vehicle specific traversability analysis of pathways · road examples potholes and open gutters ......

Muhammad Mudassir KhanPhD Student in Electrical Engineering,

SBA School of Science and Engineering, LUMS

Vehicle Specific Traversability Analysis of Pathways

Joint project: Abubakr Muhammad (LUMS) and Haider Ali (DLR)

31/07/2015 WFAR-8, Schloss Dagstuhl 2

Nearly 1.3 million people die in road

crashes each year.

An additional

20-50 million are injured or disabled.

Road crashes cost USD $518 billion

globally.

Over 90% of all road fatalities occur in low

and middle-income countries.

Road injuries are predicted to become the

5th leading cause of death by 2030.

Statistics of Road AccidentsWorld Health Organization (WHO) data


“On a Crash Course: The dangers and health costs of deficient roadways”, a survey by The Pacific Institute for Research and Evaluation.

Effect of Road Conditions 52.7% deaths in road casualties were caused by road conditions in US. Road accidents due to road conditions cost U.S. economy more than $217 billion

each year. Road accident casualties in developing countries due to road conditions are 73

times more than that of developed countries.

4

Reduce Casualties from Road Accidents

Solution: Methodology:

Equip every vehicle with advanced technologies.

Pre-record road information and store it

50% of the crashes can be prevented by advanced technologies (Kingsley et. al. 2009).

8–25% fatal crash reduction with advisory system (WHO World Report on Road Traffic Injury Prevention).

Scientists are aiming at nearly 100% crash prevention with autonomous vehicles. (Google Autonomous Car)


Route Planning Software Given start and destination:

Generate a shortest route from start to destination Same route for all vehicle types No information about whether the route is safe for vehicle or not


Disaster Scenario Send help to disaster effected area Find beforehand whether road is safe or not


Scenario 1 Vehicle 1 can drive through the road Vehicle 2 can not drive through road, no matter what

maneuver it takes


Scenario 2 Vehicle 1 can not drive through road. Vehicle 2 can drive through road with some maneuvers, keeping to left of the road.


Given 3D data of road, some vehicle parameters and vehicle motion constraints, compute how safe it is for the vehicle to drive on that road.

Assign a value indicating safety of road for the vehicle. Practically usable index

Problem


Proposed Framework


Each data frame consists of RGBD pointcloud

RGB-D sensor directed towards road surface

Robot Operating System (ROS) on Ubuntu

Data stored in the form of ROSBAG

Sensing System


Pre-processing using PCL filters Remove outliers Crop pointcloud to remove unwanted region

Pre Processing


Road Model

Vehicle Parameters

Configurations Space

Collision Checking

Probabilistic Roadmaps (PRM)

Interaction between vehicle and road.

Motion Planning


Road Model

Assume road as a planar surface. Extract road parameters by plane fitting on

pointcloud using RANSAC. Plane parameters from equation

Find distance of each point from road using equation:

d iroad> thobs

ax+by+cz+d=0pi

If , point is obstacle.

Red are obstacle and green are part of road.


Anything that hinders the motion of vehicle. Two types:

Negative obstacles are depressions in the road

Examples potholes and open gutters

Positive obstacles are humps or anything above surface of the road

Examples: speed breakers and roadblocks

Obstacles


Find interaction of vehicle with road model.

Length: Length of the vehicle Width: Width of the vehicle Ground Clearance: Distance

between vehicle and road. Wheelbase: distance between

center of front and back tires Track: distance between center of

back tires Contact patch of the tire with road

Tire width Tire length in contact with road

Vehicle Parameters


Minimum no of variables needed to uniquely identify vehicle configuration. All possible interactions between vehicle and road. is the 5-Dimensional C-Space of our vehicle. Collision checking is performed to find valid and invalid configurations.

Configurations Space


Whether vehicle collide with any obstacle or not. Valid:

No collision with obstacle. Vehicle is in stable condition.

Invalid Configuration: Any of vehicle’s tires collide with obstacle. Any of vehicle’s tire is outside road boundary. Vehicle body collide with obstacle. Vehicle does not obey stability constraints.

Collision Checking in 3D pointcloud


Radius search is an approximation of bounding

box

Approximate the tire contact patch with a circle or

radius Tirewidth/2.

Project original pointcloud on road plane

Find all pointcloud points in the radius Tirewidth/2 of

the center of tire on road.

Find distance of each point from road surface.

If percentage of valid points is greater than some

threshold for all tires then it’s a valid vehicle

configuration.

Collision checking for negative obstacles


Kernel based full body model

Represent the vehicle by a box

Find all pointcloud points in the vox

Find distance of each point from road surface.

If percentage of valid points is greater than some

threshold for all tires then it’s a valid vehicle

configuration.

Collision checking for Positive obstacles


Probabilitic Roadmaps (PRM)

PRM is an approximation of CSpace. PRM is a graph where each node is a random

configuration and each edge is a valid path. Two nodes and are connected in G is both are valid

and there is no invalid configuration between them that is invalid.


Given road data, divide it into smaller patches. Traversability is defined as no of unique paths from start to

the end of each road patch

Generate adjacency matrix of PRM graph . Study properties of the PRM graph using its

adjacency matrix. Use graph theoretic concepts like maxflow/mincut and

connected component analysis to perform traversability analysis.

Traversability Analysis


Road Traversability Index (RTI)

Pointclouds

Configuration Space

• RTI is a mapping from PRM graph to a real value between

• RTI=0, if there is no path from start to end of road patch. Fig (c)

• RTI=1, if all possible paths exist from start to end. Fig (a)

• Anything in between shows relative traversability.


Road Traversability Index (RTI)

Road Patch• Identify start S, intermediate I and goal F configurations.

• Find all connected components Gi in G.

• Perform maxflow/mincut on every connected component from start S to goal F configurations.


• RTI of a connected component

• is an indicator function, returns 0 if no start S or goal F configurations are

in the connected component.

• is the mincut of the nominal road with no obstacle.

• Putting everything together, we get

RTI Equation

1(Gi)


Experiment and Results

• Perform RTI analysis on synthetic and field road data• Each synthetic road patch is 4x6 meters capturing different scenarios.• Field data was captured using our sensing system.• Each pointcloud in field data is 2x3 meters.• We used vehicle parameters as shown in table on right.


Synthetic Dataset


Synthetic Dataset in C-Space


Probabilitic Roadmaps (PRM) Graph

Traversable Road Non-Traversable Road


Synthetic Dataset Results

5 10 15 20 25 30 35Frame


Comparison with ground truth


Difference with ground truth


Field Experiments

33


Field Experiments Result

34


Original pointcloud Plane segmentation Configuration Space

Challenges

Planar road model is not ideal in real roads.


Application Scenarios

• Road Repair using RTI• Find best possible road deteriorations to repair with

limited resources.• Repair spots that has maximum RTI impact.

• Shortest Route• Like google maps a mapping system that gives

shortest route based on vehicle traversability maximization.

• Rescue operations in disaster• Aerial vehicle to record road data• Process for different available vehicles• Send the one that can traverse the damaged road.


Future Work

● Improve road model● Kinematic Stability Constraints● Dynamic Stability Constraints● Fast collision checking● Stitching pointclouds to get detailed road information


• Framework for vehicle specific traversability analysis of roads.• Graph and Network properties for traversability instead of using

search algorithms to find actual paths.• A novel human readable metric RTI to indicate how safe a road is

for the vehicle.

Conclusion


Thanks

vehicle specific traversability analysis of pathways · road examples potholes and open gutters ......

Documents