Integrated message display system for a vehicle6289332Abstract An integrated message system for a vehicle provides an extendable, prioritized message scheme. Using this scheme, the message system acts as a centralized message provider for variety of alerts and operating data originating throughout the vehicle. The message system defines a hierarchy of message levels, each having a unique output protocol. The protocol defines attributes associated with messages at a particular level such as textual or graphical message, an auditory alert, as well as the scheme for playing these messages and alerts. The system integrates a variety of subsystems that conventionally have separate driver interfaces such as a collision warning system and an adaptive cruise control system. Claims We claim: Description TECHNICAL FIELD
TABLE 1
AUDITORY CODING
Pause VISUAL
between CODING
Number Length tones Frequency ON OFF
LEVEL of tones (msec) (msec) of tones (msec) (msec)
DANGER 7 200 14 560/840 400 200
WARNING 4 200 70 560/840 400 350
CAUTION 2 200 140 560/840 400 500
NOTE 1 300 n/a 450 n/a n/a
MESSAGE 1 300 n/a 250 n/a n/a
A message from the ICU transitions through a series of states, including "unacknowledged" and "acknowledged." In particular, the message center initially generates a message, the message is in an "unacknowledged" state, meaning that the ICU is seeking a confirmation from the driver that he/she is aware of it. To get the driver's attention, the ICU emphasizes the significance of the message by flashing the text on the display and accompanying the message with audible tones. When the driver presses the acknowledgment key, the message center transitions to an "acknowledged" state. A text message remains on the display until the driver has an opportunity to read and acknowledge it a second time by pressing the acknowledge key again. The ICU is programmed so that the minimum time between the first and second acknowledgement is long enough (e.g., 3-5 five seconds) to prevent the driver from removing the message by pressing the acknowledgement key rapidly in succession (e.g., a quick double-click of the key). During this time, the acknowledgement key is essentially deactivated to prevent the driver from erasing a message without reading it. When the acknowledgment key becomes active, the message center displays a graphical symbol to inform the driver that he/she can press the acknowledgement key to remove the message. In a case when the driver presses the acknowledgement key before the acknowledge symbol is displayed, the ICU emits an error beep to provide the driver with feedback indicating that he/she acknowledged the warning message too soon. FIGS. 5-8 illustrate the operation of the danger, warning, caution, and note message levels in the message center. When the message center detects a level one condition, it displays the word "DANGER" on the first line of the display and a text message associated with the danger condition on the second line of the display (e.g., STOP ENGINE QUICKLY) as shown in FIG. 5. Initially, the ICU flashes the text message and generates beeping tones as reflected by the graphic 500 at the top of FIG. 5. The graphical symbol 502 indicates to the driver that he/she can disable the flashing and beeping by pressing the acknowledgement key 504. In response to actuation of the acknowledgment key, the message center transitions to the state shown in the rectangular box 506 at the bottom of FIG. 5. The box reflects that the message center is no longer flashing or emitting beeping auditory tones. At the danger level, the message center cycles between a flashing and beeping message state 500 and a non-flashing display without beeping in response to the acknowledgement key. The repeat time of the message is a pre-determined parameter in the ICU that controls when the message center repeats the "unacknowledged" state. For level two conditions, the message center initially generates a flashing and beeping warning message as reflected by the graphic 600 at the top of FIG. 6, and transitions to three other states before repeating. On the first line of the display, the message center displays the word "WARNING" along with a symbol of the acknowledgement key. On the second line, the message center displays descriptive text associated with the level two condition, such as LOW OIL PRESSURE as shown in FIG. 6. In response to a first press of the acknowledgement key 602, the message center transitions to a first "acknowledged" state shown as a rectangular box 604 on the right side of FIG. 6. The message center remains in this state for a pre-determined delay period (e.g., 3-5 seconds), and then transitions to a second state shown in the rectangular box 606 at the bottom of FIG. 6. The only difference between the first and second states is the presence of the graphical symbol 608 indicating that the acknowledgement key is active. This symbol informs the driver that pressing the acknowledgement key another time will remove the message from the display. In response to the driver pressing the acknowledgement key 610 a second time, the message center reverts to the driver selectable default screen, as illustrated by the rectangular box 612 on the left-hand side of FIG. 6. If the level 2 condition still persists, the message center repeats the message after a pre-determined period of time has elapsed (i.e. the repeat time). For level three conditions, the message center progresses through similar states as in level two. However, as reflected by graphic 700 at the top of FIG. 7, the initial message is less intense in that the pause between the tones is longer. Initially, the message center displays the word "CAUTION" on the first line of the display along with the symbol 702 of the acknowledgement key. On the second line of the display, the message center displays descriptive text associated with the warning condition such as "TURN SIGNAL ON." In response to the driver pressing the acknowledgement key 704, the message center transitions to a first state where the message is no longer flashing and beeping and the acknowledgment symbol is no longer illuminated as shown in the rectangular box 706 on the right side of FIG. 7. After a predetermined delay, the message center transitions to a second state where the acknowledgement key is included on the display as shown in the rectangular box 708 at the bottom of FIG. 7. In response to the driver pressing the acknowledgement key 710 a second time, the message center transitions to a driver selectable default screen as shown by the rectangular box 712 on the left-hand side of FIG. 7. The level 3 message will repeat after a predetermined period of time if the condition causing the message is still active. For level four conditions, the message center begins with a flashing message and a single beep at a lower frequency than the higher level warning messages. This initial state is represented by the graphic 800 at the top of FIG. 8. On the first line of the message display, the message center displays the word "NOTE" and on the second line displays a text description of the warning condition such as "LOW WIPER FLUID." After a pre-determined delay, the message center transitions to a state 802 where the ICU adds a graphical symbol of the acknowledgement key 804 to the display. In response to the driver pressing the acknowledgement key 806, the message center transitions to a driver selectable default screen as shown by the rectangular box 808 on the left side of FIG. 8. The message center then repeats after a pre-determined period of time if the warning condition is still active. The prioritization scheme implemented in the ICU enables it to integrate several messages and warning indicators for a variety of different electronic subsystems and sensors onboard the vehicle. When the manufacturer wishes to add a new message, it assigns it a priority level within the prioritization scheme. The ICU then determines when and how to display the warning message relative to other messages based on its priority and a set of priority rules. Table 2 below gives an example of the type of warning messages that are integrated into the prioritization scheme.
TABLE 2
LEVEL 1 LEVEL 2 LEVEL 3 LEVEL 4
DANGER WARNING CAUTION RECIRC MODE
PARK BRAKE HIGH TURN ENGAGED
OFF COOLANT SIGNAL ON STALE AIR IN 20
TEMP MIN.
DANGER WARNING PROVIDE INCOMING
PARK BRAKE LOW OIL FRESH AIR MESSAGE
ON PRESSURE STOP text
RECIRC.
MAX A/C
WARNING CAUTION
LOW VOLTAGE CHANGE AIR
FILTER
WARNING
AIR FILTER
CLOGGED
In the current implementation, the ICU is programmed to adhere to the following priority rules. First, higher priorities override lower priorities such that a danger condition has the highest priority, followed by warning, caution, and finally note/message. When more than one monitored condition is active at a given time for messages of the same priority level, the most recent message overrides the older message. Danger messages that occur within the same detection period in the ICU alternate every second. In the current implementation, the detection period is 200 milliseconds. The ICU manages warning messages that occur in the same detection period by showing one warning or caution for at least fifteen seconds and then switching to the second warning or caution. Finally, the ICU displays messages that are received in the same detection period sequentially. Integration of Collision Warning System into the Message Center The ICU and its message center act as the driver interface for the collision warning system. When the CWS detects a collision warning condition, it communicates the condition to the ICU, which in turn, generates the appropriate message from the message center, which typically includes a visual and an accompanying auditory warning. According to human factors studies, auditory signals are the most dominant source of information to the driver. Therefore, the auditory warnings associated with each collision warning condition are selected to ensure that they are not confused with other sounds in the vehicle, or masked by other sounds. In addition, for quick and accurate interpretation of visual signals, the message center provides the visual warnings associated with each warning condition in the driver's line of sight (see, for example, the position of the display on the dash in FIG. 3). FIG. 9 is diagram illustrating an implementation of the visual indicators for the collision warning system integrated into the message center. The current implementation of the message center displays five different visual indicators 900-908. As the closing distance between the truck and the vehicle in front of it decreases, the message center displays progressively stronger visual warnings and generates corresponding auditory warnings. For example, the top three visual indicators 900-904 shown in FIG. 9 illustrate the display screen of the message center for first, second and third stage distance alerts from the collision warning system. As the closing time between the truck and the obstacle reaches predetermined values associated with each stage, the message center displays a progressively larger triangle and the words, "DANGER AHEAD." The message center also displays the large triangle alert 904 in response to warning messages associated with the detection of a stationary or slow moving object. When the collision warning system detects an object within a predetermined distance (e.g., 350 feet), but this object does not represent a significant threat of collision, the message center displays a small triangle 906 in the default screen 910 of the message center. In other words, the visual indicator of the detection does not overwrite the current default screen, but instead is combined with it. In the example shown in FIG. 9, the default screen displays the short term average fuel economy 912, a bar graph representing changes in fuel economy 914, and the odometer reading 916. This default screen is merely one example of the type of normal operating condition data that may be displayed with the object detection indicator 906. In an alternative implementation, the visual indicator of a detected object may be designed to overwrite the current default screen. Another collision warning message integrated into the message display is the creep alert (see screen 908, FIG. 9). The message center displays the creep alert screen 908 when the collision warning system detects a object less than a predetermined distance ahead (e.g., 15 feet) and the truck is creeping (e.g., the truck speed is less than 2 MPH). In addition to integrating collision warnings into the message center, the current implementation also integrates control switches for the collision warning system into the dash of the vehicle. FIG. 3 shows an example of these controls, which include a volume control 350, an ON/OFF control 352 and range control 354. The volume control allows the driver to adjust the volume of auditory warnings, while the range control allows the driver to control the range of the forward object sensor. Both the volume and range controls are implemented with rocker switches in the current implementation. The ON/OFF button is implemented with a back lit push button. In addition to the visual warnings illustrated in FIG. 9, the message center generates auditory warnings as well. Tables 3A and 3B below provide a brief summary of message protocol codings in alternative implementations of the ICU.
TABLE 3A
Auditory Coding
Pause
Be- Fre-
Number tween quency
Tone Warning of Length Tones of Visual
No. Description Tones (msec) (msec) Tones Coding
0 side 3 100 14 1400, red LED in
detection 2000, right dash
1600 display
1 Stationary 7 200 14 1800/ Large
object 1200 triangle in
Slow moving Message
object ahead Center plus
1 Sec. DANGER
Following AHEAD
Distance
2 2 Sec. 4 200 70 1800/ Medium
Following 1200 triangle in
Distance Message
Creep Alarm Center plus
DANGER
AHEAD
3 3 Sec. 2 200 140 1800/ Small
Following 1200 triangle in
Distance Message
Center plus
DANGER
AHEAD
Table 4 provides a more detailed description of an integration of features of the collision warning system into the message center (M.C.) and dash display.
TABLE 4
Integrated Format
Display
Feature Auditory Visual
Control/Sensing Unit
Power-On None light on switch illuminates when
Rocker switch
Drivers Card Status system is on (M.C. NOTE if
card
is not inserted)
Volume Control 1 short tone for each change M.C. display
Rocker switch (default setting = 3/4
increment (at the new RADAR VOL 75%
maximum volume)
volume level) (displayed for 7 seconds after
each change)
Speaker all auditory output n/a
adjusted by volume control
Range 1 short tone for each 1/10 M.C. display:
Rocker switch dash or steering
control/accident second change in range MAX RADAR RANGE 2.5
wheel (default setting at maximum
recorder setting SECONDS
range)
(gives current maximum range
setting based on following
distance)
System failure M.C. tones for warning TELLTALE: RADAR FAIL (red)
System check sensor (performed
M.C. message:
every 15 seconds during normal
WARNING RADAR SYSTEM
operation)
FAILURE
Adjustments in n/a n/a
Message Center is automatically
Lighting
dimmed
Vehicle detection none very small triangle on default
object detected within 350 feet
screen of M.C. and/or detect
indicator light
1.sup.st stage See tone No. 3, Table 3A DANGER AHEAD 3
second sensor
distance alert small triangle
(figure below)
2.sup.nd stage See tone No. 2, Table 3A DANGER AHEAD 2
second sensor
distance alert medium triangle
(figure below)
3.sup.rd stage See tone No. 1, Table 3A DANGER AHEAD 1
second sensor
distance alert large triangle
(figure below)
Stationary object See tone No. 1, Table 3A DANGER AHEAD
Should be set for a distance
large triangle
appropriate to speed of vehicle (to
(figure below)
reduce false alarms)
Slow moving object See tone No. 1, Table 3A DANGER AHEAD
Should be set for a distance
large triangle
appropriate to speed of vehicle (to
(figure below)
reduce false alarms)
Creep alarm See tone No. 2, Table 3A CREEP ALERT
Vehicle speed <2 mph & object less
row of small triangles
than 15 feet ahead
(figure below)
No vehicle detected none yellow light on dash display
Stays on when no vehicle is detected
in blind spot by
the blind spot sensor
Vehicle detected in See tone No. 0, Table 3A red light on dash display
Activated when objects are detected
blind spot by
the blind spot sensor
As explained above, the message center integrates messages from a variety of different vehicle systems using a prioritization scheme. It also uses a prioritization scheme to integrate the messages from the collision warning system. In the current implementation, the priority rules for integrating collision warning messages are as follows. The warning messages for a stationary object, slow moving object, and the shortest monitored following distance (one second) are assigned the highest priority and override level 1 danger alerts. As such, the immediate external threat takes precedence over in-vehicle dangers. The level 1 danger alerts have the next highest priority and override collision warning alerts for following distances of two and three seconds and the creep alarm. The rationale for ranking level 1 danger alerts ahead of these collision alerts is that severe in-vehicle dangers take precedence over less immediate external threats. Level two warning messages and level three caution messages may override collision warnings for two and three second following distances if those collision warnings have been displayed for at least fifteen seconds. The rationale is that the driver has most probably chosen a particular distance to the vehicle ahead and intends not to change the following distance. In this case, the driver is aware of the situation and a level two or level three message override the collision warning conditions. A summary of the priority assignments for the message center and collision detection warnings is provided below in Table 5. Note that Table 5 represents only an example of one possible implementation. Alternative codings are possible, such as the auditory codings shown in Table 3B.
TABLE 5
Overview of Priority Assignments and Auditory Signals for
Message Center
Pause
Be- Fre-
Prior- Number tween quency
ity Warning of Length Tones of
Level Description Tones (msec) (msec) Tones
1 Stationary Object 7 200 14 1800/
Slow Moving Object 1200
1 Sec. Following Distance
2 Message Center: 7 200 14 560/840
DANGER
3 2 Sec. Following Distance 4 200 70 1800/
Creep Alarm 1200
4 3 Sec. Following Distance 2 200 140 1800/
1200
5 Message Center: 4 200 70 560/840
WARNING
6 Message Center: 2 200 140 560/840
CAUTION
7 Message Center: 1 300 n/a 450
NOTE/MESSAGE
inde- Side Object Detection (may 3 100 14 2400,
pen- be given with any other 2000,
dent warning) 1600
level
Message Center: "Key 1 300 n/a 250
press not available" or
"improper use" tone
The priority level specified in the Table refers to the priority of a message from the perspective of the ICU. In particular, the ICU is programmed to arbitrate among messages of different priority according to these levels. This priority level scheme is separate from the priority of messages in the J1587 protocol. The J1587 protocol implements a priority scheme for controlling which messages take precedence when transmitted concurrently on the data link. While the above table provides specific implementation details, it is possible to deviate from these specifications without departing from the scope of the invention. A number of additional design details are worth noting, keeping in mind that these details are not necessary for implementation of the invention. First, the auditory signal should be at least ten dB above in-cab sound level in the particular frequency range. In general, auditory warnings should be prioritized based on the number of tones and the pauses between the tones. In particular, the greater the number of tones (e.g., 1, 2, 4, 7) and the shorter the pauses between the tones (e.g., 14 msec., 70 msec., 140 msec.), the higher the priority. Preferably, the auditory tones for collision warnings should be distinguishable from the auditory tones used for other messages in the message center. In the current implementation, the non-collision warnings have a noticeably lower frequency (e.g., 560-840 Hz) than the collision detection warnings (e.g., 1200-1800 Hz). In addition, to allow the driver to better distinguish between different types of warnings, the message center warnings use a repeating tone sequence of low to high, while the collision warning tones use a tone sequence from high to low. In the current implementation, the CWS ECU communicates visual messages to the ICU via the J1708 data bus according to the J1587 communication protocol. The CWS ECU is wired to the speaker of the ICU and drives the speaker directly to generate auditory warnings. In alternative implementations, the CWS ECU could communicate messages for both auditory and visual warnings over the data link using the J1587 standard, via discrete wiring, or some combination of both. To communicate instructions for visual warnings, the CWS ECU broadcasts data bus messages over the J1708 data link. FIG. 10 illustrates a table listing the display message and the corresponding data bus message used to instruct the ICU to display it. The messages are listed in order of priority. If the ICU receives a message with higher priority than the one it is currently displaying, it displays the higher priority message as soon as it receives the message from the data bus. As noted above, the priority scheme implemented in the ICU is different than the priority of message transmission on the J1587 data link. The internal priority controlled within the ICU is reflected by the ordering of the messages in the left-most column. The J1587 message priority is noted in the right-most column. Message 22 in the table shown in FIG. 10 is the data required to display the following text message on the message center: Cruise Set to: xxMPH Headway Set to: eee_s where eee is the headway data in ASCII characters, example: 3.0, to be used in data bus message 219 226 8 48 8 2 16 140 e e e chksum. Following is a description of data bus message 22 (it applies to other messages as well): 219 226 8 48 8 2 16 140 e e e chksum. 219=MID (CWS ECU) 226=PID (Text Message to Display) 8=Number of bytes following 48=Status Character 1 (48 decimal=00110000 binary) Bit 8=0 (Use selected language) Bit 7=0 (Message OK) Bit 6=0 (Predefined text) Bit 5=1 (Display buffered message) Bit 4=0 (No sound; sound is controlled by the EVT-300 directly) Bit 3=0 (No acknowledgement) Bit 2=0 (Do not expect acknowledgement from operator) Bit 1=0 (Do not send acknowledgement) 8=Status Character 2 (8 decimal=00001000 binary) Bits 8-4=00001 (defined as 1 Second; actually is less than 1 second) Bits 3-1=000 (Priority 0) 2=Message row/line number (second line of display) 16=Message column number (16th column) 140=Proprietary message (defined as the MID of the device that has the display; MID 140=ICU) e e e=Proprietary message (defined as the ASCII value for the headway, ex. 3.0). For more information on the message format, see Appendix C of the J1587 standard. In managing the output of collision warning messages, the ICU follows a set of predetermined guidelines. For each message in the table of FIG. 10, the message center displays the corresponding message for a predetermined period of time, namely 1.0 second. To display the message a longer period of time, the CWS ECU sends the same message again after 0.5 seconds, and continues re-sending at this rate. Upon receiving a data bus message, the ICU sets a timer to 1.0 second, and continues to display the message as long as the timer has not elapsed. The ICU resets the timer (to a full 0.75 seconds) upon receiving a new message. This approach for re-sending messages and re-setting the timer with each new message ensures that the delay between transmissions of messages will not produce a flicker in the ICU display. Another feature relating to the integration of collision warnings into the message center is the ability to select a driver for the purpose of logging events on a per driver basis. The ICU provides a display that enables the driver to enter a driver identification (ID), and is programmed to broadcast a message on the data bus including the driver ID. The CWS ECU and other ECUs are programmed to store the driver ID and record it along with events that they monitor. In particular, the current implementation of the ICU broadcasts the driver ID in PID 507 of the J1587 protocol, in response to a request from another ECU (e.g., the CWS ECU) using MID 219. In the current implementation, the ICU prompts the driver to enter the driver ID during the ignition sequence. During the ignition sequence, the message center displays screens that prompt the driver to accept the currently active driver ID or to select a new one. FIG. 11 illustrates an example of the message center displays 1100, 1102 used to prompt the driver for the ID. The driver can either select the active driver ID by pressing the set key in response to the first screen, or select a new driver by pressing an arrow key as shown. After the driver presses the acknowledgement key at either screen 1100, 1102, the message center continues with the ignition sequence as shown in the third screen 1104 in FIG. 11. In response to the selection of the driver ID, the ICU sends a PID 507 message, Driver Identification, over the SAE J1708/1587 data link to indicate what driver is active (Driver 1 or Driver 2) as soon as the driver acknowledges the ICU screen prompt, per the following message formats:
Driver 1
MID PID n ASCII ASCII
140 507 2 49 42 Cksum
(1) (*)
Note that PID 507 is sent as two consecutive bytes: 255 followed by 251.
Driver 2
MID PID n ASCII ASCII
140 507 2 50 42 Cksum
(2) (*)
Again, note that PID 507 is sent as two consecutive bytes: 255 followed by 251. The message will be available from the ICU also upon request, per the following message format:
Request
MID PID a b
219 384 251 140 Cksum
Note that PID 384 is sent as two consecutive bytes: 255 followed by 128. Integration of Adaptive Cruise Control into the Message Center The driver interface for adaptive cruise control is integrated into the ICU and its message center. In the current implementation, the driver interface for the ACC system includes the ICU's message center and indicator lights as well as input switches on the dash. The ICU integrates ACC related information and warnings into the message center and also controls ACC related indicator lights. When the driver enters ACC input via dash switches, the ICU displays visual feedback to the driver via alphanumeric messages on the display screen. The ACC system includes the CWS ECU, the ICU, the engine ECU, the transmission ECU, the anti-lock brake ECU, and the engine retarder ECU. The ACC software executing on the CWS ECU uses the collision warning sensors to track targets and send messages to other ECUs to reduce vehicle speed when a target is too close to the truck. For example, in the current implementation based on the EVT-300 collision warning system from Eaton VORAD technologies, the CWS ECU maintains a constant headway with a lead vehicle by sending messages to: 1) control the throttle; 2) invoke the engine brake; and 3) downshift the transmission. Depending on the circumstances, the CWS ECU sends messages to the engine ECU to defuel the engine via the speed/torque limit override mode of the J1939 standard. It may also send messages to the engine brake to retard the engine via the torque control override mode of the J1939 standard. Finally, it may send a message to the transmission ECU to downshift the transmission according to the J1939 standard. The CWS ECU communicates ACC related information to the ICU via either discrete wiring, a data link, or some combination of discrete wiring and a data link. In the implementation based on the EVT-300 collision warning system, the CWS ECU communicates instructions for visual messages to the ICU via the J1708 data link, and sends control signals for auditory warnings directly to the ICU speakers via discrete wiring. In an alternative implementation based on the ADC adaptive cruise control system, the CWS ECU communicates control messages for auditory and visual messages to the ICU via the J1939 data link. The driver provides ACC related input via dash controls in the cabin. These controls include cruise control switches such as an ON/OFF/mode switch, and a SET/RESUME switch. The ON/OFF/mode switch enables the driver to turn on and off cruise control and, in some implementations, switch between ACC and conventional cruise control (i.e. cruise control without headway control). The operation of this control switch varies, depending on the implementation. For example, in one implementation, ACC is always active when the driver turns on the cruise control. The only exception is failure of ACC, in which case, the system reverts to conventional cruise control operation. In an alternative implementation, the driver can switch between no cruise control (OFF), adaptive cruise control (Adaptive Cruise), and conventional cruise control (Cruise). In this case, the ON/OFF/mode switch is a three-position switch with positions for Adaptive Cruise, Cruise and OFF. The SET/RESUME switch is similar to conventional cruise control in that it allows the driver to enter the set speed and resume cruise control operation. When the driver actuates this switch, the cruise control within the engine ECU communicates the set speed to the CWS ECU and the ICU via the J1708 data link. Another ACC related switch is a volume control, which is similar to the volume control used in the collision warning system to adjust the volume for auditory warnings. In implementations where this switch is wired to the CWS ECU, the CWS receives the input and formulates a message to the ICU, instructing it to display a message showing the volume level. Similar functionality may be achieved in an implementation where the volume switch is wired to the ICU directly. In this case, the ICU displays the volume level in response to direct inputs from the volume control. Finally, there is a headway control switch, which enables the driver to set the headway. In implementations where the headway control is wired to the CWS ECU, the CWS receives the input and formulates a message to the ICU for the J1708 data link, instructing it to display a message showing the selected headway. Similar functionality may be achieved in an implementation where the headway control is wired to the ICU directly. In this case, the ICU displays the selected headway in response to direct inputs from the headway control and formulates a message to the CWS ECU for the J1708, informing it of the headway setting. The method for communicating driver input to the ACC system varies, depending on the implementation. In the implementation that integrates the EVT-300 collision warning system, the switches are wired into the CWS ECU, and the CWS communicates instructions for visual messages to the ICU. In the implementation that integrates the ADC distance control system, the switches are wired directly into the ICU, the ICU communicates headway parameters to the distance control system. The ICU provides three microprocessor controlled indicator lights for ACC functions located near the message center. One light indicates whether the adaptive cruise control is active. The ICU detects this condition from the data link via messages from the engine ECU and CWS ECU. The condition for this active light is: no active fault from the CWS ECU (MID 219), battery voltage (PID 168) is normal in the CWS ECU, and the cruise control is active (PID 85) from the engine ECU (MID 128). A second light indicates that the ACC system has detected a target. The ICU activates this light for preprogrammed duration (e.g., 200 ms) on receipt of a pre-determined message (e.g., 219.sub.-- 226.sub.-- 6.sub.-- 48.sub.-- 8.sub.-- 1.sub.-- 1.sub.-- 140.sub.-- 4_CHKSUM) from the CWS ECU on the data bus. Finally, the third light indicates that the ACC system has failed from the CWS ECU. The ICU detects this condition by detecting an active fault or no battery voltage PID 168 signal from the CWS ECU (MID 219). In this implementation, the battery voltage signal from the CWS ECU acts as a "heartbeat" indicating that the CWS ECU is operating. In addition to the ACC-related indicator lights, the ICU also displays visual messages on its display screen. In the current implementation, the ACC related display screens fall into three categories: function set messages, failure warnings, and danger ahead warnings. FIG. 12 illustrates examples of the ACC related indicator lights and these display screens. The ICU displays function set messages in response to input from the driver setting parameters relating to adaptive cruise control. When the driver enters the set speed using the SET/RESUME switch, the ICU displays a screen 1200 with a text message indicating that radar cruise is active, the value of the set speed, and the time headway as shown in FIG. 12. Also, when the driver sets the headway via the headway switch on the dash, the message center displays a screen 1202 showing the time headway setting. The terms "min" and "max" are the lower and upper limits of a bar graph display, graphically depicting time headway. As the driver increments or decrements the current value of the headway, the message center displays the current value of the headway. The ACC system uses the ICU's indicator lights to show changes in its status. When the driver activates the adaptive cruise control system, the ICU illuminates the radar cruise indicator light 1204. While in adaptive cruise control mode, the ICU illuminates a DETECT indicator light 1206 when the collision warning system is tracking a vehicle. The message center displays a warning screen 1208 in FIG. 12 when the radar system fails. In addition, the ICU illuminates a radar fail indicator light 1210. While the adaptive cruise control system is active, the message center also displays "danger ahead" messages 1212, 1214 in response to collision detection events from the collision warning system. These messages are triggered as described above in connection with the integration of the ECU collision warning system into the ICU message center. The message center displays the set speed along with the "danger ahead" message as shown in screen 1212. However, as the urgency of the "danger ahead" message increases, the ICU removes the set speed and displays a larger triangle to emphasize the increase in danger as shown in screen 1214. In the event that the adaptive cruise control system becomes inactive while the vehicle is in cruise control mode, the message center displays a warning such as the one shown in display screen 1216 in FIG. 12 to indicate to the driver that the radar cruise control is off. At the same time, the ICU turns off an indicator light 1218 to indicate that the vehicle is not in cruise control mode. While the vehicle is in cruise control mode, the collision warning system and the ICU revert back to the message scheme described above in connection with collision detection warnings. In particular, the message center displays progressively more intense warning messages such as the ones shown in screens 1220 and 1222 in FIG. 12 when the collision warning system detects that the following distance has fallen below pre-determined thresholds such as headway values of one and two seconds. The difference between the collision warnings shown in screens 1220 and 1222, and the collision warnings during ACC mode is that the ICU displays the set speed (e.g., screen 1212) during ACC mode, as long as the severity of the message has not increased to the point where the warning triangle dominates the display screen (e.g., screen 1214). The ICU determines when to display failure related messages by monitoring the status of the adaptive cruise control system via the J1708 data link. The collision warning system conducts periodic self checks (e.g., every fifteen seconds) to determine if it is operating properly. It then sends a message on the J1939 data link indicating that the adaptive cruise control system is active every 100 msec, as long as it has not detected any critical faults that might prevent proper operation. In the event that the CWS ECU determines that it has a critical fault, then it discontinues sending the message onto the J1939 data link, and sends a fault message via the J1587 data link to the ICU for the driver display. In response to the lack of heartbeat from the CWS ECU, the engine ECU reverts back to normal throttle control rather than cruise control mode. In response to the fault message on the data link, the ICU displays message screen 1208 shown in FIG. 12 indicating a radar cruise control failure. The engine ECU is programmed to monitor the status of the ACC system when the ACC system is installed on the vehicle. The engine ECU monitors the status of the adaptive cruise control system via the J1939 databus. The collision warning system is powered on when the ignition is switched on. After a self-check, the ACC system starts transmitting the heartbeat. The engine ECU is programmed to check whether the heartbeat is present on the databus at ignition startup. If the heartbeat is not present at that time, the engine ECU disables its ACC mode and returns to throttle mode. After power-up, the engine ECU continually monitors for the heartbeat and is programmed to assume that the ACC is no longer functioning if it does not receive a heartbeat for over a pre-determined period of time (e.g., 350 msec). In this case, it disables the cruise control and returns to throttle control. To enable conventional cruise control when ACC fails, the driver can toggle the cruise control ON/OFF switch twice within ten seconds. Once this sequence is accomplished, the engine ECU enables conventional cruise control. If the ACC heartbeat comes back to the databus, then the engine ECU will allow ACC operation, but only at the next cruise control power ON cycle. This avoids the possibility of the engine being in conventional cruise control mode and adaptive cruise control being reactivated without driver notification and acknowledgement. The adaptive cruise control messages are integrated into the ICU's message center in a similar manner as the collision warning messages. Table 5 above illustrates the priority of collision warning messages in the context of the ICU's prioritization scheme, which includes danger, warning, and caution alerts. When the CWS ECU detects collision warning events during operation of the ACC system, it sends messages to the ICU communicating these events. The ICU treats these messages as having the same priority as in the case where the ACC is not active. When the ICU detects a condition from the data link indicating that the ACC system has failed or has become inactive, it generates a "warning" level message (see, e.g., priority level 5 in Table 5, showing the priority of a "warning" level message relative to collision alerts and other ICU messages). Finally, in response to user input relating to the ACC system, the ICU displays function set messages, such as the time headway setting (see, e.g., messages 6-13 in FIG. 10), and the alert volume (see, e.g., messages 14-21 in FIG. 10). When the driver changes/enters the set speed or headway, the ICU displays the set speed and headway information as illustrated in screen 1200, FIG. 12. The ICU also displays screen 1200 while in ACC mode in response to detecting that the vehicle speed from the engine ECU has dropped an increment of 5 MPH below the set speed. FIG. 10 shows this message as message number 22. Note that the ICU prioritizes this message below that of the function set messages (e.g., messages 6-21 in FIG. 10) and the collision warning messages (e.g., messages 1-5 in FIG. 10). Integration of Transmission Display into the Message Center The ICU integrates the transmission display into the message center. One particularly advantageous feature of the ICU is the ability to provide a standard interface for a variety of transmission types, such as automated mechanical transmissions, automatic transmissions, and mechanical (i.e., manual) transmissions. The message center displays the current gear of the vehicle and, for some transmission systems, the driving mode of the transmission (e.g., automatic or manual mode for an automated mechanical transmission). The message center may also display indicators (e.g., up/down arrows) to prompt the driver to shift for better fuel economy. In addition to visual information, the ICU provides auditory information as well. The ICU generates an auditory warning to indicate to the driver that an inappropriate gear has been selected. In the case of both visual and auditory information, the transmission ECU communicates instructions for this information to the ICU via the J1708 link according to the J1587 standard. FIG. 13 illustrates examples of display screens 1300, 1302 that display transmission information in the current implementation. In providing this display information, the ICU works in conjunction with the transmission ICU. The transmission ECU receives instructions for shifting the transmission and selecting the driving mode from a shift lever in the vehicle. For more information on the operation of the shift lever, see co-pending application entitled, "Lever Assembly for an Electronically Controllable Vehicle Transmission", which is incorporated by reference above. As illustrated in display screen 1300 shown in FIG. 13, the message center displays at least three characters (e.g., 1304, 1306, 1308) that are related to the transmission display. At least one character 1306 displays the current gear. Another character 1308 displays the driving mode of the transmission. Another character 1304 may be used to separate the transmission display from other messages. Since the message center always provides a transmission display, it indicates the characters relating to the transmission display along with whatever else is currently displayed, which is either the driver's selectable default screen or an alert screen. The second display screen 1302 shown in FIG. 13, illustrates the case where at least one character 1310 display an up or down arrow to prompt the driver to shift to improve fuel economy. In this case, the arrow character also functions to separate the transmission information from other information that is currently presented on the same line of the display. As noted above, the ICU can provide visual and auditory information for a variety of transmission systems. In one implementation, the message center is used to display transmission information for an automated mechanical transmission. The driver controls the transmission via a shift lever that enables the driver to select a gear by actuating the lever, and also allows the driver to select the driving mode via a switch on the stalk of the lever. In this particular implementation, the message center displays the current gear at all times in which the automatic shifting mode is selected. The message center displays the current gear in manual shifting mode until the driver selects a new gear through actuation of the shift lever. The new gear may be flashed for a pre-determined time period (e.g., 500 msec intervals) until the shift is completed. For normal up or down shifting, the transmission display will not appear to shift to the driver because one cycle of the flash interval corresponds roughly to the average time that the automated mechanical transmission system takes to complete a shift. When a driver makes a shift request for activation of the shift lever, the message center only displays the selected gear if it is currently available. The message center informs the driver that the selected gear has been engaged by ceasing the flashing of the selected gear. When a driver selects a gear or mode that is unavailable via the shift lever, the ICU generates an auditory tone indicating that it is unavailable. In the current implementation, for example, the ICU generates a pure square wave tone at 250 Hz for 300 msec. This particular tone was selected because it is not easily masked in the cabin environment and is used with other systems to represent an action that is inappropriate, not allowed, or requires different input. The same tone is used to signal an unavailable mode selection (e.g., moving the mode switch to reverse at highway speed). Instead of a single tone, the ICU repeats this tone at periodic intervals until the selector has been put back into the appropriate position. In addition, the message center generates a level 2 warning message with the corresponding auditory tone and display protocol. CONCLUSION While the invention is described with reference to a specific implementation, it is important to emphasize that the invention is not limited to the specific design details of this implementation. The message display integrates message displays from a variety of different types and models of ECUs and other sensors onboard the vehicle. The format of the data does not have to be in the form of serial data from a serial data link as in a system built for a J1708 data link. Instead, the data can be obtained from another type of data bus or through discrete wiring. The software implementation can vary as well. The precise logic used to prioritize messages can vary. Having described and illustrated the principles of our invention with reference to a specific implementation and possible alternatives, it should be apparent that the invention can be modified in arrangement and detail without departing from its principles. Accordingly, we claim all modifications as may come within the scope and spirit of the following claims.
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