Saskia Baltrusch

132 Chapter 5 be calculated: (6) This allows to calculate the bending angle Ө( ) as a function of the force F , the Young’s modulus E , the second moment of area I , the length L and the position along the beam (Figure 9A). Similarly, this equation can be used to estimate the Young’s modulus E , when the force F , the angle Ө( ) , the second moment of area I and the position along the beam and the overall length of the beam L is known. (7) Qualitatively, the linear and non-linear displacements look similar. However, for large displacements, additionally a displacement along takes place (Figure 3A), which is not captured by the linearized equation. Misalignment Compensating and Fitting Module Hip The misalignment compensation and fitting mechanism is manufactured out of aluminum (Figure 5B). The distance between two parallel steel axis is 30 mm. Two parallel custom designed torsion springs are mounted on the first two joints. For future testing, the first two joints can be locked with steel pins in discrete positions, additionally, encoder mounts are foreseen on all joints. Torque Source Hip Inverse pendulum models of the trunk predict a torque profile required around the hip to have a sinusoidal profile. In order to deliver such a torque profile, a force generated with a linear die compression spring (Sodemann ST52890), with a spring constant of 21 , is routed over a profile disk to generate a non-linear profile with two 2 mm Dyneema cables (Figure 5C). The design is a purely passive version of a Mechanically Adjustable Compliance and Controllable Equilibrium Position Actuator (MACCEPA 2.0) as described by Vanderborght et al. (2011) [34]. The actuator is designed in such a way, that by changing manually the pretension, the peak output torque can be adjusted in a range of 10-30 Nm per joint, amounting to a total of 20-60 Nm.