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79 The platform The company manufactures a range of straddle carriers that typically measure roughly two to four containers in height, as well as being 5 m wide and 9.2 m long. Less immediately noticeable are the variations in their powertrains. The basic system is designed around a diesel- electric architecture: a diesel engine provides continuous power to a variable- speed generator, creating electrical energy to be used for driving and lifting, with resistors installed to consume excess power from the electric motors. However, increasingly the company also provides hybrid options, which differ from the standard diesel-electric powertrain by having a battery for storage and continuous supply of energy. Instead of being always active, the diesel generator recharges the battery intermittently, reducing fuel consumption by 30-40%. “Fully electric systems are also growing in popularity, so when asked, we can get rid of the diesel generator and power everything using a battery pack,” says Timo Alho, vice-president of terminal design services at Kalmar. “The cumulative weight of the batteries is about the same as the diesel engines – a few hundred kilos or so – so there’s not much of a challenge with integrating or switching between them in terms of weight distribution. It doesn’t make sense to put on huge amounts of battery power; the continuous, non-stop nature of cargo terminal work is such that it makes far more sense to set up opportunity charging, so that the carriers can charge for a short time when convenient.” Battery voltage is usually 600 V (although that can vary) and capacity is set to enable about 50 minutes of operations, after which 5 minutes of charging is needed to replenish the packs fully. Terminal connectivity Terminal-wide wi-fi connections have to be installed on all carriers before they can operate autonomously. These are critical for consistent, secure reporting of navigation information on the position and heading of each carrier, as well as the arrival of and destinations for containers, as they are lowered onto the ground from ships, stacks or trucks by way of manned and autonomous cranes. “You don’t need to program any of the carriers or feed in any tasks, because they’re persistently connected wirelessly to Kalmar One, our central automation system,” Alho explains. “This automatically dispatches and controls the work orders that dictate where straddle carriers need to be moving at any given time. “It also determines the directions inherent in the work orders based on information fed to it from the planning system, which maintains the records for inventory and deliveries.” As such, humans are not routinely needed for any active commands or jobs; technicians overseeing the central automation system can make ad hoc adjustments based on (for example) last-minute changes to work orders. Alternatively, they can choose to alter the number of active carriers if they perceive that there are more than are required on the terminal floor, and that saving fuel or battery power would be more prudent. Tomi Tuulkari, head of product Kalmar AutoStrad | In operation Unmanned Systems Technology | December/January 2021 The AutoStrads can greatly reduce the running costs and accidents at cargo terminals by taking human error out of their operations (Images courtesy of Kalmar Global) Ground-based localisation solutions are used in place of GNSS, with IMUs for aiding, and Lidars for obstacle detection and avoidance