Human-Oriented Representation Learning for Robotic Manipulation

By Dr. Sampath LonkaReviewed by Susha Cheriyedath, M.Sc.Oct 9 2023

In a recent submission to the arXiv* server, researchers introduced a novel approach to robot representation learning that underscores the significance of human-oriented perceptual skills in achieving robust visual representations.

*Important notice: arXiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as definitive, used to guide development decisions, or treated as established information in the field of artificial intelligence research.

Background

In the domains of robotics and artificial intelligence, the challenge of enabling machines to engage with their surroundings efficiently has persisted. Unlike humans, who effortlessly navigate and manipulate their environment with remarkable adaptability, robots often falter, especially in unfamiliar settings. This ability to perceive and interact with our surroundings forms the foundation for mastering complex manipulation skills, a topic of significant interest in the field.

Existing approaches to representation learning in robotics can be categorized into three main streams. First, there are traditional methods that involve manually crafting representations. Second, modern state-of-the-art techniques seek to automatically discover adaptable representations from data through methods such as contrastive learning and masked image modeling. However, they often fail to capture human-specific behavior cues essential for robotic manipulation. Third, recent human-in-the-loop approaches attempt to refine representations with human feedback, but they are constrained by the need for substantial human labels and are limited to low-dimensional data.

Human priors for improved representation learning

Representation learning, a cornerstone of computer vision and robotics, is pivotal in enabling machines to understand their environment. Current methods predominantly rely on unsupervised and self-supervised techniques. While cost-effective, these methods often miss crucial attributes needed for downstream tasks. Another approach involves human guidance to refine representations, but it is labor-intensive. This work bridges the gap, proposing human-oriented representation learning by simultaneously acquiring perceptual skills from well-labeled video datasets containing human priors.

Multitask learning, which aims to optimize shared representations for multiple tasks, holds promise for enabling robots to transfer knowledge to new tasks. Existing methods manually define task relationships or rely on computational sampling, limiting scalability. This work advances multitask learning by enabling models to automatically learn task relationships during training, enhancing training efficiency and task transfer.

Enhancing visual-motor control with human-guided fine-tuning

In recent advancements in visual-motor control, there has been a notable emphasis on utilizing the impressive generalization capabilities of machine learning models to craft distinct representations for robot learning. Notably, visual encoders for Universal visual representation for robot manipulation (R3M), masked visual pre-training for motor control (MVP), and egocentric video-language pre-training (EgoVLP) have introduced models for behavior cloning and reinforcement learning.

To enhance these representations for robotic manipulation, the approach involves fine-tuning these vision backbones with human-guided input from diverse human action-related tasks. This process is facilitated by the Task Fusion Decoder, a versatile decoder compatible with various encoder networks. It addresses the crucial influence of human motion in representations, encompassing both temporal and spatial tasks simultaneously.

The decoder structure comprises 10 task tokens and leverages self-attention and cross-attention mechanisms to integrate task-specific information and interconnect different tasks. For joint training, three mutually related tasks are selected: object state change classification (OSCC), state change object detection (SCOD), and point-of-no-return temporal localization (PNR). OSCC involves the binary classification of state changes in video clips. PNR localizes keyframes with state changes, utilizing a distribution label. SCOD focuses on object detection, using a Hungarian algorithm to select bounding boxes for hands and objects. The joint training balances these tasks through a variance constraint, ensuring comprehensive learning harmoniously.

Evaluating fine-tuning effects and task relationships

The authors conducted experimental verification of their fine-tuning strategy's effectiveness in improving the robot's imitation learning across three simulation environments: Franka Kitchen, MetaWorld, and Adroit. They compared their approach to directly using pre-trained backbones.

For R3M, training an actor policy involves over 20,000 steps with 50, 25, and 100 demonstrations in the respective environments. For EgoVLP and MVP, they used 10, 50, and 100 demonstrations, evaluating the policy every 5000 training steps. The results consistently demonstrated that their fine-tuning strategy improved policy success rates compared to using the backbones directly.

In the ablation study, they evaluated the impact of temporal-related and spatial-related tasks on success rates. While most environments benefited from both types of tasks, some were better suited to one over the other. This aligns with human behavior, where specific perceptions are prioritized based on the environment.

They also introduced the Fanuc Manipulation dataset, which includes 17 manipulation tasks and 450 expert demonstrations. Behavior cloning was conducted using joint velocities instead of direct imitation, resulting in flexible learning and improved performance across multiple tasks.

Finally, their Task Fusion Decoder was evaluated on the Ego4D Hand and Object Interactions benchmark, demonstrating improved accuracy in object state change classification and temporal localization. This affirms the model's ability to capture task relationships and enhance computer vision representation, particularly in multi-task scenarios.

Representation analysis

The authors conducted a visual analysis to illustrate the effectiveness of their method. They used attention maps and t-distributed stochastic neighbor embedding (t-SNE) for visualization. In the attention map visualization, they compared the attention maps for the original model, their fine-tuned model, and an ablative model with only time-related tasks. They also presented t-SNE figures for representations of entire manipulation task sequences in various kitchen environments.

The results showed that their method effectively emphasized the manipulation area, especially after manipulation occurred, highlighting the effectiveness of their spatial-related task design.

Conclusion

In conclusion, researchers introduced a novel technique for robot representation learning. The proposed Task Fusion Decoder module facilitates the acquisition of multiple critical perceptual skills, enhancing representation learning for robotic manipulation. This approach improves the performance of state-of-the-art visual encoders in diverse robotic tasks, spanning simulation and real-world settings.

*Important notice: arXiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as definitive, used to guide development decisions, or treated as established information in the field of artificial intelligence research.