Kinematic analysis of connection of hydraulic cylinders of a forwarder crane under execution of defined motion of grapple

The article deals with the kinematic analysis of forwarder crane; it determines the parameters of extension of hydraulic-cylinder rods for execution of defined trajectory of grapple motion. The current systems of forwarder crane control do not allow an operator to realize optimal trajectories and speed ability of motion of crane links. This disadvantage can be partly corrected, for example, with the use of automatic control of crane motion in certain phases of technological cycle. The analysis of matched connection of hydraulic cylinders of a typical forwarder crane is presented in the article. It determines how hydraulic-cylinder rods should move to provide the linear trajectory of grapple at the stage of motion from the moment of log gripping to the moment of its lodging in the middle of upper edge of a forwarder load space. It is necessary to provide a smooth acceleration at the start and a smooth deceleration at the end of grapple motion. The hydraulic-cylinder rods should also smoothly accelerate at the start of motion and smoothly decelerate at its end. The kinematic analysis uses well-known methods that are presented in the article in shortened form. It is shown that for typical design of a forwarder crane both conditions of smooth motion and linearity of trajectory cannot be fulfilled simultaneously. The results can be used for developing the algorithms of automatic control of crane at a separate phase of log loading when there are numerous points of log gripping (gripping control provided by operator) and one delivery point. There is no necessity in additional systems of environmental objects recognition at this phase, that allows to integrate these algorithms into the control system of a forwarder by low-cost facilities.

crane, forwarder, kinematic analysis, hydraulic cylinder