JPH04251585A - Protective method for motor under locked state - Google Patents

Abstract

PURPOSE:To protect a locked motor and a motor circuit against overcurrent and to automatically reset quickly from protected state when the motor is unlocked. CONSTITUTION:When motor current exceeds a predetermined level, failure of a control circuit is detected and if the control circuit is normal, the control is branched to protective mode. Under the protective mode, control output is lowered thus lowering the motor current. If the motor is unlocked when the control is being branched to protective mode and the control signal is lowered or when a drive command is fed reversely to the locking direction, the control is reset from the protective mode.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for protecting a motor in a rotationally restricted state by reliably detecting a rotationally restricted state of the motor that occurs due to a sudden increase in load, etc.

0002

2. Description of the Related Art When a large load is applied to the output shaft of a motor, a large current flows through the motor circuit, which may cause burnout of the motor and drive circuit. Conventionally, a method has generally been adopted in which the motor current is detected and when the current reaches a predetermined value, the circuit is interrupted by a circuit breaker or the like.

0003

However, in the above-described method, in order to restart the device when the load becomes small, it is often necessary to restore the device manually or turn on the power again. For example, if a large load is likely to be applied suddenly, such as the motor that drives the rudder or elevator of an aircraft, and rapid recovery is essential when the load decreases, the circuit should be shut off using a circuit breaker, etc. is inappropriate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for protecting a motor in a rotationally restrained state, which can reliably protect a motor that has fallen into a restrained state, and can quickly and automatically return the motor when the motor is released from the restrained state. There is a particular thing.

[0005]

[Means for Solving the Problems] The gist of the present invention to achieve the above-mentioned object is to generate a control signal based on the difference between a detected value of the rotation amount or rotation speed of the motor and a command value input from the outside. When adjusting the motor current to be output and input from the control circuit, the motor current is detected, and if the detected current value exceeds a predetermined value, the control circuit is checked for failure, and as a result, the control circuit When rotation is restricted and determined to be normal, the output of the control circuit remains unchanged until at least either the command value in the reverse rotation direction is input or the control signal falls below a predetermined value. A method for protecting a motor in a rotationally restrained state is characterized in that the motor is reduced to a predetermined value regardless of the command value.

[0006]

[Operation] The method for protecting the motor in a rotational restraint state having the above-mentioned configuration limits the motor current by detecting the rotational restraint state and reducing the control output, and also when a reverse rotation command value is input at the time of restriction. or when the restraint is released and the control signal becomes smaller, it automatically returns from the restricted state.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail based on the illustrated embodiments.

FIG. 1 shows an example of the configuration of a motor control circuit for carrying out the method of the present invention, and 1 is a microcomputer.
, an AD converter 1b, a DA converter 1c, a ROM 1d, a RAM 1e, and an interface circuit 1f connected to the CPU 1a. The motor control signal from the DA converter 1c is sent to the pulse width modulator 2a and predriver 2b.
The signal is applied to the drive unit 2 consisting of the following and becomes a drive signal. This drive signal is input to an inverter circuit 4 connected to a DC power source 3, thereby making the rotation of the motor 5 variable. Furthermore, CPU1
In response to the command a, the drive section 2 is turned on and off via the interface circuit 1f, and the motor 5 is turned on and off by the predriver 2b.
The direction of rotation can be changed. The rotation of the motor 5 is transmitted via a reduction gear 6 etc. to an output part such as a ball screw in a linear type or a link in a rotary type, but these output parts are equipped with a sensor such as a position detector 7 or a tachometer. is installed, and these detection signals are sent to the microcomputer 1.
feedback has been provided.

The microcomputer 1 adjusts the control signal given to the drive section 2 so that the detected value successively matches the command value given from outside the system, and the entire system forms a so-called servo loop system. . Furthermore, in this embodiment, in order to measure the current applied to the motor 5, a resistor 8 or a Hall element is provided in the DC portion of the inverter circuit 4, and this detected current value is input to the microcomputer 1. are doing.

The motor control circuit configured as described above operates based on a control flowchart as shown in FIG. 2, for example. First, normally, the current value detected by the resistor 8 is within a predetermined value or less, and a normal servo loop operation is performed to drive the output section according to the command value. On the other hand, if the detected current value exceeds a predetermined value, the step branches, and the presence or absence of a failure in the control circuit itself is detected based on a method described later. As a result, if it is determined that there is no failure in the control circuit, and this state continues for a predetermined time period of, for example, 5 to 10 seconds, it is determined that the motor 5 is in a rotationally restricted state due to overload. Branches into a protection mode that reduces and maintains the motor current at a predetermined safe value. This prevents the motor 5 and the inverter circuit 4 from burning out.

Furthermore, during this current drop, the load decreases and the motor 5 rotates, and the difference between the detected position value of the output section and the command value becomes small, or a drive command value is given in the direction opposite to the restraining direction. When this happens, it exits protection mode and returns to the normal servo loop. This makes it possible to quickly perform normal control when the load decreases.

[0012]Failures in the control circuit can be detected, for example, in the following manner. First, when the detected current value exceeds a predetermined value, the CPU 1a superimposes a reduction pulse with a width of about 2 milliseconds on the control signal at appropriate intervals as shown in FIG. 3, and outputs it from the DA converter 1c.

[0013] Here, if the control circuit is normal and the increase in current is simply due to an increase in the load on the motor, the reduced pulse is normally output from the DA converter 1c and the pulse width modulator 2a and the preamplifier are output. Since the driver 2b also operates normally, the motor current generated by the inverter circuit 4 also decreases in a pulsed manner. On the other hand, if the current increase is due to a failure in the control circuit, the reduction pulse will not be reflected in the motor current. Therefore, it is possible to determine whether the control circuit is normal or abnormal by detecting whether the current detection value obtained through the resistor 8 or the like decreases in a pulse-like manner.

If a failure in the control circuit is determined, it is impossible to operate in the protection mode as described above, and appropriate measures such as issuing an alarm and stopping operation are appropriate.

As described above, according to the method of the present invention, it is possible to reliably determine the rotational restraint state of the motor 5, prevent burnout of the motor 5 and the inverter circuit 4, and quickly return to the normal state when the restraint state is released. Can return to control state.

[0016] In addition to the control circuit having the above-mentioned configuration, the present invention also applies to a method of determining a control signal from the difference between the detected value of motor rotation and the command value, or the difference between the detected position value of the output section and the command value. It can be applied to any control circuit.

[0017]

[Effects of the Invention] As explained above, the method for protecting a motor in a rotationally restrained state according to the present invention can determine the rotationally restrained state of the motor, prevent burnout of the motor and inverter circuit, and release the restrained state. Since the normal control state can be quickly returned to, it is suitable for use when a large load is suddenly applied or when a quick return is required when the load decreases.

[Brief explanation of the drawing]

FIG. 1 is a block circuit configuration diagram for implementing a method for protecting a motor in a rotationally restrained state according to the present invention.

FIG. 2 is a flowchart diagram.

FIG. 3 is a waveform diagram of a reduced pulse.

[Explanation of symbols]

1 Microcomputer 1a CPU 2 Drive part 3 DC power supply 4 Inverter circuit 5 Motor 6 Reduction gear 7 Position detector 8 Resistor

Claims (1)

[Claims] Claim 1: In the case where the control circuit outputs a control signal based on the difference between the detected value of the rotational amount or rotational speed of the motor and the command value inputted from the outside to adjust the motor current to be applied, detecting the current, and if the detected current value exceeds a predetermined value, inspecting the control circuit for failure;
As a result, when the control circuit is determined to be normal and the rotation is restricted, the operation is continued until at least either the command value in the reverse rotation direction is input or the control signal is below a predetermined value. A method for protecting a motor in a rotationally restrained state, characterized in that the output of the control circuit is reduced to a predetermined value regardless of the command value.