System Tuning

This guide covers the control loop tuning parameters for optimizing ASI BAC motor controller performance.

Control Loop Overview

ASI BAC controllers use multiple control loops to regulate motor operation:

Control Loop	Function
Current Regulation	Controls phase current feedback (FOC)
PLL Regulation	Tracks sensorless angular position
Speed Regulation	Controls output current based on speed setpoint
Acceleration Control	Shapes acceleration and deceleration behavior

Current Regulation Control Loop

The phase current control loop manages current feedback for Field-Oriented Control (FOC). Adjusting current regulation affects overall acceleration and current overshoot behavior.

Bandwidth Tuning

Current Regulator bandwidth calculates the feedback gains:

Current regulator Kp (Proportional gain)
Current regulator Ki (Integral gain)

Bandwidth Effect	Result
Higher bandwidth	Faster current correction, less overshoot, less integrator windup
Too high	Instability, audible noise, overcurrent faults
Too low	Poor acceleration performance

Recommended Values

Motor Type	Current Regulator Bandwidth
Higher speed motors	3000-5000
Lower speed motors	1500+

General Guideline

Maintain sufficiently high Current Regulator bandwidth for desirable acceleration and performance while avoiding instability.

Manual Tuning

If Current Regulator bandwidth is set to 0, you can manually set individual PI gains:

Parameter	Rise Time	Overshoot	Settling Time	Steady-State Error	Stability
Increase Kp	Decrease	Increase	Small change	Decrease	Degrade
Increase Ki	Decrease	Increase	Increase	Eliminate	Degrade

Manual Tuning

Manual PI tuning is not recommended. Use bandwidth tuning when possible.

PLL Regulation Control Loop

The Phase-Locked Loop (PLL) tracks sensorless angular position for motor flux frequency calculation and controls output frequency.

Bandwidth Effects

PLL bandwidth calculates:

PLL Kp (Proportional gain)
PLL Ki (Integral gain)

Bandwidth Effect	Result
Higher bandwidth	Faster lock time, faster frequency adjustment
Too high	Instability, output noise, audible noise, vibrations, jitter amplification
Too low	Jitter removed from reference clock

Tuning Guidelines

Motor Type	PLL Bandwidth
Higher electrical frequency motors	300+
Geared hubs, mid-drive motors	300+ (prevents instantaneous phase overcurrent faults)
Lower electrical frequency motors	Lower values tolerable
Direct drive hubs	Lower values tolerable

Adjustment approach: If experiencing jitter, adjust by increments of 100 (up/down), up to 500.

PLL Damping

PLL damping affects the auto-calculated PLL Kp factor. Increasing damping increases the Kp component.

Manual Tuning

If both PLL bandwidth and PLL damping are set to 0, you can manually set:

PLL Kp old
PLL Ki old

Parameter	Rise Time	Overshoot	Settling Time	Steady-State Error	Stability
Increase Kp	Decrease	Increase	Small change	Decrease	Degrade
Increase Ki	Decrease	Increase	Increase	Eliminate	Degrade

Speed Regulation Control Loop

The speed regulation loop controls output current based on measured speed to achieve the target speed setpoint.

Key Parameters

Parameter	Function
Speed regulator Kp	Proportional gain for speed error
Speed regulator Ki	Integral gain for speed error

Tuning Effects

Parameter	Rise Time	Overshoot	Settling Time	Steady-State Error	Stability
Increase Kp	Decrease	Increase	Small change	Decrease	Degrade
Increase Ki	Decrease	Increase	Increase	Eliminate	Degrade

Step-by-Step Tuning Procedure

Initialize Values

Set Speed regulator Ki to 0 and Speed regulator Kp to 1.

Test Step Response

Under intended operating conditions/load, induce a step response:

Command full throttle from 0 speed
Observe system acceleration

Adjust Kp

Too fast/aggressive or oscillating: Reduce Kp by 25%
Too slow: Double Kp (up to less than 8)
Repeat until proportional response is satisfactory

Add Integral Gain

Set Speed regulator Ki to 1 and test at target speed setpoint.

Adjust Ki

Still undershooting: Double Ki (up to less than 128)
Overshooting: Reduce Ki by 25%
Repeat until steady-state is satisfactory

Final Balance

Test response from various speeds. If system became too aggressive with Ki, reduce both Kp and Ki proportionally.

Tuning Goals

Kp goal: Set as low as tolerable for desired response without overshooting target speed
Ki goal: System settles at setpoint without oscillating above/below

Acceleration Control

Acceleration is primarily affected by:

Available torque-producing current
Imposed power limits
Acceleration ramp limits
Current regulation control loop
Speed regulation control loop (for speed-limited modes)

Motor Limitations

If acceleration is insufficient despite tuning, the application may need a motor with better torque constant (Kt in Nm/A) or more current than the controller can output.

Speed Regulator Modes

Mode	Value	Ramp Rates Used
Speed mode	0	Speed mode ramps
Torque mode	1	Torque mode ramps
Torque with speed limiting	2	Torque mode ramps

Torque Mode Ramp Rates

Acceleration Ramps

Parameter	Function
Positive motoring torque ramp	Current ramp-up when commanding (throttle on)
Negative motoring torque ramp	Current ramp-down when reducing (throttle off)
Pedalec positive motoring torque ramp	Pedal sensor current ramp-up
Pedalec negative motoring torque ramp	Pedal sensor current ramp-down

Guidelines:

Too low: Acceleration becomes jarring, may damage mechanical components
Too high: Acceleration seems slow (positive ramp) or continues too long (negative ramp)
To disable: Set values to 1 ms

The ramp is linear and specifies the time (in ms) to reach peak current from zero (positive) or zero from peak (negative).

Speed Limit Ramp Time

For Speed regulator mode 1 (Torque with speed limiting):

Speed limit ramp time limits acceleration relative to speed limit by limiting current output.

Use cases:

Improve engagement in geared hub drives
Reduce clutch wear
Take up slack in chain drive systems
Reduce instantaneous overcurrents when accelerating with drivetrain slack

Note: Linear ramp only takes effect from 0 RPM. Set to 0 to disable.

Braking Ramps

Parameter	Function
Positive braking torque ramp	Regen current ramp-up
Negative braking torque ramp	Regen current ramp-down

Wheel Lock Prevention

Setting Positive braking torque ramp too low can cause wheel lock-up. Recommended: 200 ms or longer.

Speed Mode Ramp Rates

For Speed regulator mode 0 (Speed mode):

Parameter	Function
Speed mode positive acceleration	Target acceleration rate
Speed mode Regen ramp	Target deceleration rate

Value interpretation:

Value	Meaning
16	1× rated RPM in 1 second
32	0.5× rated RPM in 1 second
8	2× rated RPM in 1 second

Recommended values:

Speed mode Regen ramp: 48 (good default)
Speed mode positive acceleration: 4, 8, or 16 (starting points)

Speed Mode Requirements

Speed mode positive acceleration should be less than Speed mode Regen ramp
Regeneration battery current limit must be > 0% for regen ramp to function
Features bit 13 (engine braking) must be enabled when Control command source ≠ 0

Key Parameters Reference

Current Regulation

Address	Parameter	Function
110	Current Regulator bandwidth	Bandwidth for auto-calculation (Hz)
111	Current regulator Kp	Proportional gain
112	Current regulator Ki	Integral gain

PLL Regulation

Address	Parameter	Function
113	PLL bandwidth	Bandwidth for auto-calculation (Hz)
114	PLL damping	Damping factor for Kp
115	PLL Kp	Proportional gain
116	PLL Ki	Integral gain

Speed Regulation

Address	Parameter	Function
117	Speed regulator Kp	Proportional gain
118	Speed regulator Ki	Integral gain
119	Speed regulator mode	0=Speed, 1=Torque, 2=Torque+Limit

Acceleration Ramps

Address	Parameter	Function
120	Positive motoring torque ramp	Acceleration ramp (ms)
121	Negative motoring torque ramp	Deceleration ramp (ms)
122	Positive braking torque ramp	Regen ramp-up (ms)
123	Negative braking torque ramp	Regen ramp-down (ms)
124	Speed limit ramp time	Speed-based current limit (ms)
125	Speed mode positive acceleration	Speed mode accel rate
126	Speed mode Regen ramp	Speed mode decel rate

Next Steps

Configure Motor Setup before tuning control loops
Review Braking Systems for regen configuration
Set up Protection Systems for safe operation

System Tuning

General Guideline

Manual Tuning

Initialize Values

Test Step Response

Adjust Kp

Add Integral Gain

Adjust Ki

Final Balance

Tuning Goals

Motor Limitations

Wheel Lock Prevention

Speed Mode Requirements

Related Articles

Position Sensor Tuning

ASI BAC Motor Controller Overview

Battery Configuration