Figure 9.

Musculoskeletal model for learning reaching tasks. A model of a human arm with eleven muscles shown in Table A5 in the appendix was used to learn six reaching skills in the sagittal plane (A). As reward signal we encoded the distance to a marker placed on the radial stylion (denoted by the plus symbol) and punished large muscle excitation signals. Targets are denoted by large dots. We focused on fast reaching skills of 500 ms duration, where an example movement is shown in (B). To simulate how muscles wrap over underlying bone and musculature wrapping surfaces are implemented as cylinders, spheres and ellipsoids (Holzbaur et al., 2005).