Biped-Wheeled Exoskeleton in OpenSim: Test and Simulation

Nowadays exoskeletons are becoming really important in everyday tasks of our life. Starting from assistance in operations, passing through rehabilitation due to multiple diseases, ending up to be used for enhancing the human capability in field’s operations. Therefore, the study of the design and the construction of a Biped-Wheeled Exoskeleton is necessary to understand the capability of integration between this particular exoskeleton and the human body structure. In order to provide the best wearability fit, several analysis are conducted with the main purpose to get as close as possible to a normal gait, minimizing the impact of the exoskeleton to the human body. The novel approach used in the construction of this model is based on a descendent kinematics to resemble the normal gait when walking or running. It starts from the back cube, behind the human back, going through the lower limb to arrive at the skates level. As soon as the right side does not presents any problem, the left side leave an “uncovered point” between the left horizontal support and the back cube due to build constraints. A smart solution is analyzed and presented to solve this problem and to provide the full kinematic link. To achieve this goal, Notepad++ compiler associated with OpenSim simulation tools, have been used to build and simulate every single piece of the exoskeleton from scratch. Every component has: mass, inertia and reference systems both related to the environment and to the proximal piece. The blocks are connected each other’s by joints, in particular it is mostly used the custom joint because of its adaptability in different scenarios, and its flexibility allowing all six motions in space within the three directions X, Y, Z. The exoskeleton is attached to the human body by means of three points using specific constraints: the back, the right foot and the left foot. From literature review, some principal values of the human gait related to the lower limb such as vertical translation of the back, hip and ankle’s angles are used to replace the values of the exoskeleton. Subsequently, some tests are performed in OpenSim to collect the data about kinematics and dynamics simulations. For kinematics and dynamics analysis will be evaluated the following joints’ output: the hip, the knee and ankle, both for the right and the left side. Results in this procedure lead to obtain the correct human body parameters. During dynamics tests will be performed muscle analysis and joint reactions. The overall simulation’s results will be used to compare values of a normal human model to another wearing an exoskeleton . All of these results will give also a comfort analysis perceived by the human body in terms of wearability and flexibility of this exoskeleton when performing daily tasks. A specific example of the compared trends result related to the knee angle joint is shown in the figure below.