Redundant Position Sensing Using Motor Drive Variables
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Solution Overview
Problem
Conventional multi-chip position sensors for motors are complex, expensive, and prone to simultaneous failure due to spatial and functional proximity, compromising safety in safety-critical applications.
Innovation Solution
A position sensor system comprising a primary sensor for direct position detection and a secondary sensor that estimates position based on drive motor variables, utilizing multiple signal paths to ensure redundancy and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-chip position sensors are used for redundant position detection, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The invention segments the redundant detection system into two functionally independent parts: a primary sensor for direct position measurement and a secondary sensor for deriving position from drive variables. This segmentation avoids the complexity of integrating multiple chips into a single sensor assembly while maintaining redundancy through functional differentiation.
Solution Approach 2:
The evaluation device performs multiple functions: it processes signals from both primary and secondary sensors, determines position from either sensor independently, and evaluates whether the sensors agree. This multi-functionality consolidates what would otherwise require separate dedicated circuits into a single integrated evaluation unit, reducing overall device complexity.
2Reliability
If multi-chip position sensors are used for redundant position detection, then reliability is improved, but manufacturing cost increases
Solution Approach 1:
The invention replaces expensive multi-chip sensor assemblies with more economical components: a standard position sensor (primary) and existing drive motor variables (secondary). The secondary sensor utilizes already-present motor parameters (current, voltage, frequency) rather than requiring additional expensive sensor chips, significantly reducing manufacturing cost while maintaining redundancy.
Solution Approach 2:
Instead of using physical copies (multiple sensor chips) to achieve redundancy, the invention creates a functional copy through the secondary sensor that derives position information from drive variables. This virtual copying approach achieves the same redundancy goal without the cost of duplicate physical sensor hardware.
3Reliability
If multiple chips are integrated into a single position sensor, then redundant position detection is achieved, but susceptibility to simultaneous failure increases
Solution Approach 1:
The invention extracts the secondary position information from the drive motor system itself, using drive variables (current, voltage, frequency) that are already present in the motor control system. By taking out the position detection function and implementing it through the motor's own operational parameters rather than through additional sensor chips, the system achieves redundancy while eliminating the spatial proximity that causes simultaneous failure.
Solution Approach 2:
The evaluation device acts as an intermediary that compares and reconciles information from the primary sensor and the secondary sensor. It determines position from either sensor independently and evaluates whether they agree, providing a mediation layer that prevents single-point failures from affecting the entire system while maintaining spatial separation between the actual sensing elements.
4Device complexity
If conventional position sensors are used, then device simplicity is maintained, but safety in safety-critical applications is compromised
Solution Approach 1:
The invention introduces dynamic evaluation where the system continuously monitors agreement between primary and secondary position sensors and can adaptively switch between them or trigger safety protocols when discrepancies occur. This dynamic behavior adds safety functionality without requiring a completely complex redundant sensor architecture, maintaining relative simplicity while achieving safety-critical reliability.
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
Reduces the risk of total system failure by using cost-effective single-die sensors with redundant signal paths, enhancing safety and flexibility in safety-critical applications.
Implementation Method 1
The primary sensor can measure a change in the magnetic field caused by the movement of the magnetic element and use this to determine the position
Data Source
Figure 1
Figure 2
AI summary
A position sensor for redundantly determining the position of an element (10) that is movable by a drive motor (20), comprising a primary sensor (110) and a secondary sensor (120). The primary sensor (110) is designed to directly sense the position of the movable element (10). The secondary sensor (120) is designed to derive the position of the movable element (10) from at least one secondary measurement (25), wherein the secondary measurement (25) is based on a drive variable of the drive motor (20).