Ensemble Control of a 2-DOF Parallel Link Arm in a Capsule Robot Using Oscillating External Magnetic Fields

Providing oral capsule robots with additional degrees of freedom (DOF), such as robotic arms, is crucial for enhancing their functionality within the body. However, a key challenge arises when using rotating magnetic fields to drive the motor within the robot, as the resulting torque causes the entire capsule to rotate. In this work, we propose a novel approach to actuate a 2 DOF parallel link robot arm integrated into a capsule robot, using external magnetic fields. Our method employs two identical magnetic motors we proposed in a previous study, each driven by an oscillating magnetic field, which alternates direction along a specific axis. By independently controlling the rotation of each motor through the same magnetic field, ensemble control is achieved. The symmetrically arranged motors exhibit different angular velocities, enabling dexterous movement of the robot arm. We further theoretically show that this approach significantly reduces the torque exerted on the robot compared to traditional approaches using rotating magnetic fields. Finally, we demonstrate the performance of the robot by moving its arms and the attached end-effector along a pre-defined trajectory.