Abstract
Haptic exploration is a process of using haptic feedback to interact and perceive an unknown object. It is an essential approach to understand the physical and geometrical properties of the object. While numerous research has been carried out for haptic exploration on static objects, haptic exploration on objects with dynamic movements has not been reported. It is due to the significant challenges to achieve robust force and velocity control when the object is nonstationary. In this work, a novel adaptive force and velocity control algorithm based on intrinsic contact sensing (ICS) for haptic surface exploration of dynamic objects is presented. A fuzzy-logic control framework making use of the information obtained from ICS has been developed. To validate the proposed control algorithm, extensive surface exploration experiments have been carried out on objects with different surface properties, geometries, stiffness, and concave or convex patterns. The validation results demonstrate the high accuracy and robustness of the proposed algorithm using different experimental platforms.
Highlights
Haptic exploration of the surface is a fundamental tool for humans to understand the surface properties of unknown objects with only tactile sensing (Lederman and Klatzky 1993, 2009), especially in reduced visibility scenarios like underwater, smoky disaster environment and inside tissues during surgery
Lepora et al have been working on the development of the optical tactile sensors with bio-mimetic morphologies (Ward-Cherrier et al 2018), and they have used sensors for robust contour following with deep learning method (Lepora et al 2019)
The reason could be that the complex geometries and changing stiffness of the object surface will induce dramatic force changes during the haptic exploration, and the force errors can not be eliminated completely and quickly with the control algorithm, as a consequence, the error accumulates and the mean square error (MSE) and standard deviation (SD) become larger than the situation when exploring the smoother objects
Summary
Haptic exploration of the surface is a fundamental tool for humans to understand the surface properties of unknown objects with only tactile sensing (Lederman and Klatzky 1993, 2009), especially in reduced visibility scenarios like underwater, smoky disaster environment and inside tissues during surgery. If the explore velocity can be controlled, more information of the explored object such as surface viscosity (Liu et al 2012), break-away ratio (Song et al 2014) can be revealed These all showed the paramount importance of the good control of contact forces and scanning velocity during haptic exploration. The following contributions have been made: (1) A robust and adaptive normal force and explore (scanning) velocity control algorithm was developed based on haptic information during surface exploration. It was evaluated using a self-fabricated contact sensing finger on non-stationary objects. The algorithm was validated successfully with a 6 DoFs robot arm (with a contact sensing tip mounted) using objects with different stiffness and geometries. (4) Even though the type of contact was point contact in the tests, it works for surface contact (using tactile array sensor) if contact locations can be obtained in real-time
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