Optimizing Active Spinal Exoskeletons to Minimize Low Back Loads

The design and control of exoskeletons is not a straight forward task and presents a lot of challenges. Especially in cases of preventing biomechanical damages, for example low back loads, exoskeletons should be able to provide the necessary amount of support without hindering or hurting the user in any way. To this extend, this study exploits optimal control to evaluate cost functions that minimize (a) cumulative low back loads, (b) peak low back loads and (c) a combination of the previous, while constraining contact (interaction) forces between human and exoskeleton. The results are compared to a kinematic reconstruction from a human without exoskeleton performing the same task of lifting a 10 kg box. Cost function (c) performs the best in terms of achieving an equilibrium between minimizing cumulative and peak lumbar torques—subject to the actuator’s torque and speed limit—reducing the peak torque by 48%.