Active materials are a type of material that can respond to external stimuli and change their physical properties as a response. Neutrally stable compliant mechanisms are a class of compliant mechanisms that use the flexibility of their members to deform and maintain that deformed configuration without requiring external work. In order to make a compliant mechanism neutrally stable, pre-stress is required. In most cases, this pre-stress is applied when the neutrally stable compliant mechanisms are being made. Therefore, neutrally stable compliant mechanisms are always in a zero-stiffness state. In this research, a new Compliant Active Neutrally Stable joint (CANS-J) is developed in which this pre-stress can be turned on and off using active materials. This means that the joint can switch between a stiff state and a zero-stiffness state. This change in the stiffness is realized by a Flexinol SMA wire. A Flexinol wire can contract when it is heated. This active behavior of the Flexinol wire is used to turn on and off the pre-stress when required. Results show that the CANS-J shows behavior which is close to neutral stability in the active state with a significant range of motion. The CANS-J can for instance be used to transport a satellite with solar panels to its orbit around the world. During transportation the solar panels are folded for which the joints are required to be in a stiff state. In orbit, the solar panels are unfolded for which the joints are required to have zero stiffness.

The company Intespring is currently developing a load-carrying exoskeleton for military personnel in order to reduce the impact of the ever increasing backpack load on their body: the Exobuddy. The current mechanical design gives rise to problems, i.e. the exoskeleton occupies a large space and applies torques on the legs of the user during operation, rendering it unsuitable for use in the field. This research is comprised of the redesign of the mechanical structure, where the functionality of the current exoskeleton is maintained, while eliminating the mentioned problems. The chosen solution, based on Storable Tubular Extendible Members (STEMs), is further developed and dimensioned according to a set of requirements. Finally a prototype is built to validate the design. It is shown that the proposed design is capable of carrying loads matching backpack loads of military personnel. Additionally, it is shown that the anisotropic material properties of Fibre Reinforced Composites can be exploited in such a way that a compact mechanism can be obtained.

Passive exoskeletons that support the weight of the surgeon’s arms could yield a significant ergonomic improvement in the Laparoscopic theatre. However, the cost and regulations associated with sterilization complicates adoption of such devices. In this work a compact passive arm support mechanism is designed that can be worn underneath the surgical gown to circumvent sterility requirements. The design utilizes shape optimized compliant shell mechanisms who’s geometry can remain substantially close to the body as well as achieve the nonlinear stiffness characteristic that is desired for balancing the arm’s weight. A shell design with the desired torque-rotation characteristic is designed using shape optimization and fabricated for validation testing. Measurements show the prototype balances 19% of an average adult’s arm weight within ±4 percentage points between 0 and 90 degrees of arm abduction and or flexion. A prototype of the mechanism remains within 34mm of the arm, nearly twice as compact as the state of the art.