Because the sun gear in a hybrid unit is pre-aligned within the gearhead rather than affixed to the engine shaft, these gearheads can be utilized in contouring applications like a glue-dispensing servo gear reducer 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 must be perfectly smooth; or else a ripple in velocity alters the bead diameter and causes messy glue application.

Smooth motion, which means the lack of torque and velocity variations (ripple), is essential in contouring applications. But, it really is difficult to regularly achieve smooth motion where the sun gear is installed on the engine shaft. A good slight misalignment in sunlight gear (engine 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 whole system. This info is usually offered from the gearhead manufacturer.
Contouring applications usually involve end-effectors or tool-points that stick to mathematically defined paths. Sealant and bonding machines, water and flame cutters, laser beam welders and cutters, motion managed cameras, and CNC machine equipment are good examples.

Software compensation is achieved by commanding the motor to move beyond the apparently desired position by a quantity add up to the system’s lost movement, thereby bringing the strain 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 movement and the system 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, thus compensating for the 0.1-in. lost motion.

Backlash is the extra space between two adjacent gear teeth and its engaging tooth; lost motion may be the total looseness or movement at a reducer’s output 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 could be programmed to pay for backlash and dropped movement in planetary gearheads. This technique compensates for backlash actually where an application requires accuracy much better than the minimal backlash of the gearhead.