Modelling and Control Design for a Hydraulic Forestry Crane

In the industry of forestry cranes, the design of automated machines that improve productivity has been a challenge for many researchers and engineers in the field of Control Systems and Robotics. An appropriate control design requires a detailed knowledge of the physical phenomena involved in the real system. At this point it is needed to perform simulation tests more rapid than experimental ones. In order to run those simulations, a model of the real machine is required. In this project the MATLAB/Simulink package for both modelling and simulation has been used. Basic mathematical models of components involved in the system as well as the final block diagrams are presented in this report. In heavy-duty machinery, friction may reduce the performance significantly and negative side effects such as tracking errors, large settling times or limit cycles are usually introduced. In todays high-performance motion systems such effects have to be taken into account in the control design in order to gain accuracy. For this reason certain types of tests must be performed to understand and interpret the friction phenomena hidden in the system. The identification of friction parameters based on experiments is explained in this report and a corresponding model for the system is presented. The derived control system is based on an empirical tuned PID controller with an additional feedforward term for friction compensation. Generally, friction models require the velocity as input. Due to the fact that only positions are measured, an elaborate estimation algorithm is proposed. As result of this report, two examples of an autonomous motion are presented and an outlook on further improvements is given. A comparison of the derived simulation model with the behaviour of the real machine is also shown.