DE102004021210A1 - Communication and / or control device and method for transmitting measurement, control and / or control signals in the form of signal values via a data bus - Google Patents

Abstract

In a method for the transmission of measurement, control and / or regulation data in the form of signal values via a data bus (2), to which a plurality of communication and / or control devices (SG¶i¶) is connected, the Signal length of the respective signal value as a function of the size of the signal value to be transmitted.

Description

The The invention relates to a method for transmitting measurement, control and / or control data in the form of signal values via a data bus to which a plurality of communication and / or ECUs are connected.

The The invention further relates to communication and / or signaling devices for carrying out such Process.

Especially In complex technical systems, there is a need for capacity utilization a data bus to reduce and the efficiency of data transmission to improve.

This is in the DE 198 54 788 A1 for a data bus used in a motor vehicle, it is proposed to directly calculate all variables required for anti-lock control of a wheel in a wheel module, so that these variables do not have to be sent from a central module via a data bus.

From the JP 111 63 905 A For example, a motor vehicle multiplex transmission method is known in which a data change is evaluated and transmitted with additional information for indicating whether updated data is present. A similar procedure is in the JP 111 63 907 A described.

task The invention is an improved method of transmission of measurement, control and / or regulation data in the form of signal values via a Data bus to which a plurality of communication and / or control devices connected are to create as well as improved communication and / or control devices, the scope of messages on data bus systems, especially in motor vehicles to reduce.

The Task is with the generic method solved by the invention Defining the signal length the respective signal value depending on the size of the to be transmitted Signal value.

While conventional Way signals over the Data bus to be transmitted with constant resolution, It is now proposed, the signal length as a function of the numerical size of the value to be transferred Adjust the signal value. This is the case in the case of small signal values a fine signal resolution needed for example, the wheel speed of a motor vehicle at less Transfer speed. For larger signal values, for example, the wheel speed at high speed, the resolution and thus the message length be reduced.

In order to the data bus is relieved and there is additional message space for the transmission other information about the data bus available.

Preferably occurs with digitally transmitted Signal values a definition of the bit length as a function of the size of the signal value. It should have a larger bit length small signal values and smaller bit length for larger signal values so that the resolution with smaller signal values larger and smaller for larger signal values is.

Especially it is advantageous if threshold values are defined and certain Signal lengths for signal values which are in the value range of the defined thresholds lie. This makes it possible when approaching to switch the signal length from above or below to the threshold of a state. The determination of the signal length determining Condition can then be supplemented with additional information about the Data bus to be transmitted. Alternatively, the switching can also be observed by the receiver, for example by storing a pre-value and the current state. By Shifting the signal value when changing the resolution can be the additional information be saved.

The Task is further characterized by the generic communication and / or control device solved, that this example, by appropriate programming of a Microcontroller for implementation of the method described above is formed.

The The invention will be explained in more detail with reference to the accompanying drawings. It demonstrate:

1 - Sketch of a motor vehicle with data bus and distributed communication and / or control devices;

2 - Blocks of digital signal values with different lengths depending on the size of the transmitted signal value.

The 1 leaves a sketch of a motor vehicle 1 with a data bus 2 recognize, to which a plurality of communication and / or control units SG _i with i = 1 ... N are connected. To the traffic on the data bus 2 and thus the utilization of the data bus 2 It is proposed to reduce the signal length of the individual signal values to be transmitted as a function of the size of the signal value to be transmitted. The signal values may be measurement, control and / or regulation data which is available between the communication and / or control devices SG _i over the data bus 2 be transmitted.

The 2 has a first data block a) with 12 bits and a second data block b) with 8 bits detect. Furthermore, a status bit indicated by diamond pattern is optionally provided.

To transmit, for example, a wheel speed, the number of bit coding results as a quotient between the maximum speed v _max and the necessary resolution. At the assumed values of
maximum driving speed v _max = 250 km / h
Resolution = 1/16 km / h / bit
This results in a number of bit codings of 250 x 16 bits = 4000 bits, which correspond to a word width ≥ In 4000 / In 2 = 11.96 bits in dual-coded form.

The signal values for wheel speed must therefore be transmitted with a word width of 12 bits (2 ¹² = 4096).

According to the invention will now for small signal values a high resolution and for large signal values a lower resolution selected.

For example becomes a threshold of vehicle speed proportional to wheel speed from ≤ 16 km / h.

To At this driving speed is the high resolution of 1/16 km / h bit and Above the threshold, a low resolution of 1 km / h bit set.

For the fine resolution up to the said threshold value of 16 km / h, the number is the bit encoding = 16 x 16 Bit = 256 bits. Dual coded this corresponds to a word width of In 256 / In 2 = 8 bits.

For over the Threshold of 16 km / h going beyond driving speeds a lower resolution chosen from 1 km / h. this leads to to a number of bit encoding of 250 bits and dual coded to a maximum word width of 8 bits.

In spite of constant resolution lead this up to the threshold for reducing the required signal length of 4 bits. Above the threshold value, the definition of the signal length leads to dependence on the size of the signal value to be transmitted also to a saving of 4 bits compared to the constant Signal length. It should be understood that in the former case of signal values in the value range up to the threshold value the signal length Reason for the reduction of the maximum signal value for this Value range is reduced. In the second case of signal values above of the threshold leads however, reducing the resolution to a reduced Signal length. Ultimately, so the signal length by selecting different resolutions dependent on on the size of the transferred Signal value.

Additionally with the signal value can, for example, with at least one additional bit the respective value range transferred so that the signal receiver the definition of the signal length knows the determining state. Alternatively, the immediately preceding Signal value and the corresponding state stored and by comparison with the newly transferred Signal value a switching and thus a change of state be recognized.

The Switching from one state to another can also be done by evaluating the approach be determined from above or below the threshold value of the state. In this case, the saving of additional information about the state is possible by the signal value shifted when changing the resolution or is inverted.

Claims (7)

Method for transmitting measurement, control and / or regulation data in the form of signal values via a data bus ( 2 ) to which a plurality of communication and / or control devices (SG _i ) are connected, characterized by setting the signal length of the respective signal value in dependence on the size of the signal value to be transmitted. Method according to claim 1, characterized by stipulation the bit length a digitally transmitted Signal value depending on on the size of the signal value. Method according to claim 2, characterized by stipulation a larger bit length smaller signal values and smaller bit lengths for larger signal values. Method according to one of the preceding claims, characterized by defining thresholds and specifying signal lengths for signal values, which are in the value range of the defined threshold values. Method according to one of the preceding claims, characterized through additional transmission an information for identifying the determination of the signal length determining State. Method according to one of the preceding claims, characterized in that the signal length as a quotient of the maximum signal value in a Wertebe fixed by threshold values rich and the resolution of the signal in the value range (SL = SW _max / resolution) and the resolution is varied depending on the respectively defined value range. Communication and / or control device (SG _i ) with an interface for connection to a data bus ( 2 ) to provide measurement, control and / or regulation data in the form of signal values via a data bus ( 2 ) to others on the data bus ( 2 ) connected communication and / or control devices (SG _i ), characterized in that the communication and / or control device (SG _i ) is designed for carrying out the method according to one of the preceding claims.