Design and Evaluation of a Propulsion System for Small, Compact, Low-Speed Maneuvering Underwater Vehicles

Underwater vehicles used to perform precision inspection and non-destructive evaluation in tightly constrained or delicate underwater environments must be small, have low-speed maneuverability and a smooth streamlined outer shape with no appendages. In this thesis, the design and analysis of a new propulsion system for such underwater vehicles is presented. It consists primarily of a syringe and a plunger driven by a linear actuator and uses different inflow and outflow nozzles to provide continuous propulsive force. A prototype of the proposed propulsion mechanism is built and tested. The practical utility and potential efficacy of the system is demonstrated and assessed via direct thrust measurement experiments and by use of an initial proof-of-concept test vehicle. Experiments are performed to enable the evaluation and modelling of the thrust output of the mechanism as well as the speed capability of a vehicle employing the propulsion system

Developing a control framework for self-adjusting prosthetic sockets incorporating tissue injury risk estimation and generalized predictive control

To perform activities of daily living (ADL), people with lower limb amputation depend on the prosthetic socket for stability and proprioceptive feedback. Poorly fitting sockets can cause discomfort, pain, limb tissue injuries, limited device usage, and potential rejection. Semi-passively controlled adjustable socket technologies exist, but these depend upon the user’s perception to determine safe interfacial pressure levels. This paper presents a framework for automatic control of an adjustable transtibial prosthetic socket that enables active adaptation of residuum-socket interfacial loading through localized actuators, based on soft tissue injury risk estimation. Using finite element analysis, local interfacial pressure vs. compressive tissue strain relationships were estimated for three discrete anatomical actuator locations, for tissue injury risk assessment within a control structure. Generalized Predictive Control of multiple actuators was implemented to maintain interfacial pressure within estimated safe and functional limits. Controller simulation predicted satisfactory dynamic performance in several scenarios. Actuation rates of 0.06–1.51 kPa/s with 0.67% maximum overshoot, and 0.75–1.58 kPa/s were estimated for continuous walking, and for a demonstrative loading sequence of ADL, respectively. The developed platform could be useful for extending recent efforts in adjustable lower limb prosthetic socket design, particularly for individuals with residuum sensory impairment.</p

Predictive control for an active prosthetic socket informed by FEA-based tissue damage risk estimation

This paper presents an architecture for generalized predictive control for an active prosthetic socket system, based on a cost function performance index measure for minimization of residual limb tissue injury. Finite element analysis of a transtibial residuum model donned with a total surface bearing socket was used to provide controller training data and biomechanical rationale for deep tissue injury risk assessment, by estimating the internal deformation state of the soft tissues and the residuum-socket interface loading under a range of prosthetic loading instances. The results demonstrate the concept of this approach for interface actuation modelled as translational spring and damper systems