Sensorless Multiphase Brushless Motor Stall Detection Control
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Solution Overview
Problem
Existing methods for detecting lock or stall in multiphase brushless DC motors controlled in microstepping mode are complex, require position or torque sensors, and lead to untimely stoppages due to increased resistance, often involving high computational demands and inappropriate error reporting.
Innovation Solution
A control system for multiphase brushless motors without position sensors, utilizing switching means, overload detection, and space vector modulation to dynamically adjust operating points based on detected overloads and external conditions, avoiding the need for complex algorithms and sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position or torque sensors are used to detect lock or stall conditions, then detection accuracy is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The motor system uses its own phase currents and voltages to detect stall conditions through the power transistors already present in the drive circuitry. The control unit analyzes the relationship between applied voltages and resulting currents to determine stall, eliminating the need for external sensors.
Solution Approach 2:
The power transistors serving their primary function of current control also act as intermediaries for measuring phase voltages during specific time intervals. By measuring voltages across the transistors when they are in specific states, the system obtains stall detection information without additional measurement devices.
2Reliability
If complex detection algorithms are implemented to accurately detect stall conditions, then detection reliability is improved, but computational requirements and processing time increase
Solution Approach 1:
The detection process is divided into distinct time intervals within each microstep cycle: a first interval for applying voltage and measuring current, and a second interval for measuring voltage without current. This segmentation allows simple measurements at different times to be combined for reliable stall detection without complex continuous analysis.
Solution Approach 2:
The control unit performs voltage measurements during specific periodic intervals within each microstep cycle. By sampling voltages at regular intervals when transistors are in known states, the system builds reliable detection data through repeated periodic measurements rather than requiring complex real-time analysis.
3Manufacturing precision
If all power transistors are used simultaneously for microstepping control, then motor precision is improved, but access to induced voltage measurement becomes difficult
Solution Approach 1:
The control unit measures voltages across power transistors during specific time intervals before using that information for stall detection. By performing these measurements preliminarily during normal operation intervals, the system accumulates data that can be analyzed for stall conditions without interrupting microstepping control.
Solution Approach 2:
The system dynamically switches transistor states to create measurement opportunities. During specific microstep intervals, transistors are switched to states that enable voltage measurement while maintaining overall microstepping operation. This dynamic state changing allows both precise control and measurement functionality.
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
Effectively detects overloads and adjusts operating points to prevent motor stall, reducing computational requirements and ensuring precise positioning without untimely stoppages.
Implementation Method 1
the control electronics being arranged to use space vector modulation to generate a sinusoidal waveform from a DC voltage
Implementation Method 2
The usual methods for detecting lock or stall in stepper motor gearboxes use means for detecting the value of the voltage induced in the motor phases
Data Source
AI summary
A control system for a multiphase brushless motor without a position sensor, incorporating drive control electronics, comprising: a switching means, provided with two-state switches for varying the electrical voltage applied to each of the phases; a means for detecting overloading of the motor; and a means for determining an operating point, allowing at least two operating points to be applied, the control electronics being arranged to use space vector modulation or vector modulation to generate a sinusoidal waveform from a DC voltage, and the control electronics being arranged to modify the operating point at least once if an overload is detected by the overload detection means.