Because the sun gear in a hybrid unit is pre-aligned within the gearhead rather than affixed to the engine shaft, these gearheads can be used in contouring applications like a glue-dispensing nozzle for affixing a windshield to an automobile. Motion of the nozzle as it follows the seam between a windshield and its own window frame should be perfectly smooth; or else a ripple in velocity alters the bead diameter and causes messy glue software.
Smooth motion, this means the absence of torque and velocity variations (ripple), is essential in contouring applications. But, it really is difficult to consistently achieve smooth motion where the sun gear is servo motor gear reducers installed on the engine shaft. A good slight misalignment in sunlight gear (motor shaft runout or coupling inaccuracies) could cause rough operation and noise.
Many servo controllers use software compensation, and their success depends upon knowing the lost motion of the entire system. This info is usually available from the gearhead manufacturer.
Contouring applications usually involve end-effectors or tool-points that adhere to mathematically defined paths. Sealant and bonding machines, water and flame cutters, laser welders and cutters, motion managed cameras, and CNC machine equipment are good examples.
Software compensation is accomplished by commanding the engine to move beyond the apparently desired position by an amount equal to the system’s dropped motion, thereby bringing the strain 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 motion and the machine has 0.1-in. lost motion, then your controller tells the motor to move 110,000 encoder counts to get 1.0 in. of motion, therefore compensating for the 0.1-in. lost motion.
Backlash is the excess space between two adjacent equipment teeth and its engaging tooth; lost motion may be the total looseness or movement at a reducer’s result shaft when the insight shaft is fixed. Dropped motion includes backlash, plus losses from bearing looseness, tolerances and matches, and shaft and equipment tooth compliance.
Servo controllers could be programmed to compensate for backlash and lost movement in planetary gearheads. This system compensates for backlash actually where an application requires accuracy better than the minimal backlash of the gearhead.