Keywords: Vibration Mode, System Identification, Independent Component Analysis


Robots, or mechanical systems in general, are often subject to disturbance (i.e., unexpected effects, noise) from their environments. We are developing software which detects either a system is in a normal or abnormal mode by monitoring with sensors the vibration caused by the disturbance. This is done by modifying the Independent Component Analysis (ICA), a well-known tool for multivariate analysis, to the form suitable for mechanical systems, because the disturbance arises independently of the machine's motion. By applying thus developed ``system identification method for unknown inputs'', we have succeeded in on-line seperation of the disturbance mixed into the signal.

It is difficult as well as expensive to measure the disturbance in itself, because additional sensors are required. The above method has made it possible to estimate both disturbance and system dynamics simultaneously by merely indirect measurement of the vibration. At present, we are performing an experiment in which we vibrate a structure (see below) composed of thin pipe poles, measure the effect by displacement sensors, and analyze the signals. Furthermore, by using the dynamics thus obtained, we will be able to actively eliminate the disturbance by means of feedback.


Experimental System
mechanical system concept
mechanical system photo