JP2006290510A - Carrying device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stop control device simply and surely correcting an elevation stop position or a travel stop position of a stacker crane or the like. <P>SOLUTION: A fixed position sensor 22 is disposed to an elevator platform 12 of a stacker crane. When the fixed position sensor stops at a turnoff position, the elevator platform 12 is moved down to an original point to correct an original position. The elevator platform is moved up to a position opposed to the original point to correct a counter value with respect to a stroke between the original position and the position opposed to the original position. A stop position between the original point and the point opposed to the original point is corrected by using a ratio between the corrected counter value with respect to the stroke and a counter value before the correction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stacker crane, an overhead traveling vehicle, a tracked carriage, an elevating shelf, an elevating / transferring device, and the like, and in particular, correcting an extension of a suspension material such as a chain, a wire, and a rope, and a change in a wheel diameter. About.

  In a stacker crane used in an automatic warehouse, it is necessary to stop the lifting platform at a correct height and a correct horizontal position with respect to a predetermined shelf. In the lifting control of the lifting platform and the traveling control of the carriage, the servo motor is used to read the rotation speed with an encoder or the like to obtain the position and height and feed back to the motor.

  By the way, elongation is a problem in suspension materials such as chains, ropes, and wires, especially chains. However, a suspension material such as a chain is suitable for lifting a heavy object, and is used, for example, in a stacker crane for transporting a liquid crystal substrate. In order to correct the elongation of the suspension material, a mark such as a color tape is attached to each shelf, and the mark is read and controlled by an external sensor on the lifting platform side. However, in this case, it is necessary to attach marks to a large number of shelves, and in addition to the control by the encoder, the control by the external sensor overlaps and double control is required.

In addition to this, when the wheel of the carriage is worn or replaced, its diameter changes. In travel control, the travel distance is obtained from the rotational speed of the motor shaft and the rotational speed of the axle, so that a control error occurs when the wheel diameter changes. And measures against changes in the diameter of the wheel are hardly studied.
JP 2004-287555 A

A basic problem of the present invention is to easily correct an error in raising and lowering or traveling due to an extension of a suspension material or a change in wheel diameter.
An additional problem in the invention of claim 2 is to accurately correct the stop data with respect to the reference position.
An additional problem in the invention of claim 3 is to correct the stop data for each stop position collectively and accurately.

  The present invention detects the movement position of the transport device based on the output of the encoder and detects that the transport device has stopped at an inappropriate position that deviates from the normal stop position in a device that performs stop control. At least from the output of the encoder when the transport device is moved to the reference position side and the transport device is stopped with the reference position as the target position when it is detected that the stop has occurred at an inappropriate position. And a means for correcting stop data for the position.

  Preferably, in the movement of the transport device to the reference position side, the transport device is stopped at the reference position by an external sensor, and stop data for the reference position is corrected by the output of the encoder at that time.

  Particularly preferably, the reference position is a first reference position on one end side of the movement path of the transport apparatus, and the transport apparatus is further moved to a second reference position side on the other end side of the movement path to The sensor is stopped at the second reference position by a sensor, and the ratio between the actual output difference of the encoder from the first reference position and the output difference of the encoder from the first reference position on the stop data is obtained and transported. For each stop position of the device, the encoder output difference from the first reference position on the stop data is updated with the output difference multiplied by the ratio.

  In the present invention, correction is started by using the stop at an inappropriate position as a trigger, the transport device is moved to the reference position, the reference position is stopped as the target position, and the stop data at the reference position is corrected. Therefore, there is no need to provide a mark on each shelf of the rack and perform stop control based on the mark.

  According to the second aspect of the present invention, since the sensor is stopped at the reference position by an external sensor such as a fixed position sensor, accurate data for stopping at the reference position can be obtained. Then, when the output of the encoder at the reference position is used as an offset value, the offset amount can be easily corrected for each stop position.

  In the invention of claim 3, stop data for each stop position can be corrected by stopping at the first reference position and the second reference position using an external sensor. Since the first reference position and the second reference position are arranged on both ends of the travel path of the transport apparatus, in other words, the first reference position and the second reference position are both ends of the stroke of the transport apparatus. Since the distance between them is increased, the encoder output can be accurately corrected. In addition, stop data for each stop position can be corrected collectively.

  In the following, an optimum embodiment for carrying out the present invention will be shown.

  1 to 4 show an embodiment. In the figure, 2 is a stacker crane, 4 is a truck, and 6 is a traveling wheel. Reference numeral 8 denotes a travel motor, which is composed of, for example, a servo motor, and is provided with a travel drive system (not shown). Reference numeral 10 denotes a mast, and the elevator 12 moves up and down along the mast. Reference numeral 14 denotes a slide fork, which may be another transfer means such as a SCARA arm.

  Reference numeral 16 denotes a chain, which may be another suspension material such as a rope or a wire, 18 is a sprocket, and 20 is a counterweight. Then, the sprocket 18 is driven by a lifting motor (not shown) to stop the lifting platform 12 at a predetermined position. A fixed position sensor 22 is an external sensor such as a photoelectric sensor, and detects a mark 24 provided at a predetermined position along the mast 10. Among the plurality of marks 24, the mark at the lowest position is the origin mark, the mark at the highest position is the mark at the anti-origin, and the distance between them is the stroke.

  Other marks may be provided corresponding to a stop position 25 on a shelf (not shown), the mark 24 may be provided corresponding to all the shelves, or the mark 24 may be provided only for a part of the shelves. good. In addition, the origin and the opposite origin may or may not correspond to the bottom shelf or the top shelf. The fixed position sensor 22 detects the mark 24, and the sensor 22 is turned on when the lifting platform 12 stops at the correct stop position, and in other cases, the sensor 22 is turned off. The traveling motor 8 and the encoder of the traveling motor may be referred to as an internal sensor, and the fixed position sensor 22 may be referred to as an external sensor.

  In FIG. 2, 30 is a servo motor, which may be a lifting motor or a traveling motor, and 32 is a servo drive unit. The rotation speed of the shaft of the servo motor 30, the sprocket 18, or the traveling wheel 6 is read by the encoder, and the output pulses are accumulated by the counter 34 and input to the servo drive unit 32. The output of the counter 34 corresponds to the encoder output. The servo drive unit 32 obtains the position of the carriage of the lifting platform based on the output of the counter 34 and performs control so as to stop at a point that matches the counter value described in the stop position table 35. Reference numeral 36 denotes a correction unit, which starts a correction operation when the position sensor is off when the position where the mark 24 exists is stopped as a target position. In the correction operation, the elevator platform is lowered to the origin position or the carriage 4 is moved to the origin position via the servo drive unit 32. The offset value of the stop position table 35 is corrected at the origin position, and then moved up or down to the opposite origin position to correct the stroke. At this time, an elongation coefficient corresponding to the reciprocal of the chain elongation rate is obtained, and the data in the stop position table 35 is corrected. Reference numeral 38 denotes an origin correction unit that corrects data relating to the origin, and reference numeral 40 denotes a stroke correction unit that corrects a stroke when the vehicle moves up and down or travels to the opposite origin position.

  In the example of the stop position table 35 shown in FIG. 3, the counter value when stopped at the origin is stored as an offset value. For the counter-origin, the counter value difference from the offset value is stored. For an appropriate stop position between the origin and the non-origin, the difference between the offset value at the origin and the counter value is stored.

  FIG. 4 shows an algorithm of the embodiment, taking as an example correction of the lift position of the lift base. Raise and lower the elevator to an appropriate target position and stop. If it is stopped correctly, the home position sensor is turned on. If it is off, the correction operation is started. That is, the correction is triggered by the fact that the home position sensor is off at the stop position. In the correction operation, the lifting platform is moved up and down toward the origin, and the elevation by the encoder is not reliable in this case. Therefore, the position is controlled to stop using the fixed position sensor after being lowered to the position before the origin. Next, the offset value at the origin of the stop position table is updated with the counter value at the time of stopping at the origin.

  The elevator is moved up and down to the opposite origin, and similarly, stop control is performed using a fixed position sensor. Next, find the difference between the actual counter value at the anti-origin and the corrected counter value at the origin, and calculate the ratio between the counter value at the anti-origin before correction and the counter value at the origin before correction. The elongation coefficient is θ. The meaning of θ is the reciprocal of the elongation rate of the suspension member such as a chain, and is a stroke correction coefficient when viewed from the encoder output. The elongation coefficient θ is generally smaller than 1. Since the difference between the counter value and the origin is stored for each stop position in the stop position table, the difference before correction is multiplied by the expansion coefficient θ and updated.

  In the embodiment, the stop position is stored as an offset value with respect to the origin, and the difference from the origin is stored for other stop positions. On the other hand, when the counter values are stored as they are for all the stop positions, the table can be corrected by a method other than that shown in FIG. For example, the sensor is stopped at a fixed position sensor with respect to the origin and the counter-origin, and the table value is replaced with an actually measured counter value, and at this time, the elongation coefficient θ is obtained. For each halfway stop position, the difference between the counter value and the origin in the data before correction is multiplied by the expansion coefficient θ, and the corrected origin counter value is added and updated.

  In the examples, correction was performed for the lifting platform of the stacker crane. The type of the suspension material is arbitrary, but in the case of a chain, it is particularly important because the elongation is generally large. For example, the embodiment is particularly meaningful when a lifting platform for transporting heavy objects such as a liquid crystal substrate is lifted and lowered by a chain. In the embodiment, the lifting / lowering correction of the lifting platform is shown, but a change in the diameter of the traveling wheel 6 may be corrected.

  Further, as the transport device, an overhead traveling vehicle or the like other than the stacker crane may be used to correct the stop position of the lifting platform of the overhead traveling vehicle. Further, the travel position may be corrected for a tracked vehicle that travels on the ground by rail travel. In addition to this, an elevating shelf is known in which a large number of shelves are connected by a chain and moved up and down by driving the chain. In this case, if a fixed position sensor is provided on any shelf of the lifting shelf and it is not possible to stop at a predetermined height position, if correction is performed in the same manner as in the embodiment, each shelf of the lifting shelf is accurately positioned. Can be stopped.

In the embodiment, the transport device is stopped at the origin, which is the reference position, by an external sensor, and the encoder value at that time is set as a deviation amount, that is, an offset value. However, for example, the actual stop position may be obtained by an external sensor such as a distance sensor or a linear sensor, and the error may be used as a deviation amount, that is, an offset value, based on an encoder.

Side view of main part of stacker crane of embodiment The block diagram which shows the drive system of the servomotor in the Example, and its correction | amendment part The figure which shows typically the stop position table in an Example. The flowchart which shows the algorithm of the raising / lowering position correction in an Example

Explanation of symbols

2 Stacker crane 4 Cart 6 Traveling wheel 8 Traveling motor 10 Mast 12 Lifting platform 14 Slide fork 16 Chain 18 Sprocket 20 Counterweight 22 Fixed position sensor 24 Mark 25 Stop position 30 Servo motor 32 Servo drive unit 34 Counter 35 Stop position table 36 Correction Unit 38 origin correction unit 40 stroke correction unit

Claims (3)

In the transfer device that determines the moving position based on the output of the encoder and performs stop control,
Means for detecting that the transport device has stopped at an inappropriate position that deviates from the normal stop position;
When it is detected that it has stopped at an inappropriate position, the transport device is moved to the reference position side, and at least stop data for the reference position is obtained from the output of the encoder when the transport device is stopped with the reference position as the target position. And a means for correcting the transfer device. The movement of the transport device to the reference position side stops the transport device at a reference position by an external sensor, and corrects stop data for the reference position by an output of an encoder at that time. Transport device. The reference position is a first reference position on one end side of the movement path of the transport device,
Further, the transport device is caused to travel to the second reference position side on the other end side of the movement path, stopped at the second reference position by the external sensor, and the actual output difference of the encoder from the first reference position; Find the ratio of the encoder output difference from the first reference position on the stop data,
The difference in encoder output from the first reference position on the stop data is updated for each stop position of the transport device by multiplying the output difference by the ratio. The transfer apparatus according to claim 2.

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