查看更多>>摘要：This paper presents a unique design concept, dynamic modeling, and control strategies for efficient coverage path planning of a glass facade cleaning robot (GFCR). The robot design has been conceptualized using mechanisms for adhesion, motion, steering, and cleaning. The dynamic model for robot vertical glass facade cleaning is derived using Lagrangian formulation. A modified particle swarm optimization (PSO) is used to autotune the proportional, integral, and derivative (PID) parameters for the trajectory tracking simulation and it is more efficient and robust compared to the standard PSO algorithm. The path planning algorithm using hybrid PID-PSO approach is also developed for energy-efficient coverage of the robot for glass facade cleaning. The coverage algorithm illustrates the energy-performance of the GFCR for different paths viz., horizontal line sweep (HLS), vertical line sweep (VLS), spiral line sweep (SLS), and special cell diffusion (SCD) motion. Simulation reveals the robot motion for HLS path is the most energy efficient. The GFCR model with minimum energy consumption has been validated by working trials. The GFCR has potential applications for cleaning high-rise glass facade buildings and photovoltaic (PV) solar panels.
Chang-Siu, EvanSnell, AntonyMcInroe, Benjamin W.Balladarez, Xavier...
21页
查看更多>>摘要：The Omni-Wrist III, invented by Ross-Hime Designs, Inc. (Rosheim, 1999, 2002), is a well known two-degree of freedom wrist mechanism that incorporates parallel links with double universal joints (N-UU). It has the advantage of singularity-free operation over the entire hemispherical work-space and maintains a constant axial distance between the two joints. These characteristics make it an appealing choice for mobile robotic appendages that require dexterous maneuvers. While the two active input joint angles are coupled, this paper presents an accessible exposition of the forward and inverse kinematics for the position and velocity of the mechanism. The novelty of this analysis lies in the parameterization of the kinematics in terms of the vector between the origins of the tool and space frames. The results of this paper provide concise equations that are readily implementable in simulation and on low power microcontrollers enabling the use of the Omni-Wrist III for highly dynamic mobile robot maneuvers.
查看更多>>摘要：This paper evaluates the railway catenary's wind deflection under crosswind based on wind tunnel experiments and a nonlinear finite element model. A catenary model is constructed based on the absolute nodal coordinate formulation to describe the geometrical nonlinearity of the system. The aerodynamic forces acting on the catenary are derived according to the quasi-steady theory, and the aerodynamic coefficients are obtained by wind tunnel experiments. A procedure to generate the three-dimensional fluctuating wind field along the catenary is presented. The extreme value of the wind deflection is estimated based on a Poisson approximation of the extreme value distribution. The numerical accuracy is validated by wind tunnel experimental results of an aeroelastic catenary. The response, statistics, frequency characteristics and extreme value of the contact wire's wind deflection are investigated through numerical simulations. The analysis results indicate that the maximum wind deflection will exceed the safety limit for the analysed catenary with a turbulence intensity of more than 15%. The adjustment of some critical parameters of the catenary system can reduce the maximum wind deflection.
查看更多>>摘要：A novel 1T2R parallel mechanism (PM), applied in loading test of hydraulic support, is proposed, whose kinematic performance is studied in detail. The analytical expression of forward kinematic positions are derived by means of vector method. With the aid of Jacobian matrix, the singular configurations are investigated. The orientation capacity of end-effector is depicted through the azimuth and tilt angles. Using screw theory as the mathematical tool, this paper establishes the evaluation indices for motion/force transmission performance such as input transmission index, output transmission index and local transmission index (LTI). The definitions and calculation methods of good transmission orientation workspace (GTOW), regular transmission orientation workspace, and average transmission index in regular workspace are presented, respectively. Furthermore, the distributions of GTOW and the surface of LTI are plotted. Finally, the analysis results indicate that PU-RPU-UPS PM has good kinematic performances, which can be used as loading actuator of the new hydraulic support test-bed.
查看更多>>摘要：Study of dynamic performance of variable stiffness actuators has become more important for high safety in human-robot interaction. In this paper, based on the human knee joint, a variable stiffness actuator for the knee joint is proposed and its feasibility is experimentally verified. Then by considering connection compliance between motor and internal load inside actuator, twoinertia-system model is developed, and the accuracy of this model is experimentally verified. Finally, effects of friction and gap characteristics on the dynamic performance of this actuator are analyzed. Results show that both gap and friction characteristics have significant effects on the dynamic performance of variable stiffness actuator with high precision and micro-motion, and they both cause significant dead zones when forward and reverse rotations of motor are transformed; During adjustment of stiffness, variable stiffness actuator is caused to vibrate by gap, and motor is required to provide more energy to counteract effects of friction. So the control of variable stiffness actuator still needs to be studied more thoroughly to meet requirements of vibration suppression and high accuracy.
查看更多>>摘要：This paper proposes a concept of the reconfiguration parallel mechanism (RePM) based on friction self-locking composite joints, which can transform between a truss and a mechanism. This kind of RePMs not only have infinite continuous locking configurations, high payload and impact resistance capabilities, but also decrease energy consumption. The type synthesis method of the RePMs is proposed, including four stages: 1, determination of the motion characteristics of the task; 2, motion design of limbs, including the special and common parts; 3, assembly of limbs and selection of actuated joints; 4, qualitative type evaluation. Based on the friction force principle, a family of self-locking composite joints are presented, including the translation self-locking joint (JSLT), revolution self-locking joint (JSLR) and JSLTr joint. Two applications of the mechanisms with self-locking joints are executed. For application I, some RePMs for in-situ robots are proposed, which have high payload capability and save energy in the locked configuration. For application II, numerous novel RePMs for legged landers with terrain-adaptive landing capability are proposed, which have the infinite continuous landing configurations for landing on various uneven terrains. The proposed concept and design method of RePMs with self-locking joints have wide potential applications in the robots with high payload or impact resistance capabilities.
查看更多>>摘要：Taking into account that the velocity and acceleration limits of the end-effector are specified rather than the physical limits of the actuators in the design purpose of a robot, this paper proposes a novel method to evaluate the dynamic performance of the robot along joint-space directions. Based on the given ranges of end-effector velocity and acceleration in task space, the required torque along all joint-space directions are obtained based on the velocity term and the acceleration term in dynamic model, respectively. Furthermore, the actual torque range of each actuator is derived to produce the required torque along all joint-space directions. Considering all the effects of the acceleration term, the velocity term and the gravitational term, two global dynamic performance indices that reflect the minimum range of actuator torque and the ratio of the required torque range to the actual torque range in the whole workspace are presented. This method is validated by utilizing it to evaluate the dynamic performance of a novel 4-DOF parallel manipulator with translational and rotational motion for FSW. This method conforms with the design process of robotic manipulators and would be useful for optimum design, dynamic performance evaluation and actuator selection of a robot.
查看更多>>摘要：There have been a number of studies on the analysis and design of planar compliant mechanisms. However, it is more difficult to obtain an exact and concise description of the kinetostatics and dynamics for spatial compliant mechanisms. A general approach is herein presented for analyzing and designing spatial compliant mechanisms by combining a three-dimensional (3-D) dynamic stiffness model with the Pareto multi-objective optimization strategy. The investigation is devoted to small deformation providing a programmable solution for serial-parallel configurations with out-of-plane degrees of freedom (DOFs). Particularly, the 3-D dynamic stiffness model is well applicable to describe the kinetostatic and dynamic behaviors of spatial compliant mechanisms with both distributed and lumped compliance involving irregular-shaped rigid bodies. The Pareto optimal solution set in terms of concerned performances is provided and the optimum structural parameters can be straightforwardly determined. With the presented method, a new piezoelectric Z-theta x-theta y precision tilting manipulator is optimally designed. Experimental results show the strokes of 0.27 mm, 4.3 mrad, 4.3 mrad and the fundamental resonance frequencies of 470 Hz, 520 Hz and 520 Hz in the three motion DOFs.
查看更多>>摘要：Relating geometric interpretations to analytic procedures for solving mechanical problems improves their comprehension and gives a deeper insight on how to eliminate unwanted behaviors of the studied machine. This aspect is well stated in Newton-Euler formulation of mechanism dynamics. Unfortunately, many approaches of analytical mechanics build dynamic models of mechanisms that are difficult to put in relation with clear geometric constructions. D'Alembert principle, which is based on the virtual work principle, is one of these approaches. Here, a systematic way for modeling single-degree-of-freedom (single-DOF) planar mechanisms through the D'Alembert principle and the instant centers' (ICs') positions is presented which is related to geometric interpretations of the terms appearing in it. The proposed geometric interpretation is so effective that, formally, the model could be written starting from it without any analytic consideration as same as the equilibrium equations can be written from free-body diagrams in the Newton-Euler formulation. The resulting dynamic model is novel and general. The proposed model and the associated solution algorithms of the dynamic problems are also illustrated through a case study. The obtained results are of interest in mechanism analysis and design and, due to their simple theoretical bases, can be presented in courses for undergraduate or graduate students.
NSTL
Elsevier