Because the sun equipment 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 utilized in contouring applications such as a glue-dispensing nozzle for affixing a windshield to a car. Motion of the nozzle as it comes after the seam between a windshield and its own window frame must be perfectly smooth; or else a ripple in velocity alters the bead diameter and causes messy glue app.
Smooth motion, which means the absence 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 motor shaft. A good slight misalignment in sunlight gear (electric motor shaft runout or coupling inaccuracies) can cause rough operation and noise.
Many servo controllers use software compensation, and their success depends on knowing the lost movement of the whole system. This information is usually available from the gearhead manufacturer.
Contouring applications generally involve end-effectors or tool-points that adhere to mathematically defined paths. Sealant and bonding machines, water and flame cutters, laser beam welders and cutters, movement controlled cameras, and CNC machine tools are good examples.
Software compensation is accomplished by commanding the electric motor to go beyond the apparently desired position by a quantity add up to the system’s dropped movement, thereby bringing the strain to the truly desired position. For instance, 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 machine has 0.1-in. dropped motion, then your 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 extra space between two adjacent equipment teeth and its own engaging tooth; lost motion is the total looseness or motion at a reducer’s result shaft when the insight shaft is fixed. Dropped motion contains backlash, plus losses from bearing looseness, tolerances and suits, and shaft and equipment tooth compliance.
Servo controllers could be programmed to compensate for backlash and lost movement in planetary gearheads. This technique compensates for backlash even where a credit card applicatoin requires accuracy better than the minimal backlash of the gearhead.