Because the sun equipment 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 such as a servo gear reducer glue-dispensing nozzle for affixing a windshield to a car. Movement of the nozzle since it comes after the seam between a windshield and its window frame should 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 is difficult to consistently achieve smooth movement where the sun equipment is installed on the engine shaft. Even a slight misalignment in the sun 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 whole system. This details is usually offered from the gearhead manufacturer.
Contouring applications usually involve end-effectors or tool-points that adhere to mathematically defined paths. Sealant and bonding devices, drinking water and flame cutters, laser welders and cutters, motion controlled cameras, and CNC machine equipment are good examples.
Software compensation is accomplished by commanding the electric motor to move beyond the apparently desired position by an amount add up to the system’s lost movement, 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 machine has 0.1-in. dropped motion, then the controller tells the electric motor to go 110,000 encoder counts to obtain 1.0 in. of motion, hence compensating for the 0.1-in. lost motion.
Backlash is the excess space between two adjacent equipment teeth and its own engaging tooth; lost movement is the total looseness or motion at a reducer’s output shaft when the input shaft is fixed. Dropped motion contains backlash, plus losses from bearing looseness, tolerances and matches, and shaft and gear tooth compliance.
Servo controllers can be programmed to compensate for backlash and dropped motion in planetary gearheads. This technique compensates for backlash actually where a credit card applicatoin requires accuracy better than the minimal backlash of the gearhead.