Correction Scheme for Tool Point Velocity Control of a Flexible Hydraulically Actuated Manipulator

M.K. Ebbesen and M.R. Hansen (Norway)


Path generation, compensation, optimization, flexibility.


In the current paper tool point control of hydraulically actuated manipulators is investigated. The considered application is a mobile loader crane. It is modeled as a planar mechanism with three degrees of freedom. In previous work a path planner has been developed that handles the redundancy by means of power consumption minimization while observing the different saturation phenomena associated with hydraulic actuation of mobile machinery. In this way a reference velocity is continuously computed and served to the controller that determines the optimal cylinder actuation. However, since one of the main competition parameters for mobile loader cranes is low weight it is clear that the deflection of the tool point caused by structural flexibility is something that cannot be ignored. In this paper this problem is handled by adding a correction procedure to the path planner that effectively reduces the trajectory error. The method utilizes only two of the three degrees of freedom and emphasis is on vertical adjustment and the simulation results show highly encouraging results. The method calls for increased instrumentation in the shape of strain gauge measurements at a number of strategic points on the structure.

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