Evaluate Levitation Mechanism

Select appropriate levitation mechanism → define reqs, screen hard constraints, score survivors soft, document reproducible trade study.

Use When

• Choose approach new product/experiment
• Compare magnetic/acoustic/aerodynamic/electrostatic for contactless handling
• Justify design in review/proposal
• Re-evaluate existing when reqs change (new payload, env, cost)
• Feasibility study before detailed design

In

• Required: Application (what levitated, why contactless)
• Required: Payload (mass, material, geometry, temp sensitivity)
• Required: Env (temp, atmosphere, cleanliness, vibration)
• Optional: Power budget (W)
• Optional: Cost target (prototype + prod)
• Optional: Precision (position accuracy, stiffness, vib iso)
• Optional: Lifetime + maintenance

Do

Step 1: Requirements

All reqs before evaluate.

1. Payload: Mass (min-max), dims, material, magnetic props (ferro? conductive? diamagnetic?), temp limits (cryo? heat?), surface sensitivity (contact = contamination/damage?).
2. Performance: Gap (mm-m), load capacity, accuracy, stiffness (N/m), damping, dynamic range (static hold vs controlled motion).
3. Env constraints: Temp range, atmosphere (air, vacuum, inert, liquid), cleanliness (fab, biological, industrial), acoustic noise, EMC.
4. Op constraints: Power, envelope (size + weight of system), maintenance interval, lifetime, operator skill.
5. Economic: Prototype cost, unit cost prod, dev timeline.

## Requirements Summary
| Category | Requirement | Value | Priority |
|----------|------------|-------|----------|
| Payload mass | Range | [min - max] kg | Must have |
| Payload material | Magnetic class | [ferro/para/dia/non-magnetic] | Must have |
| Gap | Levitation height | [value] mm | Must have |
| Precision | Position accuracy | [value] um | Want |
| Temperature | Operating range | [min - max] C | Must have |
| Power | Budget | [value] W | Want |
| Cost | Unit cost target | [value] | Want |
| Environment | Cleanliness | [class or none] | Must have |
| Noise | Acoustic limit | [value] dB | Want |
| EMC | Field emission limit | [value or none] | Want |

→ Req table each classified "Must have" (hard, pass/fail) or "Want" (soft, scored). ≥5 reqs.

If err: vague → interview or boundary analysis (loosest acceptable). No reqs → arbitrary/biased study.

Step 2: Catalog Candidates

Mechanisms + principles + limits.

1. Passive diamagnetic: Diamagnetic susceptibility in permanent magnet. No power. Small (mg-g) w/ strong diamagnetic (pyrolytic graphite, bismuth). Room temp.

2. Active EM feedback: Electromagnets + sensors + controller. g-100+t (maglev). Continuous power + control. Ferro/conductive.

3. Superconducting: Type-II SC + flux pinning → passive, powerless, stable. Cryo (LN2 YBCO 77K, LHe conventional). Payload limited by SC size + critical current. Extremely stiff.

4. Acoustic standing wave: Ultrasonic transducers → pressure nodes trap small. Sub-wavelength (<5mm in air at 40kHz). Continuous drive. Any material regardless magnetic/electrical. Audible harmonics + acoustic streaming.

5. Acoustic phased array: Multiple indep transducers → 3D manipulation + repositioning. Higher complex/cost, great flex.

6. Aerodynamic (air bearings): Thin pressurized air film. Precision stages, air hockey, hovercraft. Continuous air. Very low friction. Gap 5-25μm precision, larger hovercraft.

7. Aerodynamic (Coanda/Bernoulli): Jet over curved surface → low-pressure suspends. Simple + inexpensive. Low precision/stiffness. Demos + industrial handling.

8. Electrostatic (Coulomb): Charged electrodes suspend charged/dielectric. Very low force (μN-mN). Vacuum ok. Space (grav wave detectors, inertial sensors), MEMS.

9. Electrostatic (ion trap): Oscillating E fields (Paul) or static+B (Penning) confine charged particles. Single ions-nanoparticles. Lab technique atomic physics + mass spec.

## Candidate Mechanisms
| # | Mechanism | Payload Range | Power | Temperature | Any Material? |
|---|-----------|--------------|-------|-------------|--------------|
| 1 | Passive diamagnetic | mg - g | None | Room temp | No (diamagnetic only) |
| 2 | Active EM feedback | g - 100+ t | Continuous | Room temp | No (ferro/conductive) |
| 3 | Superconducting | g - kg | Cryocooler | < 77 K | No (above SC) |
| 4 | Acoustic standing wave | ug - g | Continuous | Room temp | Yes |
| 5 | Acoustic phased array | ug - g | Continuous | Room temp | Yes |
| 6 | Air bearing | g - t | Air supply | Room temp | Yes |
| 7 | Coanda/Bernoulli | g - kg | Air supply | Room temp | Yes |
| 8 | Electrostatic Coulomb | ug - mg | Minimal | Any (vacuum ok) | No (charged/dielectric) |
| 9 | Ion trap | atoms - ug | RF power | Any (vacuum) | No (ions only) |

→ Catalog all plausible mechanisms + fundamental chars. ≥4 mechanisms ≥2 physical principles.

If err: fundamental limits uncertain → consult lit or related skills (analyze-magnetic-levitation, design-acoustic-levitation). No screen by guess.

Step 3: Screen Hard Constraints

Eliminate mechanisms failing any "Must have".

1. Each hard constraint = pass/fail. Single fail eliminates.
2. Common screens:
   • Mass: Payload exceeds limit → eliminate (acoustic can't handle kg).
   • Material: Non-magnetic + requires magnetic → eliminate.
   • Temp: Cryo infeasible → eliminate SC.
   • Vacuum/atm: Vacuum → eliminate aero. No-magnetic-fields EMC → eliminate magnetic.
   • Contact: Air bearings need proximity to flat. True non-contact → eliminate.
3. Document eliminations + reasons → can revisit if reqs change.

## Screening Results
| # | Mechanism | Pass/Fail | Eliminating Constraint | Reason |
|---|-----------|-----------|----------------------|--------|
| 1 | Passive diamagnetic | [P/F] | [constraint or N/A] | [reason] |
| 2 | Active EM feedback | [P/F] | [constraint or N/A] | [reason] |
| ... | ... | ... | ... | ... |

→ Reduced list passed all hard. ≥1 survives; ideally 2-4 for scoring.

If err: none pass → reqs mutually contradictory. Relax least critical "Must have" (→"Want") + re-screen. Multiple relax → may need hybrid (magnetic primary + aero stabilization).

Step 4: Score Soft Criteria

Rank survivors via weighted matrix.

1. Define criteria + weights: Convert "Want" → scoring criterion. Weights reflect importance (1-5 or % summing 100%). Common:
   • Cost (prototype + unit): weight by economic sensitivity
   • Complexity: components, electronics, alignment criticality
   • Precision: accuracy, stiffness, vib iso
   • Power: op W, standby W
   • Scalability: payload range, manufacturability
   • Controllability: ease adjust gap/position/stiffness dynamically
   • Maturity: TRL, commercial component availability
   • Noise: acoustic, EM, vibration emissions
2. Score each: Consistent scale (1=poor, 3=adequate, 5=excellent). Quant data Steps 1-3 not subjective.
3. Weighted: Score × weight, sum. Highest = top.
4. Sensitivity: Vary top 2-3 weights ±20%. Ranking change? If sensitive → flag, present alts.

## Scoring Matrix
| Criterion | Weight | Mech A | Mech B | Mech C |
|-----------|--------|--------|--------|--------|
| Cost | [w1] | [s1A] | [s1B] | [s1C] |
| Complexity | [w2] | [s2A] | [s2B] | [s2C] |
| Precision | [w3] | [s3A] | [s3B] | [s3C] |
| Power | [w4] | [s4A] | [s4B] | [s4C] |
| Scalability | [w5] | [s5A] | [s5B] | [s5C] |
| Controllability | [w6] | [s6A] | [s6B] | [s6C] |
| Maturity | [w7] | [s7A] | [s7B] | [s7C] |
| **Weighted Total** | | **[T_A]** | **[T_B]** | **[T_C]** |
| **Rank** | | [rank] | [rank] | [rank] |

→ Complete matrix all weighted + scored. Clear rank, top candidate. Sensitivity confirms robust (or fragile documented).

If err: 2 mechanisms within 10% → too close on paper. Prototype both + select on experiment, or identify discriminating test.

Step 5: Document Recommendation

Final trade study.

1. Recommendation: Recommended mechanism + 1-paragraph justification referencing scoring + key discriminators.
2. Runner-up: 2nd place + conditions under which it becomes preferred (fallback).
3. Eliminated: List + disqualifying constraints for completeness.
4. Risks + mitigations: Recommended → top 3 risks + mitigations.
5. Next steps: Detailed design work (analyze-magnetic-levitation, design-acoustic-levitation, etc.).

## Trade Study Summary

### Recommendation
**[Mechanism name]** is recommended for [application] because [2-3 sentence justification
referencing the key scoring advantages].

### Runner-Up
**[Mechanism name]** would be preferred if [condition changes, e.g., "cryogenics become
available" or "payload mass decreases below X grams"].

### Eliminated Mechanisms
- [Mechanism]: eliminated by [constraint]
- [Mechanism]: eliminated by [constraint]

### Risks
| Risk | Impact | Likelihood | Mitigation |
|------|--------|-----------|------------|
| [Risk 1] | [H/M/L] | [H/M/L] | [action] |
| [Risk 2] | [H/M/L] | [H/M/L] | [action] |
| [Risk 3] | [H/M/L] | [H/M/L] | [action] |

### Next Steps
1. [Detailed analysis using specific skill]
2. [Prototype or simulation task]
3. [Experimental validation milestone]

→ Self-contained doc other engineer could review/challenge/act. Recommendation traceable to reqs + scoring not unstated prefs.

If err: recommendation can't be justified by scoring alone (top has showstopper criteria missed) → revisit Step 1, add missing req. No override scoring w/o documenting.

Check

• Reqs quant + priority classified
• ≥4 mechanisms ≥2 physical principles
• Hard screen consistent + documented
• ≥2 mechanisms survive for compare
• Criteria explicit weights, scores justified
• Sensitivity on top 2-3 weights
• Recommendation traceable to matrix
• Runner-up + fallback documented
• Risks + mitigations
• Study complete for indep review

Traps

• Anchor preferred mechanism first: Start w/ conclusion, reverse-engineer reqs/weights. Cure: reqs + weights before eval. If know what want → validation not selection, be honest.
• Omit mechanisms unfamiliar domains: Magnetic engineers overlook acoustic + vice versa. Include ≥1 from 4 families (magnetic, acoustic, aerodynamic, electrostatic) even if screened out.
• Confuse hard/soft: Preference as hard eliminates viable early. Only non-negotiable (safety, physics, regulatory) = hard. Rest scored.
• Equal weighting default: Same weight = decision (all equal). Stakeholders prioritize. Refuse → pairwise (AHP) to elicit implicit.
• Ignore system-level: Mechanism not isolated. Acoustic → noise affects instruments. Active magnetic → time-varying fields violate EMC. SC → cryo infra. Evaluate in system context.
• Single-point score no uncertainty: "4" on cost = false precision. Express ranges ("3-5"), propagate uncertainty. 2 mechanisms overlap → rank not definitive.

→

• analyze-magnetic-levitation — detailed analysis magnetic recommended/candidate
• design-acoustic-levitation — detailed design acoustic selected
• analyze-magnetic-field — compute field profiles for magnetic assessment
• argumentation — structured reasoning + decision justification