In this thesis, terrain adaptive aperiodic gait for a quadruped walking robot is investigated. Especially, we study on straight gait and spinning gait.
In the straight gait study, we focus on the straight motion having the leg-lifting sequence of wave gait because this sequence is usually shown in the previous researches on periodic or aperiodic straight motion. We derived the necessary and sufficient condition of support pattern for the forward straight motion having the leg-lifting sequence of wave gait. The support condition is called the proper support condition for the forward straight motion in this thesis. The necessity implies that any support pattern of the forward straight motion having the lifting sequence of wave gait satisfies the proper support condition for straight motion. The sufficiency implies that if the proper support condition is satisfied by the given support pattern, it is always possible to generate the forward straight motion having the lifting sequence of wave gait. Based on the proper support condition, we propose a aperiodic straight motion planning method called "diagonal line planning method." When the given support pattern satisfies the proper support pattern, the diagonal line planning method generates the forward straight motion having the lifting sequence of wave gait and plans simultaneously the motion variables of two legs not adjacent to each other. The diagonal line planning method searches for the motion variables having good mobility. Moreover, we prove that if the given support pattern satisfies the proper support pattern, it is always possible to transform the support pattern to the support pattern of wave gait during the forward motion in 4 steps. This means that direct transformation to the support pattern of wave gait is possible and the mobility of wave gait can be obtained in even terrain. For the cases that the given support pattern does not satisfy the proper support pattern, we propose conditions of support pattern from which it is possible to transform to the proper support pattern in one or two steps. In addition, we provide the maximum size of rectangular obstacle that can be crossed over by static gait. Even though the analysis is performed on such a simple obstacle, it may be useful for the trajectory planning.
In spinning planning gait, we focus on the spinning motion having z type leg-lifting sequence. Similar to the case of the straight gait, we provide the necessary and sufficient condition of support pattern for spinning motion having the z type leg-lifting sequence and rotating only with the desired direction. The support condition is called proper support condition for the spinning motion. We propose an aperiodic z type spinning gait planning method based on the proper support condition. Even though the proper support condition is derived with a assumption that the distances from the mass center to the support point of any leg are all the same, It may lead to more general cases.
