FPGA-PLC-based multi-channel position measurement system

Abstract

The existing Programmable Logic Controller (PLC) based on microprocessors (μp) or micro-controllers (μc) are commonly used in the industry for various instrumentation and control applications. PLC exhibits limitations such as less flexibility, poor scanning time, slower speed, and degraded response for high-speed industrial applications due to its fixed hardware and serial execution mechanism. A new Field Programmable Gate Array (FPGA) based PLC multi-channel High Speed Counter (HSC) module has been proposed, enhancing performance and flexibility compared to the existing PLC-HSC module. The proposed FPGA-PLC-HSC module has a 2-phase 2-Input counter with resolutions of 1X, 2X, and 4X which improve performance in terms of accuracy for position speed, and direction measurement applications. The FPGA-PLC-HSC module is implemented with the feedback node method and the shift register method inside LabVIEW FPGA along with device utilization. The simulation results show that the FPGA-PLC-HSC module has faster scanning time, good linearity, better resolution, maximum supporting input frequency, and counting frequency. For experimental purposes, an optical encoder M110960 (E8P-512-118-S-D-M-B) with a signal conditioning circuit is connected to the NI-myRIO-1900 FPGA platform. The experimental results point out that the proposed FPGA-PLC-HSC module offers faster scanning time, better accuracy and linearity in 1X, 2X, and 4X resolution.