Introduction:
Accurate estimation of bone kinematics is fundamental in biomechanics, rehabilitation, and human motion analysis. Traditional marker-based motion capture systems are widely used but suffer from soft tissue artefacts (STA), where skin-mounted markers do not accurately represent the motion of underlying bones. A-mode ultrasound sensing provides a promising complementary approach by detecting strong reflections from bone surfaces, allowing distance measurements along the ultrasound beam. When multiple transducers are used, bone position and orientation can be estimated.
Despite its potential, a key limitation of current A-mode ultrasound tracking systems lies in maintaining proper alignment between the transducer and the bone surface during movement. Soft tissue deformation can cause misalignment, leading to weaker signal reflections and reduced tracking accuracy. Addressing this challenge requires a system capable of actively adjusting the transducer position and orientation in real time based on signal feedback.
This thesis aims to develop a mechatronic system that integrates actuation and sensing feedback to maintain optimal ultrasound alignment, thereby improving the robustness and accuracy of bone motion tracking.
Objectives:
- To investigate the impact of soft tissue artefacts on A-mode ultrasound-based bone tracking and identify key factors affecting signal quality.
- To design and develop a compact actuation mechanism capable of adjusting the position and/or orientation of A-mode ultrasound transducers (one or more at the same time) during motion.
- To develop a real-time feedback control strategy based on ultrasound signal characteristics (e.g., amplitude or signal quality indicators) to optimize transducer alignment.
- To integrate the actuation and feedback system into a unified framework for adaptive ultrasound-based bone tracking.
- To experimentally evaluate the system’s performance in terms of tracking accuracy, robustness, and consistency under dynamic conditions.
Research Approach:
The project will be structured into two main development phases:
- Actuation System Design:
Development of a mechatronic mechanism to actively control the positioning and orientation of the A-mode ultrasound transducer. This includes mechanical design, actuator selection, and system integration.- First level: Actuate one transducer
- Next level: Actuate two transducers simultaneously.
- Feedback Control System:
Implementation of a sensing-driven feedback loop that uses ultrasound signal properties to guide the actuation system. The goal is to maintain optimal alignment between the transducer and the bone surface in real time.
Expected Outcomes:
- A functional prototype of an actively controlled A-mode ultrasound sensing system.
- A novel feedback-based alignment strategy improving signal consistency and reliability.
- Demonstrated reduction in the effects of soft tissue artefacts on bone tracking accuracy and robustness.
- Experimental validation showing improved performance compared to passive ultrasound setups.
- Contribution to advanced sensing and mechatronic solutions for motion analysis and biomedical applications.
Conclusion:
This thesis focuses on bridging sensing and actuation through a closed-loop mechatronic system for ultrasound-based bone tracking. By combining active transducer positioning with intelligent feedback control, the proposed approach aims to significantly enhance the reliability of non-invasive bone motion estimation, opening new possibilities in biomechanics and medical technology.