FEATURE Automated warehousing
Autonomous towing robots speeding up material handling
“
In 2018, I was with a friend who owned a warehouse that moved a mix of large and heavy goods on both carts and pallet trucks. He
showed me the diffi culty in moving these carts quickly and accurately, and he asked me for help. I realised that with a special robot design, it could be possible to handle a variety of carts that are already in use, removing the challenges of size, weight and time,” says Keshav Chintamani, CEO of Tractonomy Robotics, a startup based in Ghent, Belgium.
Chintamani found that many automated guided vehicles (AGV) built for cart handling were based on a design that lifted the payload from below. However, this took time – sometimes over several minutes for the robot to position itself below the cart, and if the cart was slightly misaligned, the AGV was forced to stop and reset. There were often limitations on the weight that these robots could lift, including risks of the cart toppling over. Research turned to AGVs that could tow a cart; however, these AGVs were either permanently attached to the cart, or they off ered connection mechanisms with limited accuracy that still took a long time to dock. But, by discovery of a robotic gripper arm as a docking mechanism that could snap on securely to the cart, Chintamani’s new design would adapt and safely tow any type of cart. To give freedom over travel, Chintamani planned to combine this docking mechanism with an autonomous mobile robot (AMR) platform. Navigating by lasers to help avoid obstructions and achieve dynamic and accurate motion, the evolution to the AMR would help achieve faster and more-effi cient warehouse handling. The AMR still needed to travel within a
space-restricted warehouse to accurately dock with a cart positioned in a densely- packed row. Using mecanum wheels, this omni-directional design would let the AMR move in crowded spaces with three degrees of freedom. However, the vital step to optimise docking speed and accuracy, as well as onward movement, was the specification of a precise four-
32 September 2023 | Automation
wheel drive motion system. “Maxon motors are used in many academic research projects because of their performance and reliability, including the space sector research I’d worked on, so they were my fi rst point of investigation,” says Chintamani.
The motion system had to enable high weight towing, generating suffi cient torque to move a payload of several hundred kilograms from a standing start. Operating within cramped warehouse environments, Chintamani ’s fi rst AMR design measured just 70cm long and 50cm wide, so a compact motor footprint was vital. Following trials, a fl at brushless DC Maxon motor, the EC60, was specifi ed for the task. With four motors per robot – one per wheel – the design also had to be cost- eff ective for scaled production, considering the motors also needed integrated high- resolution encoders. “We tried these motors in the ATR1
prototype and they were really impressive. They pulled a cart with the weight of three people onboard – and these were really tiny motors, just 60mm wide,” says Chintamani. With the concept confi rmed, Tractonomy Robotics was born, with the inaugural design named the ATR1 – the Autonomous Towing Robot. The ATR1 can pull any type of cart weighing up to 400kg, at speeds of over 1m/s.
Above: ATR1 AGV by Tractonomy Robotics towing loads; it uses Maxon motors – see below
Aided by a special navigation stack, the
robot quickly docks, and the ATR1 can even detect free spaces and automatically park carts. This navigation system uses cameras and computer vision feedback; its control accuracy is a result of the motors’ speed of response. “The ATR1 can accurately and reliably dock with carts in under 20 seconds and position itself in tight spaces thanks to sideways manoeuvres, known as ‘strafi ng’, with subtle adjustments to ensure pinpoint accuracy,” says Chintamani.
CONTACT:
Maxon UK
www.maxongroup.co.uk
automationmagazine.co.uk
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