TWI390183B - High-precision absolute type encoder apparatus and method for operating the same - Google Patents

Description

High-resolution absolute type coding device and operation method thereof

The present invention relates to a high resolution absolute type encoding device and an operating method thereof, and more particularly to a high resolution absolute type encoding device and a method of operating the same that can be provided during power down.

Conventional AC servo motors typically include an optical encoder that provides the angle of the rotor for information on a motor speed that can be fed back to the associated speed control unit to precisely control the motor speed.

The first figure is a block diagram of a conventional AC servo motor control system. The angular position of the rotor of the motor 10 is detected by an optical encoder 12 and processed by a signal processing unit 20 to obtain an angle information θ. The angle information is sent to a controller 14 for processing to obtain a motor estimated speed, and then a speed controller 30 receives the motor estimated speed and a speed command to control a controller module 32 and an insulated gate bipolar transistor ( The IGBT) module 34 generates a control motor speed signal to precisely control the motor 10 speed.

More specifically, in the servo drive motor, the position sensor attached to the motor shaft is the optical encoder 12. The positioning accuracy of the servo motor depends on the resolution of the encoder. The optical encoder (or rotary encoder) 12 is further divided into an incremental encoder and an absolute encoder.

The incremental encoder can only provide information about the position relative to the previous position, so after the power is interrupted, the information change of the position must be reset to zero to confirm. The incremental encoder cannot be immediately turned on after the power is turned off. Know where the current organization is. The absolute position encoder can output the absolute value of the shaft angle (position) at any time without losing the position information due to the power interruption. Therefore, the zero return procedure is not required after the power is turned off and the control system is simplified.

Referring to the second figure, the basic configuration of an optical encoder, a light source (e.g., a laser diode LD) 260 emits light through a rotating disk 200 and a fixed sub-code mask. 220 reaches a light sensing component (eg, a photodiode PD) 240, and the intensity of the light received by the light sensing component 240 varies with the position of the rotating code wheel 200, and is transmitted through the light sensing component 240. The signal change can detect the location message.

Referring to the third figure, it is a schematic diagram of a rotary encoder 300 of an absolute encoder, wherein the rotary encoder 300 is a 6-bit (6-bit) Gray code code disc design. The rotary code wheel 300 includes a circular body 302 and a plurality of gratings. The grating includes one first grating 304A occupying the innermost circumference coding track and occupying 1/2 circumference, two second gratings 304B and three third gratings 304C occupying the track on the inner side and occupying 1/4 circumference each. The fourth grating 304D, the fifth grating 304E, and the 32 sixth gratings 304F each occupying the tracks at the outermost side and occupying 1/64 of the circumference. Therefore, different light and dark signals can be generated along the radial direction, and a resolution of =64 can be achieved along the circumferential direction. However, in the absolute encoder architecture shown in Figure 3, for each bit added to the resolution, the code wheel must add one more code track. The higher the resolution, the more the number of encoded tracks, the larger the size of the encoder; in some cases where there is a volume limitation, the absolute encoder is fine. There are limits to the degree.

Referring to FIG. 4A, a schematic diagram of a rotary encoder 400 for one of the encoders, the rotary encoder 400 includes a circular body 402 and a plurality of gratings. The gratings include a main grating 404A, a first sub-grating 404B, and a second sub-grating 404C. Referring to FIG. 4B, it is a schematic diagram of the sub-code disc 420; the sub-code disc 420 includes four rows of gratings 420A.

Referring to FIG. 4C, which is a schematic diagram of a light sensing element 440, the light sensing element 440 includes main sensing units 442A, 444A, 442B, 444B corresponding to the main grating 404A (also labeled as A+, B+, A- , the area of B-). When the rotary code wheel 400 is rotated, the four unit main sensing units 442A, 444A, 442B, 444B (A+, B+, A-, B-) of the light sensing element 440 generate a signal similar to a sine wave. The phases of the four sine waves are 0/90/180/270 degrees, respectively, and the 0/180 signals (A+, A-) are differentially amplified to obtain a sinusoidal signal A that eliminates common mode noise. The same 90/270 signal (B+, B-) is used for differential amplification to obtain the cosine signal B that cancels the common mode noise. The phase difference between the two signals of AB is 90 degrees, which can be used to judge forward or reverse. .

The volume encoder basically only needs the AB pulse signal to detect the position information, but since the position information only provides information relative to the previous position, the origin signal sensing unit 446A, 446B (Z+) needs to be additionally set. , Z-), the absolute position message can be obtained after returning to the original zero point each time the system is powered on. The advantage of the incremental encoder is that it only needs six signals, and the sine signal and the cosine signal with two-phase difference of 90 进行 can be interpolated to obtain high-resolution position information. The disadvantage is that each time the power is turned on. The homing action must be performed. This practice is not only a waste of time but also does not allow the return to the original point. For the application of the sequence, the quantized encoder can not meet the demand and an absolute encoder is required.

In order to solve the problem of absolute addressing of multiple turns during power failure, there are two ways to count the number of turns in the related art: (1) Mechanical gear type For the counting of the number of turns, each of the gears of the gear set meshes with each other to form an encoder shaft to drive the first gear, and the first gear drives the second gear (as shown in the fifth figure).

An absolute code is engraved on each gear, and there are n absolute addresses in one circle, which are read by the distributed laser diode LD and the photodiode PD. At the same time, this gear set can record the encoder axis rotation n*n*n circle

(2) Single-turn absolute type with battery counting laps Under power failure, the battery is powered by a dedicated chip. The dedicated chip only triggers the laser diode (LD) at intervals, so that the photodiode (PD) generates a data signal that is absolutely addressed at intervals. With this absolutely addressed data signal data, it can be judged whether or not it is rotated or reversed one turn, and then the number of turns is accumulated.

When re-powering, the encoder's chip will read the accumulated number of turns, and also read the current value of the angle code on the disc, and then interpolate to get a finer angle value. However, when reading the angle code, there are sometimes critical value problems, or the dust on the disc causes some deviation from the real position, and some correction points are needed to correct these deviations. In general, when the power is turned on, the value returned by the encoder is still somewhat biased, and the angle value will be correct after some calibration points are passed. In other words, when power is restored, it is only close to the angle value at the beginning; after the calibration point is reached, the correct angle value is obtained.

Therefore, the object of the present invention is to provide a high-resolution absolute encoder and an operation method thereof, which can accurately and power-savingly calculate the rotation angle during power-off, so as to promptly start after power-on.

In order to achieve the above object, the present invention provides a high-resolution absolute type encoding apparatus which performs absolute angle measurement during power-off using a measuring encoder and a battery, and includes: a controller electrically connected to the measuring unit An encoder and generating a control signal to the measurement encoder; a comparator electrically coupled to the output of the measurement encoder for operating the measurement encoder output to obtain a first pulse signal; a latch a lock unit electrically connected to the output of the comparator to perform a latching operation on the output of the comparator to obtain a second pulse signal; wherein the controller drives the control signal to be a discontinuous conduction pulse when the controller is powered off The wave signal, and calculating the count generated by the second pulse signal, knows an absolute angle information.

In order to overcome the problems caused by the foregoing, the present invention counts as the main content by generating the correct A and B pulse waves at the time of power failure, instead of counting the number of turns. Thus, between the power-off and the re-power, the A and B pulse counts are identical, and there is no difference. The count of the number of turns is also counted from the A and B pulse counts.

6 is a block diagram of a high resolution absolute encoding device 60 according to the present invention. The high resolution absolute encoding device 60 includes a controller 100, a power switch 120, a volume encoder 140, and a comparator. 160, a latch unit (latch) 180 and a battery (not shown, supplied Power Vcc), the battery supplies power to the above unit. The measurement encoder 140 is a conventional incremental encoder and includes a laser diode LD, a photodiode PD and a corresponding rotary code wheel (not labeled). The controller 100 is electrically connected to the power switch 120 and provides a control signal SW to the power switch 120 to selectively control the laser diode LD power supply to be continuously lit (normal power supply mode, or normal mode) (quasi-normal mode) or pulse mode operation (battery mode). Moreover, the controller 100 is also electrically connected to the comparator 160 and the latch unit 180 to provide the control signal SW to the comparator 160 and the latch unit 180. The 0/180 signals (A+, A-) and 90/270 signals (B+, B-) received by the photodiode PD are processed by the comparator 160 to obtain the first pulse signals A1 and B1; The wave signals A1 and B1 are processed by the latch unit 180 to obtain the second pulse signals A2 and B2. The second pulse signal A2 and B2 are processed by the counter 102 of the controller 100 to know the angle of rotation. The controller 100 can know the current absolute angle from the angle before the power-off and the angle after the power-off.

The seventh figure shows a waveform diagram of a part of the signal in the high resolution absolute type encoding device 60 of the sixth figure. The control signal SW of the seventh figure can be generated by the firmware design or logic design of the controller 100. The control signal SW illuminates the laser diode LD in a high state, and thus the photodiode PD also generates a light-sensing signal. The light sensing signal is determined by whether the rotating disk and the sub-code mask are masked. The output signals of the laser diode LD are amplified and compared to generate first pulse signals A1 and B1. The first pulse signals A1 and B1 control the latch unit through a control signal SW 180 is latched to obtain second pulse signals A2 and B2. The signals obtained by the second pulse signal A2 and the B2 signal and the laser diode LD are continuously turned on (On) are the same. Just as the speed of rotation increases, the interval time is shorter (see below for details).

Since the pulse waves A1 and B1 are counted, the interval time of the control signal SW needs to be relatively short compared to the number of counting turns. For example, if the resolution of the rotary disk is 512 ppr, then the pulse period of the first pulse signals A1 and B1 is 60/60/512=1/512s=:2 ms when the rotational speed is 60 rpm. The interval of the control signal SW needs at least 2/5 ms = 0.4 ms in order to correctly count the pulse wave number. The continuous on time of the control signal SW is determined by the reaction time measurement of the laser diode LD and the photodiode PD. When the power is normally supplied, the control signal SW signal is always in the on state. Therefore, when the power failure is detected, the controller 100 calculates the rotation speed according to the angle, and waits until the rotation speed is sufficiently low (for example, less than 30 rpm) to switch to the battery mode, at which time the interval of the control signal SW is performed at 0.4 ms. The current speed can be estimated by the accumulation of the counter 102. When the speed exceeds 30 rpm, the control signal SW signal will be set to the On state, so that the high speed can be safely counted. When the rotational speed is sufficiently low, the interval of the control signal SW is performed at 0.4 ms (that is, once every 0.4 ms). As shown in the seventh figure, in the case of power failure, the encoder rotation speed is generally not fast, so that the rotation angle count can be accurately known by the intermittently conducting control signal SW in conjunction with the latch. As shown in the figure, the counter counts 88, 87, 86, 85, and the controller 100 can accurately know the current absolute position based on the counter count result and the angle information before the power is turned off.

Referring to FIG. 8 , the method for operating the high-resolution absolute encoding device of the present invention first detects whether the power is normally supplied (S100). If the power is normal, the controller 100 drives the control signal SW to be continuously turned on (normal mode) to continue. Detecting the rotation speed of the rotary disk (S102); if it is not normal power supply (for example, when the three-phase power of the motor is abnormal), the control signal SW is supplied in a battery power supply and in an interval manner to estimate the rotation speed in the power saving state (battery) Mode) (S104). Then, the controller 100 determines whether the rotation speed exceeds 30 rpm (S110). If the rotation speed exceeds, the controller 100 controls the control signal SW to be continuously turned on (On) to continuously detect the rotation speed of the rotary disk (disk). However, in order to detect a relatively high speed rotary code wheel rotation, a control signal SW that is continuously turned on is sent, and this mode is called a quasi normal mode (S112); if the rotation speed is not exceeded, the controller 100 The control signal SW is supplied in a spaced manner to estimate the rotational speed (battery mode) in the power saving state (S104).

The technical features of this patent are as follows 1) When the power is off, the number of turns is not counted in the absolute position of the single turn, but the laser diode LD is triggered at intervals, and the pulse wave signals A and B are obtained to count the angular position data, and also includes the number of turns. Grand total.

2) The pulse signal A and B of the interval are restored by the latch mode to become a normal continuous pulse wave, so that the counter still maintains a normal count when the power is turned off.

3) Use different switching cycles to normally count the number of pulses at different speeds.

The above are only the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. That is, the equal variation made by the scope of the patent application of the present invention Both modification and modification are covered by the scope of the invention.

[Practical]

Motor ‧‧10

Optical encoder ‧‧12

Controller ‧‧14

Signal Processing Unit ‧‧20

Speed controller ‧ ‧ 30

Controller module ‧‧32

Insulated Gate Bipolar Transistor (IGBT) Module ‧‧34

Rotary code wheel ‧‧200,300,400

Deputy code ‧‧‧220,420

Light sensing element ‧‧‧240,440

Light source ‧‧‧260

Round body ‧‧‧302,402

First grating ‧‧‧304A

Second grating ‧‧‧304B

Third raster ‧‧ ‧304C

Fourth grating ‧‧‧304D

Fifth raster ‧‧‧304E

Sixth grating ‧‧ ‧304F

Main grating ‧‧ 404A

First light barrier ‧‧‧404B

Second light barrier ‧‧‧404C

Raster ‧‧ 420A

Main sensing unit ‧‧‧442A, 444A, 442B, 444B

Origin signal sensing unit ‧‧‧446A,446B

【this invention】

High resolution absolute coding device ‧‧60

Controller ‧‧100

Power switch ‧‧‧120

Measuring encoder ‧‧140

Comparator ‧‧160

Latch unit ‧‧‧180

Counter ‧‧‧102

Control signal ‧‧‧SW

Battery power ‧‧VCC

First pulse signal ‧‧‧A1, B1

Second pulse signal ‧‧‧A2, B2

Step ‧‧S100-S112

The first figure is a block diagram of a conventional AC servo motor control system.

The second picture shows the basic construction of an optical encoder.

The third figure is a schematic diagram of a conventional rotary encoder with an absolute encoder.

Figure 4A is a schematic diagram of a conventional rotary encoder with an incremental encoder.

Figure 4B is a schematic diagram of a conventional sub-coded disc.

Figure 4C is a schematic diagram of a conventional light sensing element.

The fifth picture is a schematic diagram of the mechanical gear.

Figure 6 is a block diagram of a high resolution absolute type encoding apparatus in accordance with the present invention.

The seventh figure shows the waveform diagram of some signals in the high resolution absolute type encoding device of the sixth figure.

The eighth figure is a method for operating the high resolution absolute type encoding device of the present invention.

High resolution absolute coding device ‧‧60

Controller ‧‧100

Power switch ‧‧‧120

Measuring encoder ‧‧140

Comparator ‧‧160

Latch unit ‧‧‧180

Counter ‧‧‧102

Control signal ‧‧‧SW

Battery power ‧‧VCC

First pulse signal ‧‧‧A1, B1

Second pulse signal ‧‧‧A2, B2

Claims (7)

A high-resolution absolute type encoding device performs absolute angle measurement during power-off using a measuring encoder and a battery, comprising: a controller electrically connected to the measuring encoder and generating a control signal To the measurement encoder; a comparator electrically connected to the output of the measurement encoder for outputting the first encoder signal to the output of the measurement encoder; and a latch unit electrically connected to the comparison The output of the comparator is latched to obtain a second pulse signal; wherein the controller drives the control signal to be continuously turned on when the power is off; when the speed is lower than a speed setting The control signal is driven as a pulse signal that is intermittently turned on, and a count generated by the second pulse signal is calculated to obtain an angle information. The high resolution absolute type encoding device of claim 1, wherein the latch unit latches the first pulse signal when the control signal is high during power down. The high resolution absolute type encoding device of claim 1, wherein the controller drives the control signal to be continuously on (On) when the rotating code wheel speed of one of the measuring encoders exceeds 30 RPM. The high resolution absolute encoding device of claim 3, wherein the rotating encoder has a resolution of 512 ppr and the control signal has an interval of 0.4 ms. A high-resolution absolute type encoding method uses an encoder and a battery to perform absolute angle measurement during power-off, including: When the power is off and the speed of the encoder is lower than a speed setting, the measuring encoder is driven by a discontinuous conduction control signal to generate a first pulse signal; the first signal is latched by the control signal a pulse wave signal for generating a second pulse wave signal; and calculating a rotation angle of the one of the volume encoders by using the second pulse wave signal; wherein the control signal is driven to be restored when the power is turned off and the rotation speed is higher than the speed setting value A signal that is continuously turned on. For example, the high resolution absolute encoding method of claim 5, wherein the speed setting value is 30 RPM. The high resolution absolute coding method according to claim 5, wherein the one of the measurement encoders has a rotation code resolution of 512 ppr, and the control signal has an interval of 0.4 ms.