Design and Implementation of Torque Control and Estimation for an Electric Hand-Tool

This paper proposes the design and implementation of torque control and torque estimation for an electric hand-tool. This hand-tool does not require any torque transducer or any Hall-effect sensor. Only some low-cost resistances are used to measure the stator currents of a brushless DC motor, which is used to drive the hand-tool. Novel 3-phase current commands are proposed here to obtain greater torque than traditional 3-phase, square-wave current commands. The output torque of the hand-tool can be estimated and displayed by an LED display. A PI controller is used to achieve the current-loop control. A digital signal processor, TMS-320-F2808 that was manufactured by Texas Instruments, is used to execute the control and estimation algorithms. Experimental results show the correctness and feasibility of the proposed methods.