Riddle, Steven MSME, Purdue University, May 2013. Modeling Tools for Conformal Orthotic Devices. Major Professor: Justin Seipel, School of Mechanical Engineering. The purpose of this thesis is to advance the design of conformal orthotic devices through the development of two modeling tools to address knowledge gaps in the field. The field of human orthotics has been continually troubled by identifying successful methods of harnessing devices to the body. Past orthotics have utilized a rigid framework with minimal degrees of freedom (DOFs) driven by hard actuators attached to the body at select anchor points. Many devices design the structure and anchor points such that they reduce the degrees of freedom of a targeted joint, limiting the user’s mobility and often causing the structure to slide relative to the body as much as actuate a given joint. There has been a recent shift in the orthotic field toward biologically inspired conformal structures to address the limitations of hard systems. By focusing on conformal devices that move with the body, limited DOFs and mobility restrictions can be addressed while also enabling new possibilities in human augmentation devices. Conformal orthotics have the opportunity to allow more DOFs in a joint while performing the same task as their rigid counterparts. By allowing these additional DOFs, the overall mobility of the user could be increased and more nuanced and particular interactions with the body and the environment may be possible. More channels of actuation could lead to finer joint control and enable more complicated tasks to be performed. The task of designing conformal orthotic structures can be broken into four parts: developing 3D skin strain models; identifying minimum strain contours for orthotic

The clock-torqued spring-loaded inverted pendulum (CT-SLIP) model describes the robust dynamic stability properties observed in most animals and some legged robots. However, the model's behavior is sensitive to changes in liftoff conditions such as those experienced on realistic terrain. Here the incorporation of friction at the foot-ground interface is explored on the CT-SLIP model with specific interest in improving the transient center-of-mass dynamics. Multiple friction models are presented and tuned to reflect a periodic center-of-mass gait. The transient dynamics with friction are analyzed in comparison to the CT-SLIP model and improvements to the settling time and disturbance rejection were found. This addition of foot-ground contact friction may allow for better understanding of center-of-mass system dynamics on realistic terrain.