## 3 Path Planning and Motion Control
In this kind of robots, the Multitask-based Trajectory-Planning Problem (MTTP) is of utmost importance, as it would enable the robot to perform two or more tasks in each mission, what would suppose a save of energy. The authors use piecewise continuous sine functions to create the trajectories along the waypoints and transform this problem into a parameter optimization, using an improved genetic algorithm to optimize the unknown parameters. Numerical simulations are carried out with a base spacecraft and a 7-degrees of freedom manipulator in two simulation cases, and they prove the efficiency of the approach. Trajectory planning is also a relevant technology for autonomous Unmanned Aerial Vehicles (UAV). [PERSON] et al. [12] propose a flight path planning algorithm to find collision-free, minimum length and flyable paths for such vehicles in three-dimensional urban environments with fixed obstacles, for coverage missions. This problem consists in finding a low cost path that covers the free space of an area of interest with minimum overlapping. The authors address this problem based on a novel footprints' sweeps fitting method. They generate a sparse waypoint graph by connecting footprints' sweeps endpoints considering the obstacles, maneuverability constraints and footprints' sweeps visiting sequence. Simulation results prove the good performance of the algorithm in a variety of scenarios. In the field of movement control of legged mobile robots, [PERSON] et al. [13] aim attention at the problem of energy consumption, as it can be considered a performance index of quadruped robots. In their work, they model and analyze the energy consumption of the robot SCalf with a trot gait, and they study the effect of different gait parameters, such as step length, gait cycle, step height, and duty cycle. The experiments show which is the optimal choice of these relevant parameters, as far as energy consumption is concerned. To this purpose, the authors build the dynamics model of the robot, based on an analysis of the foot force distribution and derive a complete energy model which includes mechanical power and heat rate. Also, they use a foot trajectory based on cubic spline interpolation to describe the motions of the robot. Finally, path planning is also a crucial problem in the field of industrial robotics. The work of [PERSON] et al. [14] concentrates on the field of industrial manipulator robots, more concisely on machining and fabrication applications, among which deburring plays an important role. They develop a hybrid manipulator robot with five degrees of freedom. Also, they propose in the paper a deburring framework focusing on tool path planning (position and orientation) and robotic layered deburring planning; and a process parameter control based on fuzzy logic. A variety of experiments are performed to prove the dexterous manipulation and the orientation reachability of the manipulator and to verify the effectiveness of the two proposed methods in a deburring process. This work was partially supported by the Spanish Government through the project DPI2016-78361-R (AEI/FEDER, UE) and the Generalitat Valenciana through the project AICO/2019/031. This special issue would not have been possible without the valuable contributions of the authors, peer reviewers, and editorial team of Applied Sciences. We give our most sincere thanks to all the authors for their hard work, independently on the final decision about their submitted manuscripts. Also, all our gratitude to the peer reviewers for their help and fruitful feedback to authors. Finally, our warmest thanks to the editorial team for their untiring support and hard work during all the stages of development of this special issue and, in general, congratulations on the great success of the journal Applied Sciences. The authors declare no conflicts of interest.