VWGoA - Ex. 1001
`Volkswagen Group of America, Inc. - Petitioner
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`US. Patent
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`Sep.21, 1999
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`Sheet 1 012
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`5,954,775
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`LFTI LFTI
`W
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`MESSAGE
`f— PERIOD—1
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`——>‘ F1 FTI (LOW OR HIGH RATE)
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`US. Patent
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`Sep. 21, 1999
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`Sheet 2 0f 2
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`5,954,775
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`5,954,775
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`1
`DUAL RATE COMMUNICATION PROTOCOL
`
`FIELD OF THE INVENTION
`
`This invention relates to a method of simultaneous digital
`data communication at different rates and particularly to
`communication in a supplemental restraint system for trans-
`mitting occupant presence and occupant position data to a
`control circuit.
`
`BACKGROUND OF THE INVENTION
`
`The expanding use of supplemental inflatable restraints
`(SIRs) or air bags for occupant protection in vehicles
`increasingly involves equipment for the front outboard pas-
`senger seat. The driver side air bag has been deployed
`whenever an imminent crash is sensed. The position and size
`of the driver is fairly predictable so that such deployment
`can advantageously interact with the driver upon a crash.
`The passenger seat, however, may be occupied by a large or
`a small occupant including a baby in an infant seat. It can not
`be assumed that a passenger of any size is at an optimum
`position (leaning against or near the seat back). An infant
`seat is normally used in a rear facing position for small
`babies and in a forward facing position for larger babies and
`small children. While the forward facing position approxi-
`mates the preferred position for air bag interaction, the rear
`facing position places the top portion of the infant seat close
`to the vehicle dash which houses the air bag. In the latter
`event, it is desirable to prevent deployment of the air bag.
`Moreover, if the passenger seat is unoccupied, it is desirable
`to prevent deployment to avoid the expense of replacing the
`air bag and repairing incidental damage due to deployment.
`It has been proposed in US. Pat. No. 5,474,327 issued
`Dec. 12, 1995, entitled VEHICLE OCCUPANT
`RESTRAINT WITH SEAT PRESSURE SENSOR and
`
`assigned to the assignee of this invention, to incorporate
`pressure sensors in the passenger seat and monitor the
`response of the sensors by a microprocessor to evaluate the
`weight distribution and determine the type of occupant and
`the facing direction of an infant seat. Seat pressure sensors
`can to some extent determine the position of the occupant or
`distance from some reference point. Other means of detect-
`ing occupant position are also known. In any case the
`occupant position and presence sensors are likely to be
`remote from the SIR control circuit and it is necessary to
`address the communication of the presence and position data
`to the control so that the decision of when and whether to
`
`deploy can be made on the basis of current information.
`A communication link between the sensing unit and the
`SIR control would be required to handle occupant presence
`information, occupant position information, or both,
`depending on the configuration of the SIR system. Occupant
`presence information is simple and would require a rela-
`tively slow update rate (seconds) since it would change
`infrequently and slowly, such as when an occupant exits the
`vehicle or when a small child crawls form one seat
`to
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`another. The presence of an infant seat and whether it is
`facing the front or rear is also information which changes
`infrequently and slowly. Occupant position information,
`however, would be subject to continuous and more rapid
`change, and therefore requires a
`faster update
`(milliseconds). The type of information required to describe
`the position would likely be a discrete measured distance
`between an occupant and a reference point. Thus there is a
`dramatic difference in the information rate or bandwidth
`
`required between occupant presence and occupant position
`systems. Ordinarily,
`these divergent requirements would
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`necessitate separate systems and communication techniques.
`It is preferred to have in place a communication system
`having the capability to accommodate either high or low
`bandwidth, or both simultaneously, and forego the expense
`of changing over or adding a new system when higher
`bandwidth is needed.
`
`The expected progression of implementing SIR advances
`in vehicles would be to first introduce the simplest technol-
`ogy (occupant presence) followed later by more complex
`technology (occupant position). It is thus desirable to have
`a communication method which would permit
`the low
`bandwidth application for occupant presence to be serviced
`initially and to allow the high bandwidth application to be
`added (without further cost) when occupant position is
`introduced. With such an arrangement, a product supplied as
`a portion of a SIR system can be supplied to manufacturers
`of systems requiring either high or low message rates or
`both, the only change being setting a software configuration
`bit.
`
`SUMMARY OF THE INVENTION
`
`It is therefore an object of the invention to communicate
`at low and high bandwidths over the same communication
`link, particularly to supply occupant presence and/or posi-
`tion information to an SIR system. Another object in such
`communication is to implement low bandwidth communi-
`cation alone at low cost but with the capability of accom-
`modating a high bandwidth communication. Afurther object
`in such communication is to use high and low bandwidths
`separately or in combination.
`A SIR system, as is well known, has a control unit
`comprising an acceleration sensor to detect an impending
`crash, a microprocessor to process the sensor signal and to
`decide whether to deploy an air bag, and a deployment unit
`fired by the microprocessor. An occupant detection system
`can determine if an occupant or infant seat is present and the
`position of an occupant. Acommunication link transfers the
`position and presence information to the control unit.
`A combined protocol having both low and high bandwidth
`protocols can support both bandwidth needs separately or
`simultaneously. These protocols can be implemented on
`either uni-directional of bi-directional communication sys-
`tems. The compound communication protocol consists of a
`low rate protocol
`for occupant presence information
`(including infant seat position) combined with a high rate
`protocol for occupant position information. Each protocol is
`based on a fundamental time interval (FTI) that defines the
`shortest meaningful time interval for that protocol. The low
`and high rate protocols are combined when the FTI for the
`high rate protocol is selected so that an entire high rate
`message can be contained within a single FTI for the low
`rate protocol. The low rate FTI has a period reserved for a
`high rate message; thus the high rate FTI must be short
`enough to permit sufficient intervals for the high rate mes-
`sage. The remainder of the low rate FTI is held at a high or
`low logic state which comprises a fragment of the low rate
`message. A variety of message structures and encoding
`techniques are suitable candidates for use with either pro-
`tocol.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The above and other advantages of the invention will
`become more apparent from the following description taken
`in conjunction with the accompanying drawings wherein
`like references refer to like parts and wherein:
`FIG. 1 is a schematic diagram of a SIR system with a
`communication link for occupant presence and position
`data;
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`5,954,775
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`FIG. 2 is a diagram of combined high rate and low rate
`message protocols according to the invention;
`FIG. 3 is a waveform illustrating the structure of an ID
`message;
`
`FIG. 4 is a waveform illustrating the structure of a low
`rate message;
`FIG. 5 is a waveform illustrating the detailed structure of
`a single high rate message;
`FIG. 6 is a waveform illustrating the positions of a
`plurality of successive high rate messages; and
`FIG. 7 is a waveform illustrating the structure of the
`messages of FIGS. 4 and 6 combined.
`
`DESCRIPTION OF THE INVENTION
`
`While the ensuing description is directed to a dual rate
`communication technique for use in SIR systems, it will be
`appreciated that the invention is applicable to communica-
`tions in other environments.
`
`Referring to FIG. 1, a SIR system includes an electronic
`control unit (ECU) 10 coupled to a pair of air bags 12
`through firing circuits having a squib or initiator 14 which is
`fired by an electrical
`impulse and an inflator 16 which
`generates gas for rapid air bag inflation when the initiator is
`fired. One of the air bags is for the driver side and the other
`for the passenger side. An occupant presence and position
`sensing (OPPS) device 18 includes an ultrasonic sensor 20
`situated to detect occupant position and a pressure sensor 22
`in a vehicle seat 24, for example of the type disclosed in the
`above mentioned US. Pat. No. 5,474,327 for the detection
`of an infant seat presence and position. Information gleaned
`by the OPPS is encoded as digital data and transmitted over
`a communication link 26 to the ECU which uses the infor-
`
`mation to help determine whether and when to deploy the air
`bag for the passenger side.
`The occupant presence data is updated only slowly while
`the position data is updated frequently and rapidly. This is
`accomplished on the communication link 26 by a combined
`protocol which has a low message rate protocol for the
`presence data and a high message rate protocol for the
`position data. The rules for combined protocol are:
`1. Each component protocol must be based on a funda-
`mental time interval (FTI); a low rate FTI (LFTI) for
`the occupant presence component, and a high rate FTI
`(HFTI) for the occupant position component.
`2. The ratio of the LFTI to the HFTI must be great enough
`to allow at lest one complete high rate message to be
`contained within a single LFTI and leave sufficient time
`remaining within the LFTI that its state can be deter-
`mined without ambiguity.
`This is illustrated in FIG. 2 which shows two consecutive
`
`LFTI intervals. Each LFTI has a nominal logic state which
`is interrupted by the high rate message. Each interval
`contains a period reserved to the high rate message;
`the
`period is somewhat shorter than the LFTI so that there is
`sufficient time for determining the state of the LFTI. The
`expanded message period shows that the period consists of
`many HFTI intervals affording sufficient bandwidth to con-
`tain at least one complete occupant position message.
`The given rules for the combined protocol definition leave
`a high degree of flexibility for defining specific protocols for
`a given implementation. These rules can be used for uni-
`directional or bi-directional communication systems. They
`can also apply to systems using a single device or multiple
`devices in the OPPS subsystem. The above rules do not limit
`encoding techniques. Manchester, pulse width modulation,
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`variable pulse width modulation, and other RZ or NRZ
`techniques can be employed for either the low or high rate
`component protocol. Further it is not necessary to use the
`same encoding technique for both component protocols,
`though it may simplify system design to do so. System
`architecture, bit rate, communication link drive, message
`structure and length, synchronization, and error detection are
`all issues which must be addressed in the definition of each
`component protocol in a specific application of the com-
`pound protocol technique.
`An example of a specific implementation is given to
`illustrate a protocol definition based on the above techniques
`and rules. The LFTI is chosen to be 50 ms and the HFTI is
`
`selected to be 500 us. Then a high rate message comprising
`54 FTIs will require only 27 ms and the remainder of the
`LFTI will be in a state required for the low rate message.
`Shortly after start up, an ID message will be transmitted
`twice on each protocol. This establishes the identity of the
`source at both the high an low message rate and thus allows
`a different source for each rate. Each protocol has an ID
`prefix of a high pulse two FTI wide followed by a low pulse
`three FTI wide, and a suffix of a high pulse three FTI wide
`and a low pulse two FTI wide. A value of 0 is represented
`by a pulse one FTI wide and a value of 1 is denoted by a
`pulse of either polarity two FTI wide. A sample ID message
`is shown in FIG. 3. In addition to the prefix and the suffix,
`the ID consists of a 3 bit manufacturer code, a 5 bit model
`identifier, a 4 bit revision code, and a 6 bit field specifying
`the configuration of the system. The same message structure
`is used for the high rate and the low rate protocols.
`Following the ID messages, the low rate message contains
`the presence information which includes the position of an
`infant seat. Each condition is coded by a combination of
`high and low pulses according to the following table.
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`CONDITION
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`Occupant Present
`Occupant Not Present
`Infant Seat Facing Rearward
`Infant Seat Facing Forward
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`LOW PULSE
`WIDTH
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`HIGH PULSE
`WIDTH
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`1
`2
`1
`2
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`1
`2
`2
`1
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`Thus the low rate message is completed in two to four LFTIs
`or 100 ms to 200 ms. FIG. 4 depicts the signal for a rear
`facing infant seat (1 low and 2 high FTIs) which is continu-
`ously repeated. This message requires 150 ms and is con-
`tinuously repeated.
`The high rate message is more complex. An example
`shown in FIG. 5 includes
`
`1) a start of message (SOM) symbol comprising a low
`pulse I HFTI wide followed by a high pulse 3 HFTI
`wide,
`2) a tag (3 bits) identifying the type of data to follow,
`3) the data (8 bits) representing the information identified
`by the tag, e.g., the distance between the driver and the
`steering column on a half centimeter scale,
`4) a parity bit creating even parity, and
`5) an end of message (EOM) symbol comprising a single
`low pulse 1 HFTI wide.
`A maximum of 54 HFTIs or 27 ms is required for the
`complete message if the data bits were all ones, and less time
`is required when the message includes zeros.
`FIG. 6 shows a series of occupant position messages only,
`each message represented by a shaded block. FIG. 7 shows
`the presence and position messages of FIGS. 4 and 6
`combined. Thus although the high rate messages override
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`5,954,775
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`each LFTl, there is ample time to sample the state of each
`LFTI which carries a fragment of the low rate message.
`When the SOM symbol is recognized in a transmission, the
`high rate message can be read. Accordingly both low and
`high rate messages can coeXist without compromise, allow-
`ing the high rate information to be rapidly and frequently
`transmitted and the low rate information to be sent less
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`often. The low and high rate protocols may be used sepa-
`rately or simultaneously.
`The embodiments of the invention in which an exclusive
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`property or privilege is claimed are defined as follows:
`1. In a supplemental restraint system having means for
`acquiring data on occupant presence and/or occupant posi-
`tion and a communication system for communicating such
`data to a control circuit, a method of accommodating com-
`munication of occupant presence data and/or occupant posi-
`tion data at different rates over a common communication
`
`link comprising the steps of:
`establishing a series of message rate intervals on the
`common communication link;
`devoting a first portion of each message rate interval to
`occupant presence data and reserving a second portion
`of each message rate interval for occupant position
`data;
`the first portion being sufficient to accommodate only a
`fragment of a complete transmission of occupant pres-
`ence data thereby requiring a series of message rate
`intervals for a complete transmission of occupant pres-
`ence data;
`establishing an occupant position message rate sufficient
`to accommodate a complete transmission of occupant
`position data within the second portion of each message
`rate interval; and
`transmitting the occupant presence and/or occupant posi-
`tion data in the respective portion of each message rate
`interval.
`
`2. The method as defined in claim 1 wherein the step of
`transmitting the occupant presence data includes the step of:
`encoding the occupant presence data by setting nominal
`logic states in the series of message rate intervals to
`values in accord with an occupant presence code.
`3. The method as defined in claim 2 including:
`sensing the presence of an occupant;
`sensing the presence and position of an infant seat; and
`encoding occupant presence data by setting the nominal
`logic states of the series of message rate intervals to
`values representing the sensed presence and position in
`accord with said occupant presence code.
`4. The method as defined in claim 2 wherein the step of
`transmitting the occupant position data includes the step of:
`encoding the occupant position data by overriding said
`nominal logic states during the second portion of each
`message rate interval in accord with an occupant posi-
`tion code.
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`5. In a supplemental restraint system having means for
`acquiring data on occupant presence and/or position and a
`communication system for communicating such data to a
`control circuit, a method of communicating occupant pres-
`ence data and occupant position data at different rates
`comprising the steps of:
`establishing a low message rate interval for presence data;
`devoting a first portion of each interval
`to low rate
`presence data and reserving a second portion of each
`interval for position data;
`the first portion being sufficient for only a fragment of low
`rate presence data thereby requiring a plurality of
`consecutive intervals for complete presence data;
`to
`establishing a high message rate interval sufficient
`accommodate a complete position data message within
`the second portion of each low message rate interval;
`encoding occupant presence data into a message by
`setting the nominal logic states of successive intervals
`to values in accord with a code;
`sensing occupant position to acquire position data;
`encoding occupant position data at a high rate into said
`message by overriding said nominal logic states during
`the second portion of each interval; and
`transmitting said message.
`6. A method of accommodating communication of first
`and second types of data at first and second message rates
`over a common communication link comprising the steps of:
`establishing a message rate interval on the common
`communication link;
`devoting a portion of each message rate interval to the first
`type of data and reserving a remaining portion of each
`message rate interval for the second type of data;
`providing the first type of data at a first message rate
`sufficient
`to form a complete message within the
`devoted portion of each message rate interval;
`providing the second type of data at a second message rate
`sufficient to form only a fragment of a complete mes-
`sage in the remaining portion of each message rate
`interval, thereby requiring a plurality of consecutive
`message rate intervals to form a complete message of
`the second type of data; and
`transmitting at least one of the first and second types of
`data in the respective portions of each message rate
`interval.
`
`7. The method as defined in claim 6 including encoding
`the second type of data on a plurality of successive message
`rate intervals by setting each bit of the message rate interval
`to a nominal logic state.
`8. The method as defined in claim 7 including encoding a
`complete message of the first the of data on a message rate
`interval by overriding the nominal logic state in the devoted
`portion to impose a series of logic pulses representing the
`first type of data.
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