Minimum-Time Trajectory Planning of a Dual-Manipulator CT System With Synchronization and Task Constraints

In industrial and clinical applications, CT scanning is expected to be as fast as possible to improve the scanning efficiency in industrial CT or to reduce the radiation dose to patients in clinical CT. However, the kinematic constraints of the dual manipulators pose limits on shortening the scanning time. In addition, the X-ray tube and detector mounted on the end-effectors of the dual manipulators must be precisely aligned during the scanning motion, which imposes the synchronization motion constraint on the dual manipulators. In this letter, considering the kinematic constraints (velocity and acceleration constraints) in the task space of dual manipulators and the synchronization motion constraint, we propose a minimum-time trajectory planning algorithm for a dual robotic manipulator CT system. Specifically, the CT scanning paths of both the X-ray tube and detector are formulated as a parametric form. Then, a novel unified bound estimator is proposed to convert the task constraint and synchronization constraint into the parametric constraints. Finally, the minimum-time trajectory planning issue of the dual manipulators is solved in real time by a nonlinear filter in the parameter space. Comparative experiments are conducted on two UR20 manipulators. The experimental results confirm that the planned trajectories by the proposed approach are time-optimal and satisfy all the task and synchronization motion constraints as well.