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Miniature servos provide dynamic performance

An Inmoco product story

Edited by the Engineeringtalk editorial team Feb 5, 2003

The Elmo Harmonica range of miniature servo drives offers machine builders all the performance and features of much larger digital servo drives in a smaller and more cost effective package.

Inmoco's new Elmo Harmonica range of miniature servo drives offers OEM machine builders all the performance and features of much larger digital servo drives in a smaller and more cost effective package measuring just 82 x 25.4 x75mm.

Providing unmatched levels of flexibility, the Harmonica is available as a fully digital velocity or current mode amplifier, as a network drive in distributed motion systems using the CANOpen interface, or as a standalone motion controller for single-axis servo control.

The combination of small size, ease of setup and commissioning, simplicity in mounting (panel or DIN rail), and communication facilities offered by the Harmonic and Harmonica "Advanced" models mean that they are the ideal product for OEM machine builders.

Although extremely compact, the drives sacrifice nothing in functionality, offering all the dynamics, precision and functionality of much larger servo drives with a specification that integrates position loop, and both digital current and digital velocity loops, all with auto tuning adjustment.

Conveniently for the user, adjustments to these loops can also be undertaken using Elmo's Windows based Composer software, which is part of the automated setup, startup and tuning package that supports the amplifier.

The many onboard facilities of the Harmonica Series provide OEMs with the widest range of operating possibilities, including point-to-point positioning, dual loop operation - which compensates for mechanical backlash - PT1, PVT2, follower and pulse and direction modes and ECAM, or electronic CAM.

ECAM is the ideal operating mode for periodic operation, especially in applications such as flying shears, rotating knives and packaging systems, where varying gear ratios are required along the motion cycle.

Optimising the performance of the Harmonica Series in all of its operating modes is a comprehensive list of supplementary features.

These include: smart multipurpose inputs, programmable as enable, forward and reverse limit switch, home and capturing; event triggered programming; uncommitted programmable I/O; differential 12bit analogue I/O; automatic feedback alignment; committed I/O for forward and reverse limit switches; enable input limit switches; emergency stop and many, many more.

Also complementing drive functionality is a range communication interfaces designed to aid integration into larger automation systems.

Both versions of the Harmonica are provided with a serial RS232 interface, with, in addition, a further CANOpen function provided on "Advanced" versions of the drive.

This presents a low cost solution for implementing the connection of the servo drive with other machine elements using one of the most popular fieldbus networks.

The architecture of Harmonica series employs advanced unipolar PWM switching to ensure high motor operating efficiencies at the rated current.

In addition, the amplifier's sinusoidal commutation function helps to maintain smooth motion and low torque ripple at low speeds, enabling nearly constant torque to be achieved throughout the motorcycle.

Added to this, a zero deadband feature ensures that motor transitions from forward to reverse are seamless, and linearity is also excellent.

Rated for operation in the range from 3.5 to 8.5A RMS, the Harmonica series operates from a 12-180V DC power source.

A major feature of the unit is that the control and the auxiliary supplies are derived from a 24V AC/DC supply that is isolated from the internal DC bus.

This allows a safe and an economical "power backup" feature that is essential for positioning systems.

Despite their extremely small size, the Harmonica amplifiers provide users with high levels of protection against possible fault conditions occurring.

The drives are designed to provide software error handling and to detect and provide safeguards against conditions such as excessive temperature, under/overvoltage, loss of commutation signal, short circuits between the motor power outputs and between outputs and ground.

Finally, protection is provided against failure of the internal power supplies, loss of velocity feedback and communication errors.

The fully functioned Harmonica Series is the ideal product for modern, servo-based applications, where high-speed and/or high precision, motion control is critical.

Such applications include feeders, up- and downloaders, transportation belts and production lines.