Stepper Motor Position Initialization via Abutment Detection
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Solution Overview
Problem
Stepper motor apparatuses used in automotive dashboards face inaccuracies due to vibrations and noise, leading to discrepancies between the actual and commanded positions of pointers, and variations in indication caused by thermal expansion and aged deterioration of components.
Innovation Solution
A stepper motor apparatus with a stopper and detection coil system that initializes the pointer's position by rotating it backward to abut the stopper, using a position detection device to determine abutment and store a predetermined phase, allowing the motor to maintain accurate rotation despite changes in the abutment position due to thermal or aged-related shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the stepper motor rotates the pointer based on commanded position without mechanical reference, then the system operation is simple, but the indication accuracy deteriorates due to vibrations and noise causing discrepancy between actual and commanded positions
Solution Approach 1:
The patent applies preliminary action by mechanically pre-positioning the pointer at a known zero point using a stopper before operation begins. The pointer is forced to abut the stopper during initialization, establishing a reliable mechanical reference position before any commanded rotation occurs, thereby eliminating accumulation of positioning errors
Solution Approach 2:
The patent implements feedback by continuously detecting the pointer's actual position using a detection coil that senses the position of a protrusion on the pointer. This actual position information is fed back to the control device, which calculates the difference between commanded and actual positions, and adjusts the driving signal accordingly to eliminate positioning errors caused by vibrations and noise
2Measurement precision
If the pointer position is initialized by forcing abutment with stopper, then the initial position accuracy is improved, but the device complexity increases due to additional stopper and detection mechanisms
Solution Approach 1:
The patent applies universality by making the detection coil serve dual functions: it detects both the pointer's position during normal operation and detects the abutment state between the protrusion and stopper during initialization. The same coil that monitors position continuously also triggers the initialization sequence when abutment is detected, eliminating the need for separate detection mechanisms
Solution Approach 2:
The patent implements self-service by designing the initialization mechanism to be self-activating. When the pointer rotates backward and the protrusion abuts the stopper, the detection coil automatically detects this position and triggers the control device to initiate the initialization sequence without external intervention. The system uses its own position detection capability to initiate its own initialization process
3Measurement precision
If the driving signal is continuously adjusted to correct position errors, then the indication accuracy is improved, but the energy consumption increases due to frequent corrections
Solution Approach 1:
The patent applies preliminary action by establishing an accurate mechanical reference position at the zero point before operation begins. By pre-positioning the pointer at this known accurate location through forced abutment with the stopper, the system eliminates the need for continuous energy-consuming corrections to maintain baseline accuracy, reducing overall energy consumption while preserving position accuracy
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
Ensures the pointer maintains accurate positioning by initiating rotation at a predetermined phase, preventing variations in indication caused by thermal expansion or aged deterioration, thus stabilizing the pointer's position on the dashboard dial.
Implementation Method 1
a detection coil producing an induced voltage by means of rotation of the stepper motor
Data Source
AI summary
The object of the invention is to provide a stepper motor apparatus and a method for controlling a stepper motor, and particularly relates to a stepper motor apparatus for driving a pointer and a method for controlling the stepper motor. When an ignition switch is turned on, CPU 12 starts to feed a driving signal into the stepper motor in order to cause the stepper motor to rotate in a backward direction. Upon detecting that a protrusion 9 is in abutment with a stopper 10 on the basis of induced voltage generated on excitation coils 5 and 6, CPU stop rotation of the stepper motor 3 by maintaining the driving signal's phase at which the abutment is detected. Subsequently, CPU 12 feeds the driving signal into the stepper motor 3 in order to drive the stepper motor 3 to rotate in a direction where the protrusion 9 is driven against the stopper 10, and then stops rotation of the stepper motor 3 in a forward direction by maintaining a predetermined phase at which the driving signal arrives. Thereafter, CPU 12 drives the stepper motor to rotate such that a pointer 1 homes in on its commanded position θi.