Motor Drive STO Redundancy and Diagnosis
Solution Overview
Problem
Existing motor drive systems lack a robust redundancy infrastructure for safety torque off (STO) modules, which can lead to accidents due to unexpected motor startups or failures, necessitating a solution for diagnosing and ensuring the reliability of STO modules.
Innovation Solution
A motor drive system with two STO modules and a diagnosis module that compares control signals to determine module functionality, ensuring a two-channel STO redundancy infrastructure and proactive fault diagnosis to meet safety requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single STO module is used in the motor drive system, then the device complexity is reduced, but the safety and reliability are insufficient due to lack of redundancy
Solution Approach 1:
The STO function is segmented into two independent STO modules (first STO module and second STO module), each capable of independently executing the STO function. This segmentation provides redundancy where if one module fails, the other can still ensure safety, thus improving reliability while maintaining manageable complexity through modular design
Solution Approach 2:
Different STO modules are assigned to control different switches: the first STO module controls the high-voltage side switch while the second STO module controls the low-voltage side switch. This local differentiation ensures that safety functions are distributed across critical components, improving overall system safety without requiring complete redundancy of entire control circuits
2Reliability
If two STO modules are implemented for redundancy, then the safety is improved, but the device complexity increases
Solution Approach 1:
The diagnosis function is merged into an existing microcontroller unit rather than being implemented as a separate dedicated hardware system. The microcontroller captures and compares driving signals from both STO modules, determining their operational status through software logic. This merging approach provides the necessary redundancy monitoring while avoiding the complexity of adding entirely separate diagnostic hardware
Solution Approach 2:
The microcontroller serves multiple functions: it controls the overall motor drive system operation and simultaneously performs the diagnostic function for monitoring STO module status. This multi-functionality reduces the need for dedicated diagnostic hardware, thereby improving safety through redundancy monitoring while keeping the overall device complexity manageable
3Reliability
If STO modules are added to meet safety requirements, then the safety is improved, but the manufacturing cost increases
Solution Approach 1:
Instead of implementing a completely redundant dual-STO architecture with separate diagnostic hardware, the system uses a cost-effective approach by copying the STO function across two modules while utilizing the existing microcontroller for diagnosis. This copying strategy with shared diagnostic resources meets safety requirements through functional redundancy while avoiding the high costs associated with fully independent redundant systems
Solution Approach 2:
The STO modules and diagnostic system are designed to be self-monitoring through the microcontroller's automatic capture and comparison of driving signals. The system performs self-diagnosis without requiring external monitoring equipment or complex additional hardware, thereby reducing manufacturing costs while ensuring safety through automated fault detection
Data Source
AI summary
A motor drive system and a control method are provided. The motor drive system is electrically connected to a motor. The motor drive system includes two safe torque off (STO) modules to achieve a two-channel STO redundancy infrastructure, so as to improve the safety of the motor drive system. In addition, the motor drive system includes a diagnosis module to diagnose malfunction of the STO modules. It ensures the STO modules to meet the related safety requirements.