Logosol Multifunctional Servo Drive LS-231SE
Doc # 712231004 / Rev. A, 05/05/2011
Logosol, Inc. • 1155 Tasman Drive • Sunnyvale, CA 94089 Tel: (408) 744-0974 • www.logosolinc.com
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Changing communication rates
The default baud rate after power-up is 19.2Kb/S. Baud rates up to 1250Kb/S may be used at maximum
servo rate. After communication has been established with all servo drives on a single network, the baud
rate may be changed to a higher value with the Set Baud Rate command.
Servo control
LS-231SE uses a “proportional-integral-derivative”, or PID filter. The position, velocity and acceleration
are programmed as 32-bit quantities in units of encoder counts per servo ticks. For example, a velocity
of 10 revolutions per second of a motor with a 500 line encoder (2000 counts/rev) at a tick time of 51.2
µSec. would correspond to a velocity of 1.024 counts/tick. Velocities and accelerations use the lower 16
bits as a fractional component so the actual programmed velocity would be 1.024 x 65536 or 67109. An
acceleration of 40 rev/sec/sec (which would bring us up to the desired speed in ¼ sec) would be
0.00021 counts/tick/tick; with the lower 16 bits the fractional component, this would be programmed as
0.00021 x 65536 or 14. Position is programmed as a straight 32-bit quantity with no fractional
component. Note that if the servo rate divisor is modified, the time dependent velocity and acceleration
parameters will also have to be modified.
PWM mode
If the position servo is disabled, the motor is operated in a raw PWM output mode and no trapezoidal or
velocity profiling is performed. In this mode, a user specified PWM value is outputted directly to the
amplifier. A PWM value of 255 corresponds to 100% and a value of 0 corresponds to 0%. Command
position is continually updated to match the actual position of the motor and there will be no abrupt jump
in the motor’s position when position or velocity modes are entered. Also while the position servo is
disabled, the command velocity is continually updated to match the actual velocity of motor. Thus, when
velocity mode is entered, there will be no discontinuity in the motor’s velocity. Trapezoidal profile
motions, however, will still force the motor to begin at zero velocity.
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