  With the potential applications of capsule robots in medical endoscopy,
accurate dynamic control of the capsule robot is becoming more and more
important. In the scale of a capsule robot, the friction between capsule and
the environment plays an essential role in the dynamic model, which is usually
difficult to model beforehand. In the paper, a tethered capsule robot system
driven by a robot manipulator is built, where a strong magnetic Halbach array
is mounted on the robot's end-effector to adjust the state of the capsule. To
increase the control accuracy, the friction between capsule and the environment
is learned with demonstrated trajectories. With the learned friction model,
experimental results demonstrate an improvement of 5.6% in terms of tracking
error.
