Digital Hydraulic Drive Flatness Control
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Solution Overview
Problem
Current digital hydraulic drive systems face challenges in achieving high control quality with low computational effort and reduced costs, particularly due to high computational requirements for timely actuator control.
Innovation Solution
The implementation of a flatness-based follow-up control method using volume flows as manipulated variables, combined with a digital-hydraulic full-bridge circuit employing pulse-width-modulated or pulse-code-modulated valve units, and an observer-assisted load estimation to control pressure drop and prevent cavitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If advanced control methods are used to improve control quality, then control quality is improved, but computational effort increases
Solution Approach 1:
The control system is segmented into a follow-up control unit that handles high-level control decisions and a lower-level control unit that executes specific valve configurations. This segmentation allows complex control tasks to be divided into manageable parts, reducing the computational burden on any single unit while maintaining overall control quality.
Solution Approach 2:
The system pre-calculates and stores optimal valve configurations in lookup tables based on desired actuator positions and velocities. During operation, the controller simply retrieves pre-computed control signals rather than performing real-time optimization calculations, significantly reducing computational effort while maintaining control precision.
2Manufacturing precision
If digital-hydraulic full-bridge circuit with PWM/PCM valve units is used, then control precision is improved, but device complexity increases
Solution Approach 1:
The digital-hydraulic full-bridge circuit is designed to support multiple control modes (PWM and PCM) using the same hardware architecture. This multi-functionality allows the system to achieve high control precision through different modulation techniques without requiring separate hardware configurations for each method, thereby managing device complexity.
Solution Approach 2:
The patent uses standardized digital valve units that can be replicated and configured in different bridge arrangements. These modular valve units serve as reusable components that can be copied and assembled into various control configurations, reducing the overall device complexity while maintaining control precision through consistent performance characteristics.
Data Source
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Figure 3
Figure 4a~4c
AI summary
1. Digital hydraulic drive system. 2. The invention relates to a digital hydraulic drive system comprising: - an actuator, such as a hydrostatic constant-speed motor (10) or a working cylinder with preferably connected hydropneumatic damping accumulators (12) at both assignable actuator ports (14, 16), and - at least one independently actuated valve assembly (20) for controlling the volume flows in the inlet and/or outlet ports (14, 16) of the actuator, characterized in that a flatness-based follow-up control is used, which uses the volume flows as a manipulated variable, and a subordinate control is used, which depends on the configuration of the valve assembly (20).