The feedback control algorithm specially developed and tested for control of test engineering applications ensures high performance control and ease of operation thanks to a clear, easily adjusted set of parameters. Control performance is additionally enhanced by, model-based control engineering methods such as feed-forward control, inertia and oscillation compensation as well as adaptive control (gain boost).
For higher-frequency control engineering applications, additional control engineering methods such as preliminary filter techniques (Inverse Control) and RPC (Remote Parameter Control) are available, these being based on the frequency transfer matrix of the plant as identified by means of signal excitation. These are essential for the reproduction of high-quality tracking profiles or rugged command time signals at test rigs.
In addition, a multi-channel function generator with the following features is integrated into the system:
- multiple configurable curve and excitation forms, signal frequency of up to 150 Hz
- frequency and phase sweep
- peak/valley control
- superposition of a low frequency offset onto higher-frequency signals
Fully automatic and stable workflow is ensured by the following process and control mechanisms.
- monitoring of limit values and tracking errors
- peak-valley monitoring
- configurable action for limit detection
- activation and shutdown procedures
- process controls and main operation modes
- up to configurable 300 monitoring contacts
- static and slow-motion operation modes
- control and monitoring of pneumatic subsystems
- dynamic data logging
- interface to external static data logging device
The structure of the controllers comprises the basic control unit (GE), the measurement unit (ME) and further control units (ZE). These units are interconnected by a real-time communication system
Control units are available in the following standard versions:
- Variant 1: as a unit with up to four control and monitoring channels and a control loop sampling frequency of up to 2000 Hz.
- Variant 2: as a unit with up to ten control and monitoring channels and a control loop sampling frequency of 500 Hz.
The processor units and peripheral devices are identical in both variants and are interchangeable. The measurement unit executes such tasks as data logging, post-mortem analysis and communications with the touch panel.
FIELD LEVEL
Our control systems are offered in modular structure as field units and also as customized cabinet units, thus allowing the configuration of almost arbitrarily extendable linear or star-like topologies. The advantages of this for the user are that in the field the control units can be located in the vicinity of the corresponding sensors and actuators. The control units are interconnected by a real-time communication system, which simultaneously serves as a plant and field bus. Cabling effort is thus reduced to a minimum. The modular extendibility and exchangeability ("plug and play") is a standard feature of our control units.
OPERATION LEVEL
The multi-project capability of the operation level allows efficient implementation of multi-project applications using the control and monitoring system. Application-oriented scalability of the control system and the multi-project capability of the operation level ensure efficient operation.
- Current events of the control process are visualized in a special log display
- All event data are stored to enable full traceability
- Extensive visualization and analysis options of time signals and fine-tuning of the control system using both online and offline visualization tools
- Optional operation of the controller using a touch panel or programmable logic controller (PLC) instead of a PC. If a PLC or an external operation panel is used, the system executes operation commands via the controller's digital/analogue I/O. On the basis of the current processing status, any user-defined operating modes and process controls can be executed in real-time under control from "outside", allowing implementation of stable "scripting".
MODEL GENERATION
The easy-to-use FE model generation environment, allows the user to intuitively build up the physical model of the plant. The model structure here is modular so that even users with no experience in FEM modeling techniques reach their goal quickly and efficiently.
Implementation:
The library contains the main model classes and is equipped with an optimization-based modeler. Via a graphical interface, the user assigns the basic geometric data of the mechanical system as well as the positions of the actuators, supports and bearings.
Following this, automatic model adaptation is carried out via the optimization-based model identification, whereby the user enters assessed characteristic features of the mechanical system (bending lines, masses, and, where available, natural frequencies and inertia tensors). The appropriate physical model adjustments are then made automatically using the modeler's numeric parameter optimization function.
Result:
- The resulting non-linear model of the plant is highly scalable, allowing great flexibility of use in the underlying control engineering application.
- The plant model is already available in early project phases for design optimization.
- As part of system simulation, a well-founded design of the pressure oil supply unit and the supporting frame structures is achieved.
- In higher-frequency control engineering applications (vibration tests, complex road-tracking profiles on vehicle test rigs), the plant's transfer matrix as derived by plant excitation is used instead of the physical model.
SYSTEM SIMULATION
System simulation is based on the plant model and comprises the following processes:
- automated closed-loop system design optimization
- trajectory optimization method for generating the time-optimum (profile optimized) command signal
- RPC-method to optimize the command signal at higher-frequency control applications
- automated pre-optimization of RPC-signals based on the physical test-rig model
- editor for RPC-Signals; PSD, rainflow-classifications and damage calculations
- analysis and design tool for an optimal dimensioning of the servo-hydraulic actuator system
The closed-loop system design optimization tool automatically calculates conservative controller parameter settings for a ready-to-start control and monitoring system configuration. This is an important feature to ensure fast controller setup and high automation level.
Safe operation of complex or large-scale closed-loop mechanical systems at maximum tracking speed requires a command signal profile that is optimized to the technical requirements and constraints. This requirement is met by the numerical method of the trajectory optimization tool. This automatically calculates the minimum-time command signals on the basis of a set-point file such as a loading program, taking into account all the given technical constraints.
Technical constraints:
- limits for permissible piston speeds
- acceleration values* and inertial forces
- performance limits of the servo-hydraulic actuators and the pneumatic subsystems
*By default, acceleration limits are calculated automatically by means of system simulation based on a pre-optimization run, thus eliminating extreme acceleration peaks.
Optimization of the command signal is achieved:
- by means of trajectory optimization for low-frequency control engineering applications,
- by means of RPC-method for higher-frequency control engineering applications
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