Core Insights - The article discusses the catastrophic forgetting problem in the context of fine-tuning Visual Language Models (VLMs) into Visual Language Action Models (VLAs) for robotic control, highlighting the mismatch between pre-training and fine-tuning data distributions [2][4]. Group 1: Catastrophic Forgetting - Catastrophic forgetting occurs when the model loses its original reasoning and multimodal understanding capabilities during the action generation training process [2]. - The root cause of this issue is the distribution mismatch between the internet-scale pre-training data (primarily image-text pairs) and the low-dimensional action vector data used for robotic fine-tuning [2]. Group 2: VLM2VLA Approach - VLM2VLA aims to address the distribution mismatch by converting low-dimensional actions into natural language descriptions, aligning the fine-tuning data with the pre-training data [3][4]. - The method employs low-rank adaptation (LoRA) for fine-tuning, minimizing modifications to the VLM backbone and avoiding catastrophic forgetting [4]. Group 3: Hierarchical Action Representation - The VLM2VLA framework decomposes action prediction into a three-level reasoning process, utilizing natural language descriptions at all levels [6]. - High-level subtask prediction generates intermediate tasks based on initial observations and overall task instructions [6]. - Mid-level motion planning produces spatially oriented movement descriptions, while low-level action generation creates executable action sequences with language annotations [6]. Group 4: Data Reconstruction Pipeline - VLM2VLA utilizes Gemini 2.5 to automatically reconstruct raw robotic trajectory datasets into language-annotated datasets, ensuring compatibility with VLM pre-training formats [9]. - The reconstruction process involves providing context, decomposing trajectories into subtasks, and standardizing the format to align with VLM data [9]. Group 5: Efficient Fine-Tuning Strategy - The fine-tuning of the Gemma-3-12B-IT model is conducted using LoRA on linear layers without altering the VLM architecture or requiring joint training with internet-scale data [12][13]. - Key training parameters include a LoRA rank of 16, learning rate of 5e-5, and an effective batch size of 8 [12][13]. Group 6: Experimental Validation - Experiments focus on three core questions comparing VLM2VLA with baseline models, assessing the retention of multimodal understanding, competitive robotic manipulation performance, and the ability to generalize knowledge to new scenarios [14][15]. - VLM2VLA demonstrates competitive performance in both in-distribution and out-of-distribution tasks, showcasing its hierarchical reasoning capabilities [17][19]. Group 7: Limitations and Future Directions - The model currently faces challenges such as reasoning delays and the need for larger-scale robotic language-annotated datasets to enhance generalization capabilities [19]. - Future improvements may include optimizing decoding strategies, expanding language annotation for dexterous actions, and integrating validation capabilities within the VLM itself [19][22].