Apparatus and a method for sliding mode control

Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing

Reexamination Certificate

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Details

C123S090160, C123S090170, C123S090180, C318S802000

Reexamination Certificate

active

06431131

ABSTRACT:

BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to the art of controlling sliding mode, for example, to the art of controlling sliding mode used for feedback controlling rotation phase of a camshaft relative to a crankshaft for an internal combustion engine to a target value.
A conventional valve timing apparatus is known as a vane type valve timing controlling apparatus disclosed in Japanese Unexamined Patent Publication 10-141022 such as an apparatus for successively changing opening and closing timing of intake and exhaust valves by changing rotation phase of a camshaft relative to a crankshaft.
This apparatus forms concave portions in the inner surface of a cylindrical housing fixed to a cam sprocket in which vanes of an impeller are accommodated in the concave portions wherein the camshaft rotates relative to the cam sprocket within the range where the vanes of the impeller can move in the concave portions and by relatively supplying and discharging oil into a pair of oil pressure chambers, the vanes are held in the mid position of the concave portions and thus successive changing of rotation phase can be carried out.
When oil pressure of the pair of the oil pressure chambers is adjusted to the level by which a target value of rotation phase can be obtained, a control valve closes an oil pressure passage to stop supplying and discharging oil.
PID (proportional-integral derivative) control is generally adopted as control method of the camshaft rotation phase wherein a control amount is calculated with a deviation (error amount) between an actual angle and a target angle of the camshaft as only one variable.
However, in order to carry out the PID control with a good response characteristic it is preferable that a feedback gain is set variable since viscosity of oil changes with oil temperature and oil pressure, but matching the setting as above is not easy.
In the case of oil pressure control there is wide operation dead band for a switching valve (spool valve) to switch oil supply and oil discharge and therefore dither control is executed with dither components in addition to PID to go beyond the dead band wherein judgement of addition of dither components is required to do with accuracy, bringing a complicated control and more capacity of ROM and RAM. In order to decrease variations of dead band width for each part for securing control accuracy, improvement in machining for parts is required, causing increase of machining costs.
Therefore, there has been considered a sliding mode control which has less influence due to disturbances, instead of a general PID control into.
Then, there is review of application of a sliding mode control into the above oil pressure type valve timing control apparatus and when the sliding mode control is designed according to the conventional theory, the influence due to disturbances such as changes of the oil temperature and the oil pressure is restrained but it is found out that the above sliding control is not effective to the dead band and is no alternative and no supplement for the above dither control.
And also in the case of application of a sliding mode control into a component with a dead band, the feedback control is executed by setting a basic control amount to a central value of an operation dead band and adding a feedback control amount to go beyond the operation dead band to the basic control amount whereby due to component variations and aging deviation between the central value of the operation dead band and the basic control amount may arise, and variations in size of operation dead bands may bring in decrease of response characteristic and occurrence of hunting.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention has an object of carrying out a sliding mode control with higher robust by restraining decrease of response characteristic caused by operation dead band in a control object having the operation dead band to a control amount such as an oil pressure control system.
Another object of the present invention is to provide an apparatus to carry out higher accuracy control in an apparatus with a feedback control by a sliding mode control.
A further object of the present invention is to carry out a control with higher accuracy and in quicker response by avoiding influence caused by component variations and aging by a learning control in a sliding mode control of a control object having operation dead band as above.
The present invention for achieving the above first object is constituted to set a linear term of a control amount as a function of deviation between a target position and an actual position of a control object in an apparatus for sliding-mode controlling a control object having an operation dead band.
Thus even when the actual position of the control object does not change by entering within the operation dead band, since there exists a deviation (≠0) between the target position and the actual position of the control object, transfer velocity to the switching line to switch a feedback gain is given properly by a linear term set as the function of deviation, resulting in convergence to the target position with a good response characteristic.
The control object of the present invention may be applied to an oil pressure control system and in the oil pressure control system having a wider operation dead band by a switching valve and the like, the control can be carried out with quicker response by restraining influence caused by the wider operation dead band.
In particular, in a case that a valve timing control apparatus in an internal combustion engine is the control object, wherein rotation phase of a camshaft relative to a crankshaft is controlled variably and successively by the oil pressure control, and the supply and discharge of oil to an oil pressure actuator controlled by oil pressure is selectively controlled by the switching valve, in the oil pressure control type valve timing control apparatus having a wider operation dead band by the switching valve, the control with quick response is carried out by restraining influence due to the dead band.
A linear term may be set by adding a term proportional to the deviation between the target position and the actual position of the control object to a term proportional to operation velocity of the control object.
By this, transfer velocity to the switching line is given properly even on entering into the dead band by a term proportional to the deviation between the target position and the actual position of the control object and when out of the operation dead band, since transfer velocity adjustment function to the switching line caused by a term proportional to operation velocity of the control object is added, more adequate transfer velocity can be obtained and the response can be improved.
A linear term may be set based only on the term proportional to the deviation between the target position and the actual position of the control object.
As described above, even in the case the linear term of the control object is set only by the term proportional to the deviation between the target position and the actual position of the control object, since not only within entering into operation dead band but also out of the operation dead band, transfer velocity to the switching line is given properly, the sliding mode control can be realized and by omitting the term proportional to operation velocity of the control object, easy control (calculation) can be done to thereby save program capacity.
Next, the present invention for achieving the above second object is constituted to feedback control a control object to a target value by correcting a control amount calculated based on a sliding mode control by a dither control.
According to this constitution, based on the sliding mode control, a control with higher robust can be carried out with less influence due to disturbance compared with the feedback control by an ordinary PID control, as well as the control with more accuracy can be carried out based on the correction by th

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