Example of Energy Analysis in
Machine Design
Problem Definition and Overview of Analysis
The objective of this analysis is to determine the feasibility
and method for lifting the hammer shown below. The hammer is to be rotated
about a pivot from an initial position to a desired final upright position as
shown in the figure. The energy for raising the hammer is to be provided from a
given DC brush motor. The analysis first determines how much energy and power
the motor needs to raise the hammer within the specified time limit. A separate
analysis will be needed to determine an appropriate gear ratio between the
motor and the arm necessary to accomplish the task.
Energy and Power Need Analysis
The objective of this analysis is to provide a rough
estimate of the energy source requirements. This rough analysis will be useful
for selecting what is a viable energy source for this component.
The energy required to lift the hammer into the upright
position is equal to the change in potential energy:
The amount of energy needed from a motor must include the
factor of safety:
The power required to lift the hammer within the specified
time limit is given by:
Conclusion
The energy analysis provided
the means for determining the energy requirement for raising the hammer. It was determined that a motor that is
capable of producing approximately 0.196 W of power is needed to overcome the
change in potential energy in the desired 20 second span. It is important to note that meeting
energy and power needs is a necessary condition, but not a sufficient
condition. An actual torque analysis will be required at a later stage to
determine if a gear reduction or other mechanical advantage is needed. |