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Unformatted text preview: EECS 314 Winter 2008 Homework set 2 Students name ___________________________ Discussion section # _______ (Last, First, write legibly, use ink) (use ink) Instructor is not responsible for grading and entering scores for HW papers lacking clear information in the required fields above 2008 Alexander Ganago Page 1 of 2 Scores for the HW set: Problem 1 2 3 4 5 6 7 Total Score Problem 1 Potentiometer as an angular position sensor The circuit shown on this diagram shows a potentiometer used as a sensor for the angular position (angle ) of a robotic arm. At = 0, the potentiometers tap is in its middle position so that R X = R = R P /2 At an arbitrary, non-zero angle (in degrees) the resistance equals R X = R P /2 + K where K is constant measured in k /degrees. As shown in lectures, the output voltage is a linear function of the angle: V OUT = a + b The coefficients a and b depend on the source voltage and the potentiometer. Part 1 (10 points) Assume R P = 250 k , K = 1.25 k /degree, V S = 12 V Calculate a in volts and b in volts/degree a = ______________ volts b = _______________ volts/degree Continued on the next page. Part 1 2 3 4 Total EECS 314 Winter 2008 Homework set 2 Students name ___________________________ Discussion section # _______ (Last, First, write legibly, use ink) (use ink) Instructor is not responsible for grading and entering scores for HW papers lacking clear information in the required fields above 2008 Alexander Ganago Page 2 of 2 Problem 1, continued Part 2 (10 points) Make a computer-generated plot of V OUT vs. the angle over the interval from 75 degrees to +75 degrees; attach your computer code or show your work in hand-written form. Part 3 (10 points) Determine the angles in degrees: 4 corresponding to V OUT = 4 V and 7 corresponding to V OUT = 7 V 4 = ____________ 7 = ____________ Assume that the error of readout of V OUT is 10 mV and calculate the error of readout of the angle . = ____________ Briefly discuss how to reduce the error of readout of the angle : increase/decrease R P ; increase/decrease K; increase/decrease V S , etc. Part 4 (10 points) Suppose you have to monitor the angular position of a robotic leg over the interval from negative 90 to positive 90, with a readout device that accepts voltages within the range from 0 to +5 V, with +2.5 V readout at the middle position of the potentiometers tap. Can you use the device discussed above (Parts 1 3)? Yes / No If Yes , explain/prove with calculations....
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This note was uploaded on 09/04/2008 for the course EECS 314 taught by Professor Ganago during the Winter '07 term at University of Michigan.
- Winter '07