Because the sun gear in a hybrid unit is pre-aligned within the gearhead and not 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 as it follows the seam between a windshield and its own window frame must be perfectly smooth; otherwise a ripple in velocity alters the bead diameter and causes messy glue software.
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 motion where the sun gear is installed on the motor shaft. Even a slight misalignment in sunlight gear (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 available from the gearhead producer.
Contouring applications servo motor gear reducers generally involve end-effectors or tool-points that adhere to mathematically defined paths. Sealant and bonding devices, drinking water and flame cutters, laser welders and cutters, movement controlled cameras, and CNC machine tools are good examples.
Software compensation is accomplished by commanding the motor to move beyond the apparently desired position by an amount add up to the system’s dropped movement, thereby bringing the strain to the truly desired position. For instance, 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 your controller tells the engine to move 110,000 encoder counts to obtain 1.0 in. of motion, hence compensating for the 0.1-in. lost motion.
Backlash is the extra space between two adjacent equipment teeth and its engaging tooth; lost motion is the total looseness or motion at a reducer’s result shaft when the input shaft is fixed. Lost motion includes backlash, plus losses from bearing looseness, tolerances and suits, and shaft and gear tooth compliance.
Servo controllers could be programmed to compensate for backlash and dropped movement in planetary gearheads. This technique compensates for backlash even where a credit card applicatoin requires accuracy much better than the minimal backlash of the gearhead.