System and method for positioning an auxiliary device connected to a work machine

Abstract

The invention relates to a system for positioning an auxiliary device connected to a work machine, wherein the work machine includes a frame, an attachment element connected in an articulated manner to the frame for the attachment of the auxiliary device, a first actuator for changing a position of the auxiliary device, and a second actuator for changing a position of the auxiliary device in a different direction to the first actuator. The system includes an inertial measurement unit configured to be attached to the auxiliary device for determining a position of the auxiliary device as positional data, and a control unit which includes computing means for generating control commands based on the positional data for the first actuator and the second actuator so as to maintain the auxiliary device in a target position by means of the first actuator and the second actuator. The control unit is configured to adjust the position of the auxiliary device in relation to the direction of the gravitational force vector of the Earth determined by the inertial measurement unit and independently of the position of the work machine in relation to the substrate on which the work machine is supported. The invention also relates to a method for positioning the auxiliary device.

Description

[0001] SYSTEM AND METHOD FOR POSITIONING AN AUXILIARY DEVICE CONNECTED TO A WORK MACHINE

[0002] The invention relates to a system for positioning an auxiliary device connected to a work machine, wherein the work machine includes a frame, an attachment element connected in an articulated manner to the frame for the attachment of the auxiliary device, a first actuator for changing a position of the auxiliary device, and a second actuator for changing a position of the auxiliary device in a different direction to the first actuator, wherein the system includes

[0003] - an inertial measurement unit configured to be attached to the auxiliary device for determining a position of the auxiliary device in the form of positional data, and

[0004] - a control unit which includes computing means for generating control commands based on said positional data for the first actuator and the second actuator so as to maintain the auxiliary device in a target position by means of the first actuator and the second actuator .

[0005] The invention also relates to a method for positioning an auxiliary device .

[0006] The positioning of auxiliary devices of work machines can be critical for the operation of the auxiliary device . An example of such an auxiliary device is a fertiliser or seed spreader suspended from a tractor . A spreader can spread fertiliser in a fan pattern up to 50 metres in width . The spreader is attached to the tractor, but it is essential for its operation that the spreader is completely horizontal . A problem is that spreading does not occur as intended when the tractor is driving uphill or over a bumpy field, on account of which the spreader does not remain horizontal . Analogous challenges are also associated with other tasks carried out with auxiliary devices attached to a work machine, such as ploughing, sand spreading andlevelling . The problem is generally known and acknowledged by all users of tractors .

[0007] The document WO 2024118664 Al known from the prior art describes a three-point attachment element for a tractor, wherein the three-point attachment includes articulated arms and a support member, and the articulated arms can be moved by means of actuators to position an auxiliary device connected to the three-point attachment element . The actuators for positioning the auxiliary device are controlled by an inertial measurement unit or IMU that belongs to the control unit . However, an issue with this type of attachment element is that the adjustment of the two lifting arms does not permit an adjustment of the position of the auxiliary device in three-dimensional space, because the path of movement of the attachment points of the lifting arms is arc-shaped so that an adjusting movement produced by a movement of the lifting arms is mainly vertical .

[0008] The document CN 205740237 U known from the prior art describes an automatic positioning of forklift forks of a forklift , but only via adjustments in the forward or rearward direction of travel of the forklift . This kind of solution does not solve the problem, however, in cases where the inclination is transverse to the direction of travel .

[0009] The object of the invention is to provide a system and a method that are more freely adjustable than the solutions of the prior art and by means of which a full adjustability is achieved with respect to the position of the auxiliary device . The characteristic features of the invention are set out with regard to the system in the attached patent claim 1 and with regard to the method in the attached patent claim 14 .The object of a system according to the invention is achieved with a system for positioning an auxiliary device connected to a work machine, wherein the work machine includes a frame, an attachment element connected in an articulated manner to the frame for the attachment of the auxiliary device, a first actuator for changing a position of the auxiliary device, and a second actuator for changing a position of the auxiliary device in a different direction to the first actuator . The system includes an inertial measurement unit configured to be attached to the auxiliary device for determining a position of the auxiliary device in the form of positional data, and a control unit which includes computing means for generating control commands based on the positional data for the first actuator and the second actuator so as to maintain the auxiliary device in a target position by means of the first actuator and the second actuator . The control unit is configured to adjust the position of the auxiliary device in relation to the direction of the gravitational force vector of the Earth determined by the inertial measurement unit and independently of the position of the work machine in relation to the substrate on which the work machine is supported .

[0010] The system according to the invention positions the auxiliary device of the work machine in the longitudinal and transverse directions in real time by changing the length of the actuators based on the positional data produced by the inertial measurement unit in relation to the Earth' s gravitational acceleration and disregarding the position of the work machine . In other words , positioning is carried out in relation to an entire plane, and not just in relation to a single axis . The first actuator is used to produce a movement mainly in one direction, while the second actuator is used to produce a movement mainly perpendicular to that direction for the adjustment of the auxiliary device . The auxiliary device canthus be continuously positioned in a desired target position during travel , which, for example when the auxiliary device is a fertiliser spreader, allows fertiliser to be spread evenly .

[0011] The system according to the invention is very reliable in operating conditions compared to, for example, optical measurements , which are easily contaminated . The robust system according to the invention operates optimally regardless of terrain conditions . The improved positioning of the auxiliary device makes it possible to perform work faster and to avoid material waste, for example when the auxiliary device is a spreader for fertiliser .

[0012] In this context , positioning denotes a setting of the auxiliary device in a desired position, which is often horizontal , but can also be any other selected position permitted by the attachment element between its end positions .

[0013] In the following, the abbreviation IMU stands for inertial measurement unit .

[0014] In other words , the first actuator and the second actuator produce a movement of the lifting arm along one axis and a movement of the support member along a second axis . This enables a three-dimensional positioning of the auxiliary device freely in three-dimensional space .

[0015] A change in the position of the first lifting arm is brought about by changing the length of the first actuator .

[0016] The attachment element preferably includes a first lifting arm connected in an articulated manner to the frame and a support member connected in an articulated manner to the frame or to the first lifting arm .The inertial measurement unit preferably contains at least two different sensors . These can be two or more of the following sensors : an accelerometer, a gyroscope sensor and a magnetometer .

[0017] The control unit in the system is preferably configured to generate control commands for controlling the actuators based solely on the positional measurement data received from the single inertial measurement unit without using any other positional data . In other words , the system does not include any other sensors that directly or indirectly determine the position of the auxiliary device, which makes the system simple and fast .

[0018] The system according to the invention can be used in many different applications , the work machine taking the form, for example, of a tractor, a bucket loader, a telescopic handler or a forklift . In the case of a tractor, the auxiliary device can be, for example, a spreader, a leveller, a plough or the like, while in the case of a telescopic handler or a forklift , the auxiliary device can be forklift forks , roll clamps or an analogous device . For example, in the case of a forklift , the positioning of the forklift forks is important so that the forklift forks do not push the forklift pallet but are precisely aligned with the openings in the forklift pallet . A lateral positioning is also important , however, so that the items on the forklift pallet do not fall over sideways .

[0019] It should also be understood that the system according to the invention can be used in auxiliary devices that are suspended from the end of an arm of a work machine, for example in grapples used for processing trees , which are found at the end of an articulated boom crane attached to a work machine, or ingrapples and buckets attached to excavators . In these cases , the work machine can also be in any position relative to the ground, and the position of the auxiliary device is adjusted so as to be perpendicular to the direction of the Earth' s gravitational force vector .

[0020] The system according to the invention is preferably configured to hold the auxiliary device in the target position essentially continuously, i . e . the system repeatedly steers the auxiliary device into the target position when the position measured by the IMU deviates from the target position . The auxiliary device is thus in the target position for most of its time of operation, except for the time employed for the adjustment .

[0021] The system according to the invention is quite inexpensive in terms of its investment costs and can be implemented both in a retrofitting of existing work machines and as a factory installation in new work machines . The system according to the invention is quite simple in terms of its structure , whereby it is easy to use and requires very little maintenance .

[0022] The control unit preferably includes a filter for filtering the positional data prior to the calculation of the control commands in order to prevent a swaying of the positioning of the auxiliary device . The IMU generates measurement data on the position up to 100 times per second, so that isolated measurement data cannot be used directly as a basis for control , but this necessitates a filtering of this data to prevent the control from oscillating as the result of, for example, sporadic abrupt holes in the ground .

[0023] The positional measurement of the auxiliary device can be repeated by the IMU at a frequency of 0 . 1-200 Hz . This provides data on the position of the auxiliary device at a sufficientdensity to enable the auxiliary device to be positioned quickly enough to keep it in the correct position for almost the entire time of operation .

[0024] The system preferably includes adjustment means for adjusting the filtering manually . Users thus have the possibility of setting the filtering parameters for the positioning themselves so that said parameters are adapted to the auxiliary device in question and the operating environment in order to achieve an optimal result . A manual adjustment reduces the computation effort required of the computing means .

[0025] Alternatively, there can be different programs installed in the memory of the computing means for different auxiliary devices , wherein said programs can include preset filter settings that the control unit sets automatically for the filter .

[0026] The filter is preferably configured to filter out positional deviations that are smaller than a selected threshold value from the calculation of the control commands , wherein the threshold value for the positional deviation can be freely selected between 0 . 1 and 5 ° . Users can thus select the sensitivity of a positioning adjustment according to the work machine used, the auxiliary device and the conditions .

[0027] The filter is preferably configured to filter the positional data generated by the inertial measurement unit in such a manner that an average of the positional measurements taken within a selected filtering interval is calculated for the calculation of the control commands , wherein the filtering interval can be selected freely between 0 . 1 and 5 seconds . Users can thus select the sensitivity of a positioningadjustment according to the work machine used, the auxiliary device and the conditions .

[0028] Alternatively, a filtering interval can also be used to monitor the position based on a given time interval , and if a change in position returns to the target position within the selected time interval , no adjustment is initiated .

[0029] According to one embodiment , the filter includes both an adjustment based on a threshold value for a positional deviation and an adjustment based on a filtering interval .

[0030] The control unit preferably includes position-adjustment means for setting a target position that deviates from the horizontal plane of the auxiliary device . The user can thus set the target position of the auxiliary device to a position that deviates , for example, by 1 ° from the horizontal plane when operating on an inclined surface . In addition, when an auxiliary device is being mounted on the three-point attachment element of the work machine, it is possible to make use of the position-adjustment devices in such a manner that the user can steer the attachment points to suitable positions for the mounting of the auxiliary device .

[0031] The second lifting arm is preferably configured to form a fixed support point for the auxiliary device . One support point can be fixed in a three-dimensional positioning, as the position of the lifting arm and the length of the support member can be adjusted to achieve the positioning . The formation of a fixed support point also makes the calculation of the control commands easier .

[0032] According to one preferred embodiment , the first actuator and the second actuator are hydraulic cylinders , and the systemfurther includes a first directional control valve configured to control the flow of hydraulic oil to the first actuator, and a second directional control valve configured to control the flow of hydraulic oil to the second actuator, and the control unit is configured to control the directional control valves by means of control commands .

[0033] In this case, the system preferably includes a first tee connector for connecting the first directional control valve to the first actuator in parallel with the hydraulic inlet line of the work machine, and a second tee connector for connecting the second directional control valve to the second actuator in parallel with the hydraulic inlet line of the work machine . The system according to the invention can thus be connected in parallel with the hydraulic control system of the work machine, as well as disconnected when necessary .

[0034] Preferably, the hydraulic line running through the first directional control valve includes first adjustable throttle mechanisms for adjusting the operating speed of the first actuator, and the second hydraulic line running through the second directional control valve includes second adjustable throttle mechanisms for adjusting the operating speed of the second actuator . The throttle mechanisms allow the speed of movement of the actuators to be adjusted so that said speed is suitable for the auxiliary device in order to achieve an optimal final result .

[0035] The work machine is preferably a wheeled or tracked, freely steerable and movable work machine , such as a truck, a tractor, a wheel loader or the like, in which a three-point attachment element is used .The work machine is preferably a tractor and said lifting arms are the articulated arms belonging to a three-point attachment element of a rear hitch device of a tractor . The system according to the invention is particularly useful in connection with a rear hitch device, since the three-point attachment element of the latter is generally not actively adjusted, unlike, for example, a front hitch device .

[0036] Alternatively, the work machine can be a forklift or a telescopic handler, and the auxiliary device can be forklift forks or roll clamps or a man basket .

[0037] According to one embodiment , the system includes a transparent vessel provided with a liquid surface and quick-attachment means for attaching the vessel to the auxiliary device for a visual observation of the positioning of the auxiliary device . A vessel provided with a liquid surface makes it easy for a user to observe the direction and magnitude of a change in position without separate actuators or sensors .

[0038] The lifting arms are preferably the lower support arms of the three-point attachment element while the support member is the upper support arm .

[0039] According to one advantageous embodiment , the inertial measurement unit is arranged on the auxiliary device at a distance of 0-50 cm, preferably 0-15 cm, from the attachment point of the auxiliary device to the attachment element in order to minimise vibrations affecting the inertial measurement unit . An inertial measurement unit located close to the attachment point of the auxiliary device is not as exposed to vibrations as a unit located at the end of a long arm . Vibrations can cause errors in the sensor measurements . In this connection, the attachment point refers to the articulatedjoint of the positionally adjustable auxiliary device in relation to which the position is adjusted .

[0040] According to one embodiment , the inertial measurement unit is wireless and the system further includes a transmitter unit for transmitting the positional data determined by the inertial measurement unit and a receiver for receiving the positional data . It is thus possible to transfer the positional data wirelessly and to utilise, for example, the data transfer bus of the work machine to position the auxiliary device via the control of the actuators of the work machine .

[0041] Preferably, the control unit is configured to convert the positional data generated by the inertial measurement unit from a binary form into a numerical value that describes the angle of inclination of the position . The numerical value of the angle of inclination can be converted by the computing means into control commands that can even be used directly to control the actuators of the work machine using the data transfer bus , for example a CAN bus , of the work machine . This allows the user interfaces and control buttons of the work machine to be used for a manual control .

[0042] The object of a method according to the invention is achieved with a method for positioning an auxiliary device, in which method the auxiliary device is suspended from a work machine by means of a first lifting arm of the work machine , which first lifting arm is equipped with a first actuator, and a control unit is linked to the actuator to control the positioning of the auxiliary device . In the method, in addition, a position of the auxiliary device is determined by an inertial measurement unit belonging to the control unit so as to generate positional data, and control commands are generated for the first actuator and the second actuator basedon the positional data using computing means so as to hold the auxiliary device in a target position, and the position of the auxiliary device is adjusted by the control unit in relation to the direction of the gravitational force vector of the Earth determined by the inertial measurement unit and independently of the position of the work machine in relation to the substrate on which the work machine is supported .

[0043] The system and the method according to the invention support a sustainable green transition by significantly reducing the amount of driving required of the work machine as well as the resulting carbon dioxide emissions by optimising the operation of the auxiliary device . The invention enables an optimal operation of the auxiliary devices of the work machine, which permits planned work to be carried out in less operating time . In an agricultural setting, for example, the invention makes it possible for land areas that are currently hard to tend to with a tractor to be used as new farmland .

[0044] The system and the method according to the invention use an inertial measurement unit , or IMU, because an IMU contains at least two different sensors , often three . These are an accelerometer, a gyroscope sensor and a magnetometer . When the angle of a structure is measured in relation to the direction of the Earth ' s gravitational pull , magnetometry is not needed because it indicates the direction of the Earth ' s magnetic field, i . e . the direction of the tangent . An accelerometer, on the other hand, is capable of measuring the gravitational acceleration caused by the Earth . This acceleration is constant , so its direction can be inferred in many places , even in the presence of other small acceleration vectors . It is , however, a problem if other acceleration vectors increase as a result of the movement of the attachment structure of the sensor . In this case, it is difficult or even impossible todetermine the direction of the Earth' s gravitational acceleration . For this case, the IMU offers a second solution in the form of a gyroscope sensor . The main function of the gyroscope sensor is to measure movements based on inertia . When the outer structure of the sensor accelerates , the mass inside tries to stay still . This results in a measurable force between the outer structure and the mass . However, the gyroscope sensor is not able to measure its position in relation to the Earth ' s gravitational pull . The data produced by both sensors is needed to calculate the direction vector of the Earth ' s gravitational pull in all static and dynamic operating situations .

[0045] Preferably, the data from the accelerometer is filtered with a low-pass filter and the data from the gyroscope sensor is filtered with a high-pass filter . It is often necessary to filter the measurement data provided by a sensor in order to eliminate values that are interpreted as noise . In the case of the accelerometer, it is essential to filter out the noise of higher frequencies from the signal and focus on measuring the relatively stable gravitational force vector . To this end, what is known as a low-pass filter is used . The gyroscope sensor, on the other hand, ideally only measures relatively fast movements , as slow movements cause its value to drift and this measurement error accumulates over time . It is therefore advisable to filter out low frequencies with a high-pass filter .

[0046] Other filters are preferably not used in the system and the method according to the invention, because a low-pass filtering of the accelerometer eliminates the noise that is characteristic of this sensor type to a sufficient degree . Adding other filters increases the computing power required . Applications are also so diverse that it is not possible to set the filtering for a specific set of circumstances . The useof a low-pass filter on its own is consequently the simplest solution for an embodiment in which a gyroscope sensor is also provided as support . In principle, the data provided by the gyroscope sensor is fairly clean . The biggest issue with this type of sensor is that the value drifts over time . This is countered by using a high-pass filter and integrating sensor data from the accelerometer .

[0047] The data from the accelerometer and the data from the gyroscope sensor are preferably combined . In a static situation, the measurement results of a three-axis accelerometer can be used to determine the angle of the sensor in relation to the Earth ' s gravitational pull relatively precisely . During dynamic motion, however, other acceleration vectors affect the sensor and interfere with the determination of the angle . In cases where one or more of the three axes of the sensor are subjected to an acceleration caused by motion, this has a direct impact on the calculation result and leads momentarily to an incorrect reading . A gyroscope sensor, on the other hand, measures a relative movement without a direct connection to the Earth ' s gravitational pull . Even if the gyroscope sensor is calibrated on a straight surface, the measurement error that accumulates in a back-and-forth movement soon leads to an incorrect value of the angle . A high-frequency vibration can produce a significant error very quickly . The combination of the sensor data, which is known as fusion, takes the strengths of both sensor types and produces reliable data in both static and dynamic situations . The mathematical representation of what is known as a complementary filter is as follows :

[0048] a=k(3 + ( 1-k) y

[0049] where a is the angle value obtained as the result of the combination, k is a weighting factor, p is the angle value provided by the gyroscope sensor, and y is the angle valuedetermined based on the accelerometer . The weighting factor k is typically close to 1 .

[0050] The advantages of a complementary-type filter over other filters , such as Kalman, Madgwick and Mahony filters , are its simplicity and speed . The system has a very wide range of applications , so a simple filtering is most likely to be suitable for most applications . Setting the filter for each specific application adds complexity to the system and significantly increases the possibility of malfunctions . Speed, however, is necessary because the movements of the structure controlled by the cylinder can be fast , and if the angle value provided by the sensor lags behind the filtering too much, the control will repeatedly overshoot the target value, which results in oscillation .

[0051] According to one alternative application, it is possible to also use other filters if the accuracy of the system needs to be increased at the expense of speed for a specific application .

[0052] The challenges entailed by the use of an accelerometer lay in the management of noise and interference . In particular vibrations and rapid movements caused by the hydraulics interfere with the acquisition of reliable angle values . The sensitivity of the sensor is one obvious source of problems . If it is set so as to be too sensitive, the result is poorquality data, because the system mounted on the machine is subject to high accelerations . The magnitude of the Earth ' s gravitational pull is 1g, so that it would be logical to set the sensitivity range to be 2g, for example . However, the conditions occurring in machines render the use of a wider sensitivity range necessary . Another factor that has an impact on data quality is the selection of the upper frequency limitof the low-pass filter . The gravitational force is very stable, which allows the use of a very low upper frequency limit . It effectively filters out interference caused by movements and vibrations of the sensor structure . The manner in which the data from the accelerometer and the gyroscope sensor is combined is also important .

[0053] The IMU preferably additionally includes a fusion filter or derivative filter, or both . Some IMUs of another type did not function properly when there was a steady vibration in the structure of the attachment element , for example caused by a diesel engine . This typically causes gyroscope sensor drift , which was also observed in tests . In practice, this causes a significant error, i . e . the control pursues a reading that systematically drifts further away from the actual value . The idea of the combination algorithm is that the drift inherent in the gyroscope sensor can be prevented by utilising the data from the accelerometer . It turned out , however, that only data from the gyroscope sensor is used in the internal logic of many IMUs if there is a continuous vibration . This feature is built-in and cannot be turned off . Drift is thus the inevitable result in machine applications , and the only option is to replace the sensor .

[0054] In addition to these technical factors relating to the sensors , the manner and location of the attachment of the sensor were also found to be of great importance . The IMU holder must be fixed to the frame very firmly . If it can sway even slightly, the result is a movement that interferes in particular with the accelerometer . The location of the IMU, on the other hand, affects both sensors . If it is arranged far from the articulated joint , i . e . at the end of a long arm, vibrations and accelerations caused by the movement of the structure increase significantly . Tests have shown that an arrangementfar from the articulated joint can even be impracticable for the IMU, i . e . it is not possible to obtain reliable results because the intensity of the vibration prevents a determination of the direction of the gravitational force and causes the gyroscope sensor to drift significantly . The choice of location for the IMU is an essential part of setting up the system for an application .

[0055] In many applications , it is possible for dynamic movements and a swaying of structures to occur, for example due to uneven terrain . A fast-acting sensor also measures an angle during the aforementioned momentary oscillations . In this case, the control logic begins to perform a corrective movement , which can be inappropriate for the application . This kind of inappropriate control can be reduced by taking an average of the angle values over a given time period . An average of , for example, a back-and-forth oscillation is consequently used as an approximately appropriate reading for an application in which, for example, the load on a lifting fork is on average horizontal . The downside is that the angle value is available slightly after the time period of the average, so that the system is not necessarily able to keep up with a rapid motion and follows the oscillation . It is therefore simultaneously necessary to slow down the control in cases where a longer average is ideally used .

[0056] Surprisingly, it has been found that Hall-based angle sensors or encoders are not suitable for the system according to the invention . This is because the Hall effect occurs when a magnet rotates in relation to the sensor . In practice, this means that the sensor and the magnet are on different sides of the articulated structure . In the case of an encoder, the sensor and the interrupter disk are likewise located on different sides of the articulated joint . The aforementioned structurecan be used to measure the gravitational force by allowing one side of the articulated joint to hang freely . In this case, the sensor is able to measure the angle of the hanging structure and thus indirectly its own angle in relation to the gravitational pull of the Earth . The problem is dynamic motion . A freely hanging structure can easily end up in a pendulum motion that dissipates slowly . In this case, the sensor is unable to provide a precise angle in relation to the gravitational force because of the resulting oscillation caused by the pendulum motion . One could try to dampen the pendulum motion mechanically, but in this case the problem is how strong the damping should be . A greater damping prevents the pendulum motion, but then the freely suspended structure can no longer keep up with rapid movements and the sensor momentarily measures the wrong angle . The mass of the freely suspended structure also has a significant effect on the dynamics . A light structure is easily disturbed, for example, by vibration . A heavy structure, on the other hand, remains more stably in the direction of the gravitational force, but takes up a lot of physical space, requires an expensive bearing arrangement , and the pendulum motion generated under suitable dynamic conditions dissipates more slowly .

[0057] Distance-measuring sensors known from the prior art , such as ultrasonic, laser and radar sensors , are not suitable for the system according to the invention, because these sensors measure a distance to a reference surface . The distance measured by two different sensors can be used to calculate the angle of a structure in relation to the reference surface to which the sensors are attached . If the reference surface is the surface of the ground, then the angle of the structure is measured in relation to this ground surface and not in relation to the direction of the gravitational pull of the Earth . If this ground surface is inclined in any direction, the sensorreading will deviate from the gravitational force . In this case, a load on a fork, for example, can fall over because the reference level is inclined in relation to the gravitational pull of the Earth . Alternatively, it is possible to measure the distance to the freely suspended structure and, based on a known geometry, to calculate the angle of the same in relation to the structure to which the sensor is attached . The principle and limitations are the same as in the case of a Hall sensor . An additional limitation is the range of operation of the sensor around the axis of rotation : as the angle increases , an increasing proportion of the signal transmitted by the sensor is deflected away and the sensor is ultimately unable to read the distance .

[0058] A pulse control is preferably used in the adjustment of the actuator . Adjustment occurs via a hysteresis-based algorithm with a target of 0 ° . It is permissible for the measurement result produced by the IMU to deviate from the target by + -1 ° , i . e . by a threshold value . In a situation where the measurement result is -1 . 5 ° , an adjustment is carried out in the + direction until the measurement result of the IMU is 0 ° . Afterwards , no further adjustments are carried out until the +-1 ° threshold value is exceeded . Since the measurement lags behind the control and adjustment temporally, and the speed of movement of the cylinders can be high, it is advantageous to use a pulse control for the control and adjustment and to employ a throttling mechanism .

[0059] According to one embodiment , a minimum control pulse size is 50 ms , which can be varied up to 500 ms . It is possible to start out with a long pulse and, as the target position is approached, to shorten the pulse so as not to overshoot the target position when the measurement lags behind the control temporally . The pulse control can occur at a frequency of , forexample, 2-100 Hz , preferably 5-20 Hz . A PID controller is not used in this type of control , but rather an error is measured and this error is multiplied to obtain a pulse length . Thanks to the pulse control , the system can use the simplest valve of an on-off type, which is highly immune to conditions such as temperature or the quality and purity of the hydraulic fluid used in the hydraulics . The use of on-off valves is particularly well suited to applications involving a retrofitting .

[0060] Alternatively, it is also possible to use a proportional valve for the control , whereby a smoother movement can be achieved . Proportional valves , however, are more expensive than on / off valves in terms of investment and operating costs and more difficult to control , as they are affected by factors such as temperature through the viscosity of the oil , oil quality and oil purity . The use of proportional valves is especially suitable for new devices .

[0061] The use of a double-acting valve instead of a proportional valve has certain advantages , which are described in the following . The system is intended to be implemented in a very wide range of applications , so reliability is considered essential . The biggest problem with proportional valves in this connection is contamination of the hydraulic oil . In agricultural environments , for example, dirty hydraulic connectors are constantly being connected to the machine . When dirt gets into the narrow gap between the spindle and the block of a sensitive proportional valve, it can interfere with the operation of the valve or even cause it to jam . In this case, there is the particular risk that the valve jams in such a manner that the valve remains partially open and the movement continues , although the control algorithm is no longer supplying control current to the valve .Double-acting valves are simpler in terms of their structure and operation, which prevents problems caused by dirt . Another important factor for reliability is adjustment . Proportional valves require a relatively complex control system . The pressure, the viscosity of the oil used, the operating temperature, etc . vary in different hydraulic systems . The algorithm must include different compensations and take their interacting effects into account . The basic operation of the system, i . e . keeping the angle sensor straight , is also more complex to implement since a PI or PID control is required . Determining the aforementioned algorithm parameters in such a manner that they work in all operating conditions is a major challenge . Risks include an imprecise operation and oscillation . It is also necessary to offer the user a simple way of adjusting the amount of volume flow permitted by the valve in different conditions .

[0062] Double-acting valves , on the other hand, are controlled binarily, which is very simple compared to the continuous flow control of a proportional valve with dither frequencies for preventing a jamming . The flow rate is adjusted by throttle mechanisms on the inlet side of the cylinder, which is a manner of adjustment that most machine users are familiar with and that is extremely reliable in terms of its operation . A third important factor is the EMC environment . Proportional valves react to current fluctuations of a magnitude of milliamperes . Sources of interference that can cause interference currents of the cited magnitude are easily encountered in practical applications , for example in the control cable for the proportional valve . More attention and costs must be invested in protection than with a double-acting valve . A proportional valve is also a more expensive component and, as controlrequirements are more complex, development and testing costs are also significantly higher .

[0063] Using a double-acting valve is also associated with certain drawbacks compared to a proportional valve . When controlled by a double-acting valve, the movements of the cylinder start and stop abruptly . A flow rate that is adjusted too quickly can lead to oscillations and jolts that are unpleasant for the user . A smoother operation could be achieved with a proportional valve, as the flow rate can be adjusted in a continuous manner during starting and stopping . In controlled conditions , precision would probably also be better, i . e . it would be possible to slow the movement of the cylinder as the angle approaches the target value . This would also result in a faster operation of the system, because adjustments of movements carried out further away from the target value could be programmed to be faster .

[0064] In a control using a double-acting valve, a behaviour similar to that of a proportional valve has been partially achieved by implementing the control signal in pulsed form . As the target value is approached, the valve is controlled by transmitting short current pulses to it . This slows the average change in angle of the structure controlled by the cylinder, so the angle sensor data remains more up to date and the angle can be adjusted to the target position with the precision of the incremental movement produced by the pulses . However, this can result in a vibration or even a resonance arising in the structures of the machine . The intensity of this phenomenon depends mainly on how quickly the movements of the cylinders are adjusted using the throttle mechanisms . In some applications , a fast movement is desired and the precision requirement is not high . For this situation, the system offers the user the option of a second control method or directcontrol . If the algorithm determines that it is outside the range of precision specified by the user, it tries to adjust the angle of the attachment structure of the sensor back to the target value directly . In this case, the expected result is that the angle will overshoot the target value slightly . In applications with low precision requirements , however, this is of no particular consequence, so long as an oscillation is prevented by selecting a sufficiently wide range of precision . In many cases , a behaviour is achieved that is reminiscent of a manual control of the cylinders , in which superfluous movements do not occur . However, this control strategy does not work in situations in which a precise adjustment of the angle to the target position is required .

[0065] According to one alternative embodiment , it is possible to use two valves for one direction of movement , one fast and one slow, so that the movement can be cushioned at the end by the control switching to the use of the slow valve when the target position is being approached .

[0066] According to one alternative embodiment , the system can also employ its own hydraulic pump, so that the speed can be varied by adjusting the pump speed, which also saves energy .

[0067] The invention, which is not limited to the embodiments described in the following, is explained in more detail with reference to the accompanying drawings , wherein

[0068] Figure 1 schematically shows a first embodiment of the system according to the invention in a side view,

[0069] Figures 2a and 2b schematically show side views of a three-point attachment element of thefirst embodiment in two different positions ,

[0070] Figure 3 shows a hydraulic diagram of a system according to the invention,

[0071] Figure 4 shows an axonometric view of a valve block of a system according to the invention,

[0072] shows an axonometric view of one way of implementing the adjustment means of a system according to the invention,

[0073]

[0074] schematically shows the system according to a second embodiment in a side view,

[0075]

[0076] schematically shows the system according to a second embodiment in a front view,

[0077] shows a block diagram of steps of a method according to the invention,

[0078]

[0079] shows a block diagram of steps of a method according to the invention in more detail than Figure 7 ,

[0080]

[0081] shows a block diagram that illustrates the control logic of Figure 8a in more detail ,

[0082] shows a block diagram of the system according to another embodiment ,

[0083]

[0084] shows a diagram illustrating the control logic of the embodiment of Figure 9a,

[0085] Figures l Oa-l Oc show diagrams illustrating different embodiments of a wireless inertial measurement unit .Figure 1 shows a preferred first embodiment of a system 10 according to the invention, in which the work machine 14 is a tractor and the auxiliary device 12 is a spreader 70 for spreading manure or seed . It is , however, understood that the applications of the system according to the invention are not limited to a tractor and spreader, but rather that it is also possible to implement the invention when the work machine is a wheel loader, a truck or other analogous work machine that includes a three-point attachment element connected to an auxiliary device . For its part , the auxiliary device can also be, for example, a plough, a sand spreader, a leveller, an auger, a drill, or an agricultural auxiliary device . Alternatively, the work machine can also be, for example, a forklift or a telescopic handler, wherein the auxiliary device can be forklift forks , roll clamps or the like .

[0086] The basic parts of the system 10 always include an inertial measurement unit 28 for determining the positional data of the auxiliary device and a control unit 26 for controlling the positioning of the auxiliary device 12 . The work machine 14 includes a frame 16 , an attachment element 25 connected in an articulated manner to the frame 16 for the attachment of the auxiliary device 12 , a first actuator 22 for changing a position of the auxiliary device 12 , and a second actuator 32 for changing a position of the auxiliary device 12 in a different direction to the first actuator 22 .

[0087] In the first embodiment shown in Figure 1 , in addition to a first lifting arm 18 , the attachment element 25 includes a second lifting arm 20 , wherein the lifting arms 18 , 20 are the towing arms of the three-point attachment element of the tractor while the support member 24 forms the pushing arm . As shown in Figures 2a and 2b, the first lifting arm 18 is equipped with a first actuator 22 , which enables the rotation of thefirst lifting arm 18 relative to the frame 16 about an articulation point 80 . The second lifting arm 20 can also be lifted and rotated around the articulation point 80 , but the second lifting arm does not necessarily have an actuator to produce a lifting movement , as the support point 82 formed by the second lifting arm 20 on the auxiliary device is preferably fixed during positioning . Instead of using an actuator, the position of the second lifting arm can be adjusted by means of , for example, a length-ad ustable arm, which can be, for example, a turnbuckle . The length-adjustable arm thus supports the second lifting arm 20 in its position so as to form a fixed support point 82 . In the system according to the invention, the support member 24 is a length-adjustable second actuator 32 by means of which, in the first embodiment , an upper support point 86 of the auxiliary device 12 can be moved essentially horizontally towards or away from the work machine 14 .

[0088] Thanks to the structure just described, in the first embodiment , a three-point attachment element 25 is formed for supporting the auxiliary device 12 on the work machine 14 , which three-point attachment element 25 has a fixed support point 82 formed by the second lifting arm 20 , a support point 84 that is formed by the first lifting arm 18 and that can be moved mainly vertically by means of the first actuator, and a third support point 86 that can be moved essentially horizontally by means of the length-adjustable second actuator 32 . This type of support makes it possible for the auxiliary device to be positioned freely in three-dimensional space according to the desired target position . The positioning of the auxiliary device thus occurs by changing the lengths of the first actuator and the second actuator .

[0089] To control the actuators , the system 10 according to the invention includes a control unit 26 , which can be attached tothe work machine 14 or to the auxiliary device, and an inertial measurement unit 28 , or IMU, for determining the position of the auxiliary device 14 in the form of positional data . The task of the control unit 26 is to generate control commands for the actuators 22 , 32 based on the determined positional data in order to change their lengths in such a manner that the auxiliary device is moved to a target end position . For the calculation of the control commands , the control unit 26 additionally includes computing means 30 for generating the control commands based on said positional data .

[0090] The IMU can be a commercially available unit , for example the IMU known by the product name BNO055 from Bosch Sensortec GmbH . The IMU is preferably powered by the work machine or can include its own battery unit . The computing means can include a microprocessor, a memory, software means and data transfer means for receiving the positional data from the IMU as well as for transmitting the generated control commands to the actuator controllers . The computing means can be implemented using known microcomputers , for example using a Raspberry Pi computer . The actuator controller depends on the type of actuator used, but preferably it is a directional control valve when the actuators are hydraulic cylinders , or an electric controller in cases where the actuator is , for example, an electric linear actuator .

[0091] Figure 3 shows a preferred mode of implementation of the invention, in which the first actuator 22 and the second actuator 32 are hydraulic cylinders . In this case, the controllers of the actuators 22 , 32 are directional control valves 50 , 52 , the first directional control valve 50 controlling the first actuator 22 and the second directional control valve 52 controlling the actuator 32 . The directional control valves 50 and 52 can be combined into a single valveunit 55 , which is arranged downstream of the pump 70 on the pressure side of the hydraulic line of the work machine and connected, preferably by tee connectors , to lines that lead to a tank 72 , so as not to impede the work machine' s standard hydraulic control for the actuators . In other words , the control unit of the system according to the invention is in parallel with the control of the work machine, and the control of the work machine can be blocked by a separate valve during the use of the system according to the invention . The tee connectors 56 and 58 are shown in more detail in Figure 4 , which also shows the valve unit 55 as a whole .

[0092] The directional control valves 50 and 52 preferably enable an independent control of both actuators 22 and 32 in both directions in order to position the auxiliary device based on the control commands from the control unit 26 . The directional control valves 50 and 52 can be controlled by electrical control commands that move the directional control valves between different flow positions and block the flow when a target position has been reached . Figure 3 also shows throttle mechanisms 66 and 68 by means of which it is possible to limit the speed of movement of both actuators 22 and 32 to an optimal speed for the intended operation .

[0093] The system 10 according to the invention preferably includes a filter 34 by means of which it is possible to influence the generation of the control commands . The purpose of filtering is to stabilise the positioning of the auxiliary device and to prevent fluctuations in a positioning adjustment . The filter is preferably a programmable part of the computing unit by means of which it is possible to influence which part of the positional data is used for calculating the control commands as well as how said control commands are calculated . In practice, the functions provided by the filter are preferablyan angle filtering of the positional data for each actuator and a temporal filtering of the positional data for each actuator .

[0094] The idea of an angle filtering is to filter all measured positional changes that are smaller than a preselected limit value out of the positional data, so that small changes in position do not immediately cause a change in the length of the actuators . This is an important feature when, for example, driving over an uneven surface, whereby small changes in position occur continuously in the form of vibrations .

[0095] The idea of a temporal filtering is to filter the positional data over time, for example by calculating the average of all changes occurring within a preselected limit value, which average is then used to calculate the control commands . Alternatively, if the position changes for 0 . 1 seconds and the limit value is 1 second, then the momentary change in position caused by a bump is filtered out and does not trigger a control command .

[0096] The system 10 preferably includes adjustment means 35 for carrying out a manual adjustment of filtering . The user can thus simply adjust the filtering to a desired level according to the work machine, auxiliary device and environment . Figure 5 shows an example of an implementation of the adjustment means 35 . In this embodiment , the adjustment means 35 are implemented by means of mechanical buttons and adjusting knobs . In Figure 5 , the power buttons 78 . 1 and 78 .2 turn the control of both actuators on and off . The adjusting knobs 72 . 1 and 72 .2 enable a continuous manual adjustment of the position filtering for the actuators , while the adjusting knobs 74 . 1 and 74 .2 enable a continuous manual adjustment of the temporal filtering for the actuators .The system preferably also includes position-adjustment means 36 by means of which it is possible to change the target position of the auxiliary device manually . For this purpose, rocker switches 76 . 1 and 76 .2 are shown in Figure 5 , which can be used to set the position of the auxiliary device manually to the target position by controlling the first actuator and the second actuator . The position-adjustment means also allow the cylinders being used as actuators to be controlled in such a manner that the cylinder is not at either end of its path of movement when operation of the auxiliary device begins .

[0097] The combined unit of the adjustment means and the positionadjustment means can be called the adjustment unit . The adjustment unit is preferably connected electronically to the control unit 26 , which transmits the commands to the computing unit that generates the control commands .

[0098] Instead of an implementation of the adjustment unit as described in the foregoing in connection with Figure 5 , it is also possible for the adjustment unit to be implemented using a separate touchscreen or a remote-control application . The connection between the adjustment means / position-adjustment means and the control unit can be wireless or wired, and preferably takes the form of either a wireless LAN connection or a wired CAN bus connection .

[0099] Figures 6a and 6b show a second embodiment of the system according to the invention, in which the work machine 14 is a forklift truck and the auxiliary device 12 is forklift forks 90 . In this embodiment , the first lifting arm 18 is a forklift mast , which is connected in an articulated manner to the frame of the forklift by means of a transverse articulated joint 92 . The first actuator 22 , preferably a hydraulic cylinder, isconnected in an articulated manner between the forklift frame and the forklift mast in order to rotate the forklift mast around the articulated joint 92 , thus producing a movement of the auxiliary device in the direction of travel of the forklift . The support member 24 here is the forklift turntable, which forms a second articulated joint 94 in the direction of travel of the forklift , around which the auxiliary device 12 can be rotated by means of a second actuator 32 . The second actuator thus produces a movement around the second articulated joint 94 in a direction that is essentially perpendicular to the direction of movement produced by the first actuator 22 .

[0100] The operation of a system according to the invention and the steps of a method according to the invention are shown in the process diagram in Figure 7 . The operation of the system according to the invention and the method according to the invention begin at step 100 , in which an auxiliary device is suspended from a work machine using a first lifting arm, a second lifting arm equipped with an actuator, and a support member of the working machine, which form a three-point attachment element for the attachment of the auxiliary device . The support member is implemented in the form of a second actuator that is adjustable in length . In step 102 , the control unit is linked to the first actuator and to the second actuator to control the positioning of the auxiliary device . In step 104 , a target position is set for the auxiliary device, wherein the target position preferably includes , for the auxiliary device, both a pitch value, i . e . the inclination around the articulation points between the transverse lifting arms and the frame, and a roll value, i . e . the inclination around the direction of travel of the work machine . In step 106 , the position of the auxiliary device is determined by the inertial measurement unit belonging to the control unit so as to generate positional data for both the pitch and roll values .In step 108 , the measured positional data is compared with respect to the pitch and roll values with the corresponding values of the target position in order to identify any discrepancies . If no difference is detected, the measurement is repeated by returning to step 106 . In cases where a discrepancy is detected, the computing means calculate, in step 110 , the necessary control commands based on the discrepancies in the pitch and roll values for both the first actuator and the second actuator in order to control the first actuator and the second actuator in such a manner that the target position is achieved . In practice, the correct position of , for example, the directional control valve is determined so that the hydraulic cylinder moves in the right direction, and the movement duration is determined during which the directional control valve must be maintained in that position for the target position to be reached . The algorithm then again returns to step 106 , i . e . to the measurement of the position of the auxiliary device .

[0101] The foregoing description of the method presents one embodiment of an implementation of the method according to the invention . It is understood, however, that , instead of hydraulic actuators and their controllers , it is possible to use a linear actuator and its electrical controller analogously to implement the method and the system according to the invention .

[0102] According to one embodiment , the user can change the location of the support points of the three-point attachment element by means of the adjustment unit for the mounting of an auxiliary device . Traditionally, the user has been unable to freely control the lifting arms and support member of the three-point attachment element in an attachment situation . In the system according to the invention, the adjustment unit can be attached in a detachable manner to the cabin of the work machine, andthe user can use the adjustment unit in a portable manner at the auxiliary device to facilitate the mounting of the auxiliary device .

[0103] According to one embodiment , the control unit or IMU of the system can include geopositioning means with which it is possible to automate a positioning as a function of location .

[0104] Figures 2a and 2b show a transparent vessel 40 provided with a liquid surface and quick-attachment means 42 for attaching the vessel 40 to an auxiliary device 12 for a visual observation of the positioning of the auxiliary device 12 . The vessel can be, for example, a vessel made of a transparent plastic that resembles a fishbowl and that contains oil or some other liquid with a suitable viscosity that always indicates the horizontal . A high viscosity prevents the liquid from sloshing about . Markings can be made on the side of the vessel to identify different degrees of inclination, for example 1 ° , 2 ° , 3 ° . The quick-attachment means can be, for example, a magnet attached to the bottom of the vessel .

[0105] It is understood here that the vessel described in the foregoing can also be used as an independent invention, separately from the system described in this application .

[0106] The components required to implement the system and the method according to the invention are often already available in various work machines such as tractors , forklifts , telescopic handlers or various loading machines . The aforementioned work machines often come with displays that can be used as a user interface for setting a target position, for displaying the position as well as possibly for carrying out , in the capacity of an adjustment unit , filter adjustments or a position adjustment . Work machines further often come with means foroperating the actuators of the lifting arm and support member, more specifically the hydraulic valves , hoses and valve units required to produce the movements of the actuators . The aforementioned work machines often come with means for transferring data internally within the work machine, such as a CAN bus ( ISObus ) . Such already existing data transfer channels can be used to transfer the positional data produced by the IMU to the work machine, and this data can be used to control the existing hydraulic control devices and actuators to produce a desired result .

[0107] When existing components of work machines are mainly used, it is possible to merely retrofit existing work machines and their auxiliary devices with the IMU and the computing means of the control unit to implement the system according to the invention . The IMU provides the positional data of the auxiliary device, which the computing means can use to calculate control commands for positioning the auxiliary device . The system can thus utilise existing components to achieve the technical effect according to the invention . In other words , the system according to the invention is very well suited for a retrofitting of existing work machines and auxiliary devices .

[0108] Figure 8a shows in more detail the data generated by the inertial measurement sensor 28 and its processing . The inertial measurement sensor 28 simultaneously generates gyroscopesensor measurement data 110 and acceleration measurement data 112 . In the determination 110 of the measurement data of the gyroscope sensor 43 , it is preferably possible to simultaneously carry out a high-pass filtering with a high-pass filter 37 (Figure 3 ) , which removes the small accelerations from the gyroscope-sensor measurement data that cause an error through drift . In the determination 112 of themeasurement data of the accelerometer 41 (Figures 2a, 2b) , it is preferably possible to simultaneously carry out a low-pass filtering with a low-pass filter 33 (Figure 3 ) , which removes large accelerations from the measurement data of the accelerometer, because the accelerometer ideally focuses solely on determining the direction of the acceleration of the Earth ' s gravitational pull .

[0109] This measurement data can be combined in a fusion step 114 with a fusion sensor 45 (Figure 2a) , after which, in step 116 , an average is calculated that consists of the fused measurement data and an additional control parameter input by the user . Alternatively, a derivative filter 47 (Figure 2a) can be used instead of a fusion filter . The additional control parameter is the user ' s choice of how many data points transmitted by the inertia measurement sensor are to be included in the calculation of the running average .

[0110] After averaging, a filtered angle value is generated in step 120 , which is sent to the control unit 26 . The control unit 26 carries out a comparison in step 122 in which the filtered angle value and the angle set by the user 124 are compared to check whether the angle deviates from the target position . If not , it is determined that the system is in its target position and no further action is taken . If , on the other hand, a deviation is detected, a control function 128 is carried out , which causes a physical change in the position of the auxiliary device in step 130 . The new position of the auxiliary device is again detected by the inertial measurement unit 28 , and the check loop starts afresh .

[0111] Figure 8b shows the logic of the generation of the control commands carried out by the control unit 26 in Figure 8a in more detail . The starting point for the control is the filteredangle value 120 calculated in the diagram of Figure 8a, a deviation of which from the target position is checked in step 122 . The target position 162 and the maximum deviation setting 164 for the auxiliary device set by the user are input into this check . The maximum deviation setting denotes the maximum permissible deviation of the position of the auxiliary device from the target position . Next , in step 168 , the control mode, which was specified by the user in step 166 , is selected . The control mode can be either a direct or a pulse control . The logic is designed so that when the average changes , the inputs provided by the user in steps 162-166 in Figure 8b also change . This is because a continuous / f ast control causes the system to overshoot the target position while the data points of the average are being collected, i . e . the averaged angle value always arrives late . The control is consequently adjusted to emit pulses at slower intervals , and adjustments are made in relation to the length of the average . The longer the interval over which the average is calculated, the less frequent the pulses are . This gives the average of the measurement data time to reach the current value during the pauses .

[0112] A direct control includes steps 170-174 , in which the hydraulic valve is first opened in step 170 to produce a movement of the actuator, the current position of the auxiliary device is measured by means of the inertial measurement unit in step 172 , and the hydraulic valve is closed, in step 174 , when the measurement data is the same as the target position .

[0113] A pulse control includes the same steps 170 and 172 , after which the pulse control of the valve is started in step 176 based on a pulse frequency, pulse width and pulse start time specified by the user in step 178 . The hydraulic valve is closed, in step 180 , when the measurement data of the position of the auxiliary device determined by the inertial measurementunit is less than the sum of the target position and the deviation limit .

[0114] Figure 9a shows an implementation of the system according to the invention according to another embodiment . The main function of the system is the automatic control of doubleacting hydraulic valves based on the data provided by the sensors of the inertial measurement unit . The valves control the two hydraulic cylinders that tilt the structure to which the sensor is attached . This creates a closed bidirectional control loop . The system can also be used unidirectionally . The operation of the inclination sensor is based on the Earth ' s gravitational pull , i . e . the system controls structures in relation to the force of gravity .

[0115] As shown in Figure 9a, the system 10 includes a user interface 150 that is connected to a touchscreen 140 for a manual control and monitoring, which is connected to the control unit 26 by means of , for example, a TTL serial bus . The control unit 26 is in turn connected to the inertial measurement unit 28 by, for example, an RS485 serial bus . The control unit 26 controls the valve solenoids 146 of the hydraulic block 50 , preferably using a 12V control current 148 .

[0116] The control of the system shown in Figure 9b is based on the feedback from the inertial measurement unit .

[0117] 1 . The user sets the target value 152 for the angle of the structure to which the inertial measurement unit is attached via the user interface .

[0118] 2 . The logic controller or control unit 26 receives data regarding the current angle of the structure from the inertial measurement unit .

[0119] 3 . Based on the received data, the control unit 26 supplies control current 148 to the valve solenoids 146 , which in turncontrol the flow 156 of hydraulic fluid to the hydraulic cylinders preferably acting as the actuators 22 . The current is supplied as a function of both internal adjustment parameters 154 and adjustment parameters 154 received as user inputs from the interface .

[0120] 4 . The auxiliary device moves in step 158 , i . e . turns , when one or two cylinders receive a volume flow from the valves . 5 . The inertial measurement unit measures the real-time angle data and inclination data 160 for its control unit 26 , which controls the valve solenoids 146 so as to try to manage the angle of the structure in accordance with the target value . 6 . When the angle reaches the target value within the limits set by the parameters , the control unit no longer supplies current to any of the valve solenoids .

[0121] The valve solenoid to which control current is supplied is controlled as follows :

[0122] 1 . The longitudinal angle value (pitch) provided by the inertial measurement unit is smaller than the target value . a . Current is supplied to the valve solenoid 1 (direction UP ) .

[0123] 2 . The longitudinal angle value (pitch) provided by the inertial measurement unit is greater than the target value . a . Current is supplied to the valve solenoid 2 (direction DOWN)

[0124] 3 . The transverse angle value (roll ) provided by the inertial measurement unit is smaller than the target value .

[0125] a . Current is supplied to the valve solenoid 3 (direction RIGHT)

[0126] 4 . The transverse angle value (roll ) provided by the inertial measurement unit is greater than the target value .

[0127] a . Current is supplied to the valve solenoid 4 (direction LEFT)As a result of the control logic, the cylinders tilt the structure in the opposite direction to the angle error .

[0128] According to one implementation, the control current is supplied in a binary manner, i . e . the valve is either on or off . As the target angle is approached, the system begins to supply the control current in intervals in order to slow down the approach . The reason for slowing the approach is to prevent the control movement from overshooting the target value, as the feedback signal is slightly delayed due to the filtering of the sensor data .

[0129] According to an alternative embodiment , the control current is supplied in a binary manner, i . e . the valve is either on or off . The target angle is approached with a direct control , i . e . there does not occur any kind of pulse control . The sensor data arrives with a slight delay, so that the extent to which the target is overshot depends on the speed of the cylinder . To prevent an oscillation, it is necessary to select a precision parameter that is large enough for the angular velocity . This is the responsibility of the user, and to this end an obvious sliding adjustment control is provided in the user interface .

[0130] According to one embodiment , the inertial measurement unit can be wireless and configured to operate on battery power . In this case, the wireless inertial measurement unit includes a transmitter-receiver pair with which the positional data determined by the inertial measurement unit can be sent to the control unit using a wireless protocol . The control unit can be configured to receive positional data, which is used in the algorithm of the computing means to provide a suitable valve control signal according to the selected parameters . In the case of a CAN bus , the valve control signal is preferably a message to the CAN bus . Alternatively, the control unit canact as a mere intermediary that receives the positional data and packs it into a CAN message . In this case, the actual control logic can be the control unit (PLC) of the work machine .

[0131] If the CAN valves in the work machine are of an on / off type, they can be controlled in such a manner that one CAN message opens the valve and another closes it . It is also possible for an opening duration to be included in the first message, in which case a closing time is not provided . The use of valves of an on / off-type is advantageous in retrofit applications in which the work machine already includes on / off valves .

[0132] Another valve type is the proportional valve . I f the work machine has proportional valves , then the control mode is continuous , i . e . the greater the angle error, the more the valve is opened . It is possible in this case to use a PI or PID control algorithm in which the integral component takes into account the past and the derivative component takes into account the future .

[0133] The adjustment of the speed depends on the bus-based valve used . If the valves are of an on / off type, physical throttle mechanisms may be needed . If proportional valves are used, the speed can be adjusted with a control algorithm .

[0134] The principle behind the signal processing is in itself quite simple . The positional data determined by the inertial measurement unit is a binary message that is interpreted by the control unit as a variable containing an unambiguously readable value . This is used in the calculation of the computing means with which a command (open, close, open 50% , etc . ) is produced in the format specified by the valve manufacturer, which produces a physical movement of the actuator, for example in a hydraulic cylinder .In some cases , the system control unit can also be formed by the control unit (PLC) of the work machine . In this case, a wireless signal receiver handles the packing of the angle data into a data field of the CAN message but does not create command messages for the valves .

[0135] Figures l Oa-l Oc show three alternative implementations .

[0136] The diagrams here are intended to be as general as possible . The first alternative shown in Figure 10a is implemented by a wireless inertial measurement unit 28 using conventional hydraulic valves and their solenoids 146 . In this implementation, the filtered angle value 120 generated from the positional data of the inertial measurement unit is transmitted - using any wireless protocol 182 such as, for example, Bluetooth®, BLE or MESH, Wi-Fi®, Zigbee®, LoRaWAN®, Thread, Z-Wave® - to the control unit 26 , which creates , based on this data, a control current 148 representing a control command, which controls the hydraulic valve by means of the solenoid 146 .

[0137] In the second embodiment shown in Figure 10b, the first two steps are identical to the embodiment shown in Figure 10a, but in this case the bus-controlled valve 186 is controlled using a wired bus 184 . In the third embodiment shown in Figure 10c, the filtered angle value 120 is sent to the control unit 26 using a separate transmitter-receiver pair 188 , 188 ' , after which the control commands are transmitted to the bus-controlled valve 186 using the wired bus 184 , as in the second embodiment shown in Figure 10b .

[0138] According to one embodiment , the system can include two or three inertial measurement units , so that the system can be implemented more reliably . In the case of two inertialmeasurement units , the second inertial measurement unit can be used as a reference for the first inertial measurement unit , and if one fails , operation can continue based on the other inertial measurement unit . In applications where an uninterrupted operation is essential , it is possible to use three inertial measurement units , wherein the third monitors the operation of the other two in accordance with general safety principles .

Claims

CLAIMS1 . A system ( 10 ) for pos it ioning an auxi l iary device ( 12 ) connected to a work machine ( 14 ) , wherein the work machine ( 14 ) includes a frame ( 1 6 ) , an attachment element ( 25 ) connected in an art iculated manner to the frame ( 1 6 ) for the attachment of the auxi l iary device ( 12 ) , a f irst actuator ( 22 ) for changing a pos it ion of the auxi l iary device ( 12 ) , and a second actuator ( 32 ) for changing a pos it ion of the auxi l iary device ( 12 ) in a di f ferent direct ion to the f irst actuator ( 22 ) , wherein the system includes— an inert ial measurement unit ( 28 ) conf igured to be attached to the auxi l iary device ( 12 ) for determining a pos it ion of the auxi l iary device ( 14 ) as a pos it ional data , and— a control unit ( 2 6 ) which includes comput ing means ( 30 ) for generating control commands based on the pos it ional data for the f irst actuator ( 22 ) and the second actuator ( 32 ) so as to maintain the auxi l iary device ( 12 ) in a target pos it ion by means of the f irst actuator ( 22 ) and the second actuator ( 32 ) ,characterised in that the contro l unit ( 2 6 ) i s conf igured to adjust the pos it ion of the auxi l iary device ( 12 ) in relat ion to the direct ion of the gravitat ional force vector of the Earth determined by the inert ial measurement unit ( 28 ) and independent ly of the pos it ion o f the work machine ( 14 ) in relat ion to the substrate ( 100 ) on which the work machine ( 14 ) i s supported .2 . A system according to claim 1 , characterised in that the control unit ( 2 6 ) includes a f i lter ( 34 ) for f i ltering the pos it ional data prior to calculat ion of the control commands in order to prevent a swaying of pos it ioning of the auxi l iary device ( 12 ) .3 . A system according to claim 2 , characterised in that the inert ial measurement unit ( 28 ) includes at least an accelerometer ( 41 ) and a gyroscope sensor ( 43 ) , and the f i lter ( 34 ) includes a low-pas s f i lter ( 33 ) for f i ltering data from the accelerometer and a high-pas s f i lter ( 37 ) for f i ltering data from the gyroscope sensor .4 . A system according to claim 2 or 3 , characterised in that the f i lter ( 34 ) includes a fus ion f i lter ( 45 ) or a derivat ive f i lter ( 47 ) or both .5 . A system according to any of claims 1 to 4 , characterised in that the inert ial measurement unit ( 28 ) i s arranged on the auxi l iary device ( 12 ) at a di stance of 0 -50 cm, preferably 0 - 15 cm, from the attachment point ( 25 ) of the auxi l iary device ( 12 ) in order to minimi se vibrat ions af fect ing the inert ial measurement unit ( 28 ) .6 . A system according to any of claims 1 to 5 , characterised in that the contro l unit ( 2 6 ) i s conf igured to use a pul se cont rol in adjustment of the f irst actuator ( 22 ) and the second actuator ( 32 ) .7 . A system according to any of claims 1 to 6 , characterised in that the f irst actuator ( 22 ) and the second actuator ( 32 ) are hydraul ic cyl inders and the system ( 10 ) further includes— a f irst direct ional control valve ( 50 ) conf igured to control the f low of hydraul ic oi l to the f irst actuator ( 22 ) , and— a second direct ional control valve ( 52 ) conf igured to control the f low of hydraul ic oi l to the second actuator ( 32 ) ,and the control unit ( 2 6 ) i s conf igured to control the direct ional control valves ( 50 , 52 ) by means of control commands .8 . A system according to claim 7 , characterised in that the system ( 10 ) includes— a f irst tee connector ( 56 ) for connect ing the f i rst direct ional cont rol valve ( 50 ) t o the f irst actuator ( 22 ) in paral lel with the hydraul ic inlet l ine of the work machine ( 10 ) ,— a second tee connector ( 58 ) for connect ing the second direct ional control valve ( 52 ) to the second actuator ( 32 ) in paral lel with the hydraul ic inlet l ine of the work machine ( 10 ) .9 . A system according to any of claims 1 to 8 , characterised in that said inertial measurement unit ( 28 ) i s wireles s and the system ( 10 ) further includes a transmitter unit ( 188 ) for transmitt ing the pos it ional data determined by the inert ial measurement unit ( 2 8 ) and a receiver ( 188 ' ) for receiving the pos it ional data .10 . A system according to claim 9 , characterised in that the control unit ( 2 6 ) i s conf igured to convert the pos it ional data generated by the inert ial measurement unit ( 28 ) from a binary form into a numerical value that describe s an angle of incl inat ion of the pos it ion .11 . A system according to any of claims 1 to 10 , characterised in that the attachment element ( 25 ) belonging to the work machine ( 14 ) includes a f irst l i ft ing arm ( 18 ) connected in an art iculated manner to the f rame ( 1 6 ) and asupport member ( 24 ) connected in an art iculated manner to the frame ( 1 6 ) or to the f irst l i ft ing arm ( 18 ) .12 . A system according to claim 11 , characterised in that the work machine ( 14 ) i s a tract or ( 38 ) and said l i ft ing arms ( 18 , 20 ) are the art iculated arms belonging to a three-point attachment element ( 25 ) of a rear hitch device ( 70 ) of a tractor ( 38 ) .13 . A system according to claim 11 or 12 , characterised in that the l i fting arms ( 18 , 20 ) are the lower support arms and the support member ( 24 ) i s the upper support arm of a three-point attachment element ( 25 ) .14 . A method ( 10 ) for pos it ioning an auxi l iary device ( 12 ) connected to a work machine ( 14 ) , wherein the work machine ( 14 ) includes a frame ( 1 6 ) , an attachment element ( 25 ) connected in an art iculated manner to the frame ( 1 6 ) for an attachment of the auxi l iary device ( 12 ) , a f irst actuator ( 22 ) for changing a pos it ion of the auxi l iary device ( 12 ) , and a second actuator ( 32 ) for changing a pos it ion of the auxi l iary device ( 12 ) in a di f ferent direct i on to the f irst actuator ( 22 ) , in which method — the auxi l iary device ( 12 ) i s suspended from the work machine ( 14 ) us ing a f irst l i ft ing arm ( 18 ) of the work machine ( 14 ) , which f irst l i ft ing arm ( 18 ) i s equipped with a f irst actuator ( 22 ) , and a support member ( 24 ) , which form the attachment element ( 25 ) for the attachment of the auxi l iary device ( 12 ) ,— a control unit ( 2 6 ) i s l inked to the f irst actuator ( 22 ) to control the pos it ioning of the auxi l iary device ( 12 ) , — a pos it ion of the auxi l iary device ( 12 ) i s determined by an inert ial measurement unit ( 28 ) belonging to a control unit ( 2 6 ) so as to generate pos it ional data , and— control commands are generated for the f irst actuator ( 22 ) and the second actuator ( 32 ) based on the pos it ional data us ing comput ing means ( 30 ) so as to hold the auxi l iary device ( 12 ) in a target pos it ion by changing at least the pos it ion of the f irst l i ft ing arm ( 18 ) ,characterised in that the pos it ion of the auxi l iary device ( 12 ) i s adjusted by the control unit ( 2 6 ) in relat ion to the direct ion of the gravitat ional force vector of the Earth determined by the inert ial measurement unit ( 28 ) and independent ly of the pos it ion o f the work machine ( 14 ) in relat ion to the substrate ( 100 ) on which the work machine ( 14 ) i s supported .15 . A method according to claim 14 , characterised in that a method according to the invent ion i s used in con junct ion with a system ( 10 ) according to any of claims 1 to 13 .

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