MT400 lost, Charging issues

Information about the Adept MT400 line of mobile robots

MT400 lost, Charging issues

Postby Peter R. » Fri Sep 21, 2012 10:37 am

Hello, i have a mt400 that will become lost in the middle of a delivery, would there be a reason for this? Also another issue i am experiencing is that when it goes to the dock to charge over night, in the morning the techs. notice that he is off/batteries may have died or depleted. We have to push the green button o turn him on and the localize him. Any help would be great. Thank you
Peter R.
 
Posts: 1
Joined: Thu Sep 20, 2012 8:06 am

Re: MT400 lost/senile/ Charging issues

Postby ToddR » Fri Sep 21, 2012 3:24 pm

Hi Peter,

Thanks for the note. I'll do my best to address your questions below.

Becoming lost

There are a number of reasons that a robot could become lost while navigating between goals. The most common reason is that in a particular area of your facility, the features of the robot's environment (what it sees in the plane 11" off the floor) have changed enough that the robot can't accurately determine it's own position. My succinctly, the robot expects to see certain things which were mapped, and when it sees a significantly different landscape it get's confused. By default the robot wants to match at least 20% of the laser readings it sees with points on the map. When the laser score drops below 20% the robot can only drive for a set distance (1 meter by default) before declaring itself lost and stopping. If the score rises above 20% then the 1 meter clock is reset.

For example, if there is a desk on the map, a semi-permanent object, and that desk is moved a foot or two to one side, the robot has no way of knowing this, and it's laser score will be reduced. For this reason after a map is made if there are transient, or temporary items on the map it is best to erase them. If an area changes significantly, for example, if a desk is moved and a refrigerator is added to a lab, then it is best to use the robot to remap. It is not necessary to remap the entire space, just enough to insert a small region into the main map. I posted a quick video on how to do this on youtube here:

http://www.youtube.com/watch?v=qqeir4P4A4Q&list=SP472BC0328FDC590C&index=4&feature=plpp_video

Another culprit for loss of localization can be wheel slip. Are there wet/slippery, or just generally slick areas of the facility where you might see one of the robot's wheels slip? If only one wheel slips then the robot will think that it has turned when it hasn't, if this error is large enough the robot might become lost.

One trivial reason that a robot can become lost is if it is moved by hand when the robot is powered down, or while it is still booting up. Even if the robot is on, pushing the robot any significant distance will usually cause it to become lost. Driving the robot with a joystick will not cause this problem, so if for any reason the robot needs to be move by hand the joystick is the recommended method if one is available.

It is a good idea to keep track of where the robot gets lost most frequently so that the problem can be pinpointed and removed.

Sending your debug info file along with a copy of the map and any relevant screenshots to support@adept.com will allow us to take a closer look.

Batteries

What type of batteries does the robot have? Lead acid batteries or NiMH (Nickel-metal hydride)? How old are the batteries? In normal production we recommend replacing the batteries every 3-6 months depending on how many cycles the batteries are put through in that time frame. During that time the overall capacity of the battery is slowly reduced, just like your laptop of cell phone battery. To get the most out of the robots it is best to keep on top of the battery replacement schedule. In general the NiMH batteries require less charging time for the same amount of run time as a Lead Acid battery.

The idea that the robot was on the charger all night and not charged in the morning doesn't sound like normal behavior though. Was the robot pushed onto the dock by hand? In this case it is common for the operator to forget to push the charging button to initiate charging, where this is not necessary when the robot drives to the dock itself.

In MobileEyes does the robot report that it is charging when this happens? If MobileEyes shows that the robot is charging but it's batteries continue to drain then there is most likely a hardware problem with an element in the charging circuit which can be replaced. It's best to contact Adept customer service in that case. I'll continue to discuss this issue with you from that medium.

Thanks Again,
Todd
ToddR
 


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