METHOD AND SENSOR BUS SYSTEM

Abstract

A method for transmitting data in a sensor bus system and a sensor bus system. The sensor bus system includes an electronic controller, a plurality of sensors, and a twisted two-wire line between the electronic controller and the sensors, wherein the electronic controller is designed to supply electrical energy to the sensors via the twisted two-wire line, and the sensors are designed to transmit received information to the electronic controller in an I/Q-modulated manner via the twisted two-wire line.

Claims

1-12. (canceled).

13. A sensor bus system, comprising: an electronic controller; a plurality of sensors; and a twisted two-wire line between the electronic controller and the sensors, wherein the electronic controller configured to supply the sensors with electrical energy via the twisted two-wire line, and wherein the sensors are configured to transmit received information to the electronic controller in an I/Q-modulated manner the twisted two-wire line.

14. The sensor bus system according to claim 13, wherein the two-wire line connects the electronic controller and the sensors via a ring structure or a linear structure, in terms of information technology and energy.

15. The sensor bus system according to claim 13, wherein the sensors include: ultrasonic sensors, and/or acceleration sensors, and/or near range radar sensors.

16. The sensor bus system according to claim 13, wherein the I/Q modulation includes PSK or QPSK or 8-PSK or 16-PSK or DPSK, and/or includes a quadrature amplitude modulation, and/or uses a fundamental frequency of at least 100 kHz.

17. The sensor bus system according to claim 13, further comprising an equalizer in a reception path of the electronic controller and/or in a transmission path of the sensors, the equalizing being set up to compensate an attenuation of the twisted two-wire line.

18. The sensor bus system according to claim 13, wherein the sensors are configured to transmit, during reception of signals, the received information to the electronic controller via the twisted two-wire line in the I/Q-modulated manner.

19. The sensor bus system according to claim 13, wherein the electronic controller is configured to transmit an amplitude-modulated carrier signal to the sensors via the two-wire line, and the sensors are configured to transmit the received information via the carrier signal synchronously in the I/Q-modulated manner to the electronic controller via the twisted two-wire line.

20. The sensor bus system according to claim 13, wherein the sensors are configured to transmit the received information, in a time-division multiplex method and/or in a frequency multiplex method, to the electronic controller via the twisted two-wire line in the I/Q-modulated manner.

21. The sensor bus system according to claim 13, wherein the controller is configured to assign to the sensors a corresponding time window, dynamically, within which time window the sensors are permitted to transmit the received information via the twisted two-wire line.

22. The sensor bus system according to claim 13, wherein each of the sensors stores a data set representing preconfigured behaviors with respect to: transmission of measurement signals into an environment, and/or reception of echoes of the measurement signals, and/or transmission of the received information, in a sensor-specific manner, as raw data or as echo data evaluated in the sensor, which echo data can in each case be selectively activated using the electronic controller.

23. A method for data transmission in a sensor bus system, in which a plurality of sensors and an electronic controller are connected to one another in terms of information by a twisted two-wire line, the method comprising the following steps: supplying electrical energy to the sensors by the electronic controller via the twisted two-wire line; receiving information by the sensors; V/Q modulating the information in the sensors; and transmitting the I/Q-modulated information from the sensors to the electronic controller via the twisted two-wire line.

24. The method according to claim 23, wherein the sensors and the electronic controller are connected to one another in terms of information in a linear or ring-shaped manner by the twisted two-wire line.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Exemplary embodiments of the present invention are described in detail below with reference to the figures.

[0036] FIG. 1 is a schematic representation of a means of transport having a sensor bus system designed according to the present invention.

[0037] FIG. 2 is a schematic representation of the components of a sensor that can be used according to the present invention in the form of an ultrasonic sensor.

[0038] FIG. 3 is a schematic representation of components of a receiver in the form of an electronic controller.

[0039] FIG. 4 shows a power density spectrum of the modulated current signal at the output of a sensor.

[0040] FIG. 5 shows a power density spectrum of the D-QPSK signal at the input of the receiver and after the equalizer.

[0041] FIG. 6 shows a constellation diagram and a histogram of the phase position of the symbols in the receiver (electronic controller) without an equalizer.

[0042] FIG. 7 shows a constellation diagram and a histogram of the phase position of the symbols in the receiver (electronic controller) after the equalizer.

[0043] FIG. 8 shows a flow chart illustrating steps of an exemplary embodiment of a method according to the present invention for data transmission in a sensor bus system.

[0044] FIGS. 9A and 9B shows timing diagrams of different exemplary embodiments of the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0045] FIG. 1 shows a passenger car 10 in which an exemplary embodiment of a sensor bus system 1 according to the present invention is arranged. The sensors 3 are arranged as ultrasonic sensors in the front bumper and in the rear bumper and are connected to an electronic controller 2 via a twisted two-wire cable 4 in terms of information and energy. Both the electronic controller 2 and the sensors 3 are supplied with electrical energy via a starter battery 5.

[0046] FIG. 2 shows components of a transmitter (reference sign 3 in FIG. 1) . Binary input data 6 are sent as a binary data stream to a frame 7, where they are provided with a preamble and a cyclic redundancy check is enabled. The data are then fed as binary words to a D-M-PSK modulator 8, which converts them into complex-valued symbols. In the case of a QPSK, a data word made up of two bits results in a symbol. The transitions between the symbols are smoothed using a pulse shaping filter 9, which largely suppresses harmonics in the resulting spectrum. In the UP converter 11, the complex baseband signal is converted by multiplication with a carrier frequency into a real bandpass signal, which is applied to the data line as a modulated current after a digital/analog converter 12.

[0047] FIG. 3 shows components of a receiver in the form of an electronic controller which is connected to the twisted two-wire line 4. From here the receiver receives the analog input signal, which is bandpass-filtered by the two-wire line 4. After an anti-aliasing filter 14, the bandpass-filtered signal is fed to an analog/digital converter 15, which in the example has a resolution of >five bits. The digital output signal of the analog/digital converter 15 is fed to a down-converter 17 after passing through an equalizer 16, which has an infinite impulse response (IIR) filter and a finite impulse response (FIR) filter. Here the received signal is transformed into the complex baseband by multiplication with the carrier frequency. This is then fed to an adapted filter 18 which suppresses the high-frequency spectral signal components, for which purpose it is adapted to the pulse shape and acts as a low-pass filter. The symbol synchronizer 19 synchronizes the sampling of the symbols with the data stream with regard to frequency and optimum sampling time. The scanned symbols are demodulated in a D-M-PSK demodulator 20 and the frames are separated from each other in a frame synchronizer 22 using the preamble bit sequences detected in a preamble detector 21. With the aid of a cyclic redundancy check (CRC) 23, the CRC checksum bits are checked and corrected with regard to any transmission errors. Optionally, the CRC 23 can also be replaced by a block code, which also enables automatic error correction, if the block code used supports this. The output data of the CRC 23 are supplied to the logic unit 24 of the receiver, and the findings obtained here can be used for driver assistance or autonomous driving.

[0048] FIG. 4 shows an exemplary power density spectrum which has the current signal modulated with D-QPSK at the output of the sensor (reference sign 3 in FIG. 1). The concentration of the signal power in a frequency range between 100 kHz and 400 kHz is clearly recognizable, while the sensitive frequency bands below 60 kHz and above 500 kHz are not significantly occupied. The power density is plotted on the ordinate and the frequency in Hz is plotted on the abscissa.

[0049] FIG. 5 shows the power density spectrum of the D-QPSK signal at the input of the electronic controller compared to the signal obtained after the equalizer. The modulated signal generated by the sensor is attenuated during transmission via the bus line, wherein higher frequencies are usually attenuated more than lower frequencies. This corresponds to a low-pass characteristic of the twisted two-wire line. Additional sensors connected thereto also contribute to the low-pass characteristic with their capacitive load. The attenuation of the amplitude is accompanied by a phase shift of the signals, which increases with the frequency. Without an equalizer in the electrical controller (receive path or receiver), decoding of the symbols would in some cases be possible only to an imperfect extent, as the pulse shape would be distorted and inter-symbol interference would prevent reliable separation of the symbols. This relationship is shown in FIG. 6.

[0050] FIG. 6 shows a constellation diagram and histogram of the phase position of the symbols in the receiver without an equalizer. In the upper diagram, the quadrature is plotted over the in-phase, while in the lower diagram the synchronized demodulation histogram at 250 kbaud =Fo is plotted over the angle. An equalizer in the receiver that is adapted to the transmission function (all-pass filter in combination with high-pass filter) can reverse the distortion caused by the channel (the bus line) and the symbols can be successfully decoded without errors. This relationship is plotted in FIG. 7.

[0051] FIG. 7 shows a constellation diagram and a histogram of the phase position of the symbols in the receiver (electronic controller) after treatment by the equalizer. In the upper diagram, the quadrature is plotted over the in-phase, while in the lower diagram the synchronized demodulation histogram at 250 kbaud =Fo is plotted over the angle. Due to the treatment by the equalizer, the distortion caused by the channel (twisted two-wire line) can be reversed and the decoding of the symbols is successfully done without errors.

[0052] FIG. 8 shows steps of an exemplary embodiment of a method according to the present invention for data transmission in a sensor bus system in which a plurality of smart sensors and an electronic controller are connected to one another in terms of information and energy by a twisted two-wire line. In step 100, energy from an on-board electrical system battery is used, by means of the electronic controller, to supply the sensors with electrical energy required for their operation and for communication. This takes place via the twisted two-wire line. In step 200, the sensors are used to receive operational and/or environmental information. The sensors prepare the transmission via the twisted pair cable in step 300 by I/Q modulation of the information, and send the I/Q-modulated information to the electronic controller via the twisted pair line in step 400. Due to the increased data rate compared to the related art, a linear or ring-shaped bus topology can be used, whereas the related art always requires a star-shaped topology between the sensors and a (central) controller.

[0053] FIGS. 9A and 9B shows timing diagrams of different exemplary embodiments of the present invention.

[0054] In FIGS. 9A and 9B the embodiments according to the present invention are shown by way of example and are described in detail below.

[0055] Partial diagram A) shows a typical measurement cycle of point-to-point system in current use today.

[0056] Measurement cycle T2 begins with the transmission of the sensor data, including monitoring/diagnostic variables and checksums slm_d(n-1), followed by the transmission request and the ultrasonic transmission pulse SP(n) * and the subsequent echo reception in the measurement window. The measuring cycle then starts again from the beginning. The scheme is applied in parallel for all N sensors in the system. A sensor can also be only a (cross-echo) receiver. In this case, a different action can be carried out in the sensor in the phase marked SP.

[0057] The duration of the data communication phase is determined by the available data rate and the number of bits to be transmitted. In typical systems, this phase lasts up to 5 ms at around 200 kBit/s. The measurement window is substantially determined by the sound propagation time and the required measurement range, and is approximately 30 ms at a range of 5m. That is, the communication window is significantly shorter compared to the measurement window. A disadvantage of current systems, besides the prolongation of the measuring cycle, is that there is a latency of up to one complete measuring cycle between echo detection and data transmission.

[0058] The method proposed here can be used for data rates >500 kBit/s.

[0059] Further communication schemata for the method according to the present invention are shows in subdiagrams B1) to B5).

[0060] In bus operation, the following schemata are proposed according to the present invention:

[0061] B1) Optimization of the measurement data repetition rate

[0062] In this measurement mode, the measuring cycle is shortened due to the fact that the individual sensors communicate one after the other during echo reception. An additional communication window outside of the measurement operation is omitted. Advantageously, the complete data packets of a sensor are transmitted completely before it is the turn of the next sensor, in order to achieve the best possible utilization of the net data rate. Disadvantageous here is the latency of up to almost two (shortened) measurement cycles (if, in the example shown, echoes from sensor 6 were detected at the beginning of cycle (n-1) but are not transmitted until the end of cycle(n)) .

[0063] B2) Optimization for maximum bandwidth utilization

[0064] Under the boundary condition that the total measurement cycle time should not be lengthened compared to a currently used system, while at the same time the entire communication time is utilized, B2) is a suitable solution. The communication windows per sensor can also be of different lengths if different data contents are to be communicated. This mode is suitable for raw data transfer, for example. The sensor status or the monitoring variables are sent between measurement cycle (n-1) and (n) to reduce error tolerance times. The sensor (raw) data from the previous cycle is transferred in full in the measurement window of the subsequent cycle. Variant B2) can use a rigid timing scheme, but also generates a latency in the transmitted sensor data.

[0065] B3) Latency-minimized transmission

[0066] In contrast to B1) and B2) , in this mode data from the current cycle and previous cycle are transferred. First, the monitor and diagnostic information from the current cycle is transmitted for each sensor, i.e. the sensor self-diagnosis takes place during the phase marked SP. This is followed by the transfer of the remaining data from the previous cycle. This is followed by the transmission of the echoes that have already been detected, or raw data from the current cycle, until the start of the data transmission. This mode minimizes the latency for monitoring and diagnostic information by one measurement cycle compared to today, as well as for the echoes detected in the near-medium distance range. This mode is appropriate in particular for safety-relevant applications in which short error tolerance times and low latency are important.

[0067] B4) Optimized for functions at higher speeds

[0068] Whereas in B1) to B3) the order of the sensors that transmit the data was shown in ascending order without restriction of generality, B4) and B5) emphasize that the order of the time slots in which the sensors can communicate can be assigned variably. For a USS system, it is advantageous e.g. at higher speeds, when the parking space measurement or blind spot detection is active, that the corner sensors S1 and S6 can transmit their data with priority (B4) . Or more generally: speed or function-dependent assignment of the transmission sequence of the bus users and the data content.

[0069] B5) Optimized for functions that require raw data transmission in the front area

[0070] In variant B5), the basic idea is that some functions benefit if raw data evaluation of sensors in the controller is possible, but at the same time the transmission bandwidth is so limited that not all sensors can transmit raw data. It is proposed, for example, to transmit in a bandwidth-saving manner the echo data of the corner sensors evaluated in the sensor, and the raw data from the middle sensors. Here, up to the middle of the measurement window, the data from the previous cycle (echoes and second half of the raw data) are transmitted, as well as the raw data from the distance range up to the middle of the measurement window (approx. 2.5 m) . Monitoring variables are transferred from the current cycle. A slight increase in the measuring cycle time is accepted in this case.

[0071] More generally, this can be formulated as follows:

[0072] The type of data (echo or raw data) as well as the time slot available for this and, in the case of raw data, the time range can be varied dynamically from cycle to cycle. In addition, there can also be mixed operation of echo and raw signal data transmission. [0073] i. In this way, it would also be possible to deliberately not assign a slot to specific sensors, i.e. sensors that could possibly be dispensed with in the current measurement (e.g. the remote echo sensor) . These sensors would then transmit only status data. [0074] ii. In the case of raw data, the time section could be configured variably so that, for example, at higher speeds only the clutter area or only the long range is transmitted (for road condition estimation) or the immediate near range is not transmitted. For example, at low speeds data relating to the long-distance range can be excluded from transmission, because at low speeds the long-distance range is not relevant to collisions. [0075] iii. A combination is also possible: For example, the oscillation of the sensor and the echoes can always be transmitted. Alternatively or additionally, the clutter region or the noise region can always be transmitted in addition to the echoes.

[0076] In summary, it can be said that, on the basis of the method according to the present invention for data transmission, new possibilities result for ultrasound-based driver assistance systems with regard to flexibility (selection via a priori configuration and/or during running operation) and design of the bundling and temporal arrangement of data packets.