Motor Modeling 3 1. Go to https://www.pololu.com/product/2269 and find the follo
ID: 2267548 • Letter: M
Question
Motor Modeling 3
1. Go to https://www.pololu.com/product/2269 and find the following specs: Maximum(no load) RPM, stall torque, stall current, free running current, and voltage the motor was tested at to obtain those numbers.
2. compute torque and speed constants using the equations above.
3. Using kv & V , plot the linear speed-torque curve as a function of wmotor (put wmotor along
the x-axis).
4. Using the expression for Pmechanical plot the mechanical power curve as a function of wmotor
(put wmotor along the x-axis). Identify the motor operating point(speed) which produces
the most power.
5. Using (I), solve for I and use to compute the electrical power as a function of wmotor.
6. Using the expression for eff, plot the motor e ciency as a function of wmotor (put wmotor
along the x-axis). Identify the motor operating point(speed) which is the most e cient.
7. Using the motor requirements derived in week 1, and the loss you determined in week 2, select an operating speed which balances power, e ciency, and specifications. Discuss why other operating points do not balance those considerations as e ectively. Consider
total power usage, current limitations, e ciency, size, weight, etc in your answer.
Explanation / Answer
1. Max (no load) RPM: 10000
stall torque: 5 oz.in
stall current: 6.5 A
free running current: 275 mA
Voltage : 6 V
2. Torque and speed constant can be found out by drawing Current Vs. Torque and Speed Vs. Torque curves
{Prepare a graph with motor torque on the horizontal axis, motor speed on the left vertical axis, and motor current on the right vertical axis. Scale the axes based on the measurements taken in lab. Draw a straight line from the left origin of the graph (zero torque and zero current) to the stall current on the right vertical axis (stall torque and stall current). This line represents a plot of the motor current as a function of the motor torque. The slope of this line is the proportionality constant for the relationship between motor current and motor torque (in units of current per unit torque). The reciprocal of this slope is the torque constant of the motor (in units of torque per unit current) }
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