Frank L. Merat

MEMS applications in optical systems

We describe progress in the development of micro-optomechanical components which are compatible with MEMS and integrated circuit processing. Devices which have been developed include polygon and diffraction grating scanners, tunable laser diodes, tunable IR filters, and optical waveguides.

An agile manufacturing workcell design

This paper introduces a design for agile manufacturing workcells intended for light mechanical assembly of products made from similar components (i.e., parts families). We define agile manufacturing as the ability to accomplish rapid changeover from the assembly of one product to the assembly of a different product. Rapid hardware changeover is made possible through the use of robots, flexible part feeders, modular grippers, and modular assembly hardware. The division of assembly, feeding, and unloading tasks between multiple robots is examined with prioritization based upon assembly time. Rapid software changeover will be facilitated by the use of a real-time, object-oriented software environment utilizing graphical simulations for off-line software development. An innovative dual VMEbus controller architecture permits an open software environment while accommodating the closed nature of most commercial robot controllers. These agile features permit new products to be introduced with minimal downtime and system reconfiguration.

Advances in agile manufacturing

An agile workcell has been developed for light mechanical assembly in collaboration with industrial sponsors. The workcell includes multiple Adept robots, a Bosch conveyor system, multiple flexible parts feeders at each robots workstation, CCD cameras for parts feeding and hardware registration, and a dual VMEbus control system. Our flexible pairs feeder design uses multiple conveyors to singulate the parts and machine vision to locate them. Specialized hardware is encapsulated on modular grippers and modular worktables which can be quickly interchanged for assembly of different products. Object-oriented software (C++) running under VxWorks, a real-time operating system, is used for workcell control. An agile software architecture was developed for rapid introduction of new assemblies through code re-use. A simulation of the workcell was developed so that controller software could be written and tested off-line, enabling the rapid introduction of new products.

Defeating distributed denial-of-service attack with deterministic bit marking

Distributed denial-of-service (DDoS) attack is a serious threat in Internet. We propose a bit marking concept to identify and drop the DDoS attack packets. Bit marking is a variation of the packet marking technique that modifies packet headers at each router. However instead of storing the router information in the packets, bit marking alters one or more bits in the marking field. The bit marking process discussed in this paper is performed to all the packets and at all the routers along the path; hence it is called deterministic bit marking (DBM). DBM creates a common path signature for all the packets originating from the same location upon arriving at a destination. Since different source networks generate virtually unique path signatures, DBM makes it possible to isolate and discard DDoS attack traffic. From the Internet topology of autonomous systems we observe that the source networks are quite uniformly distributed over the path signature space. In our simulation over 99% of the attack traffic is blocked using DBM while up to 99% of the legitimate traffic passes. DBM can also be used for source traceback using reverse bit marking. DBM can be independently deployed for each ISP and the DBM-based networks can be protected from the attacks coming from nonDBM networks.

Design of an agile manufacturing workcell for light mechanical applications

This paper introduces a design for agile manufacturing workcells intended for light mechanical assembly of products made from similar components (i.e. parts families). We define agile manufacturing as the ability to accomplish rapid changeover from the assembly of one product to the assembly of another product. Rapid hardware changeover is made possible through the use of robots, flexible part feeders, modular grippers and modular assembly hardware. The flexible feeders rely on belt feeding and binary computer vision for Dose estimation. This has a distinct advantage over non-flexible feeding schemes such as bowl feeders which require considerable adjustment to changeover from one part to another. Rapid software changeover is being facilitated by the use of a real-time, object-oriented software environment, modular software, graphical simulations for off-line software development, and an innovative dual VMEbus controller architecture. These agile features permit new products to be introduced with minimal downtime and system reconfiguration.

Design lessons for building agile manufacturing systems

Summarizes results of a five-year, multi-disciplinary, university-industry collaborative effort investigating design issues in agile manufacturing. The focus of the project is specifically on light mechanical assembly, with the demand that new assembly tasks be implementable quickly, economically, and effectively. Key to achieving these goals is the ease of equipment and software reuse. Design choices for both hardware and software must strike a balance between the inflexibility of special-purpose designs and the impracticality of overly general designs. We review both our physical and software design choices and make recommendations for the design of agile manufacturing systems.

A flexible software architecture for agile manufacturing

The flexibility required of an agile manufacturing system must be achieved largely through computer software. The systems control software must be adaptable to new products and to new system components without becoming unreliable or difficult to maintain. This requires designing the software specifically to facilitate future changes. As part of the Agile Manufacturing Project at Case Western Reserve University, we have developed a software architecture for control of an agile manufacturing workcell, and we have demonstrated its flexibility with rapid changeover and introduction of new products. In this paper, we describe the requirements for agile manufacturing software and how our software architecture addresses them.

Static and electrically actuated shaped MEMS mirrors

A novel digitally-actuated shaped micromirror for on-off optical switch applications is described. Reflective static spherical mirrors were designed and fabricated using conventional surface micromachining and the MultiPoly process, a technique for depositing multilayers of LPCVD polysilicon in order to control the overall stress and stress gradient. The resulting mirrors were measured to have radii of curvature of approximately 9 mm in agreement with design predictions. Based upon these static mirrors, an actuatable micromirror (diameter=500 /spl mu/m, static radius curvature=6.4 mm) was designed for snap action. This mirror was simulated using an electromechanical coupled-field model and fabricated using the MultiPoly process. Its performance was measured dynamically using an interferometer. A curved-to-flat digital actuation of the mirror was successfully achieved with a pull-in voltage of 38 V.

Visual segmentation of lawn grass for a mobile robotic lawnmower

We investigate the existence of computationally inexpensive first and second order statistics that uniquely describe grass for application in an autonomous lawnmower. We then segment images based on these statistics to determine locations of driveable terrain in an image. Tight statistical clustering of illuminated grass versus artificial texture suggests that this method is sufficient for identifying driveable terrain for an autonomous lawnmower.

Vision-based obstacle detection and avoidance for the CWRU cutter Autonomous Lawnmower

This paper describes the vision-based obstacle detection system of the CWRU Cutter, an autonomous lawnmower developed for the annual “Institute of Navigation (ION) Autonomous Lawnmower Competition.” Unlike LIDAR sensors commonly found on autonomous vehicles, computer vision systems can provide similar information at drastically reduced prices. Though significantly more cost-effective than LIDAR, these systems have inherent problems due to changing lighting conditions and shadows. This paper investigates the use of image hue and intensity to create a robust, real-time vision-based obstacle detection system for use during the ION competition. Data abstraction methods used to process incoming images for easy combination of information from multiple sensors are also discussed. Using this system, CWRU Cutter correctly identified obstacles in 89% of frames containing fence, 78% of frames containing flowerbeds, and 84% of frames containing boundary lines.