JP2004215410A - Current detecting accuracy improving means for dc motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current detecting precision improving means for a DC motor controller which can improve detection accuracy of a current detecting circuit. <P>SOLUTION: In the DC motor control apparatus which is provided with a current detecting circuit, at least one serial communication circuit and a storage device capable of writing, an output value from the current detecting circuit is stored in the storage device when a set command is received through the serial communication circuit. The DC motor control apparatus computes variation (c) of the current detecting circuit from a stored current value (a) and a theoretical value (b) of a constant current at the time of receiving the command, by feeding a constant current in the DC motor control apparatus and storing a current value in the storage device when the set command is received through the serial communication circuit. After that, the DC motor control apparatus corrects an output value of the current detecting circuit by using the variation (c) and improves current detecting accuracy. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a means for improving current detection accuracy of a DC motor control device. In particular, it relates to a DC motor control circuit having a current detection circuit.
[0002]
[Prior art]
Conventionally, a resistor for current detection is mounted in the current detection circuit.However, the resistance tolerance of the current detection resistor becomes an output error of the current detection circuit. Had to choose a resistor.
[0003]
[Problems to be solved by the invention]
By making the current detection circuit output error due to the resistance tolerance of the current detection resistor in the current detection circuit of the DC motor control device negligible, the resistance tolerance can select a general resistor. Thus, the manufacturing cost can be reduced.
[0004]
SUMMARY OF THE INVENTION It is an object of the present invention to provide means for improving the current detection accuracy of a DC motor control device capable of improving the detection accuracy of a current detection circuit.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a DC motor control device according to the present invention basically includes an arithmetic processing device that calculates a control program, and also supplies a constant current by a specific signal in a test state by a serial communication signal. By performing correction using a value stored in a writable storage device capable of storing the current value at the time of performing the detection, the current detection accuracy can be improved.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a DC motor control device according to the present invention will be described in detail with reference to the drawings.
[0007]
FIG. 1 is a block diagram showing a first embodiment of the DC motor control device. The DC motor control device 100 includes a DC motor drive circuit 101, a drive signal processing circuit 102, an arithmetic processing unit (CPU) 103, and a current detection circuit 104.
[0008]
Further, the DC motor control device 100 captures a signal from a serial communication signal (not shown) and detection signals from various other sensors (not shown), performs an arithmetic operation based on the captured detection signal, and sends the signal to the drive signal processing circuit 102. By outputting a drive signal, a signal is output to the DC motor drive circuit 101 to drive the DC motor.
[0009]
Further, the signal of the current detection circuit 104 is A / D converted and output to the arithmetic processing unit 103. The arithmetic processing unit 103 has a function of taking in the A / D conversion result and executing a predetermined control program stored in the ROM.
[0010]
Note that the calculation result and the A / D conversion result are temporarily stored in the RAM, and the calculation result is output as a control output signal through the output circuit and used for controlling the DC motor drive.
[0011]
Further, the DC motor control device 100 is connected to the test device 110 via a connector, and inspects the characteristics of the DC motor drive circuit 101, the drive signal processing circuit 102, and the current detection circuit 104 to determine whether the drive is good or not. Only products that pass after being separated from the test apparatus 110 are used as DC motor control apparatuses 107 in actual equipment.
[0012]
The test apparatus 110 includes a constant current power supply 107, a resistor 108 corresponding to an actual load, and a serial communication circuit 106 that sends a serial communication signal to the DC motor controller 100.
[0013]
The arithmetic processing unit 103 in the DC motor control device 100 outputs a signal of the forward rotation and the ON duty 100% to the drive signal processing circuit 102 to the drive signal processing circuit 102 by a specific serial communication signal from the serial communication circuit 106 of the test device 110. I do.
[0014]
A specified current is supplied to the DC motor control device 100 by the constant current power supply 107 of the test device 110. The DC motor control device 100 performs A / D conversion on the output value of the current detection circuit 104 after a predetermined time has elapsed after outputting the prescribed signal to the drive signal processing circuit 102 and stores the output value in a writable storage device in the arithmetic processing device 103. . The arithmetic processing device 103 in the DC motor control device 100 outputs a signal indicating completion of the end of storage of the current value to the communication circuit 106 of the inspection device 110. The test apparatus 110 stops the output of the constant current power supply 107 by the signal input to the communication circuit 106.
[0015]
The ratio c is calculated from the theoretical value b of the specified current value by the test device 110 based on the current value a stored in the arithmetic processing test device 103 in the DC motor control device 100. On the other hand, by correcting the detected current value by the ratio c calculated as described above, the output error of the current detection circuit 104 due to the tolerance of the resistance of the current detection resistor 105 of the current detection circuit 104 can be ignored.
[0016]
FIG. 2 is a block diagram showing a second embodiment of the DC motor control device. The DC motor control device has the same configuration as that of FIG. 1 except for a connector 112 for connection to the test device 120. The process until the A / D value of the output value of the current detection circuit 104 is captured by the connection connector 112 will be described.
[0017]
The test apparatus 120 includes a constant current power supply 109 and a serial communication circuit 106. The arithmetic processing device 103 of the DC motor control device 110 outputs a signal to the drive signal processing circuit 102 to turn off the DC motor according to the communication signal from the serial communication circuit 106. The constant current power supply 109 of the test apparatus 120 sends a specified current to the current detection resistor 105 by changing the connector 112. The output of the current detection circuit 104 is A / D converted, and the current value is stored in a writable storage device in the arithmetic processing unit 103. The arithmetic processing device 103 stops the output of the constant current power supply 109 in the test device 120 by sending the end of storage to the serial communication circuit 106 in the test device 120 by a serial communication signal. Thereafter, the DC motor control device 110 obtains the ratio c from the current value a stored in the storage device in the arithmetic processing device 103 and the theoretical value b at the specified current value of the constant current power supply 109 in the test device 120. During operation, the DC motor control device 110 corrects the output value of the current detection circuit 104 by the ratio c and uses the corrected value for the control, whereby the current detection circuit based on the tolerance of the resistance of the current detection resistor 105 of the current detection circuit 104 is used. The output error of 104 can be ignored.
[0018]
As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above embodiments, and various changes may be made in the design without departing from the spirit of the present invention described in the claims. You can do it.
[0019]
For example, in the embodiment, the detected current value is stored in a writable storage device in the arithmetic processing device. However, the present invention can be implemented by providing a writable storage device outside the arithmetic processing device.
[0020]
Further, in the embodiment, the specified current is supplied to the DC motor control device in the test apparatus, and the current value is stored by serial communication. However, in the configuration in which the DC motor control device does not have serial communication, other input is performed. It is also possible to store a combination of input signals that cannot be used in normal operation by a signal.
[0021]
As described above, the DC motor control device according to the present invention uses the test device to apply the specified current to the DC current control circuit when the output of the current detection circuit fluctuates from the theoretical value due to the resistance tolerance of the current detection resistor in the current detection circuit. The output of the current detection circuit at that time is stored in the motor control device, and during normal operation, the detected current value is corrected based on the stored current value, so that the current detection circuit varies from the theoretical value due to the tolerance of resistance. By correcting the value, the resistance tolerance can be ignored. Therefore, the detection accuracy of the current detection circuit is improved. According to the present invention, since the resistance tolerance can be ignored, a general resistor having a resistance tolerance can be used, so that the manufacturing cost can be reduced.
[0022]
【The invention's effect】
According to the present invention, it is possible to provide a means for improving the current detection accuracy of a DC motor control device capable of improving the detection accuracy of a current detection circuit.
[Brief description of the drawings]
FIG. 1 is a block diagram of a DC motor control device according to a first embodiment.
FIG. 2 is a block diagram of a DC motor control device according to a second embodiment.
[Explanation of symbols]
100 DC motor control device, 101 DC motor drive circuit, 104 current detection circuit, 105 current detection resistor, 106 serial communication circuit, 109 constant current power supply, 108 resistor (equivalent to actual load), 120 … Test equipment, 112… connector.

Claims (3)

In a DC motor control device having a current detection circuit and at least one serial communication circuit and a writable storage device,
A DC motor control device, wherein the output value from the current detection circuit is stored in the storage device when the set command is received after returning to the serial communication circuit. The DC motor control device is configured to store a constant current in the DC motor control device and store the current value in the storage device when the set command is received by returning the serial communication circuit. The deviation c of the current detection circuit is calculated from the value a and the theoretical value b of the constant current when the command is received. Thereafter, the DC motor control device increases the current detection accuracy by correcting the output value of the current detection circuit by the deviation c. The DC motor control device is characterized in that a constant current is applied to both ends of a current detection resistor which is a part of a current detection circuit by an external power supply which is a part of a test device, and the current value is stored in the storage device. DC motor control device.

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