Research on the path planning integrated with multi-steer modes for heavy reconfigurable unit

Heavy reconfigurable units (HRUs) can form the heavy transportation vehicular platform (HTVP) to perform transportation for large equipment, by combining with each other. With all-wheel-independent-steered, the HRU can realize multi-steer modes (MSMs) such as Ackermann steer mode (ASM), diagonal steering mode (DSM), and zero radius steer mode (ZSM). However, with heavy weight and long wheelbase, the HRU’s mobility is poor if it only employs ASM. Therefore, this paper proposes a hierarchical path planning architecture, realizing path planning integrated with the above steer modes. This architecture includes the MSMs behaviors planning layer (upper layer) and smooth path planning layer (low layer). Firstly, this paper innovative proposes the MSM graph-based search algorithm in the upper layer, which extends nodes through graph-based searching on the grid map considering MSMs information. Then, the upper layer generates MSMs nodes sequence considering improved cost function for MSMs. Secondly, smooth path planning methods for the MSMs are respectively applied to the ASM sequence, DSM sequence, and ZSM sequence. Comparative simulations are shown as results based on measured parameters from real HRU. The results from the proposed method have the lowest or one of the lowest time cost compared with pure ASM planner and special steer modes planner used in the simulations. The maximum optimization rate can reach 10% or more.