Adjustable Shock Absorber for Oversized Application

Navy SBIR 24.1 - Topic N241-009
NAVAIR - Naval Air Systems Command
Pre-release 11/29/23   Opens to accept proposals 1/03/24   Now Closes 2/21/24 12:00pm ET    [ View Q&A ]

N241-009 TITLE: Adjustable Shock Absorber for Oversized Application

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Sustainment

OBJECTIVE: Develop a large, adjustable shock absorber that can be tuned prior to compression in order to absorb energy and shock that varies in magnitude from one event to the next.

DESCRIPTION: The Navy requires a shock absorber that is larger in size than typical shock absorbers and that can be adjusted/ programmed to a specific setting prior to an event in order to optimize the resistance (i.e., rate of energy absorption for a given velocity and stroke position) given the expected initial conditions. This shock absorber will be required to dampen initial shock impulses and resist forces applied to it by converting kinetic energy to another form (such as heat or electricity) that can be safely dumped to the ambient environment. State-of-the-art shock absorbers are comparatively much smaller in size than required for this application. Prior research in this area of study has primarily focused on the fields of electromagnetism, and materials and fluid sciences, including rheology and tribology. However, innovative solutions leveraging other advances or developing new technologies are also welcome and encouraged. Although non-mechanical adjustment is preferred, the Navy is open to all ideas and will not limit innovation or disqualify a particular class of concepts. Many Navy and commercial applications utilizing relatively smaller shock absorbers and/or hydraulic cylinders would benefit from this technology if successful. The requirements of this shock absorber are as follows:

1. A shock absorber that is larger in size than typical shock absorbers, and that can be adjusted/programmed to a specific setting prior to an event in order to optimize the resistance (i.e., rate of energy absorption) given the expected initial conditions.

2. The shock absorber shall be required to damp initial shock impulses and resist forces applied to it, converting kinetic energy to another form of removable energy.

3. Heat must be released; electricity must be dumped/recovered.

4. The shock absorber design may include typical components, such as a cylinder, piston rod, accumulator, and check valve; or utilize a completely novel design.

5. Non-mechanical settings adjustment is preferred, but not mandatory.

6. Scalability of this technology is a desired objective.

7. The shock absorber shall satisfy all requirements in the military standards for vibration (MIL-STD-167-1A [Type 1]), shock (MIL-DTL-901E [Grade A]), electromagnetic interference (MIL-STD-461G), and environmental factors (MIL-STD-810H).

8. The shock absorber shall be operable in an industrial and marine environment.

9. Shock absorber shall fit within a space of 23 in. by 23 in. by 109 in. (58.42 cm by 58.42 cm by 276.86 cm) compressed.

10. Shock absorber stroke shall be no greater than 9 ft (2.74 m).

11. The shock absorber weight, including supports, shall not exceed 10,500 lb. (4,762.72 kg).

12. The shock absorber connects to a wire rope via multiple sheaves. Due to the nature of the application, the piston rod (or equivalent) will experience a different amount of input force and speed each time it is cycled. The velocity and force of the cable shock absorber shall be predictable in nature for set input loads.

13. The shock absorber shall be adjustable by adjusting the rate of stroke/energy absorption for low, medium, and high energy events (or with greater granularity).

14. The shock absorber shall compress during an event, and then extend to its original position after an event; this application does not call for a shock absorber that oscillates in the positive and negative directions during operation.

15. The shock absorber shall be adjustable to satisfy all specifications of the existing shock absorber operations.

16. The shock absorber shall be controllable/programmable to provide a force from nominally 0 lbf to 250,000 lbf, throughout its stroke and speed range, with a max stroke of 9 ft (2.74 m) and a speed range of 0 ft/s to 40 ft/s (0 m/s to 12.2 m/s), all while maintaining positive tension on the wire rope.

17. The shock absorber shall be controllable/programmable in its return to starting position by providing nominally 0 lb. to 35,000 lb. (0 kg to 15,875.73 kg) of force and 0 ft/s to 5 ft/s (0 m/s to 1.52 m/s).

18. The shock absorber shall provide a resistive force of up to 35,000 lb. (15,875.73 kg) indefinitely while in its starting position.

19. The tunable shock absorber shall have a minimum of 3 settings.

20. It is desirable that the shock absorber is capable of adjusting its setting within 5 seconds; however, if longer times are necessary to adjust the shock absorber setting, the setting shall be constantly maintained throughout repetitive cycles without deliberate adjustment.

21. The shock absorber shall operate within a temperature range of -13F and 149F (-25C and 65C) and withstand a storage temperature range of -27 F and 160 F (-33 C and 71 C).

22. The shock absorber shall provide functionality repeatedly for multiple cycles, at a minimum cycle time of 45 seconds, for 28 consecutive cycles in 21 minutes.

23. The shock absorber will experience cyclic loading so consideration in later phases shall be given to how repeated use will affect performance from a thermal and stress/fatigue standpoint.

24. The shock absorber shall be capable of supporting a cyclic operation sustained rate of 4,200 (Threshold)/5,600 (Objective) total cycles sustained over 30 operating days (12 hrs.).

25. The shock absorber shall be capable of supporting a surge cyclic operation sustained rate of 270 (Threshold)/310 (Objective) total cycles sustained over four (4) (Threshold)/6 (Objective) operating days (24 hrs.).

26. The shock absorber shall be capable of supporting a cyclic operation of at least 500,000 cycles within a 25-yr life without failure in fatigue.

27. The shock absorber shall be capable of monitoring and providing real-time information on the stroke position as well as the conditions of the system (e.g., hydraulic pressure and temperature).

The ability to provide dynamic control throughout the shock absorber stroke is not required.

Innovative solutions leveraging other advances or developing new technologies are also welcome and encouraged.

PHASE I: Design and develop a concept for an adjustable shock absorber that utilizes technologies that will allow it to function at the scale required for this application. Demonstrate feasibility using modeling and simulation, including 3D computer-aided design (CAD), fluid mechanics, stress analysis, control theory, and other appropriate design methodologies. Clearly explain the means by which the shock absorber response is adjusted. Full-scale designs are preferred, even at this preliminary stage, as size is considered one of the primary challenges. Subscale designs are allowable assuming the concept is scalable. A subscale design has value in that it can be used to inform creation of a physical prototype, which will be required in Phase II. If only a subscale design is provided during Phase I, supporting documentation will be required to assess whether the subscale system can be scaled-up effectively to meet requirements. Prepare a Phase II plan that includes prototype development plans.

PHASE II: Design and build a shock absorber prototype based on Phase I work. Prototype design may also include design of a system capable of subjecting the shock absorber to forces that vary in magnitude. Demonstrate the technology by performing preliminary tests that impart characteristic forces on the shock absorber. Utilize sensors and data acquisition to illustrate how the shock absorber absorbs energy/shock, and how the absorption changes when tuned to different settings. Employ iterative design, incorporating changes based on lessons learned during repeated testing. Complete the design, perform final testing, and validate that the concept meets operational needs and will work at scale. Prepare a Phase III commercialization/transition plan that includes construction of a full-scale prototype and verification against requirements.

PHASE III DUAL USE APPLICATIONS: Design, develop, and fabricate a full-scale working adjustable shock absorber based on work completed during earlier phases. Perform final testing at full-scale velocities and forces to validate and verify performance. Demonstrate adjustability by absorbing low, medium, and high energies as described.

Shock absorbers are used in countless mechanical applications in both the private sector and the DoD to attenuate unexpected shocks and in hydraulic and pneumatic mechanical control systems. The most commonly known applications for shock absorbers are in automobiles to prevent excessive bouncing when a vehicle wheel encounters a road hazard or a pothole. With an adjustable shock absorber, a mechanical control system can increase its functional range without being physically replaced, dramatically increasing the functional range of hydraulic and pneumatic control systems.

REFERENCES:

  1. Department of Defense. (2019, January 31). MIL-STD-810H. Department of Defense test method standard: environmental engineering considerations and laboratory tests. http://everyspec.com/MIL-STD/MIL-STD-0800-0899/MIL-STD-810H_55998/
  2. Department of Defense. (2017, June 20). MIL-DTL-901E: Detail specification: Shock tests, H. I. (high-impact) shipboard machinery, equipment, and systems, requirements for. http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-DTL/MIL-DTL-901E_55988/
  3. Department of Defense. (2005, November 2). MIL-STD-167/1A. Department of Defense test method standard: Mechanical vibrations of shipboard equipment (Type I-environmental and Type II-internally excited). http://everyspec.com/MIL-STD/MIL-STD-0100-0299/MIL-STD-167-1A_22418/
  4. Department of Defense. (2015, December 11). MIL-STD-461G: Department of Defense interface standard: Requirements for the control of electromagnetic interference characteristics of subsystems and equipment. http://everyspec.com/MIL-STD/MIL-STD-0300-0499/MIL-STD-461G_53571/

KEYWORDS: Shock Absorbers; Hydraulics; Dampeners; Control Systems; Rheology; Tribology; Electromagnetics


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The DoD issued its Navy 24.1 SBIR Topics pre-release on November 28, 2023 which opens to receive proposals on January 3, 2024, and now closes February 21, (12:00pm ET).

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Topic Q & A

1/12/24  Q. During the return-to-start-position movement noted in #17, is 5 ft/s the maximum speed required, or the maximum speed allowed? 5 ft/s would be a full stroke of <2 sec, which leaves nearly all of the 45 sec cycle time as non-moving time. Would a slower return movement be acceptable, using more of the total cycle time, with a lower maximum speed?
   A. The technology must be able to retract at that speed range; there will be a lot of external equipment moving in that process, so that speed is a hard requirement. The 45 seconds is the required time in between full event cycles. With the existing non-adjustable shock absorber, you are correct in assuming it stays fixed for a period of time between the retract and the next event. In practice, the retracting of the shock absorber is often a little slower than 5 ft/s, and it goes back into place over a few additional seconds. If it took up the full 45 seconds to retract, however, that would not be acceptable; any adjustable shock absorber must be able to withstand a 5 ft/s retract.
1/4/24  Q. 1) Can any more information be provided about the location and end use of this shock absorber?
2) Can the shock absorber make use of external electrical input power? If so, what is the available voltage and current?
3) Can the shock absorber make use of external hydraulic input power? If so, what is the available pressure and flow?
4) Can the shock absorber make use of external pneumatic input power? If so, what is the available pressure and flow?
   A. 1) For the purpose of Phase 1, the exact application is not relevant. As stated, it will need to satisfy all standard mil-specs, as listed in the SBIR call: "The shock absorber shall satisfy all requirements in the military standards for vibration (MIL-STD-167-1A [Type 1]), shock (MIL-DTL-901E [Grade A]), electromagnetic interference (MIL-STD-461G), and environmental factors (MIL-STD-810H)." The ultimate goal is for this to replace an existing non-adjustable cable shock absorber that currently is in use inside of a ship.
2) The specifics of this are not relevant until Phase II. But in a general sense, if a technology needs access to ship power, that will be available in the space. 120V AC is widespread, and should not be a problem if modest amperage is required. If necessary, 440V power is available, but challenges may come up and allocation may need to be implemented if large amperages are required.
3) There are no hydraulic power lines proximate to the desired application.
4) There are sources of pneumatic air up to 5,000 psi onboard the ship, but I cannot answer definitively if it will be available at the location and in what pressures and volumes. An electrically powered self-contained device will, in general, be easier to integrate onto the ship. It is safe to assume that air will be locally available in sufficient enough volumes to store in an accumulator or operate control valves.
12/24/23  Q. Requirement #13 "adjustable by adjusting the rate of stroke/energy absorption for low, medium, and high energy events" :
  1. What range of deviation between L - M - H is the expected performance compared to the total shock absorbing response?, i.e. like on a scale of 1:10 with high being a 10 would medium be comparable to an 8 and low be like a 6 or would it be more like high is a 10 and medium is a 6 and low more like a 2 (meaning does the adjustment selection span cover most of the operating range and strength or a smaller amount?
  2. Are the vernier / small increment tuning adjustments only at one place in each stroke or "on-again - off-again a multiple of times during the stroke?
  3. How much margin of deviation is there in percentage of stroke at begin and end is tolerated as to where precisely in the stroke non-linear evolution must it begin and end?
  4. Am I correct that regardless of H-M-L setting that the Shock Absorbing device must be able to restrain 35,000 lb. when at rest?
  5. Is it correct to assume that the heat conversion from the mechanical energy transfer may be gotten rid of outside the space of 23 in. by 23 in. by 109 in. shock absorber confine area?
   A.
  1. There is no minimum required range; all that is absolutely required is that it can meet the existing performance of the legacy shock absorber we hope to replace. Obviously, the greater the range both lower and higher in damping, the better. In general, we would like to see a shock absorber that can be stroked at 1/10 the force as the legacy shock absorber; this is not an absolute requirement. The option to increase the force per stroke compared to the legacy shock absorber is a lower priority but desirable.
  2. We do NOT want the shock absorber to adjust during a stroke. While the option isn't a problem, for the application we intend, we would like to set the shock absorber to a desired force-vs-velocity, and maintain that setting throughout the stroke. The shock absorber wont be adjusted until it has returned to the original state.
  3. There isnt a hard requirement on this, so long as the performance (force vs speed and position) are well understood. The less it deviates the better, as far as designing the control system is concerned.
  4. "The device shall provide a resistive force of up to 35,000 lbs. indefinitely while in its starting position." That is the maximum; it can be less than that force. In a nutshell, this project is hoping to replace a non-adjustable shock absorber (piston and cylinder), and the 35,000 lbf is the maximum allowable static friction of the shock absorbers seals. If a proposed new technology has less of a static friction, even better.
  5. That size specification is the size of the legacy shock absorber; the heat from reducing the kinetic energy can bleed off into the ambient environment, as that happens on the legacy shock absorber. If you were to install cooling systems or thermal management, and exceed that size envelope, there is a risk it wont fit on the ship

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