Rotatable Load Hydraulic Control With Valve-Displacement Switching

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Solution Overview

Problem

Hydraulic systems in construction machines face inefficiencies in controlling rotatable loads due to high energy losses at high rotational speeds and mechanical play issues, particularly when using over-center four-quadrant hydraulic machines without a valve arrangement, leading to difficulties in start-up and stopping processes.

Innovation Solution

A method that determines the operating state of the hydraulic system based on rotational speed, torque, or power to switch between valve control and displacement control modes, applying a non-zero absolute minimum displacement limitation, and using a valve arrangement to control the rotatable load, thereby reducing energy losses and facilitating start-up and stopping processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If valve control mode is used to control rotatable load at high rotational speeds, then control precision is maintained, but energy losses increase significantly

Engineering Contradiction:

Improvecontrol precisionVSAvoidenergy losses

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The system dynamically switches between valve control mode and displacement control mode based on operating conditions (rotational speed, torque, power). At low speeds, valve control provides precise control; at high speeds, displacement control reduces energy losses by maintaining a more open valve position, thereby resolving the contradiction between control precision and energy efficiency across different operating ranges.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control system changes the dominant control parameter based on operating state: using valve opening degree as the primary control parameter at low speeds for precision, and using hydraulic machine displacement as the primary control parameter at high speeds for energy efficiency. This parameter switching resolves the contradiction by optimizing the control approach for each speed range.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If over-center four-quadrant hydraulic machine is used without valve arrangement, then device complexity is reduced, but start-up and stopping processes become difficult due to mechanical play

Engineering Contradiction:

Improvedevice complexityVSAvoidstart-up and stopping processes

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The valve arrangement acts as an intermediary component between the hydraulic machine and the rotatable load. It provides a controlled fluid connection that eliminates the mechanical play issues present in direct over-center hydraulic machine connections, thereby facilitating smooth start-up and stopping processes while maintaining relatively simple device architecture.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system replaces direct mechanical connection (which causes play and control issues) with hydraulic control through the valve arrangement. This substitution of mechanical coupling with fluid-based control resolves the start-up and stopping difficulties while keeping the overall device complexity manageable.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of energy

If displacement control mode is used at high power operations, then energy losses are reduced, but control accuracy may be compromised

Engineering Contradiction:

Improveenergy lossesVSAvoidcontrol accuracy

Core Design Contradiction:

Loss of energyVSMeasurement precision

Solution Approach 1:

The system dynamically adapts the control mode based on power level and operational requirements. During high-power operations, displacement control minimizes energy losses; during precision-critical operations, valve control restores accuracy. This dynamic adaptation resolves the contradiction by allowing each control mode to operate in its optimal performance range.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control range is segmented into different operational zones: displacement control handles high-power, less precision-critical operations to minimize energy losses, while valve control handles low-power, precision-critical operations. This segmentation allows the system to optimize for energy efficiency or control accuracy depending on the specific operational context.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS11795661B2Method of controlling a rotatable load, a hydraulic system and a working machine

Publication Date: 2023.10.24 NORRHYDRO

AI summary

A method of controlling a rotatable load by a hydraulic system, the method includes determining if the hydraulic system is in a first operating state or a second operating state; controlling the rotatable load in a valve control mode if the hydraulic system is in the first operating state, the valve control mode including controlling the rotatable load by controlling a valve arrangement; controlling the rotatable load in a displacement control mode if the hydraulic system is in the second operating state, the displacement control mode including controlling the rotatable load mainly by controlling the displacement of a hydraulic machine; and applying a non-zero absolute minimum displacement limitation to the hydraulic machine at least in the valve control mode.