An Engineering Feat and an Industry First
"We’ll come up with something.” That’s what Bastian Solutions, a Toyota Advanced Logistics company, said to the customer when asked to engineer a stacker crane for a new automated warehouse. Bastian Solutions’ response belied the magnitude of the challenge.
The automated stacker crane is a central component of the customer’s new automated storage and retrieval system (AS/RS). It swiftly transfers packages of fiber cement boards from an immense racking system to workers at ground level. The boards are over 12 feet long and weigh 12,000 pounds per package. (Typical crane loads are 2,000 to 3,000 pounds.)
Bastian Solutions knew a standard crane just wouldn’t cut it. It couldn’t be a scaled up version of a smaller crane. In fact, the specifications for this crane were so demanding, the safety, mechanical and structural analysis was in design for almost two years.
- The racking system for the AS/RS had to be built around the crane
- The crane couldn’t be attached to the top of the building, because it could potentially take down the entire building
- Multiple points of redundancy needed to be accommodated to meet safety
It's Like Lifting Five Toyota Sequoia SUVs
The density and length of the load made drive selection and torque outputs challenging to say the least. The end user specified a Mitsubishi Electric control system, but Bastian Solutions selected Mitsubishi Electric for the drive components.
A specialized automated warehouse drive was just being introduced to the U.S. market and Mitsubishi Electric distributor, Allied Automation was more than happy to provide it. Allied Automation also brought in a third-party provider, SICK Sensor Intelligence, for the crane's dual-laser distance sensor. That meant the drive had to interface with the laser feedback device.
Bastian Solutions would be one of the first in the industry to benefit from the industry-leading performance and built-in functionality of the new drive. The crane-specific capabilities included load slippage prevention and anti-sway control for automatic suppression of swinging objects as they're being moved by the crane — without any adjustment by the operator.
The crane would be lifting the equivalent of five Toyota Sequoias throughout the day. The size, shape and weight of the load necessitated two vertical axes and two horizontal axes. The Bastian project manager says, "We had to have multiple drives per axis working in coordinated motion to make it work.” And while some crane functionality was already engineered into the drive, there was a fair amount of custom firmware required.
Bastian Solutions got a lot of support from Mitsubishi Electric field application engineers. The project manager says, "They went right to work, making the firmware changes that would allow us to do what was required.” They added:
- Droop control to accommodate the dual pulleys on the crane assembly for the large payload
- Horizontal sway control to make sure the load stayed level
- Dual-laser position control of the vertical axis to provide precise positioning measurement in a matter of milliseconds