Journal of Mechanisms and Robotics Newest Issueen-usWed, 04 Oct 2017 00:00:00 GMTWed, 04 Oct 2017 11:43:39 GMTSilverchaireditor@mechanismsrobotics.asmedigitalcollection.asme.orgwebmaster@mechanismsrobotics.asmedigitalcollection.asme.orgModeling of Dive Maneuvers for Executing Autonomous Dives With a Flapping Wing Air Vehicle
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Wed, 04 Oct 2017 00:00:00 GMTRoberts LJ, Bruck HA, Gupta SK. <span class="paragraphSection">This paper is focused on design of dive maneuvers that can be performed outdoors on flapping wing air vehicles (FWAVs) with a minimal amount of on-board computing capability. We present a simple computational model that provides accuracy of 5 m in open loop operation mode for outdoor dives under wind speeds of up to 3 m/s. This model is executed using a low power, on-board processor. We have also demonstrated that the platform can independently execute roll control through tail positioning, and dive control through wing positioning to produce safe dive behaviors. These capabilities were used to successfully demonstrate autonomous dive maneuvers on the Robo Raven platform developed at the University of Maryland.</span>//article/9/6/061010/2652700/Modeling-of-Dive-Maneuvers-for-ExecutingLocomotion of a Mini Bristle Robot With Inertial Excitation
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Tue, 26 Sep 2017 00:00:00 GMTMajewski T, Szwedowicz D, Majewski M. <span class="paragraphSection">The paper presents a theory of vibratory locomotion, a prototype, and the results of experiments on mini robot, which moves as a result of inertial excitation provided by two electric motors. The robot is equipped with elastic bristles which are in contact with the supporting surface. Vibration of the robot generates the friction force which can push the robot forward or backward. The paper presents a novel model of interaction between the bristles and the supporting surface. The friction force (its magnitude and sense) is defined as a function of the robot velocity and the robot's vibrations. The analysis is done for a constant coefficient of friction and a smooth surface. Depending on the motors' speed, one may obtain a rectilinear or a curvilinear motion, without jumping or losing contact with the substrate. The results of the simulation show which way the robot moves, its mean velocity of locomotion, change of the slipping velocity of the bristles and its influence on the normal and the friction force. A prototype was built and experiments were performed with it.</span>//article/9/6/061008/2654268/Locomotion-of-a-Mini-Bristle-Robot-With-InertialOn the Solutions of Interval Systems for Under-Constrained and Redundant Parallel Manipulators
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Tue, 26 Sep 2017 00:00:00 GMTNotash L. <span class="paragraphSection">For under-constrained and redundant parallel manipulators, the actuator inputs are studied with bounded variations in parameters and data. Problem is formulated within the context of force analysis. Discrete and analytical methods for interval linear systems are presented, categorized, and implemented to identify the solution set, as well as the minimum 2-norm least-squares solution set. The notions of parameter dependency and solution subsets are considered. The hyperplanes that bound the solution in each orthant characterize the solution set of manipulators. While the parameterized form of the interval entries of the Jacobian matrix and wrench produce the minimum 2-norm least-squares solution for the under-constrained and over-constrained systems of real matrices and vectors within the interval Jacobian matrix and wrench vector, respectively. Example manipulators are used to present the application of methods for identifying the solution and minimum norm solution sets for actuator forces/torques.</span>//article/9/6/061009/2653385/On-the-Solutions-of-Interval-Systems-forModeling and Analysis of Parallel Mechanisms With Both Kinematic and Actuation Redundancies Via Screw Theory
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Wed, 20 Sep 2017 00:00:00 GMTKang L, Kim W, Yi B. <span class="paragraphSection">Two kinds of mechanical redundancies, namely kinematic redundancy and actuation redundancy, have been extensively studied due to their advantageous features in autonomous industry. Screw theory has been successfully applied to develop an analytical Jacobian of nonredundant parallel manipulators (PMs). However, to the best of our knowledge, screw theory has not been attempted for modeling of PMs with kinematic redundancies. Thus, first, through the mobility analysis of a simple nonredundant planar PM and its variations, this paper reviews kinematic and actuation redundancy systematically. Then, we demonstrated how to derive analytical Jacobian and also static force relationship for a PM with both kinematic and actuation redundancies by using the screw theory. Finally, simulations were performed to demonstrate the advantageous features of kinematic and actuation redundancies.</span>//article/9/6/061007/2653422/Modeling-and-Analysis-of-Parallel-Mechanisms-WithDesign of a Compact Gravity Equilibrator With an Unlimited Range of Motion
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Mon, 18 Sep 2017 00:00:00 GMTBijlsma BG, Radaelli G, Herder JL. <span class="paragraphSection">A gravity equilibrator is a statically balanced system which is designed to counterbalance a mass such that any preferred position is eliminated and thereby the required operating effort to move the mass is greatly reduced. Current spring-to-mass gravity equilibrators are limited in their range of motion as a result of constructional limitations. An increment of the range of motion is desired to expand the field of applications. The goal of this paper is to present a compact one degree-of-freedom mechanical gravity equilibrator that can statically balance a rotating pendulum over an unlimited range of motion. Static balance over an unlimited range of motion is achieved by a coaxial gear train that uses noncircular gears. These gears convert the continuous rotation of the pendulum into a reciprocating rotation of the torsion bars. The pitch curves of the noncircular gears are specifically designed to balance a rotating pendulum. The gear train design and the method to calculate the parameters and the pitch curves of the noncircular gears are presented. A prototype is designed and built to validate that the presented method can balance a pendulum over an unlimited range of motion. Experimental results show a work reduction of 87% compared to an unbalanced pendulum and the hysteresis in the mechanism is 36%.</span>//article/9/6/061003/2649351/Design-of-a-Compact-Gravity-Equilibrator-With-anDesign and Kinematic Analysis of a Novel 3U P S/R P U Parallel Kinematic Mechanism With 2T2R Motion for Knee Diagnosis and Rehabilitation Tasks
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Mon, 18 Sep 2017 00:00:00 GMTAraujo-Gómez P, Mata V, Díaz-Rodríguez M, et al. <span class="paragraphSection">This paper proposes a two translational and two rotational (2T2R) four-degrees-of-freedom (DOF) parallel kinematic mechanism (PKM) designed as a knee rehabilitation and diagnosis mechatronics system. First, we establish why rehabilitation devices with 2T2R motion are required, and then, we review previously proposed parallel mechanisms with this type of motion. After that, we develop a novel proposal based on the analysis of each kinematic chain and the Grübler–Kutzbach criterion. Consequently, the proposal consists of a central limb with revolute-prismatic-universal (RPU) joints and three external limbs with universal-prismatic-spherical (UPS) joints. The Screw theory analysis verifies the required mobility of the mechanism. Also, closed-loop equations enable us to put forward the closed-form solution for the inverse-displacement model, and a numerical solution for the forward-displacement model. A comparison of the numerical results from five test trajectories and the solution obtained using a virtual prototype built in <span style="text-transform:lowercase;font-variant:small-caps;">msc-adams</span> shows that the kinematic model represents the mechanism's motion. The analysis of the forward-displacement problem highlights the fact that the limbs of the mechanism should be arranged asymmetrically. Moreover, the Screw theory makes it possible to obtain the Jacobian matrix which provides insights into the analysis of the mechanism's workspace. The results show that the proposed PKM can cope with the required diagnosis and rehabilitation task. The results provide the guidelines to build a first prototype of the mechanism which enables us to perform initial tests on the robot.</span>//article/9/6/061004/2653421/Design-and-Kinematic-Analysis-of-a-Novel-3UPSRPUA Task-Driven Approach to Optimal Synthesis of Planar Four-Bar Linkages for Extended Burmester Problem
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Mon, 18 Sep 2017 00:00:00 GMTDeshpande S, Purwar A. <span class="paragraphSection">The classic Burmester problem is concerned with computing dimensions of planar four-bar linkages consisting of all revolute joints for five-pose problems. We define extended Burmester problem as the one where all types of planar four-bars consisting of dyads of type RR, PR, RP, or PP (R: revolute, P: prismatic) and their dimensions need to be computed for n-geometric constraints, where a geometric constraint is an algebraically expressed constraint on the pose, pivots, or something equivalent. In addition, we extend it to linear, nonlinear, exact, and approximate constraints. This extension also includes the problems when there is no solution to the classic Burmester problem, but designers would still like to design a four-bar that may come closest to capturing their intent. Machine designers often grapple with such problems while designing linkage systems where the constraints are of different varieties and usually imprecise. In this paper, we present (1) a unified approach for solving the extended Burmester problem by showing that all linear and nonlinear constraints can be handled in a unified way without resorting to special cases, (2) in the event of no or unsatisfactory solutions to the synthesis problem, certain constraints can be relaxed, and (3) such constraints can be approximately satisfied by minimizing the algebraic fitting error using Lagrange multiplier method. We present a new algorithm, which solves new problems including optimal approximate synthesis of Burmester problem with no exact solutions.</span>//article/9/6/061005/2653383/A-TaskDriven-Approach-to-Optimal-Synthesis-ofDynamic Structural and Contact Modeling for a Silicon Hexapod Microrobot
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Mon, 18 Sep 2017 00:00:00 GMTQu J, Choi J, Oldham KR. <span class="paragraphSection">This paper examines the dynamics of a type of silicon-based millimeter-scale hexapod, focusing on interaction between structural dynamics and ground contact forces. These microrobots, having a 5 mm × 2 mm footprint, are formed from silicon with integrated thin-film lead–zirconate–titanate (PZT) and high-aspect-ratio parylene-C polymer microactuation elements. The in-chip dynamics of the microrobots are measured when actuated with tethered electrical signal to characterize the resonant behavior of different parts of the robot and its piezoelectric actuation. Out-of-chip robot motion is then stimulated by external vibration after the robot has been detached from its silicon tethers, which removes access to external power but permits sustained translation over a surface. A dynamic model for robot and ground interaction is presented to explain robot locomotion in the vibrating field using the in-chip measurements of actuator dynamics and additional dynamic properties obtained from finite element analysis (FEA) and other design information. The model accounts for the microscale interaction between the robot and ground, for multiple resonances of the robot leg, and for rigid robot body motion of the robot chassis in five degrees-of-freedom. For each mode, the motions in vertical and lateral direction are coupled. Simulation of this dynamic model with the first three resonant modes (one predominantly lateral and two predominantly vertical) of each leg shows a good match with experimental results for the motion of the robot on a vibrating surface, and allows exploration of influence of small-scale forces such as adhesion on robot locomotion. Further predictions for future autonomous microrobot performance based on the dynamic phenomena observed are discussed.</span>//article/9/6/061006/2653384/Dynamic-Structural-and-Contact-Modeling-for-a