A method to cultivate a piece of farmland with an autonomous tractor and a system and tractor for employing the method

Abstract

The invention pertains to a method for cultivation of a piece of farmland using a permanently unmanned autonomous tractor, which tractor has an engine to propel the said tractor to enable performing an agricultural operation to attain said cultivation of the piece of farmland, the method comprising generating a cultivation plan for the piece of farmland, which plan comprises determining a starting point for the tractor on the piece of farmland, an end point on the piece of farmland, a path that extends over the piece of farmland from the starting point to the end point, and a planned progress for the autonomous tractor on the path, and after the cultivation plan has been generated, controlling the autonomous tractor to cross the piece of farmland according to the cultivation plan over the said path, by which controlling the autonomous tractor makes actual progress between the starting point and the end point on the said path, the method further comprising monitoring during the cultivation of the piece of farmland, a difference between the actual progress and the planned progress, and when the difference is above a predetermined threshold, propelling the said tractor is automatically stopped. The invention also pertains to a system and an autonomous tractor for using the method.

Description

[0001] A METHOD TO CULTIVATE A PIECE OF FARMLAND WITH AN AUTONOMOUS TRACTOR AND A SYSTEM AND TRACTOR FOR EMPLOYING THE METHOD

[0002] GENERAL FIELD OF THE INVENTION

[0003] The present invention pertains in general to unmanned autonomous tractors for completely autonomously crossing and cultivating farmland. In particular, the invention pertains to a method for cultivation of a piece of farmland using a permanently unmanned autonomous tractor, which tractor has an engine (e.g. combustion-, electric-, hybrid-, or steam engine etc.) to propel the said tractor to enable performing an agricultural operation to attain said cultivation of the piece of farmland, the method comprising generating a cultivation plan for the piece of farmland, including a path that extends over the piece of farmland, and after the cultivation plan has been generated, controlling the autonomous tractor to cross the piece of farmland according to the cultivation plan over the said path, thus with the intention that the tractor operates as determined in the predetermined cultivation plan.

[0004] BACKGROUND ART

[0005] The adoption of technology in agriculture has improved the approaches that farmers use in the farmland nowadays. Modern agriculture has made it easy for farmers to achieve high produce while using less input. According the trends in the use of technology in agriculture, there are high concerns that the future of agriculture is bright. For example, mechanization in agriculture has reduced the overuse of manpower in doing some of the farming activities. As a consequence, agricultural machines have become bigger and bigger and more dedicated towards performing one type of cultivation. The introduction of autonomous tractors is considered a next step into the future of farming and it is expected that using autonomous tractors, the trend of bigger and more dedicated (specialised) farming machines will continue. Self-driving cars are common these days. Based on the trends in regards to the advancement of technology, it is expected that the technology will also be used for cultivating farmland. At present farmers in advanced countries are giving a tactical approach to how they plant, harvest, as well as maintain their crops. A good example of new tactical approaches is the use of autonomous tractors in agriculture. The concept of autonomous tractors can be traced back prior to the introduction of the concept of precision farming in the eighties. During these days, farmers used GPS technology as a guide to the tractors across the farmland. The aim of such an approach was the reduction of fuel consumption and enhancing the efficiency of the tractors and the farming activities. As such, these initial steps formed the basis for the development of autonomous tractors, following the introduction of technologies that improved communication over wireless devices. Autonomous tractors employ much the same approach as the driverless vehicles, i.e. using advanced control systems and sensors. With the inclusion of auto-steering abilities, such tractors have added control abilities. Evidently, the launch of the autonomous tractors is considerably a manifestation of the extended use of technology in farming.

[0006] Benefits to farmers are obvious. It is an undeniable fact that farming is not an easy undertaking, it involves working for long hours and the subscription to hard labour in harsh weather conditions. Taking into consideration the common state of farmers, the majority of them have no employees to task them in the farmland and hence, have to do everything all by themselves. The autonomous tractors can be a positive outcome. Next to this, accuracy and precision are important aspects in agriculture in various aspects such as planting. Regarding for example such planting, the autonomous tractors can be equipped with automatic planting systems that ensure high accuracy when planting. With such abilities, farmers are assured of seed conservation. All in all, the use of such tractors may lead to higher return on investment since accuracy is enhanced.

[0007] One of the factors that hinder agricultural production in both developed and developing countries is the lack of enough labour. Normally, farmers grow a small section of land which they are sure to manage with their limited labour. However, with the adoption of the autonomous tractors, the problem of labour insufficiency is catered for since the number of employees needed to cultivate the farmland may be reduced.

[0008] It is generally recognized that data plays a significant role in determining the farmers’ decisions. Usually, the absence of clear and reliable data can interfere with the decisions farmers make, and subsequently, have adverse impacts on the amount of outcome obtained from the fields. There are diverse sources and types of data that a farmer needs to succeed in their farming activities. For example, data on soil is important in that it helps farmers in determining what crops will do well in a given piece of land by establishing the moisture content, and the amount of nutrients. The autonomous tractors can be fitted with various sensors that can be used in the collection of data on the conditions of the soil, and hence, offer a platform for improving the outcome of the available crops. The elimination of the human interaction in farming following the use of autonomous tractors may thus be advantageous. Stressed employees cannot achieve the required efficiency level in the fields. Similarly, it is often hard for humans to manage diverse tasks on the farm especially where a large farmland is involved. Autonomous tractors have the appropriate sensors to offer the necessary help in the management of a several tasks in the farmland hence reducing stress and the workload in the farm.

[0009] The autonomous tractors run on high level technology that can be used in gathering high profile information. For example, some models have automatic steering abilities and GPS technologies which enhance the control of the tractors’ course. The advanced sensors come in handy in the determination of soil moisture level, activities around planting and harvesting, present yield, as well as the amount of fuel needed for a given area of land. Additionally, other models of autonomous tractors can guide farmers on how to apply fertilizers.

[0010] Autonomous tractors allow precise control of work and farm equipment. This makes it possible for farmers to extend their working hours and cultivate the land more efficiently. The sensors fitted in the tractors can guide it in the right course even in conditions of reduced visibility and at night: work continues even during windy, dusty, and foggy conditions. Additionally, the ability of the tractors to reduce workload and stress on employees comes in handy in increased working hours in a day since the farmer has a greater flexibility in the management of growing tasks.

[0011] It has become a common understanding that the best way for using an autonomous tractor is to establish a cultivation plan to cultivate the piece of land, which plan for examples defines the routing and speed of the tractor over the land, as well as the way the actual agricultural machine (which may be part of the tractor or coupled thereto) is operated (for example its driving speed, its height with respect to the land, its angle with respect to the land etc.), and using the sensor technology to adapt this predetermined plan to the particular circumstances of the moment in time the land is actually cultivated. Such circumstances can for example be objects that were not present at the piece of land at the time the plan was made, the weather conditions, etc. Thus, with appropriate sensor technology, it is commonly believed that one is able to completely pre-plan the cultivation operation. However, in the art it is also recognised that sometimes intervention of the planned autonomous cultivation is desired. For this, the art describes all kinds of systems to monitor the cultivation process, including movement of the autonomous tractor over the piece of farmland, examples of which monitoring systems are given here below.

[0012] US patent application 2019 / 0364,734 (assigned to Claas Selbstfahrende Erntemaschinen GmbH) discloses a method and apparatus for controlling an agricultural harvesting campaign, in which predetermined harvesting activities are processed within a campaign timeline by a plurality of agricultural working machines of a machine fleet on a field allotment assigned to the harvesting campaign. The control of the harvesting campaign is executed on different application levels by continuously generating information, wherein the generated information is continuously provided to all of the application levels, and the generated data comprise remotely-sensed field information. In the method, use is made of so called field zones to be transmitted in the machine control routine to the respective machine control of at least one, some or all of the autonomous tractors. In the method, although in principle automated, the field zones may be displayed. The operator of the respective tractor may accordingly check whether or not the division of the field zones corresponds to the actual conditions with regard to operating quality. On this basis, the user may intervene to correct the control of the tractor.

[0013] US 10191492 (assigned to Yanmar Co Ltd) discloses an autonomous tractor which is provided with a position calculation means that measures the position of the tractor by means of a satellite positioning system, a steering actuator that operates a steering device, an engine rotation control means, a transmission means, and a central processing unit (CPU) that controls each of same. The tractor is caused to autonomously travel, along a set travel path stored in the CPU, by means of attended operation and that is mounted with a remote operation device that can co-control the autonomous tractor, and the CPU halts autonomous travel when a signal disruption from the satellites, a large deviation from the set travel path, an abnormal sensor value, fuel exhaustion, or the like is detected.

[0014] US 8985250 (assigned to Camoplast Solideal Inc) discloses a method for managing a drive mode of an autonomous vehicle provided with endless tracks, including reading an output of a sensor for sensing a magnitude of force applied by a drive wheel to the track to drive the track and, in response to the output of the sensor, performing a control action to manage the drive mode of the vehicle. The particular control strategy aims to maintain the track as much as possible in a positive drive mode, and uses a friction drive mode when the power loading on the track is significant in order to provide an assist function. This control strategy is implemented by regulating the track tension: the higher the tension the more significant the friction between the track and its sprocket is. In contrast, the lower the tension of the track the lower the friction.

[0015] EP 3725632 discloses a manned tractor (i.e. a human operator is present to control the tractor) which tractor can also be switched to an automatic mode. The tractor has a slip determination system such that based on the actual slip amount it is determined whether or not the state of a travelled ground surface is appropriate for the automatic mode. If not, the tractor is simply stopped and is switched back to manual mode for operation by the human operator present in the cabin of the tractor.

[0016] Correspondingly, WO 2023 / 191615 describes a system based on measuring longitudinal slip, which system ensures that the autonomous tractor makes an emergency stop when it is established that one or more of the wheels of the tractor slips in longitudinal direction with respect to the surface of the piece of farmland. Indeed, when one or more wheels are slipping and the tractor is not stopped, there is a risk that the tractor digs itself into the land. This typically requires an extensive operation to get the tractor back on the land to be able and recommence cultivation. Although the method as disclosed in WO 2023 / 191615 is relatively simple to use and adequate, it does not solve problems that may arise if the operation is inadequate for other reasons than slip, such as IT (software) problems, other mechanical problems, an accident, or any other problem that causes the tractor to be unable to follow the cultivation plan. Each of these problems could be taken care of through dedicated programming of the vehicle to undertake adequate action when such a specific problem arises.

[0017] JP 6682354 B2 (assigned to Yanmar Corporation ltd), discloses a method for a tractor that has an autonomous mode, in which method it is assessed what the lateral deviation of the tractor is on a path as planned in the cultivation plan. If the deviation is too high, a corrected path is generated by translating the path laterally.

[0018] OBJECT OF THE INVENTION

[0019] It is an object of the invention to devise an alternative method to cultivate a piece of farmland using an autonomous tractor, including an improved monitoring system to improve cultivation.

[0020] SUMMARY OF THE INVENTION

[0021] In order to meet the object of the invention, a method has been devised wherein the cultivation plan comprises determining a starting point for the tractor on the piece of farmland (i.e. a point where the actual agricultural operation starts on the piece of farmland), an end point on the piece of farmland, a path that extends over the piece of farmland from the starting point to the end point, and a planned progress for the autonomous tractor on the path. Also, the method prescribes that after this cultivation plan has been generated, the autonomous tractor is controlled to cross the piece of farmland according to the cultivation plan over the said path (thus with the intention that the tractor operates as determined in the predetermined cultivation plan), by which controlling the autonomous tractor makes actual progress between the starting point and the end point on the said path. The method further comprises the step of monitoring a difference between the actual progress and the planned progress during the cultivation of the piece of farmland, and when the difference is above a predetermined threshold, propelling the said tractor is automatically stopped, by which the tractor will stop. Stopping the propelling of the tractor can be done for example by shutting of the engine, putting the gearbox in neutral, disconnecting a drive axle, actuating a clutch, blocking a drive wheel etc. There are multiple options known to a skilled person for stopping propelling a motor vehicle, even without actually shutting of the engine.

[0022] In this method it is essential that part of the plan is determining a planned progress. This can be accomplished in various ways. Typically for each point along the path, or at least multiple points along the path, the period of time is calculated that the tractor needs to arrive at each of these points, starting from the moment the tractor leaves the starting point and starts cultivating. Arriving at “a point along the path” in practice means, since the path typically has a certain width, arriving (somewhere) at a line across the width of the path (the line being perpendicular to the direction in with the path extends, i.e. perpendicular to the direction for movement of the vehicle). So for determining progress, a deviation of the vehicle from the centre of the path is not relevant for the present method. It is essential to establish actual progress in the direction in which the path extends from the starting point to the end point of the plan, and to compare that with the planned progress. If the tractor has a fixed starting time, the exact time of the day can be calculated at which the tractor should arrive at these points. The invention in its broadest sense is not restricted to a particular method of determining the planned progress.

[0023] It is noted that a difference between planned and actual progress is typically a negative difference, meaning that the tractor has made less progress than originally planned at a certain point in time. However, it is also foreseen that a positive difference can arise and even that such a difference is above a particular threshold leads to automatically stopping the vehicle. In the present method by making sure that a difference can be established between actual progress and progress such as planned, any problem that leads to a (too high) deviation from plan can adequately be acted against by stopping the tractor. For example, when an axle that drives a wheel fails, it may be that there is no slip, so based on the method as disclosed in WO 2023 / 191615, this would not lead to an emergency stop. However, one wheel that is not driven leads to an unacceptable path over the land (the tractor continuously correcting a sideway movement). Since such a non-driven wheel will have a negative impact on progress, in the current method, the problem of a broken axle may lead to an emergency stop such that the problem can be fixed. This way it can be prevented that the land is cultivated inadequately.

[0024] The actual value for the threshold is not essential to the invention. It may for example be an absolute value (such as a distance in meters, or a time in seconds), but it may also be a percentage such as 5%, or even less, such as 4, 3, 2, 1 , 0.5% or even 0.1%). A high threshold means that a relatively large differences is allowed before the tractor is stopped, which means that any (in hindsight) unnecessary stop occur only rarely, if at all. However, this is at the risk of accepting situations wherein the engine is not stopped although it would have been better for various potential reasons (e.g. extra damage that needs to be repaired) that the tractor was stopped. Typically, the threshold is set at a standard value of for example 2% (which means that at most a 2% difference in distance moved over the path is accepted), and based on experience with a type of tractor and type of cultivation (i.e. the type of implement / agricultural operation), may be tuned to an optimum level.

[0025] The new method is based on the recognition that due to all kinds of unforeseen circumstances it might be that the movement of the vehicle deviates from is planned movement. Although in the art solutions are described, for example alter the driving force of the wheel, each potential problem needs its own dedicated solution. The applicant recognised that it is impossible to beforehand know each and any problem that has an effect on the performance of the tractor. However, the applicant also recognised that the problems that need attention of a human operator, for example a recovery action, will unveil themselves as a deviation from the cultivation plan, in particular a deviation in the actual progress from the planned progress. By setting a threshold value, any kind of problem can be taken into account, while preventing that very small (non relevant) differences in progress lead to an unwanted emergency stop.

[0026] The automatic stopping of the tractor is preferably followed by a recovery action such as for example pulling the tractor of the site where it has stopped, repairing a broken axle, repairing a wheel, removing an object form the piece of farmland, etc. Alternatively, after the event of stopping the tractor has been signalled to an of site operator, this operator may choose to implement an alternative drive strategy for the tractor from a remote station to try and restart the process. This may also be done by the CPU starting an automatic recovery operation after the tractor was initially stopped. It is not until the recovery action has been completed successfully that the cultivation can continue as planned. If so, the planned progress can be easily recalculated based on the original determination, typically assigning the point at which the tractor resumes its cultivation as the (new) starting point for the remainder of the cultivation.

[0027] The invention also pertains to a system for controlling a permanently unmanned autonomous tractor for cultivating a piece of farmland, which tractor has an engine to propel the said tractor to enable performing an agricultural operation to attain said cultivation of the piece of farmland, the system comprising a central processing unit (CPU) that is designed (i.e. programmed) for generating a cultivation plan for the piece of farmland, which plan comprises determining a starting point for the tractor on the piece of farmland, an end point on the piece of farmland, a path that extends over the piece of farmland from the starting point to the end point, and a planned progress for the autonomous tractor on the path, and controlling the autonomous tractor to cross the piece of farmland according to the cultivation plan over the said path, by which controlling the autonomous tractor makes actual progress between the starting point and the end point on the said path, and monitoring during the cultivation of the piece of farmland, a difference between the actual progress and the planned progress, wherein the CPU automatically stops propelling the tractor when the difference is above a predetermined threshold.

[0028] The invention also pertains to a permanently unmanned autonomous tractor that is suitable for use in a method or the system as described here above, which tractor is adapted in that it has a central processing unit that is programmed to automatically stop propelling the tractor when the difference between the actual progress made by the tractor when autonomously cultivating a piece of farmland and the progress planned beforehand according to a predetermined cultivation plan, is above a predetermined threshold.

[0029] DEFINITONS

[0030] A tractor is an agricultural vehicle that is used cultivate farmland, typically by pulling or carrying agricultural machinery, and to provide the energy needed for the machinery to cultivate the land (including any harvesting action). It commonly, but not necessarily, is a powerful vehicle with a gasoline or electric engine and large rear wheels such as for example endless belt tracks (so called caterpillar tracks).

[0031] Cultivation is any action in agriculture and horticulture, that is performed to be able and raise crop, such as the loosening and breaking up (tilling) of the soil, planting, weeding, spraying, harvesting etc.

[0032] To propel is to push or move something to a further location, typically with a lot of force.

[0033] A cultivation plan for a tractor to cultivate a piece of farmland, is a plan which defines at least the position, direction and speed of the corresponding agricultural vehicle when crossing the land such that the land in essence can be cultivated completely.

[0034] Progress is the forward movement from an upstream position to a downstream position. Progress can for example be measured in length (the distance moved since starting) or time (the time used for moving since starting).

[0035] To monitor is to observe and check a quality of something over a period of time.

[0036] An autonomous tractor is a tractor that can move over a piece of land according to a predetermined cultivation plan without a human operator controlling its movement. Such a tractor can automatically perceive its environment, make decisions based on what it perceives and recognizes, and then actuate a movement or manipulation within that environment. These decision-based actions may include, but are not limited to, starting, stopping, and manoeuvring around obstacles that are in its way. Such a tractor can cross farmland without needing continuous control of a human operator, and thus is able to autonomously cultivate the land.

[0037] A permanently unmanned tractor is a tractor wherein no human operator is on board, (preferably there is not even a human operator on site i.e. within eye distance of the tractor), at any time the vehicle is actually autonomously cultivating land.

[0038] Farmland is land that is used for or suitable for farming, i.e. growing any kind of crop. Farmland includes fields, orchards, vineyards, flower fields, etc. and may be indoors or outdoors.

[0039] An agricultural operation may be any operation used in the cultivation of land such as tillage, harvesting, spraying, spreading, weeding, cutting, monitoring etc. Typically for each type of operation a dedicated implement is coupled to the tractor (which may be a permanent coupling).

[0040] An emergency stop is a stopping process that is not pre-planned as part of a predetermined cultivation plan, but imposed as the result of a sudden, not foreseen event.

[0041] Automatically means without the need of (human) operator intervention.

[0042] A central processing unit or CPU is an electronic circuitry within a computer system that carries out the instructions of a computer program by performing the basic arithmetic, logic, controlling and input / output (I / O) operations specified by the instructions. The term "CPU" may refer to a tangible (single) processor, more specifically to its processing unit and control unit, but may also refer to multiple processors distributed over a (wireless) networked system operating as if part of one single processor (for example partly present on the tractor, a connected agricultural machine and a remote server via a cloud system).

[0043] FURTHER EMBODIMENTS OF THE INVENTION

[0044] In a first further embodiment of the method according to the invention, the difference between the actual and planned progress is monitored continuously. In this embodiment the assessment of the difference in progress is measured in essence without interruption, which in practice means that every 30 seconds or less (such as every 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 second or even within one second), the difference is newly established. This way, it will never take more than 30 seconds when the progress completely stops, before the tractor is stopped.

[0045] In another embodiment the difference between the actual and planned progress is monitored intermittently, in particular at least every 30 minutes, or less (but with more than 30 seconds in between two consecutive measurements of the difference). This embodiment requires less calculation capacity of the digital hardware and thus is more economic in construction and use, and still, major problems with an engine running while too little or no progress is made (for whatever reason) can be prevented.

[0046] There are several ways in which actual progress can be established. For example, one could monitor progress by establishing when the tractor has arrived at a particular location on the path. However, the applicant recognised this is disadvantageous in case the tractor actually stops moving and does not reach he next location where the actual progress is established. Therefore, in an advantageous further embodiment, the progress is monitored by establishing what a position is that the tractor has on the path at a particular point in time (wherein for example at every 10 seconds after leaving the starting point the position of the tractor is established, typically using common GPS tools), or by establishing which distance the tractor has crossed on the path at that point in time (using the same GPS tools).

[0047] In again another embodiment of the method according to the invention, determining the value for the threshold is part of generating the cultivation plan. That is, the value for the threshold is established in one go with establishing the cultivation plan. The value itself may be determined using an algorithm which takes into account the type of tractor, type of engine, type of farmland, weather forecast, etc. but may also be a simple choice from a memory, based for example on previous results with the tractor.

[0048] In still another embodiment of the method according to the invention, the threshold is adjustable after the cultivation plan is generated. It was found by the applicant that given the inherent time gap between generating the cultivation plan and the actual cultivation, which time gap can be anything between hours and days or even weeks and months, it may be advantageous to adjust the threshold to momentary circumstances at the time the cultivation commences (weather, presence of animals such as birds, state of the soil, presence of spectators, etc). Also, the farmer itself may wish for a lower or higher threshold based on past experiences at a particular piece of farmland and / or when performing a particular type of agricultural operation.

[0049] In again another embodiment of the method according to the invention, after the tractor is stopped, the tractor is forced to resume the cultivation either automatically (e.g. by the CPU that initiates a restart after 10 or more seconds) or by a human operator (typically from a remote location after doing some basic checks) and if it is established that the actual progress after the tractor has resumed is again less than the planned progress (recalculated from the new starting point as described here above), the engine is shut off. This new establishment typically takes place between 1 and 120 seconds after the tractor has resumed its operation. This is to avoid that the engine runs for a too long time without any progress (e.g. by running stationary and digging into the land).

[0050] In another embodiment of the method according to the invention, if at a particular point in time the difference is above threshold, the tractor is stopped only if the difference is larger at a next time the difference is established. This embodiment provides the option that a tractor may be able to autonomously correct its deviation from the planned progress. For example, if the difference in progress is only slightly above the threshold, and at the next point in time (e.g. 10 seconds later), the difference is already smaller, this means that the tractor is autonomously catching in and there appears to be no need for an automatic stop. This embodiment accepts a slightly higher risk of continuing while a stop would have been better, at the benefit of a higher efficiency (less unnecessary tractor stops).

[0051] In an embodiment the autonomous tractor has two endless tracks as wheels. Although the risk of slipping of such a track with respect to the surface is small, any other problem in the drive train can be very detrimental to the surface of the land, the mechanics of the tractor and thus the options for a complete recovery of the tractor to enable continuation of the cultivation as planned.

[0052] It is noted that any and all embodiments as described here above or exemplified here after in the examples section for the method according to the invention can also be embodied in the system and autonomous tractor according to the invention.

[0053] The invention will now be further illustrated using the following specific examples.

[0054] EXAMPLES OF THE INVENTION

[0055] Figure 1 schematically shows an autonomous tractor according to the invention.

[0056] Figure 2 schematically shows a control diagram for the tractor of figure 1.

[0057] Figure 3 schematically shows the set-up of a cultivation plan for an autonomous tractor. Figure 4 schematically shows a detail of establishing progress.

[0058] Figure 5 is a flow diagram describing a method according to the invention.

[0059] Figure 1

[0060] Figure 1 is a schematic top plan view of an autonomous tractor 1 for autonomously crossing farmland. Such a tractor as such is known from the art, and described in detail in W02020 / 106142 (assigned to Agxeed Holding BV). In particular, the tractor 1 crosses the farmland in the direction indicated as X. At is trailing end, coupled to the tractor via common triangle coupler 3 is a power harrow 2. The triangle has standard dimensions and drive axle such that various common agricultural machines can be coupled to the tractor. During the autonomous crossing of the farmland in direction X, the power harrow rests on the land for cultivating it. The tractor has an internal engine (not depicted) which drives the wheels 8 (in this case endless tracks) and the power harrow. The operative connection between the engine and the wheels comprises a common clutch and gearbox. When the engine runs, it is able to transfer power to the wheels 8, to turn the tracks in order impose a movement of the autonomous tractor over the surface of the piece of farmland to be cultivated. Using a central processing unit (see figure 2) it is continuously assessed during the cultivation operation (in this case every 5 seconds) whether the actual progress made, in this case the distance moved over the land in meters since the starting point of cultivation, differs from the planned progress according to the cultivation plan. If so, and if this difference is higher than the threshold value (in this case 5 meters), the engine of the tractor is shut off and the tractor therewith makes an emergency stop. This enables an operator to check the tractor and assess what the cause of the lack in progress was. After removal of this cause, the cultivation process can be restarted.

[0061] For making sure the tractor is not principally hindered by any obstacles, the front side is provided with several sensors (not depicted) for detection of such obstacles when crossing the farmland. Laterally, the tractor is provided with a drawbar 4 and opposite thereof, with a second set of wheels 15. The drawbar and second set of wheels are not in use when the tractor crosses the farmland. They serve to help in transporting the tractor over the road. To enable thus, the drawbar can be used for connecting the tractor to a road haulage truck for transport of the tractor over the road, whereas the set of wheels 15 acts to provide rolling support as described in the ‘142 patent application mentioned here above.

[0062] Figure 2

[0063] Figure 2 schematically shows a control diagram for the tractor 1 of figure 1. The tractor 1 has a central processing unit 11, that is connected (wired or wireless; this is the same for any other connection in figure 2) to GPS unit 5 (for locating the tractor), Lidar unit 6 (for detecting any objects in the vicinity of the tractor) and engine 7. The CPU controls the engine when cultivating a piece of farmland according to a predetermined cultivation plan that was made at a remote location 50, using computer 54 and dedicated software. The computer is connected to a server 51 that on its turn is connected to CPU 11. The tractor operates normally under the control of CPU 11 (which might also be present at a remote location, thus not being part of the actual tractor, or distributed over the tractor and one or more remote locations). The conditions for the cultivation plan are established at location 50 as well and stored in memory 52. In this memory, different sets of conditions are stored that correspond e.g. to safety regulations. Depending for example on the type of tractor, the type of cultivation, the type of farmland (size, proximity to urban areas, etc), the weather conditions, a particular set of conditions can be chosen to be used for the operation. Memory 53 holds multiple distinct sets of conditions for implements to be connected to the tractor.

[0064] When desiring to autonomously cultivate a piece of farmland, the process starts with generating a cultivation plan for the piece of farmland, which plan comprises determining a starting point for the tractor on the piece of farmland, as well as an end point on the piece of farmland (for details see figure 3). The plan also comprises a path that extends over the piece of farmland from the starting point to the end point, and a planned progress for the autonomous tractor on the path. Progress in this embodiment is the total distance that the tractor has moved over the path at a certain point in time, calculated from the starting point.

[0065] After the cultivation plan has been generated, the autonomous tractor 1 is controlled to cross the piece of farmland according to the cultivation plan over the path. This way, the autonomous tractor makes actual progress between the starting point and the end point on the said path. During the cultivation, a difference between the actual progress and the planned progress is continuously monitored (using GPS unit 6 to establish the actual position and CPU 11. In this case, every 25 seconds the actual progress is compared with the planned progress. When the difference is above the predetermined threshold of 5 meters, the propelling of the tractor is automatically stopped. If there is no manual (or automatic) restart within 5 minutes, the engine is automatically shut off.

[0066] Figure 3

[0067] Figure 3 schematically shows the set-up of a cultivation plan for cultivating a piece of farmland 20 with an autonomous tractor. The plan comprises determining a starting point 21 for the tractor on the piece of farmland 20, as well as an end point 22 on this piece of farmland. The plan also comprises determining the path 23 that extends over the piece of farmland from the starting point to the end point, which path the autonomous tractor is planned to take. In this case, part of the plan is also a planned progress for the autonomous tractor on the path, every 25 seconds after the start of the cultivation. In this embodiment, it is calculated for each of these timepoints (i.e. 25 seconds after start, 50 seconds after start, 75, 100, 125 etc.) where the tractor should be, thus what the total distance is that the tractor is planned to have moved (i.e. crossed) over the path at each particular point in time, calculated from the starting point. For example, it is calculated in the plan that 12 minutes and 25 seconds after commencing the cultivation, the tractor should be at location 24, which corresponds to a distance of 3824 meters calculated from the starting point 21 (see figure 4 for details).

[0068] If the tractor is stopped at some point along the path for a lack of progress that is above threshold, it is an option to try and resume autonomous cultivation, for example after an operator has done some basic safety and mechanic checks. If all seems OK, an operator could initiate resuming the cultivation. In that case, the point where the tractor resumes the cultivation is considered the new starting point and planned progress is determined from this starting point. Monitoring of the progress takes place correspondingly.

[0069] In another embodiment, after a tractor is automatically stopped, the basic safety and mechanic checks are done automatically and if OK, the tractor may resume cultivation also automatically. The monitoring of the progress thereafter takes place the same way as after a manual restart.

[0070] Figure 4

[0071] Figure 4 schematically shows a detail of the particulars for establishing progress. Depicted are the path 23, the starting point 21 on the piece of farmland, the end point 22 and the intermediate point 24 (as described with regard to figure 3). Progress is the forward movement in the direction from the upstream starting point 21 to a downstream position. This direction being indicated with an X in figure 4. At position 24, the progress is the distance indicated with numeral 26, and in this case (see above), is a distance of 3824 metres.

[0072] Since the path 23 has a certain width “W”, arriving at point 24 is established when the tractor (typically its centre of gravity, but it may be any other point of the tractor such as for example the centre of its front axle, or the centre of the implement), arrives at (crosses) line 25 across the width of the path (line 25 being perpendicular to the direction X in with the path extends, i.e. perpendicular to the direction for movement of the tractor). So for determining progress, a deviation of the vehicle from the centre of the path towards a side of the path is not relevant for establishing progress. At all points across line 25, progress is the same.

[0073] In general, not being related to this specific example, line 25 may have the same length as the width of the path. However, it may also be that this line is less extended, for example if a very precise type of cultivation is needed, while the planned path itself is relatively broad (for example when the implement is very wide). However, it is also possible that the path in the plan is only defined as a line (thus having no macroscopic width). In that case, line 25 is typically set at a length broader than the width of the path.

[0074] Figure 5

[0075] Figure 5 is a flow diagram describing a method according to the invention (showing only the blocks relevant to describe the current invention). In step 60, the tractor is started to be able and perform a cultivation operation on a piece of farmland. In the next step 61 , the cultivation is actually being performed while the tractor crosses the surface of the piece of farmland. During this cultivation, in a step 62 it is assessed whether there is a difference between actual and planned progress. If the answer is “No”, cultivation is continued according to step 61. If the answer is “Yes”, in a next step 63 it is established whether the difference meets a predetermined threshold value. If not, cultivation is continued according to step 61. If the answer is “Yes”, then the tractor is controlled in step 64 to make an emergency stop, in this case by shutting off the engine. If the problem is resolved in step 65, the tractor can be started again in step 60 to try and continue cultivation until the whole piece of land is cultivated according to (the adjusted) plan. Ultimately, the tractor is stopped and can be picked up to bring to another piece of farmland as described here above with reference to figure 1.

Claims

1. CLAIMS1. A method for cultivation of a piece of farmland using a permanently unmanned autonomous tractor, which tractor has an engine to propel the said tractor to enable performing an agricultural operation to attain said cultivation of the piece of farmland, the method comprising:- generating a cultivation plan for the piece of farmland, which plan comprises determining a starting point for the tractor on the piece of farmland, an end point on the piece of farmland, a path that extends over the piece of farmland from the starting point to the end point, and a planned progress for the autonomous tractor on the path,- and after the cultivation plan has been generated, controlling the autonomous tractor to cross the piece of farmland according to the cultivation plan over the said path, by which controlling the autonomous tractor makes actual progress between the starting point and the end point on the said path, the method further comprising monitoring during the cultivation of the piece of farmland, a difference between the actual progress and the planned progress, and when the difference is above a predetermined threshold, propelling the said tractor is automatically stopped.

2. A method according to claim 1, characterised in that the difference between the actual and planned progress is monitored continuously.

3. A method according to claim 1, characterised in that the difference between the actual and planned progress is monitored intermittently, in particular at least every 30 minutes, or less.

4. A method according to any of the preceding claims, characterised in that the progress is monitored by establishing what a position is that the tractor has on the path at a point in time, or by establishing which distance the tractor has crossed on the path at that point in time.

5. A method according to any of the preceding claims, characterised in that determining the value for the threshold is part of generating the cultivation plan.

6. A method according to any of the preceding claims, characterised in that the threshold is adjustable after the cultivation plan is generated.

7. A method according to any of the preceding claims, characterised in that after the tractor is stopped, the tractor is forced to resume the cultivation either automatically or by a human operator and if it is established that the actual progress after the tractor has resumed the cultivation is again less than the planned progress, the engine is shut off automatically.

8. A method according to any of the preceding claims, characterized in that if at a particular point in time the difference is above threshold, the propelling of the tractor is stopped only if the difference is larger at a next time the difference is established.

9. A system for controlling a permanently unmanned autonomous tractor for cultivating a piece of farmland, which tractor has an engine to propel the said tractor to enable performing an agricultural operation to attain said cultivation of the piece of farmland, the system comprising a central processing unit (CPU) that is designed for:- generating a cultivation plan for the piece of farmland, which plan comprises determining a starting point for the tractor on the piece of farmland, an end point on the piece of farmland, a path that extends over the piece of farmland from the starting point to the end point, and a planned progress for the autonomous tractor on the path,- controlling the autonomous tractor to cross the piece of farmland according to the cultivation plan over the said path, by which controlling the autonomous tractor makes actual progress between the starting point and the end point on the said path,- monitoring during the cultivation of the piece of farmland, a difference between the actual progress and the planned progress, characterised in that the CPU automatically stops propelling the said tractor when the difference is above a predetermined threshold.

10. A permanently unmanned autonomous tractor that is suitable for use in a method of any of the claims 1-9, or the system of claim 10, which tractor is adapted in that it has acentral processing unit that is programmed to automatically stop propelling the tractor when the difference between the actual progress made by the tractor when autonomously cultivating a piece of farmland and the progress planned beforehand according to a predetermined cultivation plan, is above a predetermined threshold.

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