Power-Window Control A design exploration using Felix VCC Claudio Pinello EE249 Fall 1998 Prof. Alberto Sangiovanni-Vincentelli Mentor: Dr. Alberto Ferrari

Outline Motivation Design description Possible architectures Simulation results Conclusions

Motivation Test the Felix design methodology on a real industrial example Evaluate different architectures and define the level of details needed to carry out the estimation correctly –communication refinement –interrupt handling

Power Window Control Window actuated by electric motor programmable logic de-couples motor commands form input switches automatic stop of motor at the end of the run conflicts resolution for multiple inputs glitches filtration (de-bouncing)

Behavioral Description

Controller Hierarchy

Controller Policy

Candidate Architectures HC11

Candidate Architectures RemoteLocal This is obviously a superset of the previous one: more electronics, less wiring (especially for symmetry)

A First Mapping No events lost: low cpu utilization

Load Models CPU load model –one asynchronous task, constant load (Poisson mean inter.time 8ms, load 700 cycles) –one periodic task, random load (period 4ms, load normal distr. mean=700 var. 100 cycles) CAN-BUS load model –two Poisson streams of integers (mean inter.time 30ms and 40ms)

Load Models

Gantt Charts Behavior I_25 has higher priority but preemption is disabled

Gantt Charts Behavior I_25 has higher priority and preemption is enabled

Communication Refinements Interrupt handler overload

Simulation Diagram (single  P)

Simulation Diagram (double  P)

Simulation Results Processor model Motorola HC11 at 10Mhz clock speed No difference in cpu utilization: in 15 seconds the number of switches operations is very limited However the time to react to a command increases due to the communication over the CAN-BUS (125000bps)

Future Work Relate reaction time to actual position change Evaluate different inputs reading techniques –polling vs. interrupt Add functionality to the controller –interaction with power door-locks –interaction with alarm and air-conditioning systems

Conclusions A model of the cpu and bus load has been developed Two mappings: –the centralized architecture has a shorter reaction time –the distributed architecture reduces greatly the wiring across the car