1. Real-Time Systems... And the Fine Print Real-Time Systems Anders P. Ravn Aalborg University September 2009

2. Literature For more material on real time operating systems, take a look at Real-Time Linux Foundation Java Real Time For material on Lego Mindstorm and Nxt, take a look at: Lego's home page for NXT Et Java OS til NXT

3. Characteristics of a RTS Timing Constraints Dependability Requirements Concurrent control of separate components Facilities to interact with special purpose hardware

4. Timing Constraints Pipe Flow meter Valve Interface Computer Input flow reading Processing Output valve angle Where does the T come from?

5. Timing Constraints Control Engineering: Plant Model Control Design Polling Frequencies Check of Stability, Robustness, Performance Software Engineering: Design, Implementation and Validation

6. The Program Architecture Meter read(int) Valve write(int) Task

7. Dependability Requirements Safety Engineering: Safety Case Fault-Effect Analyses Criticality Classification Software Engineering: Tracability and documentation Mechanisms and Validation

8. Concurrent control of separate components Valve/ Pump Pressure T-task HeaterLog_ Device Temperature P-taskLogger HeatOnTempPressValveSet

9. The Control Task LOOP wait_until(t); meter.read(y); compute(y,u); valve.write(u); t = t+T; END How do we get y and u?

10. Facilities to interact with special purpose hardware Sensors: Tachometer LightIntensity Contacts UltraSound Actuators: Light Motor

11. Sensor Properties (y= F(x)) Range y_min, y_max, x_min, x_max Accuracy x ±  (y) Linearity and offset y = a*x + b Resolution  x

12. Actuator Properties (x= G(u)) Range u_min, u_max, x_min, x_max Accuracy x ±  (u) Linearity and offset x = a*u + b Resolution  u

13. Example

14. RTS Implementation Language characteristics: Security Readability Flexibility Simplicity Portability Efficiency

15. Validation 1.Verification 2.Testing 3.Simulation ON 1.Model 2.Prototype with Test harness 3.Real System

16. Characteristics of a RTS Timing Constraints Dependability Requirements Concurrent control of separate components Facilities to interact with special purpose hardware