Servo Motor Feedback Devices

Prof. Steve presents a general overview of Servo Feedback Devices and their various uses in industrial applications--- ---SERVO FEEDBACK DEVICES--- Types of feedback devices, we've got the resolver, an incremental encoder, absolute encoder, serial encoder, hall sensors and tach generators. Tach generators aren't used very often in servo motors, because of the speed of the feedback we will use with it. The hall sensors are located on the motor and are similar to a nut runner, are basically a magnetic switch. The resolver is basically a rotating transformer, they are very, very rugged, a lot of the resolvers are physically located on the motor shaft itself, they don't have bearings, they use the motor shaft bearings, and they run even in an oily, dirty situation. There are also the resolvers with their own individual bearings, but mostly it is the former that is used. An incremental encoder has a glass lense, as does serial and absolute encoders. Great care must be taken when handling them. Incremental encoders have multiple lines coming around the outside, and a light source that is coming through and when it hits the line the light doesn't go through, and when there is no line the light goes through which sends a signal and it counts these signals, one of the signals is called home and that is our Z-Pulse. What that will do as it rotates is count the lines and when it hits the Z pulse; it starts over and does it again. Absolute encoders and serial encoders have multiple lines on the disc which are used for commutation, and also on the serial encoder it is used for feedback, where the encoder talks, has micro-processors built onto the encoder itself and talks to the drive.

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