Patent Description:
At present, a crane mounted on a working machine is in most cases still controlled in by controlling the actuator provided in connection with each boom of the crane separately. As a result, the driver has to combine the movements of various actuators in order to make the crane move in a desired way. Normally, cranes are used for moving an implement fastened to the head of the crane.

For example in a forest machine, the implement is a harvester head or a loading grapple, depending on whether the machine is a harvester or a forwarder. Largely depending on this are also the most typical movements that are usually implemented with the crane when working with the working machine. In a forwarder used for loading of timber, the crane is normally moved from the load space of the forwarder to the side of a log pile and back to the load space. When a harvester is used for felling of timber, the crane is normally moved in the horizontal direction from the working machine towards the trees to be felled and, after the felling, in a suitable direction where a pile of cut and delimbed tree trunks is placed.

Normally, however, in all working machines, also other than forest machines, the aim of the movements of the crane is to move the implement at the head of the crane from one place to another. This may be the reason why a method has been recently developed for controlling the crane in a way that serves this aim better and thereby facilitates the work of the driver of the machine. In this so-called boom tip control (or coordinated control), the driver controls the crane in such a way that the control devices of the working machine are used for directly controlling the movement of the head of the crane in different directions of motion. Thus, a single control function of the control device is used for controlling the head of the crane to move e.g. in the horizontal direction away from the working machine and back towards the working machine, another control function is used for controlling the movement upwards and downwards in the vertical direction, and a third control function is used for controlling the turning of the whole crane to the left and to the right in the horizontal direction.

For the driver, this so-called boom tip control is motorically less demanding, because when it is applied, the driver does not need to control the different actuators separately and to know how to combine the relationship between the movements of the single booms generated by them with the movements of the head of the crane, but this is performed automatically by the control system of the working machine according to the direction of motion where the driver wants the head of the crane to move. As a result, boom tip control has been found to make the work easier and more efficient, particularly for a driver with little experience. Such a method and apparatus for controlling the crane on the basis of boom tip control is described in the thesis by Markus Saarela, "Coordinated Motion Control of a Log Loader Boom".

Normally, the crane comprises two to three booms connected to each other and to the working machine in an articulated or otherwise movable manner.

For example, the forest machines manufactured by the applicant typically comprise a hoisting boom connected at its first end in an articulated manner to a traverser mounted on the body of the working machine in a swivelled manner with respect to the vertical axis, a stick boom connected at its first end in an articulated manner to the second end of the hoisting boom, as well as an extension boom movable linearly out of the second end of the stick boom, in the longitudinal direction of the stick boom, and back into the stick boom. Now, if e.g. such a crane is controlled with boom tip control, the control system has, in principle, an infinite number of alternatives selectable for implementing a movement in a given direction of motion. Depending on where the head of the boom is moving with respect to its range of motion, some of these alternatives are always such that their implementation will lead to a situation in which the movement of the crane is more difficult than the implementation of another alternative, because of one or more factors limiting the movement of the booms of the crane.

These limitations caused by the principle of operation of the crane are not taken into account in tip-control-based control methods of prior art; therefore, the cranes of prior art operated by boom tip control cannot always move the head of the crane in a desired way. This may mean, for example, that in a certain position the head of the crane will not move at all if an attempt is made to steer it in a direction whose implementation brings the control system to a situation in which it would have to move an actuator although this is, for example, in its extreme position, or in which a boom would hit the working machine, the ground, or another surrounding obstacle. In such a situation, the driver has to move the crane first in a suitable direction, in which the boom tip control can move the crane, to be able to continue the work.

The above-mentioned thesis by Markus Saarela, "Coordinated Motion Control of a Log Loader Boom", discloses a method and a system according to the preamble of claim <NUM>. The thesis by Bjorn Lofgren entitled "Kinematic Control of Redundant Knuckle Booms" discloses the preamble of claim <NUM> and a forestry machine that carries out that method.

An aim is to provide a method and system for controlling the crane of the working machine, the crane including at least two booms and a head of the crane, by boom tip control in such a way that speeds of the booms of the crane are controlled automatically in situations implementing prioritizations of movements of the booms.

To put it more precisely, the method and the system according to the invention are presented in the independent claim <NUM> and in the independent claim <NUM>, respectively.

Dependent claims <NUM>, <NUM>, and <NUM> present examples of the method and the system according to the invention.

According to an example of the method, the boom tip control is switched off in one or some of the following ways when the head of the crane is within a given area or reaches a given area by its movement: automatically, by a control function to be generated by a separate control device, or by maintaining a control function for controlling another function for a predetermined time.

According to an example of the method, the boom tip control is automatically switched on again when the head of the crane moves out of a given area.

According to an example of the system, the control system of the working machine comprises a data processing unit for controlling the movements of the crane by programmable software in the data processing unit, and the control element is software stored in the data processing unit.

In the following, the invention will be described in more detail with reference to the appended drawings, in which.

The method and the system according to the invention can be applied in a forest machine constituting a working machine equipped with a crane.

In forest machines, the method can be well utilized in, for example, forwarders <NUM> such as that shown in <FIG>, and harvesters <NUM> such as that shown in <FIG>. Most typically, the actuators used for moving different booms of a crane in a working machine are hydraulic cylinders, but in principle they could also be other actuators with linear movements, such as pneumatic cylinders or spindle motors. Furthermore, for moving e.g. a traverser that rotates the crane horizontally, it is also possible to apply actuators generating a rotary motion, such as hydraulic or electric motors.

For controlling all these actuators, however, it is possible to use a control system equipped with a programmable data processing unit and controlling the movements of the crane by means of control functions generated by control devices placed in the cabin of the working machine in such a way that that the control system converts a given control function into a control command for generating a desired movement of one or some actuators in the working machine.

The forest machine shown in <FIG> is a forwarder <NUM> intended for hauling felled tree trunks out of the forest. The rear part of the body <NUM> of the forwarder <NUM> is provided with a load space <NUM> formed for the transportation of the tree trunks in a space between bunks <NUM>. The front part of the forwarder <NUM> is provided with a driving motor <NUM> and a cabin <NUM>, with its steering and control equipment. Among other things, the control levers for the left and the right hand, shown in <FIG>, are provided within the cabin. In this forwarder <NUM>, the crane <NUM> intended for the manipulation of tree trunks is provided between the cabin <NUM> and the load space <NUM>.

The crane <NUM> consists of a hoisting boom <NUM>, a stick boom <NUM>, and an extension boom <NUM>. The crane <NUM> is mounted on the body <NUM> of the forwarder by means of a traverser <NUM> that is rotatable about a vertical axis with respect to the same in such a way that it can be rotated about the forwarder <NUM>, from the left to the right and vice versa in lateral direction with respect to the body <NUM>. The hoisting boom <NUM> is connected at its first end in an articulated manner to the traverser, to be turnable with respect to a horizontal axis. The stick boom <NUM> is connected in an articulated manner to the second end of the hoisting boom <NUM>, and the extension boom <NUM> is arranged at the end of the stick boom to be movable in its longitudinal direction in such a way that it is movable from the end of the stick boom by its range of motion out of the end of the stick boom and back into the stick boom <NUM>. Between the hoisting boom <NUM> and the traverser <NUM>, between the hoisting boom <NUM> and the stick boom <NUM>, and between the stick boom <NUM> and the extension boom <NUM>, actuators <NUM>, <NUM> and <NUM> are provided which operate in a way known as such, for example hydraulically, and by which the hoisting boom <NUM> can be turned with respect to the traverser <NUM>, the stick boom <NUM> can be turned with respect to the hoisting boom <NUM>, and the extension boom <NUM> can be moved outwards from the stick boom <NUM> and back inwards.

At the head <NUM> of the crane <NUM>, a loading grapple <NUM> is provided, equipped with gripping members <NUM> known as such, which are turned towards or away from each other by an actuator provided in them, wherein the loading grapple <NUM> can be used for gripping one or more tree trunks for hauling them to a desired location. The loading grapple <NUM> can also be rotated by a rotating device <NUM> provided therein, so that the trunks in the loading grapple <NUM> can be brought to a suitable position when they are e.g. loaded into or unloaded from the loading space <NUM>.

The control of the forwarder <NUM>, the crane <NUM> and the loading grapple <NUM> is configured to be performed from the cabin <NUM> placed in the front part of the body <NUM>. For this, the cabin <NUM> is provided with various control devices known as such, for example the control lever <NUM> for the left hand and the control lever <NUM> for the right hand as shown in <FIG>, as well as rocker levers <NUM> and <NUM> provided in these for controlling e.g. the movement of the crane <NUM> and the opening and closing of the gripping members of the loading grapple <NUM> with control functions generated by these controls. During the control, the control commands generated by the control functions given with the control lever <NUM> for the left hand and the control lever <NUM> for the right hand are transferred from these controls by communication buses to a data processing unit located in the control system and actually taking care of the control of the actuators <NUM>, <NUM> and <NUM> for generating the functions of the crane <NUM> as well as the actuator controlling the opening of the loading grapple, and the rotating device <NUM>, by means of electro-hydraulic control valves in their hydraulic circuits.

<FIG> shows a harvester <NUM> equipped with a corresponding crane. Here, the control of the crane <NUM> is implemented in a similar way but for the control of the harvester unit <NUM>, more control functions have to be generated by various control devices. Some of these may be implemented by means of control devices separate from the control lever <NUM> for the left hand and the control lever <NUM> for the right hand shown in <FIG>. However, these do not need to be presented in more detail in this context, because the subject of interest is merely the control of the crane <NUM> which is implemented in the same way in the forest machines shown in <FIG> and <FIG>.

Boom tip control is applied for controlling the crane <NUM> in the forwarder <NUM> according to <FIG> and in the harvester <NUM> according to <FIG>. Consequently, when the crane <NUM> is controlled with control devices in the cabin, particularly the control lever <NUM> for the left hand and the control lever <NUM> for the right hand can be applied for determining the desired direction of motion of the head <NUM> of the crane. For implementing this, software has been programmed in the data processing unit of the control system to calculate the speeds of motion needed for the actuators <NUM>, <NUM> and <NUM> moving the different booms, by applying kinematic equations in such a way that the desired direction and speed of motion of the head <NUM> of the crane are achieved as well as possible. In this context, however, there is no need to present the kinematic equations and control engineering required by the boom tip control, because solutions of prior art can be applied in that respect. Consequently, the calculation of the kinematics of the crane can be implemented, for example, in a way presented in the thesis by Markus Saarela, that is, for example on the basis of Denavit-Hartenberg notation. Solutions of control engineering may also be known as such, because they can be used for controlling the crane in a programmed way, that is, for example by using control commands (in other words, control currents to be input in control valves) based on the above mentioned kinematic calculations.

The factors (i.e. criteria) applied are implemented in the boom tip control of the crane <NUM> in the forwarder <NUM> of <FIG> and in the harvester of <FIG> in such a way that when a given criterion is met, the desired direction of motion of the head <NUM> of the crane, or the way of putting it into action (i.e. the booms by which the movement is implemented) is changed according to the criteria. In other words, the automatic correcting functions modify the control command for controlling a given boom or given booms <NUM>, <NUM>, <NUM> of the crane <NUM>, and/or the way in which the speeds of motion of the single booms, obtained as a result of calculation, are determined for the different booms. This is performed by software in the data processing unit of the control system of the working machine on the basis of the location of the head <NUM> of the crane and the positions of the different booms <NUM>, <NUM>, <NUM> of the crane <NUM> with respect to each other.

In the forwarder <NUM> of <FIG> and in the harvester of <FIG>, the control of the crane <NUM> by boom tip control is executed with control devices <NUM> and <NUM> of <FIG>, in a normal situation in the following way (that is, when the control system does not modify the control commands to be generated with the different control functions): When the control lever <NUM> for the left hand is turned in the direction +Yv, the head <NUM> of the crane will move away from the working machine in the horizontal direction. In a corresponding manner, when the control lever <NUM> for the left hand is turned in the direction Yv, the head <NUM> of the crane will move towards the working machine in the horizontal direction. When the same lever is turned to the side in the direction +Xv, the head <NUM> of the crane will move to the right in the lateral direction, and when the lever is turned in the direction -Xv, the head <NUM> of the crane will move to the left in the lateral direction. When the control lever <NUM> for the right hand is moved in the direction +Yo, the head <NUM> of the crane will move upwards in the vertical direction, and when it is moved in the direction Yo, the head <NUM> of the crane will move downwards. By implementing these control functions simultaneously in a suitable way, the driver of the working machine can make the loading grapple or harvester head fastened to the head <NUM> of the crane move in a desired direction at a desired speed. For example, for moving the head of the crane obliquely away from the working machine and to the left, the driver of the working machine will turn the left control lever obliquely to the left and forward (that is, in a direction between the directions +Yv and +Xv). In a normal situation, the speed of the movement of the head <NUM> of the crane is directly proportional to how much the control lever is turned in the direction of the control function for generating said movement. Furthermore, the segmentation of the movement of the head of the crane among the single booms, that is, for example in the case of the crane <NUM> of <FIG>, between the hoisting boom <NUM>, the stick boom <NUM> and the extension boom <NUM>, is automatically adjusted on the basis of certain factors (criteria) depending on the position and location of the crane <NUM>.

In the following, not forming part of the inventive method and system, programmable changes that can be made in the movements of the crane in the forwarder <NUM> of <FIG> and in the harvester of <FIG> will be presented by way of example.

If any movement of a boom of the crane <NUM> approaches its end limit (which is typically caused by the limitedness of the range of motion of the actuator for moving the same), its speed is started to reduce well in advance (at a given distance from the end limit of said movement). This distance will depend on the structure of the crane and the lengths of the booms. Furthermore, the deceleration may take place gradually in a ramp-like manner. When the speed of one boom is decreased, the speed of motion of the other boom is increased respectively so that the direction and speed of motion of the head of the crane, desired by the driver, are achieved. The increase in the speed of the other booms / one other boom may take place in a ramp-like manner similar to the deceleration of the boom approaching its end limit. This feature is effective for all booms of the crane <NUM>, that is, the hoisting boom <NUM>, the stick boom <NUM> and the extension boom <NUM>.

A more precise example is a situation, in which a loading grapple <NUM> is brought from a long distance closer to the machine. At first, all the booms are in use, that is, the hoisting boom <NUM>, the stick boom <NUM> and the extension boom <NUM>. When the extension boom <NUM> comes close to its end limit, to a certain limit distance from it, its movement is gradually decelerated. To keep the speed of the head <NUM> of the crane <NUM> constant, the speeds of the hoisting boom <NUM> and the stick boom <NUM> are increased correspondingly. After the extension boom <NUM> has been totally withdrawn into the stick boom <NUM>, the movement is continued merely with the hoisting boom <NUM> and the stick boom <NUM>.

Normally, and relating to the inventive method and system, the desired speed of motion of the head <NUM> of the crane can be achieved by a large variety of speed combinations of different booms. In these cases, it is possible to select various weightings for the application of the different booms <NUM>, <NUM> and <NUM> and thereby the actuators <NUM>, <NUM> and <NUM> for moving these. Factors on the selection of the weightings may include, for example, the maximum speed of motion of the head <NUM> of the crane, the smooth application of the boom, the relative strengths of the actuators <NUM>, <NUM> and <NUM>, and the need to keep the crane <NUM> in an advantageous position for the next movements. With respect to these, the software programmed in the control system comprises basic rules which apply in very different situations.

According to the inventive method and system, for example, in the harvester <NUM> of <FIG>, prioritizations of the movements of different booms (i.e. different actuators) to be implemented include the following:.

In some situations, not forming part of the inventive method and system, the limits of movement of the actuators <NUM>, <NUM> and <NUM> moving the crane <NUM>, and the geometry of the crane <NUM>, prevent the head <NUM> of the crane from moving in the desired direction. In these cases, a direction of motion can be sought for the head <NUM> of the crane, which direction does not deviate too much from the desired direction of motion and which will result in the crane <NUM> circumventing the obstacle to the movement. This can be implemented so that when deviating from the desired direction of movement, the head <NUM> of the crane is controlled to move more slowly than usual (that is, than the normal speed of motion corresponding to this speed of motion). Also, the transition between these two modes is implemented smoothly. As an example, a situation can be mentioned in which the head <NUM> of the crane is controlled to move upwards in the vicinity of a column. First, the head <NUM> of the crane can be moved directly upwards, but when the extension boom <NUM> is totally withdrawn in the stick boom <NUM>, a linear motion upwards will be impossible. The aim is to correct this situation by applying the hoisting boom <NUM> or the stick boom <NUM>. The resulting path of motion will deviate from the desired one, but the crane <NUM> will not stop and the "deadlock" situation will be passed.

In boom tip control, the driver of the machine determines the direction of motion of the head <NUM> of the crane. In the control of the head <NUM> of the crane, not forming part of the inventive method and system, however, the control system can intervene by changing this direction of motion controlled by a control device, if this is expedient. For example in the harvester of <FIG>, changes in the direction of motion are made in the following situations:.

The way of controlling the boom can also be changed on the basis of a work stage. As an example, we can present the control of the crane <NUM> of the forwarder <NUM> according to <FIG> when trunks are unloaded from the load space <NUM> of the forwarder <NUM>.

Also, in many other situations, the movement of the different booms <NUM>, <NUM> and <NUM> can be limited according to the need. For example, if any boom of the crane <NUM> were moving to a difficult position in view of the surrounding known obstacles, the movement of such boom can be limited and compensated by other booms.

According to an example, the boom tip control is switched off automatically, by a separate control device, or by maintaining a control function controlling another function for at least or not longer than a predetermined time when this function is in a given condition and the head of the crane is within a given area or reaches a given area by its movement. For example in the forwarder <NUM> of <FIG>, such a function could be the control function for withdrawing the extension boom into the stick boom when the extension boom is already placed completely inside the stick boom and the loading grapple is e.g. close to (within a predetermined maximum distance from) the screen of the load space. Furthermore, the boom tip control can be configured to function so that it is automatically switched on again when the head of the crane moves out of a given area.

In the above presented example embodiments, the method can be used in cranes implemented in different ways from the crane <NUM> shown. In the case of more than three booms, the number of various alternatives for providing a given direction and speed of motion increases. On the other hand, if the number of booms connected to each other is smaller than three, e.g. a linear motion cannot always be implemented, and the aim of the control can thus be to move the head of the crane by applying the closest possible direction of motion to be implemented.

Functions not forming part of the inventive method and system, affecting the direction of motion or the way of implementation of the head of the crane or the single booms, and programmed in the control system of the machine, may also be other than those presented in the examples above. In some cases, the determining factor could be, for example, the lowest possible energy consumption (e.g. when the loading grapple of the forwarder is empty when it is moved) or the greatest possible force (when it is known that the trunk in the loading grapple is very heavy) that can be achieved with the boom in connection with said movement. In view of efficient work, it is important that the head of the crane and the implement therein is brought to the desired location as soon as possible. Thus, the software in the control system can operate so that it implements most of the movement with the boom that makes the head of the crane move as fast as possible in the easiest way. This can also be performed in such a way that the implementation of the exact direction of the motion is compromised during the movement but at the end of the movement, the head of the crane is, in any case, in the location to which the driver has steered it. This can be implemented, for example, in such a way that the software calculates the theoretical realized path of motion from the different positions of the control lever, and after that (in practice, at the moment of stopping), the head of the crane is moved by the deviation between the real location and the calculated location, after which the head of the crane is, after the movement has ended, exactly in the location intended by the driver of the machine.

Claim 1:
A method for controlling the crane (<NUM>) of a working machine (<NUM>, <NUM>) by using boom tip control, in which method the crane (<NUM>) comprises at least two booms (<NUM>, <NUM>, <NUM>) and a head (<NUM>) of the crane, which booms are connected to the working machine (<NUM>, <NUM>) and to each other in an articulated manner, and which booms are moved in relation to the working machine (<NUM>, <NUM>) and each other by means of actuators (<NUM>, <NUM>, <NUM>) controlled by a control system of the working machine (<NUM>, <NUM>), and
in which method
- direction and speed of motion of the head (<NUM>) of the crane, controlled by a driver applying controls (<NUM>, <NUM>) in the working machine (<NUM>, <NUM>), are achieved by applying speeds of the booms (<NUM>, <NUM>, <NUM>) of the crane (<NUM>),
- wherein the crane (<NUM>) comprises a hoisting boom (<NUM>) connected at its first end in an articulated manner to the working machine, a stick boom (<NUM>) connected at its first end in an articulated manner to the second end of the hoisting boom (<NUM>), and an extension boom (<NUM>) connected to the stick boom (<NUM>) at its second end and movable linearly outwards and inwards in the longitudinal direction of the stick boom (<NUM>)
- wherein the working machine is a forest machine (<NUM>),
characterized in that
- the speeds of the booms (<NUM>, <NUM>, <NUM>) of the crane (<NUM>) are controlled automatically in at least one of the following manners in the respective situations implementing prioritizations of movements of the booms:
- (i) when the head (<NUM>) of the crane is moved towards the working machine, the extension boom (<NUM>) is withdrawn into the stick boom (<NUM>) as fast as possible;
- (ii) when the head (<NUM>) of the crane is farther than a predetermined maximum limit distance from the working machine, the head (<NUM>) of the crane is lowered by applying the hoisting boom (<NUM>) and the lowering movement performed by the stick boom (<NUM>) is limited;
- (iii) when the head (<NUM>) of the crane is farther than a predetermined maximum limit distance, the head (<NUM>) of the crane is hoisted by applying the hoisting boom (<NUM>) so that the hoisting movement performed by the stick boom (<NUM>) is limited correspondingly.