Glentek SMA8105, Руководство по эксплуатации и обслуживанию

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13 Glentek Inc., 208 Standard Street, El Segundo, California 90245, U.S.A. (310) 322-3026
SMA8105, SMA8205, and SMA8305 MANUAL
2.3 Servo Loops:
A basic velocity-mode servo-loop for a brush-type motor is shown in figure 2.2a. An
external controller commands a given velocity (RPM). The velocity-loop summing-amplifier
compares this command with the actual motor velocity, supplied by a DC tachometer on the
motor shaft, and produces an error voltage proportional to the difference between the actual
and commanded velocity.
The velocity error is used to command motor current in the inner servo-loop. The current-
loop summing-amplifier compares the command current (velocity error) with the actual
current in the motor and produces an error voltage proportional to the difference between the
actual and commanded current.
Finally, the current-error signal is used to produce an output (linear or PWM) to drive the
motor.
The velocity loop may be bypassed, and an external current command fed directly to the
current loop. In this case, the external command signal controls the torque of the motor,
rather than the velocity. This is known as current-mode operation.
The servo-loops of a brushless amplifier (figure 2.2b) operate in much the same way, except
there are now three current loops, one for each phase of the motor.
Figure 2.2a
Figure 2.2b