Method for operating a sensor arrangement in a motor vehicle on the basis of a DSI protocol

Abstract

The invention relates to a method for operating a sensor arrangement (2) in a motor vehicle (1) on the basis of a DSI protocol in a Power Function Class mode, wherein the sensor arrangement (2) has a central unit (3) and a multiplicity of sensor units (S.sub.1, S.sub.2, . . . , S.sub.N), the central unit and the sensor units are connected to one another in series by means of a bus cable (4), the sensor units each have a test resistor (R.sub.S1, R.sub.S2, . . . , R.sub.N) connected in series with the bus cable, an electrical test load (L.sub.1, L.sub.2, . . . , L.sub.N) that can be connected to the bus cable, and an address counter (A.sub.1, A.sub.2, . . . , A.sub.N), having the following steps: transferring information between the central unit (Z) and the sensor units by means of a predetermined lower voltage (V.sub.LOW-PWR) and a predetermined upper voltage (V.sub.HIGH-PWR) as the respective bus voltage (U.sub.Bus) in communication phases, supplying the sensor units with electrical energy by means of the central unit in energy supply phases in which an idle voltage (V.sub.IDLE) is applied as the bus voltage, which is at least 1 V greater than the upper voltage, assigning a respective address to the individual sensor units in a previous address assignment phase by means of an address assignment voltage as the bus voltage, which is at least 1 V greater than the upper voltage.

Claims

1. A method for operating a sensor arrangement in a motor vehicle on the basis of a DSI protocol in a Power Function Class mode, wherein the sensor arrangement has a central unit as a master and a multiplicity of sensor units as slaves controlled by the master, the central unit and the sensor units are connected to one another in series by means of a two-wire bus cable, the sensor units each have a test resistor connected in series with the two-wire bus cable, an electrical test load that can be connected to the two-wire bus cable, and an address counter, the method comprising: at least three different operating phases provided in the form of communications phases, on the one hand, and energy supply phases, on the other, that alternate with each other, and an address assignment phase preceding the communications phases and the energy supply phases, having the following steps: transferring information between the central unit and the sensor units by a predetermined lower voltage and a predetermined upper voltage as the respective bus voltage in the communications phases, supplying the sensor units with electrical energy by means of the central unit in the energy supply phases, in which as the bus voltage an idle voltage is applied, which is at least 1 V greater than the upper voltage, assigning a respective address to the individual sensor units in the address assignment phase by the following steps a) to f): a) storing a first address in the address counters of all sensor units, wherein the first address is the same for all sensor units, b) applying an address assignment voltage as a bus voltage, which is at least 1 V greater than the upper voltage, c) connecting the electrical test loads of all sensor units to the two-wire bus cable, so that the sensor units each draw a test current, d) detecting the current flowing through each of the test resistors, e) permanent disconnection of the electrical test load from the two-wire bus cable in the sensor unit in which no current has been detected flowing through the test resistor, and increasing the respective address by a predetermined equal value for all sensor units in the address counters of all other sensor units, whose test load has not yet been permanently disconnected from the two-wire bus cable, f) repeating the steps (d) and (e) for all sensor units, whose test load has not yet been permanently disconnected from the two-wire bus cable, until in all sensor units the electrical test load has been permanently disconnected from the two-wire bus cable.

2. The method according to claim 1, wherein the sensor units are each actuators with a respective actuator load and each have a communication load that can be connected to the two-wire bus cable for communication purposes, wherein the respective actuator load is greater than the respective communication load and the actuator loads are used as test loads.

3. The method according to claim 1, further comprising: applying an address assignment voltage as a bus voltage, which is at least 1 V greater than the upper voltage and equal to at least 50% of the idle voltage.

4. The method according to claim 3, further comprising: applying an address assignment voltage as a bus voltage, which at least temporarily corresponds to the idle voltage.

5. The method according to claim 3, further comprising: applying an address assignment voltage as a bus voltage, which is at least temporarily equal to 25 V.

6. The method according to claim 5, wherein the electrical test loads of the sensor units are connected to the two-wire bus cable in steps c) and d) in at least two stages, in such a way that in the first stage only a part of the test load is activated and then in the following stage or in the following stages each test load is gradually increased further.

7. The method according to claim 1, wherein for step d) from the first repetition of this step onward, the following applies: d) disconnecting the electrical test load from the two-wire bus cable in all sensor units, whose electrical test load has not yet been permanently switched off, and subsequently re-connecting the electrical test load to the two-wire bus cable in all sensor units whose test load has not yet been permanently disconnected from the two-wire bus cable, so that these sensor units each draw a test current, and detecting the current flowing through each of the test resistors of these sensor units.

8. The method according to claim 7, wherein in the sensor units in a subsequent stage, no further increase in the test load is made when in the previous stage a current flowing through the test resistor of the respective sensor unit has been detected, which has exceeded a predetermined threshold value.

9. The method according to claim 1, wherein the first address is 1, and when the addresses are increased an increment of 1 is made in each case.

10. The method according to claim 1, wherein the method is performed in a motor vehicle.

11. A non-volatile, computer-readable storage medium having commands stored thereon, which when executed on a processor implement the method according to claim 1.

12. A sensor arrangement, which is configured for operation by the method according to claim 1.

13. The sensor arrangement according to claim 12, which comprises ultrasonic sensor units for sending and/or receiving ultrasonic signals as the sensor units.

Description

(1) In the following, the invention is described in greater detail with reference to the drawings based on preferred exemplary embodiments. The features described can represent an aspect of the invention both individually and in combination.

(2) Shown are:

(3) FIG. 1 a schematic view of a sensor arrangement with a central unit and a multiplicity of sensor units in a motor vehicle according to a preferred embodiment of the invention,

(4) FIG. 2 a schematic view of the process of address assignment to the sensor units of a sensor arrangement according to a preferred exemplary embodiment of the invention and

(5) FIG. 3 a schematic view of the process of address assignment to the sensor units of a sensor arrangement according to another preferred exemplary embodiment of the invention.

(6) FIG. 1 shows a schematic representation of a vehicle 1 having a sensor arrangement 2 according to a preferred exemplary embodiment of the invention. The sensor arrangement 2 has a central unit Z and a number N of sensor units S.sub.1, S.sub.2, . . . , S.sub.N. The central unit Z and the sensor units S.sub.1, S.sub.2, . . . , S.sub.N are connected to each other by means of a two-wire bus cable 4. It remains the case furthermore that the sensor units S.sub.1, S.sub.2, . . . , S.sub.N are connected with one another in series with the central unit Z, i.e. in a so-called daisy chain configuration.

(7) Within the meaning of the above-mentioned DSI3 specification the central unit Z represents a master which is connected via the two-wire bus cable 4 to the sensor units S.sub.1, S.sub.2, . . . , S.sub.N acting as slaves in the sense of the DSI3 specification, with the result that overall a bus in the sense of the DSI3 specification is present. Furthermore, in the present case the sensor units S.sub.1, S.sub.2, . . . , S.sub.N are sensor units with actuators that have a relatively high energy consumption, so that the operation of this sensor arrangement 2 falls under the above-mentioned Power Function class. As already explained above, in the operation of the present sensor arrangement 2 of the Power Function class, energy supply phases, on the one hand, and communication phases, on the other, will therefore take place alternately.

(8) In the communication phases, information is transferred between the central unit Z and the sensor units S.sub.1, S.sub.2, . . . , S.sub.N by means of a lower voltage V.sub.LOW-PWR of 2V and an upper voltage V.sub.HIGH-PWR of 4 V as the respective bus voltage, while in the energy supply phases the sensor units S.sub.1, S.sub.2, . . . , S.sub.N are supplied with electrical energy by the central unit Z. In these energy supply phases the bus voltage applied U.sub.Bus is an idle voltage V.sub.IDLE, which is at least 1 V greater than the upper voltage V.sub.HIGH-PWR. In the present case the bus operates with an idle voltage which is the maximum permissible voltage of 25 V or only slightly below it.

(9) However, before the communication phases can be started, addresses must be assigned to the sensor units S.sub.1, S.sub.2, . . . , S.sub.N. To do this, the sensor units S.sub.1, S.sub.2, . . . , S.sub.N each have an address counter A.sub.1, A.sub.2, . . . , A.sub.N in which each address can be stored. In accordance with a first exemplary embodiment of the invention, the following is provided:

(10) The sensor arrangement 2 according to the first exemplary embodiment of the invention, in accordance with the drawing in FIG. 1 and a central unit Z, has a number N=5 sensor units S.sub.1, S.sub.2, . . . , S.sub.N each with a test resistor R.sub.S1, R.sub.S2, . . . , R.sub.SN connected in series with the two-wire bus cable 4, each having a test load L.sub.1, L.sub.2, . . . , L.sub.N that can be connected to the two-wire bus cable 4, and each with a previously mentioned address counter A.sub.1, A.sub.2, . . . , A.sub.N. The procedure for the address assignment is shown schematically in FIG. 2.

(11) FIG. 2 shows, in each case as a function of time t, in the top curve the profile of the bus voltage U.sub.Bus and below it the respective currents I.sub.R1, I.sub.R2, I.sub.R3, I.sub.R4, I.sub.R5 through the test resistors R.sub.S1, R.sub.S2, . . . , R.sub.SN. The procedure for assigning the addresses, i.e. the address assignment phase IP, is initiated by means of a start command SK, during which the bus voltage is decreased from 4 V to 2 V for a period of 24 μs. This is followed by a time delay V before the individual cycles Y.sub.1, Y.sub.2, Y.sub.3, Y.sub.4, Y.sub.5, in which the sensor units check their relative position in their chain to avoid the influence of potentially occurring charging currents on the address assignment. During the time delay V, the bus voltage U.sub.Bus is thus already increased to the address assignment voltage of approximately 25 V or approximately 25 V; however, the test loads L.sub.1, L.sub.2, . . . , L.sub.N are not yet connected to the two-wire bus cable 4.

(12) This is followed by the first cycle Y.sub.1 of the address assignment phase IP, in which all sensor units S.sub.1, S.sub.2, . . . , S.sub.N connect their test loads L.sub.1, L.sub.2, . . . , L.sub.N to the two-wire bus cable 4. On the basis of the test loads L.sub.1, L.sub.2, . . . , L.sub.N, which are located in the chain of the sensor units S.sub.1, S.sub.2, . . . , S.sub.N, in each case behind a respective sensor unit S.sub.1, S.sub.2, . . . , S.sub.N-1, a current I.sub.R1, I.sub.R2, . . . , I.sub.RN-1 flows through the test resistors R.sub.S1, R.sub.S2, . . . , R.sub.SN-1 respectively, which is greater the more sensor units S.sub.1, S.sub.2, . . . , S.sub.N are still arranged behind a respective sensor unit S.sub.1, S.sub.2, . . . , S.sub.N-1. Only the test resistor R.sub.SN in the last sensor unit S.sub.N in the chain of the sensor units S.sub.1, S.sub.2, . . . , S.sub.N has no current flowing through it, which is due to the fact that behind this last sensor unit S.sub.N there are no further sensor units with a test load, so that no current is drawn.

(13) This last sensor unit S.sub.N receives the address 1 and takes no further part in the subsequent address assignment procedure. All other sensor units S.sub.1, S.sub.2, . . . , S.sub.N-1 increase their address by 1. In particular, the test load of the sensor unit S.sub.N with the address 1 is permanently disconnected from the two-wire bus cable 4 for the following cycles, so that in this respect the sensor unit S.sub.N-1 becomes the “last” sensor unit in the chain, which is arranged directly in front of the sensor unit S.sub.N with the address 1. This procedure is repeated until all sensor units S.sub.1, S.sub.2, . . . , S.sub.N are assigned an address, thus the current I.sub.R1 has also become equal to zero since the sensor unit S.sub.1 has then become the “last” sensor unit in the chain. The communication phases and energy supply phases can then start.

(14) In the previously described preferred exemplary embodiment of the invention the total test load L.sub.1, L.sub.2, . . . , L.sub.N has always been activated directly in each case; thus, the total maximum current has always flowed immediately as a result of these test loads L.sub.1, L.sub.2, . . . , L.sub.N. However, this can lead to the central unit Z becoming overloaded. To avoid this, in accordance with another preferred exemplary embodiment of the invention, as shown in FIG. 3 by way of example for the sensor units S.sub.4 and S.sub.5, in each cycle Y.sub.1, Y.sub.2, Y.sub.3 the electrical test loads L.sub.1, L.sub.2, . . . , L.sub.N of the sensor units S.sub.1, S.sub.2, . . . , S.sub.N-1 are connected to the two-wire bus cable 4 in stages with in this case overall a maximum of four stages, in such a way that in the first stage only a part of the test load L.sub.1, L.sub.2, . . . , L.sub.N L.sub.1, L.sub.2, . . . , L.sub.N is activated, namely a quarter of the maximum test load L.sub.1, L.sub.2, . . . , L.sub.N, and thereafter in the subsequent stages the test load L.sub.1, L.sub.2, . . . , L.sub.N respectively is gradually increased, namely to two quarters, three quarters of the test load L.sub.1, L.sub.2, . . . , L.sub.N and finally to the entire test load L.sub.1, L.sub.2, . . . , L.sub.N. In the sensor units S.sub.1, S.sub.2, . . . , S.sub.N-1, no further increase in the test load L.sub.1, L.sub.2, . . . , L.sub.N-1 takes place in a subsequent stage if in the previous stage a current I.sub.R1, I.sub.R2, . . . , I.sub.RN-1 has been detected flowing through the test resistor R.sub.S1, R.sub.S2, . . . , R.sub.SN-1 of the respective sensor unit S.sub.1, S.sub.2, . . . , S.sub.N-1, which has exceeded a predetermined threshold value I.sub.T. In this case, the threshold value I.sub.T is equal to 60% of the current induced by a single test load.

(15) In FIG. 3, in each case as a function of time t, the bus voltage U.sub.Bus is shown at the top and below it the current I.sub.L4 on the basis of the test load L.sub.4, the current I.sub.R4 through the test resistor R.sub.4 in the sensor unit S.sub.4, the current I.sub.L5 on the basis of the test load L.sub.5 and the current I.sub.R5 through the test resistor R.sub.5 in the sensor unit S.sub.5. For the sensor unit S.sub.5 no current I.sub.R5 has been detected through the test resistor R.sub.5, because the sensor unit S.sub.5 is the last sensor unit in the chain. For the sensor unit S.sub.4 the threshold value I.sub.T of 60% of the maximum possible current has already been exceeded in the third stage, so that no further increase of the test load L.sub.4 will take place in the fourth stage. The sensor unit S.sub.4 “knows”, simply due to the sufficiently high current I.sub.R4 in excess of the threshold value I.sub.T, that it is not the last sensor unit in the chain.

LIST OF REFERENCE SYMBOLS

(16) 1 motor vehicle 2 sensor arrangement 4 bus cable I.sub.R1, I.sub.R2, . . . , I.sub.R5 current through the test resistors I.sub.T threshold value for the current through the test resistors IP address assignment phase L.sub.1, L.sub.2, . . . , L.sub.N test load R.sub.S1, R.sub.S2, . . . , R.sub.SN test resistors S.sub.1, S.sub.2, . . . , S.sub.N sensor units SK start command U.sub.Bus bus voltage V time delay V.sub.HIGH-PWR upper voltage V.sub.LOW-PWR lower voltage V.sub.IDLE idle voltage Y.sub.1, Y.sub.2, . . . , Y.sub.5 cycles of the address assignment phase Z central unit