Robotic lawn mower system

Abstract

A robotic lawn mower (14) comprises a chassis (18) and a housing (20) defining an exterior face of the robotic lawn mower (14), the housing (20) comprising a skirt surrounding the chassis (18) at a distance from the chassis. A sensor module (30; 34) comprises a chassis connection interface for mechanically connecting the sensor module (30; 34) to a module connection interface located on the chassis (18). The sensor module (30; 34) holds the sensor outside a vertical projection of the chassis (18) between the chassis (18) and the skirt. The module connection interface is located on a top face of the chassis (18) and the sensor module accommodation extends downwards to a position below the module connection interface in a vertical direction. The cantilever member holds a main accommodation body of the sensor module (30; 34) such that a horizontal gap exists between the main accommodation body and the chassis (18).

Description

Technical Field

[0001] This invention relates to a robotic lawn mower system comprising a robotic lawn mower and a sensor module. The invention also relates to a robotic lawn mower and a sensor module for use in such a system. Background Technology

[0002] Since their market launch, robotic lawnmowers have been extremely helpful in lawn maintenance. Typically, different types of robotic lawnmowers are designed for different needs and offer various functionalities. For example, WO 2019 / 238273 proposes a robotic lawnmower with a variety of optional functional modules that can be installed in corresponding cavities within the base frame. When designing a robotic lawnmower, its ability to handle difficult terrain such as slopes and obstacles must also be considered. Therefore, there is a desire to increase its versatility and ability to traverse different types of terrain, or to improve the balance between these two requirements. Summary of the Invention

[0003] The object of the present invention is to solve or at least mitigate some or all of the above-mentioned problems. To this end, according to a first aspect, a robotic lawnmower system is provided, comprising a robotic lawnmower including: a base frame having a set of wheels and at least one propulsion motor for propulsing the robotic lawnmower via the set of wheels, the base frame surrounding the propulsion motor and a controller configured to control the operation of the at least one propulsion motor; and a housing defining an outer surface of the robotic lawnmower, the housing including a skirt that at least partially surrounds the base frame at a distance from the base frame, wherein the robotic lawnmower system further includes a sensor module including a sensor and a sensor module receiving portion surrounding the sensor, wherein the sensor module includes a base frame connection interface for mechanically connecting the sensor module to a module connection interface located on the outer surface of the base frame, thereby enabling the sensor module to be carried by the robotic lawnmower, wherein when the sensor module is connected to the base frame, the sensor module holds the sensor outside the vertical projection of the base frame between the base frame and the skirt. This positioning increases the versatility of the robotic lawnmower system because a single module connection interface can be used with sensor modules that include, for example, one or both of downward-sensing and forward-sensing sensors. Furthermore, since the sensor module is located outside the base frame, it doesn't require a significant increase in the vertical height of the base frame, maintaining the low profile of the robotic lawnmower and thus improving its navigation ability under bushes and branches. Additionally, the location of the critical part of the sensor module (i.e., the sensor itself) allows the main portion of the outer surface of the sensor module housing to be exposed to free-flowing ambient air, improving cooling. Simultaneously, the sensor module is protected by a skirt to prevent dirt buildup, further improving cooling.

[0004] According to a second aspect, a robotic lawnmower system is provided, comprising a robotic lawnmower including: a base frame with a set of wheels and at least one propulsion motor for propulsing the robotic lawnmower via the set of wheels, the base frame surrounding the propulsion motor and a controller configured to control the operation of the at least one propulsion motor; and a housing defining the outer surface of the robotic lawnmower, the housing including a skirt that at least partially surrounds the base frame at a distance from the base frame, wherein the robotic lawnmower system further includes a sensor module including a sensor and a sensor module housing surrounding the sensor, wherein the sensor module includes a base frame connection interface for mechanically connecting the sensor module to a module connection interface located on the outer surface of the base frame, thereby enabling the sensor module to be carried by the robotic lawnmower, wherein the module connection interface is located on the top surface of the base frame, and the sensor module housing extends downward in a position lower than the module connection interface in the vertical direction. Therefore, the module connection interface will be located in a position unaffected by grass clippings. At the same time, the sensor module does not require a significant increase in the vertical height of the robotic lawnmower, which improves the robotic lawnmower's ability to navigate under bushes and branches.

[0005] According to a third aspect, a robotic lawnmower system is provided, comprising a robotic lawnmower including: a chassis with a set of wheels and at least one propulsion motor for propulsing the robotic lawnmower via the set of wheels, the chassis surrounding the propulsion motor and a controller configured to control the operation of the at least one propulsion motor; and a housing defining an outer surface of the robotic lawnmower, the housing including a skirt at least partially surrounding the chassis at a distance from the chassis, wherein the robotic lawnmower system further includes a sensor module including a sensor and a sensor module housing surrounding the sensor, wherein the sensor module includes a chassis connection interface for mechanically connecting the sensor module to a module connection interface located on an outer surface of the chassis, wherein the sensor module housing includes a main housing body and a cantilever member, the main housing body surrounding the sensor, the cantilever member including the chassis connection interface, wherein when the sensor module is connected to the chassis, the cantilever member holds the main housing body such that a horizontal gap exists between the main housing body and the chassis. This arrangement exposes the main portion of the outer surface of the sensor module (including the side of the main housing body facing the base frame) to air, which improves the cooling of the sensor module. According to an embodiment, the horizontal gap can be less than 50 mm, which helps to make the robotic lawnmower compact. Furthermore, a compact arrangement can be particularly useful, for example, when the skirt can move relative to the base frame, such as as part of a collision detection system. Preferably, the gap is greater than 2 mm, thereby allowing for the determination of a certain airflow. Preferably, the main housing body also maintains a gap with the skirt, which is particularly useful in conjunction with a movably mounted housing skirt. According to an embodiment, the sensor module housing can be integrally formed with the cantilever member and optionally also integrally formed with the base frame connection interface. According to an embodiment, the cantilever member keeps the lower portion of the main housing body freely suspended. According to an embodiment, the freely suspended lower portion can occupy more than 30% of the vertical height of the sensor module. According to any embodiment of the robotic lawnmower system herein, the lower edge of the skirt can be positioned lower than the sensor module in the vertical direction. Therefore, the sensor module can be completely protected from horizontal impacts (e.g., due to collisions). The housing can be formed to cover the entire top of the sensor module. The base frame can be configured to watertightly surround the controller and propulsion motor; for example, the base frame can have an outdoor foreign object protection rating, such as IP54 or higher. The base frame can be defined by a lower base frame housing and an upper base frame housing, which are interconnected to define an enclosed space. Similarly, the sensor module housing can watertightly surround the sensor with a foreign object protection rating such as IP54 or higher.

[0006] According to any of the embodiments described above, a set of wheels may include a pair of drive wheels arranged on two opposing lateral sides of the base frame adjacent to a first longitudinal end of the base frame, wherein the module connection interface is located at the first longitudinal end of the base frame. Therefore, the added weight of the sensor module will be located on the distal side of the drive wheel's axle, i.e., the side of the axle opposite to the center of mass of the robotic lawnmower. The connection between the sensor module and the base frame thus produces a favorable weight distribution, improving the traction of the drive wheels. Any wheel at the second longitudinal end opposite the first longitudinal end may be non-driveable. Depending on whether the robotic lawnmower is front-wheel driven or rear-wheel driven, the first longitudinal end may be a front or rear end. According to embodiments, the weight of the sensor module may be between 200 grams and 400 grams, thus aiding in the traction of the robotic lawnmower without excessively compressing the grass.

[0007] According to one embodiment, the module connection interface can be integrally formed with the chassis. For example, the chassis can be constructed as a chassis shell made of plastic, and the module connection interface can be defined by the shape of the chassis shell. The chassis shell can have an exemplary chassis shell wall thickness between 0.75 mm and 2.5 mm.

[0008] According to the implementation, at the location of the module connection interface, the base frame can be defined by a single, continuous, and indivisible base frame shell wall without through holes or joints. Due to the integrity of the base frame shell wall, complete watertightness of the module connection interface is guaranteed regardless of whether the sensor module is connected to the robotic lawnmower, reducing the risk of moisture entering the base frame. Furthermore, since there is no damage to the base frame shell wall defined by the galvanic-type electrical interface at the location of the module connection interface, any trapped moisture or dust in the mechanical interface defined by the mating module and the base frame connection interface will not interfere with the electrical transmission between the sensor module and the controller.

[0009] According to one embodiment, the module connection interface can be located on the top surface of the base frame, and the sensor module can include a downward-facing sensor. Therefore, the downward-facing sensor will be mechanically held in a well-protected position to prevent damage from grass clippings and debris. This will result in high reliability for the downward-facing sensor. According to another embodiment, the sensor can include a ground-facing photosensor configured to determine the spectral characteristics of the grass.

[0010] According to one embodiment, the module connection interface of the chassis may include a guide portion configured to receive the chassis connection interface of the sensor module from above. Therefore, gravity will help maintain the engagement of the sensor module with the guide portion. The lower portion of the guide portion may define a vertical stop position for the chassis connection interface. The guide portion may include: a convex portion, such as a guide rail; and a concave portion, such as a guide track or a guide groove, or both.

[0011] According to one embodiment, the guide may include a guide groove, and the base frame connection interface may include a key configured to match the shape of the guide groove. A particular case of such a joint is a so-called T-slot joint. According to one embodiment, the guide groove has a tapered cross-section configured to gradually engage with the lateral side of the key to define a vertical stop position for the key. Therefore, the guide groove and the key can be securely engaged without any clicking noise as the robotic lawnmower passes through the work area.

[0012] According to an embodiment, one of the module connection interface and the base frame connection interface may include a resilient snap-fit ​​element configured to resiliently engage with the other of the module connection interface and the base frame connection interface after the base frame connection interface has moved along the guide to the connection position. Preferably, the snap-fit ​​element is disposed on the base frame connection interface of the sensor module, so that such a base frame can be as unaffected as possible by external structures, which could easily accumulate grass or debris when the sensor module is not connected. According to an embodiment, the snap-fit ​​element may be configured to be manually released without the use of tools. As an example, the snap-fit ​​element may include a spring tab that, when connected to the base frame, may optionally extend vertically upward from the sensor module.

[0013] According to one embodiment, the base frame may include an electrical connection interface for electrically connecting the sensor module to the controller, wherein the electrical connection interface is separate from the module connection interface of the base frame. This design makes the electrical connection between the module and the base frame less susceptible to vibration, because any relative movement between the sensor module and the base frame will not interfere with their electrical connection. This allows the lawnmower system to move in fairly rugged working areas without being affected by intermittent electrical connections between the robotic lawnmower and the sensor module. According to one embodiment, the sensor module may include a flexible cable extending from a sensor module housing, the cable being provided with a connector, and the electrical connection interface may include a connector socket configured to receive the connector. According to one embodiment, the connector socket may be located on the top surface of the base frame. According to an example, the electrical connection interface may be separated from the module connection interface of the base frame by a separation distance of more than 20 mm or more than 40 mm.

[0014] According to one implementation, the sensor may include radar. The radar's location outside the chassis allows for free selection of the chassis material and thickness, regardless of radar wave transmittance. This enables the manufacture of chassis with greater mechanical strength.

[0015] According to a fourth aspect, a robotic lawnmower system is provided, comprising a robotic lawnmower including: a base frame with a set of wheels and at least one propulsion motor for propulsing the robotic lawnmower via the set of wheels, the base frame surrounding the propulsion motor and a controller configured to control the operation of the at least one propulsion motor; and a housing defining the outer surface of the robotic lawnmower, the housing at least partially surrounding the base frame at a distance from the base frame, wherein the robotic lawnmower system further includes a sensor module including sensors and surrounding the sensors. A sensor module housing, wherein the sensor module includes a base frame connection interface for mechanically connecting the sensor module within the housing to a module connection interface located on the outer side of the base frame, thereby enabling the sensor module to be carried by a robotic lawnmower, wherein the sensor is configured to transmit and / or receive electromagnetic radiation along a transmission path, the sensor module housing includes an air outlet and a first air inlet, and the sensor module includes a fan configured to move air along an air guide from the first air inlet to the air outlet, wherein one of the air outlet and the first air inlet defines a sensing orifice positioned along the transmission path. The location of the sensor module within the housing reduces the risk of moisture being drawn into the sensor module, allowing the transmission path of electromagnetic radiation to remain unobstructed. Simultaneously, by arranging the sensor in a module outside the base frame, airflow across the base frame is not required. Therefore, the fan does not draw moisture or dust into the base frame, reducing the risk of electronic malfunction within the base frame. Preferably, the air outlet defines the sensing orifice. According to an embodiment, the base frame may include a battery for operating a propulsion motor, and the fan of the sensor module may be powered by the battery of the base frame. The robotic lawnmower system can be configured according to any other aspects and embodiments defined above. For example, arranging the sensor module outside the vertical projection of the base frame, or with a horizontal gap between it and the base frame, allows for a high degree of freedom in the positioning of the air outlet and the first inlet. For instance, air can be drawn in from the top of the sensor module and expelled from the bottom. Furthermore, by positioning the sensor module on one side outside the base frame, protruding from it, the sensor module's position within the free air volume works in conjunction with the internal airflow generated by the fan to effectively cool the sensor module.

[0016] According to one embodiment, the sensor module housing may include a liquid-tight electronic component compartment, in which the sensor is disposed, and the electronic component compartment includes a transparent window located between the sensor and an air guide. For example, the electronic component compartment may have an outdoor foreign object protection rating, such as IP54 or higher. According to another embodiment, the sensor module may further include a sensor controller disposed within the electronic component housing. The sensor and the sensor controller may coexist on a printed circuit board.

[0017] According to one embodiment, the first air inlet can be located on a substantially vertical wall of the sensor module housing. This arrangement reduces the risk of debris accumulating at the first air inlet. Here, "substantially vertical wall" should be interpreted as a wall forming an angle of less than 20 degrees with the vertical axis when the sensor module is connected to the base and the robotic lawnmower is positioned on a horizontal surface.

[0018] According to one embodiment, when the sensor module is connected to the base, the first air inlet can be positioned vertically higher than the air outlet. This arrangement allows air to move from a drier and cleaner environment to a humid and uncleaner environment, which increases the reliability of the sensor. According to one embodiment, the air outlet can be located at the lowermost part of the sensor module housing. Alternatively or additionally, the first air inlet can be located at the upper end of the sensor module housing.

[0019] According to one embodiment, the first air inlet can be configured as an elongated slot with a width less than 4 mm and a length greater than 20 mm. This elongated slot can be intermittent, i.e., interrupted by a bridging portion spanning the slot, or it can be continuous. Therefore, for the purposes of this disclosure, a row of closely spaced orifices is considered an elongated slot. According to one embodiment, when the sensor module is connected to the base, the elongation direction of the slot can extend vertically. This orientation reduces the risk of debris blockage.

[0020] According to an embodiment, the module housing may include a first housing shell attached to a second housing shell, wherein the first air inlet is defined by an elongated gap extending along the interface between the first housing shell and the second housing shell.

[0021] According to one embodiment, the first air inlet can be located in the portion of the sensor module housing facing the base frame when the sensor module is connected to the base frame. This geometry reduces the exposure of the first air inlet to debris.

[0022] According to one embodiment, the sensor module housing may include a second air inlet. This arrangement reduces the sensitivity to blockage of the first air inlet. The second air inlet can be configured according to any embodiment of the first air inlet described above.

[0023] According to one embodiment, the first air inlet and the second air inlet face different directions. This arrangement reduces the sensitivity to blockage of the first and second air inlets. According to another embodiment, the first and second air inlets may face opposite directions. The sensor module housing may also include a third air inlet facing a direction different from that of the first and second air inlets.

[0024] According to one embodiment, the sensor's detection surface can face the detection direction along the detection axis, and the air guide can include: an upstream guide section located axially behind the detection surface relative to the detection axis; and a downstream guide section located axially in front of the detection surface relative to the detection axis. Optionally, the air guide can also include a flow deflector configured to deflect the airflow from the upstream guide section in a deflection direction toward the space in front of the sensor, the deflection direction forming an angle greater than 45 degrees with the detection axis. Therefore, the airflow will bend around the detection surface and brush across the sensor's detection surface or any transparent window in front of the sensor (as applicable) to keep the transparent window clean and fog-free. According to another embodiment, the flow deflector is configured to deflect the airflow in a deflection direction forming an angle greater than 60 degrees or greater than 75 degrees with the detection axis. The detection axis is defined by the surface normal of the sensor's detection surface. According to one embodiment, the upstream guide section can pass through the sensor only on one lateral side of the sensor. Such an arrangement can improve the efficiency of the deflected airflow in the space in front of the sensor to keep the detection surface / transparent window dust-free.

[0025] Optionally, and independently of any flow deflector, the upstream guide section can pass through the sensor on the side of the sensor facing away from the base. Therefore, such a sensor can be positioned as close to the base as possible. This increases the sensor's field of view because the presence of a housing, typically with a skirt extending downwards to a vertical position below the base, causes less obstruction to the sensor.

[0026] According to one embodiment, the outlet area of ​​the air outlet is less than 90% of the cross-sectional area of ​​the air guide upstream of the air outlet. This arrangement helps maintain overpressure in the air guide, thereby reducing the risk of debris entering the air guide in the opposite direction to the flow direction, while achieving low power consumption of the fan. According to another embodiment, the outlet area of ​​the air outlet is less than 70% of the cross-sectional area of ​​the air guide upstream of the air outlet.

[0027] According to one embodiment, the fan's axis of rotation is transverse to the detection axis. This allows for a compact fan arrangement. According to another embodiment, the minimum angle between the fan's axes of rotation can exceed 45 degrees; for example, it can be substantially right-angled. The fan can be an axial-flow fan. Alternatively or additionally, the fan can be a radial-flow fan, which also allows for a particularly compact arrangement of the fan within the limited space available in the sensor module. The fan can be configured to generate an airflow transverse to the detection axis in the flow direction toward an upstream guide section of the air guide, which can extend on a single lateral side of the sensor.

[0028] According to the implementation method, when the robotic lawn mower is located on a horizontal surface, the transmission path can form an angle of less than 20 degrees with the vertical axis.

[0029] The sensor may include, for example, a detector configured to detect light in the infrared and / or red wavelength range. Such a sensor may be particularly well-suited for detecting characteristics of grass beneath a robotic lawnmower system.

[0030] According to one embodiment, the sensor can be positioned at a distance greater than 6 mm from the sensing aperture. This provides good shielding against stray light. According to another embodiment, the sensor is positioned at a distance greater than 10 mm from the sensing aperture. Preferably, the distance between the sensor and the sensing aperture is less than 50 mm.

[0031] According to one implementation, the sensor can be a sensor configured to detect the presence and / or healthy quality of grass. Thus, the sensor can be configured to detect the intensity of electromagnetic radiation in two different wavelength ranges and determine a ratio based on these two intensities. Typically, these two wavelength ranges can include the near-infrared wavelength range and the red wavelength range in the visible wavelength region. Such a sensor is commonly referred to as an NDVI (Normalized Differential Vegetation Index) sensor. Optionally, the sensor can include one or more electromagnetic radiation sources adapted to emit electromagnetic radiation in both wavelength ranges. The electromagnetic radiation sources can be pulsed or modulated to be able to distinguish frequencies.

[0032] According to a fifth aspect, a sensor module is provided that is used as the sensor module in a robotic lawnmower system defined according to any of the preceding aspects.

[0033] According to a sixth aspect, a robotic lawnmower is provided, comprising: a base frame with a set of wheels and at least one propulsion motor for propulsing the robotic lawnmower via the set of wheels, the base frame surrounding the propulsion motor and a controller configured to control the operation of the at least one drive motor; a housing defining the outer surface of the robotic lawnmower, the housing including a skirt that at least partially surrounds the base frame at a distance from the base frame; and a radar module located between the base frame and the skirt, wherein the skirt includes skirt openings aligned with the radar module. This arrangement protects the radar module from dust while allowing free airflow to cool the module, enabling the module to operate at higher power. This allows for more efficient sensing. According to an embodiment, the robotic lawnmower may be provided with a rechargeable battery and a charging interface configured to charge the battery from a charging station outside the robotic lawnmower, wherein the charging interface is not aligned with the skirt openings. Positioning the charging interface separately from the skirt openings allows free airflow in front of the sensor module when the lawnmower is parked at the charging station. The radar module can be configured as an attachable / removable sensor module in a robotic lawnmower system, for example, according to any of the aspects and embodiments defined above, and may also include other sensors and functions. This robotic lawnmower system may also include a removable cover that covers the skirt panel openings. The removable cover can be used to cover the skirt panel openings when the radar module is not attached to the base frame.

[0034] According to one embodiment, the skirt panel openings can be covered by a tamper-proof protective element. This arrangement increases the security of the robotic lawnmower and makes it more difficult to tamper with the radar module beneath the housing and any moving parts. Furthermore, the tamper-proof protective element prevents the skirt panel openings from being mistaken for lifting handles. The tamper-proof protective element can be configured as a removable cover or a grille. The grille can be transparent to radar waves while effectively providing tamper-proof protection. Preferably, the tamper-proof protective element does not have any through holes large enough to allow a finger to be inserted.

[0035] According to one embodiment, the radar module may include a radar module housing separate from the base frame. Therefore, the base frame can be made of a material and thickness optimized for structural integrity and moisture-proof sealing, while the radar module housing can be made of a material and thickness optimized for radar transmittance. Thus, effective radar detection can be achieved without compromising other aspects of the robotic lawnmower.

[0036] It should be noted that embodiments of the present invention can be implemented through all possible combinations of the features stated in the claims. Furthermore, it should be understood that the various embodiments described for different aspects can be combined with each other. Attached Figure Description

[0037] The above and other objects, features, and advantages of the invention will be better understood through the following illustrative and non-limiting detailed description of preferred embodiments of the invention with reference to the accompanying drawings, in which the same reference numerals will be used for similar elements, in which:

[0038] Figure 1 This is a 3D view of a robotic lawn mower system, including the robotic lawn mower.

[0039] Figure 2 yes Figure 1 A 3D image of a robotic lawnmower;

[0040] Figure 3 yes Figure 2 A 3D view of the chassis of the robotic lawnmower, as well as the radar module and lawn quality sensor module connected to the chassis.

[0041] Figure 4 yes Figure 3 The image shows a 3D view of the base frame, radar module, and lawn quality sensor module after the sensor module is connected to the base frame.

[0042] Figure 5 yes Figure 4 A 3D view of the base frame, radar module, and lawn quality sensor module, located in... Figure 2 Inside the lawnmower casing;

[0043] Figure 6 It is viewed from above. Figure 4 A plan view of the base frame, radar module, and lawn quality sensor module.

[0044] Figure 7 This is viewed from below. Figure 4 A plan view of the base frame, radar module, and lawn quality sensor module.

[0045] Figure 8 It is viewed from above. Figure 3 A plan view of the underframe, in which the upper underframe shell has been removed to expose the interior of the underframe;

[0046] Figure 9 yes Figure 3 A 3D view of the lawn quality sensor module in the image;

[0047] Figure 10 yes Figure 3 An enlarged view of a portion shows the module connection interfaces of the chassis;

[0048] Figure 11 It is along Figure 6 The line XI-XI in the middle is intercepted Figure 4Cross-sectional view of the lawn quality sensor module and the base frame;

[0049] Figure 12 It is along Figure 6 The line XII-XII in the middle is intercepted Figure 4 Cross-sectional view of the radar module and chassis;

[0050] Figure 13A yes Figure 2 A perspective view of the front section of a robotic lawnmower shows the removal of a cover from an opening in the skirt of the robotic lawnmower, and the installation of a grille within the opening; and

[0051] Figure 13B Corresponding to Figure 13A The view shows a robotic lawnmower equipped with a grille.

[0052] All the accompanying drawings are schematic, not necessarily drawn to scale, and generally only show the parts necessary to illustrate the implementation, where other parts may be omitted. Detailed Implementation

[0053] Figure 1 The schematic diagram illustrates an overview of a robotic lawnmower system 10 configured to mow lawns within a work area 12, such as a garden, park, football field, or golf course, defined by a work area boundary 13. The robotic lawnmower system 10 includes: a self-propelled robotic lawnmower 14 configured to autonomously navigate within the work area 12 for mowing; and a battery charging station 16. The work area boundary 13 may be defined by, for example, boundary cables, or may be configured as a virtual perimeter, i.e., a geofence.

[0054] Figure 2 The robotic lawnmower 14 is shown in more detail. The robotic lawnmower 14 includes: a base frame 18; and a housing 20 that partially covers the base frame and defines the outer surface of the robotic lawnmower 14. The lower portion of the housing 20 defines a skirt 20a surrounding the base frame. The robotic lawnmower 14 extends longitudinally between a front end 14a and a rear end 14b of the lawnmower 14, and during normal operation, the robotic lawnmower 14 primarily propels itself forward in the longitudinal direction in the forward propulsion direction F. For this purpose, the base frame 18 is provided with a pair of drive wheels 22a, 22b near the front end 14a, one of which... Figure 1 As can be seen, drive wheels 22a and 22b are mounted on two opposite lateral sides of the base frame 18.

[0055] Figure 3 Shown without casing 20 ( Figure 1The robotic lawnmower 14 is shown with its base frame 18 fully exposed. In addition to the drive wheels 22a, 22b at the front, the base frame also has a pair of rear wheels 24, one of which is located at... Figure 3 As can be seen, the rear wheel 24 is a caster type and has no power to propel the lawn mower 14. Therefore, the robotic lawn mower 14 ( Figure 2 It is a front-wheel drive type.

[0056] The base frame 18 is defined by an upper base frame housing 18a and a lower base frame housing 18b, which are attached to each other to watertightly surround the internal space of the base frame 18. This internal space houses the electronics for operating the lawnmower, such as a controller, and will be further described below. At the longitudinal end of the base frame 18, more precisely, at the front end 19a of the base frame 18, are provided a first module connection interface 26 and a second module connection interface 28, which will be described in further detail below. The first module connection interface 26 is located at the lateral center of the front end 19a of the base frame 18, while the second module connection interface 28 is located at a position laterally offset from the lateral center of the base frame 18. The first module connection interface 26 is configured to mechanically connect to a first sensor module 30, which in the illustrated example includes a radar. The first sensor module 30 includes a base frame connection interface 32 configured to mate with the first module connection interface 26 of the base frame 18, thereby enabling the first sensor module 30 to be operated by the robotic lawnmower 14 (… Figure 1 The second sensor module 34 is mounted on the lateral center of the front end 19a of the base frame 18. Similarly, the second module connection interface 28 is configured to be mechanically connected to the second sensor module 34, which in the illustrated example includes a lawn quality sensor. The second sensor module 34 includes: a base frame connection interface (in...) Figure 3 (Not visible in the view), configured to mate with the second module connection interface 26 of the base frame 18, thereby enabling the second sensor assembly 34 to also be connected by the robotic lawn mower 14 (not visible in the view), and thus enabling the second sensor assembly 34 to be connected by the robotic lawn mower 14 (not visible in the view), and configured to mate with the second module connection interface 26 of the base frame 18, thereby enabling the second sensor assembly 34 to also be connected by the robotic lawn mower Figure 1 ) Load-bearing. Robotic lawn mower 14 ( Figure 1This is a fully functional, autonomous robotic lawnmower 14 without sensor modules 30, 34, but each of the first and second sensor modules 30, 34 adds corresponding optional capabilities to the robotic lawnmower 14. In the present case, the first sensor module 30 includes a forward-sensing sensor, which adds the ability to remotely map the area around the robotic lawnmower 14 in front of the lawnmower, and the second sensor module 34 is a downward-sensing sensor, which adds the ability to detect the presence and health of any grass below the robotic lawnmower 14. Each of the optional sensor modules 30, 34 is independent of the other sensor modules 34, 30 and can be added independently to the base frame 18 or in combination with other sensor modules. Both module connection interfaces 26, 28 are located on the top surface of the base frame 18 and are configured to receive the base frame interface 32 of the corresponding sensor module 30, 34 from above; therefore, it is preferable to remove any housing 20 before installing any sensor module 30, 34. Figure 1 The first module connection interface 26 is different from the second module connection interface 28, which makes it impossible for sensor modules 30 and 34 to connect to the wrong interfaces 28 and 26.

[0057] In addition to the module connection interfaces 26, 28 configured to mechanically connect to and structurally support and carry the sensor modules 30, 34, the base frame 18 also includes a corresponding electrical connection interface for each module connection interface 26, 28, configured as a corresponding connector socket 36, 38 for electrically connecting the corresponding sensor module 30, 34 to the controller. Figure 3 (Not shown in the image). More precisely, the first connector socket 36 is configured to be electrically connected to the first sensor module 30, and the second connector socket 38 is configured to be connected to the second sensor module 34. The connector sockets 36, 38 of the base frame 18 are disposed on the top surface of the base frame 18 and are geometrically separated from the corresponding module connection interfaces 26, 28. Each of the first sensor module and the second sensor modules 30, 34 includes corresponding flexible cables 40, 42, which are provided with corresponding electrical connectors 44, 46, such that the first sensor module 30 is provided with a first electrical connector 44, and the second sensor module 34 is provided with a second electrical connector 46. The first electrical connector 44 of the first sensor module 30 is configured to connect to the first connector socket 36, and the second electrical connector 46 of the second sensor module 34 is configured to connect to the second connector socket 38.

[0058] Figure 4A base frame 18 is shown, in which the first sensor module and the second sensor modules 30, 34 are mechanically connected to corresponding module connection interfaces 26, 28 located on the base frame 18, and electrical connectors 44, 46 are connected to corresponding connector sockets 36, 38 located on the base frame 18. When the sensor modules 30, 34 are connected to their respective module connection interfaces, each of the respective sensor modules 30, 34 maintains a corresponding predetermined geometric relationship with the base frame 18. The center of gravity of the robotic lawnmower 14 is located behind the wheel axis A of the drive wheels 22a, 22b, and because the sensor modules 30, 34 are located in front of the wheel axis A, i.e., on the side opposite to the center of gravity, the increased weight of the sensor modules 30, 34 contributes to the traction of the drive wheels 22b, 22a. The first sensor module 30 weighs approximately 350 grams, and the second sensor module 34 weighs approximately 250 grams.

[0059] Although Figure 4 The case 20 has been removed. Figure 1 The base frame 18, but the sensor modules 30, 34 and the housing 20 are shaped such that the sensor modules 30, 34 are assembled between the base frame 18 and the housing 20. Figure 5 The image shows a robotic lawnmower 14 with its housing 20 returned to its original position. The housing 20 is shown as completely transparent, with only its outline schematically shown in dashed lines, making the positions of the sensor modules 30 and 34 clearly visible.

[0060] Figure 6 The base frame 18 is shown from directly above. As mentioned above, the first sensor module 30 includes a first sensor implemented by radar 48, and the second sensor module 34 includes a second sensor implemented by lawn quality sensor 50. As seen from above, sensor modules 30, 34 hold their respective sensors 48, 50 outside the vertical projection of the base frame 18, as shown by the dashed outline C of the base frame. Thus, the downward-detecting second sensor module 34 can have a free vertical downward detection path while still allowing the sensor module to be attached to the base frame 18 from above. Meanwhile, sensor modules 30, 34 hold their respective sensors 48, 50 within the housing 20 (…). Figure 5 Within the vertical projection of ), more precisely, within the skirt 20a of the outer shell 20 ( Figure 5 Inside, the internal outline S of the casing is also indicated by dashed lines. The battery charging port 17 at the rear end 19b of the base frame is configured to connect to the charging station 16. Figure 1 The battery charging interface 17 can be connected to the housing 20 via the matching battery charging interface 17. Figure 1 The opening at the rear end is close to the charging port 17. This is because the charging port 17 is located at the rear end 14b of the robotic lawnmower 14. Figure 2 At point 14, the robotic lawnmower 14 reversed back to charging station 16. Figure 1 )middle.

[0061] Figure 7 Robotic lawn mower 14 is shown below. Figure 2 The base frame 18 of the robotic lawnmower 14 is shown in the bottom view. This bottom view shows a pair of drive wheels 22a, 22b and a pair of non-drive wheels 24, etc. The drive wheels 22a, 22b are configured such that the drive wheel axis A around which they are driven is perpendicular to the forward direction F of the robotic lawnmower 14, and the robotic lawnmower 14 is configured to change its course by rotating the drive wheels 22a, 22b at different speeds and / or in different directions. The bottom surface of the base frame 18 also includes a set of grass cutters, comprising a main grass cutter 52a and an auxiliary rear grass cutter 52b. Each grass cutter 52a, 52b includes a corresponding rotating blade carrier 54, each blade carrier 54 carrying a plurality of grass cutting blades 56 at its periphery, which are pivotally connected to the corresponding blade carrier 54. Each grass cutter 52a, 52b is configured to rotate the corresponding set of grass cutting blades 56 in a substantially horizontal cutting plane to cut grass.

[0062] Figure 8 The base frame 18 is shown. Figure 3 The interior of ) was modified by removing the upper base shell 18a. Figure 3 This exposes the interior surface of the lower base housing 18b and the various functional components enclosing the base housing 18. The controller 58 controls the robotic lawnmower 14. Figure 2 The main cutter motor 60a is configured to operate the main grass cutter 52a in response to a control signal from the controller 58. Figure 7 The auxiliary cutter motor 60b is configured to rotate in response to additional control signals from the controller 58, causing the auxiliary grass cutter 52b ( Figure 7 The drive wheels 22a and 22b rotate independently of the main grass cutter 52b. The drive wheels 22a and 22b are configured to be independently controlled by corresponding wheel motors 62a and 62b, which operate in response to corresponding control signals from the controller 58. The controller 58, the cutter motors 60a and 60b, and the wheel motors 62a and 62b are powered by a rechargeable battery 63 within the base frame 18, which is connected via a battery charging interface 17. Figure 6 )Charge.

[0063] Figure 9 This is a perspective view showing the base connection interface 32 of the second sensor module 34. Figure 10 This is a perspective view showing the corresponding second module connection interface 28 of the base frame 18. It should be understood that the first sensor module 30 ( Figure 3 The base frame connection interface 32 and the corresponding first module connection interface 26 can be similar. From Figure 10Starting with the view, the second module connection interface 28 includes a guide (shown by axis G) configured to receive the second sensor module 34 from above along a generally vertical direction. Figure 9 ) base frame connection interface 32 ( Figure 9 The guide groove 64. Viewed from above, the guide groove 64 has a roughly "T" shape. Figure 9 As shown, the base frame connection interface 32 includes a convex key 66 shaped as a "T" when viewed from below, and is configured to match the shape of a T-shaped guide slot 64 in a so-called T-slot connector. (See again...) Figure 10 The guide groove 64 tapers slightly in the downward direction, so that when sliding downward into the guide groove 64, the key 66 ( Figure 9 The key will reach a vertical stop position, where there is a tight and silent engagement between the guide groove 64 and the key 66. Optionally, the bottom wall 68 of the guide groove 64 may define the vertical stop position of the key 66.

[0064] refer to Figure 9 The base frame connection interface 32 includes a spring tab 70 with a barb 72, and the module connection interface 28 ( Figure 10 The device includes a recess 74 configured to receive a barb 72 after the key 66 has slid into position within the guide groove 64. The biasing of the spring tab 70 causes the barb 72 to resiliently engage with the recess 74 once the key 66 has moved along the guide groove 64 to the engagement position. The barb 72 can be released from the recess 74 by pressing the spring tab 70 in a release direction R perpendicular to the guide axis G, allowing the base connection interface 32 of the second sensor module 34 to be removed from the second module connection interface 28.

[0065] The second sensor module 34 includes a surround sensor 50 ( Figure 6 The sensor module housing 76 is a sensor module receiving portion. The shape of the sensor module receiving portion 76 defines a main receiving portion body 78 and a cantilever member 79, wherein the sensor 50 is located in the main receiving portion body, and the cantilever member extends horizontally from the main receiving portion body 78 and includes a base frame connection interface 32. The sensor module receiving portion 76 is made of plastic, and the base frame connection interface 32, including a key 66 and a spring tab 70, is integrally formed with the sensor module receiving portion 76.

[0066] The sensor module housing includes a first housing shell 76a and a second housing shell 76b attached to each other. A first elongation gap 80a between the first housing shell and the second housing shells 76a and 76b extends along a top edge adjacent to the top surface 34a of the second sensor module 34 and faces a first direction. A second elongation gap 80b between the first housing shell and the second housing shells 76a and 76b extends along a top edge of the second sensor module 34 opposite to the first elongation gap 80a and faces a second direction substantially opposite to the first direction. A third elongation gap 80c between the first housing shell and the second housing shells 76a and 76b extends between the first elongation gap and the second elongation gap and faces a third direction. Each elongation gap 80a, 80b, 80c defines an air inlet to allow air to enter an elongation slot of the second sensor module 34. Each gap 80a, 80b, 80c has a length of several centimeters and a width of approximately 2 mm. The vertical wall 78a of the main housing body 78 is also provided with an air inlet 80d, which faces the base frame 18 when the second sensor module 34 is attached to it. (See below for further details.) Figure 11 The functions of air inlets 80a, 80b, 80c, and 80d are further described. Sensing orifice 82 serves as an air outlet.

[0067] continue Figure 10 The guide groove 64 is defined by the shape of the upper base shell 18a. Thus, the second module connection interface 28 is integrally formed with the base 18. The joint between the upper base shell and the lower base shells 18a, 18b does not extend through the module connection interface 28, so that at the location of the second module connection interface 28, the base 18 can be defined by a single continuous and indivisible base shell wall without through holes or joints. The upper and lower base shells are made of plastic and have a wall thickness of approximately 1.5 mm. Figure 10 The geometric separation between the second module connection interface 28 and the second connector socket 38 is also shown by the separation distance SD.

[0068] Figure 11 A cross-section of the second sensor module 34, as well as a portion of the base frame 18 and housing 20, is shown, which is along... Figure 6 The line XI-XI shown is the cut. From Figure 11 As can be clearly seen in the view, the main housing body 78 of the second sensor module 34 extends downward beyond the vertical projection of the base frame 18 to a position lower than the module connection interface 32 in the vertical direction, and also holds the lawn quality sensor 50 lower than the module connection interface 32 in the vertical direction. Cantilever member 79 ( Figure 9The lower portion of the main housing body 78 is kept suspended freely, with a horizontal gap d1 between the main housing body 78 and the base frame 18 of approximately a few millimeters. The freely suspended portion of the main housing body 78 accounts for approximately 60% of the total vertical height of the second sensor module 34.

[0069] The housing 20 is movably connected to the base frame 18, and the controller can be configured to detect collisions of the robotic lawnmower 14 by detecting movement of the skirt 20a relative to the base frame 18. To allow movement of the skirt 20a relative to the base frame 18, the second sensor module 34 maintains a gap d2 with the skirt 20b, which can be, for example, on the order of a few centimeters. The lower edge 20b of the skirt 20a is positioned below the sensor module in the vertical direction. Furthermore, the housing 20 is also shaped to cover the upper part 34a of the sensor module 34.

[0070] Although the sensor module housing 76 is provided with multiple apertures 80a, 80b, 80c, 80d, and 82, the second sensor module 34 also includes a liquid-tight electronics compartment 84 in which the lawn quality sensor 50 is disposed. The electronics compartment 84 may include an empty volume or alternatively be encapsulated. A transparent window 86 is arranged at the bottom of the electronics compartment 84, facing the sensing aperture 82 of the sensor module housing 76 and allowing light to enter and exit the electronics compartment 84. The lawn quality sensor 50 has a detection surface 50a that faces downward along a vertical detection axis D perpendicular to the detection surface 50b of the sensor 50. The sensor 50 is configured to determine the spectral characteristics of the grass. For this purpose, the lawn quality sensor 50 is configured to detect the electromagnetic radiation intensity in two different wavelength ranges and determine a ratio based on these two intensities. These two wavelength ranges include the near-infrared wavelength range and the red wavelength range in the visible wavelength region. Therefore, sensor 50 is of the type commonly referred to as an NDVI (Normalized Differential Vegetation Index) sensor. Sensor 50 also includes a light-emitting diode that emits electromagnetic radiation across two wavelength ranges. The emitted electromagnetic radiation is pulsed, and detection is synchronized with the pulses to distinguish background noise. The electromagnetic radiation is transmitted and received via sensing aperture 82 along a transmission path coinciding with the detection axis D. Sensor 50 is approximately 10 mm from sensing aperture 82.

[0071] The interior of the second sensor module 34 is cooled by airflow passing through it, which also keeps the transparent window 86 dust-free. Fan 88 directs air along air guides 90 from air inlets 80a, 80b, 80c, 80d to the sensing aperture 82, which serves as the air outlet. Fan 88 rotates about a rotation axis FR perpendicular to the detection axis D. Although fan 88 is shown as an axial fan, a radial fan would allow for a more compact arrangement of fan 88 within the air guides 90. Fan 88 is powered by a battery 63 within the base frame 18 via wire 42. Figure 8 Power supply. The air guide 90 includes: an upstream guide section 90a, located axially behind the detection surface 50a relative to the detection direction defined by the detection axis D; and a downstream guide section 90b, located axially in front of the detection surface 50a relative to the detection direction defined by the detection axis D. The air guide 90 also includes a flow deflector 92 configured to deflect airflow from the upstream guide section 90a toward the space 90c in front of the sensor 50 in a deflection direction substantially parallel to the detection surface 50a (i.e., perpendicular to the detection axis D). This flow deflector bends the airflow around the detection surface 50, causing the airflow to brush across the outer surface of the transparent window 86, thereby removing fog and preventing dust from reaching the transparent window 86 via the sensing aperture 82. The upstream guide section 90a is several times longer than the downstream guide section 90b, so that any sticky dust particles entering the air guide 90 will be trapped before reaching the transparent window 86. Although it is not possible to... Figure 11 It can be immediately deduced from the cross-section, but the sensing orifice 82 defines an air outlet with an outlet area perpendicular to the airflow direction, which is smaller than the cross-section of the air guide upstream of the sensing orifice 82. This causes overpressure at least in the portion of the air guide 90 adjacent to the sensing orifice 82, which prevents dust from entering from below. Although it cannot be deduced from the cross-section, Figure 11 From the cross-section, it can be immediately deduced that the upstream guide section passes through the sensor 50 only on one side of the sensor 50, or more precisely, on the side away from the base frame 18. This arrangement keeps the sensor 50 as far away from the skirt plate 20a as possible within the module housing 76, so that the lower edge 20b of the skirt plate 20a does not restrict the field of view of the sensor 50.

[0072] Figure 12 A cross-section of the first sensor module 30, the base frame 18, and a portion of the housing 20 is shown, the cross-section being along... Figure 6The line XII-XII shown is cut off. Except for the lack of the air guide in the first sensor module 30, the overall geometry of the sensor module housing 76 of the first sensor module 30 is similar to that of the sensor module housing of the second sensor module 34, and will not be described further. Similar to the second sensor module 34, the first sensor module 30, as a radar module, is located between the base frame 18 and the skirt plate 20a. Similar to the second sensor module 34, the first sensor module 30 is powered by a battery 63 within the base frame 18. Figure 8 Power supply. By placing the radar in a sensor module 30 outside the base frame 18, the sensor module 30 has its own sensor module housing 76. The radar module housing 76 in front of the radar 48 can be made of materials and thicknesses optimized for radar transmittance without having to compromise with any design considerations of the material or wall thickness of the base frame 18.

[0073] When connecting the first sensor module 30 to the base frame 18, the removable cover 94 must be removed from the skirt panel 20a to expose the skirt panel opening 96. The removable cover 94 snaps into the skirt panel opening 96 for tool-free attachment and removal. The skirt panel opening 96 is aligned with the first sensor module 30 so that the transmission path P of the radar 48 within the first sensor module 30 passes through the skirt panel opening 96.

[0074] refer to Figure 13A The radar module 30 is installed on the base frame 18 (in Figure 13A When the cover 94 is not visible in the middle, remove it from the skirt panel opening 96. A tamper-proof protective element 98, configured as a coarse mesh grille, is installed at the location of the skirt panel opening to achieve... Figure 13B As shown, the grille 98 snaps into the skirt panel opening 96. The radar's polarization direction can be aligned with the grille mesh pattern to achieve maximum transmittance.

[0075] The invention has been described above primarily with reference to several embodiments. However, as will be readily understood by those skilled in the art, other embodiments besides those disclosed above within the scope of the invention as defined in the appended claims are equally possible. For example, two examples of the sensing functions of a sensor module (radar and lawn quality sensing) have been given. It should be understood that the teachings herein are also applicable to other types of sensors, such as LIDAR (light detection and ranging), SODAR (sound detection and ranging), humidity sensors, GNSS navigation sensors, etc. In the claims, the word "comprising" does not exclude other elements or steps, and the words "a" or "an" do not exclude a plural.

Claims

1. A robotic lawn mower system (10) comprising: a robotic lawn mower (14) comprising: a chassis (18) provided with a set of wheels (22a, 22b, 24) and at least one propulsion motor (62a, 62b) for propelling the robotic lawn mower (14) via the set of wheels (22a, 22b, 24), the chassis (18) enclosing the propulsion motor (62a, 62b) and a controller (58) configured to control operation of at least one of the propulsion motors (62a, 62b); and an outer shell (20) defining an exterior face of the robotic lawn mower (14), the outer shell (20) comprising a skirt (20a) at least partially enclosing the chassis (18) at a distance from the chassis (18), wherein the robotic lawn mower system (10) further comprises: a sensor module (30; 34) comprising a sensor (48; 50) and a sensor module housing (76) enclosing the sensor (48; 50), wherein the sensor module (30; 34) comprises a chassis connection interface (32) for mechanically connecting the sensor module (30; 34) to a module connection interface (26; 28) located on an outer lateral face of the chassis (18), wherein the sensor module housing (76) comprises a main housing body (78) enclosing the sensor (48; 50) and a cantilever member (79) comprising the chassis connection interface (32), wherein the cantilever member (79) holds the main housing body (78) such that a horizontal gap (dl) exists between the main housing body (78) and the chassis (18) when the sensor module (30; 34) is connected to the chassis (18).

2. The robotic lawn mower system (10) of claim 1, wherein, the sensor module (30; 34) is carried by the robotic lawn mower (14), wherein the sensor module (30; 34) holds the sensor (48; 50) outside a vertical projection of the chassis (18) between the chassis (18) and the skirt (20a) when the sensor module (30; 34) is connected to the chassis (18).

3. The robotic lawn mower system (10) of claim 1, wherein, the sensor module (30; 34) is carried by the robotic lawn mower (14), wherein the module connection interface (26; 28) is located on a top face of the chassis (18) and the sensor module housing (76) extends downwards to a position vertically below the module connection interface (26; 28).

4. The robotic lawn mower system (10) according to any one of claims 1-3, wherein the set of wheels (22a, 22b, 24) comprises a pair of drive wheels (22a, 22b) arranged on two opposite lateral sides of the chassis (18) adjacent to a first longitudinal end (19a) of the chassis (18), wherein, the module connection interface (26; 28) is arranged at the first longitudinal end (19a) of the chassis (18).

5. The robotic lawn mower system (10) according to any one of claims 1 to 3, wherein, the module connection interface (26; 28) is formed integrally with the chassis (18).

6. The robotic lawn mower system (10) according to any one of claims 1 to 3, wherein, the chassis (18) is defined by a single continuous and indivisible chassis shell wall (18a) at the location of the module connection interface (26; 28) without through holes and joints.

7. The robotic lawn mower system (10) according to any one of claims 1 to 3, wherein, The module connection interface (28) is located on a top face of the chassis (18), and the sensor module (34) comprises a downward directed sensor (50).

8. The robotic lawn mower system (10) according to any one of claims 1 to 3, wherein, The module connection interface (26; 28) of the chassis (18) comprises a guide portion (G) configured to receive the chassis connection interface (32) of the sensor module (30; 34) from above.

9. The robotic lawn mower system (10) of claim 8, wherein, The guide portion comprises a guide slot (64), and the chassis connection interface (32) comprises a key (66) configured to form a shape fit with the guide slot (64).

10. The robotic lawn mower system (10) of claim 9, wherein, One of the module connection interface (26; 28) and the chassis connection interface (32) comprises a resilient snap element (72) configured to resiliently snap engage with the other of the module connection interface (26; 28) and the chassis connection interface (32) after the chassis connection interface (32) has been moved along the guide portion (G) into a connected position.

11. The robotic lawn mower system (10) according to any one of claims 1 to 3, wherein, The chassis (18) comprises an electrical connection interface (36; 38) for electrically connecting the sensor module (30; 34) to the controller (58), wherein the electrical connection interface (36; 38) is separate from the module connection interface (26; 28) of the chassis (18).

12. The robotic lawn mower system (10) according to any one of claims 1 to 3, wherein, The sensor (48) comprises a radar.

13. A robotic lawn mower system (10) comprising: a robotic lawn mower (14) comprising: a chassis (18) provided with a set of wheels (22a, 22b, 24) and at least one propulsion motor (62a, 62b) for propelling the robotic lawn mower (14) via the set of wheels (22a, 22b, 24), the chassis (18) enclosing the propulsion motor (62a, 62b) and a controller (58) configured to control operation of at least one of the propulsion motors (62a, 62b); and an outer shell (20) defining an exterior face of the robotic lawn mower (14), the outer shell (20) at least partially enclosing the chassis (18) at a distance from the chassis (18), wherein the robotic lawn mower system (10) further comprises: a sensor module (34) comprising a sensor (50) and a sensor module housing (76) enclosing the sensor (50), wherein the sensor module (34) comprises a chassis connection interface (32) for mechanically connecting the sensor module (34) to a module connection interface (28) located on an outer side face of the chassis (18) within the outer shell (20), thereby enabling the sensor module (34) to be carried by the robotic lawn mower (14), wherein the sensor (50) is configured to transmit and / or receive electromagnetic radiation along a transmission path, the sensor module housing (76) comprises an air outlet (82) and a first air inlet, and the sensor module housing (76) comprises an air outlet (82) and a first air inlet, and The sensor module (34) comprises a fan (88) configured to move air along an air guide (90) from the first air inlet to the air outlet (82), wherein one of the air outlet (82) and the first air inlet defines a sensing aperture positioned along the transport path.

14. The robotic lawn mower system (10) of claim 13, wherein, The sensor module housing (76) comprises a liquid-tight electronics compartment (84), wherein the sensor (50) is arranged in the electronics compartment (84), and the electronics compartment (84) comprises a transparent window (86) between the sensor (50) and the air guide (90).

15. The robotic lawn mower system (10) according to claim 13 or 14, wherein, The first air inlet is located on a substantially vertical wall of the sensor module housing (76).

16. The robotic lawn mower system (10) of claim 13 or 14, wherein, When the sensor module (34) is connected to the chassis (18), the first air inlet is positioned vertically higher than the air outlet (82).

17. The robotic lawn mower system (10) of claim 13 or 14, wherein, The first air inlet is configured as an elongated slot with a width of less than 4 mm and a length of more than 20 mm.

18. The robotic lawn mower system (10) of claim 13 or 14, wherein, The sensor module housing (76) comprises a first housing shell (76a) attached to a second housing shell (76b), wherein the first air inlet is defined by an elongated gap extending along an interface between the first housing shell (76a) and the second housing shell (76b).

19. The robotic lawn mower system (10) of claim 13 or 14, wherein, The first air inlet is provided in a portion of the sensor module housing (76) facing the chassis (18) when the sensor module (34) is connected to the chassis (18).

20. The robotic lawn mower system (10) of claim 13 or 14, wherein, The sensor module housing (76) comprises a second air inlet.

21. The robotic lawn mower system (10) of claim 20, wherein, The first air inlet and the second air inlet face different directions.

22. The robotic lawn mower system (10) of claim 13 or 14, wherein, A detection face (50a) of the sensor (50) faces a detection direction along a detection axis, wherein the air guide (90) comprises: an upstream guide section (90a) located at an axial position behind the detection face (50a) with respect to the detection axis; a downstream guide section (90b) located at an axial position in front of the detection face (50a) with respect to the detection axis; and a flow deflector (92) configured to deflect an air flow from the upstream guide section (90a) in a deflection direction towards a space (90c) in front of the sensor (50), the deflection direction forming an angle of more than 45 degrees with the detection axis.

23. The robotic lawn mower system (10) of claim 22, wherein, The upstream guide section (90a) passes the sensor (50) on only one lateral side of the sensor (50).

24. The robotic lawn mower system (10) of claim 13 or 14, wherein, An outlet area of the air outlet (82) is less than 90% of a cross-sectional area of the air guide upstream of the air outlet (82).

25. The robotic lawn mower system (10) of claim 22, wherein, A rotation axis (FR) of the fan (88) is transverse to the detection axis.

26. The robotic lawn mower system (10) of claim 13 or 14, wherein, The transport path forms an angle of less than 20 degrees with a vertical axis.

27. The robotic lawn mower system (10) of claim 13 or 14, wherein, The sensor (50) is positioned at a distance of more than 6 mm from the sensing aperture.

28. The robotic lawn mower system (10) of claim 13 or 14, wherein, The sensor (50) is configured to detect electromagnetic radiation intensities in two different wavelength ranges and to determine a ratio based on the two intensities.

29. The robotic lawn mower system (10) according to any one of claims 1-3 and 13-14, wherein said sensor module is a radar module (30) located between the chassis (18) and the apron (20a), wherein the apron (20a) comprises an apron aperture (96) aligned with the radar module (30).

30. The robotic lawn mower system (10) of claim 29, wherein, said apron aperture (96) is covered by a tamper-evident protection (94; 98).

31. The robotic lawn mower system (10) of claim 29, wherein, said radar module (30) comprises a radar module housing (76) separate from the chassis (18).

32. A sensor module for use as the sensor module (30; 34) in a robotic lawn mower system (10) according to any one of the preceding claims.

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