Development of an Alternative Approach for Estimating User Load due to Screw-in Torque in User Studies

The proposed approach aims to estimate the screw-in torque load by utilizing the battery current of a cordless screwdriver. This approach is particularly designed for user studies involving cordless screwdrivers, enabling accurate estimation of user loads. By measuring battery current and establishing the correlation between battery current and screw-in torque, user load can be estimated effectively. The experimental setup includes a two-degree-of-freedom testbench, allowing a fixation of the cordless screwdriver and restricting its movement. The screwdriver is mounted on the screwdriver collar and attached to a slide mechanism for linear movement along the drilling axis and rotational movement around the axis. Data from ten consecutive screw-in processes were collected, including measurements of screw-in torque, screw-in depth, and battery current. It was observed that torque varied across different sections of the screw-in process, with an increase in torque as the screw is screwed deeper into the wood. While certain limitations exist, such as the constant push force applied during experiments and specific conditions, the proposed approach presents a practical solution for estimating screw-in torque in manual tasks and accurately assessing user load in user studies.