Realtime Scheduling of HLA Simulator Components

1
Real-time Scheduling ofHLA Simulator Components
2
Overview

• Background on Component Based Architectures and
  RCI Middleware
• Real-time Scheduling
• RCI Time management Schemes
• High Performance RTI
• Benchmark Tests
• Conclusions

3
Component Based Simulation Architecture
Federate Manager
Component
Component
RCI
DIS / HLA-RTI / ...
Support tools
Federate
Federate
Run-time Communication Infrastructure (RCI)
DIS / HLA-RTI / ...
4
Run-time Communication Infrastructure (RCI)
Functional part
component / federate
RCI interface
environment
data access

RCI
communication server
data transport
DIS comm. server
HLA comm. server
High Speed comm. server
5
RCI architecture

• Environment
• hides interoperability complexity
• presents simulation environment to
  components/federates
• activates components/federates through callbacks
• Communication Server
• keeps environment up-to-date
• encoding/decoding of network data
• transport and routing of messages(intra-component
  and intra-federate)

6
RCI Code generation

• Interface between Components and Federates is
  formalised using Object Model Templates (OMT)
• Interface code generation (C) fromformal OMT
  specifications (COM or SOM)
• Supports fast development and avoids programming
  mistakes

7
Core of Component Development

• Define interface (COM) of the component
• Define functionality of the component
• Transform COM into Code (automatic)
• Transform functionality into Code
• Integrate and Test the Component

8
Example
FOM
RCI
Aircraft Federate
COM
Flight Dynamics Component
RCI
COM
Visual System Component
SOM
RCI
COM
Mock-Up Server Component
COM
COM
9
RCI Schedule

• Update, Output, and Sync Actions
• can be scheduled within one simulation frame

10
Real-time Scheduling

• A schedule should meet the timing and
• resource requirements of the system
• Real-time means the ability to meet a deadline
• Soft real-time
• Hard real-time
• Real-time says nothing about
• processor performance, network bandwidth
• or system cost

11
Real-time Requirements for a Component Based
Simulator

• Cycle Times
• Control input 100 Hz
• Dynamic model 100 Hz
• Visual 30 Hz update rate, 60 Hz refresh rate
• Jitter
• 1 ms scheduling accuracy
• Latency (worst-case)
• End-to-End Latency between components 30 ms
• End-to-End Latency between federates 100 ms
• Bandwidth
• 3 Mbit/sec (incl. about 150 CGF's)

12
Conditions for real-time performance

• The interoperability layer (middleware, RTI and
  network) must provide a defined QoS, which
  includes a bounded latency. Obviously, the OS and
  hardware platforms must also support these RT
  performance requirements.
• The federation must provide a system wide
  synchronized clock. The synchronized clock is the
  means by which the schedules of the different
  federates are kept aligned.

13
RCI Time Management Schemes

• Default Scheduler
• no time synchronisation
• HLA-TM Scheduler
• time synchronisation by the RTI
• deadlines not guaranteed
• UTC-TM Scheduler
• Simulation time paced to globally synchronized
  time
• RCI puts a timestamp in the tag field
• deadlines are guaranteed for a feasible schedule

14
High Performance TNO-RTI

• Partial RTI FM, DM, OM, TM
• Compatible with DMSO RTI API library names
• Layered Design
• Shared Memory and/or Ethernet
• No RID file just 'rtiexec -t sm,udp,tcp'
• Automatic resign of dead federates
• OS Irix, Sun, Linux, Windows

15
Run-time Communication Infrastructure (RCI)
Functional part
component / federate
RCI interface
environment
data access

RCI
HLA comm server
data transport
RTI-API
RTI-API
DMSO RTI
TNO HP RTI
16
Run-time Communication Infrastructure (RCI)
Functional part
component / federate
RCI interface
environment
data access

RCI
HLA comm server
data transport
RTI-API
RTI-API
RTIambassador
Transporter
TNO HP RTI
DMSO RTI
Bus
SM, UDP, TCP
17
Benchmark testing pipelining
F (frequency) is the number of updates per second
depicts logical data flow
Generating Component
Processing Component
Collecting Component
Generator
Fin
Fout?
RCI
RTI
end-to-end
18
Latency Experiments
End-to-end average latency (?sec)
3000
270
110
450
780
360
Update-rate (Hz)
19
Jitter
Local Jitter (µs)
Network Jitter (µs)
SGI/Irix 250 Mhz
39
216
iHawk/Redhawk 700 Mhz
35
3
20
Conclusions

• The HLA concept itself is not "slow", but the
  implementation of the RTI is very often the
  reason why real-time requirements are not met
• The TNO HP RTI supported by a real-time OS makes
  the HLA concept suitable for real-time Component
  Based Simulators

21
Future Work

• Perform the same benchmark tests using different
  communication layers
• MÄK RTI
• OMG Data-Distribution Service (DDS)
• Extend the RCI API with QoS policies
• use DDS as a replacement of the RTI
• extend the RTI API with QoS policies

22
Questions
23
Federate Manager
SOM-FOM Mapping
RCI
RCI
Attributes, Interactions
Comp. Based Federate (SOM)
Federation (FOM)
24
Federate Manager

• Represents the Federate to the Federation
• Creates and Joins the Federate
• Exchanges data between the Components and the
  rest of the Federation (bridge)
• Co-ordinates the State of all Components
  (optional)
• Generated automatically from
• SOM
• FOM
• SOM-FOM Mapping (advanced mappings manually)
• optional STD