SMAC
LAC-26 Technical Reference Manual
4/29/2013 31
Command:
aPM
-- Enter Position Mode --
Default:
Position mode
This command causes servo axis 'a' to enter the position mode of operation. In this mode, the
servo can be commanded to move to a specific target position. The moves will be executed using a
trapezoidal velocity profile based upon parameters set by the Set Velocity (SV) and the Set Acceleration
(SA) commands.
Related Commands: EG, QM, VM
Command:
aQMn
-- Enter Torque Mode --
Argument:
0 for voltage mode, 1 for current mode
Default:
Position mode
This command places servo axis 'a' in the Torque Mode of operation. For mode 0 (or QM0), the
output PWM duty cycle (or analog output for appropriate models) can be manually controlled by the user
program. Once QM0 has been entered, the Set Torque (SQ) command can be used to set or change the
servo output (see the SQ command). Bear in mind, that if the output was being limited by an SQ
command before entering torque mode (while in PM or VM), it will remain limited while in QM and cannot
be changed until the unit is in PM or VM.
For mode 1 (or QM1), the LAC-26 will use one of its A/D channels to monitor servo output
current and attempt to maintain that output current at a steady level as commanded by the user program
(see the SQ and SC commands). In that the A/D converter has 10-bit resolution, this will result in a value
from 0 to 1023 which represents the instantaneous output current with 0 being approximately 0 Amps
and 1023 being approximately 5 Amps with intermediate values being somewhat linear.
In the case of a motor (for example), when an output command of 512 is set (or about 2.5 amps),
the PWM output begins to ramp up until the desired output current is reached. If the motor is not loaded
enough to require 2.5 amps then the PWM will ramp up to 100% putting the maximum supply voltage to
the motor. If at this point the motor is suddenly loaded, the PWM will ramp down to a level sufficient to
supply 2.5 amps to the motor.
Mode QM1 will not function with the D/A module option.
Related Commands: EG, PM, VM