Design of a compliantly actuated exo-skeleton for an impedance controlled gait trainer robot. - Herman van der Kooij; Jan F. Veneman; Ralf Ekkelenkamp (EMBC, 2006)

A Series Elastic- and Bowden-Cable-Based Actuation System for Use as Torque Actuator in Exoskeleton-Type Robots. - Jan F. Veneman; Ralf Ekkelenkamp; R. Kruidhof; Frans C. T. van der Helm; Herman van der Kooij (Int. J. Robotics Res., 2006)

LOPES: a lower extremity powered exoskeleton. - Ralf Ekkelenkamp; Jan F. Veneman; Herman van der Kooij (ICRA, 2007)

Passive and accurate torque control of series elastic actuators. - Heike Vallery; Ralf Ekkelenkamp; Herman van der Kooij; Martin Buss (IROS, 2007)

Compliant actuation of rehabilitation robots. - Heike Vallery; Jan F. Veneman; Edwin van Asseldonk; Ralf Ekkelenkamp; Martin Buss; Herman van der Kooij (IEEE Robotics Autom. Mag., 2008)