Trajectory generation for open-contoured structures in robotic fibre placement

Composites have become common engineering materials in industries where the strength to weight performance of structures is a key design consideration. The major limiting factors are the high-manufacturing costs and low-production rates. Robotic fibre placement (RFP) is one alternative process to overcome the limiting factors and it is generally suitable for open-continuous components. A novel path planning algorithm for open-contoured structures, entitled the surface curve algorithm for robotic fibre placement (SCAR) is proposed. The algorithm aims to produce a uniform lay-up of composite lamina, without gap and overlap between subsequent tows. A numerical investigation into the characteristics of the algorithm is performed and presented. The algorithm is implemented on complex contoured surface and some of the results are presented in this paper.     

微机控制水泥配料系统

通过对水泥生产过程中各工艺参数的信号分析，提出了以工业控制计算机为核心的自动配料系统的硬件软件设计原理，同时指出了提高系统测量精度的关键技术。系统的应用有助于提高水泥的产量和质量。     

3D直接操作的自动视图控制

阐述通过自动寻找虚拟相机的有效位置以增强3D直接操作过程的技术.当前许多直接操作3D几何形体的尖端技术都强烈地依赖于视角,因此需要用户在操作过程中确定视点的坐标.在某些情形下,这个过程可以自动化.这意味着系统可以自动避免退化位置,而在退化情形,平移与旋转操作是难以实现的.系统还能选择视点和视角,使得被操作的物体可见,确保不被其他物体遮挡.     

Feasibility study of robotic fibre placement on intersecting multi-axial revolution surfaces

In this paper, the first steps towards using a robotic workcell for the automated fibre placement (AFP) manufacturing of Y-shaped tubes are proposed. The proposed workcell is constituted of a standard serial manipulator holding the fibre placement toolhead combined to a rotary table on which the part where the fibres must be laid out is attached. The investigations carried out in this work explore the feasibility of this setup and more precisely the path planning aspect. To this aim two novel path planning algorithms are presented generalizing the techniques proposed in the literature for open-contoured and cylindrical surfaces. In the first, the maximal geodesic curvature typically allowed in AFP is disregarded to generate continuous paths with a constant placement angle on the branches without any gaps or overlaps. Subsequently, a second algorithm, taking into account this curvature constraint, is presented. These algorithms were implemented in a software using the MATLAB™ suite. Finally, an algorithm to optimize the motion of the robotic system is presented and simulations are discussed.     

Fabrication of drive and guide components for micro motors

This paper provides a contribution to the technology and fabrication of functional components for micro motors based on an electromagnetic principle. The focus of this research is on components for the drive, guide and bearing for magnetic actuator systems. The technology and fabrication process of an electromagnetic guide is presented in detail. Its active principle is based upon repellent magnetic forces. Furthermore, the components of a linear variable reluctance micro motor are described. An improvement of driving forces has been achieved in comparison to the first prototype by determined optimizations. In addition, the weight of the traveller could be decreased. The fabrication of compact coil designs for the electromagnetic guide as well as the optimization of components for the reluctance motor are mainly attributed to the implementation of new fabrication technologies and new materials like inorganic insulation layers and electrodepositable photo resists.     

Micromechanism fabrication using silicon fusion bonding

Silicon fusion bonding is studied as an enabling technology for the fabrication of microrobotic mechanisms. The effects of both surface activation technique and annealing temperature on bond strength are considered using a crack-opening technique. As part of the study, the relationship between patterned silicon feature size and the resulting bond strength is explored. Based on the experimental results, recommendations for an optimal silicon fusion bonding process for micromechanism fabrication are presented. The experimental results indicate that bulk silicon bonding strength can be achieved independent of feature size at temperatures as low as 300°C, with positive implications for micromechanism fabrication.     

High-throughput battery materials testing based on test cell arrays and dispense/jet printed electrodes

A cost effective and reliable technology for the fabrication of electrochemical test-cell arrays for battery materials research, based on batch-fabricated glass micro packages was developed and tested. Jet dispensing was investigated for the first time as a process for fabricating battery electrode arrays and separators and compared to micro dispense printing. The process shows the reproducibility over the whole range of investigated materials and battery cell structures that is required for battery materials research. Such setup gives rise to a significantly improved reliability and reproducibility of electrochemical experiments. Cost-effective fabrication of our test chips by batch processing allows for their single-use in electrochemical experiments, thereby preventing contamination issues due to repeated use as in conventional laboratory test cells. In addition, the integration of micro pseudo reference electrodes is demonstrated. Thus, the test cell array together with the developed electrode/electrolyte deposition technology provide a highly efficient tool for speedy combinatorial and high throughput testing of battery materials on a system level (full cell tests). Experimental results are shown for the microfabrication of lithium-ion test cells with help of several electrode and binder materials. The influence of jetting parameters on electrode lateral dimensions and thickness, reproducibility of the electrode mass as well as the use of integrated micro-reference electrodes for impedance spectroscopy and cyclic voltammetry measurements in micro cells are presented in detail.

     

Uses of electroplated aluminum for the development ofmicrostructures and micromachining processes

In this paper, electroplated aluminum is explored as both a material for the fabrication of microstructures and use in the development of micromachining processes. A method for the fabrication of aluminum microstructures based on electrodeposition from organic solutions is presented. An extension of this process involving the use of plated aluminum structures as plating molds for subsequent electrodeposition of other materials is also discussed. Maximum structure aspect ratios of 21:1 have been demonstrated using this extended micromolding process. Finally, an aluminum-based process, in which the width of a metallic microstructure or the gap between metallic microstructures is achieved by controlling the plating time, is discussed. Using this process, vertical-gap aspect ratios between metallic microstructures of 25:1 have been demonstrated. Since the width of these features is controlled by the plating time and not by photolithography, gaps between metallic microstructures or widths of electroplated features ranging from submicron to tens of microns can be easily achieved using this process     

Reversible sealing techniques for microdevice applications

Reversible sealing of two different functional layers is an advancing and effective technique for the fabrication of microdevices. Reversible sealing enables microdevices to be dismountable and reusable, which are promising features for the high throughput analysis by means of spatial, temporal, and parallel process. It is therefore reversible sealing is potentially being used for various research fields such as micro and nanodevice fabrication, flow analysis at microscale, biomolecule analysis, cell analysis and other related fields. This review reports on the materials and techniques used for reversible sealing and their applications in various research areas, and illustrates their advantages and disadvantages. We provide examples, where necessary and comment on the outlook for reversible sealing applied to microdevices.     

Anisotropically etched silicon fibre-grippers

High precision vacuum grippers for optical fibre components are fabricated by silicon bulk micromachining. Anisotropic etching of (100) and (110) silicon wafers offers high precision and lower fabrication costs than deep reactive ion etching (D-RIE) processes. Two types of grippers are introduced: a vertical, narrow one for chips where space is limited and short fibre elements have to be assembled. For longer fibres and high angular precision a horizontal gripper with multiple gripper ledges is presented.     

Wafer-level bonding and direct electrical interconnection of stacked 3D MEMS by a hybrid low temperature process

The presented fabrication technology enables the direct integration of electrical interconnects during low temperature wafer bonding of stacked 3D MEMS and wafer-level packaging. The low temperature fabrication process is based on hydrophilic direct bonding of plasma activated Si/SiO₂ surfaces and the simultaneous interconnection of two metallization layers by eutectic bonding of ultra-thin AuSn connects. This hybrid wafer-level bonding and interconnection technology allows for the integration of metal interconnects and multiple materials in stacked MEMS devices. The process flow is successfully validated by fabricating test structures made out of a two wafer stack and featuring multiple ohmic electrical interconnects.     

State-feedback H2/H-infinity controller design with D-stability constraints for stochastic systems

This paper addresses the state-feedback H2/H-infinity controller design that satisfies D-stability constraints for stochastic systems. Firstly, the concept of regional stability for stochastic systems is defined in linear matrix inequality(LMI) regions; Secondly, the characterization about stochastic D-stability is presented. This paper introduces a new technique to solve the regional stability problem for stochastic systems, which is different from the pole placement technique ever used in deterministic systems. Based on this, in the state-feedback case, mixed H2/H-infinity synthesis with D-stability constraints is discussed via LMI optimization.     

Fabrication of high-aspect-ratio polymer nanochannels using a novel Si nanoimprint mold and solvent-assisted sealing

We present a low cost nanofabrication method to fabricate high-aspect-ratio (HAR) polymer nanochannels using a novel silicon nanoimprint mold fabrication technique and a solvent-assisted sealing method. These nanofluidic channels are being developed for single biomolecule detection. The silicon nanoimprint mold fabrication process is based on the combination of anisotropic etching of silicon by potassium hydroxide (KOH) solution and the local oxidation of silicon (LOCOS) process. The resulting high-aspect-ratio silicon mold has smooth sidewalls owing to the anisotropic KOH etching process along the silicon crystalline geometry as well as the LOCOS process. The nanostructures in the nanoimprint molds that form the nanochannels can be easily controlled by the initial micropattern sizes defined using conventional UV lithography and the oxidation time, making this technique a practical solution for low cost and high-throughput HAR silicon nanoimprint mold fabrication. Nanoimprint molds having aspect ratios of more than 1:5.5 (width: 200 nm, height: 1.1 μm, length: 1 cm) were successfully fabricated. Nanoimprinting technique was used to create poly(methyl methacrylate) (PMMA) nanotrenches out of this nanoimprint mold. A novel solvent-assisted sealing technique was developed in order to seal the HAR PMMA nanotrenches. This technique enables the generation of nanochannels with various nanoscale dimensions without the need for complicated and expensive nanolithography tools.     

A versatile technology platform for microfluidic handling systems,part II: channel design and technology

Microfluidic devices often require channels of a specific size and shape. These devices are then made in a fabrication process that is often specialized to produce only those (and very similar) channels. As a result, devices requiring channels of different size and shape cannot easily be integrated on the same chip. This paper presents a method to fabricate microfluidic channels in a wide range of shape and size on the same chip by using a slit pattern through which the channels are etched. The fabrication process to fabricate these channels is discussed in detail, and an empirical model is presented to find the optimal slit pattern for a required size and shape. This part of the paper focusses on the channel design and fabrication. Details on the whole fabrication process and optional functionalization of the channels are presented in part I of this paper.     

State feedback with fractional integral control design based on the Bode’s ideal transfer function

State feedback technique through a gain matrix has been a well-known method for pole assignment of a linear system. The technique could encounter a difficulty in eliminating the steady-state errors in some states. Introducing an integral element can effectively eliminate these errors. State feedback with fractional integral control is proposed, in this work, for pole placement of a linear time invariant system. The proposed method yields simple gain formulae. The paper presents the derivation of the design formulae. The method is applied to stabilise an inherently unstable inverted pendulum-cart system. Simulation and experimental results show the effectiveness of the proposed method for set-point tracking, disturbance rejection and stabilising the inverted pendulum. Comparison with the results obtained from applying Achermann’s formula is also presented.     

State-feedback H2/H-infinity controller design with D-stability constraints for stochastic systems

This paper addresses the state-feedback H2/H-infinity controller design that satisfies D-stability constraints for stochastic systems. Firstly, the concept of regional stability for stochastic systems is defined in linear matrix inequality（LMI） regions; Secondly, the characterization about stochastic D-stability is presented. This paper introduces a new technique to solve the regional stability problem for stochastic systems, which is different from the pole placement technique ever used in deterministic systems. Based on this, in the state-feedback case, mixed H2/H-infinity synthesis with D-stability constraints is discussed via LMI optimization.     

State-feedback H2/H-infinity controller design with D-stability constraints for stochastic systems

This paper addresses the state-feedback H₂/H-infinity controller design that satisfies D-stability constraints for stochastic systems. Firstly, the concept of regional stability for stochastic systems is defined in linear matrix inequality(LMI) regions; Secondly, the characterization about stochastic D-stability is presented. This paper introduces a new technique to solve the regional stability problem for stochastic systems, which is different from the pole placement technique ever used in deterministic systems. Based on this, in the state-feedback case, mixed H₂/H-infinity synthesis with D-stability constraints is discussed via LMI optimization.     

New optomechanical technique for measuring layer thickness in MEMSprocesses

Dimensional metrology improvements are needed to achieve the fabrication of repeatable devices. This research presents a new optomechanical technique for measuring the thickness of a suspended material in two distinct microelectromechanical system (MEMS) fabrication processes. This technique includes design of test structure, choice of measurement tools, method of measurement, and computation of thickness. Two tools, the stylus profilometer and optical interferometer, are used to take measurements. Non-contact measurements are possible on structures as narrow as 5 μm. Local thickness measurements are achievable with combined standard uncertainty values of less than 10 mm. Benefits of using the new technique include greater likelihood of fabricating repeatable devices and more accurate measurements of material parameters. The proposed technique is also applicable for measuring layers that are thinner and made of materials other than the conventional suspended material used in this research     

Manufacturing of composite parts reinforced through-thickness by tufting

The paper aims at providing practical guidelines for the manufacture of composite parts reinforced by tufting. The need for through-thickness reinforcement of high performance carbon fibre composite structures is reviewed and various options are presented. The tufting process is described in detail and relevant aspects of the technology are analysed such as: equipment configuration and setup, latest advances in tooling, thread selection, preform supporting systems and choice of ancillary materials. Effects of the process parameters on the preform fibre architecture and on the meso-structure of the reinforced component are discussed. Special emphasis is given to the different options available in terms of tuft insertion and loops management.Potential fields of application of the technology are investigated as well as the limitations of its applicability in relation to preform nature and geometry. Critical issues which may arise during the manufacturing process concerning thread insertion, loops formation, alteration to the fabric fibres layout or local volume fraction are identified.