Stepper Motor Drive Control Using Variable Energization Angle
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Solution Overview
Problem
The conventional one-two-phase excitation system for two-phase stepping motors has a short one-phase excitation period, making it challenging to detect the zero crossing point of the back electromotive voltage within the available time, which can lead to unstable energization switching due to the energization angle of 135 degrees.
Innovation Solution
A motor drive control device that adjusts the energization angle between 90 and 135 degrees, allowing for a longer one-phase excitation period and determining the periods for one-phase and two-phase excitations based on the back electromotive voltage and elapsed time, ensuring stable energization switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the energization angle is set to 135 degrees in a one-two-phase excitation system, then torque is increased, but the one-phase excitation period becomes too short to detect the zero crossing point of the back electromotive voltage
Solution Approach 1:
The patent dynamically adjusts the energization angle between one-phase excitation and two-phase excitation based on operational requirements. By making the energization angle variable rather than fixed at 135 degrees, the system can extend the one-phase excitation period when zero crossing detection is needed, while still achieving high torque when two-phase excitation is employed. This dynamic adjustment resolves the contradiction between maintaining sufficient excitation period for detection and providing adequate torque output.
Solution Approach 2:
The patent changes the energization angle parameter from a fixed value (135 degrees) to a variable parameter that can be adjusted between 90 degrees (one-phase) and 135 degrees (two-phase). This parameter change allows the system to optimize the balance between excitation period duration and torque generation by selecting appropriate energization angles based on operational conditions, thereby resolving the time-loss contradiction.
2Measurement precision
If the energization angle is extended to allow zero crossing detection, then detection accuracy is improved, but the commutation frequency decreases
Solution Approach 1:
The patent employs periodic switching between one-phase excitation (with extended period for detection) and two-phase excitation (with higher commutation frequency). By alternating between these two excitation modes, the system ensures that zero crossing detection occurs during one-phase periods while maintaining high overall commutation frequency through two-phase periods. This periodic action resolves the contradiction between detection accuracy and commutation frequency.
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 enables stable energization switching and torque control by extending the one-phase excitation period, allowing for accurate detection of the zero crossing point and improved rotational speed adjustment according to load conditions.
Implementation Method 1
determines a period for performing the one-phase excitation based on a back electromotive voltage generated in the coil non-excited in the one-phase excitation
Data Source
AI summary
A motor drive control device includes a control unit generating a control signal Sd such that one-phase excitation of exciting, of coils and of two phases of a two-phase stepping motor, a coil for one phase and two-phase excitation of exciting the coils for two phases are alternately repeated, and a drive unit driving the coils of two phases based on the control signal Sd. An energization angle θ representing a magnitude of an electric angle for continuously energizing the coil of one phase in one direction is capable of being set in the control unit. Specifically, the control unit determines a period T1n for performing the one-phase excitation based on a back electromotive voltage generated in the coil non-excited in the one-phase excitation, and determines a period T2n for performing the two-phase excitation based on an elapsed time per unit angle while the two-phase stepping motor is being excited and the energization angle θ.