Network interpretation of a human-machine interaction system

This paper discusses a two-port network interpretation of a human-machine interaction system. Two-port systems are utilized widely in the bilateral teleoperations area, however, most of this large class of interaction control systems consists only of a human and a machine. We will show this human-machine system can be represented in a two-port network system. For the case where there are no force sensors available from the machine when the human is performing tasks, we define a virtual feedback force and virtual input energy in order to formulate a network representation. Stability of the human-machine system is analyzed by utilizing the time domain passivity, and the impedance and the scattering transfer functions with a state space realization in a two-port network. An inverted pendulum system is used to depict a human-machine system for the network representation in the experiment. In the system, the PD controller and the washout controller which are proposed to achieve a superior performance under the stability constraints are examined. Finally, we show the stability constraints can be related to the performance of the inverted pendulum system by monitoring the energy at each port and the maximum singular values of the scattering representation of the network systems in the experiment.