Active force cancellation using real-time PID control, friction pendulum bearings, and cable winch systems.
StabilityCore uses active force cancellation — continuously measuring platform orientation relative to gravity and applying computed counter-forces in real time. Unlike passive systems that absorb energy at fixed frequency ranges, our system adapts to any earthquake frequency, magnitude, or direction.
1. Invariant Reference. Gravity provides a perfect, constant definition of "level." The system always knows exactly what "correct" looks like — no calibration, no drift, no external dependency.
2. Speed Asymmetry. Earthquakes move at 0.05–10 Hz. Our controller runs at 100+ Hz. The system executes 10 to 2,000 corrections per seismic wave cycle. The earthquake is in slow motion from the controller's perspective.
3. Band-Limited Disturbance. Seismic energy is concentrated in a known frequency band. PID controllers excel at rejecting disturbances within predictable ranges.
Earthquake ground motion is extremely slow relative to digital control systems:
| Wave Type | Frequency | Characteristic | Control Cycles per Wave |
|---|---|---|---|
| P-wave (Primary) | 1 – 10 Hz | Compressional, fastest arrival | 10 – 100 |
| S-wave (Secondary) | 0.5 – 5 Hz | Shear, most damaging | 20 – 200 |
| Love wave | 0.1 – 1 Hz | Surface, horizontal shearing | 100 – 1,000 |
| Rayleigh wave | 0.05 – 0.5 Hz | Surface, rolling elliptical | 200 – 2,000 |
Control cycles at 100 Hz loop rate. Even the fastest P-waves get 10 corrections per cycle.
The system employs a Proportional-Integral-Derivative (PID) controller on each axis. The controller computes corrective output based on the error between measured tilt and the target (zero degrees):
Immediate response proportional to current error. Bigger tilt = bigger correction force. The "reflexes" of the system.
Accumulates error over time to eliminate steady-state offset. Corrects for spring asymmetry and mechanical bias. The "memory."
Responds to rate of change. Dampens oscillation and predicts future error. The "anticipation."
Why PID is sufficient: The target is constant (level = 0°), the disturbance is band-limited (0.05–10 Hz), and the reference is invariant (gravity). PID is the dominant algorithm in industrial control for exactly these conditions.
The hardware changes at every scale — but the PID control intelligence stays the same. The same algorithms, sensor fusion, and force-cancellation logic transfer directly across all scales.
PID algorithms, sensor fusion, and force-cancellation logic transfer identically across all scales. The cable winch approach eliminates hydraulic complexity — electric motors, geared pulleys, and steel cables are proven, off-the-shelf components. Our innovation is the real-time control intelligence.
Imagine a construction worker guiding a 2-ton steel beam with one hand — because the crane hook carries all the weight. The beam is massive, but effectively weightless in the lateral plane.
Our most advanced concept applies this same principle to entire buildings: a Space Needle-inspired tripod foundation — three angled legs anchored deep into bedrock, converging at a central hub where one large friction pendulum bearing sits. The building rests on this single bearing point. Four cable winches provide minimal-energy PID correction, requiring orders of magnitude less force than conventional systems.
The result: A building that is effectively weightless in the lateral plane during an earthquake. The triangulated tripod distributes load across three bedrock anchor points, and the PID system doesn't fight seismic force — it just guides the building like a worker guides that suspended beam.
The Seattle Space Needle is considered the safest place to be during an earthquake. Built in 1962, it survived the 2001 Nisqually M6.8 quake with zero structural damage.
The Space Needle absorbs the full seismic force through sheer strength. Our design uses the same tripod foundation but adds a pendulum bearing at the convergence point, so the building doesn't absorb the force at all.
FORCE COMPARISON
Active noise cancellation — applied to seismic waves. A distributed sensor network detects incoming waves upstream, characterizes their frequency, amplitude, and phase, then generates anti-phase counter-force before the wave arrives.
8–12 Zigbee mesh nodes at 0.5–2 km radius. Solar-powered, GPS-synced. ~$200–500 per node. IEEE 802.15.4 standard.
P-waves give 125–400ms warning. S-waves give 220–667ms from sensors at 1–2 km. Enough time for predictive counter-force computation.
Feedforward (predictive from upstream sensors) + feedback (reactive PID from local IMU) combined for maximum force reduction.
Detects when incoming wave frequency approaches building natural frequency. Increases cancellation gain to prevent catastrophic resonant amplification.
The friction pendulum bearing uses a dual-material sphere: a ferromagnetic steel core wrapped in a titanium alloy shell. Electromagnetic coils embedded in the bearing dish reduce friction on demand — energized only during earthquakes, consuming zero power during normal operation.
The electromagnetic field from the dish coils passes through the non-magnetic titanium shell and interacts with the ferromagnetic core, partially offloading contact pressure at the bearing surface. This reduces the friction coefficient from 0.02–0.05 (standard) to as low as 0.001 (electromagnetic assist).
The PID controller modulates field strength via PWM — stronger earthquakes get more friction reduction. The system doesn't levitate the sphere; it reduces contact friction just enough for near-perfect isolation.
Electromagnetic suspension carries 600+ ton trains at 375 mph (Shanghai Maglev, Japan SCMaglev). StabilityCore requires far less — friction reduction, not full levitation — at a stationary bearing point.
FRICTION COEFFICIENT
StabilityCore is the first seismic isolation system that harvests the earthquake's own energy to power its protection. The system requires zero external electrical power during the event.
Linear alternators between the building and foundation convert earthquake displacement into electricity. Larger earthquakes generate more power — automatically matching increased demand.
A piston mechanism driven by earthquake displacement compresses R-410A refrigerant gas (PV=nRT), cooling the electromagnetic coils. The earthquake powers its own thermal management.
Pre-charged capacitor bank provides instant power at system wake. Once shaking begins, the seismic generator continuously recharges it — unlimited runtime.
An 1,800-ton apartment building displacing ±2 inches at 2 Hz generates 7–36 kW of continuous electrical power from just 1–5% energy capture. The electromagnetic coils need only 0.5–10 kW. The earthquake generates more power than the system consumes. Surplus powers emergency lighting, communications, and occupant warning — even when the grid is down.
Four independent detection layers provide progressively earlier warning, from minutes to always-on:
| Tier | Source | Warning Time | Function |
|---|---|---|---|
| 1 | USGS ShakeAlert API | 20–80 seconds (Cascadia) | Wake from sleep, run self-diagnostic, start compressor |
| 2 | Zigbee IMU Mesh (8–12 nodes) | 0.5–5 seconds | 3D wavefront mapping, wave direction, predictive positioning |
| 3 | On-Building IMU | Milliseconds | Reactive PID correction, real-time force cancellation |
| 4 | Passive Isolation (bearing + springs) | Always on | Zero-power baseline protection, gravity self-centering |
During the ShakeAlert advance warning window, the system executes a 5–10 second self-diagnostic: cycling actuators, polling sensors, verifying PID responsiveness, checking Zigbee mesh connectivity, confirming supercapacitor charge, and alerting occupants — all before the first wave arrives.
High-current electromagnetic operation during sustained earthquakes generates significant heat. Five independent cooling layers ensure coil protection:
The 500+ kg steel bearing dish absorbs 360 kJ with less than 1°C temperature rise. A 3-minute earthquake at full power — the dish doesn't even notice.
The seismic piston compressor drives an R-410A cooling loop using earthquake energy. Cooling capacity automatically scales with earthquake severity.
Electric compressor provides pre-event cooling during warning window and post-event cool-down. Non-flammable R-410A refrigerant (ASHRAE A1).
High-CFM fans supplement all cooling. PID-timed EM pulses at 30–50% duty cycle cut heat generation by half. Five independent thermal layers.
Layers 1–4 are fully passive — zero electronics or power required. If all active systems fail, the building remains isolated.
| Layer | Component | Power? | Mechanism |
|---|---|---|---|
| 1 | Viscoelastic pylon sleeve | No | Hysteresis converts kinetic energy to heat |
| 2 | Friction pendulum bearings | No | Omnidirectional lateral isolation, gravity self-centering |
| 3 | Steel wire rope cables | No | Vertical restraint with flex and energy absorption |
| 4 | Worm gear locked cables | No | Self-locking gears hold cable position if power fails |
| 5 | PID cable winches (active) | Yes | Real-time differential tension for force cancellation |
A 1/25 scale prototype is under construction with two designs:
| Metric | Target | Status |
|---|---|---|
| Force reduction | >70% at 1/25 scale | Pending testing |
| Response latency | <15ms sensor-to-actuator | Pending testing |
| Magnitude range | M3.0 – M8.0 simulated | 8 profiles coded |
| Endurance | 24hr continuous operation | Pending testing |
Full technical paper with equations, firmware architecture, and experimental design available for qualified investors and engineering partners.
Request Technical Paper