Machine Description:Unmanned vehicles have made quite an evolution throughout the years. Today, unmanned vehicles are tasked to maneuver through harsher terrains and environments and serve for
a multitude of functions or operations. Unmanned vehicles are used for a variety of operations such as hauling, transportation, disposing and/or disarming of explosives, surveillance, etc.
This particular high-speed vehicle is a ground-based unit for both industrial and military use capable of reaching speeds of 25+ MPH (40+ KPH). This robotic vehicle platform is unique in the sense that it is omni-directional. Basically, all wheels steer independently
which allows the vehicle to move in any direction. It is also equipped with a manipulator arm allowing for 5° of freedom. The manipulator arm is also capable to lifting 100+ lbs (45+ kg) at full extension. |
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The Challenge:
Provide a capable and compact drive package for a wide range of power levels.
Provide a way to implement a distributed motion network.
Upgrade from competitors’ lower power & capability solutions.
The initial implementation fell short on power for the wheels and also did not provide
genuine velocity control for the wheels. As a result, the vehicle had limited drive capability on an incline. And when coming to a stop, a final corrective move would occur… as an effect of the servos closing any position error present. Additionally, the vehicle’s control system was originally based on the CANopen DSP402
protocol, a device profile for motion drives. Direct compatibility of this protocol and knowledge of the implementation was required for a simple upgrade from one manufacturer to another.
Elmo's Solution:
| The compact nature of this vehicle required comparably compact electronics and a minimal bulk from cabling. Drives designed with high power density and for distributed control system are an optimal fit. The Eagle digital drive was selected for the vehicle’s drive system and provides encoder-only velocity control for the drive wheels. The Eagle model used for this application provides 60A continuous at a 46-
195VDC bus. Weighing at less than 25oz, the Eagle is a truly unique Elmo offering high power in a relatively
compact package.
Model number and description:
EAG-R60/200
Eagle Digital drive, 60A cont / No peak, 46-195VDC
equipped with incremental encoder feedback and CANopen communications. |
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ConnectivityThe Eagle and Falcon are industrial rated drives utilizing D-sub style connectors.
The D-sub connectors are more ruggedized and can withstand the shock and vibration encountered while the vehicle travels through rough terrains.
Another key factor for utilizing the Elmo based solution was the support of the CANopen protocol. The CANopen implementation allowed the drives to be mounted very close to the electrical axis and reduce overall cabling. Supporting both CAN In and CAN Out terminals, allows daisy-chaining of the CANopen communication lines from drive to drive.
Motor connections
Control Architecture & Feedback Interface
Velocity control with only an encoder
Hall only feedback for position control
Analog, absolute position sensor interface
CANopen DSP402
Profile Velocity
Profile Position
Why Elmo:
High reliability EEC
Military “ready to use”
High power density
Versatile servo architecture
CANopen DSP402
High efficiency
High linearity and accuracy
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