Because the sun equipment in a hybrid unit is pre-aligned within the gearhead rather than servo motor gear reducers affixed to the motor shaft, these gearheads can be utilized in contouring applications like a glue-dispensing nozzle for affixing a windshield to a car. Movement of the nozzle as it follows the seam between a windshield and its own window frame should be perfectly smooth; otherwise a ripple in velocity alters the bead diameter and causes messy glue app.
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 movement where the sun gear is mounted on the engine shaft. A good slight misalignment in the sun gear (engine shaft runout 
or coupling inaccuracies) could cause rough procedure and noise.
Many servo controllers use software compensation, and their success depends upon knowing the lost movement of the entire system. This details 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 beam welders and cutters, motion controlled cameras, and CNC machine equipment are good examples.
Software compensation is accomplished by commanding the engine to move beyond the apparently desired position by a quantity add up to the system’s dropped movement, thereby bringing the load to the truly desired position. For example, look at a servomotor, gearhead, and leadscrew combination in a pick-andplace robot. If 100,000 encoder counts equals 1.0 in. of linear motion and the machine has 0.1-in. dropped motion, then the controller tells the engine to move 110,000 encoder counts to obtain 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 own engaging tooth; lost movement may be the total looseness or motion 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 gear tooth compliance.
Servo controllers can be programmed to pay for backlash and dropped motion in planetary gearheads. This system compensates for backlash even where a credit card applicatoin requires accuracy better than the minimal backlash of the gearhead.
