Agenda Servo Control • Resolvers • Encoders
Servo Control A servo control system monitors a process and uses the feedback to modify the control command.
Servo Control A servo motion controller has greater control over the velocity curve when moving to a commanded position. The shape of the curve can be changed to meet application requirements
Feedback Devices Resolvers Encoders
Resolvers Advantages over encoders. • Higher resolution • Better electronics protection • Absolute position • More rugged.
Resolver Circuit Resolvers produce signals proportional to the sine and cosine of their rotor angle. See the text, section 2-6.
Resolver Signals @ 0 degrees With the rotor at 0, the amplitude of the sine secondary is 0 since sin(0) = 0, and the amplitude of the cosine secondary is 1, since cos(0) = 1.
Resolver Signals @ 45 degrees With the rotor at 45 degrees, the secondary voltages are the same, but only 70.7 percent of their max, since sin45 = cos45 = 0.707
Resolver Signals @ 90 degrees With the rotor at 90 degrees, the sin voltage is max and the cosine is zero.
Resolver Signals @ 135 degrees • The signals are put into a resolver-to-digital converter that performs two basic functions. • demodulates the signals to remove the carrier and leave only the sin and cos signals. • calculate and provide a digital representation of the angle.