AIRCRAFT COMMUNICATION SYSTEM AND PROTOCOL

Abstract

The system of the present disclosure provides a bus network that allows digital data exchanges over the existing aircraft (115 V) A/C power line and, where present, via the 3-track slip ring that already exists for powering a de-icing device on a rotating part of the aircraft.

Claims

1. A system for communicating data and power between a first component and a remote second component, the system comprising: a power line for providing power to the first component, whereby the power line also provides a data bus for digital transmission of data from the first component to the second component, wherein said data is represented by presence and absence of a sinusoidal signal on the data bus; wherein the data transmission comprises representing a digital high level by presence of a sinusoidal signal and a digital low level by absence of a sinusoidal signal and is performed according to a time triggering mechanism; and wherein fault detection is provided on a serial bus using parity and cyclic redundancy check (CRC) mechanisms.

2. The system of claim 1, wherein the power line is an A/C power line.

3. The system of claim 1, wherein the power line is a DC power line.

4. The system of claim 1, wherein the first component is a rotating component and the second component is a relatively stationary component connected to the first component.

5. The system of claim 4, wherein the first and second components are connected via a 3-track slip ring, and whereby the data and power are communicated via the 3-track slip ring.

6. An aircraft de-icing system comprising: a de-icing device located on a first part of an aircraft; and a power line from the de-icing device to a remote power supply located on a second part of the aircraft for providing power to the de-icing device; whereby the power line also provides a data bus for digital transmission of data from the first part to the second part, said data represented by presence and absence of a sinusoidal signal on the data bus; wherein the data transmission comprises representing a digital high level by presence of a sinusoidal signal and a digital low level by absence of a sinusoidal signal and is performed according to a time triggering mechanism, and wherein fault detection is provided on a serial bus using parity and cyclic redundancy check (CRC) mechanisms.

7. The system of claim 6, wherein the power line is an A/C power line.

8. The system of claim 6, wherein the power line is a DC power line.

9. The system of claim 6, wherein the first component is a rotating component and the second component is a relatively stationary component connected to the first component.

10. The system of claim 9, wherein the first and second components are connected via a 3-track slip ring, and whereby the data and power are communicated via the 3-track slip ring.

11. A method of communicating data and power between a first component and a remote second component, comprising: a power line for providing power to the first component, whereby the power line also provides a data bus for digital transmission of data from the first component to the second component, said data represented by presence and absence of a sinusoidal signal on the data bus; wherein the data transmission comprises representing a digital high level by presence of a sinusoidal signal and a digital low level by absence of a sinusoidal signal and is performed according to a time triggering mechanism, and wherein fault detection is provided on a serial bus using parity and cyclic redundancy check (CRC) mechanisms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a schematic view of a system using a communication process of this disclosure.

[0015] FIGS. 2A and 2B show how data can be transmitted over one phase or three phases of a power line, respectively.

[0016] FIG. 3 shows the principle of a time-trigger protocol.

[0017] FIG. 4 shows an example of data bus management.

[0018] FIGS. 5A and 5B show further examples of data bus management.

DETAILED DESCRIPTION

[0019] FIG. 1 is a schematic view of a system using the communication process of this disclosure.

[0020] The process allows communication to and from embedded electronics in a propeller or other rotating part 1. As described above, the rotating part 1 is conventionally connected to the aircraft power supply and receives control commands via a three track slip ring 2 with each track associated with a respective phase of the three phase supply (usually e.g. 115 V A/C).

[0021] Data can be communicated in digital form from the propeller embedded electronics via the existing three tracks of the slip ring 2 to other parts of the aircraft e.g. to embedded electronics in other aircraft systems or computers 4, 4, 4, 4.

[0022] As with conventional systems, the aircraft power (AP) bus can be used directly on the power supply bus connected to a circuit breaker 3 provided on the A/C line.

[0023] In the embodiment shown in FIG. 1, data is communicated to the various other parts 4, 4, 4 over a data field bus. The data is sent over one or more phases of the A/C line, via a data concentrator 5 to the data field bus whereby it is distributed to the appropriate other part, using a traditional avionics bus, e.g. AFDX or CAN ARINC429.

[0024] The data is transmitted using a sinusoidal signal over time frames, where presence of the sinusoidal signal represents a digital 1 and absence of the signal represents a digital 0i.e. all-or-nothing. This will be described in more detail later.

[0025] FIG. 2A shows how the data can be communicated over one phase (here phase A) of the A/C powerline from the aircraft power supply 6. A timing system 7 controls the transmission of the sinusoidal signal containing the data according to a time triggered principle to the various other embedded electronics or the like. The resistances shown in the figure model the equivalent impedance on the bus.

[0026] Each power bus interface is coupled to the data transmission via a decoupling transformer 8. Here, one transformer is provided on the emitter side and one on the receiver side.

[0027] If different data is to be transmitted simultaneously to different receiving electronics, all three phases of the A/C power line can be used to transmit the digital signal as shown in FIG. 2B when redundancy on the bus is requested. The two lines shown for phase A will, in practice, be the same line. Alternatively two identical communication systems could be arranged in parallel on the same two phases, but with two different working frequencies.

[0028] The data could also be communicated using a DC power line (not shown).

[0029] The power line bus of this disclosure uses, in the preferred embodiment, a universal asynchronous receiver-transmitter (UART) which uses two frequencieshere 0 HZ and 1 MHz (the above-mentioned all-or-nothing principle). The frequencies can, of course, be selected according to requirements/application. The high-level signal (i.e. a digital 1) is a sinusoidal signal having the characteristics:

S(t)=S.sub.amp.Math.sin(2f.sub.0t+)+S.sub.off

[0030] The low level signal is a DC signal: S(t)=S.sub.off [0031] where S.sub.off is the offset induced on the A/C bus.

[0032] As mentioned above, the communication protocol for the data is based on a time triggered protocol having one time master for each main bus. The serial interface is provided by the UART port of a control component (e.g. MCU, PLD).

[0033] The serial data communication, when transmitted on the powerline, will include one start bit and one stop bit and can be configured with even or odd parity for error checking.

[0034] Serial data is transmitted in frames as is known, and each frame may include an identifier, a control word, the data and, if required, a CRC field for error checking.

[0035] The CRC field can be CRC-16 with polynomial considered 0AC9A. The CRC computation is performed on the identifier, the control field and the data, but can be left to be configured by the end user if required.

[0036] The system is then based on a time mastering mechanism, whereby the time master provides synchronisation to all subscribers to prevent any time lag between them. The time master frame contains information on scheduling and bus management. Each subscriber is then synchronised due to the time master frame and each has its own time allocation defined. Thus, each subscriber knows when to emit their frame according to their internal time scheduler. In order to prevent time shifting due to, e.g., variations in accuracy between the internal clocks of each subscriber, or variations in ambient temperature, the time master frame is sent at the start of each main communication cycle. This reduces the impact of such variations.

[0037] Constant bus monitoring is performed by the time master and subscribers to monitor for any unusual activity and prevent resulting bus contention, and to monitor for any breakdown in time scheduling.

[0038] As mentioned above, transmission of the data on the A/C power line is based on a time triggered protocol, an example cycle of which is shown in FIG. 3. The transmission cycle begins with a time initial cycle (Tic) followed by a preamble which starts the data exchange cycle and includes time master synchronisation and an information message for all subscribers (other embedded electronics etc.) and/or global order information. This also provides the start of the first cycle. The data is then communicated in data frames as mentioned above to the end of the transmission, controlled by the time master. A time gap, the time acquisition cycleTac- is provided after the exchange cycle to allow other subscribers to request recording on the network and/or to allow for retransmission of frames, if required.

[0039] FIG. 4 shows how the bus is managed for several data exchange cycles such as the one shown in FIG. 3.

[0040] After the Tic, the first cycle begins with the preamble (as described above) followed by data frames for that first cycle. The start of a second cycle is determined by the time master and this starts where indicated in FIG. 4, again with a preamble followed by data frames. This continues for subsequent cycles and then ends with a Tac, as described above.

[0041] A new subscriber can request access on the bus using a so-called door-knocking mechanism, whereby a subscriber can, during data transmission from other subscribers. knock at the door with a request for a new frame to be inserted in one of the cycles. The time master will acknowledge/agree/refuse. If agreed, the data frame can be inserted, where requested by the subscriber, which alters the timing of other cycles and the length of the Tac accordingly. An example can be seen in FIGS. 5A and 5B, whereby, in the Tac, after the third cycle, a subscriber requests that a new frame be inserted in the second cycle. In FIG. 5A, the time master agrees and the frame is inserted. The third cycle is then delayed accordingly and the Tac is also shortened accordingly. In FIG. 5B, the time master refuses the requestperhaps because the Tac is too short.

[0042] In preferred embodiments, various safety or protective measures are provided in the system. As mentioned above, the frame identifier and the transmitted data are controlled e.g. using CRC.

[0043] The time triggered mechanism also provides protection against failure and bus contention.

[0044] The system may also be configured to monitor for a failed emittere.g. if no signal is received for a given period of time.

[0045] Protection may be provided against the so-called babbling idiot principle. Here, a specific mechanism detects if the emitter has gone into failed mode with endless undulationi.e. if the emitter had gained access to the bus but then violates timing or timeout rules. The mechanism can cause the emitter to reset.

[0046] The communication system thus enables real-time exchange of data from embedded electronics at one aircraft component e.g. a propeller or other rotating part via the A/C power line and, where present, through a three track slip ring to enable the propeller or propeller environment to be monitorede.g. for the transmission of health monitoring data, de-icing commands, identification commands and the like.