Experimental results of using a linear step motor as a programmablespring

摘要

It is demonstrated experimentally that a variable-reluctancelinear step motor can be controlled as a programmable spring with aspring constant of dynamic range 2000 to 1 for robot applications. Thislarge dynamic range is mainly attributed to the direct-drive use of thisvariable-reluctance linear step motor. Using direct drive provides ahigh ratio of output force to friction because of the lack ofcommutation brushes and a reduction gear. The large dynamic range ofachievable spring constants also demonstrates that a very simpleelectronic commutation-logic feedback can simplify a statically anddynamically complex variable-reluctance step motor to the point that itcan be algebraically linearized. For a large operating range in force,velocity, and frequency, this linearized model can be approximated by asecond-order ordinary differential equation; i.e. the force on a massgiven by Newton's second law with the addition of a small friction force