SIRIUS 2001 A Drive-by-Wire University Project

Transcription

1 SIRIUS 2001 A Drive-by-Wire University Project ARTES - Volvo Cars Per Johannessen Volvo Car Corporation Our Vision Summer

2 Design Task Build a drive-by-wire car with four wheel steering and both right and left hand side steering November 2000 Organization Project Partners Man hours 41 M.Sc. ME students 2 Industrial Ph.D. students as project leaders Budget ~ USD 2

3 Guiding Principles Design the system as a whole, as opposed to independently designed subsystems It is the system that should be safe, not the components Utilize redundancy in a top down approach Minimize hardware, additional hardware increases complexity, cost, failure rate and weight All components will fail, sooner or later Design Process Function Class of Failure Failure Effects on System Severity Driver Acceleration Deacceleration Acceleration Omission No acceleration available Car eventualy stops Marginal Commission Sudden acceleration Car increases its speed rapidly Critical Stuck Constant acceleration Car increases its speed Critical Deacceleration Omission No deacceleration possible Car can't stop Catastrophic Commission Wheels lock Car stops during skidding Catastrophic Stuck Constant deacceleration Car continues to brake Critical Design Task Steering Use Case Steering Omission No control of steering Car looses stability Catastrophic Commission Steering when unintended Car changes trajectory unintended Catastrophic Stuck Car maintains its turning angle Car continues on its trajectory Critical FFA Design Requirements Redundancy Strategies Physical Car Non-redundant HW-architecture Redundant HW-architecture 3

4 Dependability Analysis Use Case FFA Brake car FFA Fault Tree Synthesis Driver Steer car FTA Failure OR Class Diagram IF-FMEA AND AND Brake System FL-Brake FR-Brake IF-FMEA AND RL-Brake RR-Brake IF-FMEA ABS Status Activate() Pedal Position Press() MESC HiP-HOPS Design Requirements Driver Acceleration Deacceleration Steering Function Class of Failure Failure Effects on System Severity Acceleration Omission No acceleration available Car eventually stops Marginal Commission Sudden acceleration Car increases its speed rapidly Critical Stuck Constant acceleration Car increases its speed Critical Deacceleration Omission No deacceleration possible Car can't stop Catastrophic Commission Wheels lock Car stops during skidding Catastrophic Stuck Constant deacceleration Car continues to brake Critical Steering Omission No control of steering Car looses stability Catastrophic Commission Steering when unintended Car changes trajectory unintended Catastrophic Stuck Car maintains its turning angle Car continues on its trajectory Critical Acceleration must fail in an omission state Braking must fail in a stuck state Steering must fail in a stuck state Design requirements on fail-safe or limp-home states 4

5 Non-redundant HW architecture Add a computer node wherever there is actuators or sensors Low overhead cost Integrated By-Wire Sensor A Actuator A Sensor B Sensor C. Sensor Adaption Global. Actuator B Actuator C. Sensor M Actuator N Increases the possibilities in the design of the system Increases the complexity in the system Similar for many mechatronic systems 5

6 Redundancy Strategies Sensor A Actuator A Intrinsic Redundancy Sensor B Sensor C. Sensor M Sensor Adaption Global. Actuator B Actuator C. Redundancy Actuator N Scalable Software Redundancy A system approach supports a high degree of system utilization Utilize redundancy in a top down approach Intrinsic Redundancy Already in the system More actuators or sensors than degrees of freedom Challenge to identify and utilize Steer with wheel brakes 6

7 Intrinsic Redundancy Already in the system More actuators or sensors than degrees of freedom Challenge to identify and utilize Steer with wheel brakes 3 out of 4 wheel brakes Intrinsic Redundancy Already in the system More actuators or sensors than degrees of freedom Challenge to identify and utilize Steer with wheel brakes 3 out of 4 wheel brakes Brake with engine 7

8 Scalable Software Redundancy Minimize communication Broadcast basic sensor data Allocate control to actuator nodes Increase fault tolerance for transient failures Network Topology 8

9 Electrical Architecture Using a TTP communication network Node_C1 Node_C2 s s Communication and execution of tasks are Node_FL Node_FR scheduled off-line in b b TTTech tool-suite s s b Node_RL Node_RR b Predictable in the time domain Steer System 4-wheel steering electro-mechanical actuators Individually controlled wheels 2WS Parallell 4WS 9

10 Brake System electro-hydraulical brakes Individually controlled wheel brakes Aditional functionality, e.g. ABS, can be implemented in software More powerfull than traditional system Result May

11 Pure Driving Pleasure May