Quasi-static analysis of a leg-wheel hybrid vehicle for enhancing stair climbing ability

This paper presents quasi-static analysis of a leg- wheel hybrid vehicle for enhancing stair climbing ability. The vehicle consists of four spoke-wheels. The number of spokes for each wheel can be altered by varying the number of strips attaching to the wheel hub. The effects of having different number of spokes are studied in two bases: climbing ability over an obstacle and the required coefficient of friction between spoke tips and stairs. The climbing ability is measured by the maximum height of obstacle that the vehicle is able to travel. For a certain friction coefficient, the limit for obstacle height can also be predicted. Leg-wheel vehicles with four, six and twelve spokes are also built and tested. Results from the quasi-static analysis and the experiments are shown to be comparable. The slight difference is due to deformations of the spoke strips from the vehicle weight. Calculation and experimental results are in agreement. The maximum step height of the leg wheel can roll over in each case is relatively more than its hub. The twelve- spoke wheel gives the maximum absolute height among the three cases.