On The Trajectory Planning And Trajectory Tracking Control Of Free-floating Space Robot

As the technology keeps developing, people is going further and further inexploring the outer space. Aiming at reduce cost, improve efficiency, and guardant theastronauts’ safety, different morphological and functional space robot had beenemployed in performing space tasks independently or as an assistant of astronauts.Owning to its miniaturized figure, lower cost, highly intelligent, and the ability to movefreely, the free-floating space robot is playing an important role in on-orbit servicing.Since working under microgravity circumstance in outer space, the dynamics of FFSRis different from that of fixed robot on earth. For the purpose of fulfill complete spacemissions such as assembling, maintenance, and capturing, It is necessary for us toanalyze in depth trajectory planning and motion control algorithms which are adaptiveto FFSR’s unique dynamic characteristics.Based on the analyzing of FFSR’s kinetics and dynamics, this paper put its pointon the nonholonomic trajectory planning algorithm and neural network adaptivetrajectory controller design. This paper includes:Introduced new conception of augment vector and expanded manipulator to themodeling of FFSR, and derived the corresponding kinetic function and dynamicfunction in the joint space, then analyzed FFSR’s unique motion characteristics,dynamic singularity, and work space of the end effecter of the manipulator.Giving to the non-integral conservation of moment of momentum function,dynamic singularity arose in FFSR and increased the difficulty of trajectory planning.In this paper, taking into account the dynamic singularity problem, kinetic function ofthe space robot system is transferred into a new space. With the boundary constraintsand system’s initial/final position and orientation, we could find coefficients of thepolynomials, and hence get the target trajectory. Under inverse coordinatetransformation, target trajectory is transferred back into the joint space.While FFSR is performing its space missions, there exist some dynamicparameters which are unable to be accurately determined. To tackle this issue, anadaptive controller is designed in this paper. First dynamic function under Cartesian space is derived, and adaptive parameter estimation algorithm and controller aredesigned. Moreover, in order to guaranty the end effecter could track the targettrajectory accurately, a feed-forward loop based on radial basis function neural networkis employed for supervise control.