HSO startup alignment, rotor movement, and gearbox-load considerations

[vi007]

Hello,

I have successfully implemented the High Sensitivity Observer using the following configuration:

• MCU: STM32G474RETx, 170 MHz
• Power board: EVLDRIVE102BH, configured as a Custom Power Board in STM32 Motor Control Workbench
• Phase-voltage sensing configured according to the HSO hardware requirements

HSO is operational with this configuration. However, I am observing rotor alignment movement and vibration during startup, before stable closed-loop operation is established.

Could you please clarify the expected HSO startup behavior?

1. What startup stages are performed before the HSO reaches stable closed-loop operation?
2. What is the expected extent of rotor movement during the initial alignment and observer-lock sequence?
3. Is some vibration or oscillatory rotor movement expected during this stage?
4. How does the selected startup method, such as PolPulse or RSDC, influence rotor displacement and vibration?
5. How significantly do the motor parameters, mechanical load, inertia, friction, and initial rotor position affect startup reliability?
6. Is there a method to estimate or limit the maximum rotor displacement during the startup or alignment phase?
7. Are there specific tuning recommendations for minimizing startup movement and vibration when the motor is coupled to a gearbox?
8. Can gearbox load, reflected inertia, backlash, or static friction prevent reliable initial position detection or observer convergence?

The motor will eventually be coupled to a gearbox. Therefore, we need to understand whether the present alignment movement and vibration are expected, and assess their impact on the mechanical system and the complete startup sequence.

Thank you for your support.

[Gael A]

Hello vi007,

HSO is able to immediately start in closed-loop mode as long as the initial position of the motor is provided.
As of today, two methods are available to retrieve that angle : RsDC alignment and PolPulse. RsDC align the motor at a target angle, while PolPulse aims at estimating the angle of the motor without moving it. This means RsDC can move the motor up to 180deg electrical, while PolPulse not at all if the angle got estimated correctly.

High inertia is known to cause trouble at start-up if it requires the motor to start at a very slow speed ramp. In that case, implementing an open loop start-up may be helpful.

The presence of a gearbox is not known to have much impact on IPD neither convergence. Concerning alignment, it will mostly depend on the gearbox ratio and pole pair number.