1. ATK Deployment Damper Concept
Acknowledgments
Special thanks to: John Durkee, Professor Paden, Professor
Theogarajan, Trevor Marks, Greg Dahlen, Casey Hare, Kirk
Fields, Dave Bothman, and Stephen Chen
Wyatt Rodgers, Thomas Rode, Holden Tamchin, Michael Deas, Casey Duncan
Abstract
ATK desired a novel damper design that could improve on the
linear torque-speed relationship provided by dampers today.
The goal of this project was to create a novel damping method
that resulted in a constant velocity over a range of input torques.
Multiple design concepts were considered, prototyped, and
modeled. The chosen concept was tested and compared to the
predicted performance provided by the modeling. The results of
the testing indicate that the damper concept has the potential to
provide much improved performance over dampers commonly
used in the aerospace industry today.
Modelling
The described system and SMC approach were simulated
using MATLab and Simulink with the following block diagram,
shown below in Figure 4. An accurate Simulink model is an
extremely powerful tool in optimizing the damper performance.
Physical parameters including impedances, friction, controller
speed, and motor constants can all be changed and simulated
to view their effect on damper performance. The Simulink
modeling provides the theoretical damper behavior which we
would later compare to the testing results.
Figure 1. Desired Damper Behavior
Figure 3. Proposed Ultimate Design Rendering
Figure 4. Simulink Model of SMC Damper System
Prototype Testing and Results
We built a testing mount to measure the torque-speed
relationship of the damper. A drive motor supplied an input
torque and rotation to the damper and the data was recorded
with LabVIEW. We tested the dampers at multiple control
speeds. Using the test data, we proved that our concept was a
viable method of damper control. We compared the raw data to
data from our Simulink model to prove that it accurately
predicted the damper performance. The graph in Figure 5
shows the Simulink data in blue and the raw data overlaid in
red.
Figure 5. Testing Setup and Results
Recommendations for Future Work
Our work has provided reason to believe that a better damper
can be designed using Sliding Mode Control with a DC motor
to provide a vertical torque speed relationship. Through our
testing, we proved that the Simulink model is an accurate
representation. From the modeling, we can determine the
required design parameters for a desired function. The key
design relationship of the system is given by the equation
∆𝝎 =
𝑲 𝒎
𝟐
𝑱𝑹
𝝎 𝒅𝒆𝒔∆𝒕.
For best behavior, this change in speed should be minimized.
Known values for Km and R can be cataloged from DC motor
suppliers to create a design space that, along with knowing the
limitation of the control system response time ∆𝒕, shows the
possible applications for this type of system. The concept of
using Sliding Mode Control to achieve an almost perfectly
vertical torque speed relationship has been confirmed through
the simulation.
Proposed Design Concept
The design concept was limited by not allowing fluid or friction
based dampers. We chose to explore the use of a DC motor as a
means of damping. When the leads of a DC motor are shorted,
the EMF generated by the spinning system provides a torque
that resists the motion of the motor. A DC motor has a linear
torque-speed relationship when ‘shorted’, and very little
damping when ‘open’. The region shown in figure 2a shows the
range of torques that a DC motor is capable of producing over a
range of speeds, by manipulating the resistance between the
leads. We explored the use of Sliding Mode Control (SMC) in
order to achieve constant speed over a range of torques. Figure
2b shows the theoretical torque-speed relationship that can be
achieved using SMC.
Figure 2. DC Motor Performance and SMC Concept
ME189 Team 2 June 6, 2014