Mechanical Engineering - Research Publications
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ItemEffect Of Arm Deweighting Using End-Effector Based Robotic Devices On Muscle Activity.(IEEE, 2018)Deweighting of the limb is commonly performed for patients with a neurological injury, such as stroke, as it allows these patients with limited muscle activity to perform movements. Deweighting has been implemented in exoskeletons and other multi-contact devices, but not on an end-effector based device with single contact point between the assisting robot and the human limb being assisted. This study inves-tigates the effects of deweighting using an end-effector based device on healthy subjects. The muscle activity of five subjects was measured in both static postures and dynamic movements. The results indicate a decrease in the activity of muscles which typically act against gravity - such as the anterior deltoid and the biceps brachii - but also suggest an increase in activity in muscles which act with gravity - such as the posterior deltoid and the lateral triceps. This can be explained by both the change in required muscle-generated torques and a conscious change in approach by the participants. These observations have implications for neurorehabilitation, particularly with respect to the muscle activation patterns which are trained through rehabilitation exercises.
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ItemSystem of funnels framework for robust global non-linear control(IEEE, 2016)There exist various methods for planning nominal trajectories to guide desired behaviours of non-linear systems, along with constructive methods for computing finite-time invariant sets, termed funnels, about locally-stabilized nominal trajectories. In order to achieve a desired behaviour defined by a set of nominal trajectories and their corresponding funnels, one has to switch from one local control to another at the right instances. This paper presents a general hybrid-control framework which is designed for correct switching between locally stabilizing controllers and can be used in conjunction with various approaches for funnel computation. Our framework prescribes exact connectivity conditions to be satisfied by the different funnels used such that the desired behaviour is achieved globally and in a robust manner. Due to its generality, the framework can be applied to implement a wide class of dynamic behaviours. An example of a periodic behaviour governed by our framework is provided.
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ItemStatic force dependency of bone conduction transducer as sensory feedback for stump-socket based prosthesis(Australian Robotics and Automation Association, 2018-01-01)The dependency of a novel sensory feedback for stump-socket based prosthesis on the static force is presented using a bone conduction transducer as feedback source. The stimulation was induced onto the bony landmarks of the elbow, specifically the Ulna and presented in an interval halving method. The perception threshold in the range of tactile and auditory perception at three different force levels has been tested. The inter subject variability is bigger than the intra subject variation. The small static force variation suggests a similar approach as in bone conduction hearing aids and therefore a static force bigger than 6N should be applied to perceive a constant stimulation. A mechanical design to include such a novel feedback into a stump-socket needs to account for this requirement. The inter subject variability needs to be addressed by incorporate some kind of person to person calibration of the gain.
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ItemMuscle coordination during single-leg landing: Implications for ACL injuries(Orthopaedic Research Society, 2012)