ABS 4 Presenters: Hong Jung, Binh Lai, Matthew Martin, Joe Mongiat, and Travis Ratcliff

ABS System Provides Anti-Lock Braking System Provides Anti-Lock Braking Wheels are prevented from locking up in hard braking situations where traction is low Wheels are prevented from locking up in hard braking situations where traction is low Motivation for ABS Motivation for ABS Safety - Increased control of vehicle Safety - Increased control of vehicle A selling advantage over non-ABS Equipped Vehicles A selling advantage over non-ABS Equipped Vehicles

Wheel Speed Sensors Constantly evaluate the speed of each wheel Information is sent to the controller upon request ABS Controller ABS Controller Calculates the deceleration rate for each wheel Calculates the deceleration rate for each wheel Determines when to engage the ABS for each wheel independently Determines when to engage the ABS for each wheel independently Sends messages to other components to activate them Sends messages to other components to activate them Brake Fluid Reservoirs Brake Fluid Reservoirs Hold fluid that is diverted from main reservoir Hold fluid that is diverted from main reservoir System Tests System Tests Evaluate the system upon start-up and with each application of the brakes Evaluate the system upon start-up and with each application of the brakes Features

Overview of Requirements Analysis Rapid Prototyping Rapid Prototyping Java applets Java applets Peer review Peer review Model Checking Model Checking Xspin Xspin promela promela UML Analysis UML Analysis Dome Dome

UML Analysis

Use Case Diagram

Use case Problems Problems Brakes in system or not Brakes in system or not Technician interface and actor Technician interface and actor Brake pressure valve actor name Brake pressure valve actor name Solutions Solutions Brakes not in system Brakes not in system Added technician actor and reset use case Added technician actor and reset use case Proper naming for actor, consistent Proper naming for actor, consistent

Class Model

Class Diagram Problems Problems Independent control of each wheel with one ABS controller Independent control of each wheel with one ABS controller Is Brake a class in model? Is Brake a class in model? How to model the pressure valve interface How to model the pressure valve interface Solutions Solutions Methods have associated wheel Methods have associated wheel Brake is viewed as external signal Brake is viewed as external signal Simple interface, increase and decrease Simple interface, increase and decrease

State Diagram

Problems Problems Incorporating our concurrency ideas into model Incorporating our concurrency ideas into model Brake out/in model Brake out/in model Solutions Solutions One concurrent state machine model One concurrent state machine model Brake is left out, viewed as a external signal Brake is left out, viewed as a external signal

Sequence Diagrams

Power-Up/Power-Off

Braking

Model Checking

Promela and XSpin Model Analysis Model Analysis Encoded State Diagram into Promela Encoded State Diagram into Promela Performed system simulation using XSpin Performed system simulation using XSpin

XSpin Simulation Results 1. Power is turned On 2. Test is run and passes 3. Brake is applied 4. Test is run and passes again 5. Brake is released 6. Brake is applied again 7. Test runs and passes 8. ABS engages and then disengages 9. Brake is released 10. Brake is applied once again 11. Test runs and fails this time 12. Fail light is turned on 13. Then technician reset is issued 14. Power is turned on again 15. Test runs and passes 16. Etc …

Critical Properties Safety Properties Safety Properties If the system has a failure it shall not engage until fixed by a technician If the system has a failure it shall not engage until fixed by a technician If the speed of the vehicle is below 15 MPH the system shall not engage If the speed of the vehicle is below 15 MPH the system shall not engage Liveness Properties Liveness Properties If wheel-lockup is imminent the ABS will eventually engage If wheel-lockup is imminent the ABS will eventually engage If a failure occurs within the system the dashboard failure light will eventually be turned on If a failure occurs within the system the dashboard failure light will eventually be turned on

Summary What is ABS? What is ABS? System Provides Anti-Lock Braking. System Provides Anti-Lock Braking. It ’ s embedded system. It ’ s embedded system. UML Analysis UML Analysis We tried to all diagrams simple and precise, but still making sure that we captured all requirements. We tried to all diagrams simple and precise, but still making sure that we captured all requirements. Dome is good, but sometimes difficult to manipulate. Dome is good, but sometimes difficult to manipulate. Model Checking Model Checking Verification is coming. Verification is coming.