WO2014114712A1

WO2014114712A1 - Method for changing a guide line control system for an industrial truck and industrial truck

Info

Publication number: WO2014114712A1
Application number: PCT/EP2014/051320
Authority: WO
Inventors: Robert Hämmerl
Original assignee: Jungheinrich Aktiengesellschaft
Priority date: 2013-01-25
Filing date: 2014-01-23
Publication date: 2014-07-31
Also published as: DE102013201223B4; DE102013201223A1

Abstract

The invention relates to a method for steering an industrial truck that drives under a guide line control system when changing from one guide line control system along a first guide apparatus to a guide line control system along a second guide apparatus, wherein the first guide apparatus is arranged at an angle to the second guide apparatus, such that the guide apparatuses intersect at an intersection point, wherein a steering start position for the industrial truck is determined, said position lying before the intersection point in the direction of travel of the industrial truck, and when the industrial truck reaches the steering start position with a non-steerable axle of the industrial truck, said truck is automatically steered away from the first guide apparatus by means of a steering apparatus and follows a turn-off curve to the second guide apparatus without a guide line control system, wherein a distance of the steering start position from the intersection point is defined taking into account a predefined turn-off curve.

Description

Procedure for changing a guideline guide for a

Industrial truck and industrial truck

description

This invention relates to a method of steering a guideway guided material vehicle when changing from a guideway along a first guide to a guideway along a second guide, wherein the first guide is arranged at an angle to a second guide, so that the guide in a Cross crossing point. Another aspect of the invention relates to an industrial truck.

Industrial trucks are often used in warehouses in which they are routed to assist a driver or fully automatically along a guide. Such a guide device may be, for example, a line on a road surface or particularly preferably a guide wire, which may be detected by a detection device. In particular, the Letidraht can be formed as an inductive conductor loop under the road surface. Guiding devices can be arranged, for example, in aisles of bearings. Often, a camp is equipped with a main aisle and branching off side passages. In order to store or store stored goods at storage locations in the side aisles, industrial trucks must turn from the main aisle into the side aisles. Usually, the baffles cross in the main aisle and the side aisle. Frequently, the two guidance devices are distinguishably detected in order to prevent confusion. Other constellations on which an industrial truck must turn are also found elsewhere in a warehouse.

In order to enable automatic turning under guideline guidance, two methods are known in the art. One possibility is to use an additional Provide Liche guide that leads in an arc from one of the baffles to the other guide. Such an additional guide bypasses the crossing point between the two guide devices and leads to a uniform cornering of an industrial truck, which follows it. A disadvantage of this solution, however, is that it means a considerable additional effort to move the arcuate guide devices for turning in addition to the main guide devices. In addition, an increased space required at the turnstile, since a uniform arc to the intersection point has a considerable distance and the truck accordingly far away from both baffles leads around the curve.

A second known way of effecting a change from one director to another is that an industrial truck with a non-steerable axle travels up to the intersection of two nozzles and stops there with that axle. Then, the angular orientation of the industrial truck is changed by means of a suitable steering device, for example, a rotatable by 90 ° drive wheel until it corresponds to the orientation of the second guide. In this position, the industrial truck can then follow the second guide. The disadvantage of this solution is that the truck must stop and turn on the spot. The braking process, and especially the "erasure" of the stationary tires on the ground when turning, results in relatively heavy tire wear and, in addition, the process is relatively slow due to stopping The first guide may come to a stop before it continues on the second guide, which may interfere with the traffic of other materials handling vehicles.

The object of the present invention is therefore to propose a method for steering an industrial truck when changing the guidance of the guideway, which requires little space and has a low vehicle Wear and a short change process brings with it.

The present invention is a method for steering an industrial truck, in which a steering start position for the industrial truck is determined, which lies in the direction of travel of the truck before the intersection, and the industrial vehicle, when it reaches the steering start position with a non-steerable axis of the industrial vehicle, automatically is deflected away from the first guide by means of a steering device and follows without guidance guidance a turning curve to the second guide, wherein a distance of the steering start position is determined by the intersection point involving a predefined turning curve.

A start of the automatic steering already before the crossing point makes it possible for the industrial truck to make a less sharp turn than in the case of the method according to the prior art, in which the industrial truck essentially turns on the spot. From a guideline guidance, the proposed method differs in that no guide must be laid and also the turn curve can be easily adjusted. If necessary, it can be inexpensively changed, for example in a conversion of the warehouse with new shelves or the like. In detail, the methods may differ by the steering angles that need to be adjusted to achieve a desired turn curve. The proposed method can be applied in forward or reverse direction as well as vehicles with the fixed axis in the direction of travel front or with a fixed axis in the rear direction. Particularly preferably, the method is used by forklifts with a non-steerable load axle in the direction of travel at the front of the forklift and one or two steerable wheels on the load axis opposite end of the forklift. In particular, the method can be used for a change of gear in which a material handling vehicle passes through a warehouse, in particular a rack warehouse. Frequently, the intersecting guide devices are probed frequencies of antennas for detecting the guide devices. The frequency switching of the antennas is preferably carried out after passing through the point of the guideway, which is closest to the crossing point. In this way, the second guide device approaching the industrial truck can be detected. Preferably, during the detection of the second guide device, an enable signal from an inductive loop can also be detected. If the release signal is not given, this may mean that the gear is busy, and may not be retracted there. In this case, the truck can be automatically stopped or retracted. Alternatively, the frequency switching can also be carried out with reaching the steering start position. This ensures the earliest possible detection of the second guide device within the scope of the detection device.

In one embodiment of the method, the course of the turn curve is determined before passing through the turn curve. This has the advantage that it is not necessary to carry out a calculation of the steering angle to be taken while driving. In addition, for individual or each specific branching connected with a change of the guidance devices, a separate, matching and firmly predefined turn curve can be used. For example, typical driving speeds, the available space for turning and the like can be taken into account more. In a Varainte can be made during the passage of the turn curve corrections to the still to be traveled part of the turn. In a further embodiment of the method, the course of the turn curve is stored in the industrial truck. Thus, the industrial truck is self-sufficient and can be used even in case of disturbances of surrounding systems. Alternatively, however, the course of a turning curve can also be stored in a control point outside the industrial truck and transmitted to the industrial truck.

In a further embodiment of the method, when passing through the turning curve, a detection of a position of the industrial truck is obtained performed and set a steering angle corresponding to the position of the industrial truck. As a result, the turn-off curve can be traversed regardless of the time that passes for it. For example, it may be stopped on the turn-off curve while driving and the turn-off curve may then continue to be traversed correctly. The application of mutually associated steering angle and position data is particularly advantageous for digital control of a material handling vehicle. Such a data set can curve a support point of a steering angle, which indicates the course of the steering angle relative to the position of the Furföderfahrzeugs represent. Between such support points of the steering angle curve, a control of the industrial vehicle can perform an interpolation of the steering angle.

A distance of the steering start position from the crossing point is determined by taking into account a predefined turning curve. Depending on how sharp or far a turn-off curve is provided, it is necessary to start turning into the turn-off curve sooner or later. This can be determined from the data of the turn curve. Since it is often easy to detect the intersection point between the guidance devices and integrate it into a navigation system for an industrial truck, the steering start position according to this embodiment is determined with respect to the crossing point. In alternative embodiments, other reference points may be chosen. In addition, special markers may indicate the steering start position, such as a transponder or an optical marker.

In a further embodiment of the method, a determination of the steering start position is carried out with the aid of a distance measurement by recording a wheel rotation angle, a reference transponder with position information, and / or a roadway marking or the like. The mentioned tools can be part of a navigation system for industrial trucks. Such methods are helpful because the steering start position is in front of the easily detectable crossing point and therefore can not be measured by the truck from the crossing point.

In a further embodiment, the non-steerable axle of the industrial vehicle when changing from the guideway along a first guide to a guideway along the second guide as a turning curve substantially passes through a hyperbolic curve. The advantage of a hyperbolic curve is that it causes an approximately uniform turning in by the steering device and, after reaching a maximum impact also an approximately uniform return in the direction of straight ahead. This is gentle on the steering mechanism and advantageous for tire wear. In addition, driving along a hyperbolic curve is smooth and therefore can be done quickly. Typically, a hyperbola is defined in Cartesian coordinates, passing approximately a right angle from a first asymptote along one of the axes to a second asymptote along the other axis. Accordingly, such a hyperbola is suitable for changing from a first guide to a second guide arranged at right angles thereto. However, it is also possible to transform the hyperbola into another coordinate system whose axes are not at right angles to each other. In this way, a hyperbola can be obtained, with which it is possible to make a change from a first guide to a second guide, which are not at right angles to each other. To generate the data of a hyperbola, which allows for a change of guideline guidance between two right-angled guide devices, the formula

be used. Where k is a hyperbolic displacement applied to both axes, a is an upsetting factor of the hyperbola. Due to the displacement, the curve crosses both axes. which moves the asymptotes from the first quadrant into adjacent quadrants of the coordinate system. The turn-off curve is the part left in the first quadrant with positive values of both axes. The coordinate zero point represents the crossing point of the guide devices. The above hyperbolic equation can be changed by introducing a maximum distance r of the curve to the crossing point and a steering start position z at an intersection of the shifted hyperbola with one of the axes according to the following formula:

By further shifting, the steering start position z can be calculated as a function of the distance r from the crossing point and the hyperbolic displacement k. In a forklift, the center of the load axis moves along the hyperbola section in the first quadrant. In order to arrive at the steering angle to be set, the curve is calculated on which a steerable rear wheel of a forklift or the center of a steerable rear axle of a forklift moves. For this purpose, a wheelbase b is introduced. The position for the center point of the steerable axle or the steerable wheel results from vector calculation

In this case, the first derivative of the hyperbola becomes x. XHyperbei and yHyperbei are the coordinates of the non-steerable axis on the hyperbola associated with the wheel position. From the coordinates of the course of the steerable axis can be in each of these points, the slope m _Ra d of the path of the steerable axis and determine therefrom the steering angle to be taken. For the steering angle results:

Angle (x) = arctan (nriHyp _e rbei - m _Ra d) (4) Using the formulas listed above, individual values can be assigned a steering angle on the x or y axis.

Typically, in a fork-lift truck with a single steerable wheel, the distance measurement on that wheel is removed. For the automatic adjustment of a steering angle along the hyperbola, it is preferable to use the traveled distance of this wheel as a parameter for the steering angle to be set. For this purpose, the steering angle data are not used as values as a function of the x-axis section in the Cartesian hyperbola representation, but instead are used as a function of a coordinate along the turning curve of the steerable axis. This coordinate transformation can be calculated using known mathematical methods for calculating a curve length as a function of an axis coordinate. Bases for this calculation can be found for example in the mathematics standard work Neunzert, Eschmann, Blickensdörfer-Ehlers, Schelkes: Analysis 1, Analysis 2, Springer Verlag. One approach can also be to calculate distances between adjacent interpolation points in a series of interpolation points that describe the travel curve of the steerable wheel and to sum the individual distances to a travel path. The following formula can be used to calculate the intervals to be accumulated between interpolation points :

AL = J (A x _Rud + (A y _R ^> (5)

Ax _Rad and Ay _R ad are distances between support points in the x and y directions.

In a further embodiment of the method, a deviation of the position of the industrial truck at the end of a traversed turning curve from a position of the second guide wire is reduced by a correction of the steering start position. For example, it may happen that the industrial truck is affected by deviations between a theoretical bending curve and a real turning curve over the second guide extends. Then, with a further passage through the turn curve, a correction of the theoretical turn curve can be made. In this case, the turning is initiated at a greater distance from the crossing point, so that the industrial vehicle arrives as accurately as possible at the second guide, or at least the guide comes to rest within a detection device for guide devices of the industrial truck. Accordingly, the steering start position can be moved in the direction of the crossing point when the industrial vehicle does not reach the second guide.

In a further embodiment of the method, a deviation of the angular position of the industrial vehicle is corrected after passing through the turn from a predetermined angular position after passing through the turn by adding a distance with a predetermined angle to the steering angle curve or omission of a distance from the steering angle curve. Due to the fact that, compared to the originally provided turn curve, the turn curve after such correction over a longer or shorter distance than before causes a rotation of the industrial truck, the industrial truck at the end of the turn has a different angular position than without the correction. So that the change in the distance traveled does not affect the position, but preferably almost exclusively the angular position, the predetermined angle of impact in the added or removed path is preferably at least approximately 90 °. A steering angle of 90 ° causes the industrial truck to spin virtually on the spot. Therefore, in the final position after passing through the turning curve, there is no parallel offset to the steering device to be reached. Preferably, the steering angle of the steering device along the curve from the steering start position of a few degrees to almost 90 ° and is at the end of the turn back to a few degrees back. Particularly preferably, the path to be added is inserted symmetrically at a vertex of the steering angle curve. Accordingly, it is preferred taken in the vertex of the steering angle curve distance, if a smaller starting angle is to be achieved. In a particularly preferred variant, the predetermined angle for the addition of path is independent of the original course of the steering angle curve at least approximately 90 °. This leads to an almost complete turning of the truck on the spot. While this may cause jumps in the course of the curve over the turn curve, the effects of this are small if the apex of the turn does not deviate significantly from the 90 °. If the steering angle at the apex deviates significantly from 90 °, the drive of the industrial truck may be slowed down at the jump points in order to have more time available for the steering operation.

In a further embodiment of the method, a deviation of the angular position of the industrial truck after passing through the turning curve from a predetermined angular position after passing through the turning curve is corrected by traversing a stretched or compressed turning curve with an equally stretched or compressed steering angle curve. This results in a longer track or a shorter track. This in turn has the consequence that a steering angle over a longer or shorter distance is applied. The consequence of this is that the industrial vehicle, after passing through the turn-off curve, arrives at the second guide device rotated by a larger or smaller angle. In this way, angle errors can be corrected, which can come from any source of error. However, a disadvantage of this type of error correction is that it simultaneously brings about a transverse offset of the position at which the industrial truck arrives at the second guide device. In order to compensate for this error as well, in addition to the stretching or compression of the turning curve and the steering angle curve, the steering start position can be corrected accordingly.

For a further embodiment of the method, it is proposed that a deviation of the angular position of the industrial truck, which compared with a given angular position along the turning curve resulting from a delay between setpoints and actual values of the steering angle is corrected by an angle correction measure. The effects of the mentioned delay between setpoint values and actual values of the steering angle depend not only on the delay time but also on the driving speed of the industrial truck. In a first variant, it is therefore proposed to set the driving speed of the industrial truck constant, so that a similar error results for each change in the steering angle, which can be corrected uniformly. As an angle error correcting measure, there is an addition or subtraction of a fixed angle correction value applied to the next steering angle to be set. Assuming a pre-known driving speed, an angle correction measure according to the previously discussed embodiment can also be used, in particular by stretching or swaging the steering angle curve or by inserting or removing sections into or out of the steering angle curve. In another variant of the method, the driving speed of the industrial truck can be measured and, in the next setting of a steering angle, a correction value corresponding to the speed can be added or subtracted. Other correction methods that take into account the speed of the industrial truck, are also conceivable, such as an extension or compression of the remaining distance to be traveled along the turning curve or the insertion of additional routes or the removal of intended routes in the turn and the steering angle curve. The delay can also cause a parallel offset of the final position of the industrial vehicle after passing through the turn in relation to the guide to be reached. This can be corrected according to one of the above-mentioned correction methods, in particular the selection of another start of steering position.

In a further embodiment of the method, the steering angle is set greater than predetermined to compensate for errors by interpolation between nodes in a steering angle curve. As with a digital Specification of the turn only intermittently support points are known at which the steering angle is readjusted, there is an error that due to the interpolation, the turn is not traversed exactly. Frequently, the steering device is initially progressively stronger hit along the turn, then progressively taken to a maximum impact degressive and steered progressively in the middle of the turn and finally degressive in the direction of straight ahead. In this case, a bell-shaped course of the steering angle curve results over the travel path along the turning curve. An interpolation approaches the arc of the bell by straight lines. Along the straight line, the steering angle is always set slightly differently than it would be if it ran correctly along the bell-shaped function. Most of the course of the turning curve is right-curved, whereby the steering angle is set a little too small by the interpolation in this area. This results in the end of the turn-off curve being reached with an error. In order to compensate for this, a larger steering angle is permanently set during the passage through the turn curve than predetermined by the interpolation. Preferably, a constant amount is added to all the steering angles to be set.

In another embodiment of the method, a different steering angle curve is used for steering for a given one of the possible combinations of left or right and forward or reverse than for another of the combinations to achieve specific error correction for the particular combination. Due to asymmetries of the industrial truck, such as a forklift with laterally steerable steerable wheel, different strong curve inclination in different directions and the like more, it is conceivable that a universal error correction for all of the combinations of driving and steering direction fails in each case. By dividing the correction options curves in several different turning curves with associated steering angle curves an individual and thus optimal correction can be achieved. In the calculation of a steering start position using a signal of a detector for the guide to be bent on, preferably the distance between the detector and the non-steerable axle of the truck is taken into account. The position of the guide to be bent to, for example, when driving over the guide to the industrial truck during a journey in which is not to be bent, determined and preferably stored in a navigation system. The determined position then differs from the position relevant for the turning by the distance between the detector and the non-steerable axle of the truck, on the position of which the turning curve relates.

In a further aspect of the invention, an industrial truck is proposed, which is set up to carry out a method according to one of the preceding embodiments.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 shows a schematic flow diagram of a method for steering an industrial vehicle when changing from a first guide device to a second guide device,

FIG. 2 shows in each case the profile of a turn-off curve of a non-steered and a steered axle of an industrial truck using the example of a fork-lift truck,

FIG. 3 shows by way of example a steering angle curve for a turning operation of an industrial truck,

FIG. 4 schematically shows a position error correction of an industrial vehicle when turning, Figure 5 shows schematically an angular correction of a truck when turning shows and

Figure 6 shows schematically a steering angle curve for a turn an industrial truck including angle correction measures shows.

Figure 1 shows schematically the flow of a method according to the invention for steering a material handling vehicle when changing from one guide to another guide. Individual steps can be interchanged in variants, summarized, omitted or divided into sub-steps, as far as a person skilled in the art would provide for this. The method preferably runs in a digital control of the industrial truck. In a step S1, the turn is triggered. This may be effected, for example, by an instruction of a navigation system installed in the industrial truck or in a non-traveling instance by an operator, by means of a signal of a remote control or the like. In a step S2, the position of the industrial truck is determined, for example, in a warehouse. As a result, it can be determined for the first time whether the intended turning is possible or not. In addition, the position is used to calculate a distance of the industrial truck to a steering start position for the turn. Preferably, the position is determined repeatedly in the further course of the method. In a step S3, the steering start position is calculated at a distance from the intersection with the aid of the turn, the driving direction and the steering direction, and possibly also corrections. This is useful because the crossing point is usually present in a navigation system for the truck. As a result, the distance of the steering start position from the current position of the truck can then be calculated. In particular, the orientation of the steering start position at the crossing point also makes it possible to use the same turn curve at different turning positions, whereby an associated steering start position is calculated in each case. The distance between the start of the steering Position and the intersection point can also be stored together with other data of the turn and / or the steering angle curve and be used in the calculation of the steering start position in coordinates of a navigation system or with respect to the distance of the steering start position of the Furföderfahrzeug. In a further step S4, a turning curve and a steering angle curve are initialized for execution taking into account curve parameters and corrections as well as driving and steering direction. For this purpose, the data of said curves are read from a memory, wherein the data set may depend on the driving direction and / or the steering direction. In addition, corrections can be made to the data, whereby these are changed so that expected deviations from a desired turning curve are compensated. The data comprise at least positions along the turning curve, in particular the turning curve driven through by the steerable axle, and respective associated steering angles. In a step S5, the control of the industrial truck waits for the industrial truck to reach the steering start position. For this purpose, the position of the industrial truck is determined repeatedly.

Upon reaching the steering start position, the industrial truck leaves in a step S6 the hitherto traced guide and begins by traversing the turn. The control of the industrial truck sets the steering angle as a function of the position on the turn curve in accordance with the specifications of the steering angle curve. After the turn-off curve is traversed, detects the control of the industrial vehicle, the second guide to be reached and determines their position relative to the industrial truck. In a step S8, the industrial truck threads on the guide to be reached. It can take into account signals that are transmitted via the guide, such as a conductor loop, which are emitted by other material handling vehicles. By means of such information can be avoided that forklift trucks hinder on the same guide. During the conduct of the procedure, it may be examined whether errors occur and the method, in particular dere the cornering, if necessary, be canceled. If the cornering aborted before the industrial truck has left the first guide, it preferably continues its travel along this guide.

Figure 2 shows in a diagram an x-axis, which represents the course of the first guide, and an intersection with a y-axis, which represents the course of the second guide. The intersection corresponds to the crossing point. In the first quadrant above the x-axis and to the right of the y-axis, the turning curve of a non-steerable axle of the industrial truck is shown. It has the form of a shifted hyperbola 1, whose asymptotes would each lie in the negative x or y range, but which are truncated. Thus, the middle area of the hyperbola near the origin of the coordinates remains as a turning curve. A forklift truck coming from the right in FIG. 2, in which the non-steerable axle precedes the steerable axle, leaves the first guide device at the steering start position 3 in order to drive through the hyperbolic section 1 with its non-steerable axle until it reaches an end position 4. Thereafter, the industrial vehicle threads on the second guide to be reached in the direction of the y-axis. In the lower quadrant at negative y-values, a turning curve of a steerable axle, in particular a steerable wheel of a three-wheeled forklift, is shown. The steering with the steerable axle begins at a position 5 of the steerable axle, at the same time the non-steerable axle is at the steering start position 3. The steerable axis leaves the first guide in the opposite direction as the non-steerable axle, causing rotation of the industrial truck is effected. The turning curve 2 of the steerable axle of the industrial truck is related to a steering angle curve indicating the angle to be set on the steering device in the course of the turning curve 2. After passing through the turning curve 2, the steerable axis reaches the second steering device or the y-axis at the position 6. The industrial truck is then aligned substantially in the direction of the y-axis and thus has rotated by about 90 ° to the right. The two turn curves 1 and 2 shown can also be used to a reversing industrial truck, which arrives in the figure 2 from above along the y-axis and in which the steerable axis precedes the non-steerable axis to steer to the x-axis. To turn right rather than right as shown by a right turn, a forklift truck may also turn left about x-axis along a turn of turn-off curves 1 and 2, which may also be forwards or backwards.

FIG. 3 shows a steering angle curve 7 with steering angles on the ordinate over positions of the steerable axle of a forklift vehicle on the abscissa. The steering angle can set a control of an industrial vehicle on a steering device to drive through a hyperbola 1 for turning. The steering angle curve 7 shown is a left half of a whole steering angle curve 7, which was divided in its apex 12 in two halves. To save storage space, it is sufficient to store one half of the steering angle curve 7 and read it along the course of the turn curve 1, 2 only from the left and then from the right, since both halves are line symmetrical to each other. This is clearly visible in the figure 6, in which a line of symmetry 1 1 is shown in phantom. The industrial truck is at the start of steering position 3 or 5, when the steering is started. In Figure 3, this position is the y-axis. Here, the steering is started by the steering angle deviates from 0. The steering angle increases progressively as it travels through the curve until it reaches a turning point at which the increase becomes degressive. The angle preferably increases to almost 90 °. This is almost equivalent to turning the truck on the spot. In the further course of driving through the turning curve 1, 2, the steering angle decreases according to the reversed steering angle curve 7 only progressively and then degressive again. The steering angle at the end position 4 or 6 then corresponds to that at the start of steering position 3 or 5.

FIG. 4 schematically shows an industrial truck with three wheels in a coordinate system which corresponds to that from FIG. A non-steerable Front axle 8 of the industrial truck is shown schematically as a dash. The corners 9 of the triangle 13 represent the non-steerable wheels of the industrial truck. The tip of the triangle 10, which is not disposed on the non-steerable axle, represents a steerable wheel of the industrial truck. The triangle 13, which is shown in bold lines, represents the industrial truck in one position. in which it has after passing through the turning curve 1 a parallel offset to the y-axis, which corresponds to the guide to be reached. The desired position of the industrial truck is shown with a second triangle 4 with less drawn lines. FIG. 4 shows a theoretical turning curve 1 as a hyperbola, which leads to the correct final position of the industrial truck shown in thin lines at a theoretical steering start position 3a. In fact, however, the turning curve 1 was only started at the starting position 3, which led to the final position of the industrial truck with parallel displacement to the y-axis. In order to achieve a correct end position in the case of repetition, a correction of the steering start position 3 to the steering start position 3a can be made. This correction can be stored for a steering angle curve 7 or for a specific turning point in a warehouse in the control of the industrial truck or a storage location outside the industrial truck, in particular together with the data of the turning curve 1, 2 and / or the steering angle curve 7. It should be clarified by the x-positions, which are each denoted by a plus and a minus sign, that a change in the steering start position is accompanied by a similar change in the end position of the industrial truck and this can be used to correct parallel misalignment in the end position.

FIG. 5 shows the same diagram as in FIGS. 1 and 4, with the difference that an industrial truck is illustrated here which, after passing through the turning curve, has an angular offset from the desired end position 4, 6. The truck with the angular offset is shown as a triangle 13 with bold lines, while the desired position is shown as a triangle 14 with thinner lines. The opposite to the desired position 14 of the industrial vehicle twisted actually reached position 13 is caused by deviations of the actually traversed turn curves compared to a theoretically desired turning curve. These deviations can be caused by a delayed adjustment of steering angles to a theoretical specification, by eccentric arrangement of the wheel 10 of the industrial truck, by slippage of a drive wheel 10 and a corresponding incorrectly determined position of the truck, interpolation between nodes in a steering angle curve 7 and the like ,

In order to avoid the undesired situation shown in FIG. 5 of a twisted end position of the industrial truck, the steering angle curve 7 can be adapted such that the industrial truck rotates more or less during the passage through the turn curve 1, 2, thus the angular offset in the end position to compensate. FIG. 6 shows a bell-shaped curve of the steering angle in tenths of degrees on the ordinate over a travel path of the steerable axis along its turning curve on the abscissa. To compensate for the rotation in the end position, the bell curve 7 can be widened or narrowed, which is illustrated by the arrows with plus and minus signs. In the correction, the line symmetry of the bell-shaped steering angle curve 7 preferably remains around the dot-dash line as its symmetry line 1 1. The part of the steering angle curve 7 shown on the left of the line of symmetry 1 corresponds to the representation of FIG. 3. In order to effect the correction, it is conceivable to maintain the value of the steering angle curve 7 present at the line of symmetry 11 over an additional distance. As a result, the length of the steering angle curve 7 and consequently also the lengths of the turning curves 1, 2 change. In the added section of the steering angle curve 7, the steering device is hammered in, and is preferably severely hammered, so that a stronger rotation of the industrial truck is effected. Alternatively, a part of the steering angle curve 7 may be omitted symmetrically about the line of symmetry 1 1, to effect a smaller rotation of the industrial truck. In a modification thereof, instead of the advertising tes the steering angle curve 7 at the line of symmetry 1 1, the value of 90 ° or a maximum possible value of the steering device can be selected for the addition of an additional curve section. A value of 90 ° reduces or eliminates any additional positional offset that results when adding an additional track with a steering angle other than 90 °. 90 ° steering angle corresponds to turning on the spot around the non-steerable axle of the industrial truck. Another way to prevent or reduce the rotation of the industrial vehicle after reaching the Endpostion 4, 6 is to stretch or compress the entire steering angle curve 7. For this purpose, the x-positions of the steering angle curve 7 can be recalculated. For this purpose, the position of the symmetry axis 1 1 is subtracted from the x positions, multiplied by a stretching or compression factor which is different from 1, and then the position of the symmetry axis 1 1 is added again. In principle, it is necessary in all embodiments with correction of the angular position of the industrial truck in the end position 4, 6 to change the area under the steering angle curve 7. In addition to the two methods mentioned above, other methods are also conceivable.

Claims

claims

A method of steering a guideway-guided industrial truck when switching from a guideway along a first guider to a guidebook along a second guider, the first diverter being disposed at an angle to the second diverter such that the diverters cross at a crossing point,

characterized in that a steering start position for the industrial truck is determined, which lies in the direction of travel of the truck before the crossing point, and the industrial vehicle when it reaches the steering start position with a non-steerable axle of the industrial vehicle is automatically deflected away by means of a steering device of the first guide and without guideline guidance follows a turning curve to the second guide, wherein a distance of the steering start position is determined by the intersection point involving a predefined turning curve.

A method according to claim 1, characterized in that the course of the turning curve is determined before passing through the turning curve.

A method according to claim 2, characterized in that the course of the turning curve is stored in the industrial truck.

Method according to one of the preceding claims, characterized in that when passing through the turning curve, a detection of a position of the industrial truck is performed and a steering angle is set according to the position of the industrial truck. Method according to one of the preceding claims, characterized in that a determination of the steering start position with the aid of a displacement measurement by recording a Raddrehwinkels, a reference transponder with a position information, and / or a lane marking is performed.

Method according to one of the preceding claims, characterized in that the non-steerable axis of the industrial vehicle when changing from the guideway along the first guide to a guideway along the second guide as a turn substantially passes through a hyperbola.

Method according to one of the preceding claims, characterized in that a deviation of the position of the industrial truck at the end of the traversed turn to a position of the second guide wire is reduced by a correction of the steering start position.

Method according to one of the preceding claims, characterized in that a deviation of the angular position of the industrial truck after passing through the turn from a predetermined angular position after passing through the turn by adding a distance with a predetermined angle to a steering angle curve belonging to the turn, or is corrected by omitting a distance from the steering angle curve.

Method according to one of the preceding claims, characterized in that a deviation of the angular position of the industrial truck after passing through the turning curve from a predetermined angular position after passing through the turning curve is corrected by a stretched or compressed turn curve with an equally stretched or compressed steering angle curve are passed.

10. The method according to any one of the preceding claims, character- ized in that a deviation of the angular position of the industrial truck, which results from a predetermined angular position along the turn from a delay between setpoints and actual values of the steering angle is corrected by an angle correction measure.

1 1. Method according to one of the preceding claims, characterized in that the steering angle is set greater than predetermined to compensate for errors by interpolation between nodes in a steering angle curve.

12. The method according to any one of the preceding claims, characterized in that for error correction for a certain one of the possible combinations of left or right turn and forward or reverse driving another steering angle curve is used for steering, as for another of the combinations to the specific

Combination to achieve a specific error correction.

13. Industrial truck, which is set up for carrying out a method according to one of the preceding claims.