Kinematic and dynamic design and optimization of a parallel rehabilitation robot

In this paper, a method for concurrent optimum design of a complex parallel manipulator is introduced. The manipulator is a three-degree-of-freedom mechanism used as a walking rehabilitation device. The proposal deals with several optimization issues; firstly, the methodology is applied to a system recently designed and, in the best of our knowledge, the control policy, and dynamic model have not been published before, secondly, we propose an objective function which considers dexterity and singular manipulators, as well as energy and position error, and thirdly, we propose an optimization algorithm which successfully approximates the optimum solution, delivering low-cost feasible designs with fewer function evaluations than a comparing Genetic Algorithm. A set of numerical simulations validate the methodology and evidence its robustness since it delivers quite similar designs in several independent executions.

     

Kinematic and dynamic identification of parallel mechanisms

In this paper, we provide a comprehensive method to perform the physical model identification of parallel mechanisms. This includes both the kinematic identification using vision and the identification of the dynamic parameters. A careful attention is given to the issues of identifiability and excitation. Experimental results obtained on a H4 parallel robot show that kinematic identification yields an improvement in the static positioning accuracy from some 1 cm down to 1 mm, and that dynamic parameters are globally estimated with less than 10% relative error yielding a similar error on the control torque estimation.     

Kinematic analysis of a flexible six-DOF parallel mechanism.

In this paper, a new type of six-degrees of freedom (DOF) flexible parallel mechanism (FPM) is presented. This type of parallel mechanism possesses several favorable properties: (1) its number of DOFs is independent of the number of serial chains which make up the mechanism; (2) it has no kinematical singularities; (3) it is designed to move on rails, and therefore its workspace is much larger than that of a conventional parallel manipulator; and (4) without changing the number of DOFs and the kinematics of the mechanisms, the number of the serial chains can be reconfigured according to the needs of the tasks. These properties make the mechanism very preferable in practice, especially for such tasks as joining huge ship blocks, in which the manipulated objects vary dramatically both in weights and dimensions. Furthermore, the mechanism can be used as either a fully actuated system or an underactuated system. In the fully actuated case, the mechanism has six DOF motion capabilities and manipulation capabilities. However, in the underactuated case, the mechanism still has six DOF motion capabilities, but it has only five DOF manipulation capabilities. In this paper, both the inverse and forward kinematics are studied and expressed in a closed form. The workspace and singularity analysis of the mechanism are also presented. An example is presented to illustrate how to calculate the kinematics of the mechanism in both fully-actuated and underactuated cases. Finally, an application of such a mechanism to manufacturing industry is introduced.     

Dynamic characterization and modification of dynamic properties of a micro scanner

Micro electro mechanical systems (MEMS) are used in many application areas in different disciplines and took their place among the most promising technologies. The performance of such systems is primarily related to their dynamical characteristics. This study presents the dynamic characterization techniques that are used to identify the modal parameters of a MEMS device and the methods that can be implemented to change its dynamic response. An electrostatic scanner is chosen as the case study to demonstrate the developed methodologies. Initially, the micro scanner is characterized using experimental modal analysis techniques to obtain frequency response function, modal damping, resonance frequencies, and mode shapes. Then, velocity and position feedback control loops are implemented to the scanner system to alter the damping and stiffness characteristics. A closed-loop Simulink model of the scanner is developed to verify the experimental measurements. Several curve fitting methods are used in order to have an accurate representation of the scanner system. Using the model, the influence of both position and velocity feedback on the effective damping, resonance frequency and the transient behavior of the scanner is investigated. The stability limits of the scanner under velocity feedback are also studied via numerical simulations. Based on the experimental and simulation results, the methodology developed in this study proves itself to be very efficient to alter the dynamical characteristics of the MEMS structures and it can be easily adapted to other MEMS applications.     

Kinematic and dynamic analysis of a hexapod walking-running-bounding gaits robot and control actions

Kinematic and dynamic analysis, and control actions of a hexapod robot were realized for walking, running and bounding gaits in this study. If biological inspiration can be used to build robots that deal robustly with complex environments, it should be possible to demonstrate that legged biorobots can function in natural environments. Firstly, we tried to report on theoretic work with a six legged robot designed to emulate spider behavior like walking, running and bounding. We demonstrated theoretically that it can successfully walk, run and bound like a spider over natural terrain. Secondly, limitations in its capability were evaluated, and many biologically based important improvements were obtained for future experimental work. Thirdly, the hexapod robot with bounding gait was controlled by proportional-derivative control algorithm and was carried out by using spring loaded inverted pendulum model. Consequently, the developed kinematic and dynamic methods, and control action method makes both the system control easy and the system performance is improved by decreasing the run time for each loop.     

虚拟环境下并联坐标测量机几何建模与运动仿真

与普通直角型坐标测量机相比，并联坐标测量机具有结构简单、测量精度高、测头位姿灵活等一系列优点。但因该坐标测量机的驱动参量与测头输出位姿之间的非线性对应关系，致使其实体样机的设计工作变得十分复杂。该文以3-RPS型三自由度并联机构坐标测量机为研究对象。在虚拟环境下对其进行了三维实体造型和运动过程仿真，从而为新型坐标测量机实体样机的开发奠定了理论基础。     

Energy-efficiency analyses of heterogeneous macro and micro base station sites

Due to the introduction of newer technologies like Long Term Evolution (LTE) in already deployed cellular access networks, changes in the energy-efficiency of networks consisting predominantly of macro base station sites (BSSs) can be expected. An investigation has been performed for two prominent energy metrics of cellular networks: Power per Unit Area (PUA) and Energy per bit and Unit Area (EbUA). Analytical relations have been developed that express the influence of parameters such as BSs’ transmit (Tx) powers, inter-site distances (ISDs), and a number of heterogeneous macro or LTE micro BSSs on the PUA and EbUA. It has been shown that appropriate selection of these parameters can ensure significant energy savings. Besides the possibility of finding an optimal trade-off among ISDs and Tx powers of macro BSSs, which will minimize PUA and maximize EbUA, adding micro LTE BSs to such heterogeneous networks contributes to the improvement of network energy efficiency.     

两种用于微型生化分析的光探测方法

针对微流控分析芯片样品剂量少与微流体芯片集成等要求,设计了两种易于集成在芯片内的,用分光光度法对混合后液体的吸收光谱进行探测的方法。实验利用460～800nm的可见光光源,采用了直接探测法和消逝波探测法对样品进行探测。通过两种方法的比较证明:直接探测法具有原理简单、消耗样品量少、结构容易实现等优点;消逝波探测法具有需要样品量极少、灵敏度高、易于集成等优点。     

Kinematic analysis of the 3-CUP parallel mechanism

This paper investigates the kinematics of a parallel mechanism that is composed of three identical CUP legs evenly distributed on the fixed base. The platform of the mechanism has three degrees-of-freedom, namely: two rotations and one translation along the axis perpendicular to the base. The paper obtains closed form solutions for the inverse and forward kinematics problems. Furthermore, the Jacobian matrix is determined in order to solve the instantaneous kinematics analysis. It is used for the identification of the singular configurations of the mechanism, which are investigated by applying screw theory. The parasitic motions of the platform are determined by means of a workspace analysis. This paper uses several simulations and numerical examples to prove the accuracy of the analytical results.     

Kinematic and dynamic models of hybrid robot manipulator for propeller grinding

In this article, we develop a hybrid robot manipulator for propeller grinding and derive its kinematic and dynamic models. The manipulator is constructed by combining a parallel mechanism and a serial one to increase high stiffness as well as workspace. Based on geometric constraints, inverse–direct kinematics and Jacobian are derived to be implemented in real time control. The velocity control is used to measure the surface of a propeller blade and the position control is conducted to grind the removal depth. The dynamic model, which is developed by a motor algebra, can compute the forces and moments acting at a passive joint and an active one. ©1999 John Wiley & Sons, Inc.     

A micro gearing system based on a ratchet mechanism and electrostatic actuation

This paper presents the design and fabrication of a silicon micro gearing system (MGS) that utilizes electrostatic comb-drive actuators to rotate a gear ring through a ratchet mechanism. The rotational comb-drive actuator is engaged with the gear ring through a spring system and ratchet teeth at one end, reciprocally rotates around an elastic point at the other end based on the electrostatic force. Rotational motion and torque from the driving gear ring are transmitted smoothly to driven gears through involute-shaped gear teeth. Smart design of anti-gap structures helps to overcome the unavoidable gap problem occurred in deep reactive ion etching (deep-RIE) process of silicon. The MGS has been fabricated and tested successfully by using SOI (silicon-on-insulator) wafer and one mask only. The angular velocity of the gear ring is proportional to the driving frequency up to 40 Hz.     

Kinematic design of a redundant parallel mechanism for maskless lithography optical instrument manipulations

A new precision parallel mechanism having actuation redundancy will be introduced in this paper. Physical contribution of the actuation redundancy for the precision parallel mechanism is reviewed. In addition, several kinematic configurations have been analyzed for degrees of freedom verification and actuation redundancy. A new kinematic configuration which is 4-[P P]PS is suggested. The suggested 4-[P P]PS mechanism which has actuation redundancy provides six degrees of freedom to the mobile platform. For position control and path planning of the mobile platform, the inverse and the forward kinematics are solved for closed-form solutions. In order to verify the inverse and the forward kinematics, a numerical simulation result is presented. In addition to the inverse and forward accuracy proof, the numerical analysis provides other information such as independent translation motion, calibrated rotation arm at tilting motion, and symmetric motion at rotating motion.     

Behind the scenes in SANTE: a combination of static and dynamic analyses

While the development of one software verification tool is often seen as a difficult task, the realization of a tool combining various verification techniques is even more complex. This paper presents an innovative tool for verification of C programs called Sante (Static ANalysis and TEsting). We show how several tools based on heterogeneous techniques such as abstract interpretation, dependency analysis, program slicing, constraint solving and test generation can be combined within one tool. We describe the integration of these tools and discuss particular aspects of each underlying tool that are beneficial for the whole combination.     

Design and control methodology of a 3-DOF flexure-based mechanism for micro/nano-positioning

A 3-DOF (X–Y–θ_Z) planar flexure-based mechanism is designed and monolithically manufactured using Wire Electro-Discharge Machining (WEDM) technology. The compact flexure-based mechanism is directly driven by three piezoelectric actuators (PZTs) through decoupling mechanisms. The orthogonal configuration in the x and y directions can guarantee the decoupling translational motion in these axes. The rotational motion and translational displacement in the x direction can be decoupled by controlling the piezoelectric actuators in the x axis with the same displacement values in same and opposite motion directions, respectively. The static and dynamic models of the developed flexure-based mechanism have been developed based on the pseudo-rigid-body model methodology. The mechanical design optimization is conducted to improve the static and dynamic characteristics of the flexure-based mechanism. Finite Element Analyses (FEA) are also carried out to verify the established models and optimization results. A novel hybrid feedforward/feedback controller has been provided to eliminate/reduce the nonlinear hysteresis and external disturbance of the flexure-based mechanism. Experimental testing has been performed to examine the dynamic performance of the developed flexure-based mechanism.     

Singularity-consistent path planning and motion control through instantaneous self-motion singularities of parallel-link manipulators

The newly proposed singularity-consistent path tracking approach is applied to nonredundant parallel-link manipulators. We analyze the singularities of such manipulators under the assumption that the output-link moves on a pre-defined and parameterized path. Special attention is paid to the so-called instantaneous self-motion type singularity. We propose a velocity-command generator type closed-loop controller that guarantees asymptotic stability when tracking paths through such singularities. As a comprehensive analytical example we use a planar five bar mechanism. Results from computer simulations with the five bar mechanism and the HEXA parallel robot are also presented. © 1997 John Wiley & Sons, Inc.     

Finite element investigation into proposed bearing mechanism for a fluid driven micro actuator

 This paper investigates the effect of introducing a stepped stator surface directly under the rotating component of a micro fabricated turbine. The main aim of this work is to determine if a sufficient pressure can be created at the step locations, due to the shape and relative motion of the bearing surfaces, which is capable of raising the rotor from the stator surface. In this paper results are presented, based on finite element analysis, for two very simple stator designs. Using finite element models, the effect of rotational speed, step height and number are investigated, the results of which are presented in this paper.     

Collective mechanism of molecular motors and a dynamic mechanical model for sarcomere

A non-equilibrium statistical method is used to study the collective characteristics of myosin II motors in a sarcomere during its contraction. By means of Fokker-Planck equation of molecular motors, we present a dynamic mechanical model for the sarcomere in skeletal muscle. This model has been solved with a numerical algorithm based on experimental chemical transition rates. The influences of ATP concentration and load on probability density, contraction velocity and maximum active force are discussed resp...     

The effects of a trust mechanism on a dynamic supply chain network

Recognizing trust as the basis for firm cooperation, we investigate how a trust mechanism affects a supply chain network using a dynamic multi-agent and multi-stage model that incorporates three supplier selection rules: a preferred price rule, a preferred trust rule, and a preferred random rule. We use this model to explore the impact of the three rules on supply chain performance and bankruptcy propagation under the conditions of external disruption, bank rate, and new firms entering the market. Our results identify the preferred trust rule as the supplier selection method that can in most cases best improve the total revenue of the whole supply chain network. In terms of firm bankruptcy, on the other hand, it is the preferred random rule that has the least impact and the preferred price rule that has the most.     

Experimental and fuzzy modelling analysis on dynamic cutting force in micro milling

Prediction of cutting forces is very important for the design of cutting tools and for process planning. This paper presents a fuzzy modelling method of cutting forces based on subtractive clustering. The subtractive clustering combined with the least-square algorithm identifies the fuzzy prediction model directly from the information obtained from the sensors. In the micro-milling experimental case study, four sets of cutting force data are used to generate the learning systems. The systems are tested against each other to choose the best model. The obtained results prove that the proposed solution has the capability to model the cutting force in spite of uncertainties in the micromilling process.     

Kinematic and dynamic control model of wheeled mobile robot under internet of things and neural network

The Journal of Supercomputing - This study aims to solve the issues of nonlinearity, non-integrity constraints, under-actuated systems in mobile robots. The wheeled robot is selected as the...