Because the sun equipment in a hybrid unit is pre-aligned within the gearhead rather than affixed to the electric motor shaft, these gearheads can be used in contouring applications like a glue-dispensing nozzle for affixing a windshield to an automobile. Motion of the nozzle since 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 essential in contouring applications. But, it is difficult to consistently achieve smooth movement where the sun equipment is mounted on the engine shaft. A good slight misalignment in the sun gear (electric motor 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 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 tools are good examples.
Software compensation is achieved by commanding the engine to go beyond the apparently desired position by an amount equal to the system’s lost 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 movement and the system has 0.1-in. lost motion, then your controller tells the electric motor to move 110,000 encoder counts to obtain 1.0 in. of motion, hence compensating for the 0.1-in. lost motion.
servo motor gear reducers backlash is the extra space between two adjacent gear teeth and its engaging tooth; lost motion is the total looseness or movement at a reducer’s result shaft when the insight shaft is fixed. Lost motion includes backlash, plus losses from bearing looseness, tolerances and fits, and shaft and equipment tooth compliance.
Servo controllers can be programmed to compensate for backlash and lost motion 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.