Because the sun gear in a hybrid unit is pre-aligned within the gearhead rather than affixed to the motor 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 comes after the seam between a windshield and its window frame should be perfectly smooth; or else a ripple in velocity alters the bead diameter and causes messy glue program.
Smooth motion, this means the lack of torque and velocity variations (ripple), is important in contouring applications. But, it is difficult to regularly achieve smooth motion where the sun gear is installed on the motor shaft. A good slight misalignment in the sun gear (engine shaft runout or coupling inaccuracies) could cause rough servo gear reducer procedure and noise.
Many servo controllers use software compensation, and their success depends upon knowing the lost motion of the whole system. This details is usually available from the gearhead manufacturer.
Contouring applications generally involve end-effectors or tool-points that follow 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 electric motor to move beyond the apparently desired position by an amount equal to the system’s dropped movement, thereby bringing the strain to the truly desired position. For instance, look at 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. dropped motion, then the controller tells the engine to go 110,000 encoder counts to obtain 1.0 in. of motion, therefore compensating for the 0.1-in. lost motion.
Backlash is the extra space between two adjacent gear teeth and its engaging tooth; lost motion is the total looseness or motion at a reducer’s output shaft when the insight shaft is fixed. Lost motion contains backlash, plus losses from bearing looseness, tolerances and suits, and shaft and equipment tooth compliance.
Servo controllers can be programmed to pay for backlash and dropped motion in planetary gearheads. This system compensates for backlash also where an application requires accuracy better than the minimal backlash of the gearhead.