G-force | EPFL Graph Search

The gravitational force equivalent, or, more commonly, g-force, is a measurement of the type of force per unit mass – typically acceleration – that causes a perception of weight, with a g-force of 1 g (standard gravity force; not gram in mass measurement) equal to the conventional value of gravitational acceleration on Earth, g, of about 9.8m/s2. Since g-forces indirectly produce weight, any g-force can be described as a "weight per unit mass" (see the synonym specific weight). When the g-force is produced by the surface of one object being pushed by the surface of another object, the reaction force to this push produces an equal and opposite weight for every unit of each object's mass. The types of forces involved are transmitted through objects by interior mechanical stresses. Gravitational acceleration (except certain electromagnetic force influences) is the cause of an object's acceleration in relation to free fall. The g-force experienced by an object is due to the

Three-Dimensionally Printed Biological Machines Powered by Skeletal Muscle

Mahmut Selman Sakar

Combining biological components, such as cells and tissues, with soft robotics can enable the fabrication of biological machines with the ability to sense, process signals, and produce force. An intuitive demonstration of a biological machine is one that can produce motion in response to controllable external signaling. Whereas cardiac cell-driven biological actuators have been demonstrated, the requirements of these machines to respond to stimuli and exhibit controlled movement merit the use of skeletal muscle, the primary generator of actuation in animals, as a contractile power source. Here, we report the development of 3D printed hydrogel “bio-bots” with an asymmetric physical design and powered by the actuation of an engineered mammalian skeletal muscle strip to result in net locomotion of the bio-bot. Geometric design and material properties of the hydrogel bio-bots were optimized using stereolithographic 3D printing, and the effect of collagen I and fibrin extracellular matrix proteins and insulin-like growth factor 1 on the force production of engineered skeletal muscle was characterized. Electrical stimulation triggered contraction of cells in the muscle strip and net locomotion of the bio-bot with a maximum velocity of ∼156 μm s−1, which is over 1.5 body lengths per min. Modeling and simulation were used to understand both the effect of different design parameters on the bio-bot and the mechanism of motion. This demonstration advances the goal of realizing forward-engineered integrated cellular machines and systems, which can have a myriad array of applications in drug screening, programmable tissue engineering, drug delivery, and biomimetic machine design.

2014

WAPA: A wearable framework for aerobatic pilot aid

Sylvain Cardin, Xavier Righetti, Daniel Thalmann

Disorientation induced by G-forces during aerobatic flight generates difficulties for the pilots to perfectly align their aerobatic maneuver. This paper presents a modular wearable system for enhancing training of aerobatic pilots. A combination of accelerometers and a gyroscope is used to detect possible deviations compared to the optimum trajectory. The wearable system informs the user in real time about the corrections to apply via vibrotactile actuators and speech synthesis. This publication presents a work in progress in order to validate the system in simulation.

Springer2009

An Instrumented High-Speed Rotor With Embedded Telemetry For The Continuous Spatial Pressure Profile Measurement In Gas Lubricated Bearings: A Proof Of Concept

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Gas lubricated bearings are capable of supporting high speed rotors with satisfactory load capacities. Pressure is one of the constitutional quantities governing the flow field in gas lubricated bearings. Knowledge of the pressure is of principal importance in the fundamental understanding of such bearings and for the calibration of reduced order models. These measurements can be done from the bearing side using pressure taps in the bushings, however, the measurement points will yield a spatially sampled profile consisting of discrete points relative to the bearing bushing. This measurement technique is simple, yet, several details cannot be captured. In order to acquire a continuous scan of the pressure field inside the bearing, it is necessary to measure from the rotor side. Such onboard measurement technique is challenging due to constraints in volume, G-force, and data and power transmission through the rotor. This paper presents an instrumented measurement rotor with embedded pressure probes and a wireless telemetry, which is capable of the continuous pressure field measurement inside a high-speed externally pressurized gas journal bearing. The bearing under investigation has a diameter of 40mm, L/D = 1, and was tested up to 37.5 krpm. The bearing is of the annular type, with 2x18 00.1mm restrictor orifices. Measurements at discrete points using pressure taps inside the test bearing were also performed for the sake of comparison. The measurements from both sides (bushing and rotor) were in good agreement at quasi-static conditions. At higher operational speeds, it was necessary to perform an in -situ system identification and calibration for the embedded pressure probes using the bearing side measurements as a reference. The in-situ system identification technique was successful to reconstruct the attenuated pressure signals for a wide range of supply pressures and rotor speeds. The instrumented rotor was proven qualified to perform time-resolved pressure measurements within the gas film ofjournal bearings up to 37.5 krpm.

Amer Soc Mechanical Engineers2019

An Instrumented High-Speed Rotor With Embedded Telemetry For The Continuous Spatial Pressure Profile Measurement In Gas Lubricated Bearings: A Proof Of Concept

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Amer Soc Mechanical Engineers2019