01OC2000 Slide 1 © 2000 General Motors Corporation James B. Kolhoff Real Time Scheduling Issues in Powertrain Controls James B. Kolhoff Engineering Group Manager Front Wheel Drive Controller Team General Motors Powertrain

01OC2000 Slide 2 © 2000 General Motors Corporation James B. Kolhoff Overview of Presentation n GMPT Electronics Integration & SW - Group & Product n Scheduling Requirements and Problem n Solution n Distributed architecture n Next step

01OC2000 Slide 3 © 2000 General Motors Corporation James B. Kolhoff Group and Product Background Group GMPT is a division of General Motors, responsible for engine, transmission, powertrain controls engineering and manufacture Electronics Integration & Software (EI&S) is a product engineering team responsible for the electronics and software for powertrain controls Product EI&S end product is an embedded microprocessor control module(s) that controls and diagnoses engine, transmission, and vehicle functions. n Multiple end products (ECM, TCM, PCM) with different feature content (internal GM and external customers) n Multiple controller and compiler suppliers n Other vehicle module interfaces n Development and production tool interfaces n Controller: 32bit uc, 1Mb ROM, 150+ pins

01OC2000 Slide 4 © 2000 General Motors Corporation James B. Kolhoff Scheduling requirements n Two categories of task - time synchronous, engine event synchronous u Time: 3.125ms, 6.25, 12.5, 25, 100 ms u Engine: crankshaft synchronous, cam synchronous n The engine event tasks cause the processing power to be consumed in direct proportion to engine speed n Engine event synchronous tasks have harder deadlines and higher priorities than time based tasks u 8 cylinder engine engine, event sw task execution time 1ms u 600 rpm: 25ms event rate, 4% available processor thruput u 7000 rpm: 2.1ms event rate, 48% available processor thruput

01OC2000 Slide 5 © 2000 General Motors Corporation James B. Kolhoff Task scheduling

01OC2000 Slide 6 © 2000 General Motors Corporation James B. Kolhoff Scheduling Problems n Most critical scheduling problem was task deadlines missed at higher engine speeds n Basic root cause: Limited processing power u Using low cost microprocessor u Low clock speed for EMC performance u Too late in program to make processor change n ROM limited so we can’t do ROM tradeoffs for thruput n Fixed point math operations u Library not optimized for performance n Requirement of ANSI-C for code portability u Not designed for performance n SW Design and Coding Standards u Designed for reuse and readability, not performance

01OC2000 Slide 7 © 2000 General Motors Corporation James B. Kolhoff Solutions applied n Re-design software for improved efficiency u Significant work effort, potential loss of function, repeat verification n Optimize libraries to take advantage of processor specifics u Significant work effort, reduces reuse, increases verification requirements n Revise coding standards to maximize efficiency u At the expense of portability and reuse u Rework and revalidation across large number of engineers n Biggest bang for the buck - dynamic scheduling u Can localize redesign at areas of maximum benefit u Time tasks slower than 25ms rates are insignificant to the problem

01OC2000 Slide 8 © 2000 General Motors Corporation James B. Kolhoff Dynamic scheduling n Objective: Reduce execution requirements at higher engine speeds u Difficult to individually disable or redesign functions n Developed engine speed zones approach u Different function level in each zone u Simplifies coordination of scheduling change n In middle engine speed range, divide function across multiple engine events u Balance load across multiple cylinder events n At highest engine speeds, significantly simplify some functions u Engine states don’t change every cylinder

01OC2000 Slide 9 © 2000 General Motors Corporation James B. Kolhoff Effect of Dynamic Scheduling

01OC2000 Slide 10 © 2000 General Motors Corporation James B. Kolhoff Controller System Topologies PCM Vehicle Electrical System Engine Electrical System Transmission Electrical System ECM TCM Vehicle Electrical System Engine Electrical System Transmission Electrical System Legend Electrical System Control Module Electrical Interface Powertrain Control ModuleEngine/Transmission Control Modules

01OC2000 Slide 11 © 2000 General Motors Corporation James B. Kolhoff Distributed architecture n Controller systems architecture for GMPT is changing to separate engine controller / transmission controller u For reasons of powertrain portfolio management n This architecture reduces the computing power needed in any single controller n Scheduling and thruput still needed to be carefully managed u System partitioning plays a key role u Inter-module Communications uses some of the freed up thruput

01OC2000 Slide 12 © 2000 General Motors Corporation James B. Kolhoff Future n Microprocessor power has grown dramatically over the past 5 years n At the same time, costs have fallen dramatically for this power n With the microprocessors available for the projects planned, thruput will not be the significant problem it has been in the past n Simulation and schedule/thruput budgets are the next steps