Developing a decentralized peripheral Profibus core for a Xilinx FPGA

Abstract

The McTronX research group of the North–West University has over some years established a knowledge base in active magnetic bearing (AMB) systems. In 2009, an AMB system that met industrial standards in being robust, reliable and economical was developed by the research group. The digital control of the AMB system was implemented with the use of a dedicated single–board computer and communication hardware that interface with the motor drive electronics, power amplifiers and sensor drive units of the AMB system. A Xilinx® field programmable gate array (FPGA), connected to the single–board computer, was used to control the AMB system. The AMB system was designed to be used in a helium blower application and to form a basis for AMB and digital control research. A programmable logic controller (PLC) is connected to the controller to operate the AMB system. To establish communication between the PLC and the FPGA, the Fieldbus standard PROFIBUS DP was chosen as being a robust industrial standard communication protocol. To reduce the cost of the entire system, the need arose to implement the PROFIBUS DP protocol on the current FPGA of the system. This project involves the research, design, implementation, verification and validation of the PROFIBUS DP protocol on a Xilinx® Virtex©–5 FPGA. The PROFIBUS DP standard was researched, analyzed and developed in VHDL for the specific Xilinx® Virtex©–5 FPGA. The implemented protocol is used to establish a standardized PROFIBUS DP network between the PLC and the FPGA controller. Through simulation the basic protocol was tested and later implemented in the real–time environment. Intensive verification and validation was done to ensure that the developed protocol conforms to the robust PROFIBUS DP standard and simultaneously meet the requirements and specifications of the AMB control system. This dissertation documents the entire PROFIBUS implementation process, from standard analysis through to verification and validation of the developed protocol. In conclusion, the developed protocol is compared against a commercial off–the–shelf PROFIBUS PMC module. It was found that the VHDL–based PROFIBUS DP protocol not only competes well with the commercial PROFIBUS device, but also outperforms the device in various aspects.