19.8 Light Detection, Image, and Vision Systems Stanley S.. Regardless of complexity, the purpose of a light detector is to measure light, and the section ‘‘Basic Radiometry’’ introduces
Trang 1Vranish, J.M., McConnel, R.L., Mahalingam, S., “Capaciflector collision avoidance sensors for robots,” Product Description, NASA Goddard Space Flight Center, Greenbelt, MD, Feb., 1991
Vuylsteke, P., Price, C.B., Oosterlinck, A., “Image sensors for real-time 3-D acquisition, part 1,” in
Traditional and Non-Traditional Robotic Sensors, T.C Henderson, ed., NATO ASI Series, Vol F63,
Springer-Verlag, pp 187–210, 1990
Wavering, A.J., Fiala, J.C., Roberts, K.J., Lumia, R., “TRICLOPS: a high-powered trinocular active vision
system,” IEEE International Conference on Robotics and Automation, pp 410–417, 1993.
White, D., “The hall effect sensor: basic principles of operation and application,” Sensors, pp 5–11, May,
1988
Wildes, R.P., “Direct recovery of 3-D scene geometry from binocular stereo disparity,” IEEE Transactions
on Pattern Analysis and Machine Intelligence, Vol 13, No 8, pp 761–774, Aug., 1991.
Williams, H., “Proximity sensing with microwave technology,” Sensors, pp 6–15, June, 1989.
Wojcik, S., “Noncontact presence sensors for industrial environments,” Sensors, pp 48–54, Feb., 1994 Wood, T., “The hall effect sensor,” Sensors, pp 27–36, March, 1986.
Woodbury, N., Brubacher, M., Woodbury, J.R., “Noninvasive tank gauging with frequency-modulated
laser ranging,” Sensors, pp 27–31, Sep., 1993.
Young, M.S., Li, Y.C., “A high precision ultrasonic system for vibration measurements,” Rev Sci Instrum.,
Vol 63, No.11, pp 5435–5441, Nov., 1992
19.8 Light Detection, Image, and Vision Systems
Stanley S Ipson
Introduction
Light detectors span a broad spectrum of complexity The simplest are single sensors whose output signals are easy to interpret and to interface to other components like microprocessors In contrast, the image sensors in video and digital cameras, incorporating arrays of up to several million detectors, produce output signals which are complicated to interface and require powerful processors to interpret Regardless of complexity, the purpose of a light detector is to measure light, and the section ‘‘Basic Radiometry’’ introduces a number of radiometric terms that are employed in the characterization of light, light sources, and detectors However, manufacturers often specify the performance of their devices using photometric units, which take into account the human visual response to light, and so it is necessary
to understand both radiometric and photometric measures of light Sources of light are briefly discussed
in section ‘‘Light Sources.” There are several types of light detector in common use and the principles
of operation and characteristics of the most widely used, including pyroelectric, photoresistive, photo-diode, and phototransistor are summarized in section ‘‘Light Detectors.” Vision systems have optical components to form an image and an image sensor to convert the light image into an electrical signal Image formation is reviewed in section ‘‘Image Formation,” before introducing the most widely used detectors, based on charge-coupled device (CCD) technology and complementary metal oxide semicon-ductor (CMOS) technology, in section ‘‘Image Sensors.” The elements required to complete a vision system are discussed briefly in the final section
Basic Radiometry
Visible light is electromagnetic energy radiated with very short wavelengths in the range between about
400 and 700 nm At shorter wavelengths, to about 30 nm, is invisible ultraviolet light and at longer wave-lengths, up to about 0.3 mm, is invisible infrared radiation Although electromagnetic radiation displays wave behavior including interference and diffraction, it can also behave like a stream of particles and is emitted and absorbed by matter in discrete amounts of energy called photons The energy ε of a light
Trang 2Vranish, J.M., McConnel, R.L., Mahalingam, S., “Capaciflector collision avoidance sensors for robots,” Product Description, NASA Goddard Space Flight Center, Greenbelt, MD, Feb., 1991
Vuylsteke, P., Price, C.B., Oosterlinck, A., “Image sensors for real-time 3-D acquisition, part 1,” in
Traditional and Non-Traditional Robotic Sensors, T.C Henderson, ed., NATO ASI Series, Vol F63,
Springer-Verlag, pp 187–210, 1990
Wavering, A.J., Fiala, J.C., Roberts, K.J., Lumia, R., “TRICLOPS: a high-powered trinocular active vision
system,” IEEE International Conference on Robotics and Automation, pp 410–417, 1993.
White, D., “The hall effect sensor: basic principles of operation and application,” Sensors, pp 5–11, May,
1988
Wildes, R.P., “Direct recovery of 3-D scene geometry from binocular stereo disparity,” IEEE Transactions
on Pattern Analysis and Machine Intelligence, Vol 13, No 8, pp 761–774, Aug., 1991.
Williams, H., “Proximity sensing with microwave technology,” Sensors, pp 6–15, June, 1989.
Wojcik, S., “Noncontact presence sensors for industrial environments,” Sensors, pp 48–54, Feb., 1994 Wood, T., “The hall effect sensor,” Sensors, pp 27–36, March, 1986.
Woodbury, N., Brubacher, M., Woodbury, J.R., “Noninvasive tank gauging with frequency-modulated
laser ranging,” Sensors, pp 27–31, Sep., 1993.
Young, M.S., Li, Y.C., “A high precision ultrasonic system for vibration measurements,” Rev Sci Instrum.,
Vol 63, No.11, pp 5435–5441, Nov., 1992
19.8 Light Detection, Image, and Vision Systems
Stanley S Ipson
Introduction
Light detectors span a broad spectrum of complexity The simplest are single sensors whose output signals are easy to interpret and to interface to other components like microprocessors In contrast, the image sensors in video and digital cameras, incorporating arrays of up to several million detectors, produce output signals which are complicated to interface and require powerful processors to interpret Regardless of complexity, the purpose of a light detector is to measure light, and the section ‘‘Basic Radiometry’’ introduces a number of radiometric terms that are employed in the characterization of light, light sources, and detectors However, manufacturers often specify the performance of their devices using photometric units, which take into account the human visual response to light, and so it is necessary
to understand both radiometric and photometric measures of light Sources of light are briefly discussed
in section ‘‘Light Sources.” There are several types of light detector in common use and the principles
of operation and characteristics of the most widely used, including pyroelectric, photoresistive, photo-diode, and phototransistor are summarized in section ‘‘Light Detectors.” Vision systems have optical components to form an image and an image sensor to convert the light image into an electrical signal Image formation is reviewed in section ‘‘Image Formation,” before introducing the most widely used detectors, based on charge-coupled device (CCD) technology and complementary metal oxide semicon-ductor (CMOS) technology, in section ‘‘Image Sensors.” The elements required to complete a vision system are discussed briefly in the final section
Basic Radiometry
Visible light is electromagnetic energy radiated with very short wavelengths in the range between about
400 and 700 nm At shorter wavelengths, to about 30 nm, is invisible ultraviolet light and at longer wave-lengths, up to about 0.3 mm, is invisible infrared radiation Although electromagnetic radiation displays wave behavior including interference and diffraction, it can also behave like a stream of particles and is emitted and absorbed by matter in discrete amounts of energy called photons The energy ε of a light
Trang 3
20 Actuators 20.1 Electromechanical Actuators
Introduction • Type of Electromechanical Actuators—Operating Principles • Power Amplification and Modulation—Switching Power Electronics
20.2 Electrical Machines
The dc Motor • Armature Electromotive Force (emf) • Armature Torque • Terminal Voltage • Methods of Connection • Starting dc Motors • Speed Control of dc Motors • Efficiency of dc Machines • AC
Machines • Motor Selection 20.3 Piezoelectric Actuators
Piezoeffect Phenomenon • Constitutive Equations • Piezomaterials • Piezoactuating Elements • Application Areas • Piezomotors (Ultrasonic Motors) • Piezoactuators with Several Degrees of Freedom 20.4 Hydraulic and Pneumatic Actuation Systems
Introduction • Fluid Actuation Systems • Hydraulic Actuation Systems • Modeling of a Hydraulic Servosystem for Position Control • Pneumatic Actuation
Systems • Modeling a Pneumatic Servosystem 20.5 MEMS: Microtransducers Analysis, Design, and Fabrication
Introduction • Design and Fabrication • Analysis of Translational Microtransducers • Single-Phase Reluctance Micromotors: Microfabrication, Modeling, and
Analysis • Three-Phase Synchronous Reluctance Micromotors: Modeling and Analysis • Microfabrication Aspects • Magnetization Dynamics of Thin
Films • Microstructures and Microtransducers with Permanent Magnets: Micromirror Actuator • Micromachined Polycrystalline Silicon Carbide Micromotors • Axial Electromagnetic Micromotors • Conclusions
20.1 Electromechanical Actuators
George T.-C Chiu
Introduction
As summarized in the previous sections, a mechatronics system can be partitioned into function blocks illustrated in Fig 20.1 In this chapter, we will focus on the actuator portion of the system Specifically,
we will present a general discussion of the types of electromechanical actuators and their interaction
George T.-C Chiu
Purdue University
C J Fraser
University of Abertay Dundee
Ramutis Bansevicius
Kaunas University of Technology
Rymantas Tadas Tolocka
Kaunas University of Technology
Massimo Sorli
Politecnico di Torino
Stefano Pastorelli
Politecnico di Torino
Sergey Edward Lyshevski
Purdue University Indianapolis
0066_Frame_C20 Page 1 Wednesday, January 9, 2002 5:41 PM
Trang 4
energy side of the device Typically, an LED source is combined with either a phototransistor or photo thyristor, see Fig 20.35 In addition to signal isolation, optoisolators also help to reduce ground loop issues between the logic and power side of the circuit
Grounding
It is important to provide common ground among the different devices For electromechanical actuators, the high energy side is often switching at high frequency; if the ground point of the high energy side of the circuit is directly connected to the ground of the low energy side of the circuit, switching noise may propagate through the ground wire and negatively affect the operation of the low energy side of the system It is recommended that separate common grounds are established for the high and low energy side and the two grounds are then connected at the power supply In addition, an adequate-sized ground plane needs to be provided to minimize the possibility of differences among grounding points
20.2 Electrical Machines
C J Fraser
The utilization of electric motors as the power source in a mechatronic application is substantial Electric motors, therefore, often feature as the prime mover in a variety of driven systems It is usually the mechanical features of the application that determines the type of electric motor to be employed The torque–speed characteristics of the motor and the driven system are therefore very important It is perhaps then a paradox that while the torque–speed characteristics of the motor are readily available from the supplier, the torque–speed characteristics of the driven system are often quite obscure
The dc Motor
All conventional electric motors consist of a stationary element and a rotating element, which are separated
by an air gap In dc motors, the stationary element consists of salient “poles,” which are constructed of laminated assemblies with coils wound round them to produce a magnetic field The function of the laminations is to reduce the losses incurred by eddy currents The rotating element is traditionally called the “armature” and this consists of a series of coils located between slots around the periphery of the armature The armature is also fabricated in laminations, which are usually keyed onto a location shaft
A very simple form of dc motor is illustrated in Fig 20.56
The single coil is located between the opposite poles of a simple magnet When the coil is aligned in the vertical plane, the conventional flow of electrons is from the positive terminal to the negative terminal The supply is through the brushes, which make contact with the commutator segments From Faraday’s laws of electromagnetic induction, the “left-hand rule,” the upper part of the coil will experience a force acting from right to left The lower section will be subject to a force in the opposite direction Since the
Magnet
N +ve
-ve
Brush
Coil
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