Swing Motor Pressure Switching for Excavator Speed and Acceleration
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Solution Overview
Problem
Existing swing motor systems in construction machines, such as hydraulic excavators, face inefficiencies in rotational acceleration due to unadjusted swing motor torque, leading to inconsistent rotational speed and inability to achieve desired rotational acceleration.
Innovation Solution
A construction machine equipped with a rotational speed sensor, pressure sensor, and a controller that adjusts the swing motor's driving pressure based on the moment of inertia and rotational speed deviation to match the target rotational speed, ensuring precise control of the swing motor's rotational speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the swing motor supply flow rate is controlled based on deviation between target and actual rotational speed, then the speed following characteristic is improved, but the swing motor torque cannot be adjusted and desired rotational acceleration cannot be obtained
Solution Approach 1:
The patent applies dynamics by making the control strategy adaptive based on the swing motor's operating state. The controller dynamically switches between flow rate control (for speed following) and pressure control (for rotational acceleration) depending on whether the swing motor is in acceleration phase or steady-state operation, allowing both speed following characteristic and rotational acceleration to be optimized at different times
Solution Approach 2:
The patent changes the controlled parameter from flow rate alone to a combination of flow rate and pressure based on operating conditions. By detecting the swing motor's rotational speed and comparing it with target speed, the system determines whether to prioritize flow rate control or pressure control, thereby achieving both speed following and rotational acceleration requirements
2Productivity
If the driving pressure of the swing motor is controlled to coincide with target driving pressure, then the rotational acceleration is improved, but the rotational speed deviation from target speed increases
Solution Approach 1:
The patent implements periodic action by alternating between pressure control mode and flow rate control mode based on the swing motor's acceleration state. During acceleration phase, pressure control is applied to maximize rotational acceleration; once target speed is approached, the system switches to flow rate control to eliminate speed deviation, creating a periodic control cycle that optimizes both acceleration and speed accuracy
3Force
If high pressure fluid is discharged from the relief valve to maintain swing motor differential pressure, then the swing motor torque is maintained, but energy efficiency deteriorates due to energy discarded as heat
Solution Approach 1:
The patent applies feedback by continuously detecting the swing motor's rotational speed and comparing it with the target rotational speed. Based on this feedback, the controller determines whether the swing motor is in acceleration phase or steady-state, and accordingly adjusts the hydraulic pump flow rate to match actual demand, preventing unnecessary high pressure discharge through the relief valve and reducing energy waste
Solution Approach 2:
The system performs self-service by using the detected rotational speed information to automatically regulate the hydraulic pump flow rate. The controller enables the pump to deliver flow rates that match the swing motor's actual requirements, eliminating the need for constant high pressure discharge and allowing the system to serve its own control needs without external intervention
Data Source
AI summary
Provided is a construction machine which can promptly adjust the rotational speed of a swing motor to a target rotational speed. A controller calculates a target rotational speed of the swing motor based on input from an operation device, calculates a degree of deviation of a rotational speed detected by a rotational speed sensor from the target rotational speed, sets a target driving pressure of the swing motor according to a moment of inertia about a swing axis of a swing structure and a work device and controls a pressure adjusting device in such a manner as to reduce a difference between a driving pressure detected by a pressure sensor and the target driving pressure, when the degree of deviation is larger than a predetermined value, and controls the pressure adjusting device in such a manner as to reduce a difference between the rotational speed detected by the rotational speed sensor and the target rotational speed, when the degree of deviation is equal to or smaller than the predetermined value.