JPH0147120B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a speed control device for various operations such as turning, traveling, and traversing in industrial machines such as cranes, and is designed to prevent deterioration of low-speed starting characteristics and inching characteristics when equipped with a soft start function. This is what I did.

When operating a crane, if the amount of operation of the controller's handle is directly given as a speed command to the drive motor, it will be difficult to perform sharp notches (sharply operating the handle) or reverse notches (reversely operating the handle without stopping). Doing so may put stress on the machine and cause it to malfunction. It is also dangerous because the suspended cargo swings a lot.
Therefore, so-called soft start and cushion stop methods have been considered, which slow down operations such as starting, stopping, and reversing even if the controller is suddenly operated. In the conventional soft start and cushion stop, as shown in FIG. 1, the amount of operation of the controller is integrated to obtain a speed command for the drive motor. However, with this type of device, the speed command rises slowly, so when trying to control by inching (steps) as shown in Figure 2, the speed command does not increase sufficiently and the motor's followability deteriorates. There was a drawback.

This invention was made in view of the above points,
The present invention aims to provide a speed control device for industrial machines such as cranes that prevents deterioration of low-speed starting characteristics and inching characteristics when equipped with a soft start function.

According to the present invention, the above object is achieved by combining a speed command with a soft start characteristic with a signal corresponding to the amount of change in the operation amount of the controller.

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

In Figure 3, power lines 1u, 1v, 1w
A three-phase alternating current voltage is supplied from the motor, and is supplied to a drive motor 3 for a controlled object (turning, traveling, traversing, etc.) via a primary voltage control and phase switching thyristor circuit 2.

The controller 4 instructs the moving direction and moving speed of the controlled object by operating the handle 5. Here, it can be operated in five stages: 0 notch (stop), +1 notch (forward rotation, low speed), +2 notch (forward rotation, high speed), -1 notch (reverse rotation, low speed), -2 notch (reverse rotation, high speed). . The controller 4 outputs a signal whose polarity and magnitude correspond to the direction and amount of operation.

The output signal of the controller 4 is input to a differentiating circuit 6 and an integrating circuit 7, respectively. The integrating circuit 7 integrates this signal, makes its rise and fall gentle, and provides soft start characteristics and cushion stop characteristics. Further, the differentiating circuit 6 differentiates the rising and falling edges of this signal. The outputs of the differentiating circuit 6 and the integrating circuit 7 are adjusted in level by volumetric volume 8 and 9, respectively, and then added by operational amplifier 10 and outputted as a speed command.

FIG. 4 shows the waveforms of each part mentioned above. The output of the operational amplifier 10 that is finally obtained as a speed command is obtained by superimposing the differential output on the rising and falling edges of the integral output, so it is possible to improve the poor followability at startup due to the soft start characteristic. . Further, since a differential signal is superimposed at the beginning of each notch operation of the controller 4, a signal sufficient to drive the motor 3 can be obtained from the operational amplifier 10 even when an inching operation is performed, as shown in FIG.

In FIG. 3, the speed of the motor 3 is detected by a tachogenerator 11. In FIG. At addition point 12, the deviation between the speed command value and the detected speed value is calculated. This deviation signal is input to the phase control circuit 14 via the speed control amplifier 13. The magnitude and polarity of the output signal of the speed control amplifier circuit 13 indicate the magnitude and rotational direction of the motor 3's torque. The phase control circuit 14 creates a firing pulse with a phase depending on the magnitude of the output signal of the speed control amplifier 13. The torque direction detection circuit 15 detects the direction in which the motor 3 should rotate based on the polarity of the output signal of the speed control amplifier 13, and switches between forward and reverse so that the output of the phase control circuit 14 fires the thyristor in the appropriate phase rotation direction. Logic 16 is operated.

The comparator 20 switches the forward/reverse switching logic 1 only when the speed of the motor 3 detected by the tachogenerator 11 becomes smaller than a preset value.
6 switching is possible. As a result, even if the reverse notch is turned on, the motor 3 will continue to operate until the speed falls below the set value.
Switching of the drive direction is prevented, and the shock caused by switching the drive direction is relieved. Note that the speed setting value is adjusted by the volume 21.

Additionally, a timer is also used to prevent shocks caused by reverse notches. That is, the -→0 operation detection circuit 22 detects that the controller 4 has been operated from (reverse rotation) to 0 (stop), drives the timer 23, and operates the switch 24 for a certain period of time.
By turning off the output of the comparator 20, switching in the + (normal rotation) direction is prevented. Further, the +→0 operation detection circuit 25 detects that the operation on the controller 4 is changed from + (forward rotation) to 0 (stop), and drives the timer 26.
By turning off the output of the comparator 20 for a certain period of time using the switch 27, switching in the - (reverse) direction is prevented. The set times of the timers 23 and 26 are adjusted by volumetric controls 28 and 29, respectively.

Note that if the tachometer generator 11 is not included, the speed command value may be used instead of the speed detection value, as shown by the dotted line 30.

Further, as a measure to prevent shock due to the brake, in this embodiment, the brake is not applied unless the speed of the motor 3 falls below a certain value, similar to the above-mentioned forward/reverse switching. That is, the brake relay 31 is turned on only when the output of the comparator 20 becomes "1", and the brake 32 becomes operable. However, when a reverse notch operation is performed, it is sufficient to simply reverse the rotation without applying the brake 32, so the AND circuit 34 is turned on only when the 0-notch (stop) operation is detected by the 0-notch detection circuit 33. Then, the brake 32 is applied.

In the above embodiment, the present invention is applied to a crane, but the present invention is not limited to this and can be applied to other industrial machines equipped with a soft start function.

As explained above, according to the present invention, a signal corresponding to the amount of change in the operation amount of the controller is synthesized with the speed command given the soft start characteristic, so that a large signal is generated at the rising edge of the speed command. As a result, it is possible to improve the deterioration of low-speed starting characteristics and inching characteristics caused by soft start characteristics.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing conventional soft start characteristics, FIG. 2 is a waveform diagram showing inching characteristics when the soft start characteristics shown in FIG. 1 is used, and FIG. 3 is a block diagram showing an embodiment of the present invention. 4 is a waveform diagram showing the operation of each part of the circuit of FIG. 3, and FIG. 5 is a waveform diagram showing the inching characteristics of the circuit of FIG. 3. 1u, 1v, 1w...Power line, 2...Thyristor circuit for primary voltage control and phase switching, 3...
Induction motor, 4...controller, 6...differentiation circuit, 7...integrator circuit, 31...brake relay, 32...brake.

Claims (1)

[Claims] 1. A controller that outputs a signal according to the amount of operation of the controller, a first circuit that outputs the output signal of the controller with a slower change, and a first circuit that outputs a signal that corresponds to the amount of change in the output signal of the controller. A speed control device for an industrial machine such as a crane, comprising: a second circuit; and means for combining output signals of the first circuit and the second circuit and outputting the synthesized signal as a speed command for a controlled object.