Stepper Motor Position Control via Magnetic Sensor Feedback
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Solution Overview
Problem
Stepper motors used in HVAC systems of motor vehicles face issues with position errors during stall events and inability to detect rotation anomalies, making precise position control and shortest path determination challenging.
Innovation Solution
A method for controlling the angular position of a stepper motor without stops, including a correspondence test, verification step, and mode switching to relative mode to detect anomalies and record faults, allowing for optimized diagnosis and calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stepper motors use stops to limit movement and check position, then the motor position can be checked with respect to stops, but position errors are introduced during stall events and the location procedure becomes relatively long
Solution Approach 1:
The patent removes the physical stop mechanism from the system entirely. Instead of using mechanical stops to limit and detect end positions, the invention uses a magnetic field sensor to detect the position of a magnet attached to the motor shaft. This extraction of the mechanical stop allows for continuous, non-contact position detection without the delays and errors associated with mechanical blocking and stall event identification.
2Measurement precision
If stepper motors block several motor steps on stops to identify them, then the final position can be determined, but the location procedure becomes relatively long and errors in direction of rotation cannot be detected
Solution Approach 1:
The patent implements continuous feedback by using a magnetic field sensor to constantly monitor the position of the magnet on the motor shaft. The sensor provides real-time position information to the control system, enabling immediate detection of position errors and direction errors without requiring the motor to block steps or enter stall events. This continuous feedback loop allows for dynamic correction and eliminates the need for periodic position checking that slows down the system.
3Measurement precision
If stepper motors use stops to determine position, then the position can be checked, but it is not possible to detect operating anomalies
Solution Approach 1:
The patent introduces a magnetic field sensor as an intermediary between the motor shaft and the control system. This sensor detects the position of a magnet attached to the shaft and provides continuous position information. The intermediary sensor enables the detection of operating anomalies such as unexpected position deviations, direction errors, and mechanical issues without requiring the motor to interact with physical stops or enter stall conditions.
4Ease of operation
If stepper motors make an almost complete revolution to go from one position to another, then the shortest path can be determined, but the operation becomes less efficient
Solution Approach 1:
The patent performs preliminary action by continuously tracking the motor shaft position using a magnetic field sensor and magnet. This continuous position information allows the control system to calculate the shortest path between any two positions in advance, without requiring the motor to make unnecessary complete revolutions. The pre-available position data enables efficient path planning and direct positioning, improving motor operation efficiency while maintaining the capability to determine the shortest path.
Data Source
Figure 1~2
Figure 3a~3f
AI summary
The invention relates to a method for controlling the angular position [STP_POS] of a rotating, unrestricted moving part [1] of a stepper motor, said moving part [1] being intended to cooperate with at least one fixed part [2] whose state is capable of being modified during the rotation of the moving part [1] according to parameters [CAM_POS] previously defined as a function of the angular position [STP_POS] of the moving part [1]. The method includes a test step [18] for the correspondence of the state of the fixed part [2] with the parameters [CAM_POS] of the predefined modifications, in a mode where the position of the motor [STP_POS] is considered to be defined.The method further advantageously includes the verification steps [13], triggered when the matching test [18] is negative, during which at least one complete turn of the moving part [1] is carried out to verify the occurrence of changes in the state of the fixed part [2] according to the parameters previously defined [CAM_POS] as a function of the position [STP_POS] of the moving part [1] and of the decision to place the motor in normal mode [12] when the matching test [18] is positive or when the verification [13] is correct or in a relative mode [17] where the position [STP_POS] of the moving part [1] is relative when the verification [13] is erroneous.