DESIGN AND PERFORMANCE ASSESSMENT OF MULTI-MODAL MOBILE ROBOTS

Abstract

This thesis is focused on developing multi-modal mobile robots, i.e. robots that can operate in more than one domain. For decades, researchers have been trying to improve locomotion capabilities of robots that operate in a single domain: on the ground, on inclined surfaces, in the air, or in water. A prevailing approach in design of hybrid robots is to simply attach systems designed for a single domain together. In order to reduce the complexity of the hybrid robot, a different design approach is taken in this thesis by attempting to keep the hardware resources on the system as low as possible. To this end, two hybrid aerial and terrestrial platforms have been developed: the walking quadrotor and the HyTAQ, the Hybrid Terrestrial and Aerial Quadrotor. In both platforms, ight is achieved through a quadrotor configuration; four actuators provide the required thrust. The walking quadrotor uses a single actuator set for both walking and ying by means of a unique compliant mechanism. This mechanism uses two separate linear movements to make walking possible. The horizontal movement of the leg is driven by running the propellers in reverse and the vertical movement is actuated by shape memory alloy (SMA) wires. An experimental prototype of this robot proves the functionality of the design. However, the experiments suggest that the application of the robot is efficient only where ground movement is a small portion of the whole mission. This is mainly due to the low efficiency of the propellers rotating in reverse and large time constant of the SMA wires, which makes walking slow. The terrestrial locomotion of HyTAQ has been made possible by adding a cylindrical cage, connected to the quadrotor through a revolute joint. This allows the cage to roll freely with respect to the body of the quadrotor, making the terrestrial locomotion possible. Moreover, the same ight actuators and control commands can be used to control terrestrial mode. An analysis of the system's energy consumption shows that the addition of the terrestrial locomotion improves the efficiency of the aerial-only quadrotor by increasing the overall operation range and time. This has been experimentally verified by showing that the HyTAQ's terrestrial range is 11 times greater compared to ight range of the quadrotor at the same speeds. Developing a hybrid aerial and scansorial robot is the next goal of this research. The first step toward this goal has been taken as part of this thesis by developing a method that enables a quadrotor to land and take-off from smooth vertical surfaces autonomously. A Microsoft Kinect sensor is used to localize the MAV and a PID controller is used to control the perching maneuver. A servo actuated gripper, mounted in front of the robot, makes attachment and detachment possible. The experimental results show that the robot can perch successfully in more than 90% of the experiments, which indicates the robustness of the proposed method.Ph.D. in Mechanical and Aerospace Engineering, May 201