Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
2001-12-14
2003-11-11
Zanelli, Michael J. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S067000, C701S068000, C477S166000, C477S180000, C192S003510, C192S003610
Reexamination Certificate
active
06647333
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of regulating the position of a clutch actuator, specifically in a motor vehicle equipped with an automated shift transmission and an electronic clutch management system.
The term “shift transmission” in the present context is used primarily for a transmission with different gear ratios that are shifted manually by the driver of the vehicle by means of a shift lever. Shift transmissions of a variety of configurations are known in the prior art. A common trait of shift transmissions is that the gear shift process has two phases: a) moving the shift lever in a selector track to one of a plurality of shift tracks of the transmission, and b) moving the shift lever within the selected shift track to engage the intended gear ratio.
In addition to the manual shift transmissions just described, the state of the art also includes automated shift transmissions, in which the phases of selecting the shift plane and engaging the intended gear ratio are performed by actuators that are coupled by means of a force transfer mechanism to internal shifter elements of the transmission such as a central shift-control shaft and shift-control rods.
The known automated shift transmissions of the foregoing description are used in combination with an electronic clutch management system which automatically engages and disengages the clutch, so that all the driver has to do is select the intended gear. The clutch is operated by the electronic clutch management system.
In the course of recent technical efforts to optimize the shift process in an automated shift transmission, the requirements have substantially increased for the clutch actuator to move into and hold a given actuator position precisely. However, with the requirement for increased precision in a position-seeking control loop in an actuator driven by an electric motor, the latter has to work for longer time intervals, which increases electric power consumption. When regulating the clutch to a given target position, the electric motor performs only very small movements, so that a disproportionate amount of the power supplied to the electric motor is converted into heat.
A position-seeking controller turns off when the targeted actuator position has been set within a given hysteresis bandwidth where the deviation from the control target is less than a given regulation threshold in the order of 0.1 to 0.2 mm. A steady bias current to the actuator is active only at times when the position controller is turned off.
A so-called hunting or after-regulation behavior of the position control loop occurs if the actuator does not have an adequate amount of holding force or holding torque, so that the counteracting force can push the actuator outside the aforementioned hysteresis bandwidth of the regulated position. This can occur only at a time when the position controller is turned off. As the hysteresis bandwidth is exceeded, the position controller is reactivated to regulate the actuator back to the target position. The back-and-forth movement where the actuator is pushed out of and then regulated back into the target position is referred to herein as after-regulation or hunting.
OBJECT OF THE INVENTION
The present invention therefore has the objective of providing a method of regulating the position of a clutch actuator, specifically in a motor vehicle equipped with an automated shift transmission and an electronic clutch management system, so that the power consumption of the clutch actuator is minimized while the full functionality of the electronic clutch management system is maintained.
SUMMARY OF THE INVENTION
To meet the foregoing objective, the invention proposes a method of regulating the position of a clutch actuator in a vehicle that is equipped with a clutch control device, for example of the kind known as electronic clutch management system. The method can be described in three steps, as follows:
a) The clutch control device determines the current operating state of the vehicle based on a plurality of operating parameters of the vehicle.
b) The clutch control device selects a set of regulation parameters out of a plurality of available regulation parameter sets.
c) The clutch control device regulates the position of the clutch actuator through a position-control loop, using the selected set of regulation parameters.
This method has the advantage that the regulation parameters are adapted to different operating states of the vehicle, so that the regulation process depends on the situation. The adaptation of the parameters is such that the regulation process is made more efficient, resulting in reduced energy consumption.
In road tests of the method, it was found that the regulation could be performed at a reduced level of precision more than 50% of the time without a loss in driving comfort.
In a preferred embodiment of the invention, at least two predetermined sets of regulation parameters are available, from which the clutch control device selects a specific parameter set dependent on the operating state of the vehicle. With the different parameter sets, the regulation can be better adapted to different situations.
Instead of transmitting the entire set of regulation parameters, a binary flag is used to transmit the operating status from the clutch control device to the position-regulating control loop and to thereby communicate which of the regulation parameter sets is to be selected. If there are more than two sets of parameters, an appropriate number of flags has to be used for the data transmission. The object is to minimize the volume of data communication between the clutch control device and the position-regulating control loop.
A set of regulation parameters preferably includes the servo loop constants known, respectively, as the P-, I- and D-coefficient for the proportional, integrating, and differentiating term of the control function, a precision criterion, as well as the limits of the hysteresis band, i.e., the points where the position controller is switched off and back on.
The precision requirement can be divided into a fine and coarse precision criterion, to work with two precision ranges in the most elementary application of the inventive concept. It is also possible to use a higher number of ranges.
If two ranges are used, the switch-off threshold under the fine-precision criterion is preferably around 0.02 mm from the target position and the threshold for switching the controller back on is preferably around 0.1 mm from the target position. Under the coarse-precision criterion, the preferred switch-off threshold is around 0.1 mm from the target position and the preferred threshold for switching the controller back on is around 0.2 mm from the target position.
The clutch actuator has an electric motor, whose speed and direction are controlled in order to actuate the clutch. An electric motor has numerous advantages over a hydraulic system. Importantly, the problems of leakage and of aggressive hydraulic fluids are avoided with an electric motor.
In a preferred embodiment, a position sensor is integrated in the clutch actuator to determine the current actuator-travel position in absolute terms.
After the actuator has been set and regulated to a prescribed target position and the position controller has been switched off, it is possible that the position-holding force or holding torque of the clutch actuator is not strong enough to keep a lever of the clutch mechanism in a set position, particularly if the clutch requires a strong clutch-release force. Thus, the lever is pushed back by the force of the clutch, so that a position control loop has to regulate the actuator back to the target position. This increases the load on the clutch actuator, and the after-regulation can also manifest itself through a chattering of the clutch.
To prevent after-regulation, it is necessary to oppose the clutch force with a counteracting force. This counteracting force is generated by applying a steady bias current to the clutch actuator during the time phases when the
Berger Reinhard
Gerhart Jürgen
Jäger Thomas
Jung Mario
Renfer Alexander
Darby & Darby
Gibson Eric M
LuK Lamellen und Kupplungsbau Beteiligungs KG
Zanelli Michael J.
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