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Physics LibreTexts

6: Actuators, Sensors, Motors and Generators

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  • 6.1: Force-induced electric and magnetic fields
    This page covers the principles of motors and actuators, explaining how mechanical motion can generate electrical power through moving conductors in magnetic fields, as described by the Lorentz force law. It discusses the conversion of mechanical to electrical power and the interaction between electrical and mechanical energies using Thevenin's circuit theory. A motor runs effectively when mechanical power output is positive, while a generator operates under different voltage conditions.
  • 6.2: Electrostatic actuators and motors
    This page explores Chapter 6 of an introduction to Micro-Electromechanical Systems (MEMS), covering motors, generators, and sensors, with a focus on electrostatic actuators. It discusses the principles of force generation in capacitors, optimization of actuator design, and the efficiency of rotary MEMS motors and dielectric actuators. Key concepts include torque and power calculations, voltage management in motor design, and limitations like electrical breakdown.
  • 6.3: Rotary magnetic motors
    This page covers the operational principles of commutated rotary magnetic motors and reluctance motors, emphasizing torque generation, back-voltage, and design parameters for efficiency. Key points include the continuous rotary motion ensured by commutation, the relationship between maximum speed and back-voltage, the role of magnetic fields in torque production, and the importance of rotor/stator gap widths.
  • 6.4: Linear magnetic motors and actuators
    This page covers solenoid actuators, which use cylindrical coils and a high-permeability core that moves with current. It examines the behavior of internal magnetic fields and their forces, including fringing fields and energy density. Additionally, it discusses magnetic fields' application in MEMS switches, detailing how magnetic pressures and the Lorentz force law facilitate current-induced movements in a beam, enabling logical functions in these devices.
  • 6.5: Permanent Magnet Devices
    This page explores the properties of permanent magnets, focusing on residual flux density and magnetic energy density. It describes how external fields affect magnet behavior and calculates attractive forces with high-permeability materials. The text also addresses temperature effects on magnets and their applications in motors, highlighting the need for precise physical modeling in complex systems like motors and generators.
  • 6.6: Electric and magnetic sensors
    This page discusses various MEMS sensors including electrostatic sensors that respond to environmental factors, capacitive sensors that detect small displacements, and magnetic sensors which face challenges at micro-scales. It highlights the functionality of Hall effect sensors in measuring magnetic fields through the motion of charge carriers.

Thumbnail: Animation showing operation of a brushed DC electric motor. (CC BY-SA 3.0; Wapcaplet via Wikipedia)


This page titled 6: Actuators, Sensors, Motors and Generators is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by David H. Staelin (MIT OpenCourseWare) via source content that was edited to the style and standards of the LibreTexts platform.

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