Precise slave-side force control for security enhancement of bilateral motion control during application of excessive force by operator

The high probability of a future environment featuring human–robot coexistence is motivating studies on man–machine interface safety. Bilateral control that enables contact including haptic sensations to distant locations through master–slave actuators is an emerging technology in the fields of human tele support, care, and assistance. This paper proposes a safe operating technique for bilaterally controlled robots based on environmental properties. This technique protects the remote environment from excess force applied by the master operator. We have described the operation as the normal mode and safe mode. The system follows four-channel acceleration-based bilateral control throughout normal mode operation. The safe mode operation corresponds to virtual environmental sensation of the master operator together with force-position limitation on the slave side. In this work, a conventional virtual stiffness controller was modified to overcome the loss of environmental sensation from the remote slave side. Precise simultaneous force-position control is achieved on the slave side by focusing on the object safe force limit. The modified method is applied to the bilateral controller preserving the common mode force servoing property. The proposed method is validated using experiments.