Analysis of grasping strategies and function in hemiparetic patients using an instrumented object

Abstract

This paper validates a novel instrumented object, the iBox, dedicated to the analysis of grasping and manipulation. This instrumented box can be grasped and manipulated, is fitted with an Inertial Measurement Unit (IMU) and can sense the force applied on each side and transmits measured force, acceleration and orientation data wirelessly in real time. The iBox also provides simple access to data for analysing human motor control features such as the coordination between grasping and lifting forces and complex manipulation patterns. A set of grasping and manipulation experiments was conducted with 6 hemiparetic patients and 5 healthy control subjects. Measures made of the forces, kinematics and dynamics are developed, which can be used to analyse grasping and contribute to assessment in patients. Quantitative measurements provided by the iBox reveal numerous characteristics of the grasping strategies and function in patients: variations in the completion time, changes in the force distribution on the object and grasping force levels, difficulties to adjust the level of applied forces to the task and to maintain it, along with movement smoothness decrease and pathological tremor.

Tactile feedback is an effective instrument for the training of grasping with a prosthesis at low- and medium-force levels

“…More specifically, we investigated the ability of learning, updating, and maintaining an accurate internal model of a myoelectric prosthesis to consistently control its grasping force in a feedforward manner. In contrast to the previous work (Dosen et al 2015), the present experiment evaluated the tactile feedback based on vibration and mixed coding, which is a practically relevant interface [instead of visual feedback used in (Jarrasse et al 2013)]. Furthermore, the training of feedforward control was performed on multiple force levels (low, medium, and high) and the retention was tested within session as well as after 1 day.…”

“…Here, the feedback is used to detect state transitions (e.g., contact and liftoff) triggering the release of appropriate motor programs and/or to online modulate the feedforward commands to correct errors due to uncertainty in modeling and/or environment (e.g., correcting the overshoot if the bottle was empty) (Flanagan and Wing 1997; Flanagan et al 2001; Green et al 2010). Somatosensory information plays a fundamental role in the learning, maintenance, and updating of these anticipatory mechanisms (Witney et al 2004; Hermsdorfer et al 2011; Jarrasse et al 2013) and predictive force control requires at least intermittent cutaneous and proprioceptive feedback to signal the effectiveness of descending motor commands and to update internal models (Nowak et al 2004). …”

Taxonomy based analysis of force exchanges during object grasping and manipulation

“…The iBox [6] is a parallelepiped (Fig 1A) of dimension 108x70x40mm 3 and mass 0.370kg. It is equipped with an inertial unit (IMU), an embedded electronic board [40] to measure its accelerations, rotational velocities, orientations and six load cells to measure the force applied normally to its six faces (up to 42 N).…”

“…The analysis focused on the forces applied on the 6 faces of the iBox (Fig 3), on the angles computed from sensor fusion of the IMU signals [6] and on global acceleration (computed as the norm of the three vectors). The rotations were presented as Euler angles in YXZ sequence (corresponding respectively to spinning, swing and overturn).…”

“…However our hypothesis is that the dexterity to manipulate an object can be quantified from this object motion and the force exchanged between the hand and the object. Therefore we developed an instrumented object providing measurement of motion and force on all its faces [6] to examine a variety of grasping and manipulation tasks representative of object use in the daily life [7]. Towards this ambitious goal, we analyze here the exchange of forces during holding and manipulation tasks of scaled difficulties.…”