Statically balanced singular-friction locking

Locking mechanisms are used in a wide range of applications including energy saving mechanisms in the field of robotics. In this thesis a new class of locking mechanisms is investigated: a combination between a singular- and a friction locking mechanism (singular-friction locker) which is statically balanced with one additional spring. This combination of three types of locking mechanisms results in a locking mechanism that has an infinite number of locking positions, can unlock well under load and has an absolute zero actuation force in a singular configuration. In all other configurations the mechanism is theoretically in static balance. The first part of this thesis investigates rigid body type statically balanced singular-friction lockers (SBS-FLs) and works towards a classification of all possible classes of SBS-FLs. This classification contains nine types of rigid body SBS-FLs, consisting of one linkage type class of lockers and eight cam type classes of lockers. In the second part of this thesis different embodiments of SBS-FL mechanisms are investigated on their ability to become a very compact locking device. From five different concepts the highest compactness is obtained by a locking mechanism with a rotational cam input and a rotational follower connected to torsion springs. This mechanism is build and all design aspects are reported. In the third and last part of this thesis the performance and the characteristics of the prototype are investigated. The locking device has a zero actuation torque in the 'engaged' and 'disengaged' (singular) configurations and a maximum actuation torque of 0.035 Nm when switching 'on' and 'off' in 5 seconds. This is a 97% reduction of the actuation torque compared to a regular brake. The maximum braking torque is 0.83 Nm in clockwise direction and 0.75 Nm in counter clockwise direction. The locking device has a diameter of 55 mm and a length of 23 mm. This efficient and small cam based prototype seems to be the most promising approach to statically balanced locking and can find its use not only in robotics but also for example in cars, trucks, bikes and trains.

Subject

Static balance
locking device
torsion spring
singular configurations

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http://resolver.tudelft.nl/uuid:497e1b6e-aa62-4809-9ce8-1002d32aee40

Embargo date

2017-04-29

Part of collection

Student theses

Document type

master thesis

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Thesis_Tom_van_der_Hoeven.pdf

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