JPS6335199A - Drive control system for stepping motor - Google Patents

Abstract

PURPOSE:To reduce burden in control of a CPU, by a method wherein a memory storing a table of drive current values corresponding to error amount is used, and drive current is estimated from the table. CONSTITUTION:A CPU 2 reads error amount between actual rotational position of a stepping motor 9 and target position through a sensor 10. A control table 12 recording drive current values corresponding to values of the error amount in one-to-one correspondence is installed in a ROM 1, and the CPU 2 retrieves and estimates the drive current value corresponding to the error amount from the control table 12. The drive current value is applied in sequence to the stepping motor 9 thereby the error amount is decreased. In this constitution, software of the CPU 2 becomes quite simple, and burden in the control can be reduced significantly.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a method for controlling the stepping motor according to the amount of error between the actual rotational position of the stepping motor or the actual position of a member positioned by the motor and the target position. The present invention relates to a stepping motor drive control method that controls a drive current value.

[Prior Art] When delicate position control is performed in various positioning mechanisms using a stepping motor as a drive source, the stepping motor drive control method described above is used. According to the conventional configuration of such a drive control system, the CPU that constitutes the motor drive control circuit performs complex arithmetic processing from the data of the error amount to determine the drive current value of the stepping motor according to the recorded error amount. This was determined by the software.

[Problems to be Solved by the Invention] However, with such a configuration, the software of the CPU becomes complicated, and the negative phase of the control of the CPU becomes large. Furthermore, when considering changing the control characteristics of the stepping motor in response to changes in the driving characteristics of the positioning mechanism over time, there is a problem in that the change cannot be easily performed.

[Means for Solving the Problems] In order to solve the above-mentioned problems, according to the present invention, the difference between the actual rotational position of the stepping motor or the actual position of the member positioned by the motor and the target position is achieved. In a stepping motor drive control method that controls the driving current value of the motor according to the amount of error, a memory storing a table of driving current values according to the amount of error is used, and the drive according to the amount of error is determined from the table. The current value can now be calculated.

[Function] According to such a configuration, the process of determining the drive current value according to the amount of error is extremely simple compared to the conventional method of determining the drive current value by arithmetic processing, and the process of determining the drive current value according to the error amount is extremely simple, and the process of determining the drive current value according to the error amount is extremely simple compared to the conventional method of determining the drive current value by arithmetic processing. The software for the CPU that makes up the unit is extremely simple, and the control burden on the CPU is reduced.
Significantly reduced. Furthermore, by selecting and changing the tables described in "-", control characteristics can be selected and changed extremely easily.

[Embodiments] Hereinafter, details of embodiments of the present invention will be described with reference to the attached drawings.

FIG. 1 schematically shows the configuration of a stepping motor drive control device employing the method of the present invention.

Reference numeral 2 denotes a CPU (central processing unit) which is the main body of control, is attached with a ROM (read only memory) 1, and is connected to a computer of a host system (not shown). The CPU 2 drives and controls the stepping motor 9 to be controlled via the latches 3 and 4, the D/A converters 5 and 6, and the power operational amplifier 7.8.

Here, the latches 3 and 4 each hold drive current value data of the stepping motor 9 output from the CPU 2.

Further, the D/A converters 5.6 each D/A convert the drive current value data held in the latches 3.4 into drive signal currents.

Further, each of the power operational amplifiers 7 . 8 accurately amplifies the drive signal current inputted from the D/A converters 5 and 6 and applies it to the stepping motor 9 .

In this case, the stepping motor 9 is configured as a two-phase motor having an A phase and a B phase, and is driven by two-phase excitation by applying amplified drive signal currents to the A phase and B phase, respectively. A driven member (not shown) is driven by the driving of the stepping motor 9, and is positioned according to the rotational driving direction and driving amount of the stepping motor 9.

In addition, the stepping motor 9 includes a stepping motor 9.
A sensor 10 comprising a rotary encoder or the like is attached to detect the deviation between the actual rotational position and the target rotational position, that is, the amount of error. sensor lO
The output signal is sent to the A/D controller 8 through 11.
The data is converted and input to the CPU2.

Based on such a configuration, the CPU 2 controls the driving of the stepping motor 9 according to the control program stored in the ROMI in response to commands input from the host system, and in this case, the CPU 2 controls the driving of the stepping motor 9 from the sensor 10 to the A/D. The drive current value of the stepping motor 9 is controlled according to the amount of error input via the converter 11.

Here, in this embodiment, the method of determining the drive current value according to the error amount is different from the conventional method, and the control table in which the drive current values corresponding to each error amount are recorded one-to-one in the ROMI. 12 is provided, and the CPU 2 searches the control table 12 for a drive current value corresponding to the amount of error.

The details of the control operation are performed as follows according to the control procedure of the CPU 2 shown in FIG.

When a positioning command is received from the host system, C
The PU 2 starts the control shown in FIG. 2, and first, in step S1, drives the stepping motor 9 by an amount corresponding to the positioning target position ordered from the host system. That is, drive current value data is sequentially output from the CPU 2, and the data is D/A converted into a drive current by the D/A converters 5 and 6, and then accurately amplified by the power operational amplifier 7. By applying the voltage to the phase and B phase, the stepping motor is rotationally driven.

At the point when the drive of the drive amount according to the target position is completed, the CPU
Step 2 moves to step S2, where the amount of error between the actual rotational position of the stepping motor 9 and the target position is read via the sensor 10.

Next, the CPU 2 checks whether the error amount read in step S3 is within a predetermined tolerance range, and if it is not within the tolerance range, in step S4, the drive current value data corresponding to the error amount is stored in the ROMI control table. 12 is searched for and output to latches 3 and 4. Then, the process returns to step S2, and steps 52 to S4 are repeated as a loop.

By repeating this, a drive current corresponding to the amount of error is sequentially applied to the stepping motor 9, and as a result, the excitation of the stepping motor 9 changes and the amount of error is reduced.

Then, when the error amount falls within the allowable range in step S3, C
The PUI moves to step S5, stops the stepping motor 9, and ends the control.

According to this embodiment as described above, the process in which CPtJ2 obtains the driving current value of the stepping motor 9 according to the above-mentioned error amount involves searching the control table 12, compared to the conventional method using complicated arithmetic processing. It's extremely simple. Therefore, the software for the CPU 2 is extremely simple, and the control burden on the CPU 2 is significantly reduced.

The contents of the control table 12 stored in ROMI are as follows:
For example, a table in which the waveform of the drive current value becomes a triangular wave as shown in FIG. 3 in relation to the displacement amount of the stepping motor 9.

Alternatively, a table with a sine wave as shown in FIG. 4 can be considered. By selecting such a table, control characteristics can be arbitrarily selected extremely easily.

In addition, if the drive characteristics of the positioning mechanism (not shown) using the stepping motor 9 as a drive source are expected to change over time, such as becoming dull due to wear, etc., the In addition, a plurality of types of control tables are stored in the ROMI, the contents of which realize different control characteristics corresponding to the stages of change in the drive characteristics, respectively, and the optimum control tables 12A to 12A are stored in the ROMI when the influence of the change in the drive characteristics appears. 12c and switch to use it.

In this way, the control characteristics can be changed very easily in response to changes in the drive characteristics.

In the above-described embodiment, control was performed by taking the amount of error between the actual rotational position of the stepping motor 9 and the target position. Control may be performed by taking the error ψ, and in this case, of course, a control table corresponding to the latter error amount is prepared.

[Effect] As is clear from the above description, according to the present invention, the above-mentioned rotational position is adjusted according to the amount of error between the actual rotational position of the stepping motor or the actual position of the member positioned by the motor and the target position. In a stepping motor drive control method for controlling a drive current value of a motor, a memory storing a table of drive current values corresponding to the error amount is used, and a drive current value corresponding to the error amount is determined from the table. Therefore, the process of determining the drive current value is extremely simple, the control software is extremely simple, and the control burden can be significantly reduced. Furthermore, by selecting or changing the tables marked with "-", an excellent effect can be obtained in that the control characteristics can be selected or changed extremely easily.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an embodiment of a stepping motor drive control device adopting the method of the present invention, Fig. 2 is a flow chart showing the control procedure by the CPU of Fig. 1, and Figs. 3 and 4 respectively. FIG. 5 is a diagram showing the waveform of the drive current value with respect to the displacement of the stepping motor to explain different control characteristics. FIG. 5 is an explanatory diagram of the ROM storing a plurality of control tables. 1-ROM 2 ・CP U3.4...Latch 5.6...D/A converter 7.8...Power operational amplifier 9...Stepping motor 10...Sensor 11...A/D converter 1'2, 12A-12C...Control table, %E
Igrqsnoihiiili → Japan゛I Teteshi V, S*C
]1 Figure 3 Figure 5

Claims (1)

[Claims] 1) A stepping motor that controls the driving current value of the motor according to the amount of error between the actual rotational position of the stepping motor or the actual position of a member positioned by the motor and the target position. A drive control method for a stepping motor, characterized in that the drive control method uses a memory storing a table of drive current values according to the error amount, and calculates the drive current value according to the error amount from the table. method. 2) The stepping motor drive control method according to claim 1, wherein a plurality of types of the tables are stored in the memory and are selectively used.