Gabriela Achtenová - Czech Technical University in Prague
Martin Škopek - Czech Technical University in Prague
Vojtěch Formánek - Czech Technical University in Prague
The Scaled Mobility on a Laboratory Level (SMALL) project is based on usage of a scaled vehicle, which is further denoted as SMALL vehicle (approximate scale with respect to a real vehicle is 1:5). The target of the project is low-cost testing of advanced transportation systems, which can be applied in the future for autonomous drive of vehicles.
If we intend to transform the linearized differential equations of movement of the vehicle into the dimensionless form, we need to obtain the same mathematical representation for both the real full-size vehicle and the scaled SMALL vehicle. Through the transformation of equations into the dimensionless form, we must define the coefficients of mass relation, different length relations, position of centre of gravity, and more. We can use these coefficients to tune the SMALL vehicle according to the parameters of the real vehicle. This means we can predict, based on the parameters measured on the SMALL vehicle, the behavior of the real vehicle. It means that with the help of low-cost tests made in the laboratory with the SMALL vehicle, we can obtain a realistic estimate of behavior of the full-size vehicle and/or prove the proposed algorithms.
The challenge of the presented study is to instrument the SMALL vehicle with all necessary sensors that sense its movement, behavior, position, and surroundings. Furthermore, the SMALL vehicle needs to be equiped with a control unit that sends the commands to its main systems (motor, steering, and brakes). The sensed values must be transfered to the main control computer, where all data is processed, and the control commands are sent back to the main systems of the SMALL vehicle.
For testing algorithms of autonomous drive such as lane assist, following leading vehicle, and others, the SMALL vehicle comes equipped with an IP camera Axis212ptz. We use Vision Assistant and some of its preprogrammed algorithms for image processing. The system searches for the position of the line depending on the intensity of grey colors of any single pixel on the vector perpendicular to the line of roadside. When approaching a situation similar to a highway exit, the straight ahead direction or the turn can be chosen through a switch on the control panel of the main computer.
The SMALL vehicle features ultrasound and a laser distance sensor for tests of algorithms of adaptive cruise control. The Single-Board RIO device together with the IP camera share the data with the main control PC through network communication. On the main control PC the evaluation and control algorithms programmed with LabVIEW software run.
The SMALL vehicle can be used as a single vehicle, a vehicle with a one-axle trailer, a truck-trailer combination, or a truck with a two-axle trailer. Both trailer axles can be steerable. For tuning the SMALL vehicle with regard to the full-size vehicle, we designed a special cage to facilitate the measurements of the moments of inertia around all three axles.
We created a functional scaled vehicle equipped with all the necessary sensors and a control unit that allows the repeatable tests of different algorithms for autonomous vehicle drive.
Czech Technical University in Prague
Prague 166 07
Tel: +420 2 24 35 24 99
Fax: +420 2 24 35 25 00