Image Measurement Method for Automatic Insertion of Forks into Inclined Pallet

TL;DR

This paper presents an image measurement method using a wide-angle camera to automatically control a forklift's fork insertion by accurately measuring pallet inclination and calibration between camera and fork systems.

Contribution

It introduces a novel image measurement technique for estimating pallet tilt and calibration data to enable autonomous fork insertion in forklifts.

Findings

Error within allowable range for safe fork insertion

Effective measurement of pallet inclination and position

Calibration method improves measurement accuracy

Abstract

In order to insert a fork into a hole of a pallet by a forklift located in front of a pallet, it is necessary to control the height position, reach position, and tilt angle of the fork to match the position and orientation of the hole of the pallet. In order to make AGF (Autonomous Guided Forklift) do this automatically, we propose an image measurement method to measure the pitch inclination of the pallet in the camera coordinate system from an image obtained by using a wide-angle camera. In addition, we propose an image measurement method to easily acquire the calibration information between the camera coordinate system and the fork coordinate system necessary to apply the measurements in the camera coordinate system to the fork control. In the experiment space, a wide-angle camera was fixed at the backrest of a reach type forklift. The wide-angle images taken by placing a pallet in front of the camera were processed. As a result of evaluating the error by comparing the image measurement value with the hand measurement value when changing the pitch inclination angle of the pallet, the relative height of the pallet and the fork, and whether the pallet is loaded or not, it was confirmed that the error was within the allowable range for safely inserting the fork.