Because the sun equipment 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 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 application.
Smooth motion, this 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 gear is installed on the electric motor shaft. A good slight misalignment in sunlight gear (engine shaft runout or coupling inaccuracies) can cause rough procedure and noise.
Many servo controllers use software compensation, and their success depends on knowing the lost movement of the whole system. This details is usually offered from the gearhead producer.
Contouring applications generally involve end-effectors or tool-points that adhere to mathematically defined paths. Sealant and bonding devices, water and flame cutters, laser beam welders and cutters, motion managed cameras, and CNC machine equipment are good examples.
Software compensation is accomplished by commanding the motor to move beyond the apparently desired position by a quantity add up to the system’s lost movement, thereby bringing the load to the truly desired position. For example, 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 the controller tells the electric motor to go 110,000 encoder counts to get 1.0 in. of motion, therefore compensating for the 0.1-in. lost motion.
servo gear reducer backlash is the extra space between two adjacent gear teeth and its own engaging tooth; lost movement is the total looseness or motion at a reducer’s result shaft when the input shaft is fixed. Dropped motion includes backlash, plus losses from bearing looseness, tolerances and suits, 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 better than the minimal backlash of the gearhead.