Manipulator sketch

Manipulator architecture

The manipulator is 165 mm in length and 30 mm in diameter.
It is composed of three modules (Module 1, 2, 3) having a length of 50 mm. The distance between two modules is 5 mm. An external braided sheath is integrated along the modules in order to improve the motion capabilities.

Single module architecture

The modules have been connected by means of silicon pipelines (outer diameter = 1.5 mm) passing through the actuation chambers. A total of nine tubes are housed in the manipulator: three for each module.  They supply the pressure inside the actuation chambers thus the modules move. These tubes are made of soft silicone which allows easy integration and maintains flexibility during motion. 

Actuation System
Each module is actuated by three embedded fluid chambers (actuation chambers), in which the air is supplied by pneumatic pipelines connected to external air valves. The possible movements of one single module are the following:
a) If one actuation chamber is actuated, the module bends;
b) If two chambers are simultaneously actuated with the same pressure, the module bends along intermediate directions;
c) If all chambers are simultaneously inflated with the same pressure, the module elongates.
These movements are replicated and amplified when three modules are integrated (see Testing Section).

Single module movements

Here, a movie on the motion performance of the single module is shown:

Variable Stiffness Mechanism
Each module is provided of a stiffening channel where  granular jamming mechanism is integrated. Granular jamming is based on a membrane filled with granular material. When a vacuum pressure is applied to the membrane, the density of the granular material increases and the membrane becomes stiffer than the initial state. Coarse coffee, used as filler granular material, and latex, used as membrane, demonstrated good stiffness performance [Allen et al., Cheng et al.]. For this reason, in each channel of the manipulator, a membrane filled of coarse coffee has been inserted. Three membranes are in-series connected by the vacuum line allowing their simultaneously activation. Different values of vacuum pressure are applied to the vacuum line controlling the stiffness level of the manipulator.
Single granular jamming membrane


Below is an example of three membranes in-series connected is shown:

Activation Set up

Manipulator is controlled by an intuitive user interface connected to an external set up which includes:
- 9 air valves (one for each actuation chamber);
- 1 air compressor for supplying the valves;
- 2 air filters for cleaning air from compressor;
- 1 vacuum pump for activating the granular jamming by vacuum line;
- 1 board for the electronics.