Paraplegic standing controlled by functional neuromuscular stimulation: Part I--computer model and control-system...

Area of Science:

• Biomechanics
• Neuroprosthetics
• Robotics

Background:

• Paraplegic individuals often face challenges with standing and mobility.
• Functional neuromuscular stimulation (FNS) offers a potential solution for restoring motor function.
• Developing effective control strategies for FNS-induced standing is crucial for practical applications.

Purpose of the Study:

• To develop a planar computer model simulating paraplegic standing via FNS.
• To investigate the relationship between stimulation parameters and muscle activation.
• To create a control strategy that minimizes energy expenditure and enhances balance.

Main Methods:

• Developed a nonlinear computer model incorporating musculotendon and body-segmental dynamics.
• Modeled muscle activation dynamics using an analytic expression.
• Modified Hill's muscle model to include submaximal activation and tendon elasticity.
• Implemented a linear output-feedback control law and an energy-minimization algorithm.
• Accounted for multi-joint body dynamics and modeled arm movement as a disturbance.

Main Results:

• The model successfully simulates paraplegic standing using FNS.
• Established a relationship between stimulation parameters (pulse width, interpulse interval) and muscle activation.
• A control strategy was developed to distribute net muscle activation for energy efficiency.
• The model provides a framework for analyzing balance control during FNS-induced standing.

Conclusions:

• The developed computer model provides a valuable tool for investigating FNS-induced paraplegic standing.
• The energy-minimization algorithm shows promise for improving the efficiency and sustainability of FNS.
• Further research, including application in Part II, is needed to validate the control strategy's effectiveness in maintaining balance.