Mobile Robot Control 2020 Group 1

Group Members

	Name	Student Number
1	T.J.M. Snijders	1017557
2	B.P.J. Reijnen	0988918
3	J.H.B. de Zwart	1020347
4	S.C.M. Mennen	1004332
5	A.C.C.E. Vissers	0914776
6	B. Godschalk	1265172

Introduction

This Wiki-page reports the progress made by Group 1 towards completion of the Escape Room Challenge and Hospital Challenge. The goal of the Escape Room Challenge is to escape a rectangular room as fast as possible without bumping into walls. The goal of the Hospital Challenge is to deliver medicines from one cabinet to another as fast as possible and without bumping into static and dynamic objects.

Logs

Meeting	Date	Time	Chairman	Secretary	Summary	Download
1	24-04-2020	15.00	-	-	Introduction
2	28-04-2020	15.00	-	T.J.M. Snijders	Introduction to tutor, discussed contents of Design Document	Notes
3	01-05-2020	14.00	B. Godschalk	S.C.M. Mennen	Discussed software architecture	Notes
4	03-05-2020	14.00	-	-	Discussed strategy for Escape Room Challenge
5	05-05-2020	14.00	-	-	Discussed Escape Room Challenge software structure
6	08-05-2020	15.00	S.C.M. Mennen	B.P.J. Reijnen		Notes
7	11-05-2020	14.00	-	-	Decided that the current solution for the escape room challenge is sufficient
8	12-05-2020	14.00	-	-	Last meeting before Escaperoom Challenge
9	15-05-2020	14.00	B.P.J. Reijnen	J.H.B. de Zwart	Start architecture and flow chart for Hospital Challenge
10	19-05-2020	14.00	-	-	Decided upon Hosptial Challenge strategy
11	22-05-2020	14.00	A.C.C.E. Vissers	J.H.B. de Zwart	Continue in same groups on specific parts
12	26-05-2020	14.00	-	-
13	29-05-2020	14.00	J.H.B. de Zwart	T.J.M. Snijders	Discussion about presentation and Hospital Challenge
14	02-06-2020	14.00	-	-
15	05-06-2020	14.00	T.J.M. Snijders	B. Godschalk	Continue with separate parts, more testing required
16	09-06-2020	14.00	-	-	Last preparation for Hospital Challenge
17	12-06-2020	13.00	-	-	Division of tasks for Wiki page

Design document

In order to get a good overview of the assignment a design document was composed which can be found here. This document describes the requirements, the software architecture which consists of the functions, components and interfaces and at last the system specifications. This document provides a guideline to succesfully complete the assignment.

Escape Room Challenge

Strategy

Strategy for Escape Room Challenge

To create a solid strategy a number of options have been outlined. Two solid versions were considered; wall following and a gap scan version. After confirming that the gap scan version can, if correctly implemented, be a lot faster than following the wall, the gap scan version is used in the escape room challenge since the goal of the escape room challenge is to escape as fast as possible. On the right the strategy flow has been mapped in a flow chart, which starts at 'Inactive' and ends at 'Move forwards' until the PICO (simulation) is stopped.

The first step that will be executed is the 'Initialize' step. This step will be used to clear and set all variable values to the default state from which it will continue to the '360° scan'. In this scan all Laser Range Finder measurements will be mapped into wall objects. When walls do not connect a gap occurs which can be a possible exit or a faulty measurement.

The next step 'Gap?' is checking if the gaps found can be considered as a exit. If no gaps meet the specifications of a gap, the next step will be 'Move to better scan position' and PICO will redo the previous steps. If a gap meets the specifications the next step is 'Path planning', which will be executed to calculate the best possible way to the exit. When the path is set the following step will be 'Move to gap'.

The final step will be 'Center?' which will center the robot in the corridor of the exit to prevent that incorrect alignment with the exit will result in a crash with the walls.

Parallel to this flow PICO will continuously keep track of objects with the laser range finder. Whenever a object is detected in a specific range of the robot a flag will be thrown. This flag can be used to update the path planning, which will prevent crashes when the robot is heading in the wrong direction.

Functions

To perform the strategy described above, the following functions are used.

Finding walls and gaps

To differentiate between the walls and the exit a least squares regression line algorithm has been written. The Laser Range Finder (LRF) data points are fed into this algorithm and gives all the walls in the field of view (VOF) of the LRF. By connecting the walls together it can be possible that a gap occurs, which will be saved into the global reference frame. To collect the data the robot starts with a 360 degree VOF rotation, while doing so collecting all gaps. When the scan stops, all the collected gaps are checked based on some criteria to see if it is a exit and if it is the best exit possible and, if needed, fixed (straightened based on the adjacent walls).

Potential field corridor

When PICCO drives in the corridor, PICCO starts to monitor the left and right wall to center itself between the walls of the corridor while moving towards the finish line.

Simulation

Simulation in emc-sim for Escape Room

With the used strategy and the created functions, the simulation is showed in the created gif of emc-sim. The heightmap used for this simulation is shown below.

Escape Room heightmap used in emc-sim simulation

When the scan can not find any gaps in the walls, PICO will move 1 meter to the furthest point measured in the scan and performs a new scan. If, for any reason, PICO tends to walk into a wall, the robot will move backwards and starts a new scan. This is showed in the gif below.

Escape Room no gap simulation in emc-sim

Escape Room Challenge results

Escape Room Challenge live stream result.

Immediately in the first attempt a record set of 55 seconds was set! After some doubt from the jury, whether a second attempt was necessary (since the robot did behave a bit strange outside of the corridor) the first attempt was declared valid. However, the moving behaviour was partly confusing since PICO decided to align himself with the reference angle using the largest rotation. In the end group 1 is proud of the result. The result can be seen in the gif on the right.

As can be seen in the scanning, the robot rotates in a smooth counterclockwise rotation in which the gap detection algorithm detects the exit. After validation of the gap, a pre-target and target are placed in relation to the detected gap location. However, the movement towards it went wrong. Normally, the motion component of the software calculates the smallest rotation between the angle of PICO and the pre-target & target of the gap. During the development and validation of the written software in the simulator, this component worked as expected. However, during the challenge it emerged that the calculation did not work when comparing positive and negative angles. As a result, the calculation showed that a positive angle had to turn into the negative direction in order to reach its target. Because of this problem PICO started to rotate 270 degrees to the right instead of 90 degrees to the left. This problem came up 2 times, both after the 360 degrees scan and after reaching the pretarget.

After the challenge we looked at this problem and applied a possible solution. If the simulation would be performed again with the right rotations the simulation time could be reduced to 25 seconds which would have resulted in a 2nd place during the challenge, instead of our 4th place that we were placed this time.

In summary, every software component worked fine without failing completely. However, after a bug fix in the motion component, everything works optimally without any known errors. Since the software is built via Agile, the wall detection and motion software can be taken to the hospital challenge and made usable with some additions without starting from scratch again. The used heightmap in the live stream Escape Room Challenge can be found below.

Escape Room Challenge live stream heightmap