Electric Actuator Control System Fail-Safe Transition

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Solution Overview

Problem

Existing control systems for electric actuators fail to reliably transition to a fail-safe state when a failure occurs, as they rely on a single diagnostic signal that may not be cut off due to broken circuits or temporary abnormalities, leading to potential improper control.

Innovation Solution

Implementing a diagnostic process where multiple control units communicate and output abnormal determination signals to an AND circuit, ensuring that if any unit detects abnormality, the electric power to the actuator is cut off, even if one unit's signal is faulty, thereby preventing mistaken control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single diagnostic signal is used to control electric power supply, then the control system is simple, but the reliability of fail-safe transition is insufficient when circuit breakdown occurs

Engineering Contradiction:

Improvereliability of fail-safe transitionVSAvoidcomplexity of diagnostic system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The diagnostic function is segmented into multiple independent control units (first control unit and second control unit), each capable of independently diagnosing abnormality. This segmentation ensures that a failure in one unit does not compromise the entire diagnostic system, thereby improving reliability of fail-safe transition while maintaining manageable complexity through modular design.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system incorporates redundant diagnostic capabilities as a preventive measure against circuit breakdown. By having multiple control units that can independently detect abnormalities and both being able to forcefully cut off electric power, the system cushions against the risk of single-point failures, ensuring reliable fail-safe transition even when one diagnostic path is compromised.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Reliability

If electric power is cut off when abnormality is detected, then mistaken control is prevented, but the system cannot forcefully transition to fail-safe state when diagnostic circuit breaks down

Engineering Contradiction:

Improveability to forcefully transition to fail-safe stateVSAvoidrisk of improper control due to circuit failure

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

Instead of relying on a single diagnostic unit to control power cutoff, the system inverts the logic by enabling both control units to independently forcefully cut off electric power to the drive circuit. This inversion ensures that even if one diagnostic circuit fails, the other unit can still execute the fail-safe power cutoff, preventing improper control while maintaining high reliability.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The electric power cutoff mechanism acts as an intermediary that both control units can directly activate. This intermediary power cutoff function serves as a common fail-safe execution path that bypasses potential diagnostic circuit failures, allowing either control unit to forcefully transition the system to a fail-safe state by cutting power to the drive circuit.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If multiple control units are used for diagnosis, then reliability of abnormality detection is improved, but the system complexity increases

Engineering Contradiction:

Improvereliability of abnormality detectionVSAvoidnumber of control units

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The diagnostic system is divided into two independent control units, each capable of autonomous abnormality detection. This segmentation improves reliability through redundant detection capabilities while controlling complexity by using a manageable number (two) of discrete units rather than a continuous or highly complex single-unit system.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Both control units share the common function of being able to forcefully cut off electric power to the drive circuit. This merging of the power cutoff capability into both units creates a unified fail-safe execution mechanism that simplifies the overall system architecture compared to having separate diagnostic and execution paths, thereby improving reliability without proportionally increasing complexity.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS9121361B2Control system of electric actuator and control method thereof

Publication Date: 2015.09.01 ASTEMO LTD

AI summary

In an aspect of the present invention, each of plural control units which controls drive of an electric actuator diagnoses existence of abnormality in drive control of the electric actuator, the abnormality differing from control unit to control unit; the control unit transmits diagnostic result thereof to another control unit; the control unit outputs an abnormal determination signal as a signal indicating diagnostic result therefrom when at least one of the diagnostic result thereof and the diagnostic result of another control unit indicates abnormality; and the control unit transfers the drive control of the electric actuator to an abnormal use control state when the abnormal determination signal is output from at least one of the plural control units.