Because the sun gear in a hybrid unit is pre-aligned within the gearhead and 
not affixed to the engine shaft, these gearheads can be utilized in contouring applications such as a glue-dispensing nozzle for affixing a windshield to an automobile. Movement of the nozzle since it comes after the seam between a windshield and its window frame should be perfectly smooth; otherwise a ripple in velocity alters the bead diameter and causes messy glue application.
Smooth motion, this means the absence of torque and velocity variations (ripple), is essential in contouring applications. But, it really is difficult to regularly achieve smooth movement where the sun equipment is installed on the electric motor shaft. Even a slight misalignment in sunlight gear (engine shaft runout or coupling inaccuracies) can cause rough operation 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 manufacturer.
Contouring applications generally involve end-effectors or tool-points that adhere to mathematically defined paths. Sealant and bonding devices, drinking water and flame cutters, laser beam servo motor gear reducers 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 an amount add up to the system’s lost movement, thereby bringing the strain to the truly desired position. For instance, 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. lost motion, then the controller tells the 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 excess space between two adjacent gear teeth and its engaging tooth; lost movement is the total looseness or motion at a reducer’s result shaft when the input shaft is fixed. Dropped motion contains backlash, plus losses from bearing looseness, tolerances and suits, and shaft and equipment tooth compliance.
Servo controllers can be programmed to compensate for backlash and dropped movement in planetary gearheads. This system compensates for backlash even where a credit card applicatoin requires accuracy better than the minimal backlash of the gearhead.