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Overview for Red Robin
Red Robin – Your Little Helper
Red Robin was designed to provide modularity and thereby the possibility to being adapted to a wide range of scenarios. By substituting a module by another module with other properties, the drone can be adapted to circumstances which are characteristic for a specific application (e.g. if no VTOL-ability is needed). Also completely new substitute modules can be developed in order to approach new challenges, which have not been considered during the initial development of the Drone. The overall idea of “Red Robin” is to provide a construction kit with a wide range of variations on each module.
Furthermore, “Red Robin” is supposed to be easily assembled in the field. The Drone uses a self-securing quick-lock connector system in order to be assembled and disassembled without the need of any tools. All modules can identify themselves regarding their individual specifications/properties and are able to communicate with the flight computer, which then combines these information into the overall configuration and the resulting properties of the aircraft. All of the drones systems are purely electric.
A propellers load is calculated over its circle-surface which results from his diameter. As the surface grows proportional to the square of the diameter, one big propeller is beneficial against many small ones when it comes to saving installation space. That said, the best solution would be to equip the drone with one big VTOL-propeller. Since the use of only one propeller is problematic as it require to be in the centre of gravity (where the cargo should be), we have to use at least two VTOL-propellers. They have to be placed in front and behind the centre of gravity while being located over the roll-axis of the drone. Placing them beside the centre of gravity (where also the wings are located) would cost a lot of wing surface and thereby reduce lift during cruise flight. Also the big propellers and motors should always be located as close to the roll axis as possible as this provides an improved cruise flight behaviour by having the heavy weights close to the aircrafts centre. Since the two VTOL-propellers cannot stabilise the aircraft around its roll axis, the drone uses two VTOL-balancing-propellers, which are located of-centre, on the wingtips of the tail unit. Positioning the balancing propellers on the tips of the tail unit saves additional structures which otherwise would be needed for mounting the propellers. This saves mass and lowers the wind resistance. It also saves wing surface of the main wings, since they otherwise would have to be integrated into the wings (which would require holes in the wings).
In order to provide thrust for cruise flight, a cruise flight propeller is attached to the rear-VTOL-module. Having a separate cruise flight propeller is only one option for cruise flight. By applying a slidable textile cover to the bottom sides of the VTOL-holes (variation of the principle described in the chapter “Hull Design”) the motor induced air current can be redirected to the rear, resulting in cruise flight propulsion. Therefore, the textile cover has to be tensioned in cruise flight direction and lose and open on the rear side, in order to form a bag-shaped cover under the propellers for redirecting the VTOL-propellers air current and create vectored thrust.
The hulls width and high are a result of the propeller diameter which is necessary for the required VTOL-ability as well as of the required cargo space and of the space for the avionics equipment. The front part (Front-VTOL-Module) and the rear part (Rear-VTOL/Propulsion-Module) are partially wing-shaped, in order to create additional lift during cruise flight.
In in order to achieve the wing-effect on the front and the rear module, the openings for the VTOL-propellers are covered by an industrial grade textile during cruise flight. This forms the wing-shaped surfaces and lowers the wind resistance on the openings by avoiding local vorticities. During VTOL, the textile is stored in front of the rotor-openings. When stored, the textile is wrapped up on a roll, similar to a roller blind and can be dragged over the openings after cruise flight is initiated and creates sufficient lift to keep the drone flying. In order to provide a support structure which keeps the textile in shape while covering the openings, the openings are spanned by splines which are orientated in cruise flight direction. The splines also serve the safety in operation, as they prevent persons from accidentally grapping into operating propellers.
Since the wing span is limited, the wings have to become larger in the direction of the drones roll-axis as the wings have to create sufficient lift for the aircraft, also at low speeds. The main wings are separate modules of the drone. They can be replaced by other wings with different geometries in order to gain specific properties which are crucial for a specific scenario (e.g. larger wings for high altitudes, smaller arrow-tip-shaped wings for high speed cruise fight, wings with aileron for improved manoeuvrability…). The Wings are produced via additive manufacturing, in order to achieve lightweight structures at low costs. The wings core structure is covered by a durable lightweight fabric or foil, which makes the wing airtight and forms the wings surface. In order to mount the wings, they simply become attached to the cargo-module by using two carbon-fibre-bars, which connect the wings to the aircrafts main body as well as the both wings to each other.
Take-off and Landing
By using its strong VTOL-Motors, the aircraft is able to perform a vertical take-off as well as a vertical landing. The VTOL-engines produce enough thrust for a take-off mass of 25kg while providing enough thrust reserves for maintaining manoeuvrability.
Since the aircraft also possesses a wheeled three-point-landing gear, the aircraft is also able to perform conventional take-offs as well as conventional landings. The landing gear is located at the front-VTOL-module as well as at both tips of the V-shaped tail unit and thereby provides a high stability to the aircraft while take-off and landing.
In case of a critical system malfunction during flights, the drone has an emergency parachute system. Once ejected, it can bring the drone down to the ground, minimizing the risk of damaging the drones structure which would occur by an uncontrolled impact on the ground.
Cargo and Batteries
Cargo and batteries can be accessed from the bottom of the aircraft. The cargo is located in a cargo container which provides possibility to secure the cargo (e.g. by strings or Styrofoam pieces). The cargo container itself fits precisely in the cargo space of the aircraft and is secured by a quick lock system, which can be easily released by hand in order to remove the cargo container.
The batteries (of the shelf) are located in front of the cargo space in a separate cavity. They are combines into one module, which can be extracted and replaced via a similar quick lock mechanism which is also used for securing the cargo container.
By using quick lock mechanisms combined with an easy accessibility of the battery module and the cargo container, downtimes during flights can be minimized.
Besides the camera, the avionic systems are directly accessible via the cargo bay after the cargo container has been removed.
Energy Distribution and Inter-Module-Communication
Energy and information are distributed to the modules via a bus-system which is integratet into the carbon fibre mounting rails. It connects all modules to the flight computer which controls the modules systems.
Assembly in the Field
The aircraft can be easily assembled by just sliding the seperate modules onto the mountingrails, just one after another. A quick-lock mechanism keeps them in place but also allows a quick dissasembly without the need of any tools.
An easy transportation is guaranteed by the fact that no part is longer than two meters. Even the V-shaped tail unit can be disassembled into two parts (the two wings of the tail unit can be seperated - not displayed in the picture).
Concept and Design by Tobias Meyer