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Dry Clutch Modeling, Estimation, and Control
Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, The Institute of Technology.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Increasing demands on comfort, performance, and fuel efficiency in vehicles lead to more complex transmission solutions. One such solution is the Automated Manual Transmission (AMT). It works just like an ordinary manual transmission but the clutch and the gear selection are computer controlled. In this way high efficiency can be accomplished with increased comfort and performance. To be able to control and fully utilize an AMT, it is of great importance to have knowledge about how torque is transmitted in the clutch.The transmitted torque in a slipping dry clutch is therefore studied in a series of experiments with Heavy Duty Trucks (HDT). It is shown that material expansion with temperature can explain torque variations up to 900 Nm for the same clutch actuator position. A dynamic clutch temperature model that can describe the torque variations is developed. The dynamic model is validated in experiments, and shown to reduce the error in transmitted torque from 7 % to 3 % of the maximum engine torque compared to a static model. Since all modeling, parameter estimation, and validation are performed with production HDTs, i.e. production sensors only, it is straightforward to implement the model in a production HDT following the presented methodology.

The clutch model is extended with lock-up/break-a-part dynamics and an extra state describing wear. The former is done using a state machine and the latter uses a slow random walk for a parameter corresponding to the thickness of the clutch disc. Two observability analyses are made: one with production sensors, and one with a torque sensor in addition to the production sensors. The analyses show that, in both cases, the temperature states and the wear state are observable both during slipping of the clutch and when it is fully closed. The latter is possible since a sensor measures the actuator position. The unknown offset in the torque sensor is possible to observe (at all times) if the model is further augmented with engine inertia dynamics. An Extended Kalman Filter (EKF) is developed and evaluated on measurement data for both cases. The estimated states converge from poor initial values, enabling prediction of the translation of the torque transmissibility curve and sensor offset. The computational complexity of the EKF is low and it is thus suitable for real-time applications.

The clutch model is also integrated into a driveline model capable of capturing vehicle shuffle (longitudinal speed oscillations) and engine torque fluctuations. Parameters are estimated to fit an HDT and the complete model shows good agreement with data. It is used to show that the effect of thermal expansion, even for moderate temperatures, is significant in clutch control applications. One such application is micro-slip control. A control structure has been made and the basic components are a reference-slip calculator, an LQ controller and an EKF that can compensate for the thermal dynamics of the clutch. The controller isolates the driveline from the engine oscillations without dissipating more heat than the clutch can handle. An analysis shows a noticeable fuel consumption increase. Nonetheless, the real benefits of micro-slip control will only be evident when combined with other cost-reducing changes in the powertrain. The feasibility of a micro-slip control system for a dry clutch HDT has been proven.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. , 32 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1612
National Category
Control Engineering
Identifiers
URN: urn:nbn:se:liu:diva-108838DOI: 10.3384/diss.diva-108838ISBN: 978-91-7519-261-1 (print)OAI: oai:DiVA.org:liu-108838DiVA: diva2:733204
Public defence
2014-09-19, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Projects
LINK-SIC
Funder
Vinnova, LINK-SIC
Available from: 2014-07-11 Created: 2014-07-08 Last updated: 2014-08-21Bibliographically approved
List of papers
1. Torque Model with Fast and Slow Temperature Dynamics of a Slipping Dry Clutch
Open this publication in new window or tab >>Torque Model with Fast and Slow Temperature Dynamics of a Slipping Dry Clutch
2012 (English)In: 2012 IEEE VEHICLE POWER AND PROPULSION CONFERENCE (VPPC), IEEE , 2012, 851-856 p.Conference paper, Published paper (Refereed)
Abstract [en]

The transmitted torque in a slipping dry clutch is studied in experiments with a heavy duty truck. It is shown that the torque characteristic has little or no dependence on slip speed, but that there are two dynamic effects that make the torque vary up to 900 Nm for the same clutch actuator position. Material expansion with temperature can explain both phenomena and a dynamic clutch temperature model with two different time constants is developed. The dynamic model is validated in experiments, with an error of only 3% of the maximum engine torque, and is shown to improve the behavior significantly compared to a static model.

Place, publisher, year, edition, pages
IEEE, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-96527 (URN)10.1109/VPPC.2012.6422728 (DOI)000316957600171 ()978-1-4673-0953-0 (ISBN)
Conference
IEEE Vehicle Power and Propulsion Conference (VPPC), Oct. 9-12, 2012, Seoul, Korea
Available from: 2013-08-21 Created: 2013-08-20 Last updated: 2014-07-11Bibliographically approved
2. The Effect of Thermal Expansion in a Dry Clutch on Launch Control: Advances in Automotive Control, Volume # 7, Part # 1
Open this publication in new window or tab >>The Effect of Thermal Expansion in a Dry Clutch on Launch Control: Advances in Automotive Control, Volume # 7, Part # 1
2013 (English)Conference paper, Published paper (Refereed)
Abstract [en]

A dry clutch model with thermal dynamics is added to a driveline model of a heavy-duty truck equipped with an automated manual transmission. The model captures driveline oscillations and can be used to simulate how different clutch-control strategies affect vehicle performance, drivability and comfort. Parameters are estimated to fit a heavy-duty truck and the complete model is validated with respect to shuffle, speed trajectory, clutch torque and clutch lock-up/break-apart behavior. The model shows good agreement with data. Furthermore the model is used to study the effect of thermal expansion in the clutch on launch control. It is shown that the effect of thermal expansion, even for moderate temperatures, is significant in launch control applications.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-96914 (URN)10.3182/20130904-4-JP-2042.00088 (DOI)
Conference
7th IFAC Symposium on Advances in Automotive Control, September 4-7, Tokyo, Japan
Available from: 2013-08-29 Created: 2013-08-29 Last updated: 2014-07-11Bibliographically approved
3. Modeling, Observability, and Estimation of Thermal Effects and Aging on Transmitted Torque in a Heavy Duty Truck with a Dry Clutch
Open this publication in new window or tab >>Modeling, Observability, and Estimation of Thermal Effects and Aging on Transmitted Torque in a Heavy Duty Truck with a Dry Clutch
2015 (English)In: IEEE/ASME transactions on mechatronics, ISSN 1083-4435, E-ISSN 1941-014X, Vol. 20, no 1, 61-72 p.Article in journal (Refereed) Published
Abstract [en]

A transmission with both high comfort and high efficiency is the Automated Manual Transmission (AMT). To be able to control and fully utilize this type of transmission it is of great importance to have knowledge about the torque transmissibility curve of the clutch. The transmitted torque in a slipping dry clutch is therefore studied in experiments with a heavy duty truck (HDT). It is shown that the torque characteristic has little or no dependence on slip speed, but that there are two dynamic effects that make the torque vary up to 900 Nm for the same clutch actuator position. Material expansion with temperature can explain both phenomena and a dynamic clutch temperature model that can describe the dynamic torque variations is developed. The dynamic model is validated in experiments, and it is shown to reduce the error in transmitted torque from 7 % to 3 % of the maximum engine torque compared to a static model. Clutch wear is also a dynamic phenomenon that is of interest to track and compensate for, and therefore the model is augmented with an extra state describing wear. An observability analysis is performed showing that the augmented model is fully or partially observable depending on the mode of operation. In particular, by measuring the actuator position the temperature states are observable, both during slipping of the clutch and when it is fully closed. An Extended Kalman Filter (EKF), which observes the temperature states, was developed since it is straight forward to incorporate different modes of operation. The EKF was evaluated on measurement data and the estimated states converged from poor initial values, enabling prediction of the translation of the torque transmissibility curve. The computional complexity of the EKF is low and thus it is suitable for real-time applications. Modeling, parameter estimation, observer design and validation are all carried out using production sensors only and therefore it is straight forward to implement the observer in a production HDT following the presented methodology.

Place, publisher, year, edition, pages
IEEE, 2015
Keyword
clutch control, temperature, observer, Extended Kalman Filter (EKF)
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-96857 (URN)10.1109/TMECH.2014.2303859 (DOI)000352060700006 ()
Projects
LINK-SIC
Funder
VINNOVA, LINK-SIC
Note

On the day of the defence date the status of this publication was Manuscript.

Available from: 2013-08-28 Created: 2013-08-27 Last updated: 2017-12-06Bibliographically approved
4. Thermal Clutch Model Observability and Observer Effects of a Torque Sensor in the Powertrain
Open this publication in new window or tab >>Thermal Clutch Model Observability and Observer Effects of a Torque Sensor in the Powertrain
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Torque sensors for automotive powertrains are becoming cheaper and a viable option for production vehicles. It is investigated how a torque sensor located on the input shaft of an Automated Manual Transmission (AMT) in a Heavy Duty Truck (HDT) affects the observability of a clutch model for torque transmission that includes thermal effects and aging. In order to handle an offset that is introduced with the new sensor the model is augmented with a random walk and an equation for the engine inertia dynamics. The sensor offset is observable regardless of mode of operation of the clutch and observability of the states in the original model is unchanged. Furthermore the design of an Extended Kalman Filter (EKF) built upon the augmented model requires a new mode of operation compared to an EKF built upon the original model. In addition a mode dependent process noise covariance matrix is used. The new EKF is evaluated using measurement data from an HDT equipped with a magnetoelastic torque sensor. The EKF is demonstrated to work and the estimates converge rapidly, even from poor initial values. It is also computationally simple and therefore suitable for real-time applications.

Keyword
clutch control, temperature, Extended Kalman Filter (EKF), modeling
National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-108836 (URN)
Projects
LINK-SIC
Funder
Vinnova, LINK-SIC
Available from: 2014-07-08 Created: 2014-07-08 Last updated: 2014-07-11
5. Dry Clutch Micro-Slip Control and Temperature Considerations
Open this publication in new window or tab >>Dry Clutch Micro-Slip Control and Temperature Considerations
(English)Manuscript (preprint) (Other academic)
Abstract [en]

With an automatic clutch in the powertrain it is possible to micro-slip the clutch. Micro-slip is a continuous small slip in the clutch used to isolate the driveline from the oscillations in the torque produced by a combustion engine. A control structure has been designed for a micro-slip controller. The basic components are a Linear Quadratic (LQ) controller based on a linearized driveline model and an Extended Kalman Filter (EKF) that can compensate the torque request from the LQ controller for the thermal dynamics of the clutch. To remove some stationary errors, integral action has been added to the LQ controller by adding an extra state. An anti-windup scheme is used, and the additional parameters depend on clutch conditions. The reference slip value is set according to a derived formula for the flywheel-speed-oscillation amplitude together with a dynamic safety margin that can increase during transients. Altogether the controller has a simple structure and there should be no technical problems to implement it in a production vehicle. In simulations with transient torque, unknown road grades, and a mass parameter that has been varied by a factor of 2, the controller is able to follow the slip reference without locking up. The simulations are performed on a non-linear driveline model, previously validated with data, that has been augmented with a model for the oscillative torque produced by the engine in order to more accurately describe micro-slip conditions. The torque model is a sinusoidal model and has been fitted to high resolution data. The oscillation amplitude and frequency agree well with the data. The thermal behavior of a clutch with micro slip is analyzed and the EKF should be used for temperature surveillance together with some suggested counter measures although there were no excessive temperatures during simulations of recorded driving missions. However, the simulations show that the fuel consumption increase might be too large for a heavy-duty-truck application if micro-slip control is to be used at all operating conditions. Further analysis of costs versus benefits are required on a vehicle level but the feasibility of a micro-slip control system for a dry clutch truck has been proven.

National Category
Control Engineering
Identifiers
urn:nbn:se:liu:diva-108837 (URN)
Projects
LINK-SIC
Funder
Vinnova, LINK-SIC
Available from: 2014-07-08 Created: 2014-07-08 Last updated: 2014-07-11
6. Road Slope Analysis and Filtering for Driveline Shuffle Simulation
Open this publication in new window or tab >>Road Slope Analysis and Filtering for Driveline Shuffle Simulation
2012 (English)Conference paper, Published paper (Refereed)
Abstract [en]

In powertrain analysis, simulation of driveline models are standard tools, where efficient and accurate simulations are important features of the models. One input signal with high impact on the accuracy is the road slope. Here it is found that the amplitude discretization in production road-slope sensors can excite vehicle shuffle dynamics in the model, which is not present in the real vehicle. To overcome this problem road-slope information is analyzed with the aid of both measured and synthetic road profiles, where the latter are generated from regulatory road specifications. The analysis shows that it is possible to separate vehicle shuffle resonances and road-slope information, and designs are proposed for on- and off-line filtering of the road-slope-sensor signal in spatial coordinates. Applying the filter to measured data shows that vehicle shuffle is significantly attenuated, while the shape of the road slope profile is maintained. As a byproduct the use of smoothing the rolling resistance is shown.

Place, publisher, year, edition, pages
International Federation of Automatic Control, 2012
Series
Engine and Powertrain Control, Simulation and Modeling, ISSN 1474-6670 ; 3
Keyword
Driveline Simulation; Driveline Modeling; Validation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-96849 (URN)10.3182/20121023-3-FR-4025.00014 (DOI)978-3-902823-16-8 (ISBN)
Conference
IFAC Workshop on Engine and Powertrain Control Simulation and Modeling (ECOSM 2012), 23-25 October 2012, IFP Energies nouvelles, Rueil-Malmaison, France
Projects
LINK-SIC
Funder
Vinnova, LINK-SIC
Available from: 2013-08-27 Created: 2013-08-27 Last updated: 2014-07-11

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