Machine and behaviour co-design of a powerful minimally actuated hopping robot

Machine and behaviour co-design of a powerful minimally actuated hopping robot

Driessen, J.J.M.

Featherstone, R. (mentor)
Vallery, H. (mentor)

Mechanical, Maritime and Materials Engineering

BioMechanical Engineering

Biomechanical Design, Biorobotics

2015-10-30

This thesis presents the first steps of a design study on the robust hopping and balancing robot Skippy. The purpose of the overall design study is to challenge a new design approach for robots with high physical performance. This approach comprises an iterative study of machine (physical system) and behaviour (action strategy) co-design. Skippy is maximally simple in that it has only two actuators to control itself in 3D, and it is to be made from COTS components. It should be able to hop up to heights of 4m and in addition be able to balance, do acrobatic manoeuvres and survive its crashes. The goal of this thesis is to design a realistic action strategy and mechanism for Skippy in 2D to hop up to 4m that is compliant with Skippy's required additional abilities and physical limitations. In 2D, Skippy only requires one actuator. A study that uses the new design approach is presented in this thesis. The initial model of Skippy assumes a perfect actuator and simplified transmissions. The thesis proceeds step-by-step to a more realistic model. The physical system is designed to consist of linkage mechanisms and two non-linear passive elastic elements. The action strategy is designed such that Skippy acts in saturation. Saturation is determined by various physical limits such as the limited nut velocity of the driveline's ball screw and electrical limitations of the motor's armature. The system's behaviour is improved by a redesign of the physical system that moves the cause of the saturation, which increases the mechanical power output of the motor. This redesign includes tuning of inertial, dimensional and stiffness parameters. It is shown that Skippy is able to reach its target height while having basic control over lift-off momenta, which is required for performing acrobatic manoeuvres. In addition, Skippy's balancing performance has been investigated. By adjusting the inertial and dimensional parameters that favour balance, the jumping height is reduced to 3.8m. This suggests that it is important to take additional abilities, like balancing, at an early stage into consideration for design decisions of the iterative design process. Step-by-step introduction and alteration of parts and their parameters in alternation with restrictions and secondary requirements have allowed for well-understood system behaviour and have built towards a more realistic system that works.

legged robot
design method
physical performance
dynamic behaviour

http://resolver.tudelft.nl/uuid:f4140401-707f-4d73-acc3-1f6c281a0d91

Student theses

master thesis

(c) 2015 Driessen, J.J.M.