Proposed EME-185A Mechanical Systems Design Project
Force Actuator System Overview
A brief description of a force actuator project is given here only to provide the necessary
background for the EME-185A project described below. The proposed force actuator
project enables the generation of various resultant forces in two dimensions such as
circular, elliptic, and straight-line forces. An application for the actuator is to balance
undesirable forces that are created on a machine element regardless of the actuators
planar orientation on the machine.
The force actuator consists of the two parallel configurations shown below mounted to a
common frame. Motor assemblies 1 and 2 rotate in opposite directions. Each disc is
fitted with a mass at its outer radius shown as point masses below. Although each of the
two discs per assembly are fitted to their common shaft, their position relative to each
other may be varied. Thus, mass m1 may be positioned from zero to180 degrees relative
to mass m2. As a result, each assembly is capable of generating its own resultant force.
Several means exist to vary the relative angles between the masses on the discs for each
assembly. Investigating and implementing one of these methods is the scope of the
proposed EME-185 design project.
m4
m3
2
discs
motors
m2
m1
1
Proposed EME-185 Design Project
During steady state operation of the force actuator, the relative angle between each
assemblies discs must be maintained, quite possibly for long durations. One method of
doing this while still allowing for relative motion when required is proposed by Professor
Margolis. Discs one and two are to be held in position by fitting each with evenly spaced
magnets. Note that the figure above exaggerates the distance between common-shaft
discs since they will be only narrowly spaced for this magnetic hold design. Although
one disc per assembly will be rigidly fixed or “keyed” to the shaft, the other will be
mounted to the shaft via a bearing, thereby allowing for its rotation about the shaft.
To induce its rotation from one magnetically held position to the next, the following is
proposed. If torque T is the normal running motor torque on the shaft, then let T be
given by T = T + T1 where T1 is an additionally applied torque for a finite time. This
T1 will be accomplished by way of a pulse supplied to the motor. In short, the goal is to
pulse the motor such that temporary torque T will rotate the disc to its next magnetic
position.
Summary of Objectives
Although many possible objectives for the project exist, they can be summarized into two
main categories:
1.) Calculate the magnitude and duration required for torque T to rotate the
disc to one or, possibly, multiple magnetic positions. This can be done
based on a design for the magnetically-held disc pairs which is also
encompassed in this project. Motors and their specifications will tentatively
be supplied.
2.) Demonstrate the designs practicality by building and implementing it.