Electric Motor Sensor Layout for SIL 3 Fault Separation
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Solution Overview
Problem
Existing sensor arrangements for electric motors do not adequately meet safety integrity level (SIL) requirements, particularly in terms of functional safety and resistance to common cause failures, while also lacking a compact design.
Innovation Solution
A sensor arrangement with spatially separated first and second sensor elements on a carrier plate, utilizing different sensor principles and a serial communication interface, including a safety-related transmission protocol like BiSS Safety, and allowing for independent design and implementation of sensor elements, with galvanic isolation and standard ICs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensor elements are arranged on a single chip with redundant structures, then device complexity is reduced, but resistance to common cause failures decreases
Solution Approach 1:
The sensor system is divided into spatially separated sensor elements mounted on different sides of a carrier plate, with each element having independent communication interfaces. This segmentation prevents common cause failures from affecting all sensors simultaneously while maintaining manageable device complexity through modular architecture.
Solution Approach 2:
A serial communication protocol acts as an intermediary between spatially separated sensor elements and the control unit, enabling coordinated operation while maintaining physical separation. This allows redundancy without requiring complex direct interconnections between sensors.
2Reliability
If multiple sensors are spatially separated to increase resistance to common cause failures, then reliability improves, but device complexity increases
Solution Approach 1:
Multiple sensor elements perform the same measurement function (detecting rotor position) and are processed through a unified serial communication protocol. This multi-functionality approach allows spatial separation for safety while using standardized interfaces to manage complexity.
Solution Approach 2:
The system changes the spatial parameter of sensor placement (separating them on different sides of the carrier plate) while maintaining electrical parameter standardization through serial communication. This allows improved reliability without proportionally increasing complexity.
3Ease of manufacture
If standard integrated circuits are used instead of specialized safety sensors, then cost is reduced and availability increases, but functional safety certification becomes more challenging
Solution Approach 1:
Instead of using specialized safety-certified sensors, the system uses copies of standard sensor ICs mounted in a redundant configuration. The serial communication protocol ensures that multiple independent sensor copies provide safety-related information, achieving functional safety through architecture rather than component certification.
Solution Approach 2:
The system changes the safety approach from component-level parameters (using certified sensors) to system-level parameters (using redundant standard sensors with serial communication validation). This allows use of readily available standard ICs while achieving required functional safety levels.
4Volume of moving object
If a compact sensor arrangement is implemented with sensors on opposite sides of a thin carrier plate, then motor size is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The sensor elements are nested on opposite sides of the thin carrier plate, with the plate itself serving as the mounting structure. This nesting approach achieves compact motor design while the standardized carrier plate provides reference surfaces that simplify placement precision requirements.
Solution Approach 2:
The carrier plate structure itself provides the mounting function for sensor elements, eliminating the need for separate mounting brackets or complex positioning mechanisms. The plate's physical structure naturally defines the sensor spacing and orientation, reducing manufacturing precision requirements.
Data Source
Figure 1~2
AI summary
The invention relates to a sensor arrangement (12) for an electric motor (10), comprising at least one carrier plate (14) having a top (16) and a bottom (18), wherein a first sensor element (20) is arranged on the top (16) and a second sensor element (22) is arranged on the bottom (18), wherein the first sensor element (20) and the second sensor element (22) each have a serial communication interface (24) for serial communication with each other. The invention further relates to an electric motor (10).