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Shakerpresentation

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Denis Vasilescu

The document describes a 3 degree of freedom vibration test platform being developed at Northern Illinois University. It addresses vibrating commonly causes discomfort or damage and how existing vibration testing platforms are bulky and expensive. The design uses non-orthogonal axes, is lean, has a large load capacity, and an on-board control system. It details the mechanical design process, including CAD modeling, simulation showing it is structurally sound. The design controls actuators with an H-bridge and has been functionally tested though simultaneously running all 3 actuators has resulted in broken parts.

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Vibration Test Platform Northern Illinois University Department of Engineering and Engineering Technology Anthony Smith Denis Vasilescu
Overview ? What is the problem we¡¯re addressing? ? What solutions already exist? ? What are we doing different? ? What¡¯s the marketability of our design? ? What have we accomplished so far?
What's the problem at hand? ? Vibrations are everywhere, and can create effects ranging from discomfort to physical illness, or even structural damage and wear. ? Vibration control systems need to be tested to make sure they work ? Specifically targeted for AVCS developed through EE grad program, which requires 1-10Hz range with minimum of 0.2g's of acceleration
What solutions are out there? ? Vibration testing platforms ¡°shaker tables¡± have a well established market and development ? Most are 1 DOF ? Have difficulty going below 10Hz ? Are very bulky ? Cost in the tens of thousands $ ? Multi-DOF cost more and take a great deal of space ? Requires DAQ board to interface with PC through software
What are we doing different? ? 3 DOF using nonorthogonal axes ? Lean frame ? Large load capacity (1500 lbs) ? On-board control system
The Mechanical Design Process
CAD Modeling ? Design using Pro/Engineer Wildfire ? Model each part as best as possible
The joints
Joint DOF
Simulation ? The CAD model was simulated in Ansys WorkBench for load and resonance ? Conclusions: Structurally sound design ? Validity of simulation based on accuracy of modeling
Completed Frame
Controlling the actuators ? Nonlinear transfer function of actuator requires use of PWM
H-bridge motor control ?You can think of an H- bridge as 4 switches directing current in a system ?Using different pairs of the switches we are able to have more control over than motor than typical systems ?Replacing these switches with MOSFET¡¯s or (Metal- Oxide Semiconductor Field- Effect Transistors) we can begin to see the true form of the H-bridge.
Design Issues ? MOSFET¡¯s need to be turned on with a +12V from gate to source thus requiring external circuitry or driver IC to switch them properly. ? Actuators being used are very high power and create many possible problems on the FET¡¯s unless circuit protection is in place. ? It can also be very difficult to switch direction on motors as large as needed at a rate that will be acceptable for the design.
Completed Design
Budget Analysis ? A rough estimate of the cost including cost of labor is in the range of $10,000 ? This cost keeps the design close to existing Shaker Tables on the market. ? Some of our budget came from a $2500 USOAR grant received in the Spring of 2006. ? Special thanks to Danaher Motion for donating many of the parts needed for the frame and taking the time to help us out when we ran into problems
Functional Testing ? H-bridge driver system has been fully tested and design said to be complete ? PIC code can produce basic PWM, but not PWM-encoded harmonic motion ? Current system can run each of the 3 actuators and have been tested, although in attempts to run all three in one system all attempts have resulted in a changing of broken parts ? Based on crude estimates, the motion meets the design specifications based on ? a = -¦Ø^2*x

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Shakerpresentation

  • 1. Vibration Test Platform Northern Illinois University Department of Engineering and Engineering Technology Anthony Smith Denis Vasilescu
  • 2. Overview ? What is the problem we¡¯re addressing? ? What solutions already exist? ? What are we doing different? ? What¡¯s the marketability of our design? ? What have we accomplished so far?
  • 3. What's the problem at hand? ? Vibrations are everywhere, and can create effects ranging from discomfort to physical illness, or even structural damage and wear. ? Vibration control systems need to be tested to make sure they work ? Specifically targeted for AVCS developed through EE grad program, which requires 1-10Hz range with minimum of 0.2g's of acceleration
  • 4. What solutions are out there? ? Vibration testing platforms ¡°shaker tables¡± have a well established market and development ? Most are 1 DOF ? Have difficulty going below 10Hz ? Are very bulky ? Cost in the tens of thousands $ ? Multi-DOF cost more and take a great deal of space ? Requires DAQ board to interface with PC through software
  • 5. What are we doing different? ? 3 DOF using nonorthogonal axes ? Lean frame ? Large load capacity (1500 lbs) ? On-board control system
  • 7. CAD Modeling ? Design using Pro/Engineer Wildfire ? Model each part as best as possible
  • 10. Simulation ? The CAD model was simulated in Ansys WorkBench for load and resonance ? Conclusions: Structurally sound design ? Validity of simulation based on accuracy of modeling
  • 12. Controlling the actuators ? Nonlinear transfer function of actuator requires use of PWM
  • 13. H-bridge motor control ?You can think of an H- bridge as 4 switches directing current in a system ?Using different pairs of the switches we are able to have more control over than motor than typical systems ?Replacing these switches with MOSFET¡¯s or (Metal- Oxide Semiconductor Field- Effect Transistors) we can begin to see the true form of the H-bridge.
  • 14. Design Issues ? MOSFET¡¯s need to be turned on with a +12V from gate to source thus requiring external circuitry or driver IC to switch them properly. ? Actuators being used are very high power and create many possible problems on the FET¡¯s unless circuit protection is in place. ? It can also be very difficult to switch direction on motors as large as needed at a rate that will be acceptable for the design.
  • 16. Budget Analysis ? A rough estimate of the cost including cost of labor is in the range of $10,000 ? This cost keeps the design close to existing Shaker Tables on the market. ? Some of our budget came from a $2500 USOAR grant received in the Spring of 2006. ? Special thanks to Danaher Motion for donating many of the parts needed for the frame and taking the time to help us out when we ran into problems
  • 17. Functional Testing ? H-bridge driver system has been fully tested and design said to be complete ? PIC code can produce basic PWM, but not PWM-encoded harmonic motion ? Current system can run each of the 3 actuators and have been tested, although in attempts to run all three in one system all attempts have resulted in a changing of broken parts ? Based on crude estimates, the motion meets the design specifications based on ? a = -¦Ø^2*x