Author ORCID Identifier

https://orcid.org/0009-0003-5417-1892

Semester

Fall

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Nicholas Szczecinski

Committee Member

Sergiy Yakovenko

Committee Member

Yu Gu

Abstract

Force feedback is a type of robotic control where forces are measured, fed back into the control system, and actuation is adjusted to compensate for environmental forces, with the goal of quick and precise limb positioning in walking. Robots of today use single force sensors (e.g. pressure sensitive pads, load cells) per leg which are often bulky, expensive, and susceptible to crosstalk. Walking robots often employ model predictive controllers or policy controllers trained through reinforcement learning (RL) to actuate their limbs, but these methods are time and energy consuming. Biomimetic robots offer an alternative approach, investigating biological theories with the goal of creating robots with animal-like characteristics. Biomimetic control is advantageous because its objectives include fast, low-energy computation, with one structure built for a wide range of environmental and movement scenarios.

One biomimetic alternative to state of the art force controllers for robots is to study insect campaniform sensilla (CS), organs that sense cuticular strains near their joints. CS are dynamically sensitive, meaning that they respond to the magnitude and the rate of change of forces applied to the leg. These neurons are known to have direct connections with motor neurons allowing for actuation adjustment. CS also strongly influence the timing of joint central pattern generators (CPGs) which control the phasing of steps.

In this thesis, I compared theoretical findings of dynamic sensing and actuation with physical tests on a biomimetic, Carausius morosus (stick insect) robot leg. External forces were measured by multiple strain gauges distributed across the leg in analogous locations and orientations to the stick insect’s strain sensing organs (campaniform sensilla), offering lightweight, affordable, and redundant force sensing. Viscoelastic effects from the 3D printed limb segments, made from Onyx®, were accounted for in biomimetic and viscoelastic controllers. Controllers were built from experimental data and system modeling, instead of incorporating RL or optimization. I tested these controllers in three tests: Leg standing tests in which the leg adjusted its posture to resist external forces; Stepping tests in which the force feedback reflexively adapted motor output during stance phase; and a robustness test, in which I artificially changed the controllers’ viscoelastic model and analyzed controllers’ performance changes. I applied a bistable phase controller which uses proprioceptive information to time the transitions to and from stance and swing phases of stepping.

Results show the biomimetic controller offers smoother motions and increased robustness over the viscoelastic controller. Increased dynamic sensitivity improves postural compensation during the stance phase of stepping/standing and consistency of transition time from stance to swing phase with the bistable phase controller. I discuss how this work may be used in biomimetic and non-biomimetic robots alike, and future avenues of biomimetic force feedback implementation.

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