A macro-micro controller for pallet picking by an articulated-frame-steering hydraulic mobile machine

This paper addresses the macro-micro configuration of a mobile manipulation problem for a forklift; specifically, it investigates pallet picking with visual feedback. A manipulator with limited degrees of freedom and differential constraint mobility, together with the large dimensions of the machine, requires reliable visual feedback (pallet pose) and navigation from relatively large distances. It has been shown that the problem can be divided into two parts in order to solve the related issues based on path following theories and visual servoing. Moreover, visual pallet detection is non-real-time and unreliable, especially due to large distances, unfavorable vibrations, and fast steering. To address these issues, we introduce a simple and efficient method that integrates the vision output with odometry and realizes a smooth and nonstop transition from global navigation to visual servoing. Real-world implementation on a small-sized forklift demonstrates the efficacy of the proposed macro-micro architecture.