Because the sun equipment in a hybrid unit is pre-aligned within the gearhead and not affixed to the electric motor shaft, these gearheads can be used in contouring applications such as a glue-dispensing nozzle for affixing 
a windshield to a car. Movement of the nozzle as it comes after 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 app.
Smooth motion, which means the lack of torque and velocity variations (ripple), is important in contouring applications. But, it really is difficult to consistently achieve smooth motion where the sun equipment is mounted on the electric motor shaft. A good 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 movement of the whole system. This details is usually obtainable from the gearhead manufacturer.
Contouring applications generally involve end-effectors or tool-points that stick to mathematically defined paths. Sealant and bonding devices, drinking water and flame cutters, laser welders and cutters, motion managed cameras, and CNC machine equipment are good examples.
Software compensation is achieved by commanding the engine to go beyond the apparently desired position by a quantity equal to the system’s lost motion, thereby bringing the strain to the truly desired position. For example, consider a servomotor, gearhead, and leadscrew combination 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 move 110,000 encoder counts to obtain 1.0 in. of motion, hence compensating for the 0.1-in. lost motion.
servo gear reducer backlash is the extra space between two adjacent gear teeth and its engaging tooth; lost motion may be the total looseness or movement at a reducer’s result shaft when the input shaft is fixed. Dropped motion contains backlash, plus losses from bearing looseness, tolerances and matches, and shaft and gear tooth compliance.
Servo controllers could be programmed to pay for backlash and dropped motion in planetary gearheads. This system compensates for backlash even where an application requires accuracy much better than the minimal backlash of the gearhead.