Mechanical Haptic Interface for EMG-Controlled Robotic Prosthesis

My Role

I engineered an electro-mechanical haptic feedback mechanism for an EMG-controlled ankle prosthesis, leading the full process including conceptualizing and CAD modelling, prototyping and human-subject experiments.

Project Type

Research Project at UNC Chapel Hill and NC State University

Impact

Mechanical haptic interface create an intuitive feedback pathway between the user and prosthesis by converting prosthesis dynamics into perceivable mechanical cues, enhancing motor awareness, control precision, and user embodiment.

Technical Approach

Mechanical Design & Fabrication: SolidWorks, 3D printing, machining, tooling
Control & Integration: Simulink / dSPACE, sensor calibration, microcontroller programming, pneumatics systems
Human Factors Research: Study protocol design, psychophysical testing, data analysis

Overview

The design connects a custom knee brace to an EMG-controlled ankle prosthesis via a biarticular pneumatic actuator that mimics the natural gastrocnemius muscle, which spans knee and ankle joint. By linking the joints through a shared actuator, movement at the ankle generates force feedback, creating a physical communication channel between the user and the prosthesis.

Technical Approach

Concept & Design: Developed a bioinspired haptic feedback mechanism mimicking the gastrocnemius muscle to connect knee and ankle joints.
CAD & Prototyping: Modeled the system in SolidWorks, and fabricated components via 3D printing and machining with custom mechanical fixtures.
System Integration: Integrated load sensors, microcontrollers, and a Simulink/dSPACE control interface for real-time actuation and feedback control.
Bench Testing: Characterized actuator performance, validated load response, and refined control logic for stability and comfort.
Human-Subject Experimentation: Developed study protocols for psychophysical testing and validation trials with amputee and able-bodied users to assess feedback perception and usability.

Ideation

Prototyping

Human Subject Testing

Initial tests with able-bodied participants showed that the haptic interface could be distinguishable with different level of feedback corresponding to ankle torque and ankle movement. Participants reported clear perception of feedback intensity changes and rapid adaptation after short familiarization trials. Project is ongoing with amputee participant experiments.