A. Sensor Signal Observer
Since a sensor signal observer estimates a strain gauge sensor
signal from an input torque and a reaction force, we give a brief
review of a reaction force observer proposed in [5] first. Secondly,
we introduce a relationship between a reaction force and
a strain gauge sensor signal, and show that a strain gauge sensor
signal can be constructed from a reaction force. Furthermore,
an adaptive gain is incorporated into the sensor signal observer
to improve estimation accuracy and robustfy estimation against
disturbances and parameter variations.
1) Reaction Force Observer: A reaction force observer is
proposed to estimate a reaction force τ reac acting on a motor
in a 2-mass resonant system as shown in Fig. 3, and some
successful applications are reported (e.g., vibration suppression
control of 2-mass resonant system [5] and sensor-less force
control [6]). A flexible arm model (1) and (2) can be modeled as