This project seeks to develop an orthotic knee joint system that includes a non-linear torsion spring coupled with a novel concept called Morphological Switching (MorS) that changes the mechanical properties of the joint in response to user behavior. The research objectives are to prototype and functionally test the medial side of a Morphological Switched Orthotic Joint (MSOJ) assembly. Tasks include: a) fabricate and test prototypes of all joint components; b) mechanically integrated all prototype joint components and functionally test the MSOJ with control algorithms; and c) the MSOJ will be tested to assess functional benefits. Telemetry data will be collected during 200 steps at slow, medium and fast walking speeds and descending 200 stairs and be processed with a program that assesses biomechanical benefits. We expect the results to provide convincing quantitative proof of the ability of the MSOJ to create an energy efficient knee brace. The intellectual merit of the proposed project stems from the application of MorS to take the springs in the system, which are clearly passive, and allow the user to perceives the springs as having a dynamic stiffness whose behavior changes dependent on what the user does.
The broader impact / commercial potential of this project stems from its impact on the estimated worldwide population of 150 million people who have mild/moderate walking dysfunction not currently addressed by any existing orthosis device. MSOJ offers new biomechanical benefits to this population group including adapting to whatever leg strength the user provides, adapting to the user selected speed and step length, reducing the effort needed to walk, providing complete torso support while ascending and descending stairs and preventing falls due to knee collapse resulting from insufficient leg strength. Novel technologies introduced include a synthesis methodology for designing non-linear hardening spring, actuators that need no battery energy to generate holding forces, sensors for measuring gait parameters and a distributed fault tolerant electronics architecture. The orthoses created with MOSJ would be the first assistive appliance that stores all sensor data and enables real time and/or background access of the data. These joints are expected to allow rehabilitation therapy to be delivered and monitored in remote settings during all Activities of Daily Living. MOSJ components will also be made available to researchers to allow fabrication of custom appliances for their rehabilitation research.
This report summarizes the results of the NSF SBIR Phase I feasibility work to prototype a novel orthotic knee joint for use in portable rehabilitative systems associated with gait training for patients with leg paresis (weakness). The Morphological Switched Orthotic Joint (MSOJ) that was developed and tested couples a non-linear torsion spring that varies the spring’s stiffness with a scheme that dynamically changes the structure of the join under microprocessor control (Morphological Switching (MorS)). MSOJ feasibility was demonstrated in Phase I work by prototyping and testing all MSOJ components and testing integrated component assemblies to demonstrate that the MSOJ is likely to produce the anticipated biomechanical benefits which include providing full torso support at all knee flexion angles, providing full support while descending stairs and potentially reduces the amount of muscle supplied energy needed to perform these activities. The intellectual merit addresses the problems of creating an energy conserving knee brace that provides benefits of: assisting the leg in supporting the torso regardless of the amount of support generated by the user’s leg muscles; allowing the user to walk with any step length/speed; making it easier for the user to walk because the springs absorb the kinetic energy lost by the torso following heel strike and later release the stored strain energy thereby partially restoring the torso’s lost kinetic energy; completely preventing knee collapse, a common cause of falls. The broader impact and commercial potential of this project is that it will enhance scientific understanding on creating mobility assistive devices using Morphological Switching (MorS) and non-linear mechanical energy storage elements. MorS is a novel solution to the problem of enabling an orthoses to adapt to the gait selected by the user rather than requiring the user to adapt to the orthosis. The joint design methodology utilizes a novel nonlinear spring synthesis program (NSSP) to synthesize the shape of a torsion spring having a specified torque versus angle profile, fit within a specified volume, have minimum weight and have a specified cutting kerf. Other novel joint elements include a fault tolerant architecture to improve functional reliability and microprocessor actuated clutches that advance the state-of-the art in holding torque/Kg and holding torque/watt by more than an order of magnitude. If successful, the project it will initiate new research and development in the field of robotic rehabilitation devices with the potential to benefit the health of millions of people each year.
