# Supplement: Design and Model-Based Safety Verification of a Volitional Sit-Stand Controller for a Powered Knee-Ankle Prosthesis

> **NIH NIH F31** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 2024 · $36,093

## Abstract

ABSTRACT OF PARENT AWARD
Sit-stand transitions, the motions executed by individuals to stand up or sit down, are an important determinant
of overall mobility and a common source of falls. Unilateral amputees using standard passive prostheses are
further challenged by sit-stand transitions due to muscle and joint asymmetries they exhibit between the sound
and amputated sides, often resulting in debilitating back pain. Powered knee-ankle prostheses can produce
enough torque to assist meaningfully during sit-stand transitions and can meet design criteria such as producing
smooth motion on the amputated side that matches the sound side. Controllers for these prostheses can be
designed to allow user-driven control of the leg. However, the production of high torques not directly commanded
by the user comes with increased risks. This is of particular concern because these legs must be adopted outside
of controlled lab environments. Thus, any powered prosthesis must demonstrably meet design and safety
criteria. While safety-critical medical devices, such as pacemakers, are subjected to extensive testing and
validation procedures, there is no agreed-upon standard in the powered prosthetics field for how to define and
measure safety. Prior work on sit-stand controllers has focused only on measuring a limited number of outcomes
with respect to one design criterion on a small number of subjects, providing no guarantees about safety. The
set of techniques known as formal verification provides powerful tools to reason about the behavior of systems
that are composed of interacting mechanical, software, and biological modules. Given a model of a system,
formal verification allows us to probe the system’s behavior over an infinite range of possibilities that cannot be
replicated in the lab during a typical testing session. These methods can then guide real-world testing, and alert
system designers to problematic regions of execution. In this project, I propose to apply formal verification
techniques to design a volitional controller for sit-stand transitions with provable safety guarantees, using
physics-based models and novel mathematical formulations of safety.

## Key facts

- **NIH application ID:** 11122564
- **Project number:** 3F31EB032745-02S2
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **Principal Investigator:** Daphna Raquel Raz
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $36,093
- **Award type:** 3
- **Project period:** 2024-06-21 → 2025-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11122564

## Citation

> US National Institutes of Health, RePORTER application 11122564, Supplement: Design and Model-Based Safety Verification of a Volitional Sit-Stand Controller for a Powered Knee-Ankle Prosthesis (3F31EB032745-02S2). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/11122564. Licensed CC0.

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