Backlash is basically “play” between the gears and mechanical linkages within a system. FLIR`s PTUs utilize specially designed worm gears and robust mechanical linkages which have very low native backlash.
Over time, as the PTU moves, the teeth of the gears in the drivetrain slide into each other and can develop minute spaces between the teeth faces due to wear. Several factors affect the rate and amount of gear wear. In general, reducing tooth stresses will reduce the amount of wear that occurs. As such, payload weight and imbalance, environmental shock and vibration, as well as speed, acceleration and duty cycle all affect the rate of backlash development.
Gear wear, and the corresponding development of backlash, can be reduced by proper payload design and balancing, slowing down the speed and acceleration settings, and reducing shocks and vibrations incurred by the PTU/Payload system.
Note that flexure of the PTU and mount is not considered backlash. FLIR PTUs are designed to be very rigid to minimize pointing error due to flexure. Mount strength and stiffness must also be designed to properly reduce pointing errors.
For camera systems, vibrations that the PTU experiences -- whether internally caused by the stepper motors or externally caused by factors such as wind or the mounting platform -- may be perceived on the cameras. The severity of the vibration depends on the amount of backlash present and the focal length of the camera system.
In some cases, backlash can be reduced or even eliminated at FLIR`s factory by simply re-adjusting the gears. In severe cases, the PTU will have to be disassembled and the gears replaced.