Hairong Wang; Shaowei Fan; Hong Liu
J. Mech. Des. 2016; 139(1):012304-012304-12
doi: 10.1115/1.4034837

The force and/or motion transmissibility and the analyticity of inverse kinematics for a thumb mechanism depend on thumb configuration. This paper presents a general framework for the thumb configuration and performance evaluation in the design of dexterous robotic hand. The thumb configuration is described by the functional analysis of human thumb, and the thumb of robotic hand is generalized into fifteen configurations. A performance evaluation method is proposed based on kinetostatic and dynamic dexterity as well as workspace. The kinetostatic dexterity is based on a Jacobian matrix condition number. A dynamic dexterity measure is presented via acceleration analysis, which keeps a clear geometric meaning. The proposed method is applied to evaluate the performance of three examples, which cover thumb configurations of most existing dexterous hands. Performance evaluation results demonstrate the effectiveness of the proposed method. Using these results and the proposed performance evaluation method, meaningful design principles are presented to guide the design of the thumb configuration.

The synthesis of functional molecular mechanisms is constrained by the notorious difficulties in fabricating nano-links of prescribed shapes and sizes. Thus, the classical mechanism synthesis methods, which assume the ability to manufacture any designed links, cannot provide a systematic process for designing molecular mechanisms. We propose a new approach to build functional mechanisms with prescribed mobility by only using elements from a predefined "link soup". The resulting synthesis procedure is the first of its kind that is capable of systematically synthesizing functional linkages with prescribed mobility constructed from a soup of primitive entities. Furthermore, the proposed systematic approach outputs the ATLAS of candidate mechanisms, which can be further processed for downstream applications. Although the scope of this technique is rather general, its immediate application is the design of molecular machines assembled from nano-links that either exist in nature or can be fabricated.

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Authors: Lei Cui, Paul Cheong; Ridge Adamson, Thomas Johnson
J. Mech. Des. (2014); doi:10.1115/1.4028094

The Swan-Canning River, which features relatively shallow and slow-moving water with sandy soils, is the most important estuary system in Perth, Western Australia. Currently, the Department of Water Western Australia sends personnel to manually survey and collect water and sand samples at thirty-two routine sampling sites along the Swan-Canning River weekly. The excessively large monitoring areas make the sample collection a costly practice, and the safety of personnel is potentially put at risk during the seasonal collection of mosquito-larvae samples and the occasional collection of toxic-waste samples. At the Department of Mechanical Engineering, Curtin University, we developed the AmBot, an amphibious robot, to automate this operation. The major challenge in developing the AmBot lies in that the limited physical size of the robot allows only one type of propulsion system to be used both on land and on water. On the contrary, large amphibious robots that use wheels or track systems when on land can switch to propellers when on water. We took inspiration from centipedes and morphed the multi-leg actuation into tracks by simplifying each leg-mechanism into a track piece consisting of a base and a polystyrene-foam block. This design makes the tracks essentially both floats and paddles that are also capable of withstanding the weight of the vehicle. When on water, the tracks provide propulsion force and buoyancy so that the waterline is well controlled; when on land, the tracks effectively spread the contact force across multi-blocks, leading to effective actuation and low pressure on the sandy terrain, hence protecting the beach eco-system. The AmBot uses an Android-based remote-control system via the Internet, where the accelerometer, gyroscope, GPS, and camera on the Android device provide integrated navigation and monitoring sensing.