System and method of optimizing the static segment schedule and cycle length of a time triggered communication protocol
View Patent ↗An internal communication system adapted for communicatively coupling a plurality of nodes during a cycle, wherein the cycle presents a cycle length and a plurality of static temporal slots. The system includes at least one communication channel, and an electronic control unit configured to optimize a schedule of time-triggered internodal messages, and the cycle length.
1. An internal communication system adapted for communicatively coupling a plurality of nodes during a cycle, wherein the cycle presents a cycle length and a plurality of static temporal slots, and optimizing a schedule of time-triggered internodal messages and the cycle length, said system comprising:
at least one host electronic-control-unit (ECU); and
at least one channel communicatively interconnecting the nodes and ECU, said ECU and channel being cooperatively configured to transmit the messages to and from at least a portion of the nodes within the static slots, wherein each node is individually assigned to at least one slot, during the cycle, and a static segment, and number of unused slots is presented,
said ECU being programmably configured to autonomously determine an optimal schedule for transmitting the plurality of messages within the static slots, and an optimal cycle length, wherein the number of unused slots is maximized,
said ECU being further configured to fragment at least a portion of the messages into a plurality of signals prior to optimization, and defragment the signals, so as to reconstitute the original messages after optimization,
said ECU being further configured to determine for each signal (s ij ) an originating node, a size in bytes, a period in microseconds (T ij ), and a transmission window, including start and end times (ws ij , we ij ), such that 0≦ws ij ≦we ij ≦T ij , wherein i represents the node number and j represents the signal number.
2. The system as claimed in claim 1 , wherein based on the transmission window [ws ij , we ij ] of each signal (s ij ), a slot-cycle range (scr (ij) ) for the signal is determined such that scr (ij) ={(k, h)|1≦k≦gNumberOfStaticSlots, 1 ≦h≦n cc , and (k, h) satisfies the following formulas:
( h −1)* gd Cycle+( k −1)* LengthStaticSlot≧ ws ij , and
( h −1)* gd Cycle+ k * LengthStaticSlot≦ we ij .
3. The system as claimed in claim 2 , wherein the slot-cycle assignment for each signal is encoded using integers 0 and 1, the number 1 indicates that signal (s ij ), is scheduled for the particular slot and cycle, and the sum of slot-cycle values for all combinations of differing nodal signals for any given slot is not greater than 1.
4. The system as claimed in claim 1 , said ECU being further configured to determine a common period, T, equal to the least common multiple of a plurality of differing periods T ij .
5. The system as claimed in claim 4 , said ECU being further configured to determine the length of the communication cycle in microseconds (gdCycle), the number of static slots in the static segment (gNumberOjStaticSlots), the payload length of a static frame for the static slot (gPayloadLengthStatic), the duration of a static slot in the number of macroticks (gdStaticSlot), the duration of a nominal macrotick in microseconds (gdMacrotick), and the duration of a static slot in microseconds (LengthStaticSlot), wherein the LengthStaticSlot is equal to the product of gdStaticSlot and gdMacrotick.
6. The system as claimed in claim 5 , wherein the length of the communication cycle in microseconds (gdCycle) is a factor of the common period T.
7. The system as claimed in claim 5 , wherein gPayloadLengthStatic, gdStaticSlot, and gdMacrotick are predetermined prior to receipt of the messages.
8. The system as claimed in claim 5 , wherein optimal values for gdCycle, and gNumberOfStaticSlots are determined from a predetermined set of available combinations based on the period and/or communication cycle length.
9. The system as claimed in claim 5 , wherein the optimal schedule and cycle length are determined according to a plurality of requirements, including that each slot is assigned to at most one node, each signal is scheduled within its transmission window, and the total size of all signals that are assigned to the same slot in a communication cycle is less than or equal to the payload size of a static frame.
10. The system as claimed in claim 9 , said schedule and cycle length being determined by modeling the system as a multiple choice integer program (MCIP) problem.
11. The system as claimed in claim 9 , said ECU being further configured to terminate the determination of the optimal schedule and length for a given set of signals, when the requirements are not able to be met, and reinitiated upon receipt of a second plurality of messages.