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This robotic hand is capable of performing the delicate task of picking up and holding an egg without breaking it. A tactile array sensor located on the right half of its gripping mechanism sends information to the robot's control computer about the pressure the robotic hand exerts; given this information, the control computer instructs the robotic hand to loosen, tighten, or maintain the current gripping force. This feedback loop repeats continuously, enabling the robotic hand to stay in between the two extremes of dropping and crushing the egg.
"Robotics," Microsoft® Encarta® Encyclopedia 2000. © 1993-1999 Microsoft Corporation. All rights reserved.
In gas and steam turbines and internal-combustion engines, where fuel furnishes the energy to the machine, the governor regulates the flow of fuel. To control the speed of a hydraulic turbine generator, a governor can alter the water flow by opening and closing gates and valves. Another type of mechanical governor, used to regulate the speed of aircraft engines, varies the pitch of the propeller blades attached to the engine.
The most common type of mechanical governor operates by means of the forces of inertia (the resistance to change or motion) that arise from longitudinal or rotary motion. For example, when a spring-loaded mechanical governor is rotated, the flyweights, or flyballs, are flung outward by centrifugal force (see Centripetal Force). At a given speed, the flyweights are in an equilibrium position and the spring is partially compressed. An increase in speed causes the flyweights to rise as they pull farther out from the axis of rotation. This causes a further compression of the spring. The spring sets up a control force that may close a valve or in some other way decrease the energy input to the machine. As a result, the speed of the machine decreases, at which point the flyweights begin to fall. Then, the spring becomes less compressed and valve is opened once again.
The piezoelectric effect occurs in several crystalline substances, such as barium titanate and tourmaline. The effect is explained by the displacement of ions in crystals that have a nonsymmetrical unit cell, the simplest polyhedron that makes up the crystal structure (see Crystal). When the crystal is compressed, the ions in each unit cell are displaced, causing the electric polarization of the unit cell. Because of the regularity of crystalline structure, these effects accumulate, causing the appearance of an electric potential difference between certain faces of the crystal. When an external electric field is applied to the crystal, the ions in each unit cell are displaced by electrostatic forces, resulting in the mechanical deformation of the whole crystal
The Hall effect occurs when a conductor or semiconductor carrying an electric current is placed in a magnetic field. A voltage, called the Hall voltage, is created across the conductor or semiconductor perpendicular to both the current and the magnetic field. This voltage arises because the magnetic field distorts the flow of electrons or other charge carriers that constitute the current, pushing the charged particles to one side of the conductor.
 The Hall voltage is proportional to the current and magnetic field and inversely proportional to the number of electrons or other charged particles. For instance, the Hall voltage across a metal is much smaller than across a semiconductor carrying the same current in the same magnetic field because the metal contains more charged particles than the semiconductor.
Resistors with adjustable resistance are called rheostats or potentiometers. These types of resistors are used in appliances when the current needs to be adjusted or when the resistance needs to be varied, as with lights that dim or adjustable generators.
Pairs of machines known as synchros, selsyns, or autosyns are used to transmit torque or mechanical movement from one place to another by electrical means. They consist of pairs of motors with stationary fields and armatures wound with three sets of coils similar to those of a three-phase alternator. In use, the armatures of selsyns are connected electrically in parallel to each other but not to any external source. The field coils are connected in parallel to an external AC source. When the armatures of both selsyns are in the same position relative to the magnetic fields of their respective machines, the currents induced in the armature coils will be equal and will cancel each other out. When one of the armatures is moved, however, an imbalance is created that will cause a current to be induced in the other armature. The magnetic reaction to this current will move the second armature until it is in the same relative position as the first. Selsyns are widely used for remote-control and remote-indicating instruments where it is inconvenient or impossible to make a mechanical connection.
"Electric Motors and Generators," Microsoft® Encarta® Encyclopedia 2000. © 1993-1999 Microsoft Corporation. All rights reserved.
Some devices act as both sensor and transducer. A thermocouple has two junctions of wires of different metals; these generate a small electric voltage that depends on the temperature difference between the two junctions. A thermistor is a special resistor, the resistance of which varies with temperature. A variable resistor can convert mechanical movement into an electrical signal. Specially designed capacitors are used to measure distance, and photocells are used to detect light (see Photoelectric Cell).
The image-orthicon tube and the vidicon tube were invented in the 1940s and were a vast improvement on the iconoscope. They needed only about as much light to record a scene as human eyes need to see. Instead of camera tubes, most modern cameras now use light-sensitive integrated circuits (tiny, electronic devices) called charge-coupled devices (CCDs).
A CCD used for recording visual information is made of an array of photodiodes (devices that conduct electricity when light strikes them) on top of a semiconductor (a material that conducts electricity better than electrical insulators but not as well as electrical conductors). When light strikes a photodiode, an electric current proportional to the amount of light is sent to a capacitor, which stores the charge. The semiconductor processes the signal from the capacitor and sends it to a computer or other device that can analyze the data about the light that hit the CCD.
The applied sensor system consists of two grayscale CCD-cameras mounted on a pan-tilt-verge camera mount. The movements of the camera mount and the image processing are controlled by the  local coordination layer.

MARVIN generates the three-dimensional model only from discrete positions during a still stand to avoid vibrations of the cameras. During the motion the sensor system is used as an optical bumper scanning the free space in front of the vehicle for obstacles. The other possible behavior is shown in this  MPEG -video, where the optical bumper was switched off. A moving object occluded the planned path and caused a collision. The vehicle moves back several centimeters to inspect the unexpected obstacle.
The exploration system consists of several processes communicating with each other via the
RPC-mechanism. This allows a free distribution of the processing power among the available computers.
The whole system can be subdivided into three layers with different tasks: processing layer             - data acquisition and interpretation, hardware control local coordination layer - planning and control of the system based on cartesian coordinates global planning              - abstract topological planning, interaction with the user
The binocular stereo camera system shown in this  MPEG -video does not use any specialized hardware. The image processing and the three-dimensional reconstruction is computed on a single Pentium-PC @ 133 MHz running LinuxOS. The achieved cycle time of 0.6s is sufficient for this application. An example of a 3D reconstruction is shown in the following MPEG.
The actuators which we have implemented were designed in our lab and are known as the Fast Eye Gimbals (FEGs). The FEGs provide directional positioning for our cameras using a similar drive mechanism as the WAM. The two joints are cable driven and have ranges of motion of +/- 90 degrees and +/- 45 degrees in the base and upper joint axes respectively. These two FEGs are currently strategically mounted on ceiling rafters with a wide baseline for higher position accuracy using stereo vision methods. The independent nature of the FEGs allow us to position each one at different locations in order to vary the baseline or orientation of the coordinate frame as well as easily add additional cameras to provide additional perspectives.
Initially focusing on spherical balls of various sizes, we are now experimenting with various objects of unknown dynamic characteristics, such as sponge balls, long cylindrical cans, and paper airplanes. Our system uses low cost vision processing hardware for simple information extraction. Each camera signal is processed independently on vision boards designed by other members of the MIT AI Laboratory (the Cognachrome Vision Tracking System). These vision boards provide us with the center of area, major axis, number of pixels, and aspect ratio of the color keyed image. The two Fast Eye Gimbals allow us to locate and track fast randomly moving objects using "Kalman-like" filtering methods assuming no fixed model for the behavior of the motion. Independent of the tracking algorithms, we use least squares techniques to fit polynomial curves to prior object location data to determine the future path. With this knowledge in hand, we can calculate a path for the WAM to match trajectories with the object to accomplish catching and smooth object/WAM post-catching deceleration. In addition to the basic least squares techniques for path prediction, we study experimentally nonlinear estimation algorithms to give "long term" real-time prediction of the path of moving objects, with the goal of robust acquisition. The algorithms are based on stable on-line construction of approximation networks composed of state space basis functions localized in both space and spatial frequency. As a initial step, we have studied the network's performance in predicting the path of light objects thrown in air. Further application may include motion prediction of objects rolling, bouncing, or breaking up on rough terrains. Some recent successful results for the application of this network have been obtained in catching of sponge balls and even paper airplanes!
Sonar is a device that is used to detect objects through sound waves. There are two main types of sonar: Active and Passive. Sonar technology enters a signal into the water in a narrow beam which has the speed of about 1500 m/s. If there is an object in the beam, its sends sound energy back to the sonar dish. Then the distance is calculated by range = sound speed x travel time / 2. In active sonar a pulse signal is sent to a transducer which changes the electrical signal into a sound signal. After that it is put out into the water and it detects returning echos. A receiver amplifies the soft echos and measures the range of each object. Passive Sonar is used mostly to detect submaries and surface ships. Passive Sonar does not reveal any sound so it is primarly used in submarines. The weak point is that it can not detect the range. The aproximate range can be calculated by measuring the curvature of the received sound wave. Passive sonar relys on detecting noise that is generated by motors and hull vibrations.
Building environment maps from sensory data is an important aspect of mobile robot navigation, particularly for those applications in which robots must function in unstructured environments. Ultrasonic range sensors are, superficially, an attractive sensor modality to use in building such maps, due mainly to their low cost, high speed and simple output. Unfortunately, these sensors have a number of properties that make map building a non-trivial process. In particular, standard sensors have very poor angular resolution and can generate misleading range values in specular environments. The first of these problems can be largely overcome by combining range measurements from multiple viewpoints. Elfes [1] and Moravec [2] describe an approach in which range measurements from multiple viewpoints are combined in a two-dimensional `occupancy grid'. Each cell in the grid is assigned a value indicating the probability that the cell is occupied. Unfortunately, the occupancy grid approach does not work well in specular environments. Specular reflection may occur whenever an ultrasonic pulse encounters a smooth extended surface. In such cases the pulse may not be reflected back to the ultrasonic sensor; in effect, the surface may appear to be invisible. In ordinary office environments which contain smooth walls and glass doors specular reflection is common. In this research, we have improved on earlier grid-based approaches by introducing the concept of a `response grid'. The intent of the response grid framework is to produce an approach which has the advantages of the occupancy grid framework, but also performs well in specular environments.

The response grid framework attempts to model the behaviour of ultrasonic range sensors in a more physically realistic fashion. The basic notion that the response grid encapsulates is that a cell may generate a response (ie appears to be occupied) when viewed in one direction, but will not generate a response when viewed from another. For example, a smooth planar surface will only generate a response when the angle of incidence between the surface normal an the beam emitted by the sensor is close to zero. At larger angles of incidence the surface will generate no response. In the original occupancy map framework, this would present a contradiction, since this approach assumes that an occupied cell should generate responses in every direction. A full description of the response grid framework can be found in [3] and [4].
Our edge detection algorithm consists of searching in 20 small windows. The windows are opened along the predicted edge positions which were given by dynamical model. In each window we find a most likely edge and finally linear-fit these data to get the whole stripes. GOAL: Develop a navigation system for the robot to recognize and walk along the building corridors. Analyzed the geometric relation of the system, developed the algorithm to estimate robot's distance and angle position.
Implemented edge detection algorithm for image information processing.
Designed the motion control strategy. The robot can walk stably along the hallway from arbitrary position in tens of seconds.
Robot walks at it mechanical speed 0.5m/s in the corridor.
A pressure sensor for a mechanical hand gives better feedback of the gripping force and more-sensitive indication of when the hand contacts an object. Optical fibers bring light into cells on the gripping surface. Light is reflected from a flexible covering into other fibers leading to detectors. Distortion due to tactile pressure changes the amount of reflected light. The new device is superior to previous sensors. For example, television or other direct-viewing systems are not sensitive to contact pressure, and the contact area is often hidden from view. Electrical sensors are subject to electrical noise, especially at the low signal levels associated with low contact pressure. Optical sensors have been used to detect proximity or contact but not contact pressure. The new optical sensor is illustrated in the figure. The sensing surface of the hand is divided into cells by opaque partitions. An optical fiber brings light into each cell from a lamp, light-emitting diode, or other source. Another fiber carries light from the cell to a detector; for example, a photodiode or phototransistor. The cells are covered by an elastic material with a reflective interior surface. The rest of the cell is coated with a nonreflective material. As shown in the figure, pressure against a cell cover causes a distortion, which changes the internal reflection of light. The change is sensed by the detector, and the output signal informs the operator of contact. The greater the pressure and distortion, the greater is the change in light reflection. Thus, grip pressure can be sensed using analog circuitry. If only a touch indication is desired, a threshold detector can be included in the electronics. In an automatic manipulator, the detector signal could control the manipulator movements. The cells can be arranged such that those in each row share one light source, while those in each column share one detector. This reduces the number of sources and detectors and facilitates scanning. For example, a 10-by-10 matrix would have 100 sensing points while requiring only 10 sources and 10 detectors. The array can be scanned by sequentially pulsing sources and detectors.
A sensor system measuring the surface pattern of objects by using a spatial filtering tactile sensor. The sensor has a band-pass spatial filtering function and changes its center of spatial frequency with the tactile motion. The idea of this method is based on the nervous system in human finger.
It is said that cutaneous receptors exist by 50 pieces per 1 mm2 at the tip of a human finger and nervous units are distributed 1 unit per 1 mm2 . As the result, (1) the cutaneous receptors construct a spatial filter and signals from them are summed within the nervous unit. (2) In the touch motion performed by a man, the delay of the signal transmission through nervous unit and touch motion velocity changes the spatial filtering characteristic to make the spatial resolution higher.
This sensor system is characterized by (1) robust measurement system for non-uniform contact state and (2) adaptable for a wide spatial frequency range in the surface pattern of objects. And high spatial resolution can be realized.
The horizontal arm of the CMM carries an analog touch sensor (red) and a video camera (black) to inspect mechanical parts. The camera "finds" the part and its features on the table so high accuracy inspection can be done using the touch sensor
Next Generation Inspection System (NGIS)Intelligent Systems Division
Photoelectric Cell, also phototube, electron tube in which the electrons initiating an electric current originate by photoelectric emission. In its simplest form the phototube is composed of a cathode, coated with a photosensitive material, and an anode. Light falling upon the cathode causes the liberation of electrons, which are then attracted to the positively charged anode, resulting in a flow of current proportional to the intensity of the irradiation. Phototubes may be highly evacuated or may be filled with an inert gas at low pressure to achieve greater sensitivity. In a modification called the multiplier phototube, or the photomultiplier, a series of metal plates are so shaped and arranged that the photoelectric emission is amplified by secondary electron emission. The multiplier phototube is capable of detecting radiation of extremely low intensity; hence, it is an essential tool for those working in the area of nuclear research.

The photoelectric cell, popularly known as the electric eye, is employed in operating burglar alarms, traffic-light controls, and door openers. A phototube and a beam of light (which may be infrared or invisible to the eye) form an essential part of such an electric circuit. The light produced by a bulb at one end of the circuit falls on the phototube located some distance away. Interrupting the beam of light breaks the circuit. This in turn causes a relay to close, which energizes the burglar-alarm, or other, circuit. Various types of phototubes are used in sound recording, television, and the scintillation counter (see  Particle Detectors). They are also used in exposure meters (see  Photography: Lenses: Light Metering).
Similar to mail couriers used in large corporations, Line Tracker follows a designed course. By using a infrared emitter and light-sensor circuitry, it demonstrates how robots "see" a pathway. Make a pathway with a black felt marker or black tape and watch how infrared sensors enable the robot's motors to make course corrections.