Because the sun gear in a hybrid unit is pre-aligned within the gearhead and not affixed to the engine shaft, these gearheads can be used in contouring applications like a glue-dispensing nozzle for affixing a windshield to an automobile. Movement of the nozzle as 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 app.
Smooth motion, which means the lack of torque and velocity variations (ripple), is important in contouring applications. But, it is difficult to regularly achieve smooth movement where the sun gear is installed on the engine shaft. Even a slight misalignment in sunlight gear (motor shaft runout or coupling inaccuracies) can cause rough procedure and noise.
Many servo controllers use software compensation, and their success depends upon knowing the lost movement of the entire system. This details 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, water and flame cutters, laser welders and cutters, movement controlled 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 equal to the system’s lost motion, thereby bringing the strain to the truly desired position. For instance, look at a servomotor, gearhead, and leadscrew mixture 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 the controller tells the electric motor to go 110,000 encoder counts to obtain 1.0 in. of motion, therefore compensating for the 0.1-in. lost motion.
servo motor gear reducers backlash is the extra space between two adjacent equipment teeth and its engaging tooth; lost motion may be the total looseness or motion at a reducer’s result shaft when the input shaft is fixed. Lost motion contains backlash, plus losses from bearing looseness, tolerances and matches, and shaft and equipment tooth compliance.
Servo controllers can be programmed to compensate for backlash and lost movement in planetary gearheads. This technique compensates for backlash actually where a credit card applicatoin requires accuracy better than the minimal backlash of the gearhead.