A Novel User-Controlled Assisted Standing Control System for a Hybrid Neuroprosthesis

[摘要] Spinal cord injury (SCI) is a serious condition with 17,000 new cases each year and an estimatedtotal of 282,000 people in the United States who have SCI. Some people with SCI who haveparaplegia suffer from paralysis, muscle spasticity, bone changes, chronic pain and otherproblems. Active orthoses such as the ReWalk, EXPOS, and Ekso have improved the quality oflife of people with SCI. The hybrid neuroprosthesis is an active orthosis that uses functionalelectrical stimulation (FES) at the quadriceps and has two main purposes: restoring mobility inpeople with SCI and providing physical therapy for the user outside of a clinical setting.To mobilize people with SCI, the neuroprosthesis must provide assisted movement for asitting to standing motion. A standing control system developed by the Pitt NeuromuscularControl and Robotics Laboratory (NCRL) before this proposed system did not give enoughcontrol of the movement to the user and FES alone did not provide enough torque at the kneesfor standing. The NCRL neuroprosthesis was modified to include a harmonic gearmotor at theknees, a thumb joystick for user control, and a force sensing walker.A control system using a finite state machine (FSM) was designed to perform hybridstanding in the neuroprosthesis. The FSM is divided into 3 states and uses 5 separate controllers:a tracking controller for forward leaning during sitting, a tracking controller to synchronize theknees, a tracking controller to lock the knees during standing, a hip tracking controller, and openloopFES. Four experiments were performed on subjects to analyze control performance, powerusage, and energy consumption during motors only and hybrid standing. A subject with SCIsuccessfully performed several trials of hybrid standing. The controllers performed sufficientlyaccurately, and several minor control problems were fixed. The highest average energyconsumption at the knee motors was 88.4 joules during experiment 1. The hybrid standingexperiment demonstrated a modest energy reduction of 15% in a subject with SCI. The hybridstanding demonstrated a high energy reduction of 74% in the right knee in experiment 2, throughhybrid actuation and a slower standing speed.

[发布机构] the University of Pittsburgh