The purpose of a newly developed foot prosthesis is to improve frontal plane foot adaptability for over 1 million adults living with lower extremity amputation in the US. On uneven ground, side slope, and turning corners, the anatomical foot can adapt but most prosthetic feet cannot. The innovative prosthesis mimics biomechanical aspects of anatomical joints that use ligaments in tension throughout the range of motion while the joint surface acts as a specialized load-bearing structure similar to that of a cross four-bar linkage. In the current prototype cam linkage, we found deviation between the instantaneous center of rotation (ICR) and the point of contact (POC) as it rotated through the frontal plane. The error in this distance could cause unexpected wear on the prosthesis. The goal of this project was to reduce the error caused by the difference in location of the ICR and POC during rotation and translation of the four-bar linkage. In a crossed four-bar linkage, the ICR is found at the intersection of the crossing links. To find the path of the ICR, we plotted a series of points by rotating the linkage about a fixed link in space. The continuous ICR path was estimated by smoothing the ICR points. The curved shape developed becomes the load-bearing surface of the linkage. To create the upper and the lower load-bearing surface, the upper and lower link must be fixed and the opposite rotated, respectively. Using the method described, we built linkage assemblies that showed an error of 0.96 mm per 20 degrees of rotation compared to 2.17 mm of error in the original prototype. The International Organization for Standardization (ISO) requires that foot prostheses undergo wear and fatigue testing. Reducing potential wear on the prosthesis is advantageous because engineers can design for optimal product durability for the foot.

Current research and development of robotic arms aims to increase both functionality and versatility. In the agriculture industry autonomous harvesting machines have the potential to be cost effective tools that efficiently pick crops, and robotic arms are a key component of that process. The agricultural robotics market was valued at $7.4 billion in 2020. Robotic arms available are typically designed to pick up one specific object. The market lacks solutions that can harvest a wide variety of crops quickly and carefully. The goal of this research is to develop an adaptable and robust grasping mechanism to attach to robotic arms for harvesting crops from a prototype developed for prostheses. This design adapts in position in response to the object geometry to reduce pressure on the object and requires less time to position the arm. Reducing pressure is a key metric in this study because of the fragile nature of many crops. Utilization of this mechanism reduces articulation time because it can adapt to the shape of the object being grasped at any orientation. My work in the lab has been to develop testing methods to prove these theories, both in simulation and through printing my own prototypes and performing physical tests. Preliminary virtual models and prototype tests consist of repeated grasp tests on a standard set of different grasp test objects including plastic fruits, cleaning supplies, and children’s toys. The objects are grasped repeatedly with and without the linkage mechanism attached. Results show that the mechanisms are adaptable and provide more contact area with the grasped object, reducing point pressure and requiring less articulation of the robotic arm. Further testing will apply the mechanisms in an agriculture setting and include prototyping with different materials and improved design.