Sensorless Motor Position Detection via Current Ripple Analysis
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Solution Overview
Problem
Existing motor control systems for seat positioning in vehicles rely on expensive Hall Effect sensors to determine motor positions, which can be costly and impractical for systems with multiple motors, and fail to accurately estimate motor positions during power discontinuation due to inertia.
Innovation Solution
A sensorless system that measures motor current ripples to estimate motor positions, inertia, and resting positions without physical sensors, using decay factors and rotational speeds to predict motor positions after power discontinuation, allowing for accurate seat recall functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall Effect sensors are used to sense motor positions, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the position sensing function from physical Hall Effect sensors and implements it through software-based detection of current ripples. The motor controller measures current variations during commutation to determine motor position, eliminating the need for separate sensor hardware while maintaining position detection capability
Solution Approach 2:
The patent replaces the mechanical/electronic sensor system with an electrical measurement system. By analyzing current ripple characteristics during motor commutation, the system substitutes physical sensors with electronic signal processing to achieve position sensing
2Measurement precision
If Hall Effect sensors are used for each motor, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent makes the motor controller perform multiple functions: it both controls motor operation and senses motor position simultaneously. The same current measurement circuit used for motor control is also used for position detection, eliminating the need for separate sensor hardware and reducing overall system cost
Solution Approach 2:
The motor's own current consumption during commutation is used to provide position information. The system leverages the existing current flow required for motor operation to generate the sensing signal, making the motor itself serve the dual purpose of actuation and sensing
3Measurement precision
If motor position is determined during power discontinuation, then seat recall precision is improved, but measurement precision deteriorates due to inertia
Solution Approach 1:
The patent performs position measurement during the active power phase before discontinuation, when current ripples are clearly detectable. The measured position and speed data are then used to predict the rest position, avoiding the need to measure during the unreliable coasting period
Solution Approach 2:
The system uses feedback from current ripple measurements during active operation to continuously update motor position and speed estimates. This feedback loop allows accurate tracking of motor state, enabling reliable prediction of rest position even during power discontinuation when direct measurement would be unreliable
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
Enables accurate determination of motor positions and inertia without Hall Effect sensors, reducing costs and improving seat recall precision by estimating motor positions and inertia based on current and voltage measurements.
Implementation Method 1
determine a first position of the motor at a first time when power supply to the motor is initially discontinued based on ripples in the current supplied to the motor during a first period before the first time
Implementation Method 2
determine a second position of the motor at a second time when the motor stops rotating after power supply to the motor is discontinued based on the first position of the motor and a rotational speed of the motor at the first time
Data Source
AI summary
A system includes a motor control module and an occupant weight classification module. The motor control module is configured to supply power to a motor to move a seat in a first direction from a first position to a second position when the seat is unoccupied and supply power to the motor to move the seat in a second direction from a third position to a fourth position when an occupant is in the seat. The occupant weight classification module is configured to measure a first frequency of ripples in current supplied to the motor as the seat is moved from the first position to the second position, measure a second frequency of ripples in the current supplied to the motor as the seat is moved from the third position to the fourth position, and determine a weight of the occupant based on the first and second frequencies.