Glentek Inc. 208 Standard Street, El Segundo, California 90245, U.S.A. (310) 322-3026
63
APPENDIX H
H - Amplifier Terms and Technology
This appendix contains information that describes and explains the terms and concepts referred to in
this manual. The information contained here is generic to amplifiers and motion control technology in
general and does not apply specifically to the SMA9800 series amplifiers. The TERMS section is a
glossary that defines the terms used when discussing amplifiers. The TECHNOLOGY section de-
scribes methods or concepts that involves the usage of multiple terms.
TERMS
Analog Current Command Mode
Analog current mode, also called Torque mode or Current mode, indicates that the amplifier is being
commanded by an analog signal and that the amplifiers’ control loop is controlling current. This com-
mand mode is used when one needs to control torque. The analog signal, in volts, is a scaled repre-
sentation of desired current as measure at the output. For instance -10 volts to 10 volts at the analog
input becomes -15 amps to 15 amps at the amplifiers output. The scaling is different for different am-
plifiers.
Command Mode
A term used to refer to the method by which a command is given to an amplifier. The amplifier uses
this command in its’ control loop as a target to be achieved. The command mode usually includes how
the amplifier is to interpret the command. That is, is the command to represent current, velocity or po-
sition. There are many forms and methods by which commands are submitted to an amplifier. Tradi-
tionally the command was given as an analog voltage input to the amplifier. Today there is analog,
digital, serial communications or some combination of these.
Commutation
Commutation is the term used to describe the method by which current is applied to the
windings of a motor such that the applied current moves the motor in a desired direction,
or to a desired position, with the minimum current. Brushes are the method of commuta-
tion in a brush motor. In a three phase brushless motor, Sinusoidal Commutation is the
usual method of commutation. See Sinusoidal Commutation.
Commutation Initialization Method
In order to properly commutate a brushless motor, the servo drive must know the absolute position of
the rotor with respect to the motor windings in the stator. Since incremental shaft encoders only supply
“relative” rotor position, the servo drive must perform a power-on, phase-finding scheme to determine
the absolute position of the shaft. This is known as commutation initialization. Once the absolute posi-
tion is determined, the position from the encoder can be used to maintain the absolute position. The
SMA9800 amplifiers have three power-on commutation initialization methods available for finding the
absolute position of the rotor. The first two methods, Twang and Dither, require the rotor to move; the
third scheme, Hall, does not require motion. The Hall method does require the addition of Hall sensors
or commutation tracks. Commutation tracks are simulated Hall sensors built into the shaft encoder.
Appendix H
Summary of Contents for Omega SMC9930
Page 73: ...Glentek Inc 208 Standard Street El Segundo California 90245 U S A 310 322 3026 73 Appendix K...
Page 75: ...Glentek Inc 208 Standard Street El Segundo California 90245 U S A 310 322 3026 75 Appendix K...
Page 77: ...Glentek Inc 208 Standard Street El Segundo California 90245 U S A 310 322 3026 77...
