JPS6158490A - Digital drive device of dc motor - Google Patents

Abstract

PURPOSE:To improve the protecting performance and to alleviate the processing content of a more significant digital controller by composing a protecting circuit of a digital circuit independently from the controller. CONSTITUTION:A more significant controller 2 detects the rotating speed and position of a DC motor 3 by the output of an encoder 4 and outputs a control command. On the other hand, when the current detection value detected by a current detector 7 becomes larger than a peak current value, a peak current detector 10 outputs a peak current detection signal, and a current limiter 11 interrupts a drive command to a drive circuit 6. If the peak current detection signal is output continuously for the prescribed time or longer, an overload protecting circuit 12 outputs a drive stop signal to an interlock circuit 13. Similarly, if the current detection value becomes larger than the allowable upper limit current value, an overcurrent detector 14 outputs an overcurrent detection signal to an overcurrent protecting circuit 15.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a drive device for a DC motor.

Conventional configurations and their problems Traditionally, control and protection circuits for DC motor drive devices have been constructed of analog circuits, which are susceptible to temperature and aging changes, have reliability issues, and are difficult to maintain and adjust. It had such drawbacks. For this reason, digitization of the control circuit of the DC motor drive device has been considered. FIG. 1 shows a digital control block diagram of a conventional DC motor.

Reference numeral 1 denotes a drive device which receives control command input from a host digital control device mainly composed of a microcomputer and drives the DC motor 3. Reference numeral 4 denotes a relative value output pulse encoder (hereinafter abbreviated as encoder) for detecting the rotation angle of the DC motor 3.

The rotational speed and rotational position of the DC motor 3 are detected by the encoder 4 and fed back to the host digital controller 2. Based on this information, the host digital controller 2 issues drive commands, drive device protection commands, start-up and Drive device 1 sends stop commands, etc.
Output as a control command to.

Further, the current flowing through the DC motor 3 is detected by a current detection circuit 7, the detected value is amplified by an amplifier circuit 8, and converted into a digital value by an AD conversion circuit 9.

The digital value is fed back to the upper digital control device 2,
The drive command is adjusted to limit the current so that it does not exceed a preset peak current value.

However, the above-mentioned configuration has the drawback that the protection function of the drive device is entrusted to the higher-level digital control device, so that the protection function is not guaranteed when the higher-level digital control device is abnormal.

In addition, since the upper digital control device uses time-sharing processing,
Simplification of the processing algorithm is required to obtain high-speed response. In this sense, it is disadvantageous to provide a protection function and a current limiting function to a higher-level digital control device.

OBJECTS OF THE INVENTION In view of the above drawbacks, the present invention provides a digitally controlled drive device for a DC motor that has the advantages of digital control and has stable protection performance even when an abnormality occurs in the upper level digital control device.

Structure of the Invention The present invention comprises a drive circuit that drives a DC motor, which is composed of a bridge circuit of drive elements, a synchronization circuit that has a digital circuit configuration that synchronizes control command input from a higher-level digital control device, and transmits it to the drive circuit; A current detection circuit that detects the current flowing through the DC motor, and a peak current detection port that outputs a peak current detection signal when the current detection value detected by the current detection circuit reaches a preset peak current value. a current limiting circuit with a digital circuit configuration that limits the flowing current; an interlock circuit that is controlled by a digital signal and forcibly cuts off control command input to the drive circuit to stop driving; and the peak current detection signal. An overload protection circuit with a digital circuit configuration that outputs a drive stop signal to the above-mentioned interlock circuit to perform overload protection when the above-mentioned current detection value is detected continuously for a certain period of time or more, and the above-mentioned current detection value is a preset allowable upper limit current value. An overcurrent detection circuit that outputs an overcurrent detection signal when the overcurrent detection signal is detected, and a digital circuit that outputs a drive stop signal to the interlock circuit to perform overcurrent protection when the A protection loop is provided in a digital circuit independent of the main control loop by the upper-level digital control device, which improves protection performance and reduces the sampling frequency by reducing the amount of processing in the upper-level digital control device. DESCRIPTION OF EMBODIMENT OF THE INVENTION One embodiment of the present invention will be described below with reference to the drawings.

Figure 2 shows a block configuration diagram of digital control of a DC motor in an embodiment of the present invention. In Figure 2, 1o is a peak current detection circuit, 11 is a current limiting circuit, and 12 is an overload protection circuit. , 13 is an interlock circuit, 14 is an overcurrent detection circuit, 15 is an overcurrent protection circuit, and 16 is a digitally controlled drive device for the DC motor.

The operation of the digital control and digital control drive device for a DC motor configured as described above will be described below.

First, the control command input from the higher-level digital control device 2 is synchronized by the synchronization circuit 6, and the drive command is transmitted to the drive circuit 6. The drive circuit 6 drives the DC motor 3 in accordance with the drive command, and feeds back the output of the encoder 4 directly connected to the shaft of the DC motor 3 to the host digital control device 2. The host digital control device 2 detects the rotational speed and rotational position of the DC motor 3 from the output of the encoder 4, calculates and outputs a control command from the detected rotational speed and rotational position. The above control loop is called a main control loop.

The operation of the current limiting and protection loops configured independently of the main control loop will be described.

The current flowing through the DC motor 3 is detected by the current detection circuit, and the detected current value is compared with a preset peak current value, and the peak current is detected from the peak current detection circuit 10 between the detected current value and the peak current value. Output a signal. The open current limiting circuit 11 to which the peak current detection signal is output cuts off the drive command to the drive circuit 6 and limits the current flowing to the DC motor 3.

In addition, if the peak current detection signal is output continuously for a certain period of time or more, it is determined that the DC motor 3 is in an overload state, and the overload protection circuit 12 outputs a drive stop signal to the interlock circuit 13. By cutting off control command input from the digital control device 2, overload protection of the drive circuit 6 and the DC motor 3 is performed.

Similarly, as a result of comparing the current detection value from the current detection circuit 7 and the preset allowable upper limit current value, the current detection value
> When the allowable upper limit current value is reached, the overcurrent detection circuit 14 outputs an overcurrent detection signal, and upon receiving the overcurrent detection signal, the overcurrent protection circuit 16 outputs a drive stop signal to the interlock circuit 13, Thereafter, control command input from the higher-level digital control device 2 is cut off. Due to this, for some reason the DC motor 3
Also, it is possible to prevent excessive current from flowing into the drive circuit 6, thereby providing overcurrent protection.

As described above, according to this embodiment, by configuring the protection circuit with a digital circuit inside the drive device, a protection loop is provided independent of the main control loop, improving protection performance and The processing content can be reduced.

Effects of the Invention As described above, in digital control of a DC motor, the present invention improves protection performance and reduces processing content of the upper digital control device by configuring a protection circuit with a digital circuit independently of the upper digital control device. This shortens the sampling period and has a significant effect on the digital control of DC motors.

[Brief explanation of the drawing]

Fig. 1 is a digital control block diagram of a conventional DC motor, and Fig. 2 is a digital control block diagram of a DC motor according to an embodiment of the present invention. ...DC motor, 4...
... Encoder, 5 ... Synchronization circuit, 6.
...Drive circuit, 7...Current detection circuit, 1
0...Peak current detection circuit, 11...
Current limiting circuit, 12...Overload protection circuit, 13
...Interlock circuit, 14...Overcurrent detection circuit, 15...Overcurrent protection circuit, 1
6...Digital control drive device.

Claims (1)

[Claims] A drive circuit that drives a DC motor consisting of a bridge circuit of drive elements, a synchronization circuit with a digital circuit configuration that synchronizes control command input from a host digital control device and transmits it to the drive circuit, and a synchronization circuit that controls the current flowing through the DC motor. When the current detection circuit to be detected and the current detection value detected by the above current detection circuit reach a preset peak current value,
a peak current detection circuit that outputs a peak current detection signal;
a current limiting circuit having a digital circuit configuration that limits the current flowing to the DC motor by blocking control command input to the first half drive circuit only during the period when the peak current detection signal is output;
When the interlock circuit, which is controlled by a digital signal and forcibly cuts off the control command input to the drive circuit to stop driving the DC motor, and the peak current detection signal mentioned above are detected continuously for a certain period of time or more. , an overload protection circuit with a digital circuit configuration that sends a drive stop signal to the interlock circuit to perform overload protection; A direct current circuit equipped with an overcurrent detection circuit that outputs to the lock circuit, and an overcurrent protection circuit with a digital circuit configuration that sends a drive stop signal to the interlock circuit and performs overcurrent protection when the overcurrent detection signal is detected. Digital control drive device for electric motor.