Skid steer tracked-based robots are popular due to their mechanical simplicity, zero-turning radius and greater traction. This architecture also has several advantages when employed by mobile platforms designed to climb and navigate ferrous surfaces, such as increased magnet density and low profile (center of gravity). However, the suspension design plays a critical and unique role in track-based climbing systems relative to their traditional counterparts. In particular, the suspension must both accommodate irregularities in the climbing surface as well as transfer forces to the robot chassis required to maintain equilibrium. Furthermore, when properly designed, the suspension will distribute the climbing forces in a prescribed manner over the tractive elements. This paper will present a model for analysis and design of a linkage-type suspension for track-based climbing robot systems. The paper will further propose a set of requirements termed “conditions of climbing” that must be met to ensure stable (no falling) climbing for a given robot design over a range of climbing surface geometries. A recursive strategy is proposed to implement these conditions and yield a factor of safety in the current climbing state. This model will be compared through empirical testing with several prototype climbing robot systems. A method will also be demonstrated to use this model in the design of a preferred suspension system.
CLIMBING ROBOT DESIGN FOR NDT INSPECTION
