Model-Based Position Control of Dielectric Fluid Actuators via High-Frequency Modulation

This work presents a simulation study of a model-based closed-loop control strategy for zipping dielectric fluid actuators (DFAs). Due to their intrinsic multilayer structure, DFAs are prone to charge retention, which causes force and stroke relaxation over time. Charge retention is typically mitigated by periodically reversing the polarity of the applied voltage, to maintain the fluid–polymer interfaces electrically neutral. This polarity inversion is generally implemented heuristically in open-loop control strategies. Here, we formalize this modulation within a closed-loop control framework, and derive model-based tuning laws for the controller parameters. The proposed control architecture consists of a proportional–integral regulator cascaded with a square root term, whose output modulates the amplitude of a fixed-frequency polarity-inverting voltage signal. The theoretical analysis of the resulting closed-loop system is carried out using a physics-based model of the DFA, calibrated to reproduce the response of an experimental prototype. Simulations are conducted to evaluate controller performance under different design parameters, reflecting various target closed-loop behaviors. The proposed formulation provides a foundation for future investigations into more advanced control strategies for DFAs.