q uantitative e valuation of e mbedded s ystems
Post on 15-Jan-2016
216 Views
Preview:
TRANSCRIPT
Quantitative Evaluation of Embedded Systems
Quantitative Evaluation of Embedded Systems
TDMA in a cyber physical system:preparation for the SDF3 assignment
Sharing Resources
No sharing – dedicated resources
Alternating access, round robin
Fixed priority
First-come first serve
?
Time Division Multiplexing (1)
Perio
d =
P Slice = S
Task = T
P-S TP/S
Time Division Multiplexing (2)
Perio
d =
P Slice = S
Task = T
P-S
q
qT = rS
S/q rr
P-(S/q)
0 NEW!!Publication under submission...
RTAS 2014
Comp.Inner control
Physical World
Sensor 1Temperature
Actor 1Valve
Actor 2Motor xyzComp.
Emergency detection
Comp.Image processing
Sensor 2Pressure
Sensor 4Microphone
Actor 3Motor rot.
Sensor 3Camera
A cyber physical system
Comp.1Inner control
Sensor 1Temperature
Actor 1Valve
Actor 2Motor xyzComp.2
Emergency detection
Comp.3Image processing
Sensor 2Pressure
Sensor 4Microphone
Actor 3Motor rot.
Sensor 3Camera
Dataflow of the control cycle
Comp.1Inner control
Sensor 1Temperature
Actor 1Valve
Actor 2Motor xyzComp.2
Emergency detection
Comp.3Image processing
Sensor 2Pressure
Sensor 4Microphone
Actor 3Motor rot.
Sensor 3Camera
Packet-flow of the control cycle
p2
p1
p3
p4
p5
p6
p7
p8
p9
p10 p11
p12
p13
p14
p15
p16
p17
p18
Comp.Inner control
Sensor 1Temperature
Actor 1Valve
Actor 2Motor xyz
Comp.Emergency detection
Comp.Image processing
Sensor 2Pressure
Sensor 4Microphone
Actor 3Motor rot.
Sensor 3Camera
Network topology
Comp.Inner control
Sensor 1Temperature
Actor 1Valve
Actor 2Motor xyz
Comp.Emergency detection
Comp.Image processing
Sensor 2Pressure
Sensor 4Microphone
Actor 3Motor rot.
Sensor 3Camera
Network topology
Comp.1Inner control
Sensor 1Temperature
Actor 1Valve
Actor 2Motor xyzComp.2
Emergency detection
Comp.3Image processing
Sensor 2Pressure
Sensor 4Microphone
Actor 3Motor rot.
Sensor 3Camera
Packet flow + Network hops
Sensor 1Temperature
Actor 1Valve
Actor 2Motor xyz
Sensor 2Pressure
Sensor 4Microphone
Actor 3Motor rot.
Sensor 3Camera
Packet flow + Network hops + Processor sharing
Actor 1Valve
Actor 2Motor xyz
Actor 3Motor rot.
Packet flow + Network hops + Processor sharing + Sampling times
Packets + Network + Processor + Sampling + Feedback
Latency 1
L2
L3
Time Division Multiplexing (2)
Perio
d =
P Slice = S
Task = T
P-S
q
qT = rS
S/q rr
P-(S/q)
0
Filling in the details: Network sharing
Perio
d =
P Slice = S
Task = T qT = rS
• One packet per slice in the network, therefore T = S = 0.01 ms • One slice per node in the network• But... each node schedules its routing
in a TDMA fashion as well...So for each hop P = (C+1)*N*S where C is the number of connections and N is the total number of nodes in the network.
Filling in the details: Proc. sharing
Perio
d =
P Slice = S
Task = T qT = rS
• Three computations = three slices, so P = S1 + S2 + S3• Task times may be bigger than slice times!• T1 = 0.5 ms• T2 = 3 ms• T3 = 7 ms• It is part of the assignment to figure
out how P should be chosen anddivided over S1,S2 and S3.
Filling in the details: The rates
• Sensor 1 and 2 produce 1 packet every 2 ms• Sensor 3 produces 50 packets every 100 ms• Sensor 4 produces 10 packets every 20 ms• Computation 1 needs 1 packet from sensor 1 and 2,
and produces 1 packet for computation 2 and one for actor 1• Computation 2 takes 50 packets from computation 1 and 1 packet from
computation 3 and produces 1 for actors 2 and 3 and for computation 3.• Computation 3 takes 50 packets from sensor 3, 50 from sensor 4 and
1 packet from compation 2 and produces 1 for computation 2.
The dataflow graph I prepared for you:
Sensor1
Sensor2
Sensor3
Sensor4
Actuator1
Actuator2
Actuator3
hop1 hop2
hop3hop4
hop5
hop6
hop7 hop8
hop9 hop10 hop11 hop12
hop13
hop14hop15
Comp1
Comp2
Comp3
1
1
50
10
50
50
50
2 ms
2 ms
100 ms
20 ms
2 2
22
2
top related