Development of a PPO-Reinforcement Learned Walking Tripedal Soft-Legged Robot using SOFA
Yomna Mokhtar, Tarek Shohdy, Abdallah A. Hassan, Mostafa Eshra, Omar Elmenawy, Osama Khalil, Haitham El-Hussieny
TL;DR
The paper tackles stable locomotion for a soft-bodied tripedal robot on uneven terrain by integrating PPO-based reinforcement learning with a SOFA-based real-time physics simulation. It builds a cable-driven soft legged robot in SOFA, connects a Gym-like environment, and trains a policy to reach spatial goals under dynamic conditions. The results show an 82% single-goal success rate with an average deviation of 18.76 mm over about 400 steps, and successful trajectory following with roughly 19 mm deviation over 694 steps, demonstrating the viability of PPO-RL for soft robotics in simulation. The work provides a publicly available codebase and points to future directions such as curriculum learning and sim-to-real validation for broader practical impact.
Abstract
Rigid robots were extensively researched, whereas soft robotics remains an underexplored field. Utilizing soft-legged robots in performing tasks as a replacement for human beings is an important stride to take, especially under harsh and hazardous conditions over rough terrain environments. For the demand to teach any robot how to behave in different scenarios, a real-time physical and visual simulation is essential. When it comes to soft robots specifically, a simulation framework is still an arduous problem that needs to be disclosed. Using the simulation open framework architecture (SOFA) is an advantageous step. However, neither SOFA's manual nor prior public SOFA projects show its maximum capabilities the users can reach. So, we resolved this by establishing customized settings and handling the framework components appropriately. Settling on perfect, fine-tuned SOFA parameters has stimulated our motivation towards implementing the state-of-the-art (SOTA) reinforcement learning (RL) method of proximal policy optimization (PPO). The final representation is a well-defined, ready-to-deploy walking, tripedal, soft-legged robot based on PPO-RL in a SOFA environment. Robot navigation performance is a key metric to be considered for measuring the success resolution. Although in the simulated soft robots case, an 82\% success rate in reaching a single goal is a groundbreaking output, we pushed the boundaries to further steps by evaluating the progress under assigning a sequence of goals. While trailing the platform steps, outperforming discovery has been observed with an accumulative squared error deviation of 19 mm. The full code is publicly available at \href{https://github.com/tarekshohdy/PPO_SOFA_Soft_Legged_Robot.git}{github.com/tarekshohdy/PPO$\textunderscore$SOFA$\textunderscore$Soft$\textunderscore$Legged$\textunderscore$ Robot.git}