JPH0323192A - Control method of crane - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling a crane, and particularly to a method for controlling the speed of a drive motor during startup. [Prior Art] As a method for controlling the speed of the induction motor for driving the crane, for example, there is a method of controlling the speed of the electric thin film applied to the induction motor. It is known that when this frequency 1t(f) is changed, a constant torque characteristic can be obtained by changing the voltage (v) applied to the motor in proportion to frequency < f). When controlling this v/f ratio as constant, at low speed (
During startup and acceleration), the voltage drop due to motor winding resistance becomes significant, and the generated torque decreases. For this reason, in the low frequency range, a method is used to compensate for the decrease in torque by increasing the motor terminal voltage, so-called torque boost. The outline is shown in Figures 5 and 6. Fifth
The figure is a V1f characteristic curve diagram showing the relationship between voltage V and frequency f, in which X is a normal characteristic curve and y is a characteristic curve with torque boost TB. FIG. 6 is a torque characteristic diagram showing the relationship between dark wave number and torque, in which xL x2. x3 is a normal torque characteristic curve without torque boost, 3/I. V2 is the case when torque is boosted, and by performing torque boost, the generated torque becomes large for the same frequency. [Problems to be Solved by the Invention] However, when operating a crane, the required torque is determined by the magnitude of the load, and the load is not necessarily constant.

Conventionally, torque boost is set constant regardless of the size of the load.

Therefore, if the above-mentioned torque booth TB is set in accordance with the case where the load is large, an excessive current will flow to the motor at startup even when the load is small, resulting in wasted power consumption and
There are problems such as excessive acceleration force, shock to the load, or large swing of the load. Furthermore, if the torque booth is set in response to a small load, there will be problems such as difficulty in starting when the load is large. In view of this, an object of the present invention is to automatically select the optimum torque boost even when the load fluctuates, thereby achieving efficient operation.

[Means to solve the problem]

In order to achieve the above object, the crane control method of the present invention measures the suspended load and drives the drive motor at a predetermined frequency, that is, the number of rotations, and a corresponding voltage. [Operation] The load is detected, and the voltage corresponding to the frequency f, that is, the torque boost, can be determined based on this load to a value suitable for the load. [Example] Fig. 2 shows the first example of the present invention, and shows the characteristic of the dark wave number f - voltage V, which shows the relationship between the frequency f and the corresponding voltage V when the hanging load changes. Shows a curve. The boost voltage V is increased or decreased in proportion to the load W, and as the load increases from a low load, the boost voltage increases to vl.
The characteristic curve T of the frequency f and the voltage V increases as v2, v3...vn, and the acceleration process from the start of the crane to the constant speed is
S1. T party. TS3● ● ◆Set TSn. Figure 4 shows a relationship diagram in which the vertical axis shows the v/f ratio and the horizontal axis shows the load, setting the relationship between the two. That is, when the load is large, v/f is set large, and when the load is small, v/f is set small, and the boost voltage can be determined by this. Figure 1 schematically shows a control mechanism that implements the control method according to the present invention. This control mechanism 1 includes a hanging load measuring device 2, a computing unit 3, and an inverter 4 that sets the voltage and frequency of a power source for a crane driving electric motor M.

The load measuring device 2 uses a load cell, for example, and upon startup, first measures the hanging load W and applies it to the computing device 3.
The arithmetic unit 3 calculates the v/f ratio for the measured load W using the v/f ratio-load characteristic curve shown in FIG. In the inverter 4, this v/f ratio allows the boost voltage at startup to be set to vl. v2,
v3...Vn is determined and set frequency f - voltage V
Characteristic curves TSI, TS2. TS3-・TS
Start the crane based on n, sequentially increase the frequency f, apply a voltage corresponding to the dark wave number f to the drive motor M,
Start the drive motor M and perform acceleration. FIG. 3 shows a second embodiment of the invention. In this embodiment, in the acceleration process from starting the crane to achieving a constant speed, first, at the time of starting, the boost voltages vl, v2, which are determined by the load, are set as in the first embodiment. v3...the first determined by vn
Characteristic curves of frequency f and voltage ■TI, T2. T
3...●Start with Tn, PI, P2, in the middle of acceleration
P3◆・●Pn is designed to accelerate by switching to the second frequency f-voltage V characteristic curve TS preset, and the overall frequency f-voltage V characteristic curve from startup to constant speed is lower. It has a convex shape. The reason why the characteristic curve of frequency f and voltage V is made convex downward is to enable smooth acceleration of the crane.

In each of the embodiments, the characteristic curve of frequency f and voltage V is a straight line, but it is not limited to a straight line and may also be a curved line. [Effects of the Invention] According to the present invention, in the control method of controlling the speed by changing the power frequency f and voltage V for the drive motor of the crane, the load is automatically measured, and when the load is light according to the r# weight, The torque boost is relatively small, and the crane can be started and accelerated by gradually increasing the torque boost as the crane reaches heavy rtI weights, and the crane does not shock the load or swing significantly when starting the crane. This has the effect of allowing the crane to operate efficiently without excessive current flowing through the electric machine.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram of a crane control mechanism for implementing the method of the present invention, Figs. 2, 3, and 4 are explanatory diagrams of the principle of the present invention. characteristic curve diagram,
Figure 4 is a relationship diagram between v/f ratio and load, Figure 5 is an explanatory diagram of torque boost, and Figure 6 is a torque characteristic diagram using torque boost. 1 is a crane control mechanism, 2 is a hanging load measuring device, 3 is a computing unit, 4 is an inverter, and M is a crane driving electric motor.

Claims (2)

[Claims] (1) Power frequency (f) for the crane drive motor
In the control method of controlling the speed by changing the voltage (v), the suspended load is measured, and the torque boost voltage is set high when the load is large and low when the load is small, and the crane is started and accelerated. A crane control method characterized by: (2) Power frequency (f) for the crane drive motor
In the control method of controlling the speed by changing the voltage (v), in the acceleration process from starting the crane to reaching a constant speed,
First, the first power supply frequency (f
) - Voltage (v) characteristic curve, switch to the second power frequency (f) - Voltage (v) characteristic curve during acceleration, accelerate, and maintain the overall power frequency from startup to constant speed. (f) - Voltage (v) Set the characteristic curve to be a downward convex characteristic curve, measure the hanging load, and set the torque boost voltage to be high when the load is large and low when the load is small. A method for controlling a crane, comprising setting, starting and accelerating the crane.