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Wind-tunnel tests of a helicopter rotor with active flaps
19 June 2023
Within the frame of a project called DTP RPA (Développement Technique Probatoire Rotor à Pale Active), also known as Active Blade Concept, carried out in cooperation between ONERA, Eurocopter, DLR and Eurocopter Deutschland, a four-bladed Mach-scaled rotor was tested in December 2005 in ONERA S1 Modane wind-tunnel. The main objective of this test was to validate the concept of using active flaps located on the trailing edge of the blades of the main rotor of a helicopter to decrease the vibration level generated by this rotor.
Extreme performance of piezo system: High stroke, high frequency, high temperature
19 June 2023
This paper presents research and development results of the high performances piezoelectric actuators. Performed studies were concentrated on the improvement of three major parameters: stroke, maximum driving frequency and operational temperature. Two, new actuators were presented and described in this paper. First presented actuator has increased maximum displacement. This actuator has doubled the stroke of standard, long stroke actuators. Improvement of the second actuator was concentrated on increase of constant driving frequency. Finally, special encapsulations designed for both actuators allow using them at high temperatures. Development of these two, new actuators was done simultaneously to the improvement of the electronics. High power amplifier presented in this paper provides sufficient current to drive both actuators at high frequencies.
Force Stepping Piezo Actuator : a motorised solution for high resolution positioning and external forces resistance
19 June 2023
Typical holding force of piezo motors is defined by friction force, required to make motor move. However, increase of friction force is not inconsequent for motor performances in terms of speed, max motion force and lifetime (tribology). In this paper, a new motor, offering high resolution positioning and holding position when unpowered, is presented. Based on a Stepping Piezo Actuator [1] at its core, this new design decouples the outer forces from the most sensitive parts of the motor. This allows the motor to propose a high force/mass ratio and sustain even higher forces without supply. Results obtained on prototype are presented, giving the reader the benefits of proposed technology.
Frequency Dependence of Mouse Brain Tissue Stiffness Measured in vivo with MR Elastography
19 June 2023
Magnetic resonance elastography (MRE) is a non-invasive imaging technique for quantitative measurement of the mechanical properties of biologic tissue in vivo [1]. The clinical interest in MRE has largely been driven by the direct relationship between tissue health and stiffness. As a result, MRE may provide significant clinical value for the non-invasive diagnosis of pathology and response to therapy by tracking tumor development and monitoring therapeutic response. MRE may also have considerable value in the development of treatment protocols in pre-clinical, rodent models of cancer. Because of cost and versatility, the mouse, in particular, is widely employed in oncologic studies. To resolve its small anatomic features, MRE experiments in mice must be performed with high driving frequencies (>600 Hz). However, high-frequency waves exhibit increased attenuation, reducing wave penetration depth and making it more difficult to impart motion deep into tissue with sufficient amplitude to overcome background noise. Also, biologic tissue is viscoelastic; hence, its response to load depends on the driving frequency. Recent MRE studies in mouse brain have been performed in high-field scanners (7 – 11.7T) at single driving frequencies of 1000 and 1200 Hz [2,3]. Here, we perform elastography in mouse brain tissue at 4.7T and report viscoelastic material properties over a range of driving frequencies (600 – 1800 Hz).
From the Test Benches to the First Prototype of the muFly Micro Helicopter
19 June 2023
The goal of the European project muFly is to build a fully autonomous micro helicopter, which is comparable to a small bird in size and mass. The rigorous size and mass constraints infer various problems related to energy efficiency, flight stability and overall system design. In this research, aerodynamics and flight dynamics are investigated experimentally to gather information for the design of the helicopter’s propulsion group and steering system. Several test benches are designed and built for these investigations
FSPA and BSMA Nanometric positioning actuators for ground and space applications
19 June 2023
Many applications and more specifically space projects show need for a stable sub-micrometre positioning actuator. In order to meet this need, Cedrat Technologies has designed the new FSPA brand. This linear stepping actuator offers sub-micrometric positioning resolution along 5mm stroke combined with high actuation force (>100N) and the ability to hold its position without power.
The IASI-NG instrument is one of the key payload on-board METOP-SG which is a new meteorological satellite for Europe. The instrument is based on a Mertz interferometer and requires a very precise positioning of an optical blade used to separate the interferometer’s branches. A dedicated version of the FSPA, the Beam Splitter Mechanisms Actuator (BSMA) is then developed to achieve this nanometric positioning which is a key parameter for the overall instrument performance.
This paper firsts present the internals of both FSPA and BSMA actuators. Major design differences and their respective impact on the resulting performances are detailed. Results from the acceptance and qualification test campaigns are also presented.
