Rotational speed

About: Rotational speed is a research topic. Over the lifetime, 23327 publications have been published within this topic receiving 151696 citations. The topic is also known as: speed of revolution & revolution rate.

Method and apparatus for controlling an electric motor the rotational speed of which is automatically reduced in no-load idling operation

Abstract: A method and apparatus for controlling an electric motor, in particular a motor for driving hand tools, saws, and the like, the rotational speed of which is automatically reduced in no-load idling operation and increased when working under load to pre-determined speed values corresponding to desired working speeds. A current sensor picks up the current absorbed by the electric motor and causes the speed of the electric motor to be abruptly changed when a load condition has been detected. A timing relay maintains the electric motor at the higher working speed for a pre-determined period of time after termination of the operation under load. The threshold value of the sensitivity of the current sensor is raised simultaneously with the change-over to the higher working speed.

Active feedback loop to control body pitch in STOL/VTOL free wing aircraft

Abstract: An aircraft control system for controlling an aircraft, particularly a free wing aircraft in low speed or hover regimes. An air speed sensor measures air speed of the aircraft and outputs an air speed signal to a control processor which processes the air speed signal with a speed control input signal. A control actuator actuates an aircraft control surface in response to the control surface control signal. The air speed sensor may include a shaft mounted impeller located in an airstream of the aircraft. A rotational speed sensor, coupled to the impeller, measures a rotational speed of the impeller and outputs a rotational speed signal as the air speed signal. In an alternative embodiment, the air speed sensor may include a vane located in an airstream of the aircraft and deflected in response to air flow in the airstream. In another embodiment, the speed sensor may include an angular position sensor which measures an angle between a free wing and the aircraft fuselage and outputs an angle measurement signal as the air speed signal. The aircraft control surface may comprises a control boom pivotally attached to a fuselage of the aircraft of a trim tab pivotally attached to a fuselage of the aircraft.

Real-Time Detection of the Dynamic Eccentricity in Permanent-Magnet Synchronous Motors by Monitoring Speed and Back EMF Induced in an Additional Winding

Abstract: We developed a real-time method to detect the dynamic eccentricity of a rotor in a permanent-magnet (PM) motor by monitoring a fault detection signal induced in an additional winding, without performing any further postprocessing, even under a nonstationary rotational speed. After deriving a mathematical equation of the back electromotive force (EMF) induced in a tooth-coil winding, we proposed a fault detection signal, which is the back EMF in an additional winding divided by the rotational speed, when the additional winding is wound around the teeth corresponding to an even number of pole pitches. We used the 2-D finite-element model of a three-phase PM motor with eight poles and 12 slots to verify the proposed method. We also developed an experimental setup which can change the dynamic eccentricity of a PM motor and we performed the experiment for PM motors with dynamic eccentricities of 0%, 25%, and 50% to verify the proposed method. Through the mathematical equation, numerical simulation, and experiment, we confirmed that the fault detection signal proposed in this paper can successfully detect the dynamic eccentricity in a PM motor in real time.