Current control process

Details Current control process Current control process

1998-10-15

2001-01-02

Paladini, Albert W. (Department: 2836)

Electrical transmission or interconnection systems

Vehicle mounted systems

Automobile

C327S108000, C327S110000

Utility Patent

active

06169335

ABSTRACT:

The invention relates to a current control process for an inductive load, particularly an electrohydraulic pressure regulator in an automatic transmission.
BACKGROUND OF THE INVENTION
In automatic transmissions, an electronic control device controls the course and pressure level in the clutches and brakes using electromagnetic pressure regulators. Precise information about the real pressure level or the adjusted current value is very important insofar as it directly affects shifting smoothness and the orderly operation of the automatic transmission. In connection with this, DE-OS 40 34 081 discloses a current regulator switch for an inductive load. The current flowing through the inductive load is measured by a precision resistor. This current actual value and a current reference value are passed to a comparator. The error is thus the output value of the comparator. A regulator connected downstream from the comparator controls a timed performance final stage so that the inductive load is ultimately controlled with a PWM signal.
Another variant of a current control method consists in converting the current actual value detected by means of a precision resistor via an A/D converter. The reference/actual values are compared and the correction variable controlled by means of a program. Since the load is controlled via a clocked final stage with a PWM signal, there occurs at each switch flank a superimposition of interferences (transients) on the current actual value. Thus there exists the possibility that the measured value may be a transient instead of the real current actual value. The prior art described thus has the disadvantage that a misinterpretation of the current actual value is possible.
Consequently, the problem to be solved by the invention is to ensure perfect measuring and control of the current.
SUMMARY OF THE INVENTION
According to the invention, the problem is solved by synchronizing a measuring moment, via an inquiry cycle of an A/D converter, delayed by a presettable time in relation to the cycle of the output signal of the regulator. The advantage here is that the solution, according to the invention, can be integrated in an already existing program without great additional expense. As an added advantage, an increased regulation dynamic results because a software filter such as a sliding mean value formation for stabilizing the transients can be eliminated. Software filters are known to cause the evaluation process to slow down and to cause heavy loading on the computer.
In a further development, it is proposed that in case of considerably great changes in the current reference value a pilot control second signal, together with the output signal delivered by the regulator, acts upon the load. The second signal can be generated by means of a pilot control block. This development offers the advantage known per se of a pilot control. A pilot control is known to have a high dynamic, since in case of considerably great changes only the least ten percent, for example, are compensated by the regulator.


REFERENCES:
patent: 5038247 (1991-08-01), Kelley et al.
patent: 5166543 (1992-11-01), Schneider et al.
patent: 5406150 (1995-04-01), Austin
patent: 5757214 (1998-05-01), Stoddard et al.
patent: 5763963 (1998-06-01), Zydek et al.

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