LQR-Assisted Whole-Body Control of a Wheeled Bipedal Robot with Kinematic Loops
This work addresses the challenge of robust locomotion for wheeled bipedal robots in complex environments, representing an incremental improvement in control methods for such systems.
The researchers tackled the problem of controlling a wheeled bipedal robot on rough terrain by developing a hierarchical whole-body controller that incorporates full rigid body dynamics and kinematic loops. The result was a computationally lightweight controller that significantly extended the robot's rough-terrain capabilities and robustness, as demonstrated in experiments.
We present a hierarchical whole-body controller leveraging the full rigid body dynamics of the wheeled bipedal robot Ascento. We derive closed-form expressions for the dynamics of its kinematic loops in a way that readily generalizes to more complex systems. The rolling constraint is incorporated using a compact analytic solution based on rotation matrices. The non-minimum phase balancing dynamics are accounted for by including a linear-quadratic regulator as a motion task. Robustness when driving curves is increased by regulating the lean angle as a function of the zero-moment point. The proposed controller is computationally lightweight and significantly extends the rough-terrain capabilities and robustness of the system, as we demonstrate in several experiments.