BUCKET WHEEL EXCAVATOR AND METHOD OF CONTROLLING A BUCKET WHEEL EXCAVATOR

Abstract

The present invention relates to a bucket wheel excavator whose bucket wheel is rotationally drivable and is supported at a pivotable bucket wheel boom and to a method of controlling such a bucket wheel excavator. In accordance with the invention, a mass flow and/or material flow adopted on the removal conveyor after a specific advance on the pivoting of the bucket wheel at the predetermined pivot angle speed is/are determined over the pivot angle, a desired mass flow and/or volume flow is/are specified on the removal conveyor, and then the previously specified pivot angle speed is automatically corrected using the determined mass flow and/or volume flow and the specified desired mass flow and/or volume flow to then perform the pivot cycle at the corrected pivot angle speed of the bucket wheel.

Claims

1. A method of controlling a bucket wheel excavator whose bucket wheel rotating at a constant speed is pivoted at an angle speed over a pivot angle by a bucket wheel boom pivot drive and in so doing places removed material on a removal conveyor, the method comprising: a first advance moving of the bucket wheel excavator by its undercarriage toward the rock mass to be removed with a detection of the implemented advance distance, wherein the first moving occurs after completion of a pivot by the bucket wheel over the pivot angle during a removal of material; pivoting the bucket wheel boom in a pivot cycle with a determination of the pivot angle speed over the pivot angle and of the mass flow and/or volume flow on the removal conveyor over the pivot angle; a second advance moving of the bucket wheel excavator by its undercarriage toward the rock mass to be removed with a detection of the implemented advance distance, wherein the second moving occurs after completion of the pivot cycle; specifying a constant wanted desire mass flow and/or volume flow on the removal conveyor; automatically correcting the pivot angle speed determined in a last pivot cycle in dependence on the pivot angle using the mass flow and/or volume flow previously determined using the pivot angle, wherein the desired mass and/or volume flow of an immediately previous implemented advance distance and an advance distance implemented before the last pivot so that the adopted mass flow and/or volume flow are close to the wanted desired mass flow and/or volume flow; and pivoting the bucket wheel boom in a further pivot cycle at the corrected pivot angle speed in dependence on the pivot angle.

2. The method of claim 1, further comprising the following upon the determination of the mass flow and/or volume flow adopted on the removal conveyor over the pivot angle: detecting the mass flow and/or volume flow at the removal conveyor, wherein the detecting is by a mass flow and/or volume flow sensor relative to the pivot angle of the bucket wheel; determining a dead time between a release of the material of a bucket up to the detection of this material at the removal conveyor; and correcting by the determined dead time the association of the measured mass flow and/or volume flow with the pivot angle, wherein the correcting occurs while taking account of the determined pivot angle speed over the pivot angle.

3. The method of claim 2, wherein determination of the dead time, a transport path of the bucket wheel excavator from the release of the material of a bucket up to a mass flow and/or volume flow sensor, and of a bucket wheel speed and a removal conveyor speed, a time offset between a load change of the bucket wheel and/or a change of the rotational speed of the bucket wheel, and a signal change of the mass flow and/or volume flow sensor, is determined with said load change and/or rotational speed of the bucket wheel being measured by a load pick-up sensor system and/or by a rotational speed of the bucket wheel sensor system.

4. The method of claim 3, further comprising determining the dead while taking account of the transport path of the bucket wheel excavator from the release of the material of a bucket up to a mass flow and/or volume flow sensor, and of a rotational speed of a bucket and a removal conveyor speed.

5. The method of claim 4, further comprising monitoring a load of the removal conveyor and/or a strain of at least the bucket wheel drive and/or of the removal conveyor drive, wherein the monitoring is performed by a power limiter) and the method further comprises limiting and/or reducing the corrected pivot angle speed when the load of the removal conveyor and/or the strain on the at least one drive reaches and/or exceeds a strain limit.

6. A bucket wheel excavator comprising: a bucket wheel supported in a rotationally drivable manner at a bucket wheel boom that is pivotable about a pivot axis by a pivot mechanism and a control apparatus for controlling a pivot angle speed in dependence on a pivot angle, wherein the control apparatus comprises: a determination device for determining a mass flow and/or volume flow adopted on the pivoting of the bucket wheel at a specified pivot angle speed on a removal conveyor in a preceding pivot cycle via the pivot angle; an inputter for inputting a desired mass flow and/or volume flow on the removal conveyor; a first determiner for determining the advance distance of the bucket wheel excavator between two pivot procedures; a second determiner for determining the pivot angle speed in dependence on the desired mass flow and/or volume flow, with the second determiner configured to deliver a calibration device for an automatic correction of the specified pivot angle speed using the determined mass flow and/or volume flow and the desired mass and/or volume flow; and a pivot control device for pivoting the bucket wheel.

7. The bucket wheel excavator of claim 6, wherein the inputter comprises a selection module for a variable selection of desired mass flow and/or volume flow from a range between a mass flow and/or a volume flow selectable as a minimum and a mass flow and/or a volume flow selectable as a maximum.

8. The bucket wheel excavator of claim 6, wherein the second determiner device is on the removal conveyor over the pivot angle and comprises: a mass flow and/or volume flow sensor for detecting the mass flow and/or volume flow at the removal conveyor; a pivot angle sensor for detecting the pivot angle of the bucket wheel boom relative to the pivot angle of the bucket wheel; an advance sensor system for detecting the advance distance of the bucket wheel excavator between two pivots by the undercarriage; and a recording device for recording the detected mass flow and/or volume flow at the removal conveyor and the detected pivot angle of the bucket wheel.

9. The bucket wheel excavator of claim 8, wherein the second determiner further comprises: a dead time determination device for determining a dead time between a release of the material of a bucket up to the detection of this material at the removal conveyor; and a corrector for correcting a recorded association of the measured mass flow and/or volume flow with the pivot angle by the determined dead time while taking account of the specified pivot angle speed.

10. The bucket wheel excavator of claim 9, wherein the dead time determination device is configured to determine a time offset between a load change of the bucket wheel and/or a change of the rotational speed of the bucket wheel, and a signal change of the mass flow and/or volume flow sensor, using the signals of a load pick-up sensor system for detecting a load pick-up of the drive of the bucket wheel and/or a bucket wheel speed sensor system for detecting the bucket wheel speed, and the signals of the mass flow and/or volume flow sensor.

11. The bucket wheel excavator of claim 9, wherein the dead time determination device is configured to determine the dead time while taking account of a transport path of the bucket wheel excavator from the release of the material of a bucket up to a mass flow and/or volume flow sensor, and of a bucket wheel speed and a removal conveyor speed.

12. The bucket wheel excavator of claim 6, further comprising a power limiter superposed on the control apparatus, wherein the power limiter is configured to monitor a load of the removal conveyor and/or a strain of at least the bucket wheel drive and/or the removal conveyor drive, and wherein the power limited is configured to limit and/or reduce the corrected pivot angle speed when the load of the removal conveyor and/or the strain on the at least one drive reaches and/or exceeds a strain limit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The invention will be explained in more detail in the following with reference to a preferred embodiment and to associated drawings. There are shown in the drawings:

[0028] FIG. 1: a schematic representation of a bucket wheel excavator; and

[0029] FIG. 2: a schematic representation of the sickle cut resulting with the bucket wheel excavator of FIG. 1.

DETAILED DESCRIPTION

[0030] As FIG. 1 shows, the bucket wheel excavator 1 can have in a known manner a bucket wheel 2 that is rotationally drivable about a horizontal bucket wheel axis and can have buckets at the peripheral side to be able to release and pick up material of an area or of a terrace to be machined, in particular earth and/or rocks.

[0031] Said bucket wheel 2 can be supported at a bucket wheel boom 3 in the form of a boom that can be pivotably connected in an articulated manner to a superstructure 10 and that can be pivoted by a pivot mechanism having a pivot drive. Said bucket wheel excavator 3 can more precisely be pivoted together with the superstructure 10 about said upright pivot axis 4 with respect to the undercarriage 11 that can in particular have a crawler chassis 12.

[0032] To be able to convey away the material picked up by the bucket wheel 2, a removal conveyor 5, for example in the form of a continuously revolving conveyor belt, can be associated with said boom or bucket wheel boom 3. Said removal conveyor 5 conveys the material taken over by the bucket wheel 2 along the boom to the superstructure 10, where the material conveyed away can be transferred via a chute 8 to a further removal conveyor 9 that can, for example, likewise comprise a continuously revolving conveyor belt and that can be configured as a loading conveyor.

[0033] As FIG. 1 further shows, the bucket wheel boom 3 can be connected in an articulated manner to the superstructure 10 luffable about a horizontal transverse axis 7.

[0034] FIG. 2 illustrates the cut relationships at the bucket wheel 2 that are adopted in working operation, with the arc 2.1 illustrating the arcuate pivot path of the bucket wheel 2 in a first pivot cycle n1 and with the arc 2.2 illustrating the again arcuate path of the bucket wheel in a further pivot value cycle n after the bucket wheel excavator 1 has experienced an advance by traveling the crawler chassis 12 in the longitudinal direction of the bucket wheel excavator 1. The sickle cut illustrated in FIG. 2 that has a maximum cutting depth in the direction of the longitudinal excavator axis or of the food that becomes smaller and smaller toward the side slope results from said advance, on the one hand, and the arcuate path of the bucket wheel 2, on the other hand.

[0035] In this respect, the pivot angle of the boom or of the bucket wheel boom 3 can be designated by the angle that typically amounts to =0 when the bucket wheel boom 3 so-to-say stands neutral at the center along the longitudinal excavator axis or along the advance 13 and that, on the other hand, amounts to ()=90 when the bucket wheel 2 has reached the side slope. In a pivot cycle, the bucket wheel 2 can thus therefore generally be pivoted in a range from 90+90, with, however, optionally even smaller pivot angle ranges of, for example, +/80 or +/70 being able to be provided, but with asymmetrical designs in accordance with FIG. 2 also equally being possible.

[0036] A control apparatus 15 of the bucket wheel excavator 1 that has an electronic data processing unit, for example comprises a microprocessor and software stored in a memory can in particular control the bucket wheel excavator 1 as follows:

[0037] The bucket wheel excavator 1 can first be pivoted in a calibration run n1 at a specified pivot angle speed .sub.act, in that the pivot mechanism is controlled accordingly and the bucket wheel boom 3 is correspondingly pivoted about the axis 4. In this process, the bucket wheel 2 runs in a rotationally driven manner in a manner known per se to release material and to unload it on the removal conveyor 5. The specified pivot angle speed .sub.act can, for example, be constantly specified or can have a predetermined cosine progression.

[0038] In this pivot cycle n1, the material flow adopted on the removal conveyor 5 is measured by sensor, and indeed in particular in the form of a mass flow and/or in the form of a volume flow. For this purpose, a mass flow sensor device 16 and/or a volume flow sensor device 17 that determine the mass conveyed through on the removal conveyor 5 in the corresponding removal conveyor section or the volume conveyed through can be associated with the removal conveyor 5 so that the signal of the mass flow sensor device 16 indicates the mass flow m and the signal of the volume flow sensor device 17 indicates the volume flow v.

[0039] In said pivot cycle n1, the pivot angle and the pivot angle speed of the bucket wheel excavator 3 are simultaneously detected by an angle sensor 18 and an angle speed sensor 19 that can be associated with the pivot mechanism.

[0040] The operation variables mass flow m, volume flow v, pivot angle , and pivot angle speed hereby detected are supplied to the control apparatus 15, in particular to a recording device 20 implemented therein to record the adopted mass flow and/or volume flow relative to the pivot angle and to the pivot angle speed.

[0041] Furthermore, the dead time, i.e. the time period between the release of the material of an excavator bucket up to the detection of the material by said mass flow and/or volume flow sensor devices 16 and 17, is determined by a dead time determination device 21. Said dead time determination device 21 can in this respect comprise a load pick-up sensor, for example in the form of a current consumption sensor 22 for detecting the current consumption of the rotary drive to rotate the bucket wheel 2, and/or a pressure sensor with a hydraulic design of the drive, and/or a speed sensor 23 for detecting the speed of the bucket wheel. Said dead time can specifically be determined in that, for example, a characteristic increase of the energy consumption, for example the current consumption, or a pressure increase and/or a characteristic drop of the speed of the bucket wheel 2 is determined, with the point in time at which this change occurs being able to be evaluated as the point in time of the release of the material. On the other hand, the signal of the mass flow and/or volume flow sensor device 16 or 17 respectively is monitored as to when a certain increase starts. The time difference between the occurrence of both changes can be evaluated as the dead time. The dead time T can, however, also be determined using the knowledge of the geometry (bucket wheel, lead angle, distance up to the belt scale) and of kinematics (speed of the bucket wheel, belt speed).

[0042] The control apparatus 5 can then correct the mass flow m.sub.act and/or volume flow v.sub.act recorded in the pivot cycle n1 via the pivot angle to correct said dead time. The angular offset that is caused by the dead time can advantageously be determined from the likewise recorded and/or already known pivot angle speed .sub.act in the pivot cycle n1, whereupon the control apparatus 15 can accordingly correct the mass flow and/or the volume flow using the pivot angle.

[0043] For a next pivot cycle n, the control apparatus 15 can then use the basis of a desired material flow in the form of a wanted desired mass flow m.sub.des and/or in the form of a desired volume material flow v.sub.des on the removal conveyor 5, with the control apparatus 15 being able to have input means 24, for example in the form of a slide control, a rotary knob, a joystick, or a touchscreen by means of which a machine operator or a control station can input the wanted desired mass flow or desired volume flow.

[0044] The control apparatus 15 scales or calibrates the pivot angle speed using the detected material flow and the wanted desired material flow and the respective advance path. A scaling or calibration device 25 that can be implemented in the control apparatus 15 can in particular determine the desired pivot angle speed .sub.des() using the following relationship:

[00003]${}_{\mathrm{des}}\left(\right)=.Math.{}_{\mathrm{act}}\left(\right).Math.\frac{m_{\mathrm{des}}\left(\right)}{m_{\mathrm{act}}\left(\right)}.Math.\frac{s_{n-1}}{s_n}.$

where .sub.des() is the desired pivot angle speed for the pivot cycle n, .sub.act() is the specified pivot angle speed in the pivot cycle n1, m.sub.des() is the desired mass flow specified by the input means 24 for the pivot cycle n, m.sub.act is the mass flow measured by sensor in the pivot cycle n1, s.sub.n-1 is the previous advance distance before the pivot cycle n1, and s.sub.n is the advance distance before the pivot cycle n.

[0045] If a volume flow control is provided or if a desired volume flow should be achieved, said scaling or calibration module 25 can proceed using the following relationship:

[00004]${}_{\mathrm{des}}\left(\right)=.Math.{}_{\mathrm{act}}\left(\right).Math.\frac{v_{\mathrm{des}}\left(\right)}{v_{\mathrm{act}}\left(\right)}.Math.\frac{s_{n-1}}{s_n},$

where .sub.des() is the desired pivot angle speed for the pivot cycle n, .sub.act() is the pivot angle speed in the preceding pivot cycle n1, v.sub.des is the set desired volume flow, v.sub.act() is the volume flow measured in the previous cycle n1, s.sub.n-1 is the previous advance distance before the pivot cycle n1, and s.sub.n is the advance distance before the pivot cycle n.

[0046] The desired mass flow m.sub.des and the desired volume flow v.sub.des are advantageously desired as constant and are therefore not specified as a function of the pivot angle , although this would nevertheless be possible.

[0047] The control apparatus 15 advantageously further comprises a power limiter 26 that is superposed on the control of the pivot angle speed and limits or reduces the desired pivot angle speed determined as previously explained when the drives of the bucket wheel excavator 1 are at risk of entering the overload range and/or too great a material amount is at risk of being unloaded on the removal conveyor 5. Said power limiter 26 can monitor the power consumption of the drives via corresponding sensor devices and/or monitor the signals of the mass flow and/or volume flow sensors 16 and 17 as input variables and can limit or reduce the pivot angle speed on the basis of these input variables.