Control system with pilot controller, especially for a roll stand
AssigneeSiemens Aktiengesellschaft
InventorsAndre Berghs, Hans-Peter Trondle, Peter Hopf, Georg Bytomski, Hans-Joachim Felkl
Life of this patent
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Abstract
In a control system, especially a hydraulic screw-down control system for a roll stand, the controller output is acted upon by a pilot control value (v.sub.1.sup.*). At the same time, a reference value (x.sub.M ') is delivered to the controller via a subtractor as a setpoint value. The reference value (x.sub.m ') is determined in a model control loop based on the pilot controller. Parasitic response characteristics of the overall system are largely accounted for in the model control loop, so that on a time-averaged basis the controller is not activated.
Claims25
A control system for controlling a process, said control system being externally supplied with a guide value, and comprising:
- a) an actuator having an input;
- b) a transducer adapted to measure an actual value of said process and having an output adapted to provide said measured actual value;
- c) a controller, said controller
- i) having a first input, and a second input, said second input being coupled to said output of said transducer,
- ii) adapted to determine a controller manipulated variable based on its inputs, and
- iii) having an output adapted to provide said controller manipulated variable;
- d) a model control loop, said model control loop
- i) having an input adapted to accept said guide value,
- ii) adapted to determine a pilot control value based on said guide value and a predetermined expected value,
- iii) adapted to continuously determine an expected value for said actual value, said expected value being based on said pilot control value,
- iv) adapted to determine a reference value from said expected value, and
- v) having a first output adapted to provide said determined pilot control value, and a second output adapted to provide said determined reference value, said second output being coupled with said first input of said controller;
- and
- e) an adder, said adder
- i) having a first input being coupled to said output of said controller, and a second input being coupled with said first output of said model control loop,
- ii) adapted to add said pilot control value onto said controller manipulated variable to determine an actuator signal, and
- iii) having an output adapted to provide said actuator signal and being coupled to said input of said actuator.
The control system of claim 26, wherein said pilot control value and further pilot control value (v.sub.1.sup.* to v.sub.4.sup.*), expected value and further expected value (x.sub.1 " to x.sub.4 "), and reference value and further reference value (x.sub.1 ' to x.sub.4 ') are determined using untransformed variables
A hydraulic screw-down control system for a roll stand having four hydraulic cylinders, each having a screw down reading (x.sub.1 -x.sub.4), said roll stand having a screw-down center point (x.sub.m), a screw-down tilt (x.sub.s), and synchronizations (x.sub.G12,X.sub.G34) being defined by said screw down readings, said hydraulic screw-down control system being supplied with externally supplied guide values and comprising:
- a) a hydraulic actuator assigned to each of said four hydraulic cylinders, each of said hydraulic actuators having an input;
- b) a transducer assigned to each of said four hydraulic cylinders and being adapted to measure an actual value of said screwdown reading of a corresponding one of said hydraulic cylinders and having an output adapted to provide said measured actual value;
- c) a controller assigned to each of said four hydraulic cylinders, each of said controllers
- i) having a first input and a second input, said second input being coupled to a corresponding one of said transducers,
- ii) adapted to determine a controller manipulated variable based on its inputs, and
- iii) an output adapted to provide said controller manipulated variable;
- d) a model control loop assigned to each of said hydraulic cylinders, each of said model control loop
- i) having an input adapted to accept said guide value,
- ii) adapted to determine a pilot control value based on its input and a predetermined expected value,
- iii) adapted to continuously determine an expected value for an actual value, said expected value being based on said pilot control value, and
- iv) adapted to determine a reference value from said expected value, and
- v) having a first output adapted to provide said determined pilot control value, and a second output adapted to provide said determined reference value and being coupled to said first input of a corresponding one of said controllers;
- and
- e) an adder assigned to each of said hydraulic cylinders, each of said adders
- i) having a first input being coupled with said output of a corresponding one of said controllers, and a second input being coupled with said first output of a corresponding one of said model control loops,
- ii) adapted to add said pilot control value onto said controller manipulated variable to determine said actuator signal, and
- iii) having an output adapted to provide said actuator signal and being coupled with said input of a corresponding one of said actuators.
In a system having a transducer for measuring an actual value and a actuator, and being provided with a guide value, a control method comprising the steps of:
- a) subtracting a predetermined expected value from said guide value to determine a pilot control value;
- b) continuously applying said pilot control value determined in step (a) to a functional element which models the system to determine an expected value of said actual value;
- c) determining a reference value based on said expected value determined in step (b);
- d) subtracting said actual value measured by the transducer from said reference value determined in step (c) to determine a controller manipulated value;
- e) adding said controller manipulated value determined in step (d) and said pilot control value determined in step (a) to determine an input value for said actuator which is applied to said actuator for controlling its operation.
Dependencies are inferred from the claim text.