“…Impedance control has triggered off a number of developments for interaction control. These include, for instance, a Lyapunov-based approach (Mendoza et al, 2012), model predictive impedance control (Falaki and Towhidkhah, 2012), model-free impedance control or intelligent control like neural networks (Dehghani et al, 2010;Modares et al, 2016), fuzzy logic (Deneve et al, 2008;Akdogan and Adli, 2011;Ju et al, 2005), or a combination of both (Kiguchi et al, 2007;Xu et al, 2011), as well as stiffness control in the task-space as in the work of Chávez-Olivares et al (2015), where some case studies of different stiffness regulators are proposed and the corresponding Lyapunov's stability analysis is presented.…”