The MDS (Mobile-Dextrous-Social) is a robotic platform that is able to communicate verbally and non-verbally. Designed primarily with Human Robot Interaction (HRI) research in mind, it is the brainchild of Prof Cynthia Breazeal, Director of the Personal Robots Group at MIT Media Lab, who has pioneered the field of human-robot interaction. With the ultimate research goal being to develop human to robot interaction to a level akin to the way humans interact with other humans, potential applications for these robots include care of the elderly, healthcare and education.
Xitome Design – a long-standing Kvaser customer – was commissioned by Breazeal to build ‘Nexi’. At the core of this robot is a series of high-density motor controllers designed by Xitome and based on Denali hardware. A dedicated microcontroller and power amplifier is employed for each control channel. With communication between motor control units needed in a way that achieves flexible position control in a decentralised manner, Xitome Design uses a 1Mbit Controller Area Network (CAN) bus to daisy chain the microcontrollers together. This results in just two wires to provide motor control, power and CAN communication to the head.
Kvaser’s PC104+ dual channel CAN card can be found in the computational stack in the base of the robot, where all motor control and position feedback sensing take place. Meanwhile, Kvaser’s CANLib has been incorporated into Xitome Design’s own API to interface to the bus. Of Kvaser’s input, Kailas Narendran, Xitome Design’s co-founder, says: “There were lots of software and hardware implementation questions that we worked on with Kvaser and they were very responsive and helpful.”
Asked why Xitome Design chose CAN above other communications protocols for this application, Narendran says: “It’s a very robust and fast hardware protocol, with built in error detection and re-transmission, so good for noise immunity performance. In addition, the hardware implementation is relatively simple and compact and it’s daisy chained nature helps with cabling issues.” Narendran goes on to explain that fault isolation is achieved through CAN and the MDS’ inherent design. If a channel fails, its communication failures are isolated via the CAN mechanism, whilst other control failures are isolated by the natural separation of control to a dedicated microcontroller.
Whilst high degree of freedom humanoids might seem a niche market just now, human-robot interaction is an emerging research field with huge implications for society as a whole. Xitome Design has had commercial interest in its robots, but for now, the company is concentrating on the research market, in addition to offering its high-density motion control and electromechanical systems expertise wider a field.
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