Saturday 21 August 2010

Digital servo amplifier

Aerotech has launched a new digital servo amplifier with a linear power stage for ultra-high resolution brushed or brushless linear and rotary motion control systems. The new compact ML series amplifier is intended for lower power use but maintains the very high performance characteristics required for nanometre and microradian level precision positioning applications that are acutely susceptible to electrical noise, and where PWM servo amplifiers become unusable. The DSP based ML range is designed for minimal radiated noise to allow the servo system to provide exceptional levels of speed control and in-position stability for ultra-smooth motion profiles, and to ensure negligible interference levels for sensitive processing and measuring equipment.

Aimed at very high resolution motion systems applications as found in NDT, MEMS, vision systems and microscopy but with less dynamic performance requirements, the new amplifier is available in three versions: as the Ndrive ML option for Aerotech's A3200 software only motion controller; as an entry level version of the Soloist™ ML integrated single-axis position controller range; and as a low-cost linear drive stage solution for the multi axis Ensemble™ ML, a networkable and panel mount motion control system.

The basic specifications for the ML series linear amplifiers in all configurations includes 5A continuous/10A peak current rating with a customer supplied DC bus voltage of +/- 40 V and a control supply requirement of 18-36 VDC. A single 16-bit ±10 V analogue input is used for direct interfacing to the motion controller with an ESTOP sense input included.

The ML features primary and secondary incremental encoder interfaces which are optionally equipped with Aerotech's MXH hardware based multiplied encoder technology for up to 65536 times quadrature output. Using a 1V p-p sinusoidal encoder which does not require a costly power supply, this level of multiplication has a 2MHz analogue input frequency that allows nanometre or microradian level resolution across Aerotech's wide range of high precision direct-drive positioning mechanics, without compromise on top speed.

The MXH encoder option also enables the single axis Position Synchronised Output (PSO) feature to be implemented at the highest level. Aerotech's PSO is a powerful algorithmic software tool that precisely coordinates the real-time position from a linear or rotary encoder with high speed output pulses from the controller which are be used to trigger external events.

This feature is widely used in applications such as laser micromachining or position critical NDT where exacting, no compromise synchronisation is required between laser firing or sensor reading and the axis path position.

For the alternative software based MXU encoder version, the encoder interfaces have a 4096 multiplication factor and both MXU and MXH encoder options include end-of-travel limits and home inputs on the primary feedback encoder. An optional I/O expansion board is also available to equip the ML drive with 8 opto-isolated digital inputs and 8 digital outputs (sinking or sourcing) in addition to single 16-bit analog inputs and outputs, and a brake relay output.

As the ML series linear stage amplifier does not include an integrated power supply and the I/O expansion option may not be required for some applications, the drive can be a low cost solution and additionally its small footprint may be advantageous in space restricted OEM applications.

The ML drive's 10A peak current rating will provide more than sufficient power for the majority of micropositioning applications, however where more useful power may be required and in areas where amplifier temperature rise must be kept to a minimum, a water cooled version is available. This version can provide a 35% increase in usable power.

In addition to the ML range, Aerotech also produce linear stage amplifiers with 2 & 3 axis PSO capabilities, integral mains power supplies and built-in I/O and fieldbus interfaces - offering the superb linearity, high bandwidth, zero crossover distortion and ultra-quiet EMC characteristics of the ML series. These control options and higher power versions are available throughout the A3200, Soloist and Ensemble ranges, and in addition Aerotech offer a full complement of PWM stage amplifiers for very high speed and heavy load precision positioning applications.

All of these Aerotech drive technologies may be freely mixed for multi-axis positioning systems ensuring that each axis is cost and performance optimised. A choice of PC-based software-only, rack or panel mounted motion controls in single or multi-axis formats allow optimal performance with diagnostics and comprehensive features that aim to ensure fast product development and commissioning, reduce positioning errors, improve throughput performance and ensure time-saving and quality improving benefits.

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