Millimeter size machines based on modern precision machining have potential application in industry.Specially in case of small pipe with diameter samller than 1 inch

it is required to develop new type micro robot for maintenance or inspection of inside defects.Considering of the advantage of electro magnet type actuators with simple structure

long stroke

high response and easy control

we do try to develop of a new mobile micro robot in pipe based on interaction of magnetic attraction and spring force.This paper describes the structure and design.The dimension of prototype is Φ15×30mm

weight is 25g.It can climb in pipe of Φ20mm diameter with speed about 6～8mm/s in horizontal and in vertical under applied voltage 14～20V

30～70Hz.