Because the sun gear in a hybrid unit is pre-aligned within the gearhead and not affixed to the electric motor shaft, these gearheads can be used in contouring applications such as a glue-dispensing nozzle for affixing a windshield to an automobile. Movement of the nozzle since 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 app.
Smooth motion, which 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 motor shaft. A good 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 motion 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 welders and cutters, movement managed cameras, and CNC machine equipment are good examples.
Software compensation is accomplished by commanding the engine to move beyond the apparently desired position by an amount add up to the system’s lost motion, thereby bringing the load 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 machine has 0.1-in. dropped motion, then your controller tells the electric motor to move 110,000 encoder counts to obtain 1.0 in. of motion, thus compensating for the 0.1-in. lost motion.
servo motor gear reducers backlash is the extra space between two adjacent equipment teeth and its own engaging tooth; lost movement may be 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 fits, and shaft and equipment tooth compliance.
Servo controllers could be programmed to compensate for backlash and lost motion in planetary gearheads. This system compensates for backlash actually where an application requires accuracy better than the minimal backlash of the gearhead.