NUM>. In other examples, it will be appreciated that the threshold distance may be any suitable distance.

In this example, the laser curtain pattern <NUM> in the entry mode extends from the wheels <NUM> of the mobile unit <NUM>, along the axial direction <NUM> up to the maximum axial distance <NUM>, and in the width direction <NUM> up to the maximum width distance <NUM> (i.e., with a similar pattern to the default mode). The laser curtain pattern <NUM> in the entry mode differs from that in the default mode by the laser curtain pattern <NUM> excluding at least one channel <NUM> from processing by the safety module <NUM>, which channel <NUM> corresponds to the position of the row <NUM>. This channel <NUM> ensures that the safety output from the safety module <NUM> is not erroneously generated by the posts and crops in the rows <NUM>, whilst maintaining the laser curtain pattern <NUM> to surround the rest of the mobile unit <NUM>, particularly between the mobile unit <NUM> and the rows <NUM>, where there remains a risk of crushing a person therebetween. The channel <NUM> may be configured to grow dynamically based on the location of the mobile unit <NUM> relative to the row <NUM>. For example, as the mobile unit <NUM> is entering a row <NUM>, the channel is configured to grow to accommodate the row <NUM> whilst ensuring that the rest of the space between the end of the row <NUM> and the mobile unit <NUM> remains covered by the laser curtain pattern.

In other examples, the laser curtain pattern for the entry mode may be similar to the crabbing mode, and the first threshold distance may be the same as the minimum axial distance. Alternatively, the laser curtain pattern may have any suitable extents, whilst excluding at least one channel corresponding to the row. For example, the entry mode may be similar to the default mode excluding the channel when the deviating criterion is met directly after the default mode has been active, and the entry mode may be similar to the crabbing mode excluding the channel when the deviating criterion is met directly after the crabbing mode has been active.

<FIG> shows the mobile autonomous agricultural system <NUM> with a laser curtain pattern <NUM> in a row mode. The row mode is selected by the safety module <NUM> when a third deviating criterion is met, the third deviating criterion comprising the mobile unit <NUM> being within a second threshold distance from an end of a row <NUM> or within the row <NUM> (i.e., with a row <NUM> received within the inner zone <NUM> of the mobile unit <NUM>).

In this example, the laser curtain pattern <NUM> in the row mode extends from the wheels <NUM> of the mobile unit <NUM>, along the axial direction <NUM> up to the maximum axial distance <NUM>, and in the width direction <NUM> up to a minimum width distance <NUM>. In this example, the minimum width distance <NUM> takes the laser curtain pattern <NUM> up to the side laser curtain sensor 18b.

The row mode therefore ensures that the safety output from the safety module <NUM> is not erroneously generated by the posts and crops in the rows <NUM>, whilst maintaining the laser curtain pattern <NUM> to surround the rest of the mobile unit <NUM>, in any direction in which a person could approach the mobile unit <NUM>.

Although only four modes have been described, there may be any number of different modes which take account of different configurations of rows, and of movements that the controller is configured to control the mobile unit to make. For example, the rows may be non-linear, and the modes may be configured to take account of this, and to dynamically change based on the configuration of the rows. Further, the laser curtain patterns may be dependent on the specific shape of the mobile carrier, which may have different angles of approach for a person, and therefore different potential vulnerabilities in use.

Having the laser curtain processed in different modes of operation with different laser curtain patterns, dependent on the location of the mobile unit relative to rows of crops, makes the mobile autonomous agricultural system very versatile in use whilst maintaining the safety of people around it.

In this example, for each of the modes of operation, the laser curtain pattern also extends downwards from each of the laser curtain sensors <NUM> towards the ground (best shown in <FIG>) up to a threshold ground distance <NUM> from the ground. In this example, the threshold ground distance <NUM> is <NUM>. Limiting the laser curtain pattern for each mode of operation up to the threshold ground distance <NUM> means that the mobile autonomous agricultural system <NUM> can be used on uneven ground, as the safety module <NUM> will not erroneously detect an interruption in the laser curtain pattern due to an uneven surface, whilst still triggering a safety output for a person who may attempt to crawl under, or may be lying prone on the ground. In some examples, the threshold ground distance may be any distance between <NUM> and <NUM>. In other examples, there may be no threshold ground distance, such that the laser curtain pattern extends all the way to the ground.

Further, for each of the modes of operation, the laser curtain sensors <NUM> are also configured to monitor and map the ground surface, which may be uneven, undulating, or inclined. The laser curtain pattern for each mode of operation may be dynamically altered based on the mapped ground surface, for example, if it is determined that the inclination of the ground is above an inclination threshold, the laser curtain pattern may be dynamically altered to make the axial distance or the width distance for the respective mode of operation shorter.

Although the laser curtain sensors are described as projecting a laser plane, it will be appreciated that the laser plane may be a single linear laser which is moved rapidly back and forth through a plane or about a pivot axis to form an effective laser plane. Further, although it is described that there are six laser curtain sensors, there may be any suitable number of laser curtain sensors, such as a single laser curtain sensor or more than one laser curtain sensor which are configured to project a laser curtain away from the mobile unit.

Further, although the laser curtain patterns are described in specific examples above, it will be appreciated that any suitable laser curtain pattern may be used for each of the different modes of operation, and the laser curtain sensors can be angled at any suitable angle to ensure that the safety output is not erroneously generated.

<FIG> is a flow chart showing steps of a method <NUM> of controlling the powered mobile unit <NUM> of the mobile autonomous agricultural system <NUM>.

In block <NUM>, the method <NUM> comprises projecting the laser curtain away from the mobile unit <NUM> with the laser curtain sensors <NUM> to surround the mobile unit <NUM>. In other examples, the laser curtain may not surround the mobile unit, but may be placed, for example, in strategic positions.

In block <NUM>, the method <NUM> comprises determining the location of the mobile unit <NUM> relative to a row <NUM>, based on the signal from the location module <NUM>. For example, the safety module <NUM> may determine the mobile unit <NUM> to be in one of the following five locations, based on the location signal received from the location module <NUM> and optionally also a signal from the controller <NUM>:.

In this example, in block <NUM>, the method <NUM> comprises determining whether any deviating criteria are met. The deviating criteria may include, for example, any of the first deviating criterion, the second deviating criterion and/or the third deviating criterion described with reference to <FIG>. It will be appreciated that other deviating criteria may be applied.

If it is determined that there are no deviating criteria met, the method <NUM> proceeds to block <NUM>, in which the default mode is selected, for example, as described with reference to <FIG> and <FIG>.

If it is determined in block <NUM> that any deviating criteria have been met, the method proceeds to block <NUM> in which a mode other than the default mode is selected. For example, depending on the deviating criterion which is met, the method <NUM> may select a crabbing mode as described with reference to <FIG>, an entry mode as described with reference to <FIG>, or a row mode as described with reference to <FIG>. As described above, each mode of operation comprises a different laser curtain pattern which is configured to be processed.

In other examples, blocks <NUM>-<NUM> may comprise any suitable method for selecting different modes of operation based on the location of the mobile unit relative to a row. From both blocks <NUM> and <NUM> the method <NUM> proceeds to block <NUM>, in which it is determined whether the laser curtain has been interrupted within the respective laser curtain pattern for the selected mode of operation.

If the laser curtain has been interrupted within the selected laser curtain pattern, the method proceeds to block <NUM> which comprises generating a safety output such as sending a signal to control the mobile unit <NUM> to stop, or to control the robot arms to stop, or any other suitable safety output such as described above.

If the laser curtain has not been interrupted within the selected laser curtain pattern, then the method <NUM> returns back to block <NUM> to start again. This method <NUM> is carried out continually to ensure the safety of users around the mobile unit <NUM>.

Claim 1:
A mobile autonomous agricultural system (<NUM>) comprising:
a powered mobile unit (<NUM>) for carrying agricultural equipment (<NUM>), and configured to move along rows (<NUM>) of crops;
at least one laser curtain sensor (<NUM>) configured to project a laser curtain away from the mobile unit (<NUM>);
a location module (<NUM>) configured to monitor a location of the mobile unit (<NUM>) relative to a row (<NUM>);
a controller (<NUM>) configured to control the travel of the mobile unit (<NUM>);
a safety module (<NUM>) configured to:
to generate a safety output in response to determining that the laser curtain is interrupted within a laser curtain pattern (<NUM>, <NUM>, <NUM>, <NUM>);
characterised by the safety module being configured to:
receive a location signal from the location module (<NUM>) related to the location of the mobile unit (<NUM>) relative to a row (<NUM>), and
select a mode of operation to process the laser curtain in a predefined laser curtain pattern (<NUM>, <NUM>, <NUM>, <NUM>), based on the received location signal, each mode of operation corresponding to a different predefined laser curtain pattern (<NUM>, <NUM>, <NUM>, <NUM>).