Model-Based Estimation of Muscle Forces Exerted During Movements

Estimation of individual muscle forces during human movement can provide insight into neural control and tissue loading and can thus contribute to improved diagnosis and management of both neurological and orthopaedic conditions. Direct measurement of muscle forces is generally not feasible in a clinical setting, and non-invasive methods based on musculoskeletal modeling should therefore be considered. The current state of the art in clinical movement analysis is that resultant joint torques can be reliably estimated from motion data and external forces (inverse dynamic analysis). Static optimization methods to transform joint torques into estimates of individual muscle forces using musculoskeletal models, have been known for several decades. To date however, none of these methods have been successfully translated into clinical practice. The main obstacles are the lack of studies reporting successful validation of muscle force estimates, and the lack of user-friendly and efficient computer software. Recent advances in forward dynamics methods have opened up new opportunities. Forward dynamic optimization can be performed such that solutions are less dependent on measured kinematics and ground reaction forces, and are consistent with additional knowledge, such as the force–length–velocity–activation relationships of the muscles, and with observed electromyography signals during movement. We conclude that clinical applications of current research should be encouraged, supported by further development of computational tools and research into new algorithms for muscle force estimation and their validation

Design and technical construction of a tactile display for sensory feedback in a hand prosthesis system

<p>Abstract</p> <p>Background</p> <p>The users of today's commercial prosthetic hands are not given any conscious sensory feedback. To overcome this deficiency in prosthetic hands we have recently proposed a sensory feedback system utilising a "tactile display" on the remaining amputation residual limb acting as man-machine interface. Our system uses the recorded pressure in a hand prosthesis and feeds back this pressure onto the forearm skin. Here we describe the design and technical solution of the sensory feedback system aimed at hand prostheses for trans-radial/humeral amputees. Critical parameters for the sensory feedback system were investigated.</p> <p>Methods</p> <p>A sensory feedback system consisting of five actuators, control electronics and a test application running on a computer has been designed and built. Firstly, we investigate which force levels were applied to the forearm skin of the user while operating the sensory feedback system. Secondly, we study if the proposed system could be used together with a myoelectric control system. The displacement of the skin caused by the sensory feedback system would generate artefacts in the recorded myoelectric signals. Accordingly, EMG recordings were performed and an analysis of the these are included. The sensory feedback system was also preliminarily evaluated in a laboratory setting on two healthy non-amputated test subjects with a computer generating the stimuli, with regards to spatial resolution and force discrimination.</p> <p>Results</p> <p>We showed that the sensory feedback system generated approximately proportional force to the angle of control. The system can be used together with a myoelectric system as the artefacts, generated by the actuators, were easily removed using a simple filter. Furthermore, the application of the system on two test subjects showed that they were able to discriminate tactile sensation with regards to spatial resolution and level of force.</p> <p>Conclusions</p> <p>The results of these initial experiments in non-amputees indicate that the proposed tactile display, in its simple form, can be used to relocate tactile input from an artificial hand to the forearm and that the system can coexist with a myoelectric control systems. The proposed system may be a valuable addition to users of myoelectric prosthesis providing conscious sensory feedback during manipulation of objects.</p

A pneumatic semi-active control methodology for vibration control of air spring based suspension systems

This research investigates a pneumatic suspension system containing an air spring, air flow valve, and an accumulator, where the spring and damping functions are combined into one package. The spring and accumulator provide the spring characteristics, and the computer controlled adjustable valve provides the damping characteristics by automatically adjusting the air flow between the air spring and the accumulator. An extensive analysis and investigation of the plant dynamics is performed. A dynamic plant model is developed and tuned to experimental data. The plant model is then used in the design of a semi-active control system. A detailed description of the model tuning procedure is provided. Based upon the insights gained through analysis and system identification, a semi-active control methodology is developed, which exploits certain unique features of the system. Three potential controllers are developed and compared, where each controller uses different measurement feedback signals. However, all three controllers measure direct force generation through a pressure feedback signal. Both experimental and simulation data for the controllers is provided. The first controller uses an LQI (Linear Quadratic Impulse) optimal solution, based on Covariance Control Theory, to generate an optimal active damping control force, along with a Set-Point plus PI tracking controller to adjust the valve opening to cause the system to track this desired force during a switching event or control window of opportunity. The second controller uses a Modified Skyhook solution to generate the ideal tracking signal, along with a Set-Point plus PI tracking controller. The LQI controller is used in simulation (offline) to aid in setting the skyhook gain on the Modified Skyhook controller. The third controller uses a Relative Displacement solution to generate the ideal tracking signal, along with a Set-Point plus PI tracking controller. The LQI controller is used (offline) to aid in setting the gain on the Relative Displacement controller. This controller is probably the most useful for vehicular applications, since only relative coordinates and a pressure are required for feedback. It was found that all three controllers could track an optimally generated active signal during the switching event, provided the proper gains were chosen

on bare trees

'on bare trees' is a version of my piece for large ensemble 'things whole and not whole' (2011). The starting point for that piece was the analysis of flocking behaviour in birds made by Craig Reynolds, in which he made computer-graphic simulations of flocking ‘boids’. Their movement was governed by three simple rules: a clumping force which keeps the flock together, a separation force which keeps them apart, and an ability to match velocity. The individual boids follow these rules, and the flock movement emerges from their interaction. Inthings whole and not whole and on bare trees, the interaction of the players is governed by rule-based cueing: players make sounds in response to those made by other players, choosing different reference players for each new sound. In on bare trees, the players also have a series of pitches which they work through independently, occasionally pausing as a group before setting off again. From the perspective of the birds or players, the immediate world is in flux, but seen from the outside the whole is more readily apparent. Both pieces develop my interest in group behaviour as an organising principle. First performed: Plus Minus Ensemble, Material, City University Experimental Music Group, Performance Space, City University, London, 08.04.1

Development of plasmonic sensor using gold nanobipyramids for detection of glyphosate based pesticide

The development of plasmonic sensor using gold nanobipyramids (GNBPs) as sensing material for detection of glyphosate based pesticide (GBP) has been performed. The GNBPs was synthesised using seed-mediated growth method (SMGM). In the synthesis process, the effect of three different additive acid types which are chloric, sulfuric, and fluoric acid, and its concentration in growth solution were investigated to obtain optimum surface density and aspect ratio of GNBPs. The structure obtained is gold with face-centered cubic (FCC) crystal structure and diffraction peaks at 2θ values of 38.2º and 44.5º, which corresponding to (111) and (200) planes, respectively. The GNBPs have surface density from 5.21±0.44 to 91.46±3.32% and aspect ratio from 2.00±0.02 to 2.76±0.05. It exhibits two resonance peaks at wavelength around 550 and 580 nm, corresponding to transverse surface plasmon resonance (t-SPR) and at wavelength around 720 and 780 nm, corresponding to longitudinal surface plasmon resonance (l-SPR). In sensing study, the changes in the peak position and intensity for both t-SPR and l-SPR, respectively, in de-ionized water (DIW) as reference and glyphosate solutions as target analyte were measured. The presence of glyphosate as low as 1 mg/mL was successfully detected using this sensor. Besides, gold bone nanorods (GBNRs) and gold nanorods (GNRs) have been employed as sensing material and the results show the GNBPs�based plasmonic sensor demonstrate improved sensitivity compared to other sensors. For t-SPR band, the GNBPs provided sensitivity factor as high as 4.76 and 5.17 times larger than the sensitivity factor of GBNRs and GNRs, while for l-SPR band, the sensitivity factor of GNBPs are 2.87 times larger than GBNRs and 1.57 times larger than GNRs. Also, the selectivity of GNBPs-based plasmonic sensor towards glyphosate is higher than its response to four different analytes, ie. chlorpyrifos, acetic acid and acetone. As a conclusion, the additive acid types and concentrations influenced the morphological of GNBPs and the implementation as a sensing vi material in plasmonic sensor has been proven improved the sensitivity and has good selectivity towards glyphosate

Accelerating Nearest Neighbor Search on Manycore Systems

We develop methods for accelerating metric similarity search that are effective on modern hardware. Our algorithms factor into easily parallelizable components, making them simple to deploy and efficient on multicore CPUs and GPUs. Despite the simple structure of our algorithms, their search performance is provably sublinear in the size of the database, with a factor dependent only on its intrinsic dimensionality. We demonstrate that our methods provide substantial speedups on a range of datasets and hardware platforms. In particular, we present results on a 48-core server machine, on graphics hardware, and on a multicore desktop

Joint Contour Net Analysis for Feature Detection in Lattice Quantum Chromodynamics Data

In this paper we demonstrate the use of multivariate topological algorithms to analyse and interpret Lattice Quantum Chromodynamics (QCD) data. Lattice QCD is a long established field of theoretical physics research in the pursuit of understanding the strong nuclear force. Complex computer simulations model interactions between quarks and gluons to test theories regarding the behaviour of matter in a range of extreme environments. Data sets are typically generated using Monte Carlo methods, providing an ensemble of configurations, from which observable averages must be computed. This presents issues with regard to visualisation and analysis of the data as a typical ensemble study can generate hundreds or thousands of unique configurations. We show how multivariate topological methods, such as the Joint Contour Net, can assist physicists in the detection and tracking of important features within their data in a temporal setting. This enables them to focus upon the structure and distribution of the core observables by identifying them within the surrounding data. These techniques also demonstrate how quantitative approaches can help understand the lifetime of objects in a dynamic system.Comment: 30 pages, 19 figures, 4 table