ISR-LLM: Iterative Self-Refined Large Language Model for Long-Horizon Sequential Task Planning

Motivated by the substantial achievements of Large Language Models (LLMs) in the field of natural language processing, recent research has commenced investigations into the application of LLMs for complex, long-horizon sequential task planning challenges in robotics. LLMs are advantageous in offering the potential to enhance the generalizability as task- agnostic planners and facilitate flexible interaction between human instructors and planning systems. However, task plans generated by LLMs often lack feasibility and correctness. To address this challenge, we introduce ISR-LLM, a novel framework that improves LLM-based planning through an iter- ative self-refinement process. The framework operates through three sequential steps: preprocessing, planning, and iterative self-refinement. During preprocessing, an LLM translator is employed to convert natural language input into a Planning Domain Definition Language (PDDL) formulation. In the plan- ning phase, an LLM planner formulates an initial plan, which is then assessed and refined in the iterative self-refinement step by a validator. We examine the performance of ISR- LLM across three distinct planning domains. Our experimental results show that ISR-LLM is able to achieve markedly higher success rates in sequential task planning compared to state- of-the-art LLM-based planners. Moreover, it also preserves the broad applicability and generalizability of working with natural language instructions.