Browsing by Author "Potgieter, Frederik Jacobus"
Now showing 1 - 1 of 1
Results Per Page
Sort Options
- ItemNavigational precision of an autonomous ground vehicle using multiple sensors(Stellenbosch : Stellenbosch University, 2016-03) Potgieter, Frederik Jacobus; Smit, W. J.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.ENGLISH ABSTRACT: This thesis investigated the navigational precision of an autonomous ground vehicle by fusing different sensors as a means of localization and navigation. Different GPS (Global Positioning System) modules (regular, RTK (Real Time Kinematic) and differential GPS) in conjunction with a digital compass and optical encoders were used as sensors for capturing data regarding the robot’s position. The Arduino Mega 2560 with an 8-bit Atmel microcontroller was used to control all robot functions while MATLAB was used to plot all navigational output data. To implement the localization and navigation, background information had to be gained regarding the functioning of the GPS, motor speed control, fusion of sensor data and algorithms used by the sensors. After this was done all the hardware required to implement navigation was purchased, compatibility between all the components was ensured, housings for the sensors were manufactured, the current platform was modified and a power source sufficient to power everything was selected. Next software was implemented to: control the hardware, capture all the data from the sensors, fuse sensor data, map the environment, establish localization and navigate between waypoints and finally display all the captured data to the user. Before determining the navigational precision of the robot, it needed to be confirmed whether the Piksi RTK GPS could be used as a benchmark for precision comparison of the other sensors. Next case studies tested the navigational precision when: doing multiple runs of the same map, using different complimentary filter values, enabling differential GPS, altering the robot’s speed, introducing wheel slippage, magnetic interference and GPS drift is present and when sensors fail. The high precision with which the Piksi RTK GPS is able to locate the robot gives it the ability to be implemented in various other autonomous and navigation scenarios. Multiple runs of the same map concluded that the consistency of the navigational precision was good enough that data between different runs could be compared. The optimal complimentary filter constant was found experimentally, it was seen that differential GPS resulted in more precise navigation and that the lowest robot speed resulted in the most precise navigational results. Wheel slippage and magnetic interference had a large effect on the robot’s position estimation while GPS drift had little effect. Finally it was seen that any single sensor failure resulted in the robot being unable to navigate. Future work that affects the navigational precision can include: use of different data fusion algorithms, fusion of Piksi RTK GPS data with odometry data, more stable or different robot platform, additional sensor to detect wheel slippage, algorithm to detect magnetic interference and the use of stronger Piksi RTK GPS direct communication antennas.