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Control-Aimed Kinematics, Actuation, and Sampling for a Tendon-Driven Metamorphic Hand with a Spherical Palm

Student thesis: Doctoral ThesisDoctor of Philosophy

Metamorphic mechanisms are mechanisms which have many different motion branches, regions in configuration space where the mechanism has different kinds of motion. Such mechanisms are able to transition from one branch to another to adapt to changing task requirements. This metamorphosis happens at the points in configuration space where these branches intersect, which are usually singular configurations. Analysing and controlling these mechanisms with generalised methods is usually very tedious and inefficient.

This thesis starts by examining the kinematics and singularities of one kind of metamorphic mechanisms with the aim of visualisation and control. The type of mechanisms studied are metamorphic mechanisms based on spherical linkages. In particular, the variable axis (vA) joint-based metamorphic manipulator and the KCL metamorphic hand. Then simulations, a prototype, and a carton folding operation using the metamorphic hand are presented.

First, the metamorphosis of a metamorphic manipulator is studied. The manipulator comprises three limbs, a fixed base, and a moving platform. The limbs are connected to the base and platform by the vA joint. A vA joint metamorphosis trajectory generation algorithm in the context of the metamorphic manipulator is developed. Spherical trigonometry takes centre stage in the development of this metamorphosis algorithm.

Next, the kinematics of spherical ve-bar mechanisms are solved through spherical trigonometry. This kind of mechanism is used as the palm of the KCL metamorphic hand. The singularities of this class of mechanisms are identified. Singularity avoidance design criteria are presented. A solution is derived for the singular but controllable configurations.

A new antagonistic tendon drive system is developed for the hand. The most important hand joints are controlled by two antagonistic tendons. The rest of the finger joints use tendons antagonised by springs and coupled with passive tendons.

Force sensitive resistors are used in the design of tendon tension sensors. These sensors are then integrated into compact tendon sensing and actuation assemblies.

Sampling time issues are identified and analysed. A CAN bus is used with the CANOpen protocol. A CANOpen protocol router is developed to reduce sampling time and control loop iteration duration.

Finally, an integrated metamorphic hand is built. Its control system is discussed and the hand is used to manipulate an articulated object, an origami-style packaging carton.
Original languageEnglish
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Award date2016

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