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Unread 03-09-2010, 09:05
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Re: Speed Controller Design

Quote:
Originally Posted by Al Skierkiewicz View Post
For all,
It is my understanding that both Jags leave the low side FETs ON during all throttle conditions except zero (subject to which direction pair is selected) and during locked anti-phase (where the direction is changing at a 50% duty cycle rate). I think it has to do with the need for charging of the gate drive bootstrap capacitor. The Victor designers chose to open both FETs during the OFF period. In early designs of the Victor, the switching frequency was 2kHz. Engineers at IFI chose to move to 150Hz to give maximum low throttle torque for the motors we were using at the time. 150Hz is less affected by the inductance of the motors. It does however, give the impression that low speed linearity suffers and it does cause some acoustic output for the motors it is controlling. 15kHz switching does interact with the inductance of the motors and is sufficiently high to cause no discernible acoustic noise except in the smaller motors.
Would this affect the choice of speed controller for a robotic subsystem? For example, would fine PID control on a shoulder joint that needs more low-throttle torque be more efficient with a Victor over a Jag? Or is the difference (mostly) negligible?
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