This paper addresses an analog input shaper introduced in haptic control to improve the stability when interacting
with virtual environments. High frequency inputs to a haptic device, which can occur in collision with a virtual
wall with high stiffness, can bring limit cycle oscillations and instabilities. In order to reduce the high frequency
input to an haptic device an analog input shaper is added to the control system. Since the input shaper acts as
a low-pass filter, when a haptic pointer leaves the virtual wall with high stiffness, a user may feel slow decrease
of impedance, moreover there may be negative impedance as if the wall is pulling. In order to prevent this,
we add half-wave rectifiers which allow fast decrease of impedance and no negative input to a haptic device.
The input shaper reduces the total energy supplied to a haptic device by preventing inputs with high frequency
from flowing into a haptic device. Therefore it can be regarded as an artificial damping element. In order to
apply the Energy-Bounding Algorithm (EBA),1 which can guarantee the stable haptic interaction, to a scaled
teleoperation in a virtual nano-environment two scaling factors (velocity and force) are incorporated into EBA.
By applying the analog input shaper to EBA in scaled teleoperation, the range of virtual wall stiffness which
can be stably rendered by a haptic device is significantly extended.