Human ​upper-limb workspace computation by interval analysis

The human-robot collaboration is based on the robot ability of interacting with the operator, enhancing its capacities: thus, it is necessary that the robot is able to adapt its behaviour each time to the particular motor strategy used by the specific operator. The aim of the project is to define a kinematic model of the human arm, with particular interest on the solution of the inverse kinematics problem. After applying biomechanical constraints, it is possible to distinguish between feasible and non-feasible configurations of the human arm. This study is then extended to the use of interval analysis, in order to consider the variability of the parameters of a human arm among different people. In this context, classical Denavit-Hartenberg parameterization provides equations that are not suitable for interval analysis, due to the presence of rotation matrices and non-monotonic functions. For this reason, a different method that takes the unit vectors of each frame as variables is employed. The algorithm based on interval analysis is tested through a comparison between the solution of the non-interval model (i.e. all parameters are real numbers) and the solution of the interval one in which the model parameters are degenerate intervals.