AIMing for Automated Vehicles 
Recent Posts
- Steam Powered Servo Motor
- Charlie Wilson's War
- Robots and Books
- Friday Night Work Crew
- Farm Grown Diesel Fuel
- Truck Vision
- Proportional Response
- Farming goes high tech and hands free
- Precision Farming
- Introductions
Recent Comments
- highvoltagepowerlineman at msn.com on Truck Driver Shortage
- highvoltagepowerlineman at msn.com on Truck Driver Shortage
- highvoltagepowerlineman at msn.com on Precision Farming
- Anna on Applied Robotics
- Tara_Reid on Applied Robotics
Most Commented On
- Applied Robotics (3)
- Truck Driver Shortage (2)
- Precision Farming (1)
- The Five Senses - Touch (1)
- THE UNKNOWN (1)
Archives
- May 2008
- April 2008
- March 2008
- February 2008
- January 2008
- December 2007
- November 2007
- October 2007
- September 2007
- August 2007
- July 2007
- June 2007
- April 2007
Blog
Link This | Email this | Blog This | Comments (1)
The Five Senses - Touch
AS A BACKUP
In this age of complex far ranging sensors and motion prediction software the sense of touch is not the focus of development. It instead has been relegated, for the moment, as the sensor of last resort. When all the other high tech stuff fails or is confounded by some unexpected situation, a simple micro switch in the bumpers halts the machine's motion. This is a very important function, but micro switches are not very exotic. That though is their strength in complex systems. They are incredibly simple and hugely reliable. Touch is also used at the last moment when AGV's dock with other machines, to pick up loads or to swap batteries but in these cases is expected and is part of the process, not requiring manual reset.
THE ART
There is an art to the design of touch sensors. Machines do not halt instantaneously and some over travel needs to be allowed for. Pictures of most AGV's show bumpers that loop out a short distance from the vehicle itself and are flexible or are on flexible mounts. Touch bumpers have been part of AGV's from the start. Even hallway robots of university years gone by had bumpers or cat like whiskers to keep them out of trouble. On factory AGV's, in most cases touching (hitting something) is cause for a vehicle shutdown that requires a manual reset. The manual reset in this case is so that a human will be required to investigate the situation before the vehicle is allowed to resume its travel.
In the case of hallway robots, an some robot toys, the bumpers are part of the guidance system that allows them to feel their way around in their environment, check for closed doors, sense stairs etc. Some of the other behaviors of hallway bots are things like "untangle". Should a hallway bot become tangled the jungle of cords hanging down from desks and its continued motion prevented the untangle behavior kicks in which is a series of forward and back motions along with turning. If this fails to allow the hallway bot to go free the next behavior to kick in is "thrash around". In this behavior the machine jerks wildly in every direction to try to free itself. If this fails the next behavior to kick in is "call for help". In this behavior the machine stops all motion and signals for assistance. A pitiful sounding electronic wailing sound or sobbing is good for attracting people to help it.
EXAMPLE
I mention these behaviors because although they are common in hallway bots they appear to have been overlooked by people designing bigger machines. There were several cases in each of the three DARPA races where these behaviors would have given vehicles the chance to continue to compete for the millions of dollars of prize money. For example in the 2007 DARPA Urban Challenge one of the vehicles mistook a driveway as the road it was supposed to turn onto and found itself in a garage. The sensors did not know what to make of its unexpected situation and just sat there until race officials shut it down and took it out of the race. There needs to be a plan of what the machine should do if its forward progress is stopped by outside forces. In another example from an earlier race, the vehicle was PAUSE'd and it rolled forward until its front tire was resting against a football size rock. When it was returned to RUN, it could not move forward because the rock acted as a wheel chock. The rock, against the tire, was out of view of the massive amount of sensors mounted on bumpers and the roof. Later pictures of this teams vehicle show they added a curb feeler front of both front tires to detect wheel obstructions. A simple sub routine of backing up a short distance and turning a bit when the vehicle is not moving forward when it should be would have taken care of it too and might have addressed the more general case.
Another vehicle nosed up to a large boulder because its sensors failed to detect it and when the boulder prevented its forward progress the bot's answer was to redline the engine, spinning the tires until the rubber was gone down to the steel cords then the tires caught fire. Race officials DISABLED the vehicle, put the fire out, "game over" for that vehicle. If it had stopped when its forward progress was interfered with, backed up, turned a little bit to the right and gone forward it would have been able to continue its way toward the finish line and prize money. A touch sensitive bumper would have helped in this case too.
2007 DARPA URBAN CHALLENGE
The Five Senses - Touch
December 12, 2007
AS A BACKUP
In this age of complex far ranging sensors and motion prediction software the sense of touch is not the focus of development. It instead has been relegated, for the moment, as the sensor of last resort. When all the other high tech stuff fails or is confounded by some unexpected situation, a simple micro switch in the bumpers halts the machine's motion. This is a very important function, but micro switches are not very exotic. That though is their strength in complex systems. They are incredibly simple and hugely reliable. Touch is also used at the last moment when AGV's dock with other machines, to pick up loads or to swap batteries but in these cases is expected and is part of the process, not requiring manual reset.
THE ART
There is an art to the design of touch sensors. Machines do not halt instantaneously and some over travel needs to be allowed for. Pictures of most AGV's show bumpers that loop out a short distance from the vehicle itself and are flexible or are on flexible mounts. Touch bumpers have been part of AGV's from the start. Even hallway robots of university years gone by had bumpers or cat like whiskers to keep them out of trouble. On factory AGV's, in most cases touching (hitting something) is cause for a vehicle shutdown that requires a manual reset. The manual reset in this case is so that a human will be required to investigate the situation before the vehicle is allowed to resume its travel.
In the case of hallway robots, an some robot toys, the bumpers are part of the guidance system that allows them to feel their way around in their environment, check for closed doors, sense stairs etc. Some of the other behaviors of hallway bots are things like "untangle". Should a hallway bot become tangled the jungle of cords hanging down from desks and its continued motion prevented the untangle behavior kicks in which is a series of forward and back motions along with turning. If this fails to allow the hallway bot to go free the next behavior to kick in is "thrash around". In this behavior the machine jerks wildly in every direction to try to free itself. If this fails the next behavior to kick in is "call for help". In this behavior the machine stops all motion and signals for assistance. A pitiful sounding electronic wailing sound or sobbing is good for attracting people to help it.
EXAMPLE
I mention these behaviors because although they are common in hallway bots they appear to have been overlooked by people designing bigger machines. There were several cases in each of the three DARPA races where these behaviors would have given vehicles the chance to continue to compete for the millions of dollars of prize money. For example in the 2007 DARPA Urban Challenge one of the vehicles mistook a driveway as the road it was supposed to turn onto and found itself in a garage. The sensors did not know what to make of its unexpected situation and just sat there until race officials shut it down and took it out of the race. There needs to be a plan of what the machine should do if its forward progress is stopped by outside forces. In another example from an earlier race, the vehicle was PAUSE'd and it rolled forward until its front tire was resting against a football size rock. When it was returned to RUN, it could not move forward because the rock acted as a wheel chock. The rock, against the tire, was out of view of the massive amount of sensors mounted on bumpers and the roof. Later pictures of this teams vehicle show they added a curb feeler front of both front tires to detect wheel obstructions. A simple sub routine of backing up a short distance and turning a bit when the vehicle is not moving forward when it should be would have taken care of it too and might have addressed the more general case.
Another vehicle nosed up to a large boulder because its sensors failed to detect it and when the boulder prevented its forward progress the bot's answer was to redline the engine, spinning the tires until the rubber was gone down to the steel cords then the tires caught fire. Race officials DISABLED the vehicle, put the fire out, "game over" for that vehicle. If it had stopped when its forward progress was interfered with, backed up, turned a little bit to the right and gone forward it would have been able to continue its way toward the finish line and prize money. A touch sensitive bumper would have helped in this case too.
2007 DARPA URBAN CHALLENGE
John McElroy's interviews with some of the sponsors can give you a good idea of why sponsors are now getting involved in the race that they avoided early on. Here are links to Autoline Detroit broadcast about the race - part 1 http://www.autolinedetroit.tv/show/1141?play ; part 2 http://www.autolinedetroit.tv/show/1142?play John's
enthusiasm for the race is contagious.
PHOTO
AIM Team member Linda Graham behind the wheel of Team Oshkosh Truck's vehicle in the pit area of the 2007 DARPA Urban Challenge. Linda thanked each of the teams for the work they are doing to save lives and said later "each of the teams was so nice to me and Tom that after spending a week in Victorville with them we hated to see them leave."
GO ROBOTS !
enthusiasm for the race is contagious.
PHOTO
AIM Team member Linda Graham behind the wheel of Team Oshkosh Truck's vehicle in the pit area of the 2007 DARPA Urban Challenge. Linda thanked each of the teams for the work they are doing to save lives and said later "each of the teams was so nice to me and Tom that after spending a week in Victorville with them we hated to see them leave."
GO ROBOTS !
Paul F. Grayson - Chief Engineer
AMERICAN INDUSTRIAL MAGIC, LLC
Racing to build technology that saves soldier's lives.
390 4-Mile Rd. S.
Traverse City, MI 49686-8411
(231) 946-0187, (231) 883-4463 Cell
pgrayson@aimagic.org
http://aimagic.org
http://tech.groups.yahoo.com/group/robotcluboftraversecitymi/
http://www.controleng.com/index.asp?layout=blog&blog_id=1180000318
AMERICAN INDUSTRIAL MAGIC, LLC
Racing to build technology that saves soldier's lives.
390 4-Mile Rd. S.
Traverse City, MI 49686-8411
(231) 946-0187, (231) 883-4463 Cell
pgrayson@aimagic.org
http://aimagic.org
http://tech.groups.yahoo.com/group/robotcluboftraversecitymi/
http://www.controleng.com/index.asp?layout=blog&blog_id=1180000318
Posted by Paul Grayson on December 12, 2007 | Comments (1)
December 14, 2007
In response to: The Five Senses - Touch
elektro commented:
In response to: The Five Senses - Touch
elektro commented:
Wow. I want to play too.
Advertisement
Advertisements
