JPH0543603B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a steady rest method for reducing the swing of a stacker crane suitable for use as a cargo handling machine in automated warehouse equipment.

[Background of the invention]

A stacker crane is usually used as a machine for carrying out cargo handling work in automated warehouses. The stacker crane travels on rails laid on the floor between warehouse shelves, lifts and lowers the cargo loaded onto the elevating body at the entrance to the destination shelf, and uses the fork device installed on this elevating body. Then, the user carries out the work of storing the baggage on the desired shelf. On the other hand, the cargo stored on the shelves is loaded onto the elevating body using a fork device, and the crane is driven to take the cargo out to the exit. In such work using a stacker crane, it is essential to move the crane to a predetermined position and stop it, but it is common for the stacker crane to sway considerably immediately after it has stopped. It is not desirable for safety to operate the fork device with large vibrations. Therefore, the fork device is operated only after the vibration has subsided. However, if the vehicle waits for the vibration to naturally attenuate after the vehicle has stopped, cargo handling efficiency will deteriorate.

For this reason, various steady rest devices have been developed for forcibly damping the swing of stacker cranes. Examples of this type of technology include:
Those disclosed in Japanese Utility Model Publication No. 49-10624 and Japanese Utility Model Publication No. 52-3267 are known.

Now, this type of conventional device requires a special device or mechanism for applying a damping force against the vibration of the stacker crane. When aiming to increase the size of the stacker crane or increase the traveling speed in order to improve cargo handling efficiency,
Attempting to deal with this problem with a conventional mechanical anti-sway device would result in an undesirably large or complicated anti-sway device.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for preventing the stacker crane from swinging, which is simple in structure and can reduce swinging immediately after the stacker crane stops.

[Summary of the invention]

The present invention inputs the lifting weight of the stacker crane and the lifting position of the lifting body, and based on the period of the stacker crane obtained using the input amounts, 1/4 to 1/4 of the period. Calculate twice the deceleration time, and from the time when the stacker crane reaches near the target stop position, decelerate the stacker crane running motor for the calculated deceleration time, then operate the brake to stop the stacker crane. It is characterized by decelerating and stopping.

[Embodiments of the invention]

Before describing specific embodiments of the present invention, the principle of the steady rest control method will be described. In a normal stacker crane, the relationship between the vibration of the crane post or the lifting body (hereinafter simply referred to as vibration or vibration of the crane) during the stopping operation at the target position is as shown in FIG. In other words, the crane is
It vibrates at a vibration period T of a natural frequency that is closely related to the lifting weight m and the lifting position l of the lifting body. In FIG. 4, it is assumed that there is no initial vibration of the elevating body. If the crane has an initial vibration when it stops, the phase and amplitude of the initial vibration and the phase and magnitude of the acceleration are determined by the fifth
The state is as shown in FIGS. Figure 5 shows the phase of runout at the start of braking during a stop operation when φ = 0°, Figure 6 when φ = 45°, Figure 7 when φ = 90°, and Figure 8 when φ = The case of 135° is shown.
As you can see, the phase of runout at the start of braking φ
Depending on the difference, the runout situation after stopping varies greatly. FIG. 9 shows the phase of the runout at the start of braking and the relationship between the damping of the runout. In FIG. 9, the solid line shows the maximum value of runout, and the broken line shows the time until the runout falls below ±5 mm. As is clear from Fig. 9, when the phase φ of the runout at the start of deceleration is between 90° and 180°, that is, when deceleration control is performed in the range where the differential value of acceleration is positive, the runout at the time of stopping becomes smaller. .
On the other hand, if deceleration braking is performed in a range where the differential value of acceleration is in the negative range, vibration will be aggravated and vibration will increase when stopped. Therefore, in the embodiment of the present invention, before the brake is applied for stopping, the period T determined from the natural frequency is
Decelerate the movement motor for 1/2 the time to make the direction of acceleration of the stacker crane positive, and in this state decelerate to a stop using the brake to reduce vibration when the crane stops. do.
The period T is determined by the following formula.

T=2π/ω...(1) Also, the angular frequency ω can be obtained from the simple model of the stacker crane using the following equation.

Here, K: Constant m: Weight of the elevating body g: Deceleration l: Distance to the center of mass of the main column system (i.e., a function of the elevating position l of the elevating body) Therefore, the deceleration time by the traveling motor,
That is, the time T _f from 1/4 to 1/2 of the period T has a value within the range of the following equation.

Then, deceleration and stopping by the brake after deceleration by the motor is started after deceleration for this T _f time.
By the way, in stop control of a stacker crane, weight is required to prevent swinging and to stop the crane at a target position. Therefore, even when performing steady rest control as described above, it is necessary to be able to stop the vehicle at the target position. This will be discussed using FIGS. 10A to 1C. Now, as shown in Fig. 10A, when the target position P ₀ (considered as the distance from the origin) is specified, the stacker crane starts moving.
Its current position P changes. Assuming that the speed pattern of the Stadka crane is given as shown in Figure 10B, when P approaches _P0 ,
The traveling speed of the Stadka crane is v ₁ . At this point, since the speed control pattern for the steady rest has been determined, the start timing t ₀ of the steady rest control can be determined. That is, this timing is the point in time when the difference between the traveling position P of the stacker crane and the target position P ₀ becomes the distance a _s that the stacker crane travels during the steady rest control period. That is, P ₀ -P=a _s (4) This distance a _s is represented by the shaded area shown in FIG. 10C. The deceleration of the travel motor is α, the deceleration during braking is g, and the deceleration time of the travel motor is
T _f is the speed at the end of deceleration in the travel motor.
v ₂ , and the time from the start of braking to the stop of the stacker crane is T _x , the following relational expression can be derived.

v ₆ = v ₁ −α・T _f ……(5) O=v ₂ −gT _x ……(6) a _s = v ₁・T _f −1/2(v ₁ −v ₂ )・T _f +1 /2v ₂ ·T _x ...(7) When formulas (5), (6), and (7) are transformed into formulas that do not include T _x and v ₂ , a _s is expressed as the following formula.

a _s = v ₁・T _f −αT _f ² + (v ₁ − αT _f ) ² / 2g ...(8) As can be seen from equation (8), set constants for v ₁ , α, and g. Then, if T _f is found, a _s can be obtained.

Based on the above, embodiments of the present invention will be described below.

FIG. 1 shows an operational flow diagram in one embodiment of the present invention. FIG. 2 shows a block diagram of an embodiment of the present invention. FIG. 3 shows a schematic diagram of an automated warehouse to which an embodiment of the present invention is applied.

First, an outline of a stacker crane used in an automated warehouse will be explained with reference to FIG. A stacker crane 2 is arranged along a rack 1 for storing incoming goods. The stacker crane 2 is placed on rails 3 laid on the floor between the racks, and can run on the rails 3 by running wheels and a running motor 4 that provides driving force to the wheels. Although not shown, a guide roller is provided at the top of the stacker crane, and the crane runs along a guide rail. On the other hand, the elevating body 5 is provided with fork equipment for storing loads in the rack 1 and carrying in the loads stored in the rack. The elevating body 5 is moved up and down by an elevating motor (not shown). Travel distance detection methods for detecting the travel distance of a stacker crane include methods using a striker installed on the ground, methods using a pulse encoder, etc., and methods using other methods such as sound waves. The position of the elevating body 5 can be detected by measuring the amount of winding of the elevating rope, in addition to the same method as the traveling distance detection. The weight of the elevating body is obtained by multiplying its own weight by the weight of the load, but since the own weight does not change, it can be detected, for example, by measuring the weight of the load with a load meter. In addition, the load current applied to the lifting motor is proportional to the weight of the lifting object, so
It can also be detected by measuring this load current.

Next, the hardware configuration in one embodiment of the present invention will be explained with reference to FIG. The travel motor 4 and brake 11 are controlled by a travel drive device 12. The traveling drive device has a function of changing the speed of the motor 4 according to an input speed pattern (speed control function).
have. The lifting motor 14 is driven by electric power supplied from a power source 15, and raises and lowers the lifting body. Note that the elevating control will be omitted here. The current transformer 16 and the load current of the motor 14 are detected and supplied to the computer 21 as a physical quantity corresponding to the total weight m of the elevating body 5. Pulse detector 1
Reference numeral 8 is for detecting the ascending and descending position l of the elevating body 5, and the detected physical quantity l is supplied to the computer 21. The pulse detector 13 is for detecting the traveling distance P of the stacker crane, and this P is supplied to the computer 21. l ₀ is the target position of the elevating body and is input to the calculator 21. P ₀ is the destination address of the run and is input to the computer 21 . calculator 2
Data 19 of the stacker crane structure is input in advance to 1, and for example, the vibration natural frequency of the crane, the vibration constant of vibration according to the vertical position of the elevating body, the damping constant, etc. are stored. calculator 21
uses such various data on the crane side, each detected value, and each set input value to calculate the control amount to reduce the swing when the stacker crane stops moving, and then calculates the control amount to reduce the swing when the stacker crane stops moving. Output to the drive device 12.

Below, the calculation of this control amount and output control will be explained in the first section.
This will be explained using the operational flow shown in the figure. Various data (for example, v ₁ , α, g, K) and control program necessary for this control are input into the computer 21 in advance,
Assume that it is stored in internal memory. When a work command is given to the stacker crane 2, the computer 21 determines the target position P ₀ to which it should move and the target lifting/lowering position l ₀
Enter. Thereby, the computer 21 calculates a speed pattern and outputs it to the traveling drive device 12.
The traveling motor 4 is driven by the traveling drive device 12, and the stacker crane starts traveling.
When the stacker crane starts traveling, processing for steady rest control is also started. First, the detection values l, m, and p of each detector are input (step F1).
The deceleration time of the traveling motor is determined by the input l and m.
Calculate T _f (step F2). This uses equations (1) to (3). Next, the pre-stored v ₁ ,
Using α, g, and T _f obtained in step F2, (8)
The distance a _s that the crane travels during the steady rest control period is calculated using the formula (step F3). Step F4
Then, it is checked whether the steady rest control start timing has arrived, and if not, the process returns to step F1. When the stacker crane travels to the point where a _s remains until reaching the target position P ₀ , steady rest control using T _f determined in step F2 is started. first,
At this point t ₀ , start the timer (step
F5), and at the same time, the traveling motor starts decelerating at a deceleration α (step F6). In step F7, the deceleration due to deceleration α is the time T _f obtained in step F2.
Check whether it has been continued. After the travel motor has decelerated for a time T _f , the brake is applied (deceleration g) to stop the stacker crane at the target position (step
F8, F9). An example of such control is shown in the 11th example.
Shown in the figure. As can be seen from the figure, the vibration is attenuated in a short time after the crane stops. Therefore, the operation waiting time of the fork device is reduced,
The efficiency of cargo handling work will be improved.

〔Effect of the invention〕

As explained above, according to the present invention, vibrations immediately after the crane stops can be significantly reduced with a simple configuration without the need for a special vibration damping device.

[Brief explanation of drawings]

Fig. 1 is a diagram showing a control operation flow in an embodiment of the present invention, Fig. 2 is a block diagram showing a hardware configuration in an embodiment of the invention, Fig. 3 is a diagram showing an outline of an automated warehouse, and Fig. 4 is a diagram showing an outline of an automated warehouse. Figures 8 to 8 are diagrams showing the relationship between the swing of the crane during the stopping operation of the stacker crane, Figure 9 is a diagram showing the relationship between the phase of the swing of the crane at the start of braking and the attenuation of the swing, and Figure 10A 10C is a diagram for explaining the control start timing when steady rest control is performed, and FIG. 11 is a diagram showing the swing of the crane when steady rest control is performed. 2...Statuka crane, 3...Rail, 4...
...Travel motor, 5... Lifting body, 11... Brake, 12... Travel drive device, 13... Pulse detector, 14... Lifting motor, 16... Current transformer, 1
8... Pulse detector, 21... Calculator.

Claims (1)

[Claims] 1 Input the lifting weight of the stacker crane and the lifting position of the lifting body, and based on the cycle of the stacker crane obtained using the input lifting weight and lifting position, calculate 1/4 of the period. ~ 1/2 times the deceleration time is calculated, the traveling motor of the stacker crane is decelerated by the deceleration time from the time when the stacker crane reaches the vicinity of the target position, and then the brake is activated to stop the stacker crane. A method for stabilizing a static crane, which is characterized by stopping the crane.