Fully automatic depalletizing with VMT DeStack

The VMT DeStack system allows for the fully automatic depalletizing of arbitrarily stacked pallets with various KLT crate types, sizes, and colors, all without prior knowledge of the stacking scheme, using a robot. This technology is implemented in the software platform VMT MSS.

Depalletizing

The main application area for the VMT DeStack depalletizing system is logistics. The requirements for such a depalletizing system can be summarized simply: the pallet should be destacked as quickly and accurately as possible. This includes several conditions that are included and fulfilled by VMT DeStack.

• Reliable detection of different crate types without type specification
• High-accuracy position detection (±1 mm)
• Definable depalletizing sequence, from front to back and from top to bottom
• Fast overall cycle time (<10 seconds) with no waiting times for the robot
• Handling of errors such as severely tilted crates and objects in the gripping holes that could damage the gripper
• The contents of the crate, whether screws, film, or a lid, should not affect the system. In some cases, detecting the crate fill level to sort it into empty and full categories is also necessary 

The conditions in logistics are often difficult to predict. For this reason, the system must not be susceptible to lightly damaged crates, stickers, color variations, or slightly protruding films.

All these requirements have been considered and integrated into the development of the VMT DeStack system.

Stereo vision in 3D

Stereoscopic vision in 3D forms the basis of the system. The VMT DeepScan 3D stereo sensor is centrally installed above the depalletizing station and captures a point cloud of the pallets and the small load carriers stacked on them. The highly accurate point cloud is generated using a stereo method with supporting projection patterns and provides the image processing software with the raw data for subsequent vision algorithms.

Multi-layered evaluation methods

In its evaluation process, VMT DeStack employs a multi-stage image processing method to extract all necessary information from the point cloud.

In the first step, the point cloud is cropped so that only the top level is visible, ensuring that only this layer can be used for picking. Next, the crate to be picked from this layer is selected using a direction-based search method, type determination is performed, and the crate is validated based on hole spacing. The holes are then checked for their condition. If there are any tears or obstructions in the hole area, the crate is excluded. Finally, the crate’s position is determined and transmitted.

Since logistics conditions can be versatile and high availability is a top priority, automated fallback levels are in place at every stage of these evaluation methods. These fallback levels enhance the system’s reliability and ensure optimal performance even under difficult conditions.

Application-specific additional tests related to depalletizing can be easily extended through the modular software platform. These include, among others, the detection and removal of pallet covers, detection of crate fill levels, and identification of label positions on the crate for correct alignment on the conveyor belt.

More than just depalletizing

Due to its flexible and modular design, the VMT DeStack system is not only suitable for detecting and picking small load carriers from a pallet but can also be used for many other depalletizing applications. These include handling cardboard boxes and EPP containers, depalletizing pallets from a pallet stack, or picking objects from trays.