Electricity: motive power systems – Positional servo systems – With protective or reliability increasing features
Reexamination Certificate
2000-01-31
2003-03-18
Dang, Khanh (Department: 2837)
Electricity: motive power systems
Positional servo systems
With protective or reliability increasing features
C318S565000
Reexamination Certificate
active
06534942
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention concerns an intelligent control and regulating device, especially for use in the process technology for flowing materials and mediums which i) is integrated into the housing of an actuator or attached to an actuator and, ii) has a regulating arrangement which controls an actuator from an auxiliary energy unit in dependence on signals from sensors.
So far, actuators used in process technology have a sensor located in the process field which transmits a signal of the actual condition of the process to a central controller which is, for example, located in a control room or a similar process control unit.
The central controller compares this feedback value of the process with a preselected setpoint process value. When this comparison is evaluated, a corresponding positioning signal is sent to the actuator. A positional controller, which is mounted in the actuator, receives the positioning signal from the central controller and transposes it into the proportional stroke position or angle of turn which is passed on to the actuator by an electric motor.
Such regulators are extremely expensive and complex especially when many measurement and regulating points are necessary because they require numerous individual units and an extensive cable network.
In order to avoid the extensive cabling between actuator and central controller, which are always separated, a unit for regulating and controlling an electrical drive system is known from the DE 39 28 451 A1 where the motor is mounted in the same housing together with devices for the recognition of position and monitoring of the speed of rotation, for electronic commutation, for control and regulation and for accomplishing the communication.
This has the disadvantage that the computer in the process control center is not fast enough to tap all magnitude cycles and to calculate their feedback position values if there is a multitude of control loops or very rapid regulation, so that unwelcome delays occur and the quality of control is reduced.
SUMMARY OF THE INVENTION
It is therefore the task of the invention to present a control and regulating device which reacts reliably and rapidly to changes in the process conditions, especially changes in the ambient conditions.
The invention solves this task by using a regulating arrangement with a parameterised process controller which receives input control signals from external sensors.
The invention has the advantage of the process controller being built into the actuator itself thus forming an independent system. The load on the process control center is reduced and less installation work is required.
Provided that the feedback value of the control parameter, i.e. the output signal of the external sensor, is directly connected to the actuator, the integrated process controller calculates the manipulated magnitude independently and can act on the actuator without delay so that shorter cycle times are realized.
The process controller is freely parametered so that the control and regulation characteristics can be modified and adjusted to new conditions at any time.
In an advanced version, the process controller becomes part of a power module which is connected to a central control unit bi-directionally using an interface module. It is now possible to reduce the process control unit to display data and the adjustment to the set reference variables and setpoint values.
The power module has, besides the process controller, an auxiliary energy control which is connected through inlets to the internal sensors which collate actuator-specific data and to the external sensors providing the process-specific data. The integration of these elements reduces costs while making the control more reliable.
The interface module can be designed as a plug-in unit. This has the advantage of an easy adjustment of the control and regulating device to the conditions of communication in the process control unit simply by changing to the desired interface module.
The data exchange with the central control unit can be facilitated using analogue or binary signals. Serial data transfer using a data bus is also possible provided that the interface module is equipped for it. Conventional interface modules have at least one potential-free relays for setting up an electrical connection between the interface module and the environment.
The modular setup permits the use of standardized systems.
It is recommended to parameterize the process controller with the actuator-specific parameters after the assembly of the individual modules onto the actuator. This means that the actuator can be configured after assembly and the control start-up is simplified. The specific application need not be known when the actuator is manufactured.
The actuator can be easily adjusted to the specific conditions of application through the software and without any module exchange.
In another design, the process controller can be a digital controller of the type P, PI or PID. The PID controller permits the setting of the proportionate range, holding and adjusting times independently of each other, following the initial assembly of the modules onto the actuator.
Parametering is easy if a micro-processor is used as process controller.
An operating panel is mounted to the power module for manual control of the actuator and/or to parameterize the actuating functions. The operating panel can be either mounted to the actuator or designed as a plug-in connection. It is also possible to prepare the operating panel for permanent wall fixing near the actuator. The operating panel is then connected by cable to the power module.
To monitor the operating conditions of the actuator, the process controller is connected to internal sensors for monitoring the actual position and/or the actuating forces or torques exerted at the output of the actuator.
The process controller acts upon the auxiliary energy unit using the auxiliary energy controller. If this auxiliary energy unit is an electronically regulated electric motor, preferably a DC motor, the torques and actuating forces can be easily measured by measuring the motor current.
However, the auxiliary energy unit is not restricted to electric motors. Hydraulic and pneumatic units may also be used.
In an advanced version, internal, actuator-specific data required for diagnostic purposes are non-erasably stored in the power module. A self-diagnosis is carried out through the constant monitoring of this data, permitting a fast reaction to errors and the early identification of the source of error.
The internal actuator-specific data stored may be read out using a serial interface which is integrated into the power module or an interface module via a data bus.
The serial interface in the power module can also be used for the input of actuating parameters.
It is more advantageous to calculate the values measured by the internal and external sensors as process characteristics in the power module and to assign them to the central control unit for further processing, using the interface module.
A regulating correction magnitude which has been stored as a table or a characteristic curve in the power module improves the quality of control.
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Dang Khanh
Pendorf & Cutliff
PS Automation GmbH für Gesellschaft Antriebstechnik
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