Abstract
The article describes the process of development of an essentially new wheel suitable both for moving on flat ground and for travelling on stairs. The stair-climbing wheel is composed of rotary circular segments arranged around a shared carrier with arms to form a complete circular profile of the wheel adapted for moving on flat ground; for travelling on stairs, individual segments are rotated by an appropriate angle to touch down tangentially on the stepping surface of the stairs. The dimensions of individual segments, the centre of rotation of individual segments and the angle of their partial turn have been chosen so that the length of the arc along which the circular segment rolls is equal to the length of the stepping surface of an average stair, and, at the same time, the circular segment touches down tangentially on the stepping surface while the wheel turns around the edge of the previous segment. Using the rotation angle of the turnable segments, the wheel can be adapted to the height of non-standard stairs. The segments can be inclined in both directions for bidirectional movement of the wheel up and down the stairs. An undercarriage equipped with these wheels can be used in the field of exploratory robots and for the transportation of persons and materials on stairs.
Highlights
The development of a wheel that would be able, besides moving on flat ground, to travel on stairs or to run up a curb has a long history in the field of engineering, and thousands of different technical solutions have been patented
The circle was divided into segments installed as turnable segments on the arms of the carrier; when travelling on stairs, these segments would allow reconfiguration to obtain a shape approaching the requirement for the wheel rolling on solid protrusions; for movement on flat ground, the circular segments form a perfect and full circle
In order to find an optimal value of the wheel diameter D based on the values of the distance d of the segment rotation axis and of the segment inclination angle, it is apparent that values in the left part of the graph are more advantageous, as the partial turn angle of individual segments is relatively small in this part of the graph, which is convenient especially for the use of pull rods to incline the segments
Summary
The development of a wheel that would be able, besides moving on flat ground, to travel on stairs or to run up a curb has a long history in the field of engineering, and thousands of different technical solutions have been patented. The widest range of applications for travelling on stairs and over obstacles was achieved by a group of solutions based on reconfigurable belt undercarriages.[2] A very interesting principle with reconfigurable belt’s outer circumference between wheel and track was introduced in Xueshan et al.[3] Some of these belt undercarriages are completed with auxiliary mechanisms to raise the undercarriage up to the first stair To this group belong the undercarriages with belts on swinging arms.[4,5] Higher energy demands of the tracks while moving both on flat ground and on stairs, problems with shear control of movement direction and problems due to small objects getting wedged between the belt and the wheels are the disadvantages of the belt undercarriages. The well-done comparison of various stair-climbing principles including their stability analysis is carried out in Tao et al.[26]
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