Position Sensor Tuning

Position sensors can experience significant electromagnetic interference. ASI BAC controllers provide parameters to tune position sensors for higher accuracy and filtering in high-noise applications.

Hall Sensor Configuration

Hall Interpolation

Hall interpolation smooths motor operation by interpolating rotor angle transitions instead of using discrete six-step Hall transitions.

How Interpolation Works

1. Above the start frequency: Controller interpolates rotor angle based on time between Hall sensor edges
2. Creates smooth triangle wave instead of six-step transitions
3. Below the stop frequency: Interpolation stops

Tuning Guidelines

• Set Hall interpolation start frequency at twice the Hall interpolation stop frequency
• Lower interpolation frequencies are generally better
• This is especially true for high pole count direct drive motors
• Tuning is iterative and requires trial and error

Factors Affecting Low-Speed Chatter

Hall to Sensorless Transition

Firmware 6.026+: Use Sensorless to Hall Transition Frequency to tune the transition point between Hall-based and sensorless operation.

Troubleshooting Hall Sensors

Hall vs Sensorless Position Fault

Problem: Motor Position Sensor Type is set to 0 (Hall) or 1 (Hall start + sensorless run) and throws an error.

Solution: Set Motor Position Sensor Type to 2 (Sensorless) for motor speed autotune, then restore original setting.

Hall Table Issues

Motor Power Requirement

Hall sensor discovery requires Rated motor power (Race mode Throttle power) to be filled in with at least the motor's rated power for:

• Analyze Hall wiring
• Offset calibration
• Rated motor speed analysis

Sine-Cosine Encoder Setup

Prerequisites

Low-Speed Noise Threshold

Reduces encoder angle fluctuations from analog input noise at low motor speeds.

Converting RPM to Electrical Hz:

Electrical Hz = (RPM ÷ 60) × Pole Pairs

Example: For 50 RPM threshold with 6 pole pairs:

Encoder Noise Frequency = (50 ÷ 60) × 6 = 5 Hz

Noise Threshold Behavior

Encoder Fault Range (FW 6.025+)

Fault ranges define the tolerance above and below Encoder Sine/Cos High/Low Voltage that triggers a fault.

Values within this range are considered min/max voltage to allow for system-level measurement errors.

Post-Configuration

After encoder setup, you can restore:

• Switching frequency to 13 kHz
• Baud rate port2 to 115200

This recovers Bluetooth connectivity if applicable.

Sensorless Motor Tuning

Sensorless operation eliminates Hall sensors by detecting motor position through back-EMF. Motor startup response is adjusted through two key parameters:

• Sensorless open loop starting current
• Sensorless closed loop enable frequency

Sensorless Startup Sequence

The startup sequence consists of four phases:

Phase 1: Current Ramp
└── Duration: Sensorless open loop injection current ramp time (default 200ms)
└── Target: Sensorless open loop starting current (default 0.5 pu)

Phase 2: DC Current Hold
└── Duration: Sensorless open loop dc current hold time (default 15ms)
└── Purpose: Force motor into known position

Phase 3: Frequency Ramp
└── Duration: Sensorless open loop freq ramp time ms (default 1500ms)
└── Target: Sensorless closed loop enable frequency (default 20 Hz)

Phase 4: Closed-Loop Operation
└── Controller switches to closed-loop regulation

Sensorless Parameters

Tuning Guidelines

Sensorless open loop starting current:

• Higher current = more startup torque
• Common setting: 50% or more of max phase current
• Increase if motor fails to start under load

Sensorless open loop freq ramp time:

• Shorter time = quicker startup
• Too short = motor may lose synchronization under load
• Balance between responsiveness and reliability

Sensorless closed loop enable frequency:

• Should be as low as possible while maintaining stable back-EMF
• Motors with higher RPM/V constants need higher transition frequency
• Starting point: ~10% of rated electrical frequency

Key Parameters Reference

Hall Sensor Parameters

Encoder Parameters

Sensorless Parameters

Next Steps

• Complete Motor Setup before tuning position sensors
• Configure System Tuning for control loop optimization
• Review Protection Systems for safe operation