JPH0733209A - Drive control method of picking device - Google Patents

Abstract

PURPOSE:To aim at shortening of the track time of picking work by comparing natural frequency of a manipulator driven mechanism system in each axial direction and stopping the shaft of lower natural frequency first. CONSTITUTION:Regarding a picking device which takes out the desirable article from an out-going rack by an orthogonal three axle manipulator, as a driving method of simultaneously driving two axles or a plurality of axles among the manipulator driven axles, for example, in case of simultaneously driving two axles, a shaft of lower natural frequency is stopped first. Thus amplitude of the residual frequency in the direction of the shaft of lower natural frequency starts damping earlier than the shaft of high natural frequency. When the shaft of high natural frequency stops, the amplitide of the residual frequency of the shaft which stopped eariler has become sufficiently small. The time required for damping of the residual frequency is short if the natural frequency is high. Therefore frequency settling time after stopping can be set short and the tact time of the picking work can be shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a picking device, and more particularly to a picking device for shortening a tact time as a drive control method for a picking device having a flexible mechanism.

[0002]

2. Description of the Related Art Conventionally, as a method for improving the tact time with a picking device, in addition to speeding up by increasing the acceleration / deceleration, damping control by an acceleration / deceleration curve that hardly causes residual vibration when stopped is used. There is. On the other hand, a picking device for improving the tact time in consideration of the occupied space and the arrangement of constituent parts is described in, for example, Japanese Patent Laid-Open No. 4-99798.

[0003]

In the conventional method, when the manipulator is driven at a high speed, the mechanical member of the manipulator is elastically deformed, and so-called residual vibration occurs in which the vibration continues when stopped. In order to secure the positioning accuracy, the time for damping the residual vibration, that is, the vibration settling time is set to be long, and there is a problem that the tact time cannot be shortened.

An object of the present invention is to provide a picking device which has a short takt time for picking work.

[0005]

A picking device provided with a shipping rack for storing articles, wherein a desired article is taken out from the shipping rack by a manipulator, and a drive for simultaneously driving two or more of the manipulator drive shafts. As a method, it is achieved by comparing the natural frequencies of the drive mechanism systems of each axis of the manipulator, and generating a drive pattern so as to stop the axis in the direction in which the natural frequency of the drive mechanism system is low first. It

[0006]

When, for example, two manipulator drive shafts are driven simultaneously, the amplitude of the residual vibration in the direction of the shaft having the low natural frequency is reduced by stopping the shaft having the low natural frequency first. Attenuation starts earlier than the axis with the higher number. When the shaft with a high natural frequency stops, the amplitude of the residual vibration of the previously stopped shaft is sufficiently small. If the natural frequency is high, the time required for damping the residual vibration is short. Therefore, the vibration settling time after the stop can be set short. Thus, according to the present invention, it becomes possible to provide a picking device having a short tact time for picking work.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic diagram of a compact disc (hereinafter referred to as CD) picking device according to an embodiment of the present invention.
Shown in. The picking mechanism is the hand 1 that holds the CD 11.
Cartesian coordinate type manipulator 20 having a function of moving 2 in three directions including a traveling direction, a hand arm direction, and a lifting direction.
And a rack 10 installed behind it. The CDs 11 are stored in the racks 10 in a form filled in the magazines 8, and each magazine 8 has different types of Cs.
D11 is stored. A roller conveyor 9 is installed under the rack 10, and a plurality of shipping buckets 7 for receiving the CDs 11 taken out from the rack 10 are placed on the roller conveyor 9. The shipping bucket 7 is carried out toward the next work area.

The operation procedure of the picking mechanism will be described below with reference to FIG. FIG. 3 is an operation flowchart in which a series of flows from warehousing to shipping is divided for each operation. First, operation A is a desired CD from the work origin.
This is an operation of moving the hand at high speed in the XZ plane to the position of the magazine in which is stored. Here, the work origin is
The X-axis direction is the center of the rack, the Z-axis direction is the upper part of the shipping bucket, and the Y-axis direction is the retracted position so that the tip of the hand does not interfere with the rack. After the movement of the hand on the XZ plane is completed, the operation B is an operation of inserting the hand into the rack at high speed until just before the CD. After that, the operation C is to bring the hand closer to the CD at a low speed. The operation of simultaneously grasping the number of CDs taken out by the hand is D. The operation of ejecting the stored CD after completing the gripping of the CD is E, and when the lower end of the CD exceeds the upper end of the magazine, the hand is moved in the Y-axis direction at high speed to extract it from the rack. It is an operation F. After that, the operation G is to move the hand to the work origin at high speed, the hand is further inserted into the shipping bucket at a high speed (operation H), the hand is opened, and the CD taken out to the shipping bucket is delivered (operation I). One picking operation is completed by the operation J of retracting the hand to the work origin. These series of operations are repeatedly executed. Simultaneous driving in this embodiment is operations A, E, and G. This is a method of shortening the settling time in the movement stop operation of the operations A, E and G.

Next, the drive control method of the mechanism will be described with reference to FIG. FIG. 4 shows the relationship between the acceleration, speed and moving distance of the mechanism. In the figure, short distance travel,
The three movement states of the long-distance movement and the movement of the distance that transits from the short-distance movement to the long-distance movement state are also shown.
In short-distance movement, acceleration and deceleration are continuously performed, and the movement distance is controlled by changing the acceleration / deceleration time while keeping the peak value of acceleration constant. In this state, the maximum value of the speed required for the mechanism increases as the moving distance increases. In the state, the speed reaches the maximum value Vm. If the moving distance becomes longer and shifts to this state as a boundary, the acceleration and deceleration waveforms are kept constant, and a period during which the speed is constant is set between acceleration and deceleration. To control. After that, the residual vibration settling time is set,
This completes the operation. Here, the moving distance to reach the state is Lsw.

As an example of the drive waveform, in the case of a uniform acceleration waveform, the switching distance, the switching time, and the moving time are described separately for short-distance movement and long-distance movement.

[0012]

[Table 1]

Here, short-distance movement is defined as movement that decelerates before reaching the maximum speed, and long-distance movement is defined as movement that reaches the maximum speed, decelerates after moving at a constant speed.

An example of simultaneous driving in the XZ plane will be described based on the above-described operation and driving waveform. FIG. 1 shows an example of a control algorithm for simultaneous driving. The axis with the lowest natural frequency is given the upper rank, and each axis is ranked. At the time of simultaneous driving, the ranks are compared with each other, and a drive pattern is generated so that axes of higher ranks stop first. Here, assuming that the natural frequency in the X direction is fx and the natural frequency in the Z direction is fz, and the residual vibration waveform after stopping is damped to the set accuracy with n waves, the times Tsx and Tsz required for damping are Indicated by 1.

[0015]

[Equation 1]

Here, Tsx is the time required for attenuation in the X direction, and Tsz is the time required for attenuation in the Z direction.

[0017]

[Equation 2]

From the condition that the natural frequency is expressed by the equation 2, the time required for settling may be short in the Z direction where the natural frequency is high. In this case, the X axis has a higher rank. Therefore, the settling time required for simultaneous driving of the XZ plane may be shortened by stopping the X direction having a low natural frequency first. FIG. 5 shows a schematic diagram of the relationship between the velocity pattern and the residual vibration. By stopping the axis with the low natural frequency first, the amplitude of the residual vibration in the direction of the axis with the low natural frequency starts to decay earlier than the axis with the high natural frequency. When the shaft with a high natural frequency stops, the amplitude of the residual vibration is sufficiently small. Therefore, the vibration settling time after the stop can be set short. By setting the maximum speed and acceleration of each axis from the relational expressions of the moving time shown in Table 1, it is possible to stop driving the axis in the direction of low natural frequency first. By shortening the settling time, the takt time for picking work can be shortened.

[0019]

According to the present invention, since the settling time required for simultaneous driving can be set short, it is possible to obtain a picking system with a short tact time for picking work.

[Brief description of drawings]

FIG. 1 is a flowchart of a drive control method for simultaneous driving according to an embodiment of the present invention.

FIG. 2 is a perspective view of a CD picking device according to an embodiment of the present invention.

FIG. 3 is an operation explanatory view of the CD picking device according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram of a relationship among acceleration, speed and movement distance of the mechanism according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of a relationship between a velocity pattern and residual vibration according to an embodiment of the present invention.

[Explanation of Codes] 1 ... Traveling frame, 2 ... Traveling motor, 3 ... Traveling carriage,
4 ... Elevating motor, 5a, 5b ... Timing belt.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Matsubara 603 Kandamachi, Tsuchiura-shi, Ibaraki Hitate Works Co., Ltd. Tsuchiura factory

Claims (1)

[Claims] 1. A picking device comprising a shipping rack for storing articles, wherein a desired article is taken out of the shipping rack by an orthogonal three-axis manipulator, as a drive control method for simultaneously stopping movement of a plurality of drive shafts of the manipulator. , The natural frequency of the drive mechanism system of the manipulator obtained by the drive shaft, the drive transmission element, and the moving element is compared in each axial direction, and the axis having the low natural frequency is stopped first. Drive control method for picking device.