Comb-drive actuators for large displacements

The design, fabrication and experimental results of lateral-comb-drive actuators for large displacements at low driving voltages is presented. A comparison of several suspension designs is given, and the lateral large deflection behaviour of clamped - clamped beams and a folded flexure design is modelled. An expression for the axial spring constant of folded flexure designs including bending effects from lateral displacements, which reduce the axial stiffness, is also derived. The maximum deflection that can be obtained by comb-drive actuators is bounded by electromechanical side instability. Expressions for the side-instability voltage and the resulting displacement at side instability are given. The electromechanical behaviour around the resonance frequency is described by an equivalent electric circuit. Devices are fabricated by polysilicon surface micromachining techniques using a one-mask fabrication process. Static and dynamic properties are determined experimentally and are compared with theory. Static properties are determined by displacement-to-voltage, capacitance-to-voltage and pull-in voltage measurements. Using a one-port approach, dynamic properties are extracted from measured admittance plots. Typical actuator characteristics are deflections of about at driving voltages around 20 V, a resonance frequency around 1.6 kHz and a quality factor of approximately 3

Quick-cast: A method for fast and precise scalable production of fluid-driven elastomeric soft actuators

Fluid-driven elastomeric actuators (FEAs) are among the most popular actuators in the emerging field of soft robotics. Intrinsically compliant, with continuum of motion, large strokes, little friction, and high power-to-weight ratio, they are very similar to biological muscles, and have enabled new applications in automation, architecture, medicine, and human-robot interaction. To foster future applications of FEAs, in this paper we present a new manufacturing method for fast and precise scalable production of complex FEAs of high quality (leak-free, single-body form, with <0.2 mm precision). The method is based on 3d moulding and supports elastomers with a wide range of viscosity, pot life, and Young's modulus. We developed this process for two different settings: one in laboratory conditions for fast prototyping with 3d printed moulds and using multi-component liquid elastomers, and the other process in an industrial setting with 3d moulds micromachined in metal and applying compression moulding. We demonstrate these methods in fabrication of up to several tens of two-axis, three-chambered soft actuators, with two types of chamber walls: cylindrical and corrugated. The actuators are then applied as motion drivers in kinetic photovoltaic building envelopes

Exploiting Multi Stability of Compliant Locking Mechanism for Reconfigurable Articulation in Robotic Arm

This study analyzes a biology inspired approach of utilizing a compliant unit actuator to simplify the control requirements for a soft robotic arm. A robot arm is constructed from a series of compliant unit actuators that precisely actuate between two stable states. The extended state can be characterized as a rigid link with a high bending stiffness. The compressed state can be characterized as a flexible joint with a low bending stiffness. Without the use of an external power source, the bistable mechanism remains in each of the stable states. The unit actuator can demonstrate pseudo-linkage kinematics that require less control parameters than entirely soft manipulators. An advantage of using compliant mechanisms to design a robotic arm is that the bending stiffness ratio between the extended and compressed states is related to the frame and flexural member geometry. Post buckling characteristics of thin flexural members, combined with a cantilever style frame design gives the unit actuator versatile advantages over existing actuator designs like layer jamming and shape memory polymers. To achieve efficient movement with the optimized unit actuator design, experimental validation was performed, and a robotic arm prototype was fabricated. The tendon-driven robotic arm consisted of three modules and proved the capability of transforming and rotating in the eight configurations. The deformations of the robotic arm are accurately predicted by the kinematic model and validate the compliant mechanism arm and simple control system