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Features

• Highly and easily configurable:

  • Mechanical flexibility and motor inertia modelling
  • Sensor noise, jitter and delay modelling
  • Support external forces on frames (both impulse or via time-continuous callback)
  • Support user-defined internal dynamics
  • Support both finite time and time-continuous update period for each sensor and the controller independently
  • Model uncertainties regarding the kinematics and dynamics properties
  • User-defined ground profile using an implicit function: f(x,y) = [z, vect_normal]

• Deterministic or non deterministic on demand but still PERFECTLY REPEATABLE

• Designed for fast and efficient optimal control research :

  • Support step-by-step (optimized for performance) or one-shot simulation
  • Fully wrapped in Python. Designed for (almost) never have to recompile C++.
  • Add variables to the logger on-the-fly without compiling
    • Useful to debugging and dynamic plots updated over time (not implemented so far)

• Fast Python Interface:

  • C++ / Python shared pointer to avoid boost converts back-and-forth

• Very fast:

  • No real-time reading/writing on hard drive (only in CPU cache then RAM)
    • The log can be exported in CSV or binary on demand afterwards
  • No real-time display by default
    • A Python class offering this functionality is available
  • Cartpole: 20ms for 1000 integration steps, corresponding to about 3s of simulation

• Highly parallelizable:

  • Thread safe (single process - single core)
  • Synchronous by default (a Python class offering asynchronous controller update is available)
  • No shared memory

• Well-suited for Reinforcement Learning:

  • Fully compatible with Gym OpenAI and any libraries built on top of it

Drawbacks

• Support only multiple point contact with the ground applied on frame
  • Collision with vertical surface is impossible
    • The simulation will fail if it happens
  • No modelling of internal collisions contrary to Gazebo, ie for rotary joints
  • No collision between links

Development status

• Open-source Jiminy core: stable
• Open-source Gym/Jiminy interface: stable
• Mock of a High-Level Controller: none
• Modelling still to be improved:
  • Only "perfect" sensor data with noise/delay/jitter is available
    • No complementary filter for IMUs, no voltage to force converter for Force sensors...
  • Only "perfect" torque motor control:
    • No voltage-current to torque-velocity conversion. No response time.
• Error handling could be improved
  • Old-fashioned message + return code