Mechatronic strategies for torque control of electric powered screwdrivers

The paper presents the results of a study on using mechatronics to enhance the performance and reliability of small electric powered screwdrivers (SEPS). A mechatronic solution to control the final tightening torque replacing the mechanical clutch of a purely electromechanical SEPS is presented. Torque estimation methods based on motor armature current measurements are integrated with an SEPS driven by a direct current motor. Strategies for controlling the final tightening torque of the screw fastening process are developed. The control strategies are tested in accordance with the ISO 5393 standard. It is shown that the mechatronic controller gives comparable performance to a SEPS with a mechanical clutch. The mechatronic solution has the advantage of reduced cost, size and complexity. The paper demonstrates the application of low-cost mechatronics in industrial power tools.