Design of Jumping Legs for Flapping Wing Vehicle

Jumping is one of the common methods that flight capable birds use to initiate the take-off phase. Flapping-wing robots that can achieve jumping take-off similar to birds will be significantly valuable since they can reduce the workload of the wing in producing the instantaneous power required for take-off and enables remote operations as well. This thesis progresses the state of the art in leg based jumping systems for flapping-wing robots through a contribution to the fundamental understanding of jumping dynamics and the development of experimentally validated simulation tools. Three reference leg postures are identified from video analysis of a rook take-off: stand, crouch and extended. Birds often use different kinematic patterns for the leg flexion (stand to crouch) and extension (crouch to extended) phases. This is made possible by their multi degree of freedom (Dof) leg structure and complex, multi actuated muscle systems. As an alternative strategy, a conceptual design of a singly actuated jumping leg is proposed where a multi Dof segmented leg is linked to a single actuator. The structure is based on the avian leg and foot anatomy. The study identifies that a dynamically unstable jumping take-off using a tilt and jump approach enables a singly actuated robotic leg to achieve jumping performance similar to birds. A combination of analytical, numerical and physical modelling approaches is used in this study. A generic analytical jumping model is used to establish fundamental understanding of jumping dynamics. The study shows that the take-off dynamics of a jumping system can be idealised as an inelastic collision between the dynamic and static rigid bodies of the system. This provides a simpler way to understand jumping dynamics in general. A physical prismatic jumping model is fabricated principally for validation purposes. A motion capture system is used to quantitatively analyse the jumping kinematics of the model. The take-off velocities predicted through analytical and numerical models agree closely with the experimental data. A multi-segmented numerical simulation model is then developed based on the proposed singly actuated jumping leg design. In the same way an analytical model is developed. It is found that the singly actuated design concept with the assumption of massless segments greatly reduced the complexity of the multi-segmented analytical model. The proposed analytical approach and simulation tool are demonstrated by designing a multi-segmented jumping leg for an example robotic bird. The transparency of the approach enables the designer to understand how design parameters such as take-off weight, actuation properties, leg postures and sizes of the segments affect the take-off velocity. Numerical simulation analysis confirms that jumping performance similar to birds is achieved in the proposed singly actuated jumping legs with the integration of tilt and jump method. For the presented case study, the use of the dynamic tilting method improves the minimum achievable take-off angle from 73° to 12° with respect to the horizontal axis.