Design, sensing, and control of soft multi-axis fluidic actuators for robotic manipulation

The emergence of actuators with controllable compliance, such as soft fluidic actuators, has been indispensable for complex robotic manipulation and human-robot interaction research. In this work, we develop novel modular soft robotic pneumatic actuator arrays capable of carrying out complex motions and manipulation tasks. First, the design and manufacturing of a soft bi-directional pneumatic bellows actuator module, which can contract in vacuum and extend in positive pressure, is outlined. To sense motions and achieve closed loop control of orientation and actuator array length, inertial measurement units and custom soft wire potentiometers are used. Then, three bi-directional pneumatic bellows actuators are combined with sensors into modular arrays that can extend, contract, bend, and twist depending on the amount of pressure applied to each module. These arrays can be stacked in series to achieve even more complex motions and to complete unique manipulation tasks. To showcase the versatility of the soft robotic manipulator, several peripheral mechanisms are also developed including a particle jamming gripper that is used to grip and unscrew items, a center contraction module to promote buckling for twisting, and contraction-based foam plates for gripping. For this system, simulation environments, kinematic models, and multi-actuator multi-axis control strategies are developed. Demonstrations are shown to illustrate the manipulation capabilities of this system. Additionally, the use of magnetorheological fluid for soft hydraulic actuation is also explored. For these soft actuation mechanisms, the use of magnetorheological fluids, liquid metal coils, compliant magnetic composites, and silicone flexures are tested. Magnetic field models and fluid scaling laws are outlined. Finally, these actuators are used to demonstrate the operation of compliant bistable valves, soft multi-fingered PneuNets, and a new force-amplified magnetorheological fluid gripper.M.S