Stability of a robust interaction control for single-degree-of-freedom robots with unstructured environments

Experimental verification on the robustness and stability of an interaction control: Single‐degree‐of‐freedom robot case

“…Moreover, it will also inspire researchers to develop advanced control schemes that make smarter use of joint friction to handle tasks that require robots to be in frequent contact with various environments. In this paper, with a single DOF robot and different environments, the controller stability proof given in [2] was, thus, experimentally verified for the first time.…”

“…Moreover, it is preferable for practical implementation that the control law is independent of the robot and environment models. The nonlinear bang‐bang impact control (NBBIC) was able to deal with such tasks without changing gains and without using a robot and environment dynamics [1, 2]. Moreover, to absorb the impact force and energy at the sudden contact with an unknown environment, the controller takes advantage of the nonlinear joint frictions, which are usually known to degrade the control performance [1, 2].…”

“…However, only recently (almost 20 years after its first proposal), its stability was formally proved by the authors [2] for one DOF robot due to the difficulty of tackling the highly nonlinear complicated impact situations. In [2], the stability condition predicted that the controller is robust to environment changes (e.g. stiffness) and disturbances, and the nonlinear joint frictions are indeed helpful for the stabilization of the robot experiencing a rapidly changing impact force due to sudden impact to an extremely stiff environment at very high velocity.…”

Experimental study on a robust interaction control with unknown environments

“…To address the issue, non-linear bang-bang impact control (NBBIC) had been proposed with the experimental verification of its superior performance in impact conditions in settling time and oscillation in force response [16]. NBBIC may be theoretically innovative in that, instead of the dynamics of environment and robot, NBBIC uses time-delay estimation (TDE)-requiring only the most recent control torque, acceleration, and a constant inertia estimation matrix-to compensate for the robot dynamics and disturbances [16][17][18][19]. Moreover, the non-linear bang-bang action (NBBA) subsides the impact energy by utilizing the non-linear robot joint frictions through wise turning off of the control action [16][17][18][19].…”

“…NBBIC may be theoretically innovative in that, instead of the dynamics of environment and robot, NBBIC uses time-delay estimation (TDE)-requiring only the most recent control torque, acceleration, and a constant inertia estimation matrix-to compensate for the robot dynamics and disturbances [16][17][18][19]. Moreover, the non-linear bang-bang action (NBBA) subsides the impact energy by utilizing the non-linear robot joint frictions through wise turning off of the control action [16][17][18][19]. Further, NBBIC does not need any change of gains and/or structure throughout the tasks consisting of free-space motion, impact, and constrained-space motion.…”