Method for contactlessly transmitting serial signal and transmission device for method

Abstract

To provide a method and a device for receiving, delaying, and in a synchronized state forwarding a signal, without changing its bit rate.SOLUTION: In a method for contactless transmission of a serial signal 17 from a transmitter 2 to a receiver 3, the serial signal is received in the form of a first bit stream 12 with a first bit clock 10, and is evaluated by a control unit 6, and a delay time 14 is set. A delay circuit 8 samples, delays, and stores all bits of the serial signal in the first bit stream. The control unit also searches for a start bit 15 of the serial signal in the first bit stream, the delay circuit stores all the bits of the serial signal sequentially with a second bit clock 11 in a FIFO memory 9, and sequentially reads out the bits present in synchronism with the second bit clock, and the bits are transmitted as a second bit stream 13 by inductive transmission units 4, 5 through an air gap 7 to a receiver.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for contactless transmission of a serial signal from a transmitter to a receiver, in which the signal is received from the transmitter in the form of a first bit stream at a first bit clock, evaluated by a control unit, a delay time is set and transmitted to a delay circuit, in which all bits of the signal in the first bit stream are sampled, delayed by the delay time and stored, and to a transmission device for said method.

[0002] Such a method and such an apparatus are already known from US Patent Application Publication No. 2015 / 207616, see also US Patent Application Publication No. 2020 / 241591 and US Patent Application Publication No. 2018 / 275714.

[0003] It is already known to transmit data signals of the machine control to a receiver via an inductive coupler. This is already commonly done in robot arms to ensure that they can rotate freely. Due to the inductive transmission, both energy and data signals can be transmitted in the direction of a gripper attached to the robot arm without the need for a continuous cable line. This allows multiple rotations, which would otherwise be twisted and would at some point cause shortening or mechanical damage.

[0004] However, on the one hand, it is necessary that the data connection has the highest possible quality in order to completely transmit the adjustment signals transmitted to the gripper, and on the other hand, it is necessary that the transmission take place as quickly as possible in order to be able to operate in a synchronized manner.

[0005] The signals here are transmitted in duplicate using the serial interfaces that are widespread both in industry and in information technology over individual and partially redundant lines, where "serial" means that the data to be transmitted is transmitted bit by bit as a serial data stream, i.e. as a bit stream, successively in time.

[0006] In this case, the various transmission protocols of the possible interfaces each specify how many individual bits are grouped together into larger transmission units and how they are coded information-technically. Depending on the interface used, the larger transmission units here are called, for example, octets in the case of IO-Link, frames in the case of CANbus or Ethernet, and words in the case of RS232 interfaces. In the framework of this document, they are generally referred to below as signals. In addition to the pure information to be transmitted, the transmission units here can contain further defined bits for identifying start and end positions, or for identifying and correcting errors, or for adapting the transmission channel to the physical requirements, i.e. for synchronization.

[0007] All the above mentioned transmission protocols use one or more fixedly defined transmission rates, referred to in the following as bit rates. In the case of IO-Link, the transmission rates are 4.8 Kbit / s, 38.4 Kbit / s or 230.4 Kbit / s. To provide a basis for a transmission that is as safe as possible against disturbances, the permissible tolerances for the time position and thus the transmission rate are partly defined very precisely for the transmission standards. The sender must observe the tolerances, the receiver must accept time deviations of a larger order.

[0008] If the data transmission by the above-mentioned interface, for example in a robot arm, takes place by means of an inductive transmission device via an air gap, the useful signal must be adapted depending on the physical properties of the transmission channel, i.e. the inductive interface consisting of the transmission coil, the air gap and the receiving coil, since the transmission channel transmits only certain frequency ranges well. In the simplest case, this would be a re-encoding of the bits to be transmitted, whereas in the case of an output-capable transmission, an appropriate modulation method is selected. In principle, this applies not only to inductive transmission, but also to all wireless or wired transmissions such as PowerLine, DSL, etc., and also to optical methods.

[0009] Now, in order to nevertheless be able to transmit acceptable bit rates over an inductive interface, the bandwidth of which is strongly limited due to the inductance of the transducer coils used above, the bits must be transmitted synchronously between the transmitter and the receiver, where bit synchronization means that the transmitter or the receiver is synchronized to the exact time position of the individual bits via a synchronization mechanism, so that both sides have exact knowledge of the time position of the start and end edge of each bit.

[0010] In the case of transmission over an inductive interface, the problem arises that the time position of the individual bits on the serial interface of the transmitter does not coincide with the time position of the transmission instants on the inductive interface. Similarly, the exact frequencies of the two bit rates differ according to a tolerance, even if they are tuned to the same frequency.

[0011] To solve the above problem, it is conceivable to configure the inductive interface in such a way that the bit rate of the inductive interface during inductive transmission is several times the bit rate of the serial signal. However, in the receiver, the bits for the serial signal output must be resynchronized in order to meet the requirements for the serial signal. Otherwise, the receiver must be operated at a very high clock rate, which can be 20 to 1000 times the bit rate of the transmitter. However, due to the abovementioned large increase in bit rate, such a solution must be considered very disadvantageous, because for high-speed interfaces above 200 Kbit / s, the above solution can only be realized in an inductive manner at a very high cost. In this case, there are also areas where the transmission quality is not optimal.

[0012] Against this background, the problem on which the invention is based is to provide a method and a transmission device for contactless transmission of serial signals, in which delays in the transmitted messages are minimized while at the same time the transmission quality is impaired as little as possible.

[0013] The above problem is solved by a method for contactless transmission of a serial signal according to the characterizing part of independent claim 1 and a transmission device for said method according to the characterizing part of independent claim 8. Advantageous configurations of the method and the device are given in the respective subsequent dependent claims.

[0014] In this respect, the present invention provides a method for contactless transmission of a serial signal from a transmitter to a receiver, in which the signal is received from the transmitter in the form of a first bit stream with a first bit clock and evaluated by a control unit, a start bit of the signal is searched for in the first bit stream using the control unit, a delay signal is set and transmitted to a delay circuit, all bits of the signal in the first bit stream are sampled and delayed by a delay time by the delay circuit and stored sequentially in a FIFO memory, respectively with a second bit clock, and for reading from the FIFO memory, the present bits are read out sequentially, respectively in synchronization with the second bit clock and transmitted as a second bit stream by an inductive transmission unit through an air gap to the receiver.

[0015] Furthermore, according to the present invention, there is provided a transmission device for contactlessly transmitting a serial signal from a transmitter transmitting at a first bit clock to a receiver, the transmission device including an inductive transmission unit transmitting at a second bit clock, a control unit evaluating a received signal and setting a delay time, a FIFO memory for delaying and temporarily storing the signal, and a delay circuit for sampling all bits of the signal, delaying it by the delay time, and transferring it to the FIFO memory, the control unit being data-connected to the inductive transmission unit, the delay circuit, and the FIFO memory, the inductive transmission unit including an inductive transmitting unit separated from the inductive receiving unit via an air gap, and the inductive transmitting unit being further data-connected to the receiver.

[0016] That is, instead of ensuring that the original signal is accurately detectable and reproducible by increasing the sampling rate, it is instead determined how much the first bit clock of the transmitter deviates from the second bit clock of the inductive transmission device. Correspondingly, the signal is offset by a delay, so that the first bit stream of the incoming signal is inductively transmitted and forwarded to the receiver in synchronism with the second bit clock of the inductive transmission device, this is done by delay elements and entries in a FIFO memory, i.e. entries in a memory from which the bits written first are read out first again. As a result, the transmission of the signal via the inductive transmission device takes place with only a minimal time offset.

[0017] In detail, this can be done by the control unit detecting the time offset between the first and second bit clocks and setting a delay time that corresponds at least to the time interval between the end edge of the starting bit and the next edge of the second bit clock, and at most to the time interval between the start edge of the starting bit and the next edge of the second bit clock, but preferably such that the central area of ​​each bit received at the first bit clock is synchronized with the second bit clock. The signal is usually not strictly rectangular as shown. Rather, the edges undergo transient oscillations until the signal settles to the set value. Therefore, in order to always have the most reliable value possible, the delay can be selected such that the sampling of the first bit stream is always performed in the central area of ​​each bit, where the transient oscillation state is reached.

[0018] Preferably, in this case, the control unit compares each signal with a template and, if no end bit is received in the signal, can complete the missing end bit if necessary. Since it is possible that, based on the delay, the end bit does not occur within the set tolerance, the control unit monitors the structure of the signal and compares it with a known template for this. In the case of an RS232 word, for example, the start bit is set to 0, followed by 8 bits of information, then 1 parity bit, and a final stop bit is placed and held for the quiet time. Now, if the stop bit is cut off, based on the information about the protocol used, set in the control unit, it can be completed and inserted into the FIFO memory even if the stop bit was not sampled.

[0019] Here, the control unit can set a specific delay time for each signal, and it may be advantageous to synchronize each signal anew in order to ensure that individual bits are not persistently cut off from the signal according to the corresponding tolerances.

[0020] Particularly advantageously, the second bit clock of the induced transmission unit has the same clock rate as the first bit clock, preferably corresponding at most to the first bit clock of the transmitter or an integer multiple thereof, which is possible for the signal protocol used. In this way, the induced transmission can be performed with a normal clock, since no high-resolution sampling is required and no exchange of clock rates is required. This means that no further synchronization is required after the induced transmission, since the receiver already receives the received signal at the expected clock rate. For this purpose, if the transmission is performed at a higher clock rate. Preferably, an integer multiple of the clock rate can be selected, so that several signals can be transmitted within the time of one signal. In this case, the signal can also be simply output again (for example via another FIFO memory) in the opposite direction to the receiver. In this connection, particularly preferably, a clock rate of 4.8 Kbit / s, 38.4 Kbit / s or 230.4 Kbit / s is provided as the first bit clock.

[0021] Furthermore, the control unit can use suitable means for setting the clock rate of the first bit clock to determine said clock rate and to synchronize it with the second bit clock, where the clock rate of the second bit clock of the control unit is essentially known, but in the framework of the communication with the transmitter the clock rate of the transmitter can be handled on the input side or can also be determined by time measurements from the signal itself.

[0022] Also preferably, within one clock of the second bit clock, several bits of one or several signals of the transmitter can be transmitted simultaneously to the receiver. In the case of such a multiplexing method, the signals can be superimposed on one another, for example by modulation or demodulation, so that a rapid and comprehensive communication can take place. This can be particularly advantageous when several devices, i.e. several grippers, sensors, actuators or control devices, are driven via individual inductive transmission units. For this purpose, a multiplexer can be assigned to the inductive transmitter side of the transmission device, in which case a demultiplexer must be provided on the inductive receiver side.

[0023] In a specific implementation, the transmission device can be constructed entirely as software on a CPU, or as programmable logic on an FPGA or CPLD, or as integrated logic on an IC or ASIC, or by hardwired logic, or from a mixture of these components. Since the transmission device is formed entirely from simple components, there are accordingly a large number of implementations that can be used advantageously.

[0024] Finally, the inductive transmission unit can be configured bidirectionally, i.e. it can have combined inductive transmitting / receiving units on both sides, or one inductive transmitting unit and one inductive receiving unit on each side. This allows signals to be conveyed in both directions through the air gap, for example actuation signals in the direction of the robot arm and confirmation and error messages as well as sensor measurements in the opposite direction. If the same device is used on both sides as a transmitting coil and a receiving coil, it is possible to use effectively half the time for each direction, and therefore the above-mentioned method using a bit rate multiple of the first bit rate and a multiplexer can be used, even if there is no available transmission time to transmit the required data within the correct time window.

[0025] The above-mentioned invention will be described in detail below with reference to examples. [Brief description of the drawings]

[0026] [Figure 1] 1 is a basic circuit diagram showing a transmission device including a transmitter and a receiver; [Diagram 2] FIG. 2 illustrates the basic scheme of the bit clock and bit stream of the transmitter and the guided transmission unit.

[0027] 1 shows a basic circuit diagram of a transmission device 1 with a data connection to a transmitter 2 and a receiver 3. The transmitter 2 transmits a signal 17 to the receiver 3 by means of the transmission device 1. Here, the transmitter 2 is arranged at the base of a robot arm, and the receiver 3 is arranged on the rotatably supported arm itself. Between the transmitter 2 and the receiver 3, an air gap 7 exists to allow free rotation of the robot arm, which air gap 7 is bridged by an inductive transmission part 22 using a coil pair consisting of an inductive transmission unit 4 and an inductive receiving unit 5.

[0028] The signal 17 is arranged serially and contains the bit stream 12 shown in Fig. 2. In this case, the first bit clock 10 used by the sender 2 is different from the second bit clock 11 used in the transmission device 1, but in this example the clock rates of the two bit clocks 10, 11 are chosen to be equal, so that the transmission device 1 transmits the signal 17 at the same bit rate as the sender 2.

[0029] When a signal 17 is applied for transmission, it is checked and sampled by the control unit 6 of the transmission device 1. First, the first bit clock 10 is detected and compared with the second bit clock 11 of the guiding transmission unit 4, so as to find out how the two bit clocks 10, 11 behave relative to each other. The control unit 6 then detects that the clock rates are equal on both sides, but are simply not synchronized. That is to say, the control unit 6 sets the delay time 14 such that when the value of the corresponding bit is read out, the delay time 14 is applied in the central region of the bit, ideally located in the central region of the start bit 15.

[0030] The delay time 14 set by the control unit 6 is transferred to a delay circuit 8 which receives the first bit stream 12 from the transmitter 2. The individual bits of the first bit stream 12 are delayed by the delay time 14 and written in the form of the second bit stream 13 as delayed signals 18 into the FIFO memory 9, and furthermore a respective write signal 19 is sent by the control unit 6 to the FIFO memory 9. If a comparison of the delayed signals 18 stored in the FIFO memory 9 with a template of the transmission protocol shows that a stop bit 16 has been cut off due to the delay and the tolerance, this stop bit 16 is written into the FIFO memory due to an additional write signal 19 of the control unit 6.

[0031] Then, based on the read signal 20 of the control unit 6, each one bit of the delayed signal 18 is read out with the second bit clock 11 in the second bit stream 13 and transmitted as a synchronized signal 21 from the inductive sending unit 4 through the air gap 7 to the inductive receiving unit 5 in the course of an inductive transmission 22. The signal 23 transmitted through the air gap 7 is now conveyed to the receiver 3 and finally reaches the receiver 1 at the same bit rate, delayed by the delay time 4 with respect to the first bit clock 10.

[0032] Thus, what has been described above is a method and a transmission device for contactless transmission of serial signals, in which delays in the messages transmitted are minimized while at the same time the transmission quality is impaired as little as possible. [Explanation of symbols]

[0033] 1 Transmission equipment 2 Transmitter 3 Receiver 4 Guidance Transmitter Unit 5. Induction receiving unit 6. Control Unit 7 Air gap 8 Delay Circuit 9. FIFO Memory 10 1st bit clock 11 Second Bit Clock 12 First bitstream 13 Second Bitstream 14 Delay Time 15 start bit 16 End Bits 17 Serial Signals 18 Delayed Signal 19 Write Signal FIFO 20 Read signal FIFO 21 Synchronized Signals 22 Inductive transmission 23 Transmitted Signals

Claims

1. A method for contactlessly transmitting a serial signal (17) from a transmitter (2) to a receiver (3), comprising: said signal (17) is received from said transmitter (2) in the form of a first bit stream (12) at a first bit clock (10) and evaluated by a control unit (6), a delay time (14) is set and transmitted to a delay circuit (8), and by said delay circuit (8) all bits of said signal (17) in said first bit stream (12) are sampled, delayed by said delay time (14) and stored; In the method, Using the control unit (6), a start bit (15) of a signal (17) is searched for in the first bit stream (12), and all bits of the signal (17) are sequentially stored in a FIFO memory (9) by the delay circuit (8) with a second bit clock (11), For reading from the FIFO memory (9), the bits present are sequentially read out, each in synchronization with the second bit clock (11), and transmitted as a second bit stream (13) by an inductive transmission unit through the air gap (7) to the receiver (3), the second bit clock (11) is the bit clock of the induced transmission unit, and the control unit (6) detects a time offset between the first bit clock (10) and the second bit clock (11); The delay time (14) is set to at least correspond to the time interval between the ending edge of the start bit (15) and the next edge of the second bit clock (11), and at most to correspond to the time interval between the starting edge of the start bit (15) and the next edge of the second bit clock (11), but preferably to be set such that the central region of each bit received on the first bit clock (10) is synchronized with the second bit clock (11). A method comprising:

2. 2. The method of claim 1, wherein the control unit (6) compares each signal (17) with a template and, if a termination bit (16) is not received in a signal (17), completes a missing termination bit (16) as necessary.

3. 3. The method according to claim 1, wherein the control unit (6) sets a unique delay time (14) for each signal (17).

4. 4. The method according to claim 1, wherein the second bit clock (11) of the induced transmission unit has the same clock rate as the first bit clock (10), preferably corresponding at most to the first bit clock (10) of the transmitter (2) or an integer multiple thereof, as is possible for the signal protocol used.

5. 5. The method according to claim 4, wherein as the first bit clock (10) a clock rate of 4.8 Kbit / s, 38.4 Kbit / s or 230.4 Kbit / s is provided.

6. 6. The method according to claim 1, wherein the control unit (6) determines a clock rate of the first bit clock (10) and uses it to synchronize it with the second bit clock (11).

7. 7. The method according to claim 1, wherein within one clock of the second bit clock (11), multiple bits of one or more signals (17) of the transmitter (2) are transmitted simultaneously to the receiver (3).

8. A transmission device for contactlessly transmitting a serial signal (17) from a transmitter (2) that transmits at a first bit clock (10) to a receiver (3), comprising: A transmission device including a control unit (6) for evaluating a received signal (17) and setting a delay time (14), The transmission device further includes an induction transmission unit that transmits with a specific bit clock as a second bit clock (11), a FIFO memory (9) that delays and temporarily stores the signal (17), and a delay circuit (8) that samples all bits of the signal (17), delays the signal by the delay time (14), and transfers the sampled signal to the FIFO memory (9); The control unit (6) is data-connected to the inductive transmission unit, the delay circuit (8) and the FIFO memory (9); The inductive transmission unit includes an inductive transmission unit (4) separated from an inductive receiving unit (5) via an air gap (7), the inductive receiving unit (5) being further data-connected to the receiver (3); the control unit (6) having means for detecting a time offset between the first bit clock (10) and the second bit clock (11); The delay time (14) can be set by the control unit (6) to correspond at least to the time interval between the ending edge of a start bit (15) and the next edge of the second bit clock (11) and at most to the time interval between the starting edge of a start bit (15) and the next edge of the second bit clock (11), but preferably to such an extent that the central region of each bit received on the first bit clock (10) is synchronizable with the second bit clock (11). A transmission device comprising:

9. 9. A transmission device according to claim 8, wherein the control unit (6) comprises means for setting the clock rate of the first bit clock (10).

10. 10. The transmission device according to claim 8 or 9, wherein the control unit (6) comprises a multiplexer for simultaneously transmitting a plurality of signals via the inductive transmission unit.

11. 11. The transmission device according to claim 8, wherein the transmission device is constructed entirely as software on a CPU, as programmable logic circuitry on an FPGA or CPLD, as integrated logic circuitry on an IC or ASIC, or by hardwired logic circuitry, or from a mixture of these components.

12. 12. The transmission device according to claim 8, wherein the inductive transmission unit is configured bidirectionally, i.e., has an inductive transmitting / receiving unit combined on both sides, or has an inductive transmitting unit (4) and an inductive receiving unit (5) on each side.

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