Filtrado Digital

Raw ADC streams from wireless power hardware contain switching ripple, CM noise from nearby drives, and broadband EMI from long cable runs in AGV chassis. Digital filtering extracts control-grade fundamental components and metrology-grade DC averages without introducing phase lag that destabilizes current loops or masks foreign-object signatures.

SiCore filter chains are designed offline in floating-point models, then converted to fixed-point with verified frequency response and step response before deployment on resource-constrained receivers.

01Filter types in WPT firmware

• First-order or biquad low-pass on current feedback — cutoff below Nyquist of control loop, above load bandwidth.
• Notch or comb filters at switching frequency and harmonics for FOD residual analysis.
• Moving-average or decimate-by-N for slow power and energy integration to fleet telemetry.
• High-pass or band-pass on alignment sense for AC coupling coil signal extraction.
• Median filters on temperature channels to reject single-sample spike artifacts.

02Implementation constraints

Direct Form II transposed biquads minimize state variables and suit CMSIS-DSP arm_biquad_cascade_df1 routines on Cortex-M4. Filter execution runs in ADC DMA completion context or dedicated control task — never split across unsynchronized tasks without atomic buffer swap. Group delay of current feedback filter is included in loop phase margin calculations; aggressive filtering improves noise but reduces phase margin.

Cascaded stages use Q-factor limits to prevent coefficient quantization instability at corner frequencies near 1–5 kHz on 100 ksps effective streams.

03Validation

Frequency response verified with injected sine sweep on HIL; step response timed against BMS current request ramps. Field logs compare filtered vs raw FOD metrics during controlled metal plate insertion to confirm detection latency meets safety timing. Filter coefficient updates ship only via signed OTA because they directly affect protection sensitivity.