GSoC 2021: Stable Baseline and Ray in Deepots (DeepbotsZero project).

Table of Contents

1. DeepbotsZero
   1. Project
   2. Completed Work
   3. Enhancements / To be done / Optional
2. Weekly Update
3. Many, many thanks to my mentors!

DeepbotsZero

Mentors: @ManosMagnus, @tsampazk, @passalis

Project

My objectives for this proposal were to implement two humanoid environments for the deepbots framework, using KONDO's KHR-3HV (17 degrees of freedom) and Nao (25 degrees of freedom) as agents. In both environments, I used Robot-Supervisor scheme that exists on deeepbots framework, due to the reason for the high-dimensional observation space that exists on both robots. As the goal of each agent would be to maximize the simple objective of walking the largest possible distance.

I planned to use the Proximal Policy Optimization (PPO) [Done] and the Twin Delayed DDPG (TD3) [Futur-work]. Both are provided by the stable-baseline and RLlib codebase. The choice of the algorithms is not arbitrary, the two algorithms belong to different families (policy gradient and actor-critic) which exploit different environment properties. Moreover, PPO doesn’t need to spend a lot of time on the hyperparameter tuning and it behaves better than any other on-policy gradient-based algorithm (REINFORCE, TRPO). While the TD3 is a better implementation of DDPG using Clipped Double Q-learning, which reduces the overestimation bias on the maximization of the Q value in the loss function.

Finally, since the purpose is to have a reusable environment I dedicate a considerable amount of effort to documenting examples of usage and possible parameters that can be taken into account. I addition, I have created a docker image, allowing the user for greater ease of use of configuration enforcing consistency across different platforms.

Completed Work

• Make the cartpole example to be used with stable-baseline PPO #43 -Merged.
• Create a docker image for deepbot framework, which combine Stable-Baseline and Ray framework #91 - Merged.
• Finalize the khr-3hv environment #49, which
  • Works with Ray and Stable-Baseline PPO,
  • Logging on Wandb website,
  • Having step-by-step documentation,
• Finalize the Nao environment , which
  • Works with Ray and Stable-Baseline PPO,
  • Logging on Wandb website,
  • Having step-by-step documentation,

Enhancements / To be done / Optional

• Keep the same actions on the time frame of 10. Since the simulator is quite fast this might help the policy.
• Use TD3 which has a memory buffer. Then compare the results with the PPO.
• Extend the current API (i.e.,gym.make("CartPole-v1") from OpenAI gym) to allow other users to create new environments easily.
• Work on accumulative learning. Such as train a policy using lots of robots and evaluate it on all of them.
• Work on zero-shot learning. Such as train a policy on one robot and evaluate it on another.

Weekly Update

• 19/05/21 - Initial Meeting

  • Replicate panda example.
  • Initialize the KHR-3HV environment.

• 26/05/21 - Catch up meeting

  • Make the cartpole example to be used with stable-baseline PPO #43 -Merged.
  • Verify cartpole example is compatible with Stable-baselines #43 -Merged.
  • Create a small script that moves the KHR-3HV hands Done.
  • Get the list of all the devices names (i.e head, left arm) on RobotUtil.
  • Have a normalize/denormalize util function on RobotUtil.

• 2/06/21 - Catch up meeting

  • Keep track observations and reward functions file.
  • (Optional) Check webots-gym repo for vectorization and multiple workers.

• 9/06/21 - Catch up meeting

  • Add scale weight on reward for the battery, expirments on file.
  • Add penalty on the reward function on the x-axis, expirments on file.

• 16/06/21 - Catch up meeting

  • Run webots on docker #91 - Merged.

  • Run experiments with different reward functions

    • Mujoco reward,

     reward = min(7, self.robot.getVelocity()[2]) - \
           0.005 * (np.power(self.robot.getVelocity()[2], 2) + np.power(self.robot.getVelocity()[0], 2)) - \
           0.05 *  self.robot.getPosition()[0] - \
           0.02 * np.power(np.linalg.norm(self.robot.getVelocity()),2) + 0.02   

    • Custom reward 1term.

    r = 1.26 * self.robot.getPosition()[2] 

    • Custom reward all terms.

       reward = 1.26 * self.robot.getPosition()[2] - \
               0.02 * np.sum(np.power(self.actuators, 2)) - \
               0.05  *  math.pow(self.robot.getPosition()[0],2)

    • Video reward, the video which illustrate this reward.

      reward = self.robot.getVelocity()[2] + 0.0625 - \
                50 * math.pow(self.robot.getPosition()[1],2) - \
                0.02 * np.sum(np.power(self.actuators, 2)) - \
                3 *  math.pow(self.robot.getPosition()[0],2)

  • Use Ray with Wandb for better logging of experiments #49.

• 07/07/21 - Catch up meeting

  • Check actions output (if there are on the scale of -2.35 to 2.35 on the khr-3hv robot). Note: Both Ray (tanh or relu) and SB output actions in the range of -2.35 to 2.35.
  • Use keyboard wrapper for verification.
  • Change tanh to ReLU on the Ray.
  • Check the Ray with Cuda. Note: it is possible since the Master thread is using GPU for the SGD and slave thread 1 CPU for the environmental interactions. For more CPUs or GPUs there is an error from the environment.

• 14/07/21 - Catch up meeting

  • Initialize Nao
  • Change the MLP to RNN. (Not possible at stable-baseline3 PPO the use of RNN instead of MLP policy)
  • Frame window on states #49.
  • Add the velocity of the robot as a state. Velocity on axis z only #49.
  • Add on reward term: current_pos - prev_pos, khr-3hv, Nao

Many, many thanks to my mentors!

Thank you all for being so willingly giving me your time and guidance throughout our conversation.