The figure depicts the exterior appearance of a pistol-grip rotary power tool that can be used to turn a drill bit, wrench socket, screwdriver, or other tool bit clockwise or counterclockwise at a controlled speed or torque. This tool is an updated version of the one described in "Pistol-Grip Torques-Measuring Power Tool" (GSC-13706), NASA Tech Briefs, Vol. 23, No. 7 (July 1999), page 36. Like other tools that it superficially resembles, it contains an electric motor drive powered by either a battery or a power-supply circuit with a standard power-line connection. Unlike other such tools, this tool also contains the following:

  • Torque and temperature sensors;
  • Shaft-rotation pulse-counting and timing circuitry for measuring speed;
  • External controls for setting the mode of operation, the direction of rotation, and the desired value of speed or torque;
  • An onboard computer that generates its own timing signals and monitors and controls the overall operation of the tool;
  • A drive circuit through which the onboard computer controls the electric current applied to the motor;
  • An alphanumeric display for use in programming and monitoring operational parameters;
  • Light-emitting-diode (LED) torque, power-on/off, and fault indicators; and
  • A port for communication between the onboard computer and an external computer.

This Rotary Power Tool superficially resembles other such tools but includes additional circuitry, including an onboard computer, that provides enhanced capabilities for control of speed and torque, detection of faults, and analysis of operation.

In the customary manner, the operator of the tool presses a trigger to put the tool in a running state and releases the trigger to put the tool in an idling state. During operation, the digital outputs of the torque and temperature sensors and of the speed-measuring circuitry are presented to the onboard computer. The software in the onboard computer implements an interrupt-driven state machine for the purposes of monitoring operational parameters, controlling speed or torque, keeping a history of operation, and communicating with the external computer.

The history of operation includes records of two types: (1) data on torque and shaft angle as functions of time during the tightening and/or loosening of fasteners; and (2) records of events (e.g., turn-on of power or overheating). These records are stored in nonvolatile memories in the onboard computer. The onboard and external computers communicate with each other for the purpose of transferring these records so that the external computer can be used to analyze operation and/or to modify operational parameters. Operational parameters can be transferred from the external computer to a nonvolatile memory in the onboard computer; thus, in effect, the external computer can program and remotely control the tool.

This work was done by Kenneth W. Wagner, James C. Taylor, and Paul W. Richards of Goddard Space Flight Center. For further information, access the Technical Support Package (TSP) free on-line at  under the Machinery & Automation category.

This invention has been patented by NASA (U.S. Patent No. 5,903,462). Inquiries concerning nonexclusive or exclusive license for its commercial development should be addressed to

the Patent Counsel
Goddard Space Flight Center; (301) 286-7351.

Refer to GSC-13879.

NASA Tech Briefs Magazine

This article first appeared in the November, 2000 issue of NASA Tech Briefs Magazine.

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