ODC001 Servo Motor Driver
reached by moving the pot slider, the next velocity value is applied. These settings
are applicable in either direction of pot deflection, i.e. 4 possible velocity settings in
the forward or reverse motion directions. The parameters displayed above indicate
that when the pot has been deflected to 20 (approx 1/6 full scale deflection) the motor
will start to move at 0.1mm/sec. At a deflection of 50 (approx 2/5 full scale deflection)
the motor velocity will increase to 0.2m/sec, and so on.
Note. It is acceptable to set velocities equal to each other to reduce the number of
speeds, however this is not allowed for the deflection settings, e.g. the Velocity 4 Pot
Deflection value must be greater than Velocity 3 Pot Deflection value.
Servo Loop (PID) Control Settings
The OptoDCDriver implements a full servo control loop for motor velocity and position
control. The loop response to demanded position moves is determined via
Proportional, Integration and Derivative settings. These settings can be altered using
the ‘Servo Loop (PID) Control Settings’ parameters.
Proportional – This term provides the ‘restoring’ force used to drive the motor to the
demand position, reducing the positional error. It accepts values in the range 0 to
32767.
Integral – This term provides the ‘restoring’ force that grows with time, ensuring that
the static position error is zero under a constant torque loading. It accepts values in
the range 0 to 32767.
Derivative – This term provides the ‘damping’ force proportional to the rate of change
of the position error. It accepts values in the range 0 to 32767.
Integral Limit – This term sets a maximum limit for the integration term to prevent an
excessive build up over time of the restoring force. It accepts values in the range 0 to
32767.
Note. The default values programmed into the APT software will give acceptable
motor performance in most cases. These PID parameters are set according to the
stage or actuator type associated with the driver using the APTConfig utility (see
APTConfig helpfile or the handbook supplied with the unit). However, under extreme
loading conditions it may be necessary to alter these factory default values.
