Femtocore: An Application Specific Processor for Vertically Integrated High Performance Real-Time Controls

Filippo Savi,Jayakrishnan Harikumaran,Chris Gerada,Giampaolo Buticchi,Pat Wheeler,Davide Barater

doi:10.1109/ojies.2021.3112124

Abstract

In applications that require a high availability and high performance (for example aerospace),modular power electronics and multi-phase machines represent an advantageous choice. In this framework, a control system able to handle a high number of PWM signals and communication interfaces as well as featuring a high computational power is required. This paper proposes a novel HDL plus soft-core approach to be implemented on System-on-Chip hardware which allows for the efficient and modular implementation of the modern control techniques with strong guarantees in terms of determinism. The proposal lies in the adoption of a very simplified and optimized floating-point soft-core, the femtocore (fCore) and its tool-chain, which allows C-like implementation of complex algorithms in a HDL-design power electronics control framework. Several fCore units can be arranged for parallel processing to handle the time requirements of a complex modular system even with low sampling time (100 kHz or more). The proposed architecture is experimentally validated in a proof-of-concept, six-phase electric machine including a comparison against a traditional method.

Highlights

Advances in the field of static power conversion and machine drives have started to put a lot of strain on the traditional architectures used for their control systems
The first of several factors contributing to this issue is the advent of wide-bandgap devices, Silicon Carbide (SiC) and Gallium Nitride (GaN) transistors, which can be operated at very high switching frequencies in the range of hundreds of kilohertz to megahertz range [1], [2], without significant increases in switching losses, reducing the need for bulky and expensive filtering components
Another trend exacerbating this issue is the ever growing adoption of modern high performance control techniques, such as Model Predictive control (MPC) [3], [4] where a mathematical model is used to predict the effect that the controller actions will have on the physical system, one or more cycles in the future

Summary

INTRODUCTION

Advances in the field of static power conversion and machine drives have started to put a lot of strain on the traditional architectures used for their control systems. SAVI ET AL.: FEMTOCORE: AN APPLICATION SPECIFIC PROCESSOR FOR VERTICALLY INTEGRATED HIGH PERFORMANCE REAL-TIME CONTROLS the critical mission components can have catastrophic consequences, like the loss of a vehicle, large oil spills and potentially even loss of lives For these reasons, both reliability and fault tolerance are key design specifications in such mission critical applications. As high frequency designs need to employ caches and deeper pipelines in order to hit the required frequencies, and multi-core processors, while utilizing unaltered cores, need to deal with the problems brought about by inter process communication (IPC) and shared resource access contention,with similar effects [12]–[14] While these trade-offs might be acceptable in most applications, they are not acceptable for mission critical hard real-time.

SYSTEM ARCHITECTURE

COMPARATIVE ANALYSIS

CONCLUSION