JP2000166275A - Servo control device by detecting current ripple - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a servo control device by detecting a current ripple that eliminates the need for a limit switch and can detect the locked state of a motor. SOLUTION: A current ripple detection part 20 outputs a pulse signal in synchronization with the rotation of a motor 1. A control part 10 and a motor drive part 11 compose a motor control part for controlling the motor 1 with servo based on a pulse signal from the current ripple detection part 20. The current ripple detection part 20 is provided with an amplifier 21 for amplifying a detection voltage that is proportional to the detection current of a resistor R that is a current detection means. A discrimination means 30 gives an instruction so that the motor to the control part 10 is stopped when the output value of the amplifier 21 is larger than a specific value and a pulse signal from the current ripple detection part 20 is not detected continuously for a specific amount of time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control apparatus for detecting a current ripple of a DC motor and detecting the rotation of the motor to perform servo control of the motor.

[0002]

2. Description of the Related Art Conventionally, servo controllers have been widely used to control the rotational speed and rotational position of a motor in accordance with designated values. For example, in a movable lighting device that can raise and lower a lamp or change a lighting direction using a motor, a moving speed and a position of the lighting device are determined by using a servo-controlled motor. ing.

FIG. 9 shows a configuration of a servo control device for a motor. This servo control device uses a brushed DC motor as a motor 1 for driving a load (not shown), and a so-called full bridge type in which four switching elements Q1 to Q4 are bridge-connected to drive the motor 1. The motor drive unit 11 including the bridge circuit is used. That is, each pair of switching elements Q1,
A bridge circuit is formed by connecting the series circuits of Q2, Q3, and Q4 in parallel, and the motor 1 is connected with the connection point of the switching elements Q1, Q2, Q3, and Q4 forming each arm of the bridge circuit as an output terminal. A DC power supply Vcc is connected between both ends of the parallel circuit of the arm. Therefore, by appropriately controlling the switching elements Q1 to Q4, the energizing direction to the motor 1 can be switched, and the amount of power supplied to the motor 1 can be adjusted to adjust the rotation speed of the motor 1. The amount of power supplied to the motor 1 is determined by the switching element Q
The switching elements Q1 to Q4 are adjusted by controlling the pulse width (PWM) of each of the switching elements Q1 to Q4
, The amount of power supply to the motor 1 increases.

Therefore, each of the switching elements Q1 to Q4 of the bridge circuit is a PWM generated by the control unit 10.
On / off control is performed by a signal (a pulse signal having a pulse width corresponding to the amount of power supplied to the motor 1). A resistor R as a current detecting means is connected in series to the motor 1, and this series circuit is connected to the output terminal of the bridge circuit. Therefore, the voltage across the resistor R is proportional to the motor current (armature current).

In this servo control device, a motor current (usually an armature current) is detected by a resistor R, and a current ripple included in the detected motor current is detected by a current ripple detecting section 20 to cause the motor 1 to rotate. A synchronized current ripple pulse is generated. The current ripple pulse is input to the control unit 10, and a control signal is generated such that the rotational speed and the rotational position of the motor 1 at each time detected by the current ripple pulse coincide with target values separately given to the control unit 10. The control signal controls the motor 1 via the motor drive unit 11. That is, the motor drive unit 11 energizes the motor 1 in accordance with the rotation speed and the rotation amount (including the rotation direction) of the motor 1 specified by the control signal.

The current ripple detecting unit 20 removes noise of a detection voltage proportional to the detection current by the resistor R by a noise circuit 22 and amplifies the noise by an amplifier 21. Outputs the current ripple pulse according to the magnitude relationship between the output of the differentiating circuit 23 and the reference value. That is, from the current ripple detection unit 20,
A current ripple pulse, which is a pulse signal synchronized with the rotation of the motor 1, is output. Therefore, the control unit 10 can detect the rotation speed and the rotation position of the motor 1 by counting the current ripple pulses from the current ripple detection unit 20.

[0007] A servo control device for detecting a current ripple included in a motor current flowing in a brushed DC motor and controlling the rotation speed and rotation position of the DC motor is disclosed in, for example, Japanese Utility Model Laid-Open Publication No. 56-7496. 57-189
294, JP-A-58-54888, JP-A-58-195664, JP-A-61-62380, JP-A-4-71383, and JP-A-4-172.
No. 984 (Japanese Patent Publication No. 7-73434).

As described above, the servo control device shown in FIG. 9 detects the rotation speed and the rotation position of the motor 1 based on the current ripple included in the motor current. Since a sensor for detecting the position is not separately provided, there is an advantage that the configuration is simple.

By the way, in a servo control device that servo-controls a DC motor that moves a movable body that reciprocates between two specified positions, such as a lighting device that moves up and down, limit switches are provided at both ends of the movable range of the movable body. By providing the motor, the motor and the motor drive unit are prevented from being burned due to the lock of the motor at both ends of the movable range. The motor is stopped to prevent danger.

[0010]

However, if limit switches are provided at both ends of the movable range as described above,
There was a problem that the cost was increased and space saving was hindered.

Therefore, instead of providing a limit switch, it is conceivable to determine whether or not the motor is in a locked state based on whether or not the above-described current ripple pulse is detected.

When the DC motor rotates at high speed (appropriate load condition)
Since the current ripple waveform becomes as shown in FIG. 10A, for example, the current ripple waveform can be easily determined. On the other hand, immediately before the motor enters the locked state, FIG.
As shown in the waveform shown in FIG. 5, when the rotation speed of the motor becomes extremely low (for example, the rotation speed is several hundred rpm or less), and when the motor reaches the lock state, current ripple is not detected, and it is difficult to determine the noise level. Become. In addition, when the load is light at low speed rotation, the current ripple waveform has more low frequency components and a smaller peak value than at high speed rotation as shown in FIG. Some rotation speed ranges are not available. Therefore, there is a problem that it is not possible to determine whether the motor is in the locked state or rotating at a low speed with a light load only by detecting the current ripple.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a servo control device based on current ripple detection which does not require a limit switch and can detect a locked state of a motor. is there.

[0014]

According to the first aspect of the present invention, there is provided an electric vehicle comprising: a current detecting means for detecting a motor current flowing through a DC motor; and a DC current detecting means for detecting a current ripple included in the motor current. A current ripple detection unit that outputs a pulse signal synchronized with the rotation of the motor, a motor control unit that servo-controls the DC motor based on the pulse signal from the current ripple detection unit, and a magnitude of the current value detected by the current detection unit Is larger than a predetermined value, and when the pulse signal is not continuously detected for a predetermined time, the motor control unit is instructed to stop the motor. When the magnitude of the current value detected by the means is larger than a predetermined value and the pulse signal is not continuously detected for a predetermined time, the motor is stopped by the motor control unit. Since instruct so that, without providing the limit switch, the motor is a motor that is highly safe is stopped when the hand or fingers or a locked state sandwiched.

According to a second aspect of the present invention, in the first aspect of the present invention, the DC motor reciprocates the movable body between two prescribed positions, and the motor control unit includes a movable body for performing initialization. Counting means for detecting a count value corresponding to the stop position of the motor by counting the pulse signal when reciprocating the movable member, and a movable body corresponding to each count value corresponding to the stop position detected by the count means. Movable range setting means for storing limit pulse values for setting respective limit positions of both ends of the movable range, and the count value of the pulse signal from the current ripple detecting section has reached the limit pulse value stored in the movable range setting means. In this case, the position control means for instructing the motor control unit to stop the motor is added. The limit pulse value for setting each limit position at both ends of the movable range of the movable body according to each count value corresponding to the stop position is automatically stored in the movable range setting means. When the count value of the pulse signal reaches the limit pulse value, the position control unit instructs the motor control unit to stop the motor, so that the movable range of the movable body is regulated without providing a limit switch. It becomes possible.

According to a third aspect of the present invention, in the first aspect of the present invention, the DC motor reciprocates the movable body between two prescribed positions, and the motor control unit includes a movable body for performing initial setting. Counting means for detecting a count value corresponding to the stop position of the motor by counting the pulse signal when reciprocating the movable member, and a movable body corresponding to each count value corresponding to the stop position detected by the count means. And a movable range setting means for storing limit pulse values for setting respective limit positions of both ends of the movable range. After the limit pulse value is stored in the movable range setting means, based on the stored contents of the movable range setting means. To determine whether or not the movable body is in the movable range. If the movable body is within the movable range, an instruction to stop the motor is given by the determination means, and the overload state is recognized. At the time of the initial setting, the limit pulse value for setting the respective limit positions at both ends of the movable range of the movable body in accordance with each count value corresponding to the stop position detected by the counting means is automatically stored in the movable range setting means. However, after the initialization, if the motor control unit issues an instruction to stop the motor within the movable range from the determination unit, the motor control unit may cause a hand, finger, or obstacle to be caught in the movable range of the movable body, causing the motor to overrun. It is possible to recognize that there is a load.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the DC motor reciprocates the movable body between two specified positions, and the motor control unit includes a movable body for performing initialization. Counting means for detecting a count value corresponding to the stop position of the motor by counting the pulse signal when reciprocating the movable member, and a movable body corresponding to each count value corresponding to the stop position detected by the count means. Movable range setting means for storing stop positions at both ends of the movable range, and position control means for performing relative position control between the two positions after the count value is stored in the movable range setting means. Therefore, the stop positions at both ends of the movable range of the movable body are automatically transmitted to the movable range setting means in accordance with each count value corresponding to the stop position detected by the counting means at the time of the initial setting. Since the relative position control between the stop positions is performed by the position control means after the initial setting is completed, it is not necessary to know the movable range of the movable body in advance, and when the movable range of the movable body is different. Can also be accommodated.

[0018]

(Embodiment 1) The basic configuration of this embodiment is substantially the same as the conventional configuration shown in FIG.
As shown in (5), when the detection voltage value proportional to the detection current of the resistor R as the current detection means is larger than a predetermined value and the pulse signal is not continuously detected for a predetermined time, the control unit 10 is instructed to stop the motor. It is characterized in that a discriminating means 30 is provided. Note that the same components as those of the conventional configuration shown in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted. Further, the control unit 10 and the motor drive unit 11 constitute a motor control unit that servo-controls the motor 1 based on a pulse signal from the current ripple detection unit 20.

In this embodiment, the motor 1 moves the movable body movable between two specified positions to the above two positions or two positions.
It reciprocates to an appropriate position between the positions.

As shown in FIG. 2, the discriminating means 30 performs A / D conversion on the cycle counter 31 for accumulating the current ripple pulse output from the current ripple detecting section 20 and the output of the amplifier 21 of the current ripple detecting section 20. And an A / D converter 32. Further, the determination means 30 includes a period counter 31
Of the digital value A / D converted by the A / D conversion unit 32 is 1
A logic gate 33 whose output changes from 0 to 1 at the time. The number of current ripple pulses generated corresponds to the rotation amount of the motor 1, and the generation interval of the current ripple pulses corresponds to the rotation speed of the motor 1.

Here, when the integrated value of the cycle counter 31 is, for example, 0, the current ripple pulse is output to the cycle counter 3
In this case, it is highly likely that the motor 1 is in the locked state or is rotating at a low speed with a light load. On the other hand, in order for the higher-order specific bit of the digital value converted by the A / D converter 32 to become 1, the output of the amplifier 21 needs to be relatively large. That is, it means that the current value of the detection current of the resistor R becomes larger than the predetermined value. Therefore, when the upper specific bit is 1, the possibility that the motor 1 is in the locked state is high. On the other hand, when the motor 1 is rotating at a low speed with a light load, the level of the current ripple is small as shown in FIG. Note that as the current value of the detection current of the resistor R, an average value, a peak value, or the like of the detection current is used.

Accordingly, when the detection voltage value proportional to the detection current of the resistor R is larger than the predetermined value and the pulse signal is not continuously detected for a predetermined time, the output of the logic gate 33 changes from 0 to 1 Changes to

The output of the logic gate 33 is input to the control unit 10. When the output of the logic gate 33 becomes 1, the control unit 10 is instructed by the determination means 30 to stop the motor 1. It is supposed to be considered.

According to the present embodiment, when the average value or peak value of the detection current of the resistor R as the current detection means is larger than a predetermined value and a pulse signal as a current ripple pulse is not continuously detected for a predetermined time, Since the determination means 30 instructs the control unit 10 to stop the motor 1, the motor 1 is stopped. In short, in the present embodiment, the motor 1 can be reliably stopped when the motor 1 is locked or a hand or finger is caught without providing a limit switch.

(Embodiment 2) The basic configuration of this embodiment is substantially the same as that of Embodiment 1, and as shown in FIG.
It is characterized in that a position control means 40 for giving an instruction regarding position control to 0 is added. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

Here, the position control means 40 is provided as shown in FIG.
As shown in (1), a preset up / down counter 41 for counting the current ripple pulse input from the current ripple detection unit 20 is provided. As described in the first embodiment, the number of generated current ripple pulses corresponds to the rotation amount of the motor 1, and the generation interval of the current ripple pulse corresponds to the rotation speed of the motor 1.

The position control means 40 has an input terminal U of a preset up / down counter 41 for inputting the output of the current ripple detecting section 20 in accordance with the rotation direction of the motor 1.
A switch SW for switching between C and DC is provided.
When the switch SW is connected to the input terminal UC, the current ripple pulse is counted up (+1), and when the switch SW is connected to the input terminal DC, the current ripple pulse is counted down (-1). The changeover switch SW is
Switching is performed in conjunction with the switching of the rotation direction of the motor 1 by the motor drive unit 11. For example, when the motor 1 rotates clockwise, the current ripple pulse is counted up,
When rotating in the counterclockwise direction, the current ripple pulse is counted down.

The position control means 40 supplies a target value of the control position of the movable body from the host system to the preset terminal PRESET of the preset up / down counter 41 as a preset pulse, and controls the count value until the count value matches the preset value. It instructs the unit 10 to drive the motor 1.

Further, the position control means 40 compares the output value (count value) of the preset up / down counter 41 with the limit pulse value stored in the memory constituting the limit pulse value holding means 50 as the movable range setting means. A comparator 42 for comparison is provided, and when the count value of the preset up / down counter 41 overflows or underflows the limit pulse value,
A switch (not shown) is turned off, and a command to drive the motor to the control unit 10 is interrupted. Thus, the control unit 10
When the command from the position control means 40 is interrupted, the motor 1
The motor drive unit 11 is controlled so as to stop. In addition,
Reverse rotation may be performed by a specified amount.

That is, the position control means 40 receives a current ripple pulse as a pulse signal from the current ripple detection unit 20, and the number of current ripple pulses is held in the limit pulse value holding means 50. When the limit pulse value is reached, the control unit 10 is instructed to stop the motor 1.

The limit pulse value is set as follows. When the power is turned on for the first time, the motor control unit performs the initial setting, so that the movable body is reciprocated and the stop position of the movable body is detected based on the output of the determination unit 30 when the motor is locked. The limit pulse value for setting the limit positions at both ends of the movable range of the movable body is stored in the limit pulse value holding means 50 according to each count value of the current ripple pulse when each stop position is detected. In the present embodiment, the discriminating means 30 includes a counting means for detecting a count value corresponding to the stop position of the motor 1 by counting a pulse signal when the movable body is reciprocated for performing initial setting. Also serves as.

In the present embodiment, when the power is first turned on, the movable body reciprocates and the stop position is detected based on the output of the discriminating means 30, and each of the movable positions corresponds to the limit position at both ends of the movable range. The limit pulse value is automatically stored, and thereafter (after completion of the initial setting), when the output of the preset up / down counter 41 reaches the limit pulse value, the position control means 40 causes the control unit 10 to stop the motor 1. Thus, the movable range of the movable body can be regulated without providing a limit switch.

(Embodiment 3) The basic configuration of this embodiment is substantially the same as that of Embodiment 2, and as shown in FIG. 5, an output of the position control means 40 and a movable range pulse value holding means as a movable range setting means. A movable range comparing means for comparing the movable range pulse value held in the movable range;
However, it is characterized in that when the locked state of the motor 1 is detected while the movable body is determined to be within the movable range by the movable range comparison means 70, the motor 1 is recognized as being in an overload state. . Note that the same components as those in the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

The in-movable range comparing means 70 is constituted by a comparator as shown in FIG. 6, and outputs the output value (count value) of the preset up / down counter 41 of the position control means 40 and the movable range pulse value holding means 60. A comparison is made with a movable range pulse value written in a memory constituting the memory to inform the determination means 30 whether or not the movable body is within the movable range. The determination unit 30 includes the period counter 31 described in the first embodiment,
An obstacle within the movable range is detected together with the result of the determination of the lock state by the lock detection means including the A / D converter 32 and the logic gate 33. In other words, when the lock state of the motor 1 is detected by the lock detection unit and the movable unit is recognized as being within the movable range by the movable range comparison unit 70, it is determined that an obstacle is sandwiched within the movable range. It has become.

The limit pulse value is set as follows. When the power is turned on for the first time, the motor control unit performs the initial setting, so that the movable body is reciprocated and the stop position of the movable body is detected based on the output of the determination unit 30 when the motor is locked. The limit pulse value for setting the limit positions at both ends of the movable range of the movable body is stored in the limit pulse value holding means 50 according to each count value of the current ripple pulse when each stop position is detected. In the present embodiment, the discriminating means 30 includes a counting means for detecting a count value corresponding to the stop position of the motor 1 by counting a pulse signal when the movable body is reciprocated for performing initial setting. Also serves as.

In this embodiment, when the power is turned on for the first time, the movable body is reciprocated and the stop position is detected based on the output of the discriminating means 30, and each of the movable positions corresponds to the limit position at both ends of the movable range. The limit pulse value is automatically stored, and thereafter (after the end of the initial setting), if the control unit 10 receives an instruction from the determination unit 30 within the movable range, the control unit 10
Can recognize that the hand, finger or obstacle is sandwiched within the movable range of the moving body and the motor is overloaded.

(Embodiment 4) The basic configuration of this embodiment is substantially the same as that of Embodiment 2, and as shown in FIG. 7, an upper command from an upper system (not shown) is converted into a position control pulse. This is characterized in that a command conversion means 80 for transmitting the command to the position control means 40 is added. Note that the same components as those in the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 8, the position command conversion means 80 includes an interpretation means 81 for interpreting an upper command (analyzing the meaning of the command), and an output of the interpretation means 81 and a memory serving as a movable range pulse value holding means 60. A calculating means 82 performs a predetermined calculation based on the stored ripple pulse value corresponding to the position of the movable range, generates a position control pulse, and outputs it as a preset pulse to the preset up / down counter 41.

The calculating means 82 converts a higher-order command into a position control pulse by, for example, proportional calculation with the ripple pulse value stored in the movable range pulse holding means 60.

In this embodiment, the stop position of the movable body is detected based on the output of the determination means 30 when the movable body is reciprocated and the motor 1 is locked in order to perform the initial setting when the power is first turned on. Then, each count value corresponding to the stop position at both ends of the movable range is automatically stored. Here, the count value of the ripple pulse at one of the two stop positions is stored as the ripple pulse value at the origin.

By the way, the host system defines the position command as a command easily recognized by humans (a command that is a physical host concept) such as "center" of the movable range or "one-third point near the origin". Output. On the other hand, the position command converting means 80 interprets the command by the interpreting means 81, obtains a ripple pulse value at a position corresponding to the position command by the calculating means 82, and outputs it as a preset pulse to the preset up / down counter 41.

In the present embodiment, when the power is first turned on, the stop position is set based on the output of the determination means 30 when the movable body is reciprocated and the motor 1 is locked to perform the initial setting. The count values corresponding to the detected stop positions at both ends of the movable range are automatically stored, and thereafter (after the end of the initial setting), the relative position control between the stop positions is performed by the position control means 40. It is not necessary to know the movable range of the movable body in advance, and it is possible to cope with the case where the movable range of the movable body is different.

Further, since the position command from the host system can be given by the above-mentioned command instead of giving by the number of pulses, it is not necessary to know in advance the movable range of each mechanism in the mechanism driven by the motor. In addition, the higher-level system can be instructed in terms of the physical upper concept even for mechanisms with different movable configurations and ranges of each mechanism. It is possible to eliminate the necessity of changing the data.

[0044]

According to the first aspect of the present invention, there is provided a current detecting means for detecting a motor current flowing through a DC motor, and a current for detecting a current ripple included in the motor current and outputting a pulse signal synchronized with the rotation of the DC motor. A ripple detection unit, a motor control unit that servo-controls the DC motor based on the pulse signal from the current ripple detection unit, and a magnitude of the current value detected by the current detection unit is larger than a predetermined value and the pulse signal is generated for a predetermined time. A determination unit that instructs the motor control unit to stop the motor when the detection is not performed continuously, so that the magnitude of the current value detected by the current detection unit is larger than a predetermined value and the pulse signal is continuously generated for a predetermined time. If it is not detected, the discriminating means instructs the motor control unit to stop the motor. Motor motor there is an effect that high safety is stopped when a hand or finger or in a locked state sandwiched.

According to a second aspect of the present invention, in the first aspect of the present invention, the DC motor reciprocates the movable body between two specified positions, and the motor control unit includes a movable body for performing initial setting. Counting means for detecting a count value corresponding to the stop position of the motor by counting the pulse signal when reciprocating the movable member, and a movable body corresponding to each count value corresponding to the stop position detected by the count means. Movable range setting means for storing limit pulse values for setting respective limit positions of both ends of the movable range, and the count value of the pulse signal from the current ripple detecting section has reached the limit pulse value stored in the movable range setting means. In this case, the position control means for instructing the motor control unit to stop the motor is added. The limit pulse value for setting each limit position at both ends of the movable range of the movable body according to each count value corresponding to the stop position is automatically stored in the movable range setting means. When the count value of the pulse signal reaches the limit pulse value, the position control unit instructs the motor control unit to stop the motor, so that the movable range of the movable body is regulated without providing a limit switch. There is an effect that it becomes possible.

According to a third aspect of the present invention, in the first aspect of the present invention, the DC motor reciprocates the movable body between two prescribed positions, and the motor control unit includes a movable body for performing initial setting. Counting means for detecting a count value corresponding to the stop position of the motor by counting the pulse signal when reciprocating the movable member, and a movable body corresponding to each count value corresponding to the stop position detected by the count means. And a movable range setting means for storing limit pulse values for setting respective limit positions of both ends of the movable range. After the limit pulse value is stored in the movable range setting means, based on the stored contents of the movable range setting means. To determine whether or not the movable body is in the movable range. If the movable body is within the movable range, an instruction to stop the motor is given by the determination means, and the overload state is recognized. At the time of the initial setting, the limit pulse value for setting the respective limit positions at both ends of the movable range of the movable body in accordance with each count value corresponding to the stop position detected by the counting means is automatically stored in the movable range setting means. However, after the initialization, if the motor control unit issues an instruction to stop the motor within the movable range from the determination unit, the motor control unit may cause a hand, finger, or obstacle to be caught in the movable range of the movable body, causing the motor to overrun. There is an effect that it is possible to recognize that the vehicle is in the load state.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the DC motor reciprocates the movable body between two prescribed positions, and the motor control unit includes a movable body for performing initial setting. Counting means for detecting a count value corresponding to the stop position of the motor by counting the pulse signal when reciprocating the movable member, and a movable body corresponding to each count value corresponding to the stop position detected by the count means. Movable range setting means for storing stop positions at both ends of the movable range, and position control means for performing relative position control between the two positions after the count value is stored in the movable range setting means. Therefore, the stop positions at both ends of the movable range of the movable body are automatically transmitted to the movable range setting means in accordance with each count value corresponding to the stop position detected by the counting means at the time of the initial setting. Since the relative position control between the stop positions is performed by the position control means after the initial setting is completed, it is not necessary to know the movable range of the movable body in advance, and when the movable range of the movable body is different. There is an effect that it can respond to.

[Brief description of the drawings]

FIG. 1 is a schematic circuit block diagram illustrating a first embodiment.

FIG. 2 is a circuit diagram of the same.

FIG. 3 is a schematic circuit block diagram showing a second embodiment.

FIG. 4 is a circuit diagram of the same.

FIG. 5 is a schematic circuit block diagram showing a third embodiment.

FIG. 6 is a circuit diagram of the same.

FIG. 7 is a schematic circuit block diagram showing a fourth embodiment.

FIG. 8 is a circuit diagram of the same.

FIG. 9 is a schematic circuit block diagram showing a conventional example.

FIG. 10 is an operation explanatory view of the above.

[Explanation of symbols]

 Reference Signs List 1 motor 10 control unit 11 motor drive unit 20 current ripple detection unit 21 amplifier 30 determination means R resistance

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) JJ23 KK06 LL14 LL22 LL31 MM04

Claims (4)

[Claims] A current detecting means for detecting a motor current flowing in the DC motor; a current ripple detecting section for detecting a current ripple included in the motor current and outputting a pulse signal synchronized with the rotation of the DC motor; A motor control unit that servo-controls the DC motor based on a pulse signal from the detection unit; and a control unit that controls when the magnitude of the current value detected by the current detection unit is larger than a predetermined value and the pulse signal is not continuously detected for a predetermined time. A determination unit that instructs the motor control unit to stop the motor. 2. The DC motor reciprocates a movable body between two prescribed positions, and a motor control unit counts a pulse signal when the movable body reciprocates for initial setting. Counting means for detecting a count value corresponding to the stop position of the motor, and a limit for setting limit positions at both ends of the movable range of the movable body in accordance with each count value corresponding to the stop position detected by the counting means. A movable range setting means for storing a pulse value, and a motor control section for stopping a motor when a count value of a pulse signal from the current ripple detecting section reaches a limit pulse value stored in the movable range setting means. 2. The servo control device according to claim 1, further comprising a position control means for indicating. 3. The DC motor causes the movable body to reciprocate between two specified positions, and the motor control unit counts a pulse signal when the movable body is reciprocated for initial setting. Counting means for detecting a count value corresponding to the stop position of the motor, and a limit for setting limit positions at both ends of the movable range of the movable body in accordance with each count value corresponding to the stop position detected by the counting means. A movable range setting means for storing a pulse value is added, and after the limit pulse value is stored in the movable range setting means, it is determined whether or not the movable body is in the movable range based on the stored contents of the movable range setting means. 2. The system according to claim 1, wherein when it is determined that the motor is within the movable range, an instruction to stop the motor is issued from the determining means to recognize that the motor is overloaded.
A servo controller based on current ripple detection as described. 4. The DC motor causes a movable body to reciprocate between two prescribed positions, and a motor control unit counts a pulse signal when the movable body is reciprocated for initial setting. Counting means for detecting a count value corresponding to the stop position of the motor, and movable means for storing stop positions at both ends of the movable range of the movable body in accordance with each count value corresponding to the stop position detected by the count means. 2. The current according to claim 1, further comprising a range setting means and a position control means for performing relative position control between the two positions after the count value is stored in the movable range setting means. Servo control device by ripple detection.