Modeling and analysis of miniaturized magnetorheological valve for fluidic actuation

Fluidic actuation enables movement in a wide range of mechanical systems, from simple laboratory devices to more complex industrial machinery. Fluids are used to generate motion of mechanical pieces. The term "fluids" encompasses two types of technologies: hydraulics, employing fluids in a liquid state, and pneumatics, which uses gases. Fluidic systems offer significant advantages over traditional mechanical actuation systems, including a high power-to-weight ratio and high forces and torques. Valves are an integral part of fluidic control and are based on different working principles, such as solenoids and servo valves. These mechanisms are quite bulky and power-consuming.Alternatively, valves are enabled by smart materials, such as dielectric elastomer actuators, shape memory alloys, electrorheological, or magnetorheological fluids. This thesis focuses on magnetorheological valves due to their advantages of controllable viscosity, low power consumption, fast response, and simple and compact structure. Magnetorheological fluids consist of ferromagnetic particles dispersed in a carrier medium that align parallel with the lines of an external magnetic field increasing the fluid viscosity. This property is exploited in valves for their switching. The current thesis focuses on the miniaturization of a magnetorheological valve and modeling with regard to the distribution of magnetic field in its interior and with the pressure drop that is developed between its two sides. The functionality is validated experimentally and the results are analyzed. The conventional design of the valve is enhanced by the addition of a soft magnetic material in its core, which together with a coil plays the role of an electropermanent magnet. This addition allows for zeroing of the valve steady-state power consumption, while energy consumption takes place only during state switching.Magnetorheological valves are also used in combination with sensors as part of control systems of dampers providing damping feedback for the valve control. Inthis direction, multiple works studied the creation of displacement and force self-sensing valves avoiding the use of external sensors and increasing the compactness and robustness of the system. This thesis aims at investigating further the pressure self-sensing phenomenon in magnetorheological valves, which is based on electromagnetic induction. Induced signals are measured in a magnetorheological valve with two coils. Additionally, a microfluidic device attempts to imitate the structure of the valve, in order to observe the phenomenon microscopically.Finally, the application of the developed miniaturized valve in a wearable device for diabetic patients is studied. Diabetic amputation is attributed to two reasons: high plantar pressures and peripheral neuropathy that leads to the loss of pain feeling and ulceration creation. Existing ulceration prevention methods rely on bulky mechanical systems, reducing patients' quality of life. This work presents a wearable device in the form of an insole, consisting of multiple modules and battery-powered electronics for control. Each module contains a MR valve and is filled with MR fluid, while it is capable of sustaining or offloading foot load. The entire footwear system is presented, including a 31-module insole, plantar pressure measurement methods, control electronics, and preliminary results that are promising for the future use of the application as a prescribed medical devic