Transmission path and method for transmitting incremental encoder signals

Abstract

A method for transmitting incremental encoder signals, wherein signals (17) generated by an incremental encoder (11) are serially transmitted to a signal receiver (12) via a transmission line (13), wherein the signals of the incremental encoder are encoded by an encoder (14) according to a line code and transmitted to a decoder via a connecting line, wherein the decoder decodes the signals according to the line code, wherein the encoder and the decoder process the signals at a coding frequency and transmit the line code at the coding frequency via the connecting line, characterized in that the encoder determines a temporal position indication of a signal edge (18) of the signal at a sampling frequency that is comparatively higher than the coding frequency, wherein the encoder supplements codewords of the line code with the temporal position indication, wherein the decoder uses a period (T) K) the coding frequency according to the temporal position of the signal edge by a number of periods (T A ) of the sampling frequency shifts, with the decoder determining the period (T K ) outputs with a delay of the coding frequency.

Description

[0001] The invention relates to a transmission link and a method for transmitting incremental encoder signals, wherein signals generated by an incremental encoder are transmitted serially to a signal receiver via a transmission link, wherein the signals of the incremental encoder are encoded with a line code by an encoder and transmitted to a decoder via a connecting line, wherein the decoder decodes the signals according to the line code, wherein the encoder and the decoder process the signals at a coding frequency and transmit the line code at a transmission frequency via the connecting line, wherein the decoding frequency is comparatively lower than the transmission frequency.

[0002] Serial transmission of incremental encoder signals over a transmission line to a signal receiver is well established. To ensure DC voltage compensation on the transmission line, a standardized line code is regularly used to encode the incremental encoder signals before transmission and to decode them after transmission at the receiver. Encoding is performed by an encoder and decoding by a decoder in the transmission line at a specific coding frequency. At this coding frequency, a signal generated by the incremental encoder, for example, a rotary encoder, is detected or sampled. This allows the encoder to recognize signal edges of the incremental encoder signal and convert them into the line code according to the coding frequency.The encoding frequency is regularly higher than the signal frequency in order to ensure the most accurate possible detection and reproduction of the signals generated by the incremental encoder.

[0003] However, the length of a period in the coding frequency always results in temporal clock jitter, which is a fluctuation in the accuracy of the transmission clock or the coding frequency. Since the coding frequency essentially corresponds to the transmission frequency at which the line code is serially transmitted over the connecting line, an increase in the coding frequency is necessary to reduce the accuracy fluctuation of the signal caused by the clock jitter. Because industry standards have already been established for signal transmission via fiber optics, a coding frequency can only be increased to the extent that it is possible within the framework of the established industry standard, for example, due to the electronic components used or the type of connecting line.If an even higher coding frequency with lower accuracy fluctuations in the transmission clock is desired, a technological change to, for example, a telecommunications standard is necessary. However, such a technological change is significantly more expensive due to the components used and required, which is why a technological change to improve the quality of a transmission link is not being pursued. Within the framework of the currently used industry standard, simple and inexpensive components with low power dissipation and thus low heat generation, such as Field Programmable Gate Arrays (FPGAs), can be used together with standardized interconnects to form the transmission link, without the need for specialized components.

[0004] German patent applications DE 10 2014 219 512 A1 and US 2016 / 0 094 336 A1 disclose a method for transmitting an incremental encoder signal, wherein a signal from a position detection unit or an incremental encoder is transmitted to a processing unit. The signal is then transmitted from the processing unit via an interface unit to downstream electronics. The signal transmission is encoded and decoded at the receiver within the downstream electronics. In addition, a clock signal CLK (sampling frequency) is supplied to the interface unit (encoder) and synchronized with the incremental encoder signal. Signal edges can be encoded according to the underlying time grid.

[0005] US 2017 / 0300723A1 concerns the transmission of radio frequencies between an RFID transponder and a receiver. Data transmission occurs wirelessly between an antenna of the RFID transponder and an antenna of the receiver. The data can be transmitted in coded form using a corresponding encoding frequency. The use of a sampling frequency is also permitted; however, in the case of encoding, the sampling frequency is adapted to an input signal.

[0006] US Patent 6,741,659 B1 discloses another system for transmitting signals for wireless communication and a method for encoding the position of a signal edge, whereby, analogous to a sampling frequency, four face slots are defined in which the signal edge can be located. Depending on the position of the signal edge in one of the four face slots, a code is generated with a signal that can be transmitted.

[0007] US Patent 4,603,322 A shows a decoder of a transmission link, showing a method in which an encoding frequency (input Manchester) is adapted using two sampling frequencies (44 MHz and 22 MHz).

[0008] US Patent 2013 / 0156419 A1 discloses another transmission link for transmitting an incremental encoder signal, wherein an encoder of the transmission link translates signal edges of the incremental encoder signal into a coding frequency and outputs this as a line code. The object of the invention is therefore to propose a method and a transmission link for transmitting incremental encoder signals, which enables a qualitatively improved transmission of incremental encoder signals in a cost-effective manner.

[0009] This problem is solved by a method having the features of claim 1, a transmission path having the features of claim 13 and an incremental encoder system having the features of claim 14.

[0010] In the inventive method for transmitting incremental encoder signals, signals generated by an incremental encoder, preferably a rotary encoder, are transmitted serially to a signal receiver via a transmission line, wherein the signals of the incremental encoder are encoded by an encoder according to a line code and transmitted to a decoder via a connecting line, wherein the decoder decodes the signals according to the line code, wherein the encoder and the decoder process the signals at a coding frequency and transmit the line code at the coding frequency via the connecting line, wherein the encoder determines a temporal position indication of a signal edge of the signal at a sampling frequency that is comparatively higher than the coding frequency, wherein the encoder supplements codewords of the line code with the temporal position indication.wherein the decoder shifts a period of the coding frequency by a number of periods of the sampling frequency according to the temporal position of the signal edge of the signal, wherein the decoder outputs the period of the coding frequency with a delay.

[0011] In the method according to the invention, as is known from the prior art, the signals from the incremental encoder, which it transmits to the encoder at a signal frequency, are encoded by the encoder of the transmission link using the line code and sent via the connecting line to the decoder of the transmission link, which is located at a distance from the encoder. The connecting line can be any type of line suitable for the serial transmission of data in a line code, in particular a radio link or the like. The encoder samples the signals from the incremental encoder at a sampling rate corresponding to the encoding frequency and converts them into codewords or data words of the line code. These codewords or the line code are transmitted at the encoding frequency, which is significantly lower than a transmission frequency of the connecting line, via the connecting line to the decoder, which then processes the codewords or data words.The data words of the line code are decoded at the coding frequency and forwarded to a signal receiver. Clock jitter can be reduced, in particular, by the encoder determining the timing of the signal edge of the incremental encoder signal using the sampling frequency. The sampling frequency is comparatively higher than the coding frequency, which shortens the period of the sampling frequency relative to the coding frequency, thus reducing clock jitter during encoding. The sampling frequency provides a more precise timing of the signal edge within a period of the coding frequency. This timing information is added to the codeword by the encoder, for example, by appending additional bits. When decoding the codeword, this timing information can then be restored or taken into account, making the decoding comparatively more precise.has improved.

[0012] According to the invention, the decoder shifts a period of the coding frequency by a number of periods of the sampling frequency, corresponding to the time position of the signal edge, and outputs the period of the coding frequency with a delay. Thus, the coding frequency of the decoder is shifted with respect to the beginning and end of a period such that the beginning of the period coincides with the signal edge of the signal output by the decoder. If, for example, the time position of the signal edge is immediately before a sampling point of the decoder, the data output or signal output is shifted by the corresponding number of periods or clock cycles of the sampling frequency. However, if the time position of the signal edge is immediately after a sampling point, the decoder can output the period of the coding frequency or the signals immediately.Intermediate positions of the signal edge's temporal position within the period of the coding frequency change the data output or signal output of the decoder accordingly.

[0013] The encoder can determine the timing of the signal edge within a period of the coding frequency using the sampling frequency. A sampling frequency period is therefore always smaller than the coding frequency period, and vice versa. The timing of the signal edges can be part of the codeword. This reduction in clock jitter can be achieved using cost-effective, industry-standard components for signal or incremental encoder signal transmission, as the coding frequency does not need to be changed or increased.

[0014] The decoder can decode the codewords of the line code at the coding frequency and output the signal or signal edges according to the temporal position information contained in the codeword at the sampling frequency, or transmit it to the signal receiver. The information about the temporal position of the signal edge contained in the codeword can be decoded or determined by the decoder, so that the signal edge or signal can be output by the decoder with the corresponding temporal position. In this way, it is also possible to convert the comparatively more precise temporal position of the signal edge obtained from the codeword of the line code into a signal or output signal from the decoder.

[0015] The decoder can output the signal or signal edge according to the specified time position within one period of the coding frequency after the sampling frequency. This is particularly the case when the signal edge within the period of the coding frequency has already been determined by the encoder's sampling frequency.

[0016] The sampling frequency can be higher than the encoding frequency by a factor of n. At a minimum, the sampling frequency can be twice as high as the encoding frequency, which would reduce clock jitter by half. The factor can be chosen so that the temporal position information can still be practically added to and transmitted in the codeword.

[0017] In particular, n can be 8, 16, or 32. The sampling frequency can therefore be increased by a factor of 8, 16, or 32 compared to the encoding frequency. The factor n is not limited to binary or integers.

[0018] Timing jitter can be reduced by a factor of n. For example, at an encoding frequency of 10 MHz, the jitter is 100 nanoseconds. If, for instance, the sampling frequency is chosen to be 8 times higher than the encoding frequency, the jitter can also be reduced by a factor of 8, so that in the example given here it is reduced to 12.5 nanoseconds.

[0019] An 8b10b code, a 64b66b code, or a 128b130b code can be used as the line code. This code is compatible with a wide variety of interfaces, allowing it to be used with cost-effective components or with an encoder and decoder. The process can also include transmitting additional data, such as incremental encoder signals, absolute encoder signals, diagnostic data, etc., over the transmission link or connecting line. In principle, the process is not limited to a single line code.

[0020] The incremental encoder can generate signals with a signal frequency between 0 Hz and 1 / 4 of the coding frequency, preferably greater than or equal to 500 kHz. These signals can be absolute encoder signals or incremental encoder signals.

[0021] The signals can be encoded and decoded at a coding frequency of 10 MHz to 13.3 MHz. This coding frequency can be implemented and used particularly cost-effectively within the framework of existing industry standards or with readily available components.

[0022] A metal cable or a fiber optic cable can be used as the connecting cable. Both metal and fiber optic cables can be used in a cost-effective manner.

[0023] In the transmission link according to the invention for transmitting incremental encoder signals, the transmission link comprises an encoder, a decoder, and a connecting line linking the encoder and decoder for the serial transmission of a signal generated by an incremental encoder, preferably a rotary encoder, via the transmission link to a signal receiver, wherein the signals of the incremental encoder can be encoded with the encoder according to a line code and transmitted to the decoder of the transmission link via the connecting line, wherein the signals can be decoded with the decoder according to the line code, wherein the signals can be processed with the encoder and decoder at a coding frequency, and the line code can be transmitted at the coding frequency via the connecting line, wherein a temporal position indication of a signal edge of the signal is provided at a sampling frequency that is comparatively higher than the coding frequency.is determinable by means of the encoder, wherein codewords of the line code can be supplemented with the temporal position information of the signal edge of the signal by means of the encoder, wherein a period of the coding frequency can be shifted by a number of periods of the sampling frequency by means of the decoder according to the temporal position information of the signal edge of the signal, wherein the period of the coding frequency can be output with a delay by means of the decoder.

[0024] The advantages of the transmission line according to the invention are described in the advantages section of the method according to the invention. Further advantageous embodiments of a transmission line are described in the features of the dependent claims relating to claim 1 of the method.

[0025] The incremental encoder system according to the invention comprises an incremental encoder, preferably a rotary encoder, a signal receiver and a transmission line according to the invention.

[0026] An encoder for the transmission link can be integrated into the incremental encoder. The encoder and also a decoder can be designed as a data processing unit. The decoder can, for example, be integrated into the signal receiver. In this case, it is also possible to connect an incremental encoder directly to a signal receiver via a connecting cable.

[0027] The invention is explained in more detail below with reference to the accompanying drawings.

[0028] They show: Fig. 1 a schematic representation of an incremental encoder system; Fig. 2a a representation of an incremental encoder signal over a time interval; Fig. 2b a representation of a coding frequency of an encoder with the incremental encoder signal over the time interval; Fig. 2c a representation of a decoder's coding frequency together with the incremental encoder signal over the time interval.

[0029] The Fig. Figure 1 shows an incremental encoder system 10 with an incremental encoder 11 and a signal receiver 12. The incremental encoder 11 is connected to the signal receiver 12 via a transmission link 13 of the incremental encoder system 10. The transmission link 13 itself comprises an encoder 14, a decoder 15, and a connecting line 16. Signals generated by the incremental encoder 11 at a signal frequency are sampled and processed by the encoder 14 at a coding frequency and converted into codewords or data words according to a line code. The codewords are transmitted at the coding frequency via the connecting line 16 to the decoder 15, which decodes the respective codewords at the coding frequency and outputs a signal to the signal receiver 12. In particular, it is provided that the encoder 14 determines a temporal position indication of a signal edge of the signal with a sampling frequency that is comparatively higher than the coding frequency.The encoder 14 adds the temporal position information to each codeword of the line code. The decoder 15 outputs the signal according to the temporal position information contained in the codeword.

[0030] The Fig. 2a, Fig. 2b and Fig. Figures 2c each show the representation of a signal 17 over an identical time period. In the Fig. Figure 2a shows signal 17 with a signal edge 18 from an incremental encoder (not shown here). A period T is obtained corresponding to a signal frequency of the incremental encoder. G for the signal frequency.

[0031] According to the presentation at Fig. Figure 2b shows signal 17, which is processed or sampled by an encoder (not shown) at a coding frequency. The coding frequency has a period length or period T. Kwhich essentially conforms to an industry standard. In the example shown here, the signal frequency is 500 kHz and the encoding frequency is 10 MHz. Furthermore, the signal 17 is processed or sampled by the encoder at a sampling frequency whose period T A is a factor of 8 smaller than the period length or period T K the coding frequency. Signal edge 18 can thus be detected with relatively high accuracy. The encoder then adds a time position indication of signal edge 18 to a codeword and transmits it to a decoder that is not shown.

[0032] As from the Fig. As can be seen in section 2c, the decoder also uses the coding frequency with a period T. K , with which the codewords contained by the encoder are converted into signal 17. Since the codewords contain the temporal position information of the signal edge 18, the encoder shifts the period T. Kthe coding frequency by a number of periods T G The sampling frequency is such that a clock cycle of the encoding frequency begins with the output of signal edge 18 according to the specified time position. Because the sampling frequency is eight times greater than the encoding frequency, clock jitter can be reduced by this factor. The output time of signal 17 or signal edge 18 at the decoder is determined by shifting the sampling frequency by a number of periods T. A variably adjusted and essentially corresponds to the signal 17 output by the incremental encoder.

Claims

[1] Method for transmitting incremental encoder signals, wherein signals (17) generated by an incremental encoder (11) are serially transmitted via a transmission line (13) to a signal receiver (12), wherein the signals of the incremental encoder are encoded by an encoder (14) according to a line code and transmitted via a connecting line to a decoder, wherein the decoder decodes the signals according to the line code, wherein the encoder and the decoder process the signals at a coding frequency and transmit the line code at the coding frequency via the connecting line, characterized by , that the encoder determines a temporal position indication of a signal edge (18) of the signal with a sampling frequency that is comparatively higher than the coding frequency, wherein the encoder supplements codewords of the line code with the temporal position indication, wherein the decoder uses one period (T K) the coding frequency according to the temporal position of the signal edge by a number of periods (T A ) of the sampling frequency shifts, with the decoder determining the period (T K ) outputs with a delay of the coding frequency. [2] Method according to claim 1, characterized by , that the encoder (14) provides the temporal position of the signal edge (18) of the signal (17) within one period (T K ) the coding frequency is determined by the sampling frequency. [3] Method according to claim 1 or 2, characterized by , that the decoder (15) decodes the codewords of the line code and outputs the signal (17) according to the temporal position information contained in the codeword. [4] Method according to claim 3, characterized by , that the decoder (15) interprets the signal (17) according to the temporal position specification within one period (T) K ) outputs the encoding frequency after the sampling frequency. [5] Method according to any of the preceding claims, characterized by , that the sampling frequency is higher than the encoding frequency by a factor of n. [6] Method according to claim 5, characterized by , that n = 8, 16 or 32. [7] Method according to claim 5 or 6, characterized by , that temporal clock jitter is reduced by a factor of n. [8] Method according to any of the preceding claims, characterized by , that the decoder (15) outputs the temporal position information of the signal edge (18) of the signal (17) within one period (T K ) the coding frequency occurs immediately if the temporal position specification of the signal edge is immediately after a sampling time. [9] Method according to any of the preceding claims, characterized by , that an 8b10b code, a 64b66b code or a 128b130b code is used as the line code. [10] Method according to any of the preceding claims, characterized by, that the incremental encoder (11) generates signals (17) with a signal frequency between 0 Hz and ¼ of the coding frequency, preferably of ≥ 500 kHz. [11] Method according to any of the preceding claims, characterized by , that the signals (17) are encoded and decoded with a coding frequency of 10 MHz to 13.3 MHz. [12] Method according to any of the preceding claims, characterized by , that a metal cable or an optical fiber cable is used as the connecting line (16). [13] Transmission link (13) for transmitting incremental encoder signals, wherein the transmission link comprises an encoder (14), a decoder (15) and a connecting line (16) linking the encoder and the decoder for serial transmission of signals (17) generated by means of an incremental encoder (11) via the transmission link to a signal receiver (12), wherein the signals of the incremental encoder can be encoded with the encoder according to a line code and transmitted via the connecting line to the decoder of the transmission link, wherein the signals can be decoded with the decoder according to the line code, wherein the signals can be processed with the encoder and the decoder at a coding frequency and the line code can be transmitted at the coding frequency via the connecting line, characterized by, that a temporal position indication of a signal edge (18) of the signal can be determined by means of the encoder with a sampling frequency that is comparatively higher than the coding frequency, wherein codewords of the line code can be supplemented with the temporal position indication of the signal edge of the signal by means of the encoder, wherein a period (T K ) the coding frequency according to the temporal position of the signal edge by a number of periods (T A ) the sampling frequency can be shifted by means of the decoder, where the period (T K ) the coding frequency can be output with a delay using the decoder. [14] Incremental encoder system (10) comprising an incremental encoder (11), a signal receiver (12) and a transmission link (13) according to claim 13. [15] Incremental encoder system according to claim 14, characterized by , that an encoder (14) of the transmission path (13) is integrated in the incremental encoder (11).

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