DE102022200769A1 - Method, control unit and control system for electrohydraulic hitch control - Google Patents

Abstract

The invention relates to a method for electrohydraulic hitch control in a working machine, comprising receiving a signal (312), a value (368`) of the signal in a signal range (360`) between two limit values (354', 356`) being continuous or may vary quasi-continuously; selecting one of at least two control functions of the electro-hydraulic hitch control as a function of a current value (368', 468') of the signal and/or a change in the value (368', 468') of the signal over time, and causing or carrying out the selected ones Control function depending on a current value (368`) of the signal and/or a change in the value (368`) of the signal over time.

Description

The present invention relates to a method, a control unit and a control system for electrohydraulic hitch control in a work machine such as a tractor, and a computer program for carrying out the method.

Background of the Invention

Attachments can be attached to working machines, in particular mobile working machines such as vehicles or other mobile or mobile machines, e.g. tractors, which can be moved by means of a hoist, i.e. in particular can be raised and lowered. Such attachments can be, for example, agricultural equipment such as ploughs, sowing machines and the like, which can be attached to a tractor as a mobile working machine.

Disclosure of Invention

According to the invention, a method, a control unit and a control system for electrohydraulic hitch control and a computer program for carrying out the method with the features of the independent patent claims are proposed. Advantageous configurations are the subject of the dependent claims and the following description.

The invention deals with lifting mechanisms (or lifting devices) for work machines, in particular mobile work machines such as tractors, and in particular their operation. The lifting gear can in particular be what is known as a three-point power lift, also known as a three-point hydraulic system; this is a hydraulic device on tractors or other work machines to couple and lift attachments (implements). Such a lifting gear is often attached to the rear of the working machine (rear lifting gear; attached to the front of the working machine it is referred to as a front lifting gear). The downward movement takes place either hydraulically or, in the case of simpler systems, by the weight of its own elements (lower links) or the attachments. The system is called three-point because the implements are attached to the working machine at three points.

Such lifting gears are nowadays typically controlled electronically or electrohydraulically, this is also referred to as the so-called electrohydraulic lifting gear control (EHR). Such is usually standard in modern tractors, but can also be used in other (mobile) work machines. The movements and forces on the suspension can be recorded electronically. The links are attached to the tractor with force measuring bolts, for example. The exact height can be determined and set with a position sensor on the three-point linkage.

With an electro-hydraulic hitch control, the hitch (the actual lifting device) can typically be controlled in two ways. Either the tractive force applied to the mobile working machine (force control) or the position (position) of the hoist (position control) is controlled. For position control, the position or attitude is determined, for example, by means of a position or attitude sensor (typically as an angle sensor). For force control, the tensile force is determined using a force sensor, for example. The force or position can be regulated accordingly via a suitable activation of a lifting gear valve by a control device (control device with functional software). Here, the tractive force typically serves as an indirect value for the working depth, i.e. the tractive force on the force sensor is increased by lowering a tillage implement as an attachment into the soil. By lifting, the tractor or the mobile work machine is relieved and the value currently output by the force sensor decreases.

The power control is primarily required for tillage implements (such as ploughs), since a constant tractive power ensures optimal work results and good utilization of the tractor. For other applications such as fertilizer spreading (with a spreader as an attachment) or spraying, the location or position (ie the height above the ground or relative to the work machine) of the lifting mechanism should preferably be kept constant. A major advantage of the electro-hydraulic hitch control is the so-called mixed control. A certain amount of position control can be "added" to the force control. The advantage of this is that the position of the linkage fluctuates less than with pure power control and the working depth can therefore be kept more constant. This function is particularly advantageous for inhomogeneous soils.

An operator control unit is generally provided for a user of the work machine, via which he can set or specify the desired type of regulation, a setpoint value or other functions. For this purpose, many different control or actuation elements such as potentiometers, switches or buttons are typically provided as components of the control unit.

The control setpoint can typically be set on the control unit using a potentio meters or a similar control element. A potentiometer can be adjustable between two end stops, for example (eg rotatable in the case of a rotary potentiometer), so that depending on the specific position between the two end stops, a corresponding target value for the control can be set.

In addition to the regulation of force and position, an "Active Float" function can be provided, e.g. in one (e.g. lowest) position of the potentiometer (e.g. the lower end stop); this is a float position or float control. Here, the hydraulic valve is permanently opened against the tank, which means that the attachment follows the contours of the ground, since there is no pressure in the hydraulic cylinder. This is useful, for example, for attachments that should always rest on the ground, such as a roller.

With conventional operating concepts, the mixing ratio of the mentioned mixed control, ie force and position control, can also be adjusted by means of a (further) potentiometer. If this potentiometer is at one of the end stops, this corresponds to pure force or pure position control. You can work with two modes, which can be set using a (toggle) switch. First, there is a transport mode. Here, the hoist is extended or raised to the maximum. The lifting height in transport mode is usually limited with another potentiometer. The second mode is the work mode or control mode. In this, the position, force or mixed control is activated and the hoist is controlled to the set operating point or setpoint (setpoint).

With typical operating concepts, the lowering speed of the hoist can be limited, e.g. by means of an additional potentiometer. In the transport mode, the possibility of vibration damping can be provided. It is usually switched on and off via a button or button. When driving with attached attachments, it compensates for the effects of uneven roads and prevents the mobile working machine from swinging up.

Additional functions can also be provided. The so-called quick retraction causes, for example, the lowering or lowering of the lifting mechanism at maximum speed, for example to allow the plow to penetrate the ground quickly when the corresponding button is pressed. A switch can also be provided to unlock the system, for example when starting the mobile work machine or in the event of errors.

Such operating concepts for the electrohydraulic hitch control are sometimes very complex due to the large number of operating elements and are therefore usually very confusing and difficult to operate for the user. Although some controls could be omitted, this is accompanied by a reduction in the range of functions.

Against this background, an operating concept for an electrohydraulic hitch control is proposed, which simplifies this complexity, but without reducing the scope of functions or at least without reducing them excessively.

To this end, a control system is proposed that includes a control unit and an operating unit that interacts with it. A method for the control is also proposed. In the following, the procedure, control unit, operating unit and control system are to be described together and comprehensively.

The operating unit has an operating element (or actuating element), the operating element being adjustable in an adjustment range between two end stops or end points, specifically continuously or quasi-continuously. This operating element can in particular be a potentiometer, e.g. a rotary potentiometer, which can be rotated between two physical end stops, for example by hand. Such a control element thus generates in particular a signal that lies between two values that correspond to the end stops. For example, a voltage can be changed continuously (or quasi-continuously) between an upper and a lower value (level). Corresponding to the adjustment range, there is a signal range for the signal in which a value of the signal lies.

In principle, a virtual operating element is also conceivable, which is displayed, for example, on a touchscreen or another display and input device, and which can be moved between two end stops or two end points by touching the touchscreen. Here, too, a signal can be generated that lies in a signal range between two values that correspond to the end stops.

The control unit (e.g. a control unit or another computing unit) is set up to selectively carry out or cause at least one of several control functions of the electrohydraulic hitch control (additional components within the scope of the hitch control can be activated if necessary). The multiple control functions preferably include at least one position controller for controlling a position of a hoist and a force controller tion for controlling a force on the hoist. In addition, the multiple control functions can also include float control, vibration damping, and mixed control for controlling a position of the hoist and a force on the hoist.

Depending on requirements, for example, the force control or position control mentioned at the beginning can be carried out. The control unit is also set up to interact with the operating unit, ie to receive a signal from the operating unit and thus to implement the desired control or other function specified by means of the operating unit or its operating element.

A value of the received signal lies in a signal range between two limit values, it being possible for the value to vary continuously or quasi-continuously within this signal range (a variation occurs when the operating element is actuated). Depending on the value and/or (over time) change in the value of the (received) signal, at least one of the plurality of control functions is then selected and carried out or initiated.

Only one control element is therefore required, which can be adjusted continuously or quasi-continuously in an adjustment range between two end stops, in order to still be able to carry out or initiate several different control functions of the electrohydraulic hitch control. The invention thus enables the EHR system to be operated in a comparatively easy, intuitive manner by reducing the number of operating elements, ideally to just one, e.g. a single potentiometer, and two, preferably mechanical, end stops. A display device, in particular a lamp such as an LED, can be used to signal a system status, i.e. to output information about a currently selected control function within the scope of the electrohydraulic hitch control. This achieves greater customer acceptance of both mechanical systems and existing operating concepts of EHR systems. In addition, the operating unit is cheaper to manufacture than conventional operating parts.

Various options are preferred for mapping a number of different control functions onto the signal range (or adjustment range). The signal area preferably comprises at least two, in particular mutually exclusive, partial areas. It is conceivable, for example, to subdivide the signal range into an upper and a lower half - or to divide the adjustment range into two areas of approximately the same size, for example. Then the at least two partial areas are each assigned to different control functions. It is conceivable, for example, that with a potentiometer as an operating element, starting from an (upper) end stop within one half of the adjustment range, a setpoint for position control (from maximum to minimum) can be specified, but from the second half, then up to the (lower) end stop, a setpoint for force control (from minimum to maximum). It is also conceivable that between the two sub-areas a (smaller, possibly also punctiform) further sub-area (the other two would then be e.g. each somewhat smaller) is provided, to which a float control (“active float”) is assigned. By (mechanically) adjusting the end stops, for example, the setpoint that can be specified for force or position control can be limited.

By means of additional software functionality, for example, the functionality of mixed control, i.e. position control and force control at the same time, can be achieved. Here, position fluctuations during pure force control are compensated to a certain extent. This is a type of control that offers advantages particularly with inhomogeneous soils. The mixed control (AHC=Automatic Hitch Control) can always be automatically activated in both of the operating concepts described, for example, if force control is selected. An additional switch can also be provided to turn AHC on or off.

It is also preferred if the signal area or at least a partial area of the signal area is assigned to at least two different control functions. In this case, the assignment of the current value of the signal is changed from one to another of the at least two different control functions if the change in the value of the signal over time corresponds to a predetermined pattern. The predetermined pattern includes, for example, that the value of the signal is within a predetermined switching range of the signal range for at least and/or at most a predetermined period of time. For example, (almost) the entire signal range can be used for position control; If the operating element is then moved into a switching range for a certain period of time, e.g. at or near one of the end stops, and then moved out again, it is possible to switch to force control. Then (almost) the entire signal range can be used for force control. Several of these switchover areas can also be provided.

In this way, one control element can be used in many different ways. In addition to the above-mentioned examples, other possibilities are also conceivable for carrying out or initiating various control functions by means of an operating element. Two more detailed examples will be explained in the context of the description of the figures.

It should be mentioned that in order to use the proposed operating unit, a control unit is required which can display the control functions mentioned using the value of a signal within a signal range. It is also conceivable here that the method is carried out by an additional function with which the value of a signal within a signal range is converted into other signals, such as are required in conventional control units for electrohydraulic hitch control, which previously interacted with several operating elements. A software update is conceivable here, for example.

A control unit according to the invention, e.g. a control unit of a tractor, is set up, in particular in terms of programming, to carry out a method according to the invention.

The implementation of a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is advantageous because this causes particularly low costs, especially if an executing control device is also used for other tasks and is therefore available anyway. Suitable data carriers for providing the computer program are, in particular, magnetic, optical and electrical memories, such as hard drives, flash memories, EEPROMs, DVDs, etc. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and refinements of the invention result from the description and the attached drawing.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

The invention is shown schematically in the drawing using exemplary embodiments and is described in detail below with reference to the drawing.

character list

• 1 shows schematically a work machine with a control system for electro-hydraulic hitch control in a preferred embodiment.
• 2 shows schematically a sequence of a method according to the invention in a preferred embodiment.
• 3 shows schematically a control unit according to the invention in a preferred embodiment.
• 4 shows schematically a control unit according to the invention in a further preferred embodiment.

Detailed description of the drawing

In 1 a working machine 100 designed as a tractor with a control system for electrohydraulic hitch control is shown schematically and by way of example in a preferred embodiment. The tractor includes a lifting mechanism 130 to which an attachment 102 designed as a plow is attached, for example.

The lifting mechanism 130 in turn has a hydraulic cylinder 132 with which a linkage 134 can be moved, in particular raised and lowered. Furthermore, a hydraulic pump 134 is provided, by means of which hydraulic fluid can be conveyed to the hydraulic cylinder 132 via a valve or a valve block 136 (possibly with several valves) in order to raise the lifting mechanism. Hydraulic fluid can be drained by opening the valve to lower the hitch.

Furthermore, a control unit 120 is provided, by means of which the valve or the valve block 136 can be controlled, possibly also the hydraulic pump. Furthermore, an operating unit 110 is provided, by means of which a user can make specifications for control functions of the electrohydraulic hitch control, which are transmitted to the control unit 120 as a signal 112 . In addition, a force sensor 140 and a position sensor 142 are provided in order to detect a position (possibly via an angle) of the lifting gear 130 or a force on the lifting gear 130 . The control unit 120 receives the values from these sensors in order to be able to carry out the control or regulation in accordance with the specification via the operating unit 110 .

In addition, a rear button arrangement 144 with, for example, two so-called rear buttons is provided, by means of which a user can also make specifications for control functions of the electrohydraulic hitch control; this are typically limited to lowering and/or raising.

In 2 a sequence of a method according to the invention is shown schematically in a preferred embodiment. In a step 200, a user can make specifications for control functions of the electro-hydraulic lifting gear regulation, ie, for example, specifying a specific desired value for the position control or lowering the lifting gear. This can be done via the operating unit 110 or the rear button 144. For example, a setting or position of the potentiometer can be transmitted as a signal 212 to the control unit 120 via the operating unit 110 . Likewise, if necessary, a button position can be transmitted as a signal 214 to the control unit 120 by the rear buttons 144 .

A position 202 of the lifting mechanism 130 is detected by means of the position sensor 142 (possibly as an angle sensor) and transmitted to the control unit 120 as a position value 204 . A load or force 208 on the lifting mechanism 130 is detected by means of the force sensor 140 . This may require a conversion or consideration 206 of the location or position of the lifting mechanism in or on the force (this can depend, for example, on the surface on which the attachment is moving, the weather, the attachment itself or the speed of the tractor. This force 208 is then transmitted to the control unit 120 as a force value 210.

In control unit 120, using signals 212, 214 (typically only one of them is specified/received at a time), position value 204 and force value 210, the system state of lifting mechanism 130, for example, is first determined, a setpoint value is calculated (which is specified via signal 212), the desired open-loop or closed-loop control function is determined (which is also specified via signal 212) and, if necessary, a control difference is calculated. A position control 220 and a force control 222 are provided for selection here as an example. The relevant control or regulation function is then initiated or carried out, e.g. by activating the valve block of the lifting gear 130. This is used, for example, to fill or empty the hydraulic cylinder in order to raise or raise or lower the lifting gear.

In addition, the control unit 120 can output information 216 about a currently selected control function on a display means, such as an LED.

In 3 a control unit 310 according to the invention is shown schematically in a preferred embodiment. The operating unit 310 has an operating element 350 designed as a rotary potentiometer with a nose 352 . Furthermore, two end stops 354 and 356 are provided, between which an adjustment area 360 is provided. The operating unit 350 can be adjusted continuously or quasi-continuously in the adjustment range 360 (by turning) between the two end stops 354, 356. For this purpose, the lug 352 is provided, which comes into abutment against the end stops. In addition, the nose 352 shows the currently set value 368. The end stops 354 and 356 can, if necessary, be adjusted manually, for example, so that the usable portion of the adjustment range is reduced.

The operating unit or the operating element is used to generate a signal 312 which is transmitted to the control unit. The signal 312 schematically indicated here can be a voltage signal, for example. The signal can assume a value between two limit values 354' and 356', e.g., an upper and a lower voltage level. These two limits correspond to the end stops 354 and 356 when attached to their respective ends so that the maximum range of adjustment can be selected. The (maximum) adjustment range 360 corresponds to a signal range 360'.

The adjustment range can be subdivided into several sub-areas, here for example three sub-areas 362, 364 and 366. Accordingly, the signal range 360' is also sub-divided into three sub-areas 362', 364' and 366'. The current value 368 set using the control element (position of the potentiometer) corresponds to the current value 368` in the signal 312.

The three sub-areas 362, 364 and 366 or 362', 364' and 366' can now be assigned to three different control or regulation functions within the scope of the electrohydraulic hitch control, which can be selected and implemented according to the current value 368 or 368' or, if necessary, its change over time. This will be explained in more detail below using an example.

The actual control functions depend on the position of the potentiometer. The upper section 362 is assigned to the position control; all setpoints for position control of the hoist can be set there and the position control is active. For example, by adjusting the value 368 or turning the potentiometer from one end of the sub-range 362 to the other end, the setpoint of the position can be lowered.

The "Active Float" function (float control) is implemented in sub-area 364. This is in the lowest position at or after the position control. It should be noted that the Partial area 362 can be very small (eg only in the form of a point), since no different setpoint values have to be specified here.

The lower sub-area 366 is assigned to force control. All setpoints of the force for tensile forces are shown here (the setpoint increases downwards, for example). In this partial area 366, it is not possible to excavate from the ground, since regulation of the traction force always means that the attachment is in a position below the field surface.

The sub-areas 362, 364 and 366 can be labeled accordingly on the operating unit, e.g. with "position control", "active float" and "force control". Position control and force control can also be scaled to provide a reference point for setpoints (at least maximum and minimum adjustable setpoint).

By means of additional software functionality, for example, the functionality of mixed control can also be achieved. Here, position fluctuations during pure force control are compensated to a certain extent.

If the hoist is to be raised during force control, you must switch to sub-area 364 and then 362. However, since the position setpoints that occur are initially very small and possibly smaller than the current actual value of the position sensor, this could lead to an unwanted lowering of the hoist. In order to prevent this, it is preferably provided that when leaving the sub-area 366, lowering of the hoisting gear is initially prevented, e.g. by locking the system. This can be indicated visually, e.g. by the LED flashing. Only when the position setpoint exceeds the actual value or sensor value of the position is the lifting gear released again (and the LED stops flashing). As a result, there is no large control difference after unlocking, which could lead to uncontrolled movement of the hoist.

It is preferably possible, even during such a blockage, to return to the area of force control, where the lifting gear is released again for tilling the soil.

The lowering speed is determined by the movement of the potentiometer, i.e. the faster the potentiometer is turned, the faster the lifting gear will be lowered or raised (as long as sub-range 362 is selected).

Vibration damping can, for example, be activated automatically if there is position control, the hoist has exceeded a certain height and the setpoint has not been changed by the potentiometer for a certain period of time. Vibration damping is deactivated when the potentiometer is moved again.

The LED 390 (display means) indicates, e.g. by lighting up after the system has started, that it needs to be unlocked. Errors can be output by flashing codes. With the blocking described above, the LED flashes at 4Hz, for example.

In 4 an operating unit 410 according to the invention is shown schematically in a further preferred embodiment. The operating unit 410 has an operating element 350 designed as a rotary potentiometer with a nose 352 . Furthermore, two end stops 354 and 356 are provided, between which an adjustment area 460 is provided. The operating unit 350 can be adjusted continuously or quasi-continuously in the adjustment range 460 (by turning) between the two end stops 354, 356. For this purpose, the lug 352 is provided, which comes into abutment against the end stops. In addition, the nose 352 shows the currently set value 368. The end stops 354 and 356 can, if necessary, be adjusted manually, for example, so that the usable portion of the adjustment range is reduced.

The operating unit or the operating element is used to generate a signal 412 which is transmitted to the control unit. The signal 412 schematically indicated here can be a voltage signal, for example. The signal can have a value between two limit values 454` and 456`, e.g. an upper and a lower voltage level. These two limits correspond to the end stops 354 and 356 when attached to their respective ends so that the maximum range of adjustment can be selected. The (maximum) adjustment range 460 corresponds to a signal range 460`.

It should be mentioned that the mechanical structure of the operating unit 410 can be identical to that of the operating unit 310; there is a difference in the way in which the current value within the adjustment range 460 or the signal range 460' is converted into a control or regulation function in the control unit. The labeling of the operating unit is also different.

The adjustment area 460 can now be subdivided into several subareas, here for example three subareas 462, 464 and 466. Accordingly, the signal area 460' is also subdivided into three subareas 462', 464' and 466'. The current value 468 set using the control element (position of the potentiometer) corresponds to the current value 468' in the signal 412.

The partial areas 462 and 466 at or near the end stops serve as switching areas; these two sections can be very small; if necessary, only the value directly at the end stop can serve as the switching range. Accordingly, the partial area 364 corresponds almost to the entire adjustment area 460.

The sub-range 464 or almost the entire adjustment range 460 thus represents both the entire setpoint range of the position control and the setpoint range of the force control.

Force control is activated by moving the potentiometer into the switching range or sub-range 466 and then leaving the switching range or sub-range 466 within a certain time period (if this sub-range were not left within this time period, "Active Float" would be activated). Due to the position of the switching area 466 at the lower end stop, the switching process is secured (no uncontrolled movement) since the attachment is on the ground. As with the variant according to 3 the software functionality can also be used for mixed control.

If the potentiometer is not moved at the switching point, the control function does not change. The switching process can be started again after the potentiometer has been moved out of the switching range. Analogously to switching over or changing over from position control to force control, the switching area 462 switches from force control to position control.

The sub-areas 462 and 466 can be labeled accordingly on the operating unit, e.g. with "Switch to position control" and "Active float + switch to force control". The portion 464 may also be provided with a scale to provide a reference point for the setpoints (at least maximum and minimum adjustable setpoint). The partial area 464 can also be labeled “position control/force control”.

In contrast to the variant according to 3 can be excavated here in force control, since the entire range for force setpoints is mapped. In this operating mode, it can be provided in particular that there is no area switchover from force/mixed control (use of the force measuring bolt for the sensor signal) to position control (use of the position sensor for the sensor signal). The sensor signal is therefore constant and the control does not need to be blocked in the switchover range in order to absorb a sudden behavior of the hoist. If the weight of the attachment is exceeded by the force setpoint, the lifting mechanism would immediately lift to the maximum since the control difference can no longer be compensated for by lifting. In order to prevent this, the lifting height can also be limited in force control using the potentiometer. If the potentiometer is turned further up, the maximum height increases, which ensures safe lifting. Thus, the (upper) end stop always limits the lifting height.

The operating point can also be set using one of the end stops. Can be unlocked as per the variant 3 become. After unlocking, for example, there is always position control. The lowering speed is specified by the potentiometer movement. In position control, the vibration damping in the variant according to 3 be activated by staying in the upper area, and deactivated by moving the potentiometer again.

If LED 390 is off, the system is in position control. In force control, the LED flashes at 0.5 Hz, for example. During switching processes, the LED flashes at 4 Hz, for example. As with the variant according to 3 After starting the tractor, the LED indicates, for example, that the system is locked, for example by lighting up continuously, and errors are signaled by flashing codes.

Claims (14)

Method for electro-hydraulic hitch control in a working machine (100), comprising: Receiving a signal (112, 212, 312, 412), wherein a value (368`, 468`) of the signal in a signal range (360', 460`) can vary continuously or quasi-continuously between two limit values (354', 356`, 454`, 456`), Selecting one of at least two control functions of the electrohydraulic hitch control depending on a current value (368`, 468`) of the signal and/or a change in the value (368', 468`) of the signal over time, and Initiating or performing the selected control function (220, 222) depending on a current value (368`, 468`) of the signal and/or a change in the value (368', 468`) of the signal over time. procedure after claim 1 , wherein the signal area (360', 460`) comprises at least two, in particular mutually exclusive, partial areas (362`, 364`, 366`, 462`, 464', 466`), and wherein the at least two partial areas are separate from each other assigned to different control functions. procedure after claim 1 or 2 , wherein the signal area or at least a sub-area (464`) of the signal area is assigned to at least two different control functions, and wherein the assignment of the current value (368', 468`) of the signal is changed from one of the at least two different control functions to another if the change over time in the value (368', 468`) of the signal corresponds to a predetermined pattern. procedure after claim 3 , wherein the predetermined pattern comprises that the value (368`, 468`) of the signal is within a predetermined switching range (462', 466`) of the signal range for at least and/or at most a predetermined period of time. A method according to any one of the preceding claims, wherein the plurality of control functions include at least the following: - a position controller (220) for controlling a position of a hoist, and - A force control (222) for controlling a force on the hoist. procedure after claim 5 , whereby a reference value for the position control or the force control is specified based on the current value (368', 468`) of the signal. A method according to any one of the preceding claims, wherein the plurality of control functions further comprise at least one of the following: - a swimming regulation, - vibration damping, and - a mixed control for controlling a position of the hoist and a force on the hoist. Control unit (120) for the electro-hydraulic hitch control of a work machine (100), which is set up to carry out a according to one of the preceding claims. Control system for the electro-hydraulic lifting mechanism control of a working machine (100), with a control unit (120). claim 8 and with an operating unit (110) cooperating therewith. control system according to claim 9 , wherein the operating unit (110) has an operating element (350) which can be adjusted continuously or quasi-continuously in an adjustment range (360, 460) between two end stops (354, 356), the operating unit (110, 310, 410) being set up to output a signal (112, 212, 312, 412) depending on a position of the operating element in the adjustment range . control system according to claim 10 , wherein at least one of the two end stops (354, 356) is adjustable in order to change the adjustment range (360, 460). control system) after claim 10 or 11 , wherein the operating unit also has a display means (390), in particular a lamp, which is set up to display information about a currently selected control function as part of the electrohydraulic hitch control. Computer program that causes a computing unit, in particular a control unit (120) for electro-hydraulic hitch control, a method according to one of Claims 1 until 7 to be performed when it is executed on the computing unit. Machine-readable storage medium with a computer program stored on it Claim 13 .

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