As part of a microrobot we present a micromachined gripper system which has both force sensor and actuator integrated. This gripper is used for handling and assembling and allows control of the gap of the gripper and the gripping force continuously. We use a thermal bimorph actuator for the operation of the gripper. For the force sensor we utilize the piezoresistive effect, known to be very strong in silicon. As compared to previous realizations we have optimized the design: the proposed folded bimorph beam delivers a multiple of the actuators stroke as compared to a simple beam structure. This folded bimorph beam design can also be applied to other bimorph actuators (e.g. piezoelectric, SMA). The actuators maximum stroke is 800 micrometers at a finger length of 1600 micrometers and the maximum force generated is in the order of 1 mN. That means an improvement of a factor of five with respect to designs published earlier. The sensitivity of the sensor finger is about 100 mV/VmN which is an improvement by a factor of three and its shows a good linearity.
Stick and slip actuators are particularly well adapted to microrobotics. A simple design, a very high intrinsic resolution (a few nanometers) and a high rigidity makes them specially interesting for high precision micro manipulations. Moreover, a smart design allows the user to combine the guiding and actuating functions. Parallel architectures are attractive to microrobotics too. They present a high rigidity and the actuators are fixed on the base. This paper deals with the integration of stick and slip actuators in a 6-degrees-of-freedom parallel structure dedicated to the micro assembly of optical components. In section 3 we describe and characterize inertial actuators using the stick and slip effect. We demonstrate their performances (velocity higher than 1.5 mm/s, 10 nm precision) and limits. In section 4 we describe the 6- degrees-of-freedom parallel architecture that we developed for our application and how the actuators are integrated into it. Its kinematics, the joins' forces and the working volume have been calculated. A resolution better than 30 nm is possible within a working volume of 140 mm3. Orientations of several degrees (up to plus or minus five degrees) are possible for the three rotational angles.
Grippers for an automated assembly cell are being developed for handling individual sub-millimeter hard-disc drive components. Processing requirements dictate positive gripping with a strong actuator that meets clean room specifications. Proof-of-concept testing of shape memory alloy (SMA) as an actuator was performed. The response time of Ni-Ti 0.076 mm diameter shape memory wire was found to be 0.15 seconds under forced air convection conditions. Positioning accuracy was held to steady-state oscillations of 0.076 mm proving that SMA actuators meet performance requirements for a precision microactuator. SMA was then used for the actuation of several candidate gripper designs. One promising design consisted of a two-fingered gripper with integral spring sections at the arm base. SMA wire provided the closing actuation force and the spring sections returned the fingers to their rest position. Another design used an external spring to provide the gripping force, while the SMA wire provided the force required to open the gripper. The paper describes design methodologies and overall results. The addition of closed-loop control and improved heat dissipation mechanisms are needed before SMA materials can be used robustly as actuators for sub-mm robot grippers in high volume applications.
As microsystems and micro structures become smaller, it is necessary to build a micro robot ((mu) -robot) capable of manipulating these systems and structures. The movements and positions of the robot have to be controlled and guided. The first part of our project was to develop a real time 3D computer graphics (virtual reality) environment man-machine interface to guide the newly developed robot. Secondly, we calibrated the camera and microscope system to evaluate measurement techniques to verify robots' position in the region of interest (workspace) at a sub micron accuracy. Our latest developments of using a high resolution vision system as well as the controlling strategy of a new type of micro robot are discussed. The simple and compact design of the robot is believed to be promising in the micro robotics field. Stepping motion allows speeds up to 4 mm/s. Resolution smaller than 10 nm is achievable. Using high resolution camera calibration, passive auto focus algorithms and 2D object recognition the position of the robot can be controlled in the 3D workspace to guide the micro assembly. We focus on the vision system and on the virtual reality interface of the complex system. Basically the user interacts with the virtual 3D microscope and sees the micro- robot as if he is looking through a real microscope. He is able to simulate the assembly of the missing parts, e.g. parts of a micromotor, beforehand in order to verify the assembly manipulation steps such as measuring, moving the table to the right position, or performing the manipulation. Micro manipulation the in form of a teleoperation is then performed by the real robot-unit and the position is controlled by vision in an internal loop. Results have shown, that a guided manipulation with sub micron absolute accuracy of the robot can be achieved. A key idea of this approach is to use the intuitiveness of immersed vision to perform robotic tasks in an environment where the operator only has access using high performing measurement and visualization systems. Using also the virtual scene exactly reconstructed from the CAD-CAM-databases of the real environment being considered as the a priori knowledge, human observations and computer-vision based techniques improve the robustness and speed of such an application tremendously. Robust computer vision is used for 3D micro- object recognition and very promising for micro assembly, microsystem measurement and quality assurance of micro fabrication techniques.
To fabricate 3D microstructures, the authors designed, constructed and evaluated a tabletop factory called 'nano manufacturing world (NMW).' We designed a compact, concentrated layout of fabricating/handling machines around a workpiece for an integrated production, and an image- assisted tele-operation system between the processing site and the operating site. Using various working processes developed in NMW, e.g. dry-etching with a fast atom beam or assembling with a concentrated motion manipulator under a scanning electron microscope, we demonstrated fabricating some 3D microstructures such as a micro-tower or a micro- airplane. In addition to fabricate functional film features on the 3D microstructures, we are producing a micro magnetic head or a micro optical circuit in NMW. Through the demonstration, we evaluate that NMW functions effectively as designed and will become a solution for micro manufacturing systems.
One of the main problems of present-day research on microsystem technology (MST) is to assemble a whole micro- system from different microcomponents. This paper presents a new concept of an automated micromanipulation desktop- station including piezoelectrically driven microrobots placed on a high-precise x-y-stage of a light microscope, a CCD-camera as a local sensor subsystem, a laser sensor unit as a global sensor subsystem, a parallel computer system with C167 microcontrollers, and a Pentium PC equipped additionally with an optical grabber. The microrobots can perform high-precise manipulations (with an accuracy of up to 10 nm) and a nondestructive transport (at a speed of about 3 cm/sec) of very small objects under the microscope. To control the desktop-station automatically, an advanced control system that includes a task planning level and a real-time execution level is being developed. The main function of the task planning sub-system is to interpret the implicit action plan and to generate a sequence of explicit operations which are sent to the execution level of the control system. The main functions of the execution control level are the object recognition, image processing and feedback position control of the microrobot and the microscope stage.
At the interface of micro and macro world, vision plays a fundamental role in localizing targets and positioning micro- or nanorobots relative to them. Traditionally, far- field optics are used to achieve this task. However, in most practical applications optical diffraction limits resolution to the micrometer-range although image processing may provide us relative accuracies on the order of several nanometers in a few special cases. At ambient pressure, capillary condensation of water vapor severely hampers reproducible and reversible manipulations of micrometer- sized or smaller objects since the resulting adhesive forces between tool and object easily exceed the object's weight. The size of objects also dictates the useful dimensions of sensors and actuators and generally necessitates integration of several sensing and/or actuation functions into a single device. To overcome above mentioned difficulties in accessing the micro and nano world, sensing and actuating principles derived from scanning probe microscopies such as atomic force or optical near-field provide us with the necessary extension of the capabilities offered by traditional far-field systems. A fluid environment also prevents those hard-to-control effects of capillary forces.
To conduct micro-tasks, microscopic images are indispensable. Of course, the primary function of the images are observation. The images, however, can execute some other advantageous functions to micro-tasks. In this paper, the authors introduce an operation system utilizing the images actively for micro-assembly, namely an 'image-driven operation system (IDOS).' The IDOS acts as a hidden operation agent which mediates between the operator and the micro-tasks. In the function of the IDOS, user interface, layered image database, automatic repositioning are constructed and confirmed.
This paper aims at describing a miniaturized CMOS implant- circuit for human medical telemetry. The chip includes a silicon antenna working on the principle of inductive coil coupling through the skin, an rf rectifier for power supply, an hf filter and logic circuitry for chip control. A CMOS compatible temperature sensor is included in the same chip. The obtained measurements are sent back to the coupled antenna and received outside the patient's body. Two prototype chips have been designed in a CMOS 1.0 micrometer technology with encouraging results. The chips include the separate basic blocs of the micro-system: rectifier, integrated or external antenna, analog filters, sensors and logic systems.
Different small-scale devices for particle micro-handling using an ac electric field boundary wave were proposed in an earlier paper of the authors. These devices, with various novel transportation and manipulation features, that instantly generate particle driving forces through electric field creation, have been designed and produced. In a further endeavor, the mechanisms of particle conveyance are here subsequently validated in experiments. Particles on a thin protecting and insulating film interface above a series of encased and insulated parallel field electrodes become either tribo-electrically or induction charged through the application of balanced three- or six-phase voltages. The created non-uniform traveling field-wave conveys the charged particles perpendicular to the electrodes by repulsive forces in a hopping mode from electrode to electrode. In a temperature and humidity controlled environment, experiments surveying particle conveyance dynamics on these electric devices have been carried out. Various particle materials with diameters up to 400 micrometers have been examined; metal, glass, and plastic spheres showed the best performances. The transient charge distribution on particles and on the activated electric device, which is responsible for the particle conveyance, has been statically and dynamically inspected by a modified scanning electron microscope. Theoretical considerations underline the experimental findings. Further, angular speckle contouring measurements reveal the manipulation surface profile. Finally, a selection of cover materials are examined for their particle conveyance qualities.
This paper proposes a system design concept of a 'concentrated visual field' for micro object handling. The proposed concept features: (1) multiple microscopes, (2) fields of view concentrated on manipulators' work space, and (3) rotational DOF for tilting manipulators and a worktable. Micro Object Handling System II, which consists of two microscopes (a scanning electron microscope and an optical microscope), two manipulators (primary and secondary) and a worktable, is constructed based on the design concept. The primary manipulator is equipped with two rotational DOFs, and three highly precise translational DOFs. The secondary manipulator is utilized to fix objects on the worktable. The paper also proposes new micro object handling skills to control the adhesive forces which are crucial for micromanipulation. These skills feature: (1) graspless handling of an object by a needlelike tool, (2) changing adhesive force between a tool and an object by changing the contact area between them, and (3) cooperating two tools whose adhesive forces differ. Several micro object handling experiments were successfully performed by the system to prove the feasibility of the new handling skills and the system effectiveness.
Automatic assembly becomes an important issue as hybrid micro systems enter industrial fabrication. Moving from a laboratory scale production with manual assembly and bonding processes to automatic assembly requires a thorough re- evaluation of the design, the characteristics of the individual components and of the processes involved. Parts supply for automatic operation, sensitive and intelligent grippers adapted to size, surface and material properties of the microcomponents gain importance when the superior sensory and handling skills of a human are to be replaced by a machine. This holds in particular for the automatic assembly of micro-optical components. The paper outlines these issues exemplified at the automatic assembly of a micro-optical duplexer consisting of a micro-optical bench fabricated by the LIGA technique, two spherical lenses, a wavelength filter and an optical fiber. Spherical lenses, wavelength filter and optical fiber are supplied by third party vendors, which raises the question of parts supply for automatic assembly. The bonding processes for these components include press fit and adhesive bonding. The prototype assembly system with all relevant components e.g. handling system, parts supply, grippers and control is described. Results of first automatic assembly tests are presented.
Presented is an assembling method for the fabrication of a piezoelectric miniature motor. The fabrication is done by placement and soldering of actuator elements to a substrate. The assembly of the miniature motor demands high precision (plus or minus 1 micrometer), four-axes positioning which is fulfilled by a special micropositioning stage. A particular assembling sequence is used and critical process and performance parameters are evaluated. One of the important factors is the joint strength between actuator element and substrate. A joint strength as high as 100 MPa has been measured which would allow for torque values in the range of 15 mNm for a 4 mm diameter motor.
An automated assembly technique for small optical components has been developed. It concerns components such as, e.g., laser diodes and LEDs, fibers, lenses beamsplitters, polarizers, mirrors, crystals, prisms, diffractive elements or photodiodes. It is based on the flexible 2-dimensional arrangement of a universal tripod holder (10 by 10 by 4 mm) on a planar mounting plate. Its particular mechanical structure allows to align the optical elements on-line and to attach them to the mounting plate in a one step procedure. The different elements are aligned with an accuracy of plus or minus 1 micrometer and attached one after the other. Very good position stability (plus or minus 0.7 micrometer, plus or minus 0.2 mrad) during the attachment procedure has been achieved by laser point welding. They are optically interconnected by free-space propagation of a light beam with diameter of up to 8 millimeters. Mass production has been shown with a collimator as test vehicle. The collimator is composed of two elements (laser diode and collimating lens) and is mounted entirely automatically by two co-working robots. Easy prototyping has been shown with the realization of the optical position sensing system featuring a high precision linear magnetic bearing. Flexibility, simple handling, high packaging density and low cost make this new assembly technique satiable to both mass production and prototyping of small opto electronical devices.
This paper describes a tele-micro machining system which works under a stereo SEM and has operational environment transmission capability. The system includes a 3-axis force sensing table, the signal from which is converted into auditory information to enhance the operability of the system. Furthermore, the cutting state in micro-cutting is reflected as force feedback to the master joystick using a newly introduced index which represents the cutting state. The MMM (micro-machining machine) located at the University of Tokyo was operated from Karlsruhe University in Germany using ISDN. The cutting force in the micro-world using micro-endmill is analyzed and compared with that in the macro-world. The dependency of the crystal direction while scratching a single crystal silicon was analyzed. Finally, the internal damage while scratching a single crystal magnesium oxide was observed in real-time and analyzed.
Recently, so many kinds of micro machines have been developed. Yet, the design and control methodology,of these micro machines is not well established. Difference of dimensions between the macro and micro world causes difference of the influential physical phenomena, motion of the objects, and relative change of the system performance between those worlds. To understand the physical phenomena in the micro world is very important to design, fabricate and control the micro robotic system. For example, attractive forces are dominant in the micro world compared with the gravitational force. Brownian motion is not negligible in the liquid. Since the dominating physical law is completely different between the macro and micro world, we must consider physics in the micro world in designing, fabricating, and controlling miniaturized objects. However, these problems have not been treated so seriously before. In this paper we present a new design and control strategy which will be essential for the microrobotics. Our approach is based on the attractive force reduction. Attractive force reduction methods are mainly focused in this paper. Application example to the micromanipulation is introduced and some experimental results are shown.
Handling objects in the microworld requires a set of abilities and tools which differ from the ones used to interact with objects in the macro world. A whole new set of handling limitations is present, as well as an array of new possibilities. Due to the small dimensions, the operator has no direct access to the objects and must assemble them by teleoperation. Therefore a user interface to interact with the micro world must be specifically designed. Thus, this paper presents the implementation of a graphical user interface for a high precision robot operating on the micro world developed at the Swiss Federal Institute of Technology. In this interface the operator is provided with a set of visualization and manipulation tools on a workstation. The visualization tools are: live microscope video images with top and side view, and a 3D virtual solid model of the robot with perspective as well as orthogonal views available at the same time. The manipulation tools are: a control panel used to check the status and to operate both the camera and the robot itself and an interface wit ha 6 degree of freedom joystick-like manipulator. Several combinations of visualization and manipulation tools have been tested, as well as several manipulation strategies. The user interface and the results of this investigation are presented in this paper, as well as a description of the robot system.
The trend towards the integration of a multitude of functions in e.g. data end-, medical- and communication systems pushes the miniaturization of actuators for linear or rotational motions. Technical advantages of these devices are their low energy consumption, their potential for high precision positioning and their low inertial masses, which allow e.g. huge rotational frequencies. Appreciable forces and torques as well as appropriate mechanical interfaces to integrate these drive units into complete systems are necessary prerequisites for robotic applications, but rarely found up to now. Most of these difficulties arise due to the application of monolithic fabrication techniques, leading to structures of essentially planar nature and severe material restrictions. It turned out that only hybrid concepts and the assembly of components made from the most appropriate material open the chance to build up microactuators which are well suited for microrobotic systems. The contribution starts with a short description of the LIGA technique, which constitutes the major 3-D microfabrication method for the production of individual actuator components with structural heights of up to several millimeters made from a variety of function adapted materials. The assembling of these components results in microactuators with typical dimensions in the millimeter range. Examples are powerful electromagnetic micromotors, delivering torques much larger than one (mu) Nm and high rotational speeds which may be converted by use of LIGA fabricated gear-wheels to furthermore increase the torque. Huge forces are obtained in addition by use of microfabricated fluidic systems. Although small in size, the actuators still offer good handling opportunities and interfacing facilities to build up more complicated robotic systems.
Miniaturized, integrated sensors and actuators called microsystems are a rapidly growing field with great future potential. In order to promote their use further, specialists must make them more accessible to system designers at all stages of development. This can be done through behavioral modeling of sensors and actuators which can be used in conjunction with models of the associated electronics to simulate a complete microsystem. Additionally, models of microsystem components realized during modeling and simulation can be retrieved for use in the assembly phase of manufacture. Here virtual-reality environments are used to aid in the realization and use of automated robot systems working with miniature components in the micron scale. The use of computer aided design and simulation tools in this field is critical owing to the high prototyping costs. Data exchange between the various systems is advantageous and reduces design and manufacturing costs while speeding up time to market.