Whole-body humanoid control from upper-body task specifications
A system, method, and computer program product for generating dynamically feasible whole-body motion of a humanoid robot while realizing specified upper-body task motion are described. A kinematically feasible upper-body motion is generated based on the specified upper-body motion. A series of zero-moment points (ZMP) are computed for the generated motion and used to determine whether such motion is dynamically feasible. If the motion is not dynamically feasible, then the torso acceleration is modified to make the motion dynamically feasible, and otherwise synchronized as needed. A series of modified ZMP is determined based on the modified torso acceleration and used to distribute the resultant net ground reaction force and moment to the two feet.
1. A computer based method comprising:
computing a zero-moment point (ZMP), a net force, and a net moment for a whole body motion of a system including performing a specified upper-body task motion;
determining whether the specified upper-body task motion is dynamically feasible based on the computed ZMP;
responsive to a determination that the specified upper-body task motion is dynamically infeasible,
modifying the ZMP to generate a modified ZMP within a support of the system;
determining a modified net force and a modified net moment based on the modified ZMP, the net force, and the net moment,
wherein the modified net force has a same normal component as the net force, and
wherein the modified net moment has a same moment about a torso origin of the system as the net moment;
determining a bias torso acceleration based on the modified net force;
determining a modified whole body motion based on the bias torso acceleration; and
performing the modified whole body motion to perform the specified upper-body task motion.
2. The method of claim 1 , wherein determining whether the specified upper-body task motion is dynamically feasible comprises:
determining that the ZMP is outside a support base of the system; and
responsive to a determination that at least one of the computed ZMP is outside the support base, determining that the ZMP is outside the support base, determining that the specified upper-body task motion is dynamically infeasible.
3. The method of claim 1 , wherein the system comprises a humanoid robot or a human model, and the body segment comprises a torso.
4. The method of claim 1 , further comprising:
distributing a resultant force to two feet of the system.
5. The method of claim 4 , wherein distributing the resultant force to the two feet of the system comprises:
distributing the resultant force to the two feet such that roll and pitch ankle torques of the system are minimized.
6. The method of claim 1 , further comprising:
synchronizing the modified motion with the specified upper-body task motion within a synchronization period.
7. The method of claim 6 , wherein the synchronization period is determined such that the synchronizing step does not introduce additional significant dynamic effects causing the resulting motion to be dynamically infeasible.
8. The method of claim 6 , wherein synchronizing the modified motion comprises:
synchronizing the modified motion using a bang-bang solution which results in a minimum acceleration required over a synchronization period.
9. A computer based method, the method comprising:
computing a zero-moment point (ZMP), a net force, and a net moment for an original whole body motion of the system including performing a specified upper-body task motion;
modifying the ZMP of the original whole body motion to generate a modified ZMP within a support of the system;
determining a modified net force and a modified net moment for the system based on the modified ZMP, the net force, and the net moment,
wherein the modified net force has a same normal component as the net force, and
wherein the modified net moment has a same moment about a torso origin of the system as the net moment;
determining a bias force for a torso of the system based on the modified net force and the modified net moment;
determining a bias acceleration for the torso based on the determined bias force; and
determining a modified whole body motion of the system based on the determined bias acceleration, the modified whole body motion capable of performing the specified upper-body task motion.
10. The method of claim 9 , wherein the system comprises a human model or a humanoid robot, and said link comprises a torso.
11. The method of claim 9 , wherein the original whole body motion is dynamically infeasible and the modified whole body motion is dynamically feasible.
12. The method of claim 9 , wherein modifying the ZMP of the original whole body motion comprises modifying the ZMP to be inside a support base for the system.
13. The method of claim 12 , wherein the support base comprises a region bounded by one or more links of the system in contact with a support surface that exerts a counterforce.
14. The method of claim 13 , wherein the system comprises a human model or a humanoid robot, the one or more links comprises two feet, the support surface comprises the ground, and the counterforce comprises the ground reaction force.
15. The method of claim 13 , wherein the modified net force has a same normal component as an original net force and a same moment about said link.
16. The method of claim 9 , wherein the system comprises an upper-body connected with a lower-body, the original motion comprises an upper-body motion.