Release Name: Two legs and a HAT, version 2.1
Update: September 7, 2011 Corrected a bug in the knee_angle_r and knee_angle_l coordinate ranges that was introduced in the 2-leg, OpenSim versions of this model. The range was increased from 0-100 degrees to 0-120 degrees, which introduced invalid moment arms at knee angles above 100. The error has been corrected by reducing the range of motion to the original 0-100 degrees, which was validated against experimental measurements of moment as described the above publication. Additionally, wrapping surface display properties have been hidden by default. Update: April 12, 2011 version 2: The patellar joint and corrseponding coupler constraints were altered to work around a problem with coordinate coupler constraints that occurs during scaling in OpenSim. Translational coordinate coupler constraints were scaled incorrectly in the OpenSim 2.2 Scale tool. This affected constraints that were used to define patellar motion as a function of knee_angle_l and knee_angle_r. This issue is worked around here by replacing the three coordinates defining rotational and translational motion in the left and right patella bodies with a single rotational coordinate in each, knee_angle_beta_*, and coupling the new coordinates to equal knee_angle_*. This model includes the following additions and changes relative to the single-leg version 2: Left leg with same architecture and mirrored geometry as right leg. 6 degrees of freedom for the pelvis segment (translational x,y, and z) rotational tilt, list, and rotation. Torso segment with composite head-arms-torso (HAT) mass. 3 degree of freedom lumbar joint (extension, bending, and rotation), Torso muscles with architecture as defined in the OpenSim default model gait_2392. Activation dynamics parameters to produce same activation/deactivation timing for all muscles: Schutte1993Muscle (activation1 = 7.6, activation2 = 2.5) Thelen2003Muscle (activation_time_constant = 0.01, deactivation_time_constant = 0.04) Markers set placed according the convention used at the University of Delaware Neuromuscular Biomechanics Lab. Two strength levels: Default - the <max_isometric_force> values are the same as reported in the paper and used in the single leg version. 50% Stronger - All lower limb muscles (i.e. not back muscles) have been strengthened by increasing <max_isometric_force> 50%. This model is strong enough to produce a CMC simulation of walking for an average sized, healthy, adult male.