JPH0550385A - Position controller of gantry robot - Google Patents

Abstract

PURPOSE:To improve the positioning accuracy of a moving gantry robot by pulling the timing belt stretched on a guide rail. CONSTITUTION:For example, the gantry robot 220 arranged on the top of a machine tool runs on a guide rail 200 and carries workpieces and jigs by means of the hand secured to an arm 280. A timing belt 21 is belted on the rail 200 and meshes with the driving timing pulley 250 of the gantry robot 220. The timing pulley is rotated by a specified quantity by a servo motor, and the gantry robot is moved by the rotation quantity of the timing pulley. On the rail 200, a magnetism generator 265 is provided, and the detector 260 of the gantry robot detects the location of the magnetism generator 265. At this moment, the number of pulses which are output to the servo motor is compared, correcting the error. Positioning accuracy is improved by this correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position control device for a gantry robot used in a device such as a lathe cell.

[0002]

2. Description of the Related Art A lathe cell is equipped with a combined machining lathe, a stock device for workpieces and jigs supplied to the combined machining lathe, and a gantry robot for conveying workpieces and jigs to achieve unmanned machining for a long time. This equipment is disclosed in, for example, Japanese Patent Application Laid-Open No. 2-71948. The gantry robot disclosed in the above publication is provided with a straight guide rail connecting the lathe and the upper part of the stock device, and the gantry robot travels by being guided by this rail and stops at a predetermined position to execute the service. Is configured. A timing belt with rack-shaped teeth is stretched on the rail, and the gantry robot has a timing pulley that meshes with this timing belt.
A mechanism for pulling the timing belt by this timing pulley is driven on the rail. The amount of rotation of the timing pulley is controlled by the servo motor, and accurate positioning is achieved.

[0003]

The timing belt is
Since it is stretched over the timing pulley and meshes with it, it must have flexibility. Although the tensile rigidity is increased to prevent the occurrence of positioning error due to elongation, elongation due to use is unavoidable, and if the movement distance is long, such as with a lathe cell, the cumulative error cannot be ignored. Become. Therefore, the present invention provides a position control device capable of correcting an error due to expansion and contraction of a timing belt.

[0004]

In the position control device of the present invention, a magnetizing body is arranged at a predetermined position on a guide rail on which a timing belt is stretched. The distance from the origin position to the magnet is measured accurately. A gantry robot having a timing pulley that meshes with a timing belt includes a detector. The timing pulley of the gantry robot is driven by a servo motor.

[0005]

The pulse required for moving to the service position is supplied to the servo motor of the gantry robot, and the gantry robot travels toward the service position. It emits a signal when the detector of the gantry robot reaches the top of the magnetizer. When the number of pulses when receiving this signal is different from the initial value, the difference is corrected and the initial value is updated.

[0006]

1 is a perspective view showing the whole lathe cell for carrying out the present invention, FIG. 2 is a front view, and FIG. 3 is a plan view. The lathe cell, which is generally denoted by reference numeral 1, includes a combined machining lathe 10, a stocker device 30, a transfer device 20, and a control device 90. The combined machining lathe 10 includes, for example, two spindles and two tool rests, and the first spindle and the second spindle have the same machining ability and are independently controlled. The first turret that cooperates with the first spindle and the second turret that cooperates with the second spindle are turret turrets having the same ability and are arranged back to back. The turret turret is equipped with multiple tools to process workpieces chucked on each spindle. The two spindles have an indexing function, and the work can be milled by using a rotary tool. It is possible to complete all the machining steps by subjecting the workpiece chucked by the first spindle to the first machining step, then passing the workpiece to the second spindle side and performing the second step. The machining program is managed by the NC controller 95.

The tool rest is capable of automatic tool exchange, and the mounting and dismounting of the work on the spindle is also automated. Further, the jaws of the chuck mounted on the spindle can be automatically replaced, and various works can be dealt with. The stock device 30 includes a pallet stock area S1 and a jig / tool stock area S2. The work is directly sent from the stock area S1 of the pallet to the processing area W of the lathe. The jigs and tools are conveyed from the stock area S1 of the pallet to the stock area S2 of the jig and stand by, and are supplied from the stock area S2 of the jig and tool to the machining area W as necessary.

A stocker 40 is mounted on the base of the stock device 30 so as to be movable along the axis X3. Stocker 4
A hand that is detachably attached to the arm 280 of the gantry robot 220 is housed in the 0. As types of hands, there are a tool hand 282 handling a tool, a jaw hand 284 handling a jaw, a work hand 286 handling a work, and the like.

On the flange portion of the stocker 40, the tool 1
60 and jaw 170 are housed. These tools 16
0 and the jaw 170 are carried from the pallet 80 onto the stocker 40 by using the tool hand 282 and the jaw hand 284, and are further supplied to the tool rest and the spindle of the lathe 10. That is, the stocker 40 has a buffer function in the tool-jaw supply path. If necessary,
The tools and jaws on the pallet 80 can be directly supplied to the lathe 10. The out-of-machine measuring device 50 connected to the stocker 40 includes the V block 502 and the measuring means 510 on the base 500, and measures the machined work in comparison with the master model. On the base of the stocker device 30, a traveling carriage 60 is movably mounted along an axis X4 parallel to the axis X3. The traveling carriage 60 supports the fork device 70 so as to be vertically movable along the axis F in the vertical direction.

The fork device 70 includes a cross beam 705 and arms 710 protruding from both ends of the cross beam 705. The fork device 70 is vertically controlled by a screw shaft 720 driven by a servomotor 610 on the traveling carriage side. The arm 710 of the fork device 70 holds the uppermost pallet 800 of the pallet group 80 supplied in the stacked state and lifts the pallet 800 to the service position. In the service position, the hand of the gantry robot 220 grips the work 150, tools, jaws, etc. on the pallet 800 and conveys them to a designated place. Each pallet 800 has its own data
A memory 815 for recording data of members such as works, tools and jaws placed on a pallet is provided. The horizontal beam 705 of the fork device 70 has a read / write head 917, and reads / writes data of each pallet 800.

The data in the pallet memory 815 is sent to the control device 90, and the transfer program is determined. With this transfer program, the stock device 30 and the transfer device 2
0 is controlled. The pallet stock area S1 is 2
The stations 820 and 825 are provided. The pallet group 80 is carried into one station 820 by a forklift or the like. The pallet in which the transportation of the members is completed and the pallet in which the processed work is placed are transported to the station 825 on the unloading side. When all the pallets are loaded in the carry-out station, the pallet group 80 is carried out of the cell by a forklift or the like. A chip conveyor 190 and a chip bucket 195 are provided at the rear of the lathe 10 to collect chips and cutting fluid.

FIG. 4 is an explanatory view showing the outline of the carrying device. The rail 200 of the transfer device 20 is composed of a highly rigid girder, and is linearly arranged by connecting the upper part of the pallet station and the upper part of the lathe 10. A casing 222 of the carriage of the gantry robot 220 is movably mounted on the rail 200 by wheels as shown. A timing belt 210 is stretched on the upper surface of the rail 200, and both ends of the timing belt 210 are fixed on the rail 200 by stoppers 212 and 214, respectively.

Casing 2 of the gantry robot 220
The traveling drive device 230 provided in the unit 22 has a servo motor 232. The pulley 236 driven by the motor shaft 234 drives the pulley 240 via the timing belt 238 and the shaft 24 integrated with the pulley 240.
2 drives a driving timing pulley 250. Guide rollers 252, 2 are provided on both sides of the timing pulley 250.
54 is arranged. The timing belt 210 laid on the upper surface of the rail 200 is guided by the guide rollers 252 and 254, and is stretched over the timing pulley 250. The timing belt 210 has rack teeth,
The rack teeth mesh with the pin-on teeth of the timing pulley 250. Therefore, when the timing pulley 250 is rotated by a predetermined rotation amount by the servo motor 232, the timing pulley 250 is moved by the timing belt 210.
The gantry robot 220 runs along the rail 200 for a predetermined distance while being rotated while being engaged with. When driving, the timing pulley 250 and the timing belt 21
Since there is no slippage at 0, the positional error due to slippage is eliminated and accurate positioning is achieved.

However, in the lathe cell embodying the present invention, the length of the rail 200 is long and the length of the timing belt 210 to be laid is as long as 5,000 mm. Although the timing belt 210 has high tensile rigidity and an extremely small amount of elongation per unit length, the amount of elongation due to use cannot be ignored when the total length becomes long. In the lathe cell 1, the main stop positions of the gantry robot 220 on the rail 200 are the service position P1 of the pallet 800, the service position P2 of the stocker 40, and the service position P3 of the lathe 10. It is necessary to precisely control the coordinate position of the axis 220 on the axis B.

Therefore, in the present invention, a means for measuring the distance from the origin position of the gantry robot 200 is provided at a key position on the rail 200, and the difference from the travel distance by the servo motor of the gantry robot 200 is checked to perform correction. It is a thing. As the position detecting means, a magnetizing body arranged on the rail 200 and a magnetic detector mounted on the casing side of the carriage of the gantry robot are used.

FIG. 5 shows the details of the position detecting means. A magnet 265 is fixed to the rail 200 by a plate 267 and a dog 275 is fixed to the plate 276. Casing 222 of gantry robot 200
Is a timing pulley 250 and guide rollers 252, 2
54, equipped with a detector 260 and a limit switch 270.

FIG. 6 shows a mounting device for the magnetized body and the detector. The magnetized body 265 is mounted on a plate 267, and the plate 267 is fixed to the rail 200 via a slot 268 by bolts. The height position of the magnetism generating body 265 is adjusted using the elongated hole 268. The detector 260 has a plate 262.
The plate 262 is fixed to the casing 222 with bolts through the long holes 263. The lateral position of the plate 262 is adjusted using the slot 263. The detector 260 is kept in a non-contact state of about 1 millimeter with the gap between the detector 260 and the magnetizer 265.
When the detector 260 attached to the magnet reaches the position directly above the magnetism generating body 265, the magnetism of the magnetism generating body 265 is detected and a signal is emitted. The position where the signal is emitted is highly accurate.

FIG. 7 is an explanatory view showing the arrangement position of the position detecting means and the correction method. The gantry robot 220 travels on the rail 200 along the axis B, and, for example, the end position PO on the loading / unloading side of the pallet is the coordinate origin BO. A detector 260 having a first magnetism generating body 265A disposed at a service position P1 between the stocker and the gantry robot.
Can detect the magnetism from the magnetism generator even while traveling. However, the accuracy of the detection position is naturally improved when the traveling speed is low. Therefore, it is desirable to dispose the magnetizing body at the service position where the gantry robot 220 stops. The distance L1 on the rail 200 from the original position PO to the first magnetic body 265A arranged at the service position P1 of the stocker can be accurately measured. The gantry robot 220 has a controller 9
It moves from 0 by the number of pulses corresponding to the traveling distance given to the servo motor 232.

Now, it is assumed that the gantry robot 220 receives a command to move a distance L1 from the origin position PO (origin coordinates BO) to the stocker service position P1. The output required for moving to the target coordinate B1 corresponding to the position P1 is given to the servo motor 232 of the gantry robot 220 as the number of pulses, and the timing pulley 250 meshes with the timing belt 210 and travels toward the target coordinate B1. .. Gantry robot 220
When reaches the position P1, the detector 260 detects the magnetism of the magnetizer 265A and emits a signal. At this time, in principle, the pulse corresponding to the coordinate B1 by the servo motor 232 coincides, but an error may occur due to the elongation of the timing belt 210 or the like.

FIG. 8 shows the machine coordinates of the axis B on the horizontal axis and the axis B on the vertical axis when the elongation of the belt is directly proportional to the distance.
It is a graph when the control coordinate of is taken. Although the belt is adjusted at the time of assembling, the user also makes adjustments at the time of starting and after the belt is re-tensioned, for example. In FIG. 8, a: detection position of the first magnetizer during adjustment b: detection position of the second magnetizer during adjustment c: detection position of the first magnetizer after re-tension d: after re-tension Detected position of the second magnetizer e: Arbitrary point during adjustment f: Arbitrary point after re-tensioning Δa: Belt extension amount of the first magnetizer Δb: Belt extension amount of the second magnetizer Δe: At the arbitrary point The amount of belt elongation.

When the elongation coefficient is k, k = (Δb−Δa) / (ba) is obtained. In addition, the position coordinate f of the arbitrary point after re-tensioning
Is calculated by f = e-[[Delta] a + k (e-a)]. For example, if a = 1000 b = 3000 c = 999 d = 2995 e = 2000, k is k = [(3000-2995)-(1000-99)
9)] / (3000-1000) = 1/500. Moreover, f is f = 2000- [1+ (2000-1000) / 50
0] = 2000−3 = 1997.

Next, the flow of processing for correcting the parameters of the control device and instructing the replacement of the belt by the expansion and contraction of the belt will be described. FIG. 9 shows the allowable range and the limit range of expansion and contraction of the belt in the control coordinates of the axis B. When the gantry robot moves in response to the command value, when the belt stretches, the magnetizing body is detected before the command value and the switch turns on. When the belt contracts, the switch does not turn on even if the command value is exceeded. If the expansion / contraction of the belt exceeds the allowable range, the allowable range is set. If the expansion / contraction of the belt exceeds the allowable range, it will be corrected if it is within the limit range.

FIG. 10 shows a processing flow. Step 1
At 000, the position up to a predetermined magnetizing body at the time of assembling and adjusting the carrying device is detected to obtain the coordinate value a1 on the axis B. In step 1010, the coordinate value a1 and the allowable value ε of belt elongation (contraction) are stored in the control device. In the lathe cell that has started to operate on the user side, in step 1020, for example, the position detection of a predetermined magnetizing body is executed at the start of every morning, and the coordinate value a2 at that time on the axis B is obtained. In step 1030, it is determined whether a2 is within the allowable range from a1, and if it is within the allowable range, the process proceeds to step 1040 and no processing is required. In step 1040,
Although the belt elongation exceeds the allowable range, judge whether it is within the limit range. If it is within the limit range, the process proceeds to step 1060, correction calculation of the belt position is executed, and step 1070 is executed.
The coordinate value a1 is rewritten to the corrected value with. If the stretch of the belt exceeds the limit, proceed to step 1080,
An alarm is displayed and the belt is replaced in step 1090.

In the processing described above, the amount of elongation of the belt is detected and the amount of elongation is compared with the allowable value and the limit value. Instead of comparing the elongation amount itself, the elongation rate can be calculated and compared with the allowable value or the limit value of the elongation rate. The elongation rate α is expressed by α = [(number of command pulses / number of pulses when detection switch is ON) -1]. This elongation rate α is set to the allowable value α1 and the limit value α2.
The position correction and the belt replacement processing are executed in comparison with.

The above processing is performed by the gantry robot 220.
May be performed each time the vehicle stops at the service positions P1 and P2, or may be performed every predetermined number of stops. In any case, in a gantry robot that runs with a servomotor for a long distance of about 5,000 mm using a timing belt as a reference, the data for controlling the servomotor is corrected at a service position that requires an accurate stop position. Since it is updated, accurate robot work can be performed, and the number of maintenance steps can be reduced.

[0026]

As described above, the present invention has a linear guide rail, a timing belt stretched on the guide rail,
A gantry robot supported by a guide rail and a timing pulley that meshes with a timing belt as a driving device for the gantry robot are provided. The timing pulley is driven and controlled by a servo motor to control the moving distance of the gantry robot. A magnetizing body is arranged at a predetermined position on the guide rail, and a signal is emitted when a detector provided in the gantry robot passes over the magnetizing body. When the movement amount of the gantry robot to which the pulse number of the servo motor is given is different from the position of the magnet body, the pulse number is corrected based on the position of the magnet body. By this control processing, the positioning error caused by the expansion and contraction of the timing belt can be automatically corrected. Therefore, accurate positioning is always achieved, and the reliability of transportation and delivery of members by the gantry robot is improved. Since the guide rail is arranged on the upper part of the lathe cell, the workability is poor and a lot of man-hours are required for tensioning and adjusting the timing belt. However, according to the present invention, maintenance and the like are simplified and productivity is improved. Also improves.

[Brief description of drawings]

FIG. 1 is a perspective view of a lathe cell embodying the present invention.

FIG. 2 is a front view of a lathe cell.

FIG. 3 is a plan view of a lathe cell.

FIG. 4 is an explanatory view showing a drive device of a gantry robot.

FIG. 5 is a front view of a gantry robot.

FIG. 6 is an explanatory diagram of a position detection device.

FIG. 7 is an explanatory diagram of operation.

FIG. 8 is a graph showing the relationship between the machine coordinates of axis B and the control coordinates.

FIG. 9 is an explanatory view showing an allowable range and a limit range of expansion and contraction of the belt.

FIG. 10 is a flowchart of processing.

[Explanation of symbols]

 1 Lathe Cell 10 Combined Processing Lathe 20 Conveyor 200 Rail 210 Timing Belt 220 Gantry Robot 230 Drive 250 Timing Pulley 260 Detector 265 Magnetizer

Claims (3)

[Claims] 1. A guide rail linearly arranged, a timing belt stretched on the guide rail, a gantry robot having a casing movably supported by the guide rail, and a gantry robot provided in the casing. A drive device having a timing pulley that meshes with the timing belt and a servo motor that drives the timing pulley, a magnetizing body arranged at a predetermined position on the guide rail, and a gantry robot casing equipped to detect the magnetism of the magnetizing body. A position control device for a gantry robot, comprising a detector that emits a signal and a unit that corrects the number of pulses output to the servomotor based on the signal from the detector. 2. The position control device for a gantry robot according to claim 1, wherein the magnet switch is arranged at a coordinate position of the origin of the gantry robot and at a position where the gantry robot stops to execute a service. 3. A guide rail, a transmission body stretched over the guide rail, a gantry robot having a casing movably supported by the guide rail, and a transmission body mounted in the casing. A drive device for moving the gantry robot relative to the guide rail by a predetermined number of pulses along the guide rail, a detected object disposed at a predetermined position on the guide rail, and a casing mounted on the gantry robot. A detector that detects a detection object and emits a signal, and when the transmission signal does not emit within the predetermined pulse range corresponding to the position of the detected object due to expansion or contraction deformation of the transmission object, A position control device for a gantry robot, comprising means for instructing replacement of the transmission body.