Because the sun gear in a hybrid unit is pre-aligned within the gearhead rather than 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. Motion of the nozzle since it comes after 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 software.
Smooth motion, which means the lack of torque and velocity variations (ripple), is essential in contouring applications. But, it is difficult to regularly servo gear reducer achieve smooth movement where the sun equipment is mounted on the electric motor shaft. Even a slight misalignment in the sun 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 whole system. This information is usually obtainable from the gearhead producer.
Contouring applications usually involve end-effectors or tool-points that stick to mathematically defined paths. Sealant and bonding machines, drinking water and flame cutters, laser beam welders and cutters, motion controlled cameras, and CNC machine tools are good examples.
Software compensation is accomplished by commanding the engine to move beyond the apparently desired position by a quantity equal to the system’s dropped movement, thereby bringing the strain to the truly desired position. For instance, consider 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 machine has 0.1-in. dropped motion, then the controller tells the motor to go 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 equipment teeth and its own engaging tooth; lost motion is the total looseness or motion at a reducer’s output shaft when the insight shaft is fixed. Dropped motion contains backlash, plus losses from bearing looseness, tolerances and fits, and shaft and gear tooth compliance.
Servo controllers can be programmed to compensate for backlash and lost movement in planetary gearheads. This system compensates for backlash even where an application requires accuracy much better than the minimal backlash of the gearhead.