Method for Transmitting a Value Measured by a Sensor, Method for Receiving the Measured Value, Sensor, Control Device

Abstract

A method for transmitting a value measured by a sensor. The measured value is copied onto a data word by a function in order to be transmitted.

Claims

1. A method for transmitting a measured value by a sensor, comprising: mapping the measured value onto a data word according to a function in order to be transmitted.

2. The method as claimed in claim 1, wherein the mapping takes place in such a way that predetermined value ranges are mapped with a higher resolution.

3. The method as claimed in claim 1, wherein the function is a non-linear and/or non-symmetric and/or non-continuous function.

4. A sensor configured to map a measured value onto a data word according to at least one function and to transmit the measured value.

5. The sensor as claimed in claim 4, wherein the at least one function is stored in the sensor.

6. The sensor as claimed in claim 5, wherein, in an initialization phase, the sensor is configured to transmit the at least one function selected for the mapping.

7. The sensor as claimed in claim 4, wherein during manufacture of the sensor the at least one function is stored in the sensor.

8. The sensor as claimed in claim 4, wherein the measured value is determined from a received data word according to another function.

9. The sensor as claimed in claim 8, wherein: in an initialization phase, the other function is received, and the other function for determining the measured value depends on the received function.

10. The sensor as claimed in claim 4, wherein a control device is configured to carry out all steps of the method.

11. The method as claimed in claim 1, wherein a computer program is configured to carry out the method.

12. The method as claimed in claim 11, wherein the computer program is stored on a machine-readable storage medium.

Description

[0034] Forms of embodiment of the present invention are represented with reference to figures and explained below. Here:

[0035] FIG. 1 shows a linear mapping of measured sensor values onto sensor signals of a communication bus according to today's prior art;

[0036] FIG. 2 shows a mapping of measured sensor values onto data words for transmission according to the present invention;

[0037] FIG. 3 shows a mapping of sensor signals onto measured sensor values after reception according to the present invention;

[0038] FIG. 4 shows a flow diagram of a form of embodiment of a method for transmitting a measured value according to the present invention;

[0039] FIG. 5 shows a flow diagram of a form of embodiment of a method for receiving a measured value according to the present invention.

[0040] FIG. 1 shows a linear mapping of measured sensor values onto data words for transmission of the measured sensor values of a communication slot, for example on a communication slot according to the PSI5 protocol, or on a point-to-point connection according to the prior art. The data range of a 10-bit sensor for a sensor channel according to FIG. 1 is here formed linearly from the measured sensor values from 480 LSB up to +480 LSB.

[0041] The measured sensor values are plotted on the abscissa. The values of the data word are plotted on the ordinate. The red line here represents the linear assignment of the range of measured sensor values to the data word range of +/480 LSB.

[0042] FIG. 2 shows a mapping of measured sensor values onto data words for transmission according to the present invention. As shown in FIG. 2, the measured sensor values of the sensor are initially mapped up to a range of +/200 LSB with a high resolution onto the sensor signals of the communication bus. This can be recognized through the steep, straight section between the measured sensor values that are mapped onto the data word range from +/200 LSB. The measured sensor values between +/200 LSB and +/480 LSB are then transferred with a lower resolution onto the data words for transmission on the communication bus. This is illustrated through the straight sections with lower gradients.

[0043] The illustration in FIG. 2 is only to be looked on as an example. The converse case is, of course, also conceivable, as is the mapping by means of curves or functions.

[0044] According to the present invention, the straight lines, curves or functions in the sensor are encoded by means of mathematical functions or approximations, or with the aid of case distinctions, so that the mapping of the measured sensor values onto the data words or sensor signals of the communication bus are calculated automatically depending on the measured sensor value.

[0045] The calculation can then take place either in software on the sensor or through a logic within the sensor ASIC. A transmission of the sensor signals calculated from the measured sensor values then takes place over suitable communication means, for example on a communication slot according to the PSI5 protocol, or on a point-to-point connection.

[0046] The mapping function that is illustrated in FIG. 2 is symmetric, but the straight lines, curves or functions for mapping the measured sensor values onto data words can, of course, also be configured asymmetrically for the relevant regions. What is, however, crucial is that the more critical measuring ranges have a higher resolution than the less critical measuring ranges.

[0047] Whether a measuring range is deemed to be critical or less critical depends on the application that operates on the measured sensor values. Taking the example of a trigger algorithm as an application for the measured sensor values, the measured value ranges around the trigger thresholds are to be considered as critical. The resolution of the transmitted measured value is to be considered as rather less critical for measured value ranges for which no resolution clearly comes into question, or for which a resolution would clearly come into question.

[0048] FIG. 3 shows a mapping of data words or sensor signals onto measured sensor values after reception according to the present invention.

[0049] The sensor signals that are transferred to a communication bus according to the method for transmitting measured values are then, for example, received and processed at a control device such as an airbag control device.

[0050] In order that the sensor signals of the communication bus are correctly interpreted at the control device, a determination of the measured sensor value transmitted in the data word, including a conversion of the sensor signals of the communication bus, is performed according to the method for receiving measured values according to the present invention.

[0051] To this end, suitable determination rules are stored at the control device corresponding to the straight lines, curves or functions of a sensor type for mapping the measured values onto data words. Mathematical functions, for example. A mapping onto the value range of the control device thus takes place with the aid of the received sensor signals.

[0052] As is shown in FIG. 3, a straight line with a gradient again in the control device through an inverse mapping of the received data words or sensor signals. It is, however, noticeable, that the value range at the control device, with +/600 LSB, is now significantly above the value range (+/480 LSB) on the communication bus. Through the non-linear and variable resolution of the mapping of the sensor, it is thus possible in the context of the invention for a changed measuring range, increased in the illustrated example, to be transmitted on a communication bus.

[0053] The communication bus of the illustrated example is operated in accordance with the PSI5 protocol. This means that the data word has a length of 10 bits, and only has the possibility of transmitting +/480 LSB.

[0054] Through the conversions at the sensor and control device end, +/600 LSB is nevertheless created from this in this example. The resolution of the sensor signals above +200 LSB and below 200 LSB is, of course, rather worse than in the +/200 LSB range. This, however, is intentional, since a high sensor resolution usually only has a high importance in the lower range (in this case +/200 LSB). In the upper value range, a resolution in the range of single LSBs is usually no longer necessary.

[0055] FIG. 4 shows a flow diagram of a form of embodiment of a method for transmitting a measured value according to the present invention.

[0056] A measured value is acquired in step 401.

[0057] The acquired measured value is mapped onto a data word by means of a function in step 402. The function here describes the mapping of the measured value range onto the data word value range.

[0058] In step 403, the data word is transmitted over a communication means by means of a communication protocol. The PSI5 protocol here represents a preferred communication protocol. A communication bus or a point-to-point connection in accordance with the specifications of the PSI5 protocol is then a preferred communication means.

[0059] FIG. 5 shows a flow diagram of a form of embodiment of a method for receiving a measured value according to the present invention.

[0060] In step 501, a data word is received over a communication means by means of a communication protocol.

[0061] In step 502 the measured value that was transmitted with the data word is determined by means of a function.