SIMPLE ARCHTECTURE FOR A MANUAL AND SERVO ASSISTED, HYBRID SYSTEM FOR POSITION CONTROL IN MACHINE TOOLS

The objective of this work is the proposal of a new strategy for controlling the position of a cutting tool relative to a machined part. This works starts with the comparison between manual machine tools and the numerically controefled (NC) machine tools. Despite the high eficciency in terms of accuracy and speed, NC machine requires a considerable time to preparing it, i.e., it requires time for generating the cutting path and then, programming the machine, by using specif programming codes. Besides, the prepared program must be debuged. On the other hand, manual conventional machine tool, although having an elevate flexibility - it does not require programming, has low efficiency, compared with NC machines, since fine positionings must be executed manually, by moving handles carefully. The final goal of this work is the development of a machine tool that has a characteristic intermediate between a NC machine and a manual machine tool, i.e., a machine in which, the motion of the cutting tool is defined by the human operator and a servo system helps the operator to reach the desired positioning faster. For this goal, this work presents a positioning strategy composed of: a) a manually driven sliding table, b) a position sensor that monitores the table position, c) a magnetic brake that locks the handle when the table reaches the desired position and d) a computer that executes the control algorith. The control strategy is presented considering a motion in only one direction. A prototype is developed and constructed. By positioning tests, the effectiveness of the strategy is demonstrated. The system enables a fast and precise positioning of the table, with the operator driving the table through handles. Comparison with completely manual positioning shows that by the proposed strategy, a faster positioning is possible.