Hardware Fuzzy Scheduler for Real-Time Independent Tasks

Several scheduling algorithms that have been proposed for Real-Time Operating System (RTOS) are supposed to be optimal. However, optimal scheduling is only theoretical due to the possibility of system overload where it cannot meet the deadlines of tasks. Besides, these algorithms are implemented in the RTOS, which generates additional overheads that can lead to the "nonscheduling" of certain independent tasks. In this paper, we propose an original solution for nonschedulable independent tasks in embedded systems. This solution, named Hybrid Fuzzy Earliest Deadline First Scheduling algorithm (HFEDFS), is based on the Earliest Deadline First algorithm (EDF) and Fuzzy Logic. It is characterized by a rejection policy and a rescheduling mechanism. The experimental results show that our proposed algorithm improves the system's performance. To reduce extra overheads of RTOS, this algorithm is implemented on a Field-Programmable Gate Array (FPGA) circuit (Xilinx Virtex-5 LX50T-1156 board from DIGILENT).