Product Requirements
Ch. 8
TRACKMASTER
62
TMX428 TMX428CP & TMX58 Service Manual
317-160-406 Rev 4
May 2021
references. The first is a magnetic reed switch located on the motor side of the belt pulley, and the
second is a speed reference supplied by the motor controller. A speed calibration is required to
provide a target speed output for a given set point. After the initial target is reached, the speed inputs
are constantly monitored to make adjustments to the speed output and to detect over speed, zero
speed, or speed sensor comparison fault conditions. In the case of a fault condition, the belt is
stopped and operation is suspended.
Elevation position control is done using relays to turn on the elevation motor in the up or down
direction depending on the current set point. A micro switch input is used to determine the position
of the elevation motor by counting revolutions o
f the elevation motor’s internal gearing. An elevation
calibration is required to provide an accurate number of counts from zero to full elevation. No closed
loop control is done for positioning elevation.
Power may be removed from the unit by opening the normally closed switch connected to the
emergency stop input, or by removing AC power from the system. In both cases, the outputs will be
put into a non-energized state that will correspond to the belt being shut off and the elevation motor
being disengaged.
SOFTWARE REQUIREMENTS
SPEED CONTROL
There are two outputs required for speed control. The belt enable output must be energized to put the
belt into a run mode. The speed control output is a 4kHz 1024 count pulse width modulated (PWM)
output supplied directly to the motor controller. Based on calibration, the speed is controlled by
outputting a PWM speed reference to the motor controller and enabling the belt run output. The
speed inputs are averaged over a two second period to provide measured speed accuracy of 0.01
MPH
or less.
If the speed of either input is measured to be more than 0.5
MPH over the set point, or the difference
between speed inputs is measured to be more than 0.5
MPH, the belt will shut off automatically. If
the speed measured is more than 3.0
MPH over the set point, the belt enable signal will be turned off
immediately. If the motor controller activates a fault signal to the UPS, the system will shut down
immediately.
If the measured speed is within range, it is used to make minor adjustments to the speed output when
it is determined that the actual speed and measured speed differ by more than 0.08 MPH. These small
adjustments (1:1024) are only allowed to be at 4 second intervals to provide for the settle time of the
motor and heavily averaged speed input.
ELEVATION CONTROL
The elevation position is constantly monitored by counting and recording changes in the state of the
elevation micro switch sensor. Each de-bounced state is counted as positive if the elevation motor is
engaged in the up direction and negative if it is engaged in the down direction. Using this count and
the calibration numbers, the elevation position is controlled by turning on the motor in the desired
direction and counting until the target number of counts has been reached. At that time, the elevation
motor is disengaged until another set point position is requested.
