JP3278462B2 - Initial position setting device for automation equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an initial position setting device for an automatic device having position detecting means for detecting an absolute position in combination with a counter, such as an incremental encoder.

[0002]

2. Description of the Related Art Conventionally, there is an automation apparatus having a moving part driven by a driving means, the operation range of which is defined by a mechanical stopper, and position detecting means for detecting the position of the moving part.

[0003] The position detecting means of this type of automation apparatus includes an absolute position detector such as a potentiometer, a differential detector or an absolute encoder capable of detecting the absolute position when the power is turned on, and sets the absolute position after the power is turned on. Otherwise, only the relative displacement is known, and the speed detector is roughly classified into a relative position detector such as an incremental encoder or a resolver, which has a strong element.

The latter relative position detector performs a counting operation in accordance with its output, and plays a role in combination with an up / down counter whose count value is the position information of the moving part. However, the relative position detector is smaller than the absolute position detector. It is widely used in automated devices such as robots because it can perform position detection with high resolution and high resolution. However, on the other hand, in order to know the absolute position of the moving part, it is necessary to perform a process called a counter value initial setting operation.

[0005] One of the conventional examples will be described below with reference to FIG.

In this figure, first, 10 is a moving part, 2
2 is a motor, 23 is a ball screw, 24 is a coupling,
32 is a guide bar. Motor 22, ball screw 2
3, the coupling 24 and the guide bar 32 constitute driving means of the moving unit 10, and the ball screw 23 is
3 is connected to the output shaft 3 by a coupling 24. The ball screw 23 and the guide bar 32 extend in parallel,
The moving part 10 is screwed with the ball screw 23 and slidably inserted into the guide bar 32. by this,
When the motor 23 rotates, the rotational power is transmitted to the ball screw 23, and the moving unit 10 moves in one of the arrow directions according to the rotation direction of the ball screw 23.

A mechanical stopper 31a is arranged at one end of the guide bar 32, and a mechanical stopper 31b is arranged at the other end.
The movements to various directions are mechanically and forcibly prevented by a and 31b, and the operation range is defined.

Reference numeral 41 denotes an encoder, and reference numeral 42 denotes an up / down counter, which constitute a relative position detector. The encoder 41 is connected to the motor 22, and the counter 42 performs a counting operation based on the frequency and the sign.

Reference numeral 52 denotes a control unit, 43 denotes an F / V (frequency / voltage) converter, 21 denotes a servo driver, 54a and 54b denote limit sensors comprising photoelectric switches, 53a and 53b.
Denotes a photoelectric sensor amplifier, and the operation of the driving means including the motor 22 and the like is controlled by this. That is, an output of the encoder 41 is input to the servo driver 21 via the F / V converter 43 as speed information of the motor 22, and a speed command and a rotation direction command are input from the control unit 52. The servo driver 21 monitors the speed of the motor 22 based on the output of the encoder 41,
The motor 22 is driven so as to respond to the command from. The output of the counter 42 is input to the control unit 52, and the control unit 52
Monitors the position of the moving unit 10 based on the position information based on the count value, and sets the speed command to the servo driver 21 to "0" when the moving unit 10 comes to the stop position. Limit sensor 54
a detects the presence of the moving part 10 at the stop position corresponding to the mechanical stopper 31a, and the limit sensor 54b
The presence of the mechanical stopper 31b at the stop position corresponding to the zero mechanical stopper 31b is detected, and each output is given to the servo driver 21 as a stop instruction by the corresponding photoelectric sensor amplifier 53a or 53b. Therefore, when the movement unit 10 reaches the stop position, the servo driver 21 receives not only the speed “0” command from the control unit 52 but also the stop command from the limit sensors 54a and 54b, and
Stop the operation of. Although the stop control of the motor 22 can be performed by only one of the speed command “0” and the stop instruction, the limit sensors 54 a and 54 b provided for initial setting of the counter 42 are improved in safety here. It is effectively used with the intention of.

The encoder 41 and the counter 42 constitute a relative position detector, and the initial position must be set as described above. The operation is described below with reference to FIG.
Will be described with reference to FIG. FIG. 7 shows an algorithm of the counter value setting operation.

First, the control unit 52 issues a constant speed command (step ST701). Then, the motor 22 is driven by the servo driver 21 in the same manner as described above, and the moving unit 10 moves. Thereafter, the control unit 52 starts monitoring the outputs of the photoelectric sensor amplifiers 53a and 53b (step ST70).
2,703). When the movement unit 10 operates the limit sensor 54a or 54b, the photoelectric sensor amplifier 53a or 53b detects that the limit has been detected, and the detection signal is input to the control unit 52 as an interrupt signal IRQ. Then, the control unit 52 outputs a speed command “0” (step ST704), and at the same time, activates an operation limit stop switch (not shown) incorporated in the servo driver 21 as a driving unit, thereby stopping the motion unit 10. Upon receiving the interrupt signal from the photoelectric sensor amplifier 53a or 53b, the control unit 52 receives the interrupt signal from the limit sensor 54a or 5b.
Since the absolute position of 4b is known, the counter value corresponding to the detected limit sensor position is preset in the up / down counter 42 (step ST705). After the initial setting, the counter value becomes the absolute position information.

Although FIG. 7 shows an algorithm of the interrupt generation process performed by the photoelectric sensor amplifier 53, it is basically equivalent.

Other known methods include an initial setting operation using an origin sensor and a method of initializing a counter value based on the absolute position using an absolute position detecting means.

[0014]

As described above, the initial setting of the conventional relative position detecting means requires a limit sensor such as a photoelectric switch, which undesirably increases the number of parts of the automation device.

In addition, it is not desirable to increase the number of sensor signal lines because the wiring must be designed so as not to hinder the movement of the moving part. In particular, the problem becomes more serious as robots have more degrees of freedom.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to provide an initializing apparatus for an automatic device that obtains initial position information for initial setting from existing parts other than a limit sensor. It is to propose a position setting device.

According to the present invention, there is provided an automatic apparatus having a moving part moved by a driving means and a relative position detecting means for detecting a relative movement amount of the moving part. A mechanical stopper disposed at a fixed position to be restricted, a driving force detecting means for detecting a driving force generated by the driving means, a comparing means for comparing the detected driving force with a set value, and a comparison result of the comparing means Overload detecting means for detecting that the moving section has reached the position of the mechanical stopper based on the position, and converting the relative movement amount into an absolute movement amount based on the position detected by the overload detecting means. And a moving amount converting means.

In such a configuration, when the control unit outputs a constant speed command to the driving unit, the moving unit moves at a constant speed by the driving unit. As long as the moving part does not hit the mechanical stopper, the driving force does not increase so much.However, when the moving part hits the mechanical stopper and stops, the driving means generates a large driving force in order to accelerate the moving part to the commanded speed. As a result, the output signal of the driving force detecting means is equal to or larger than the set value of the comparing means.

The comparing means compares the driving force signal with the set value which is a threshold value. If the driving force is large, it is determined that the mechanical stopper is hit, and the control unit is notified of this.
As a result, the control unit presets the absolute position of the mechanical stopper to the relative position detecting means.

Here, the driving force detecting means may be a detecting means such as a current monitor (armature current detector) normally incorporated in a servo driver which is a part of the driving means. This is because the armature current that the servo driver passes through the motor is substantially proportional to the driving torque of the motor, and an approximate driving force can be estimated from this current value.

Further, some robots and the like that require force control include a force sensor provided on the drive shaft. In this case, a force detector may be used as the drive force detecting means.

Further, the comparator may be included in the control unit and may not appear explicitly.

As described above, it is not necessary to provide a photoelectric sensor or the like for the initial setting of the counter, and the initial setting operation of the position detector can be performed only by the device required in the normal automation processing. Further, the driving force detecting means has a current detector for detecting an armature current of the driving means, and the comparing means compares the armature current detected by the current detector with a set value. Good. Further, the driving unit includes a gear coupling mechanism that rotationally drives the moving unit,
A rotating shaft connected to an input gear of the gear coupling mechanism, wherein the driving force detecting means includes torque detecting means for detecting a driving torque of the rotating shaft, and the comparing means includes the torque detecting means. The drive torque detected by the means may be compared with a set value.

[0024]

According to the present invention, the initial position is detected by capturing an increase in the driving force applied to the moving part when the movement of the moving part is forcibly prevented by the mechanical stopper. A limit sensor for initial setting of the means can be omitted, and problems in the number of parts and wiring of the automation device can be solved.

[0025]

FIG. 1 shows a system configuration of a first embodiment of the present invention.

The system according to the embodiment of the present invention is different from the system shown in FIG. 6 in that a limit sensor is not provided and a current detector 25 and comparators 51a and 51b are provided instead.

FIG. 3 shows an initialization algorithm of the present system.

The control section 52 outputs a constant speed command to the servo driver 21 which is a part of the driving means (step ST3).
01), and enters an output monitoring state of the comparators 51a and 51b (steps ST302 and ST303). Servo driver 21
Performs the speed feedback so that the speed of the moving unit becomes the commanded speed, and passes the armature current to the motor 22 which is a part of the driving means. The speed of the moving section, which is feedback information at this time, is obtained by converting the output signal of the encoder 41 into an F / V converter 4.
3 can be obtained by conversion. Servo driver 21
Is approximately proportional to the driving torque of the motor 22. By monitoring this current with the current detector 25, an approximate driving force is estimated. The current detector 25 is generally built in an ordinary servo driver and is already existing.

The moving unit 10 operated by the driving means moves at a substantially constant speed at a command speed unless it hits the mechanical stopper 31. In this case, the motor current, that is, the driving force does not become too large. However, when the moving unit 10 hits the mechanical stopper 31 and stops, the servo driver 21 serving as a driving unit is stopped.
The motor 22 generates a large driving force in order to accelerate the moving part to the command speed, and as a result, the output signal of the current detector 25 as the driving force detecting means exceeds a certain set value.

The comparator 51a or 51b compares the output signal of the current detector 25 with a preset threshold value, and if the observed signal is large, the moving unit 10
It is determined that it has hit 1 and an operation limit stop switch (not shown) included in the driver 21 is operated, and an interrupt signal is generated to the control unit 52 to notify the detection of the mechanical stopper position.

When the control unit 52 receives this interrupt,
The speed command to the servo driver 21 is cleared (step ST304), and a process of presetting a counter value corresponding to the absolute position of the mechanical stopper 31 to the up / down counter 42 is performed (step ST305).

The preset process does not necessarily need to be performed at this position, but may be performed after moving the moving unit by a certain number of counters from the mechanical stopper position.

FIG. 2 shows a system configuration according to a second embodiment of the present invention.

In this embodiment, the control unit directly monitors the output signal of the driving force detecting means, and the control unit includes a comparator. The initial setting algorithm is determined by the control unit 5
3 is basically the same as that shown in FIG. 3 except that the second unit 2 directly receives the output of the current detector 25 and performs the comparing means.

After the control unit 52 outputs a constant speed command to the servo driver 21, the control unit 52
The signal of the current detector 25 existing in the current detector 25 is monitored, and if the value is smaller than a preset value, the current detector 25 is again monitored.
Continue to detect the current monitor signal. If the input current monitor signal is larger than the set value, the control
It determines that 0 is at the mechanical stopper position, clears the speed command to the servo driver 21 as the driving means, and performs a process of presetting the counter value corresponding to the absolute position of the mechanical stopper 31 to the up / down counter 42.

In this example, for safety, the control unit 52 outputs a speed command clear to the servo driver 21 and also operates an operation stop switch (not shown) included in the servo driver.
Also performs n / off.

In the so-called normal automation processing after the initial setting of the counter value, it is not desirable to set the operation range to the mechanical stopper position.
If the operation of the driver is stopped or an interrupt generation process is performed, the operation range can be set inside the mechanical stopper, and a limit sensor is not required.

FIG. 4 shows a system configuration according to a third embodiment of the present invention. The system shown in this figure is characterized in that the present invention is applied to a multi-degree-of-freedom robot having a force sensor on each axis. It is to be noted that here, one degree of freedom is shown, and in practice, what is shown in this figure is installed for each axis.

26 is a speed reducer, 27 is a gear coupling mechanism, 10
′ Is a link-type moving unit. The input shaft of the reduction gear 26 is connected to the output shaft of the motor 22, and the input gear of the gear connection mechanism 27 is fixed to the output shaft of the reduction gear 26. The movement unit 10 ′ is fixed to an output gear of the gear coupling mechanism 27, and is configured to rotate integrally with the output gear of the gear coupling mechanism 27.

Reference numeral 55 denotes a torque sensor, and 56 denotes a torque sensor amplifier, which constitute driving force detecting means. The torque sensor 55 detects the drive torque of the output shaft of the reduction gear 26 at the connection between the output shaft of the reduction gear 26 and the input gear of the connection gear mechanism 27, and its output is amplified by the torque sensor amplifier 56 and is driven to the control unit 52. Given as force information.

FIG. 5 shows an initialization algorithm in this embodiment.

The control unit 52 executes a step S described later for each axis.
The processing of T501 to 508 is performed.

First, the control section 52 sets a control target (step ST501), outputs a constant speed command for the axis to the servo driver 21, and the control section 52 outputs the output of the sensor amplifier 56 of the torque sensor 55 for the axis. The signals are monitored (steps ST503 and ST504).

The torque sensor 55 and the sensor amplifier 56 of each axis are force detecting means for monitoring the external force. When the link 10 of the drive shaft contacts the mechanical stopper 31 and stops, the external force and the driving force of the motor are reduced. Therefore, the output of the torque sensor amplifier 56 becomes equivalent to the output of the driving force.

The control unit 52 compares the value of the torque sensor with a preset threshold value. If the detected force is larger than the set value, the control unit 52 clears the speed command to the servo driver 21 (step ST505). A process of presetting the counter value corresponding to the absolute position to the up / down counter 42 is performed (step ST506). The control unit 52 thereafter controls the position of the moving unit 10 ', which is the moving unit, to the initial position serving as a reference (step ST507), and confirms whether or not the initialization of all axes has been completed (step ST50).
8) The counter value initial setting operation of the next drive axis is started. This operation is repeated until the initialization of the counters of all the drive axes is completed.

Although the torque sensor 55 is used as the driving force observation means in this example, a current detector (not shown) built in the servo driver may be used as the driving force observation means.

[0047]

As described above, according to the present invention, the initial position is detected by capturing the increase in the driving force applied to the moving part when the movement of the moving part is forcibly prevented by the mechanical stopper. This eliminates the need for counter initial setting parts such as limit sensors, which were required in automated devices using relative position detectors. In addition, since the need for a limit sensor and the like is eliminated, the number of signal cables can be reduced, and a cleaner design can be achieved with a multi-degree-of-freedom automation device such as a robot.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a system configuration of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a system configuration of an apparatus according to a second embodiment of the present invention.

FIG. 3 is a flowchart showing an initialization algorithm in the system shown in FIGS. 1 and 2;

FIG. 4 is a block diagram showing a system configuration of an apparatus according to a third embodiment of the present invention.

FIG. 5 is a flowchart showing an initialization algorithm in the system shown in FIG. 4;

FIG. 6 is a block diagram showing a system configuration of a conventional device.

FIG. 7 is a flowchart showing an initialization algorithm in the system shown in FIG. 6;

[Explanation of symbols]

 10, 10 'Moving part 21 Servo driver 22 Motor 23 Ball screw 24 Coupling 25 Current detector 26 Reduction gear 27 Connecting gear mechanism 31a, 31b Mechanical stopper 32 Guide bar 41 Encoder 42 Up / down counter 43 F / V converter 51a, 51b Comparison Container 52 Control unit 55 Torque sensor 56 Torque sensor amplifier

Claims (3)

(57) [Claims] 1. An automation apparatus comprising: a moving part moved by a driving means; and a relative position detecting means for detecting a relative movement amount of the moving part, wherein an operation range of the moving part is mechanically limited. A mechanical stopper disposed at a fixed position, a driving force detecting unit that detects a driving force generated by the driving unit, a comparing unit that compares the detected driving force with a set value, and a comparison result of the comparing unit. An excessive load detecting means for detecting that the moving part has reached the position of the mechanical stopper, and a movement for converting the relative movement amount to an absolute movement amount based on the position detected by the excessive load detecting means. An initial position setting device for an automation device, comprising: a quantity conversion unit. 2. The driving force detecting means has a current detector for detecting an armature current of the driving means, and the comparing means compares the armature current detected by the current detector with a set value. The initial position setting device for an automation device according to claim 1, wherein: 3. The driving means includes: a gear coupling mechanism that rotationally drives the moving part; and a rotation shaft connected to an input gear of the gear coupling mechanism. 2. The automation device according to claim 1, further comprising: a torque detecting unit configured to detect a driving torque of the shaft, wherein the comparing unit compares the driving torque detected by the torque detecting unit with a set value. 3. Initial position setting device.