376 research outputs found
High-efficiency sma-based actuator
Design proposal and implementation analysis of an alternative high displacement
flexible SMA-based actuator topology, targeting improved energy
efficiency and actuation time, by completely overhaulingSMAwire’s surrounding
conditions, specifically adding high heat capacity fluids and improving
thermal management.IngenierÃa Electrónica Industrial y Automátic
Mechanical design and friction modelling of a cable-driven upper-limb exoskeleton
This paper presents a lightweight and low-inertia cable-driven upper-limb exoskeleton powerful enough to meet the requirements for activities of daily living. It presents the mechanical design, kinematic structure,the underlying actuation system, sensors, other electronic components as well as the controller of the exoskeleton.
The extensive effect of friction on cable-driven designs, such as the one presented in this paper, requires proper mathematical modelling for controller design. Thus, we propose a current actuator model that describes the relationship between the motor current, velocity, and external load. The model relies on an underlying Stribeck+Coulomb friction representation and an additional parameter that modifies its Coulomb friction representation with an offset to represent adhesion between a cable and sheath.
The model has been validated based on experimental data collected with the exoskeleton. The results show that the proposed model better captures the non-linear behaviour of the exoskeleton’s actuation system, increasing overall descriptive performance by 15%. However, adding the adhesion offset to extend the relation of static friction, does not improve the model
Cable-driven parallel robot for transoral laser phonosurgery
Transoral laser phonosurgery (TLP) is a common surgical procedure in otolaryngology.
Currently, two techniques are commonly used: free beam and fibre delivery. For free beam
delivery, in combination with laser scanning techniques, accurate laser pattern scanning can
be achieved. However, a line-of-sight to the target is required. A suspension laryngoscope is
adopted to create a straight working channel for the scanning laser beam, which could
introduce lesions to the patient, and the manipulability and ergonomics are poor. For the fibre
delivery approach, a flexible fibre is used to transmit the laser beam, and the distal tip of the
laser fibre can be manipulated by a flexible robotic tool. The issues related to the limitation
of the line-of-sight can be avoided. However, the laser scanning function is currently lost in
this approach, and the performance is inferior to that of the laser scanning technique in the
free beam approach.
A novel cable-driven parallel robot (CDPR), LaryngoTORS, has been developed for TLP.
By using a curved laryngeal blade, a straight suspension laryngoscope will not be necessary
to use, which is expected to be less traumatic to the patient. Semi-autonomous free path
scanning can be executed, and high precision and high repeatability of the free path can be
achieved. The performance has been verified in various bench and ex vivo tests. The technical
feasibility of the LaryngoTORS robot for TLP was considered and evaluated in this thesis.
The LaryngoTORS robot has demonstrated the potential to offer an acceptable and feasible
solution to be used in real-world clinical applications of TLP.
Furthermore, the LaryngoTORS robot can combine with fibre-based optical biopsy
techniques. Experiments of probe-based confocal laser endomicroscopy (pCLE) and
hyperspectral fibre-optic sensing were performed. The LaryngoTORS robot demonstrates the
potential to be utilised to apply the fibre-based optical biopsy of the larynx.Open Acces
Catheter steering in interventional cardiology: Mechanical analysis and novel solution
In recent years, steerable catheters have been developed to combat the effects of the dynamic cardiac environment. Mechanically actuated steerable catheters appear the most in the clinical setting; however, they are bound to a number of mechanical limitations. The aim of this research is to gain insight in these limitations and use this information to develop a new prototype of a catheter with increased steerability. The main limitations in mechanically steerable catheters are identified and analysed, after which requirements and solutions are defined to design a multi-steerable catheter. Finally, a prototype is built and a proof-of-concept test is carried out to analyse the steering functions. The mechanical analysis results in the identification of five limitations: (1) low torsion, (2) shaft shortening, (3) high unpredictable friction, (4) coupled tip-shaft movements, and (5) complex cardiac environment. Solutions are found to each of the limitations and result in the design of a novel multi-steerable catheter with four degrees of freedom. A prototype is developed which allows the dual-segmented tip to be steered over multiple planes and in multiple directions, allowing a range of complex motions including S-shaped curves and circular movements. A detailed analysis of limitations underlying mechanically steerable catheters has led to a new design for a multi-steerable catheter for complex cardiac interventions. The four integrated degrees of freedom provide a high variability of tip directions, and repetition of the bending angle is relatively simple and reliable. The ability to steer inside the heart with a variety of complex shaped curves may potentially change conventional approaches in interventional cardiology towards more patient-specific and lower complexity procedures. Future directions are headed towards further design optimizations and the experimental validation of the prototype
Pressure-Constrained, Reduced-DOF, Interconnected Parallel Manipulators with Applications to Space Suit Design
This dissertation presents the concept of a Morphing Upper Torso, an innovative pressure suit design that incorporates robotic elements to enable a resizable, highly mobile and easy to don/doff spacesuit. The torso is modeled as a system of interconnected, pressure-constrained, reduced-DOF, wire-actuated parallel manipulators, that enable the dimensions of the suit to be reconfigured to match the wearer. The kinematics, dynamics and control of wire-actuated manipulators are derived and simulated, along with the Jacobian transforms, which relate the total twist vector of the system to the vector of actuator velocities. Tools are developed that allow calculation of the workspace for both single and interconnected reduced-DOF robots of this type, using knowledge of the link lengths. The forward kinematics and statics equations are combined and solved to produce the pose of the platforms along with the link tensions. These tools allow analysis of the full Morphing Upper Torso design, in which the back hatch of a rear-entry torso is interconnected with the waist ring, helmet ring and two scye bearings. Half-scale and full-scale experimental models are used along with analytical models to examine the feasibility of this novel space suit concept. The analytical and experimental results demonstrate that the torso could be expanded to facilitate donning and doffing, and then contracted to match different wearer's body dimensions. Using the system of interconnected parallel manipulators, suit components can be accurately repositioned to different desired configurations. The demonstrated feasibility of the Morphing Upper Torso concept makes it an exciting candidate for inclusion in a future planetary suit architecture
The 12th Aerospace Mechanisms Symposium
Mechanisms developed for various aerospace applications are discussed. Specific topics covered include: boom release mechanisms, separation on space shuttle orbiter/Boeing 747 aircraft, payload handling, spaceborne platform support, and deployment of spaceborne antennas and telescopes
Piston-ring lubricant failure in diesel engines
Imperial Users onl
The 24th Aerospace Mechanisms Symposium
The proceedings of the symposium are reported. Technological areas covered include actuators, aerospace mechanism applications for ground support equipment, lubricants, latches, connectors, and other mechanisms for large space structures
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