JP2005215912A - Encoder system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an encoder system suitable for applying high-speed and highly accurate driving control to a body to be driven. <P>SOLUTION: The encoder system involves: detecting quantity of light passing through the slits of a rotation section 10 interposed at a machinery device side by a light emitting device and light receiving device; generating analog signals A, B, and Z-phase voltages. A delta sigma modulator 14 applies A/D conversion to each phase voltage. A/D-converted digital signals are of no protocol and are given, through a transmission driver 16 and a reception receiver 18, to a digital filter 20 composing a sensor processing section 2 at a controller side, and are converted into a pulse sequence corresponding to a detection position by the digital filter and are given to a position detector 22. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an encoder system for generating a position feedback signal required when driving a driven body of an articulated robot, an electric injection molding machine, a numerical control machine tool or the like (hereinafter referred to as a mechanical device) using a servo motor. In particular, the present invention relates to an encoder system suitable for driving and controlling the driven body at high speed and with high accuracy.

  An encoder, for example, a rotary encoder, has a function of generating a digital signal as an output thereof, so that it is frequently used to generate a position feedback signal required when driving a driven body in a mechanical device. . The encoder includes an incremental type and a serial absolute encoder that uses an asynchronous communication system that provides high resolution.

  FIG. 3 shows the configuration of a serial absolute encoder using asynchronous communication. As shown in FIG. 3, the serial absolute encoder 100 arranged on the mechanical device side is usually provided with a plurality of pairs of light-emitting elements and light-receiving elements 112 constituting the detection part through slits formed in the rotation part. A / B / Z phase signals (analog signals) are generated, these analog signal voltages are A / D converted by the A / D converter 113, and the pulse train that is the output of the A / D conversion is up / down. -The counter 114 detects the position within one rotation of the rotating unit 110 as the counter value. Here, the rotating unit 110 is coupled to a drive shaft (not shown) of a servo motor disposed in a drive mechanism of the mechanical device. Therefore, the value of the counter 114 corresponds to the position within one rotation of the servo motor.

The value of the counter 114 is converted into a serial signal sequence by an LSI (hereinafter referred to as serial communication MAC (Media Access Controller)) 115 that performs hardware processing in the communication protocol, and is transmitted through the RS422 transceiver 116. 300.
On the other hand, in the sensor processing unit 200 on the control device side, the serial signal sequence transmitted through the transmission path 300 is given to the serial communication MAC 120 via the RS422 transceiver 118 and the value of the counter 114 is reproduced, and the position is detected. This is given to the detection unit 122. Further, the output of the position detecting unit 122 is given to the speed calculating unit 124, and the speed is calculated as a time derivative of the detected position. The output of the speed calculation unit 124 is used for signal processing for drive control of the servo motor in the control device. Here, processing X126 is collectively displayed.

Further, in the asynchronous communication shown in FIG. 4, when a request is issued from the sensor processing unit 200 to the encoder 100, a plurality of response frames are transmitted from the encoder 100. The request and response frame signals are formed by the serial communication MAC 115 in accordance with communication rules (protocols) determined in advance. The time from when the sensor processing unit 200 gives a request to the encoder 100, when response data is returned from the encoder, and when the sensor processing unit 200 can issue a request is called one sampling period. It is also the response speed of the encoder 100 itself.
When the rotation unit 110 rotates more than half a rotation within one sampling cycle, the sensor processing unit 200 cannot detect the rotation direction of the rotation unit 110, so the time required for one rotation of the encoder rotation unit 110 is at least twice the sampling cycle. is necessary.

  However, the high-speed rotation to the servo motor coupled with the encoder, for example, demands such as high-speed rotation of the spindle spindle and high-speed of the arm speed of the robot in NC machine tools has become stronger along with higher resolution. There is a problem that the configuration of the serial absolute encoder using asynchronous communication cannot cope with such a request.

The inventor of the present application has made extensive studies to solve the above problems, and as a result, in the configuration of the serial absolute encoder using asynchronous communication shown in FIGS. 3 and 4, the encoder side temporarily uses an up / down counter. While the detection position is generated, the signal related to the detection position is converted into a serial signal for transmission to the control device side, and this is reproduced on the control device side. Further, the request is made according to a predetermined protocol. Also, because the method of transmitting and receiving response data on the encoder side and the control device side, paying attention to the restriction of one sampling period, the detection position is generated twice by the sensor processing unit on the encoder side and the control device side. By avoiding the transmission, the protocol is not dependent on the protocol (protocolless). Problems were found that can be resolved.
Accordingly, an object of the present invention is to provide an encoder system suitable for driving and controlling a driven body at high speed and with high accuracy.

In order to achieve the above object, an encoder system according to the present invention comprises:
A control device that gives a drive command to the drive means of the driven body and a detection means that includes an encoder that detects the drive position of the drive means and feeds back the detection signal to the control device.
A detector coupled to the drive means;
A delta-sigma modulation unit that modulates a detection signal from the detection unit;
Transmission means including transmission and reception drivers for transmitting the output of the delta-sigma modulation unit to the control device;
A sensor processing unit including a digital filter that performs digital processing of a reception signal on the control device side and converts the detection signal into a pulse train corresponding to the drive position;
It is configured with.
In that case, the transmission means can be constituted by a protocolless transmission path.
The driving means can be constituted by a servo motor.

  The encoder system according to the present invention has the property that the limit rotational speed that can be followed is higher than the conventional one, although the accuracy is low during low-speed rotation and the accuracy is low during high-speed rotation. Therefore, it becomes possible to use a high-resolution encoder rotated at a higher speed than before.

Embodiments of the present invention will be described below in detail with reference to FIGS.
In FIG. 1, a rotating unit 10 of an encoder 1 arranged on the mechanical device side is coupled to an output shaft of a servo motor provided in a drive mechanism (not shown).
The rotating part 10 is disk-shaped glass, and a slit cut in the normal direction along the circumference of a circle centering on the rotation center of the rotating part 10 is provided on the surface thereof. When the light from the LED (light emitting element) hits the slit, the light passes through the slit. Accordingly, when the LED and the light receiving element (phototransistor) are faced each other with the disk-shaped glass interposed therebetween, and the rotating unit 10 is rotated while applying the light from the LED, the light receiving element is caused by the intensity of light that occurs each time the transmitted light crosses the slit. A SIN wave of an electric signal is obtained on the detection unit 12 side including This slit is formed so as to repeat the intensity of transmitted light several times within one round. The number of repetitions is defined as the limit at which the light receiving element can distinguish the strength even if it rotates at the maximum number of rotations.

Reference numeral 14 denotes a delta sigma modulator, which is a 1-bit A / D converter, that is, a delta sigma type A / D converter. The output of the delta-sigma type A / D converter is a 1-bit 1 or 0 bit string, and the conversion result is usually obtained by inputting this output to a high-order digital filter. The digital filter is publicly known, and details thereof are omitted.
A detailed description of the delta-sigma modulator is described, for example, in “Experiment of ΔΣ Type A / D Converter Using FPGA” in the December 2003 issue of “Transistor Technology” published by CQ Publisher.

Reference numeral 16 is a transmission driver that transmits the output of the delta-sigma modulator 14 to the sensor processing unit 2 on the control device side via the transmission path 3 and is received by the reception receiver 18 of the sensor processing unit 2. The output of the reception receiver 18 is given to the digital filter 20, and the output of the digital filter 20 is given to the position detection unit 22 as a pulse train. The position detection unit 22 includes a counter, and the count value corresponds to a position within one rotation of the rotating unit 10, that is, a drive position within one rotation of the servo motor. The speed detection unit 24 calculates the rotation speed of the rotation unit 10 of the encoder 1 by calculating a difference between the outputs of the position detection unit 22.
The process 26 performs the same process as the process X of FIG.

  FIG. 2 shows a detailed control block of the delta-sigma modulator 14 of FIG. 1, where an input analog voltage is integrated by an integrator 14A, and this value is compared with a reference voltage and quantized by a quantizer 14B. . The binary signal obtained as a result becomes a ΔΣ modulation signal. Further, by constructing a feedback system in which the ΔΣ modulation signal delayed by the delay device 14C is subtracted from the analog input voltage, the output duty ratio is proportional to the input signal. Further, a digital signal is formed from the ΔΣ modulation signal through a high-order digital filter 20.

  Therefore, in the conventional encoder system shown in FIG. 3 and FIG. 4, since the data is responded to the request from the sensor processing unit, its performance depends on the communication specifications, but the performance of the present invention shown in FIG. In the encoder system, the ΔΣ modulation signal itself is transmitted at any time by communication, so it does not depend on the communication specifications at all and constitutes a so-called protocol-less system, and no encoder or serial communication MAC is required on the encoder side. Therefore, the apparatus can be simplified and the cost can be reduced.

It is a control block diagram of an encoder system according to the present invention. FIG. 2 is a detailed block diagram of the delta-sigma modulator in FIG. 1. It is a control block diagram of a serial absolute encoder using a conventional asynchronous communication system. It is a figure which shows the frame of the request and response data in 1 sampling period of the asynchronous communication system in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Encoder part 2 Sensor processing part 3 Transmission path 10 Rotation part 12 Detection part 14 Delta-sigma modulator 14A Integrator 14B Quantizer 14C Delayer 16 Transmission driver 18 Reception receiver 20 Digital filter 22 Position detection part 24 Speed calculation part 26 Process

Claims (4)

A control device that gives a drive command to the drive means of the driven body and a detection means that includes an encoder that detects the drive position of the drive means and feeds back the detection signal to the control device.
A detector coupled to the drive means;
A delta-sigma modulation unit that modulates a detection signal from the detection unit;
Transmission means including transmission and reception drivers for transmitting the output of the delta-sigma modulation unit to the control device;
A sensor processing unit including a digital filter that performs digital processing of a reception signal on the control device side and converts the detection signal into a pulse train corresponding to the drive position;
An encoder system comprising:   2. The encoder system according to claim 1, wherein the transmission means is configured by a protocolless transmission path.   3. The encoder system according to claim 1, wherein the driving unit is a servo motor.   4. The encoder system according to claim 3, wherein the driven body is a component of a machine tool or a robot.

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