Distributed Hydraulic Actuator Control Architecture
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Solution Overview
Problem
Centralized control architectures for hydraulic actuators result in high costs and wiring complexity due to the need for extensive cabling and high-end PLCs to manage multiple axes, with limited control update rates caused by bandwidth constraints in field bus or network communication, leading to performance latency.
Innovation Solution
Implementing a distributed control architecture where state feedback control algorithms are executed locally on each hydraulic valve, reducing network bandwidth usage and allowing direct sensor connection, enabling local command trajectory generation and simplifying the central PLC's role to supervisory coordination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a centralized control architecture is used to coordinate all hydraulic axes through a single PLC, then centralized coordination is achieved, but cabling costs and wiring complexity increase significantly
Solution Approach 1:
The control system is segmented into multiple independent control units, each responsible for a specific hydraulic axis or function. Each control unit contains its own microprocessor and can operate autonomously, eliminating the need for extensive cabling to a central PLC while maintaining coordinated operation through local decision-making capabilities.
2Extent of automation
If a single high-end PLC is used to run multiple state feedback control algorithms simultaneously, then all hydraulic axes can be coordinated, but the cost of the PLC increases significantly
Solution Approach 1:
The control algorithms are distributed across multiple independent control units, each running its own state feedback control algorithm locally. This eliminates the need for a single expensive high-end PLC while achieving the same multi-axis coordination functionality through affordable microprocessors in each distributed unit.
3Device complexity
If field bus or network communication is used to replace analog interfacing, then cabling cost and wiring complexity are reduced, but control update rates are limited by bandwidth constraints
Solution Approach 1:
The control units are equipped with direct digital interfaces to actuators and sensors, extracting the need for field bus communication for control updates. This allows high-speed local processing and actuation while field bus is used only for supervisory functions, thereby achieving both wiring simplicity and high control update rates.
4Loss of information
If all sensor signals are routed to a single machine PLC, then centralized monitoring is achieved, but the PLC requires high end specifications increasing cost
Solution Approach 1:
Sensor signals are processed and monitored locally by distributed control units rather than being routed to a central PLC. Each control unit maintains its own sensor data for local control decisions, while only essential status information is communicated to the supervisory system, reducing the specifications and cost of the central PLC.
5Productivity
If a distributed control architecture is implemented with local microprocessors, then control update rates increase and costs decrease, but the need for user-programmable algorithms arises to protect intellectual property
Solution Approach 1:
The distributed control units incorporate user-programmable microprocessors that can execute various control algorithms including state feedback control. This universal programming capability allows different control strategies to be implemented on the same hardware platform, protecting intellectual property while maintaining cost efficiency and high update rates.
Data Source
AI summary
A hydraulic actuator control system for controlling the motion of a master actuator and at least one slave actuator may include an external supervisory computer for sending command signals. A hydraulic control system may be connected to the master actuator and the supervisory computer. The hydraulic control system may include a microprocessor and a master hydraulic control valve for controlling the flow of a pressurized fluid to the master actuator based on the command signals. The hydraulic actuator control system may include at least one slave actuator having at least one slave sensor connected to the microprocessor and having at least one slave control valve for controlling the flow of pressurized fluid to the slave actuator. The slave control valve and the slave sensor may be controlled by the microprocessor.