DiffTactile: A Physics-based Differentiable Tactile Simulator for Contact-rich Robotic Manipulation

Anonymous authors
Under review at ICLR 2024
Surface Following

Surface Following

Box Opening

Box Opening

Cable Manipulation

Cable Manipulation

Object reposing

Object reposing

Abstract

We introduce DiffTactile, a physics-based and fully differentiable tactile simulation system designed to enhance robotic manipulation with dense and physically-accurate tactile feedback. In contrast to prior tactile simulators which primarily focus on manipulating rigid bodies and often rely on simplified approximations to model stress and deformations of materials in contact, DiffTactile emphasizes physics-based contact modeling with high fidelity, supporting simulations of diverse contact modes and interactions with objects possessing a wide range of material properties.

Our system incorporates several key components, including a Finite Element Method (FEM) -based soft body model for simulating the sensing elastomer, a multi-material simulator for modeling diverse object types (such as elastic, plastic, cables) under manipulation, a penalty-based contact model for handling contact dynamics. The differentiable nature of our system facilitates gradient-based optimization for both 1) refining physical properties in simulation using real-world data, hence narrowing the sim-to-real gap, and 2) efficient learning of tactile-assisted grasping and contact-rich manipulation skills. Additionally, we introduce a method to infer the optical response of our tactile sensor to contact using an efficient pixel-based neural module.

We anticipate that DiffTactile will serve as a useful platform for studying contact-rich manipulations, leveraging the benefits of dense tactile feedback and differentiable physics.

Experiments

pixel-wise tactile marker mean squared errors

pixel-wise tactile marker mean squared errors

Metrics of tasks trained by different algorithms

Metrics of tasks trained by different algorithms

System Identification

We show how we collect real world data and the predicted (yellow) and real (green) markers of three different trajectories.

Surface Following

Real Press-slide

Surface Following

Real Press-twist-x

Surface Following

Real Press-twist-z

Box Opening

Press-slide markers

Box Opening

Press-twist-x markers

Box Opening

Press-twist-z markers

Real-world box opening with the trajectories optimized in simulation from our system idenfied parameters (a success) and baseline parameters (a failure).

Surface Following

E=0.37e3 (SysID)

Box Opening

E=4.00e4 (failed)


Optical Simulation

We simulate how surface of Gelsight deform when interact with different things. The result is almost the same as real world.

Surface Image Simulation

Surface Image Simulation


Sim2real of Contact-rich Manipulation Tasks

We apply trained trajectories of contact-rich manipulation tasks like surface following and box openning in real world.

Surface Following

Surface Following

Box Opening

Box Opening


Sim2real of Grasping Tasks

We apply our trained adaptive grasping policy in real world. We compare the result to forceful grasp and light grasp.

Surface Following

Forceful grasp

Surface Following

Light grasp

Surface Following

Adaptive policy


RL & CMA-ES Trained Results

We visualize trained results of RL algorithms(PPO and SAC) and CME-ES here to show their failure modes.

Surface Following

Surface Following (PPO)

Surface Following

Surface Following (SAC)

Surface Following

Surface Following (CMA-ES)

Box Opening

Box Opening (PPO)

Box Opening

Box Opening (SAC)

Box Opening

Box Opening (CMA-ES)

Cable Manipulation

Cable Manipulation (PPO)

Cable Manipulation

Cable Manipulation (SAC)

Cable Manipulation

Cable Manipulation (CMA-ES)

Object reposing

Object reposing (PPO)

Object reposing

Object reposing (SAC)

Object reposing

Object reposing (CMA-ES)