First-of-its-kind hybrid rubber tired gantry (RTG) crane lowers emissions by 80 percent and reduces fuel usage by 70 percent.  In addition operators found it smooth and easy to drive, and were able to pick and lift containers 20 percent faster than a hydraulic crane.

The rubber tired gantry crane (RTG) market is very competitive, so to meet a growing demand for a more energy efficient solution, US company Mi-Jack began actively developing an electronic hybrid RTG.

 Hybrid concept

Their idea was to develop a battery powered electronic hybrid crane that would recharge the crane’s battery pack. This way, if the crane was low on power it could recharge itself from a small onboard diesel engine.  Since they only needed to size the generator to charge the batteries and not actually lift the load they were able to use a generator one-third the size of a typical generator.  The benefit is that customers see a substantial decrease in fuel costs since the generator is much smaller and only used part time.

One of the major challenges was in converting hydraulic functions to electric drive functions.  Since electronic drive controls are less forgiving than hydraulics, it required precise calculations were made for stopping and starting, and a lot of time was spent fine-tuning the drives and synchronizing multiple motors.

Schneider Electric helped Mi-Jack develop a solution for its MJ 1200 REH hybrid RTG crane using the Modicon LMC058 controller, which is both a motion controller and PLC in one product.  Movement and handling was controlled by eleven Altivar 71 drives and a Magelis HMI. The LMC058 controller gives us greater flexibility and control in connecting the CAN networks, making our communication more reliable.

MachineStruxure

The LMC058 controller is part of Schneider Electric MachineStruxure architecture, a comprehensive automation solution for industrial machines, based on flexible hardware platforms and SoMachine, a single modular, reusable software suite.

MachineStruxure helps OEMs design more energy-efficient and cost-effective machines that maximize performance using tested, validated, and documented architectures and application function block libraries.

The absolute speed of the hybrid crane is the same as a hydraulic, but the programming of the PLCs and drives give the operators more finite control over the motions. The operator has more precision and the 1200 REH is the operators’ favourite crane. It gets the most hours per day.

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