Trajectory Planning And Quasi-static Deformation Compensation Control For Vehicle-mounted Flexible Manipulators

With the rapid progress and development of science and technology, robottechnology has been applied to industrial production widely. However, the developmentof science and technology and the needs of the society also promoted to improve theindustrial robots themselves. From the initial simple industrial robots to the complexintelligent ones, and to today’s automatic intelligent ones which are lighter, fasterresponse and higher precision, they were always in constantly up-grading. In terms ofvehicle-mounted manipulators, the research direction had changed from the rigid ones tothe flexible ones. Compared with the rigid ones, the flexible ones had the advantages oflarger payloads, wider operating range, faster response and longer working life, etc.Therefore, the research and development of vehicle-mounted flexible manipulators wouldbe a trend in the field of vehicle-mounted manipulators.However, at the same time of the vehicle-mounted flexible manipulators were indevelopment, lots of problems were also brought in, such as whether there was deviationbetween the desired target point and the actual one, and the deformation of flexible linkcaused by the lager payloads, and so on. In order to get application in practicalengineering, above-mentioned problems must be solved. In particular, the deformation offlexible link must be compensated when a large payload was transported. The accuracy ofend position would be reduced without compensating the deformation. Therefore, in thiscontext, to propose an effective and reliable scheme for trajectory planning, trajectorycompensation, deformation compensation and system controlling was quite important forits theory and application.In this paper, related researches on trajectory planning, trajectory compensation andflexible deformation compensation had been done aimed at the situation of whether therewas deviation between the desired position target point and the actual one, also with theproblem of flexible deformation caused by a large payload. And the main contents andworks of this paper were as follows:Firstly, the structure of the vehicle-mounted flexible manipulators was described, andthe structural picture of the model was given. According to the given picture, the forwardkinematics model of this system was established by the D-H method. Then, the inversekinematics model was abstained by traditional anti-conversion method. And afterestablishing the kinematics model, the dynamic model of the system was build accordingto Lagrange method and the assumed mode method.Secondly, trajectory planning and trajectory compensation for the case whether therewas deviation between the desired target point and the actual one. In the first place,considering there was no deviation, the whole period of transportation of the system was divided into seven sub-processes, and every sub-process was divided into twosub-processes contained horizontal transportation and vertical lift up and down. Then,trajectory of the horizontal sub-process was planned by quintic polynomial interpolationmethod while trajectory of the vertical sub-process was planned by nine six polynomialinterpolation method. In the second place, considering there was deviation, the jointangles need to be compensated, caused by the position error, could be obtained bycombining forward kinematics equations with variation method, and then the joint anglesafter compensation could be calculated. So, the trajectory after compensation could alsobe obtained.Thirdly, in order to make the flexible link accurately transport the goods to thedesired point, the deformation caused by payload must be compensated. In view of thiscase, an effective elastic deformation compensation method was proposed in this paper,which was called desired joint angles based quasi-static deformation compensation. Firstof all, the deformation of flexible link was calculated according to the assumed modemethod, and then the desired joint angles need to be compensated was also obtained.Moreover, the deformation was compensated respectively for the case of whether therewas deviation. Once more, an observer was designed to estimate the vibration modals andtheir derivatives which were immeasurable. Finally, an observer based sliding modecontroller was designed to track the desired trajectory of the system.Finally, the proposed methods were tested and verified in this paper, and couples ofcomparisons were done: the comparison between the trajectories before compensation andthe ones after compensation, the comparison between the trajectories tracking beforecompensation and the ones after compensation, and the comparison of trajectory trackingamong different payloads. The results shown that the methods of trajectory planning,trajectory compensation and deformation compensation were effective. At last of thispaper, a summary of the paper was given and what would be researched in the future waslisted.