Electric Turning Motor Gravity Torque Compensation
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Solution Overview
Problem
Existing construction machines experience loss of turning operability on sloping ground due to torque components generated by gravity, which are not adequately addressed by current control methods, leading to unintended drops and reduced performance.
Innovation Solution
A construction machine equipped with an electric turning motor, attitude sensor, and a control system that calculates and compensates for gravity-induced torque components, using a feed-forward control to correct torque commands and cancel gravity effects before they impact rotation speed, thereby maintaining stable turning motion on sloping ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control is performed by detecting rotation speed and reducing deviation from target rotation speed, then the deviation is corrected, but the control takes effect only after gravity torque has already adversely affected the rotation speed, resulting in loss of turning operability
Solution Approach 1:
The control device calculates and applies gravity torque component in advance based on the detected attitude (slope angle) before the turning operation is executed. This preliminary calculation allows the system to pre-compensate for the adverse gravity torque that would otherwise affect the rotation speed, eliminating the delay inherent in feedback control that only acts after deviation is detected.
Solution Approach 2:
The control device introduces an intermediate calculation step that determines the gravity torque component as a separate parameter before applying it to the torque command. This intermediary approach allows the system to account for gravity effects independently and compensate for them proactively, rather than reacting to their effects on rotation speed after they occur.
2Stability of the object's composition
If switch from speed control to position control is performed when operation lever is in neutral position and target speed falls below threshold, then stationary state is maintained on sloping ground, but turning operability is degraded during active turning operations
Solution Approach 1:
The control device applies different control strategies for different operational states: during active turning operations, it uses torque command correction based on gravity compensation, while during stationary periods it maintains position control. This localized approach ensures optimal performance for each specific operational condition without compromising overall turning operability.
Solution Approach 2:
The control system dynamically switches between control modes based on the operational state detected from the operation lever position and target speed threshold. This dynamic adaptation allows the system to maintain stability when stationary while preserving full turning operability during active operations, resolving the contradiction between the two requirements.
3Object-generated harmful factors
If control that reduces turning motion in opposite direction is implemented, then opposite direction turning is reduced, but unintended drop of upper turning body occurs before detection
Solution Approach 1:
The control device applies preliminary anti-action by calculating and compensating for gravity torque component before opposite direction turning can occur. By proactively counteracting the gravity-induced torque that causes unintended drops, the system prevents the harmful effect rather than reacting to it after detection, thereby maintaining both turning control and body stability.
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 enables comfortable and stable turning on sloping ground by pre-compensating for gravity-induced torque, preventing unintended drops and improving operability by canceling torque components before they affect rotation speed.
Implementation Method 1
an attitude sensor that detects a current attitude of the upper turning body
Implementation Method 2
on sloping ground, gravity generates a torque about the rotation axis of the upper turning body in a descending direction of the sloping ground
Data Source
AI summary
A construction machine includes an attitude sensor that detects the current attitude of an upper turning body; a reference angular acceleration calculation unit that calculates a reference angular acceleration to be generated when an electric turning motor is driven by a torque command value generated according to the operation amount of an operation part; a reference gravity torque calculation unit that, on the basis of the current attitude and the deviation between an actual angular acceleration, calculates a reference gravity torque; a gravity compensation torque calculation unit that calculates a gravity compensation torque for compensating a torque component generated about the turning axis by the gravity in the current attitude; and a correction unit that corrects the torque command value by using the gravity compensation torque so as to cancel the torque component generated about the turning axis by the gravity in the current attitude.