cbse course

<<AutoComp>>

Power Supervison

Desired Output level

Source

Diesel Valve

Sink

Diesel Valve

<<AutoComp>>

Valve RegulatorSink

T = 40 ms

Air Valve

Air Valve

CBSE CourseThe SaveComp Component Technology

Vehicular Systems• Software Charateristics

– Safety – Reliability – Resource efficiency – Predictability

• Engineering Activities– Targeting non general System

Architecture– Early Analysis– Modelling– Verification

21/04/23 Mikael Åkerholm, CBSE Course 2005 2

Example: The architecture of a car control system

, April 21, 2023

Vehicle mechanics

ECU

Sensor ActuatorSensor

ECU

SensorActuatorSensor

ECU

SensorActuatorSensor

gateway

(CAN) BUS

brake injection

Infotaiment

ECU – Electronic Control Unit

The architectural design challenge

, April 21, 2023

Vehicle stability Suspension Drive by wire …… Complex functions

Local Control Functions


Basic functionsLocal Control Functions


How to implement complex functions based on local control functions?

Problem: resource sharing

, April 21, 2023

Sensor 1

Sensor 2

Sensor 3

Sensor ..

Networkresources

++++++++++

++++++++++

++++++++++Sensor ..

Executionresources

Node 1

Node 2

Node 3

Node …

Node …

Actuator 1

Actuator 2

Actuator 3

Actuator …

Actuator …

Can functions of different criticality be allowed to share resources?

Challenge – open and dependable platform

, April 21, 2023

sensors

Vehicle

actuators

Engine Control Local brake Control Transmission ………local

Vehicle stability

Cruise control

Antispin Global (complex) functions

Hardware

Input/output drivers

Middleware

ECU ECU ECU

Applications

SOFTWARE COMPONENTS

Collision detection

Challenge – open and dependable platform

, April 21, 2023

Hardware

Input/output drivers

Middleware

ECU ECU ECU

Applications C1 C2

RequirementsSeparation of hw from SW developmentSeparation of SW component development

Example: A task as a componentComponent-model used in REBUS (Volvo construction equipment)

• The timing requirements are specified by release-time, deadline, WCET and period

April 21, 2023Ivica Crnkovic (c) : Component-based

real-time systems

Task: BrakeLeftRight Period: 50 ms Release time: 10 ms Deadline: 30 ms Precedes: outputBrakeValues WCET: 2 ms

oil pressure

speed

….

brake left wheel

brake right wheel

Task state information

Real time attributes


Task: BrakeLeftRight Period: 50 ms Release time: 10 ms Deadline: 30 ms Precedes: outputBrakeValues WCET: 2 ms

oil pressure

speed

….

brake left wheel

brake right wheel


What isTaskPeriodDeadlineWCETPrecedance

Challenges when constructing RT systems

Most of the real-time systems are based on following:1. Several parallel activities are given some unique priorities2. A resource manager makes sure the task with the highest

priority will execute

April 21, 2023Ivica Crnkovic (c) : Component-based real-time systems

1 3

Activities

Resource manager

timeCPU

1

2

3

ready

ready

Definition – task

Task• A sequential program performing an activity

and that possibly communicates with other tasks in the system. A task often has a priority relative to other tasks in the system.

• Sometimes thread is used instead of task.

Process• A virtual processor that can handle several tasks

with a common memory space.April 21, 2023

Ivica Crnkovic (c) : Component-based real-time systems

Periodic tasks

An infinite sequence of identical activities – invocations (jobs)


real-time systems

timeTask A A1

(Inv. 1)

A2

(Inv. 2)

A3

(Inv. 3)

period period

Analogy from real life:Example:

• Audio and video sampling

• Regulating

• Monitoring of temperature and pressure

Execution time

What is a release time and deadline?


real-time systems

Task release time is the earliest point in time we can activate (release) the task

Airbag-example:

Crash

Too late

time

Too early

Release time Deadline

Relations between components and tasks

• Components – design Units• Tasks – execution Units• Mapping:

– Simplest: a Component is a task– Complex

• A set of components makes a task

• A component can be split into several tasks


Composition of Components


real-time systems

Task:BrakeLeftRight

oilpressure

speed

brake left

brake right


Task:OutputBrakeValues


Component: BrakeSystem

pressure

speed

What is with time attributes?

• How do we specify properties of an assembly?– Execution time (WCET,…)

• How do we map assembly properties to the components being composed?– Period?– Priority?


real-time systems

Properties of Composed components

• Can we use WCET?– No– WCET cannot be computed since its parts may be executing with different

periods.

• End-to-end deadlines – Are set such that the system requirements are fulfilled – Should be specified for the input to and output from the component

• Latency – time for an assembly to respond to input signal– Average, Worst case (end-to-end deadline), best case


real-time systems

Task:BrakeLeftRight

oilpressure

speed

brake left

brake right


Task:OutputBrakeValues


Component: BrakeSystem

pressure

speed

EXAMPLESAVECOMP COMPONENT MODEL

SaveCCM


SaveComp Overview


Task Allocation

Win 32

APPLICATION

SaveCCM

XML - representation

Design-Time

Compile-Time

Run-Time

<<SaveComp>>

PC

<<SaveComp>>

Compose

<<Assembly>>

P

Set ActualControl

AttributeAssignment

Code Generation & Analysis

C-compiler

RTXC

APPLICATION

Simulation Target

SaveCCM Component Model

• Tradeoff: – Freedom vs. Restrictions

• SaveCCM restrictive, but expressive power focused on domain specific needs, e.g.,– Mode Changes– Static Configuration– Control Feedback


Architectural Elements

• Components– In and Output ports, (1) data only, (2) triggering, (3) triggering and

data (for all elements, not only components)– Basic units of encapsulated behavior – Execution model: read input, execute, write output


<<SaveComp>>

name

Input port, data

Input port, triggering

Input port, data and triggering

Output port, data

Output port, triggering

Output port, triggering and data


• Switches, special type of component• Conditionally changes the component

interconnection structure– Static or dynamic configuration of conditions


<<Switch>>

name

P I D

INP

INI

IND

OUTP

OUTI

OUTD

Switch name { Inports: INP:Pport, INI:Iport, IND:Dport, P:Setport, I:Setport, D:Setport; Outports: OUTP:Pport, OUTI:Iport, OUTD:Dport; Switching: P: INP->OUTP; I: INI->OUTI; D: IND->OUTD;}


• Assemblies, special type of component• Consists of components and switches• Naming of sub-systems, hiding internal structure


<<Switch>>

S1

<<SaveComp>>

PC

<<SaveComp>>

IC

<<SaveComp>>

DC

<<Switch>>

S2

<<SaveComp>>

Compose

Set Actual

P I D

Control

<<Assembly>>

PID

Compile-Time Overview


Design- Time

Component model

Real-Time Analysis

Real-time model

Synthesis

Compile- Time

Model transformation

Run- Time

Target application

RTOS

t

Task Allocation

Attribute Assignment

Analysis

Glue CodeGeneration

TargetCompiler

Component model

RTOS RTOS

Fully Automated Fully Automated Compile-Time StepCompile-Time Step

Run-Time System• Applications have no dependencies to operating systems, all operating

system dependencies are automatically generated glue code, gives portable and reusable components

• Prototype: – Win32 for Simulation with the CCSimTech simulation technique– RTXC RTOS for target


SaveCCM Application Programmer ’s Interface

SaveCCM Application

MS Windows

SaveIO

PC

SaveMemory SaveCAN

CCSimTech

Sim

ulation Fram

ework

Sim

ulation Fram

ework

Target F

ramew

ork


SaveCCM Application

SaveCAN

SaveCCM Hardware Abstraction Layer

SaveIO

SaveRTOS

HW Platform

SaveMemory

Device Drivers

Target F

ramew

orkT

arget Fram

ework


SaveCCM Application

SaveCAN

SaveCCM Hardware Abstraction Layer

SaveIO

SaveRTOS

HW Platform

SaveMemory

Device Drivers

Target F

ramew

ork


Road Signs Enabled

Current Speed

Road Sign SpeedACC Max Speed

Distance

ACC Enabled

Brake Pedal Used

<<Assembly>>50 Hz

10 Hz

Brake Signal

Throttle

Brake Assist

<<SaveComp>>

Logger HMI Outputs

<<SaveComp>>

Object Recognition

<<SaveComp>>

Mode Switch

<<Switch>>

ACCController

<<Assembly>>

Brake Assist

ACC

Max Speed

ACC ApplicationSpeed Limit

<<SaveComp>>

cbse course

Documents

ivica crnkovic c

msrelease time

local control functions

realtime systemsanalogy

cbse coursproblem

msreal time attributes

car control systempage

brakeleftright period