Electricity: motive power systems – Positional servo systems – With compensating features
Patent
1995-02-17
1996-08-27
Cabeca, John W.
Electricity: motive power systems
Positional servo systems
With compensating features
318501, 318 66, 364483, G05D 23275
Patent
active
055504493
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for driving electric, current-controlled actuators. Electric, current-controlled actuators such as proportional valves, the current intensity of which is regulated in an open or closed control loop according to influencing factors relevant to the process are being increasingly used in vehicle technology. Such control loops are known from multiple sources, for instance, VDI News No. 38, Sep. 8, 1981, page 16; or VDI Reports No. 418, 1981, page 186, VDI-Verlag GmbH, Heinrich Strasse 24, 40239 Dusseldorf; or Automotive Engineering, 1984, page 79.
In closed control loops, a set value quantity for the current intensity is determined and issued, by means of a microprocessor, from influencing factors for effecting an adjustment of the actuators, and is compared with the actual value of the current intensity of the actuator. The regulated quantity is increased or reduced according to the difference between the set value and the actual value. Current-measuring devices corresponding to the number of actuators are needed to detect the intensity of the current in each actuator. A relatively powerful microprocessor is required for processing the data. The time constant of such control loops decisively depends on the efficiency of the microprocessor used.
Control processes where the actual value of the current intensity is not measured and compared with the set value work more quickly. But, as a rule, those controls are not accurate enough, since they do not sufficiently take into consideration interference levels which affect the actuators and the influencing factors relevant to the process. It is known to separately detect the most important interference levels and compensate the effect thereof by adequate programs. But this is very costly when numerous interference levels and actuators have to be taken into consideration. Besides, not all of the interference levels are directly detectable.
The problem to be solved by the invention is to provide a process for driving electric, current-controlled actuators, which ensures a quick and accurate driving of the actuators at low cost.
The problem is solved by a process according to the preamble of the claim and by the characteristic part thereof.
The process according to the invention is an open-control process where the set values for the current intensities of the individual actuators is conventionally determined and issued by a microprocessor in accordance with influencing factors relevant to the process. However, current intensities are not individually detected, instead, only the joint influence thereof upon the current intensity of the actuators is detected. For this purpose, in the time intervals in which no adjustment signals in the form of influencing factors are provided by the inputs of the microprocessor, a program is activated for determining correction factors (modulation program) according to which output signal (modulation), which lie below the response level of the process, are separately and successively generated for each actuator. The current of the actuators is simultaneously measured and from the current signals compensation values are detected and temporarily stored. As soon as adjustment signals relevant to the process are provided as input to the microprocessor, they are processed together with the last stored compensation values, and issued as set values for the individual actuators.
The cost for such a process is especially small when, according to an embodiment of the invention, the total current of several or all of the actuators is detected with a single current-measuring device and, in the modulation mode, the microprocessor successively issues the modulation values for the individual actuators. Since the set values are modulated for one actuator at a time during the modulation program and the set values for the remaining actuators are constant, it is possible at different times, to determine the effect of the interference levels upon the individual actuators from the total current signal.
The invention is exp
REFERENCES:
patent: 4547858 (1988-10-01), Horak
patent: 5097171 (1992-03-01), Matsunaga et al.
patent: 5179330 (1993-01-01), Nikolaus
patent: 5343078 (1994-08-01), Bullmer
patent: 5350983 (1994-09-01), Miller
patent: 5400872 (1995-03-01), Skalski et al.
Automotive Engineering, vol. 93. No. 3, Mar. 1984, p. 79.
VDI News No. 38, Sep. 8, 1981, p. 16.
VDI Reports No. 418, p. 186.
Ege Hans-Jurgen
Horsak Gunther
Wiggermann Peter
Cabeca John W.
ZF Friedrichshafen AG
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