Hydraulic Actuator Velocity Control for Precise Work Machine Motion
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Solution Overview
Problem
Existing work machines face delays in the response of hydraulic actuators to velocity commands, leading to inaccurate control of work implements, particularly in operations requiring precise velocity control like horizontal excavation.
Innovation Solution
A work machine with a controller that computes velocity commands based on actual hydraulic actuator velocities and past command histories, using posture sensor data to minimize delays and ensure accurate actuator control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If velocity commands are issued to hydraulic actuators based on posture sensor data, then manufacturing precision of work implement actions is improved, but response speed deteriorates due to delays in actuator velocity response
Solution Approach 1:
The controller predicts future actuator velocities based on current velocity commands and system characteristics before actually issuing new velocity commands. This preliminary prediction allows the control system to compensate for the inherent delays in hydraulic actuator response, ensuring that the predicted velocity matches the target velocity calculated from posture sensor data, thereby maintaining both accuracy and responsiveness
Solution Approach 2:
The system continuously monitors actual actuator velocities and uses this feedback information to refine velocity command predictions. By comparing predicted velocities with actual velocities and adjusting subsequent commands accordingly, the system compensates for response delays and maintains precise control of the work implement
2Manufacturing precision
If the control system waits for actual actuator velocity to match commanded velocity before issuing new commands, then manufacturing precision is improved, but productivity deteriorates due to control delays
Solution Approach 1:
Instead of waiting for actuator velocity to actually change, the controller performs preliminary predictions of what the velocity will be and issues compensated velocity commands in advance. This eliminates the need to wait for velocity matching while still ensuring accurate control, thereby maintaining both precision and productivity
Solution Approach 2:
The system replaces the traditional mechanical waiting approach (where the controller would wait for velocity to match before proceeding) with a computational prediction approach. By using mathematical models to predict future velocities and pre-compensating commands, the system achieves the same control accuracy without the time delay, thus maintaining productivity
3Speed
If the controller uses operation device input for velocity computation during start of movement, then response speed is improved, but manufacturing precision deteriorates due to velocity computation inaccuracy
Solution Approach 1:
The controller predicts the actual actuator velocity that will result from operation device input before the movement fully commences. By pre-computing the expected velocity based on system characteristics and operation input, the controller can issue accurate velocity commands from the start of movement, achieving both fast response and high precision without relying solely on posture sensor data which has inherent delays
Data Source
AI summary
A work machine includes hydraulic actuators that drive a work implement, and a controller configured to output a control signal for controlling each hydraulic actuator on the basis of a velocity command to each actuator computed at each computation cycle. When controlling an action of a first hydraulic actuator under a predetermined condition according to an action of a second hydraulic actuator, the controller computes a velocity command to the first hydraulic actuator at a current computation cycle, with use of an actual velocity of each hydraulic actuator at the current computation cycle computed on the basis of a sensing signal of a posture sensor and a history of past velocity commands to each hydraulic actuator computed at previous computation cycles before the current computation cycle, and outputs a control signal according to the velocity command to the first hydraulic actuator at the current computation cycle.