The Role of Compliant Fingerpads in Grasping and Manipulation: Identification and Control

Abstract

Manual exploration and manipulation of unknown objects in unstructured environments require sensory guided motor control strategies. For humans or general purpose robots, the presence of compliant fingerpads is crucial in enhancing the stability of grasp and manipulability, and the objects they encounter are often compliant. In this paper, we apply well known system identification and control methods to enable successful grasping and manipulation of compliant objects using compliant fingerpads. Through the use of linear and nonlinear lumped parameter models, we describe the dynamic relationships between the external forces exerted on the fingers and the contact forces imposed on the object. We present two approaches to realize the necessary control actions, one where the identification of the system parameters is followed by control, and the other where an adaptive control strategy is used. We illustrate the importance of tactile information in not only satisfying the necessary interface constraints, but also in simplifying the identification and control procedures for successful performance of grasping and manipulation tasks.

Sensitive Manipulation: Manipulation Through Tactile Feedback

“…This punctual force will produce a large stress in an object that could damage it. In practice, this model is usually invalid because the rigid fingertip is covered by a soft material to improve the grasp and avoid damaging the object 15 . We use a conformable skin that can estimate directly the force distribution applied avoiding the punctual contact model.…”

“…One of the aspects is the development of tactile sensors that has been addressed using a number of different technologies 4,5,6,7,8,9 . A second aspect is the use of compliance elements for soft contact 10,11,12 and conformational grasping 13,14,15 . Another aspect is the algorithms and strategies developed to perform tasks using tactile feedback and compliance elements 16,17,18,19,20,21,22,23,24 .…”

Towards Humanlike Social Touch for Sociable Robotics and Prosthetics: Comparisons on the Compliance, Conformance and Hysteresis of Synthetic and Human Fingertip Skins

“…Previous works in robotics have found compliance and conformance to be important for grasping, manipulation and sensing [10,11,43,[54][55][56][57][58] but have not compared these properties directly to the human fingertip. As for hysteresis, this property is beneficial to absorb the energy from impacts and is present in the highly hysteretic nature of human and animal skins.…”

Ambient touch

“…Hence, the actuator should be able to generate variable skin displacements. 3. Wide frequency bandwidth.…”

“…when rapidly successive data needs to be resolved, the feel of touch is about five times faster than vision [19]. Hence, it allows for precise and fast motor con- Figure 1: TouchEngine™ actuator -a new vibrotactile actuator for designing tactile interfaces for small handheld computing devices; it is only 0.5 mm thick trol: When we roll a pencil in our fingers, we can quickly and precisely re-adjust the 3D positions and grasping forces of our fingers by relying entirely on touch [3]. Furthermore, these complex motor operations produce little cognitive load and can be performed in parallel with other activities, such as reading a newspaper.…”