Reduced-Dimensional Whole-Body Control Based on Model Simplification for Bipedal Robots With Parallel Mechanisms

The presence of parallel mechanisms in bipedal robots increases the complexity of modeling and control, making it crucial to manage the trade-off between model accuracy and real-time control. In this letter, we propose a reduced-dimensional whole-body controller for series-parallel bipedal robots, utilizing a floating-base multi-rigid body model with kinematic loops. Notably, we neglect the joint acceleration and closed-loop acceleration constraints of the parallel mechanisms, reducing the dimensionality of variables and constraints in the whole-body optimization problem while ensuring compliance with actuated joint torque limits. Quantitative experiments indicate that, compared to the complete series-parallel model, the impact of inertial forces resulting from the parallel joint acceleration is negligible. Additionally, physical locomotion and disturbance tests demonstrate that our proposed controller can enhance computational efficiency by over 20%, with comparable locomotion performance and disturbance rejection ability.