Path-constrained Trajectory Planning and Time-independent Motion Control: Application to a Forestry Crane

In this paper we consider the problem of motion planning and control of a kinematically redundant manipulator which is used on forestry machines for logging. Once a desired path is specified in the 3D world frame, a trajectory can be planned and executed such that all joints are synchronized and path-constrained. A speed profile can be chosen according to particular costs (time, fuel consumption, etc.) and certain constraints of the mechanical construction and dynamics. We suggest a time-independent control scheme for the planned trajectory which is built upon the standard reference tracking controllers. Experimental tests underline the benefits and efficiency of the model-based trajectory planning and show success of the proposed control strategy.