RU2810297C2 - Autonomous tractor and method for cultivating farm lands using such tractor - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: autonomous tractor (1) for autonomously crossing farm land contains one or more sensors for detecting an obstacle when crossing agricultural land, and a central processing unit (CPU) for receiving input signals from one or more sensors and for controlling the movement of the tractor (1) based on the input signals , in order to avoid an obstacle, a hitch for coupling an agricultural machine selected from a group of agricultural machines, each of which is configured to couple with a tractor, and each of which contains one or more additional sensors for detecting the obstacle. The agricultural machine clutch comprises operatively connecting one or more additional sensors to a CPU and automatically providing data to the CPU regarding the location of each of the one or more additional sensors on the agricultural machine and one or more specifications of each of the one or more additional sensors. When detecting an agricultural machine, the CPU is configured to turn off the tractor sensors (1) to prevent the detected agricultural machine from continuously being seen as a regular obstacle. The method for cultivating agricultural land includes a step in which farm land is autonomously crossed using the specified autonomous tractor (1).

EFFECT: provides improvements to autonomous tractors for crossing farm land.

12 cl, 11 dwg

Description

Field of technology to which the invention relates

The present invention relates generally to autonomous tractors for autonomously moving and cultivating agricultural land.

State of the art

The application of technology in agriculture has improved the approaches that farmers use in their farmlands these days. Modern agriculture has made it easy for farmers to achieve high yields while using less inputs. According to the trends in the use of technology in agriculture, there are strong hopes that the future of agriculture is bright. For example, mechanization in agriculture has reduced the overuse of human resources in some of the agricultural activities. As a consequence, agricultural machines are becoming larger and larger and more specialized to perform one type of cultivation. The introduction of autonomous tractors is considered the next step in the future of agriculture, and with the use of autonomous tractors, the trend for larger and more domain-specific (specialized) agricultural machines is expected to continue.

Self-driving cars are common these days. Based on the trends in technology improvement, it can be expected that the technology will also be used for agricultural land cultivation. Nowadays, farmers in developed countries allow a tactical approach to how they plant, harvest, and also maintain their crops. A good example of new tactical approaches is the use of autonomous tractors in agriculture. The idea of autonomous tractors can be traced back to the introduction of precision farming in the eighties. These days, farmers used GPS technology to guide tractors through their farmlands. The goal of this approach was to reduce fuel consumption and improve the efficiency of tractors and farming operations. Essentially, these initial stages formed the basis for the development of autonomous tractors, following the introduction of technologies that improved communication through wireless devices. Autonomous tractors take exactly the same approach as self-driving vehicles, using advanced control systems and sensors. With the inclusion of autonomous steering functionality, such tractors have additional steering functionality. Undoubtedly, the launch of autonomous tractors is an important manifestation of the increased use of technology in agriculture.

The benefits for farmers are clear. It is an undeniable fact that farming is not an easy undertaking, it involves working long hours and adopting the principles of hard work in harsh weather conditions. Considering the known condition of farmers, most of them do not have workers to give them work in the agricultural lands and, therefore, have to do everything themselves. Autonomous tractors could be a positive solution. Against this backdrop, accuracy and precision are important aspects in agriculture in various aspects such as sowing. Considering such seeding for example, autonomous tractors can be equipped with autonomous seeding systems that provide high precision during seeding. With such opportunities, farmers are confident in saving the seeds they plant. In general, the use of such tractors can lead to a higher return on investment as accuracy improves.

One of the factors that hinder agricultural production in developed and developing countries is the lack of sufficient labor. Typically, farmers cultivate a small plot of land, which they definitely have to manage with their limited labor force. However, with the application of autonomous tractors, the labor shortage problem is addressed as the number of workers required to cultivate agricultural land can be reduced.

Data also plays an important role in guiding farmers' decisions. Typically, the lack of clear and reliable data can interfere with farmers' decision-making and consequently have an adverse impact on the volume of production obtained from the fields. There are various sources and types of data that a farmer must follow in his farming activities. For example, soil data is important in that it helps farmers determine which crops will do well on a given piece of land by establishing moisture content and nutrient levels. Autonomous tractors can be equipped with various sensors that can be used in collecting data on soil conditions, and therefore offer a platform for improving the yield of available crops. Eliminating human interaction in farming following the use of autonomous tractors could thus be beneficial. Stressed workers are unable to achieve the required level of efficiency in the fields. Likewise, it is often difficult for people to manage various tasks on a farm, especially when it involves a large farmland. Autonomous tractors have appropriate sensors to offer the necessary assistance in organizing multiple tasks in the farmland, hence reducing stress and workload on the farm.

Autonomous tractors operate on high-level technology that can be used to collect valuable information. For example, some models have automatic steering functionality and GPS technology that improve tractor directional control. Advanced sensors come in handy in determining soil moisture levels, planting and harvesting activities, current yields, and the amount of fuel required for a given area of land. Additionally, other autonomous tractor models can guide farmers on how to apply fertilizer.

Autonomous tractors provide the ability to precisely control farm operations and equipment. This makes it possible for farmers to extend their working hours. Sensors installed in the tractors can guide it on the correct course even in low visibility conditions and at night: work continues even during windy, dusty and foggy conditions. Additionally, the ability of tractors to reduce worker workload and stress is beneficial during longer work hours, as the farmer has greater flexibility in managing crop production tasks.

As stated here above, autonomous tractors can be equipped with various sensors that can be used in collecting data on soil conditions, and therefore offer a platform for improving the yield of available crops. Information can be collected or exchanged through smartphones, laptops, GPS sensors, RFID tags and other environmental sensor networks. Current developments in sensor technology may lead to the pervasiveness of computing across all domains. Companies such as Ag Leader, Farm Works and SST sell handheld devices with improved features, including more powerful processors, GPS sensors, high-definition cameras and built-in wireless and cellular interfaces. Increasingly, fields and farm equipment are being equipped with smart sensors that can read everything from plant health and water needs to soil nitrogen levels and thus help optimize irrigation and avoid crop failure. New optical detection technologies for monitoring crop health include Trimble's GreenSeeker, Topcon's CropSpec and Ag Leader's Opt-Rx. These intelligent systems measure light reflectance from leaves, match them to soil nitrogen levels, and control application systems to apply optimal amounts of fertilizer. Sensors can also be interrogated to provide information about obstacles that prevent or reduce the autonomous tractor's ability to traverse farmland smoothly. However, developments here rely primarily on developments in the field of autonomous vehicles for road use.

Objective of the invention

The object of the invention is to provide an improved autonomous tractor for autonomously crossing agricultural land.

The essence of the invention

In order to satisfy the objects of the invention, an autonomous tractor has been invented, the tractor includes one or more sensors for detecting an obstacle when crossing agricultural land, and a central processing unit (CPU) for receiving input signals from the one or more sensors and for controlling the movement of the tractor based on the inputs. signals for avoiding an obstacle, a clutch for coupling an agricultural machine selected from a group of agricultural machines, each of which is configured to couple with a tractor, and each of which contains one or more additional sensors for detecting an obstacle, wherein the clutch of the agricultural machine includes operably connecting one or more additional sensors to the CPU and automatically providing data to the CPU regarding the location of each of the one or more additional sensors on the agricultural machine and one or more specifications of each of the one or more additional sensors.

The applicant recognized that significant improvement could be achieved in the area of obstacle detection. Although it is known in the art to use sensors on an autonomous vehicle to detect obstacles, as well as to use sensors on the part of the tractor that holds the actual tillage machine (which is part of a specialized tractor), no attention has been paid to small utility tractors that are invented to connect to all sorts of different agricultural machines. Applicant has realized that it is useful in such a situation that the agricultural machine clutch comprises operatively connecting sensors of the attached agricultural machine to the tractor CPU and automatically providing data to the tractor CPU regarding the location of each of one or more additional sensors on the agricultural machine and one or more specifications for each of these one or more additional sensors. This means that the sensors of the agricultural machine are combined into a system in such a way that the entire system can operate autonomously in the best possible way.

DEFINITIONS

A tractor is an agricultural vehicle that is used to pull farm machinery and provide the power needed to allow the farm equipment to cultivate the land (including any harvesting activity). Typically, but not necessarily, it is a powerful vehicle with a petrol or diesel engine and large rear wheels or endless belt tracks (called crawlers).

An autonomous tractor is a tractor that can perceive its environment, make decisions based on what it perceives and recognizes, and then move or perform manipulation in that environment. These decision-based actions include, but are not limited to, starting, stopping, and maneuvering around obstacles that are in its path. Such a tractor can move across agricultural land without the need for constant supervision by a human operator, and when the agricultural machine is functionally attached to the tractor, it can independently cultivate the land.

A road freight truck is a motor vehicle designed to be able to transport objects on a public road, either by towing the object (if it has wheels for road transport) or by transporting the object in a (semi-)trailer. A truck for road freight transport may, for example, be a conventional human-driven tractor or a combination of a truck and a trailer (the trailer, for example, is a loading platform).

A road is a long, narrow section of leveled or paved surface designed for movement by motor vehicle, vehicle, etc. between two or more points. A road is also called a street or (highway).

Agricultural land is land that is used or suitable for farming.

A sensor is a device that responds to a physical stimulus such as heat, light, sound, pressure, magnetism or discrete movement and transmits a resulting impulse, for example to measure or control an operation.

An obstacle is any object that obstructs or interferes with the free movement of an object in the environment. An obstacle can be a stationary physical object such as a large rock or river, a moving object such as an animal or people, but can also be an imaginary object such as a boundary or piece of land.

Above means in or to a place that is above someone or something.

The occupied area of an object is the space that the object occupies when viewed from above.

A vehicle wheel is an object configured to rotate on an axle, such as a conventional spoked automobile wheel or track, which is used to convert rotation (of the axle) into translational motion of the vehicle.

A sensor specification denotes a parameter that is relevant to the functionality of the sensor to capture signals and provide a corresponding output signal. Typical specifications are "range", "accuracy", "resolution", "repeatability", "drift", "hysteresis", "stability", "response time", "settle time", "voltage requirement", "current consumption" , "output" and "sensor noise estimate".

Automatically means without the need for operator (human) intervention. Does not automatically exclude the operator from occasionally initiating or aborting an action, as long as the process can be performed without the need for operator intervention.

A central processing unit or CPU is an electronic circuit in a computer system that executes the instructions of a computer program by performing basic arithmetic, logical, control, and input/output (I/O) operations specified by the instructions. The term "CPU" may refer to a physical (single) processor, more specifically its processing unit and control unit (CU), but may also refer to multiple processors distributed over a (wireless) network system operating as part of one single processor (e.g. partially present on the tractor, machine and remote server via the cloud system).

Embodiments of the Invention

In an embodiment of the tractor according to the invention, the output signal of the sensor is controlled by the CPU. Typically, the output of a sensor is controlled only by its input. The sensor simply provides an output signal based on the input signal. However, the applicant has realized that in the tractor according to the invention it can be very useful to place the sensor output signal also under the control of the CPU. In this way, the combination of sensors present, the type of tractor, the type of agricultural machine attached and all other variables can be used to fine-tune the output signal to help achieve the best possible autonomous cultivation of the farmland. For example, under CPU control, a sensor that is present on the tractor and that faces the connected machine can be switched to a "no output" mode in order to prevent the detected machine from continuously being seen as a regular obstacle, which would prevent the tractor from moving across the farmland .

In a further embodiment, the tractor motion control calculated by the CPU is thus additionally, in addition to the presence or absence of obstacles, based on one or more environmental circumstances for the tractor (excluding the presence or absence of any obstacle as such). Preferably, the environmental circumstances are selected from the group consisting of 1) the presence of an agricultural machine near the sensor, 2) the type of agricultural machine present, 3) the operating conditions of the agricultural machine, 4) the presence of a second autonomous tractor, 5) the physical properties of the cultivated land, 6) weather conditions , 7) the type of person mentioned.

In another embodiment of the autonomous tractor according to the invention, the tractor includes a coupling device for connecting the tractor to a commercial vehicle for transporting the tractor on a road, wherein the direction of movement of the tractor for crossing agricultural land is perpendicular to the direction of movement when the tractor is transported on the road. To be economically competitive, many machines simply need a working width of at least 3 meters. Even more strictly, many modern machines have working widths exceeding 5-6 meters, even up to 20 meters or more. This in itself makes such vehicles unsuitable for road transport and there is no legal solution. This problem also applies to an autonomous tractor: many machines simply need to have a working width of at least 3 meters. However, the applicant has recognized that this problem can also be overcome by inventing a tractor which is configured such that the direction of travel of the tractor when crossing a piece of land is perpendicular to the direction of travel during road transport. This means that when driving on the road, the agricultural machine is pulled in the direction of transport, and thus in the longitudinal direction of the road, which means that there are far fewer legal restrictions. According to EU regulation, for example, a truck and trailer combination can be up to 18.75 meters long. At the same time, while keeping the length of a stand-alone tractor, for example, below 2.55 (thus being quite small), during transport its width will not exceed 2.55, which means compliance with the EU regulation during road transport. In addition, a second recognition had to be achieved on the tractor of this very useful embodiment: autonomous driving on public roads requires new legislation and is far from reality. However, equipping the tractor with a cab for the driver to be able to drive the tractor will increase the cost very much and may even completely contradict the economic advantage of autonomy. In order to solve this, the inventors recognized that a mechanically simple coupling device (tow hitch, fifth wheel coupling device, winch, etc.) to connect a tractor to a truck for transport to transport the tractor on the road would achieve the goal: for transport On a public road, the tractor appears like a trailer or load being transported rather than a motorized vehicle. This, combined with the small width due to the perpendicular transport direction, ensures that the tractor according to the invention satisfies most of the important laws and regulations that currently apply in Europe and North America.

In an embodiment of the autonomous tractor according to the invention, the hitch is configured to move the coupled agricultural machine between two positions, the first of which is a position lateral to the tillage tractor, and the second of which is a position above the tractor. In this embodiment, the agricultural machine can be raised to and from the cultivated land between the cultivation position and the position above the tractor, away from the ground. Preferably, the second position, i.e. the position above the tractor, coincides with the occupied area of the tractor. In this preferred embodiment, the machine can be lifted virtually directly above the tractor. This is very useful when transporting a tractor with an attached machine on the road, since it means that the width in the transport direction is no greater than the width of the tractor, and also since keeping a large weight, such as the weight of an agricultural machine directly over the object, makes it easier on the mechanics compared to the situation of maintaining a large weight at an angle (i.e. less than 90°, e.g. 45°) above that object.

In another embodiment, the tractor has a first set of wheels suitable for traveling across agricultural land and a second set of wheels suitable for transporting the tractor along a road. Although one set of wheels can be used in a tractor of the invention, for example, when arranged so that they can rotate such that their axle experiences a 90° rotation to suit perpendicular directions of travel, it has been found useful to use two sets of wheels, each set corresponding either the direction of movement when crossing agricultural land, or the direction of transportation along the road. In a further embodiment, the second set of wheels is configured to be movable at a distance from the cultivated land to prevent contact with it when the tractor crosses agricultural land.

In yet another embodiment, in which the coupling device includes a tow hitch so that the tractor can be pulled onto a trailer or connected for towing as a trailer, the tow hitch is configured to be placed in a vertical position when the tractor is crossing agricultural land.

The invention will now be further explained with the help of the following drawings.

Examples

Fig. 1 is a schematic top view of an autonomous tractor.

Fig. 2 is a schematic top view of the autonomous tractor of FIG. 1 with agricultural machine in raised position.

Fig. 3 is a schematic side view of the tractor corresponding to FIG. 1.

Fig. 4 is a schematic side view of the tractor corresponding to FIG. 2.

Fig. 5 is a schematic view of an alternative autonomous tractor.

Fig. 6 is a schematic view of two autonomous tractors towed by a human-operated tractor serving as a road transport truck for road transport.

Fig. 7 is a schematic view of an alternative combination arrangement as shown in FIG. 6.

Fig. 8 is a schematic view of a further alternative combination arrangement as shown in FIG. 6 and 7.

Fig. 9 is an example of an autonomous tractor suitable for autonomous road transport.

Fig. 10 schematically shows the implementation of various sensors in accordance with the invention.

Fig. 11 schematically shows the layout of the sensors and the CPU.

Fig. 1

Fig. 1 is a schematic top view of an autonomous tractor 1 for autonomously crossing agricultural land. The tractor crosses the agricultural land in the direction indicated by X. At its rear end, an active harrow 2 is attached to the tractor through a conventional triangular hitch 3. The triangle has standard dimensions and a drive axle, so that various widely used agricultural machines can be coupled to the tractor. When autonomously crossing agricultural land in the X direction, the power harrow rests on the ground to cultivate it. The tractor has an internal engine (not shown), which drives the wheels 6 and the active harrow. To ensure that the tractor will not be hindered by any obstacles in principle, the front side is equipped with several sensors (not shown) to detect such obstacles when crossing agricultural land. On the side, the tractor is equipped with a towing hitch 4 and opposite it with a second set of wheels 5. The towing hitch and the second set of wheels are not used when the tractor crosses agricultural land. They serve to help transport the tractor along the road. To enable this, a towing hitch may be used to couple the tractor to a road transport truck for transporting the tractor on the road, while the wheel set 5 acts to provide rolling support. According to the invention, the driving direction of the tractor for crossing agricultural land (X) is perpendicular to the driving direction when the tractor is transported on the road. The latter direction is indicated in Fig. 2.

Fig. 2

Fig. 2 is a schematic top view of the autonomous tractor of FIG. 1 with agricultural machine 2 in raised position. The hitch 3 functions to move the coupled harrow between two positions (without excluding the fact that the harrow can be placed in any intermediate position), the first of which is a position transverse to the tillage tractor (as depicted in Figs. 1 and 3), and the second of which is a position above the tractor. This position is shown in Fig. 2. A corresponding side view is shown in FIG. 4. As a result of taking the second position above the tractor, the second position coincides with the occupied area of the tractor, i.e., the occupied area of the harrow overlaps completely (across the width of the tractor) with the occupied area of the tractor. The result is that the combination in the transport direction indicated as Y is no wider than the width of the tractor itself.

Fig. 3

Fig. 3 is a schematic side view of the tractor corresponding to FIG. 1. In this side view, the set of wheels 5 and the towing hitch 4 are placed in a raised position so as not to interfere with the autonomous operation of the tractor.

Fig. 4

Fig. 4 is a schematic side view of the tractor corresponding to FIG. 2. In this side view, the set of wheels 5 and the towing hitch 4 are placed in a lowered position in order to enable and support the tractor's truck transport. A tow hitch is used to attach to a human driven truck. The wheels 5 serve to provide rolling support to the tractor during road haulage (see FIGS. 6, 7 and 8 for the combination of autonomous tractors with a human driven truck for road haulage).

Fig. 5

Fig. 5, consisting of FIG. 5A and 5B provide a schematic view of an alternative autonomous tractor 1. FIG. 5A the tractor is shown in a "cultivation" mode with agricultural implements 2 and 2' attached to the front end and rear end. The towing coupling 4 and wheels 5 are in a raised position so as not to interfere with the cultivation of agricultural land. Fig. 5B shows the same tractor with machines 2 and 2' in a raised position, and towing hitch 4 and wheels 5 in a lowered position, allowing for road transport. As can be seen, the advantage of not having a cab for a human operator is that the machines can be raised to a fully vertical position, resulting in the smallest possible width during road haulage, and also resulting in less stringent mechanical requirements for the couplings: forces, the stress on these couplings during transport is much less when the machines are directly above the couplings, compared to situations in which the machines are hitched at an angle of, for example, 45°.

Fig. 6

Fig. 6 is a schematic view of two autonomous tractors 1, which is shown in FIG. 5, towed by a human-operated tractor 10 serving as a truck for road transport. Both tractors 1 have agricultural machines raised in a vertical position to provide the smallest possible width.

Fig. 7

Fig. 7 is a schematic view of an alternative combination arrangement as shown in FIG. 6. In this embodiment, the tractor 10 is towed by two autonomous tractors 1 and 1', to which various agricultural machines are coupled.

Fig. 8

Fig. 8 is a schematic view of a further alternative combination arrangement as shown in FIG. 6 and 7. In this combination, the towing couplings 4 and the wheel set 5 are placed on opposite sides of each tractor (compared to each other), providing the advantage that agricultural machines are present on opposite sides of each tractor during road transport. This reduces the risk of machines mechanically obstructing road transport.

Fig. 9

Fig. 9 schematically depicts an example of an autonomous tractor suitable for autonomous road transport. In this embodiment, at least one of the axles of the wheels 5 is driven by the tractor motor, and this axle, and/or the other axle, can be arranged as a steering axle that can be used for road navigation. The technology for autonomously transporting/driving this tractor on the road may be the same as the technology used for autonomous cars today.

Fig. 10

Fig. 10, containing supporting drawings 10A, 10B and 10C, schematically shows the implementation of various sensors in accordance with the invention. In fig. 10A shows a stand-alone tractor without a farm machine attached to it. Sensors (not shown) create a virtual guardrail 30 in an area 20. If an obstacle, such as a person, is detected in the virtual guardrail 30, the CPU will respond to control the movement of the tractor to avoid hitting the person, such as stopping the machine, or (assuming) slowing down and at the same time providing a light and sound signal to warn a person in the vicinity of the tractor.

Fig. 10B shows a situation in which the agricultural machine 2 is attached to a tractor (the machine 2 itself is not shown in FIG. 10B for reasons of transparency; see FIG. 10C for the actual machine 2 present). According to the invention, as soon as the machine is (electronically) coupled to the tractor CPU (which may be via a hardware connection via connector/ISOBUS etc. or via a wireless connection), the CPU is automatically provided with data regarding the location of each of the one or more additional sensors on the agricultural machine and one or more specifications for each of these one or more additional sensors. In this embodiment, the CPU automatically turns off the tractor sensors that detect the agricultural machine, resulting in an adjusted virtual fence 30' (as depicted in FIG. 10B). This virtual 30' guard is actually the same guard as the 30, minus the part facing the farm machine. Once connected, the CPU also automatically switches on the agricultural machine's sensors. This results in a virtual fence 30'' as shown in FIG. 10C. As a consequence, the tractor and machine combination can operate with integrated sensors on the tractor and machine, in essence, the tractor and farm machine combination "looks" like a single module for crossing farmland.

In practice, it may be that several independent tractors cross the same piece of farmland at the same time to cultivate the land together. If so, it is important that the various tractors (plus machines) do not see each other as constant obstacles, which can lead to a situation where they react to each other, stop and do not continue to work. Thus, as soon as different autonomous tractors operate close to each other, there must be an exchange of data between the combinations about the position, speed and direction of movement, as well as the dimensions that the equipment has. Sensors can be useful in this regard.

Another aspect of the invention is that tractors can be adapted to differentiate between (curious) observers and the operator. While the machine must be 100% safe for the general public to see, the operator must sometimes inspect the tractor and/or machine closely in order to make real-time adjustments and check the result of the cultivation job performed by the machine. This could, for example, lead to a system in which if a normal observer is detected within 10 meters of a tractor at some speed, the machine begins to provide light and sound signals, or even stops if the observer is within 5 meters of the tractor, whereas for operator, such actions are taken only at 3 and 1 meters, respectively, when the tractor is moving at the same speed. The operator may, for example, be recognized through wireless communication between the tractor CPU and the operator's smartphone or other handheld device, or through detection of a physical property of the operator (such as an iris, face, or any other physical characteristic). Also, the output signals of one or more sensors attached to the operator can be used as input data to the CPU. In an embodiment, once the operator is present in the virtual fence, he or she receives a signal to this effect. This improves the safety of the working environment.

Fig. eleven

Fig. 11 schematically shows the arrangement of sensors 41-45 and CPU 40 in a tractor and agricultural machine combination according to the invention. Sensors 41, 42 and 43 are part of the tractor and have a fixed connection to the CPU 40. They provide an output signal to the CPU, which in turn controls and drives the tractor motor 50 ("M"), the light and sound warning system 51 (“LS”) and/or the (virtual) steering wheel 52 (“W”). The sensors 44 and 45 are part of the agricultural machine and are connected to the CPU through a connecting device 60.

Claims (12)

1. An autonomous tractor for autonomously crossing agricultural land, comprising one or more sensors for detecting an obstacle when crossing agricultural land, and a central processing unit (CPU) for receiving input signals from one or more sensors and for controlling the movement of the tractor based on the input signals, in order to to avoid an obstacle, a hitch for coupling an agricultural machine selected from the group of agricultural machines, each of which is configured to couple with a tractor, and each of which contains one or more additional sensors for detecting an obstacle, wherein the clutch of the agricultural machine includes a functional connection of one or more additional sensors from the CPU and automatically providing data to the CPU regarding the location of each of the one or more additional sensors on the agricultural machine and one or more specifications of each of these one or more additional sensors, characterized in that when the agricultural machine is detected, the CPU is configured to disabling tractor sensors to prevent a detected agricultural machine from continuously being seen as a regular obstacle. 2. Autonomous tractor according to claim 1, characterized in that the sensor output signal is controlled by the CPU. 3. The autonomous tractor as claimed in any one of the preceding claims, wherein the tractor motion control calculated by the CPU is further based on one or more environmental circumstances for the tractor. 4. An autonomous tractor according to claim 3, characterized in that the surrounding circumstances are selected from the group containing 1) the presence of an agricultural machine near the sensor, 2) the type of agricultural machine present, 3) the operating conditions of the agricultural machine, 4) the presence of a second autonomous tractor, 5) the physical properties of the land being cultivated, 6) weather conditions, 7) the presence of a person in the vicinity of the tractor, 8) the type of person mentioned. 5. An autonomous tractor according to any of the preceding paragraphs, characterized in that the tractor contains a connecting device for connecting the tractor to a truck for road freight transport for transporting the tractor along the road, and the direction of movement of the tractor for crossing agricultural land is perpendicular to the direction of movement when the tractor is transported on the way to. 6. An autonomous tractor according to claim 5, characterized in that the hitch is configured to move the attached agricultural machine between two positions, the first of which is a position transverse to the tractor for cultivating land, and the second is a position above the tractor. 7. Autonomous tractor according to claim 6, characterized in that the second position coincides with the occupied area of the tractor. 8. Autonomous tractor according to any one of paragraphs. 5-7, characterized in that the tractor has a first set of wheels corresponding to movement when crossing agricultural land, and a second set of wheels corresponding to transporting the tractor along the road. 9. An autonomous tractor according to claim 8, characterized in that the second set of wheels is designed to move away from the cultivated land to prevent contact with it when the tractor crosses agricultural land. 10. Autonomous tractor according to any one of paragraphs. 5-9, characterized in that the connecting device contains a towing hitch, wherein the towing hitch is configured to be positioned in a vertical position when the tractor crosses agricultural land. 11. Autonomous tractor according to any one of paragraphs. 5-10, characterized in that the agricultural machine has a fixed length of at least 3 meters. 12. A method for cultivating agricultural land, including the step of autonomously crossing agricultural land using an autonomous tractor according to any of the preceding paragraphs.