Residual RL--MPC for Robust Microrobotic Cell Pushing Under Time-Varying Flow
This work provides an incremental improvement in robust microrobotic cell pushing for researchers and engineers working with microfluidic systems.
This paper addresses the challenge of contact-rich micromanipulation in microfluidic flow by developing a hybrid controller for a magnetic rolling microrobot pushing cells. The controller, combining MPC with a SAC-trained residual policy, improves robustness and tracking accuracy over pure MPC and PID under nonstationary flow, and generalizes to unseen trajectories.
Contact-rich micromanipulation in microfluidic flow is challenging because small disturbances can break pushing contact and induce large lateral drift. We study planar cell pushing with a magnetic rolling microrobot that tracks a waypoint-sampled reference curve under time-varying Poiseuille flow. We propose a hybrid controller that augments a nominal MPC with a learned residual policy trained by SAC. The policy outputs a bounded 2D velocity correction that is contact-gated, so residual actions are applied only during robot--cell contact, preserving reliable approach behavior and stabilizing learning. All methods share the same actuation interface and speed envelope for fair comparisons. Experiments show improved robustness and tracking accuracy over pure MPC and PID under nonstationary flow, with generalization from a clover training curve to unseen circle and square trajectories. A residual-bound sweep identifies an intermediate correction limit as the best trade-off, which we use in all benchmarks.