Analog Lockout Lever Sensing for Closed-Circuit Failure Detection
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Solution Overview
Problem
Existing systems fail to detect closed circuit failures in dual sensor detection systems for hydraulic lockout levers in excavators, leading to unsafe operation when both switches malfunction, as the system cannot differentiate between a locked and unlocked position, potentially allowing hydraulic fluid flow despite the operator's belief in safe locking.
Innovation Solution
A hydraulic lockout lever failure detection system utilizing two analog sensors and an electronic control module (ECU) to monitor voltage outputs, where specific voltage levels indicate the lever's position, and a lockout solenoid valve controls hydraulic fluid flow, preventing operation when a closed circuit failure is detected by ensuring the solenoid valve remains locked or unlocked based on sensor outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual switches are used to detect hydraulic lockout lever position, then the system can detect open circuit failures, but the system cannot detect closed circuit failures when both switches malfunction simultaneously
Solution Approach 1:
The patent replaces the mechanical switch system with an analog sensor system that provides continuous voltage signals corresponding to lever position. This substitution eliminates the binary on/off state limitation of switches and enables continuous monitoring of lever position, allowing detection of closed circuit failures where both sensors would output identical voltages indicating a stuck position.
Solution Approach 2:
The patent changes the detection parameter from binary switch states (open/closed circuit) to continuous analog voltage levels. By monitoring voltage thresholds (e.g., 0.5V for locked position, 4.5V for unlocked position), the system can detect failures when both sensors report the same voltage level, indicating they are stuck in one position rather than accurately reflecting the actual lever position.
2Device complexity
If switches are used in the detection system, then the system structure is simple, but the system cannot differentiate between locked and unlocked positions when both switches fail
Solution Approach 1:
The patent replaces mechanical switches with analog sensors that output continuous voltage signals. This substitution maintains relative simplicity while dramatically improving measurement precision, as the analog voltage level directly corresponds to the lever position angle, enabling accurate differentiation between locked and unlocked positions even when failure occurs.
3Ease of operation
If the hydraulic lockout lever position is monitored using two switches, then the system can alert the operator of switch malfunctions, but the system cannot prevent operation when both switches fail in the unlocked position
Solution Approach 1:
The patent implements a feedback system where the ECU continuously monitors analog sensor voltages and compares them against expected thresholds. When both sensors report identical voltage levels (indicating they are stuck in the same position), the ECU detects this as a failure condition and provides feedback by preventing solenoid valve actuation, thereby preventing hydraulic operation and ensuring safety.
Solution Approach 2:
The patent applies preliminary anti-action by preventing the solenoid valve from actuating when a failure condition is detected. The ECU monitors sensor voltages before allowing operation and blocks the control signal to the solenoid valve if both sensors indicate the same position, thereby preventing potentially unsafe hydraulic operation before it can occur.
Data Source
AI summary
A hydraulic lockout lever failure detection system preferably includes a first analog sensor, a second analog sensor, at least one electronic control module (ECU) and a solenoid valve. The voltage output level of the first and second analog sensors is monitored by the ECU. The solenoid valve controls the flow of hydraulic fluid to operate an excavator or other equipment. The operation of the solenoid valve is controlled by the ECU. However, a second ECU may be used to control the operation of the solenoid valve. A hydraulic lockout lever causes the first and second analog sensors to output either a low voltage to indicate a closed position, or to indicate an open position to the ECU. If the first and second analog sensors output a voltage that is above a low set value or above a high set value, a fault is detected.