Analysis of sit-to-stand in sit-to-walk with an admittance controlled robotic walker

Abstract

We examined the effects of the robotic walker’s dynamic characteristics on postural stability, operating forces, ground reaction forces (GRF), and muscle activity in young healthy adults during sit-to-stand (STS) and sit-to-walk (STW) tasks. All study participants were evaluated under eight conditions where the dynamic characteristics, inertia, damping, and frictional forces were changed during the STW test. We analyzed the effects of the robotic walker’s dynamic characteristics on postural stability, force, and muscle activity during STS and STW tasks. A multiple regression analysis revealed that the robotic walker’s inertia and frictional force altered vastus lateralis loading while standing. Here, inertia increases, and friction is applied as a load. The vastus lateralis muscle was activated due to changes in the center of gravity (COG) acceleration and postural stability resulting from inertia and friction loading. Participants compensated for changes in postural stability associated with loading using medial direction operating forces on the hand pad and delaying the “seat off” movement. These changes were analyzed according to COG position and GRF.

Keywords

• stw analysis
• dynamic characteristics
• robotic walker
• postural stability
• operating force
• muscle activity