Due to progressive muscle weakness, the arm function in boys with Duchenne muscular dystrophy (DMD) reduces. An arm support can compensate for this loss of function. Existing arm supports are wheelchair bound, which restricts the ability to perform trunk movements. To evaluate the function of a body-bound arm support, a prototype (based on the Wilmington robotic exoskeleton (WREX) arm support) that allows trunk movements was built. In order to examine the effect of this device and to compare it with an existing wheelchair-bound device, three healthy subjects performed single joint movements (SJMs) and activities of daily living (ADL) with and without the devices. The range of motion (RoM) of the arm and the surface electromyography (sEMG) signal of five different arm muscles were measured. The range of motion increased when compared to the wheelchair-bound device, and the trunk motion was perceived as important to make specific movements easier and more natural, especially the more extreme movements like reaching for a far object and reaching to the top of the head. The sEMG signal was comparable to that of the wheelchair-bound device. This means that an arm support with trunk motion capability can increase the range of motion of the user, while the amount of support to the arm is equal. ... Read more

A static balancer is a mechanism used to force compensate mechanical systems and has been used in applications such as improving haptic feedback in surgical instruments and lowering motor loads in robotic systems. Currently no complete overview exists of all SB methods, this paper can be seen as an extension to earlier work by introducing more static balancing categories and methods. The goal is to have a comprehensive overview of state-of-the-art to aid designers in selecting the appropriate static balancer technology for mechanical systems. Existing designs are categorized based on the energy storage mechanism, e.g. elastic energy storage mechanisms. Critical design parameters are extracted from published literature to form the basis of comparison of the different categories. A performance criterium is defined to illustrate balancing capabilities as a function of system size. The three comparison parameters are: CompensatedForce Volume ; SBStroke Volume ; Energy Volume The comparison results show that compliant flexure balancers are the best selection for balancing systems while keeping minimal size. Theoretical calculations show that there is still ample room to improve current balancers with regard to the chosen balancer criteria. ... Read more

A statically balanced system is in equilibrium in every pose. In classical balancing solutions for serial linkages, each DOF is balanced by an independent element. Disadvantages are increased mass and inertia for counter-mass, and auxiliary links for spring solutions. Recent literature presents a method for balancing serial linkages without auxiliary links; using multi-articular springs. This method obtains constraint equations from the stiffness matrix. Downsides are different coordinate systems for describing locations and states, and criteria constraining attachments to fixed lines In the present paper Cartesian coordinates are implemented in the stiffness matrix approach. Goal is comparing the use of this single coordinate system to using multiple, and obtaining increased insight in and providing a visualization of parameter relations. The Cartesian coordinates are implemented, providing a simple, intuitive method for designing statically balanced serial linkages allowing for recognition of the full design space. Obtained parameter relations are visualized in an example. ... Read more