Crane Control System Prevents Load Drop via Hydraulic Leakage Detection
Solution Overview
Problem
Hydraulic cranes with hydraulically actuated tools face safety issues due to hydraulic liquid leakage, which can cause tools to lose their holding position when inactive, leading to unintentional object dropping during lifting.
Innovation Solution
A method that detects when the tool is in a holding position and the arm is unloaded, registers a time period, and activates a safe operation mode if the condition persists beyond a threshold, preventing arm movement until the tool is confirmed in a holding position, either manually or automatically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the crane operator waits a period of time before lifting the object after commanding the tool to grip, then the operator can prepare for the lifting operation, but hydraulic liquid leakage may cause the tool to lose its holding position and drop the object
Solution Approach 1:
The control system performs preliminary verification of the holding position before allowing lifting operations. The system detects whether the tool is in the holding position and the arm is unloaded, then requires a specific sequence of operations (moving arm away and back) to be completed before enabling lifting, ensuring the tool is properly positioned in advance
Solution Approach 2:
The control system continuously monitors the holding position status and provides feedback control. The system detects the holding position condition and uses this information to control whether the arm can be moved, creating a closed-loop control that prevents lifting unless the tool is verified to be in the correct holding position
2Reliability
If the tool is mechanically locked in holding position during active lifting, then the object can be securely held, but leakage during inactivity may result in the tool not being in the perfect holding position when lifting starts
Solution Approach 1:
The control system performs preliminary verification of the holding position before allowing lifting operations. The system detects whether the tool is in the holding position and the arm is unloaded, then requires a specific sequence of operations (moving arm away and back) to be completed before enabling lifting, ensuring the tool is properly positioned in advance
Solution Approach 2:
The control system prevents the harmful effect of leakage by requiring a specific sequence of operations to be completed before lifting is enabled. The system blocks the lifting function until the tool has been verified to be in the correct holding position through the predetermined operation sequence, counteracting the potential negative effect of leakage
3Reliability
If the control system prevents arm movement during safe operation mode, then object dropping is prevented, but the crane operator cannot perform lifting operations until the safe operation mode is deactivated
Solution Approach 1:
The control system can automatically deactivate the safe operation mode by actuating the second hydraulic valve to move the tool to the holding position, without requiring manual intervention from the operator. This self-service capability reduces the time the crane is non-operational while maintaining safety
Data Source
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AI summary
A crane (1) comprising a movable arm (2), and a tool (9) provided at an end of the movable arm (2). The crane (1) comprises a control system configured to a) detect a first condition in which the tool (9) is in a holding position and the movable arm (2) is in an unloaded condition in which it is not actively lifting an object held by said tool (9), b) registering a first point of time at which the first condition is obtained and counting a period of time (t) from the first point of time, and, c) when the counted period of time (t) exceeds a threshold value (tthreshold), activating a safe operation mode in the control system which prevents a first hydraulic device (3, 4, 5) from moving the movable arm (2), said safe operation mode being deactivatable by an actuation of a second hydraulic valve for controlling the holding position of the tool (9).