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Inmoco’s Elmo range of Eagle, Falcon and Harmonica intelligent digital servo drives have been integrated to provide a highly capable and compact drive package for a new, unique Autonomous Guided Vehicle.  A ground-based unit for both industrial and military use, the autonomous vehicle is capable of reaching speeds of 25+ MPH (40+ KPH). The vehicle’s robotic platform is unique in that it is omni-directional. Basically, all the wheels steer independently, which allows the vehicle to move in any direction. The AGV is also equipped with a manipulator arm allowing for 5° of freedom, and the capability to lift in excess of 45kgs (100+ lbs) at full extension.

The AGV is the latest evolution in a range of vehicles that today are tasked with manoeuvring across harsh terrain in difficult environments while providing a flexible range of operations including hauling, transportation, disposing and/or disarming of explosives, surveillance and recovery.

The challenge faced by Elmo motion control engineers in the design of the AGV was threefold. First, to provide a capable and compact drive package for a wide range of power levels. Second, to devise a way to implement a distributed motion network. Third, to upgrade from the lower power & capability solutions provided by competitors.

Elmo systems expertise was required after the initial system for the AGV fell short on power, and did not provide genuine velocity control for the drive wheels. As a result, the vehicle had limited drive capability on an incline. Also, when coming to a halt, a final corrective move would occur, as an effect of the servos closing any position error present. In addition, the vehicle’s control system needed to be based upon the CANopen DSP402 protocol. Direct compatibility with this protocol, and knowledge of its implementation, was required to effect simple upgrades from one manufacturer’s equipment to another.                                                                  

The compact nature of the AGV required comparably compact electronics and also minimised bulk from cabling. The Elmo Falcon, Eagle and Harmonica drives, all of which offer high power density, and are designed for distributed control systems, were found to fit this requirement perfectly.

The military- specification Eagle digital drive was selected for the vehicle’s drive system, providing encoder-only velocity control for the drive wheels. Weighing less than 25ozs, the Eagle nevertheless offers high power - 60amps in this application from a 46-195VDc bus – in relatively compact package, together with CANopen communications.

Another military specification digital drive, the Elmo Falcon, was specified for manipulator arm control on the AGV: specifically on the upper of the higher power arm joints. Designed, in common with its sister drive, for use in extreme environments, the Falcon also offers high power density from a highly compact package and CANopen communications. It controls the manipulator arm in encoder-only velocity mode, with absolute position feedback from an analogue absolute encoder.

The final areas of servo control on the AGV, the lower power manipulator arm joints and the platform steering are handled by Elmo’s Harmonica digital drives. The Harmonica drives were selected for their compact size and ability to support up to a 200VDC bus. The platform steering is achieved in position mode using only Hall effect sensors. As with the Falcons, the Harmonicas control the manipulator arm in encoder-only velocity mode.

In addition to their high performance and efficiency, the Elmo drives were also specified for use on the AGV due to their robust connection facilities and interface capabilities. The Eagle and Falcon are military specification drives that utilise D-sub style connectors. These are ruggedised and can withstand the shock and vibration encountered while the vehicle travels over rough terrain.

As regards interface capabilities, all the Elmo drives support the CANopen protocol. This allowed the drives to be mounted very close to the electrical axis, reducing overall cabling. In addition, supporting both CAN In and CAN Out terminals, allows simple daisy-chaining of the CANopen communication lines from drive to drive.


For further information contact : Gerard Bush, Sales Engineer, INMOCO Limited, 4 Brunel Close, Drayton Fields, Daventry  NN11 8RB. Tel: 01327 307600   Fax: 01327 300319. E-mail


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