JPH03124292A - Linear sensor for linear servo motor - Google Patents

Abstract

PURPOSE:To improve reliability of a cable by detecting the arbitrary position of a movable element by partly interrupting an incident light to a phototransistor array in an image sensor by a sensor yoke when the yoke longitudinally moves through a gap between a light emitting source and a lens without contact. CONSTITUTION:A light emitting source LED 12 emits a light to a chip 11 through an optically focusing fiber lens 13. The chip 11, the lens 13 and the LED 12 are so disposed longitudinally as to cover the operating stroke of a movable element 3. A sensor yoke 7 longitudinally moving together with the element 3 and having a predetermined width is so disposed as to partly interrupt the LED 12 and the optical axis of the lens 13, and the light to the chip 1 is interrupted at a place where the yoke 7 exists. Thus, the arbitrary absolute position of the element 3 is detected. In this manner, improvement of the reliability of a cable for long stroke motion, high speed motion of the element 3, highly frequent reciprocation are achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a linear sensor that uses a linear servo motor and is necessary when constructing a high-speed conveyance device, a high-speed positioning robot, etc.

BACKGROUND OF THE INVENTION In recent years, linear servo motors, which do not require a rotational linear mechanism and can be relatively easily adapted to high speed and high precision, have been increasingly used in various office automation equipment, robots, high speed conveyance devices, and the like.

FIG. 9 is a configuration diagram of a conventional near DC servo motor with movable magnet type brushes. In FIG. 9, 63 is a stator core, 64 is a magnetic pole tooth, 65 is a drive coil wound around the magnetic pole tooth 64, and the drive coil 65 is connected to a commutator segment 66. 67 is a brush that contacts the commutator segment 66 and runs integrally with the movable element 68; 69 is a brush 67;
This is a power supply daple for supplying current to the drive coil 65 through the drive coil 65. The movable element 68 is composed of a magnetic pole yoke 70 and a permanent magnet 71, and the movable element 68 has a running guide movable in the longitudinal direction of the stator core 63, although it is omitted in the drawing. Reference numeral 72 denotes a head portion of a linear encoder fixed to the movable element 68 for detecting the position of the movable element 68, and is configured as a pair with a glass scale 73 on the fixed side.

The operation of the movable magnet type brushed linear servo motor configured as described above will be described below. FIG. 10 is a control system block diagram of an example of the drive circuit. The position command signal 75 output from the function generator 74 and the incremental position feedback signal 77 output from the linear encoder 76 are calculated by the deviation counter 78, and the D/A
A speed command signal 80 is generated by a converter 79. Further, a velocity feedback signal 81 is generated by an F/V converter 82 from the signal of the linear encoder 76.

A speed error signal 84 output from the speed difference calculator 83 is current amplified by an amplifier 85, and drives the drive coil 65 selected by the brush 67 in FIG. In the positioning operation, the position command signal 75 is generated until the number of pulses of the position command signal 75 output from the function generator 74 shown in FIG. 10 becomes equal to the number of pulses fed back from the linear encoder 76, and the linear motor is driven. By controlling the number of pulses output from the function generator 74 to drive the coil 65, it is possible to position the movable element 68 in FIG. 9 at any desired location. Note that the return-to-origin operation for setting the reference position before the positioning operation and the control of the acceleration/deceleration profile are handled using the same concept as in the conventional rotary servo motor system.

Problems to be Solved by the Invention However, in the case of the conventional structure, reliability of cables connected to the movable element becomes a problem when the movable element is operated at higher speeds, frequently reciprocated, or has a longer stroke. In other words, the cable moves frequently and at high speed (the movable element puts a lot of stress on the cable, which can cause breakage of the core wire in the cable, so the cable needs to be replaced frequently. Also, it is configured with a long stroke linear servo motor). In this case, the cable wiring method is also difficult.

As a countermeasure, the power supply cable can be eliminated by using a Hall element or the like to create a coil switching signal according to the position of the movable element in order to eliminate the power supply brush. Further, regarding the cable to the linear sensor head, if the sensor head is fixed, the glass scale is attached to the movable element side, and the glass scale is configured to move, it is possible to eliminate the linear sensor cable as well.

However, in this case, if the mover movement stroke is significantly longer than the mover length in the mover movement direction, the long glass scale that covers the mover movement stroke will move together with the mover, resulting in space This method is not practical due to problems such as difficulty in fixing the surface or the long glass scale to the movable element with a predetermined precision.

In view of the above problems, the present invention provides a linear sensor for detecting the position of a movable element of a linear servo motor, which eliminates the need for a cable to the movable part.

Means for Solving the Problems In order to solve the above-mentioned problems, the linear sensor for a linear servo motor of the present invention includes a phototransistor array in which phototransistors as photodetecting elements are arranged in a longitudinal direction in the form of fibers, and each of the above. The sensor yoke of the linear servo motor movable element has an image sensor including a current switch array that scans a phototransistor, and a light emitting source arranged in the longitudinal direction so as to face the image sensor through a lens. The gap between the source and the lens in the longitudinal direction,
Further, the linear servo motor movable element is configured to detect an arbitrary position of the linear servo motor movable element by partially blocking light from entering the phototransistor array of the image sensor by the sensor yoke when moving in a non-contact manner. It is.

Function: With the above-mentioned configuration, the present invention can detect the position of the movable element by equipping the movable element with only a sensor yoke for optical opening, and eliminates the need for cables to the movable parts as in the conventional example. Therefore, there is no need to consider the reliability of the cable during high-speed, high-frequency operation of the mover. .

EXAMPLE Hereinafter, a linear sensor for a linear servo motor according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of the configuration of a linear sensor for a linear servo motor in this embodiment. In the same figure, 1 is a stator core,
1a is a stator magnetic pole tooth. A drive coil 2 is wound around each stator magnetic pole tooth 1a. 3 is a mover, and a permanent magnet 4
It is composed of a seven-magnet yoke 5. Although not shown in the figure, a travel guide is provided so that the movable element 3 can move longitudinally over the stator core 1 while maintaining a predetermined gap. Reference numeral 6 denotes a linear sensor main body in this embodiment, which is mainly composed of a sensor yoke 7 that moves in the longitudinal direction integrally with the movable element 3. The linear sensor main body 6 is disposed over the entire operating stroke region of the movable element 3, and the sensor yoke 7 moves in the longitudinal direction through the gap between the light shielding detection section 8 without contacting it. FIG. 2 is a longitudinal sectional view of the linear sensor main body 6. An image sensor (for example, from a contact type image sensor manufactured by Matsushita Electronics Parts ■) 9 is a ceramic substrate 1
The chip 11 is composed of a phototransistor array chip 11 pasted on the surface of a ceramic substrate 10, a current switch array formed on the surface of a ceramic substrate 10, etc., and has a predetermined length.
A plurality of current switch arrays corresponding to each chip 11 are arranged linearly in the longitudinal direction. 12 is the light source 1
．． ED, and is configured so that light enters the chip 11 via a light-converging fiber lens (such as "Selfoc Lens" manufactured by Nippon Sheet Glass Co., Ltd.) 13. Note that these chips 11. The lens 13 and the LED 12 are arranged in the longitudinal direction so as to cover the operating stroke of the movable element 3. On the other hand, the sensor yoke 7, which has a predetermined width in the longitudinal direction and moves together with the movable element 3, is connected to the LED 12.
The optical axis of the lens 13 is partially blocked, and light to the chip 11 is blocked at the location where the sensor yoke 7 is present.

The operation of the linear sensor for a linear servo motor configured as above will be explained. Figure 3-3
6 to 6 are diagrams showing the operating principle of the linear sensor. FIG. 3 is a diagram showing the operating principle of one depth of a phototransistor array. In FIG. 3, the image sensor 9 includes a chip 11 of the phototransistor array as a photodetecting element, and a current switch array that sequentially scans each phototransistor array. It consists of 16. The chip 11 is manufactured by a semiconductor high-density bipolar process and consists of 512 phototransistors, and the pitch of each phototransistor is 63.5 μm. In operation, the clock pulse CK output from the clock generator 17 sequentially turns on each switch of the current switch array 16 to scan each phototransistor. One side of each switch is a constant current source 19
When the switch is turned on and light enters the phototransistor while current is flowing through the phototransistor, an output signal proportional to the amount of light is output from the phototransistor. The outputs of each phototransistor are connected in common, and by scanning phototransistor 1 (PTI) to phototransistor 512 (PT 512) once, a signal V is generated as many times as there are phototransistors receiving light. is output. The output signal V. is shaped by the waveform shaping circuit 20 and synchronized with the clock CK by the gate 21, and then input to the binary counter 22. 23 is a latch circuit that temporarily holds the data of the binary counter 22, and its output is connected to the CPU 24 data bus. work flag 2
5 is a flag that is set when the count I value of the binary counter 22 reaches 512. The timing control circuit 26 resets the data of the latch circuit 23 l-1, or the CPU 2.
Adjust the timing of data exchange with 4. The clock generator 17 start signal ST is supplied to the binary counter 23.
It is cleared to zero and initialized before scanning, and also serves as a reference signal to the timing control circuit 26.

FIG. 4 is an explanatory diagram of operating waveforms in a state where light is incident on all phototransistors in one chip of FIG. 3. The start signal is at L level and the binary counter 2
First, initialize step 2. The numbers (1) to (512) attached to each pulse of the clock pulse CK output from the clock generator 17 correspond to the respective phototransistors PTr1 to PTr1 of the chip 11 of the phototransistor array in FIG.
The numbers correspond to the numbers of the current switch elements connected to the PTr 512, and a current flows into the corresponding phototransistor at level (4), and when light is received, a signal proportional to the amount of light is output from the phototransistor. Further, no output signal is output from the phototransistors that are not selected by the current switch. 30 is a signal V output from the phototransistor. Due to the response speed of the phototransistor, the waveform rises gently. 31 is the phototransistor output signal V
. This is a signal obtained by waveform shaping by the waveform shaping circuit 20 in FIG. 3 and synchronization with the clock pulse CK, and is input to the binary counter 22. R is a reset signal for clearing the latch circuit 23 after the latch circuit 23 passes latch data to the CPU 24.

As a result of the above operation, the pinano counter 22 counts 512 pulses within one scanning time when light is incident on all the phototransistors of the chip 11 shown in FIG.

Next, FIG. 5 shows operating waveforms when light is partially blocked by the sensor yoke 7 described above. FIG. 5 shows P4 to PTr512 of the phototransistor array 11 in FIG.
The figure shows a case where the light is blocked. In the light-blocking section, even if the current switch 16 in FIG. 3 scans, the output signal V is not generated. It doesn't appear. Therefore, only three phototransistor output waveforms, such as 33, are output within one scanning time, and only three pulses 34 are input to the binary counter 22. Therefore, by multiplying the phototransistor pitch of 63.5 μm by the count number, the distance from the scanning start position to the light-blocking position can be detected, and by repeating the scanning at high speed, the light-blocking position can be continuously detected. becomes possible.

Naturally, the sensor yoke used for light shielding is approximately 32.5 μm, which is 63.5 μm, which is the length of one scan, multiplied by 512.
It is necessary to maintain a width of 5 μm or more in the longitudinal direction.

Also, the calculation of multiplying the above count number by 63.5 μm, which is the transistor pitch, is C
The PU 24 is configured to process it.

The work flag 25 in FIG. 3 is the binary counter 2.
Since the count value of 2 is 512 pulses, that is, it stands only when light is incident on all phototransistors, it can be used to determine whether all light is incident in one scan. By the way, the explanation in FIG. 3 is based on the case where the number of chips 11 in the phototransistor array is one, but as mentioned above, the number of chips 11 in the phototransistor array is 63.5 μ×512 ξ
Since only a detection range of 32 and 5 cylinders can be obtained, the actual configuration is as shown in FIG. That is, the detection range is expanded by arranging n pieces of the configuration shown in FIG. 3 in the longitudinal direction. The image sensor 9 has n phototransistor array chips 11 linearly arranged on the surface of a ceramic substrate 10 (see FIG. 2), and a current switch array 16 for scanning the phototransistor array connected to each phototransistor array chip. There are n LEDs corresponding to 11. 12 is a light emitting source LED.
, 13 is a lens.The light from the light emitting source LED 12 is transmitted through lens 1.
The phototransistor array is arranged such that light enters all of the chips 2 of each phototransistor array through the phototransistor array. The length of the sensor yoke 7 is set to be slightly longer than the length of one chip of the phototransistor array in the scanning direction. Waveform shaping circuit 20. Binary counter 22° latch circuit 23. n work flags 25 are arranged, each corresponding to the chip 11. The CPU 24 connects to the latch circuit 23 via the data bus.
is connected to the work flag 25 and the timing control circuit 26. As for the operation, the chip 11 of the phototransistor array in which n pieces of the operation explained in FIGS. 3 to 5 are provided.
operate in parallel. That is, in the image sensor 9 equipped with n chips 11, each chip 11 starts scanning in synchronization with the clock CK of the clock generator 17, and completes one scan in synchronization. Therefore, in one scan, the chip 11 that is shielded from light by the sensor yoke 7 has a count value of less than 512, and the chip 11 that is not shielded has a count value of 512 and a work flag is set. Next, when one scan is completed, the CPU 24 sequentially looks at the work flags 25 corresponding to each chip 11 in the direction from the first chip 11 to the 0th chip 11, and selects the chips for which no work flag is set. Reads the number of chips with work flags that exist up to this point. Next, the data of the latch circuit 23 that latches the count value m of the first chip 11 with no work flag set, that is, the chip 11 that is shielded from light is loaded, and after the loading is completed, all work flags 25 are reset and timing control is performed. The latch circuit 23 is also reset via the circuit 26 to start the next scan. The CPU 24 calculates the captured data while the next scan is being performed and determines the light shielding position of the sensor yoke 7. The calculation of the light shielding position is (MX63.5μm) + (mX
63.5 μm). By repeating the above scanning and calculation at high speed, the absolute position of the sensor yoke 7 can be continuously determined.

In addition, in the above explanation, parts that require relatively high-speed processing were processed by the hardware circuit, and other parts were processed by the software, but the CPU 24
If the processing speed is high, the range of software processing can be expanded and the circuit can be simplified. Furthermore, in the above description, the case where there is one light-shielding sensor yoke has been explained, but the same concept can be applied to the case where there is a plurality of light-shielding sensor yokes, so it is possible to detect the positions of a plurality of movable elements with one sensor.

FIG. 7 is a block diagram of a control system using the linear servo motor of FIG. 1 and the linear sensor described above.

The linear sensor outputs movable element position information 48 for each scan. The position information 48 and the value of the position command 49 are subjected to a differential calculation by a position deviation calculator 50, and a position deviation peak number 51 is output. The position deviation output 51 is converted into a speed command signal 53 by a D/A converter 52 and input to a speed deviation calculator 54. The linear sensor position information 48 is also input to the speed detection circuit 55 and the energized section calculator 56. The speed detection circuit 55 is a part that differentiates the position information 48 and creates a signal proportional to the speed of the sensor yoke, that is, the movable element. The speed signal 57 is input to the speed deviation calculator 54 and outputs a speed error signal 58. The speed error signal 58 is amplified by an amplifier 59 and inputted to a distributor 60. The energization section calculator 56 is a circuit that calculates which drive coil 2 in FIG. 1 should be energized based on the movable element position information 48 from the linear sensor 47.
As shown in the figure, depending on the position of the mover, 61-(ha ~ 6l-U)
Three-phase energized section signals having a 120° phase difference of 2 are output corresponding to the required number of drive coils, respectively. The distributor 60 is a circuit that distributes the output of the amplifier 59 to the energized section signal corresponding to each drive coil 2 output from the energized section calculator 56. The power units 62-U to 62-W2 are power-up units for amplifying each drive coil signal output from the distributor 60 and causing current to flow through each drive coil 2.

Next, the operation of the linear servo motor shown in FIG. 7 and the linear sensor of this embodiment will be explained. In FIG. 7, when the target position is set by the position command 49, a signal proportional to the speed error is outputted from the amplifier 59 by calculating the difference with the current position information of the linear sensor 47. On the other hand, the coil 2 to be driven according to the current position of the movable element 3 is connected to the energized section calculator 5.
6, the signal proportional to the signal from the amplifier 59 is sent by the distributor 60 to the corresponding power unit 62-U to 62-
The signal is transmitted to W2 and drives the drive coil 2. Next, the movable element 3 obtains a thrust in one direction due to the magnetic flux from the drive coil 2 and the magnetic flux of the permanent magnet of the movable element shown in FIG. 1, and starts moving. In response to the movement of the movable element 3, the energizing section calculator 56 sequentially selects the driving coils 2 to be driven, so that the movable element 3 can obtain continuous thrust in one direction. Next, when the target position is reached, the output of the amplifier 59 becomes zero, completing the positioning.

As described above, the linear sensor of this embodiment can continuously obtain the absolute position information of the mover 3 in a non-contact manner without having a cable or the like in the movable part. By selecting the coil 2 according to the position of 3, that is, by generating two signals of the phase switching signal as a brushless morph, the movable part is the permanent magnet 4 and the sensor yoke 7.
This makes it possible to construct a highly reliable linear servo motor.

Note that in Example 1, the pitch of the photo-I transistor array was explained as 63.5 μm, but it goes without saying that it is possible to improve the positional resolution by further minimizing the pitch. .

Effects of the Invention As described above, the present invention detects any absolute position of a linear servo motor mover by partially blocking light from entering the phototransistor array of an image sensor using a sensor yoke, and performs position control based on the position information. Furthermore, by selecting a drive coil according to the position of the movable element, that is, by switching the phase of the brushless linear servo, it has become possible to configure a linear servo motor with only permanent magnets as the movable element.

As a result, there is no need for power supply cables, sensor cables, etc. to the mover, which eliminates problems with cable wiring and reliability when moving the mover at higher speeds, frequent reciprocating operations, long stroke movements, etc. The results are great.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a linear servo motor equipped with a near sensor for a linear revo motor according to an embodiment of the present invention, FIG. 2 is a longitudinal cross-sectional view of the same near sensor, and FIGS. 7 and 8 are explanatory diagrams of the linear servo motor control system using the same near sensor. FIG. 9 is a diagram of the conventional linear servo motor configuration.
Figure 0 is an explanatory diagram of the control system. 3...Mover, 7...Sensor yoke,
9... Image sensor, 11... Phototransistor array chip, 12... Light emitting source L
E D, ]3...Lens, 16...
Current switch array.

Claims (1)

[Claims] an image sensor including a phototransistor array in which a plurality of phototransistors as photodetecting elements are arranged linearly in the longitudinal direction, a current switch array for scanning each of the phototransistors, and an image sensor facing the image sensor through a lens. and a light emitting source arranged in the longitudinal direction,
When the sensor yoke of the linear servo motor movable element moves longitudinally through the gap between the light emitting source and the lens in a non-contact manner, the sensor yoke partially blocks light from entering the phototransistor array of the image sensor. A linear sensor for a linear servo motor, characterized in that the linear sensor is configured to detect the position of the linear servo motor movable element.