Because the sun equipment in a hybrid unit is pre-aligned within the gearhead and not affixed to the engine 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 servo gear reducer alters the bead diameter and causes messy glue software.
Smooth motion, this means the lack of torque and velocity variations (ripple), is essential in contouring applications. But, it really is difficult to regularly achieve smooth movement where the sun gear is mounted on the electric motor shaft. A good slight misalignment in sunlight gear (engine 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 obtainable from the gearhead producer.
Contouring applications usually involve end-effectors or tool-points that follow mathematically defined paths. Sealant and bonding machines, drinking water and flame cutters, laser welders and cutters, motion controlled cameras, and CNC machine equipment are good examples.
Software compensation is accomplished by commanding the motor to go beyond the apparently desired position by an amount add up to the system’s dropped motion, thereby bringing the load to the truly desired position. For instance, 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 the controller tells the electric motor to go 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 gear 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 matches, and shaft and gear tooth compliance.
Servo controllers can be programmed to compensate for backlash and lost motion in planetary gearheads. This technique compensates for backlash actually where a credit card applicatoin requires accuracy much better than the minimal backlash of the gearhead.
