A novel and advanced control method based on Fuzzy-PI for joint wear simulators

Abstract

Background This research presents a novel approach to improve the control performance of joint wear simulators that are used for testing prostheses. For this application, precise controller tuning and minimal tracking errors are essential to meet compliance standards like ISO 18192-1 or ISO 14242-3, and to test under realistic activities of daily living (ADL) scenarios. Methods To address these challenges, the authors propose employing a single-input-multiple-output (SIMO) fuzzy logic control system to augment the traditional proportional-integral (PI) tuning process for joint simulation. To facilitate the development and testing of potential controllers, we utilize a benchtop hardware-in-the-loop (HiL) simulation environment, which facilitated cost-effective rapid control prototyping (RCP). This HiL simulation mimicked joint motion and loading conditions akin to real spinal and hip wear simulators. The objectives of the study are to develop a robust controller for tribological applications and joint simulators and investigate the use of Fuzzy Logic as a possible enhancement of the control system. The Fuzzy-PI controller combines the conventional PI controller with Fuzzy Logic acting as a supervisor, enhancing overall control performance and robustness. The controller adapts to the system's operating range and performance characteristics through a combination of membership functions and control rules. Results Results indicate that for ISO profiles with a fixed 1Hz frequency, both the traditional PI controller and the Fuzzy-PI controller perform equally well. However, as the frequency of the ISO profile increases or when handling ADL profiles with multiple frequency components, the Fuzzy-PI controller outperforms the PI controller. This was attributed to Fuzzy-PI's real-time adaptive capability to tune PI gains as frequency demands changed through a profile, providing a more robust and superior performance, particularly in challenging scenarios. Conclusions In conclusion, the Fuzzy-PI controller represents a promising advancement for joint wear simulators, offering improved control capabilities and better simulation of real-world physiological conditions.