User Manual

Table Of Contents
Modes Description
Advanced Digital Motor Controller User Manual 145
SECTION 11
Closed Loop
Relative and
Tracking Position
Modes
This section describes the controller’s Position Relative and Position Tracking modes, how
to wire the motor and position sensor assembly and how to tune and operate the control-
ler in these modes.
Modes Description
In these two position modes, the axle of a geared-down motor is coupled to a position
sensor that is used to compare the angular position of the axle versus a desired position.
The controller will move the motor so that it reaches this position.
This feature makes it possible to build ultra-high torque “jumbo servos” that can be used
to drive steering columns, robotic arms, life-size models and other heavy loads.
The two position modes are similar and differ as follows:
Position Relative Mode
The controller accepts a command ranging from -1000 to +1000, from serial/USB, analog
joystick, or pulse. The controller reads a position feedback sensor and converts the signal
into a -1000 to +1000 feedback value at the sensors min and max range respectively. The
controller then moves the motor so that the feedback matches the command, using a con-
trolled acceleration, set velocity, and controlled deceleration. This mode requires several
settings to be configured properly but results in very smoothly controlled motion.
Position Tracking Mode
This mode is identical to the Position Relative mode in the way that commands and feed-
back are evaluated. However, the controller will move the motor simply using a PID com-
paring the command and feedback, without controlled acceleration and as fast as possible.
This mode requires fewer settings but often results in a motion that is not as smooth and
harder to control overshoots.