Working Machine Safety System Using ZMP Stability Monitoring
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Solution Overview
Problem
Existing working machines, such as hydraulic excavators, face challenges in maintaining stability during dynamic operations due to inertia forces generated by quick motions, which are not adequately considered in conventional stability monitoring systems, leading to reduced operator efficiency and potential tipping risks.
Innovation Solution
A safety system equipped with state quantity sensors, a ZMP calculating means, and a stability computing means that provides real-time stability information and tipping warnings to operators, using a ZMP (Zero Moment Point) as a stability evaluation index, allowing for precise recognition of stability during dynamic operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional stability monitoring systems are used, then the system structure is simple, but the stability assessment is inaccurate during dynamic operations due to ignoring inertia forces
Solution Approach 1:
The system continuously monitors the ZMP position and provides real-time feedback to the operator through display devices and warning systems. The controller calculates the ZMP based on sensor data and compares it with the support polygon boundaries, creating a closed-loop feedback system that enables dynamic stability assessment during operations.
Solution Approach 2:
The patent introduces a ZMP (Zero Moment Point) as an intermediary concept to represent the combined effect of gravity and inertia forces. Instead of directly measuring complex dynamic forces, the system calculates the ZMP position which serves as a mediator to indicate stability status, simplifying the measurement while maintaining accuracy.
2Loss of information
If real-time stability monitoring is implemented, then operator awareness of stability is improved, but the device complexity increases due to additional sensors and computing means
Solution Approach 1:
The controller serves multiple functions: it controls the front working mechanism, calculates the ZMP position, determines stability status, and triggers warning signals. By making the controller multi-functional, the system avoids adding separate dedicated devices for each function, thereby reducing overall system complexity while maintaining comprehensive stability monitoring.
Solution Approach 2:
The system uses the existing sensor network of the working machine to gather necessary data for ZMP calculation. Instead of requiring a completely separate monitoring system with its own sensors, the stability monitoring function utilizes the machine's existing state quantity sensors, allowing the system to monitor its own stability using available resources.
3Measurement precision
If dynamic motion effects are considered in stability calculation, then the stability assessment becomes more accurate, but the computational complexity increases
Solution Approach 1:
The system transforms the complex dynamic stability problem into a parameter-based ZMP calculation. By changing the approach from directly analyzing multiple force vectors to calculating a single ZMP position coordinate, the system maintains accuracy in assessing dynamic stability while simplifying the computational process to coordinate geometry operations.
Data Source
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AI summary
Disclosed is a safety system for a working machine, which allows an operator to instantaneously, readily and precisely recognize current stability during work including operations of a front working mechanism and swing operations. In a safety system for a working machine, a controller is provided with a ZMP calculating means (60f) for calculating coordinates of a ZMP by using position information, acceleration information and external force information on respective movable portions of a main body, which includes a front working mechanism, and undercarriage, and a stability computing means (60d) for calculating a support polygon formed by plural ground contact points of the working machine with a ground, and, when the ZMP is included in a warning region formed inside a perimeter of the support polygon, producing a tipping warning; the safety system is provided with a display (61d) for displaying a top plan view of the working machine and a ZMP position of the working machine relative to the support polygon; the ZMP calculating means and stability computing means compute and display the ZMP position and the support polygon including the warning region therein; and the safety system produces a tipping warning when the calculated ZMP position is included in the warning region formed inside the perimeter of the support polygon.