Electromyographic Mapping of Finger Stiffness in Tripod Grasp

In the first part, I described and validated a sensorized object with easy to change contact surfaces of customizable stiffness; in this chapter, this device is profitably integrated in a new setup to identify the stiffness of hand finger tips in a tripod grasp pose. Understanding the policy used by human to modulate the stiffness in grasping task is important to develop suitable control in robotics, rehabilitation, and teleoperation. As previously said in Chap. 1, few studies investigate about finger stiffness control performed by human in grasping tasks. Toward the twofold purpose of investigating the presence of coordinated regulations of the finger stiffness in human hand and the establishment of a real-time technique in modeling and identification of the finger stiffness while grasping, this study (Rossi et al, Electromyographic mapping of finger stiffness in tripod grasp: A proof of concept, (2015) [1]) explores the relation between the fingertip stiffness and the EMG activity of the antagonist muscles contributing to this profile. To achieve this, the experiments are performed with a custom version of tripod grasp device presented in Chap. 2. While constrained in a tripod posture, subjects held a stable level of stiffness and experienced a series of perturbations provided by the KUKA lightweight robot arm. EMG was recorded alongside force/torque measurements. Consequently, the map between the fingertip stiffness profiles is calculated from the force/torque measurements and the EMG data.