Adaptive control to actively damp bistabilities in highly interrupted turning processes using a hardware-in-the-loop simulator

Interruptions in turning make the process forces non-smooth and nonlinear. Smooth nonlinear cutting forces result in the process of being stable for small perturbations and unstable for larger ones. Re-entry after interruptions acts as perturbations making the process exhibit bistabilities. Stability for such processes is characterized by Hopf bifurcations resulting in lobes and period-doubling bifurcations resulting in narrow unstable lenses. Interrupted turning remains an important technological problem, and since experimentation to investigate and mitigate instabilities are difficult, this paper instead emulates these phenomena on a controlled hardware-in-the-loop simulator. Emulated cutting on the simulator confirms that bistabilities persist with lobes and lenses. Cutting in bistable regimes should be avoided due to conditional stability. Hence, we demonstrate the use of active damping to stabilize cutting with interruptions/perturbations. To stabilize cutting with small/large perturbations, we successfully implement an adaptive gain tuning scheme that adapts the gain to the level of interruption/perturbation. To facilitate real-time detection of instabilities and their control, we characterize the efficacy of the updating scheme for its dependence on the time required to update the gain and for its dependence on the levels of gain increments. We observe that higher gain increments with shorter updating times result in the process being stabilized quicker. Such results are instructive for active damping of real processes exhibiting conditional instabilities prone to perturbations.

A Circuit-Level Implementation of Voltage-Tuning Scheme for Realizing Optical PAM-4 Using Three-Segment Microring Modulator

Silicon Photonics, as one of the solutions to satisfy ever-increasing data bandwidth growth, becomes more challenging due to the latest technologies such as Internet of Things (IoT). Higher order pulse amplitude modulation (PAM) schemes is one of the answers to push towards higher data transmission in the presence of bandwidth limited optical devices. In this paper, we have implemented a circuit-level PAM-4 transmitter design based on the voltage-tuning scheme for realizing optical PAM-4 using a three-segment microring modulator. Simulation results based on the extracted layout using TSMC 65nm LP technology and IMEC-ePIXfab SiPhotonics ISIPP50G technology show that our proposed circuit-level transmitter structure is able to achieve PAM-4 data rate of 25-Gb/s with extinction ratio of 9dB and PAM-4 energy efficiency of 0.5pJ/bit. The results also verify that the scheme is able to achieve high tuning flexibility, but the proposed transmitter will consume more power as a result.

PID controller tuning using bacterial Quorum Sensing (QS)

Objective: PID controllers are widely used to operate AC motors due to their simplicity and easy implementation. However, adjusting its parameters in search of an optimal scheme can be complex because it requires manual tuning by trial and error. This research aims to implement an optimized tuning scheme through a search based on the idealized behavior of a community of bacteria and its Quorum Sensing (QS). Methodology: A closed-loop system model with PID control considering disturbances is proposed in order to tune a disturbance-resistant controller. The response of the model is calculated using a search that mimics a simplified model of bacterial behavior. The scheme uses ITSE (Integral Time Squared Error) as the performance index. Results: The tuning resulting from the proposed scheme was evaluated by simulation and compared with tunings of the same model made by Root Locus and Genetic Algorithms (GA). The results showed a satisfactory response according the design criteria. Conclusions: Nowadays, PID controllers are still basic industrial control tools, particularly important in motor operation. The performance of these controls depends fundamentally on the design of their gain. In the case of complex plants, additional tools are required to facilitate PID tuning. We propose an intelligent and bio-inspired tuning scheme that demonstrates high performance in laboratory tests. Financing: University Francisco José de Caldas through the project 1-72-578-18.