Fig 1.
Schema of the iBox (A), and experimental set-up (B).
Fig 2.
Schema of the holding and turning tasks.
PG: Precision Grip, PI: Pinch Grip; PO: Power Grasp, TO: Top Grasp and Move, SWI: Internal Swing, SWE: External Swing, OTD—OTI: Direct or Indirect Overturn according to the direction of the arrow; SPU: Unimanual Spinning, SPB: Bimanual Spinning.
Fig 3.
Presentation of the typical times and phases.
Example of the forces applied on the faces of the object during Pinch Grip. The forces on the front and rear faces (black) are positive during grasping. The force on the bottom of the object (green) is negative when unloaded, the forces on the lateral and top faces are null. The vertical stippled lines represent the typical times which separate the different phases of the action: P0: unloading (between tg, onset of grasping and tl, onset of lifting); P1: lifting (between tl and tp); P2: holding (between tp, end of peak force and tf, end of plateau); P3: preparation to deposit (between tf and td, end of lifting) and P4: deposit (between td and te, end of grasping).
Fig 4.
Median forces observed during the different tasks.
The front face is illustrated on the left and the rear on the right. The vertical lines correspond to the typical times (same legend as Fig 3) that separate the phases of action. Each point represents the median of 3 repetitions in 24 subjects (median were calculated over values at typical times or over median of the values during P1-P3 phases). The black symbols represent lifting tasks (PG: precision grip, PI: Pinch; PO: Power; TO: Top grasp) and color symbols translation (TR) and turning tasks (SWI: internal swing, SWE: external swing, OTD Direct overturn, OTI: indirect overturn; SPU: unimanual spinning, SPB: bimanual spinning).
Table 1.
Frequency of “touches” before grasping and downward “pushes” during P0.
Fig 5.
Comparison of unloading and deposit phases.
A: Forces applied to the front and rear faces at the times of lifting (tl) and deposit (td). Each line represents the median values of 3 repetitions in 24 subjects for the given task (see legend). The forces on the front and rear faces are represented by a full and a dashed line respectively. B: Duration of the lifting (P0) and deposit phases (P4). Same legend. C: Rate of force change during the unloading and deposit phases.
Fig 6.
Lifting phase for the different tasks.
Averages of forces, acceleration and angle signals performed across participants and trials after synchronization on the time of lifting (tl).
Fig 7.
A: Precision Grip (PG), B: Pinch Grip (PI), C: Power Grasp (PO), D: Top Grasp and move (TO). Each figure represents one trial in the same representative subject. The upper part of each figure represents the evolution of the time forces on the faces of the object and the lower part the variations in the orientation of the object according to the 3 axis (see color legends in D). Phases and vertical stippled lines: same legend as Fig 4.
Fig 8.
Same legend as Fig 7.
Fig 9.
A: Internal Swing (pretending to drink). B: External Swing (pretending to read). Same legend as Fig 7.
Fig 10.
A: Direct Overturn OTD. B: Indirect overturn OTI. Same legend as Fig 7.
Fig 11.
A: Unimanual. B: Bimanual. Each figure represents the evolution of the time forces on the faces of the object. Phases and vertical stippled lines: same legend as Fig 4.
Table 2.
Frequency of downward “pushes” during P4 and “touches” after releasing the object.