Technology
ServoTube Linear Actuator & Motor
The advanced magnetic design of ServoTube enables up to 12 micron repeatability from built-in Hall sensors. A linear encoder is not required. The ServoTube feedback output is standard sin/cos 1Vpk-pk.
With fully enclosed magnets and coils, the tubular linear motor is rugged and easy to install. ServoTube Actuator incorporates a lubrication-free internal bearing for moving-rod applications. For gantry pick-and-place applications, the load can be mounted directly to the moving forcer. The tubular motor is inherently thermally efficient and with a heatsink built-in, forced air cooling is not required.
Field Oriented Control
Field oriented control is a motor commutation scheme which enables brushless motors to run faster and cooler. This is made possible by maintaining optimal orientation of the rotating magnetic field and permanent magnets at all speeds.
In a traditional control scheme, the commanded current is modulated by sinusoidal waveforms to create a rotating magnetic field in the motor stator. The frequency of the sinusoids is speed dependent. At higher speeds, current phase lag occurs causing misalignment of the magnetic fields. This causes motor heating and limits speed.
Typical Modulation
Copley Modulation
Precision Positioning
In low friction systems (air-bearing linear motors and voice-coil motors), the amplifier drives small positive and negative currents to maintain zero error when holding position. Amplifier crossover distortion now becomes a factor as non-linearities around zero current can compromise precision.
Copley amplifiers employ two techniques to eliminate crossover distortion in analog amplifers: carrier cancellation - an optimal solution for brushless motors, 50% modulation - typically used for voice coil motors.
Without Edge Filter
With Edge Filter
Edge Filtering
A PWM amplifier generates switching transients that can couple into other sensitive circuits. Although careful attention to shielding and grounding can eliminate many problems, Copley Controls offers optional Edge Filters to limit
the generation of transient noise.