  Aiming to mimic the brachiation locomotion of primates, we establish a
brachiation robot model capable of swinging between different bars. The robot's
design is based on a four-link underactuated structure. We propose an offline
trajectory generator with optimization for minimizing energy consumption, which
is implemented by direct collocation method to generate joint-space
trajectories. We also propose a linear Model Predictive Control (MPC) algorithm
as the feedback controller. The proposed MPC concurrently tracks both
trajectories in joint space and Cartesian space. In simulation experiments, we
analyzed the influence of lower-to-upper arm length ratio and swing time on the
motion performance. The simulation results also demonstrate the robot has
satisfied ability in trajectory tracking, obstacle avoidance and robustness.
