In this paper, we propose a new modeling and identification approach for piezoelectric-actuated stages cascading hysteresis nonlinearity with linear dynamics, which is described as a Hammerstein-like structure. In the proposed approach, the hysteresis and linear dynamics together with the delay time and higher order dynamic behaviors are obtained with three data-driven identification steps under designed input signals. In the first step, the step input signal is applied to estimate the delay time of the piezoelectric-actuated stages. In the second step, the autoregression with exogenous signal identification algorithm is adopted to identify the linear dynamics using a small-amplitude band-limited white noise input signal. In the third step, with the identified linear dynamics model, the parameters of the rate-independent Prandtl-Ishlinskii hysteresis model are identified by the particle swarm optimization algorithm using a simple low-frequency triangle input signal with different amplitudes. Finally, the experimental results on a piezoelectric-actuated stage show that both the hysteresis and dynamic behaviors of the piezoelectric-actuated stage are well predicted by the proposed modeling method. In addition, we provide the analysis of quantitative prediction errors of the identified model with comparison to experimental data, which clearly demonstrate the effectiveness of the proposed approach.
EDITORIAL article Front. Robot. AI, 30 April 2021 | https://doi.org/10.3389/frobt.2021.676406
No abstract is provided for this article.
Guoying Gu designs bioinspired soft robots, with applications including soft wearable rehabilitation robots, bioinspired robotic systems for grasping and manipulation, and soft sensing systems for human-robot interaction. He discusses the inherently multi-disciplinary nature of soft robotics research and particularly the deep back-and-forth connection with neuroscience.
Fabric-based pneumatic actuators (FPAs) are promising in the design of soft wearable assistive gloves, owing to the lightweight and compliant advantages. However, the existing FPAs generally suffer from small output force, limiting users' applications. This letter presents a new class of high-force FPAs (HFFPAs) that harness asymmetric chambers and interference-reinforced structure for soft wearable assistive gloves. Different from the classical FPAs with symmetric chamber (i.e., Line chamber) fabricated by two identical layers of textiles, we design FPAs with asymmetric chambers (i.e., Arch and Semicircle chambers) fabricated by two unidentical layers of textiles. To further improve the output force, we introduce interference pads on adjacent-pleat surfaces to reinforce the stiffness of the FPAs. We next characterize the joint torque and the tip blocked force of six kinds of FPAs (i.e., Line, Line-pad, Arch, Arch-pad, Semicircle, and Semicircle-pad FPAs). Experimental results demonstrate that the Semicircle-pad FPA shows the best performance, whose joint torque and tip blocked force are improved by 510% and 478% at 150 kPa than the commonly used Line FPA. We further integrate HFFPAs on soft wearable assistive gloves and verify the improved assistive capability in grasping multiscale objects with irregular geometry, covering a wide weight range (8-559 g) in activities of daily living (ADLs).
This paper presents a novel real-time inverse hysteresis compensation method for piezoelectric actuators exhibiting asymmetric hysteresis effect. The proposed method directly utilizes a modified Prandtl-Ishlinskii hysteresis model to characterize the inverse hysteresis effect of piezoelectric actuators. The hysteresis model is then cascaded in the feedforward path for hysteresis cancellation. It avoids the complex and difficult mathematical procedure for constructing an inversion of the hysteresis model. For the purpose of validation, an experimental platform is established. To identify the model parameters, an adaptive particle swarm optimization algorithm is adopted. Based on the identified model parameters, a real-time feedforward controller is implemented for fast hysteresis compensation. Finally, tests are conducted with various kinds of trajectories. The experimental results show that the tracking errors caused by the hysteresis effect are reduced by about 90%, which clearly demonstrates the effectiveness of the proposed inverse compensation method with the modified Prandtl-Ishlinskii model.