Stepper Motor Startup Commutation Using Back-EMF Mode Switching
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Solution Overview
Problem
Stepping motors experience instability and a high likelihood of 'step-out' during startup, especially under heavy loads, due to the inability to detect zero crossing points of back electromotive voltage in one-phase or one-two-phase excitation systems at low speeds.
Innovation Solution
A motor drive control device with a control unit that employs a dual commutation control mode: initially using a first mode based on preset energization conditions and switching to a second mode based on detected zero crossing points, ensuring stable operation by adjusting energization angles and excitation periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If zero crossing point detection method is used for commutation control, then commutation accuracy is improved, but operation stability deteriorates at startup and low speeds
Solution Approach 1:
The patent applies dynamics by switching between two commutation control modes based on operating conditions. At startup and low speeds, the first commutation control mode (time-based) is used to ensure stable operation. When the motor reaches a predetermined speed, the control unit switches to the second commutation control mode (zero crossing point detection) to improve commutation accuracy. This dynamic switching resolves the contradiction by adapting the control method to the operational phase.
Solution Approach 2:
The patent changes the commutation control parameter from time-based control to zero crossing point detection based on speed threshold. The control unit monitors motor speed and switches the commutation mode accordingly. This parameter change allows the system to leverage the advantages of each method at appropriate operating conditions, resolving the stability-accuracy trade-off.
2Device complexity
If one-phase or one-two-phase excitation system is used, then device complexity is reduced, but step-out likelihood increases under heavy loads
Solution Approach 1:
The patent applies preliminary action by using time-based commutation control at startup to ensure stable motor initialization under heavy loads. This preliminary control mode guarantees proper motor启动 before switching to the simpler zero crossing point detection method. By preparing the motor operation in a controlled manner at startup, the system prevents step-out occurrences while maintaining overall system simplicity.
3Measurement precision
If zero crossing point detection is used at low speeds, then commutation precision is improved, but detection reliability deteriorates
Solution Approach 1:
The patent implements dynamics by dynamically selecting the commutation control mode based on motor speed. At low speeds where zero crossing point detection is unreliable, the system uses time-based commutation control. When speed exceeds a predetermined threshold, the system switches to zero crossing point detection. This dynamic adaptation ensures both detection reliability and commutation precision across the full speed range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the stability of stepping motor operation at startup, reducing the likelihood of 'step-out' occurrences even under heavy loads by effectively utilizing both energization modes.
Implementation Method 1
a control unit configured to generate a control signal for controlling driving of a two-phase stepping motor; and a drive unit configured to drive coils of two phases of the two-phase stepping motor based on the control signal
Implementation Method 2
a second commutation control mode for commutating the coils based on a detection result of a zero crossing point of a back electromotive voltage of the coils
Data Source
AI summary
To increase the stability of an operation when the driving of a stepping motor is started. A motor drive control device includes a control unit configured to generate a control signal (Sd) for controlling driving of a two-phase stepping motor, and a drive unit configured to drive coils of two phases of the two-phase stepping motor based on the control signal (Sd). The control unit has, as control modes, a first commutation control mode for commutating the coils according to a target energization time based on a preset commutation condition, and a second commutation control mode for commutating the coils based on a detection result of a zero crossing point of a back electromotive voltage of the coils, and the control unit generates the control signal (Sd) in the first commutation control mode at the start of activation of the two-phase stepping motor, and generates the control signal (Sd) in the second commutation control mode when the detection result of the zero crossing point satisfies a predetermined condition.