Reducing back displacement in the powered reclining wheelchair

Area of Science:

• Rehabilitation Engineering
• Assistive Technology
• Biomechanics

Background:

• Powered reclining wheelchairs are essential for individuals with severe disabilities, including quadriplegia.
• Repeated recline can induce shear forces, causing user displacement and limiting functional independence.
• Current wheelchair designs may not adequately address shear force mitigation during recline.

Purpose of the Study:

• To investigate modifications for powered reclining wheelchairs to minimize shear forces and user relocation during recline.
• To evaluate the effectiveness of different mechanical solutions in enhancing user stability.
• To identify practical design solutions for improving independent functioning in wheelchair users.

Main Methods:

• Three modifications were tested: a freely sliding back, a powered sliding seat, and a 4-bar linkage.
• A counterbalanced sliding back was constructed and instrumented to measure user displacement.
• Displacement curves were recorded for 8 quadriplegic subjects during simulated recline.

Main Results:

• The sliding back modification was deemed impractical due to the need for a heavy, rigid frame.
• The sliding seat offered minimal reduction in back motion during recline.
• The 4-bar linkage system demonstrated a significant reduction in relative motion between the user and the chair back.

Conclusions:

• The 4-bar linkage is a promising mechanism for eliminating shear forces and user slippage in reclining wheelchairs.
• This modification holds potential for both new wheelchair designs and retrofitting existing models.
• Implementing the 4-bar linkage can enhance user stability and independent function for individuals with severe disabilities.