Look-ahead control
The aim here is to utilize an on-board database with road topography information in combination with a positioning system in order to calculate fuel-optimal velocity trajectories and gear shifting schemes.
Results
For publications, please see the publications page.
A movie about the project is available via YouTube.
Watch video »
During the last workshop on May 18, 2010, the recent work on look-ahead control was presented. The main topics in RHC, the prevailing approach for the look-ahead problem, are choosing a residual cost and selecting a proper horizon length, and these are given a thorough investigation.
View the poster »
The development since last year was presented on the annual workshop on May 14, 2009. It is shown that an energy formulation allows a substantially more computationally efficient algorithm. Furthermore, a residual cost is proposed that is derived purely from engine and driveline characteristics.
View the poster »
The project was also presented on the workshop on May 6, 2008. The project milestone was to have a prototype demonstration implemented and tested in a vehicle by the mid-term evaluation during the fall of 2008, and this had been accomplished.
View the poster »
During the first workshop on May 9, 2007, the progress was shown on a poster. A control algorithm had been realized and evaluated.
View the poster »
Figure: Screen shot from the video.
About Look-ahead Control
Look-ahead control is a predictive control strategy where information about some of the future disturbances to the controlled system is assumed to be available. In this application the system is a long-haulage heavy truck and the additional information includes the road topography ahead of the vehicle.
Scenario
The scenario studied is a drive mission for a heavy diesel truck. The mission route is considered to be known. It is however not assumed that the vehicle constantly operates on the same route. Instead, it is envisioned that there is road information onboard and that the current heading is predicted or supplied by the driver.
It is assumed that a model exists to enable prediction of vehicle motion and energy consumption as a function of control signals and known disturbances. The control signals that are supposed to be available are fueling level, brake level and gear ratio selection. The road slope can be obtained from the altitude information and is thus a known disturbance.
Objectives
A drive mission is given by a route, an allowed velocity range and a desired maximum trip time. The objective is to minimize the fuel energy required for a given mission. The purpose of the control is to take advantage of the look-ahead information in order to actuate fuel-optimal velocity trajectories and gear shifting schemes.
Realization
The road topgraphy information is obtained by the combination of an on-board database with altitude information and a global positioning unit (GPS). The conventional cruise controller is fed with set points from an optimization algorithm.
Figure: Information flow in the prototype demonstration.
The figure above shows the flow of information. A GPS unit connected to a laptop receives the global position. The position is then matched to the road database to obtain slope information about the road ahead. The computer repeatedly calculates the optimal velocity trajectory for the considered horizon and feed the result to the cruise controller in the truck. Further, the computer interface reads data sent from the truck regarding current velocity, currently selected gear and an estimate of the total vehicle mass.