| During activities of daily living humans create internal models of the external world. For example, when manipulating an object that behaves according to a spring law a model of the object's stiffness is estimated. Humans do not have sensors that indicate stiffness, thus the object's stiffness must be estimated based on available sensors. In the absence of an internal model of the external world, activities of daily living become challenging. For example, those suffering from the absence of proprioceptive information can generate motor commands yet cannot perceive the locations and motions of their limbs in space, and, in turn, are unable to create an accurate model of the external world. For this population of humans, activities of daily living are nearly impossible. Current upper-limb prostheses enable motor control, yet do not provide proprioceptive cues. We propose that the prosthesis experience can be improved by artificially relaying proprioceptive information to the user so that creation of an internal model of the external world based on sensed information is possible.;Contributions of this dissertation are presented in three parts. In the first part, we discuss the design and characterization of a haptic device we created that mimics the experience of using a simple upper-limb prosthesis for a physically intact human. We quantified human perception capabilities of proprioception (position), force, and stiffness using psychophysics testing, and we proposed a novel model to identify a plausible underlying mechanism by which stiffness perception occurs. Our findings indicate that stiffness perception can be described by a fusion of one's ability to sense proprioceptive and force cues.;In the second part, we characterized the role of proprioceptive and visual motion cues in a spring discrimination task. We showed that relaying non-stationary proprioceptive motion information can minimize the necessity to rely on visual information to perform the task.;In the third part, we investigated the efficacy of a skin stretch device for relaying proprioceptive information artificially. We found that attention to visual indicators during a spring discrimination task could be minimized if position and motion cues are relayed to the user by the skin stretch device. |
