Torsional actuators are a class of artificial muscle technology that generates torque and produces rotary motion in response to various stimuli. This paper presents a novel torsional actuator combining an origami-inspired twisting skeleton and an artificial muscle. The process of torsional actuator design starts from identifying a foldable twisting skeleton which is capable of achieving helical motion thereby translating linear motion to rotational motion. This is followed by the integration of an artificial muscle to drive the twisting skeleton. Kinematics of both the twisting skeleton and artificial muscle are analyzed. Following the design and kinematic analysis, a prototype is developed by bonding 3D printed polylactic acid (PLA) parts and thermoplastic polyurethane (TPU) films to form the twisting skeleton and laminating TPU membranes by using heat sealing tools to form the artificial muscle. A pneumatic control system is built to evaluate the performances of torsional actuator by testing the relationship between twisting angle, air pressure, driving force and output torque. Experimental results show that the relationship between air pressure, driving force and output torque is proportional at a given twisting angle. The novel torsional actuator augmenting an origami-inspired skeleton and soft artificial muscle leads to simplified analytical model and has potential of driving robotic systems in environment where pneumatically actuated systems are preferred over electrical machines and drives.

This paper presents a novel approach for developing robotic grippers with variable stiffness hinges for dexterous grasps. This approach for the first time uses pneumatically actuated pouch actuators to fold and unfold morphable flaps of flexure hinges thus change stiffness of the hinge. By varying the air pressure in pouch actuators, the flexure hinge morphs into a beam with various open sections while the flaps bend, enabling stiffness variation of the flexure hinge. This design allows 3D printing of the flexure hinge using printable soft filaments. Utilizing the variable stiffness flexure hinges as the joints of robotic fingers, a light-weight and low-cost two-fingered tendon driven robotic gripper is developed. The stiffness variation caused due to the shape morphing of flexure hinges is studied by conducting static tests on fabricated hinges with different flap angles and on a flexure hinge with flaps that are bent by pouch actuators subjected to various pressures. Multiple grasp modes of the two-fingered gripper are demonstrated by grasping objects with various geometric shapes. The gripper is then integrated with a robot manipulator in a teleoperation setup for conducting a pick-and-place operation in a confined environment.

Minimally invasive surgery (MIS) is one of the most challenging techniques for robot designers due to the limited size of access points, the high miniaturization level, and the dexterity needed for performing surgical tasks. Conversely, only a few microfabrication technologies are currently available for developing such small-sized systems, which allow safe operations in human bodies. In order to match these challenges in MIS, both design and integration of actuation systems should proceed in parallel with an identification of most effective transmission mechanisms and kinematics. In this paper, an origami parallel module that generates two rotations and one translation is integrated with a twisting module and a compliant gripper to form a novel four-degree-of-freedom grasper. The rotational motion leads to the pitch and yaw motion of the gripper, while the translational motion is converted to a roll motion of the gripper via the twisting module that is stacked on top of the parallel module. In light of plane-symmetric properties of the origami structure in the parallel module, both inverse and forward kinematics are resolved with a geometric approach, revealing a unique joint space and a kinematic mapping of the parallel module, leading to the design of two sets of on-board actuation systems. During the analysis, bending motion of a central spring and static properties of the compliant gripper are modeled using finite-element methods. The structure of the twisting module for motion transmission of the grasper is designed and fabricated using origami folding techniques. Gripping forces of the compliant gripper are evaluated in experimental tests. Further analyses of the system performance are addressed in accordance with the scaling ratio of miniaturization and the scalability of the system is demonstrated by a millimeter-sized origami parallel module produced by the smart composite microstructure fabrication process.

Minimally invasive Surgery (MIS) is one of the most challenging fields for robot designers due to the limited size of the access points, to the high miniaturization level and to the dexterity needed for performing surgical tasks. For this reason, the integration of actuators should proceed in parallel with the identification of the most effective transmission mechanisms and kinematics. Conversely, only a few microfabrication technologies are adequate for developing small size mechanisms with safe operation in the human body. In this paper a SMA actuated, miniaturized, origami-enabled, parallel structure is presented as a versatile module for novel robotic tool in MIS, the parallel structure has been combined with a twisting module and a gripper obtaining a 4-DOFs on board actuated end-effector.