# sol01 - MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of...

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Unformatted text preview: MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Mechanical Engineering 2.004 Dynamics and Control II Fall 2007 Problem Set #1 Solution Posted: Friday, Sept. 14, ’07 1. For each one of the following systems, argue if in your opinion it is open–loop or closed–loop. In your argument, include your definitions of the system’s inputs and outputs. Brieﬂy describe how feedback is effected in the systems which you decide are closed–loop. a) Washing machine. Answer: Input: switch–on; output: clean clothes. Open loop. The washing machine does not feed back the cleanliness of clothes. b) T Green line subway car. Answer: Input: Operator pedal applied at start- ing station; output: position along track (stop at appropriate location at arrival station). Open loop: the car navigation equipment does not feed back position along the tracks. However, the (human) operator typically takes into account the position where the car presently is and applies the brakes so as to stop properly. Subway cars in other more advanced networks (e.g., Tokyo) and unmanned airport shuttles (e.g. San Francisco and Denver airports) actually do have position sensors and accurately stop themselves upon arrival. c) Audio speaker. Answer: Input: electrical signal from readout device (e.g. laser in a CD player); output: microphone vibration. Open loop. The output audio level and quality is not used to determine the input to the speaker. d) Air conditioner. Answer: Input: desired temperature; output: temperature. Closed loop. The vast majority of air conditioners have temperature sensors (often, a simple bimetal switch) so they turn themselves on when the tem- perature is outside a prescribed range, off when it is inside the prescribed range. e) Manual gear train in an automobile. Answer: Input: lever location set by driver; output: wheel RPM. Open loop. The wheel speed is not used in determining the gear setting (though a good driver would probably apply a sense of the vehicle’s present speed to decide the proper gear to apply so as not to stall or rev up the engine.) 1 f) Automatic gear train in an automobile.automobile....
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sol01 - MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of...

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