Hydraulic Excavator Velocity Control for Stable Front Implement Deceleration
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Solution Overview
Problem
Conventional work machines, such as hydraulic excavators, face challenges in maintaining stability and ride quality during operations involving abrupt changes in disturbance and lever operation, leading to inaccurate velocity estimation and inadequate control interventions like slow deceleration and velocity limiting, resulting in reduced workability and operability.
Innovation Solution
A work machine equipped with a controller that includes target operating velocity generation, detection, estimation, and correction sections, along with center-of-gravity position prediction and control intervention determination, allows for appropriate velocity limiting and slow deceleration of the front work implement without external force sensors, even during sudden changes, by establishing and correcting operating velocities based on actual and estimated data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the operation lever is instantaneously returned to neutral position from operation state, then the movable section is suddenly stopped and inertial force is produced, but the track structure floats from ground and the work machine tilts, causing intense vibration and impact to the driver
Solution Approach 1:
The control device predicts the operating velocity of the movable section before actual sudden stop occurs, and in advance determines whether control intervention is needed based on predicted dynamic center-of-gravity position, preventing the stability problem before it happens
Solution Approach 2:
The system uses motion information sensors to detect actual operating velocity, compares it with predicted velocity, and adjusts control commands based on the difference, creating a closed-loop feedback system that maintains stability
2Measurement precision
If velocity estimation model is used to predict operating velocity, then control intervention can be implemented, but the model becomes inaccurate during abrupt changes in disturbance or lever operation amount
Solution Approach 1:
The system dynamically determines whether control intervention is needed by comparing predicted and actual velocities, adapting the control strategy based on current operating conditions rather than using a fixed estimation model
Solution Approach 2:
The system changes the control approach based on the degree of mismatch between predicted and actual velocities, adjusting parameters such as control intervention activation and deceleration rate limiting based on operating conditions
3Stability of the object's composition
If control intervention is executed to suppress floating and tilting, then stability is improved, but the front work implement deceleration rate is limited and operating time is extended
Solution Approach 1:
The control device predicts operating velocity in advance and determines control intervention needs before the sudden stop occurs, allowing for optimized deceleration control that balances stability and time
Solution Approach 2:
The system adjusts the deceleration rate limit parameter based on the predicted dynamic center-of-gravity position and stability assessment, optimizing the balance between suppressing tilting and minimizing stopping time
4Measurement precision
If external force sensors are added to improve velocity estimation accuracy, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system uses motion information sensors already present in the work machine to detect operating velocity, making the existing sensing system serve multiple functions including stability control without adding external force sensors
Solution Approach 2:
The system changes the approach from direct force measurement to velocity-based prediction and comparison, using parameter transformation rather than additional sensors
Data Source
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AI summary
It is determined whether a velocity estimation model is established from an actual operating velocity Vr and a target operating velocity Vt of each of actuators 20A, 21A, and 22A; in a case in which the velocity estimation model is established, a dynamic center-of-gravity position of a hydraulic excavator 1 in a case in which each of the actuators 20A, 21A, and 22A is suddenly stopped from a driven state is predicted from an estimated operating velocity Ve; in a case in which the velocity estimation model is not established, the dynamic center-of-gravity position is predicted from the actual operating velocity Vr and it is determined whether to execute control intervention using the predicted dynamic center-of-gravity position; and in a case in which it is determined to execute the control intervention, the target operating velocity Vt is corrected in such a manner that each of the actuators 20A, 21A, and 22A slowly decelerate. It is thereby possible to appropriately carry out operating velocity limiting on a front work implement 2 and slow deceleration of the front work implement 2 and to suppress reductions in workability and operability, a deterioration in a ride quality, and the like even in a case of work involving an abrupt change in disturbance or a change in the lever operation amount within minute time.