Motion System Design Research Articles

Closed-Form Dynamic Modeling and Performance Evaluation of a 4-Degrees-of-Freedom Parallel Driving Mechanism

Abstract Kinematic estimations and dynamic performance assessments are fundamental theoretical issues to realize the mechanism from conceptual design to engineering application. In this article, the closed-form dynamic formulations of a 4-degrees-of-freedom (DoFs) parallel driving mechanism are derived by combining the Lagrange method and the virtual work principle. The selection principle of generalized coordinates and the steps for inverse dynamics modeling of the manipulator are proposed. Simulation results verify the correctness of the dynamic model, and a physical prototype has been built. Based on the dynamic modeling, the concise algebraic expression of the operational space inertia matrix of the parallel driving mechanism is deduced. Because the translation and rotation degrees-of-freedom are inconsistent in the operational space, the Jacobian matrix is adopted to map the inertia matrix from the operational space to the joint space. Based on the inertia matrix in joint space, the average energy transfer efficiency (AETE) index is proposed. Finally, two control techniques for the manipulator implementable in joint space are compared. The AETE index and dynamic modeling method suggested in this article can be further used in other manipulators for dynamic analysis and motion system design.

Defect-driven rotating system based on a double-walled carbon nanotube and graphene

A nanoscale rotating system that consists of a double-walled carbon nanotube (DWCNT) and graphene and is driven by a defect in the graphene is proposed, and its rotating dynamics and driving mechanism are investigated through molecular dynamics simulations. A potential energy difference caused by the presence of the vacancy defect on the graphene substrate causes the outer tube in the DWCNT to stably rotate in a specific direction. The rotational speed of the outer tubem initially increases before reaching a stable speed. This phenomenon indicates that the driving torque is a difference between the sides of the outer tube in the van der Waals potential; this difference in potential is caused by the presence of the defect in the graphene. In addition, the effects of the system temperature, the radius and chiral vectors of the DWCNT, and the location of the defect in the graphene are investigated. The theoretical work reported here should provide a reference for the design of motion systems based on carbon nanotubes and graphene and their applications.

Assessment criterionof structural resources offlight simulator motion system

Assessment criterionwas formulated for evaluating of structural resources of motion systems of aircraft flight simulators on the basis of taking into account peculiarities of pilot's perception of information about both displacement and attitude of aircraft and features of spatial piloting. The developed criterion was used in the design of motion systems of flight simulators of aircrafts Ilushin-96-300 and Tupolev-204 (Russia, Penza’ Modeling Design Bureau), Antonov-74TK-200 and Antonov-140 (Ukraine, state enterprise "Antonov"). The force cueing fidelitywas improved on basis of both evaluation of structural resources of motion systems and their effective use.

Motion system design of a thin and compact linear switched reluctance motor with disposable-film mover

Motion system design of a thin and compact linear switched reluctance motor with disposable-film mover

Integrating topology optimization in precision motion system design for optimal closed-loop control performance

In pursuit of better accuracy, higher speed and larger scale, manufacturers of high-performance devices increasingly rely on components which have been designed with a multidisciplinary approach from the outset. In the context of motion systems, this means that for instance structural mechanics, control engineering and thermal analysis are considered early in the design. In addition, the prospect of producing freeform device components using additive manufacturing at full scale allows designers to even further refine components to a specific purpose, or even integrate multiple functions into a single component. The design freedom offered by additive manufacturing is far greater than that offered by traditional techniques. To exploit this freedom a topology optimization framework is proposed that allows to determine the optimal material quantity and distribution within a design volume. In particular, this article focuses on the closed-loop control performance of a motion system component, while simultaneously ensuring that mechanical requirements are met. Based on an example, it is demonstrated that this leads to nontrivial and non-intuitive designs which provide improved performance at lower structural mass compared to eigenfrequency designs. The framework allows rapid development of prototype designs, which may eliminate some of the costly design iterations which are currently made in industrial practice.

Direct current-dielectrophoresis assisted microscale machining of metal by femtosecond pulsed laser

Accumulation of ablation debris particles interferes with femtosecond laser micromachining of high-aspect ratio grooves in metal. Debris removal from such grooves by an air or inert gas jet requires that the gas jet axis be aligned with the groove. This requirement constrains the motion system design and programming as well as the gas nozzle design for cutting of arbitrary shapes. Gas jet debris removal is also not feasible in vacuum environments. In this study, a novel technique based on DC-dielectrophoresis (DEP) for removing debris from the cut groove was investigated. Femtosecond laser ablation of linear and circular grooves from thick sections of aluminum was performed with no debris removal and with debris removal by air jet or DC-DEP force. Ablation depth and precision were compared for the three experimental conditions. Debris removal by DC-DEP force resulted in the most accurate, consistent, and orientation-independent machining of high-aspect ratio grooves. Moreover, larger electric fields exerted stronger DC-DEP force on debris particles and resulted in better ablation precision and machining rate.

Motion Scaling for High-Performance Driving Simulators

Advanced driving simulators aim at rendering the motion of a vehicle with maximum fidelity, which requires increased mechanical travel, size, and cost of the system. Motion cueing algorithms reduce the motion envelope by taking advantage of limitations in human motion perception, and the most commonly employed method is just to scale down the physical motion. However, little is known on the effects of motion scaling on motion perception and on actual driving performance. This paper presents the results of a European collaborative project, which explored different motion scale factors in a slalom driving task. Three state-of-the-art simulator systems were used, which were capable of generating displacements of several meters. The results of four comparable driving experiments, which were obtained with a total of 65 participants, indicate a preference for motion scale factors below 1, within a wide range of acceptable values (0.4-0.75). Very reduced or absent motion cues significantly degrade driving performance. Applications of this research are discussed for the design of motion systems and cueing algorithms for driving simulation.

Research on the inertia matching of the Stewart parallel manipulator

With the development of the parallel manipulator, inertia matching as an essential factor to realize good potentials of the parallel manipulator is taken serious gradually. However, neither definite inertia index nor inertia matching method has been proposed so far. In this paper, the above issues are discussed by taking the Stewart parallel manipulator as a study object. Firstly, adopting limb Jacobian matrices, the concise algebraic expression of the joint-space inertia matrix of the Stewart parallel manipulator is deduced, based on the dynamic modeling. Next, on the basis of the coupling analysis of the joint-space inertia matrix, the inertia index of the parallel manipulator, the Joint-Reflected Inertia, is proposed. Then, the practical inertia matching principles of the Stewart parallel manipulator are concluded on the basis of simulations, considering multiple factors, such as mechanical resonance frequency, acceleration torque and dynamic performance. Finally, the available range of the motor inertia is deduced, and the inertia matching of the Stewart parallel manipulator is finished as the case study. The inertia index and inertia matching method suggested in this paper can be further used in other parallel manipulators for dynamic analysis and motion system design.

Design Considerations for Micro- and Nanopositioning: Leveraging the Latest for Biophysical Applications

Biophysical applications ranging from fluorescence microassays to single-molecule microscopy are increasingly dependent on automated nanoscale positional control and stability. A whirlwind of motion-industry innovation has resulted in an array of new motion options offering significant improvements in application performance, reproducibility and throughput. The challenge to leverage these developments depends on researchers, engineers and motion vendors acquiring a common language of specifications and a shared understanding of the challenges posed by application needs. To assist in building this shared understanding, this article reviews today's motion technologies, beginning with a concise review of key principles of motion control focusing on applications. It progresses through illustrations of sensor/encoder technologies and servo techniques. A spectrum of classical and recent motion technologies is explored, from stepper and servo actuation of conventional microscopy stages, to advanced piezo stack nanopositioners capable of picometer precision, to novel ultrasonic resonant piezomotors and piezo-ceramic-based mechanisms capable of high-force positioning over many millimeters while providing resolutions down into the sub-nanometer range. A special emphasis is placed on the effects of integrating multiple motion technologies into an application, such as stacking a fine nanopositioner atop a long-travel stage. Examples and data are presented to clarify these issues, including important and insightful new stability measurements taken directly from an advanced optical trapping application. The important topics of software and interfacing are also explored from an applications perspective, since design-and-debugging time, synchronization capabilities and overall throughput are heavily dependent on these often-overlooked aspects of motion system design. The discussion is designed to illuminate specifications-related topics that become increasingly important as precision requirements tighten. Throughout, both traditional and novel techniques and approaches are explored so that readers are left with a solid overview of the state of the art, and an actionable perspective that readies them to discuss and evaluate specifications and vendor capabilities against practical application requirements.

実時間並列計算モデルに基づく自律ロボットの運動システムの構造化記述と設計

実時間並列計算モデルに基づく自律ロボットの運動システムの構造化記述と設計

Structural flexibility of motion systems in the space environment

The state-of-the-art is summarized, focusing on interdisciplinary approaches and positions, and future directions in the design, analysis, and control of lightweight robotic and telerobotic motion systems for space application are discussed. The emphasis is on providing a logical connection between the special demands of space applications and the design of the motion system. Flexibility is presented as a natural consequence of these demands. A number of technologies are relevant to extending feasible performance into regions of the design space previously avoided due to the resulting flexibility of the structures and drives. Control technology is considered foremost, but passive damping, structural materials, structural design, operational strategy and sensor technology are closely related. Numerous references are presented for those wishing to employ these technologies.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>