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 utilized in contouring applications such as a glue-dispensing nozzle for affixing a windshield to 
a car. Motion of the nozzle since it comes after the seam between a windshield and its own window frame must 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 important in contouring applications. But, it is difficult to regularly achieve smooth movement where the sun gear is mounted on the motor shaft. Even a slight misalignment in sunlight gear (electric motor shaft runout or coupling inaccuracies) could cause rough operation and noise.
Many servo controllers use software compensation, and their success depends on knowing the lost movement of the entire system. This info is usually obtainable from the gearhead producer.
Contouring applications generally involve end-effectors or tool-points that stick to mathematically defined paths. Sealant and bonding devices, water and flame cutters, laser welders and cutters, motion controlled cameras, and CNC machine equipment are good examples.
Software compensation is achieved by commanding the motor to go beyond the apparently desired position by a quantity add up to the system’s dropped movement, thereby bringing the strain to the truly desired position. For example, 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 system has 0.1-in. dropped motion, then the controller tells the electric motor to move 110,000 encoder counts to obtain 1.0 in. of motion, thus compensating for the 0.1-in. lost motion.
Backlash is the extra space between two adjacent gear teeth and its own engaging tooth; lost motion may be the total servo gear reducer looseness or movement at a reducer’s result shaft when the insight shaft is fixed. Lost motion contains backlash, plus losses from bearing looseness, tolerances and matches, and shaft and gear tooth compliance.
Servo controllers could be programmed to compensate for backlash and lost motion in planetary gearheads. This technique compensates for backlash also where a credit card applicatoin requires accuracy better than the minimal backlash of the gearhead.