Design of Interface in Co-simulation for Electric Power Assisted Steering System Development

Interface and causality have important effects on the co-simulation used in vehicle system development. In this paper we analyzed these effects by modeling a co-simulated dual mass-spring-damper system as a sampled-data system. By stability and frequency domain analysis we find that the co-simulation interface needs be designed where the coupling interface is less stiff and the force variable should be applied in the direction of larger mass, natural frequency and damping ratio. The analytical results have been verified through two test cases of co-simulation in electric power assisted steering (EPAS) system development: a multi-rate offline co-simulation and a hardware-in-loop (HIL) simulation. Both test cases showed more consistent and stable results using the suggested interface design.