Development of a Real-time Controller to Estimate Walking Performance Using a Bilateral Ankle Exoskeleton

Controller Development to Enable Individualized Assistance in Robotic Ankle Exoskeletons

This study is developing and testing a new controller for a robotic ankle exoskeleton (Biomotum) that can adjust itself in real time to better support people while they walk. The system learns how each person moves and automatically changes the amount and timing of assistance to make walking feel easier and more efficient. By using information from the person wearing the device, the exoskeleton can quickly find the level of support that works best for them. The long-term goal is to create personalized walking assistance that can help people with mobility limitations move more comfortably and with less effort.

Study Overview

• Status: Not yet recruiting
• Conditions: Healthy Young Adults
• Intervention / Treatment: Device: Adaptive Torque Control System for Ankle Exoskeleton

Detailed Description

This project aims to develop and test a real-time adaptive controller for a robotic ankle exoskeleton (Biomotum) that personalizes assistance to each user by minimizing metabolic cost and optimizing muscle activation patterns during walking. Using human-in-the-loop optimization and advanced musculoskeletal modeling, the controller will dynamically adjust torque magnitude and timing to achieve optimal performance more quickly than current methods.

• Study Type: Interventional
• Enrollment (Estimated): 6
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Farah Fallahtafi, PhD; Phone Number: 4025543075; Email: ffallahtafti@unomaha.edu

Study Locations

• United States
  • Nebraska
    • Omaha, Nebraska, United States, 68108
      • Biomechanics Research Building, University of Nebraska at Omaha

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• able to walk independently on a treadmill for 10 minutes,
• free of neurological, cardiovascular, pulmonary, or musculoskeletal conditions that limit walking and exercising,
• no current lower extremity pain or injury,
• able to wear an exoskeleton and safety harness, can provide informed consent

Exclusion Criteria:

• history of neurological disease that affected gait or balance,
• current or recent lower extremity musculoskeletal injury or surgery,
• chronic lower extremity pain during walking,
• inability to participate in moderate-intensity exercise,
• require an assistive device for walking,
• any metabolic or systemic diseases that may be exacerbated by exercise

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Device Feasibility
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Single-Arm Study of a Personalized Robotic Ankle Exoskeleton Controller; This arm employs a within-subject design with two methods of estimating metabolic cost versus the gold standard measure of metabolic cost, wherein a single participant is subjected to two distinct measurements. This design allows for a direct comparison of the effects of each method (i.e., estimation versus gold standard) within the same individual, minimizing intersubject variability and enhancing the statistical power of the analysis.

Device: Adaptive Torque Control System for Ankle Exoskeleton; This intervention uses a robotic ankle exoskeleton equipped with a real-time adaptive controller that adjusts plantarflexion torque based on each participant's walking mechanics. Unlike standard exoskeleton controllers that use fixed or pre-programmed assistance levels, this system employs human-in-the-loop optimization to continuously update torque magnitude and timing during treadmill walking. The controller integrates metabolic estimations, kinematic data, and musculoskeletal modeling to identify individualized assistance patterns that reduce walking effort and improve muscle activation efficiency. Participants complete multiple walking trials while the controller automatically modifies assistance to determine the optimal personalized settings.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Successful Real-Time Operation of the Robotic Ankle Exoskeleton Controller	Device feasibility will be evaluated by the successful real-time operation of the robotic ankle exoskeleton and adaptive controller during treadmill walking. Feasibility is defined as the controller's ability to continuously generate, update, and apply assistive torque in real time based on incoming biomechanical and physiological data without system failure, interruption, or safety-related termination. Successful operation will be confirmed by continuous controller function and synchronized data acquisition across walking trials.	through study completion, an average of 1 year

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Net Metabolic Rate During Exoskeleton-Assisted Walking Measured by Indirect Calorimetry	Net oxygen consumption (VO₂) and carbon dioxide production (VCO₂) will be measured during treadmill walking using indirect calorimetry (Cosmed K5, Cosmed USA Inc., Chicago, IL). Metabolic rate will be calculated using standard equations during steady-state walking conditions. Measurements will be collected at regular intervals to characterize metabolic demand under different exoskeleton assistance configurations.	through study completion, an average of 1 year
Estimated Metabolic Rate Derived From Joint-Space Musculoskeletal Modeling	Estimated metabolic rate will be derived from joint-space musculoskeletal models using kinematic and kinetic data collected during treadmill walking. Model-based estimates will be computed on a stride-by-stride basis to provide an indirect estimate of metabolic demand that can be compared with direct measurements from indirect calorimetry.	through study completion, an average of 1 year
Estimated Lower-Limb Muscle Activation Derived From Joint-Space Musculoskeletal Modeling	Lower-limb muscle activation patterns will be estimated using joint-space musculoskeletal models based on motion capture and ground reaction force data collected during treadmill walking. Estimated muscle activation values will be computed on a stride-by-stride basis to characterize neuromuscular engagement during exoskeleton-assisted gait.	through study completion, an average of 1 year
Lower-Limb Muscle Activation Measured by Surface Electromyography During Walking	Muscle activation of lower-limb muscles (e.g., tibialis anterior, gastrocnemius medialis, gastrocnemius lateralis, soleus) will be measured during treadmill walking using surface electromyography (Delsys). EMG signals will be collected continuously and processed to quantify muscle activation patterns during exoskeleton-assisted gait.	through study completion, an average of 1 year
During treadmill walking trials conducted at a single study visit	Controller parameter convergence will be assessed during human-in-the-loop optimization trials by evaluating changes in controller gain and timing parameters across successive walking bouts. Convergence is defined as stabilization of controller parameters within a predefined range during the optimization process.	through study completion, an average of 1 year

Collaborators and Investigators

• Sponsor: University of Nebraska
• Collaborators: Madonna Rehabilitation Hospital
• Investigators: Principal Investigator: Farah Fallahtafti, PhD, Department of Biomechanics, University of Nebraska at Omaha

Study record dates

Study Major Dates

• Study Start (Estimated): June 1, 2026
• Primary Completion (Estimated): August 1, 2026
• Study Completion (Estimated): December 1, 2026

Study Registration Dates

• First Submitted: December 5, 2025
• First Submitted That Met QC Criteria: January 30, 2026
• First Posted (Actual): February 6, 2026

Study Record Updates

• Last Update Posted (Actual): June 2, 2026
• Last Update Submitted That Met QC Criteria: June 1, 2026
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: wearable robotics; robotic ankle exoskeleton; human-in-the-loop optimization; musculoskeletal modeling; muscle activation analysis
• Other Study ID Numbers: 0587-25-FB; 55136 (Other Grant/Funding Number: Nebraska Research Initiative)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: IPD will not be shared because direct measurements are only taken for baseline measurements that the modeling software will be using. The scripts and code used will be shared through opensource, but that does not include subject data.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes