Because the sun gear in a hybrid unit is pre-aligned within the gearhead rather than affixed to the servo gear reducer electric motor shaft, these gearheads can be used in contouring applications like a glue-dispensing nozzle for affixing a windshield to an automobile. Motion of the nozzle since it follows 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 program.
Smooth motion, which means the lack of torque and velocity variations (ripple), is important in contouring applications. But, it really is difficult to consistently achieve smooth motion where the sun gear is mounted on the electric motor 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 entire system. This information is usually offered from the gearhead manufacturer.
Contouring applications generally involve end-effectors or tool-points that follow mathematically defined paths. Sealant and bonding devices, drinking 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 engine to go 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 example, consider a servomotor, gearhead, and leadscrew mixture in a pick-andplace robot. If 100,000 encoder counts equals 1.0 in. of linear motion and the system has 0.1-in. dropped motion, then your controller tells the motor to go 110,000 encoder counts to get 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 engaging tooth; lost movement is the total looseness or motion at a reducer’s result shaft when the insight shaft is fixed. Lost motion contains backlash, plus losses from bearing looseness, tolerances and matches, and shaft and equipment tooth compliance.
Servo controllers could be programmed to compensate for backlash and dropped motion in planetary gearheads. This system compensates for backlash actually where a credit card applicatoin requires accuracy better than the minimal backlash of the gearhead.