Load-Sensing Hydraulic Safety Control for Stationary Demolition Arms
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Solution Overview
Problem
Construction equipment, particularly demolition robots, pose hazards due to unexpected movements of their movable members, which can injure nearby persons and fail to meet safety standards like ISO 13849.
Innovation Solution
A hydraulic system with a load sensing (LS) circuit and a control unit that configures the system in a safe mode, using pressure feedback to ensure movable members remain stationary, thereby protecting nearby individuals from unexpected movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydraulic system operates without additional safety sensors, then the device complexity and cost are reduced, but the safety and reliability are insufficient to meet ISO 13849 standards
Solution Approach 1:
The patent utilizes the existing load sensing circuit pressure feedback to monitor the state of movable members. The control unit continuously receives pressure feedback signals from the LS circuit and compares them against threshold values to detect unexpected movements, thereby implementing a safety function without adding separate sensors.
Solution Approach 2:
The patent makes the existing load sensing circuit serve a dual purpose: its original function of controlling hydraulic valve operation and an additional safety monitoring function. By using the same pressure feedback infrastructure for both control and safety purposes, the system avoids the need for separate safety sensors and reduces overall system complexity.
2Reliability
If a hydraulic system is equipped with separate safety sensors to detect unexpected movements, then the safety and reliability improve, but the device complexity and cost increase
Solution Approach 1:
The patent implements a multi-functional use of the load sensing circuit by enabling it to perform both its traditional hydraulic control function and an additional safety monitoring function. The same pressure feedback signal is used for both valve control and unexpected movement detection, eliminating the need for separate safety sensors and reducing system complexity.
Solution Approach 2:
The control unit continuously monitors the pressure feedback signal from the load sensing circuit and compares it against predetermined threshold values. This feedback mechanism enables the system to detect unexpected movements of movable members and trigger appropriate safety responses without requiring additional sensing hardware.
3Reliability
If the hydraulic system triggers a safety-related action immediately upon detecting unexpected movement, then the safety response time is reduced, but the productivity and operational continuity are affected
Solution Approach 1:
The patent differentiates between hazardous and non-hazardous functions by implementing separate monitoring thresholds and response strategies for each. The control unit can trigger safety actions for hazardous functions while allowing non-hazardous functions to continue operating, thereby maintaining operational continuity where safe to do so.
Solution Approach 2:
The system uses different pressure threshold values to distinguish between normal operational variations and unexpected movements requiring safety intervention. By adjusting and monitoring pressure parameters against predefined thresholds, the system achieves rapid safety response only when genuinely needed, avoiding unnecessary shutdowns of productive operations.
Data Source
AI summary
A hydraulic system for controlling one or more movable members on construction equipment such as a demolition robot, where the hydraulic system is configurable in a safe mode of operation in which at least one of the movable members is intended to be stationary. The system comprises a load sensing (LS) circuit and a first hydraulic pressure sensor arranged to sense a first LS pressure in a first LS circuit part of the LS circuit. The system also comprises a control unit arranged to monitor the sensed first LS pressure, compare the first LS pressure to a predetermined acceptance criterion associated with stationarity of the one or more movable members, and trigger a safety-related action by the hydraulic system in case the first LS pressure does not satisfy the acceptance criterion even though the safe mode of operation is configured.