24.6 PRACTICE PROBLEMS
(Note: Problem solutions are available at http://sites.google.com/site/automatedmanufacturingsystems/)
1. A stepping motor is to be used to drive each of the three linear axes of a cartesian coordinate robot. The motor output shaft will be connected to a screw thread with a screw pitch of 0.125". It is desired that the control resolution of each of the axes be 0.025"
a) to achieve this control resolution how many step angles are required on the stepper motor?
b) What is the corresponding step angle?
c) Determine the pulse rate that will be required to drive a given joint at a velocity of 3.0"/sec.
2. For the stepper motor in the previous question, a pulse train is to be generated by the robot controller.
a) How many pulses are required to rotate the motor through three complete revolutions?
b) If it is desired to rotate the motor at a speed of 25 rev/min, what pulse rate must be generated by the robot controller?
3. Explain the differences between stepper motors, variable frequency induction motors and DC motors using tables.
a) Compare the various types of motors discussed in the class using a detailed table.
b) When using a motor there are the static and kinetic friction limits. Will deadband correction allow the motor to move slower than both, one, or neither? Explain your answer.
c) What is the purpose of a calibration curve?
