Patent Application
20080065309
The present invention relates to a method and a system for controlling an operation of an actuating device of a valve element of an intake system and/or an exhaust gas system of an internal combustion engine.
In modern internal combustion engines, the air flow in the intake system and/or the exhaust gas flow in the exhaust gas system are controlled or regulated by electronically controlled valve devices. The appropriate valve devices are, for example, a throttle valve, and exhaust gas recirculation valve, a bypass valve of a supercharger, etc. Such valve devices normally include a channel through which the air stream and the exhaust gas stream flow, a rotatable or displaceable valve element which controls the flow quantity as a function of its setting, an electrical actuating device, for instance a DC motor, a mechanical connection between the valve element and the actuating device, a sensor that records the current setting of the valve element, and a control and regulation device that ascertains the actuating signal that is applied to the actuating device in order to obtain a desired position of the valve element.
The known control and regulation devices typically include a digitized, closed control loop by which the actuating signal is determined that is applied to the actuating device. The basis for this is the actual value of the setting of the valve element recorded by the sensor and a setpoint value.
An object of the present invention is to provide a control method so that the internal combustion engine operates at as high an efficiency as possible, so that the fuel usage is optimized and the emission of pollutants is reduced.
In usual internal combustion engines, in normal operation, the flow in the intake channel as well as in the exhaust gas channel are subjected to periodic pressure fluctuations that are brought about by the discontinuous flow to and from the combustion chambers based on the opening and closing intake and exhaust valves. These pressure fluctuations generate periodic disturbing forces at a valve element of a valve device situated in such a channel, which lead to undesired vibrations (“disturbing vibrations”) of this valve element, which, in turn, reduce the efficiency in the flow channel.
The method according to the present invention compensates for such disturbing vibrations of the valve element of a valve device situated in a flow channel, in that a compensation signal is generated which generates a periodic counterforce at the valve element which is directed in the opposite direction from the periodic force exerted by the air flow on the valve element. The disturbing vibrations of the valve element are reduced in this manner or are even completely eliminated, so that the air flow or the exhaust gas flow are able to flow past the valve element at a higher efficiency. Finally, the fuel consumption of the internal combustion engine is reduced thereby, and its exhaust emission behavior is improved. In the process, the advantages according to the present invention are achieved without the dynamics of the valve device being made worse, for example, by mechanical damping elements. Lastly, the advantages according to the present invention are able to be implemented solely by a software design approach, by which an additional compensation signal is generated which is, for example, added to the actual actuating variable and which acts in the counterphase and at the same frequency and the same amplitude of the observed “disturbing vibrations.”
It is particularly advantageous if the method according to the present invention is subdivided into an initialization portion and a compensation portion. During the initialization portion, the actual compensation of the undesired vibrations is prepared by ascertaining starting variables and/or fixed variables that are used in the generation of the compensation signal. The actual compensation signal is generated only during the compensation portion, and it is based, at least at the beginning, on the starting values ascertained during the initialization portion. As starting values, advantageously, first of all an amplitude and a phase of the current vibrations of the valve element are ascertained.
During the compensation portion, the properties of disturbing vibrations of the valve element, that are still present, continue to be currently recorded or ascertained, and are used to generate and/or optimize the compensation signal. In this context, the compensation signal is generally characterized by three essential parameters: amplitude, frequency and phase difference from the disturbing vibrations.
The amplitude of the compensation signal is advantageously ascertained while taking into consideration the starting amplitude ascertained during the initialization portion as fixed value, and a frequency of the current vibrations of the valve element. This is possible to do using little computation effort, and leads to a stable and surprisingly efficient optimization. In practice, a look-up table may be constructed for this purpose, using frequency analysis, from values previously recorded, for instance, on a test stand, which gives the appropriate amplitude of the compensation signal with the aid of the frequency used of the disturbing vibrations and the fixed starting amplitude.
The frequency of the compensation signal is optimally equal to the frequency of the disturbing vibrations, and the frequency, in turn, can in many cases be derived very simply from the current rotary speed of the internal combustion engine, namely, in all those cases in which the disturbing vibrations are related to the rotary speed-dependent, discontinuous charging and discharging of the combustion chambers.
The phase difference between the compensation signal and the disturbing vibrations of the valve elements corresponds to a starting value. The latter is ascertained in a similar way as the amplitude, as a function of the frequency of the disturbing vibrations and the starting phase ascertained during the initialization portion, which leads to a rapid reduction in the disturbing vibrations, while requiring small computational effort.
The method according to the present invention may use the phase difference as the optimization parameter. This means that the phase difference is changed within an admissible range in such a way that the ascertained amplitude of the current disturbing vibrations is minimized.
According to the present invention, a monitoring algorithm is provided for switching between initialization portion and compensation portion, which algorithm carries out the switching as a function of certain conditions. This may be implemented by software technology. The conditions are selected, in this instance, in such a way that it is ensured that the compensation signal has no undesired effect on the setting of the valve element. In particular, the functional section, and consequently the application of the compensation signal to the actuating element is terminated, and an initialization portion is initiated anew when certain parameters lie outside predefined ranges and/or the optimization of the phase difference that is carried out leads to no satisfactory result.
In
The setting of throttle valve 16 is influenced by an actuating device 18, for instance, a DC motor or a stepper motor. The current setting of throttle valve 16 is recorded by a position sensor 20. A rotary speed of a crankshaft 22 of internal combustion engine 10 is recorded by a rotary speed sensor 24.
The operation of internal combustion engine 10 is controlled or regulated by a control or regulating device 26. To do this, among other things, an actuating variable is generated in control or regulating device 26, which is supplied to actuating device 18. The actuating variable, among other things, is a function of the signal of position sensor 20, so that a closed loop control circuit is formed.
The flow speed inside intake port 14 is subjected to periodic fluctuations which are caused by the discontinuous charging of combustion chambers of internal combustion engine 10. These fluctuations of the flow speed within intake port 14 are able to lead to undesired vibrations within intake port 14 (“disturbing vibrations”) of throttle valve 16.
As may be seen in
Compensation signal Scomp is determined in block 30 shown in
In block 30, for the generation of compensation signal Scomp, the method proceeds in two portions that are separate from each other (see
The execution of initialization portion 32 will now be explained in greater detail, with reference to
A similar nonlinear processing leads to starting phase Pini in 42. For this, the last zero crossing before the end of initialization portion 32 of the absolute quantity of the difference signal determined in block 36 is recorded, and the starting phase that is determined is stored as reference value for periodic compensation signal Scomp.
The sequence of compensation portion 34 may be seen in detail in
In a second step 46 within compensation portion 34, the properties and parameters Fcomp, Acomp and dPcomp of periodic compensation signal Scomp are determined, based on the parameters which were ascertained during initialization portion 32 and during first step 44 within compensation portion 34.
Frequency Fcomp of compensation signal Scomp is set equal to frequency F of the disturbing vibrations that was ascertained in first step 44. Amplitude Acomp of periodic compensation signal Scomp is determined with the aid of a formula based on amplitude Aini, which was ascertained during initialization portion 32, and frequency F. In the present exemplary embodiment, the formulaic connection in 48 is implemented by processing the elements of a look-up table. The elements of the look-up table, in turn, were obtained by a frequency analysis of values ascertained on a test stand.
Phase difference dPcomp is obtained by an on-line optimization in 49. For this purpose, in the present exemplary embodiment, compensation signal Scomp is changed starting from a starting value dPini in such a way that amplitude A of the disturbing vibrations, ascertained in 44, decreases. Starting value dPini for the phase difference is ascertained from a formula that is based on phase position Pini, which was ascertained during initialization portion 32, and frequency F. Here, too, the implementation of the formulaic connection in 50 takes place by the processing of values stored in a look-up table. These values, in turn, were obtained from such values that were measured on a test stand, using frequency analysis.
Compensation portion 34 having online optimization 49 is carried out repeatedly in iterative fashion, so as to optimize phase difference dPcomp of compensation signal Scomp, starting from starting value dPini in such a way that amplitude A of the disturbing vibrations tends to a minimum. In the present case, a gradient-based algorithm is used as the online optimization algorithm.
A third step (reference numeral 52) in
The switchover between initialization portion 32 and compensation portion 34 takes place using a monitoring algorithm 56. Switchover is carried out from initialization portion 32 to compensation portion 34 when properties Aini and Pini, that are required for compensation portion 34, of the current disturbing vibrations of throttle valve 16 have been recorded and ascertained.
The switchover in the opposite direction, that is, from compensation portion 34 to initialization portion 32, takes place when compensation signal Scomp can no longer compensate for, or reduce the disturbing vibrations in the desired manner. This is detected in the present exemplary embodiment when frequency F and/or amplitude A lie outside a certain frequency range and amplitude range. The same applies to the case in which the absolute setting of throttle valve 16 lies outside a certain range. Finally, a switchover takes place from compensation portion 34 to initialization portion 32 when the online optimization of phase difference dPcomp in 49 is not (any longer) in a position significantly to reduce amplitude A of the disturbing vibrations. An appropriate boundary value is able to be used for this too.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 048048.9 | Oct 2005 | DE | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11543633 | Oct 2006 | US |
| Child | 11982077 | Oct 2007 | US |
