The stability investigation of variable viscosity control in the human-robot interaction
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Updated: Sep 22, 2025
Experimental Methods to Study Human Postural Control
Published on: September 11, 2019
Lin Dong1, Nicolas Perrin1, Florian Richer1
1Institut des Systèmes Intelligents et de Robotique, Sorbonne Universités UPMC Univ. Paris 06, Paris, France.
Background:
For many co-manipulative applications, variable damping is a valuable feature provided by robots. One approach is implementing a high viscosity at low velocities and a low viscosity at high velocities. This, however, is proven to have the possibility to alter human natural motion performance.
Methods:
We show that the distortion is caused by the viscosity drop resulting in robot's resistance to motion. To address this, a method for stably achieving the desired behaviour is presented. It involves leveraging a first-order linear filter to slow the viscosity variation down.
Results:
The proposition is supported by a theoretical analysis using a robotic model. Meanwhile, the user performance in human-robot experiments gets significantly improved, showing the practical efficiency in real applications.
Conclusions:
This paper discusses the variable viscosity control in the context of co-manipulation. An instability problem and its solution were theoretically shown and experimentally evidenced through human-robot experiments.
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