Closed-Loop Swing Control for Excavator Oscillation Damping
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Solution Overview
Problem
Existing hydraulic swing control systems for machines like excavators and mining shovels face challenges in controlling swing speed and torque due to large inertial loads and the lack of effective damping, leading to oscillations and inefficiencies, especially when using displacement control pumps and closed-loop hydraulic circuits.
Innovation Solution
A closed-loop hydrostatic circuit system with an electronic displacement control pump, pressure sensors, and a controller that allows for both speed and torque control modes, using a single user interface to manage swing motor operations, thereby controlling the actual speed and torque of the swing motor based on user input and mode selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If displacement control pumps are used to control swing motor speed, then speed control is achieved, but the swing speed oscillates due to large inertial forces, compressible fluid volume in hoses, and lack of oscillation damping
Solution Approach 1:
The patent implements a closed-loop control system using feedback from sensors (load cell, encoders, pressure transducers) to continuously monitor and adjust swing motor operation. The microprocessor controller receives feedback signals and modifies pump displacement in real-time to maintain stable swing speed, eliminating the oscillations inherent in open-loop displacement control systems.
Solution Approach 2:
The patent replaces traditional hydro-mechanical swing control valves with an electronically controlled displacement pump system. This substitution allows precise electronic control of pump displacement based on feedback signals, enabling stable speed control without the oscillations caused by mechanical valve dynamics and compressible fluid volumes in traditional hydraulic systems.
2Adaptability or versatility
If hydro-mechanical valves are used in the hydraulic circuit, then swing control characteristics are determined by valve selection and setting, but the system cannot provide both torque control and speed control with the same hydraulic circuit
Solution Approach 1:
The patent designs a universal hydraulic control system where a single electronically controlled displacement pump can operate in multiple modes (speed control and torque control) depending on feedback signal configuration. The same hardware circuit provides both control functions by adjusting pump displacement based on different sensor inputs and control algorithms, eliminating the need for separate hydraulic circuits for each control mode.
Solution Approach 2:
The patent replaces traditional hydro-mechanical control valves with an electronically controlled pump system that uses sensors and a microprocessor to determine control characteristics. This electronic control system can dynamically switch between speed control and torque control modes without requiring physical reconfiguration of the hydraulic circuit, reducing overall system complexity while increasing versatility.
3Ease of operation
If the upper carriage swings through the air without ground contact, then there is no significant oscillation damping from resistive contact, but oscillations are not effectively reduced
Solution Approach 1:
The patent uses feedback from load cells and encoders to detect oscillations during swing operations. The microprocessor controller processes this feedback and adjusts pump displacement in real-time to counteract oscillations, providing active damping control that works effectively whether the upper carriage is in contact with the ground or swinging through air.
Solution Approach 2:
The patent introduces an electronic control system as an intermediary between the operator's swing command and the hydraulic actuation. This intermediary processes feedback signals and modulates pump displacement to provide oscillation damping, effectively adding a control layer that compensates for the lack of natural mechanical damping from ground contact.
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
The system effectively reduces oscillations and improves control precision by allowing seamless transition between speed and torque control modes, enhancing operator flexibility and machine performance across various operations.
Implementation Method 1
The electronic displacement control pump is configured to control the supply of a fluid to a first swing motor based on a final pump displacement command
Implementation Method 2
The speed sensor is configured to measure an actual speed of the first swing motor
Implementation Method 3
The first pressure sensor is configured to measure an input pressure of the fluid received by the first swing motor. The second pressure sensor is configured to measure an output pressure of the fluid discharged from the first swing motor
Implementation Method 4
The first swing motor is fluidly connected to the electronic displacement control pump. The first swing motor is configured to rotate the upper carriage of the machine
Data Source
AI summary
A system and method for controlling the swing of a machine is disclosed. The system may comprise a hydrostatic circuit that includes an electronic displacement control pump and a first swing motor fluidly connected in a closed loop circuit. The electronic displacement control pump configured to control the supply of fluid to the swing motor based on a final pump displacement command. The first swing motor configured to rotate the upper carriage of the machine. The hydrostatic circuit configured to control (a) an actual speed of the first swing motor when the final pump displacement command results from a requested swing motor speed and (b) a torque of the first swing motor when the final pump displacement command results from a requested swing motor torque.