JPH0378483A - Load torque detecting method for carrying machine - Google Patents

Abstract

PURPOSE:To reduce control error by operating total GD<2>, including inertia moment of load, based on data in two intervals where the acceleration of motor is different and determining the load torque based on the operated total GD<2>. CONSTITUTION:When the rotary speed of a DC motor 1 detected through a rotary speed detector 2 reaches the set value of a rotary speed setter 6, a current operation memory 7 stores the variation n1 of the rotary speed during (t)sec after that time and further operates the average value I1 of motor current detected through a current detector 16. In similar manner, a variation memory 10 stores the rotary speed n2 and the average value I2 of motor current during the interval of (t)sec after the time point when the rotary speed of the DC motor 1 reaches the set value of a rotary speed setter 9. A GD<2> operating unit 11 operates the GD<2> of load based on the stored values. A load torque operating unit 12 operates the load torque based on the operated GD<2>.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting load torque of a conveying machine such as clay, which is controlled to have a constant output during light load.

[Conventional technology]

In conveyance machines such as cranes, conveyors, and traveling vehicles that are driven by motors, in order to increase cargo handling efficiency, formula (1) is calculated from the motor current during acceleration, that is, the motor generated torque, and the rotational speed change rate during acceleration. Load torque was calculated by , and constant output control was performed based on this.

Here, TL: Load torque T: Motor generated torque during acceleration dn/dt: Rotational speed change rate during acceleration GD': Moment of inertia of load (constant) [Problem to be solved by the invention] However, in this case, In the conventional method, GD" (moment of inertia of the load) is set as a constant, so GD"
Errors due to changes in the load torque were included in the calculated load torque values.

Also, the GD2 of the load is proportional to the weight of the load, but in the case of cranes, etc., the load weight generally changes each time, so
The load GD" also changes. At this time, if the load GD2 accounts for a small proportion of the total GD' (motor GD' + brake GD2 + load GD'...), the load GD
Since the influence of the amount of change 2 on the whole is small, it can be set as a fixed value, but if its proportion to the total GD2 is large, it cannot be specified as a fixed value. In the latter case, constant output control could not be performed based on equation (1).

The present invention has been made in view of such conventional problems, and eliminates the need to set the moment of inertia (GD2) of the load when detecting the load torque, and also eliminates the error caused by changes in the moment of inertia (GD2) of the load. The aim is to eliminate

[Means to solve the problem]

To achieve this objective, the conveying machine load torque detection method of the present invention has a motor controlled by a variable speed control device, and when the load torque of the motor is less than the rated torque at the base speed of the cough motor. In a conveying machine that performs constant output control, when the motor is accelerated, a period in which the motor accelerates at a certain acceleration and a period in which it accelerates at an acceleration different from the acceleration is provided, and the average value of the motor current and the rotation detected during the same period are set. A moment of inertia GD2 of the load is calculated based on a temporal rate of change in speed, and a load torque is calculated from the average motor current value in the one period, the rate of change in rotational speed, and the calculated value of the moment of inertia GD2 of the load. shall be.

[Effect]

In the present invention, during the acceleration period from a stopped state to the base speed, the speed command is increased by an acceleration α1, and the motor average current I l (P, U) for a certain period (seconds) in that state is
and rotational speed change Δn+ (rpm), then increase the speed command with an acceleration α2 different from the acceleration α1, and calculate the motor average current I 2 for a certain period (seconds) in that state.
(P, II) and the rotational speed change Δn 2 (rpm) are detected.

Figure 1 shows the speed command, rotational speed, and motor current status.

■1 above. For ΔnI+I2+Δn2, the following (2
) and (3) hold true.

Here, TI: Motor generated torque (p, u) corresponding to motor current 1, (P, U) T2: Motor generated torque (p, u) corresponding to motor current 12 (P, Ll) T7: Base speed Motor rated torque (P, II) TL at
:Load torque (P, U) Based on equations (2) and (3), calculate the moment of inertia GD of the load using equation (4).

Moment of inertia of the load obtained by equation (4)) GD2
The load torque TL can be calculated by substituting the equation (2) or (3) into the equation (2) or (3).

As a result, the load torque can be accurately detected regardless of changes in the moment of inertia GD2 of the load, and
Even if the moment of inertia GD2 of the load cannot be specified,
It becomes possible to detect load torque during acceleration.

〔Example〕

Hereinafter, the present invention will be specifically explained based on Examples.

FIG. 2 is a control block diagram showing a configuration example for implementing the detection method of the present invention.

In Fig. 2, 1 is a DC motor, 2 is a rotation speed detector,
Reference numeral 3 designates a linear command device that converts stepwise changes in the speed command into a ramp shape, 4 designates a speed controller, and 5 designates a thyristor conversion device.

6 is a rotation speed setter for setting the rotation speed at which the first motor current detection is started, and when the rotation speed of the DC motor 1 detected by the rotation speed detector 2 reaches the set value of the rotation speed setting device 6, , in the current calculation storage device 7, the rotational speed change lΔn per second is calculated thereafter.

At the same time, the average motor current value (1) for the same period detected by the current detector 16 is calculated and stored.

Similarly, in the variation storage device 10, the rotation speed of the DC motor 1 detected by the rotation speed detector 2 is stored in the rotation speed setting device 9.
When the rotation speed reaches the set rotation speed (which has a rotation speed setting value different from the rotation speed set by the rotation speed setting device 6), the rotation speed change amount Δn2 per second is stored, and the current detector 16 The motor current average value I2 for the same period detected by the calculator 1. α.

The GD2 calculator 11 calculates the moment of inertia of the load (GD) according to the equation (4) above, based on the current value and rotational speed change amount obtained by the current calculator 1.1 device 7 and the change amount storage device 10. The load torque calculator 12 calculates the load torque TL using the obtained GD2 and the equation (2) or equation (3).

Reference numeral 8 denotes a speed increase setting device that increases the acceleration of the linear command device 3 upon receiving a computation/storage completion signal from the current computation/storage device 7.

14 is a field command device that determines the motor field current from the maximum rotation speed determined by the maximum rotation speed calculation unit 13, and gives a command to the field current controller 15 to control the field current of the field 17 of the DC motor 1. Determine the current.

〔Effect of the invention〕

As described above, in the present invention, the total GD including the load inertia moment is calculated from data for two periods in which the motor accelerations are different, and the load torque is obtained based on this.

As a result, it is possible to accurately detect the load torque (related to the change in the moment of inertia GD2 of the load, and
Even if the moment of inertia GD2 of the load cannot be specified,
Since it is possible to detect the load torque during acceleration,
Control errors can be significantly reduced. therefore,
It becomes possible to perform constant output control, and cargo handling efficiency can be improved.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing changes in rotational speed and motor current during acceleration for calculating load GD according to the present invention, and FIG.
The figure is a control block diagram showing an example of the configuration of a control circuit for implementing the present invention. 1: DC motor 2: Rotation speed detector 3: Linear command device 4: Speed controller 5: Thyristor conversion device 6: Rotation speed setting device 7: Current calculation storage device 8: Speed increase setting device 9: Rotation speed setting device 10 : Change amount storage device 11: GD2 calculator 12: Load torque calculator 1
3: Maximum rotation speed calculator 14: Field current command unit 15:
Field current controller 16: Current detector 17: Field

Claims (1)

[Claims] 1. A conveyance machine that has a motor controlled by a variable speed control device and performs constant output control when the load torque of the motor is less than the rated torque at the base speed of the motor, a period during which the motor accelerates at a certain acceleration;
providing a period of acceleration at an acceleration different from the acceleration,
The moment of inertia GD of the load is determined based on the average value of the motor current detected in both periods and the temporal change rate of the rotation speed.
^2 is calculated, and the motor current average value, rotational speed change rate, and moment of inertia GD of the load in the one period are calculated.
^2 A method for detecting load torque of a conveying machine, characterized by calculating load torque from a calculated value.