GB2468123A

GB2468123A - Offset plough guidance system and apparatus

Info

Publication number: GB2468123A
Application number: GB0903122A
Authority: GB
Inventors: Thomas Lequey
Original assignee: AGCO SA
Current assignee: AGCO SA
Priority date: 2009-02-25
Filing date: 2009-02-25
Publication date: 2010-09-01
Also published as: GB0903122D0

Abstract

A guidance system for a tractor (12) and offset plough (10) combination is provided. The plough (10) comprises a frame with a plough wheel (44L, 44R) pivotally mounted thereto which may serve also as a depth control wheel. During normal ploughing the plough wheel moves along an open furrow exposed by a previous pass of the plough and is angularly displaceable by contacting sidewalls of the open furrow. Sensing means are provided to sense the angular displacement of the plough wheel relative to the frame. The output from the sensing means is communicated to an electronic control unit (62) on the tractor and is used to produce a steering correction signal which is indicative of a required steering correction to maintain a substantially constant distance (W) between the tractor and the open furrow.

Description

OFFSET PLOUGH GUIDANCE SYSTEM AND APPARATUS

The invention relates to ploughing with an offset plough which is mounted to a tractor so that the tractor has a footprint which remains completely on unpioughed land during normal ploughing. In particular, the invention relates to mouldboard ploughing in which a rectangular strip of sod is overturned to one side in each of a plurality of furrows, For many centuries farmland has been cultivated by ploughing which releases nutrients from deep within the soil. One common form of ploughing is mouldboard ploughing in which a rectangular strip of soil, or sod, of approximately 40cm wide and 15cm deep is overturned to one side in a continuous process. Modern mouldboard ploughs, hereinafter termed ploughs, typically comprise several ploughing units each offset from one another so as to plough several furrows in one pass of the implement.

Since the early 20th century ploughs have been tractor hauled and, with the increasing available power of tractors, the number of furrows which an implement can simultaneously plough has also increased. Traditionally, the tractor which hauls a mouldboard plough is guided across the field by driving with the wheels of one side running along the open furrow which has been exposed by the previous pass of the plough. This ensures a substantially constant distance between the tractor (and thus the plough) and the already ploughed land. In turn this ensures that, with correct initial plough settings, the width of the first (or front) furrow remains substantially the same as that for the other furrows, thus delivering a uniform result.

The increase in tractor power has also accompanied an increase in the width of tractor wheels which allows the available power to be transmitted to the ground without excessive slipping.

However, the width of the exposed furrow has remained at around 30cm and so ploughing with a tractor of wheels greater than this becomes a problem. In a best case scenario an over width tyre will mark the last ploughed furrow of the previous pass creating uneven ploughing.

In a worse scenario the full power of the tractor cannot be transmitted to the ground evenly because the wheels in the furrow do not have 100% ground contact.

In order to overcome the aforementioned problems of ploughing with tractors having wide tyres, offset ploughs have been developed in which the tractor is driven entirely on the unploughed ground at a substantially constant distance from the ploughed area.

Advantageously, this allows much wider tyres to be employed, or even twin wheels, which increases the power that can be transmitted whilst reducing the contact pressure on the ground. However, without the direct guidance of the open furrow on the steerable front wheel, the driver is required to maintain a steady distance from the ploughed area using skill and judgement. Not only does this make the task of ploughing more difficult for the driver, but the consequences of deviating from the optimum distance include non-uniform ploughing caused by unfavourable variation in the width of the front furrow. In turn this leads to a reduction in efficiency and worked area per unit time.

It is thus an object of the invention to provide a guidance system for a tractor-hauled offset plough which alleviates the aforementioned problems and is simple to implement.

In accordance with the invention there is provided a guidance system for a tractor and plough combination, the plough being of an offset type which is mounted to the tractor so that the tractor has a footprint which remains completely on unploughed land during normal ploughing, the plough comprising a frame with a plough wheel pivotally mounted thereto which during normal ploughing moves along an open furrow exposed by a previous pass of the plough and is angularly displaceable by contacting sidewalls of the open furrow, and plough wheel angle sensing means which senses the angular displacement of the plough wheel relative to the frame and generates signals which are representative of said angular displacement, wherein said signals are communicated to an electronic control unit (ECU) and can be used to produce a steering correction signal which is indicative of a required steering correction to maintain a substantially constant distance between the tractor and the open furrow.

The plough wheel is guided along the open furrow of the previous pass and any deviation from the optimum alignment causes the plough wheel to pivot around a vertical axis. The invention involves the recognition that this pivoting motion can be measured and exploited to provide information to the tractor to assist with steering to ensure that the optimum alignment is maintained.

Such plough wheels already exist on offset ploughs to serve as a depth wheel which limits the maximum depth of the ploughed furrows. This is often adjustable with a telescopic arm to vary the desired depth of furrow. Therefore, with respect to the plough, the invention requires only the addition of a plough wheel angle sensor thus making implementation relatively inexpensive.

As with the majority of modem day ploughs, the plough in accordance with the invention is preferably a reversible plough which can plough furrows to the left or to the right by simple rotation (or reversal) of the frame. It will be understood that reversing of the plough direction affects the output of a plough wheel angle sensor and so a reversible plough preferably comprises direction sensing means to detect the orientation of the frame and generate a direction signal representative thereof, said direction signal being communicated to the electronic control unit.

A reversible plough may comprise a pair of plough wheels, one for each plough direction, which are both mounted to a common wheel support member which is pivotally mounted to the frame. In this case the plough wheel angle sensing means senses the angle of the common wheel support member which can rotate around a vertical axis as the lower wheel is guided within the open furrow.

Alternatively, a reversible plough may comprise a single plough wheel which can move from one position associated with left-hand ploughing to a second position associated with right-hand ploughing.

In one preferred embodiment the tractor comprises automatic steering apparatus to steer the tractor in response to steering signals communicated from the ECU, the automatic steering apparatus comprising steering angle sensing means which communicates steering angle signals to the ECU, wherein the steering signals are a function of the steering correction signal. By exploiting automatic steering apparatus (which may already exist on the tractor) the guidance system requires minimal input from the driver thus reducing the concentration and effort required to drive across the field. Advantageously, many modern tractors are fitted with automatic steering apparatus which may also be responsive to GPS applications.

Therefore, the invention requires no additional hardware to be fitted to such tractors thus making the system relatively simple and cheap to implement.

The automatic steering apparatus may comprise an electro-hydraulic distributor to which the steering signals are communicated, wherein the distributor controls the application of hydraulic pressure to steering cylinders.

Preferably, the automatic steering apparatus is selectively activated by a driver via a user interface device such as a simple switch located on a console within the cab. Alternatively, where a central control terminal is provided, the system may be activated by a touch sensitive button on a screen for example. Preferably further still, the system further comprises means to sense movement of a steering wheel wherein a sensed movement of the steering wheel caused by the driver triggers automatic deactivation of the system thereby allowing the driver to override the automated guidance when desired.

The system is preferably automatically deactivated when the plough is lifted into a transport position. Modern tractors fitted with ECUs typically comprise lift-arm sensing means to detect the status of the linkage to which a plough is be attached. Therefore, the data associated with linkage position is often already available and can be simply exploited by the inventive system without any additional hardware.

The relationship between the steering correction signal provided by the plough wheel angle sensing means and the steering signals delivered to the automatic steering apparatus may default to factory settings. However, in a preferred arrangement, the relation ship may be adjusted by a driver via a user interface device such as a driver's control terminal. Such parameters which may be included in the relationship include the sensitivity of the automated steering to changes in the sensed plough wheel angle. For example it may be desirable to provide a damped signal so as to ignore any high frequency fluctuations in sensed wheel angle caused by uneven terrain.

Although the invention lends itself well to a tractor having automated steering apparatus, steering of the tractor may be performed manually without deviating from the scope of the invention. For example, the tractor may comprise a display element viewable by a driver, and wherein the display element is arranged to display an indication of said required steering correction to aid the driver in manually correcting the steering as required. Advantageously, this allows the invention to be implemented in low technology tractors which are not fitted with automatic steering apparatus, and therefore require only the addition of the display element. Advantageously further still, the display element may be provided on an existing display screen thus requiring no additional hardware to the tractor.

The plough wheel angle sensing means may be calibrated via a user interface device on the tractor such as a control terminal. This allows the system to cater for any mechanical variation caused by long term wear in the sensing apparatus. Such a calibration process may involve defining the zero point at which the plough wheel is known to be in the position associated with optimum (or straight) ploughing.

In accordance with a further aspect of the invention there is provided a plough for use in the aforementioned system which comprises a plough wheel pivotally mounted to a frame and which, during normal ploughing, moves along an open frirrow exposed by a previous pass of the plough and is angularly displaceable by contacting side walls of the open frirrow, and plough wheel angle sensing means which senses the angular displacement of the plough wheel relative to the frame and generates signals which are representative of said angular displacement.

In yet another aspect of the invention there is provided a tractor for use in the aforementioned system, the tractor being arranged to receive steering correction signals from a plough and means to process the steering correction signal to provide a guidance tool which allows for either automatic or manual correction of the steering to maintain a substantially constant distance between the tractor and an open furrow whilst ploughing.

Further advantages of the invention will become apparent from the following description of specific embodiments in which: Figure 1 is a side view of a tractor and plough combination: Figure 2 is a plan view of the tractor and plough combination of Figure 1; Figure 3 is a perspective view of part of a plough in accordance with the invention; Figure 4 is a diagrammatic plan view of a tractor and plough combination in accordance with the invention illustrating the front furrow pulling wide'; Figure 5 is another diagrammatic plan view of a tractor and plough combination in accordance with the invention illustrating the front furrow pulling narrow'; Figure 6 is a schematic view of the main components of a guidance system in accordance with a first embodiment of the invention; Figure 7 is a flow chart showing the process steps executed by the system of Figure 6; and, Figure 8 shows a display element of a guidance system in accordance with a second embodiment of the invention.

With reference to Figures 1, 2 and 3, a multi-furrow offset plough 10 is attached to rear linkage of a tractor 12. The plough 10 comprises on each side ten ploughing units 14 each unit serving to plough a respective furrow. It will be appreciated that only six ploughing units 14 are shown in Figure 1 and only two complete units in Figures 2 and 3.

The plough 10 comprises a set of ploughing units for ploughing in the right-hand direction, shown in the figures as engaged with the ground, and a set of ploughing units 14 for ploughing to the left-hand side shown in the figures uppennost on the frame. It will be appreciated that, as is well known for reversible ploughs, the frame 16 is rotatable around a central longitudinal axis X to allow the plough 10 to plough either to the left-or the right-hand side. Therefore, during normal operation the plough is reversed at each end of the field by hydraulic actuators (not shown).

As per known ploughs each ploughing unit 14 comprises a skim unit 18 mounted on an adjustable stem 19 attached to the frame 16. The skim 18 serves to scrape the top ground layer, to a depth of around 2cm, and direct that skimmed layer into the bottom of the open furrow preceding the associated plough unit 14. The plough unit 14 further comprises a mouldboard 20 which includes a replaceable point 22 at the leading end which engages with the soil. The point 22 carves away a rectangular strip of soil 15cm deep, the soil sliding over the mouldboard 20 which flips over the sod onto the previous furrow whilst covering the skimmed top layer at the same time. A landside 24 is provided on each unit and slides along the side wall of the newly created fUrrow.

The plough 10 fUrther comprises at its leading end an attachment body 26 which secures to the three-point linkage of the tractor 12. The linkage comprising two lower arms 28 and a top-link 30. A plough support body 32 is pivotally connected at 34 to attachment body 26. The positioning of plough support body 32 and attachment body 26 remains substantially constant with respect to the tractor 12 during normal operation.

Transverse beam 36 is rotationally mounted at one end to plough support body 32 by a bearing 38. By means of hydraulic actuators (not shown) transverse beam 36 rotates on bearing 38 together with frame 16 to reverse the plough from the right-hand ploughing side (as shown) to the left-hand ploughing side and vice versa.

Frame 16 comprises an elongate beam which attaches to the transverse beam 36 at the end remote bearing 38. Each ploughing unit 14 is secured to frame 16 at spaced intervals along its length. The frame 16 is secured to the transverse beam 36 at an angle which places each ploughing unit 14 with the desired transverse separation which dictates the width of the ploughed furrow. A rear depth wheel (not shown) is disposed at the rear of the frame 16 to support the weight of the plough and limit the maximum to which the rear of the plough penetrates.

A sensor 40 is disposed within the casing of plough support body 32 and serves to sense the orientation of the plough. The sensor may be a simple magnetic onloff sensor which switches when in close proximity to a magnet. However, it will be appreciated that there are several options to provide a sensor which can detect the orientation of the plough. The output from the sensor 40, either "orientation left" or "orientation right", is communicated to an electronic control unit (ECU) on tractor 12 via wired or wireless technology.

A support structure 42 is pivotally mounted at the outside end of transverse beam 36. Support body 42 serves to support a pair of front depth wheels, 44L and 44R. Each of the front depth wheels 44 is secured to a telescopic arm 45 by an axle 46 wherein the depth of each wheel 44 can be manually adjusted by setting the associated telescopic arm 45 to the desired length.

Support structure 42 can pivot around vertical axis Z by an appropriate pivoting connection.

Enclosed within the body of supporting structure 42 there is disposed an angle sensor 48 which measures the angular displacement of the support body 42 away from a zero position.

The measured angle is communicated to the ECU from sensor 48 by wired or wireless technology.

Plough 10 is of the offset type wherein the tractor 12 is driven so that its footprint remains completely on the unploughed land during nonnal ploughing. This is illustrated in Figure 2 in which the ploughed land is represented by hatched area 50 and the open furrow exposed by the previous pass of the plough is referenced at 52. The separation between the central longitudinal axis X and the outside of open furrow 52, represented at W, remains substantially constant during normal ploughing. The invention seeks to assist in guiding the tractor 12 to maintain distance W at a substantially constant value.

Turning to the tractor 12, a driver is seated in driver's seat 54 which is positioned in cab 56.

The tractor 12 comprises two rear wheels 58 and two front steerable wheels 60.

With reference also to Figure 6, the constituent parts of the guidance system will be described in relation to the tractor U. An ECU 62 is housed within a control consul which is viewable by the driver. The ECU 62 includes a microprocessor which controls implementation of the invention as described below. The tractor 12 comprises automatic steering apparatus which includes an electro-hydraulic steering distributor 64 which controls the application of hydraulic pressure to steering cylinders associated with steerable wheels 60. Control of the automatic steering is a two-way process wherein steering signals are communicated from the ECU 62 to the electro-hydraulic steering distributor 64 and a steering angle sensor (not shown) communicates steering angle signals to the ECU 62, thereby providing a closed-loop feedback process.

A steering wheel 66 located in the cab has an associated sensor 68 for sensing movement of the steering wheel by the driver. The output from steering wheel sensor 68 is communicated to the ECU 62 for use as will be described below.

A user input terminal 70 in the form of a touch sensitive display screen is located in the cab and is in wired communication with ECU 62. User input terminal 70 allows the driver to monitor and adjust parameters associated with the guidance systems and other functions of the tractor.

A linkage sensor 72 senses the position of the lift arms 28 and communicates the measurement to the ECU 62 via a wired link.

In accordance with the invention, plough wheel angle sensor 48 and plough orientation 40 both communicate their readings to ECU 62.

With reference again to Figure 2, front depth wheel 44R is guided along the open furrow 52.

In the event of the separation between the tractor U and the ploughed land 50 exceeding the optimum distance W, front depth wheel 44R and support structure 42 is angularly displaced by an angle 0 (Figure 4). Conversely, when the tractor 12 is driven too close to the ploughed land 50, the front depth wheel 44R is displaced in the opposite direction as shown in Figure 5.

In accordance with the invention, the angle sensor readings from sensor 48 are exploited to automatically adjust the steering of tractor 12 to maintain separation W at a substantially constant value.

With reference to Figure 7, the process by which ECU 62 operates the guidance system will now be described. In order for the guidance system to be active the plough must be in the working position, that is lowered into the ground. This is determined by ECU 62 from the sensed linkage position provided by sensor 72. Furthermore, a positive activation of the system by a touch sensitive switch on display unit 70 must also occur to activate the system.

If, at any point, the driver commands deactivation of the system via the display unit 70, or the plough is lifted in to the transport position, ECU 62 automatically deactivates the guidance system. In addition, in the event of ECU 62 receiving a positive signal from steering wheel sensor 68, thus indicating a manual override of the steering by the driver, the guidance is deactivated.

A repetitive process of comparing the sensed angle from angle sensor 48 with a predetermined calibration value is carried out to determine whether a steering correction is required. In the event that the sensed angle is equal to the calibration value then no steering correction is required.

However in the event that the sensed angle deviates from the calibration value for a predetermined period of time, then a steering correction is required. Depending on the magnitude of the deviation, and the sensed plough direction, the electro-hydraulic steering distributor is commanded with a steering signal from the ECU 62 so as to automatically steer the tractor 12 to the left or to the right as required.

It should be appreciated that the measuring of the plough wheel angle and the resulting steering correction is an iterative process and, especially for straight line ploughing, the tractor and plough combination should converge towards a steady state.

The inventive system lends itself well to a tractor fitted with an existing automatic steering system such as AutoGuideTM which is optionally fitted to Massey Ferguson 8400 series tractors for example. In the embodiment shown, tractor 12 comprises a GPS receiver 74 disposed on the roof of the cab 56. GPS receiver 74 communicates with ECU 62 to guide the tractor in response to signals received from a satellite. Such a GPS-based system may be overridden by the driver to run the plough guidance system in accordance with the invention.

It will therefore be appreciated that, in some existing tractors, the only hardware to be added in order to implement the invention is receiving means to receive the outputs of plough wheel angle sensor and orientation sensor.

In a second embodiment the tractor is not fitted with automatic steering apparatus and an ECU simply drives a display module having several steering status indicators. The display module 80, as shown schematically in Figure 8, comprises a straight-ahead indicator 81 which illuminates in green when the sensed plough wheel angle is equal to the calibration value within a predetermined tolerance. To either side of indicator lights 81, a left-hand and right-hand moderate deviation indicator 82,83 is provided which illuminates in yellow when the sensed plough wheel angle deviates from the calibration value by a predetermined moderate amount. Further still major deviation indicators 84,85 are provided for major left-hand and right-hand deviations respectively between the plough wheel angle sensor and the calibration value. The major deviation indicators 84,85 illuminate in red. During correct operation only one of the indicators is illuminated.

When activated, the driver manually steers the tractor 12 in response to the lit indicator on panel 80 with the aim to keep green indicator 81 illuminated. In the event that, say, moderate right-hand deviation indicator 83 illuminates then the driver steers to the left to compensate with the result of maintaining a substantially constant distance from the ploughed ground.

The guidance system in accordance with the invention provides a calibration mode regardless of whether the steering correction is performed manually or automatically. In the calibration mode the driver informs the ECU 62 that the front depth wheel 44 is in the straight ahead, or optimum, direction by appropriate data entry through the data terminal 70 for example.

Although the plough described is mounted to the three-point linkage of a tractor, it is envisaged that a semi-mounted or trailed plough may instead be used without deviating from the scope of the invention. Furthermore, the invention is applicable to offset ploughs of any size and having any practical number of ploughing units.

In summary, a guidance system for a tractor and offset plough combination is provided. The plough comprises a frame with a plough wheel pivotally mounted thereto which may serve also as a depth control wheel. During normal ploughing the plough wheel moves along an open furrow exposed by a previous pass of the plough and is angularly displaceable by contacting sidewalls of the open furrow. Sensing means are provided to sense the angular displacement of the plough wheel relative to the frame. The output from the sensing means is communicated to an electronic control unit on the tractor and is used to produce a steering correction signal which is indicative of a required steering correction to maintain a substantially constant distance between the tractor and the open furrow.

From reading the present disclosure, other modification will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the field of tillage equipment and component parts therefore and which may be used instead of or in addition to features already described herein.

Claims

CLAIMS1. A guidance system for a tractor and plough combination, the plough being of an offset type which is mounted to the tractor so that the tractor has a footprint which remains completely on unploughed land during normal ploughing, the plough comprising a frame with a plough wheel pivotally mounted thereto which during normal ploughing moves along an open furrow exposed by a previous pass of the plough and is angularly displaceable by contacting sidewalls of the open furrow, and plough wheel angle sensing means which senses the angular displacement of the plough wheel relative to the frame and generates signals which are representative of said angular displacement, wherein said signals are communicated to an electronic control unit and can be used to produce a steering correction signal which is indicative of a required steering correction to maintain a substantially constant distance between the tractor and the open furrow.
2. A guidance system according to Claim 1, wherein the tractor comprises automatic steering apparatus to steer the tractor in response to steering signals communicated from the electronic control unit, the automatic steering apparatus comprising steering angle sensing means which communicates steering angle signals to the electronic control unit, wherein the steering signals are a function of the steering correction signal.
3. A guidance system according to Claim 2, wherein the automatic steering apparatus comprises an electro-hydraulic distributor to which the steering signals are communicated, wherein the distributor controls the application of hydraulic pressure to steering cylinders.
4. A guidance system according to Claim 2 or 3, wherein the automatic steering apparatus is selectively activated by a driver via a user interface device.
5. A guidance system according to Claim 4, wherein the tractor comprises a steering wheel and means to sense movement of the steering wheel, and wherein automatic steering of the tractor is deactivated in response to a sensed movement of the steering wheel.
6. A guidance system according to any one of claims 2 to 5, wherein the plough can be lifted from a working position into a transport position, the system further comprising lift position sensing means to detect when the plough is in the working position andlor the transport position, and wherein the automatic steering is deactivated when the plough is in the transport position.
7. A guidance system according to any one of Claims 2 to 6, wherein parameters defining the relationship between the steering correction signal and the steering signals can be adjusted by a driver via a user interface device.
8. A guidance system according to Claim 1, wherein the tractor comprises a display element viewable by a driver, and wherein the display element is arranged to display an indication of said required steering correction to aid the driver to manually correct the steering as required.
9. A guidance system according to any preceding claim, wherein the plough is a reversible plough and comprises a plough wheel for each direction, the plough further comprising direction sensing means to detect the orientation of the frame and generate a direction signal representative thereof, said direction signal being communicated to the electronic control unit.
10. A guidance system according to Claim 9, wherein both plough wheels are mounted to a common wheel support member which is pivotally mounted to the frame.
11. A guidance system according to Claim 10, wherein the plough wheel angle sensing means senses the angle of the common wheel support member.
12. A guidance system according to any preceding claim, wherein the plough wheel serves also to limit the maximum depth of the ploughed furrows.
13. A guidance system according to any preceding claim, wherein the plough wheel angle sensing means can be calibrated via a user interface device on the tractor.
14. A plough for use in a system according to any preceding claim.
15. A tractor for use in a system according to any one of Claims I to 13.