The DEXMART hand: Mechatronic design and experimental evaluation of synergy-based control for human-like grasping

Abstract

This paper summarizes recent activities carried out for the development of an innovative anthropomorphic robotic hand called the DEXMART Hand. The main goal of this research is to face the problems that affect current robotic hands by introducing suitable design solutions aimed at achieving simplification and cost reduction while possibly enhancing robustness and performance. While certain aspects of the DEXMART Hand development have been presented in previous papers, this paper is the first to give a comprehensive description of the final hand version and its use to replicate human-like grasping. In this paper, particular emphasis is placed on the kinematics of the fingers and of the thumb, the wrist architecture, the dimensioning of the actuation system, and the final implementation of the position, force and tactile sensors. The paper focuses also on how these solutions have been integrated into the mechanical structure of this innovative robotic hand to enable precise force and displacement control of the whole system. Another important aspect is the lack of suitable control tools that severely limits the development of robotic hand applications. To address this issue, a new method for the observation of human hand behavior during interaction with common day-to-day objects by means of a 3D computer vision system is presented in this work together with a strategy for mapping human hand postures to the robotic hand. A simple control strategy based on postural synergies has been used to reduce the complexity of the grasp planning problem. As a preliminary evaluation of the DEXMART Hand's capabilities, this approach has been adopted in this paper to simplify and speed up the transfer of human actions to the robotic hand, showing its effectiveness in reproducing human-like grasping

Motion Planning by Demonstration With Human-Likeness Evaluation for Dual-Arm Robots

“…These synergies were suggested to be an emergent consequence of neuromuscular impedance [28]. The synergies existing in the human hand [29] were also used for other objectives such as the analysis and design of robotic hands in order to mimic human grasps [30], the selection of grasping forces [31] and the design of specific hand control systems [32]. Later, a compliant model for synergies, called "soft synergies", was introduced and used in the selection of grasping forces, in their control, and in the control of the motion of the grasped object [33], [34].…”

Position Control of Asymmetric Nonlinearities for a Cable-Conduit Mechanism

“…In addition, it is able to work in complex environments and narrow paths [1], [5]. Hence, many applications have used CCM as the main mode of transmission such as wearable robot [6], robotic hands [7], surgical robot [8], rescue robots [9], and exoskeleton robots [2]. Although the CCM offers many advantages, the interactions between the cable and the conduit generally introduce large friction, deadzone, hysteresis, and backlash nonlinearities that degrade the accurate control of position and system performances [10]- [12].…”

The UC Softhand: Light Weight Adaptive Bionic Hand with a Compact Twisted String Actuation System

“…The same concept was applied in the DEXMART hand [24,25], where several actuators with twisted string systems are placed outside the palm and in a relatively large forearm. While placing the actuators at a remote distance from the driven object is advantageous for some applications, it is not desired in many others.…”