Because the sun gear in a hybrid unit is pre-aligned within the gearhead rather than affixed to the electric motor shaft, these gearheads can be utilized in contouring applications such as a glue-dispensing nozzle for affixing a windshield to an automobile. Motion of the nozzle as it comes after the seam between a windshield and its own window frame should be perfectly smooth; otherwise a ripple in velocity alters the bead diameter and causes messy glue application.
Smooth motion, this means the lack of torque and velocity variations (ripple), is essential in contouring applications. But, it really is difficult to consistently achieve smooth motion where the sun equipment is mounted on the engine shaft. Even a slight misalignment in sunlight gear (electric motor shaft runout or coupling inaccuracies) can cause rough procedure and noise.
Many servo controllers use software compensation, and their success depends upon knowing the lost motion of the whole system. This info is usually offered from the gearhead producer.
Contouring applications usually involve end-effectors or tool-points that adhere to mathematically defined paths. Sealant and bonding machines, drinking water and flame cutters, laser beam welders and cutters, movement controlled cameras, and CNC machine equipment are good examples.
Software compensation is servo gear reducer achieved by commanding the motor to move beyond the apparently desired position by an amount equal to the system’s dropped motion, thereby bringing the load to the truly desired position. For instance, consider a servomotor, gearhead, and leadscrew mixture in a pick-andplace robot. If 100,000 encoder counts equals 1.0 in. of linear movement and the machine has 0.1-in. lost motion, then your controller tells the engine to go 110,000 encoder counts to obtain 1.0 in. of motion, thus compensating for the 0.1-in. lost motion.
Backlash is the excess space between two adjacent equipment teeth and its own engaging tooth; lost movement may be the total looseness or movement at a reducer’s result shaft when the input shaft is fixed. Dropped motion includes backlash, plus losses from bearing looseness, tolerances and fits, and shaft and equipment tooth compliance.
Servo controllers could be programmed to compensate for backlash and dropped movement in planetary gearheads. This technique compensates for backlash even where a credit card applicatoin requires accuracy much better than the minimal backlash of the 
gearhead.
