Contact-stability areas and volumes are conditions used to prevent contacts from slipping or detaching during motion. The examples in the contact_stability folder illustrate these conditions: static-equilibrium COM polygon, multi-contact ZMP support areas, etc.
In these examples, you can move contacts by selecting them in the OpenRAVE GUI. Contact wrenches are computed at each contact to support the robot in static-equilibrium. Try moving the blue box (in the plane above the robot) around, and see what happens when it exits the polygon.
In this example, we make the JVRC-1 model walk forward on a flat horizontal floor. The COM trajectory is generated on the fly by linear model predictive control.
This examples illustrates the tutorial Prototyping a walking pattern generator. The concepts it introduces are the same as those implemented in a full-fledged walking controller applied for walking and stair climbing with the HRP-4 humanoid.
The inverse_kinematics.py script shows how to use
inverse kinematics (IK)
to achieve a set of whole-body tasks. It contains two equivalent
implementations of the IK solver setup. The former is best for beginners as it
uses the simpler Stance interface. The latter is for more advanced users
and shows how to add individual tasks one by one.
The example loads the JVRC-1 humanoid model, then generates a posture where the robot has both feet on pre-defined contact locations. The robot tracks a reference COM position given by the red box, which you can move around directly by using the interaction mode of the OpenRAVE GUI.
This example implements a basic stabilizer for the inverted pendulum model based on proportional feedback of the divergent component of motion.
Balancing is the action of constantly compensating undesired motions of the center of mass by regulating interaction forces with the environment. The core question is: what forces should be applied in response to an undesired center of mass motion? This example illustrates the solution based on feedback of the 3D DCM which is both efficient and simple to implement.
In this example, we make the JVRC-1 model walk accross a circular staircase where all contacts are tilted.
The environment is generated so as to make the locomotion task difficult. We solve it using a multi-contact linear MPC where the formulation is kept linear thanks to the pendular COM acceleration cone.
This script comes with the research paper Biped Stabilization by Linear Feedback of the Variable-Height Inverted Pendulum Model. It compares two stabilizers for the inverted pendulum model. The first one (baseline) is based on proportional feedback of the 3D DCM. The second one (proposed) performs proportional feedback of a 4D DCM of the same model; see the paper for details.