Because the sun gear in a hybrid unit is pre-aligned within the gearhead rather than affixed to the electric motor shaft, these gearheads can be used in contouring applications like a 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 own window frame must be perfectly smooth; otherwise a ripple in velocity alters the bead diameter and causes messy glue software.
Smooth motion, this means the lack of torque and velocity variations (ripple), is important in contouring applications. But, it really is difficult to regularly achieve smooth movement where the sun equipment is installed on the engine shaft. Even a slight misalignment in sunlight gear (motor shaft runout or coupling servo motor gear reducers inaccuracies) can cause rough procedure and noise.
Many servo controllers use software compensation, and their success depends on knowing the lost motion of the whole system. This details is usually available from the gearhead producer.
Contouring applications generally involve end-effectors or tool-points that follow mathematically defined paths. Sealant and bonding machines, drinking water and flame cutters, laser beam welders and cutters, movement controlled cameras, and CNC machine equipment are good examples.
Software compensation is accomplished by commanding the electric motor to go beyond the apparently desired position by an amount add up 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 motion and the system has 0.1-in. lost motion, then the controller tells the electric motor to move 110,000 encoder counts to obtain 1.0 in. of motion, therefore compensating for the 0.1-in. lost motion.
Backlash is the excess space between two adjacent gear teeth and its own engaging tooth; lost motion is the total looseness or movement at a reducer’s output shaft when the insight shaft is fixed. Lost motion contains backlash, plus losses from bearing looseness, tolerances and fits, and shaft and equipment tooth compliance.
Servo controllers could be programmed to pay for backlash and lost movement in planetary gearheads. This technique compensates for backlash also where an application requires accuracy better than the minimal backlash of the gearhead.