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motor encoder and linear scale

4/8/2011 12:08 PM	Rate (0)
saeedplc Posts: 288 Rating: (4)	hello. in most of cnc machines there is linear scale on axis and servo motor with built in encoder on ball screw. i know the linear scale measures axis movement but i don't know function of encoder of motor! can anyone please explain me function of motor encoder on control loop? best regards.
saeedplc Posts: 288 Rating: (4)
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4/8/2011 2:32 PM	Rate (0)
Pee Ell Sea Posts: 672 Rating: (57)	Hi, Variable speed ac and brushless dc need to know where the rotor is to be able to control the motor correctly. The axis card can then control the amount of current going to each motor winding to do this. It is similar to a tacho on a dc motor but does a lot more than just close the speed loop. The motor encoder can usually also be used to close the position loop. i.e. provide position feedback. The downside is that it is connected via the motor to a ballscrew and so is subject to errors caused by backlash in the mechanical system. Linear scales because they run directly in parallel with the axis provide a position feedback free of backlash errors. Pee
Pee Ell Sea Posts: 672 Rating: (57)
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4/8/2011 2:35 PM	Rate (0)
metwally mustafa Silver Member Joined: 10/10/2010 Last visit: 7/5/2025 Posts: 309 Rating: (15)	did you see before a weaving machine with stepper motor and the stepper motor had abuilt in resolver feedback? although one of the advantages of stepper motor no feedback so that in CNC machines you have linear encoder in the axis and rotary encoder with the motor in order to perform high performance position control with accurate velocity

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4/10/2011 7:28 AM	Rate (0)
Ekalavya Posts: 2964 Rating: (485)	Hi..... In addition to @Pee information....you can alsocheck this attachment.... hope this may be useful... Regards, Ekalavya Attachment Basics of Motion Control.pdf (284 Downloads)
Ekalavya Posts: 2964 Rating: (485)
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