🚀 go-pugleaf

G'day,

I am working on a collision prevention project for our U.M.I. RTX robot arm.
The arm has a reach of approximately 1.3m (~4.25ft) and a stopping distance
of the order of a few centimetres (a few / 2.54 inches).

Collisions will be prevented by sensors mounted on the arm that alert the
controller when an obstacle is approaching the arm's stopping distance.  
The controller then halts the arm before collision with the obstacle can
occur.

I have considered using ultra-sonic sensors (such as the Polaroid sensor),
but have read that this sensor behaves poorly for distances less than 30cm
(~1ft).  Active damping of the transducer can improve performance for such
distances.  Also in order to completely protect the RTX arm would require a 
number of sensors.  They cost about $500 each here.

Alternatively, I could use I-R sensors.  These sensors operate well at
distances under 30cm (~1ft) and are less prone to specular reflections than
ultra-sonic sensors.  They are however affected by surface colour and have a
fairly narrow beam width (so I may literally have to plaster the arm with
sensors to completely protect it).  Again cost may be a limiting factor
here.

I would appreciate any information (operating ranges, prices, problems etc.) 
you have that would help me choose a sensor suitable for the task outlined 
above.  Stories of proximity sensors you have used are also welcome.

AtDhVaAnNkCsE.
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Chris Pudney 

Department  of  Computer  Science,    PHONE: (local: 09) (int'l: +61 9) 380 3455
University  of Western  Australia,   
Nedlands, Western AUSTRALIA, 6009.    FAX:   (local: 09) (int'l: +61 9) 382 1688 
E-MAIL:  chrisp@cs.uwa.oz.au
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--------------------------------------------------------------------------------
Chris Pudney 

Department  of  Computer  Science,    PHONE: (local: 09) (int'l: +61 9) 380 3455