Anita M. Flynn

Piezoelectric micromotors for microrobots

The authors have begun research into piezoelectric ultrasonic motors using ferroelectric thin films. The authors have fabricated the stator components of these millimeter diameter motors on silicon wafers. Ultrasonic motors consist of two pieces: a stator and a rotor. The stator includes a piezoelectric film in which bending is induced in the form of a traveling wave. A small glass lens placed upon the stator becomes the spinning rotor. Piezoelectric micromotors overcome the problems currently associated with electrostatic micromotors such as low torque, friction, and the need for high voltage excitation. More importantly, they may offer a much simpler mechanism for coupling power out. Using thin films of lead zirconate titanate on silicon nitride membranes, various types of actuator structures can be fabricated. By combined new robot control systems with piezoelectric motors and micromechanics, the authors propose creating micromechanical systems that are small, cheap and completely autonomous. >

Mobile robots: inspiration to implementation

Revised and updated, the second edition includes several new chapters with projects and applications. The authors keep pace with the ever-growing and rapidly expanding field of robotics. The new edition reflects technological developments and includes programs and activities for robot enthusiasts. Using photographs, illustrations, and informative text, Mobile Robots guides the reader through the step-by-step process of constructing two different and inexpensive yet fully functional robots.

Combining sonar and infrared sensors for mobile robot navigation

Multiple sensors can be used on a mobile robot so that it can perceive its environment with better accuracy than if either sensor were used alone. Sonar and infrared sensors are used here in a complementary fashion, where the advantages of one compensate for the disadvantages of the other. The robot then combines the information from the two sensors to build a more accurate map. Another representation, a modified version of the curvature primal sketch, is extracted from this perceived workspace and is used as the input to two path planning programs: one based on configuration space and one based on a generalized cone formulation of free space.

Ferroelectric thin film ultrasonic micromotors

Ferroelectric thin films of lead zirconate titanate (PZT) of morphotropic phase-boundary composition have been fabricated by a sol-gel spin-on technique for application to a new family of flexure-wave piezoelectric micromotors characterized by low speed and high torque. The high relative dielectric constant (1300) and breakdown strength (1 MV/cm) of the films lead to high stored energy densities. The piezoelectric coefficients d/sub 33/ and d/sub 31/ were measured to be 220 pC/N and -88 pC/N, respectively; the electromechanical coupling factors calculated from these data were k/sub 33/=0.49, k/sub 31/=0.22, and k/sub p/=0.32. The development of the piezoelectric ultrasonic micromotors from the PZT thin films and the architecture of the stator structure are described. Nonoptimized prototype micromotors show rotational velocities of 100-300 rpm and net normalized torques in the pN-m/V/sup 2/ range.<<ETX>>

MIT mobile robots-what's next?

The MIT mobile robot project began in January of 1985 with the objective of building machines that could operate autonomously and robustly in dynamically changing environments. Five working robots, each progressively more intelligent and sophisticated, are now available. These robots are reviewed, focusing on their innovative aspects. These include novel ideas in the areas of control systems, sensors, actuators, power supplies, and power processing. Perspectives on mobile robotics are outlined, including objectives, experiences, mistakes, and future plans.<<ETX>>

Building Robots: Expectations and Experiences

In tlie four years that llie MU Mobile lbbot Project has been 1 General Theme at the Start in existence, we have built ten robots that focus research in various areas, aimed primarily towards discerning what is involved in building intelligent, useful autonomous creatures. Many of the preconceived notions entertained before we started turned out to be misguided, many issues we thought would be hard have worked successfully from day one, and subsystems we imagined to be trivial have become tremendous time sinks. Oddly enough, one of our biggest failures has led to many of our favorite successes. The general problem we set out to solve four and a half years ago was how to build a brain, or, to answer the question of what it would take to build something that we would consider clever. What were the essential components that would be needed to create an intelligent entity and how should those components be put together? The ideas we started with took a route that was different from the traditional thinking in Artificial Intelligence at that time. Namely, our From early meter-high, offboard-computer based robots, to sleek walking creatures, soda can collection machines and one cubic inch bugs, the MIT Mobot Line exhibits a wide variety of talents, sensing strategies and locomotion approaches. Central throughout is a common methodology for organizing the sensors, actuators and computational elements to effectively control complexity. A basic tenet is that it is important to build complete systems that exist in real world noise. This avoids the trap of building

Intelligence for miniature robots

Abstract It seems clear that small robots which take advantage of recent reductions in packaging size and costs of microelectronics can potentially be very useful; even more so if similar savings could be achieved in the actuation and power supply areas. Typically, the computational power required in a robotic system that connects perception to action is enormous, but if the organization of the sensors, actuators and computing elements is carefully laid out, the actual silicon area required for the intelligence system becomes quite small. A viable avenue of pursuit, then, is to aim towards scaling down the rest of the subsystems in a robot to the same scale as the control system, integrating motors, sensors, computation and power supplies onto a single piece of silicon; the advantages being mass productibility, lower costs and the avoidance of the usual connector problems encountered in combining discrete subsystems. By rethinking implementation strategies with this new form of robotic technology (i.e., the application of many very small robots), it may be possible to solve many problems more cost effectively, albeit in novel ways. As the completely integrated robot faces many technology hurdles, it seems necessary to focus on just one or two of the problem areas at a time. It turns out that many of the cost-saving benefits still accrue at small, but macroscopic scales. This paper describes an exercise of building a complete system, aimed at being as small as possible, but using off the shelf components exclusively. The result is an autonomous mobile robot slightly larger than one cubic inch, which incorporates sensing, actuation, onboard computation and on-board power supplies. Nicknamed Squirt, this robot acts as a ‘bug’, hiding in dark corners and venturing out in the direction of last heard noises, only moving after the noises are long gone.

Performance of ultrasonic mini-motors using design of experiments

This paper describes speed-torque characteristics of a parametrized set of 8 mm diameter tall ultrasonic motors fabricated using design of experiments. Design of experiments methods provide for a way of developing a model based on the gathering of data and a way of analysing the data to compute both quantitative and qualitative results which can point towards an optimal set of parameters for the final design. Ultrasonic motors are known for their high-torque, low-speed characteristics. These devices have demonstrated maximum no-load speeds of 1710 rpm and peak power outputs of 27 mW. Stall torques of these 8 mm motors have been measured as high as , yielding roughly 50 times the stall torque density of the smallest commercially available DC motors. Results of the study yield insight into optimizing stall torques and no-load speeds of miniature ultrasonic motors.

The world's largest one cubic inch robot

The authors describe an exercise of building a complete robot system, aimed at being as small as possible, but using off-the-shelf components exclusively. The result is an autonomous one (almost) cubic inch robot which incorporates sensing. actuation, onboard computation, and onboard power supplies. Nicknamed Squirt this robot acts as a bug hiding in dark corners and venturing out in the direction of last-heard noises, only moving after the noises are long gone.<<ETX>>

Recognition algorithms for the connection machine

This paper describes an object recognition algorithm both on a sequential machine and on a single instruction multiple data (SIMD) parallel processor such as the MIT connection machine. The problem, in the way it is presently formulated on a sequential machine, is essentially a propagation of constraints through a tree of possibilities in an attempt to prune the tree to a small number of leaves. The tree can become excessively large, however, and so implementations on massively parallel machines are sought in order to speed up the problem. Two fast parallel algorithms are described here, a static algorithm and a dynamic algorithm. The static algorithm reformulates the problem by assigning every leaf in the completely expanded unpruned tree to a separate processor in the connection machine. Then pruning is done in nearly constant time by broadcasting constraints to the entire SIMD array. This parallel version is shown to run three to four orders of magnitude faster than the sequential version. For large recognition problems which would exceed the capacity of the machine, a dynamic algorithm is described which performs a series of loading and pruning steps, dynamically allocating and deallocating processors through the use of the connection machines global router communications mechanism.