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In this paper, modeling and robust control strategy for a new control-optimized piezoelectric microgripper are presented. The device to be controlled is a piezoelectric flexible mechanism dedicated to micromanipulation. It has been previously designed with an emphasis to control strategy, using a new topological optimization method, by considering innovative frequency-based criteria. A complete non-linear model relating the voltage and the resulting deflection is established taking into account hysteresis as a plurilinear model subjected to uncertainties. The approach used for controlling the actuator tip is based on a mixed High Authority Control (HAC) / Low Authority Control (LAC) strategy for designing a wide-band regulator. It consists of a Positive Position Feedback (PPF) damping controller approach combined with a low-frequency integral controller which is shown to have robustness performances as good as a RST-based robust pole placement approach for the microgripper. The rejection of the vibrations, naturally induced by the flexible structure, and the control of the tip displacement have been successfully performed. Because we had taken into account frequency-based criteria from the first designing step of our device, we demonstrate that the tuning of the HAC/LAC can be easily performed and leads to low regulator order.

In this work, the design modeling and testing of a compact and lightweight hydraulic actuation system is presented. Compared to similar compact actuators found in the literature, our system considerably increases the work density while maintaining an equivalent force-to-volume ratio. An analytical model that is able to accurately predict the quasi-static behavior of the actuator has been developed and experimentally validated. Existing models in the literature are able to predict only one performance parameter at a time – either the force or the contraction – from the imposed pressure and the exteroceptive measurement of the other performance parameter. Due to the design configuration chosen for the actuator, our analytical model is able to simultaneously predict both the force and the contraction by using theknowledge of two proprioceptive parameters of the fluid circuit (imposed volume and measurement of the pressure). The latter is particularly interesting, as it enables a precise estimate of the muscle behavior, only through the known parameters located at the fluid-transfer system, and not directly in the muscle, which is of crucial importance to simplify instrumentation and compactness of the actuation system. Four in-house fabricated muscles, with diameters down to 1.5 mm, have been tested with internal pressures up to 1.7 MPa. Theexperimental results showed in all cases a very good agreement with the predicted performances, thus validating the analytical model developed.