A Smart Fluid-Hydraulic System Based on MRF Valve Control and Its Application in Flexible Grasping

This study proposes a smart fluid hydraulic system based on magnetorheological fluid (MRF) valve control for flexible gripping. An MRF micro-servo valve (MRF-MSV) that integrates an excitation coil and micro-textured damping channels has been designed. Through experiments and simulations based on the Bingham model, the hydraulic resistance characteristics of the valve under different currents are analyzed, which confirms the enhancing effect of the micro-textured channels on hydraulic resistance. Furthermore, experiments demonstrate that at an excitation current of 3 A, the valve body's resistance pressure reaches 1191.4 kPa with a micro-textured height of 0.2 mm, representing an 81.9% increase compared to the valve without micro-textured channels (655 kPa). Integrating the MRF-MSV with a soft actuator enables dynamic control of bending and grasping motions, with a maximum bending angle of 180°. Then, an MRF variable-stiffness soft actuator (MRF-VSSA) is developed. When a current of 1.2 A is applied to the variable-stiffness module, the fingertip force increases from 2.69 to 5.05 N, showing an 87.7% increase. Finally, an MRF-based smart fluid-hydraulic system is constructed, and a magnetically driven manipulator is developed. Experiments indicate that this manipulator can execute complex hand movements and stably grasp objects of various shapes without causing damage.