Unmanned agricultural rover having a fuel cell propulsion

Abstract

An unmanned off-road rover comprises: One or more electric motorwheels having a reduction gear (R); - A satellite localization module; - An obstacle detection module; - A fuel cell driving module; and - An electric power take-off and / or an electric socket to power an electric implement.

Description

[0001] Unmanned agricultural rover having a fuel cell propulsion.

[0002] FIELD OF INVENTION

[0003] The present invention refers to an unmanned agricultural rover having a fuel cell drive.

[0004] PRIOR ART

[0005] Drones for agricultural tasks are large and complex to handle.

[0006] SUMMARY AND SCOPES OF THE INVENTION

[0007] The scope of the present invention is to provide a now tool to be used in agricultural tasks on field. The scope of the present invention is achieved by an unmanned rover according to claim 1.

[0008] A rover according to the invention is compact and, at the same time, enables use of green hydrogen e.g. hydrogen generated by electrolysis using sun panel electricity.

[0009] According to an embodiment, the rover comprises a metal hydride canister to store hydrogen. This improves safety of the rover.

[0010] BRIEF DESORPTION OF THE DRAWINGS

[0011] The present invention is now described according to a non limiting embodiment whose description is supported by the following drawings wherein:

[0012] Fig. 1: is a functional sketch of a drivetrain within a rover according to the present invention;

[0013] Fig. 2: is a functional sketch of input devices for an autonomous drive module of the rover according to the invention; Fig. 3: is a functional sketch an autonomous drive module of the rover according to the invention;

[0014] Fig. 4 is an exploded view of a non-limiting embodiment of the rover according to the invention;

[0015] Fig. 5 is a perspective view of the rover of figure 4; and

[0016] Fig. 6 is a front view of an enlarged detail of the rover in figure 4; and

[0017] Figg. 7 and 8 are respective perspective view of alternative embodiments of the present invention.

[0018] DETAILED DESCRIPTION OF THE INVENTION

[0019] An agricultural rover is a smart and automated vehicle, designed to execute different operations such as soil preparation, harvesting, spraying, and monitoring field health status. Autonomous agricultural rovers can lead to the better management of the use of pesticides and water. Agricultural rovers are often equipped with electric powertrains and are lighter than the traditional forms of machinery, reducing greenhouse gas emissions and, at the same time, soil compaction. The practice of precision farming enabled by agricultural robots can help famers to improve their resource management, such as fertilizer use or harvesting time, thus increasing crop productivity and quality. Agricultural rovers can be of different sizes depending on the specific mission they have to accomplish. Larger robots can be used in case of harsh work-conditions. Smaller multiple rover fleet can operate in a coordinate manner to carry out tasks that nowadays require the use of large-size tractors. The consequences are a lower execution time and soil compaction. Agricultural rovers can act in all the phases of the productive cycle. However, they must be equipped with several innovative devices in order to perform their tasks. Obviously, one of the key elements of an autonomous agricultural robot is its autonomous driving system and control logic. Thanks to them, the vehicle can make decisions in terms of the best strategy that must be adopted in order to perform a predetermined task .

[0020] Figure 1 shows a fuel cell drivetrain of rover according to the invention. The drivetrain comprises a fuel cell system, a battery pack, preferably a low voltage 48V pack, and a power converter positioned between the DC bus and the fuel cell. This configuration provides flexibility, robustness and reduced stress on the fuel cell system. However, in other circumstances where there is a need for high power capability in short time, supercapacitors might be a better solution due to their high-power density. Finally, either batteries or supercapacitors can be used to enhance the vehicle' s performance. Nevertheless, in the latter case a higher complexity of the powertrain should be expected.

[0021] Depending on the rated power of the fuel cell system with respect to the electric motor power and the batteries capacity, the powertrain can be classified as range extender or load follower .

[0022] In the first case, the batteries are the primary energy source, while the fuel cell, whose rated power is low compared to vehicle's power capabilities, is used to recharge them in order the autonomy. In case of a load follower configuration, the fuel cell is the primary energy source, and its role is to satisfy the low dynamic part of the electric motor power demand, while the batteries are used to satisfy the transient part.

[0023] In greater detail, as shown in figure 1, the fuel cell is electrically connected to both the batteries or electric storage batteries and the electric traction motors and the storage batteries to supply electrical energy but not to receive it. The storage batteries are electrically connected to the electric motors (e.g. , traction motors) and to the fuel cell to both receive and supply electrical power.

[0024] In one embodiment, the nominal voltage of the fuel cell is higher than the nominal voltage of the storage batteries so that, when the electrical load from the traction motors and / or the electric power take-off (ePTO) and / or the on-board electrical plug exceeds a predefined threshold value, the fuel cell voltage tends to drop below the nominal voltage of the storage batteries . To balance the electrical loads, the batteries come into play, contributing to the supply of electrical power, particularly the missing portion. Furthermore, when the electrical load from the electric traction motors and / or ePTO and / or electrical plug is relatively low and therefore the fuel cell operates at its nominal voltage, the storage batteries also act as a load for the fuel cell so they can be recharged. The rover has an electrical outlet on board, either in place of or in addition to the electrical plug. For example, the motors are 2 kW each, the batteries / accumulators are 4 kWh at 48 V, and the fuel cell is 1 kW with a range between 48 and 60 V, so as to supply, in an 8-hour work period, double the energy of the batteries / accumulators.

[0025] Preferably, a chassis of the rover is in steel and comprises tubular beams to provide a tubular frame structure, which, thanks to its robustness and solidity, allows the vehicle to accomplish several tasks, for example cultivations monitoring, handling of loads through the field and, finally, small precision farming practices. If monitoring and handling of loads can be directly performed by the rover itself, for other farming practices implements must be used.

[0026] Furthermore, the traction force is generated by four independent electric motors, each one connected to one wheel through a mechanical gearbox with a planetary system. The wheels are fixed, thus torque vectoring is adopted to perform turns and maintain stability. Figure 1 shows in a sketch the planetary gearbox for a single wheel, provided that the remaining wheels have each the same rig. Furthermore, the rover comprises a power take-off, in particular an electrically driven power take-off and / or an electric socket / plug connected to the battery for electric power supply, preferably 48V DC and / or AC power supply for an electrical agricultural implement. The socket / plug is preferably according to a MIL standard.

[0027] According to a preferred embodiment the socket on the rover or the plug of the implement has a disengageable hook, latch or similar device to hold, after connection in a slot or with a pin of the plug, the plug connected to the socket avoiding disconnections due to tensioning of the electrical wire of the plug. Furthermore, the socket on the rover has a cover to seal the electric connectors when the plug is disconnected.

[0028] Preferably, a polymer electrode membrane fuel cell (PEMFC) is adopted on the rover, which is characterized by relatively low operating temperature (generally < 100 °C) , compactness and high efficiency, with a peak around 60%. Furthermore, a PEMFC also features high durability, with an expected life of several thousands of hours. The only by-products of the reaction between hydrogen and oxygen are heat and water. However, a fuel cell system comprises not only the fuel cell stack, which is the element that produces electricity, but also all the auxiliaries that are necessary for its optimal operation, which constitute the Balance- of-Plant of the system (BoP) . The BoP includes the hydrogen storage and adduction system, the air supply system, the water and heat management systems. Hydrogen storage device preferably comprises a metal hydride canister for low pressure and hi.

[0029] The agricultural rover according to the invention comprises also an autonomous driving system programmed to capture data from sensors onboard the vehicle and to process such data from the surrounding environment for establishing a route or a route change. First, the rover must know its position in the state space. This task is performed using GPS sensors and antennas onboard the rover. There are several techniques to implement GPS sensors on the rover. The most performing ones exploit the GPSRTK (GPS Real Time Kinetics) technology which allows to reach a centimetric level of precision. At the basis of this technique, there is the use of two GPS receivers. The first one is mounted on the vehicle, whereas the second one is in a fixed position e.g. removably, in particular transportable in a bag, on the near field ground. In concrete terms, the rover compares its position with the fixed point, compensating the locating error and acquiring a high-precision measure (accuracy error < 2cm) .

[0030] The position is not sufficient to elaborate an accurate motion strategy. Indeed, also the rover orientation in the state space is necessary. Compass and gyroscope sensors serve this purpose and are onboard the rover. The combined action of the gyroscope and of an inertial measurement unit (IMU) allow to integrate in the data flow also the vehicle dynamics in the 3D operative environment. In particular, the gyroscope provides inputs to a rollover algorithm and the IMU provides inputs to a shock detection algorithm. Lastly, an autonomous driving system, must be equipped with distance sensors e.g. LIDAR. They enable the vehicle to generate a local map in order to identify unpredictable obstacles and elaborate an appropriate obstacle avoidance strategy. In the following figure the architecture of an autonomous driving system is resumed.

[0031] Therefore, distance sensors, gyroscope and / or compass, GPS module and IMU and / or gyroscope are connected in data exchange to an electronic control unit programmed to implement an autonomous drive algorithm based on the data received as inputs from such units .

[0032] According to a preferred embodiment, the autonomous driving algorithm represents the strategy adopted by the agricultural rover in order to reach a predetermined target point. It essentially comprises three steps:

[0033] - Path planning.

[0034] - Path following.

[0035] - Obstacle avoidance algorithm (O.A.A) .

[0036] The first task of the algorithm comprises the calculation of the ideal optimal trajectory that the agricultural rover must follow in order to reach a user defined or predetermined target point. The results of this step, called path planning, is the definition of the optimal path, in the form of sequential waypoints, which takes into account the presence of known obstacles and the kinematic and dynamic behaviour of the vehicle (i.e. vehicle dimensions, minimum turning radius and so on...) . The determined trajectory represents the input of the subsequent step, namely path following phase. During this step, the rover compares its actual position with the ideal trajectory. The outputs are the commands, in terms of vehicle speed and steering angle, that the vehicle must apply to follow the predetermined route. The last step of the algorithm is necessary, since the agricultural rover operates in an unstructured environment, where the presence of unknown obstacles may occur. In this case, the obstacle avoidance algorithm recalculates the trajectory in the short range in order to avoid the obstacle safely. In figure 3, a non limiting architecture of the autonomous driving algorithm according to the invention is shown.

[0037] Figure 4 shows an embodiment of the rover comprising a 2D elongated frame F supporting fuel cell C and DC / DC converter in a rear longitudinal portion and inverters I and electronical connectors in a front longitudinal portion of the frame. Anticollision device, compass, global position module are located in front / lateral position. Metal hydride canister M is attached to frame F on the same side of wheels W and a lower shield S encloses canister M on frame F to avoid collision with e.g. stones on the ground in dedicated frame.

[0038] Figure 5 shows the rover of the invention having an outer cladding defining lateral shoulders L and a load bed B laterally delimited by shoulders L. Bed B is above cell C and each motor wheel is attached to frame F via a corresponding stirrup S.

[0039] According to an aspect of the invention (figure 6) electric motor E of wheels W have a substantially vertical axis and are coupled to the corresponding wheel via a reduction gear R comprising a bevel gear and a planetary gear.

[0040] Specifically, each drive wheel cantilevers vertically from the lower shield C, defining a portal structure in both the transverse and longitudinal directions, with each upright supporting a wheel W. Thus, e.g. without axle shafts and / or differentials and / or suspensions, each upright defines a substantially rectangular window with the adjacent upright, in which the shield C is positioned above both the wheels W and the electric motors E, arranged with a vertical axis, facilitating the rover's movement on rough terrain.

[0041] The fuel cell can significantly increase the electrical energy available on board per unit of weight. Therefore, the rover can be equipped with one or more of the following modules: one or more electric charging modules (Fig. 7) , preferably wireless induction charging for drones, placed on the loading platform B so that one or more drones can land on the loading platform and be electrically recharged while on board the rover; a short-range wireless communication module, e.g. Wi-Fi to allow, through appropriate programming of the electronic control unit, the drones to move in a fleet, e.g. , two or more drones follow the same pre-set path and maintain a pre-defined distance from each other. Preferably, when the rovers are moved in a fleet, each performs its own specific task, e.g. monitoring via sensors, spraying a treatment, e.g. a pesticide, etc. ; a module with one or more sensors for physical or chemical environmental parameters such as humidity and / or pressure and / or temperature and / or wind speed and / or light, in order to detect specific values or time histories; a spraying module comprising a removable tank T, preferably positioned above and in contact with the loading platform B, one or more nozzles U, and a working machine fluidically connected to the tank to power the nozzles .

Claims

CLAIMS1. Unmanned off-road rover comprising:- One or more electric motorwheels having a reduction gear (R) ;- A satellite localization module;- An obstacle detection module;- A fuel cell driving module to power the motorwheels; and- An electric power take-off and / or an electric plug for an electrical implement, powered by the fuel cell driving module .

2. Unmanned rover according to claim 1, wherein the reduction gear (R) comprises a bevel gear and a planetary gear.

3. Unmanned rover according to claim 2, wherein a motor of the motorwheels has an axis that is transversal, preferably perpendicular, to an axis of a wheel (W) of the motorwheel.

4. Unmanned rover according to any of the preceding claims, further comprising at least one of a gyroscope and a compass and an inertial measurement unit.

5. Unmanned rover according to any of the preceding claims, comprising a metal hydride hydrogen storage unit (C) .

6. Unmanned rover according to any of the preceding claims, comprising a load bed (B) laterally delimited by a first and a second shoulder (L) .

7. Unmanned rover according to any of the preceding claims, wherein wheels (W) are angularly fixed and steering isprovided via differential driving of the wheels (W) and slipping on the ground.

8. Unmanned rover according to any of the preceding claims, comprising a further near field positioning module, preferably a real time kinectic module to increase precision of the satellite localization module.

9. Unmanned rover according to any of the preceding claims, comprising an electronic control unit programmed to provide a path planning to generate a path reaching a pre-defined target location, a path following of the generated path by driving the motorwheels and an obstacle avoidance based on the obstacle detection module.

10. An unmanned rover according to any of the preceding claims, further comprising an electric energy storage battery connected in parallel with the power module and one or more electric drive wheels to provide a hybrid battery / fuel cell module drive.

11. A rover according to claim 10, wherein the fuel cell supplies power at a voltage higher than the nominal voltage of the electric batteries so that the electric energy is supplied by load balancing.

12. An unmanned rover according to any of the preceding claims, wherein the electric drive wheels are mounted on at least one gantry structure.

13. A flying drone carrier comprising a rover according to any of claims 1 to 11, further comprising an electric charging station for at least one flying drone and a flyingdrone resting on said load platform (B) during charging by transferring electric power to the electric charging station .

14. A spraying unit comprising a rover according to any of claims 1 to 11 comprising a removable tank carried on the loading platform, spray nozzles fluidly connected to the tank and a working machine, fluidly connected to the tank and electrically connected to the electrical power outlet and / or electrical plug to power the nozzles.

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