Co-simulation Design towards Cyber-Physical Robotic Applications: Leveraging on FMI Standard and CSP Semantics

Designing a software controller for multi-task automated service robotics is becoming increasingly complex. The combination of discrete (cyber) and continuous (physical) domains and multiple engineering fields makes it quite challenging to couple different subsystems as a whole for further verification and validation. Co-simulation is widely used to evaluate connected subsystems in the very early design phase and in an iterative development manner. Leveraging on our previous efforts for a Model-Driven Development and simulation approach, that mainly focused on the software architecture, we propose a co-simulation approach adopting the Functional Mock-up Interface (FMI) standard to co-simulate the software controller with modelled physical plant dynamics. A model coupling approach is defined that involves the model transformation from a physical plant model implementing the FMI interface (denoted as Functional Mock-up Unit, FMU) to a Communicating Sequential Processes (CSP) model. The Master Algorithm is (semi-)automatically generated from a co-simulation model that is formalised with CSP syntax to orchestrate the communication between different FMUs. Additionally, an optimized algorithm with roll-back mechanism is defined to eliminate the delay existing in a feedback loop. Finally, an example is used to illustrate the co-simulation approach, verify its working (at least, for this example) and to analyse the roll-back algorithm.