Multi-physics Modelling of a Compliant Humanoid Robot

In this paper, we discuss some very important features for getting exploitable simulation results for multibody systems, relying on the example of a humanoid robot. First, we provide a comparison of simulation speed and accuracy for kinematics modeling relying on relative vs. absolute coor- dinates. This choice is particularly critical for mechanisms with long serial chains (e.g. legs and arms). Compliance in the robot actuation chain is also critical to enhance the robot safety and en- ergy efficiency, but makes the simulator more sensitive to modeling errors. Therefore, our second contribution is to derive the full electro-mechanical model of the inner dynamics of the compliant actuators embedded in our robot. Finally, we report our reasoning for choosing an appropriate contact library. The recommended solution is to couple our simulator with an open-source contact library offering both accurate and fast full-body contact modeling

Robotran-Yarp interface: a framework for real-time controller development based on multibody dynamics simulation

Multibody dynamics simulation is widely used for testing and prototyping controllers. However, the transfer of controllers initially developed in simulation to real mechatronics platforms, requires modifications of the code in order to interface with sensors and actuators. Because of this coupling with the hardware, the controller re-usability is severely impacted. In this work, we solve this issue by adding a middleware between the controller and the controlled platform (real or simulated). This framework decouples the controller from the hardware which allows fast controller development and eases collaborations on large scale projects. Moreover, it is then possible to simultaneously control the real and the simulated robot from a unique controller. This paper presents the interface of the Robotran multibody dynamics simulator with the YARP middleware. This framework is illustrated with applications on the COMAN and WALK-MAN humanoids robots