Implementation and comparative analysis of fractional order PID Embedded Controllers, applied to speed control of a robotic prosthesis

This paper is part of the 'Hand of Hope' research project, which seeks to develop low-cost robotic prostheses for people with motor disabilities in their upper limbs. The objective of this research is to design and implement a fractional order PID embedded controller (FOPID), applied to the speed regulation of the elbow joint based on DC motor, in a robotic prosthesis. The set of parameters for the tuning of a FOPID controller are five: Proportional constant, integration constant, derivative constant, and non-integer orders of the integral and derivative terms (K_P, K_I, K_D, λ, μ). In order to fulfill the objective, three phases were executed: First, the several methodologies involved in the design and implementation of FOPID controllers were applied in an autonomous embedded system; then, they were implemented and applied to a mechatronic system; finally, the performance of the fractional controllers was analyzed and compared, the comparison of the controllers was performed based on the time parameters (settling time, overshoot), and the performance indexes (IAE, ITAE, ISE, and ITSE). As results of the present work: 14 types of fractional controllers were designed, of which 9 were implemented in an embedded system based on the multicore FPGA/Processor architecture, and the programming of the mathematical control functions were developed in LabVIEW FPGA and RT; after the experimental evaluation, the embedded controller with higher performance was the FOPID Ziegler-Nichols/Nelder-Mead/ISE, the results obtained were Ts = 0.22s and PO=7.1S%.