Mini servo drives simplify machine building

Inmoco's Elmo Mini Saxophone is a series of integrated servo drives designed to offer builders of high performance automated machinery more value, flexibility and performance from a smaller package.

Inmoco's new Elmo Mini Saxophone is a series of integrated servo drives designed to offer builders of high performance automated machinery more value, flexibility and performance from a smaller package.

Offering unmatched levels of flexibility, the Mini Saxophone is available as a fully digital velocity 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 Mini Saxophone mean that it is the ideal product for OEM machine builders.

Although extremely compact, Mini Saxophone offers all the 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 - and motor commutation, can also be undertaken via RS232 or optional RS485, serial communication links.

This is achieved using Windows-based Composer software, which is part of the automated setup, startup and tuning package that supports the amplifier.

Adding to the Mini Saxophone's functionality is a list of useful features that simplify setup and broaden the application range of the drives.

These include programmable, 12bit resolution analogue I/O; committed I/O for forward and reverse limit switches, amplifier enable, fault indication and emergency stop functions; general I/O, which is optoisolated and programmable, and an auxiliary input which can be used as a master input for velocity follower mode, position follower mode, pulse and direction input, ECAM mode and dual loop operation.

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

All variations of the Mini Saxophone are provided with general RS232 or optional RS485 serial interfaces, with a further CANOpen function provided on Plus and PlusPlus 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.

Rated for operation in the range from 1.5-10A RMS, the Mini Saxophone series is able to operate directly from either a three-phase 230/480V AC supply or a one- to three-phase 115/230V AC line.

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 back up" feature that is essential for positioning systems.

The architecture of Mini Saxophone employs advanced unipolar PWM switching (up to 18kHz) 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 motor cycle.

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

Even with the most optimised architecture, servo systems can fail to deliver if their control loop is not closed properly.

The Mini Saxophone overcomes this problem by offering a wide range of feedback options, enabling the needs of individual applications to be met.

In addition to standard high-resolution resolver feedback, these options include encoders with Hall sensors, encoders only and Hall sensors only.

The Mini Saxophone's primary role is providing users with enhanced levels of servo control.

Its equally important secondary role is to provide high levels of protection against possible fault conditions occurring.

In this, as in all other respects of its design, the Mini Saxophone offers high levels of functionality.

The drive is designed to provide software error handling and to detect and report a large number of possible fault conditions, the highest priority of these being displayed for immediate attention on the seven-segment LED display.

Additional safeguards are also provided by a range of protective features against conditions such as excessive temperature, under/over voltage, loss of commutation signal, short circuits between the motor power outputs and between each output and power input return.

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

(This was Engineeringtalk's Top Story on 25 July 2002).

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