Hydraulic Load Lowering With PWM Valve Fallback Control

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Solution Overview

Problem

The complexity of electro-hydraulic systems in work machines makes it difficult to identify and isolate faults, particularly when attempting to lower or lift loads safely, as normal operating algorithms may rely on potentially faulty components, posing hazards.

Innovation Solution

A system and method for controlled lowering and lifting of loads using a hydraulic actuator with a controller that initiates a safe lowering mode, disabling normal algorithms and employing pulse width modulation (PWM) current to control the first control valve, allowing operator input to adjust the PWM duty ratio for safe load management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If normal operating algorithms are used to lower or lift loads, then automated control is maintained, but system faults may cause hazardous situations

Engineering Contradiction:

Improveautomated controlVSAvoidsafety

Core Design Contradiction:

Extent of automationVSReliability

Solution Approach 1:

The control system is segmented into normal operating mode and safe lowering mode. When a fault is detected, the system transitions from automated normal control to a segmented safe mode where the load lowering function is isolated and controlled separately through PWM signals, preventing faulty algorithms from causing hazards while maintaining essential safety functionality

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system prepares for potential faults by having a pre-configured safe lowering mode ready to activate. This mode uses a simplified control algorithm with PWM duty cycle limits that prevent hazardous situations, acting as a cushion against the potential harm of undetected or undiagnosed faults in the normal operating algorithms

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Difficulty of detecting and measuring

If automated fault detection procedures are executed, then fault isolation is improved, but dangerous situations may arise if actuators are not in safe states

Engineering Contradiction:

Improvefault isolationVSAvoidhazard

Core Design Contradiction:

Difficulty of detecting and measuringVSObject-affected harmful factors

Solution Approach 1:

Before executing fault detection procedures, the system ensures the load is in a safe state by activating the safe lowering mode if needed. This preliminary action of securing the load position eliminates the hazard of suspended loads during diagnostic procedures, allowing fault isolation to proceed safely

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The PWM control system acts as an intermediary between the fault detection procedures and the hydraulic actuator. By providing direct, simple PWM control that bypasses complex algorithms, it mediates the interaction to ensure safe operation during diagnostic testing, allowing fault isolation without exposing the system to hazards

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If complex electro-hydraulic systems are used, then work machine functionality is enhanced, but fault identification and isolation become difficult

Engineering Contradiction:

Improvework machine functionalityVSAvoidsystem complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The safe lowering mode extracts and isolates the essential load lowering function from the complex electro-hydraulic system. By separating this critical safety function from the complex algorithms and multiple sensors, it creates a simplified control path using direct PWM signals to the control valve, making fault identification easier while preserving full work machine functionality

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables safe and controlled lowering and lifting of loads without relying on potentially faulty system components, reducing hazards by allowing direct operator control of the load's descent or ascent through PWM duty ratio adjustments.

Implementation Method 1

a pulse width modulation (PWM) current is sent from the controller to the first control valve

Methodology Applied

Scientific EffectPulse width modulation (PWM):

Implementation Method 2

a hydraulic actuator for supporting a load

Methodology Applied

Scientific EffectHydraulic pressure: Pressure Increase

Data Source

PatentUS11566399B2System and methods for controlled lowering and lifting of a load

Publication Date: 2023.01.31 DANFOSS AS

AI summary

A system and method for the controlled lowering and lifting of a load are disclosed. The system and method may include operating a work machine having a hydraulic system including a hydraulic actuator for supporting a load, a first control valve in fluid communication with the actuator, and a controller for operating the first control valve. In one embodiment, the controller includes a first algorithm for operating the first control valve in a load lowering operation. When an operational fault within the hydraulic system is detected, the controller can be configured to enter into a safe lowering mode. In the safe lowering mode, the first algorithm is disabled and a pulse width modulation (PWM) current is sent from the controller to the first control valve. A user interface is provided to allow an operator to control the PWM current duty ratio to allow the load supported by the actuator to be lowered.