Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Construction or agricultural-type vehicle
Reexamination Certificate
1998-12-22
2003-12-16
Black, Thomas G. (Department: 3663)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Construction or agricultural-type vehicle
C710S100000, C710S305000, C710S060000, C710S006000
Reexamination Certificate
active
06665601
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a communication system in a work vehicle for managing communications between control units that control various functions of the vehicle. More particularly, the invention relates to controlling the transmission and reception of messages between the control units on a work vehicle over a data bus wherein only a predefined number of messages are scheduled for transmission during a predefined time period and wherein received messages are sorted using lookup tables into a set of desired messages for storage.
BACKGROUND OF THE INVENTION
Work vehicles including, but not limited to, agricultural work vehicles (e.g., tractors and combines) and construction work vehicles (e.g., dozers and loader-backhoes), perform certain functions based on the interaction of several control units which communicate with each other over a data bus. Each control unit may perform certain functions in conjunction with a particular device coupled to the control unit. For example, a transmission control unit connected to a work vehicle's transmission can direct the transmission to downshift, upshift or maintain a constant gear ratio based upon inputs received from a gear shift lever operated by the vehicle operator, and also based upon data received from other control units via the data bus. The transmission control unit may also receive feedback signals from the transmission. Further, the transmission control unit may itself transmit data (e.g., status and fault data for the transmission) over the bus to other control units. Thus, the transmission control unit may be capable of both transmitting and receiving data via the data bus.
In a typical work vehicle having a data bus populated by multiple control units (e.g., an armrest control unit, the transmission control unit, etc.), each control unit may be required to transmit and receive messages over the same data bus. For example, to properly execute its respective control functions, each control unit on the bus may need to receive certain sensed or calculated input data from other control units at predefined update rates, and may also be required to transmit certain output data for use by the other control units, also at predefined update rates. Further, upon detection of certain events or conditions (e.g., upon detection of a malfunction such as a transmission fault or upon detection of a change in status such as the actuation of an operator input device), the control units may be required to provide a “flag” signal on the bus indicative of the event or condition for use by the other control units. Some of the “flag” signals, such as those indicating a change in an important system input or fault, may need to be transmitted over the bus to the other control units immediately.
As work vehicles become increasingly sophisticated, additional control units continue to be coupled to the data bus and incorporated into the communications system. With each additional control unit, the scheduling of messages on the data bus becomes more complex. In some cases, all of the messages cannot be transmitted as quickly as desired under all conditions without exceeding the bandwidth of the bus. For example, the operator of a work vehicle expects the vehicle to respond quickly to actuations of an operator input device (e.g., actuation of a four-wheel drive switch). Thus, when the input device is actuated, the change in status must be transmitted to the appropriate control unit relatively quickly to avoid a sluggish response. However, in some communications systems, the status of infrequently changing inputs such as operator input devices are transmitted at relatively slow periodic update rates (e.g., every 500 msec), such that the response time to a change in status is correspondingly slow. In other communications systems, the status of infrequently changing inputs such as switches is transmitted only when a transition is detected, and there is no scheduled periodic update. While not performing periodic updates of these inputs decreases loading on the bus and increases the bus bandwidth available for other signals, the communications system may miss signals due to failures or transients, thereby causing a loss of system functionality. In existing vehicle communications systems, thus, the system designer must often select an appropriate balance between vehicle responsiveness, bus loading, and the ability to gracefully handle transients.
Accordingly, it would be advantageous to have a communications system for a work vehicle that provides the ability to schedule a relatively slow update transmission rate for signals that do not normally require fast update rates, while also providing the ability to transmit these signals quickly upon a change in status or upon the occurrence of an event or condition. The slow update rates normally used would allow the system to confirm that the status of a signal has not changed since the last update (e.g., that the position of an operator input switch has not changed), while the expedited update rate would allow a change in status or occurrence of an event to be communicated quickly, thereby improving the responsiveness of the system. Thus, it would be advantageous to have a communications system including an “expediting” function which transmits the values of signals that change infrequently at relatively slow periodic update rates to allow status checking and to reduce the data bus usage associated with fast update rates, and transmits the values quickly upon a change in status or occurrence of a condition or event. It would also be advantageous if the system included a “request only” function to transmit the values of certain signals only when the transmission is requested by another control unit on the data bus.
The communications system on vehicles must also insure that each control unit on the data bus can transmit its scheduled messages on the bus within a maximum delay time to avoid the use of stale data by the receiving control units. For example, a particular control unit may have messages that must be transmitted every 50, 100 or 500 msec. As the number of control units on the bus increases, however, it can become increasingly difficult for each control unit to meet its transmission update rate requirements. For example, the communications systems on some work vehicles include a data bus according to the Controller Area Network (CAN) protocol. The CAN protocol includes a message arbitration scheme to resolve conflicts which may occur when competing control units attempt to transmit messages on the CAN bus at the same time. The message arbitration scheme uses a 29-bit Arbitration Field in the ID portion of the message to specify the priority of that message. The message with a numerically lower Arbitration Field has a higher priority than a message with a higher Arbitration Field, and will win the arbitration. This arbitration scheme can cause problems in real-time control systems such as those used in work vehicles since it is difficult to guarantee a maximum time delay for any message other than the highest-priority message, and the problem worsens with increased bus loading. Accordingly, it would be advantageous to provide a communications system for a work vehicle including a CAN data bus populated by multiple control units wherein the maximum latency (i.e., delay time) for all messages transmitted over the CAN bus is guaranteed.
In addition to transmitting messages over the data bus to other control units, communications systems on work vehicles also need to manage the reception of messages transmitted over the data bus by other control units. Due to the high traffic on the data bus, each control unit of the communications system must be capable of quickly sorting all the incoming messages and of storing only the messages in which the control unit is interested (i.e., each control unit needs to listen to only a portion of the received messages). Incoming messages may be checked against a list maintained by each control unit which identifies those messages
Black Thomas G.
Case Corporation
Henkel Rebecca L.
Mancho Ronnie
Stader John William
LandOfFree
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