Patent Description:
<CIT> and <CIT> discloses that in an electric lawn mower, a rechargeable battery and an electric motor activatable by the battery are mounted in a machine body section, and a cutter blade is provided within a cutter housing and rotatable via the electric motor to cut grass. Cover member collectively covers the battery and electric motor. The cover member is shaped to progressively slant upward in a front-to-rear direction of the machine body section, and the cover member has an opening formed in its lower front end portion and an air vent formed in its rear end portion to thereby permit ventilation from the opening to the air vent such that the battery and electric motor can be cooled by air flows.

The invention relates to a robotic lawn mower according to claim <NUM>. Further embodiments are presented in the dependent claims.

The invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, in which:.

Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the application is not limited to the details or methodology set forth in the description or illustrated in the figures.

Referring to the figures, a robotic lawn mower is shown according to various exemplary embodiments. The robotic lawn mower is configured to operate autonomously to maintain grass in a yard at a desired height. The robotic lawn mower incorporates a scalable power system having a number of removable and replaceable battery modules. The robotic lawn mower includes multiple receptacles configured to selectively receive the battery modules, such that the total energy capacity of the robotic lawn mower can be varied by adding or removing battery modules from the receptacles. This allows multiple end users with different power requirements (e.g., differently sized yards, etc.) to use the same robotic lawn mower. The battery modules can also be replaced to extend the operational duration of the robotic lawn mower. The battery modules are configured to be compatible with other types of power equipment as well. By way of example, the same battery modules may be used to power robotic lawn mowers, string trimmers, leaf blowers, hedge trimmers, small chainsaws, vacuums, lights, radios, etc. Accordingly, the battery modules provide the user with additional utility when the robotic lawn mower is turned off or otherwise inactive.

Referring to <FIG>, a piece of outdoor power equipment, shown as robotic lawn mower <NUM>, is illustrated according to an exemplary embodiment. The robotic lawn mower <NUM> includes a structural chassis or housing <NUM> that supports wheels <NUM>, each of which are either unpowered or driven by drivers, shown as electric motors <NUM>. As illustrated, a pair of the wheels <NUM> are each powered by an electric motor <NUM>. In other embodiments, one motor <NUM> drives two or more wheels <NUM>. The robotic lawn mower <NUM> includes a cutting implement <NUM> (e.g., one or more blades, a hub and radially extending string, etc.) that is driven by one or more electric motors <NUM>. In some embodiments, each wheel <NUM> is driven directly by an electric motor <NUM>. As shown in <FIG>, each driven wheel <NUM> is connected to an electric motor <NUM> through a power transmission device, shown as transmission <NUM>. The transmission <NUM> may be configured to perform a gear reduction so that the driven wheel <NUM> and the electric motor <NUM> rotate at different speeds. In some embodiments, the cutting implement <NUM> and/or one or more wheels <NUM> may be powered by the same motor <NUM> (e.g., through a transmission) <NUM>. The robotic lawn mower <NUM> also includes a programmable controller <NUM> in communication with one or more sensors <NUM>-<NUM>, shown in <FIG>, and a user interface <NUM>, shown in <FIG>. A scalable power system <NUM> is provided that distributes electrical power to electric motors <NUM>, the programmable controller <NUM>, the sensor(s) <NUM>-<NUM>, the user interface <NUM>, and other components of the robotic lawn mower <NUM>.

The robotic lawn mower <NUM> is configured to autonomously navigate yards of various sizes and shapes while cutting grass in order to maintain a uniform grass length with minimal or no end user interaction. Because the robotic lawn mower <NUM> can operate without requiring a user's attention, it can operate nearly continuously without a user present. Throughout operation, the robotic lawn mower <NUM> may make a series of shallow cuts on the same area of grass as opposed to one deep cut, reducing the grass clipping size and the power requirements of the electric motor(s) <NUM> driving the cutting implement <NUM>. In some embodiments, the robotic lawn mower <NUM> includes a height adjustment device for adjusting the height of the cutting implement <NUM> relative to the ground. The height adjustment device may be manually operated or operated by an electrically-powered actuator operatively coupled to the programmable controller <NUM>. In some embodiments, the programmable controller <NUM> is programmed to adjust the height of the cutting implement <NUM> depending on the current grass length as detected by a grass height sensor (e.g., the height sensor <NUM>).

Referring to <FIG>, the scalable power system <NUM> incorporated into the robotic lawn mower <NUM> includes a number of removable and rechargeable battery packs or modules <NUM>. The total energy capacity available to the robotic lawn mower <NUM> may be modified by the user by adding or removing battery modules <NUM>. The scalable power system <NUM> allows a variety of end users to purchase the same model of robotic lawn mower <NUM> irrespective of the size of lawn that they wish to mow. End users with larger lawns may configure the system <NUM> to use a larger amount of battery modules <NUM> (e.g., four battery modules), whereas an end user with a smaller lawn may configure the system <NUM> to use a smaller number of battery modules <NUM> (e.g., two battery modules). The system <NUM> reduces costs for the manufacturer, as it allows a small number of different lawn mower variants to be properly sized for a broad variety of applications. The system <NUM> reduces costs for the end user, as it allows the end user to purchase only the amount of battery modules <NUM> necessary for their specific application.

Conventional robotic mowers do not allow a user to easily change or replace a power supply or battery pack. The battery of a conventional robotic lawn mower is fixed in place (e.g. by screws or other fasteners) and is not intended to be replaced or serviced by the end user. By way of example, such a battery may require specialized tools to be removed. This prevents the end user from replacing a depleted battery with a charged one. Also, at the end of the battery's useful life, the user must either have a dealer or service professional replace the battery or buy a new robotic mower. In contrast, the system <NUM> allows a user to quickly and easily replace a depleted or dysfunctional battery module <NUM> with a battery module <NUM> that is new and fully charged. In some embodiments, a user may be able to remove a battery module <NUM> without any tools.

The scalable power system <NUM> allows the user to manage the total energy capacity provided by the system <NUM> to meet their specific needs. When those needs change (e.g., moving to a house with a larger yard), the user can buy additional battery modules <NUM> to meet their new needs. A distributor, original equipment manufacturer ("OEM"), or other seller of equipment can provide a user with a number of battery modules <NUM> expected to meet the specific user's expected needs and then take back or add battery modules <NUM> as needed to meet the user's actual needs. The battery modules <NUM> provided to determine the user's actual needs could all be returned to the seller after the user's actual needs are determined, and the user may then purchase new battery modules <NUM> sufficient to meet those needs. A battery management system <NUM> can be programmed to monitor and track the user's use of the scalable power system <NUM> to help determine the user's actual needs and to determine the number and type of battery modules <NUM> required to meet those actual needs.

In some situations, it may be advantageous for the end user to exchange one or more of the battery modules <NUM> in the robotic lawn mower <NUM> that are partially or completely depleted of charge for one or more battery modules <NUM> having a greater charge. This would allow the end user to extend the operational duration of the robotic lawn mower <NUM>, allowing the robotic lawn mower <NUM> to continue mowing when a conventional robotic lawn mower that incorporates fixed batteries would be forced to cease operation to charge the fixed batteries. This would allow the end user to ensure the entire lawn could be cut by the robotic lawn mower <NUM> in one session, even if the lawn is larger than what the onboard battery modules <NUM> can handle on a single charge.

The battery modules <NUM> can be used in other portable power equipment as well (e.g., string trimmers, leaf blowers, small chainsaws, vacuums, lights, radios, etc.). Employing the same battery modules <NUM> in other equipment provides the end user with additional utility from the battery modules <NUM> of the robotic lawn mower <NUM> when the robotic lawn mower <NUM> is turned off or otherwise inactive. The robotic lawn mower <NUM>, one or more battery modules <NUM>, a standalone charger <NUM>, and one more additional pieces of power equipment powerable by the battery modules <NUM> can be sold in a bundle or package. For example, the end user could use a string trimmer to cut grass in any areas that the robotic lawn mower <NUM> could not reach and use a leaf blower <NUM> to blow away the grass clippings produced by the string trimmer. <FIG> and <FIG> illustrate a piece of outdoor power equipment or power tool, shown as leaf blower <NUM>, that could be bundled with the robotic lawn mower <NUM>. The leaf blower <NUM> includes a receptacle <NUM> similar to the receptacles <NUM> included in the robotic lawn mower <NUM>. The receptacle <NUM> is configured to house and electrically couple the battery module <NUM> to the leaf blower <NUM>. The leaf blower <NUM> also includes a user input device <NUM> (e.g. a trigger or button) configured to selectively activate the leaf blower <NUM>, an electric motor <NUM>, a grip or handle <NUM>, and a fan or blower <NUM> that is powered by the electric motor <NUM>. In some embodiments, other portable power equipment or tools (e.g. string trimmers) incorporate some of the same elements as the leaf blower <NUM>, including a user input device <NUM>, a receptacle <NUM>, a grip or handle <NUM>, and an electric motor <NUM> that uses electrical power from the battery module <NUM> and powers an implement (e.g., the spindle shaft that drives the trimmer head of a string trimmer, the chain of a chain saw, the impeller of a vacuum) or other essential component of the power tool (e.g., the light source of a light, an amplification circuit for a speaker of a radio, etc.).

Referring to <FIG>, the rechargeable battery module <NUM> is illustrated according to an exemplary embodiment. The battery module <NUM> can provide different system voltage (volts), capacity (amp-hours), and energy capacity (watt-hours) levels in different cell configurations (e.g., by using different types, different configurations, or different numbers of battery cells). Each battery module <NUM> includes a number of battery cells <NUM>. In some embodiments, the battery cells <NUM> are lithium-ion cells. In other embodiments, the cells <NUM> are other types of cells (e.g. lead acid, nickel cadmium, etc.). For example, a battery module <NUM> may be rated at <NUM> volts, <NUM> volts, <NUM> volts, etc., depending on the intended end use. The cells <NUM> may be arranged in groups connected in series and/or connected in parallel. In some embodiments, the battery module <NUM> is rated at <NUM> volts and is available in <NUM> Amp-hour and <NUM> Amp-hour capacities. The battery modules <NUM> each include a housing or outer shell <NUM> to house, seal, and provide structure for the cells <NUM> and protect the cells <NUM> from impact. In some embodiments, the battery modules <NUM> include an interface <NUM> that indicates to the user how much charge remains in the battery module <NUM>. The interface <NUM> may include a push button for user input and a number of lights that indicate the remaining charge to the user. By way of example, if a battery module <NUM> is currently charged to <NUM>% capacity, four lights of the interface <NUM> may be illuminated in response to the user interacting with the push button. If the battery module then drains to <NUM>% capacity, three lights of the interface <NUM> may be illuminated in response to the user interacting with the push button.

Because the power system <NUM> is scalable by installing and removing battery modules <NUM> as needed, the battery modules <NUM> need to be of a manageable size and weight for the end user to lift, carry, install, remove, etc. so that the battery module <NUM> is configured to facilitate manual portability by the user. The battery module <NUM> is small enough, light enough, and graspable enough to be manually portable by a user. The user does not need a lift, cart, or other carrying device to move the battery modules <NUM>. In some embodiments, the battery module <NUM> includes a grip or handle to facilitate manual portability by the end user. As shown in <FIG> and <FIG>, the battery module <NUM> also defines one or more channels <NUM> that are configured to receive keys or rails <NUM> raised from the surface of the receptacle <NUM> to guide the battery module <NUM> into position when installed into a receptacle <NUM>. In other embodiments, the receptacles <NUM> define channels <NUM> configured to receive raised rails <NUM> on the battery modules <NUM>. In some embodiments, the robotic lawn mower <NUM> is also of a manageable size and weight for the end user. For example, in some embodiments the robotic mower <NUM> weighs <NUM> pounds or less and the battery module <NUM> weighs six pounds (<NUM> kilograms) or less so that in embodiments of the mower <NUM> including four battery receptacles <NUM>, the maximum weight of the mower <NUM> with four battery modules <NUM> installed is sixty pounds (<NUM> kilograms) or less.

Referring to <FIG>, the scalable power system <NUM> includes a base <NUM> coupled to or integrally formed as part of the housing <NUM> of the robotic lawn mower <NUM>. The base <NUM> has multiple mounting locations, shown as receptacles <NUM>, each configured to receive one battery module <NUM>. The base <NUM> provides a structure to support the receptacles <NUM>. As shown in <FIG>, the base <NUM> is a horizontal tray or platform that includes the receptacles <NUM>. In other embodiments, the base <NUM> is arranged as a vertical or angled rack in which the receptacles <NUM> may be located one above the other. The receptacles <NUM> and the battery modules <NUM> each include electrical connectors or contacts <NUM> that allow current to flow between the battery modules <NUM> and the receptacles <NUM>. In some embodiments the receptacle <NUM> includes a set of male contacts <NUM> configured to mate with a corresponding set of female contacts <NUM> on the battery module <NUM>. In other embodiments, the receptacle <NUM> includes a set of female contacts <NUM> and the battery module <NUM> includes a set of male contacts <NUM>. In some embodiments, the receptacles <NUM> are electrically connected to one another in parallel. As shown in <FIG>, the receptacles <NUM> are electrically coupled to a terminal block or power bus <NUM> by a series of wires <NUM> or bus bars. The power bus <NUM> distributes electrical energy from the battery modules <NUM> through wires <NUM> to power a load (e.g. a motor <NUM>). An electrical disconnect switch <NUM> may be provided to disconnect the battery modules <NUM> such that no current can be supplied through the wires <NUM> to power an electrical load. The switch <NUM> may be any type of switch (e.g., a toggle switch, a push button switch, a relay, etc.) and may be mechanically or electrically actuated.

Each of the receptacles <NUM> may include one or more retainers or locking mechanisms <NUM> configured to secure the battery module <NUM> to the receptacle <NUM>. In some embodiments, as shown in <FIG>, <FIG>, and <FIG>, the receptacle <NUM> at least partially surrounds the battery module <NUM> such that the battery module <NUM> can only translate along one axis. The locking mechanism <NUM> also includes a latch <NUM> that locks into, pushes on, or otherwise engages the battery module <NUM>, securing it in the receptacle <NUM>. The locking mechanism <NUM> includes a spring <NUM> that assists the user in removing the battery module <NUM> by providing a biasing force to bias the battery modules <NUM> partially or totally out of the receptacle <NUM>. In other embodiments, as shown in <FIG> and <FIG>, the locking mechanism <NUM> includes a base or support <NUM> and one or more rails <NUM> extending outward from the support <NUM>. The channel <NUM> of the battery module <NUM> is sized to receive the rail <NUM> of the locking mechanism <NUM> in order to guide the battery module <NUM> into an engaged position relative to the receptacle <NUM> so that the contacts <NUM> of the battery module <NUM> fully engage the contacts <NUM> of the receptacle <NUM>, completing the electrical connection between the battery module <NUM> and the receptacle <NUM>. In other embodiments, the positions of the rails <NUM> and the channels <NUM> are switched so that the rail <NUM> is located on the battery module <NUM>, and the channel <NUM> is located on the locking mechanism <NUM>. The receptacle <NUM> further includes a latch <NUM> that engages the exterior of the battery module <NUM>, providing resistance against removal of the battery module <NUM>. In some embodiments, the battery modules <NUM> can be attached to and removed from the receptacles <NUM> without the use of tools. This simplifies the process of attaching or removing battery modules <NUM>. In some embodiments, different locking mechanisms are provided (e.g., latches, straps, or locks) that may be secured with or without the use of hand tools to secure a battery module <NUM> to a receptacle <NUM>.

Depending on the needs of a particular user, the scalable power system <NUM> may have one or more unused or empty receptacles <NUM>. In some embodiments, a cover or other protective device is provided to temporarily cover open receptacles <NUM> that do not have a battery module <NUM> installed (e.g., when a user has only a small area of grass to maintain). The cover may be configured to seal the unused receptacle <NUM>, preventing water and debris from accumulating in the receptacle <NUM> and limiting user access to the receptacle <NUM>. The cover may be secured in place by the same locking mechanism <NUM> as the battery modules <NUM>.

The scalable power system <NUM> includes a battery management system or controller <NUM>. The controller <NUM> includes a processor and a memory device. The processor can be implemented as a general purpose processor, an application specific integrated circuit (ASIC), one or more field programmable gate arrays (FPGAs), a group of processing components, or other suitable electronic processing components. The memory device (e.g., memory, memory unit, storage device, etc.) is one or more devices (e.g., RAM, ROM, Flash memory, hard disk storage, etc.) for storing data and/or computer code for completing or facilitating the various processes, layers and modules described in the present application. The memory device may be or include volatile memory or non-volatile memory. The memory device may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in the present application. According to an exemplary embodiment, the memory device is communicably connected to processor through a processing circuit and includes computer code for executing (e.g., by processing circuit and/or processor) one or more processes described herein. In some embodiments, the battery management system <NUM> includes both hardware and software. In other embodiments, the battery management system <NUM> is entirely hardware based. In some embodiments, the battery management system <NUM> is integrated with the programmable controller <NUM>.

The battery management system <NUM> controls charging and discharging of the battery modules <NUM> to optimize operation of the system <NUM> and individual battery modules <NUM>. The battery management system <NUM> is programmed to automatically manage current draw from the battery modules <NUM> to power an electrical load. System-wide control of the battery modules <NUM> is necessary to allow the individual battery modules <NUM> to communicate and coordinate charge levels and discharge rates and control which battery module <NUM>, or groups of battery modules <NUM>, is being discharged during particular moments of operation.

The battery management system <NUM> may allow the battery modules <NUM> to be "hot swapped" into and out of the system <NUM> without regard for the charge of the battery module <NUM> being added or the battery modules <NUM> remaining connected to receptacles <NUM>. The battery management system <NUM> controls which battery modules <NUM> supply current to the power bus <NUM>. The battery management system <NUM> communicates with and controls the operation of each battery module <NUM> connected to the base <NUM>. The battery management system <NUM> determines which battery module <NUM> or group of battery modules <NUM> provides current to the power bus <NUM> or even to another battery module <NUM> to recharge that battery module <NUM>. The battery management system <NUM> is used to control the state of charge of one or more of the battery modules <NUM> by managing the relative charge levels of the multiple battery modules <NUM> in use in the system <NUM>. In some embodiments, the battery module <NUM> with the lowest charge level is not used and does not provide power to the equipment being powered by the system <NUM> until the other battery modules <NUM> in the system have reached a similar state of charge.

In some embodiments, the robotic lawn mower <NUM> charges by driving up to or onto a charging platform <NUM>, shown in <FIG>, which serves as both a home location for the robotic lawn mower <NUM> and a charger for the battery modules <NUM>. In some embodiments, as illustrated in <FIG>, the charging platform <NUM> provides electrical power to the robotic lawn mower <NUM> through physical contacts <NUM>. In the illustrated embodiment, the contacts <NUM> on the charging platform <NUM> are male, and the contacts <NUM> on the robotic lawn mower <NUM> are female. In other embodiments, the robotic lawn mower <NUM> includes the male contacts <NUM> and the charging platform <NUM> includes the female contacts <NUM>. In yet other embodiments, as illustrated in <FIG>, the charging platform <NUM> provides power to the robotic lawn mower <NUM> through an inductive charging circuit. In this case, the charging platform <NUM> includes an inductive charging transmitter <NUM> and the robotic lawn mower <NUM> includes an inductive charging receiver <NUM>. In some embodiments, the charging platform <NUM> includes a guide <NUM> (e.g., an infrared signal emitter) that emits a signal that, when received by a receiver <NUM> (e.g., an infrared signal receiver) on the robotic lawn mower <NUM>, directs the robotic lawn mower <NUM> to the charging platform <NUM>. In some embodiments, the charging platform <NUM> includes one or more walls or rails <NUM> that contact the robotic lawn mower <NUM> and guide the robotic lawn mower <NUM> into a position where the inductive charging circuit (i.e., the transmitter <NUM> and the receiver <NUM>) and/or physical charging circuit (i.e., the contacts <NUM>) are connected.

In some embodiments, the robotic lawn mower <NUM> is charged by removing the battery modules <NUM> and placing them in a standalone charger <NUM>, shown in <FIG> and <FIG>. The charger <NUM> may be stored indoors, separate from the robotic lawn mower <NUM>, providing a convenient way for the end user to charge the battery modules <NUM> should the end user choose to use the battery modules <NUM> with another piece of power equipment (e.g., a string trimmer, the leaf blower <NUM>, a radio, etc.). The charger <NUM> may include a higher current charging circuit than the inductive charging circuit of the charging platform <NUM> and accordingly may act as a "fast charger" that charges the battery modules <NUM> more quickly than the inductive charging circuit. The standalone charger <NUM> includes a receptacle <NUM> in order to connect the battery module <NUM> to the charger <NUM>. In some embodiments, the charger <NUM> includes an electrical cord to connect to the electrical grid and a transformer, rectifier, or other voltage control device. In some embodiments the charger <NUM> includes a display <NUM> (e.g. one or more lights that change colors or flash) that provides the user with information regarding the current state of the battery module <NUM> (e.g., charged, empty, charging, battery temperature, etc.).

The robotic lawn mower <NUM> includes a programmable controller <NUM> that receives information from the sensor(s) <NUM>-<NUM>, the user interface <NUM>, and the battery management system <NUM>, and issues commands or returns information to other parts of the robotic lawn mower <NUM> (e.g. to control the speeds or directions of the motors <NUM> or to select which battery module(s) <NUM> to electrically couple to which components). The programmable controller <NUM> can include a processor and a memory device. The processor can be implemented as a general purpose processor, an application specific integrated circuit (ASIC), one or more field programmable gate arrays (FPGAs), a group of processing components, or other suitable electronic processing components. The memory device (e.g., memory, memory unit, storage device, etc.) is one or more devices (e.g., RAM, ROM, Flash memory, hard disk storage, etc.) for storing data and/or computer code for completing or facilitating the various processes, layers and modules described in the present application. The memory device may be or include volatile memory or non-volatile memory. The memory device may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in the present application. According to an exemplary embodiment, the memory device is communicably connected to processor through a processing circuit and includes computer code for executing (e.g., by processing circuit and/or processor) one or more processes described herein. The programmable controller <NUM> communicates with other parts of the robotic lawn mower <NUM> using a wired or wireless (e.g. Bluetooth) connection.

Referring to <FIG>, the robotic lawn mower <NUM> includes the programmable controller <NUM>, the motors <NUM>, and one or more sensors <NUM>-<NUM>. The robotic lawn mower <NUM> may be used with a guidance system like the one illustrated in <FIG> where a boundary wire antenna, shown as wire <NUM>, is laid in a loop around the area where the end user requires mowing. The wire <NUM> may be laid atop the ground or buried. The wire <NUM> establishes the boundary of the area to be mowed by the robotic lawn mower <NUM>. This wire <NUM> acts as an antenna and broadcasts a signal (e.g., a radio frequency signal of a first frequency, a first signal transmitting data, etc.) that is detected by a boundary detection sensor <NUM> onboard the robotic lawn mower <NUM>, allowing the robotic lawn mower <NUM> to detect the boundaries of an area which should be mowed. If the user would like to identify an obstacle <NUM> (e.g., a flower bed, a building, a pond, a tree, etc.) inside the area enclosed by the exterior boundary or loop, then the boundary wire <NUM> may be run inside the loop, around the obstacle <NUM>, and back to the exterior loop. If the wire <NUM> is in close enough proximity to itself, then the signals from both lengths of wire <NUM> interfere, creating a section <NUM> of wire <NUM> where no boundary signal can be received, allowing the robotic lawn mower <NUM> to move over this section <NUM> of wire <NUM>. Additionally, a guide wire <NUM> may be laid through the center of narrow areas that might otherwise be difficult to navigate. The guide wire <NUM> emits a signal (e.g., a radio frequency signal of a second frequency different from the first frequency, a second signal transmitting data different from the data transmitted by the first signal, etc.) detected by the boundary detection sensor <NUM>, facilitating the robotic lawn mower <NUM> following a specified path defined by the guide wire <NUM>. When the programmable controller <NUM> receives a signal from the boundary detection sensor <NUM>, it may control the motors <NUM> to run in a different direction or at a different speed, changing the direction of travel of the robotic lawn mower <NUM>. The wire <NUM> and the wire <NUM> may be electrically coupled to the charging platform <NUM>, which in turn supplies a current to the wire <NUM> and the wire <NUM> to produce the signals.

The robotic lawn mower <NUM> may incorporate a collision detection sensor <NUM> allowing it to detect and avoid other objects (e.g., a "bump" switch on one or more of the sides of the robotic lawn mower <NUM> that activates when it makes contact with another object or a distance sensor (e.g., ultrasonic, laser, etc.), etc.). Upon detection of an object in the current drive path of the robotic lawnmower <NUM>, the programmable controller <NUM> is configured to change the direction and/or speed of the motors <NUM> to execute a turn such that the robotic lawn mower <NUM> continues along a new drive path, avoiding whatever object is in the current drive path. The robotic lawn mower <NUM> may incorporate a height sensor <NUM> to facilitate detection of the vertical location of the robotic lawn mower <NUM> relative to the ground (e.g., a light sensor that detects light that enters underneath the robotic lawn mower <NUM>, an ultrasonic distance sensor, a switch that is actuated by touching the ground, etc.). The height sensor <NUM> may be coupled to the housing <NUM> near the front side of the robotic lawn mower <NUM> and configured to detect if the robotic lawn mower <NUM> is about to drive over a ledge or other rapid change in elevation, allowing the programmable controller <NUM> to steer the robotic lawn mower <NUM> away from the ledge. The height sensor <NUM> may also be used to determine the current length of the grass. The robotic lawn mower <NUM> may incorporate a location sensor <NUM> (e.g., a GPS system, a differential GPS system, an optical encoder configured to count rotations of each wheel <NUM>, etc.) to facilitate mapping of the area. With location data from the location sensor <NUM> and the information from the boundary detection sensor <NUM>, the collision detection sensor <NUM>, and the height sensor <NUM>, a map of the area with all the obstructions and current grass lengths may be generated by the programmable controller <NUM>. In some embodiments, the boundary wire <NUM> and/or the guide wire <NUM> may be removed after the area has been mapped, and the robotic lawn mower <NUM> can use the map to determine where to mow.

Additionally, the robotic lawn mower <NUM> may include a gyroscopic sensor <NUM> configured to measure the current orientation of the robotic lawn mower <NUM>. The programmable controller <NUM> is configured to use information from the gyroscopic sensor <NUM> to determine if the robotic lawn mower <NUM> has tilted beyond a certain threshold orientation (e.g., <NUM> degrees from horizontal, <NUM> degrees from horizontal, <NUM> degrees from horizontal, <NUM> degrees from horizontal, etc.), which indicates that the robotic lawn mower <NUM> has been picked up or fallen over. In this event, the programmable controller <NUM> may be configured to cease powering the motors <NUM> that run the cutting implements <NUM> to stop movement of the cutting implements <NUM>.

Conventional robotic lawn mowers have difficulty driving in a straight line when driving in a direction near perpendicular to the grade of a slope due to the effect of gravity. Using heading information from the gyroscopic sensor <NUM> or wheel slip information from the optical encoders and GPS, the programmable controller <NUM> may be configured to detect a deviation from the desired direction of travel or from the desired path and modulate the power delivered to each wheel in order to modify the course and/or eliminate any wheel slippage. As conventional robotic lawn mowers drive, the charge on their fixed batteries continuously decreases, resulting in a continuous decrease in the maximum grade of hill they can scale. Because the battery management system <NUM> can selectively draw power from one or more different battery modules <NUM>, the robotic lawn mower <NUM> can climb steep hills, even after long periods of operation. For example, the battery management system <NUM> could save one fully charged battery module <NUM> while driving on level ground and use it when it encounters a steeper slope. The battery management system <NUM> may be configured to draw from this reserve battery module <NUM> when the programmable controller <NUM> determines (e.g., using information from the gyroscopic sensor <NUM> or from the location sensor <NUM>) that the robotic lawn mower <NUM> has deviated from the desired direction of travel along a desired path by at least a threshold angle. Alternatively, the battery management system <NUM> may be configured to draw from this reserve battery module <NUM> when the programmable controller <NUM> determines (e.g., using information from the gyroscopic sensor <NUM>) that the orientation of a robotic lawnmower is within a predetermined range (e.g., indicative of a slope having at least a threshold grade).

The robotic lawn mower <NUM> includes the user interface <NUM> to display information to the user and receive control inputs from the user. In some embodiments, the user interface <NUM> includes a display screen and one or more user input devices (e.g., switches, buttons, key-switches, dials, etc.). In some embodiments, the display screen is a touch screen display that both displays information to the user and receives user inputs. In some embodiments, the user interface <NUM> includes an application installed onto a computer, smartphone, tablet, or other device. Such a device may connect to the programmable controller <NUM> through a wired connection or through a wireless connection (e.g., Bluetooth, Wi-Fi, infrared, etc.). In some embodiments, the user interface <NUM> provides the user with information related to the operation of the robotic lawn mower <NUM>. By way of example, the user interface <NUM> may indicate the state of charge of the battery modules <NUM>, the run time provided by the battery modules <NUM>, or the current status of the robotic lawn mower <NUM> (e.g., operating, charging, etc.) or alert the user if the robotic lawn mower <NUM> needs maintenance or needs user intervention in the event of being stuck, etc. The user interface <NUM> can also receive inputs from the user to control the robotic lawn mower <NUM>. By way of example, the user interface <NUM> may allow the user to select between various cutting heights, issue run and stop commands, develop a schedule for when the robotic lawn mower <NUM> will operate, or to tell the robotic lawn mower <NUM> to return to the charging platform <NUM>.

Referring to <FIG> and <FIG>, an alternative embodiment of the user-scalable power system <NUM> is shown. In this embodiment, each battery module <NUM> is associated with a separate base <NUM> having a receptacle <NUM>. The bases <NUM> are arranged with the receptacles <NUM> opening upward such that the battery modules <NUM> may each be removed by lifting the battery modules <NUM> vertically out of the receptacles <NUM>. To facilitate manual portability, each of the battery modules <NUM> includes a grip or handle <NUM> arranged along an upper surface of the battery module <NUM>. The battery modules <NUM> may be removed individually and in any order. In some embodiments, the bases <NUM> include a locking mechanism <NUM> that holds the battery modules <NUM> within the receptacle <NUM>. By way of example, the locking mechanism <NUM> may include a latch (e.g., similar to the latch <NUM>) that is configured to selectively engage a portion of the battery module <NUM>, holding the battery module <NUM> within the receptacle <NUM>. In other embodiments, the bases <NUM> are rotated such that the receptacles <NUM> open in a direction other than directly upwards. In such embodiments, the locking mechanisms <NUM> facilitate holding the battery modules <NUM> in place regardless of the force of gravity on the battery modules <NUM>.

Each base <NUM> may be used separately, or multiple bases <NUM> may be used in combination to provide the capacity for a greater number of battery modules <NUM>. Accordingly, the number of bases <NUM> may be adjusted to suit the power needs of a particular application, either during production or by the end user. By way of example, a relatively small number of bases <NUM> may be provided on a robotic lawn mower <NUM> when the end user has a relatively small lawn and, as such, the robotic lawn mower <NUM> is only required to run for a relatively short period of time. In some embodiments, additional bases <NUM> may be added to the robotic lawn mower <NUM> to allow a greater number of battery modules <NUM> to be connected at a given time, increasing the maximum total energy capacity of the robotic lawn mower <NUM>.

The bases <NUM> shown in <FIG> and <FIG> may cooperate with the battery modules <NUM> to power a piece of power equipment (e.g., the robotic lawn mower <NUM>, a leaf blower, a chain saw, etc.). In such embodiments, the receptacle <NUM> of each base <NUM> includes components that electrically couple the battery modules <NUM> to the power equipment (e.g., contacts <NUM>, etc.). Alternatively, the bases <NUM> shown in <FIG> and <FIG> may each be configured as a standalone charger similar to the standalone charger <NUM> or may be coupled together and configured as a standalone charging bank. Accordingly, in some embodiments, one or more of the bases <NUM> include an electrical cord to connect them to the electrical grid and a transformer, rectifier, or other voltage control device. In some configurations, the one or more bases <NUM> may include voltage regulation circuits to allow the robotic lawn mower <NUM> to be connected directly to the grid via the electrical cord. The receptacles <NUM> may also include electrical contacts <NUM> to facilitate electrically coupling to the battery modules <NUM>.

<FIG> and <FIG> illustrate a robotic lawn mower <NUM> according to another exemplary embodiment. This robotic lawn mower <NUM> is configured for commercial or premium residential applications. Consequently, the robotic lawn mower <NUM> shown in <FIG> and <FIG> is larger than the robotic lawn mower <NUM> shown in <FIG>, which is configured for standard residential applications. The robotic lawn mower <NUM> shown in <FIG> and <FIG> includes components similar to those of the robotic lawn mower <NUM> shown in <FIG>, however, the robotic lawn mower <NUM> shown in <FIG> and <FIG> includes a larger number of cutting implements <NUM> to facilitate cutting grass at a faster rate (i.e., requiring a shorter period of time to cut a given area of grass). The robotic lawn mower <NUM> shown in <FIG> and <FIG> utilizes the battery modules <NUM> shown in <FIG> and <FIG>, however, each base <NUM> in this embodiment has three receptacles <NUM> and is configured to hold up to three battery modules <NUM>. The robotic lawn mower <NUM> shown in <FIG> and <FIG> includes a pair of bases <NUM>, each substantially evenly spaced about the center of gravity of the robotic lawn mower <NUM>. Alternatively, a robotic lawnmower <NUM> may include a base <NUM> and/or one or more receptacles <NUM> approximately centered about the center of gravity of the robotic lawn mower <NUM>.

Referring to <FIG> and <FIG>, a stand-alone power supply <NUM> configured for use with the battery modules <NUM> shown in <FIG> and <FIG> is illustrated according to an exemplary embodiment. The power supply <NUM> may be able to supply power to devices of the user's choosing (e.g., via one or more standard electrical outlets) or may be designed for use to power a particular piece or family of equipment (e.g., hand-held power tools such as leaf blowers, string trimmers, etc.).

Power supply <NUM> includes a base <NUM> and at least one receptacle <NUM>. As illustrated, the base <NUM> is configured as a backpack and includes straps <NUM> that allow a user to carry the power supply <NUM> on his back. In some embodiments, due to weight limitations, a backpack power supply <NUM> includes a single receptacle <NUM> for receiving a single battery module <NUM>. The base <NUM> includes one or more locking mechanisms <NUM> to secure the battery module <NUM> to the receptacle <NUM>. In the embodiment shown, the locking mechanisms <NUM> are clips that engage an indentation in the outer shell <NUM> of the battery module <NUM>. As illustrated the power supply <NUM> includes a cord <NUM> for providing power to a hand-held power tool. In some embodiments, the cord <NUM> is configured to selectively electrically couple to the power tool through a standard electrical outlet such that various hand-held power tools may be coupled to the same power supply <NUM>. In the embodiment shown in <FIG>, the hand-held power tool is a leaf blower <NUM>. A portion of the leaf blower <NUM> (e.g., an electric motor, an impeller, a fan shroud, etc.) is integrated into the base <NUM>. Accordingly, the cord <NUM> may be omitted, and the power supply <NUM> may be directly electrically coupled to the leaf blower <NUM>. Alternatively, or additionally, the power supply <NUM> can include one or more standard electrical outlets, allowing the user to plug in and power electrical devices of his choosing (e.g., computers, laptops charging systems for cell phones or other portable devices, radios, etc.).

In one exemplary embodiment, a homeowner utilizes an outdoor power equipment system to facilitate total outdoor care of their property. The homeowner may set up a robotic lawn mower <NUM> (e.g., the robotic lawn mower <NUM> shown in <FIG>) along with a charging station <NUM>. The homeowner may choose to bury or otherwise lay a wire <NUM> and a wire <NUM> to facilitate controlled operation of the robotic lawn mower <NUM>. The homeowner may then set up an operating schedule for the robotic lawn mower <NUM> using the user interface <NUM> on a smartphone or other user device such that the robotic lawn mower <NUM> regularly and autonomously mows the lawn. The homeowner may have a charger <NUM> setup in their home to charge a spare battery module <NUM> for use with the leaf blower <NUM>, a string trimmer, a chain saw, or another piece of portable outdoor power equipment. The homeowner may use the portable outdoor power equipment and the robotic lawn mower <NUM> may operate simultaneously. Alternatively, the homeowner may remove the battery modules <NUM> from the robotic lawn mower <NUM> for use with the portable power equipment when the robotic lawn mower is not in use.

In another exemplary embodiment, a commercial lawn care service utilizes an outdoor power equipment system to facilitate total outdoor care of a property using only a small number of employees. One employee may arrive at a job site with one or more robotic lawn mowers <NUM> (e.g., the robotic lawn mower <NUM> shown in <FIG> and <FIG>), where the number of robotic lawn mowers <NUM> may be varied to correspond to the size of the lawn being maintained. The employee may setup the robotic lawn mowers <NUM> to begin cutting the grass autonomously. After the robotic lawn mowers <NUM> are activated, the employee may simultaneously use the power supply <NUM> to complete other outdoor tasks. By way of example, the employee may use the leaf blower <NUM> to blow leaves into an organized pile. By way of another example, the employee may connect the power supply <NUM> to a chainsaw and prune trees or break down fallen tree limbs. By way of yet another example, the employee may connect the power supply <NUM> to a hedge trimmer and shape shrubberies.

To facilitate extended outdoor care sessions, the employee may bring one or more chargers (e.g., the charging platform <NUM>, the standalone charger <NUM>, charging banks as shown in <FIG> and <FIG>, etc.) and additional battery modules <NUM>. The chargers may be connected to the electrical grid (e.g., through an electrical cord and a standard power outlet), or the vehicle used to transport the robotic lawn mowers <NUM> may be outfitted with a generator (e.g., a gasoline generator, a natural gas generator, etc.). Accordingly, the battery modules <NUM> may be charged while the outdoor tasks are performed, and the discharged battery modules <NUM> can then be exchanged for charged ones as needed. The robotic lawn mowers <NUM> may communicate to the employee that the battery modules <NUM> should be exchanged after the battery management system <NUM> determines that the battery modules <NUM> are sufficiently depleted. By way of example, the programmable controller <NUM> may issue a notification to the user interface <NUM> (e.g., a smartphone or other user device) to indicate that the battery modules <NUM> should be exchanged. By way of another example, the robotic lawn mower <NUM> may be configured to automatically return to a certain location (e.g., to the vehicle used to transport the robotic lawn mowers <NUM>, to a predetermined location such as a driveway or property line, etc.) to indicate that the battery modules <NUM> should be exchanged. The depleted battery modules <NUM> may then be exchanged for charged ones and recharged. Alternatively, the robotic lawn mowers <NUM> may each return to a charging platform <NUM> automatically (e.g., when the battery modules <NUM> are depleted, when maintenance of the lawn is complete, in response to a user command through the user interface <NUM>, etc.). The charging platforms <NUM> may be coupled to a trailer of the vehicle to facilitate transportation and minimize setup time of the charging platforms <NUM>.

Referring to <FIG>, the battery modules <NUM> are shown according to another exemplary embodiment. In this embodiment, the battery modules <NUM> are configured to be stacked atop one another. The battery modules <NUM> each include a set of female contacts <NUM> arranged along a top surface of the battery module <NUM> and a set of male contacts <NUM> arranged along a bottom surface of the battery module <NUM>. Accordingly, as a battery module <NUM> is stacked atop another battery module <NUM>, the male and female contacts <NUM> engage, electrically coupling the battery modules <NUM> together (e.g., in parallel, in series, etc.). The battery modules <NUM> may be stacked atop a base <NUM>. Such a base <NUM> may include female contacts <NUM> configured to engage the male contacts <NUM> of the bottommost battery module <NUM>.

The top surface of each battery module <NUM> is raised, and the bottom surface of each battery module is recessed, such that the battery modules <NUM> automatically engage and center themselves when stacked. Once centered, the battery modules <NUM> may be coupled to one another using a set of locking mechanisms, shown as locking mechanisms <NUM>. Each locking mechanism <NUM> includes a catch <NUM> extending laterally outward from the corresponding battery module <NUM> and a latch <NUM> rotatably coupled to the corresponding battery module <NUM>. The latch <NUM> for one battery module <NUM> is configured to rotate to selectively engage the catch <NUM> of an adjacent battery module <NUM>, coupling the battery modules <NUM> together. In some embodiments, the base <NUM> includes a set of catches <NUM> configured to engage the latches <NUM> of the bottommost battery module <NUM>.

Each of the battery modules <NUM> described herein may be configured in a variety of ways depending upon the desired application (e.g., the type of power equipment being used, the power input (e.g., voltage, current, etc.) required by the power equipment, the desired runtime of the power equipment, etc.). In one configuration, the battery module <NUM> includes seventy-eight cells. Each cell <NUM> is rated at <NUM> volts and <NUM> amp-hours. The battery module <NUM> arranges the cells <NUM> in a 13S6P configuration with <NUM> cells <NUM> connected in series in a group and six groups of cells <NUM> connected in parallel. The series configuration yields a system voltage of <NUM> volts for the battery module <NUM>. The six parallel configuration yields fifteen amp-hours capacity for the battery module <NUM>. The combination of the two provides <NUM> watt-hours of energy capacity for the battery pack.

In some embodiments, the battery module <NUM> has the cells <NUM> arranged in multiple layers. For a 13S6P configuration battery module <NUM>, each layer includes cells <NUM> arranged in six groups and the battery module <NUM> includes two layers of cells.

In an alternative embodiment, the cells <NUM> are arranged in a single layer with six groups of thirteen cells <NUM> each. In a scalable power system <NUM> using four of the 13S6P configuration battery modules <NUM>, the total energy capacity would be <NUM> watt-hours (<NUM> kilowatt-hours). In this embodiment the battery module <NUM> weighs about <NUM> pounds and is substantially shaped like a cube.

In another configuration, the battery module <NUM> includes eighty-four cells <NUM> arranged in a 14S6P configuration. Using cells <NUM> rated at <NUM> volts and <NUM> amp-hours, this configuration yields a voltage of <NUM> volts, <NUM> amp-hours of capacity and <NUM> watt-hours of energy capacity. In other embodiments using cells <NUM> rated at <NUM> volts and <NUM> amp-hours, the 13S6P arrangement would yield a voltage of <NUM> volts, <NUM> amp-hours of capacity, and <NUM> watt-hours of energy. In the 14S6P configuration, the voltage would be <NUM> volts, <NUM> amp-hours of capacity, and <NUM> watt-hours of energy.

In another configuration, the battery module <NUM> includes one hundred cells <NUM> arranged in a 20S5P configuration having five groups of twenty cells <NUM> each. Each group or row of twenty cells <NUM> is welded or otherwise connected together in series (e.g., by conductors), and each of the five groups of twenty cells <NUM> is welded or connected together in parallel (e.g., by conductors). The cells <NUM> used in the battery pack may be <NUM> form factor cylindrical cells <NUM> (<NUM> millimeter diameter and <NUM> millimeter length). These cells <NUM> may be available in <NUM> amp-hours, <NUM> amp-hours, <NUM> amp-hours, and other cell ratings. Using cells <NUM> rated at <NUM> volts, and <NUM> amp-hours, a 20S5P configuration battery module provides a voltage of <NUM> volts, <NUM> amp-hours of capacity, and <NUM> watt-hours of energy. Using cells <NUM> rated at <NUM> volts, and <NUM> amp-hours, a 20S5P configuration battery module provides a voltage of <NUM> volts, <NUM> amp-hours of capacity, and <NUM> watt-hours of energy. Using cells <NUM> rated at <NUM> volts and <NUM> amp-hours, a 20S5P configuration battery pack provides a voltage of <NUM> volts, <NUM> amp-hours of capacity, and <NUM> watt-hours of energy.

In some embodiments, the battery module <NUM> provides about one kilowatt-hour of energy (e.g., between <NUM> watt-hours and <NUM> kilowatt-hours) and weighs less than twenty pounds. End products powered by the scalable power system <NUM> may scale in increments that can be measured in kilowatt-hours of energy. For example, a standard residential lawn mower may require between two and three kilowatt-hours of energy capacity and a premium residential lawn mower may require between three and four kilowatt-hours of energy capacity. Battery modules <NUM> that provide about one kilowatt-hour of energy and weigh less than twenty pounds allow the end user to easily choose between a standard configuration and premium configuration of the lawn mower <NUM> or other end product by providing a reasonable number of battery modules <NUM> to achieve either configuration and battery modules <NUM> of a size and weight that can be easily manipulated as needed by the end user. The battery modules <NUM> are interchangeable between different pieces of equipment each equipped with the scalable power system <NUM> (e.g., between a lawn mower, a leaf blower, a string trimmer, etc.).

In the embodiment shown in <FIG>, the battery module <NUM> includes twenty cells <NUM> arranged in a 20S1P configuration. Using cells <NUM> rated at <NUM> volts (<NUM> volts nominal) and <NUM> amp-hours, this configuration yields a voltage of <NUM> volts (<NUM> volts nominal), <NUM> amp-hours of capacity and <NUM> watt-hours of energy capacity. In this embodiment, the battery module <NUM> weighs about <NUM> pounds and can be charged to <NUM> percent in <NUM> minutes and to <NUM> percent in <NUM> minutes. In an alternative embodiment, the battery module <NUM> includes forty cells <NUM> arranged in a 20S2P configuration. Using cells <NUM> rated at <NUM> volts (<NUM> volts nominal) and <NUM> amp-hours, this configuration yields a voltage of <NUM> volts (<NUM> volts nominal), <NUM> amp hours of capacity, and <NUM> watt-hours of energy capacity. In this embodiment, the battery module <NUM> weighs about <NUM> pounds and can be charged to <NUM> percent in <NUM> minutes and to <NUM> percent in <NUM> minutes. Another alternative embodiment is contemplated using a similar structure that provides <NUM> amp-hours of capacity and <NUM> watt-hours of energy capacity. In this embodiment, the battery module <NUM> can be charged to <NUM> percent in <NUM> minutes and to <NUM> percent in <NUM> minutes.

In another embodiment, the battery modules <NUM> have a weight of approximately <NUM>-<NUM> pounds. In this embodiment, the battery modules <NUM> are each <NUM> kW battery packs. In yet another embodiment, the battery module <NUM> is an <NUM>-volt lithium ion battery pack that is smaller in both physical size and capacity as compared to the battery module <NUM> of the previous embodiment. It is contemplated that different sized battery modules <NUM> could be utilized while operating within the scope of the present disclosure. In some embodiments, each of the battery modules <NUM> has the same physical size and electrical capacity. In other embodiments, different types of battery modules of various sizes are utilized in place of the battery modules <NUM> or along with one or more of the battery modules <NUM>. By way of example, the any of the battery modules <NUM> shown in <FIG>, the battery modules <NUM> shown in <FIG> and <FIG>, and the battery modules <NUM> shown in <FIG> may be used together.

<FIG> illustrates the advantages of the scalable power system <NUM> relative to a conventional power system that includes only one battery module that cannot be removed without the use of tools. Because the battery module of a conventional power system is fixed, a conventional power system has a fixed total energy capacity. In contrast, the scalable power system <NUM> allows a piece of power equipment (e.g., the robotic lawn mower <NUM>) to be selectively outfitted with a variable quantity of battery modules <NUM>, depending on the desired end use. Accordingly, the total energy capacity of the scalable power system <NUM> can be scaled up or down by adding or removing battery modules <NUM>. This allows the same piece of power equipment to be suitable for a variety of applications and end users. Additionally, the ability to scale the number of power supplies also allows the user to manage the overall weight of the piece of power equipment by using fewer of the removable battery modules. In contrast, conventional power equipment using a fixed battery module also has a fixed weight.

The construction and arrangement of the apparatus, systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, some elements shown as integrally formed may be constructed from multiple parts or elements, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the claims.

The present disclosure contemplates methods, systems and program products on any machine-readable media for accomplishing various operations. The embodiments of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the claims include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. When information is transferred or provided over a network or another communications connection (either hardwired, wireless, or a combination of hardwired or wireless) to a machine, the machine properly views the connection as a machine-readable medium. Thus, any such connection is properly termed a machine-readable medium. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

As utilized herein, the terms "approximately," "about," "substantially", and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges or geometric relationships provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the appended claims.

The terms "coupled," "connected," and the like as used herein mean the j oining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or with the two members or the two members and any additional intermediate members being attached to one another.

Claim 1:
A robotic lawn mower (<NUM>), comprising:
a first wheel (<NUM>) driven by a first electric wheel motor (<NUM>);
a second wheel (<NUM>) driven by a second electric wheel motor (<NUM>);
a cutting implement (<NUM>) driven by an electric cutting implement motor (<NUM>);
a power system (<NUM>) for powering the electric wheel motors (<NUM>) and the electric cutting implement motor (<NUM>), the power system (<NUM>) comprising:
a plurality of removable rechargeable battery modules (<NUM>);
a plurality of receptacles (<NUM>), each receptacle (<NUM>) being configured to receive one of the plurality of removable rechargeable battery modules (<NUM>); the lawn mower (<NUM>) being characterized in that it further comprises
a battery management system configured to control discharging of each of the plurality of battery modules, wherein the battery management system is configured to control which of the plurality of battery modules supply current to a power bus so that the power system is operable when an additional battery module is installed within an open receptacle that defines a different charge level than at least one of the removable rechargeable battery modules received within the plurality of receptacles; and
a controller (<NUM>) configured to control operation of the electric wheel motors (<NUM>) and the electric cutting implement motor (<NUM>) to autonomously mow a yard.